CA2106251C - Tribo-electric powder spray gun - Google Patents
Tribo-electric powder spray gun Download PDFInfo
- Publication number
- CA2106251C CA2106251C CA002106251A CA2106251A CA2106251C CA 2106251 C CA2106251 C CA 2106251C CA 002106251 A CA002106251 A CA 002106251A CA 2106251 A CA2106251 A CA 2106251A CA 2106251 C CA2106251 C CA 2106251C
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- CA
- Canada
- Prior art keywords
- powder
- charging
- outer cylinder
- inner core
- tribo
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
- B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
- B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
- B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
- B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
- B05B5/047—Discharge apparatus, e.g. electrostatic spray guns using tribo-charging
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- Electrostatic Spraying Apparatus (AREA)
Abstract
A tribo-electric powder spray gun includes a diffuser for mixing powder with a conveying gas, a charging portion downstream of the diffuser, and a sprayhead at the outlet of the charging portion for dispensing the charged powder. The charging portion has an inner core removably positioned within a hollow outer cylinder with an annular gap formed between the outer cylinder and inner core providing a charging flowpath for the powder. The inner core and the outer cylinder have undulating or wavy charging surfaces made of an electrically insulating material, so that the annular gap provides a tortuous path for the powder, enhancing powder contact and the charge imparted to the powder. Grounding is provided by surface conduction of the electrically insulating contact material through a ground ring located outside the powder path at the inlet to the charging portion of gun where the greatest amount of charging occurs. By locating the ground ring outside the powder path, thsa ground ring is kept clean and the amount of charging surface is maximized. The inner core and the outer cylinder are longitudinally symmetrical to facili-tate re-assembly.
Description
n . _ ~ L C .v . i i ;:.
f ~1~p~2.1 ~z--o/i . 1 TRIAO-ELl?CTRIC POWDrR SPRAY GUN
f ~1~p~2.1 ~z--o/i . 1 TRIAO-ELl?CTRIC POWDrR SPRAY GUN
2 33ACKGROUND OF TH:E INVENTION
Field~of the :Invention This invention relates to electrostatic powder painting, and more particularly to improved tribo-electric powder spray 6 guns.
7 Description of the Prior Art g In electrostatic powder painting, dry paint particles are 9 fluidized in a powder hopper and pumped through a hose to a to spray gun which sprays the powder onto a product to be coated.
11 The spr4y gun typically chargea the powder in one of two 12 ways--either the gun has a high voltage charging electrode, 13 or the gun has'means to charge the powder by friction, i.e., 14 tribo-electrically. This invention relates to tribo-electric powder spray guns.
16 Generally, in tribo-electric powder~'guns, the powder is 17 epoxy based, and surfaces are provided within the gun, la typically constructed from polytetrafluoroethylene (PTFE), lg which the powder particles impact numerous times to friction-,:.....
2o ally charge the particles. When the powder particles are 21 sprayed from the front of the gun, they are electrostatically 22 attracted to the product to be painted which is generally 23 electrically grounded and suspended from an overhead conveyer .
24 Once these.electrostatically charged powder particles are deposited onto the product, they adhere there by electrostatic 26 attraction until they are conveyed into an oven where they are 27 melted to flow together to form a continuous coating on the 2g product. Powder coating generally provides a tough and 29 durable finish such as would be found on many appliances, garden furniture, lawn mowers, and other products.
;i, < , _2_ 1 One commercially available tribo-electric powder spray 2 gun is shown in United States Patent No. 4,399,95. This gun 3 is available as a Tribomatic~ gun from Nordson Corporation, ' 4 Amherst, Ohio. In this gun, the powder is charged in a bundle of curved PTFE tubes which are wrapped around a core. As the 5 powder passes through the tubes, it impacts the interior walls of the tubes several times and picks up chargey upon each 8 contact. The outer layer of the tube bundle is covered by a 9 conductive material to bleed the charge to ground during operation of the gun. The grounding of the charge tubes 11 enhances the charging of the powder and promotes safety by 12 preventing the gun from storincs a capacitive charge which 13 could shock an operator or produce a spark, causing a fire or 14 explosion.
One of the important factors in the magnitude of the 16 charge imparted to the powder i:~ the velocity of the powder .~17 through the~~c~un; the higher the velocity of the powder, the 18 higher the charge on the powder. Therefore, the powder is 19 caused to flow through the gun at a high velocity in order to increase the charge on the powdE~r. However, the velocity of 21 the powder also has a detrimental effect on the wear life of 22 the powder gun parts. Wear of the parts~~is also a function 23 of velocity; the higher the ve:Locity, the higher the wear.
24 The powder abrades through the walls of the charge tubes in ,v,'~ 25 the charging portion of the gun with the result that the 26 entire gun must be periodically returned to the manufacturer 27 for rebuilding, at which time s.t is replaced by an entirely 28 new or rebuilt gun.
29 Another important element in the performance of tribo-electric powder spray guns is the electrostatic grounding of 31 the gun. Grounding of the prior art gun shown in U.S. Patent 32 No. 4,399,95 involves a very time-consuming and complicated 33 manufacturing process: The charging tubes are preformed into 3~1 convoluted shapes by heating them in special molds. The tubes were then arranged around an aluminum core and sprayed with .. 36 a black graphite type conductive coating. A conductive _ Eii ,.-. .,-". ~ , ( -3- t . .
' ~ ' y ,~",, .
1 wrapping is then applied around the entire tube bundle. A
2 ground wire is extended from the core to the control panel for ~3 the unit.
The present invention provides a tribo-electric powder 6 spray gun having an improved powder flowpath using the 7 arrangement of a core within a sleeve or cylinder, wherein the g powder flowpath is provided between the exterior of the core g and the interior of the cylindE_r. More specifically, the interior of the cylinder and the exterior of the core are z1 provided With undulating or wavy surfaces, so that an annular 12 wavy f towpath for the powder is provided within the gun . Both 13 the exterior of the core and the interior of the cylinder are 14 :~ provided with surfaces of PTFE. The wavy surfaces of the core 15V' and the cylinder cause the powder to change direction and 16 contact the PTFE charging surfaces numerous times while 17 passing through the charging portion of the gun, with the 18 powder particles picking up charge on each contact. The 19 exterior of the core and interior of the cylinder are held to a close tolerance so that the powder flowpath is very narrow, 21 further increasing the number of times each powder particle 22 hits a charging surface.
,.....
23 The present invention also provides improved electro-24 static grounding of the gun. T:he present invention provides an improved and simplified grounding path that avoids the time 26 consuming and complicated manufacturing process previously 27 required for prior art guns, such as that described in U.S.
28 Patent No. 4,399,945. The present invention improves on the 29 prior art design by incorporating a ground ring at the beginning of, but outside of, t:he powder flowpath.
31 The present invention uses the unique "wavy" core and 32 cylinder charging design in combination with an external 33 ground ring. By placing the ground ring outside of the ~ i, s r ., i. C ' 1 flowpath, the ground ring is kept clean. In addition, by 2 placing the ground ring at the inlet to the charging portion 3 of gun, the ground ring is locatESd where the greatest amount 4 of charging occurs, and this location is the ideal place to bleed off charge.
The contact surfaces in the charging portion.of the gun of the present invention are made from an electrically 8 insulating material, such as PTFE, that provides good tribo-.
Field~of the :Invention This invention relates to electrostatic powder painting, and more particularly to improved tribo-electric powder spray 6 guns.
7 Description of the Prior Art g In electrostatic powder painting, dry paint particles are 9 fluidized in a powder hopper and pumped through a hose to a to spray gun which sprays the powder onto a product to be coated.
11 The spr4y gun typically chargea the powder in one of two 12 ways--either the gun has a high voltage charging electrode, 13 or the gun has'means to charge the powder by friction, i.e., 14 tribo-electrically. This invention relates to tribo-electric powder spray guns.
16 Generally, in tribo-electric powder~'guns, the powder is 17 epoxy based, and surfaces are provided within the gun, la typically constructed from polytetrafluoroethylene (PTFE), lg which the powder particles impact numerous times to friction-,:.....
2o ally charge the particles. When the powder particles are 21 sprayed from the front of the gun, they are electrostatically 22 attracted to the product to be painted which is generally 23 electrically grounded and suspended from an overhead conveyer .
24 Once these.electrostatically charged powder particles are deposited onto the product, they adhere there by electrostatic 26 attraction until they are conveyed into an oven where they are 27 melted to flow together to form a continuous coating on the 2g product. Powder coating generally provides a tough and 29 durable finish such as would be found on many appliances, garden furniture, lawn mowers, and other products.
;i, < , _2_ 1 One commercially available tribo-electric powder spray 2 gun is shown in United States Patent No. 4,399,95. This gun 3 is available as a Tribomatic~ gun from Nordson Corporation, ' 4 Amherst, Ohio. In this gun, the powder is charged in a bundle of curved PTFE tubes which are wrapped around a core. As the 5 powder passes through the tubes, it impacts the interior walls of the tubes several times and picks up chargey upon each 8 contact. The outer layer of the tube bundle is covered by a 9 conductive material to bleed the charge to ground during operation of the gun. The grounding of the charge tubes 11 enhances the charging of the powder and promotes safety by 12 preventing the gun from storincs a capacitive charge which 13 could shock an operator or produce a spark, causing a fire or 14 explosion.
One of the important factors in the magnitude of the 16 charge imparted to the powder i:~ the velocity of the powder .~17 through the~~c~un; the higher the velocity of the powder, the 18 higher the charge on the powder. Therefore, the powder is 19 caused to flow through the gun at a high velocity in order to increase the charge on the powdE~r. However, the velocity of 21 the powder also has a detrimental effect on the wear life of 22 the powder gun parts. Wear of the parts~~is also a function 23 of velocity; the higher the ve:Locity, the higher the wear.
24 The powder abrades through the walls of the charge tubes in ,v,'~ 25 the charging portion of the gun with the result that the 26 entire gun must be periodically returned to the manufacturer 27 for rebuilding, at which time s.t is replaced by an entirely 28 new or rebuilt gun.
29 Another important element in the performance of tribo-electric powder spray guns is the electrostatic grounding of 31 the gun. Grounding of the prior art gun shown in U.S. Patent 32 No. 4,399,95 involves a very time-consuming and complicated 33 manufacturing process: The charging tubes are preformed into 3~1 convoluted shapes by heating them in special molds. The tubes were then arranged around an aluminum core and sprayed with .. 36 a black graphite type conductive coating. A conductive _ Eii ,.-. .,-". ~ , ( -3- t . .
' ~ ' y ,~",, .
1 wrapping is then applied around the entire tube bundle. A
2 ground wire is extended from the core to the control panel for ~3 the unit.
The present invention provides a tribo-electric powder 6 spray gun having an improved powder flowpath using the 7 arrangement of a core within a sleeve or cylinder, wherein the g powder flowpath is provided between the exterior of the core g and the interior of the cylindE_r. More specifically, the interior of the cylinder and the exterior of the core are z1 provided With undulating or wavy surfaces, so that an annular 12 wavy f towpath for the powder is provided within the gun . Both 13 the exterior of the core and the interior of the cylinder are 14 :~ provided with surfaces of PTFE. The wavy surfaces of the core 15V' and the cylinder cause the powder to change direction and 16 contact the PTFE charging surfaces numerous times while 17 passing through the charging portion of the gun, with the 18 powder particles picking up charge on each contact. The 19 exterior of the core and interior of the cylinder are held to a close tolerance so that the powder flowpath is very narrow, 21 further increasing the number of times each powder particle 22 hits a charging surface.
,.....
23 The present invention also provides improved electro-24 static grounding of the gun. T:he present invention provides an improved and simplified grounding path that avoids the time 26 consuming and complicated manufacturing process previously 27 required for prior art guns, such as that described in U.S.
28 Patent No. 4,399,945. The present invention improves on the 29 prior art design by incorporating a ground ring at the beginning of, but outside of, t:he powder flowpath.
31 The present invention uses the unique "wavy" core and 32 cylinder charging design in combination with an external 33 ground ring. By placing the ground ring outside of the ~ i, s r ., i. C ' 1 flowpath, the ground ring is kept clean. In addition, by 2 placing the ground ring at the inlet to the charging portion 3 of gun, the ground ring is locatESd where the greatest amount 4 of charging occurs, and this location is the ideal place to bleed off charge.
The contact surfaces in the charging portion.of the gun of the present invention are made from an electrically 8 insulating material, such as PTFE, that provides good tribo-.
9 electric charging properties. While this material is ~ZO electrically insulating,' grounding is accomplished using 11 surface discharge or surface conduction from the contact 12 surfaces to the ground ring. Since the charging portion 13 comprises separate elements, a gap is formed between these 14 elements. xn accordance with the present invention, the .surfaces of this gap are used a~> part of the surface conduc-16 t.ion path, and the gap is located adjacent to the position of 17 the ground ring.
lg .The present invention also provides an improved core and 19 cylinder design in which the core=_ with a wavy exterior surface can be inserted into and removed from the cylinder with a wavy 21 interior surface. This removabi:lity is accomplished by dimen-22 sinning the diameter of the pea~a or ridges of the inner care 23 to be less than or at most equal. to the diameter of the peaks 24 or ridges of the outer cylinder. This design provides an important advantage over the prior art designs, because, when 26 either of the charging surfaces becomes worn out, a neT~ core 27 and/or cylinder can easily be substituted in the f i el d without 28 the necessity of sending the entire gun back to the munufac-29 tuner to be rebuilt. This produces savings in time and expense.
31 The inner core and the outer cylinder each include wear 32 sleeves that are designed i:or easily removability and 33 replacement. Each of the wear sleeves if formed of stiffening 34 element of an electrically insulating, dimensionally stable material, such as NEMA.Grade G-10 material, and has a contact I ~I
. , (.._.. _5_ ~T i, _ 1 layer of an electrically insulating contact material, such as 2 PTFE.
Furthermore, wear sleeves on both the inner core and the 4 outer cylinder are longitudinally symmetrical, so that the gun can be re-assembled with either. end of the wear sleeves 6 inserted first. This 'simplifies assembly of the gun and 7 prevents improper assembly through inadvertently mounting one 8 of the wear sleeves backwards.
9 The present invention also provides a diffuser in the back of the gun to control the charge on the powder by driving 11 the powder through the charging portion at the desired 12 velocity. Prior art guns providing an annular gap for the 13 charging of powder used. an air nozzle at the rear of the 14 charging portion which was provided only for the purpose of 7.5 keeping the electrode clean.
16 These and other.advantages are provided by the present 17 invention of a powder spray gun which comprises a diffuser for 18 mixing powder with a conveying gas, a charging portion 19 downstream of the diffuser, and a sprayhead~at the outlet of the charging portion for dispensing the charged powder. The 21 charging portion includes means for electrically charging the 22 powder as it flows therethrough. The charging means comprises 23 an inner core removably positioned within a hollow outer 24 cylinder. The outer cylinder has an inner dimension, and the inner core has an outer dimension. An annular gap is formed 26 between the outer cylinder and inner core providing a charging 27 flowpath for the powder. The outer dimension of the inner 28 core increases at generally th~a same longitudinal position 29 that the inner dimension of the outer cylinder decreases . The outer dimension of the inner core decreases at generally the 31 same longitudinal position than the inner dimension of the 32 outer cylinder increases. The width of the annular gap 33 remains generally constant along the length of the outer 34 cylinder and the inner core. The frictional charge which builds up on the inner core and outer cylinder surfaces flows 36 along those surfaces to a ground ring located externally to 1 the flowpath of the powder. The powder is charged by repeated 2 contact with the surfaces during flow through the channel.
3 BRIEF DESCRIPTION OI' THE DFtIIWINGS
4 FIG. 1 is a side elevational view of the gun of the present invention with a portion of the gun body removed to 6 show the pin from the gun body in <:ross section extending into 7 the slot on the tube extension, forming the bayonet-type 8 latching mechanism.
g ~ FIG. 2 is a cross-sectional side view of the gun of FIG.
3 taken along line 2--2 of FIG. t>.
lI FIG. 3 is a detailed cross-sectional view a portion of 12 FIG. 2 to a larger scale.
13 FIG. 4 is a.detailed cros~~-sectional view of another 14 portion of FIG. 2 to a larger scale.
FIG. 5 is a detailed cross-sectional view another portion 16 of FIG. 2 to a larger scale.
FIG. 6 is a end sectional view of the gun taken along 18 line 6--6 of FIG. 1.
FIG. 7 is a sectional view taken along line 7--7 of FIG.
3.
21 FIG. 8 is a sectional detail view taken along line 8--s 22 of FIG. 7.
23 FIG. 9 is a sectional view taken along line 9--9 of FIG.
24 4.
FIG. 10 is a sectional detail view taken along line 26 IO--10 of FIG. 9.
2~ DETAILED DESCRIPTION OF THE PREFERRED E~iF30DIMENTS
2g Referring more particularly to the drawings and initially 29 to FIGS. 1 and 2, there is shown the tribo-electric powder spray gun 10 of the present invention. The gun to includes i' w ( '~ -7-un bod 11 having a central opening extending therethrough.
1 a g Y
2 A gun mount assembly 12 is attached to the gun body 11 by 3 means of fasteners 13 and ld. The: gun l0 comprises a diffuser 4 portion 15 at the inlet, a charging portion is in the middle, and the sprayhead portion 17 at the outlet.
The diffuser portion 15 of i_he gun comprises .a diffuser ~ body 21 having a central axial passageway 22. The diffuser 8 body 21 is fitted into the inlet. end of the central opening 9 in the gun body 11, and O-rings. 23 and 24 are provided in grooves around the outer surface of the diffuser body 21, 11 between the diffuser body and the interior surface of the 12 inlet end of the central opening in the gun body 11.
13 Compressed air enters the d_i.ffuser portion 15 from a gun 14 control module (not shown) through a connector 27. The connector 27 is connected to a diffuser nozzle 28 inserted . 16 into the.forward end of the passageway 22. Powder from a s' .. 17 hopper is conveyed to the dif yusE:r portion 15 - by f low air from 18 a pump such as that shown in U.~>. Patent No. 4,615,649. The 1g powder and conveying air from the pump enter the gun through a feed hose which is connects=_d to the .gun at an inlet 21 connector 29 which extends radially into the diffuser body 21 22 toward the passageway 22. As the powder 'enters the diffuser 23 portion 15 from the connector 29, the powder is mixed with the 24 diffuser air from the diffuser nozzle 28. Diffuser air flowing across the powder inlet connector 29 creates a 26 negative pressure at the powder inlet which assists the pump 27 by drawing the. powder from the powder feed hose into the 28 diffuser. The hole in the nozzle 28 in the diffuser is sized 29 to provide a high volume air flow at low pressure.
Lower pressure in the diffuser results in less back 31 pressure on the pump which in turn results in higher powder 32 flow output from the pump. The high volume of diffuser air 33 results in the powder being conveyed through the charging 34 portion 16 at high velocity further resulting in high charging of the powder. Since the magnitude of the charge imparted to 36 the powder is directly related to the velocity of the powder ~i~
,. _ . -g- (._ 1 through the gun, the volume of diffuser, air is essentially the 2 way of adjusting the charging of the powder: higher diffuser 3 air produces a higher charge on the powder, lower diffuser air 4 a lower charge. The present invention provides a diffuser in the back of the gun to control the charge on the powder by 6 driving the powder through the charging portion '16 at the 7 desired velocity. w g The charging portion 16 of the gun is located within an 9 outer extension tube 31 which is removably attached to the gun body 11 and which extends from the forward-end of the body.
11 The charging portion 16 comprises an inner core assembly 32 12 mounted within an outer cylinder assembly 33.
13 As shown in FIG. 2,~the inner core assembly 32 comprises 14 a central threaded rod 35, having a generally conical inlet distributor 36 threaded on one end, and a generally frusto-16 .conical outlet distributor 37 threaded on the other end. A
1-7 generally cylindrical inner wear sleeve 38 is captured between lg the inlet distributor 36 and thE: outlet distributor 37.~
lg The outer cylinder assembly 33 is mounted within the extension tube 31 and comprises an outer wear sleeve 4o which 21 is captured between an inlet wear sleeve 41 ;and an outlet wear 22 sleeve 42. The inlet wear sleeve 41 fits'~against a shoulder 23 39 at the outlet end of the central opening in the gun body 24 11. The outlet wear sleeve 42 has a shoulder 43 around its exterior, and the outlet end of the extension tube 31 has a 26 flange 44 which extends radially inwardly to engage the 2~ shoulder 43 through a compressible gasket 45 and hold the 28 outlet wear sleeve in place. .
2g Thus, the inlet wear sleeve 41 is positioned around the inlet distributor 36, the outer wear sleeve 4o is positioned 31 around the inner wear sleeve 3.3, and the outlet wear sleeve.
32 42 is positioned around the outlet distributor 37.
33 An annular gap 46 is formed between the inner and outer 34 wear sleeves 3B and 40. The outer surface of the inner wear sleeve 38 and the inner surface of the outer wear sleeve 40 3 6 undulate, so that the annular gap 4 6 provides a tortuous path i, a '. -~- i 1 for the powder passing through the charging portion 16.
2 Specifically, the outer diameter of the inner wear sleeve 38 3 ' increases at generally the same longitudinal position that the 4 inner diameter of the outer wear ;sleeve 40 decreases, and the outer diameter of the inner wear sleeve 38 decreases at . 6 generally the same longitudinal position that .the inner 7 diameter of the outer wear sleeve 4o increases,..so that a 8 narrow "wavy" flowpath for the powder is created by the 9 annular gap 46 between the sleeves 38 and 40. The.width of l0 the annular gap 46 remains genera:Lly constant along the length 11 of the inner and outer wear sleeves 38 and 40, although the 12 annular gap 46 varies in diameter.
13 Powder enters the charging portion 16 of the gun from the 14 diffuser portion 15 and is channelled into the annular gap 46 between the inner and outer wear sleeves 38 and 4o by the 16 converging surfaces of the inlet wear sleeve 4I and the inlet 17 distributor 36. The inlet wear sleeve 41, which is positi oned 18 within the gun body 1.1, extends :from the . outer wear sleeve 4 0 to the diffuser body 21 and def~_ries a passage for the powder exiting the diffuser portion of the gun. ' 21 The powder then flows through the narrow, "wavy" annular 22 gap ~! 6 and subsequently through a wi dening' annular gap def fined 23 by the diverging surfaces of the outlet distributor 37 and the 24 outlet wear sleeve 42 from which the powder is discharged into the sprayhead portion 17.
26 To seal the powder flowpath, a plurality of O-rings are 27 provided between various components of the gun. The inlet 2g wear sleeve 41 is sealed againsi~ the gun body 11 by an O-ring 29 48 (FIG. 3) which is provided between the gun body and the I 30 inlet wear sleeve at the beginning of the charging portion 16.
31 Another O-ring 49 is located also around the exterior of the 32 inlet wear sleeve 41. O-rings 5o and 51 are located around 33 the exterior of the outer wear sleeve 4o, with the O-ring 50 34 positioned.near the inlet end of the outer wear sleeve 40 (FIG. 3), and the O-ring 5Z positioned between the outer wear .
r'.... 10 r ~
~.. -1 sleeve 40 and the extension tube 31 at the outlet end of the 2 wear sleeve (FIG~ 4)~
3 ~ The extension tube 31 is removably attached to the gun 4 body 3.1 by a bayonet-type~latching mechanism comprised of a pin 52 extending from the gun body lI. into a slot 53 formed 6 in the extension tube 31, so that the charging portion 16 is 7 securely held to the gun body daring use and may be easily 8 removed when it is desired to clean the gun or replace one of g the wear sleeves. With the extension tube 31 securely attached to the gun body 11 by the bayonet mechanism, the 11 outer wear sleeve 4o is urged back into the central opening 12 in the body 11 by the foam neoprene gasket 45 (FIGS. 1 and 5) 13 located between the outer flange 44 of the extension tube 31 14 and the shoulder 43 of the outlet wear sleeve 42. The gasket 45 is compressible and resilient, and it forms a spring which 16 provides a force upon the outer wear sleeve 4o toward the gun 17 body ll. The O-ring 5o carried on the c:nd of the outer wear 18 sleeve 40 engages a ground ring X81. (later described) when the 19 outer wear sleeve is pushed into the gun body 11 by the gasket 45.
21 As shown in detail in FIG. 5, the inner wear sleeve 38 '22 comprises an inner PTFF contact layer 54 formed on the outer 23 diameter of an inner stiffening element or sleeve 55. The 24 outer wear sleeve 4o similarly comprises an outer PTF L contact layer 56 formed on the inner diameter of an outer stiffening 26 element or sleeve 57. The stiffening sleeves 55 and 57 are 27 made of an electrically insu:Lating, dimensionally stable 28 material and preferably are made from a NEM.A Grade G-10 29 (continuousfilament woven glass-fabric impregnated with epoxy resin) or similar material. 'the contact layers 54 and 56 31 provide a layer of electrically insulating material along the 32 powder flowpath, but also provide surface conductivity for 33 grounding. The stiffening sleeves 55 and 57 provide rein 34 forcement for the sleeves and help the "wavy" PTFF sleeves hold their shape, both radial:ly and longitudinally, during v .: -m-~~~~~:
1 machining, and over time to maintain dimensional integrity 2 along the annular gap 46.
3 ~ Referring again to FIG. 2, the .position of the inner core 4. assembly 32 with respect to the outer cylinder assembly 33 is maintained by a positioning ring 6o and a spacing ring 61.
6 The positioning ring 6o°is used both to align the.inner wear 7 sleeve 38.radially with the inlei~ distributor 36 at the inlet 8 of the charging portion 16 and to align the inner wear sleeve 38 and the distributors 36 and 3',7 axially with the outer wear sleeve 4o and the wear sleeves .41 and d2. The spacing ring 11 6i is used only to align the inner wear sl eeve 38 and the 12 outlet distributor 37 radially with the wear sleeve 4 0 and the ~3 outlet wear sleeve 42 at the outlet of the charging portion 14 16. The positioning ring 60 and the spacing ring 6~ are each made from an electrically insulating material which provides 16 surface conductivity, such as D~elrin.
As shown.. in FIG. 3, the positioning ring 6o is located 18 between the inlet wear sleeve 4~. and the outer wear sleeve 40 19 and between the inlet distributor 36 and the inner wear sleeve 38. A small recess 63 is formed around the inner surface of 21 the inlet wear sleeve 41 adjacent to the outer wear sleeve.4o 22 to provide for the positioning ring 60. Similarly, a recess 23 64 is formed around the inner surface of the outer wear sleeve ° 24 40 adjacent to the inlet wear sleeve 4I. to provide for the ''w~ 25 positioning ring 60. Corresponding recesses 65 and 66 are 26 formed in the outer surfaces of the inlet distributor 35 and 27 the inner wear sleeve 38, respectively, to provide for the 28 positioning ring 60. In this way the positioning ring 60, 29 best shown in FIG: 7, is captui:ed in the recesses 63, 64, 65 and 66.
31 The structure of the positioning ring 60 is shown in more 32 detail in FIG. 7. The positioning ring 6o comprises an outer 33 ring portion 69 which is captured in the recesses 63 and 64 34 between the inlet wear sleeve 41 and the outer wear sleeve ~io, and an inner ring portion 7o which is captured in the recesses 36° 65 and 66 between the inlet dig>tributor 36 and the inner wear n .~
1 sleeve 38. The inner ring portion 7o and the outer ring 2 portion 69 are connected by four web portions 71 which are 3 located 90° apart with respect.to each other. The web . 4 portions 71 extend through the path of the powder, and, as shown particularly in FIG. 8, the web portions have a tapered 6 or streamlined cross section to reduce the build-up of powder 7 on the web portions which would otherwise be caused by impact . 8 fusion of the powder.
g ~ The recess 64 in the outer wear sleeve 4o extends completely through the outer PTFE contact layer 56 and into 11 the outer stiffening sleeve 57. Likewise, the recess 66 in 12 the inner wear sleeve 38 extends_completely through the inner 13 PTFE contact layer 54 and into thE: inner stiffening sleeve 55.
14 The material of the stiffening sleeves 55 and 57 is more rigid than the softer PTFE material of 'the contact layers 5 d and 5 6 , 16 and the depth of the recesses into the stiffening sleeves 17 provides dimensional stability to the positior..i ng of the ring lg .60. The recesses 63, 64, 65 and 66 thus provide for precise 19 axial placement of the positioning ring so with respect to the outer. cylinder assembly 33 and the inner core assembly-32.
21 The spacing ring 61 is located between the outer wear 22 sleeve 40 and the outlet wear sleeve 42. 'As shown in FIG. 4, 23 a recess 73 is formed in the outer wear sleeve 4o at the 24 outlet edge, and a corresponding recess 74 is formed in the outlet wear sleeve 42. The spacing ring 61 fits within the 26 groove formed by the recesses 73. and 74. As shown in FIG. 9, 27 the spacing ring 61 comprises a.n outer ring portion 75 that 28 fits within the groove formed r>y the recesses 73 and 74 and 29 four projecting spacer portions 76 that extend radially inwardly from the outer ring portion 75. The spacer portions 31 7 6 are located 90 ° apart with respect to each other . The tips 32 of the spacer portions 76 engagEa the outer wall of the outlet 33 distributor 37 to radially position the outer cylinder 34 assembly 33 with respect to the inner core assembly 32. As shown in FIG. l0, the spacer portions 76 also have a tapered ' 36 or streamlined cross section, similar to the web portions 71 1 or the positioning ring 6o, to prevent the build-up of power 2 due to impact fusion.
3 A recess 78 (FIG. 4), is also provided on the other end .4 of the inner wear sleeve 38 opposite the ,recess 66. This.
recess 78 is not needed for the positioning of the spaci ng 6 ring sl since the spacing ring is not mounted in. the inner 7 core assembly. However, the recess 78 is provided'so that the 8 inner wear sleeve 38 is longitudinally symmetrical, i.e., 9 reversible. The recess 78 is thus symmetrically located with respect to the recess 66 on the other end of the inner wear 11 sleeve 38. Since the recess 78,, as shown in FIG. 4, is not 12 needed for the spacing ring 61, the outlet distributor 37 is 13 provided with a small flange 79 which fits within the recess 14 78.
In accordance with.conventional design of tribo-electric 16 powder spray guns, the charging portion 16 is grounded to 17 enhance the charging of the powder and promot~safety by ~18 preventing the gun from storing a capacitive charge which 19 could shock an operator or produce a spark, causing a fire or explosion., The present invention, however, utilizes an 21 improved grounding configuration. A ground electrode is 22 provided in the form of a ground ring 81 located within the 23 gun body 11 and around the exterior of the inlet wear sleeve 24 ;1 and the outer wear sleeve 40, near the inlet of the '.. 25 charging portion 16 where the highest charge transfer to the ' 26 powder occurs. The ground rind 81 is located away from the 27 powder flowpath, so that it i~~ kept clean, resulting in a 28 good, consistent electrical gronsnd. The O-ring 49 is located 29 between the ground ring 81 and the inlet wear sleeve 4'!, and the O-ring 5o is located between the ground ring 81 and the 31 outer wear sleeve 40.
32 The outer wear sleeve 40 ~.s a separate element from the 33 inlet wear sleeve 41 to allow for a gap 82 to b~ formed 34 therebetween. The gap 82 may not be significant in dimension, and the elements 4o and 41 forming the gap may, in fact, be . 36 touching or abutting each other'. Even if the elements 4o and . ~ ~ ~ -14-.
,~~-1 .T are abutted together in contacts, a gap 82 will be present , 2 between these elements which will be sufficient for the 3 passage of charge to the ground ring 8~.. The gap 82 is 4 annular and is shown to indicate: that exterior surfaces are provided between the outer wear ;sleeve 40 and the inlet wear 6 sleeve 41, so that surface conduction can occur along these 7 surfaces~as part of the grounding path.
g The electrical grounding of the elements of the charging.
9 portion 16 of the gun is accomplished by surface conduction . 10 along the exterior surfaces of the inner wear sleeve 38, the 11 outer wear sleeve 40, the inlet wear sleeve 41, the inlet 12 distributor 36, the outlet distributor 37 and the outlet wear 13 sleeve 42. As previously described, at least the surfaces of 14 these parts which form a part of the powder flowpath are 15 formed of an electrically ins>ulating material with good 16 charging properties, such as P:'L'FE. The PTFE material al so 17 allows for surface discharge which provides a conductive path 18 for grounding. The charge on the surfaces of the inlet wear 19 sleeve 41, the outer wear sleeve 40 and the outlet wear sl eeve 20 42 flows along those surfaces t:o the ground ring 81 through 21 the gap 82 provided between the inlet wear;'sleeve 4~. and the 22 outer wear sleeve 40. The charge on the surfaces of the inlet 23 distributor 3s, the inner. wear sleeve 38 and the outlet 24 distributor 37 flows along those surfaces and across the 25 surface of the positioning ring 6o to the ground ring 81 26 through the gap 82. Some charge from these surfaces most 27 likely also flows across the spacing ring 61, to the outer wear 28 sleeve 4o before passing along the gap 82. Because the rings 29 6o and 61 are also made of an electrically insulating mater? al 30 providing adequate surface conductivity, such as Delrin, they 31 provide sufficient discharge current transfer from the inner _ 32 core elements 36, 37 and 38 to the ground ring 8L.
33 From the ground ring 81, the current flows through a 34 ground stud 84 to a ground wire (not shown) held onto the 35 ground stud 84 by a knob 85, which leads back to the gun 36 control module where it is di:>played by means~of an ammeter 15r '.
and then flows to ground. The surface conductivity of the 2 PTFE, the length of the path to the ground ring al and the 3 electrical potential of the charge on the powder contact surfaces are all variables considered in the design of the gun for proper grounding and. optimum. charging performance.
6 The outlet end of the charging portion 16 of the gun is designed to accept various conventional sprayheads.. As shown, g the sprayhead portion 17 comprises a conventional sprayhead 9 88 which is shown to illustrate the mounting of a sprayhead to the outlet end of the charging portion 16. The sprayhead 11 88 is mounted on the outlet wear sleeve ~2 adjacent to the-12 flange 4d on the outlet end of t'.he extension tube 31. The O-13 rings 89 and 90 (FIG. 4) are located in grooves on the 14 exterior of the outlet wear sleeve 42 between the sprayhead 15' 88 and the outlet wear sleeve.
16 The magnitude of the charge imparted to the powder in the 17 charging portion I6 is a function of (1) the velocity of the 1g powder, (2) the material from which the flowpath walls are 19 made, (3) the geometry or de:~ign of the powder flowpath through the charging portion, (~~) the electrical grounding of 21. the charging surfaces, and (5) the composition of the powder 22 coating material. The gun of the present invention is 23 designed to maximize the charge imparted to the powder through 24 consideration of each of the above five factors.
. One of the important factors in the magnitude of the 26 charge imparted to the powder is the velocity of the powder 27 through the charging portion ~.6 of the gun; the higher the 28 velocity of the powder, the higher the charge on the powc,er.
29 However, the velocity of the 'powder also has a detrimental . 30 effect on the wear life of the powder gun parts. Wear of the 31 parts is also a .function of velocity; the higher the velocity, 32 the higher the wear. Therefore, it is not desirable to flow 33 the powder at any greater velocity than is required for 34 adequate charging.
In the preferred embodiment of the present invention, all 36 of the parts which the powder can contact in the charging -16- ~~~
,~., 1 portion I6 of the gun, namely the inner wear sleeve 38, the 2 outer wear sleeve .io, the inlet; wear sleeve dL, the inlet 3 distributor 36, the 'outlet distributor 37, and the outlet wear 4 sleeve 42, are made of a fluoropolymer material, preferably polytetrafluoroethylene (PTFE). This material has been found 6 to be very effective fob tribo-electrically charging powdered 7 paints of various compositions. The powder picks up charge 8 with each contact with a PTFE surface. Therefore, maximizing the PTFE surface area exposed to the powder maximizes the opportunity'to charge the powder. PTFE is an electrically 11 insulating material but has surface conductivity to provide 12 from grounding of the charges imparted to the powder.
13 The unique design of the inner and outer wear sleeves 38 14 and 40, specifically their "wa~,ry" surfaces, also serves to increase the magnitude of the charge imparted to the powder.
16 The curved surfaces of the inner and outer wear sleeves 38 and 17 .4 o cause the .:powder to f low in a tortuous path through the . 18 annular gap 46, thus forcing thE: powder against the peaks and 'lg valleys or grooves of the each of the sleeve. Each change in diameter of the sleeves 38 and 4o forces the powder to change 21 direction and further impact the PTFE surfaces of the sleeves 22 adding to the charge on the powder.
23 The magnitude of the .charge imparted to the powder i s 2~'t further enhanced by the relatively narrow width of the annular gap 46. The annular gap between the two wear sleeves 38 and 26 4o is small, on the order of 0.032 inches (0.82 nm) . The 27 powder, therefore, has a high probability of contacting the 28 surfaces of the wear sleeves 3B and d0 many times rather than 29 flowing straight through the charging portion with rel atively few contacts. As previously d~ascribed, this narrow width of 31 the annular gap 46 between thE: inlet wear sleeve 41, outlet 32 wear sleeve 42, inner wear sleeve 38 and the inlet distributor 33 36, outlet distributor 37, and the outer wear sleeve 4o is 34 maintained by the positioning ring 6o and the spacing ring 6~..
Since the charge imparted to the powder is increased by 36 increasing the velocity of th.e powder through the charging 1 portion 16 of the gun, and since increasing the velocity of 2 the powder increases the wear of the powder gun parts, It is 3 advantageous to provide~for easy replacement of worn parts.
4 The present invention facilitates replacement of the two wear sleeves 38 and 40. The two wear aleeves 38 and 4o are dimen-6 sinned so that the inner wear sleeve 38 can be removed from 7 the outer wear sleeve 4o by pushing or pulling thewinner wear g sleeve out either end of the outer wear sleeve. This remova-bility is accomplished by dimens Toning the diameter of the peaks or ridges of the inner wear sleeve 38 to be less than 11 ~ or at most equal to the diameter ~of the peaks or ridges of the 12 outer wear sleeve 40. When either of the sleeves 38 and 40 13 worn out, a new sleeve can easily be substituted in the field 14 without the necessity of sending the entire gun back to the manufacturer to be rebuilt, resulting in savings in time and 16 expense.
To assemble t'~e gun l0, the positioning ring 6o is first .. 17 lg placed into the recess 66 on one end of the inner wear sleeve 19 38. It is noted that the inner wear sleeve 38 is longitudi-nally symmetrical, so that assembly can begin by placing the 21 positioning ring 60 on either e:nd of the. inner wear sleeve.
22 The inlet distributor 36 is then positioned on the same end 23 of the inner wear sleeve...with the positioning ring in the 24 recess 65. The threaded rod :35 is then inserted into the . .. 25 corresponding threaded opening in the inlet distributor 36.
26 The outlet distributor 37 is then threaded onto the other end 27 of the rod 35, and the assembly of the inner core assembly 32 28 is complete.
29 The body 11 is preassembled with the diffuser body 21, the gun mount assembly 12, the around ring 81, the ground stud 31 84 and the knob 85 in place. The O-rings 48 and 49 are posi-32 tinned around the exterior of the inlet wear sleeve 41 in 33 groove provided for the O-rings>, and the inlet wear sleeve is 34 inserted into outlet end of t:he central opening in the gun body 11. The previously assembled inner core assembly 32 is 36 then inserted with the inlet distributor 36 fitting into the _lg_~
inlet wear sleeve 41 and the positioning ring 60 fitting into 2 the recess 63 in the inlet wear s>leeve. Next, the O-ring So 3 is positioned in the groove provided on the exterior of the.
outer wear sleeve .~o. Then, t7ze outer wear sleeve 4o is inserted into the central opening of the body 11 until the 6 .positioning ring s0 is.'seated in the recess 64 on.the end of the outer wear sleeve. zt is noted that the outerwear sleeve g 4o is longitudinally symmetrical, so that either end of the 9 outer wear sleeve may be inserted into the gun body 11 during to assembly.
11 The spacing ring 61 is than placed around the outlet 12 distributor 37 and positioned upon the outwardly extending end 13 of the outer wear sleeve 4o in the recess 73. The O-rings 89 14 and 90 are pre-assembled on the outlet wear sleeve 42 in the ~,5 grooves provided on the exterior of the outlet wear sleeve, 16 and the outlet wear sleeve 42 is then positioned on the 17~ outwardly extending er.:d of the outer wear sleeve 4o with the lg spacing ring 61 received within the recess 74' of the outlet 1g wear sleeve.d2.~ The neoprene gasket 45 is placed against the 20 shoulder d3 of the outlet wear sleeve 42, and the extension 21 tube 31 is placed over the outwardly extending assembly. As 22 the extension tube 31 is rotated, the pin 52 locates the 23 opening into the slot 53, and the extension tube is pushed 24 into the central opening of the body 11 around the outer wear 25 sleeve 40, with the flange 44 engaging the neoprene gas~:et 45 26 and compressing it. This urges the outlet wear sl eeve 42 , the 27' outer wear sleeve 40, the positioning ring 60 and the inlet 28 wear sleeve dl toward the body l.l, so that the inlet wear 29 . sleeve 41 is pressed against the shoulder 39 of the gun body 30 11. This also axially positions the inner core assembly 32 31 which is positioned within the outer wear sleeve 4o by the 32 positioning ring 6o and the spacing ring 61. The extension 33 tube 31 is locked to the body 11 by rotating it 8 turn to 34 engage the pin 52 into the detent at the end of the slot 53.
35 The desired sprayhead 88 can then be mounted on the end of the 36 outlet wear sleeve 42.
The gun can also be easily disassembled for cleaning or 2 for replacement of the wear sleeves 38 and 40. The wear 3 sleeves 38 and 4o are removed~from the gun by first removing 4 'the sprayhead 88.from outlet wear sleeve d2. The extension tube 31 is next disengaged from the gun body 11 by rotating 6 the extension tube and disengaging the bayonet mechanism.
7 Thereafter, the outlet wear sleeve d2 and the outlet distribu-g for 37 may be removed, and the inner wear sleeve 38 may be 9 removed from the outer wear sleeve 40, or the outlet wear 1p sleeve d2 and the outer wear sleEwe do may be removed from the 11 inner wear sleeve 38. , 12 The re-assembly of the wear sleeves and the replacement 13 of a worn sleeve with a new wear sleeve is further facilitated 14 by the design of the wear sleeve: 38 and 40. The wear sl eeves 38 and 4o are each symmetrical ao that they can be assembled 16 into the gun with either end first. This prevents incorrect 17 insertion of one of the wear s7_e,eve 38 or 40 into the other 1g wear sleeve in the field and prevents inadvertent misal ignment 19 of the wear sleeves and resulting incorrect dimensioning of the annular gap 46 21 Another important factor i.n the magnitude of the charge 22 imparted to the powder is proper electrical grounding of the 23 gun. The ground ring 81. is located away from the powder 24 flowpath near the inlet of the charging portion 16. The ground ring 81 is located in the region of the gun where the 26 greatest amount of charging occurs, and this location is, 27 therefore, the preferred location to bleed off charge. By 28 locating the ground ring 81. outside the powder path, the 29 ground ring is kept clean from the build-up of powder, . 30 resulting in a good, consistent electrical ground.
31 Various modifications and improvements can be made to the 32 invention shown and described. For example, the dimension and 33 geometry of the waves formed b~y the exterior surfaces of the 34 sleeves 38~and 4o can be modified. Similarly, more or fewer waves can be provided.
a . -2~
I
The exterior surfaces of t'he sleeves 38 and 4o can be 2 made of other materials that may be longer wearing and that 3 may tribo-electrically charge powder as well as PTFE does, 4 such as perfluoroalkoxy (PFA) and Tefzel~, modified ethyl-tetraf luoroethylene f luoropolymsar .
6 The inner and outer wear sleeves 38 and 4o can also be 7 injection molded to facilitate manufacture wand reduce 8 fabrication costs. In order t.o make the sleeves using an 9 injection molding process, an injection moldable material, such as PFA, FEP or Tefzel, would be used instead of PTFE, 11 which is only extrudable and compression moldable. If the 12 stiffening sleeves 55 and 57 are. made out of a NEr~ Grade G-10 13 (continuous filament woven glass-fabric impregnated with epoxy 14 resin) or similar material, the PF1~ may be injection molded onto the G-10 tube and then, if needed, the wave may be 16 finished by machining, on the PF1~ portion of the assembly..
In addition,.. instead e:f gluing the inner contact layer 17 ' -, lg 54 to the inner stiffening, sleeve 55 and the outer contact 19 layer 56 to the outer stiffening sleeve 57, these materials can be fractionally secured together. To accomplish this, the 21 inner PTFE contact layer 54 could be heated to expand it, and 22 the inner contact layer could be slid over the inner stiffen-23 ing sleeve 55 and cooled to shi:ink it onto the sleeve 55. In 24 like manner, the outer contact layer 56 can be super-cooled, such as in liquid nitrogen, to shrink it, and inserted into 26 the outer stiffening sleeve 5'7. The outer contact layer 56 27 can then be heated back to room temperature to expand it into 2g a compression fit with the sleeve 57.
29 The annular gap d 6 through which the po~,~=der .f lows may also vary in width as a function of its radius from the gun 31 centerline, so that the width of the annular gap is smaller 32 at a larger radius. This would be done in order to approxi-33 mate a constant cross-sectional area for the powder path in 34 order to maintain the powder at a relatively constant velocity as it passes through the charging portion 16.
Other variations and modifications of the specific embodiments herein shown and described will be apparent to 3 those skilled in the art, all within the intended spirit and - 4 scope' of the invention. While 'the invention has been shown and described with respect to paz:ticular embodiments thereof , 6 these are for the purpose o:f illustration rather than limitation. Accordingly, the p<~tent is not to be limited in g scope and effect to the specific: embodiment herein shown and 9 described nor in any other way i~his is inconsistent with the lp extent to which the progress in the art has been advance by 11 the invention.
,. .. .\
lg .The present invention also provides an improved core and 19 cylinder design in which the core=_ with a wavy exterior surface can be inserted into and removed from the cylinder with a wavy 21 interior surface. This removabi:lity is accomplished by dimen-22 sinning the diameter of the pea~a or ridges of the inner care 23 to be less than or at most equal. to the diameter of the peaks 24 or ridges of the outer cylinder. This design provides an important advantage over the prior art designs, because, when 26 either of the charging surfaces becomes worn out, a neT~ core 27 and/or cylinder can easily be substituted in the f i el d without 28 the necessity of sending the entire gun back to the munufac-29 tuner to be rebuilt. This produces savings in time and expense.
31 The inner core and the outer cylinder each include wear 32 sleeves that are designed i:or easily removability and 33 replacement. Each of the wear sleeves if formed of stiffening 34 element of an electrically insulating, dimensionally stable material, such as NEMA.Grade G-10 material, and has a contact I ~I
. , (.._.. _5_ ~T i, _ 1 layer of an electrically insulating contact material, such as 2 PTFE.
Furthermore, wear sleeves on both the inner core and the 4 outer cylinder are longitudinally symmetrical, so that the gun can be re-assembled with either. end of the wear sleeves 6 inserted first. This 'simplifies assembly of the gun and 7 prevents improper assembly through inadvertently mounting one 8 of the wear sleeves backwards.
9 The present invention also provides a diffuser in the back of the gun to control the charge on the powder by driving 11 the powder through the charging portion at the desired 12 velocity. Prior art guns providing an annular gap for the 13 charging of powder used. an air nozzle at the rear of the 14 charging portion which was provided only for the purpose of 7.5 keeping the electrode clean.
16 These and other.advantages are provided by the present 17 invention of a powder spray gun which comprises a diffuser for 18 mixing powder with a conveying gas, a charging portion 19 downstream of the diffuser, and a sprayhead~at the outlet of the charging portion for dispensing the charged powder. The 21 charging portion includes means for electrically charging the 22 powder as it flows therethrough. The charging means comprises 23 an inner core removably positioned within a hollow outer 24 cylinder. The outer cylinder has an inner dimension, and the inner core has an outer dimension. An annular gap is formed 26 between the outer cylinder and inner core providing a charging 27 flowpath for the powder. The outer dimension of the inner 28 core increases at generally th~a same longitudinal position 29 that the inner dimension of the outer cylinder decreases . The outer dimension of the inner core decreases at generally the 31 same longitudinal position than the inner dimension of the 32 outer cylinder increases. The width of the annular gap 33 remains generally constant along the length of the outer 34 cylinder and the inner core. The frictional charge which builds up on the inner core and outer cylinder surfaces flows 36 along those surfaces to a ground ring located externally to 1 the flowpath of the powder. The powder is charged by repeated 2 contact with the surfaces during flow through the channel.
3 BRIEF DESCRIPTION OI' THE DFtIIWINGS
4 FIG. 1 is a side elevational view of the gun of the present invention with a portion of the gun body removed to 6 show the pin from the gun body in <:ross section extending into 7 the slot on the tube extension, forming the bayonet-type 8 latching mechanism.
g ~ FIG. 2 is a cross-sectional side view of the gun of FIG.
3 taken along line 2--2 of FIG. t>.
lI FIG. 3 is a detailed cross-sectional view a portion of 12 FIG. 2 to a larger scale.
13 FIG. 4 is a.detailed cros~~-sectional view of another 14 portion of FIG. 2 to a larger scale.
FIG. 5 is a detailed cross-sectional view another portion 16 of FIG. 2 to a larger scale.
FIG. 6 is a end sectional view of the gun taken along 18 line 6--6 of FIG. 1.
FIG. 7 is a sectional view taken along line 7--7 of FIG.
3.
21 FIG. 8 is a sectional detail view taken along line 8--s 22 of FIG. 7.
23 FIG. 9 is a sectional view taken along line 9--9 of FIG.
24 4.
FIG. 10 is a sectional detail view taken along line 26 IO--10 of FIG. 9.
2~ DETAILED DESCRIPTION OF THE PREFERRED E~iF30DIMENTS
2g Referring more particularly to the drawings and initially 29 to FIGS. 1 and 2, there is shown the tribo-electric powder spray gun 10 of the present invention. The gun to includes i' w ( '~ -7-un bod 11 having a central opening extending therethrough.
1 a g Y
2 A gun mount assembly 12 is attached to the gun body 11 by 3 means of fasteners 13 and ld. The: gun l0 comprises a diffuser 4 portion 15 at the inlet, a charging portion is in the middle, and the sprayhead portion 17 at the outlet.
The diffuser portion 15 of i_he gun comprises .a diffuser ~ body 21 having a central axial passageway 22. The diffuser 8 body 21 is fitted into the inlet. end of the central opening 9 in the gun body 11, and O-rings. 23 and 24 are provided in grooves around the outer surface of the diffuser body 21, 11 between the diffuser body and the interior surface of the 12 inlet end of the central opening in the gun body 11.
13 Compressed air enters the d_i.ffuser portion 15 from a gun 14 control module (not shown) through a connector 27. The connector 27 is connected to a diffuser nozzle 28 inserted . 16 into the.forward end of the passageway 22. Powder from a s' .. 17 hopper is conveyed to the dif yusE:r portion 15 - by f low air from 18 a pump such as that shown in U.~>. Patent No. 4,615,649. The 1g powder and conveying air from the pump enter the gun through a feed hose which is connects=_d to the .gun at an inlet 21 connector 29 which extends radially into the diffuser body 21 22 toward the passageway 22. As the powder 'enters the diffuser 23 portion 15 from the connector 29, the powder is mixed with the 24 diffuser air from the diffuser nozzle 28. Diffuser air flowing across the powder inlet connector 29 creates a 26 negative pressure at the powder inlet which assists the pump 27 by drawing the. powder from the powder feed hose into the 28 diffuser. The hole in the nozzle 28 in the diffuser is sized 29 to provide a high volume air flow at low pressure.
Lower pressure in the diffuser results in less back 31 pressure on the pump which in turn results in higher powder 32 flow output from the pump. The high volume of diffuser air 33 results in the powder being conveyed through the charging 34 portion 16 at high velocity further resulting in high charging of the powder. Since the magnitude of the charge imparted to 36 the powder is directly related to the velocity of the powder ~i~
,. _ . -g- (._ 1 through the gun, the volume of diffuser, air is essentially the 2 way of adjusting the charging of the powder: higher diffuser 3 air produces a higher charge on the powder, lower diffuser air 4 a lower charge. The present invention provides a diffuser in the back of the gun to control the charge on the powder by 6 driving the powder through the charging portion '16 at the 7 desired velocity. w g The charging portion 16 of the gun is located within an 9 outer extension tube 31 which is removably attached to the gun body 11 and which extends from the forward-end of the body.
11 The charging portion 16 comprises an inner core assembly 32 12 mounted within an outer cylinder assembly 33.
13 As shown in FIG. 2,~the inner core assembly 32 comprises 14 a central threaded rod 35, having a generally conical inlet distributor 36 threaded on one end, and a generally frusto-16 .conical outlet distributor 37 threaded on the other end. A
1-7 generally cylindrical inner wear sleeve 38 is captured between lg the inlet distributor 36 and thE: outlet distributor 37.~
lg The outer cylinder assembly 33 is mounted within the extension tube 31 and comprises an outer wear sleeve 4o which 21 is captured between an inlet wear sleeve 41 ;and an outlet wear 22 sleeve 42. The inlet wear sleeve 41 fits'~against a shoulder 23 39 at the outlet end of the central opening in the gun body 24 11. The outlet wear sleeve 42 has a shoulder 43 around its exterior, and the outlet end of the extension tube 31 has a 26 flange 44 which extends radially inwardly to engage the 2~ shoulder 43 through a compressible gasket 45 and hold the 28 outlet wear sleeve in place. .
2g Thus, the inlet wear sleeve 41 is positioned around the inlet distributor 36, the outer wear sleeve 4o is positioned 31 around the inner wear sleeve 3.3, and the outlet wear sleeve.
32 42 is positioned around the outlet distributor 37.
33 An annular gap 46 is formed between the inner and outer 34 wear sleeves 3B and 40. The outer surface of the inner wear sleeve 38 and the inner surface of the outer wear sleeve 40 3 6 undulate, so that the annular gap 4 6 provides a tortuous path i, a '. -~- i 1 for the powder passing through the charging portion 16.
2 Specifically, the outer diameter of the inner wear sleeve 38 3 ' increases at generally the same longitudinal position that the 4 inner diameter of the outer wear ;sleeve 40 decreases, and the outer diameter of the inner wear sleeve 38 decreases at . 6 generally the same longitudinal position that .the inner 7 diameter of the outer wear sleeve 4o increases,..so that a 8 narrow "wavy" flowpath for the powder is created by the 9 annular gap 46 between the sleeves 38 and 40. The.width of l0 the annular gap 46 remains genera:Lly constant along the length 11 of the inner and outer wear sleeves 38 and 40, although the 12 annular gap 46 varies in diameter.
13 Powder enters the charging portion 16 of the gun from the 14 diffuser portion 15 and is channelled into the annular gap 46 between the inner and outer wear sleeves 38 and 4o by the 16 converging surfaces of the inlet wear sleeve 4I and the inlet 17 distributor 36. The inlet wear sleeve 41, which is positi oned 18 within the gun body 1.1, extends :from the . outer wear sleeve 4 0 to the diffuser body 21 and def~_ries a passage for the powder exiting the diffuser portion of the gun. ' 21 The powder then flows through the narrow, "wavy" annular 22 gap ~! 6 and subsequently through a wi dening' annular gap def fined 23 by the diverging surfaces of the outlet distributor 37 and the 24 outlet wear sleeve 42 from which the powder is discharged into the sprayhead portion 17.
26 To seal the powder flowpath, a plurality of O-rings are 27 provided between various components of the gun. The inlet 2g wear sleeve 41 is sealed againsi~ the gun body 11 by an O-ring 29 48 (FIG. 3) which is provided between the gun body and the I 30 inlet wear sleeve at the beginning of the charging portion 16.
31 Another O-ring 49 is located also around the exterior of the 32 inlet wear sleeve 41. O-rings 5o and 51 are located around 33 the exterior of the outer wear sleeve 4o, with the O-ring 50 34 positioned.near the inlet end of the outer wear sleeve 40 (FIG. 3), and the O-ring 5Z positioned between the outer wear .
r'.... 10 r ~
~.. -1 sleeve 40 and the extension tube 31 at the outlet end of the 2 wear sleeve (FIG~ 4)~
3 ~ The extension tube 31 is removably attached to the gun 4 body 3.1 by a bayonet-type~latching mechanism comprised of a pin 52 extending from the gun body lI. into a slot 53 formed 6 in the extension tube 31, so that the charging portion 16 is 7 securely held to the gun body daring use and may be easily 8 removed when it is desired to clean the gun or replace one of g the wear sleeves. With the extension tube 31 securely attached to the gun body 11 by the bayonet mechanism, the 11 outer wear sleeve 4o is urged back into the central opening 12 in the body 11 by the foam neoprene gasket 45 (FIGS. 1 and 5) 13 located between the outer flange 44 of the extension tube 31 14 and the shoulder 43 of the outlet wear sleeve 42. The gasket 45 is compressible and resilient, and it forms a spring which 16 provides a force upon the outer wear sleeve 4o toward the gun 17 body ll. The O-ring 5o carried on the c:nd of the outer wear 18 sleeve 40 engages a ground ring X81. (later described) when the 19 outer wear sleeve is pushed into the gun body 11 by the gasket 45.
21 As shown in detail in FIG. 5, the inner wear sleeve 38 '22 comprises an inner PTFF contact layer 54 formed on the outer 23 diameter of an inner stiffening element or sleeve 55. The 24 outer wear sleeve 4o similarly comprises an outer PTF L contact layer 56 formed on the inner diameter of an outer stiffening 26 element or sleeve 57. The stiffening sleeves 55 and 57 are 27 made of an electrically insu:Lating, dimensionally stable 28 material and preferably are made from a NEM.A Grade G-10 29 (continuousfilament woven glass-fabric impregnated with epoxy resin) or similar material. 'the contact layers 54 and 56 31 provide a layer of electrically insulating material along the 32 powder flowpath, but also provide surface conductivity for 33 grounding. The stiffening sleeves 55 and 57 provide rein 34 forcement for the sleeves and help the "wavy" PTFF sleeves hold their shape, both radial:ly and longitudinally, during v .: -m-~~~~~:
1 machining, and over time to maintain dimensional integrity 2 along the annular gap 46.
3 ~ Referring again to FIG. 2, the .position of the inner core 4. assembly 32 with respect to the outer cylinder assembly 33 is maintained by a positioning ring 6o and a spacing ring 61.
6 The positioning ring 6o°is used both to align the.inner wear 7 sleeve 38.radially with the inlei~ distributor 36 at the inlet 8 of the charging portion 16 and to align the inner wear sleeve 38 and the distributors 36 and 3',7 axially with the outer wear sleeve 4o and the wear sleeves .41 and d2. The spacing ring 11 6i is used only to align the inner wear sl eeve 38 and the 12 outlet distributor 37 radially with the wear sleeve 4 0 and the ~3 outlet wear sleeve 42 at the outlet of the charging portion 14 16. The positioning ring 60 and the spacing ring 6~ are each made from an electrically insulating material which provides 16 surface conductivity, such as D~elrin.
As shown.. in FIG. 3, the positioning ring 6o is located 18 between the inlet wear sleeve 4~. and the outer wear sleeve 40 19 and between the inlet distributor 36 and the inner wear sleeve 38. A small recess 63 is formed around the inner surface of 21 the inlet wear sleeve 41 adjacent to the outer wear sleeve.4o 22 to provide for the positioning ring 60. Similarly, a recess 23 64 is formed around the inner surface of the outer wear sleeve ° 24 40 adjacent to the inlet wear sleeve 4I. to provide for the ''w~ 25 positioning ring 60. Corresponding recesses 65 and 66 are 26 formed in the outer surfaces of the inlet distributor 35 and 27 the inner wear sleeve 38, respectively, to provide for the 28 positioning ring 60. In this way the positioning ring 60, 29 best shown in FIG: 7, is captui:ed in the recesses 63, 64, 65 and 66.
31 The structure of the positioning ring 60 is shown in more 32 detail in FIG. 7. The positioning ring 6o comprises an outer 33 ring portion 69 which is captured in the recesses 63 and 64 34 between the inlet wear sleeve 41 and the outer wear sleeve ~io, and an inner ring portion 7o which is captured in the recesses 36° 65 and 66 between the inlet dig>tributor 36 and the inner wear n .~
1 sleeve 38. The inner ring portion 7o and the outer ring 2 portion 69 are connected by four web portions 71 which are 3 located 90° apart with respect.to each other. The web . 4 portions 71 extend through the path of the powder, and, as shown particularly in FIG. 8, the web portions have a tapered 6 or streamlined cross section to reduce the build-up of powder 7 on the web portions which would otherwise be caused by impact . 8 fusion of the powder.
g ~ The recess 64 in the outer wear sleeve 4o extends completely through the outer PTFE contact layer 56 and into 11 the outer stiffening sleeve 57. Likewise, the recess 66 in 12 the inner wear sleeve 38 extends_completely through the inner 13 PTFE contact layer 54 and into thE: inner stiffening sleeve 55.
14 The material of the stiffening sleeves 55 and 57 is more rigid than the softer PTFE material of 'the contact layers 5 d and 5 6 , 16 and the depth of the recesses into the stiffening sleeves 17 provides dimensional stability to the positior..i ng of the ring lg .60. The recesses 63, 64, 65 and 66 thus provide for precise 19 axial placement of the positioning ring so with respect to the outer. cylinder assembly 33 and the inner core assembly-32.
21 The spacing ring 61 is located between the outer wear 22 sleeve 40 and the outlet wear sleeve 42. 'As shown in FIG. 4, 23 a recess 73 is formed in the outer wear sleeve 4o at the 24 outlet edge, and a corresponding recess 74 is formed in the outlet wear sleeve 42. The spacing ring 61 fits within the 26 groove formed by the recesses 73. and 74. As shown in FIG. 9, 27 the spacing ring 61 comprises a.n outer ring portion 75 that 28 fits within the groove formed r>y the recesses 73 and 74 and 29 four projecting spacer portions 76 that extend radially inwardly from the outer ring portion 75. The spacer portions 31 7 6 are located 90 ° apart with respect to each other . The tips 32 of the spacer portions 76 engagEa the outer wall of the outlet 33 distributor 37 to radially position the outer cylinder 34 assembly 33 with respect to the inner core assembly 32. As shown in FIG. l0, the spacer portions 76 also have a tapered ' 36 or streamlined cross section, similar to the web portions 71 1 or the positioning ring 6o, to prevent the build-up of power 2 due to impact fusion.
3 A recess 78 (FIG. 4), is also provided on the other end .4 of the inner wear sleeve 38 opposite the ,recess 66. This.
recess 78 is not needed for the positioning of the spaci ng 6 ring sl since the spacing ring is not mounted in. the inner 7 core assembly. However, the recess 78 is provided'so that the 8 inner wear sleeve 38 is longitudinally symmetrical, i.e., 9 reversible. The recess 78 is thus symmetrically located with respect to the recess 66 on the other end of the inner wear 11 sleeve 38. Since the recess 78,, as shown in FIG. 4, is not 12 needed for the spacing ring 61, the outlet distributor 37 is 13 provided with a small flange 79 which fits within the recess 14 78.
In accordance with.conventional design of tribo-electric 16 powder spray guns, the charging portion 16 is grounded to 17 enhance the charging of the powder and promot~safety by ~18 preventing the gun from storing a capacitive charge which 19 could shock an operator or produce a spark, causing a fire or explosion., The present invention, however, utilizes an 21 improved grounding configuration. A ground electrode is 22 provided in the form of a ground ring 81 located within the 23 gun body 11 and around the exterior of the inlet wear sleeve 24 ;1 and the outer wear sleeve 40, near the inlet of the '.. 25 charging portion 16 where the highest charge transfer to the ' 26 powder occurs. The ground rind 81 is located away from the 27 powder flowpath, so that it i~~ kept clean, resulting in a 28 good, consistent electrical gronsnd. The O-ring 49 is located 29 between the ground ring 81 and the inlet wear sleeve 4'!, and the O-ring 5o is located between the ground ring 81 and the 31 outer wear sleeve 40.
32 The outer wear sleeve 40 ~.s a separate element from the 33 inlet wear sleeve 41 to allow for a gap 82 to b~ formed 34 therebetween. The gap 82 may not be significant in dimension, and the elements 4o and 41 forming the gap may, in fact, be . 36 touching or abutting each other'. Even if the elements 4o and . ~ ~ ~ -14-.
,~~-1 .T are abutted together in contacts, a gap 82 will be present , 2 between these elements which will be sufficient for the 3 passage of charge to the ground ring 8~.. The gap 82 is 4 annular and is shown to indicate: that exterior surfaces are provided between the outer wear ;sleeve 40 and the inlet wear 6 sleeve 41, so that surface conduction can occur along these 7 surfaces~as part of the grounding path.
g The electrical grounding of the elements of the charging.
9 portion 16 of the gun is accomplished by surface conduction . 10 along the exterior surfaces of the inner wear sleeve 38, the 11 outer wear sleeve 40, the inlet wear sleeve 41, the inlet 12 distributor 36, the outlet distributor 37 and the outlet wear 13 sleeve 42. As previously described, at least the surfaces of 14 these parts which form a part of the powder flowpath are 15 formed of an electrically ins>ulating material with good 16 charging properties, such as P:'L'FE. The PTFE material al so 17 allows for surface discharge which provides a conductive path 18 for grounding. The charge on the surfaces of the inlet wear 19 sleeve 41, the outer wear sleeve 40 and the outlet wear sl eeve 20 42 flows along those surfaces t:o the ground ring 81 through 21 the gap 82 provided between the inlet wear;'sleeve 4~. and the 22 outer wear sleeve 40. The charge on the surfaces of the inlet 23 distributor 3s, the inner. wear sleeve 38 and the outlet 24 distributor 37 flows along those surfaces and across the 25 surface of the positioning ring 6o to the ground ring 81 26 through the gap 82. Some charge from these surfaces most 27 likely also flows across the spacing ring 61, to the outer wear 28 sleeve 4o before passing along the gap 82. Because the rings 29 6o and 61 are also made of an electrically insulating mater? al 30 providing adequate surface conductivity, such as Delrin, they 31 provide sufficient discharge current transfer from the inner _ 32 core elements 36, 37 and 38 to the ground ring 8L.
33 From the ground ring 81, the current flows through a 34 ground stud 84 to a ground wire (not shown) held onto the 35 ground stud 84 by a knob 85, which leads back to the gun 36 control module where it is di:>played by means~of an ammeter 15r '.
and then flows to ground. The surface conductivity of the 2 PTFE, the length of the path to the ground ring al and the 3 electrical potential of the charge on the powder contact surfaces are all variables considered in the design of the gun for proper grounding and. optimum. charging performance.
6 The outlet end of the charging portion 16 of the gun is designed to accept various conventional sprayheads.. As shown, g the sprayhead portion 17 comprises a conventional sprayhead 9 88 which is shown to illustrate the mounting of a sprayhead to the outlet end of the charging portion 16. The sprayhead 11 88 is mounted on the outlet wear sleeve ~2 adjacent to the-12 flange 4d on the outlet end of t'.he extension tube 31. The O-13 rings 89 and 90 (FIG. 4) are located in grooves on the 14 exterior of the outlet wear sleeve 42 between the sprayhead 15' 88 and the outlet wear sleeve.
16 The magnitude of the charge imparted to the powder in the 17 charging portion I6 is a function of (1) the velocity of the 1g powder, (2) the material from which the flowpath walls are 19 made, (3) the geometry or de:~ign of the powder flowpath through the charging portion, (~~) the electrical grounding of 21. the charging surfaces, and (5) the composition of the powder 22 coating material. The gun of the present invention is 23 designed to maximize the charge imparted to the powder through 24 consideration of each of the above five factors.
. One of the important factors in the magnitude of the 26 charge imparted to the powder is the velocity of the powder 27 through the charging portion ~.6 of the gun; the higher the 28 velocity of the powder, the higher the charge on the powc,er.
29 However, the velocity of the 'powder also has a detrimental . 30 effect on the wear life of the powder gun parts. Wear of the 31 parts is also a .function of velocity; the higher the velocity, 32 the higher the wear. Therefore, it is not desirable to flow 33 the powder at any greater velocity than is required for 34 adequate charging.
In the preferred embodiment of the present invention, all 36 of the parts which the powder can contact in the charging -16- ~~~
,~., 1 portion I6 of the gun, namely the inner wear sleeve 38, the 2 outer wear sleeve .io, the inlet; wear sleeve dL, the inlet 3 distributor 36, the 'outlet distributor 37, and the outlet wear 4 sleeve 42, are made of a fluoropolymer material, preferably polytetrafluoroethylene (PTFE). This material has been found 6 to be very effective fob tribo-electrically charging powdered 7 paints of various compositions. The powder picks up charge 8 with each contact with a PTFE surface. Therefore, maximizing the PTFE surface area exposed to the powder maximizes the opportunity'to charge the powder. PTFE is an electrically 11 insulating material but has surface conductivity to provide 12 from grounding of the charges imparted to the powder.
13 The unique design of the inner and outer wear sleeves 38 14 and 40, specifically their "wa~,ry" surfaces, also serves to increase the magnitude of the charge imparted to the powder.
16 The curved surfaces of the inner and outer wear sleeves 38 and 17 .4 o cause the .:powder to f low in a tortuous path through the . 18 annular gap 46, thus forcing thE: powder against the peaks and 'lg valleys or grooves of the each of the sleeve. Each change in diameter of the sleeves 38 and 4o forces the powder to change 21 direction and further impact the PTFE surfaces of the sleeves 22 adding to the charge on the powder.
23 The magnitude of the .charge imparted to the powder i s 2~'t further enhanced by the relatively narrow width of the annular gap 46. The annular gap between the two wear sleeves 38 and 26 4o is small, on the order of 0.032 inches (0.82 nm) . The 27 powder, therefore, has a high probability of contacting the 28 surfaces of the wear sleeves 3B and d0 many times rather than 29 flowing straight through the charging portion with rel atively few contacts. As previously d~ascribed, this narrow width of 31 the annular gap 46 between thE: inlet wear sleeve 41, outlet 32 wear sleeve 42, inner wear sleeve 38 and the inlet distributor 33 36, outlet distributor 37, and the outer wear sleeve 4o is 34 maintained by the positioning ring 6o and the spacing ring 6~..
Since the charge imparted to the powder is increased by 36 increasing the velocity of th.e powder through the charging 1 portion 16 of the gun, and since increasing the velocity of 2 the powder increases the wear of the powder gun parts, It is 3 advantageous to provide~for easy replacement of worn parts.
4 The present invention facilitates replacement of the two wear sleeves 38 and 40. The two wear aleeves 38 and 4o are dimen-6 sinned so that the inner wear sleeve 38 can be removed from 7 the outer wear sleeve 4o by pushing or pulling thewinner wear g sleeve out either end of the outer wear sleeve. This remova-bility is accomplished by dimens Toning the diameter of the peaks or ridges of the inner wear sleeve 38 to be less than 11 ~ or at most equal to the diameter ~of the peaks or ridges of the 12 outer wear sleeve 40. When either of the sleeves 38 and 40 13 worn out, a new sleeve can easily be substituted in the field 14 without the necessity of sending the entire gun back to the manufacturer to be rebuilt, resulting in savings in time and 16 expense.
To assemble t'~e gun l0, the positioning ring 6o is first .. 17 lg placed into the recess 66 on one end of the inner wear sleeve 19 38. It is noted that the inner wear sleeve 38 is longitudi-nally symmetrical, so that assembly can begin by placing the 21 positioning ring 60 on either e:nd of the. inner wear sleeve.
22 The inlet distributor 36 is then positioned on the same end 23 of the inner wear sleeve...with the positioning ring in the 24 recess 65. The threaded rod :35 is then inserted into the . .. 25 corresponding threaded opening in the inlet distributor 36.
26 The outlet distributor 37 is then threaded onto the other end 27 of the rod 35, and the assembly of the inner core assembly 32 28 is complete.
29 The body 11 is preassembled with the diffuser body 21, the gun mount assembly 12, the around ring 81, the ground stud 31 84 and the knob 85 in place. The O-rings 48 and 49 are posi-32 tinned around the exterior of the inlet wear sleeve 41 in 33 groove provided for the O-rings>, and the inlet wear sleeve is 34 inserted into outlet end of t:he central opening in the gun body 11. The previously assembled inner core assembly 32 is 36 then inserted with the inlet distributor 36 fitting into the _lg_~
inlet wear sleeve 41 and the positioning ring 60 fitting into 2 the recess 63 in the inlet wear s>leeve. Next, the O-ring So 3 is positioned in the groove provided on the exterior of the.
outer wear sleeve .~o. Then, t7ze outer wear sleeve 4o is inserted into the central opening of the body 11 until the 6 .positioning ring s0 is.'seated in the recess 64 on.the end of the outer wear sleeve. zt is noted that the outerwear sleeve g 4o is longitudinally symmetrical, so that either end of the 9 outer wear sleeve may be inserted into the gun body 11 during to assembly.
11 The spacing ring 61 is than placed around the outlet 12 distributor 37 and positioned upon the outwardly extending end 13 of the outer wear sleeve 4o in the recess 73. The O-rings 89 14 and 90 are pre-assembled on the outlet wear sleeve 42 in the ~,5 grooves provided on the exterior of the outlet wear sleeve, 16 and the outlet wear sleeve 42 is then positioned on the 17~ outwardly extending er.:d of the outer wear sleeve 4o with the lg spacing ring 61 received within the recess 74' of the outlet 1g wear sleeve.d2.~ The neoprene gasket 45 is placed against the 20 shoulder d3 of the outlet wear sleeve 42, and the extension 21 tube 31 is placed over the outwardly extending assembly. As 22 the extension tube 31 is rotated, the pin 52 locates the 23 opening into the slot 53, and the extension tube is pushed 24 into the central opening of the body 11 around the outer wear 25 sleeve 40, with the flange 44 engaging the neoprene gas~:et 45 26 and compressing it. This urges the outlet wear sl eeve 42 , the 27' outer wear sleeve 40, the positioning ring 60 and the inlet 28 wear sleeve dl toward the body l.l, so that the inlet wear 29 . sleeve 41 is pressed against the shoulder 39 of the gun body 30 11. This also axially positions the inner core assembly 32 31 which is positioned within the outer wear sleeve 4o by the 32 positioning ring 6o and the spacing ring 61. The extension 33 tube 31 is locked to the body 11 by rotating it 8 turn to 34 engage the pin 52 into the detent at the end of the slot 53.
35 The desired sprayhead 88 can then be mounted on the end of the 36 outlet wear sleeve 42.
The gun can also be easily disassembled for cleaning or 2 for replacement of the wear sleeves 38 and 40. The wear 3 sleeves 38 and 4o are removed~from the gun by first removing 4 'the sprayhead 88.from outlet wear sleeve d2. The extension tube 31 is next disengaged from the gun body 11 by rotating 6 the extension tube and disengaging the bayonet mechanism.
7 Thereafter, the outlet wear sleeve d2 and the outlet distribu-g for 37 may be removed, and the inner wear sleeve 38 may be 9 removed from the outer wear sleeve 40, or the outlet wear 1p sleeve d2 and the outer wear sleEwe do may be removed from the 11 inner wear sleeve 38. , 12 The re-assembly of the wear sleeves and the replacement 13 of a worn sleeve with a new wear sleeve is further facilitated 14 by the design of the wear sleeve: 38 and 40. The wear sl eeves 38 and 4o are each symmetrical ao that they can be assembled 16 into the gun with either end first. This prevents incorrect 17 insertion of one of the wear s7_e,eve 38 or 40 into the other 1g wear sleeve in the field and prevents inadvertent misal ignment 19 of the wear sleeves and resulting incorrect dimensioning of the annular gap 46 21 Another important factor i.n the magnitude of the charge 22 imparted to the powder is proper electrical grounding of the 23 gun. The ground ring 81. is located away from the powder 24 flowpath near the inlet of the charging portion 16. The ground ring 81 is located in the region of the gun where the 26 greatest amount of charging occurs, and this location is, 27 therefore, the preferred location to bleed off charge. By 28 locating the ground ring 81. outside the powder path, the 29 ground ring is kept clean from the build-up of powder, . 30 resulting in a good, consistent electrical ground.
31 Various modifications and improvements can be made to the 32 invention shown and described. For example, the dimension and 33 geometry of the waves formed b~y the exterior surfaces of the 34 sleeves 38~and 4o can be modified. Similarly, more or fewer waves can be provided.
a . -2~
I
The exterior surfaces of t'he sleeves 38 and 4o can be 2 made of other materials that may be longer wearing and that 3 may tribo-electrically charge powder as well as PTFE does, 4 such as perfluoroalkoxy (PFA) and Tefzel~, modified ethyl-tetraf luoroethylene f luoropolymsar .
6 The inner and outer wear sleeves 38 and 4o can also be 7 injection molded to facilitate manufacture wand reduce 8 fabrication costs. In order t.o make the sleeves using an 9 injection molding process, an injection moldable material, such as PFA, FEP or Tefzel, would be used instead of PTFE, 11 which is only extrudable and compression moldable. If the 12 stiffening sleeves 55 and 57 are. made out of a NEr~ Grade G-10 13 (continuous filament woven glass-fabric impregnated with epoxy 14 resin) or similar material, the PF1~ may be injection molded onto the G-10 tube and then, if needed, the wave may be 16 finished by machining, on the PF1~ portion of the assembly..
In addition,.. instead e:f gluing the inner contact layer 17 ' -, lg 54 to the inner stiffening, sleeve 55 and the outer contact 19 layer 56 to the outer stiffening sleeve 57, these materials can be fractionally secured together. To accomplish this, the 21 inner PTFE contact layer 54 could be heated to expand it, and 22 the inner contact layer could be slid over the inner stiffen-23 ing sleeve 55 and cooled to shi:ink it onto the sleeve 55. In 24 like manner, the outer contact layer 56 can be super-cooled, such as in liquid nitrogen, to shrink it, and inserted into 26 the outer stiffening sleeve 5'7. The outer contact layer 56 27 can then be heated back to room temperature to expand it into 2g a compression fit with the sleeve 57.
29 The annular gap d 6 through which the po~,~=der .f lows may also vary in width as a function of its radius from the gun 31 centerline, so that the width of the annular gap is smaller 32 at a larger radius. This would be done in order to approxi-33 mate a constant cross-sectional area for the powder path in 34 order to maintain the powder at a relatively constant velocity as it passes through the charging portion 16.
Other variations and modifications of the specific embodiments herein shown and described will be apparent to 3 those skilled in the art, all within the intended spirit and - 4 scope' of the invention. While 'the invention has been shown and described with respect to paz:ticular embodiments thereof , 6 these are for the purpose o:f illustration rather than limitation. Accordingly, the p<~tent is not to be limited in g scope and effect to the specific: embodiment herein shown and 9 described nor in any other way i~his is inconsistent with the lp extent to which the progress in the art has been advance by 11 the invention.
,. .. .\
Claims (30)
1. A tribo-electric powder spray gun, which comprises:
means for mixing powder with a conveying gas;
a charging section downstream of the mixing means, the charging section including means for electrically charging the powder as it flows therethrough, the charging means comprising an inner core having at least one inner core member positioned within a hollow outer cylinder having at least one outer cylinder member, the at least one outer cylinder member having an inner dimension, the at least one inner core member having an outer dimension, an annular gap being formed between the at least one outer cylinder member and the at least one inner core member providing a friction charging flowpath for the powder, the outer dimension of the at least one inner core member and the inner dimension of the at least one outer cylinder member providing undulating charging surfaces, the outer dimension of the at least one inner core member increasing at generally the same longitudinal position that the inner dimension of the at least one outer cylinder member increases, the outer dimension of the at least one inner core member decreasing at generally the same longitudinal position that the inner dimension of the at least one outer cylinder member decreases, the charging surfaces of the at least one inner core member and the at least one outer cylinder member each made of electrically insulating material, whereby the powder is frictionally charged by repeated contact with the cylinder member and the core member during flow through the annular gap; and a sprayhead downstream of the charging section for dispensing the charged powder.
means for mixing powder with a conveying gas;
a charging section downstream of the mixing means, the charging section including means for electrically charging the powder as it flows therethrough, the charging means comprising an inner core having at least one inner core member positioned within a hollow outer cylinder having at least one outer cylinder member, the at least one outer cylinder member having an inner dimension, the at least one inner core member having an outer dimension, an annular gap being formed between the at least one outer cylinder member and the at least one inner core member providing a friction charging flowpath for the powder, the outer dimension of the at least one inner core member and the inner dimension of the at least one outer cylinder member providing undulating charging surfaces, the outer dimension of the at least one inner core member increasing at generally the same longitudinal position that the inner dimension of the at least one outer cylinder member increases, the outer dimension of the at least one inner core member decreasing at generally the same longitudinal position that the inner dimension of the at least one outer cylinder member decreases, the charging surfaces of the at least one inner core member and the at least one outer cylinder member each made of electrically insulating material, whereby the powder is frictionally charged by repeated contact with the cylinder member and the core member during flow through the annular gap; and a sprayhead downstream of the charging section for dispensing the charged powder.
2. The tribo-electric powder spray gun of claim 1, further comprising a ground electrode located externally to the flowpath of the powder.
3. The tribo-electric powder spray gun of claim 2, wherein the ground electrode comprises a ground ring around the exterior of the outer cylinder.
4. The tribo-electric powder spray gun of claim 3, wherein a second gap is present between elements forming part of the powder flowpath to provide for surface conduction between elements, the second gap being positioned adjacent to the ground ring.
5. The tribo-electric powder spray gun of claim 4, comprising in addition at least one ring made from electrically insulating material provided between the inner core and the outer cylinder in contact with the charging surfaces thereof.
6. The tribo-electric powder spray gun of claim 1, wherein the inner core includes an inner wear sleeve formed of a stiffening element with an external contact layer made of an electrically insulating material forming a charging surface.
7. The tribo-electric powder spray gun of claim 1, wherein the outer cylinder includes an outer wear sleeve formed of a stiffening element with a contact layer made of an electrically insulating material forming a charging surface.
8. The tribo-electric powder spray gun of claim 1, wherein the inner core is removable from the outer cylinder, and the largest outer dimension of the inner core is smaller than the smallest inner dimension of the outer cylinder to permit the inner core to be removed longitudinally from the outer cylinder.
9. The tribo-electric powder spray gun of claim 1, wherein the width of the annular gap remains constant along the length of the at least one outer cylinder member and the at least one inner core member.
10. The tribo-electric powder spray gun of claim 1, wherein the gun has an inlet, and wherein the mixing means includes a diffuser at the inlet of the gun, the diffuser including a first inlet for the powder suspended in a gas and a second inlet for the conveying gas.
11. The tribo-electric powder spray gun of claim 10, wherein the diffuser controls the charge on the powder by driving the powder through the charging section at a selected velocity.
12. The tribo-electric powder spray gun of claim 1, wherein the at least one inner core includes an inlet distributor and the at least one outer cylinder includes an inlet wear sleeve, the inlet distributor and the inlet wear sleeve defining a diverging annular inlet to the annular gap between the at least one inner core member and the at least one outer cylinder member.
13. The tribo-electric powder spray gun of claim 12, wherein the inlet distributor and the inlet wear sleeve are constructed of electrically insulating material.
14. The tribo-electric powder spray gun of claim 1, wherein the at least one inner core includes an outlet distributor and the at least one outer cylinder includes an outlet wear sleeve, the outlet distributor and the outlet wear sleeve defining a converging annular outlet from the annular gap between the at least one inner core member and the at least one outer cylinder member.
15. The tribo-electric powder spray gun of claim 14, wherein the outlet distributor and the outlet wear sleeve are constructed of electrically insulating material.
16. The tribo-electric powder spray gun of claim 1, wherein the at least one inner core member includes an inner wear sleeve and the at least one outer cylinder member includes an outer wear sleeve, the inner wear sleeve and the outer wear sleeve each being removable from the spray gun separately from other elements of the gun.
17. The tribo-electric powder spray gun of claim 16, wherein the inner wear sleeve is longitudinally symmetrical, whereby it can be re-inserted into the outer wear sleeve in either direction.
18. The tribo-electric powder spray gun of claim 16, wherein the outer wear sleeve is longitudinally symmetrical, whereby the inner wear sleeve can be re-inserted into it in either direction.
19. A tribo-electric powder spray gun which comprises:
means for mixing powder with a conveying gas;
a charging section downstream of the mixing means, the charging section including an inlet and means for electrically charging the powder as it flows through the charging section, the means comprising an inner core positioned within a hollow outer cylinder, an annular gap being formed between the outer cylinder and inner core providing a friction charging flowpath for the powder, at least one of the inner core and outer cylinder being electrically connected to ground through an annular ground ring positioned externally to the flowpath of the powder, the ground ring located at the inlet of the charging section and extending along less than half of the charging section, whereby the powder is fractionally charged by repeated contact with the outer cylinder and the inner core during flow through the annular gap; and a sprayhead downstream of the charging section for dispensing the charged powder.
means for mixing powder with a conveying gas;
a charging section downstream of the mixing means, the charging section including an inlet and means for electrically charging the powder as it flows through the charging section, the means comprising an inner core positioned within a hollow outer cylinder, an annular gap being formed between the outer cylinder and inner core providing a friction charging flowpath for the powder, at least one of the inner core and outer cylinder being electrically connected to ground through an annular ground ring positioned externally to the flowpath of the powder, the ground ring located at the inlet of the charging section and extending along less than half of the charging section, whereby the powder is fractionally charged by repeated contact with the outer cylinder and the inner core during flow through the annular gap; and a sprayhead downstream of the charging section for dispensing the charged powder.
20. The tribo-electric powder spray gun of claim 19, wherein the ground ring is located around they exterior of the outer cylinder.
21. The tribo-electric powder spray gun of claim 19, wherein a second gap is present between elements forming part of the powder flowpath, the second gap being positioned adjacent to the ground ring.
22. The tribo-electric powder spray gun of claim 19, wherein the gun has an inlet, and wherein the mixing means includes a diffuser at the inlet end of the gun, the diffuser including a first inlet for the powder suspended in a gas and a second inlet for conveying gas.
23. A tribo-electric powder spray gun which comprises:
means for mixing powder with a conveying gas;
a charging section downstream of the mixing means, the charging section has an inlet and an outlet and includes means for electrically charging the powder as it flows therethrough, the charging means comprising an inner core positioned within a hollow outer cylinder, the inner core and the outer cylinder each having inner charging surfaces, an annular gap being formed between the outer cylinder and inner core providing a friction charging flowpath for the powder, at least one of the inner core and outer cylinder being electrically connected to ground through a ground electrode located externally to the flowpath of the powder, the ground electrode being positioned at the inlet to the charging section, a second gap being present between elements forming part of the powder flowpath, the second gap being positioned adjacent to the ground electrode, there being at least one ring made of electrically insulating material located between the inner core and the outer cylinder, the at least one ring being in contact with the charging surfaces, whereby the powder is frictionally charged by repeated contact with the outer cylinder and the inner core during flow through the annular gap; and a sprayhead at the outlet of the charging section for dispensing the charged powder.
means for mixing powder with a conveying gas;
a charging section downstream of the mixing means, the charging section has an inlet and an outlet and includes means for electrically charging the powder as it flows therethrough, the charging means comprising an inner core positioned within a hollow outer cylinder, the inner core and the outer cylinder each having inner charging surfaces, an annular gap being formed between the outer cylinder and inner core providing a friction charging flowpath for the powder, at least one of the inner core and outer cylinder being electrically connected to ground through a ground electrode located externally to the flowpath of the powder, the ground electrode being positioned at the inlet to the charging section, a second gap being present between elements forming part of the powder flowpath, the second gap being positioned adjacent to the ground electrode, there being at least one ring made of electrically insulating material located between the inner core and the outer cylinder, the at least one ring being in contact with the charging surfaces, whereby the powder is frictionally charged by repeated contact with the outer cylinder and the inner core during flow through the annular gap; and a sprayhead at the outlet of the charging section for dispensing the charged powder.
24. A tribo-electric powder spray gun which comprises:
means for mixing powder with a conveying gas;
a charging section downstream of the mixing means, the charging section including means for electrically charging the powder as it flows therethrough, the charging means comprising an inner core having at least one inner core member positioned within a hollow outer cylinder having at least one outer cylinder member, the at least one outer cylinder member having an external inner dimension and the at least one inner core member having an external outer dimension, the outer dimension of the at least one inner core member and the inner dimension of the at least one outer cylinder member providing undulating inner charging surfaces, the outer dimension of the at least one inner core member increasing at generally the same longitudinal position that the inner dimension of the at least one outer cylinder member increases, the outer dimension of the at least one inner core member decreasing at generally the same longitudinal position that the inner dimension of the at least one outer cylinder member decreases, an annular gap being formed between the at least one outer cylinder member and at least one inner core member providing a friction charging flowpath for the powder, at least one of the inner core member and outer cylinder member being electrically connected to ground through a ground electrode located externally to the flowpath of the powder, whereby the powder is fractionally charged by repeated contact with the cylinder member and the core member during flow through the annular gap; and a sprayhead downstream of the charging section for dispensing the charged powder.
means for mixing powder with a conveying gas;
a charging section downstream of the mixing means, the charging section including means for electrically charging the powder as it flows therethrough, the charging means comprising an inner core having at least one inner core member positioned within a hollow outer cylinder having at least one outer cylinder member, the at least one outer cylinder member having an external inner dimension and the at least one inner core member having an external outer dimension, the outer dimension of the at least one inner core member and the inner dimension of the at least one outer cylinder member providing undulating inner charging surfaces, the outer dimension of the at least one inner core member increasing at generally the same longitudinal position that the inner dimension of the at least one outer cylinder member increases, the outer dimension of the at least one inner core member decreasing at generally the same longitudinal position that the inner dimension of the at least one outer cylinder member decreases, an annular gap being formed between the at least one outer cylinder member and at least one inner core member providing a friction charging flowpath for the powder, at least one of the inner core member and outer cylinder member being electrically connected to ground through a ground electrode located externally to the flowpath of the powder, whereby the powder is fractionally charged by repeated contact with the cylinder member and the core member during flow through the annular gap; and a sprayhead downstream of the charging section for dispensing the charged powder.
25. A tribo-electric powder spray gun which comprises:
means for mixing powder with a conveying gas;
a charging section downstream of the mixing means, the charging section having an outlet and including means for electrically charging the powder as it flows therethrough, the charging means comprising an inner core positioned within a hollow outer cylinder, the outer cylinder including an outer wear cylinder formed of a stiffening element with a contact layer forming an outer charge surface, the inner core including an inner wear cylinder formed of a stiffening element with a contact layer forming an inner charging surface, the stiffening elements being made from a National Electrical Manufacturing Association Grade G-10 material, an annular gap being formed between the outer charging surface and the inner charging surface providing a friction charging flowpath for the powder; and a sprayhead at the outlet of the charging section for dispensing the charged powder.
means for mixing powder with a conveying gas;
a charging section downstream of the mixing means, the charging section having an outlet and including means for electrically charging the powder as it flows therethrough, the charging means comprising an inner core positioned within a hollow outer cylinder, the outer cylinder including an outer wear cylinder formed of a stiffening element with a contact layer forming an outer charge surface, the inner core including an inner wear cylinder formed of a stiffening element with a contact layer forming an inner charging surface, the stiffening elements being made from a National Electrical Manufacturing Association Grade G-10 material, an annular gap being formed between the outer charging surface and the inner charging surface providing a friction charging flowpath for the powder; and a sprayhead at the outlet of the charging section for dispensing the charged powder.
26. The tribo-electric powder spray gun of claim 25, wherein the inner core comprises a diverging inlet distributor and a converging outlet distributor installed on opposite ends of the inner wear cylinder.
27. A tribo-electric powder spray gun, which comprises:
a body;
means mounted on the body for mixing powder with a conveying gas;
a charging section removably attached to the body downstream of the mixing means, the charging section having an outlet and including means for electrically charging the powder as it flows therethrough, the charging means comprising an inner core positioned within a hollow outer cylinder, the inner core being positioned relative to the outer cylinder by at least one ring located between the inner core and the outer cylinder, an annular gap being formed between the outer cylinder and inner core providing a friction charging flowpath for the powder, a tubular extension fitting over the outer cylinder and removably attached to the body to releasably secure the inner core and the outer cylinder to the body; and a sprayhead at the outlet of the charging section for dispensing the charged powder.
a body;
means mounted on the body for mixing powder with a conveying gas;
a charging section removably attached to the body downstream of the mixing means, the charging section having an outlet and including means for electrically charging the powder as it flows therethrough, the charging means comprising an inner core positioned within a hollow outer cylinder, the inner core being positioned relative to the outer cylinder by at least one ring located between the inner core and the outer cylinder, an annular gap being formed between the outer cylinder and inner core providing a friction charging flowpath for the powder, a tubular extension fitting over the outer cylinder and removably attached to the body to releasably secure the inner core and the outer cylinder to the body; and a sprayhead at the outlet of the charging section for dispensing the charged powder.
28. The tribo-electric powder spray gun of claim 27, wherein the inner core and the outer cylinder are releasably secured to the body by a bayonet connection between the tubular extension and the body.
29. A charging element for a tribo-electric powder spray gun, which comprises an elongated, cylindrical stiffening element with a contact layer made of an electrically insulating material secure thereon, the contact layer forming a charging surface comprising part of a friction charging flowpath for the powder, the thickness of the contact layer varying to provide an undulating surface.
30. The charging element of claim 29, wherein the element is longitudinally symmetrical.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/956,615 US5344082A (en) | 1992-10-05 | 1992-10-05 | Tribo-electric powder spray gun |
| US956,615 | 1992-10-05 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2106251A1 CA2106251A1 (en) | 1994-04-06 |
| CA2106251C true CA2106251C (en) | 2001-08-21 |
Family
ID=25498451
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002106251A Expired - Fee Related CA2106251C (en) | 1992-10-05 | 1993-09-15 | Tribo-electric powder spray gun |
Country Status (12)
| Country | Link |
|---|---|
| US (2) | US5344082A (en) |
| EP (3) | EP1254720A3 (en) |
| JP (1) | JP3494680B2 (en) |
| KR (1) | KR100265911B1 (en) |
| CN (1) | CN1051033C (en) |
| AU (1) | AU666774B2 (en) |
| CA (1) | CA2106251C (en) |
| CZ (1) | CZ287182B6 (en) |
| DE (3) | DE592137T1 (en) |
| ES (1) | ES2239551T1 (en) |
| RU (1) | RU2124950C1 (en) |
| TW (1) | TW246647B (en) |
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-
1992
- 1992-10-05 US US07/956,615 patent/US5344082A/en not_active Expired - Fee Related
-
1993
- 1993-03-04 TW TW082101578A patent/TW246647B/zh active
- 1993-09-15 CA CA002106251A patent/CA2106251C/en not_active Expired - Fee Related
- 1993-09-28 ES ES02077554T patent/ES2239551T1/en active Pending
- 1993-09-28 DE DE0592137T patent/DE592137T1/en active Pending
- 1993-09-28 EP EP02077554A patent/EP1254720A3/en not_active Withdrawn
- 1993-09-28 DE DE69332517T patent/DE69332517T2/en not_active Expired - Fee Related
- 1993-09-28 EP EP01200050A patent/EP1090689A3/en not_active Withdrawn
- 1993-09-28 DE DE1090689T patent/DE1090689T1/en active Pending
- 1993-09-28 KR KR1019930020420A patent/KR100265911B1/en not_active IP Right Cessation
- 1993-09-28 EP EP93307661A patent/EP0592137B1/en not_active Expired - Lifetime
- 1993-10-01 AU AU48778/93A patent/AU666774B2/en not_active Ceased
- 1993-10-04 RU RU93056588A patent/RU2124950C1/en not_active IP Right Cessation
- 1993-10-05 JP JP24839693A patent/JP3494680B2/en not_active Expired - Fee Related
- 1993-10-05 CZ CZ19932078A patent/CZ287182B6/en not_active IP Right Cessation
- 1993-10-05 CN CN93118224A patent/CN1051033C/en not_active Expired - Fee Related
-
1994
- 1994-06-21 US US08/262,970 patent/US5402940A/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| EP0592137B1 (en) | 2002-11-27 |
| DE1090689T1 (en) | 2001-12-20 |
| JPH06206018A (en) | 1994-07-26 |
| EP1254720A3 (en) | 2003-03-12 |
| AU666774B2 (en) | 1996-02-22 |
| RU2124950C1 (en) | 1999-01-20 |
| EP1254720A2 (en) | 2002-11-06 |
| ES2239551T1 (en) | 2005-10-01 |
| KR100265911B1 (en) | 2000-09-15 |
| CZ287182B6 (en) | 2000-10-11 |
| EP0592137A1 (en) | 1994-04-13 |
| US5344082A (en) | 1994-09-06 |
| JP3494680B2 (en) | 2004-02-09 |
| KR940008792A (en) | 1994-05-16 |
| DE69332517D1 (en) | 2003-01-09 |
| DE69332517T2 (en) | 2003-09-04 |
| CA2106251A1 (en) | 1994-04-06 |
| EP1090689A2 (en) | 2001-04-11 |
| CN1051033C (en) | 2000-04-05 |
| US5402940A (en) | 1995-04-04 |
| AU4877893A (en) | 1994-04-21 |
| DE592137T1 (en) | 1998-03-12 |
| CZ207893A3 (en) | 1996-03-13 |
| EP1090689A3 (en) | 2002-01-30 |
| TW246647B (en) | 1995-05-01 |
| CN1085129A (en) | 1994-04-13 |
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Legal Events
| Date | Code | Title | Description |
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| EEER | Examination request | ||
| MKLA | Lapsed |