US2644617A - Vacuum powder feeder - Google Patents

Description

y 7, 1953 F, E. STIRN ETAL 2,644,617

VACUUM POWDER FEEDER Filed June 2, 1948 3 Sheets-Sheet l ATTORNEY July 7, 1953 I F. E. STIRN s-rm. 2,644,517

VACUUM POWDER FEEDER Filed June 2, 1948 BY M MA, 742/1 ATTORNEY July 7, 1953 F. E. STIRN ETAL VACUUM POWDER FEEDER 3 sheets-sheet 5 Filed June12,-'-1948 ATTORNEY Patented July 7, 1953 VACUUM POWDER FEEDER Frank E. Stirn, Pearl'River, and Arthur. S. Taylor, Spring Valley, N. Y., assignors to American Cyanamid Company, New York, N. Y., a corpo ration of Maine Application June 2, 1948, Serial No. 30,694

6 Claims.

This invention relates to a machine and method for continuously measuring the quantity of a comminuted or powdered material by compacting the powdered material to a uniform density in a trough of known cross section moving at a pre-' determinable rate whereby uniform quantities of the powder are discharged.

The accurate measurement of powders is a difficult operation. It is bad enough when a given weight of the powder must be used for a particular purpose, but when it is desired that a given weight per unit of time be used, the difiiculties increase markedly; and the difficulties in the uniform rate of feeding of powders have prevented the continuous operation of many processes and have been responsible for batch operations being required at a considerable in- "that an easily predictable quantity of the powder moves with the trough. Thetrough'is in turn driven at a uniform or predictable rate so that the exact quantity of powder passing a given point in the trough is readily adjustable and determinable. At a later point a gas pressureis used to release such parts-of the powderasdo' not fall from gravity into a hopper brother discharge area, within the control of the operator. The device may be used as a feeding device for feeding powders of any nature into achemi-cal process at any desired point or may be used for feed- It is a further .object of our invention to .provide an automatic machine whereby powdered materials may be uniformly compactedinto a measuring trough at a rate which is a function of suchfvariables as the operator may desire to introduce.

The feeding of powders at uniform. rates has long been considered difficult in many processes. Many powders have a tendency to bulk or'compact, depending upon vibrations or jars and to pack so that the powder does not flow uniformly. Methods of feeding powders into containers have included such devices as belts operating under .a diaphragm so that a constant cross section of powder is allowed to remain on the belt; screw type feeds and others have been used. A constant volume of powder was carried by a given point,

' but being as the powder was'not. uniformly comof the given mass is easy to determine.

pacted, undesirably large variations in the -quan-.

tity of powder being passed were thus introduced into the operation.

We have found that powders in general may be uniformly compacted by means of avacuum. When the air or other gas is removed, the particles of the powder flow uniformly and smoothly into contact with one another. By this, our invention, the powders are compacted bymeans of a vacuum to a uniform density. But being at a uniformdensity the mass is determined as a simple direct function'of the volume and accordingly by suitable'selection of doctor blades; cross sectional areas, and speeds, the rate of delivery For manytypes' of operationwhere it is desired that a considerable variation in rate of feed be easily accomplished, it is desirable that both the cross sectional area of this volume and its length, that ing powders into acontainer or hopper or for such other purposes as may require feedingof powders at a predictable rate.

It is an object of the invention to provide a method or machine whereby finely divided powders such as flour, plaster of Paris,v sugar, salt, crystalline materials, bran, ground oats, macerated feeds, cement, coal, and other materials, may be measured and discharged in accordance with the operators desires. All such materials are herein referred to as powders.

It is a further object of our invention to provide a machine and method whereby a uniform quantity of powder may be fed per unit of time.

is the speed of the trough, be variable'in order that greater flexibility may be obtained. Where this flexibility is not necessary or desirable either the cross sectional area or the speed of movement intothe trough or both may be fixed. In some cases it may be desirable to drive the trough direct from some other mechanism so that the rate ofdelivery will be proportionedtothe speed of such other mechanism; For example, the rate of addition of salt to a bath may be governed as a direct function of the pumps feeding the bath by gearing the feeder to the. pump shaft. Additionally, Genevas, square gears, elliptical gears, planetary systems, eccentric ratchet systems or any other system of mechanical linkages may be used which. will give the desired relationship betweenthe rateof drive of the feedztrough and thev rate at which any othermechanism is driven.

3 Various expedients along this line will suggest themselves to those skilled in the art. Additionally, the rate at which the trough is driven may be controlled through a positive infinitely variable gear box which may be controlled by any desirable or adjustable or controlled means.

Various methods may be used to vary the volume of the trough per unit of length. For some particular purposes it may be desired that the bottom of the trough be partially pocketed or have peculiar shaped relationships which may be incorporated for special purposes. For most purposes it is most convenient that a substantially rectangular cross sectional area be used with the bottom of the rectangle as the foraminous material and with either the top or one side adjustable to vary the cross section. The doctor blade may slide up and down in the trough so that the depth is varied, which is most convenient for variation while operating, or with certain types of powders it may be more desirable that a constant depth may be used, and accordingly a variable cutoff be used such as is later described in detail. Numerous other advantages, objects and variations of our invention .will be apparent as it is better understood from the description in the specification and accompanying drawings. Obvious mechanical equivalent uses will be readily apparent to those skilled in the art upon reading this disclosure.

' Figure 1 shows a side view of the complete machine.

Figure 2 is a front view showing a particular drive mechanism, certain details of a micrometer .depth adjustment and a particular powder agi tating system.

7 Figure 3 is a cross section taken on the line 33 of Figure 2, showing a specific internal construction of a specific filling trough.

Figure 4 is a section taken along line 44 of Figure 1, showing in more detail the interior of the filling mechanism with particular reference to valve members and air and pressure manifolds.

' Figure 5 is a top view of the mechanism.

Figure 6 is an alternative construction using vsintered metal with an adjustable side, or cutoff .on the surface of the drum.

Figure 7 is a section taken along line 11 of Figure 6 showing the adjusting slide.

Our device comprises essentially a moving member in which there is a trough to be filled with powdered material which is being measured .or fed. Aparticular modification is shown in Figures 1 to 5 in which the trough is contained in the periphery of a drum H. The drum H is mounted on a shaft [2 which is rotatably jour- 'naled in supports [3. The drum may be fastened to the shaft by means of a key M and set screw IS; The drum may be driven through the shaft by a drive chain It and sprocket wheel I! from any suitable source of power. The drive mechanism by which the sprocket is driven may be either one which rotates the drum at a constan speed or one which causes the drum to rotate in accordance with any desired speed cycle. The

drum is hollowed, as shown in Figure 4, having but one support wall journaled to the shaft.

In the face of the drum is formed a groove. Through the bottom of this groove are apertures l8-through which air or an inert gas may be evacuated and through which a suitable source of air or other gas by pressure serves to eject materials. Upon the surface of this groove is a foraminous material I9. This foraminous material may consist of a uniform .layer offelt, of sintered glass, of sintered metals, paper pulp, woven fabrics, or screens. The mesh of this foraminous material should .be such that air or other gas may comparatively readily flow through, but yet the fiow of the filled material is prevented. The porosity of this foraminous material maybe much finer for materials such as flour of finely powdered starch than for coarser materials such as sugar or salt. A material may be readily selected which is sufiiciently fine to prevent the influx of whatever material is to be filled but at the.

same time allow sufficient flow of gas so that the powdered material is uniformly packed and retained in position by vacuum and released by gas pressure without the passages through the foraminous material becomin blocked or obstructed. As shown in Figure 4 there is a fixed shoulder 20 on the drum itself and a replaceable shoulder rim 2| which is held in position by screws or other suitable fastening means. It is desirable that this rim be removable so that the foraminous material may be more easily cleaned, assembled and replaced. The shoulders 2| and 20 and the foraminous material l9 form a trough 22 which is filled with the powdered material in operation.

The depth of the trough is not normally critical but must be consistent for uniform operations. Above the drum there is positioned a hopper 23 which may be fed by a charge chute 24. The hopper itself, may be adjustable. For some operations the hopper may be fixed in relationship to the drum so that all variations in rate of delivery are based upon changes in the rate of rotation of the drum, but'for a more flexible apparatus as here illustrated, it is desirable that the hopper be adjustable. hopper is supported by a hopper carrier 25 which hopper carrier in turn is supported by carrier shoes 26, which may be made integral therewith, which ride on the surface of the drum assembly. The hopper carrier is held in slots 21 in the supports [3, previously referred to, by means of a shaft member 28 made integral therewith. The carrier shoes are held firmly against the drum by means of the hopper positioning springs 29. As so constructed the hopper carrier floats on the surface of the drum riding on the carrier shoes and flexibly positioned by the spring so that the relative positioning is constant. In this car-- rier, riding between suitable guide rods and bushings 30, is the hopper itself. The hopper is vertically. positioned in relationship to the carrier by means of a micrometer nut 3|, positioned between anvils 32, carried by the hopper carrier and shown as integral therewith. The micrometer nut has positioned therein a micrometer screw 33 which is in turn fastened tothe hopper itself by means of a stub 34. There may be an index 35 to assist in positioning the micrometer nut in the same relative position for adjustment, in accordance with the operators desires. As so constructed, the hopper itself may be caused to ride up and down between the guide rods and bushings 30 in an accurately positioned relationship thereto. The bottom of the carrier rides in the trough to prevent lateral motion and has attached thereto a doctorblade 36. It is preferred, but not necessary, that this doctor blade and the bottom of the hopper be of the same relative height with respect to the foraminous material, so that as the drum rotates the powdered material will fill the trough completely and be scraped off to a uniformheight by means of this doctor blade. Whereas the doctor blade may be made As shown in the drawing the integral with the hopper, itzisusually morefdesirable to make it' as shown as a separate member so that it may be kept sharpened, and with. different materials the exactv angle of" attack may be-modified to give a smooth, sharp, even out;

Rotating within thehopper isa spider 31: which is suitably fastened on a shaft 39 which is.journaled: inbearings 38' and driven by. a suitable belt drive 40, so that in. operation. the spider is caused to rotate through the powdered masscontained in the hopper to prevent bulking, caking and uneven flow of the powder.

Inside the drum and floatingconthesurfaces thereof is a stator 4|. The stator isprevented from rotating by means: of: a positioning. screw 42 in a positioning slot 43, or other suitablemeans. The stator is. drilled to accommodate the shaft and-"rotates with relationshipthereto; The stator fits in the drum: andbears. on the outer surface thereof with a peripheral seal 44.. This. peripheral seal member which may be made. of Micarta (a phenyl formaldehyde resin containing. fabric as a filler) or other suitable'material, isfastened firmly to the stator and slides on the flat. side of the drum, in a substantially air tight relationship thereto. On theinner surface of the stator, riding against an. inner surface of the drum. is an inner seal member 45, which may also be made of mcarta andwhich serves to prevent. air from leaking. around the shaft and into the vacuum and a pressure chests. Joining the two. circular. seal membersare radial seals. 46. As shownin. Figure 3 there are four such seals extending. from the inner seal member to the peripheral seal. These sealsmay also be made ofMicarta. and may be, if desired, urged against their bearing members by individual springs. although normally, if precisely constructed,'suoh. springs are not necessary. The entire assembly is held in contact with the surfaces of the drum by aspring 41. The four radial seals and two annular: seals form a vacuum chest 48 and a pressure chest 49. Gases are conducted from the vacuum chest by means of avacuum connection 50' andair or other" gas may be used in the pressure chest being conducted thereto by a pressure connection l. The periphery and side of the drum may be covered by a shield 52 which for convenience in operationmay be made of Lucite or'other transparent-materials. It is not necessary that the entire surface be covered as a hopper may be used beneath the drum, but by having the entire surface covered all powders are trapped to insure their dropping through the discharge opening 53 and dust is prevented from escaping into the room and contamination of the measured materials is prevented. I

In operation, powders or fine materials are fed through the charge chest 24 into the hopper 23. This feed may be by gravity as when the hopper is filled it will prevent additional material from feeding through the chest, insuring a reasonably consistent powder pressure head. The powder in the hopper is kept from bulking or channeling by means of the spider rotating which insures a comparatively uniform feed of the powder against the foraminous material in the trough. A vacuum through the vacuum connection which acts in turn through the vacuum chest and the foraminous surface of the drum pulls the powder into a uniformly packed layer in the trough which is cut off at an adjustable uniform height by the doctor blade 36. Accordingly, a volume of known size is generated with each rotation of the drum thereby insuring that a certain volume of powd'er is. discharged with of the uniform packing resulting; fromtheuseof eachrotation; andbecause vacuum,.-.av uniform density is maintained thus giving an extremelyruniform rate of flow. of the powdered material under; the doctor blade;

At-the bottomof the assembly is the pressure chest, containing a gas under pressure, which acts-through the foraminous layer asitpasses thereover, thus ejecting all powder which hasnot previously: fallenby gravity, As will be obvious from close inspection of the'gdrawings, by adjusting, the height of the doctor blade the thickness of the feed layer may be readily altered sov that a considerable variation in feed may be accomplishedat-a uniform rate of rotation. It is additionally desirable that the sprocket wheel; and drive-,chainabe driven by a variable speed. drive, asiforexampleby any: of thewell known positive .infinitely variable drive systems, so that thefeed drum may be rotated; at such speed as is desired by. the operator. I Obviouslythe; drive m chanism may be geared to rotate at different speeds dur ing this operation,. sothat fillingrates of.. fee.d may be maintained to cooperate with any specified operational cycle.

,An alternative construction is shown in Figures 6 and 7 in which an adjusting slide El is adjust.- ably mounted in the bottom. of the hopp r so that itjmay be inserted partway across the surfaceof the foraminousmaterial, thus ineifect 115111501113, a portion of the width, of 'thetrough. This gives additional flexibility that may be used to permit a constant depth of powder toinsure compacting to themost eflieient thicknessof layer-.-- The ad.- justing slide is shown as being clampedbetween adjusting screws, 58- so that it may be laterally. positioned. In this modification. the use. of-:.a sintered metal as a foraminousmaterial is' pa-rgticularly useful because the surface of the sintered metal maybe turned or ground to an extremely accurate surface so that the adjusting slide may more, accurately cooperate therewith; In .;th.e modification as shown in Figure 7,.the'front1edge of the hopper'serves as a doctor .bladeu g If fine powders are used,- it may. be necessary that auxiliary'air-inlets be formed in theahopper slightly above its point. of contact with. the drum, or; that the spider bemade hollow with air bleeds, .so1that. 'thenpowder .is kept aerated; Otherwise the; powdermay. packtoztheabottom' ofgthe, hopper will suggest themselves to those skilled in the art and such modifications as are necessary but of minor variance of the apparatus disclosed and illustrated, are regarded'as within the scope of this, our invention, in which we claim:

1. A machine for discharging powdered material at an adjustable and uniform rate comprising a traveling trough of substantially uniform but adjustable cross section, means for causing said trough to travel at a uniform but adjustable rate, a bottom portion of said trough of a foraminous material, vacuum means acting through said foraminous material, for-compacting a powdered material into said trough during a portion of said travel, aseous pressure meansffor ejecting said material from said trough during a second portion of the travel of said trough, a hopper placed in juxtaposition to said trough and adjustable in relation thereto, a doctor blade portion of said hopper, whereby a portion of said hopper will function as a doctor blade, thereby striking off the contents of said trough at a uniform but adjustable height, and micrometer adjustment means whereby the position ofisaid hopper may be varied. y 2. A machinefor the delivery of powdered .particles comprising a circular conveyor trough adapted to be moved at an adjustable predeter: mined rate, a foraminous means comprisingat least the bottom portion of said trough, manifolding means cooperating with said foraminous means, a doctor means adjustably positioned above said trough whereby the contents of the trough may be uniformly compacted into said trough and struck off at a desired height in said trough, and adjustable means positioned to laterally move across at least a portion of the bottom surface of said trough, whereby the effective widthof said trough may be varied.

A machine for discharging'powdered material at a uniform rate comprising a travelling trough-of adjustable uniform cross-section, means for causing said trough to travel at-a uniform .rate, a' foraminous material comprising. at least 'of cross-section of trough travel beneath said doct'or means.

' =4. A machine for discharging powdered material-at a uniform rate comprising a travelling trough of adjustable cross-section, means for causing said trough to travel at a predetermined rate, a hopper in juxtaposition to said trough for feeding a powdered content into said trough, a foraminous material forming at least part of the bottom of said trough, a doctor means to strike off evenly the powdered material in said trough, vacuum means actin through said foraminous material for uniformly compacting a powdered material into said trough during the portionof its travel under said hopper, and gaseous pressure means for ejecting material from said trough 'during a second portion of the travel of said section of trough travel beneath said 1doctor means.

5. A machine for discharging powdered material at a uniform rate comprising a travelling trough of adjustable uniform cross section, means for causing said trough to travel at a uniform rate, a foraminous material comprising atleast partlof the bottom portion of said trough,;a hopperplaced in juxtaposition to said trough, vacuum means acting through said foraminous material during at least .a' portionflof the travel of the trough under said hopper, thereby uniformly compactinga powdered material in the hopper into said trough during said portion of said travel, gaseouspressure means for ejecting the material from the trough during a second portion of the travel of the trough, and adjustable doctor means adjacent said trough to adjustably and uniformly strike ofithe contents of said trough. w

6. A machine for discharging powdered material at a uniform rate comprising a travelling trough of adjustable uniform cross-section, means for causing said trough to travel at an adjustable rate, a hopper in juxtaposition to and cooperating vwith said troughfor feeding a powdered content into said trough, a foraminous material forming the-bottom ofsaid troughya doctor means to strike off evenlythe powdered material in said trough, vacuum means acting through said foraminous material for uniformly compacting a powdered material into said trough during the portion of its travel under said hopper, and gaseous pressure means for ejecting material from said troughduring a second portion of the travel of said trough.

FRANK E. STIRN- ARTHUR. S. TAYLOR.

References Cited in the file of this patent j UNITED-STATES PATENTS Number Name 7 Date 1,371,517 Oliver Mar. 15, 1921 2,031,713 Johnson Feb. 25, 1936 2,243,058 Wysong May 20, 1941 2,282,477 Joa May 12, 1942 2,343,722 Wagner Mar. 7, 1944 2,488,394 Goldberg Nov. 15, 1949 2,540,059 Stirn et al Jan. 30, 1951

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