CA1152747A

CA1152747A - Belt sanding machine

Info

Publication number: CA1152747A
Application number: CA000350477A
Authority: CA
Inventors: Bertil Jonasson
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-04-25
Filing date: 1980-04-23
Publication date: 1983-08-30
Also published as: SE419193B; NL8002382A; FR2454873A1; US4416090A; DE3015874A1; FR2454873B1; IT1128301B; IT8048526A0; SE7903612L

Abstract

A B S T R A C T

Belt sanding machine intended for plane-sanding of a surface and comprising two sanding units (1 2) and, as seen in the feed direction in front of between and behind these sanding units guides or pressure beams (3-5) for setting the sanding depth and a table (9,10) for pressing the workpiece against said sanding units and said pressure beams. The table being designed in such a way as to allow bothdimensioning or adjusting a worlkpiece to an almost exact plane-parallell shape and finish sanding with an accurately predetermined sanding depth no matter if the workpiece has a thickness varying locally.

The sanding machine is characterized in that the table comprises a number of pressure studs (28) movable towards and away from the sanding units and the pressure beams the pressure studs being arranged to be actuated by a pressurizedfluid.

Description

~;274~7 Applicant l3ertil Jonasson Title of invention ~3(1t slln(1ir~ lchine The present invention L~elates to a face plate sander especialLy a belt sanding machine eg comprising two sanding units and, as seen in the feecl clirection, infront of, between and behind these units guides or pressure beams for setting the sanding depth. The inventive clevice comprises a table for pressing a work-piece against the sanclinq units and the guides the table being designed, accor-ding to the invention, in such a manner as to allow both dimensioning or adjus-ting the workpiece to an almost exact plane-parallell shape and finish sanding the workpiece with a very accurate, predetermined sanclinl~ depth no matter if the workpiece has a thickness varying considerably in the feed direction or in a direction transverse thereto.

Conventional sanding machines of the type indicated above usually comprises a feeding conveyor provided below the sanding units for feeding the workpieces through the machine. The tab]e mentioned above is provided below the feeding conveyor and has the purpose of pressing the workpiece supported by the conveyorwith a suitable force against the sanding units and the guides. In conventional sanding machines the table proper is usually completely rigid. However the table i5 resiliently suspended to allow minor deviations from the intended dimensions Of the workpieces. Even if the table is resilient in a way this does not mean that the sQr)ding depthis completely independent of the thickness distribution of the workpiece. Thus, conventional sanding machines usually has a bigger workin~J depth at such portions of the workpiece havin~ a bigger thickness as the pressing force of a rigid table, due to the spring suspen-sion, will increase with the thickness of the workpiece. The reason for this is that the spring means used provide a pressing force against the sanding units that is proportional to the way of deformation of the spring means.

Further, the rigid table of a conventional sanding machine has the drawback thatthe workpiece could be exposed to very big local loads if it l1as a loc3lly pro-truding portion facing the feeding conveyor. In such a case the total sprin~ force of the table will be concentrated to this small portion which might cause defor-mations of the workpiece in turn causing a much increasecl sanding depth at a por-tion opposite the protruding portion. In such cases it often happens that the sanding depth of a conventional sanding machine will be of sllch a magnitude as the vaneer of a vaneered worl<piece is completely sande-l-throu~Jh.
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., ,, .,,, ' '' :' .' ~ ~J.5i2747 The present inventinn has for its object to provide a sanding machine of the kind indicated above and clesigned to eliminate the above problems and difficul-ties in achieving an accurately defined sanding depth irrespectively of irre~ula-rities of the thickness of the workpiece. Thus, the invention has for its objectto provide a devic~ for defining the sanding depth so acc-Jrat~ly t:hat there isno risk of sanding--through even a thin layer of varnish on the worl<piece.

According to the invention this object is achieved if the belt sanding machine having at least one sanding unit at the f`ront and bacl< side of which, as seen in the feed direction, there is provided guide means for setting the sanding depth and at least one pressing table for pressing the workpiece against the sanding unit and the guide means, is characterized in that said pressing table comprises a number of pressure means movable towards and away from said sanding unit and said guide means said pressure means being arran~ed to be actuated towards the sanding unit and the guide means under influence of a pressurized fluid.

A practical embodiment of the invention is characterized in that the pressure means are provided in rows transversely of the feed direction of the machine thepressure means in each row cooperating with a common pressure chamber for pressu-rized fluid.

A sanding machine particularly well suited for carrying the invention into eFfect comprises, as seen in the feed direction, a first sanding unit in which a rotating drum brings a first sanding belt to contact the workpiece and then a second sand-ing unit in which a pressure shoe brings a second sanding belt to contact the workpiece, guide means or pressure beams being provided in front of , between and behind the sanding units. According to the invention such a sanding machine is characterized in that there i8 provided one row of pressure means for coopera-ting with each guide means and one row of pressure means for cooperating with the sanding unit comprising the rotating drum the pressure chamber for this row hav-ing its own supply of ressurized fluid and being located in a vertical plane com-prising the center axis of said drum the pressure chamhers for the other of saidrows being connected with each other.
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According to the invention it is preferred that the pressure rneans are designedas cylindric bodies displacably received in a carrier the inner ends of said bodies contacting a resilient diaphragm closing the pressure chamber towards said bodies.
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~o achieve, in thc l~r~sin(~ nF the workpiece against the sanding units, also a spring action and not only a uniform pressure there is foreseen that the per~su-rized fluid is air.

The invention is nnw to be de3cribed more in detail, referencc i. being macle tothe accompanyin-J drrlwings on which fig. 1 shows a schematical, longitudinal sec-tional view of the inventive sanding machine. Fig. 2 shows from below a carrier for the pressure b-)(lies the lower lid of the carrier being omitted for the sake of clarity. Fig. 3 shows a cross sectional view of the carrier, substantially on line A-A in fig. 2.

In fig 1 thereis shown the principle of the inventive sanding machine. It is evi-dent that the machine comprises two sanding units provided one after another in the feed direction B of the machine.

In fig. 1 a first sanding unit is indicated. This sanding unit indicated at arrow 1 comprises a rotating drum for bringing a first sanding belt in contact with the workpiece. Also a second (in the feed direction) sanding unit is indicated in this fig. (at arrnw 2) and comprises a pressure shoe for hringing a second sand-ing belt in contact with the workpiece. At the feeding side of the first sandingunit there is provided a guide or a so-called pressure beam 3, between the sandin() units one more guide or pressure beam 4, und finally at the exit side of the second sanding unit an exit quide or a pressure beam 5. Below the sanding units and thepressure beams there is provided a feeding conveyor assernbly, usually of be~t type and having at least two rollers 6, 7 over which an endless belt is trained (arrow r ~elow the upper run of belt ~ there is provided pressure or support tables 9, 1n.
The lower side of belt ~ contacts these tables provided to press the work-piecs carried on belt ~ along arrow B against the first and second sanding units1 and 2 resp. and a~ainst the pressure beams or guides 3-5. To allow sanding of workpieces of different thicknesseR the feeding conveyor assernbly 6-10 is acl-justable in vertical direction relative to sanding units 1,2 and pressure beams 3-5. To adjust the sanding depth of the two sanding units 1,2 their relative vertical setting torlether with the relative vertical setting of pressure beams 3-5 are adjustable in such a way that the pressure bearn 3 has a bigger verticaldistance to table 9 than the sanding surface of sandlng unit 1. Further, the sanding surface of sanding unit 1 and the intermecliate pressure beam 4 have substantially the sarne vertical distance to tables 9,10 while the pressure shoe11 and the exit prcssure beam 5 are provided at a sliyhtly lower level than the intermediate pressllre beam 4. Like pressure beam 4 al)d the sanding surface of , ~
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' ' sanding unit 1 bein3 substantially level, exit pressure heam 5 and the sanding surface of sanclin~]lmit 2 are provided at substanti~l]y the same level. Finally, pressure beam 3 is llsually resilient in an upw~rd ~irection to allow feeding of a workpiece havin~ portions protrudin~l upwardly.

According to the invontiDn sanding units 1 and 2 are of conventional type. There-fore sanding unit 1 comprises a lower drum or roller 12 and an upper roller (notshown on the drawing) imparting a suitable tension to sanding ~elt 13 moving at a high speed alonrJ arrow D. Like the first sanding unit 1 the second sandin~) unit ~ comprises a sanding belt 16 running in the direction of arrow E, about the lower rollers, a front roller 14 and a rear roller 15. Sanding belt 16 is kept in tension by a further roller not sl1own on thc drawing. At least the front roller 14 is adjustable in the vertical direction and should be set at such a level that its lowermost portion is located one or two millimetres above the lower surface of a pressure shoe 11 provided between the front and rear rollers 14 and 15 resp. Pressure shoe 11 could, according to the invention, be designed in any way well known in the art and compatible with the sanding operations to be achieved.

According to the invention the two tables 9,10 are rigidly mounted in the frame carrying conveyor assembly 6-10. Tables 9,1û are designed as substantially U-shaped beams havin~ plane upper surfaces 17 and 18 resp. supporting feeding beltB, At numerals 19-24 in fig. 1 there is indicated carriers receiving pressure means for pressinq Feeding belt 8 towards sanding units 1,2 and pressure beams 3-5. Carriers 19-24 are elongated and have such lengths transversely of the feeddirection B that the whole working width of the machine is covered.

In fig. 2 there is shown, as seen from below, the upper part of such a carrier 19-24 being fastened to the lower side of the upper portions 17,18 of tables 9 and 10 resp. The portions of carriers 19-24 fastened to tables oonstitute main portions 25 of the carriers and have a number of parallell bores 26 perpen-dicular to the ùpper sides 17 and 18 of the tables. In practice the diameter of the bores could amount tc approx. 30 millimetres and their centre to centre distance is preferably approx. 60 ~ llimetres. About the lower ends of bores 26there is a recessed, continious area 27 the depth of which is approx 3-5 milli-metres.

In fig. 3 there is shown a cross sectional view, substantially on line A-A in flg. 2. From this fig. there is clearly seen that the main portions 25 of the ,: .: . , ' ............. ' '. ~,. '-. . , .
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~SZ747 carriers are fastenod (by means of screws not shown) 1 in abutting positions to the lower surfaces of u~per pnrtions 17 and 1~ of tnb]r~s 9 and 10 resp. Further, it is evident that bQres 2f. are perpendicular to the llpper pnrtions 17 and 1~3 of the tables.

As is apparent fro~ ~ig. 3 ther~ is provided pressure means ~r studs 28 in the bores 26. Studs 2~ are of cylindric shape havin~ substantially planar end sur~aces theedges of which are some~hat rounded. Studs 2~ have loose fit in bores 26 and aredisplacable in vertical direction (in ~leir longitudinal direction) f~om the positions of fig. 3 to elevated positions projecting beyond the upper surfaces of tables 17,18. The lenght of this displacement beyond the upper surfaces of the tables corresponds to the depth of recesses 27 at the lower side of the rnain portions 25 of carriers 19-24. From fig. 3 is also evident that the carrier com-prises a lid 29 fastened to the main portion by means of scre~Ys 30 and 31. The threaded holes provided for these screws in the main portion 25 are shown in fig.

2 at numeral 32. Numeral 33 refers to through holes for receiving long screws extending from the lower side of lid 29, through the main portion 25 and clamping the whole carrier to the lower side of tables 9,10. Between lid 29 and main por-tion 25 each carrier comprises a resilient or elastic diaphragm 34 abutting withits upper surface the lower end sur~aces of studs 28. Lid 29 is provided with atleast one inlet 35 for a pressurized fluid (pressurized air). When letting pressu-rized air into the space hetween diaphragm 34 and lid 29 there is created a press-ure chamber corresponding to recess 27 at the lower ends of bores 26. Thus, wheninjecting air via inlet 35 diaphragm will flex upwardly and,at full pressure.
; abut the recessed surface 27 and the lower end surfaces of studs 28 so that the studs are lifted a distance corresponding to the depth of recess 27. At lower pressure in the pressure chamber between diapgragm 34 and lid 29 the diaphragm and the studs will take intermediate positions between the ahove upper end position and the pressure free position of fig. 3.

Though not shown in fig. 3 there is preferol,ly provided, at the upper ends of studs 28, one more diaphragm possibly recessed below the upper surfaces of tables 9,10 so that said surfaces are completely flat. Also these diaphragms must be resilient not to prevent the vertical movements of studs 28 but constitute a dust ; seal at the upper ends of bores 26. As an alternative the whole upper surfaces of tables 9,10 could be covered by a resilient sheeting fastened and sealed at the edge portions of the tables. Such a sheeting has the same purpose as the above upper diaphragms, ie to constitute a dust seal. Furthermore, such a sheet-ing and also the upper diaphragms could be made from a resilient material also d ~. .
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,, , .::' : ~ ' ~5Z747 having a low coefficient of friction together with the lower surface of feeding belt a.

As mentioned abovc th~ invol)tive sanding machin~ c~n nerform two different opera-tions. Firstly, lh~ nl~clline i; clesigned tn perforrn dimensioning or adjusting the workpiece t~ an almDst exa~t plane-parallell shape. In this m~(ie of operation the pressure charnbers between lids 29 and ~Jiaphr~gms 34 aro re]eased of pressure and studs 2~ are located -lt the positions of fig. 3 an~l n~tenga~ing the feeding belt 8.
Tables 9,1û are completely rigid, and furthermore, I-lold stationary in the frame-work of conveyor assembly 6-1n whereby workpieces having a varying thickness arebraught to contact the sancling units 1,2 only with those portions having the bigg-est thickness. As indicated above the first pressure beam 3 is spring loaded in this mode of operation to allow feeding of workpieces of the type mentioned.

Secondly, the inventive sanding machine also could operate with the tables float-ing whereby rnaking possible plane sanding or finish sanding of a workpiece having a substantially varying thickness. In this mode of oPeration the predetermined sand-ing depth is not influenced by irregularities regarding the thickness of the work-piece. Thus, it is possible to perform finish sanding of thin layers of varnish without any risk o~ sandingthrough said layers. When performing this operation the pressure chamhers in carriers 19-24 between lids 29 and diaphragms 34 are under pressure flexing the diaphragms upwardly and lifting studs 28 to a level above the upper surface of tables 9 and 10. Preferably, the pressure chambers of carriers 19 and 21-24 are connected to each other to achieve exactly the samepressure in all pressure chambers. Carrier 20 has a separate pressure fluid supply making it possible to have a different pressure in this pressure chamber.By providing a great number of vertically movable studs 28 in tables 9,10 all of them (possible except those in carrier 20) pressing with exactly the same force against the lower surface of the workpiece there is achieved a completely uniform pressing of the upper surface of the workpiece against pressure beams

3-5 and sanding units 1,2. This means that the intended sanding depth set by relative vertical adjustment of sanding units 1,2 and pressure bearns 3-5 is notinfluenced by irregularities of the thickness of the workpiece. Thus, it is possi-ble to sand with an accurately predetermined sanding depth one side of a work-~, i giece being wedge-shaped in a direction transverse to the feeding direction and without changing the wedge-shape. This is achieved by having the different studs28 of tables exposed to upward forces completely independent of the different positions of the studs said forces being influenced only by the common pressure ; in the pressurer chambers. Locally depressing one or a few studs does not result C
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:' ' ::.,: :, .,, r~ ~2747 in a corresponding local increa3e of the contact pressure against the sanding units but will only result in a very ;mal] increa;e of ~he common pressure in the pressure chambers connected to each other. This pressure could also be kept substantially constant and inclependent of such depressions of certain studs if the pressure in said cllambers is controlled by a suitablc pressure regulator.

The invention could be moclified within the scope of the following claims. Thus,it is possible to provide studs 28 in a pattern different from that mentioned above where ~he stu(ls are arranged in rows transversely of feeding direction and in lines one after another in the feeding direction. Such al-ternative patterns could inclide arranging the studs in rows transversely of the feeding direction but placing the studs of different rows in a staggered relationship. Further, itis also possible to use a more random arrangement of the studs although, in all alternatives, the pressure chambers for the different studs or groups of studs should be connected to each other as mentioned above. Finally, the sanding machine could also, contrary to that stated above, be equipped with two sanding units having sanding drums only and one sanding unit having a pressure shoe, or vice versa. In such a case the number of studs is preferably increased correspondingly.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A belt sanding machine comprising:
a sanding unit having a feed direction with a front side and a back side with respect to said feed direction;
guide means at said front and back sides for setting the sanding depth;
a feed conveyor made from a flexible material for feeding workpieces to be sanded in the feed direction past said sanding unit and a table facing that surface of said feed conveyor which is turned away from said sanding unit; said table having a plurality of openings therethrough; one pressure member movably provided in each opening and adapted to extend, when activated, above said table to movably support at a first end thereof said feed conveyor at a distance from the table;
each of said pressure members contacting with its second end remote from the first end a resilient diaphragm means, said diaphragm means being exposed to a pressurized fluid for urging each of said pressure members against said feed conveyor with equal forces regardless of the instant position of said pressure members.

2. A belt sanding machine as claimed in claim 1, in which:
said table openings are arranged in a plurality of rows, each row extending transversely of the feed direction, one row being provided adjacent each of said guide means and one row advacent said sanding belt.

3. A belt sanding machine comprising:
a sanding unit having a feed direction with a ftont side and a back side with respect to said feed direction;
guide means at said front and back sides for setting the sanding depth;

a feed conveyor made from a flexible material for feeding workpieces to be sanded in the feed direction past said sanding unit; and a pressure table on the side of said feed conveyor opposite said sanding unit for pressing a workpiece against said sanding unit and said guide means as the workpiece is fed past said sanding unit, said pressure table including a rigid and planar support member ridigly set at a preselected distance from the guide means, said support member having a plurality of openings therethrough; a plurality of pressure members, each pressure member movable through an associated pressure table opening between a retracted position in which said pressure member is retracted within said planar support member, allowing said feed conveyor to contact said planar support member so that said feed conveyor constitutes a rigid support surface for pressing a workpiece against said sanding unit, and an extended position in which said pressure member extends through said pressure table to move said feed conveyor a distance from said planar support member; and means for resiliently urging with substantially the same force each of said pressure members against said feed conveyor in their extended positions so that said feed conveyor constitutes a resilient and flexible support surface for pressing a workpiece with a substantially constant pressure at any location thereof against said sanding unit and said guide means.

4. A belt sanding machine as claimed in claim 3, in which said planar support member openings are arranged in a plurality of rows, each row extending transversely of the feed direction and in which said resiliently urging means includes means for resiliently urging with substantially the same force each of the pressure members associated with any row of planar support member openings against said feed conveyor in the extended positions of said pressure members.

5. A belt sanding machine as claimed in claim 3 or 4, in which each of said pressure members comprises a cylindrical body member having its longitudinal axis passing through said planar support member opening and in which said resiliently urging means for each row of pressure members comprises a resilient diaphragm means contacting an end of each body member in said row, said diaphragm means constituting a movable wall member of a closed chamber exposed to a pressurized fluid to exert equal forces to each body member irrespectively of the position thereof.

6. A belt sanding machine as claimed in claim 3 or 4, in which each of said pressure members comprises a cylindrical body member having its longitudinal axis passing through said planar support member opening and in which said resiliently urging means for each row of pressure members comprises a resilient diaphragm means contacting an end of each body member in said row, said diaphragm means constituting a movable wall member of a closed chamber exposed to a pressurized fluid to exert equal forces to each body member irrespectively of the position thereof, said sanding unit comprising a sanding belt running about a contact member for having the sanding belt contact said workpieces; said guide means comprising a number of components disposed one after the other in said feed direction;
said planar support member openings being arranged with at least one row thereof adjacent each of said guide means components and with one row adjacent said sanding belt; in said resilient urging means, said closed chambers associated with said guide means being interconnected with each other and said closed chamber associated with said sanding belt being separated from said other closed chambers.

7. A belt sanding machine as claimed in claim 3 or 4, in which each of said pressure members comprises a cylindrical body member having its longitudinal axis passing through said planar support member opening and in which said resiliently urging means for each row of pressure members comprises a resilient diaphragm means contacting an end of each body member in said row, said diaphragm means constituting a movable wall member of a closed chamber exposed to a pressurized fluid to exert equal forces to each body member irrespectively of the position thereof, said sanding unit comprising a sanding belt running about a contact member for having the sanding belt contact said workpieces; said guide means comprising a number of components disposed one after the other in said feed direction; said planar support member openings being arranged with at least one row thereof adjacent each of said guide means components and with one row adjacent said sanding belt; in said resilient urging means, said closed chambers associated with said guide means being interconnected with each other and said closed chamber associated with said sanding belt being separated from said other closed chambers, said sanding unit comprising a second sanding belt running about a pressure shoe;
in said feed direction, said guide means components including a first component in front of said first sanding belt, a second component between said first and said second component between said first and said second sanding belts and a third component behind said second sanding belt.

8. A belt sanding machine comprising:
(a) a sanding unit having a feed direction with a front end and a rear end relative to the feed direction:
(b) guide means at said front end and at said rear end for setting the sending depth;
(c) a feed conveyor made from a flexible material for feeding workpieces to be sanded in the feed direction past said sanding unit;
(d) a generally planar support member facing that surface of said feed conveyor which is turned away from said sanding unit;
(e) said support member having a plurality of openings therethrough;
(f) a plurality of pressure members each disposed in one of said openings to extend, when actuated by a resilient force, over the generally planar support member to thus support at one end thereof a part of said feed conveyor;
(g) means for maintaining said resilient force at a generally uniform value throughout the pressure members, regardless of the instant extent of protrusion thereof over said generally planar support member.