GB898801A - Improvement in clamping means - Google Patents

Abstract

898,801. Abrading. COSSOR Ltd., A. C. Dec. 2, 1960 [Oct. 5, 1959], No. 33726/59. Class 60. Apparatus for clamping a laminar workpiece to a movable work surface comprises a plurality of clamping members disposed above the work surface and distributed transversely to the direction of movement of the surface thereunder the clamping members being reciprocable in a direction generally perpendicular to the plane of the work surface and the ends of the clamping members adjacent to the work surface being displaceable in the direction of movement of the surface on engagement with the surface or a laminar workpiece laid thereon, and means for reciprocating the clamping members in a plurality of mutually interspersed sets in such a manner that there is always at least one set of members in engagement with the surface or a laminar workpiece laid thereon. A machine for brushing or scarfing comprises a rotating brush 12 beneath which a workpiece 16 is moved by a rotating work-table 10. The brush may rotate in a sense opposed to the movement of the table thereunder. The clamping apparatus is mounted on a frame 11 bridging the table and consists of rods 17 aligned on a radius of the table. Each rod has a foot 18 extending in the direction of movement of the table thereunder, the foot being preferably encased in resilient plastic material. Each rod is pivotally suspended from one arm of a bellcrank lever 19 and a tension spring 21 biases the foot of the rod in the direction opposite to the motion of the table thereunder, the movement of the rod under the influence of the spring being limited by a bar 30. The levers 19 are rotatably mounted on a common shaft 20. The other arm of each lever carries a follower 22 riding on a cam 23 and urged into contact therewith by a strong tension spring 24. The cams 23 are mounted on a camshaft 25, successive cams being displaced by 180 degrees, so that there are two mutually interspersed, oppositely directed sets of cams. The camshaft is driven, through gears 26, 27, shaft 28, pulley 29 and belt 14, by a motor. The shaft 28 drives, through pulley 31 and belt 15, the brush 12. In operation, the feet of the rods operated by one set of cams disengage the work-table of the workpiece thereon only after the feet of the rods operated by the other set of cams have moved into engagement therewith. The cams may be divided into three sets so that two-thirds of the feet are operative at any one time. In a wet operation, e.g. polishing laminated boards for printed circuits in the presence of a pumice slurry, the worktable has a metal surface and adhesion of the boards to the table is enhanced by the surface tension of the slurry. In a dry operation, a second clamping apparatus may be provided on the other side of the tool. For delicate work, where marking or damaging the workpiece surface is to be avoided, thin rods which bow slightly under pressure may be used, and if they are sufficiently long it may be unnecessary to provide pivot support for their upper ends or springs to bias them towards the undisplaced position. The clamping apparatus may be used with a belt or chain conveyer or with a reciprocating work-table.