GB1309088A - Workpiece clamping devices - Google Patents

Abstract

1309088 Clamping dogs POWER JACKS Ltd 17 Nov 1970 [20 Nov 1969] 56934/69 Heading B3B A workpiece clamping device comprises a base part 1 adapted to be secured to, e.g. a work table, a workpiece clamping member 5 mounted on the base so as to be movable firstly substantially rectilinearly between a withdrawn position (as shown) and an operative position (shown in chain-dot), and secondly to be movable so that a workpiece engaging part 11 moves transversely of said rectilinear movement from the operative position to a clamping position whereby a workpiece is secured to said work table, the device being operated by a single hydraulic plunger 9 which operates mechanically through two drives to effect the first and second movements, both of said drives incorporating lost motion to ensure the desired sequence of operation. The first drive comprises a bell crank 19 actuated by the body 8 of the plunger so that an arm (23) (Fig. 5, not shown) can move a rod (24) via springs (29), (30) to rotate a shaft (34) and hence a lever (35) (Fig. 1, not shown). The springs (29), (30) provide the lost motion to allow continuing movement of the plunger 9 and bell crank 19 after the lever (35) has rotated fully to move the clamping member 5 from the withdrawn to the operative position. The member 5 slides by means of slots 13 on a T-shaped support member 4 which is pivoted about a shaft 3. During the sliding of the clamping member 5 a cross pin 37 in the plunger moves along a groove 38 without applying a pivoting force to the clamping member 5. The second mechanical drive comprises a direct abutment of a part 18 of the plunger 9 with the underside of the clamping member 5 when it reaches the operative position to pivot the clamping member about shaft 3 to clamp a workpiece. The groove 38 and pin 37 provide a lost motion connection during the rectilinear sliding of the clamping member 5. The springs (29), (30) return the clamping member from the clamping position to the withdrawn position in the correct sequence after release of pressure fluid from passage 10. In alternative arrangements the clamping member may be pivotally mounted on a block slidable on the base; both movements of the clamping member are rectilinear; the second direct abutment drive may be used to effect the first rectilinear movement; and the lost motion may be provided by a sprocket having a toothless portion.