Patent GB-1042248-A (GB)
Title: Shock absorber for drawbenches
IPC: B21C19/00
Filed: 1964-06-19
Abstract: 1,042,248. Drawbenches. BLAW-KNOX CO. June 19, 1964 [Aug. 9, 1963], No 25445/64. Heading B3P. A drawbench comprises a bed, a die stand and die, a carriage movable on the bed and workpiece gripping jaws and has means for mounting said jaws on said carriage for movement with respect to the carriage in directions parallel to said bed and a spring for accelerating the gripper jaws in the forward direction with respect to the carriage when the trailing end of the workpiece is released from the die. The carriage 15 comprises side members 35, Fig. 4 (not shown), end members 37 and 38 and intermediate members 39, 40, 41 and 42 and runs on wheels 17 along tracks 18. It is propelled by chains 23 driven through gearing by a reversible electric motor. The gripper jaws 16 are mounted in a slideway 44, Fig. 9 (not shown) extending from the rear end of the carriage to the member 40. The first part of the slideway is formed by a groove in a block 45 extending to the member 39 and the remainder is built-up from plates 51 and 52. The jaw assembly is retained by jibs 50 and 53. The block 45 has tapered surfaces 49 which co-operate with surfaces 56 on the jaws 55 to close them on to a workpieee. The forward ends of the jaws are square and slidably engage jaw supporting block 57 as at 58, to which they are pivotally attached by links 59, which are urged apart by a spring 63. Detachably secured to the jaw supporting block 57, by a pin 70, is a rod 66 which passes through a guide bush 72 and a cylinder head 73 and carries a piston 75 which reciprocates in a cylinder 74, Fig. 4 (not shown). The cylinder head 73 is slidable in the cylinder 74 and is acted on by a compression spring 78 which bears against the bush 72. The cylinder has a port connected by a conduit 76 and valves 102 and 98, Fig. 13, to an air reservoir 94 and an air needle 84 which is connected to a source of high pressure air 87 when the carriage is at the die stand end of the bench. Operation.-With the carriage approaching the die stand end of the bench and the piston 75 adjacent the cylinder head 73 the jaws 55 are in the position shown in Fig. 9, ready to receive a workpiece T. When the carriage is adjacent the die stand, with the workpiece T between the jaws 55, air is admitted through the conduit 76, overcomes the force of the spring 78 and moves the jaws relative to the slideway 45, to grip the workpiece. As the draw commences the jaws automatically tighten on to the workpiece and the pressure in the cylinder 74 is reduced to a low value, determined by a pressure regulator 100. When the trailing end of the tube leaves the die the spring 78 accelerates the jaw assembly, the rod 66 and the piston 75 in the forward direction so that the drawn tube is not required to over-come the inertia and friction of these parts and is not subjected to buckling or bending. The pointed end of the tube engages a recess 80 in the block 57, but only after the block has been accelerated to a substantial velocity, and the drawn tube, the jaw assembly, rod 66 and piston 75, continue to move to the right, the motion being gradually reduced by the damping effect of the piston 75. The pressure in the cylinder 74 is not permitted to build up but is maintained at the initial valve, and the tube finally drops out of the jaws and is discharged to a collecting box. The forward movement of the draw carriage is stopped by conventional means soon after the trailing end of the tube leaves the die.