Patent GB-1153208-A (GB)
Title: Improvements in or relating to Punching Machines
IPC: B21D28/04
Filed: 1966-10-21
Abstract: 1,153,208. Punching dies. HOUDAILLE INDUSTRIES Inc. 21 Oct., 1966 [23 Oct., 1965], No. 47182/66. Heading B3W. A punching machine having a frame, an upper reciprocably driven tool carried on the frame, a lower normally stationary tool coactive therewith, means on the frame for supporting the lower tool in a normal position for punching, the support means including a vertically slidable tool retainer normally holding the lower tool in the normal position, and a movable wedge member disposed to act between the frame and the tool retainer to support the tool retainer during punching and to temporarily alter the position of the tool retainer and the lower tool to a non-punching position and restore them to the normal position. The mounting of the die provides a safety feature in presses in which the workpiece is moved to various positions under the punch. In such a press which may be manually or automatically controlled, the gripper 18 which holds the edge of the workpiece 14 and which necessarily projects below the upper surface of the die 13, prevents the workpiece being moved in a straight line from one position to the next if such a straight line path causes the gripper to pass across the die. The die is therefore lowered below the upper surface of the worktable before the workpiece is moved and is restored to its original position for the punching operation. The die mount comprises a cylindrical housing 19 having a recess which receives a wear plate 21 and a rotatable cam plate 23 which has a number of cam surfaces 24 and peripheral teeth 34 which are engaged by a rack 35 which is reciprocated by a pneumatic jack (69), Fig. 3 (not shown). A tubular die retainer 27 slides in the housing 19 and includes a flange 33 which has cam surfaces 28 which co-operate with the cam surfaces 24. The die 13 rests on a cylindrical support 32 and is retained by a turn-button 59. Rotation of the die is prevented by a key 54 between the housing 19 and the retainer 27 and a key 56 between the retainer 27 and the die 13. The movements of the work-gripper are effected by two fluid jacks 16, 17, Fig. 4, which are continually pressurized on one side by a pump 63, and selectively pressurized on the other side by a pump 64 through valves 65, 66. The outlet pressure of the pumps reduces when the pump moves the jack and pressure switches 67 and 68 are operated by this reduction, and open the circuit of a first solenoid 71 which operates a valve 70 controlling the jack 69. A second solenoid 72 which also controls the valve 70 has two switches 43 and 73 in series. The switch 73 is physically connected to a pivoted lever 74, the free end of which projects above the upper surface of the lower die and which is engaged by the gripper 18. The switch 43 is actuated by a cam surface 41 on the die retainer 27 when the die has reached its lowered position and opens the circuit of the solenoid 72 even though the switch 73 remains closed. When the movement of the jacks 16, 17 is completed, the line pressure rises, the switches 67, 68 close and the solenoid 71 is energized to move the valve 70 to the left in Fig. 4 which causes the jack 69 to raise the die.