Patent GB-1185424-A (GB)
Title: Method of Producing Control Surfaces on Planar Workpieces.
IPC: B21D43/05
Filed: 1968-09-09
Abstract: 1,185,424. Punching; shearing. NATIONAL CASH REGISTER CO. 9 Sept., 1968 [9 Oct., 1967], No. 42714/68. Heading B3W. [Also in Division G3] A set of differing control detents are produced from a set of identical blanks Fig. 8 (not shown), by removing unwanted external control surfaces Fig. 9 (not shown), in a shear and forming internal control surfaces in two stages Fig. 10 (not shown), by means of a die press. Features for each detent are recorded on a multitrack numerical control tape which controls the shearing and piercing operations, but the blanks are inserted and removed manually. The shear has a plurality of pairs of cutters 326, Fig. 14, which are disabled when bars 340 are displaced from the toe of the cutter so that it slides upwardly relative to block 330 on contact with the workpiece 28. The bars are moved by common pneumatic cylinder 350 when plungers 364 of solenoids 362 are moved into engagement with slots 368. The solenoids are controlled by the numerical punch tape system (not shown, see Heading G3N). Limit switches 374 are utilized to prove that the correct cutters have been selected, to inhibit movement of the ram motivating the cutters unless there is coincidence between the programme and actual conditions. The die inserts for the piercing operation are mounted in a separate machine. Each insert comprises a punch (76), Fig. 6a (not shown), slidably mounted in a bore (78) having a rectangular upper end (80) to receive a block 82, Fig. 2 having projecting ears 128 bearing on compression springs 130. Fasteners (84) have enlarged heads 88 which slide in slots 90 in a plate 92 which is movable upwardly by springs 132, thus withdrawing each punch (76) from its respective die (72), the latter being of conventional pattern which are located by pins (74). A pressure plate (96), one for each die unit 52, which comprises nine inserts, is resiliently secured to the underside of an extension (70) of the upper part (62) of each die unit 52 by fasteners (98) and compression springs (100) which urge plate (96) against extension (70). Plates (96) are provided with openings (102) through which the punch end (104) passes. Spring-loaded pins (112) having limited free movement and which pass through holes 108, when ram (48) and upper plate 46 descends, engage with pins (106) to force the pressure plates (96) against the workpiece 54 to hold it in place, and on further movement of the ram, plate 110 contacts plate 92 forcing hardened pieces (120) against blocks 82 to perform the punching operation. The plates (96) also act as stripper plates. On a pair of switches (278, 280), Fig. 13 (not shown), being closed, each of the die units is urged forward by a fluid-operated actuator (162) and a counting means comprising a series of slots (208) each admit light from a lamp to a photo-cell which transmits pulses to a circuit (not shown) which compares the pulses with a corresponding number derived from the tape. When there is coincidence a locking pin (182) is inserted in a rack (172) to prevent further forward movement by an actuator (180). The piercing operation is performed in two stages, and after the odd number holes have been formed the workpiece is moved sideways by an actuator (156) against a stop and the process is repeated for the even numbered holes. The two piercing operations may be performed in separate machines thus making for more economic loading of the punch.