GB1406920A - Apparatus for compressing a workpiece - Google Patents

Abstract

1406920 Electromagnetic presses AMP Inc 19 April 1973 [15 May 1972] 18978/73 Addition to 1212953 Heading B3H [Also in Division F2] An electromagnetic press with a pair of dies 22, 50 for crimping a connector T to a wire W has a pair of electromagnets 30, 32 whose coils (W I ) (W II ), Fig. 2 (not shown), have a control circuit which provides for a small current in the coils and hence a slow approach of the dies until a switch 33 of the electromagnets is closed whereupon the current is allowed to increase to produce a large crimping force. The current through the coils is controlled by a driving circuit, 104, Fig. 3, controlled by a disable circuit 109 from a let-down circuit 112. The let-down circuit limits the average drive current to the electromagnets and is deactivated when the switch 33 closes to allow the current to increase. The driving circuit is initially activated by a start circuit 108 by a foot operated switch 116. The start circuit is switched off by a force control circuit 114 supplied with signals from a force transducer 52, Fig. 1, under the lower die, 50. The force control circuit has a reference force signal and compares the measure and reference force signals. The start circuit is also controlled by a clock circuit 110, Fig. 3, which switches-off the start circuit if the switch 33, Fig. 1, is not closed before a certain predetermined time after actuation of the windings. This could happen if an object such as a screwdriver is between the dies and preventing closing of the dies. A light signal is given to indicate malfunction. An electrooptical guard is also provided to stop the press if the operator has his hand in the zone of the dies. The guard comprises a set of photocells 53 on the press base 12 and a light source under the plate 55 for the fixed electromagnet 30.