Patent GB-491160-A (GB)
Title: Improvements in or relating to electrical control systems for presses
IPC: B30B15/16
Filed: 1937-02-27
Abstract: 491,160. Switching systems. MACMILLIN, H. F. Feb. 27, 1937, No. 5962. Convention date, Aug. 24, 1936. [Class 38 (iv)] The mould-clamping plunger and the extrusion plunger of a plastic moulding-press are operated by pressure fluid under the control of a system of electric switches, relays, and time delay devices to secure delays of the reversal of movement at the completion of the strokes as required. The clamping plunger is supplied with fluid from a source 15 through forward and return pipes 16, 17 under the control of a valve 10, operated in one direction by a spring 14 and in the other by an electromagnet 13 supplied with current from the mains 47, 48 through switches 58, 59 operated by the winding 50. The extrusion plunger is operated in a similar manner by a valve 20 under the control of an electromagnet 23 and the winding 51. To prepare for the cycle of operations, switch 45 is set in the automatic position and switch 46 is set either in the same automatic position, when the press executes only one cycle of operations, or in the full automatic position in which the cycles are repeated until stopped by the operator. The starting switch 41 is now depressed and closes a circuit from main 47, through switch 45, normally closed emergency switch 42, normally closed timing switch 63, and winding 50 to main 48. Switches 57, 58, 59 are therefore closed, electromagnet 13 and valve 10 operated and the clamping plunger moves forward. When switch 41 is released, a holding circuit is completed by the closing of switch 57. When the clamping plunger has finished its forward movement, the increase of pressure of the operating fluid closes switch 38 by which a circuit is completed through normally closed timing switch 64 and winding 51 whereby the forward movement of the extrusion plunger is initiated. Closure of switch 60 by winding 51 also completes a circuit through relay winding 49 closing switches 55, 56. Switch 56 closes a circuit from switch 45 through windings 52, 53 of tuning devices each including an electromotor 66, 67. After an interval greater than the time taken to complete the extrusion stroke, motor 67 completes its movement and opens switch 64 thus de-energizing winding 51 so that the extrusion plunger commences its return stroke. If switch 40 is in its upper position, the circuit through winding 53 is completed through switch 39 which is closed at the end of the forward extrusion stroke so that the timing period starts at the end instead of the beginning of the stroke. Although switch 60 is thus opened, relay winding 49 is still energized by a holding circuit completed through switch 57 and its own switch 55. Motor 67 which is slower than motor 66 then completes its movement and opens switch 63 thus de-energizing winding 50 and initiating the return movement of the clamping plunger. The opening of switch 57 de-energizes relay winding 49. The clamping plunger on its return movement closes switch 37 which completes a circuit through winding 54 and starts timing motor 68, which, after an interval to allow cooling and the removal of the article from the press, closes switch 65. If the switch 46 is in the full automatic position, the circuit through winding 50 is closed and the cycle is repeated. A pilot light 43 is illuminated during the working of the apparatus.