Patent GB-797079-A (GB)
Title: Improvements in or relating to electric controllers
IPC: G05B19/06
Filed: 1955-02-25
Abstract: 797,079. Control of A.C. motors. IGRANIC ELECTRIC CO., Ltd. Feb. 25, 1955 [March 8, 1954], No. 5682/55. Class 38 (3). A motor 10 having a flywheel 13 is adapted to be coupled to a press 60 through a clutch and brake combination 15, means being provided for operation of the machine through a given cycle but requiring re-initiation of each cycle, together with further means for converting the system to one providing for automatically initiating repeated cycles of the machine. Momentary closure of switch 14 energizes contactor winding 12a to connect the driving motor to the power supply-lines, and, in order to operate the press for a single cycle, a selector switch is set to close contacts 24a, 24b, 24c and 24d whereupon a contactor winding 26a is energized. Simultaneous operation of manual switches 28, 30, then energizes contactor coils 20a and 22a so completing the circuit for a winding 18 of an electromagnetic air valve so that the clutch is engaged and the brake released, and the motor commences to drive the press. When the press ram has moved a predetermined distance, limit switches 36, 38 are closed, allowing release of the manual switches 28, 30, without stopping the press. Limit switches 32, 34, are then opened by movement of the press ram, thus de-energizing coil 26a. The limit switches 32, 34 are re-closed before the ram reaches the end of its travel but interlock contacts 20d, 22d actuated by windings 20a, 22a, prevent re-energization of the winding 26a at this time. At the limit of travel of the ram, limit switches 36, 38 are opened to de-energize windings 20a, 22a, so as to de-clutch the motor and apply the brake. The press is thus prevented from operating continuously even if the switches 28, 30 are held in their depressed positions. To effect continuous operation of the press, the selector switch is set to close contacts 24e-24k, manual switches 42, 44 being closed to energize contactor coil 40a which has selfholding contacts allowing immediate release of the push-buttons. A lamp 46 indicates that the system is set for continuous operation. The contactor winding 26a is energized through contacts 24e, 24f, so that depression of manual switches 28, 30 energizes windings 20a, 22a, to couple the motor to the press. Momentary closure only of both manual switches 28, 30 is necessary to initiate continuous operation, and subsequent operation of limit switches 36, 38 has no effect on the energization of winding 18. The press may then be stopped by means of switch 16 or by moving the selector switch away from its " continuous run" position. The switches 42, 44 must be closed prior to each continuous operation of the press, irrespective of the manner in which the press was previously stopped. Unless the manual switches 28, 30 are operated within a predetermined time interval after the actuation of switches 42, 44, a time delay relay 54a, 54b de-energizes the contactor winding 40a. Inching operation of the press is provided by moving the selector switch to close contacts 24l, 24m, and then depressing the manual switch 48, 50 for the necessary period.