Patent GB-1005183-A (GB)
Title: Improvements relating to control apparatus for disengageable drive transmissionmeans used with power presses and similar machine tools
Inventor: DEYKIN RONALD FREDERICK
IPC: B30B15/14
Filed: 1960-12-15
Abstract: 1,005,183. Controlling clutches; machinery safety devices; fluid pressure brakes. HORDON, MASON & EDWARDS Ltd. Dec. 14, 1961, No. 43140/60. Headings F2F, F2J and F2L. To obtain " inching " of a press or a similar machine tool, a condenser C2 is discharged through a clutch control circuit including an electromagnetic control device, the clutch control circuit in this condition being isolated from any other source of current. The clutch driving the press &c. is operatively associated with a brake, the arrangement being such that the brake is disengaged simultaneously with clutch engagement, and vice versa, by liquid pressure produced by air pressure under the control of a solenoid-actuated valve. In one form, a three-phase electric motor 11, the Figure (Provisional), is controlled by a forward drive switch S10 and a reverse drive switch S11 to drive through a clutch to a press or like machine tool. In the rest position, a transformer 13 and a full-wave rectifier are connected across a smoothing condenser C3 and through a treadleoperated switch S 1 to a condenser C 1. When the treadle switch S1 is operated, the charging circuit to the condenser C1 is opened, and the condenser is instead connected through a preset switch S4 and through contacts Sid, S1b of the treadle switch, a closed switch S5b, a closed switch S3a and a closed emergency stop switch S7b to a solenoid-actuated valve 12, which is opened to admit pressure fluid to the clutch by the pulse of current transmitted. A holding current is transmitted from the rectifier circuit through a closed test jack J1, closed contacts 5, 6 of the motor reverse switch S11 in its rest position, a resistor R1, and the closed contacts S5b, S3a, S7b. As the press rotates, the switch S3a is rotated with it, so that after one revolution, the contacts of this switch are opened, the valve 12 is de-energized, the press clutch is disengaged and the associated brake re-engaged. The treadle switch S1 can be released as soon as the cycle of operations has been commenced. To effect continuous engagement of the press clutch, the switch S4 is actuated to open the contacts S4a and instead close the normally opened contacts S4b, the latter short-circuiting the press-driven switch S3a. The switch S7 may be operated at any time for an emergency stop. For inching of the press as provided for by the invention, a switch S5 is moved from the position shown to disconnect the condenser C1 from the circuit, and instead connect the condenser C2 into the circuit. The condenser C2 is normally charged through contacts S2b from the transformer and rectifier 13, these contacts being opened, simultaneously with closure of contacts S2c, on operation of a switch S2 to discharge the condenser through a rheostat R 2 , the switch S7 and thence to the solenoid of the clutch-brake control valve 12. The duration of the current pulse, and hence the duration of clutch engagement for each actuation of the switch S2, is dependent upon the adjustment of the rheostat R 2 . With the condenser C2 connected to the circuit, the latter is isolated from any other source of current. Inching of the press in the reverse direction can be effected by operating the reverse motor switch S 11. In a modification, Fig. 1, the treadle switch is replaced by a combined treadle switch FS and guard-operated switch SG1, and a bank of switches S11 ... S19 is provided to control the various functions of the clutch-brake combination. In the first position of the switch bank, a transformer and rectifier 13 connected across a smoothing condenser C3 supply current to a condenser C1, operation of the treadle switch FS opening contacts FSa to break a charging circuit made through closed switches S11, S12, and apply the charge on the condenser through contacts FSb, a rectifier w5 contacts S3a of a press-actuated switch, a closed switch S7 and a second guardoperated switch SG2 to the air valve 12. The latter is then opened and a holding current is applied through a closed switch S13, a resistor R1 and a closed jack J1 from the transformer and rectifier circuit 13. In this form, the air valve 12 is shown as connected to an intensifier 15 supplying liquid under pressure to a brake 20 and a clutch 19, the latter being of the type described in Specification 941,306 (see Division F2). On completion of a revolution of the press, the switch S3a is opened, and the air valve 12 is closed. By moving the switch bank S11 ... S19 to a second position, switches S11, S12 and S13 are closed as before, and a switch S14 is also closed. Holding current can now be passed from the rectifier through the jack J1, resistor R1, the switches S13, S14, closed contacts FSc of the treadle switch FS, a rectifier w6 and thence to the air valve 12. Accordingly, the opening and closing of the press-actuated switch S3a does not effect operation of the air valve 12, and the press is operated continuously. On moving the selector switch bank to a third position, the condenser C1 is isolated by the opening of switches S12, S16 from the smoothing condenser C3 and the charging circuit, but the condenser C2 provided by the invention is now charged through an inching switch S2 of the push-button type, and through a closed switch S15. Operation of the push-button switch S2 breaks the circuit between the condenser C2 and the charging circuit 13, and instead connects the condenser through a rheostat R2, the rectifier w6, and the switches S7, SG2 to the air valve 12 for clutch engagement. Adjustment of the rheostat R2 controls the duration of the pulse supplied from the condenser C2, and hence the length of time during which the clutch is engaged. With the condenser C2 connected to the air valve 12, the latter is isolated from any other source of current. In this form, the clutch control is also affected by closure of a safety guard (not shown), and the switch bank is provided with a further four positions incorporating such control. In the fourth setting of the switch bank, single cycle working is obtained, the switches S12, S13 and S16 being closed. When the guard is opened, the upper contacts of the switch SG1 are closed, and the condenser C1 is charged. On closure by hand of the guard, the lower contacts of the switch SG1 are closed instead, and the condenser C1 discharges through the switches S16, S17, the rectifier w5, closed contacts S3a &c. to the air valve 12. In the fifth setting of the switch bank, the switches S13, S16, S18 and S19 are closed, and this setting is used when the guard is movable by a power-energized servo-controlled by a solenoid-operated valve GSV. The guard is closed by closing contacts FSd of the treadle switch. The sixth setting of the selector switch bank provides continuous working, the switch S14 being closed to short the press-actuated switch S3a. In the seventh position of the selector switch bank, the switch S17 is also closed, to obtain operation similar to that of the fourth setting, or of the sixth setting. In an eighth position of the selector switch bank, all the switches are open and the control circuit is inoperative. The clutch can be disengaged with simultaneous engagement of the brake at any time by opening the emergency switch S7. Specification 1,005,182 is referred to.