Patent GB-456303-A (GB)
Title: Improvements in or relating to electric control means for power driven machines
IPC: H02P29/00
Filed: 1936-01-09
Abstract: 456,303. Combined clutches and brake mechanism. IGRANIC ELECTRIC CO., Ltd., 147, Queen Victoria Street, London.-(Assignees of Hodgson, H. E. ; N. 12th Street, Milwaukee, Wisconsin, U.S.A.) Jan. 9, 1936, No. 772. Convention date, Jan. 10, 1935. [Class 80 (ii)] [See also Group XXXIV] In electrically controlled clutch and brake mechanism for presses and other machines in which the clutch and brake windings are simultaneously energized to engage the clutch and release the brake, these windings are first connected in parallel and then automatically, by a time delay relay, in series whereby the brake winding is initially over-excited to ensure prompt release of the brake before engagement of the clutch. The control also provides for automatic stopping of the machine after a cycle of operation, for continuous operation and for " inching " in steps of extent determined by the time relay. The apparatus comprises push-button switches 6 ... 9 controlling relay switches 1 ... 4 of which switches 1 ... 3 are single throw and normally open and switch 4 is double-throw with contacts 4b, 4c normally closed and open respectively. The time-relay 5 controls the change over of the brake and clutch windings B, C from parallel to series by the contacts 5b and switches 3, 4 and the " inching " operation through the contacts 5c. The relay 5 responds to a certain current-strength delay in reaching which is imposed by the inductance of the clutch winding C in the circuit of which it is included. The relay winding receives current also through a shunt circuit containing fixed resistances r, r<1> by which the time element is determined and also in the " inching " operation through main and vernier rheostats r<2>, r<3> by which the time element can be adjusted. Limit switches 10, 11 operated by the press are provided, the switch 10 being open during the down stroke of the press and closed during the upstroke while the switch 11 is closed throughout a cycle and opened only when the press slide reaches its upper limit. A manual controller 12 has contacts 15 ... 31 which can be set in the following positions to determine various methods of control of the press :-(1) " Long " : switches 7, 8 are depressed during the down stroke of the press which then completes a cycle automatically. Closing of switches 7, 8 energizes switches 1, 2 through line L<1>, switches 6, 7, 8, contacts 18, 19 and line L<2> and energizes switches 3, 4 through contacts 18, 20 and contacts 5b of relay 5. The brake and clutch windings B, C are thus connected in parallel (Fig. 2) with a resistance R in the clutch circuit, the clutch being engaged and the brake rapidly released. The winding of relay 5 receives current through the clutch circuit and also through a shunt circuit including contacts 17, 18 and resistances r, r<2>, r<1>. Operation of the relay after the time interval opens contacts 5b thus de-energizing windings 3a, 4a of switches 3, 4 thereby opening contacts 3, 4b and closing contacts 4c so that the brake and clutch windings are connected in series and the resistance R cut out (Fig. 3). The current in the brake winding is thus reduced. When the press reaches the down limit the switch 10 is closed and the switches 7, 8 may be released, the circuit through the windings of switches 1, 2 being maintained through switch 10, auxiliary contacts 1b of switch 1 and contacts 17, 19 of controller 12 until the cycle having been completed switch 10 re-opens and stops the press ; (2) " Momentary " : the press completes a cycle upon momentary depression of switches 7, 8. The limit switch 11 being closed, the circuit through the windings of switches 3, 4 initially established by the switches 7, 8 is maintained through switch 11, contacts 15, 16, contacts 1b of switch 1 and contacts 17, 18 until switch 11 is opened upon completion of the cycle. The brake and clutch windings B, C are connected first in parallel and then in series by operation of relay 5 as in the previous case ; (3) "Continuous": the press runs continuously upon momentary depression of switches 7, 8, the circuit through the windings of switches 1, 2 being maintained after release of switches 7, 8, through the normally closed push-button switch 6, contacts 26, 25 of controller 12, contacts 1b of switch 1, and windings 1a, 2a. Circuits through the brake and clutch windings and relay 5 are thus established as in Figs. 2 and 3 and the press runs until depression of switch 6 opens the circuits of switches 1, 2 and thus of the brake and clutch ; (4) " Inching " : Fig. 7 ; depression of switch 9 closes the circuit of switch windings 1a, 2a through switches 6, 9, contacts 30, 31 and contacts 5c, thus connecting the brake and clutch windings in series at once, to start the press. A circuit through relay 5 additional to that through the brake and clutch windings, is established through contacts 30, 31 and resistances r<1>, r<2>, r and another circuit through this relay through contacts 30, 27, vernier rheostat r3, slider of rheostat r<2> and resistance r. After an interval determined by the adjustment of rheostats r<2>, r<3> the relay 5 operates to open contacts 5c, thus de-energizing switches 1, 2 and stopping the press. Contacts 28, 29 with contacts 1b of switch 1 provide a shunt around the switch 9 to render momentary depression of that switch sufficient to effect a full inching step. An overload relay 13 has its winding connected between line L<2> and ground and is thus rendered responsive upon grounding of the system to de-energize switches 1 ... 4 and thus open the circuit of the brake and clutch windings.