Patent GB-711480-A (GB)
Title: Improvements relating to the actuation of electromagnetic relay means, particularly for the control of cinema programmes
Inventor: FOY WILLIAM JAMES
IPC: G03B21/32
Filed: 1951-01-26
Abstract: 711,480. Kinematograph apparatus. ESSOLDO CIRCUIT (CONTROL), Ltd. Jan. 15, 1952 [Jan. 26,1951; Sept. 4, 1951], Nos. 2107/51 and 20897/51. Class 97(1) [Also in Group XL(a)] Means for successive actuation of electromagnetic relays, used in effecting change-over between kinematograph projectors automatically, comprises an electrical current amplifying device with an input circuit comprising a pair of contacts and an output circuit so connected to the relays by a current responsive device so that successive bridging of said contacts operates the relays in succession. In the form shown in Fig. 1 (2107/51) a power transformer MT has secondaries supplying (a) cathode heating for valves T1, T2, D; (b) a rectifier providing power for projector arcs and motors and anode supplies to the valves T2, D; (c) anode supply to the valve T1; (d) grid bias supplies to the valves T1, T2. Control of power supplies to projectors 1 and 2 is effected through relays A1, A2 (arcs) and M1, M2 (motors), by way of terminals 1, 2, 3, 4, energization of each relay completing the appropriate supply circuit. Fusible conducting elements are placed between the carbons of the arcs so that they strike automatically when a voltage is applied. Movements of relay BS on energization or de-energization illuminate indicator lamps SL1, SL2 alternatively and through terminals 5, 6 to effect alternative movements of the dowsers. Similarly, relay SOF effects sound change-over. The contacts CH on relay BS are in the cathode heating circuit of the diode D and are opened when the relay is energized. The projection cycle is started by closing switches SA2, SM2, SP2 to energize relays A2, M2, BS and SOF, to bring projector 1 into action, The relays have hold-on contacts. For automatic change-over working a switch K is in the "Auto " position. To effect change-over, a succession of impulses is derived from a series of conductive traces, which may be of the kind described in Specification 711,478, near the end of the outgoing film. The impulses are applied to the grid of T1 to produce anode current pulses in the coil OC of stepping relay SS. The arm Cl moves successively over contacts S2a, S3a, S4a. Movement over S2a, S3a energizes the relays A1, M1 to switch on projector 2. Movement to S4a energizes the ends of the coils of relays BS, SOF which are normally grounded through R2 and causes the relays to drop out to effect sound and dowser change-over and to close contacts CH to heat the cathode of the diode D. The delay due to the heating, adjustable by the resistance R1, ensures that the change-over is complete before the diode anode current closes a relay CO to change-over, at contacts COC1, leads P1a, P2a by which the pulses for effecting changeover are applied from whichever projector is running in readiness for change-over to the other. The coils of relays A1, M1 or A2, M2 relating to the projector in use, are grounded through other contacts COC3 on the same relay. All the coils are also grounded through contacts on the relay I. After, change-over therefore a pulse of current through the latter relay causes the relays Al, M1 or A2, M2, relating to the projector not in use, to drop out to stop that projector. The pulse of current is derived from the valve T2 to the grid of which an impulse is applied as the film runs out from the outgoing projector, by leads P2a or P2b, the contacts COC2 of relay CO selecting whichever is appropriate. Projection is also stopped by film breakage. When further impulses are applied to the grid of T1 to effect further change-over the arm Cl of the stepping relay moves over contacts S5a, S6a, S7a to energize relays A2, M2 and to re-energize BS, SOF. During this change the contacts CH open to allow the cathode to the diode D to cool. This provides a delay before the relay CO drops out. During each change-over the arm C2 of the relay moves over contacts S2b or S5b to operate audible warning devices connected to terminals 7, 8. At the end of the second change-over it moves to a contact S7b to energize the resetting coil RC which also operates the trio TR to disconnect the arm Cl during resetting. The resetting coil can be energized, for initial setting, by a switch RS. When it is desired to break the automatic change-over sequence to insert other matter into the programme the.switch K, the position of which is shown by indicator lamps AL, DL, is switched to "Drum" during the last film of the automatic sequence. The coil CO of the stepping relay is thereby isolated and the anode current pulses from T1 applied to a relay DC1 to energize a connection 9 to a programme controller as in Specification 711,481 which may restart the automatic sequence when required. The current supply to the arm C1 may be taken through further contacts on the relays A1, A2, M1, M2 so as to be broken when neither projector is operating. The relay SOF may be located on the sound apparatus and actuated through further contacts on the relay BS. In a modification, the impulses derived from the conductive traces on the outgoing film are applied to the grid of a thyratron to cause it to fire successively. Each time it fires it discharges a condenser through a relay with hold on contacts, which relay completes the charging, circuit of a condenser which, when the thyratron fires again, is discharged through a further relay. In this way the relays necessary to start one projector are energized. The last of the sequence has contacts which effect a change-over to leave the circuit ready to operate a further sequence of relays to start another projector. The outgoing projector may be stopped manually or automatically. Specification 711,479 also is referred to.