Patent GB-449616-A (GB)
Title: Apparatus for the synchronisation of electric motors
IPC: H04N3/36
Filed: 1934-12-31
Abstract: 449,616. Automatic control systems. DAY, E. H., 17, Lisle Street, Leicester Square, London. Dec. 31, 1934, No. 37351. [Class 38 (iv)] An electric motor is synchronized with a master motor by a variable resistance in its circuit responsive to differences of speed, the master motor transmitting periodic electric impulses which allow one resistance element to be moved through a constant distance during each impulse period while the other resistance element is moved bv the electric motor through the same distance if the two motors are running at the same speed, whereas a difference of speed results in a variation of the resistance so as to correct the speed of the electric motor. The apparatus may consist of a unit mounted upon an inverted box-like base 1, Fig. 1, containing plugs, switch, &c., the shaft 6 being driven from the electric motor which drives a cinematograph projector, while the master motor driving a gramophone, which may be located at some remote position, transmits periodic electric impulses to the unit by wires. The shaft 6 drives a gear-wheel 19 mounted on a sleeve 8b either by a direct coupling 10 or through gearing 7, 14, 15, 8 and a layshaft 16 so that the apparatus may be used with generators capable of running at different speeds. The gear-wheel 19 meshes with a gear-wheel 18 driving a drum 17 mounted on the shaft 24 and enclosing an annular resistance element 20 shown also in Fig. 5, the resistance having tappings 21 engaged by a wiper 33 also independently mounted on the shaft 24. The resistance 20 thus forms the element driven by the controllable electric motor while the wiper 33 forms the other resistance element moved intermittently through a constant distance under the control of electric impulses received from the master motor. These impulses act through coils 30, Fig. 4, upon a trip lever 29 which releases a catch 31 upon a disc 26 movable with a Geneva wheel 25 co-operating with pins 28 on a disc 23 which is driven through a spring 34 and slipping friction clutch from the shaft 6. The driving force for the wiper 33 is thus received from the projector motor through the shaft 6, but the wiper is timed by the gramophone master motor. The wiring diagram of the system shown in Fig. 6 includes a plug P2 for the mains supply M, a plug P3 for the gramophone 50 with its motor and impulse sending contact 49, and plugs P1, P4 connecting the projector motor L, the speed of which is regulated. The mains wiring is shown in thick lines, the low tension wiring associating the battery B, the coils 30 and the contact 49 is shown in thin lines and the external wiring in dotted lines. The main switch 2 closes the mains circuits to the projector motor L and the gramophone motor and also enables impulses to be sent from the contact 49 to the coils 30 as soon as the shaft 6 driven by the projector motor starts rotating, whereby contact 37 is opened and contact 38 closed. Contact 37 when open puts resistance 20 and relatively adjustable wiper 33 in circuit with the projector motor L. Contacts 43, 44 operated respectively bv the members driving the two resistance elements light lamps 51, 52 simultaneously when the two are in synchronism.