Patent GB-319791-A (GB)
Title: Synchronizing means for motion picture projectors and sound reproducing mechanisms
IPC: G03B31/00
Filed: 1929-09-28
Abstract: 319,791. British Consolidated Investments Corporation, Ltd., (Assignees of Ebeling, C. W.). Sept. 29, 1928, [Convention date]. Gramophones associated with kinematographs. -In the synchronous reproduction of sound and projection of pictures wherein the two apparatus are driven by separate motors, provision is made for manually adjusting the speed of one apparatus and also for controlling it automatically from the other to maintain synchronism. As shown, the sound-reproducing machine 6, Fig. 1, is driven by a motor 7, and the picture projector 5 is driven through a shaft 43 and and a friction clutch 13 on a divided shaft from a motor 8. The motor 8 drives through a flexible coupling 14, Fig. 2, a hollow shaft carrying a flywheel 12 with friction face 13, and this hollow shaft houses one end of a shaft 10<1> geared to the shaft 43 and carrying a sleeve 31 connected through a centrifugal regulator 24, 25 slidably connected with the shaft by pins 20, 23 with a friction disc 26. The sleeve 31 has a circumferential groove engaged by a yoke 29 mounted on a fixed pivot 28 and extending between springs 35, 36 bearing against collars and capable of having their compression adjusted manually by means of a hand-operated spindle 41 and gearing so as to adjust or regulate initially the action of the regulator in engaging the disc 26. Synchronism between the two apparatus is maintained automatically by the action of electromagnets 86, 86<1>, one or other of which is excited by a switch carried by the planet wheel of a differential gear 47, through which the gramophone is geared with the projector. In case of variation in the relative speeds of the two apparatus, one or other of the electromagnets 86, 86<1> is excited and operates on the tail 49 of the yoke 29 to vary the compression of one or other of the springs 35, 36 and thereby the friction drive between the regulator 25 and the flywheel 12 to restore synchronism. A modified construction of the controlled friction transmission to avoid end thrust is shown in Figs. 5 and 6, wherein the flywheel 12<1> driven from the motor has a friction periphery and drives the transmission shaft through pivoted arms 60 integral with arms controlled by springs 62 and the centrifugal action of weights 59. The arms 60 are pivoted to the opposite ends of a bracket loose on the transmission shaft, and the springs 62 are connected to a disc plate which is in driving engagement with the transmission shaft through a stiff spiral spring and has slots to receive the tapered ends of bars extending from a sleeve rotatable with but slidable on the transmission shaft. The sleeve can be adjusted manually to advance or retract the bars for adjusting the tension of the springs 62 initially, and is also automatically adjustable for maintaining synchronism between the gramophone and the projector when one or other of two electromagnets are excited as previously described. For this purpose, the sleeve is provided with right- and left-hand threads gearing respectively with and normally driving wheels carrying ratchet wheels and, when one of the electromagnets is excited, locking of one of the ratchet wheels is effected which causes the corresponding thread and the sleeve to be moved longitudinally and advance or withdraw the tapered ends of the bars relatively to the slots in the disc plate to vary the tension of the springs 62. The Specification as open to inspection under Sect. 91 (3) (a) shows a diagram arrangement for synchronously controlling two alternately operating sound reproducing machines and also refers to U.S.A. Specification 1,303,047. This is not included in the Specification as accepted.