GB325882A - Improvements relating to means for synchronising cinematograph and sound-reproducingapparatus - Google Patents

Abstract

325,882. Hepworth, C. M. Dec. 1, 1928. Addition to 324,005. Sound-reproducing apparatus associated with kinematographs. -A synchronizing device as claimed in the parent Specification is provided with a stop or a pair of stops to prevent the brush from leaving the contacts (this provision being necessary when the contacts are arranged in the form of an arc) and with a yielding coupling in the transmission from either of the machines to the brush or to the contacts. The coupling is such that it transmits, without yielding, the necessary torque during normal working of the apparatus, but yields and prevents the transmission of excessive torque when the brush bears against one of the stops. In the construction shown, resistances 6 in the, circuit of the motor 3 driving the picture projector 1 are connected to contacts 8 mounted on a quadrant 9 on a shaft 4 rotating with the projector. An arm 11 which carries the brush 10 for engaging with the contacts, and which is rotated bv a shaft 5 driven from the gramophone 2, is prevented by stops 13 from moving in either direction beyond the end contact studs 8. The shaft 5 is divided into two parts 15, 16, Fig. 3, which are coupled by a device comprising a disc 17, from opposite faces of which project screwed stems 18, 19 having right- and lefthanded threads, respectively. These stems screw into sleeves 20, 21, the sleeve 21 being fixed to the shaft portion 15, whilst the sleeve 20 has a squared recess in which the squared end of the portion 16 slidably engages. Light springs 22. 23 normally maintain the sleeves 20, 21 screwed up against the faces of the disc 17. With this arrangement, during normal synchronous running of the two machines, the arm 11 remains in the position shown in Fig. 2, but if the kinematograph lags or leads with respect to the gramophone, sufficiently for the arm 11 to be brought up against one of the stops 13, one of the springs 22, 23 will be wound up. At the same time, relative movement between one of the sleeves 20, 21 and the corresponding stem 18, 19 will occur. This yielding action of the coupling continues so long as one of the machines tends to over-run the other, and the coupling returns automatically to its normal position. when the speeds of the machines have been equalized. In a modification, the resistances 6 are stationary. instead of being mounted on the shaft 4. and are wired to slip rings on the shaft, these rings being connected to the contacts 8.