GB1072802A - Sound film apparatus - Google Patents

Abstract

1,072,802. Film drive mechanisms. A. W. KINGSTON. July 22, 1965 [July 28, 1964; Oct. 20, 1964], Nos. 30000/64 and 42805/64. Heading G5R. [Also in Division G2] A film traction mechanism for use with the projection of cine films with magnetic sound tracks comprises a reversible motor 47 driving film sprocket 17 through a resilient coupling, and film capstan 24 through peripheral frictional engagement between an idler wheel and driving shaft 48, the peripheral speed of the capstan being higher than that of the sprocket so that the film is tensioned, the difference in speed being taken up by slip between the wheel and the shaft. The resilient coupling consists of a disc 76 on the end of the sprocket shaft 78 with two diametrically opposite pegs which are interconnected by four springs with two similar pegs on gear 75 driven by motor 47 through worm gears and a toothed belt and pulleys. The motor also drives, through a similar coupling, the rotating apertured disc shutter 44, and the cam-operated claw feed (32) of Fig. 1 (not shown). This mechanism is carried in a deck (11) on which a cassette (10) is placed, the film being carried on reels (13, 14) which are driven by separately energized motors (45, 46), as in Fig. 2 (not shown), through clutches for forward or reverse film motion. The cassette takes doublerun film and contains the sprocket, capstan (24) with pressure roller (25) and edge guide (26) on a pivoting lever (29) and rollers (20, 21) with guides (19) to hold the film straight across opening (22) which receives the sound head (23) as described in 9242/64. A second opening (27) in the cassette receives a reflector (28) which directs light from lamp 34 through projection lens (39) for subsequent reflection on to a rear projection screen. An electromagnetic brake (61) is mounted on shaft (60), as in Fig. 2 (not shown), which drives a cross-shaft (62) carrying a contact drum (63) engaging two sets of contacts (64, 65) in the circuits of clutch (54) and brake (61) as in Fig. 2 (not shown). Brake (61) is by this means operated when claw (32) disengages from the film. The forward and reverse switch is biased to a neutral position and is held in the forward position by a solenoid which is de-energized automatically at the end of the film run when a metal foil on the film completes a circuit. A heat filter of glass with one ground face is used for prolonged projection of single frames, while the lamp unit may include a dichroic mirror at 28. Brake block (102) holds the sprocket (17), as in Fig. 1 (not shown), when the cassette is removed from the deck.