GB415184A - Improved film driving mechanism for sound reproducing or like apparatus - Google Patents

Abstract

415,184. Flywheels. RADIO CORPORATION OF AMERICA, 570, Lexington Avenue, New York, U.S.A. March 25, 1933, No. 9098. Convention date, March 31, 1932. [Class 122 (i).] In sound-film reproducing, recording, &c. I apparatus the rotary film supporting member is carried by a shaft mounted on anti-friction bearings and which positively drives a very light member associated with or enclosing a flywheel, independently mounted on antifriction bearings and driven by the light member either magnetically or through a fluid, the rotary member and the shaft being driven solely by the film. The film 2 is drawn over a drum 1 which is fixed on a shaft 7 mounted on ball bearings 8, 9. A casing 10, of very light weight, is also fixed to the shaft, and encloses a flywheel 11, which can run freely on ball bearings 13 on the shaft. The space between the flywheel and the casing is filled with a fluid such as oil. The flywheel may be hollow, as shown in dotted lines, the main mass being near the periphery. As the film is drawn over the drum 1 by a sprocket 16 running at an approximately constant speed, it rotates the drum, the speed of which is kept uniform by the flywheel. The elasticity of the film causes the formation of loops above and below the drum when the flywheel has acquired its full speed, and slight variations in the speed of the driving sprocket merely alter the length of the loop 19. In a modification, the bearings for the flywheel are carried by a fixed stub shaft, in line with the shaft 7 and projecting into the casing 10 from the opposite side. In a further modification, Fig. 4, a disc 51 is mounted on the shaft 7 and drives the flywheel through an eddy-current disc 50 co-operating with magnets 52 on the flywheel. In another construction, Fig. 5, a flywheel designed to compensate for the effect of temperature changes is used. The body 11 of the flywheel is connected by springs 60 to a rim 11<1> which may be made like a compensated balance-wheel in a watch, and which is close to the wall of a casing 10 filled with oil. When the temperature changes, the rim advances towards or recedes from the casing, thereby compensating for change in viscosity of the oil. Alternatively, the casing 10 and the rim 11<1> may be made of metals having different coefficients of expansion. In another construction, Fig. 6, a flywheel is fixed yieldably with respect to an oil-container 71 by springs 72 attached to partitions 73. These extend into V-shaped notches in the flywheel and have apertures 74 through which the oil passes if relative motion between the flywheel and the casing occurs. The Specification as open to inspection under Sect. 91 also shows a construction, Fig. 4 (Cancelled), in which an eddy-current disc 40 is driven by magnets 41 energized by alternating current, providing a rotative force which overcomes the slight friction of the ball bearings. This subject-matter does not appear in the Specification as accepted.