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ABSTRACTS OF RECENT U.S. PATENTS
Reissue 18,108. Producing Silent Intervals on Sound Tracks. LEE DE FOREST. Assigned to General Talking Pictures Corporation. June 23, 1931. Silent intervals may be produced on the photoelectric sound track of a sound-onfilm positive and the sound track freed of any densities in the emulsion of the film that may produce ground noises by blackening the positive at all portions of the sound recording part of the film where silence is desired. The developed sound-on-film negative produces a sound track on a positive film and the two films are run through a printer where an auxiliary printing light produces a blackened interval on the positive film where silence is desired.
In order to blacken the positive film at appropriate intervals the negative or master film is provided with notches at those portions where a blackened positive is to be produced. These notches serve to control the operation of a switch which cuts on or off the auxiliary printing light to produce the silent portions of the positive film.
1.809.815. Safety Device for Motion Picture Projecting Machines. J. F. ADAMS. Assigned to Sentry Safety Control Corp. June 16, 1931. Safety cut-off and douser for protecting the film against ignition in the event that the driving motor on the projector should drop below a predetermined speed. A mercury switch is provided for interrupting the motor circuit when the speed falls below a predetermined value. A shutter is also electromagnetically actuated for obstructing the rays of light passing through the film when the speed falls below a safe value.
1.809.816. Centrifugal Switch for Controlling Film Feeding Mechanism. J. F. ADAMS AND THOMAS T. ALLEN. Assigned to Sentry Safety Control Corp. June 16, 1931. The film feeding mechanism is controlled by means of a centrifugal switch. The centrifugal switch has contactors which, when the film feeding mechanism and switch are operated at a predetermined speed, are held outward centrifugally. However, when the film feeding mechanism and switch fall below the required speed, the contactors are swung inward and make contact with the contact rings which break the motor circuit, and stop and intercept the light rays upon the film. By means of the centrifugal switch the proper filming may be controlled.
1.809.817. Safety Unit for Motion Picture Projectors. THOMAS T. ALLEN AND JOHN F. ADAMS. Assigned to Sentry Safety Control Corp. June 16, 1931. A safety switch for motion picture projectors which operates if the film fails to move at or about a certain speed through the path of the rays of light emanating from the projection lamp to cut off the light rays and bring the projector to a stop. A unit is provided for stopping the projecting mechanism and intercepting the rays of light passing through the film upon the occurrence of any incident or accident which might cause the film to ignite. The safety device includes an electromagnet, a relay system, and a centrifugal switch electrically connected with the motor circuit and arranged to control a shutter mechanism for insuring 462