Patent GB-804003-A (GB)
Title: Automatic apparatus for controlling synchronization of different film feeding mechanisms
IPC: G03B37/00
Filed: 1955-07-18
Abstract: 804,003. Automatic speed control systems. VITARAMA CORPORATION. July 18, 1955 [Oct. 25, 1954], No. 20774/55. Class 38 (4). [Also in Group XX] In a system in which a picture film is automatically synchronized with at least one other film, the relative timing of electric synchronizing pulses derived from the films controls the operation of synchronizing mechanism only if the error in synchronization is greater than one picture frame. In a system in which a picture mosaic is produced by a plurality of motionpicture projectors synchronized with a film from which sound is reproduced, each projector, such as 11, Fig. 2, is driven by a motor 43 through differential gearing 44 and the sound- .film unit 21 is driven by a motor 33. As in Specification 759,303 selsyns 36 and 50, driven with the sound-film unit and projector respectively, are connected to produce an output, on loss of synchronism, which is applied through an amplifier 56 to energize a reversible motor 47 providing an additional drive to differential gearing 44 to bring the projector into synchronism. A manually operated differential selsyn 66 facilitates synchronizing of the sound and picture actually produced. The present Specification introduces transducers 86, 88, responsive to synchronizing pulses recorded on the sound and picture film respectively, the outputs of which are applied to a controller 80 which compares the relative timing of the two sets of pulses and operates a reversible motor 71 as necessary to obtain synchronism between the sound and picture actually produced. Motor 71 adjusts a further differential selsyn 67 which may alternatively be structurally combined with differential selsyn 66. A switch 77, camoperated by motor 71, limits each operation of motor 71 to that required to correct by one frame. The synchronizing signals may be produced by notches, holes, protuberances or magnetic recordings on the films. In a modification, Fig. 4 (not shown), the contacts of electromagnetic relays respectively operated by the two sets of synchronizing pulses are interconnected so that one or other of two slow-operating relays is energized, according to which set of pulses is earlier in time, to directly control motor 47 to run in the appropriate direction to restore synchronism. In this arrangement the cam-operated switch ensuring correction by one frame at a time is also operated by motor 47. In modified arrangements of controller 80, Figs. 5 and 6 (not shown), a switch cam-operated by each projector is associated with a reversible ratchet motor or an electromagnetic relay counting circuit which operates to count the number of frames during the interval between operations of the relays respectively energized by the synchronizing pulses from the sound and picture films. This determines the extent of the error, correction of which commences at the end of the counting period. During correction a switch cam-operated by the correcting motor serves to reset the counting mechanism in steps so that the motor runs to correct a number of frames equal to the number of frames in error.