Patent GB-502520-A (GB)
Title: Improvements in or relating to switching systems for use in photographic sound film recording apparatus
IPC: G03B31/00
Filed: 1938-05-19
Abstract: 502,520. Actuation of switches. ELECTRICAL RESEARCH PRODUCTS, Inc. May 19, 1938, No. 14947. Convention date, May 22, 1937. [Class 38 (v)] [Also in Group XXXVIII] A sound-film recording system comprises means for marking the film while it is stationary, a shutter for screening the film from the action of photographic sound-recording means until the film is in motion, and electromagneticallycontrolled means for opening the shutter at a predetermined time after the film has started to run. The invention is particularly adapted for systems in which the film is marked by a punch, and a " take number " for co-ordinating the record with a simultaneously recorded picture film is photographically recorded by a so-called " slater." There is preferably employed a solenoid 51 which, when energized at the starting of the film, switches open the circuit of the marking devices so as to prevent their operation during movement of the film, and which simultaneously operates a second switch to bring the recording lamp (previously glowing dimly) to full brilliance. These switches consist of a mercury switch 68 (for the marking devices) and a mercury switch 36 with three fixed contacts 69, 70, 71 (for the recording lamp), both switches being carried by a tiltable holder connected by a link 12 to a rod 10, which is connected to the solenoid plunger. The rod 10 is carried by a bell-crank lever arrangement comprising arms 15, 41 pivoted at 11. An arm 40 pivoted at 42 on the arm 41 carries at one end a pin 43 adapted to engage with a worm 44 driven from the main driving motor of the recorder. At the other end of 40 is a roller 14, which when the arm 40 rotates on its pivot 42 is adapted to engage a contact-closing cam 13. An arm 29, pivoted on a bracket 16 on the arm 15, and controlled by the lever 40, has a bent extension 30 adapted to actuate a contact-spring 27, and to shift it, when required, from engagement with a contact 28 into engagement with a contact 26. Fig. 10 is a circuit diagram for the whole system, which is one such as is described in Specification 319,274, [Class 38 (iii)], in which sound and picture recording devices are interlocked with other like devices through a system diagrammatically shown at 54. The driving motor 50 for the sound film is connectible to a current source G through 54 by a switch 53; but before this switch is closed, the punching and slating devices 65 ... 67 are operated by actuation of their switches 63, 64, the mercury switch 68 being in the position shown in Fig. 2 for closing the circuits through 65 ... 67. On the closing of the switch 53, simultaneously with the starting of the motor 50, the solenoid 51 is energized. Initially, a small current is passed through the sound-recording lamp 72, which is shunted by a resistance 76 across the contacts 69, 70 of the mercury switch 36. When, however, the solenoid 51 is energized, the switches 68, 36 are tilted, disabling the circuits of the punch and of the slater lamps by the opening of 68, and bringing the recording lamp 72 to full brilliance by opening 69, 70 and closing 70, 71. The finger 43 on the arm 40 having been engaged with the worm 44 when the solenoid 51 is energized, rotation of the worm causes the finger to travel for a predetermined period after the starting of the film, at the end of which tlie roller 14 on the switch arm bears against the cam 13, whereby contacts 22, 23 are closed and a magnet 131 is energized to open a shutter which normally obscures the sound-recording beam. As described in Specification 14948 /38, the shutter is automatically latched in the open position, so that it remains open when by further movement of the roller 14 past the cam 13 the contacts 22, 23 open. When recording is stopped or finished, with the stopping of the motor 50, the solenoid 51 is de-energized, and this results in the member 30 bearing against the spring contact 27 to move it away from contact 28 into engagement with 26, thereby closing a circuit through a magnet 130, so that the shutter is closed. De-energization of the solenoid 51 also restores the mercury switches 68 ... 71 to normal and disengages the switch arm 40 from the worm gear. The switch arm is then restored to normal under the action of a spring (not shown), and causes contacts 26, 27 to open whilst contacts 27, 28 are re-closed. A safety device for stopping the motor in an emergency comprises a film-operated switch 60, which when closed-energizes a relay 52 to break the motor circuit.