Patent GB-1448043-A (GB)
Title: Sound motion-picture system
IPC: G03B31/00
Filed: 1974-06-03
Abstract: 1448043 Sound motion-picture system POLAROIDS CORP 3 June 1974 [28 June 1973] Heading G2E In a sound motion-picture system having a cassette with an audio station and an exposureprojection station, and having drive means for advancing the film through both stations, these drive means co-operate to form a free loop of film which is maintained within predetermined limits. Fig. 1 shows the cassette 10, in which the film 30 is originally driven from supply spool 26 to take-up spool 28 past the sound-recording station 30 and the exposure station 36. For this sequence of operations the cassette is inserted into the camera 96 Fig. 5. The act of inserting the cassette and closing the door 116 releases a capstan 166 and the magnetic sound head 132 which it carries to be urged by a spring 160 so that the head enters the cassette. In this position the head is just out of engagement with the film 30. On initiating operation by pressing a trigger 140, the capstan drive motor 136 is energized, and a cable extension 146 is displaced which releases the capstan assembly 134 and head 132 into film engagement. The motor draws the film 30 at a substantially constant rate across the head 32. The actuation of trigger 140 also energizes a motor 126 which drives a claw mechanism 128 which advances the film intermittently and also releases the shutter, so as to photograph the scene through the lens assembly 106 as each film frame is aligned with the optical axis. Motor 136 is designed to advance the film slightly faster than the intermittent advancement due to claw 128. This causes a loop 148 to form, which increases in size until it engages and actuates a switch 138. This alters a circuit which causes motor 126 to increase in speed so that loop 148 is reduced in size and disengages from switch 138. Thus after loop 148 is formed it is maintained within narrow bounds. A microphone 110 is coupled to the head 132 so that as the film is advanced the sound is magnetically recorded on the film strip. When the cassette is to be removed from the camera, a protuberance on the film strip engages a mechanism which stops the capstan advancement while the claw advancement continues. Thus the loop is eliminated before removal of the cassette. A mechanical arrangement is also provided whereby the loop is eliminated if the door 116 is opened. After exposure has been completed, the cassette is removed from the camera and placed in a well 218 of the processor-projector apparatus 210. This has a projection lens 220, from which the image is reflected by a mirror 223 on to a viewing screen 214. A loudspeaker 230 and appropriate circuitry 228 are provided for reproduction of the sound recorded on the film strip. In the processing operation the film is driven in the reverse direction from spool 28 to spool 26. The stepped periphery of spool 26 engages an actuating assembly 66 which tears a tab 54 in the processing station 34, so releasing a supply of processing fluid 64. This now fills a chamber 68 from which a nozzle opening 70 guides the fluid on to the film strip as it passes. For the projection operation the film is once more run in the forward direction from spool 26 to spool 28, past station 36 which now functions as the projection station, being provided with a lamp, a reflector 50 and an opening 52. Again a capstan drive motor for uniform advancement of the film, and a claw drive motor for intermittent advancement, are provided. The capstan drive advances the film faster than the claw drive, so that a loop is again formed. The size of this may be controlled by a photo-cell detector arrangement Fig. 14 (not shown).