Patent GB-1466925-A (GB)
Title: Record playback apparatus
IPC: G11B3/095
Filed: 1974-04-10
Abstract: 1466925 Capacitive playback-automatic control RCA CORPORATION 10 April 1974 [16 April 1973] 15791/74 Heading G5R In a capacitive play-back system, a manually initiated automatic control arrangement is provided for positioning and lowering a play-back stylus at the record start, for moving a carriage carrying the stylus so that the stylus tracks a radial path over the record during play-back and for raising the stylus and returning the carriage to its initial position after play. On operation of lever 22, power switch 26 having contacts 264, and 266 is operated via latched on/off lever assembly 24 to switch on a turntable drive motor 6 and apply power to the playback system, in addition a start/reject switch 36 is momentarily operated via arm 89 to bias transistors Q 1 , Q 2  to conduction and thereby pick up relay 278. The relay energizes motor 34 which drives a bracket 214 towards limit switch 240. During this movement fingers 238, 236, allow spring 116 to pivot arm 112 so that pinion 110 meshes with control gear-wheel 52 and to pivot arm 120 so that idler wheel 118 frictionally couples drive wheel 114 connected to the pinion 110 into drive engagement with shaft 28 which rotates with the turntable. The resulting rotation of the gear-wheel 52 moves carriage 18 carrying the pick up arm along rails 20 towards the record start position by engagement of a pin 54 of the carriage in a slot in the gear-wheel. The bracket movement also causes rotation of rod 178 having a D-shaped cross-section which via arm 174 disconnects the leadscrew drive of the carriage and via arms 174, 182 and 188 disposes pick up arm 14 on carriage 18 in its raised position. The movement ceases when switch 240 is contacted to open the relay and hence the circuits of motor 34. The carriage continues to move along the rails until a ball contact 42 on slide 25U, which is set in position relative to the control gear centre by manual activated set down control 40, engages a spirally shaped contact 44 on the gear-wheel, at which time transistors Q 3 , Q 4  are biased on to pick up relay 294 and thus drive motor 34 in the reverse direction to move bracket 214 towards limit switch 242. This movement causes disengagement of the drive to the carriage via pinion 110, engagement of the drive of the carriage by leadscrew 48 driven also from the turntable shaft and lowering of the pick up arm to bring the stylus into contact with the record. When the bracket reaches switch 242 the transistors and hence the motor are switched off leaving the apparatus in its play-back mode. At the end of play a signal at terminal 300 switches on transistors Q 1 , Q 2  and relay 294 so that the motor is again energized to move bracket 214 towards limit switch 240. This causes lifting of the pick up arm, disconnects the leadscrew drive and re-connects the carriage drive via pinion 140 and pin 54. This moves the carriage towards the record centre and then outwards towards its rest position. When the bracket reaches limit switch 240, the motor drive is switched off until follower member 90 on the on/off lever assembly 24 moves into a depression in cam 56 of the control wheel and causes contact 264 of power switch 26 to open (power still on via switch 268) and contact 266 to bias on transistor Q 3 , Q 4  and operate relay 294 to energize the motor in the reverse sense. The movement of the bracket towards switch 242 disconnects the drive to the carriage via pinion 140 and pin 54 and when switch 242 is actuated disconnects power from the apparatus. The position of the carriage and hence the position of the stylus in the record is indicated by a lamp 314 on arm 312 which co-operates with scale 320.