Patent GB-658794-A (GB)
Title: Apparatus for use in sound recording and reproducing using disc records
IPC: G11B25/00
Filed: 1948-12-06
Abstract: 658,794. Pick-up mountings and tool arms. ROE, D. O., and BIRMINGHAM SOUND REPRODUCERS, Ltd. Dec. 6, 1948, No. 31575. [Class 40 (ii)] A locating device for the transducer of a sound reproducing or recording apparatus using disc, cylinder or strip records having spiral or like tracks, includes means for raising and lowering the arm and a series of adjustable stops on a support parallel to the traversing movement of the transducer, the transducer being arranged to make engagement with the stops during a traversing movement when it is in the raised, inoperative position. The transducer arm 7, carrying counterweight 8, rides by means of two pairs of rollers 9 on a rail 4. It pivots about the rail 4 and has three angular positions determined by the position of an eccentrically mounted rod 11 carrying a longitudinallyextending projection 12. In the intermediate raised position shown, a spring-loaded pawl 25 mounted on the transducer carriage 6 lies in the path of the stops 20, but in the fully raised and lowered positions attained respectively by clockwise and anti-clockwise rotation of the eccentric rod 11, the pawl lies free of the stops. The stops 20 are mounted on sleeves 18 which may be clamped in chosen positions on a rod 17. The stops 20 are finely adjusted by screwing them into and out of the sleeves 18. With the transducer arm in the intermediate raised position of Fig. 4, the pawl 25 may be set against a stop 20, or a stop set against the pawl, in a position corresponding to a given passage on the record. The transducer may be set in a desired position with aid of a vernier scale 28 on the carriage 6 which moves above a scale 26 mounted on the main frame. Transparent graduation slits in the two scales 26, 28 are illuminated by a pair of lamps 30 mounted in the carriage 6. The eccentric rod 11 is screwcoupled with a control knob 45 at one end and is engaged at the other end by a return spring 46. By turning the knob 45 whilst the rod 11 is in contact with the carriage 6, the position of the transducer arm 7 can be finely adjusted. The rod 17 may be detachable from the frame so that a rod with set stops 20 may be removed and another substituted. A secondary carriage 34 is splined on to the rail 4 to be rotatable therewith and is urged to the left against the carriage 6 by a spring-loaded drum 36 to which it is connected by a cord 37. A horizontal rod 39 on the secondary carriage 34 engages the same stop 20 as the pawl 25 and continues to engage it after the transducer arm has been lowered for reproduction and has travelled to the left. When it is desired to discontinue reproduction &c., and to move the carriage 6 to the next stop 20, the rod 11 is rotated to raise the arm to the intermediate position of Fig. 4. At the same time a leaf-spring 42 on the rod 11 momentarily engages a radial arm 41, Fig. 7, on the rod 4 and causes this rod to rock in its bearings, thus rotating the carriage 34 and swinging the rod 39 away from the stop 20. A spring 43 immediately brings the rod 4 and rod 39 back to their normal positions so that, after the two carriages 6, 34 have travelled to the left under the influence of the spring 36, the rod 39 abuts against the next stop 20.