Patent GB-374908-A (GB)
Title: Improvements in or relating to gramophones
IPC: G11B17/02
Filed: 1931-02-12
Abstract: 374,908. Gramophones. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, and JACOBY, H. C. E., of General Electric Co., Witton, Birmingham. Feb. 12, 1931, No. 4484. [Class 40 (ii).] Automatic control means in a gramophone comprises two relatively-movable members one of which carries a trigger member adapted to co-operate with a shoulder on the other member, movement being transmitted from the tone-arm to one of the members and thence by resilient means to the second member, and a holding device adapted to hold but periodically to release the second member, the trigger member being operated to effect the control, which may be the application of a brake or operation of a switch, when the stylus reaches a groove of coarse pitch and relative movement between the two movable members exceeds a predetermined value. As shown in plan with parts removed in Fig. 1 and in sectional side elevation on the lines III-III in Fig. 3, a plate 7, secured to the top plate 6 of an electric driving motor, supports a pillar 8, Fig. 3, whereon is mounted rotatably a pillar 9 to which are clamped rings 12, 21 secured to arms 11, 15, respectively. The arms 11, 15 have pillars 10, 14, respectively, thereon so that when the reproducer carrier-arm 2 moves towards the centre of a record the arm 15 and sleeve 9 are moved in the same direction, whereas when the arm 2 is moved outwards the arm 11 and sleeve 9 are moved counterclockwise. Secured to the sleeve 9 to turn therewith is a lever 18 on the end of which is mounted rotatably a roller 19 which extends within a slot 22 formed in a member 23 which is mounted with a member 24 on a common bearing member 25. The members 23, 24 are connected by a tension spring 30 and their normal relative position may be adjusted by a screw 33 which is adapted to engage a stop 32 on the member 24. Pivoted to the member 24 is a trigger 36 formed with a lug 38 extending within a slot 40 in the member 23 and pivoted to the trigger 36 by a screw 44 is a link 43. Adapted to co-operate with the member 24 is a holding member comprising a two-armed lever 54 pivoted to the plate 7 and one arm of this lever is provided with a flange 55 while pivotally mounted to the other arm is a roller 62 adapted to co-operate with the part 35 of the edge of the member 24. Clamped to the lever 54 is a rubber block 58 arranged to co-operate with the part 34 of the edge of the member 24. The roller 62 and block 58 are biased towards the member 24 by a helical spring 100. Secured to the turntable spindle 5 is an arm 64 on which is mounted rotatably a roller 65 adapted to engage the flange 55. The other end of the link 43 is connected to a lever 71 which is pivoted to the plate 7, together with an arm 72 of insulating material, by a screw 73. The lever 71 is provided with a brake-block 74 and the arm 72 is fitted with a switch contact 76, the arm 72 being connected to the lever 71 through lost motion means comprising abutments 78, 79 adapted to engage the sides of the arm 72. In operation at a predetermined position of the stylus, the location of which can be selected by adjusting the arm 15 about the sleeve 9, the arm 2 engages the pillar 14 and movement is transmitted through the roller 19 to the member 23 and through the spring 30 to the member 24. The member 24 moves until the roller 62 rolls off the part 35 of its edge and the block 58 then presses against the part 34 to hold the member 24 so that relative motion of the parts 23, 24 occurs and the edge of the shoulder 41 approaches the back surface 39 of the lug 38. During the audition period, however, the roller 65 engages the flange 55 once each revolution to withdraw the block 58 and allow the member 24 to follow up the member 23. When the stylus reaches a groove of coarse pitch, at the end of playing, the movement transmitted to the member 23, while the member 24 is held, is sufficient to release the lug 38 from the shoulder 41 whereupon the spring 82 rotates the trigger 36 and lever 71 so that the switch contact 76 is moved to open the motor circuit and the brake block 74 engages the inner surface of the turntable flange. To restart rotation of the turntable, the arm 2 is moved to contact with the pillar 10 and move the lever 11 in an anti-clockwise direction. This causes the members 23, 24 to move in a clockwise direction and the trigger 36 moves with the member 24 until the tail 45 of the trigger engages a pin 47 when the trigger rotates about its pivot 37 and the lug 38 is moved along the slot 40. Shortly before the roller 19 reaches its final position it engages a step 49, and movement up this step causes an acceleration of the moving parts with the result that a rapid movement is transmitted to move the switch 76 to the closed position and to make the lug 38 re-engage with the shoulder 41 of the slot 40. A modified construction is also described wherein the common bearing of the two rotary members 23, 24 is hollow and a switch operating member slides therethrough, the member being spring-biased towards the operating position to effect the control and held inoperative during playing by a lever coupled to the trigger member.