Patent GB-802207-A (GB)
Title: Control means for sound reproducing apparatus
Inventor: GUEST LAWRENCE VINCENT
IPC: G11B3/095
Filed: 1954-12-01
Abstract: 802,207. Gramophones; stopping and starting. BIRMINGHAM SOUND REPRODUCERS, Ltd. Dec. 1, 1955 [Dec. 1, 1954], No. 34836/54. Class 40 (2). A control mechanism for sound recording apparatus for either stopping the apparatus or initiating a fresh cycle of operation. Construction.-A pick-up arm 4 (Figs. 1 and 4) is mounted in a bearing 6 on the motorboard 1 and has a pin 8 coaxial with the vertical pivot. At the lower end of pin 8 is secured an arm 10 having at its outer end a projecting pin 11, which engages a fork formed in the end 14 of the lever 13. A pin 12 depending from the motor-board carries a freely rotating washer 22 which supports the lever, a further washer (not shown) may be used resting on the upper surface of the lever. The aperture 21 in lever 13 which co-operates with pin 12 is elongated transversely of the lever which can thus pivot about, or make guided translational movements relative to the pin 12. The end 18 of the lever 13 is joggled to pass through an aperture 19 in the motor-board and then continues through a slot (which has a length greater than the width of the lever 13) in lever 34 and terminates in a double bend 20 as seen in Fig. 12. Centrally under the turntable is mounted a cam block 24 having an eccentric ramp 27 which co-operates with the bend 20 of the lever 13. The lever 34 (Fig. 6) is a flat strip of metal mounted between guide blocks 35 which constitute restraints in one horizontal plane but permit movement in the two other mutually perpendicular planes. A tongue 39 on the lever 34 passes through a slot 41 in the motor-board and is connected to a fixed pin 43 by a tension spring 42. A sear 40 co-operates with the edge of the slot 44 to retain the lever against the pull of the spring 42. The end 37 of lever 34 is connected to a switch in the driving motor circuit which is in the " OFF " position when the lever is in the position shown in Fig. 6 and is in the " ON " position when the sear 40 is engaged in the slot 44. Operation.-To start the motor the pick-up arm is moved outwardly so that the pin 11 engages one side of the forked arm 14 and pivots it about the pin 12 in a clockwise direction as seen in Fig. 1 until the end 18 of the lever 13 engages the slot in the lever 34. Translational movement of the lever 13 relative to the pin 12 then occurs until the pin 12 abuts the end of the slot 21. Rotation of the lever 13 then continues and the lever 34 is moved to the left as seen in Fig. 6 until the sear 40 drops through the slot 44. In this position the motor runs and drives the turn-table through the friction wheel 28. The pick-up arm is then swung inwards to a position to engage the stylus with the commencing groove of a record on the turn-table 3 and during the major part of the inward movement of the pick-up the pin 11 moves idly between the forks of the lever 13. During the latter part of the reproduction the pin 11 engages the end 14 of the lever 13 and causes it to pivot about the pin 12 until the free end engages the periphery 26 of the cam 24. Due to the small inward movement of the free end of the lever 13 for each turn of the record the bend 20 does not engage the ramp 27 but a wiping action occurs between the lever and the periphery of the cam resulting in translational movement of the lever 13 relative to pin 12. When the stylus reaches the quick pitch turn at the end of the recording the end 18 of the lever 13 is moved quickly toward the centre-spindle of the turn-table and the bend 20 engages the ramp 27 of the cam 24. The consequent lifting of the end 18 of the lever raises the lever 34 and disengages the sear 40 from the slot 44 allowing the lever 34 to move to the right (Fig. 6) under the influence of the spring 42 and either switch-off the motor or initiate a fresh cycle of operation.