Patent GB-715141-A (GB)
Title: Improvements in or relating to automatic control devices for gramophones and like record playing mechanisms
Inventor: RAE ALEXANDER JAMES
IPC: G11B17/02
Filed: 1951-12-05
Abstract: 715,141. Automatic gramophones. ELECTRIC & MUSICAL INDUSTRIES, Ltd. Dec. 4, 1952 [Dec. 5, 1951], No. 28566/51. Class 40 (2). In a gramophone mechanism having a recordchanging initiating control member which is moved inwardly to a predetermined position to operate the control, means are provided for adjusting the said member to operate the control when at a different predetermined position, whereby both standard records and two kinds of micro-groove records may be accommodated. In an apparatus for use with micro-groove records it is normally found undesirable to employ the more usual tap-tap method of initiation owing to the sensivity of the pick-ups employed which tend to transmit a knock at each revolution of the turntable. It is therefore found convenient to make the trip mechanism operate when the pick-up reaches a predetermined position at. the centre of the record, but as 7 inch micro-groove records revolving at 45 r.p.m. are terminated in a concentric run-off groove having a diameter larger than the last few turns of the sound groove of standard records, it is necessary to make the predetermined position adjustable according to the kind of record in use, i.e., according to the speed setting. Furthermore, as 10 inch and 12 inch micro-groove records, revolving at 33 1/3 r.p.m. have an eccentric runoff groove which is larger than either of the aforementioned records, further provision for insuring correct operation is necessary. The present invention therefore has means for automatically altering the predetermined trip position for records with concentric run-off grooves, according to the speed setting of the turntable. In Fig. 2 is shown the setting of the apparatus for standard 78 r.p.m. records in which the turntable 12 is driven by a shaft 80 via jockey pulley 79. In this setting an arm 21 pivoted about a fixed point 22, is held by plate 43 in a position in which a downward pin 20 on arm 21 engages one side of a hole 30 in the base plate 9. The pin 20 carries a trip lever 19 which is held in a counter clockwise position by spring 29 against the pin 18 of a clutch member 16 supported by the end of the lever 19. As the pick-up arm 40 moves inwardly a plate 67 is moved counter clockwise until the stylus 71 reaches a predetermined position beyond the last 'turn of the sound groove of a standard record, at which moment a pin 70 on the plate 67 engages the end 24 of the lever 19 and moves the latter clockwise to release clutch member 16 to initiate the record-changing mechanism. When the apparatus is set for a 7 inch micro-. groove record, the arm 51 is moved to a position, Fig. 3, in which intermediate pulleys 78, 82 are interposed between the driving shaft 80 and the jockey pulley 79 to drive the turntable at 45 r.p.m. The movement of the lever 51 moves, by means of a pin 50, the plate 43 past a dead centre 44 and moves the lever 21 to a new position in which the pin 20 thereon takes up the position 20<SP>1</SP>. Under these conditions the pin 70 engages the end 24 of the trip lever 19 when the stylus is farther from the centre of the record than with a standard record, in accordance with the requirements of a 7 inch micro-groove record. When the apparatus is set for 10 inch and 12 inch micro-groove records the arm 51 is set to a position in which pin 50 comes to rest in a portion N and in doing so moves the plate 43 back to the position shown in Fig. 2. In this setting, intermediate pulleys 77, 81 are interposed between the driving shaft 80 and the jockey pulley 79 to drive the turntable at 33 1/3 r.p.m. During the inward traverse of the pick-up arm, teeth 69 on the plate 67 engage a pivoted member 31 and tilt it against a light spring 33 to the position shown in Fig. 3. As the stylus 71 moves outwardly after entering the eccentric run-off groove, the lever 19 is moved clockwise to release the clutch member 16 and start the automatic mechanism. Specifications 332,004, [Class 40 (ii)], 496,764, 663,790, 688,134 and 696,481, [Group XXIV], are referred to.