Patent GB-610589-A (GB)
Title: Improvements in or relating to control mechanisms for gramophones
IPC: G11B17/02
Filed: 1946-04-11
Abstract: 610,589. Automatic gramophones. INDUSTRIAKTIEBOLAGET LUXOR. April 11, 1946, No. 11120. Convention date, May 28, 1945. [Class 40 (ii)] In a gramophone, a control mechanism which begins to operate when a record has been played and which may stop the gramophone or cause a new record to be placed in position and the pick-up to be replaced thereon, comprises a tap-tap mechanism which is tripped when the inward movement of the tone-arm is accelerated by a steep run-off groove, or when reversed in direction by an eccentric run-off groove, or when ceasing to move inwardly at all, such as when reaching a concentric inner groove or where there is no run-off groove. Fig. 2 shows one construction in which a lever 7, pivoted about a point 8 and frictionally coupled to a tone-arm, moves in a counterclockwise direction during the playing of a record. A pin 9 at the other end of the lever 7 is arranged to engage cams 10, 12 and 5 on a disc 3 which is continuously rotated by the turntable shaft, and preferably geared down from it. As the playing of the record continues, the pin 9 moves into the path of the cams 10 and 12 and is moved by them a small amount in a clockwise direction against the frictional coupling to the tone-arm. After the cam 12 has passed the pin 9, the lever 7 moves again in a counter-clockwise direction into the path of cams 10 and 12, and the process is repeated until the tone-arm increases its speed of travel, or stops, or changes its direction of travel. Should the record have a steep run-off groove, the lever 7 is moved a greater amount than normally towards the centre of the disc 3, so that it drops into a recess 23, Figs. 2 and 3, in a control-disc 15. When cam 10 again comes into contact with the pin 9 the controldisc 15 is moved clockwise by the lever 7 so that an arm 29 on a lever 30 under the control of a spring 28 slips off the raised part 27 of the control-disc 15, and the gear-wheel 32 is brought into mesh with the toothed rim 16 of the control disc 15 and thereby effects driving engagement for carrying out the automatic cycle, until the arm 29 once again rides up the raised part 27 of the control-disc 15 and thereby interrupts the drive thereto. Should, however, the record have no run-off groove, or have a concentric end groove, or have an eccentric run-off groove, the lever 7 ceases to move slowly towards the centre of the disc 3, and the cam 5 passes between the pin 9 and the centre of the disc 3 and thereby imparts a clockwise motion to the lever 7 which thereupon engages the raised edge of the recess 21 on the control disc 15, and rotates the latter so that the arm 29 will again slip from the raised part 27 of the control disc 15, and the automatic cycle thereby initiated. During rotation of the control disc 15, the lever 7 is lifted by the raised part 25, Figs. 2 and 3, of the control-disc 15 so that the pin 9 does not encounter the cams 10, 12 and 5 during the automatic cycle. The ratio of the gear-wheels 2 and 16 is such that when the lever 7 is lowered from the raised part 25 of the control disc 15 the pin 9 is lowered between cam 5 and a sloping projection 6 on the disc 3, so that pin 9 is made to pass through the gap 12 and is thus set in its correct starting position. Figs. 4 and 5 (not shown) illustrate an alternative construction.