Patent GB-680810-A (GB)
Title: Improvements in or relating to automatic gramophone control mechanism
IPC: G11B3/085
Filed: 1949-07-18
Abstract: 680,810. Automatic gramophones. FITCH, C. K. July 18, 1950 [July 18, 1949], No. 18910/49. Class 40 (ii). In an automatic gramophone means for setting down a pick-up, rigidly fixed to a pick-up arm, at the start of the record, irrespective of variations in diameter, comprises an abutment on the pickup which comes into contact with the edge of the record to arrest further inward movement of the pick-up and is withdrawn when the pick-up is lowered, an inertia-controlled detent then holding the said abutment in the inoperative position until the pick-up arm is arrested at the outer end of its travel. In one embodiment the abutment 42, Fig. 5, is arranged to slide vertically in the pick-up housing 43. After the lower end 39 comes into contact with the edge of the record 59, the pickup is lowered so that a depending member 50, pivoted at 52, comes into contact with the record and lifts the abutment 42 clear of the record by means of a notched lever 46, which is held in the upper-position by frictional engagement with a cranked lever 60 pivoted at 56 and having at its upper end a weight 55. When the pick-up reaches the outer end of its travel the inertia of the weight 55 temporarily releases the frictional engagement of the lever 60 and the notched lever 46, and the abutment 42 falls to its operative position again. When the pick-up is lifted at the end of a record, by means not shown, a pad 17, Fig. 1, on the end of an arm 16 secured to the pick-up arm shaft 15 comes into contact with the under surface of the turntable, and the pickup arm is swung outwardly beyond the edge of the record. At this point the tip of an extension 32 of the arm 16 tips a bracket 18 a small amount clockwise about a pivotal axis 19 so that a lever 30 pivoted at 28 is moved into line with the centre of the turntable through the medium of an extension 27 engaging a slot 26 in the bracket 18. Should a record be resting on the turntable, the spring-loaded centre shaft 80, Fig. 7, is pressed downwardly so that a pin 31 rotating therewith engages the end of the lever 30 rotates the bracket 18 further clockwise and a friction pulley 21 thereon engages the rim of the turntable and a roller 24 fixed to and driven by an intermediate roller 22 is lifted into contact with the arm extension 32. The bracket 18 is locked in position by the direction of rotation of the turntable. The arm 16 which lays obliquely to the roller 24 is moved by rotation of the roller 24 towards the centre of the turntable until the abutment 42 engages the edge of the record, after which a recess 38, Fig. 3, in the rim of the turntable reaches the pulley 21 so that drive is no longer transmitted to the roller 24 and the bracket 18 returns to its normal position and thereby lowering the pick-up on to the record. In another embodiment, Fig. 6, the abutment 66 engaging the edge of the record 59 is mounted on an arm 64 separate from the pickup arm 14. As the pick-up is lowered on to the record a projection 61 on the pick-up is released from a detent 72 and is free to traverse the record. Specification 680,799 is referred to.