GB778979A - Improvements in devices for placing the pick-up arm needle in the correct initial playing position on a phonograph record - Google Patents

Abstract

778,979. Phonographs. INDUSTRIAKTIEBOLAGET LUXOR. May 13, 1955 [May 25, 1954], No. 13916/55. Class 40 (2). A support member or a separate feeling member on the pick-up arm 1 releases mechanism operating to disconnect the pick-up arm 1 from the drive mechanism, not shown, of a phonograph after the known sensing of the outer edge of a record, not shown, in a device for placing the pick-up arm needle 5 in the correct initial playing position on a sound disc gramophone record to be played irrespective of the diameter thereof; this device is applicable to that kind of phonograph in which before the playing of a record the pick-up arm 1 is set down on the record, by the phonograph drive mechanism at a distance from its rotational centre not exceeding the radius of the initial turn of the round groove in a record of the smallest diameter to be played, and also in which the support member on the pick-up arm carries the arm on the record and prevents the needle 5 engaging the record when the arm is subsequently moved by the drive mechanism towards the record edge on arrival at which edge the needle is brought into engagement with the initial turn of the sound groove and the support member is moved upwards to a position above the horizontal plane through the needle point in order not to prevent playing of the record. As shown, the support member is a roller 17 and the device comprises two stirrups 6, 7 pivoted on a pin 8 and on the former of which the roller 17 is mounted. The stirrup 7 is urged upwardly by a tension spring 10 to a position determined by an adjustment screw 11 and the two stirrups 6, 7 have respectively cam edges 14 . . . 16 and a slot 12 which are engaged by the end 18 of a rectangular section rod 19 connected through a lever 20 and another rod 22 to a notched wheel 3 driven by the drive mechanism and rotatable upon the shaft 2 by which the arm 1 may be swung horizontally, a tension spring 24 urging the lever 20 in such direction that the rod 22 is disengaged from the wheel 3. In operation, at rest the rod 19 is held by an edge 13 in slot 12 and when the arm 1 is set down at the centre of a record contact by the roller 17 causes a slight anticlockwise movement of stirrup 6 which permits movement to the left by rod 19 but the latter movement is limited by the stop edge 16. By the engagement of rod 22 with wheel 3 the arm 1 is swung radially outwardly across the record and the roller remains below the needle 5 until it drops off the edge of the record, whereupon the needle engages the starting arm of the groove and the stirrup 6 drops, disengaging stop edge 16 from the end 18 and permitting rod 19 to move to the left until end 18 engages the stop edge 15, whereupon the spring 24 acting through rod 19 pivots the stirrup 6 anticlockwise until the roller 17 is above the record surface and also disengages the rod 22 from the wheel 3 to stop the horizontal swinging movement of the arm. Specification 554,282 is referred to.