GB1162097A - Improvements in or relating to Gramophones - Google Patents

Abstract

1,162,097. Supporting gramophone pick-ups. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 1 Sept., 1966 [4 Sept., 1965], No. 39003/66. Heading G5R. A gramophone having a turntable and a pickup arm pivotable about horizontal and vertical axes, and having means, connected between the pick-up arm and a fixed part, which exerts a force on the pick-up arm which influences the force of the stylus on a record during play and which also exerts a varying torque on the arm to counteract the torque produced by the varying transverse component of the tangential frictional force generated at the point of contact between stylus and record, is characterized in that the means are adjustable and are connected to the pick-up arm at a region such that, upon variation of the forces exerted on the arm by the means, the stylus force and the above - mentioned counteracting torque are varied in direct proportion to one another. As shown, a pick-up arm 7 journalled in a Cardan suspension having a horizontal pivot 9 and a vertical pivot 10 is balanced by an adjustable counterweight 13. A coiled tension spring 16 secured between a point 17 on the fixed outer ring 11 of the suspension and a part 18 slidable along a limb 15 provides an adjustable clockwise stylus pressure on the record. The point of attachment 17 is located slightly on the nearer side (as viewed in Fig. 2) of the ring 11, so that the spring 16 also exerts a torque which (in plan) is counterclockwise, thus forcing the stylus 12 towards the outside of the groove in the record to compensate for the radiallyinward component of needle drag. The spring may be below the pick-up arm, in which case the movable connection is to the right of the suspension, and the fixed connection is on the further side of ring 11. In a modification, instead of the spring of Fig. 2, a vertically polarized magnet, adjustable along limb 15, is attracted towards a vertically polarized magnetic member arcuate in horizontal plan and connected to ring 11: the centre of the arcuate member is eccentric with respect to the vertical pivot 10. One magnet may be replaced by a soft iron element. The magnets may repel. Electromagnets may be used, the forces being adjusted by varying the current through the coils.