GB388629A - Improvements in or relating to gramophones - Google Patents

Abstract

388,629. Gramophones. GELL, J., 123, Upper Tollington Park, London. June 13, 1932, No. 16681. [Class 40 (ii).] A constant linear speed drive mechanism for gramophones comprises a friction wheel mounted on a splined shaft with which is associated a rocking arm carrying half-nuts so that when the rocking arm is rocked in one direction the half-nuts engage with two threaded shafts parallel to the splined shaft but when rocked in the other direction the half-nuts are disengaged therefrom. A shaft 1, Fig. 1, connected with the driving motor, is geared to a gear wheel 3 fixed to a splined horizontal shaft 6 which carries a friction wheel 9 rotatable therewith but free to slide thereon. A rocking arm 11, Figs. 1 and 8, pivoted on the splined shaft 6 is formed of two side pieces 11a, 11b between which are the friction wheel 9 and two half-nuts 12, 13 which can engage with threaded shafts 14, 15. When, during operation of the machine, the half-nuts are in engagement with the shafts, the friction wheel 9 is rotated and traversed radially of the turntable to produce constant linear speed of the record under the stylus. The arm 11 can be rocked about the shaft 6 by means of a shaft 20 pivoted eccentrically in bearings 21, 22 and engaging with a roller 11c on the rocking arm. When the shaft 20 is turned in one direction, the half-nuts of the rocking arm engage with the threaded shafts 14, 15, but when turned in the opposite direction the half-nuts are freed from the threaded shafts. A shaft 24 carries an eccentric cam 28, Fig. 4, so that when it is given a half turn, an arm 29 pivoted on the shaft 20 and carrying a wheel 30 is moved to raise the turntable 31 and its associated mechanism so that the rocking arm can be moved to any desired position. Secured to the rocking arm are rods 32, 33 connected together by a U-piece 37 so that the rocking arm with the friction wheel may be moved manually when the half-nuts 12, 13 have been disengaged from the shafts 14, 15. A member 55 is adapted to break the circuit of the driving motor when the friction wheel has been moved almost to the end of its radial travel. The turntable 31 is fixed to a cup 45, Fig. 6, mounted on a hollow shaft 42 rotatable on ball bearings about a spindle 38. The spindle 38 is screwed to a cup 40 fixed to the base-plate of the machine. To enable the hollow shaft 42 to rise and fall when the turntable 31 is lifted by actuation of the shaft 24, the ball bearings 43, 44 are a sliding fit on the spindle 38. To the shaft 42 is fixed a worm gear 48 which drives gears 49, 50, Fig. 1, on the threaded shafts 14, 15, respectively. An additional train of gears may be inserted between the shafts 14, 15. When used for recording sound an L-shaped arm 61, Fig. 7, is attached to the tone-arm by a flexible connection 62 and is secured also to the U-shaped piece 37 to move in sympathy with the friction wheel 9.