GB690571A - Driving device for a gramophone turntable - Google Patents

Abstract

690,571. Driving sound reproducing machines. THORENS SOC. ANON., H Aug. 21, 1950 [Sept. 5, 1949], No. 20658/50. Class 40 (ii) [Also in Group XXIV] The speed of a gramophone turntable 1 is changed by moving an arm L to one of three positions where a lug 21 on the arm engages in a notch 18, 19 or 20. Movement of the arm rotates a plate S about a sleeve 7 to bring one of three members O<SP>1</SP>, O<SP>2</SP> or O<SP>3</SP> into driving engagement with the intermediate friction wheel R that drives. the turntable. The member O<SP>1</SP> is driven directly by the motor shaft 5 and the members O<SP>2</SP>, O<SP>3</SP> are driven from the member O<SP>1</SP> by a belt C. The diameters of the parts of the members O which drive the wheel R and which are driven by the belt C are arranged to give the required driving speeds. The wheel R is carried by a lever 24 which is longitudinally displaceable by a pin 25 and slot 26 and pivotally mounted about the pin 25. A spring 23 holds the wheel R in contact with the turntable and the driving members O. The angle between the radii passing through the points of contact of the wheel R with the turntable and a driving member O remains constant for each driving member. A spring Fig. 4 (not shown) holds the lug 21 in one of the notches. The motor is secured to the frame resiliently. In a modified apparatus Figs. 6 to 8 (not shown), each of the three driving members O are driven by a belt from the motor shaft. In a further modification the motor shaft is coaxial with one of the driving members and the motor is mounted on and moves with the plate S. The tension of the belt C may be adjusted by making the mounting of one or more of the driving members movable (see Fig. 9, not shown). The driving, member may be moved to a position in which the turntable is not driven.