GB682681A - Improvements in or relating to the setting mechanism of variable condensers and the like in radio and electrical apparatus - Google Patents

Abstract

682,681. Electric condensers. STRATTON & CO., Ltd., LAUGHTON, H. A. J., and COX, H. N. Dec. 27, 1950 [Sept. 28, 1949], No. 24859/49. Class 37. [Also in Groups XXIV and XL (c)] A setting mechanism for a variable condenser or other electrical component comprises a driving member and a driven member having spaced, parallel rotational axes, a crank-pin on the driving member being slidably engaged between two rail members on an arm on the driven member which are urged together by a spring, so that backlash is substantially reduced. The arrangement provides a variable ratio drive. In Fig. 3 a control knob 10 is frictioncoupled to a disc 14 which carries a pinion 16 and a split gear 17 of the type used to take up backlash. Pinion 16 drives a split gear 22 which carries a pin 30 and is mounted on shaft 23. Pin 30 engages a radial arm 36 which is fixed to the condenser spindle 37, as shown in Fig. 2, by means of two rail portions 43, 42, which are urged together by springs 45 to permit radial movement of pin 30 along arm 36 without backlash. Rotation of knob 10 thus produces rotation of arm 36 and the condenser plates at a velocity which varies according to the position of arm 36, and the arrangement may be such that the ratio of angular movement of knob 10 to the frequency of the tuned circuit is substantially constant. Gear 22 also rotates pinions 24 and 25 which are fixed to drums of insulating material and which control the movement of a cable 26 to move a pointer along a tuning scale. The split gear 17 drives a pinion 18 which is associated with a further disc bearing a scale to provide a fine tuning indicator. A fly-wheel may be associated with the control knob spindle. The end of pin 30 carries three grooved rollers to reduce friction. The device may be used to control other electrical components such as a potential divider.