GB868905A - Variable resistor with vernier control - Google Patents

Abstract

868,905. Variable resistors. INTERNATIONAL RESISTANCE CO. Nov. 17, 1959, No. 38941/59. Class 37. A reduction in gearing between the operating: shaft 8 and the rotor 19 is obtained by the use of intermediate balls 23. Overlying the rear face of the base 6 is a resistance element 12 and a metal collector ring 14, held in place by terminals 13 and 15 respectively. Resilient contact fingers 16 and 17 form part of the contactor 18, mounted on the rotor or contact carrier 19, which is rotatable about the axis of the shaft. Rotation of the shaft is transmitted to the carrier 19 by a driving element 21 provided with an inner rotatable track 21a and a stationary outer track 22 which causes balls 23 to rotate between the tracks. The track 22 is formed by the inside surface of a frusto-conical rearwardly projecting extrusion of the rear wall which is secured to the base 6 so providing a housing for the resistor mechanism and a support against rearward movement of the carrier. The carrier 19 coacts with the tracks to hold the balls in place and also provides the means for applying the rearward axial thrust of a spring 26 on the balls. The carrier has a circular wall 27, Fig. 4, projecting from its rear surface 25, shaped on its inside to provide three pockets 28, separated from one another by lugs 29 in order to provide a smooth driving connection between the balls and the carrier. When the shaft rotates the balls go into orbital motion about it at a much slower rate than the shaft rotation and this motion is transmitted directly to the carrier to effect the fine adjustment of the resistor. The adjustment is confined to less than 360 degrees by means of stop abutments 30 on the contactor carrier 19, with a stationary stop 31 on the cover, Fig. 3. In a modification, Fig. 5 (not shown), the shaft can be secured against forward usual displacement by providing its end portion with a spoolshaped configuration. U.S.A. Specification 2,632,832 is referred to.