GB497749A - Improvements in or relating to operating means for manually operated variable condensers and like toning devices - Google Patents

Abstract

497,749. Adjusting wireless apparatus; gearing. STANDARD TELEPHONES & CABLES, Ltd., and HALL, R. E. June 25, 1937, No. 17725. [Class 37] [Also in Group XXIV] A slow-motion device for variable condensers or other tuning-apparatus comprises a frictional reduction drive in series with a positive drive, the frictional drive comprising a conical driving member adapted to drive through a ball a wheel rigid with a drum which drives the tuning element positively through a cable or cables. As shown, the tuning element is driven directly by the hub 39 of a shaft 8 rigid with a disc 4 which may carry a pointer movable over a tuning scale. In the position shown in Fig. 3, rotation of the actuating knob 2 directly drives the disc 4 through the frictional engagement between flanges 3, 5. For the slow motion drive, the knob 2 is retracted, relatively to the disc 4 until the conical surface 9 of a sleeve 7, rigid with the knob 2 and rotatable on shaft 8 engages with a ball 10 carried by a stationary spring 11. Rotation of the knob 2 then drives frictionally through the sleeve 7 and ball 10 a wheel 13 rotatably mounted in a stationary cage comprising plates 15, 16. A cable 19, secured by a tensioning device to a pillar 31, Fig. 1, rigid with the disc 4, passes round guide rollers 23 .... 26 and pulleys 27, 28 mounted in the stationary cage, and is wound around and secured substantially at its midpoint to a drum 18 rigid with the wheel 13, the disc 4 therefore being driven by wheel 13 through the drum 18, cord 19 and pillar 31. The guide pulleys 27, 28 are mounted as nuts on threaded spindles to ensure the cord being applied to the drum in one layer. The angular movement of the disc 4 is limited by an arcuate slot 45 therein coacting with a rod 43 which serves to anchor the cage 14 to the panel on which the device is mounted. A flexible spring 46, Fig. 4, mounted on spring posts 47, 48, acts togglewise on the sleeve 7 to ensure good frictional contact in the drive in both actuating positions of the tuning knob 2.