GB780843A - Improvements in or relating to electrical capacitors - Google Patents

Abstract

780,843. Variable capacitors. GENERAL ELECTRIC CO., Ltd., and HARROLD, A. E. Dec. 17, 1953 (Sept. 17, 1952], No. 23346/52. Class 37. A capacitor comprises one or more sets of movable plates on a structure rotatable about an axis, and a plurality of sets of fixed plates which project outwards from supports disposed about the said axis while the movable plates project inwards from supports on the rotatable structure. In order to reduce stray capacitance between the sets of fixed plates a port with a conducting surface embracing the axis of rotation of the structure is provided. Four independent sets 1 of fixed plates in the form of sectors of annuli are mounted on segmental metal supports 4 fixed to an insulating base 5. The segmental supports enclose an earthed metal tube 10 fixed to the base, in which rotates a shaft 6 bearing at its upper end an insulating plate 7 to the periphery of which are fixed metal rods 8 carrying plates 2, and a metal counterbalance weight 11. The sets of plates subtend angles of 72 degrees and are closely grouped to leave an angular gap of similar size in which an earthed metal screen is fixed. The device may be used in conjunction with an attenuator network, tapping points on which are each connected to a different set of fixed plates, an output variable with position being taken from the moving set of plates. Alternatively several parallel attenuators are used the outputs being connected to different sets of plates. In a further arrangement two sets of fixed plates are associated in this way with a tapped or parallel attenuator and with one movable plate the output from which is fed to a further network or networks associated with the other sets of fixed plates, which are in turn associated with a second movable plate rotatable with and mounted at an angle of #/5 to the first from which the final output is taken.