GB600033A - Improvements in or relating to variable capacitors - Google Patents

Abstract

600,033. Condensers. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. July 2, 1945, No. 16730. Convention date, June 30, 1944. [Class 37] A variable condenser comprises a ceramic tube 1 provided with an external metallic coating 2 forming one electrode and a metallic tube 15 forming another electrode within the first and axially movable therein to vary the capacity, the tube being made from spring metal and having longitudinal edges which overlap, whereby the area of contact with the inner side of the ceramic tube is substantially independent of temperature variations. The Specification, as open to inspection under Sect. 91 comprises also the general idea of a metal rod or tube movable within and relatively to a metallic band or coating on a ceramic tube. In an example, Fig. 1, an inner brass rod 5 acts as the inner electrode and is reduced and screwed at the part 8, friction being exerted by a spring 14 in a slot 10A. A second metal coating 3 enables the tube 1 to be soldered to a bush 4. In other examples, the thickness of the ceramic tube 1 may taper or the metal band 2 may have a longitudinal slot of varying width to vary the " law " of the condenser. In a further example, the movable electrode comprises a metallic coating on a ceramic rod having the same thermal coefficient of expansion as the tube 1. The relative co-efficients may be made to differ for negative and positive capacity temperature relationships. This subject-matter does not appear in the Specification as accepted.