GB578828A - Improvements in or relating to inductance devices of adjustable value - Google Patents

Abstract

578,828. Transformers and Inductances. CLARKE, A. G. Jan. 9, 1945, No. 713. [Class 38 (ii)] In an inductance or transformer, a coil 1 is disposed in an annular space between two magnetic core members 2, 3 haying abutting outer flanges 4, 5 and inner bosses 6, 7 separated by an air gap 8, and having registering bores 11 through which a magnetic armature 12 is movable to vary the reluctance of the core and the inductance of the coil. The core may be of comminuted carbonyl iron with a resinous binder, and a sleeve of insulating material may be provided between the core parts 2, 3 and the armature 12, and the inner surfaces of the parts 2, 3 and the outer surface of the armature 12 may, be coated with insulating varnish such as polystyrene. A condenser forming a tuned circuit with the inductance may be provided at 20 in a cavity between two members 15, 19 of a plastic such as polystyrene, spaced from the core member 3 by a washer 21 of mica or of the material known under the Registered Trade Mark "Bakelite," and the member 15 may carry the brass screw 14 providing adjustment for the armature 12. Two such inductances may be mounted with the members 2 adjacent to form a transformer for use in the intermediate frequency stages of a radio receiver. The outer flanges 4, 5 form a closed shield, and the inductance is suitably shaped for housing in a cylindrical shield can.