GB875468A - Improvements in or relating to variable inductances - Google Patents

Abstract

875,468. Transformers and inductances. NEOSID Ltd. March 23, 1959 [May 28, 1958; Nov. 28, 1958], Nos. 17025/58 and 38420/58. Class 38 (2). In an assembly of two or more coupled variable inductors having each a toroidal core 1 (Fig. 7) the effective cross-section of each core is varied by movement in a vertical, chordal or radial hole of a tuning slug 4 of ferrite or iron dust. The tuning slug may have a threaded brass extension co-operating with tapped hole in the base 6 or vertical member 11 (Fig. 10) of former 5. Alternatively the hole in the core may be parallel-sided and tapped, the slug being adjusted by screwing it therein. The tuning slug may be flexibly connected to a screwed carrying stem by P.V.C. sleeving. The variable inductors may form an I.F. transformer and may be housed in suitable recesses 4 (Fig. 2b) of moulding or may be arranged in two mouldings 9 (Fig. 3a) spaced apart as necessary by spacers 10 or shims. Coupling may be by a common winding or by leakage fields. The inductors and tuning arrangements may be encapsulated in casting resin. Where the cores are of low permeability and coupling is by leakage fields, the apparatus is sealed in a screening can 12 (Fig. 4) held on a base plate 13 by clips 14.