GB662691A - Improvements in or relating to variable inductances - Google Patents

Abstract

662,691. Inductances. ALADDIN INDUSTRIES, Inc. June 3, 1949 [Aug. 5, 1948], No. 15006/49. Class 38 (ii). An inductor suitable for tuning H.F. circuits is varied by move ment of a conducting member which is moved so as to vary the amount by which the winding is screened by the member from a magnetic core. A helical winding 22 of copper strip is wound on an insulating tube 20 and enclosed in an insulating tube 30. A powdered magnetic core 36 is fixed inside inner tube 20 by a resilient wire 34 held in a plug 26 which is fixed to base 24 and holds tube 20. The reactance of the winding is varied by axial movement of a conducting non-magnetic sleeve 38 between core 36 and inner tube 20 whereby the core is more or less screened from the winding. Conducting sleeves of several similar inductors may be fixed to a yoke 42 by screwed rods 40 for simultaneous variation. The Q of the inductance may remain constant or vary in some desired manner with variation of inductance. To provide a predetermined variation of inductance with sleeve movement, the tube 20 may be shaped suitably, e.g. barrelshaped, Fig. 4 (not shown), or hour-glassshaped or tapered, or the winding pitch may vary along the coil. In a modification the winding comprises parallel conductors, Figs. 5, 6 (not shown), the inductor then being of the kind forming the subject matter of Specification 662,692. In other modifications the conducting sleeve may surround the winding, the core being a tube, Figs. 5, 6 (not shown), or a rod, Figs. 7, 8 (not shown), outside the sleeve. The cross-section of the tubular parts may be of any suitable shape such as circular or oval.