Patent GB-449763-A (GB)
Title: Improvements in and relating to high frequency coils provided with magnetisable coils
IPC: H01F17/04
Filed: 1934-12-31
Abstract: 449,763. Inductances. SIEMENS & HALSKE AKT.-GES., Siemensstadt, Berlin. Dec. 31, 1934, Nos. 37379, 37380, and 37381, Convention dates, Dec. 29, 1933, July 20, 1934. and July 21, 1934. [Class 37] A high-frequency coil comprises a magnetizable core of finely subdivided material on which the coil winding is firmly mounted, a supplementary magnetic body being movable relatively to the main core in order to adjust the inductance by varying the cross-section of the main core without varying the width of any air gaps between the adjusting means and the main core. As shown in Fig. 1, a mass core K of H-section is provided with a winding W, which may be of stranded wire. A displaceable magnetizable body A is variably inserted between the ends of two limbs of the core. In a modification, Fig. 2, the adjusting member A closes the magnetic circuit of an E-shaped main core K having a winding W, and is displaceable longitudinally to adjust the inductance. In another modification, Fig. 3, the body A is slidable along one side of a rectangular frame core K on which the winding W is wound. In the construction shown in Fig. 4, an H-shaped mass core K, having a winding W of stranded wire is provided with an axial hole into which fits a displaceable magnetizable body A, so that the inductance can be adjusted by varying the depth to which this body is inserted. The body A may be a screwed pin fitting into a correspondingly threaded hole in the core K. The core K may be in the shape of a yarn spool such as would be generated by the rotation of the H-shaped core shown about the axis of the pin A. The core K may be E-shaped, with or without a piece closing the magnetic circuit, or may be of recessed dish shape such as would be generated by the rotation of such an E-shaped core about its axis. Two such E-shaped or dish-shaped bodies may be joined together so as to enclose the winding. A similar shaped core may be built up of three parts, viz. two U-shaped or dish-shaped parts and a central part, the whole being bored and screw-threaded to receive the screw-threaded adjusting pin. In order to increase the sensitiveness of the adjustment, the adjusting pin may be made of material of a higher permeability than that of the main core, for example the proportion of iron in the pin may be greater than that in the main core. A reduction in sensitiveness may be attained by forming the adjusting pin with a recess, for example a conical recess as shown in Fig. 11, or the recess may be cylindrical. In another construction, shown in Fig. 12, the pin consists of a conical part 1 of mass core material and a screw-threaded part 2 of insulating material. The pin may be formed of a magnetizable core with a sleeve of insulating material on which the screw threads are formed. The main core may have the bore lined with a tube of insulating material provided with an inner screw-thread. As shown in Fig. 15, the transverse bar Q of the core K may be formed with a groove N to receive the pin. The core may be surrounded by a coil-carrier J of insulating material on which the coil W is wound. The carrier J may be of such a shape that a round adjusting-pin may be employed. Alternatively the adjusting pin may be semicircular in section, the winding-carrier J then being of rectangular cross-section. Two H-shaped cores with grooves in the cross-bars may be joined together so that the grooves face one another and form a circular hole. A screw-thread may be formed in the groove or hole to take the screwed adjusting pin, or a nut may be cemented on to the core in alignment with the groove. The complete coil may be fitted into a casing of insulating material.