GB526891A - Improvement in variable inductance mechanisms - Google Patents

Abstract

526,891. Adjusting electric coupling coils. JOHNSON LABORATORIES, Inc. March 21, 1939, No. 8960. Convention date, March 21, 1938. [Class 37] [Also in Group XXXV] In a variable-inductance tuning mechanism of the kind having an iron core adjustable within an inductance coil, the movement of the core is effected by attaching both ends thereof to the ends of a tensioned cable which passes over and around a drum operated by a rotary member so that movements of the member in either direction are transmitted positively to the core. The core 17 slides in an inclined guide 13 of insulating material round which the coil 14 is wound and is connected by means of staples 18, 19 with cables 20, 21 passing over roller 23, 25 and joined together by a tensioning spring 26. Several of such cored coil units may be mounted one behind the other with the rollers 25 mounted on a common operative shaft 24 fcr joint operation. Each coil is connected to a capacitance 27 providing a resonant circuit tunable through a desired range of frequencies and the several circuits may be aligned for joint tuning by adjustment of the drums 25 on the shaft 24 and by adjustment of a coil relative to its core by means of a screw 28 abutting on the end of the coil former and pressing it against the action of a spring 29. The cores 17 are earthed by connection to a conductive strip 30 wound in spiral form round a metal rod 31 itself connected to the earthed casing, 35. The method of connecting the cables 52 carrying cores 17a so as to move the cores in opposite directions is shown in Fig. 8. A number of coils 14b, c, d may be arranged in series and traversed in turn by one core as shown in Fig. 10 so as to tune over an extended range of frequencies, the coil in use for a particular wave-band being automatically switched into the circuit by means of spring contacts 64 engaged by a cam 67 which is moved in step with the core 58 by bars 68, 78 attached to the cable 73.