GB516852A - Improvements in continuously adjustable ohmic resistances for electric currents - Google Patents

Abstract

516,852. Variable resistances. ZEISS C. [Firm of]. July 27, 1938, No. 22298. Convention date, Aug. 14, 1937. [Class 37] Resistance wire or strip is wound from an insulating to a conducting drum, the connecting leads being attached directly to the ends of the resistance wire, As shown in Fig. 1, the resistance wire c is wound from an insulating drum a to a metal drum b, so that the part of the wire on the drum b is short-circuited. Contact pressure is provided by a wire g kept under tension by springs i, i<1> fixed to the drum b, a. A scale e indicates the resistance in the circuit. Connections are made through spiral springs f, f<1>, soldered to the axles k, k' and connected to the ends of the resistance wire c. A resistance for use with apotentiometer connection is shown in Fig. 2, in which the resistance wire c is wound from a metal drum b over an insulating drum a to a metal drum b' coaxial with drum b. Leads f<1>, f<11> are attached to the ends of the resistance, an intermediate point h being connected through the axle k and spiral spring f. Rotation of the drums causes an equal length of resistance wire to be wound on one conducting drum and off the other so that the total lengh of resistance wire in circuit remains constant but is divided into variable parts by the tapping points h. Alternatively the resistance wire may be wound from an insulating drum or other carrying body, over a carrying body of conductive material, to a third insutating carrying body, the variable potentiometer tapping being constituted by the second carrying body. Non-linear dependence of resistance variation with angle of rotation may be secured by making one or more of the carrying drums not rotation-symmetrical, e.g., in the form of an Archimedean spiral. The Specification as open to inspection under Sect. 91 comprises also the following constructions. A taut wire c, Fig. 1 (Cancelled) is pressed by a slider d against a convex metal surface b. Fig. 3 (Cancelled) shows a construction in which resistance wire c is wound from an insulating drum a to a metal drum b, connection being made to the axles k, k<1> by spiral springs f, f<1>, the axle k being insulated by a brush m. Fig. 5 (Cancelled) shows a modification with a potentiometer connection. The resistance wire c is wound from an insulating drum a over a metal drum b on to an insulating drum a<1>. Similar constructions may be employed for variable inductances. This subject-matter does not appear in the Specification as accepted.