GB660894A - Improvements in or relating to electrical instrument movements of moving magnet type - Google Patents

Abstract

660,894. Electromagnetic ammeters and voltmeters. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Feb. 8, 1950 [Feb. 8, 1949], No. 3478/49. Class 37. In a moving magnet movement assembly a generally flat one-piece or composite member is formed with an aperture from whose margin or periphery extends one or more supports locating and holding one or more stator or fixed coils over the moving magnet which projects from and rotates within the aperture. The spindle secured to the moving magnet extends within at least one bore-like passage opening into the aperture. In Figs. 4 and 5 the generally flat member comprises two contiguous rectangular copper plates 122, 123 with rectangular apertures 124, 125 and aligned grooves 126, 127 forming a passage accommodating the spindle 112. Two cheese-shaped bulges 124a, 125a constituted by material pressed out to form the apertures 124, 125 carry the stator coils 141, 142 and form an enclosure for the moving magnet 111 whose axis of rotation is within the opening formed by the registering apertures 124, 125. The copper plates 122, 123 are a tight sliding fit within slots 134, 135 in a main supporting frame 115. The limbs 162 of the control torque U-shaped magnet 161 which enter arcuate slots in the large gear-wheel 118 serve as stops limiting the travel of the magnet rotor 111. In a modification, Figs. 1, 2 and 3 (not shown), instead of utilizing integral projections to support the coils the latter are mounted on a separately formed ring which surrounds the magnet and is mounted within and projects from the extremities of the aperture in a composite support member.