GB799961A - Improvements in electrical measuring instruments - Google Patents

Abstract

799,961. Electrical measuring instruments. GENERAL MOTORS CORPORATION. Aug. 2, 1956 [Aug. 12, 1955], No. 23925/56. Class 37. In an instrument particularly for use as an ammeter in a vehicle, current in a U-shaped portion of a unitary frame provides a deflection force for an armature rotatably mounted within the arms of the U-shaped portion and magnetically attracted to a U-shaped magnetic member, the arms of which extend lengthwise of the arms of the U-shaped portion. The frame 10 is a one-piece stamping of brass or other non- magnetic metal and includes the U-shaped portion 55 having arms 58, 60 of arcuate section, flanges 61, 62 bridged by a shunt 64 (which may be omitted) flanges 38, 40 to which the dial 12 of card or a non-magnetic metal such as aluminium is riveted, an arm 42 and stiffening flanges 34, 36. The shaft 46 is journalled between the arm 42 and a recess formed in a ridge 56 in the U-shaped portion 55 and carries the armature 88 held between a flange 86 and the pointer 82, balanced by a counterweight 80. The armature 88 is a permanent magnet having arcuate ends concentric with the arms of the U-shaped portion 55 to provide a linear deflection. The frame is attached to the insulating back 18 by terminals 20, 22. The restoring force is provided by a U-shaped ferro-magnetic member 68 having flat sides 72, 74 interposed between the frame and the dial 12 and attached to the frame by tabs 76, 78. As a modification, the U-shaped member 68 may be magnetized instead of the armature 88.