GB561795A - Improvements relating to the rotors of electricity meters, small motors and the like - Google Patents

Abstract

561,795. Dynamo-electric machines. MEASUREMENT, Ltd., BATT, F. H., and CLIFFORD, C. F. Feb. 25, 1943, No. 3122. [Class 35] [Also in Group XXXVI] Means for the magnetic suspension of the rotor of an electricity meter, small motor, or the like comprises a permanent magnet having one pole of the order of 1 or 2 mm. in length projecting from the side of a mass of high coercive force alloy, the peripheral edge of which forms the other pole, there being a similar pole projecting from a mass of magnetic material at the end of the rotor shaft. A permanent magnet a, above and coaxial with the rotor shaft b, consists of a cylindrical disc of a magnetised high coercive force alloy and has a short soft iron polepiece c projecting axially from its underside. The face of the polepiece may be rounded. A similar disc d and short polepiece e is provided on the rotor shaft, but this disc may be made of permanent magnet material or of soft iron, mild steel &c. The end face of one or both polepieces c, e may be plated with non-magnetic material. The approach of the polepiece e to the polepiece c is limited by a pintle k secured to a screw m which threads into a non-magnetic part n on to which the polepiece c threads, this polepiece being a fit in the magnet a. The part n threads into a fixed bracket o and is locked by a nut p. The gap between the polepieces c, e is initially set by threading the part n through the bracket o. Nuts q, r on the screw m can be locked together in any desired position to determine the gap between the bottom of the pintle k and the bottom of a recess in the polepiece e. The polepiece c may be proportioned or constructed (as by being recessed or necked) so that it is magnetically saturated and there is, therefore, only a negligible increase in flux as the poles approach one another. The polepieces may be formed of a powdered metal product.