GB1400420A - Eddy current couplings - Google Patents

Abstract

1400420 Eddy current couplings E J DAVIES 4 Aug 1972 [12 Aug 1971] 37915/71 Heading H2A In an eddy current coupling comprising an input and an output shaft, e.g. 15, 32, one or more field windings, e.g. 42, a pole member 37 connected to one of the shafts, e.g. shaft 32 and which exhibits a series of poles (40) Fig. 2, alternate ones of which are of opposite polarity when the winding(s) is energized, and a loss member 20 connected to the other shaft and so associated with the pole member as to provide a path for magnetic flux between the poles and also a conductor for the resulting induced voltages which cause eddy currents in such loss member the reaction between the flux and currents transmitting torque between the members which are rotatable about a common axis, the loss member 20 comprises ferrous or ferromagnetic support member 21, 22, a loss ring 27 of ferromagnetic material of lower electrical resistivity than that of the support member 20 by which it is carried the ring being interposed between such member and the poles 40 so that there is only a small air gap 43 between the ring and the poles, and end rings 23, 25, e.g. of Cu of lower electrical resistivity than that of the loss ring and located at the ends of ring in good electrical contact therewith. Thus the support member may be of mild steel or spheroidal graphite east iron, and the loss ring may be of pure or ingot iron, low resistivity mild steel, nickel, or nickel alloys containing at least 95% by weight of nickel, placed in position by either electro-deposition or brazing. The pole member 37 may be laminated, and each pole 40, or alternate poles, may carry a held winding, or there may be a single serpentine winding; alternatively, it may have interdigitated poles with a single winding, or the held winding may be stationary. The input shaft 15, supported in bearings 16, 17 has keyed to it a pulley 19 drivable by a constant speed electric motor, and the output shaft 32, supported by bearings 34, 54 may carry a driven pulley, the rotor 52<SP>1</SP> of a tacho-generator 52, slip rings 47 via which brushes 50 supply regulatable current to the field winding, and part of an electromagnetically operated friction brake 51. The support member flange 21 carries a fan not shown to impel cooling air through casing end-member holes 29, 31 and flange holes 28.