Eddy current couplings

Claim 1

An eddy current coupling comprising a rotatable input shaft, a rotatable output shaft, at least one field winding, a pole member on which the field winding is mounted and which exhibits a series of poles, alternate poles of the series exhibiting the same polarity when the field winding is excited, the pole member being connected to one of the shafts for rotation therewith, and a loss member connected to the other shaft for rotation therewith and being coaxial with the pole member, said loss member being associated with the pole member so 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 the loss member whereby the reaction between the eddy currents and the flux serves to transmit torque between the member while there is slip, i.e. relative rotation, between the members; said loss member including: a support of a ferrous material having a first electrical resistivity, said support being secured to said other shaft; a loss ring of ferromagnetic material having a second electrical resistivity lower than said first electrical resistivity, said ferromagnetic material containing at least 95 percent by weight of a metal selected from the group consisting of iron and nickel, said loss ring being a relatively thick continuous membeR which is carried by a coextensive portion of said support so that there is a small air gap between the poles of the pole member and the loss ring; and end rings of nonmagnetic material having a third electrical resistivity lower than said second electrical resistivity and located at the edges of the loss ring in good electrical contact therewith.