Eddy current speed reducers

An eddy current speed reducer for slowing down a shaft, particularly a vehicle driving shaft, and comprising on the one hand an inductive stator formed from a support and ring of coils mounted on this support, having axes parallel to the shaft to be slowed down, which is mounted in two bearings carried by said support, each coil itself comprising a magnetic core surrounded by a winding of conducting wire and capped axially at its two ends by two magnetic plates forming flared pole pieces, and on the other hand an armature rotor formed from two discs made from a magnetic material fixed in rotation on the shaft to be slowed down so as to frame axially the stator and to travel past the flared pole pieces of this latter, these discs being provided with external cooling fins, characterized in that the support for the coils is formed by a closed rigid hollow and annular housing made from a non-magnetic metal or alloy, preferably liquid tight, the two walls of this housing perpendicular to the axis of the ring, having respectively therethrough openings through which pass jointingly the ends of cores of coils so that only the flared pole pieces appear outside the housing, said housing being formed as two half-shells clamped axially one against the other, the mutual axial clamping of the two half-shells being ensured, at the same time as the mounting of the coils on the housing, by screwing the flared polar pieces on cores by means of screws, the screwing of the flared pole pieces on the cores involving a prestressing effect, the axial contact between the two half-shells taking place before the axial contact between the flared pole pieces and the cores.