Magnetic hysteresis brake with adjustable air gap

A magnetic hysteresis brake, comprising an inner element having an outer surface centred on a pivot axis and an outer element having an inner surface which is centred on the pivot axis and which defines an housing for receiving the inner element, such that the inner element and the outer element are rotatable about the pivot axis to each other, one of the elements being provided with magnets and the other of the elements being made of semi-remanent material, such that the magnets generate in the semi-remanent material an induced magnetic field through said surfaces when said surfaces oppose each other, the brake comprising a member for adjusting in the axial position of one of the elements relative to the other of the elements in order to adjust a degree of engagement of the inner element into the outer element and therefore an intensity of the induced magnetic field and at least one from among the inner element and the outer element being adjustable in position and mounted to slide on a shaft, wherein the member for adjusting in the axial position comprises at least one screw which extends parallel to the pivot axis and which comprises two end sections threaded in opposite directions and engages respectively in a thread of the inner element carried by the shaft and, for the other, in a thread of a collar of the shaft and a locking of the adjustment in the axial position is ensured by needle screws engaged in threads of the collar to project from the collar and bear against the element mounted on the shaft.