A magnetic friction clutch wherein two disk-shaped armatures are movable axially of and rotate with the driven shaft. One of the armatures is adjacent to a flywheel which is rotated by the output shaft of an electric motor and the other armature is adjacent to a stationary or rotary braking member. Each armature has a ring-shaped nave which is mounted on the driven shaft and a ring-shaped rim which surrounds and is magnetically separated from the respective rim. Annular facings of magnetically non-conductive material are provided on each of the armatures between the respective nave and rim and their exposed surfaces are flush with pole faces provided on the corresponding rim and nave. Two windings are mounted in the space between the two armatures and one thereof is energizable to cause the facing and the pole faces of one armature to bear against the flywheel, the other winding being energizable to cause the facing and the pole faces of the armature to bear against the braking member. Channels in the braking member, naves of the armatures and the flywheel serve to convey streams of cooling air which are induced by annuli of blades on the flywheel. The material of those portions of each rim and nave which are adjacent to the respective pole faces exhibits the same resistance to wear as the material of the facings.

In a clutch-and-brake unit for use with a continuously rotating, motor-driven shaft, for example in an industrial sewing machine, a single disk has a clutch surface on one side and a brake surface on the other side. The disk is magnetically urged into operative engagement with clutch and brake pressure plates facing the respective clutch and brake surfaces of the disk, the clutch pressure plate being rotated by the motor-driven shaft to rotate the disk and a shaft connected thereto when operatively engaged, and the brake pressure plate being non-rotatable to brake the shaft. The brake pressure plate is also constantly urged into light contact with the brake surface sufficient to brake the disk and shaft only when the disk is not operatively engaged with the clutch pressure plate. This prevents the disk and connected shaft from rotating when neither the clutch nor the brake are operatively engaged and eliminates engagement noise when the brake pressure plate is operatively engaged.

An electromagnetic powder coupling device which can be used either as a brake or a clutch. In order to remove undesirable heat in the device, one attributable to Joule heat mainly emanated by field member, a rotor and a cylinder, and to other to frictional heat, especially inevitable for this kind of electromagnetic powder coupling device which is emanated by the friction between the rotor, cylinder and the magnetic powder filled in the space between the cylinder and the rotor, the coupling device incorporates a forced air draft cooling system. Two variations of cooling systems are disclosed, both of which have, in common with, at least a blower and a plurality of passages for forced draft air cooling not only to the external part but also to the inner part of the field member and the cylinder.

An electromagnetic single-surface clutch/brake combination, especially for textile machinery, in which a rotor assembly is locked to the shaft end encloses the magnetic body carrying the coils so that the latter can be secured to the housing flange when the unit, as delivered, is mounted on the shaft. The rotor assembly and the magnetic body are bridged by a bearing.

A rotary electromagnetic clutch brake assembly having opposed spring and magnetic forces such that on activation the clutch engages momentarily before the brake releases and on deactivation the brake engages before the clutch disengages so as to assure precise positive control of the rotary output of the assembly.