Patent ID: 7717241

Claim:
An electric braking or clutching device comprising: a set of thrust washers; a set of friction disks, with the thrust washers being interleaved between the friction disks; a housing; an armature having an axis and disposed at the housing, the armature and the housing defining a radial air gap therebetween, with the armature defining an interior cavity therein and supporting the set of thrust washers in the interior cavity for longitudinal movement relative to the armature but against rotational movement relative to the armature; a shaft rotationally mounted in the housing and armature for rotation relative thereto, and carrying the set of friction disks thereon for longitudinal movement relative to the shaft but against rotational movement relative to the shaft; and a coil positioned at least in substantial part radially outwardly of the set of friction disks and the set of thrust washers and configured to generate, when energized, a magnetic field at the housing and armature, a flux path of the field extending from the coil into the armature, from the armature into the housing, and from the housing back to the coil, with the direction of the flux path from the armature into the housing being substantially radial in orientation, wherein the air gap is of a substantially fixed, radial dimension irrespective of wear of the device and the sets of friction discs and thrust washers are held substantially contained within the cavity of the armature.