Patent ID: 8221431

Claim:
A torque-limiting driver, comprising: a) a housing having a first proximal housing section with a drive end at which drive end a drive interface is disposed, and having a second housing section mechanically communicating with the first housing section by a housing coupling, the second housing section having a distal shaft end with a shaft port that is configured to receive a shank of a driver output shaft extending along a rotation axis of the driver; b) a wear-compensated torque-limiting assembly disposed within the housing and mechanically adapted to apply a torque from the drive interface with the driver output shaft, the torque-limiting assembly being adjustable to selectively set a calibrated maximum amount of torque that can be transmitted via the drive interface of the housing to the driver output shaft and comprising: i) a cam bearing assembly having a ball cage and a plurality of ball bearings held in a departured relationship with each other by the ball cage, ii) an outer cam race in which the ball bearings of the ball cage are received, wherein the outer cam race is held in a fixed non-rotating condition relative to the housing by a cam retainer interface on an outer surface of the outer cam race received in a complementary cam retainer interface on an inner surface of the first housing section, and wherein the outer cam race has an inner race surface in mechanical contact with the ball bearings, the inner surface adapted with a plurality of cam lobes disposed to provide that each ball bearing is similarly accommodated in a lobe, each lobe having a bottom ball detent portion, two ramp portions and a cam high-point portion, and a ball through distance defined as the distance between the bottom ball detent portion and the cam high-point portion of the lobe along a radius of the rotation axis, and iii) an inner race comprising a dome shaped portion with an outer surface and a central bushing running through it perpendicular to a base of the dome shape portion and concentric with the rotation axis of the driver, the central bushing configured to be slidable over a shank of a driver output shaft along the rotation axis, iv) wherein the outer cam race is in mechanical communication with the ball bearings in a radial vector substantially along a radius of the rotation axis of the fastener driver, and the inner race is in mechanical communication with the ball bearings in a non-radial vector off-set from a radius of the rotation axis of the fastener driver by an angle defined between a radius of the rotation axis and a ball radius perpendicular to the outer surface at a point of contact of the ball bearing, the angle increasing at a rate as an axial displacement increases; and c) a bearing load assembly in mechanical communication with the torque-limiting assembly and adapted to apply a bias force thereto to selectively set the calibrated maximum amount of torque that can be transmitted via the drive interface of the housing to a driver output shaft.