Improved power operated wrench or screwdriver

Claim 1

A power operated wrench or screwdriver comprising a motor, a reduction gear driven by the motor, an output shaft for the reduction gear, a head providing support for a tool for engaging a fastener to be rotated, and a clutch driven by the output shaft of the gear and having means for driving said tool, the clutch being formed in two portions, a torque-sensitive portion and a non-torque-sensitive portion, the one being driven by the other when the torque delivered by the tool does not exceed a predetermined value, the torque-sensitive portion comprising two main members, a driving member and a driven member, mounted upon a tubular member coaxial with the output shaft of the gear, and one of which is splined thereto and is movable longitudinally of the tubular member against the action of a first spring positioned upon tubular member, said driving member and driven member of the torque-sensitive portion being provided with interengaging members therebetween which cause longitudinal movement of said splined member thereof when the torque delivered by the tool exceeds said predetermined value without disengagement of the members, the non-torque-sensitive portion comprising two main co-axial members, a driven member associated with the tool and having circumferentially spaced dogs around the outer periphery thereof, and a driving member comprising a sleeve around the torque-sensitive portion and having circumferentially spaced dogs around the inner periphery thereof drivingly engageable with the dogs on the driven member of the non-torque-sensitive portion, and which are of such length as to be permanently engaged with circumferentially spaced dogs around the periphery of one of the main members of the torque-sensitive portion, the sleeve being movable longitudinally against the action of a second spring to disengage the drive of the second portion of the clutch, said sleeve being coupled to the longitudinally movable part of the torque-sensitive portion, so that, when the torque transmitted by the tool rises to said predetermined value, the drive, by way of the non-torque-sensitive portion, is interrupted by said longitudinal movement of the sleeve, and the dogs on the latter, due to the action of the second spring and their relative rotational speed, rotate in contact with the dogs on the driven member of the non-torque-sensitive portion without engagement while the motor is operative.