Abstract

A keyless chuck for a rotary tool comprises a chuck body which is adapted to be coupled at its one end to a drive spindle of a drive source and coupled at the other end to a tool bit for establishing a driving connection from the drive source to the tool bit. Relatively rotatable to the chuck body is a handle ring which is operatively connected to a set of gripping jaws for tightening the gripping jaws on the tool bit upon being rotated in one direction and loosening the same upon being rotated in the opposite direction. The handle ring is disposed on the chuck body in such a manner as to coincide the rotating direction of the handle ring for tightening the gripping jaws with the reverse rotating direction of the chuck body for removing the tool bit from a workpiece. A clutch interconnects the handle ring and the chuck body in order to rotatively fix the handle ring to the chuck body when the latter is driven to rotate in the reverse direction of removing the tool bit, causing the handle ring to positively rotate in the direction of tightening the gripping jaws and thus preventing it from counter-rotating in the direction of loosening the tool bit when there develops an interaction between the rotating chuck body and the handle ring relatively rotatable thereto. Associated with the clutch is a control mechanism which functionally moves the clutch between an active position where it is activated for the clutch connection and an inactive where it releases the handle ring from the chuck body to permit the relative rotation of the handle ring with respect to the chuck body for enabling the hand tightening and loosening of the gripping jaws.