Self-tightening hammer-drill chuck

Abstract

A drill chuck has a chuck body centered on and rotatable about an axis and formed with a plurality of jaw guides angularly spaced about the axis and all inclined axially forwardly and with an axially directed annular inner bearing track centered on the axis. Respective jaws in the guides are each formed with a row of teeth that can mesh with a screwthread of an adjustment sleeve generally axially fixed on the body and rotatable on the body in a tightening direction to displace the jaws axially forward and radially toward one another and in an opposite loosening direction to displace the jaws axially backward and radially away from one another. The adjustment sleeve is formed with an axially directed annular inner bearing track centered on the axis and axially confronting the inner bearing track of the chuck body and one of the inner bearing tracks is substantially planar and perpendicular to the axis and the other inner bearing track is substantially frustoconical and angled outwardly away from the one inner bearing track. An array of bearing balls is axially engaged between the inner bearing tracks and a locking ring rotatable on the chuck body and formed with a radially inwardly directed and substantially frustoconical outer track bearing radially inward on the bearing balls. A tightening screwthread on the locking ring axially displaces the locking ring relative to the chuck body on relative rotation of the adjustment sleeve and locking ring.