Locking quick-change chuck assembly

A locking chuck assembly for a tool bit shank of the type which has a generally hexagonal cross-sectional shape and a circumferential groove disposed thereabout, the chuck assembly comprising:

• a chuck hub having a forward face and a fixed radial extension;
• a longitudinal bore in the chuck hub for receiving the tool bit shank, the longitudinal bore having a terminating face and a generally hexagonal cross-sectional shape;
• a shuttle disposed in the longitudinal bore, the shuttle having a bit end, a spring end, a forward lower face and a rearward interim face and the shuttle being slidable along the longitudinal bore between a rearward position and a forward position;
• a shuttle spring disposed between the spring end of the shuttle and the terminating face of the longitudinal bore, wherein the shuttle spring acts to bias the shuttle to its forward position;
• a rear bore extending radially through the chuck hub proximate the terminating face of the longitudinal bore so as to be in communication with the longitudinal bore;
• a shuttle detent ball disposed in the rear bore so as to selectively engage the shuttle;
• a front bore extending radially through the hub proximate the forward face of the longitudinal bore so as to be in communication with the longitudinal bore;
• a bit detent ball disposed in the front bore so as to selectively engage the circumferential groove of the tool bit shank;
• a sleeve disposed annularly about the chuck hub, the sleeve being slidable along the chuck hub between a tool bit loaded position and a load/unload position;
• a sleeve spring disposed between the fixed radial extension of the chuck hub and the sleeve to bias the sleeve toward its tool bit loaded position;
• wherein when the sleeve is disposed in its tool bit loaded position, the shuttle is positioned in its rearward position such that the shuttle spring is compressed and the shuttle detent ball is engaged with the forward lower face on the shuttle so as to prevent the shuttle spring from moving the shuttle, while allowing the sleeve spring to bias the sleeve;
• and
• wherein when the sleeve is disposed in its load/unload position, the shuttle is positioned in its forward position such that the shuttle spring is less compressed than when the shuttle is in its rearward position and the shuttle detent ball is engaged with an rearward interim face on the shuttle and the sleeve in a position to allow the shuttle spring to bias the shuttle away from the terminating face of the longitudinal bore.

A method for securing tool bit shanks having a hexagonally shaped cross section into a rotary power tool driver comprising:

• providing a chuck assembly having a spindle releasably securable within the rotary power tool, a chuck hub which has longitudinally extending bore therein having a closed end, an open end, and a generally hexagonal cross-sectional shape, a radially extending bit ball bore in communication with the longitudinally extending bore, and a bit ball movable in the ball bore between a first retracted position out of the longitudinally extending bore and a second engaged position partially in the longitudinally extending bore;
• providing a sleeve which is movable longitudinally on the chuck hub between a first position and a second position;
• providing a shuttle slidably disposed in the longitudinally extending bore, a compression spring for urging the shuttle away from the closed end of the longitudinally extending bore, and a single shuttle ball disposed in a radially extending shuttle ball bore in the chuck hub which is in communication with the longitudinally extending, hexagonally shaped bore of the chuck hub;
• inserting a first tool shank having a hexagonally shaped cross-section into the longitudinally extending bore so as to contact the shuttle and move the shuttle rearwardly;
• moving the shuttle ball in the shuttle ball bore between a first retracted position where the shuttle ball contacts a rearward outer section of the shuttle which has a first lateral dimension and a second extended position where the shuttle ball contacts a forward outer section of the shuttle which has a second, smaller lateral dimension so as to limit the extent of forward movement of the shuttle in the longitudinally extending bore;
• moving the bit ball into its second extended position so as to engage a circumferentially extending groove about the first tool shank having a hexagonally shaped cross-section;
• moving the sleeve to the sleeve's first position which in turn causes the bit ball to move to its first retracted position and the shuttle ball to move to its first retracted position;
• locking the sleeve into the first position with the shuttle ball;
• extracting the first tool shank from the longitudinal bore.