Fluid-operated collet chuck with centering fingers

In a method of operating a workpiece gripping chuck having a chuck body with a front end and a rear base end adapted to mount on a machine tool;

• a workpiece support surface for the front end of the chuck body for supporting a workpiece to be machined;
• a first plurality of generally radially movable prepositioning fingers supported in circumferentially spaced relation concentrically with said axis by said chuck body;
• a second plurality of both generally axially and radially movable flexible fingers supported concentrically with said axis on said chuck body in circumferentially spaced position, with certain of said second plurality of fingers radially adjacent said prepositioning fingers;
• an inflatable bladder on said chuck body in generally concentric relationship with said axis and adjacent to said second plurality of fingers;
• interengaging actuating surfaces on said prepositioning fingers and said certain of said fingers whereby movement of said certain of said fingers moves said prepositioning fingers generally radially;
• and control mechanism for first causing axial movement of said certain of said fingers to move said prepositioning fingers generally radially and then supplying fluid under pressure to inflate said bladder, the steps of:
• (a) loading a workpiece, having a radial wall to be gripped, to said workpiece support surface;
• (b) moving said certain of said fingers generally axially to actuate said prepositioning fingers and cause them to move radially and engage said radial wall to center the workpiece;
• and
• (c) inflating said bladder to cause said second plurality of fingers, other than said certain fingers to grip the centered radial wall of the workpiece.

In a workpiece gripping chuck;

• (a) a chuck body having a front end and a rear base end adapted to be mounted on a machine tool;
• (b) a workpiece support surface for the front end of said chuck body;
• (c) a first plurality of circumferentially spaced, generally radially movable, workpiece centering fingers supported concentrically with said axis on said chuck body;
• (d) a second plurality of circumferentially spaced, generally radially deflectable axially extending fingers supported concentrically with said axis on said chuck body, with certain of said fingers radially adjacent said centering fingers;
• (e) engageable interacting surfaces on said centering fingers and said certain of said fingers whereby movement of said certain of said fingers moves said centering fingers generally radially;
• (f) an inflatable bladder on said chuck body in generally concentric relationship with said axis and second plurality of fingers and radially adjacent thereto;
• and
• (g) control mechanism for causing movement of said certain of said fingers to radially move said centering fingers to grip and center the workpiece, and inflating said bladder to activate said second plurality of fingers to radially deflect and grip said workpiece.

In a workpiece gripping chuck;

• (a) an axially extending chuck body having a front end and a rear base end adapted to be mounted on a machine tool;
• (b) a workpiece support surface for the front end of said chuck body;
• (c) a collet mechanism having generally radially movable workpiece centering fingers and generally radially deflectable gripping fingers supported concentrically with the chuck body;
• (d) an inflatable bladder on said chuck body in generally concentric relationship with said fingers and radially adjacent thereto;
• and
• (e) control mechanism for first causing radial movement of said centering fingers to radially center the workpiece, and for inflating said bladder to activate said gripping fingers to radially deflect to grip said centered workpiece.