Patent ID: 6969073

Claim:
A chuck assembly comprising: a housing that defines a cylindrical inner space therein and that is formed with a hydraulic fluid inlet adapted to be connected to a hydraulic fluid supply; a sleeve that is co-axially mounted in said inner space, that is secured to said housing, that defines a shaft-receiving space therein, and that is formed with an annular groove in fluid communication with said hydraulic fluid inlet; a hollow shaft that co-axially and rotatably extends through said shaft-receiving space, that defines a chuck-receiving space therein, that is rotatable relative to said sleeve about an axis, and that is formed with a first fluid passage in fluid communication with said annular groove; a chuck unit that is co-axially mounted in said chuck-receiving space, that includes a plurality of angularly displaced jaws, and that cooperates with said shaft to define a piston-receiving chamber therebetween; a piston that is co-axially mounted in said piston-receiving chamber, that subdivides said piston-receiving chamber into first and second compartments, that is displaceable in an axial direction relative to said axis, and that is connected to said chuck unit in such a manner that axial displacement of said piston results in radial displacement of said jaws, said first compartment being in fluid communication with said first fluid passage; and an annular elastic sealing member that is received in said annular groove, that is sleeved on said shaft, and that is formed with a second fluid passage in fluid communication with said first fluid passage so as to permit flow of hydraulic fluid from the hydraulic fluid supply to said first compartment.