Patent ID: 6123341
Filing Date: 2000-09-26
Classification: B23B,Y10T

Abstract:
A chuck assembly comprising a tubular chuck body concentrically fixed to a main spindle of a machine tool, three first cylinders and a plurality of second cylinders provided in said chuck body, said first and second cylinders being arranged along a circumference in a plane perpendicular to said spindle at equal angular intervals, pistons mounted in said first and second cylinders and adapted to radially protrude under fluid pressure and retract under the force of springs or under fluid pressure, said first cylinders being arranged at equal angular intervals and, each of said first and second cylinders having a rod adapted to protrude and retract from a cylindrical surface of said chuck body, said first and second cylinders communicating with a pressure fluid source through a pressure fluid supply passage provided in said chuck body, whereby a workpiece is chucked by applying the pressure fluid from the pressure fluid source to said pistons, and a pressure-biasing means for applying pressure to the pistons of said first cylinders against the workpiece independently of the fluid pressure from said pressure fluid source.