GB962609A - An improved method and apparatus for operating a pressurised fluid actuated chuck - Google Patents

Abstract

962,609. Chucks. PRATT PRECISION HYDRAULICS Ltd. Sept. 26, 1962 [Sept. 26, 1961], No. 36511/62. Heading B3B. A fluid actuated chuck incorporates means to permit momentary reversal of the jaw pressure to free a jammed or locked workpiece without releasing it from the jaws, in order to prevent distortion of the workpiece during the finishing machining operation. In the operation of this chuck fluid is supplied to either side of a piston 6 via pipes 13, 14 and exhausted thereby as required during operation. Solenoid valves EV 1 and EV 2 control the fluid flow to and from each side of the piston, the fluid pressure being supplied sequentially from a high pressure pump P 1 and a low pressure pump P 2 . Fig. 1 shows the relative disposition of parts during the rough machining of a workpiece. Neither of the valves EV 1 or EV 2 is energized and high pressure fluid from pump P1 passes through the valves at points A, H, K and D to chamber 11 in the chuck to actuate the piston and hence the jaws 9 to grip the workpiece. At the completion of this roughing operation valve EV 1 is energized (see Fig. 2), permitting low pressure fluid to enter the system, thus reducing the pressure in the chamber 11. Valve EV 2 is now energized momentarily with valve EV 1 (see Fig. 3) which permits the transfer of the low pressure fluid to chamber 12 on the other side of the piston and chamber 11 is permitted to discharge via duct 26a and through regulator R which is adjusted to prevent the workpiece being released by the chuck jaws. Following this momentary discharge, valve EV 2 is deenergized and the arrangement reverts to that shown in Fig. 2. At the end of the finishing operation valve EV 2 is energized and EV 1 deenergized, which permits high pressure fluid to enter chamber 12 which actuates the jaws to release the workpiece from the chuck. The operation of the valves may be automatic by means of time relays or manual by way of pushbutton operation. The regulator valve R may be one of a number of types depending on whether the fluid pressure medium is oil or air.