Miller Fluid Power Corporation

Stephen K McDaniel

John F Bowbin

Ming Liu

Raymond L Ghislain

Locking apparatus for a piston and cylinder device includes a locking plunger connected to the piston and disposed between the piston and an end cap of the piston and cylinder device. The locking plunger includes a sleeve which carries a plurality of radially movable ball bearings. As the piston is moved toward an extreme position of the device, the ball bearings contact a spring loaded locking plug disposed in the head of the device, thereby moving the plug away from a first position. The piston and locking plunger continue to move the locking plug away from the first position until the balls are aligned with a circumferential groove or channel in the head. At this point the locking plug is moved to the first position under spring force, in turn moving the ball bearings radially outward into engagement with the channel or groove. The piston and piston rod of the device are thereby locked in position in the absence of fluid pressure. The locking plug includes surfaces against which pressurized fluid acts at the beginning of a return stroke to move the plug away from the first position and release the ball bearings from the channel. The piston is thereby unlocked and is free to move toward the other extreme position of the device.

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Glen Ellyn, IL, United States of America

Stephen K McDaniel