Abstract: A device comprising a cylinder and a piston slidably fitted therein and having a metal piston ring attached to its outer periphery. The cylinder has a recess in each of a plurality of portions thereof dividing the inner periphery of the cylinder circumferentially thereof and opposed to the piston ring when the piston is brought close to each of its opposite stroke ends, the recess having a width smaller than the width of fit of the piston to the cylinder. The piston has a recess corresponding to the recess in the cylinder inner periphery and formed in each of a plurality of portions of the piston in the vicinity of the piston ring and diving the outer periphery of the piston circumferentially thereof. The cylinder has two oil chambers formed on the respective opposite sides of the piston and adapted to communicate with each other through the cylinder recess and the piston recess upon the piston being brought close to each stroke end.

Abstract: A hydraulic control valve which comprises a casing having an oil inlet channel and an oil outlet channel and formed with groove portions and land portions arranged alternately in a specified direction, and a valve member having a return oil channel and attached to the casing so as to be movable relative thereto in the specified direction, the valve member having groove portions and land portions arranged alternately in the specified direction, the groove portions and the land portions of the casing being opposed to the land portions and the groove portions of the valve member respectively when the valve is in a neutral state, permitting oil supplied from the oil inlet channel to flow into the return oil channel, the valve member being movable from the neutral state relative to the casing for the land portions of the casing and the valve member to block communication betwen the oil inlet channel and the return oil channel to permit the oil supplied from the oil inlet channel to flow into the oil outlet channel