JPS5740174A - Relief valve for brake circuit - Google Patents

Abstract

PURPOSE: To prevent the swingback phenomena caused by inertia force in a brake circuit etc. for the hydraulic swinging system of an oil-hydraulic operated shovel by permitting a relief valve, to be closed when the brake is operated, to open and be closed again in accordance with change of the oil pressure.

CONSTITUTION: When the brake is applied, an oil-hydraulic motor makes pumping action with the aid of the inertia force to raise the liquid pressure in the oil- hydraulic circuit abruptly and thereby to raise the liquid pressure in the primary side passage 32. Accordingly, the pushing force applied to a poppet 19 and a moving sheet 18 gets over the force of springs 24, 28 to move the poppet 19 and moving sheet 18 to the left in the butted state, i.e. with the relief valve closed. When, thereafter, the liquid pressure in the primary side passage 32 exceeds the set pressure of the relief valve, the intermediate step part 26 of the moving sheet 18 runs against the foremost face 23 of the valve element 13 to stop the moving sheet 18, but the poppet 19 continues to move leftward to open the relief valve. Thereby the oil- hydraulic motor circuit is closed to sink the liquid pressure in the primary side passage 32 gradually, and the poppet 19 comes in contact with the moving sheet 18 to shut the relief valve. Thus the energy required for revolution of the inertia body is eliminated and the motor is stopped.

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