JPS57129904A - Backward rotation prevention valve for drive circuit of hydraulic motor - Google Patents

Abstract

PURPOSE:To prevent the backward rotation of a hydraulic motor for driving the rotary member of a construction machine or the like, by providing a backward rotation prevention valve as an integrated unit in the drive circuit of the hydraulic motor to quickly balance the pressure in the supply and drain pipes of the motor. CONSTITUTION:In a hydraulc circuit in which a hydraulic motor 1 for driving a load unit 2 is connected to a pressurized oil source through a supply and a drain pipes 3, 4, a backward rotation prevention valve 7 which functions to by-pass the pipes 3, 4 by circuits 8, 8' for a prescribed time, depending on the pressure difference between the pipes 3, 4, is connected in parallel with relief valves 5, 6 which act in response to a prescribed level of pressure. The backward rotation prevention valve 7 comprises two relief valves 71, 71' and a pressure difference adjusting chamber unit 72. When the pressure in the pipe 4 has risen, the relief valve 71' is opened by the hydraulic pressure of the circuit 8' to by-pass pressurized oil to the pipe 3. In that case, some of pressurized oil in the circuit 8' is conducted to the right-hand chamber of the pressure difference adjusting chamber unit 72 through a orifice 75' to move a spool 73 rightward. At the end of the rightward movement of the spool 73, the valve 71' is put back into the original state.