Abstract: A reverse rotation preventing apparatus for a hydraulic actuator includes a hydraulic actuator for driving an inertia member, a main valve which is switched to a driving position in which a pressure oil is supplied to one of first and second ports of the hydraulic actuator and another one thereof is communicated with a tank and to a neutral position in which the first and second ports are shut off, a relief valve adapted to flow out a pressure oil in the first or second port to the tank at a time when a pressure on the side of the first or second port is higher than a set high pressure, a suction valve adapted to suck the pressure oil to the first or second port at a time when the pressure on the side of the first or second port is negative, and a reverse rotation preventing valve adapted to communicate the first and second port sides with the tanks respectively at a time when the pressure on the sides of the first and second ports is higher than a set pressure which is a pressure lower than the set high pres

Abstract: A hydraulic pilot valve, including a plurality of pressure reduction valve portions, each having an inlet port, an outlet port and a pressure regulating valve for establishing and blocking communication between both ports by movement of the pressure regulating valve, a plurality of pistons actuating the pressure regulating valves of the pressure reduction valve portions in the direction establishing communication, an operation lever having a pushing member pushing the plurality of pistons, and springs for biasing the pistons upwardly beyond a neutral position to retain them in an abutting relation with a pushing member. An operating lever is rocked from the neutral position in one direction to place the lever in an actuating position and push one piston to place one of the pressure reduction valve portions in a pressurized fluid supply condition to establish communication between the inlet portion and the outlet portion.

Abstract: A hydraulic pilot valve includes a valve body, first, second, third and fourth pressure reduction valves formed in the valve body and respectively having, outlet ports, inlet ports and spools for establishing and blocking communication between the ports, and an operation lever pivotally mounted on the valve body and being movable between a neutral position, a first position and a second position. When the operation lever is in the neutral position, the respective spools of the second and third pressure reduction valves are placed at positions establishing communication between the respective inlet port and outlet port. When the operation lever is in the first position, the respective spools of the first and third pressure reduction valves are placed at positions establishing communication between the respective inlet port and outlet port, and in conjunction therewith, the respective spools of the second and fourth pressure reduction valves block communication between the respective inlet port and outlet port.