[Solution] A pilot check valve includes a first body that has input and output ports, a main path 13 that is in communication these ports, and a check valve element that allows a flow of a pressure fluid from the input port toward the output port. The valve element blocks or allows a flow toward the input port side by supply or discharge of a pilot fluid and has a residual pressure exhaust path connected between the main path and an exhaust hole, a seal member that is provided in the exhaust path, and a push rod that moves the check valve element to a position where a flow of a pressure fluid toward the input port side in the main path is allowed and moves the seal member to a position where a flow toward the exhaust hole is allowed.

A servo-control having at least one movable cylinder that includes a hydraulic directional control valve. The hydraulic valve includes a control shaft that is rotatable about a longitudinal axis, the control shaft being connected to a distributor slide. The servo-control including a stationary abutment member secured to a cylinder and an input lever situated outside the cylinder. The input lever is connected to the control shaft and includes a stop portion arranged in the abutment member. The servo-control includes movement means for moving the input lever longitudinally, a first abutment surface of the abutment member limiting a travel amplitude of the stop portion when the input lever is in a first position.

To provide a drift-prevention valve device, a blade device, and a working machine capable of operating an actuated unit and preventing the machine body from drifting with a simple configuration. The drift-prevention valve device is provided with a non-return valve 41 that allows the flow of hydraulic oil from a control valve 28 to a head chamber 34h of a blade cylinder 34 and blocks the flow of the hydraulic oil in the reverse direction; and a piston accommodation part 42 separately disposed from an accommodation part 70 of the non-return valve 41, configured to movably accommodate a power piston 43. The power piston 43 defines a first piston chamber 42p1 communicating with a rod chamber of 34r of the blade cylinder 34 and a second piston chamber 42p2 for drain positioned on a poppet 71 side of the non-return valve 41 and communicating with a tank 52. The power piston 43 is connected to the poppet 71 of the non-return valve 41, so that the power piston 43 can be operated by the difference between the urging force of the poppet 71 by a spring 72 of the non-return valve 41 and a rod chamber pressure of the blade cylinder 34.

[Solution] A pilot check valve includes a first body that has input and output ports, a main path 13 that is in communication these ports, and a check valve element that allows a flow of a pressure fluid from the input port toward the output port. The valve element blocks or allows a flow toward the input port side by supply or discharge of a pilot fluid and has a residual pressure exhaust path connected between the main path and an exhaust hole, a seal member that is provided in the exhaust path, and a push rod that moves the check valve element to a position where a flow of a pressure fluid toward the input port side in the main path is allowed and moves the seal member to a position where a flow toward the exhaust hole is allowed.

A spool valve is provided. A valve housing has a pilot fluid passage, and a first portion and a second portion lengthwisely spaced apart from each other. A spool is movably inserted in the valve housing, and includes a plug able to enter the pilot fluid passage between the first portion and the second portion to change a flow area of the pilot fluid passage following movement of the spool. A hydraulic machine provides that when pilot fluid is supplied to the pilot fluid passage through the first portion, at least a portion of the supplied pilot fluid is provided to the holding valve through the second portion. The holding valve allows a flow of working fluid from the first chamber to the spool valve, and the spool moves to a third position to forward working fluid to the second chamber.

The present invention relates to a hydraulic switch arrangement and a fluid switch for incorporating into a hydraulic switch arrangement that may be included in a hydraulic circuit for inhibiting flow of hydraulic fluid through a hydraulic circuit in the event of movement of an apparatus or platform from a stable to an unstable condition. Such platforms or apparatus may include for example, cranes, excavators, teletrucks and forklift trucks and roll over incidents of such machinery is common leading to numerous fatalities. Aspects of the present invention ensure fast switching in the event of a transfer from a stable to an unstable condition.

An engine-driven oil pump has an engine, a pump unit, an oil diverting device, a manual control unit, and a remote control unit. The engine is connected to the pump unit. The oil diverting device is mounted on the pump unit and selectively pumps hydraulic oil from the pump unit into the manual control unit or the remote control unit. With the engine, the engine-driven oil pump can generate power independently instead of relying on external power supply. Besides, the electromagnetic valve of the remote control unit allows the user to remotely control the oil path of the hydraulic oil, so the user is not required to stay along the engine-driven oil pump to manually switch the oil path, and therefore the engine-driven oil pump is more efficient regarding manpower.

The invention relates to a pneumatic motor (1) for a feed pump, comprising a motor cylinder (10) and a motor piston (11) which is moveably arranged in the motor cylinder (10) and to which compressed air is applied, a valve unit (30), the compressed air providing for a downward movement (17) of the motor piston (11) when the valve unit (30) is in a first valve position and for an upward movement (19) of the motor piston (11) in the motor cylinder (10) when the valve unit is in a second valve position, upper stop means for the valve unit (30), by means of which the valve unit (30) is switched from the second valve position to the first valve position and thus the upward movement (19) is changed to the downward movement (17), and lower stop means for the valve unit (30), by means of which the valve unit (30) is switched from the first valve position to the second valve position and thus the downward movement (17) is changed to the upward movement (19). According to the invention, an active stroke-switching system (50) is provided, which comprises a switching cylinder (51) and a switching piston (52) which can move in the switching cylinder (51) and is coupled to the valve unit (30). The invention further relates to a method for operating the pneumatic motor.

An engine-driven oil pump has an engine, a pump unit, an oil diverting device, a manual control unit, and a remote control unit. The engine is connected to the pump unit. The oil diverting device is mounted on the pump unit and selectively pumps hydraulic oil from the pump unit into the manual control unit or the remote control unit. With the engine, the engine-driven oil pump can generate power independently instead of relying on external power supply. Besides, the electromagnetic valve of the remote control unit allows the user to remotely control the oil path of the hydraulic oil, so the user is not required to stay along the engine-driven oil pump to manually switch the oil path, and therefore the engine-driven oil pump is more efficient regarding manpower.

The invention discloses a hydraulic control system of a leveling hydraulic cylinder of a loading head, characterized by comprising a hydraulic pump, a two-position three-way electronic control reversing valve, a three-position four-way electronic control reversing valve, a three-position four-way cam valve and a hydraulic cylinder. The invention not only can perform leveling by using the electric control system, but also comprises the hydraulic cam valve controlling the hydraulic cylinder for self-leveling, and the two leveling manners can be independently used or switched mutually, thus achieving a better leveling effect.