A grease injection valve 10 is provided having a valve body 16 including a flow path 15 the valve body. A foreign matter intrusion prevention valve 18 is provided at the upstream side of a check valve 17 in the flow path 15 of valve body 16. Grooves 47 are positioned around the periphery of a foreign matter intrusion prevention valve body 44 in the flow path 15 to provide communication between the downstream side and the upstream side of the foreign matter intrusion prevention valve body 44. When the check valve 17 has a functional failure, high-pressure grease escapes through the grooves 47 to bypass the foreign matter intrusion prevention valve body 44 and is discharged to an exterior of the grease injection valve 10. This can avoid excessive pressure caused by the grease backflow from being applied to the foreign matter intrusion prevention valve 18.

A fluid pressure control device for a power shovel includes: a first switching valve configured to permit or prohibit communication between a first pump and a first cylinder; a second switching valve configured to permit or prohibit communication between a second pump and a second cylinder; a third pump configured to allow to supply working fluid to the first cylinder and the second cylinder; a first junction control valve configured to permit or prohibit communication between the third pump and the first cylinder or the second cylinder; and a communication control valve configured to prohibit communication between the third pump and the first cylinder to guide the working fluid discharged by the third pump to the second cylinder by controlling the first junction control valve in a case where the second pump is communicated with the second cylinder by the second switching valve regardless of whether or not the first pump is communicated with the first cylinder by the first switching valve.

A hydraulic axle includes a reversible hydraulic pump. The hydraulic axle has a multi-surface cylinder with two retraction surfaces and two deployment surfaces. A first deployment surface and a first retraction surface are configured to interconnect with each other and separate from other surface during a rapid-traverse stroke. A pressure medium is configured to act on the second deployment surface to enable deployment.

A hydraulic drive unit for use in a vehicle or other application incorporates a motor connected to a pump through a porting system and an output shaft driven by the motor. A mechanical brake is used to brake the motor, while a valve provides a hydraulic brake for preventing flow between the hydraulic motor and the hydraulic pump. A brake actuator is connected to both the mechanical brake and the hydraulic brake, whereby actuation of the brake actuator causes both the mechanical brake and the hydraulic brake to be actuated.

A hydraulic drive unit for use in a vehicle or other application incorporates a motor connected to a pump through a porting system and an output shaft driven by the motor. A mechanical brake is used to brake the motor, while a valve provides a hydraulic brake for preventing flow between the hydraulic motor and the hydraulic pump. A brake actuator is connected to both the mechanical brake and the hydraulic brake, whereby actuation of the brake actuator causes both the mechanical brake and the hydraulic brake to be actuated.

Disclosed is a flow control valve for construction machinery, the flow control valve being adapted to reduce pressure loss due to flow on return to a hydraulic tank during the boom-down operation of a large-scale excavator. The flow control valve for construction machinery according to the present invention comprises: first and second boom spools which are respectively coupled to first and second boom valve blocks, and which regulate working fluid that is respectively supplied from first and second hydraulic pumps to a boom cylinder during direction reversal; a boom-up flow-adjusting means which, in direction reversal of the first and second boom spools for boom-up drive, supplies working fluid from the first and second hydraulic pumps into a large chamber of the boom cylinder via the first and second boom spools respectively, and causes part of the flow of working fluid from the second hydraulic pump to pass via the second boom spool so as to be combined with working fluid being supplied from the first hydraulic pump to the large chamber of the boom cylinder due to direction reversal of the first boom spool; and a boom-down flow-adjusting means which, in direction reversal of the first and second boom spools for boom-down drive, causes part of the flow of working fluid coming back from the large chamber of the boom cylinder to return to the hydraulic tank via the first and second boom spools respectively, and causes part of the flow of working fluid coming back from the large chamber of the boom cylinder to combine as respective regenerative flows for working fluid on the small chamber side of the boom cylinder.

Disclosed is a hydraulic system for performing land preparation works by means of a simultaneous boom-up and arm-in operation. The hydraulic system according to the present invention includes: an arm cylinder and a boom cylinder that are connected to first and second hydraulic pumps, respectively; a first boom control valve that is disposed in the discharge flow path of the second hydraulic pump; a second boom control valve that is disposed in the discharge flow path of the first hydraulic pump and causes the working fluid of the first hydraulic pump to converge with the working fluid which is supplied from the second hydraulic pump to the boom cylinder; a first arm control valve that is disposed in the discharge flow path of the first hydraulic pump; a second arm control valve that is disposed in the discharge flow path of the second hydraulic pump and causes the working fluid of the second hydraulic pump to converge with the working fluid which is supplied from the first hydraulic pump to the arm cylinder; a recycle valve that is disposed in the flow path between the working fluid inlet port of the first arm control valve and a hydraulic tank; and a second boom control valve spool having a parallel pressure section in which the boom-up pilot pressure does not increase with respect to the boom-up strokes during the simultaneous boom-up and arm-in operation.

A speed controller capable of controlling an action speed of an external cylinder in one stroke in a step-wise manner. The speed controller includes a first flow path and a second flow path that allow a first port and a second port to be in communication with each other. The first flow path is provided with a first check valve for allowing flow from the first port to the second port. The second flow path is provided with a first needle valve, and an opening hole of the first check valve is constituted as a part of a flow path. The first needle valve adjusts the flow rate by changing an opening area of the opening hole with a tip portion fixed on a piston in the cylinder chamber. The speed controller further includes a third flow path allowing the first port and the cylinder chamber to be in communication with each other. The third flow path is provided with a second check valve for allowing flow from the first port to the cylinder chamber.

The present invention relates to a hydraulic control valve for construction machinery that is used to maintain secondary pilot pressure which is formed proportionally to the switching of a switching device so as to be equal to or below a setting pressure of a pilot pump. The hydraulic control valve of the present invention includes: a port of the pilot pump into which the pilot pressure flows; a tank port to which the pilot pressure is drained; a valve body at which a secondary pilot pressure port that selectively communicates with the port of the pilot pump and the tank port is formed; the switching device that is pivotally mounted on the valve body; a pilot control valve that is linked through pressurization of the switching device and has a spool which forms the secondary pilot pressure proportional to the amount of switching of the switching device by communicating the port of the pilot pump and the secondary pilot pressure port with each other during the switching; a valve spring that elastically supports the spool so as to communicate the secondary pilot pressure port and the tank port with each other; and a check poppet that is disposed in an openable and closable manner at a pilot passage whose inlet side communicates with the secondary pilot pressure port and whose outlet side communicates with the port of the pilot pump.

The invention relates to a flow control valve adapted for use as a flow-dividing and flow-combining valve in hydraulic devices, comprising: a valve body having a first longitudinally extending bore, an outer spool slidably positioned within the bore, the outer spool having an axially extending passageway, a pair of axially extending inner spools slidably positioned within the passageway, the valve body having a first port and a pair of second ports, the outer spool having at least a first opening communicating with the first port and with the passageway, and at least two pairs of second openings therethrough. At least one second opening of each pair is of non-constant longitudinal section narrowing from the outer face of the outer spool on at least a part of the thickness of the second opening, so that a lateral side of the second opening offers an obstacle where a part of the fluid flow entering the second opening crashes before entering the inner spool.