Provided is an electrohydrostatic actuation system including an emergency shut-off circuit to be actuated stably with a simple configuration. The electrohydrostatic actuation system includes: a hydraulic cylinder (24) including a piston (25) to which a valve element is connected, a first chamber (24A), and a second chamber (24B); a hydraulic pump (21) configured to supply hydraulic fluid to the first chamber (24A) or the second chamber (24B); a servo motor (M) configured to drive the hydraulic pump (21); a shuttle valve (11) configured to establish communication to a downstream side under a state in which a hydraulic pressure generated by the hydraulic pump (21) is maintained; a solenoid valve (12) configured to receive the hydraulic pressure via the shuttle valve (11) as a pilot pressure; and a logic valve (13) including a first port configured to receive the pilot pressure from the solenoid valve (12), and a second port to be communicated to the first chamber (24A) of the hydraulic cylinder (24). When the solenoid valve (12) is brought to a de-energized state, the pilot pressure of the logic valve (13) is released, and the logic valve (13) causes the hydraulic fluid in the first chamber (24A) communicated to the second port to flow into the second chamber (24B) so that emergency shut-off of the valve element is achieved by a return spring (26).

Provided is an electrohydrostatic actuation system including an emergency shut-off circuit to be actuated stably with a simple configuration. The electrohydrostatic actuation system includes: a hydraulic cylinder (24) including a piston (25) to which a valve element is connected, a first chamber (24A), and a second chamber (24B); a hydraulic pump (21) configured to supply hydraulic fluid to the first chamber (24A) or the second chamber (24B); a servo motor (M) configured to drive the hydraulic pump (21); a shuttle valve (11) configured to establish communication to a downstream side under a state in which a hydraulic pressure generated by the hydraulic pump (21) is maintained; a solenoid valve (12) configured to receive the hydraulic pressure via the shuttle valve (11) as a pilot pressure; and a logic valve (13) including a first port configured to receive the pilot pressure from the solenoid valve (12), and a second port to be communicated to the first chamber (24A) of the hydraulic cylinder (24). When the solenoid valve (12) is brought to a de-energized state, the pilot pressure of the logic valve (13) is released, and the logic valve (13) causes the hydraulic fluid in the first chamber (24A) communicated to the second port to flow into the second chamber (24B) so that emergency shut-off of the valve element is achieved by a return spring (26).

A hydraulic excavator drive system includes a regeneration line, which connects an arm pushing and an arm crowding supply line, each of which extends between an arm cylinder and arm control valve. The regeneration line includes regeneration and switching valves. A release line that is branched off from the regeneration line at a position between the regeneration valve and the switching valve is provided with a release valve. A secondary pressure from a first solenoid proportional valve is fed to a pilot port of the regeneration valve such that the regeneration valve opens at a time of arm crowding. A secondary pressure from a second solenoid proportional valve is fed to a pilot port of the release valve such that release valve opens at a time of arm pushing. An arm pushing pilot pressure for moving the arm control valve is led to a pilot port of the switching valve.

A hydraulic excavator drive system includes a regeneration line, which connects an arm pushing and an arm crowding supply line, each of which extends between an arm cylinder and arm control valve. The regeneration line includes regeneration and switching valves. A release line that is branched off from the regeneration line at a position between the regeneration valve and the switching valve is provided with a release valve. A secondary pressure from a first solenoid proportional valve is fed to a pilot port of the regeneration valve such that the regeneration valve opens at a time of arm crowding. A secondary pressure from a second solenoid proportional valve is fed to a pilot port of the release valve such that release valve opens at a time of arm pushing. An arm pushing pilot pressure for moving the arm control valve is led to a pilot port of the switching valve.

The present invention provides an improved high-low hydraulic system for compacting machinery, such as balers, horizontal balers, compactors, transfer station compactors, and the like. The high-low hydraulic system comprises at least one double rotary pump, a plurality of directional control valves, a pilot-operated back pressure reducing valve, a flow control valve, a plurality of one-way valves, and a plurality of pressure switches. The high-low hydraulic system may be regenerative or non-regenerative and provides many advantages over conventional hydraulic systems. Such advantages include greater system efficiency due to a reduced back pressure during the time of the retraction stroke and clever flow sequencing, mitigation of hydraulic shocks at the beginning and end of compaction and retraction strokes, and reduced cycle time of the cylinder during operation due to the concurrent filling of the rod end side during decompression of the blind end side after the compaction stroke. Moreover, the present high-low hydraulic system allows for the cylinder to operate at three or more independent speeds. Additionally, the present high-low hydraulic system may also comprise an accumulator and pressure transducer that further assist with substantially maintaining a predetermined hydraulic pressure on the blind end side after the completion of the compaction stroke.

The present invention provides an improved high-low hydraulic system for compacting machinery, such as balers, horizontal balers, compactors, transfer station compactors, and the like. The high-low hydraulic system comprises at least one double rotary pump, a plurality of directional control valves, a pilot-operated back pressure reducing valve, a flow control valve, a plurality of one-way valves, and a plurality of pressure switches. The high-low hydraulic system may be regenerative or non-regenerative and provides many advantages over conventional hydraulic systems. Such advantages include greater system efficiency due to a reduced back pressure during the time of the retraction stroke and clever flow sequencing, mitigation of hydraulic shocks at the beginning and end of compaction and retraction strokes, and reduced cycle time of the cylinder during operation due to the concurrent filling of the rod end side during decompression of the blind end side after the compaction stroke. Moreover, the present high-low hydraulic system allows for the cylinder to operate at three or more independent speeds.

It is made possible to suppress variations of the speed of an actuator into which a regeneration flow rate flows, regardless of variations of the regeneration flow rate caused by posture changes of the front part and to enhance the operability when the front part moves in the free fall direction, and hydraulic fluid discharged from an actuator driving the front part is regenerated. Accordingly, a controller 19 of a hydraulic system is provided with a regeneration control calculation section 19b, and a pump flow rate control calculation section 19c, and when the regeneration control calculation section controls a regeneration valve 12 to perform regeneration, the pump flow rate control calculation section controls a pump flow rate regulation device 20 to increase the delivery flow rate of a hydraulic pump 1 as the angle of an arm 16 approaches the vertically downward direction based on posture information about the arm 16 acquired by an inertial measurement unit 31.

In order to reduce fluid consumption, a fluid return apparatus is provided for a double-acting cylinder having a first fluid connection for supplying fluid to a first cylinder chamber of the cylinder and a second fluid connection for supplying fluid to a second cylinder chamber at a piston rod-side of the cylinder. The fluid return apparatus comprises a first fluid passage providing fluid communication between the first fluid connection and the first cylinder chamber; a rapid venting valve comprising an inlet providing communication with the second fluid connection; an outlet providing communication with the piston-rod-side second cylinder chamber; a vent of the rapid venting valve, connected by a second fluid passage to the first fluid passage; and a non-return fitting in the second fluid passage, which prevents fluid from flowing from the first fluid passage to the rapid venting valve and an auxiliary outlet device.

A regeneration valve includes a housing defining a first port, a second port, a third port, and a chamber fluidly communicating with the first, second, and third ports. The chamber has a valve element movable between a first position, in which the second port fluidly communicates with the first port, and a second position, in which the second port fluidly communicates with the third port. A resilient member biases the valve element towards the first position. In operation, a flow restrictor element moves between the first port and the second port for restricting fluid flow from the second port to the first port. At a predetermined flow rate between the second port and the first port, if a supply pressure of fluid at the actuation chamber exceeds the bias of the resilient member, the valve element moves to the second position for fluidly communicating the second and third ports.

An autarkic hydraulic linear drive with a hydraulic arrangement and a method for operating the same. The hydraulic arrangement a pump unit, an equalizing reservoir, a load switching valve configured to switch between a fast extension and a load extension, and a hysteresis circuit. The hysteresis circuit is configured for triggering a first switching process of the load switching valve at a first control pressure and a second switching process of the load switching valve at a second control pressure that is different than the first control pressure.