The invention relates to a hydraulic cylinder, for example for use with a hydraulic tool, which hydraulic tool is provided with a frame and an element which is movable with respect to the frame by means of the hydraulic cylinder. A hydraulic tool which is operated by means of a hydraulic cylinder as described above is known from, for example, European patent no. 0641618. This patent discloses a frame which is coupleable to a jib of an excavator or the like and to which an assembly of two jaws can be coupled. One of the jaws is pivotable with respect to the other jaw by means of a hydraulic adjusting cylinder (a double-acting piston/cylinder combination).

A valve assembly includes a proportional valve having an opening cross section that can be continuously varied by an actuator; a sensor for sensing the valve output pressure; a digital regulating device; and a switching valve disposed parallel to the proportional valve. The opening cross section of the switching valve is smaller than the maximum opening cross section of the proportional valve. The regulating device is programmed (i) to automatically calculate, at runtime, using the currently given valve output pressure and the current position of the actuator, the maximum working pressure achievable at the maximum opening of the proportional valve with the valve, (ii) and to additionally open the switching valve when the computed maximum achievable working pressure falls below a predefinable target working pressure by a definable deviation value.

A valve assembly includes a proportional valve having an opening cross section that can be continuously varied by an actuator; a sensor for sensing the valve output pressure; a digital regulating device; and a switching valve disposed parallel to the proportional valve. The opening cross section of the switching valve is smaller than the maximum opening cross section of the proportional valve. The regulating device is programmed (i) to automatically calculate, at runtime, using the currently given valve output pressure and the current position of the actuator, the maximum working pressure achievable at the maximum opening of the proportional valve with the valve, (ii) and to additionally open the switching valve when the computed maximum achievable working pressure falls below a predefinable target working pressure by a definable deviation value.

This hydraulic drive system includes: a hydraulic pump that supplies a working fluid to a hydraulic actuator; a meter-in control valve that controls a flow rate of the working fluid flowing from the hydraulic pump to the hydraulic actuator; a meter-out control valve that controls a flow rate of the working fluid being drained from the hydraulic actuator into a tank; and a regeneration valve that supplies, to the hydraulic actuator, the working fluid drained from the hydraulic actuator. The meter-out control valve is connected to the hydraulic actuator in parallel with the regeneration valve.

This hydraulic drive system includes: a hydraulic pump that supplies a working fluid to a hydraulic actuator; a meter-in control valve that controls a flow rate of the working fluid flowing from the hydraulic pump to the hydraulic actuator; a meter-out control valve that controls a flow rate of the working fluid being drained from the hydraulic actuator into a tank; and a regeneration valve that supplies, to the hydraulic actuator, the working fluid drained from the hydraulic actuator. The meter-out control valve is connected to the hydraulic actuator in parallel with the regeneration valve.

Disclosed is a hydraulic control apparatus including a flow-path selector valve that switches a supply flow path and a flow-path switching control unit that operates the same, a regeneration valve and a regeneration release valve capable of the regenerative operation, and a regeneration control unit that operates the same. The flow-path switching control unit makes the flow-path selector valve form a flow-path providing communication between first and second pumps in a combined operation state. The regeneration control unit judges the propriety of the regenerative operation on the basis of the second pump pressure which is the discharge pressure of the second pump in a single operation state and judges the propriety of the regenerative operation on the basis of whether or not the driving state of the work actuator is within an allowable range corresponding to the target work operation amount in the combined operation state.

Disclosed is a hydraulic control apparatus including a flow-path selector valve that switches a supply flow path and a flow-path switching control unit that operates the same, a regeneration valve and a regeneration release valve capable of the regenerative operation, and a regeneration control unit that operates the same. The flow-path switching control unit makes the flow-path selector valve form a flow-path providing communication between first and second pumps in a combined operation state. The regeneration control unit judges the propriety of the regenerative operation on the basis of the second pump pressure which is the discharge pressure of the second pump in a single operation state and judges the propriety of the regenerative operation on the basis of whether or not the driving state of the work actuator is within an allowable range corresponding to the target work operation amount in the combined operation state.

A control system for a work machine includes a plurality of hydraulic pumps that discharge hydraulic oil, a hydraulic cylinder that moves a working equipment element, a plurality of flow rate control valves that are respectively connected to the hydraulic pumps and adjust a flow rate of the hydraulic oil supplied to the hydraulic cylinder, a plurality of supply flow paths respectively connected to the of flow rate control valves, a meter-in flow path that connects a collective part of the supply flow paths and an inlet of the hydraulic oil in the hydraulic cylinder, a plurality of discharge flow paths respectively connected to the flow rate control valves, a meter-out flow path that connects a collective part of the discharge flow paths and an outlet of the hydraulic oil in the hydraulic cylinder, and a throttle disposed in the meter-out flow path.

The present invention relates to a stand-alone or inbuilt logical element associated with a hydraulic system for effective regeneration to improve the efficiency of any hydraulic system of a machine or equipment, including but not limited to farm machinery, industrial machinery, construction and mining machinery which uses hydraulic system. The logical element senses the cavitation or low pressure in the hydraulic system and automatically regulates and diverts the portion of hydraulic oil flow to caveated and required areas by regenerating through the anti-cavitation feature of the valve by automatically sensing and applying selective restriction to the set or adjustable pressure limit for the passage of oil.

The present invention relates to a stand-alone or inbuilt logical element associated with a hydraulic system for effective regeneration to improve the efficiency of any hydraulic system of a machine or equipment, including but not limited to farm machinery, industrial machinery, construction and mining machinery which uses hydraulic system. The logical element senses the cavitation or low pressure in the hydraulic system and automatically regulates and diverts the portion of hydraulic oil flow to caveated and required areas by regenerating through the anti-cavitation feature of the valve by automatically sensing and applying selective restriction to the set or adjustable pressure limit for the passage of oil.