The invention relates to a press for extruding metal material. The press comprises a hydraulic oil circuit for controlling one or more extrusion pistons movable within corresponding cylinders. Such a circuit comprises a fixed displacement, circulation pump operated by an electric motor with variable rotation speed. The hydraulic circuit comprises a main line and a branch line, along which a shutoff element is arranged. The hydraulic circuit comprises a hydraulic control unit comprising a pilot valve arranged along a pilot line provided with a first segment communicating with the main line and a second discharging segment. Said hydraulic unit is provided to move the shutoff element between an opening position and a closing position of the branch line according to the difference between the oil pressure upstream of the shutoff element and that in the first segment of said pilot line. The hydraulic circuit further comprises a control element which, in an activation condition, and as a result of the activation of said pilot valve, determines a gradual increase of the pressure in the first segment of said pilot line and a corresponding gradual closing movement of said shutoff element causing a consequent gradual increase of the thrust on the piston until the reference speed is reached.

A power unit with manual override control for a hydraulic system having an initial state and at least one operational state is provided, comprising: a tank for storing hydraulic fluid that moves between a first chamber and a second chamber of a hydraulic cylinder; a pump that routes the hydraulic fluid in and out of the tank; a first relief valve; a first solenoid valve configured to shift between a plurality of positions based on the at least one operational state of the hydraulic system; a first check valve connected to the first solenoid valve; a manual override control unit comprising: a second check valve; and a second solenoid valve configured to shift between a plurality of positions based on activation of a manual override control, wherein the activation of the manual override control returns the hydraulic system from the at least one operational state to the initial state.

Provided is a hydraulic shovel capable of moving a boom, an arm, and a bucket at respective adequate speeds even during complex operations thereof, without a significant pressure loss. This hydraulic shovel includes: a first pump (31) connected to a boom actuator (24) and a bucket actuator (28); a second pump (32) connected to an arm actuator (26) and the boom actuator (24); a third pump (33) connect to the arm actuator (26); a boom control valve (54) interposed between the first pump (31) and the boom actuator (24); an arm control valve (56) interposed between the second pump (32) and the arm actuator (26); a bucket control valve (58) interposed between the first pump (31) and the bucket actuator (28); a boom merging valve (55) for speed increase interposed between the second pump (32) and the boom actuator (24); and an arm merging valve (57) for speed increase interposed between the third pump (33) and the arm actuator (26).

To provide a construction machine that has a hydraulic system mounted thereon in which a closed-circuit pump, and an open-circuit pump and a proportional valve are arranged as a pair, and that makes it possible to use an unused open-circuit pump or proportional valve to accelerate the speed of a single rod hydraulic cylinder when the single rod hydraulic cylinder and a hydraulic motor are driven simultaneously. A controller (51) controls a cap-side selector valve (46) and a rod-side selector valve (47) such that a particular open-circuit pump (15) not connected to a single rod hydraulic cylinder (3) is connected to the single rod hydraulic cylinder, and controls an opening area of a particular proportional valve (49) provided on a flow line that connects a delivery port of the particular open-circuit pump to a tank, when the single rod hydraulic cylinder and a hydraulic motor (7) are driven simultaneously.

The construction machine includes: a control valve that switchingly supplies hydraulic fluid from a hydraulic pump to a hydraulic actuator; a control valve drive device that supplies pilot secondary hydraulic fluid to the control valve in accordance with an operation of an operation lever device; a pilot hydraulic pump that supplies pilot primary hydraulic fluid to the control valve drive device; a pressure accumulation device that recovers return hydraulic fluid returned from the hydraulic actuator. The construction machine further includes: a check valve provided in a line between the pilot hydraulic pump and the control valve drive device; a pressure reducing valve that supplied the hydraulic fluid accumulated in the pressure accumulation device; a flow rate reduction device; and a controller that controls the flow rate reduction device in accordance with the pressure in the line between the check valve and the control valve drive device.

A sequentially operated hydraulic valve for regulating a hydraulic fluid pressure from a single pressurized hydraulic fluid source to two different regulated pressures controlled by a single linear spring and by varying the position of end of the spring relative to the other end of the spring.

The present disclosure relates to a hydraulic drive system having a hydraulic circuit architecture operable in first and second modes. In a first mode, a main hydraulic pump (22) is used to drive a hydraulic actuator (24) via a closed hydraulic circuit, and a charge pump (42) provides charge flow to the closed hydraulic circuit. In a second mode the main pump set to zero displacement and the charge pump (42) is used to drive the hydraulic actuator (24).

Provided is a hydraulic drive system including: first and second pumps; a first main supply fluid line and an optional supply fluid line leading to the first pump; a second main supply fluid line leading to the second pump; a main manipulating device for the main actuator; an optional manipulating device for the optional actuator; a bleed-off flow rate regulating section to change the bleed-off flow rate for the second pump; and a bleed-off control section to operate the bleed-off flow rate regulating section to change the discharge flow rate of the second pump in accordance with a control operation applied to the main manipulating device and to make a bleed-off flow rate in a specific combined manipulation state with simultaneous performance of a specific main control operation and an optional control operation be smaller than that in a single main manipulation state.

The present disclosure discloses a reducing noise double-channel oil pump including a pump body. The pump body connects an oil box and an actuator. Parallel distributed a small and a big flow oil channels are located between the oil box and the actuator. The small flow oil channel connects a first twin pump and first one-way valves. The big flow oil channel connects a second twin pump and second one-way valves. The pump body also disposes a reducing noise oil channel. A connection of the reducing noise oil channel and the big flow oil channel locates a one-way controlled valve. Another end of the reducing noise oil channel connects an oil pressure feedback oil way. A connection of the reducing noise oil channel and the oil pressure feedback oil way locates an oil pressure driving mechanism. The middle of the reducing noise oil channel connects an unloading oil way.

A power transfer unit includes a first hydraulic circuit, a second hydraulic circuit fluidly connected to the first hydraulic circuit, a pump and motor assembly fluidly connected between the first hydraulic circuit and the second hydraulic circuit, an isolation valve arranged along the first hydraulic circuit and fluidly connected to an inlet of the pump and motor assembly. The isolation valve is movable between a closed position and an open position to prevent and enable high-pressure fluid flow to the inlet, respectively. An unloader valve is arranged along the second hydraulic circuit and fluidly connected to an outlet of the pump and motor assembly, and an orifice is arranged along the second hydraulic circuit and fluidly connected to the unloader valve to reduce back pressure in the second hydraulic circuit.