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.

A lock valve including a poppet valve element which is disposed within a spring chamber, a spring which biases the poppet valve element leftward, and a valve seat which comes into contact with the poppet valve element is disposed in a cavity formed in a valve body to mount a relief valve therein and is positioned further inward than the sleeve of the relief valve. The outer peripheral portion of the poppet valve element has hole portions formed therein at regular intervals. The outer peripheral portion of the valve seat, too, has hole portions formed therein at regular intervals. The valve portion of a solenoid valve is disposed between a passage which is in communication with the spring chamber and a passage which is in communication with a second flow passage open to a low-pressure region such as a hydraulic tank.

A lock valve including a poppet valve element which is disposed within a spring chamber, a spring which biases the poppet valve element leftward, and a valve seat which comes into contact with the poppet valve element is disposed in a cavity formed in a valve body to mount a relief valve therein and is positioned further inward than the sleeve of the relief valve. The outer peripheral portion of the poppet valve element has hole portions formed therein at regular intervals. The outer peripheral portion of the valve seat, too, has hole portions formed therein at regular intervals. The valve portion of a solenoid valve is disposed between a passage which is in communication with the spring chamber and a passage which is in communication with a second flow passage open to a low-pressure region such as a hydraulic tank.

A working machine includes a lower body, a turning body, a turning manipulating member which turns the turning body, a hydraulic motor which rotationally drives the turning body, a brake device which brakes the hydraulic motor, a main hydraulic source which supplies hydraulic oil to the hydraulic motor, and a direction control valve which controls a flow direction of the hydraulic oil according to the manipulated variable of the turning manipulating member, in which in a state where the hydraulic motor is braked by the brake device based on a manipulation of a brake manipulating member, when the turning manipulation is performed by the turning manipulating member, a brake applied to the hydraulic motor by the brake device is released with respect to turning in an indication direction indicated by the turning manipulation such that the turning body turns in the indication direction.

A linear actuator system includes a linear actuator and an integrated pump assembly connected to the linear actuator to provide fluid to operate the linear actuator. The integrated pump assembly includes a pump with two fluid drivers, each fluid driver comprising a prime mover and a fluid displacement assembly to be driven by the prime mover such that fluid is transferred from a first port of the pump to a second port of the pump. The pump assembly also includes two valve assembles to isolate the pump from the system. The linear actuator system also includes a controller that establishes the pump in a normal mode of operation in which the prime movers are independently driven and switches to a fail-safe mode of operation in which only one prime mover is operated.

A hydraulic drive apparatus includes: an electric motor; a variable displacement pump driven by the electric motor, the pump including a pair of pump ports whose delivery side and suction side are switched with each other in accordance with a rotation direction of the electric motor; a hydraulic actuator connected to the pair of pump ports by a first supply/discharge line and a second supply/discharge line; and a control device that controls the electric motor based on an actuator position command value for the hydraulic actuator. The pump is configured such that a volume of the pump decreases in accordance with increase in a pressure difference between the first supply/discharge line and the second supply/discharge line.

A hydraulic drive apparatus includes: an electric motor; a variable displacement pump driven by the electric motor, the pump including a pair of pump ports whose delivery side and suction side are switched with each other in accordance with a rotation direction of the electric motor; a hydraulic actuator connected to the pair of pump ports by a first supply/discharge line and a second supply/discharge line; and a control device that controls the electric motor based on an actuator position command value for the hydraulic actuator. The pump is configured such that a volume of the pump decreases in accordance with increase in a pressure difference between the first supply/discharge line and the second supply/discharge line.

A hydraulic system (600) and method for reducing boom dynamics of a boom (30), while providing counter-balance valve protection, includes a hydraulic cylinder (110), first and second counter-balance valves (300, 400), first and second control valves (700, 800), and a selection valve set (850). The selection valve set is adapted to self-configure to a first configuration and to a second configuration when a net load (90) is supported by a first chamber (116, 118) and a second chamber (118, 116) of the hydraulic cylinder, respectively. When the selection valve set is enabled in the first and second configurations, the second and first control valve may fluctuate hydraulic fluid flow to the second and first chamber, respectively, to produce a vibratory response (950) that counters environmental vibrations (960) of the boom. When the selection valve set is not enabled, the first and second counter-balance valves are adapted to provide the hydraulic cylinder with conventional counter-balance valve protection.

A method for forming hydraulic oil passages for hydraulic actuators according to an aspect of the present invention includes: forming a valve block mount surface including first and second regions on an outer surface of a housing; collecting valves for hydraulic actuators belonging to a main function group to a main function valve block that is mountable directly or indirectly on the first region; collecting valves for hydraulic actuators belonging to an additional function group to an additional function valve block that is mountable directly or indirectly on the second region; and mounting the valve blocks on corresponding regions of the valve block mount surface, and thereby, the hydraulic actuators to be mounted are fluidly connected to each other so that the hydraulic actuators are operable by using hydraulic oil from a common oil source.

A method for forming hydraulic oil passages for hydraulic actuators according to an aspect of the present invention includes: forming a valve block mount surface including first and second regions on an outer surface of a housing; collecting valves for hydraulic actuators belonging to a main function group to a main function valve block that is mountable directly or indirectly on the first region; collecting valves for hydraulic actuators belonging to an additional function group to an additional function valve block that is mountable directly or indirectly on the second region; and mounting the valve blocks on corresponding regions of the valve block mount surface, and thereby, the hydraulic actuators to be mounted are fluidly connected to each other so that the hydraulic actuators are operable by using hydraulic oil from a common oil source.