A counter pressure valve arrangement for controlling a pressure level of a hydraulic fluid in a return line from a hydraulic actuator arrangement. The counter pressure valve arrangement comprises a counter pressure valve having: a moveable valve member; a counter pressure regulating port configured for being connected to the hydraulic actuator arrangement via the return line; a tank port configured for being connected to a tank or low pressure reservoir for storing low pressure hydraulic fluid; and a pump port configured for being connected to a source of pressurised hydraulic fluid. A first position of the valve member effects fluid communication between the pump port and the counter pressure regulating port for supplying pressurised hydraulic fluid to the return line, and a second position of the valve member effects fluid communication between the counter pressure regulating port and the tank port for discharging hydraulic fluid from the return line to the tank.

An example valve includes a valve piston configured to block fluid flow from a first port of the valve to a second port of the valve when the valve is in a closed position; a forward flow spring applying a first biasing force on the valve piston in a distal direction; a reverse flow spring applying a second biasing force on the valve piston in a proximal direction; and a pressure setting spring applying a third biasing force on a check element in the distal direction, wherein fluid from the first port applies a fluid force on the check element in the proximal direction, and fluid from a pilot port applies a respective fluid force on the check element in the distal direction.

A pilot relief valve is provided, including: a sleeve, a valve body, a piston, an adjusting member, a support base, a blocking member and an elastic member, all disposed inside the sleeve. The support base includes a head portion and a rod portion, the head portion includes an exhaust channel penetrating the first surface, the rod portion includes an air intake channel communicating with the exhaust channel. The blocking member is disposed on the head portion. As such, the air in the sleeve is discharged through the inside of the support base, and the hydraulic oil fills the sleeve to maintain pressure balance so that the support base and the blocking member will not thrust, the perforation of the valve body and the outlet of the tipping valve remains unblocked, and the pressure of the hydraulic oil is stable when the hydraulic oil enters the hydraulic cylinder.

A forklift truck includes a carriage that moves up and down by a mast assembly in a multi-stage structure including an outer mast, a first inner mast accommodated in the outer mast, and a second inner mast accommodated in the first inner mast. The forklift truck includes a first lift cylinder configured to move the first inner mast up and down; a second lift cylinder configured to move the second inner mast up and down and having a pressure reception area less than a pressure reception area of the first lift cylinder. A first lift hydraulic line supplies hydraulic oil to the first lift cylinder. A second lift hydraulic line supplies hydraulic oil to the second lift cylinder. A pressure regulating valve is provided to increase a pressure of the hydraulic oil to a pressure capable of driving the second lift cylinder.

A pilot relief valve is provided, including: a sleeve, a valve body, a piston, an adjusting member, a support base, a blocking member and an elastic member, all disposed inside the sleeve. The support base includes a head portion and a rod portion, the head portion includes an exhaust channel penetrating the first surface, the rod portion includes an air intake channel communicating with the exhaust channel. The blocking member is disposed on the head portion. As such, the air in the sleeve is discharged through the inside of the support base, and the hydraulic oil fills the sleeve to maintain pressure balance so that the support base and the blocking member will not thrust, the perforation of the valve body and the outlet of the tipping valve remains unblocked, and the pressure of the hydraulic oil is stable when the hydraulic oil enters the hydraulic cylinder.

A forklift truck includes a carriage that moves up and down by a mast assembly in a multi-stage structure including an outer mast, a first inner mast accommodated in the outer mast, and a second inner mast accommodated in the first inner mast. The forklift truck includes a first lift cylinder configured to move the first inner mast up and down; a second lift cylinder configured to move the second inner mast up and down and having a pressure reception area less than a pressure reception area of the first lift cylinder. A first lift hydraulic line supplies hydraulic oil to the first lift cylinder. A second lift hydraulic line supplies hydraulic oil to the second lift cylinder. A pressure regulating valve is provided to increase a pressure of the hydraulic oil to a pressure capable of driving the second lift cylinder.

A valve unit (V) has a valve housing (50) that includes a supply oil passage (55) configured to receive operating oil from a hydraulic pump, and a pressure adjustment valve (Va) configured to adjust the pressure of the supply oil passage (55). The pressure adjustment valve (Va) includes a pressure adjustment valve body (61) configured to open and close the supply oil passage (55), a compression coil spring (62) that keeps the pressure adjustment valve body (61) at a closed position when the pressure of the supply oil passage (55) is smaller than a set value and allows the pressure adjustment valve body (61) to open when the pressure of the supply oil passage (55) is not smaller than the set value, and a restriction member (63) configured to, when the pressure adjustment valve body (61) becomes open against the urging force of the spring (62) in response to a pressure of the operating oil, abut against the pressure adjustment valve body (61) to restrict movement of the pressure adjustment valve body (61).

A hydraulic control apparatus includes an output-side oil passage into which oil from a first oil passage and oil from a second oil passage flow, and a pressure regulating check valve regulating a hydraulic pressure in the second oil passage. The pressure regulating check valve includes first and second elastic portions housed in a spool hole between a valve body and a bottom of the spool hole. A natural length of the second elastic portion is shorter than a distance between the valve body and the bottom when the valve body closes an inflow hole. The second elastic portion applies an elastic force to the valve body in a state in which the valve body opens the inflow hole.

An example counterbalance valve includes: a poppet configured to be subjected to a fluid force by fluid received at a first port, and a fluid force by a pilot pressure fluid signal received at a pilot port, and a fluid force by fluid of a second port; a first setting spring disposed in a first chamber and applying a first biasing force on the poppet; and a second setting spring disposed in a second chamber and applying a second biasing force on the poppet, wherein the first chamber and the second chamber are fluidly coupled to the second port of the counterbalance valve, wherein the second setting spring is in parallel with the first setting spring such that an equivalent biasing force acting on the poppet in the distal direction comprises a sum of the first biasing force and the second biasing force.

An in-port sequencing valve configured to be utilized with a clamping device of a workpiece clamping system having a fixture plate, a number of fixture datums, and a number of clamping devices. The in-port sequencing valve includes a housing, a pre-load adjuster, a valve spring, and a valve piston. The pre-load adjuster is configured to be set to a selected valve activation setting. The valve spring is compressed an amount corresponding to the valve activation setting. The valve piston is configured to be shifted from a closed position to an open position when a force due to hydraulic fluid pressure overcomes a threshold spring force of the valve spring corresponding to the valve activation setting. The in-port sequencing valve can be set to a selected valve activation setting so that the clamping devices clamp the workpiece in a selected order according to the valve activation setting.