The first piston of the first cylinder and the second piston of the second cylinder are connected so that the first piston and the second piston have the same displacement. The cross-section area of one side of the first piston is the smallest, and the cross-section area on the same side of the second piston is the third smallest. The two air chambers of the first cylinder and the two air chambers of the second cylinder are referred to as a first air chamber, a second air chamber, a third air chamber, and the fourth air in ascending order in the cross-section area. The control valve connects the air pressure source to the first air chamber, connects the second air chamber to the third air chamber, and opens the fourth air chamber to the atmosphere in the forward stroke.

The present invention regards a fluid actuator arrangement comprising a first cylinder housing comprising a first piston body comprising a first through-bore and a first clamping element provided for releasable clamping onto a first piston rod. The first piston body comprises a second through-bore and a second clamping element provided for releasable clamping onto a second piston rod; a first static holding unit comprising a first clamping unit provided for releasable clamping onto the first piston rod; a second clamping unit provided for releasable clamping onto the second piston rod; a first base member coupled to the first piston rod via a first universal joint for providing a rotational motion of the first base member during longitudinal motion of the first piston rod. The present invention also regards a method for providing a rotational motion of a first base member.

Methods of modifying a GM Powerglide low range servo assembly for high line pressure applications as well as replacement components for Powerglide low range servo assemblies and replacement low range servo assemblies.

A drive system for a construction machine capable of appropriately controlling a distribution flow rate to each hydraulic actuator and improving operability by an operator is provided. A flow rate distribution section that computes a distribution flow rate of a hydraulic fluid supplied to each of a plurality of hydraulic actuators on the basis of a demanded flow rate, sets, within a distributable region set for computing a range of a distributable flow rate that is a flow rate of the hydraulic fluid suppliable to each of at least two hydraulic actuators driven by a combined operation among the plurality of hydraulic actuators from a plurality of hydraulic pump devices for the at least two hydraulic actuators, a distribution region for computing a range of the distribution flow rate of the hydraulic fluid actually supplied to each of the at least two hydraulic actuators, and computes the distribution flow rate in such a manner that the distribution flow rate falls within the distribution region and a ratio among the distribution flow rates of the plurality of hydraulic actuators is equal to a ratio among the demanded flow rates of the plurality of hydraulic actuators.

A hydraulic drive including a differential cylinder that has a first pressure chamber and a second pressure chamber and a differential piston, a first hydraulic pump that includes a pump intake and a pump outlet, a directional control valve having a first switching position and a second switching position, a high pressure tank, and an additional hydraulic cylinder that includes an additional pressure chamber hydraulically connected with the pump intake and with the high pressure tank and an additional piston limiting the additional pressure chamber, the differential piston being movably coupled with the additional piston, wherein in the first switching position of the directional control valve the first pressure chamber is hydraulically connected with the second pressure chamber, and in the second switching position of the directional control valve the second pressure chamber is not hydraulically connected with the first pressure chamber.

Many operators choose not to utilise partial-stroke testing arrangements even when the equipment required for it to be performed is available, due to a perceived risk of over-travel and/or spurious trip. To alleviate this, we describe a safety valve system comprising a valve operable to move between an operating state and a safe state, a valve actuator operatively connected to the valve to control its state, and including a bias toward the safe state, a pair of drive members powered by a pressure media, each acting against the bias to urge the valve toward the operating state, a first control valve arranged to selectively convey pressure media to both drive members and to withdraw supply on receipt of a safety trigger, and a second control valve arranged to selectively convey pressure media to one drive member only of the pair and to withdraw supply on receipt of a test signal. In this way, a partial stroke test is possible via the second control valve, but the other drive member of the pair will remain active thus acting as a buffer that prevents excessive movement of the valve.

The invention relates to a hydraulic fluid power transmission comprising: actuator apparatus having a plurality of chambers, each of the chambers having a respective fluid driving surface configured to drive or be driven by hydraulic fluid therein; a discretised pressure control system configured to selectively connect one or more first chambers of the said plurality of chambers to one of a plurality of hydraulic fluid sources or sinks, at least two of the plurality of hydraulic fluid sources or sinks having different fluid pressures; a continuous pressure control system configured to control the pressure of hydraulic fluid, or a flow rate of hydraulic fluid, input to or output from one or more second chambers of the said plurality of chambers, the pressure or flow rate of the hydraulic fluid input to or output from the second chambers being thereby variable within a range of pressures or flow rates respectively; and a controller configured to control the discretised and continuous pressure control systems to thereby regulate a property of the actuator affected by the hydraulic fluid pressure in the said chambers.

A hydraulic steering system of a work vehicle includes a hydraulic cylinder assembly configured to receive hydraulic fluid. The hydraulic cylinder assembly includes a hydraulic cylinder and a shaft assembly disposed within the hydraulic cylinder. The shaft assembly includes a first shaft part extending within the hydraulic cylinder and having a first piston integrally formed thereon and also includes a second shaft part extending within the hydraulic cylinder and having a second piston. The hydraulic cylinder assembly also includes a plurality of sealing members configured to extend radially between the hydraulic cylinder and the shaft assembly to separate the hydraulic cylinder into a first chamber supporting the first piston and a second chamber supporting the second piston. The first chamber and the second chamber are fluidly isolated from each other.

An air cylinder includes a cylinder, a piston rod, a piston, and a controller. The piston rod has one end disposed in the cylinder and the other end protruding from the cylinder. The piston is provided at the one end of the piston rod and moves the piston rod by moving in the cylinder. The controller supplies gas into one of a space, which is a space in the cylinder directed on the piston rod side with respect to the piston, and a space, which is a space in the cylinder opposite to the space with respect to the piston, and sucks gas from an interior of the other of the spaces.

An actuator device includes two drive units for an actuator output element. The first drive unit has a first piston chamber and a first piston displaceable therein and also first hydraulic means for displacing the piston. The second drive unit has a second piston chamber and a second piston displaceable therein and also second hydraulic or pneumatic means for displacing the piston. The second piston is joined to the actuator output element for conjoint movement therewith and can be coupled to the first piston for thrust, so that the second piston is displaceable in an outward direction by the first piston. The first drive unit is configured for a larger thrust force than the second drive unit, while the second drive unit is designed for a greater stroke speed than the first drive unit.