A pistonless double-acting cylinder apparatus comprises a piston rod member, a first cylinder member disposed on the piston rod member, a second cylinder member disposed on an end surface of the first cylinder member, a tie rod which connects the first cylinder member and the second cylinder member, nuts provided on both ends of the tie rod, a first sealing ring located between the first cylinder member and the second cylinder member, a first cushion and a second cushion disposed on the piston rod member. The piston rod member comprises a piston rod left section, a first sealing gasket disposed on the piston rod left section, a piston rod middle section disposed on an end surface of the first sealing gasket, a second sealing gasket disposed on an end surface of the piston rod middle section, a piston rod right section disposed on the second sealing gasket.

A fluid leakage detection device includes: a rod seal provided in a cylinder head, a rod seal being configured to seal an annular gap between a piston rod and the cylinder head; a detection seal configured to seal an annular gap, a detection seal being configured to partition the detection space together with the rod seal; a communication passage in communication with the detection space; a pressure sensor configured to detect the pressure of the working oil guided through the communication passage; and a relief valve configured to release the pressure in the communication passage, wherein the detection seal is provided between the rod seal and a dust seal, the dust seal being configured to seal the annular gap by being provided in the cylinder head so as to face the outside of the cylinder tube.

A pressure detection device is mounted within an actuator housing between a piston rod and the housing, to receive fluid leaked past a seal, via a bore in the housing. The pressure detection device is configured to provide an output indicative of the pressure or flow of the leaked fluid in the bore. Thus, the leaked fluid diverted via the bore operates the pressure detection device to provide an output indicative of leakage.

A sealing device includes: an annular seal that is disposed on an outer periphery of a rod of a hydraulic cylinder further on a side of an extending direction than a cylinder head of the hydraulic cylinder and that has a pair of opposing first facing surfaces; a holding member disposed on an outer periphery of the seal; and a fixing member disposed on an outer periphery of the holding member, the fixing member having a tapered inner surface that contacts an outer surface of the holding member and that has an inner diameter increasing toward a retracting direction.

A centre seeking actuator having an outer cylinder, a slave cylinder slidably disposed within the outer cylinder, and a rod assembly having a piston slidably disposed within the slave cylinder and a rod extending from the piston to a point outside the outer cylinder. One or more first dynamic seals are arranged to act on a side wall of the rod to inhibit working fluid leaking from the outer cylinder, and one or more second dynamic seals are arranged to act on a sidewall of the slave cylinder to inhibit working fluid leaking from the outer cylinder.

An actuator assembly includes a housing, a piston rod, and an end gland. The housing defines a housing bore that extends along a first axis between a first housing end and a second housing end. The piston rod is at least partially disposed within the housing bore. The piston rod defines a piston bore that extends from a first piston end towards a second piston end along the first axis. The end gland has a first end gland surface that engages the piston rod and a second end gland surface that engages the housing bore. The end gland defines a first gland groove that extends from the first end gland surface towards the second end gland surface. The first gland groove is arranged to receive a self-lubricating filler that engages the piston rod. A self-lubricating bushing may also be provided to deposit a lubricant into the piston bore.

A nozzle of or for a servo valve comprises a nozzle element having a fluid outlet at a first axial end and a tubular body extending from the first end to an opposed, second axial end. The nozzle further comprises a plug element mounted in and closing the second axial end of the tubular body, thereby defining an internal cavity within the tubular body. One or more openings are formed through the tubular body to fluidly communicate with the internal cavity. A filter may be mounted across the internal cavity at a position axially intermediate the openings and the fluid outlet.

A fluid leakage detection system includes: a measurement unit configured to detect leakage of working oil in a hydraulic cylinder; and a controller configured to acquire a measurement result from the measurement unit, wherein the controller diagnoses that a battery depletion has been caused in a battery in a case in which it is determined that a data from the measurement unit has not been acquired and it is determined that the battery of the measurement unit has been in a low-remaining-battery-level state, and the controller diagnoses that a communication abnormality has been caused in a first communication part of the measurement unit in a case in which it is determined that the data from the measurement unit has not been acquired and it is determined that the battery has not been in the low-remaining-battery-level state.

A dust-proof and heat-control device for hydraulic cylinder is provided, including: a fixing sleeve, an annular fan mechanism, a sealing end cap and a dust cover; wherein the fixing sleeve is sleeved on a cylinder barrel of the hydraulic cylinder, the annular fan mechanism is sleeved on the fixing sleeve, the sealing end cap is disposed on an end of the cylinder barrel, a piston rod of the hydraulic cylinder passes through the sealing end cap and the dust cover, the dust cover is fixed on the piston rod, the annular fan mechanism, the dust cover and the hydraulic cylinder enclose an inner space, a side wall of the dust cover is provided with an opening communicating with the inner space, and a filter screen is mounted at the opening. The device and method can achieve good dust proof and heat control effect on axially reciprocating telescopic hydraulic cylinder.

A hydraulic machine is described having a first part (2) and a second part (3) moveable relative to said first part (3), one of said first part (2) and said second part (3) having a first land (9) resting against the other one of said second part (3) and said first part (2), having a predetermined first height (H1), and being arranged between a high pressure area (7) and a low pressure area (8). Such a machine should have a long working life. To this end a second land (10) having a predetermined second height (H2) smaller than said first height (H1) is located adjacent to said first land (9).