A working cylinder has a cushioned end-stroke. The piston unit has a piston main part and a ring body. The exterior of the ring body receives a piston ring with a piston ring gap, and the ring opening of the ring body receives a guiding pin of the piston main part. A ring gap is formed between the ring body and the guiding pin, and the ring body has axial and radial play relative to the piston main part. The ring body has an axial ring surface on the piston main part side, and the piston main part has an axial counter ring surface on the ring body side opposite the axial ring surface. The piston unit is constructed so that during an inward movement into the cushioning zone, the piston ring passes axially over the pressure medium connection and the piston unit encloses a damping pressure medium volume. The piston unit is in a first operating state during an inward movement and a second operating state during an outward movement. In the first operating state, the axial ring surface and the axial counter ring surface lie against each other and define a seal plane the piston ring gap is configured for a throttled outflow of the damping pressure medium volume. In the second operating state, the axial ring surface and the axial counter ring surface have an axial gap for a pressure medium inflow.

A pneumatic cylinder includes a cylinder body, a piston assembly, a connecting rod, and at least one pressure-relief valve. The cylinder body is formed with a cylinder chamber, and has an exterior disposed with at least one inlet-outlet passage and at least one pressure-relief opening, wherein the inlet-outlet passage is connected to the cylinder chamber. The piston assembly is contained within the cylinder chamber. The connecting rod is connected to the piston assembly, and protrudes out from the cylinder body. The pressure-relief valve is disposed in the pressure-relief opening, and has two ends connected to an outside of the pneumatic cylinder and the cylinder chamber respectively. When a gas pressure within the cylinder chamber is greater than a threshold value, the pressure-relief valve works to allow the cylinder chamber connecting to the outside for pressure relief.

Retraction of a landing gear assembly on an aircraft is actuated by a hydraulic actuator. The actuator includes a piston that travels within a cylinder along a stroke length between a first position corresponding to the landing gear assembly when extended and a second position corresponding to the landing gear assembly when retracted. The movement of the piston along its stroke length is snubbed at one end by a different amount according to the direction of travel, for example by use of an orifice plate that has a discharge coefficient that is greater in one direction than in the opposite direction. Asymmetric snubbing is thus provided, which enables the landing gear to retract faster.

A hydraulic cylinder may include a housing having a rod end and a cap end and the cap end may include a snubbing bore. The cylinder may also include a rod having a working end outside the housing and extending through a rod end of the cylinder to a piston end. The cylinder may also include a piston arranged within the housing on the piston end of the rod and configured to articulate within the housing between the rod end and the cap end. The piston may have a longitudinal bore extending into a cap side of the piston and the bore may include a retainer lip. The cylinder may also include a snubber configured for engaging the snubbing bore of the cap end when the piston approaches the cap end of the housing. The snubber may have an annular flange configured for retention by the retainer lip.

Fail-fixed hydraulic actuator systems for aircraft include a hydraulic actuator having a piston in a housing. The piston separates the housing into a retract cavity and an extend cavity. A sleeve is moveably arranged within the housing and includes a sleeve aperture that is aligned with a piston head during normal operation. A driving mechanism is configured to drive movement of the sleeve to maintain alignment between the sleeve aperture and the piston head. A low pressure cavity is defined between an interior surface of the housing and the sleeve and, when the piston head is offset from the sleeve aperture, the low pressure cavity is hydraulically connected to one of the retract cavity or the extend cavity to cause a pressure differential with the other of the extend cavity and the retract cavity and cause movement of the piston head to align with the sleeve aperture.

A single acting actuator for an aircraft landing gear assembly is disclosed having a piston mounted in a cavity and moveable relative to a housing between a retracted position and an extended position, the piston dividing the cavity into first and second pressure chambers. At least one of the pressure chambers is associated with first and second outlets, with the actuator being arranged such that, in respect of the relative movement in which the pressure chamber is the decreasing volume pressure chamber, in a first stage of the relative movement the first and second outlets are open thereby allowing actuator fluid to flow out of the pressure chamber through the first and second outlets and in a second stage of the relative movement the second outlet is open but the first outlet is closed, thereby acting to slow the relative movement of the piston with respect to the housing.

A working cylinder which has end-position damping. A piston ring passes over an axially offset pressure medium connection and encloses a pressure medium damping volume. The piston ring includes a ring joint which has a base section and a projection section. The piston ring is of sealing construction. The pressure medium flows out of the pressure medium damping volume via an axial transfer channel, which can be defined by an axial cylinder-tube groove or an axial piston-ring groove. Also, there is a damping piston ring, which is of sealing construction and which has an axial piston-ring groove.

A single acting actuator for an aircraft landing gear assembly is disclosed having a piston mounted in a cavity and moveable relative to a housing between a retracted position and an extended position, the piston dividing the cavity into first and second pressure chambers. At least one of the pressure chambers is associated with first and second outlets, with the actuator being arranged such that, in respect of the relative movement in which the pressure chamber is the decreasing volume pressure chamber, in a first stage of the relative movement the first and second outlets are open thereby allowing actuator fluid to flow out of the pressure chamber through the first and second outlets and in a second stage of the relative movement the second outlet is open but the first outlet is closed, thereby acting to slow the relative movement of the piston with respect to the housing.

A piston (6) is hermetically inserted via a sealing member (7) in a cylinder hole (2) provided in a housing (1) so that the piston (6) is movable in an up-down direction. A communication passage (21) provided in an inner peripheral wall of the cylinder hole (2) is communicatively connected to a lock-side supply and discharge passage (13) through which pressurized oil is supplied to and discharged from a lock chamber (11) of the housing (1). An opening area (S.sub.1) of the communication passage (21) is designed to be smaller than an opening area (S.sub.2) of the lock-side supply and discharge passage (13). When the piston (6) is caused to move for releasing from a raised position to a lower limit position, the sealing member (7) is lowered from the raised position beyond the communication passage (21), to open communication between a release chamber (12) in the housing (1) and the lock-side supply and discharge passage (13) via the communication passage (21).

A hydraulic cylinder with a load distribution nut connected to an end cap reduces fatigue experience by the end cap portion of the cylinder. The load distribution nut separates the axial load generated in the system from a single to multiple load paths. By introducing additional load paths, the load experienced by the traditional load path is reduced. Additionally, the load experienced by the end cap can be tailored by modifying the design of the load distribution nut and end cap. By either increasing or decreasing the surface area of the load distribution nut the axial load reduction on the end cap is correspondingly decreased or increased.