Hydraulic systems for shrinking landing gear shrink are described. An example apparatus includes a landing gear strut, a transfer cylinder, aircraft hydraulics, a pressure vessel, and a pressure-operated check valve. The landing gear strut has an outer cylinder and an inner cylinder movable relative to the outer cylinder between a first position and a second position. The landing gear strut has a first length when the inner cylinder is in the first position and a second length less than the first length when the inner cylinder is in the second position. The transfer cylinder exchanges hydraulic fluid with the landing gear strut. The aircraft hydraulics exchange hydraulic fluid with the transfer cylinder. The pressure vessel exchanges gas with the landing gear strut. The pressure-operated check valve controls an exchange of gas between the pressure vessel and the landing gear strut based on hydraulic fluid received from the aircraft hydraulics.

A power transfer unit includes a first hydraulic circuit, a second hydraulic circuit fluidly connected to the first hydraulic circuit, a pump and motor assembly fluidly connected between the first hydraulic circuit and the second hydraulic circuit, an isolation valve arranged along the first hydraulic circuit and fluidly connected to an inlet of the pump and motor assembly. The isolation valve is movable between a closed position and an open position to prevent and enable high-pressure fluid flow to the inlet, respectively. An unloader valve is arranged along the second hydraulic circuit and fluidly connected to an outlet of the pump and motor assembly, and an orifice is arranged along the second hydraulic circuit and fluidly connected to the unloader valve to reduce back pressure in the second hydraulic circuit.

A hydraulic actuator (1) is disclosed comprising a cylinder housing (2), a piston (5) with a piston rod (6) being displaceably arranged inside the cylinder housing (2) and a pressure amplifier (10) comprising an inlet section (18) with a pressure inlet port (20), an active section (19) with a high pressure outlet port (22), a low pressure chamber (32) and a high pressure chamber (38a). It is an objective of the invention to provide a hydraulic actuator (1) with a modular pressure amplifier (10). To this end, the inlet section (18) is arranged inside the piston rod (6), and wherein the low pressure chamber (32) is stationarily arranged relative to the inlet section (18).

A hydraulic actuator (1) is disclosed comprising a cylinder housing (2), a piston (5) with a piston rod (6) being displaceably arranged inside the cylinder housing (2) and a pressure amplifier (17) comprising an inlet section (18) with a pressure inlet port (20), an active section (19) with a high pressure outlet port (22), a low pressure chamber (32) and a high pressure chamber (38a). It is an objective of the invention to provide a hydraulic actuator (1) with a modular pressure amplifier (17). To this end, the hydraulic actuator (1) comprises a cartridge pressure amplifier (10) comprising a sleeve (10a) being arranged at least partially inside the piston rod (6), and wherein the pressure amplifier (17) is stationarily arranged inside the sleeve (10a).

A fluid circuit includes first switching valve that switches between flow passages and first flow passages according to a change in a fluid pressure to be applied, a second switching valve that is switched to a flow passage which applies the fluid pressure to the first switching valve, when a piston has reached an initial position or an end position, and second flow passages. A biasing force of a biasing member when the piston reaches the end position is smaller than a pressing force acting on the piston due to the fluid pressure caused by a fluid supply device, and a biasing force of the biasing member when the piston reaches the initial position is larger than a sum of a flow passage resistance force acting on the first flow passages and a flow passage resistance force acting on the second flow passages.

A first switching valve that switches between flow passages which allow communication between a first pressure-receiving chamber and a fluid supply device side and flow passages which allow communication between a second pressure-receiving chamber and the fluid supply device side, according to a change in a fluid pressure to be applied, and a second switching valve that is switched to flow passages which apply the fluid pressure to the first switching valve, are provided. The second switching valve includes return device, and is provided to be reciprocatable between an operation position to which the second switching valve is moved by a stroke of a piston and a return position to which the second switching valve is moved by the return device. The piston and the second switching valve are movable independently of each other.

Hydraulic systems for shrinking landing gear shrink are described. An example apparatus includes a landing gear strut, a transfer cylinder, aircraft hydraulics, a pressure vessel, and a pressure-operated check valve. The landing gear strut has an outer cylinder and an inner cylinder movable relative to the outer cylinder between a first position and a second position. The landing gear strut has a first length when the inner cylinder is in the first position and a second length less than the first length when the inner cylinder is in the second position. The transfer cylinder exchanges hydraulic fluid with the landing gear strut. The aircraft hydraulics exchange hydraulic fluid with the transfer cylinder. The pressure vessel exchanges gas with the landing gear strut. The pressure-operated check valve controls an exchange of gas between the pressure vessel and the landing gear strut based on hydraulic fluid received from the aircraft hydraulics.

A hydraulic system (1) is provided comprising a pressure source (2), an output (3), and a pressure booster (6) arranged between the pressure source (2) and the output (3). The operational possibilities of such a system should be extended. To this end inactivating means are provided inactivating or activating said pressure booster.

A hydraulic pressure amplifier arrangement (1) is described comprising a supply port (A1), a pressure outlet (A2) connected to the supply port via check valve means (3), an intensifier section (5) having a high pressure piston (6) in a high pressure cylinder (7), a low pressure piston (8) in a low pressure cylinder (9) and connected to the high pressure piston (6), and a control valve (12) controlling a pressure in the low pressure cylinder (9), wherein the control valve (12) comprises a hydraulically actuated valve element (13). Such a pressure amplifier arrangement should have a good operational behavior in a cost effective manner. To this end the control valve (12) comprises spring means 16 acting on the valve element (1) in a direction towards a starting position of the control valve.

A fluid circuit includes a pressure fluid source, a switching valve, and a cylinder device having first and second chambers and partitioned by a piston. A first accumulator is configured to communicate with the second chamber when pressure fluid is supplied to the first chamber and to accumulate part of the pressure fluid from the second chamber. A pressure booster is connected in hydraulically parallel to the first accumulator, the pressure booster communicative with the second chamber when the pressure fluid is supplied to the first chamber to boost pressure of the pressure fluid by using part of the pressure fluid from the second chamber. A second accumulator accumulates the pressure fluid whose pressure is boosted by the pressure booster.