The invention relates to a hydraulic control system of a hoist drive of a lifting frame of an industrial truck, wherein the control system has a directional control valve device which is connected with a delivery line of a hydraulic pump, a reservoir line leading to a reservoir and a connecting line leading to the hoist drive, wherein the directional control valve device is configured to control the lifting operation and the lowering operation of the hoist drive. The control system has a pressure protection valve that is associated with the connecting line, wherein the pressure protection valve is configured to limit a peak pressure introduced into the lifting frame in the event of a fault scenario of the directional control valve device.

A lift arm lifting and lowering mechanism cylinder case provided with a cylinder portion into which oil is fed, a piston slidable inside the cylinder portion to define a hydraulic chamber and receiving hydraulic pressure of the hydraulic chamber on a front surface, a safety valve provided to the piston to discharge the oil inside the hydraulic chamber to the outside when the hydraulic pressure of the hydraulic chamber becomes greater than or equal to a predetermined value, and a lift arm supported by the cylinder case and rotatable in conjunction with movement of the piston, in which the piston includes an oil passage allowing communication between a rear surface of the piston and the front surface, and the oil passage includes a containing portion provided to open on the axially front surface side and capable of containing the safety valve, and a non-containing portion provided on the axially rear surface side relative to the containing portion and incapable of containing the safety valve.

Method for venting a pneumatic system of a vehicle, pneumatic system and vehicle Method for venting a pneumatic system (1) of a vehicle, the pneumatic system (1) comprising an air compressor (4), a pneumatic circuit (2), an air pressure management system (6) in communication with the air compressor (4) and the pneumatic circuit (2), and a control unit, the method comprising: —while pressure in the pneumatic circuit (1) is less than a cut-out pressure, supplying the pneumatic circuit (2) with compressed air from the air compressor (4) operated at an operating speed through the air pressure management system (6), —once pressure in the pneumatic circuit (2) reaches the cut-out pressure, lowering pressure in the pneumatic circuit (2) to a target pressure, the air compressor (4) being operated at at least one deflating speed lower than the operating speed, the deflating speed being non null, —after pressure in the pneumatic circuit (2) has reached the cut-out pressure, releasing compressed air in the air pressure management system (6) to the outside environment.

An actuation chamber (2) provided in a housing (1) is communicatively connected to a supply and discharge port (6) via a pressurized oil supply and discharge passage (7). A valve case (11) of a sequence valve (10) is attached to an attachment hole (8) provided at an intermediate portion of the supply and discharge passage (7). A valve seat (25) is provided in a cylindrical hole (20) provided in the valve case (11). A valve member (26) is biased leftward toward the valve seat (25) by a pressure-setting spring (31). When pressure of pressurized oil supplied to a first portion of the supply and discharge passage (7) which is close to the supply and discharge port (6) exceeds a set pressure, the pressurized oil moves the valve member (26) rightward for valve opening, against the pressure-setting spring (31).

Problem to be solved: To provide a hydraulic circuit for the construction machine which enables to use the relief valve of low capacity in the work tool circuit. Solution: The hydraulic circuit 2 for a construction machine has: a hydraulic pump 4 of variable capacity, a work tool 6 operated by hydraulic oil delivered by the hydraulic pump 4, a work tool operating device 10 to output a signal for operating the work tool 6, a control valve 14 allowing the hydraulic pump 4 to supply the hydraulic oil to the work tool 6 based on the signal output from the work tool operating device 10, a tool's relief valve 44 to release the hydraulic oil flowing between the control valve 14 and the work tool 6, a pressure sensor 46 to detect a pressure of hydraulic oil flowing into the work tool 6, and a controller 48 to reduce a delivery rate from the hydraulic pump 4 when the pressure detected by the pressure sensor 46 exceeds a predetermined value.

A hydraulic active suspension flow control system includes a hydraulic oil tank, a variable displacement pump with an oil suction port communicating with the hydraulic oil tank, a check valve, a servo valve, a suspension cylinder controlled by the servo valve, an engine revolution speed sensor configured to detect an engine revolution speed, a vehicle speed sensor configured to detect a vehicle speed, an oil pressure sensor configured to detect an accumulator outlet pressure, a flow controller configured to control displacement of the variable displacement pump by receiving data from the engine revolution speed sensor, the vehicle speed sensor and the oil pressure sensor, and a relief valve connected to the check valve in parallel and provided at an oil outlet of the variable displacement pump. The variable displacement pump is connected to an engine through a clutch; and an accumulator is connected between the servo valve and the check valve.

A hydraulic system can include a hydraulic actuator including a piston rod slidably disposed within a housing having a base-side port and a rod-side port, a hydraulic pump, a hydraulic reservoir, an accumulator, a first control valve operable to selectively control flow from the pump to the base-side port and from the base-side port to the reservoir, a second control valve operable to selectively control flow from the pump to the rod-side port and from the rod-side port to the reservoir, a third control valve operable to selectively allow flow between the base-side port and the accumulator, and a controller for operating the hydraulic system and including a ride control mode in which damping is provided to the hydraulic actuator by operation of the first, second, and third control valves.

A hydraulic pump to synchronize the operation of a pair of hydraulic actuators wherein each hydraulic actuator comprises a cylinder including a first fluid port and a second fluid port formed in the proximal and distal end portions thereof respectively and having a piston disposed therein coupled to a piston rod at least partially disposed within the corresponding cylinder. The dual hydraulic pump includes a triple gear assembly to alternately feed pressurized hydraulic fluid to the first fluid port of each hydraulic actuator simultaneously or the second fluid port of each hydraulic actuator simultaneously to synchronize the linear movement of each piston and piston rod in a first direction or a second direction.

A hydraulic active suspension flow control system includes a hydraulic oil tank, a variable displacement pump with an oil suction port communicating with the hydraulic oil tank, a check valve, a servo valve, a suspension cylinder controlled by the servo valve, an engine revolution speed sensor configured to detect an engine revolution speed, a vehicle speed sensor configured to detect a vehicle speed, an oil pressure sensor configured to detect an accumulator outlet pressure, a flow controller configured to control displacement of the variable displacement pump by receiving data from the engine revolution speed sensor, the vehicle speed sensor and the oil pressure sensor, and a relief valve connected to the check valve in parallel and provided at an oil outlet of the variable displacement pump. The variable displacement pump is connected to an engine through a clutch; and an accumulator is connected between the servo valve and the check valve.

Various embodiments of the present disclosure provide a rotorcraft-assisted system and method for launching and retrieving a fixed-wing aircraft into and from free flight. The launch and retrieval system includes a modular multicopter, a storage and launch system, an anchor system, a flexible capture member, and an aircraft-landing structure. The multicopter is attachable to the fixed-wing aircraft to facilitate launching the fixed-wing aircraft into free, wing-borne flight. The storage and launch system is usable to store the multicopter (when disassembled) and to act as a launch mount for the fixed-wing aircraft by retaining the fixed-wing aircraft in a desired launch orientation. The anchor system is usable with the multicopter, the flexible capture member, and the aircraft-landing structure to retrieve the fixed-wing aircraft from free, wing-borne flight.