The invention relates to a pneumatic motor (1) for a feed pump, comprising a motor cylinder (10) and a motor piston (11) which is moveably arranged in the motor cylinder (10) and to which compressed air is applied, a valve unit (30), the compressed air providing for a downward movement (17) of the motor piston (11) when the valve unit (30) is in a first valve position and for an upward movement (19) of the motor piston (11) in the motor cylinder (10) when the valve unit is in a second valve position, upper stop means for the valve unit (30), by means of which the valve unit (30) is switched from the second valve position to the first valve position and thus the upward movement (19) is changed to the downward movement (17), and lower stop means for the valve unit (30), by means of which the valve unit (30) is switched from the first valve position to the second valve position and thus the downward movement (17) is changed to the upward movement (19). According to the invention, an active stroke-switching system (50) is provided, which comprises a switching cylinder (51) and a switching piston (52) which can move in the switching cylinder (51) and is coupled to the valve unit (30). The invention further relates to a method for operating the pneumatic motor.

A hydraulic system for moving an implement of a working machine includes a hydraulic cylinder with a cylinder and a piston which is adapted to move in the cylinder to thereby move the implement relative to a body structure of the working machine, and an actuator pump arranged to provide hydraulic fluid to the hydraulic cylinder, the hydraulic cylinder having a first port and a second port adapted to be in fluid communication with the actuator pump, the hydraulic cylinder and the actuator pump being arranged so that the hydraulic cylinder is directly controlled by the actuator pump so that the rate of movement of the piston of the hydraulic cylinder is purely pump controlled, the hydraulic system further including a hydraulic accumulator for suspension of the implement, which hydraulic accumulator is arranged to be selectively connectable to the first port, the hydraulic system further including a further pump in addition to the actuator pump, the hydraulic accumulator being arranged to be pressurised by the further pump.

A length-adjustable connecting rod for an internal combustion engine, comprises a first connecting rod member, a second connecting rod member and at least one cylinder-piston assembly for adjusting the first connecting rod member relative to the second connecting rod member. The cylinder-piston assembly can be actuated by way of a hydraulic adjustment mechanism, where the hydraulic adjustment mechanism comprises at least one oil filter in order to filter the engine oil of the internal combustion engine flowing into the cylinder-piston assembly. The invention further relates to an internal combustion engine with such a length-adjustable connecting rod and the use of such a cylinder-piston assembly for a length-adjustable connecting rod of an internal combustion engine.

Apparatus and methods for metering fluid to a fluid actuator. An example apparatus may include a hydraulic actuator, a fluid chamber, and a hydraulic directional control valve. The fluid chamber may include a piston slidably movable between first and second ends of the fluid chamber and dividing the chamber into first and second chamber portions. The hydraulic directional control valve may direct a fluid from a fluid source into the first chamber portion to cause a volume of fluid to be discharged out of the second chamber portion into the hydraulic actuator to actuate the hydraulic actuator by a distance corresponding to the volume of fluid received by the hydraulic actuator.

A hydraulic actuator circuit is disclosed for use with first and second shock absorbers, which each may include a piston disposed within a housing. The piston helps define upper and lower working chambers. The circuit may have a motor, a first pump, driven by the motor, and is associated with the first shock absorber and the motor. A second pump, driven by the motor, may be associated with the second shock absorber. A first accumulator communicates with both of the first and second pumps. A first switch valve may assist in controlling fluid flow into the chambers of the first shock absorber. A second switch valve may assist in controlling fluid flow into the chambers of the second shock absorber.

The invention provides a construction machine in which the load torque at the time of engine start-up can be reduced even when the engine stops against the will of the operator. A hydraulic excavator includes a control device (35) having a pump displacement control section (37) and an unload control section (38). The pump displacement control section (37) makes the displacement of a hydraulic pump (16) variable to a minimum displacement by controlling a regulator device (20) when the speed of an engine (14) detected by a speed sensor (41) becomes equal to or less than a preset low speed N3 at the time of driving of the engine (14). The unload control section (40) controls an unloading valve (24) to the open position at the time of start-up of the engine (14).

A first case accommodating a first check valve of a switching valve switching a flow of hydraulic fluid to one of a first chamber and a second chamber of a cylinder device, an inside of which is segmented into the first chamber and the second chamber by a piston, and a second case which is stacked on the first case and in which a first actuation valve of the switching valve is accommodated to be displaced in a direction of stacking the first case are provided. A first valve chamber, accommodating the first actuation valve, of the second case has a pressure receiving surface on which pressure of hydraulic fluid that acts on the first valve chamber acts toward the first case.

When option attachment has not been attached, a reserve flow/direction control valve 8 is made to operate as a center bypass cut valve. When an option attachment has been attached, switching control is performed. In the switching control, when the option attachment is not used, the reserve flow/direction control valve 8 is made to operate as a center bypass cut valve for adjusting composite opening area of a center bypass and thereby controlling the flow rate of hydraulic fluid flowing into an actuator. When the option attachment is used, the reserve flow/direction control valve 8 is made to operate so as to supply the hydraulic fluid to an option hydraulic actuator 14.

The present disclosure relates to a hydraulic control circuit for crane slewing gear having directional valves arranged in work lines and controllable separately for the inflow and outflow to the hydraulic motor for the carrying out of a rotational movement of the slewing gear, wherein an inflow valve serves the control of the oil inflow from a hydraulic pump via the work line to the hydraulic motor and an outflow valve is provided via which the hydraulic motor can be relieved to the tank, wherein the work lines are each connected via at least one check valve to a common inlet of the outflow valve to relieve the hydraulic motor independently of the direction of rotation of the slewing gear via an outflow valve into the tank.

A fluid pressure control device includes a load holding mechanism that is configured to hold the load pressure of the load side pressure chamber. The load holding mechanism includes a switching valve having a communication passage configured to be blocked from the third pressure chamber by the second land section in a case where the spool is closed, and providing communicate between the second supply port and the discharge port in accordance with the movement of the spool in the valve opening direction. In a case where the spool is moved in the valve opening direction, at the same time when or after the second supply port communicates with the discharge port via the communication passage, the first land section is brought into sliding contact with the annular projecting section and the first supply port and the discharge port are blocked from each other.