A hydraulic system for a mobile rescue stretcher has a hydraulic cylinder, with first and second working chambers, a tank and pump. The first and second chambers are connected to the pump via first and second line arrangements, respectively, and can be pressurized by the pump. Hydraulic fluid flows out of the first chamber via the first line arrangement when pressure is applied to the second chamber. The first line arrangement has a first check valve which opens when pressure is applied to the second line arrangement. Hydraulic fluid flows out of the second chamber via the second line arrangement when pressure is applied to the first chamber. The second line arrangement has a first branch line connected to the pump and a second branch line connected to the tank. A pressure valve in the second branch line opens when pressure is applied to the second line arrangement.

To perform a work with the same operability under a dead weight of a front work equipment in any of a float work and a normal work, when a bucket descends in the air, and after contacting the ground, to perform a work with the operability being maintained as it is when performing the float work, and to perform a work while pressurized hydraulic fluid is supplied from a hydraulic pump when performing the normal work. A lower-ing control during a float working mode is performed in a valve passage state in a first region at which the lowering control is performed under the dead weight of the from work equip-ment without being supplied with hydraulic fluid from the hydraulic pump, regardless of whether or not the bucket is in contact with the ground, and the lowering control during a normal working mode is performed in a valve passage state at the first region in a non-ground-contacting state and at a second region in which the hydraulic fluid can be supplied from the hydraulic pump n a ground-contacting state.

A system for braking a displacement-controlled drive system (10), which can be driven by means of an inflow pressure and an outflow pressure at an inflow end and an outflow end thereof, respectively, for a motion, characterized in that by means of an electro-proportional adjustment of at least one valve element (26, 28, 126, 128) an outflow volume flow of the drive system (10) is controlled such that the outflow pressure is decoupled from the motion of the drive system and can be freely preset and coupled to the inflow pressure, which can in that way be lowered to the extent necessary for the motion of the drive system (10).

A hydraulic valve arrangement (1) is provided comprising comprising a supply port arrangement having a high pressure port (2) and a low pressure port (4), a working port arrangement having two working ports (6, 7), a first valve (13) arranged between said high pressure port (2) and said working port arrangement (6, 7), a second valve (14) arranged between said low pressure port (4) and said working port arrangement (6, 7), a controller (19) for controlling said first valve (13) and said second valve (14), said controller (19) having an input connection (20) for receiving a signal of an operator input device, and a regenerative flow path which can be established by means of at least one of said first valve (13) and said second valve (14). The function of such a hydraulic valve arrangement should be enhanced. To this end said controller (19) said controller interrupts said regenerative flow path when a feed pressure at said working port arrangement (6, 7) exceeds a predetermined pressure level.

A control system for a construction machine includes: a boom cylinder; a boom switching valve; a fluid pressure motor adapted to drive a motor generator by being rotated by means of a return fluid guided from a piston side chamber; a regeneration control valve adapted to adjust a first supply amount serving as a supply amount of a working fluid supplied from the piston side chamber to the boom switching valve, and a second supply amount serving as a supply amount of the working fluid supplied from the piston side chamber to the fluid pressure motor; and a controller adapted to control the regeneration control valve so that the second supply amount becomes smaller than the first supply amount in a case where a stroke amount of a spool becomes an upper limit value or more.

A pump that supplies hydraulic oil to a boom cylinder and a turning hydraulic motor; a regenerative hydraulic motor is coupled to the pump and to which the hydraulic oil discharged from the boom cylinder at a time of boom lowering and/or the hydraulic oil discharged from the turning hydraulic motor at a time of turning deceleration is/are led; an engine drives the pump; an alternator mounted to the engine and operable to rotate an output shaft of the engine when electric power is supplied to the alternator; an electrical storage device connected to the alternator; a power converter interposed between the alternator and the electrical storage device; and a controller that switches the power converter to either a servo-on state or a servo-off state and that controls the power converter either in a charging mode or in a discharging mode when switching the power converter to the servo-on state.

In order to reduce fluid consumption, a fluid return apparatus is provided for a double-acting cylinder having a first fluid connection for supplying fluid to a first cylinder chamber of the cylinder and a second fluid connection for supplying fluid to a second cylinder chamber at a piston rod-side of the cylinder. The fluid return apparatus comprises a first fluid passage providing fluid communication between the first fluid connection and the first cylinder chamber; a rapid venting valve comprising an inlet providing communication with the second fluid connection; an outlet providing communication with the piston-rod-side second cylinder chamber; a vent of the rapid venting valve, connected by a second fluid passage to the first fluid passage; and a non-return fitting in the second fluid passage, which prevents fluid from flowing from the first fluid passage to the rapid venting valve and an auxiliary outlet device.

The present disclosure relates to a hydraulic system for a construction machine, and more particularly, to a hydraulic system for a construction machine including a plurality of actuators, in which each of the actuators includes a pump/motor, is operated under a control of a corresponding pump/motor, and stores working oil in an accumulator or receives the working oil supplemented from the accumulator in accordance with a difference between a flow rate entering the actuator and a flow rate discharged from the actuator.

A safety valve which has two fluidically interconnected safety valves, each of which has a 4/2-way valve function. Each safety valve has a first connecting port and a second connecting port, which are connected to each other in such a way that a fluid flow through the two safety valves, controlled by means of a control valve, to a fluid-actuated drive is prevented if the two safety valves simultaneously adopt a first switching position and such a fluid flow is possible if both valves simultaneously have a second switching state. One safety aspect results from the fact that the above-mentioned fluid flow is also prevented if the two safety valves adopt different switching states.

The present invention relates to an electro-hydrostatic system (1) with a hydraulic machine (11) which is driven by an electric motor (10) and has a variable volume and/or rotational speed for providing a volumetric flow rate of a hydraulic fluid, a differential cylinder (20) with a piston surface and with an annular surface, and at least one equalization container (30, 37), wherein the drive system (1) has a closed hydraulic circuit and during operation has an overpressure relative to the environment by means of the hydraulic machine (11) and/or a pretensioning source (15, 37), and the drive system (1) provides a movement of the cylinder in a first direction by means of a volumetric flow rate of the hydraulic machine (11) and a volumetric flow rate from the equalization container (30, 37), and provides a movement in a second direction by means of a volumetric flow rate of the hydraulic machine (11) and a volumetric flow rate into the equalization container (30, 37), and a power operating mode and a speed operating mode are provided with the differential cylinder (20).