A hydraulic system includes a hydraulic actuator to be operated by an operation fluid, a first hydraulic pump to output the operation fluid, a second hydraulic pump to output the operation fluid, a control valve to which the operation fluid outputted from the first hydraulic pump is supplied, the control valve being configured to control the operation fluid that is to be supplied to the hydraulic actuator, a first fluid tube connecting the control valve to the hydraulic actuator, a second fluid tube to which the operation fluid outputted from the second hydraulic pump is supplied, the second fluid tube being connected to the first fluid tube, and a first switching valve disposed on the second fluid tube. The spool includes a communicating fluid passage being configured to supply the operation fluid to the first inner fluid passage, the operation fluid being received by the pressure-receiving port.

Displacement control device for providing pressure fluid to a servo unit for adjusting the displacement of a pressure fluid unit, having a control cylinder in which a control spool is mounted shiftable along the longitudinal axis of the control cylinder, an inlet port, a servo port and a discharge port are formed in the control cylinder longitudinally spaced from each other, wherein the control spool comprising: a basically cylindrical outer surface; a front face on which an actuation force can act for shifting the control spool along the longitudinal axis; a discharge area opposite to the front face; a longitudinal bore inside the control spool, wherein one end of the longitudinal bore opens towards the front face and the other end is connected via a backpressure orifice with the discharge area; a control recess provided lengthwise in the outer surface; a radial bore which connects via a flow limiting orifice the longitudinal bore with the outer surface, wherein the opening of the radial bore at the outer surface is located in circumferential direction beside the control recess, such that the opening of radial bore overlaps with the servo port in an actuated position of the control spool, in which the control recess connects the inlet port with the servo port.

A proportional pressure regulating valve has a spring-loaded valve piston (10) guided in and actuated by an actuating magnet (14) within a valve housing (12). Opposite valve piston sides are exposed to tank pressure. The valve piston (10) has a regulation surface (44) connectable to working port (A) for a regulation pressure (PR). A ring-shaped chamber (42) in the valve housing (10) opens into the working port (A). At the transition between the ring-shaped chamber (42) and the working port (A), the regulation surface (44) is active. When the actuating magnet (14) is deenergized, a maximum regulation pressure (PR) is generated.

A valve, in particular a proportional pressure regulating valve, has a valve piston (12) longitudinally movable in a valve housing (10) for alternately releasing and connecting a user connection (A) to a pressure supply port (P) or a tank connection (T). The valve piston can be actuated by an actuating magnet (14) that produces a dither signal during operation. The valve piston (12) reaches a floating position within the valve housing (10) by a hydraulic lift limitation for the receipt of the dither signal.

The invention provides a hydraulic circuit for feeding an actuator (1) comprising first and second chambers (5, 6), the circuit comprising a slide valve (10) with a slide (16) that is movable between first and second extreme positions (18, 19) on either side of a stable central position (17) so that: in the central position, it connects the chambers (5, 6) of the actuator to a return port; in the first extreme position (18), it connects the first chamber (5) to a feed port and the second chamber to the return port; and in the second extreme position (19), it connects at least the second chamber (6) to the feed port.

According to the invention, the hydraulic circuit includes pressure-maintaining means (20) for maintaining pressure in the first chamber of the actuator while the slide is passing through the central position on being moved from the first extreme position to the second extreme position.

A spool valve includes a valve portion that opens and closes a portion between an input port and an output port and a radial-direction-position changing portion provided in an outer lateral surface of the valve portion in a radial direction. When a first value is equivalent to or larger than a threshold that is larger than 0, the portion between the input port and the output port are opened to permit a flow of the oil inside the first connection oil passage, and when the first value is smaller than the threshold, the portion is closed to block the flow of the oil inside the first connection oil passage. The radial-direction-position changing portion extends in the axial direction, and a position thereof in the radial direction changes inwardly from a first side towards a second side in the axial direction.

Hydraulic valves for dampening pressure spikes and associated methods are disclosed herein. In one embodiment, a hydraulic valve for dampening pressure spikes includes: a spool configured to move axially inside the hydraulic valve; and a sleeve configured to at least partially house the spool. A location of the spool with respect to the sleeve may determine a flow of a working fluid through the hydraulic valve. A viscous damper is at least partially housed inside an opening in the spool, and a viscous friction between the viscous damper and the opening in the spool slows a motion of the spool.

An example valve includes: (i) a valve body defining a first longitudinal bore therein and including a first inlet, a second inlet, and an outlet; (ii) a cage disposed in the first longitudinal bore coaxial with the valve body, where the cage defines a second longitudinal bore therein; (iii) a pin mounted and extending longitudinally within the second longitudinal bore at an end of the cage adjacent to the first inlet; and (iv) a spool shiftably mounted within the second longitudinal bore and configured to move axially therein to shift between a first position and a second position. The spool includes a blind hole formed at an end thereof facing the pin and coaxial therewith, such that as the spool shifts from the second position to the first position, a portion of the pin is received within the blind hole of the spool.

An actuating system comprising a hydraulic actuator provided with a cylindrical cavity containing a piston configured to slide within the cylindrical cavity and a rod. The piston separates the cylindrical cavity into a first actuating chamber and a second actuating chamber. A first servo valve comprises a sheath including a first slider configured to slide within a cavity of the sheath on the basis of command signals from a command system. The cavity of the sheath comprises a first command chamber and a second command chamber on either side of the first slider. The first actuating chamber is fluidically connected to the first command chamber, and the second actuating chamber is fluidically connected to the second command chamber.

1. Valve and valve device comprising a valve of that type. 2. The invention relates to a valve comprising a valve housing (33), which has at least one service connection (A, B), a pressure supply connection (P) and a return connection (T) and in which valve housing (33) a control slide (STS) is guided so as to be movable longitudinally in order to control these individual connections. The valve is characterised in that the supply pressure, which is applied to the pressure connection (P) in order to control a consumer (10, 12) connected to the service connection (A; B), is guided across at least one control side (56) of the control slide (STS) via an orifice plate (54) and a control channel (50), the control side (56) being positioned in a control chamber (58) in the valve housing (33) such that it can move and the control chamber (58) being connected to the return connection (T) via an additional orifice plate (59).