The present invention provides a shuttle relief valve comprising a housing provided with left and right conduit holes respectively connected to the left and right conduits which are arranged between a pressure source and a hydraulic motor in a hydraulic circuit system, and a space portion communicating the conduit holes with each other. A spool is slidably disposed in the space portion so that the space portion is selectively opened or closed by the movement of the spool. A spring urges the spool into the position in which the space portion is closed, and a left cover is fitted in one hollow portion of the housing formed on one side of the space portion so that it supports the movement of the left portion of the spool. A bushing is fitted in the other hollow portion of the housing formed on the other side of the space portion so that it supports the movement of the right portion of the spool.
The invention relates to control of a hydrostatic gearbox, comprising a hydraulic pump (2), provided for pumping in a first pump-side main line (5a) or a second pump-side main line (6a). The hydrostatic gearbox further comprises a hydraulic motor (3), connected to a first motor-side main line (5b) and a second motor-side main line (6b). The first pump-side main line (5a) and the second pump-side main line (6a) may be connected to the first motor-side main line (5b) or the second motor-side main line (6b) by means of a brake valve unit (19). The first motor-side main line (5b) or the second motor-side main line (6b), arranged downstream of the hydraulic motor (3), may be connected to a tank volume (12) in a throttled manner, depending on the pressure therein.
A relief valve assembly (27) for use with first (15) and second (21) conduits, one communicating high pressure. The assembly comprises a housing (29,33) defining first (45) and second (47) ports, and a poppet seat (49). A poppet member (43) and the housing define a spring chamber (55), and a spring (39) is disposed to bias the poppet member toward the seat. The poppet member defines a shuttle cavity (51), a shuttle passage (53) communicating from the cavity to the spring chamber, and the poppet defining a seat (57), and a fluid passage (61P) communicating with the first port, and a seat (59), and a second fluid passage (63) communicating with the second port. A shuttle valve assembly (71,73,75) is provided, whereby the fluid pressure in whichever of the ports is at lower pressure is communicated to the spring chamber and adds to the force of the biasing spring.
A shock valve assembly for a hydraulic system includes a fluid path extending between a first port and a second port with a shock valve disposed in the fluid path to normally block fluid flow through the fluid path between the first and second ports. The shock valve temporarily opens to permit fluid flow between the first port and a second port through the fluid path when a fluid pressure differential between the ports exceeds a predetermined threshold. Fluid flow occurs in a first direction from the first port to the second port through the fluid path when the shock valve is temporarily opened and fluid pressure in the first port is greater than the second port. Fluid flow occurs in a second, reverse direction through the fluid path from the second port to the first port when the shock valve is temporarily opened and fluid pressure in the second port is greater than the first port.
