Loop flushing system for hydraulic units

A hydraulic fluid flushing valve for hydrostatic units usable in closed hydraulic circuit propel applications, having a flushing valve housing with a first inlet port connected to a first working line, a second inlet port connected to a second working line, and a discharge port for draining hydraulic fluid, wherein a two-sided flushing valve flushing valve spool which can be shifted is mounted within the flushing valve housing in a cylindrical valve bore, which, in a shifted position, enables a fluid flow from one of the first or the second inlet port at which the lower hydraulic pressure is present, to the discharge port, wherein the flushing valve spool comprises on each side a pressure surface each of which connected to one of the two inlet ports, wherein at each side of the flushing valve spool a flushing valve spring is located in the flushing valve housing in such a manner that, when the flushing valve spool is in its centre, non-shifted position, at each side of the flushing valve spool a distance between a spring contact surface on the flushing valve spool and a spring support surface in the flushing valve housing is greater than the axial length of the corresponding flushing valve spring, wherein the cylindrical valve bore is closed by end caps, such that spaces between the ends of the flushing valve spool and the end caps form pressure chambers each of which can be supplied by one of the two inlet ports with hydraulic fluid under pressure and wherein each of the end caps provides the spring support surface for one of the flushing valve springs, and wherein the flushing valve springs are attached to the end caps such that in the centre position of flushing valve spool a gap between each end of the flushing valve spool and correspondent flushing valve spring is present.

A hydraulic fluid flushing valve for hydrostatic units usable in closed hydraulic circuit propel applications, having a flushing valve housing with a first inlet port connected to a first working line, a second inlet port connected to a second working line, and a discharge port for draining hydraulic fluid, wherein a two-sided flushing valve flushing valve spool which can be shifted is mounted within the flushing valve housing in a cylindrical valve bore, which, in a shifted position, enables a fluid flow from one of the first or the second inlet port at which the lower hydraulic pressure is present, to the discharge port, wherein the flushing valve spool comprises on each side a pressure surface each of which connected to one of the two inlet ports, wherein at each side of the flushing valve spool a flushing valve spring is located in the flushing valve housing in such a manner that, when the flushing valve spool is in its centre, non-shifted position, at each side of the flushing valve spool a distance between a spring contact surface on the flushing valve spool and a spring support surface in the flushing valve housing is greater than the axial length of the corresponding flushing valve spring, wherein the cylindrical valve bore is closed by end caps, such that spaces between the ends of the flushing valve spool and the end caps form pressure chambers each of which can be supplied by one of the two inlet ports with hydraulic fluid under pressure and wherein each of the end caps provides the spring support surface for one of the flushing valve springs, and wherein the flushing valve springs are housed prestressed in the flushing valve housing, wherein one side of each flushing valve spring abuts against a shoulder in the cylindrical valve bore and the other end abuts against the corresponding support surface of end cap.