THROTTLE VALVE ARRANGEMENT FOR HYDROSTATIC UNITS The invention is related to valves for hydrostatic displacement units, specifically to throttle valves for hydrostatic displacement units, more specifically to hydrostatic axial piston units.

Valves are used in many different applications in the technical field of hydraulics, e.g. for throttling fluid flows in hydrostatic variable displacement units. For example in axial piston units, throtle valves are frequently applied in motoring mode to maintain a pressure level at the outlet side above a lower limit. This, especially applies, when the axial piston units are operated in an open circuit. In general, throttle valves are used in situations, when a free uncontrolled expansion / draining of hydraulic fluid should not occur, as it is often the case when a pressure potential should not be expanded freely. For example, the low pressure side of a hydraulic propel unit in a closed circuit application should not be flushed to a tank or a reservoir for regeneration, cooling and/or refreshing at maximum possible pressure, as a hard jet would generate turbulences and gas bubbles in the reservoir hindering thereby cooling and/or regeneration of the hydraulic fluid.

A person skilled in the art is aware of a plurality of applications to which throttle valves for hydraulic or gas fluids can be applied to. All these applications are covered by the present invention. Just for illustration reason the invention is explained by the help of below descript application for hydraulic axial piston units, for instance, operated in an open hydraulic circuit.

Axial piston units typically comprise a rotating cylinder block with cylinder bores arranged therein. Each cylinder bore accommodates one displacement piston moveable in a reciprocating manner, such that a pressure chamber is enclosed between the displacement piston and the cylinder bore. There are two basic design principles of hydrostatic axial piston units: Swashplate units comprising a tiltable swashplate on which the displacement pistons can slide when the pistons rotate together with the cylinder block. In the other type -bent axis units - a centerline of the cylinder block can be inclined relative to a centerline of a rotating shaft. Independently of the specific design, the pistons are pressed against a sliding surface by means of the hydraulic pressure in the pressure chambers.

The pressure in one or more pressure chambers can be low, e.g. because the pressure chambers are connected to an outlet of the hydraulic unit, e.g. to a tank or reservoir of an open hydraulic circuit. In this case, kinematic forces might cause the displacement pistons to lift from the sliding surface, as the low hydraulic pressure in the pressure chambers might not be high enough or no sufficient counterforce against the kinematic forces can be generated to avoid lifting-up of the displacement pistons and/or their guiding shoes from the sliding surface. This occurrence of lifting-up not only causes bad operating behavior of the hydraulic unit, for example, noise and extensive wear of components but in a worst case can also destroy the hydraulic unit.

To avoid the occurrence of lifting-up, a throttling device can be provided in the outlet line of the hydrostatic unit in order to maintain the pressure in the outlet line/conduct above a minimum required reference pressure and to create a (counter)force on the displacement pistons to keep contact with the sliding surface.

However, a problem occurs, when the direction of fluid flow through the lines of the hydraulic system should be switchable/bidirectional, i.e. when the output should become the input and vice versa, for instance in reversible hydraulic motors. However, the hydraulic flow through an input line must not be throttled, as this would cause a loss of efficiency. Additionally, it is an ongoing task to minimize the dimensions of hydraulic units, in order to increase the design freedom and lower the overall dimensions of the hydrostatic unit/system.

There are technical solutions on the market to solve the described problem. Those constructions are usually valves mounted on the ports of hydraulic units designed mostly as poppet valves or seat valves. The arrangement and distance of the ports to the pressure chambers, but also the periphery of the hydraulic application restricts the available mounting space and therewith the flow capacity through these throttle valve solutions known from the art. Throttling devices have to provide a low pressure drop and a high flow rate I passage capability when filling / charging pressure chambers, but also have to provide a high flow rate / passage capability when draining/discharging the pressure chamber above a predetermined minimum low pressure to avoid efficiency reduction of the hydraulic unit. At the same time, the throttle valve I device should occupy as little space as possible, e.g., in order to be applicable to a great variety of hydraulic devices.

It is therefore an objective of the invention to provide a throttle valve design for hydraulic units which is capable of throttling a fluid flow between a higher pressure level and a lower pressure level, in only one direction. In the other direction, fluid flow should not be throttled and flow resistance through the throttle valve in charging direction should be as low as possible. Simultaneously it is important for the throttle valve/device to comprise small dimensions and to require a minimum of construction space in a hydrostatic system/unit. Even if described in context with axial piston units above and as mentioned before, the application of throttle valves, in particular of throttle valves according to the invention is not limited to the above described application in axial piston units and can be applied in context with other types of hydraulic systems/units as well. The objective is solved by a throttle valve arrangement according to claim 1. Preferred embodiments are described in the subclaims dependent thereon.

A throttle valve arrangement for hydrostatic units according to the invention is of the sliding valve design and comprises a valve housing having a through bore which defines an axial direction of the throttle valve. One of the two axial openings of the through bore forms a charge port of the throttle valve and the other opening forms a discharge port. An undercut between the charge and the discharge port is formed within the valve housing, which is limited in the axial direction by two end walls, one on either side. Depending on the manufacturing method(s) chosen for the throttle valve and the operational requirements of the throttle valve, the end walls may be integrally formed with the housing, leading to a high mechanical stability of the valve. Alternatively the end walls may be attached to the housing as separate parts, which opens manufacturing alternatives of the valve housing and the further components of the throttle valve arrangement.

A cylindrical bushing is inserted in the through bore and can be secured to the end wails, e.g. by press fitting. External to / radially outside of the bushing, the undercut forms a flow chamber in the housing. The flow chamber is limited in axial direction by the two end walls and is formed in radial direction between the outer skin surface of the bushing and the inner skin surface of the undercut. The bushing comprises axial openings to form or to be connected to the discharge port and the charge port of the throtle valve. The bushing further comprises radially oriented openings at the charge side and radially oriented openings at the discharge side, which all are arranged at the respective end portions of the bushing to enable a fluid path between the charge port and the discharge port of the valve housing via the flow chamber formed by the undercut and the bushing. This means, e.g., that hydraulic fluid can enter the valve housing via the inlet at the charge side / port and can be guided through the charge-sided radial openings in the bushing to the flow chamber external to/ radially outside of the bushing, and from there the fluid can enter again the bushing via the discharge-sided radial openings in the bushing and can be guided towards the discharge side I port of the throttle valve. In general and in accordance to the invention, this flow path is enabled also vice versa, i.e. from the discharge port to charge port.

Between the charge port and the discharge port at the end portions of the bushing, an axially movable, resilient valve body assembly group is provided which comprises a hollow sliding element which, in a sealed manner, is slidably guided by/in the bushing. The general functionality of a throttle valve arrangement according to the invention is as follows:

The resilient valve body of the throttle valve according to the invention is held in its initial position, in which no external forces act on the throttle valve arrangement, by the locking spring. In this position radial oriented openings formed in the resilient valve body and the radial oriented openings of the bushing at the charge port end overlap such that a fluid flow over the flow chamber formed radially outside of the bushing is disabled. The radial openings in the bushing at the discharge side are open. This means the throttle valve arrangement according to the invention is closed in the initial position of the resilient valve body.

When a force at the charge side occurs, the axially moveable resilient valve body is moved against the force of the locking spring towards the discharge side, thereby bringing the radial oriented openings of the resilient valve body and of the bushing at the charge side in maximal overlap, i.e. lowest flow restriction from the charge side to the discharge side is enabled. Here also the radial openings in the bushing at the discharge side are open all the time.

When a force at the discharge side occurs the locking spring moves the resilient valve body towards the charge side, i.e. basically in its initial position. Additionally the pressure force at the discharge side acts also on a bottom part of the resilient valve body and can compress the backpressure spring when the pressure generated force is high enough. By compressing the backpressure spring the radial oriented openings in the resilient valve body are brought at least partially in overlap with the radial oriented openings in the bushing at the charge side end, as the resilient valve body expands in axial direction. By expanding in axial direction of the resilient valve body the flow path via the flow chamber is enabled, as the radial openings in the bushing at the discharge side are open all the times and fluid can enter the flow chamber. Therewith a discharge flow with backpressure functionality, i.e. maintaining a backpressure during discharge flow is enabled.

In general the resilient valve body can be charged with a pressure force on both sides, the charge pressure side and the discharge pressure side, wherein the travel distance of the resilient valve body, e.g. by end stops, in function of the position and axial width of the radial openings in the bushing and in the valve body itself. One end stop is reached when all radial openings at the charge port side are open respectively overlap completely, i.e. in the charge position. The other end stop is reached when all radial openings at the charge port side are closed, i.e. in the initial position with the resilient valve body in non-expanded condition, i.e. the backpressure pressure force is lower than the force of the backpressure spring.

In one preferred embodiment of the invention the radial openings in the bushing at the discharge side are open in every position of the resilient valve body, and the end stops for limiting the travel distance of the resilient valve body is realized by a through hole through the resilient valve body elongated in axial direction, which trough hole is passed by a rod, or the like, stationary with the bushing.

In a another preferred embodiment the resilient valve body comprises a sliding element showing a substantially cup-shaped cross-section, i.e. it comprises a hollow cylindrical shape, wherein one side of the cylindrical shape ~ the side facing to the discharge end of the bushing - is closed by a bottom surface. At the cylindrical part preferably at the charge end portion, the hollow sliding element comprises radial oriented openings which can be brought in an overlapping position with the radial oriented openings at the charge side of the bushing.

The axial movable, resilient valve body further comprises a spring seat element with a T-shaped cross section, which is axially movably guided by the sliding element. A head portion of the T- or mushroom shaped spring seat element, i.e. a portion with higher diameter, is oriented towards the charge port and preferably seals with its circumferential outer surface with the internal surface of the sliding element. A stem portion with a lower diameter compared to the head portion protrudes through the bottom surface/part of the sliding element. For this reason, a hole is provided in the bottom surface of the cup-shaped sliding element. The stem portion not necessarily forms a fluid tight connection with the bottom part of the sliding element.

In the resilient valve body group a back pressure spring is arranged biased between the head portion of the mushroom shaped spring seat element and the bottom of the cup-shaped sliding element around the stem portion. A securing element, e.g. a circlip, on the protruding part of the stem limits the travel distance of the spring seat element relative to the sliding element in expansion direction of the back pressure spring, i.e. in direction of the charge port of the throttle valve housing. The stem portion of the spring seat element further comprises an axial blind hole and a radial arranged elongated through hole, through which a rod passes, holding the stem portion relative to the bushing. A locking spring accommodated in the blind hole is biased between the rod secured to the bushing and the spring seat element, thereby pushing the resilient valve body group towards the charge port, wherein the elongated hole in the stem limits the axial travel distance of the resilient valve body within the bushing. Preferably, the flexibility of the locking spring is higher than the flexibility of the back pressure spring. In other words compressing the locking spring requires less force than compressing the backpressure spring. The locking spring force constitutes the opening force of the throttle valve at the charge side, i.e. in nonthrottling direction. The backpressure spring however constitutes the opening force of the throttle valve in throttling direction, i.e. the force of the backpressure spring determines the backpressure in hydraulic lines connectable to the discharge-side of the throttle valve according to the invention.

For enabling the non-restricted charge and restricted discharge functionality the bushing comprises preferably two rows of radial oriented charge openings at the charge side, using preferably both rows for the charge flow functionality and only one row for the discharge flow functionality with backpressure maintaining function.

Specifically, when no or balanced hydraulic forces are present at the charge side and at the discharge side of the throttle valve, the locking spring - biased in the blind bore of the stem of the spring seat element against the rod connecting the stem with the bushing - pushes the resilient valve body group towards the charge port into the throttle valve initial position in which all the charge-sided radial openings in the bushing are closed by the sliding element, i.e. the respective radial oriented openings in the bushing and in the sliding element do not overlap. Hence, the flow path over the flow chamber is closed, even though the radial openings in the bushing at the discharge side remain open.

When the hydraulic forces at the charge port are bigger than those at the discharge port, the locking spring will be compressed until the rod in the elongated hole in the stem of the sliding element limits the axial travel distance of the resilient valve body, in particular of the stem portion of the spring seat element. According to the invention the length and position of the elongated hole in the stem portion is determined such that the travel distance of the valve body towards the discharge port into a charging position of the throttle valve arrangement ends at a position in which preferably all radial openings in the bushing at the charge port side are open and a maximum flow from the charge side to the discharge port is enabled via the flow chamber in the throttle valve housing. The hydraulic flow enters into the bushing again via the always open radial openings in the bushing at its discharge end portion. Here the radial openings at the discharge end of the bushing are preferably designed wider as the ones at the charge-sided end portion, and preferably wider than both rows of the charge sided opening together.

To reach this charging position of the throttle valve arrangement according to the invention only the force of the locking spring has to be overcome. Therefore the locking spring can be designed to be relatively weak or relatively flexible, respectively, as the function of the locking spring is merely to move the resilient valve body into its initial positon when the throttle valve arrangement is free of external forces.

When the hydraulic forces at the discharge port are bigger than the ones at the charge port, the resilient valve body with the sliding element is moved towards the charge port until the rod in the elongated hole limits the movement. Further, pressure forces act on the bottom part of the cup-shaped sliding element and can compress the backpressure spring such that the axial length of the resilient valve body increases and radial openings in the sliding element can overlap at least partially with at least one row of the radial openings in the bushing at its charge side end portion. Thereby the stem portion of the T-shaped spring seat element is held in its initial position by the rod passing through the axially elongated radial hole in the stem portion and fixing the spring seat element axially with the bushing. From this explanation a person skilled in the relevant art derives that the force of the backpressure spring determines the backpressure which can be maintained by the throttle valve arrangement according to the invention in the hydraulic system, e.g. at the discharge side of a hydraulic axial piston unit. When the pressure force at the discharge side drops below the backpressure spring force the sliding element of the resilient valve body is moved by the backpressure spring towards the initial pressure less position closing the throttle valve arrangement.

Preferably, the valve housing is an in general rotational cylindrical part, which is manufactured, e.g. by means of turning, 3D-milling, 3D printing or any other type of manufacturing a person with skills in the relevant art is aware of.

Preferably, according to the invention, the undercut in the valve housing shows also a cylindrical form and is arranged coaxially with a through bore in the valve housing forming a ring chamber in the valve housing external to the bushing. Thereby the hydraulic fluid flow in the undercut is uniformly distributed and areas with increased pressure - e.g. areas in which the flow of hydraulic fluid is impeded by the geometry - are minimized. As appreciated by a person with skills in the relevant art, rotationally symmetric parts, especially cylindrically shaped parts can be particularly well manufactured by the above mentioned manufacturing processes.

Preferably, the rotational position of the bushing remains fixed with respect to the resilient valve body, which can be assured by a pin-and-axial-groove connection between these two parts, especially with respect to the cylindrical part of the hollow sliding element in order that the radial openings in both parts can be brought in maximum overlap or closing position. For this the T-cross section shaped spring seat element should also be secured against rotational displacement as such a displacement could be transmitted to the cup-shaped sliding element, e.g. via the axial securing device on the stem part. For that reason, the rod can be in functional interaction as well as with the bushing and with the valve housing. However it is important, that the resilient valve body, more specifically the spring seat element is capable of moving along the axial direction with respect to the bushing, even if the rotational position of the two parts is fixed with respect to each other. In one embodiment of the invention the assembly group of bushing and resilient valve body could turn /rotate inside the valve housing, when the undercut is formed cylindrical.

In a further preferred embodiment, the rod may be secured also to the housing of the valve, thereby fixing the rotational position of the bushing with respect to the valve housing, and therewith the rotational position of the resilient valve body as well. Depending on the functional connection between the rod and the bushing the rod may also fix the translational positon along the axial direction of the bushing with respect to the valve housing. However, the translational position might also be fixed by abutting the bushing against a shoulder in the housing, e.g., or by press fitting or welding, soldering or gluing the bushing to valve housing. In another embodiment according to the invention, the cup-shaped sliding element comprises a stepped design with a lower diameter on the discharge side. Such a design is favorable when a relatively long backpressure spring should be used, as the cylindrical portion of the sliding element should not overlap with the radial discharge openings in the bushing at the discharge side, when the throttle valve arrangement is in the filling/charging position, i.e. the resilient valve body is in its initial position in which fluid flow from the charge port to the discharge port should be enabled with lowest possible flow restrictions. Hence, if relatively long backpressure springs are to be used due to spring force characteristics a compromise of axial length of the valve housing and the cup-shaped sliding element has to be found. Using a stepped design of the cup-shaped sliding element could provide a design alternative, however making the manufacturing of the cup-shaped sliding element more complicated.

The charge sided radial openings and/or the discharge sided radial openings in the bushing and/or the radial openings in the sliding element may show a circular, elongated hole design or may be formed as slits. All the radial openings may be formed complementary with each other, i.e. may/should be designed that they can overlap completely in the throttle valve charge/opening/system filling position. At least the radial charge openings in the bushing should be openable completely in order not to form a bottle neck in the flow path. However, also different shapes might be chosen for the openings in the bushing compared to the shape of the openings in the sliding element. Additionally or alternatively, the radial charge openings at the charge port side in the bushing and/or in the sliding element of the resilient valve body might comprise the same shape, or be of a different shape, compared to the openings at the discharge side of the bushing.

Preferably, the locking spring may be located in a blind bore of the stem portion of the T-cross section shaped spring seat element through which a rod passes in the radial direction, e.g. through a radial bore in the stem portion respectively two elongated holes arranged opposite to each other in the cylindrical surface of the stem portion. On the side opposite to the ground of the blind bore, the locking spring preferably rests on a slider abutting against the rod and is slidably within the blind hole of the stem.

The slider can be e.g. a roller which is guided in the blind bore in the stem portion of the spring seat element however, the slider may also be a different component which is capable of reducing the frictional forces when the valve switches between its positions or functionalities, i.e. when variable pressure forces act at the discharge side of the throttle valve arrangement. For example, also components with good sliding characteristics due to a specific friction reducing material or coating can be provided for forming the slider.

The valve housing may comprise a plurality of axial oriented through holes and may be fixed to hydraulic flanges, to hydraulic hoses or to hydraulic pipes, by means of, e.g., screws penetrating the through holes and interacting with the device to which the valve housing shall be attached to.

The valve housing can comprise further an O-ring groove at the charge port side and/or the discharge port side of the housing to receive an O-ring capable to seal the throttle valve arrangement to other components of a hydraulic or hydrostatic unit /system, to which the throttle valve can be connected. After securing the throttle valve to one of the aforementioned components or to a different component of a hydrostatic unit, the force which presses the throttle valve housing against the component, deforms the O-Ring installed in the groove such that a fluid tight connection is established. Additionally, the connection might be capable of fixing the longitudinal position of the bushing with respect to the throttle valve housing, e.g. if the additional component is in contact with the bushing and therefore forces the bushing against a shoulder in the throttle valve housing.

With the help of the enclosed Figures preferred embodiments of the throtle valve arrangement according to the invention are explained in more detail in order to enhance the understanding of the basic idea of the invention. The present embodiments do not limit the scope of the idea of the invention, but only represent one possible design alternative, to which within the knowledge of a person with skills in the relevant art modification can be made without leaving the scope of the invention. Therefore all those modifications and changes are covered by the claimed invention. In the Figures it is shown in: Figure 1 a sectional view of a preferred embodiment of the throttle valve arrangement according to the invention in a first position;

Figure 2 a sectional view of the embodiment of Figure 1 in a second position; Figure 3 a sectional view of the embodiment of Figure 1 in a third position;

Figure 4 a sectional view of the embodiment of Figure 1 in a forth position;

Figure 5 the embodiment of Figure 1 in a plan view of the discharge side;

Figures 1 to 5 show a preferred embodiment of the throttle valve arrangement according to the invention, wherein same reference numbers refer to same parts. All section views of Figures 1 to 4 are taken along the section plane as indicated with line A-A in Figure 5.

The preferred embodiment is shown in three different pressure situations, wherein Figure 1 shows the preferred embodiment of the throttle valve arrangement according to the invention in its initial positon in which no or a balanced pressure acts on both sides of the throttle valve. In Figure 2 the inlet or charging situation is shown, where the pressure at the charge port 20 is higher than at the discharge port 15. A fluid flow from the charge port 20 to the discharge port 15 is indicated with the help of arrows. In Figures 3 and 4 the pressure situation is inverted, i.e. the pressure at the discharge port 15 is higher than at the charge port 20. Here the preferred embodiment for a throttle valve according to the invention is in its throttle function position, in which a fluid flow - indicated by the arrows - from the discharge port 15 to the charge port 20 is enabled. The arrangement shown in Figure 3 represents an intermediate position. The arrangement of Figure 4 represents the fully open throttle position of a throttle valve according to the invention.

Figure 1 depicts a sectional view of a preferred embodiment of the throttle valve arrangement 1 according to the invention, comprising a valve housing 5 with a through hole 6 defining an axial direction 10. Mere for illustrative reasons the left opening of the through hole 6 in the Figures 1 to 4 is denominated as the charge port 20 and the right side opening as discharge port 15. The charge port 20 can be connected, for instance, with a pressure source when the flow through the throttle valve arrangement 1 is from the left to right according to annexed Figures 1 to 4, e.g. when pressure chambers of an axial pistons unit are to be filled with pressurized fluid. In this case the charge port 20 constitutes the inlet for the throttle valve arrangement 1 according to the invention. In the other case, e.g., when fluid should be drained from the pressure chambers of an axial piston unit the discharge port 15 forms the inlet for the throttle valve arrangement I as the flow direction would be from the right to left according to annexed Figures 1 to 4, i.e. from the discharge port 15 to charge port 20.

Coaxial to the axial direction 10 of the valve housing 5 a bushing 35 is inserted in the through hole 6 for forming together with an undercut 30 formed in the valve housing 5 a flow chamber 32, which, in a preferred embodiment, is a ring chamber 32 external to the bushing 35, i.e. radially outside of bushing 35. To the bushing 35 at the respective end portions radial openings 36 and 37 are formed, wherein in the embodiment of Figures 1 to 4 at the charge port 20 side of the throttle valve arrangement 1 two rows of slot shaped charge openings 36 are formed, and on the discharge port 15 side only one row of axial wider discharge openings 37.

As a person with relevant skills in the art understands, that these radial openings 36 and 37 can be designed in great variety without leaving the gist of the invention. The denomination radial charge opening 36 and radial discharge opening 37 results merely from their respective vicinity to the charge port 20 and the discharge port 15. All radial openings 36 and 37 as well as the ports 15 and 20 can be passed through by fluid in both directions. In general the throttle valve arrangement according to the invention enables a fluid flow from the left opening identified with reference number 20 to the right opening identified with reference number 15 when a fluid pressurized by a source enters the charge port 20 of the throttle valve arrangement 1 at the left side of Figure 1 to 4 and exits the throttle valve arrangement 1 according to the invention at the discharge port 15. In the other direction the throttle valve arrangement 1 according to the invention provides a flow resistance for a fluid flow from the right side of Figures 1 to 4 towards the left side, in order to create and maintain a desired backpressure level in the system which is connected to the right side of the throttle valve arrangement 1 according to the invention.

Within the bushing 35 a resilient valve body 40 is inserted, comprising a hollow sliding element 45, a spring seat element 50 with a cross section in T-shape and a backpressure spring 55. Thereby the hollow sliding element 45 shows a cupshaped cross section, wherein the cylindrical part 48 comprises radial oriented openings 46 and seals with the internal surface of the bushing 35. The bottom part 47 serves as a spring seat for the backpressure spring 55. The radially oriented openings 46 in the cylindrical part 48 of the hollow sliding element 45 can be brought in an overlapping position with at least one row of the radial charge openings 36 in the bushing 35 (see also Figures 2, 3 and 4).

The resilient valve body 40 can move axially relative to the bushing 35 as an assembly group, this means the hollow sliding element 45 can move together with the spring seat element 50. A relative movement of these two parts, i.e. the spring seat element 50 and the hollow sliding element 45, is only possible in a resilient manner when backpressure spring 55 is compressed. For this purpose backpressure spring 55 is mounted pre-stressed between a head portion 51 of the spring seat element 50 with a T-shaped cross section, and the bottom part 47 of the sliding element 45. This mounting group / assembly group is held together by means of a securing element 57 around the stem portion 52 of the sliding element 45, e.g. a snap ring.

The axial travel distance of the valve body 45 is limited by a rod 60 accommodated in an elongated radial trough hole 53 in the stem portion 52. Further, a blind hole 54 is provided in the stem portion 52 for accommodating a locking spring 65 which is biased between the dead end of the blind hole 54 and the rod 60 which traverses the elongated through hole 53 in the stem portion 52. Hence the T- cross section or mushroom shaped spring seat element 50 can move elastically within the axial limits given by the axial length of the elongated through hole 53, and transmits this movability via the backpressure spring 55 and the securing element 57 (resiliently) to the sliding element 45.

Rod 60 connects/holds the spring seat element 50 within the bushing 35 as the rod 60 passes radially through the stem portion 52 and is fixed with both ends to bushing 35. In an further embodiment of the invention rod 60 can be enlarged to the valve housing 5 and assure thereby not only the angle position of the valve body 40 to bushing 35 but also the angle position of the bushing 35 to the valve housing 5. Preferably a pin or roller 70 arranged between the bushing 35 and the cylindrical part 48 of the hollow sliding element 45 being able to run/slide in a groove 75 provided in one of these two parts guarantees the angle position between the bushing 35 and the valve body 40.

In a preferred embodiment a slider 62 is arranged in the blind hole 54 of the stem portion 52 between locking spring 65 and rod 60 serving as moveable spring seat for locking spring 65.

Figure I shows the preferred embodiment for a throttle valve arrangement 1 according to the invention in the initial position with no or balanced pressure at the charge port 20 and the discharge port 15. Locking spring 65 pushes the slider 62 towards the rod 60, whereby the resilient valve body 40 is moved towards the left in Figure 1 . Rod 60 limits the motion as rod 60 abuts against the right end of elongated through hole 53 in the stem portion 52 of the spring seat element 50. In this position of the resilient valve body 40 the charge openings 36 of the bushing 35 are closed by the cylindrical part 48 of the sliding element 45. Simultaneously the radial openings 46 in the cylindrical part 48 of the sliding element 45 are closed by bushing 35. Hence fluid flow in both directions is disabled as all radial openings at the charge side of the throttle valve arrangement 1 according to the invention are closed. Further, backpressure spring 55 is not compressed more than predefined in the design phase, as can be seen that the bottom part 47 of the sliding element 45 abuts against the securing element 57, in this embodiment a snap-ring.

Figure 2 shows the throttle valve arrangement 1 according to the invention in the open / charge position, i.e. in a position in which the pressure forces at the charge port 20 are higher than at the discharge port 15. As a consequence of this the head portion 51 of the spring seat element 50 pushes the resilient valve body 40 towards discharge port 15 until the rod 60 abut in the elongated through hole 53 facing to the charge port 20, which limits the axial movement/travel of the resilient valve body 40. As can be seen from Figure 2 in this situation, i.e. in this position of the resilient valve body 45 respectively the sliding element 45, both rows of radial charge openings 36 in the bushing 35 are open, wherein the second, more internal row overlaps with the radial openings 46 in the sliding element 45. Hence, as indicated by the arrows a fluid flow from the charge port 20 via the flow chamber 32 to the discharge port 15 is enabled, wherein all possible openings 36 and 46 are fully open, and the lowest possible flow resistance is achieved. For bringing the throttle valve arrangement 1 according to the invention in this position merely the force of the locking spring has to be overcome, which is can be relatively low as the function of the locking spring is to close the throttle valve arrangement 1 according to the invention when no or balanced pressure is present at the charge port 20 and discharge port 15. This means locking spring 65 needs to generate a valve locking force in height to move the resilient valve body 40 when no external forces act on the resilient valve body 40. Accordingly this valve locking force can be relatively low.

Figure 3 shows the throttle valve arrangement 1 according to the invention in an intermediate throttle position, i.e. in a position in which the pressure forces at the discharge port 15 are higher than at the charge port 20, but the force difference between the forces at the discharge port 15 and the charge port 20 is relatively low. Hence pressure forces act on the front face of stem portion 52 and on the slider 62. If the fluid chambers on both sides of the slider 62 were fluidly separated, those pressure forces would compress the locking spring 65 and move slider 62 into the blind bore 54. However, in the presented embodiment, the fluid chambers on both sides of the slider 62 are fluidly connected. Therefore no pressure difference is present at the slider 62 and the slider 62 is held in contact with the rod 60 by means of locking spring 65. Fluid connection between the fluid chambers on both sides of the slider can for example be established by an appropriate tolerance of slider or by incorporating a through hole in either the slider or the stem portion 52. Both forces displace the sliding element 45 towards the charge port 20 of the throttle valve arrangement 1 . Additionally the pressure forces also act on the outer surface of the bottom part 47 of the sliding element 45 due to which the backpressure spring 55 is compressed and the sliding element 45 is lifted from the securing element 57 at the stem portion 52. Therewith the overall axial length of the resilient valve body 40 is increased resil iently/elastically and the radial openings 46 in the sliding element 45 overlap at least partially with the radial charge openings 36 in the bushing 35. In the illustrated embodiment of Figure 3 the radial openings 46 overlap partially with the outer row of radial charge openings 36. As indicated with the arrows a fluid flow from the discharge port 15 to the charge port 20 via the flow chamber 32 in enabled.

In Figure 4, a fully open throttle position of the throttle valve arrangement 1 is shown. Similar to the position shown with Figure 3, the pressure forces at the discharge port 15 are higher than at the charge port 20. However, compared to the shown position of Figure 3, the difference between the pressure forces at the discharge port 15 and at the charge port 20 is higher than in the intermediate throttle position. In consequence, the backpressure spring 55 is further compressed and the resilient valve body 40 comprises a higher longitudinal length than in the intermediate throttle position. This leads to an increased overlap of the radial openings 46 in the sliding element 45 with the charge openings 36 in the bushing 35. A lower hydraulic resistance acts against the hydraulic flow from the discharge port 15 to the charge port 20. Different design options are available, in order to limit the resilient extension of the resilient valve body 40. As shown with Figure 4, the slider 62 can abut against an end of the groove 75 and thereby limit the movement of the sliding element 45 relative to the bushing 35. Alternatively, the valve housing 5 or an additional part attached to the valve housing may comprise a shoulder in the region of the charge port 20 against which the sliding element 45 can be urged by the resulting pressure force, when the throttle valve 1 is in its fully open throttle function position.

From the intermediate throttle position and the fully open throttle (end) position of the throttle valve arrangement 1 according to the invention shown with Figure 3 and Figure 4, respectively, it can be derived, that when the pressure at the discharge port 15 drops, the compressed backpressure spring 55 will release first and push the sliding element 45 towards the discharge port 15 until sliding element 45 abuts on the securing element 57. Thereby the radial openings 46 in the sliding element 45 are displaced and the radial openings 46 in the sliding element 45 is closed as the overlap with the radial openings 36 in the bushing 35 is no longer present hence fluid flow is interrupted.

Figure 5 shows the throttle valve arrangement 1 according to the invention in a plan view from the discharge side. The valve housing 5 shows axially oriented through holes 85 for fixing the throttle valve arrangement 1 to other hydraulic components, wherein an O-ring can be placed into the O-ring groove 7 (see Figures 1 to 4) in order to seal the valve housing 5 against the other components. In this embodiment four fixation through holes 85 are provided, however this number can be reduced or increased according to design and application requirements and the knowledge of a person with skills in the relevant art. In the center part of the throttle valve arrangement 1 shown in Figure 5 the rod 60 can be detected passing through the stem portion 52 of the spring seat element 50 and assuring the angular position of the spring seat element 50 with respect to the valve housing 5. Rod 60 also limits the axial travel distance of the resilient valve body 40 as descript above.

From the above disclosure and accompanying Figures and claims, it will be appreciated that the throttle valve arrangement 1 according to the invention offers many possibilities and advantages over the prior art. It will be appreciated further by a person skilled in the relevant art that further modifications and changes known in the art could be made a to throttle valve arrangement 1 according to the invention without parting from the spirit of this invention. Therefore all these modifications and changes are within the scope of the claims and covered by them. It should be further understood that the examples and embodiments described above are for illustrative purposes only and that various modifications, changes or combinations of embodiments in the light thereof, which will be suggested to a person skilled in the relevant art, are included in the spirit and purview of this application.

Reference Number List

Throtle valve 47 Botom part

Valve housing 48 Cylindrical part

Through hole 50 Spring seat element

O-ring groove 51 Head portion

Axial direction 52 Stem portion

Discharge port 53 Elongated through hole

Charge port 54 Blind hole

End wall 55 Back pressure spring

Undercut 57 Securing element

Flow chamber 60 Rod

Bushing 62 Slider

Inlet opening 65 Locking spring

Outlet opening 70 Roller

Resilient valve body 75 Groove

Sliding element 85 Axially oriented through holes

Radial Opening