The present invention relates to a shock-valve comprising a housing having an inlet connected to a chamber and an outlet, a valve seat section having a valve seat and being arranged in the housing, a valve element cooperating with the valve seat, and biasing means acting on the valve element in a direction towards the valve seat, wherein a channel arrangement extends from the chamber to the valve seat.

Such a shock-valve is used to avoid an overpressure spike in a hydraulic system, for example, in a hydraulic steering system. Such an overpressure spike could occur, when the steered wheels of a vehicle hit against an obstacle and are moved against the force of a steering motor. Such a shock-valve can, however, be used in other systems as well.

WO 2015/143845 A1 discloses a valve base assembly for electronic expansion valves comprising a housing having an inlet connected to a chamber and an outlet, a valve seat section having a valve seat and being arranged in the housing, a valve element cooperating with the valve seat and a channel arrangement extending from the chamber to the valve seat, wherein the channel arrangement forms an odd number of flow paths larger than two.

A problem of a shock-valve is, that it produces a considerable noise during operation. Such a noise can be disturbing.

The object underlying the invention is to provide a shock-valve having low noise during operation.

This object is solved with a shock-valve as described at the outset in that the channel arrangement forms an odd number of flow paths larger than two. Shock-valves presently available always have an even number of flow paths.

In an embodiment of the invention the number of flow paths is three, five or seven. Such a number of flow paths allows for a uniform distribution of the flows through the gap between the valve element and the valve seat.

The valve seat section is formed in a valve seat element arranged between the inlet and the outlet. When the valve seat section is formed in a valve seat element, the valve seat can be produced independently from the housing and there is a larger degree of freedom when designing the valve seat and the environment of the valve seat. This allows for a design of the flow paths producing low noise during operation.

In an embodiment of the invention the valve seat element comprises a central cavity, wherein the valve seat is formed at an edge of the cavity, and the flow paths open into the cavity. In this way it is possible to arrange the flow paths in a way that the flow of hydraulic fluid does not produce too much noise.

In an embodiment of the invention the cavity comprises a central axis and the flow paths are directed towards the central axis. In other words, the flow paths are directed radially inwardly.

In an embodiment of the invention a wall section of the cavity is arranged opposite to an opening of at least one flow path into the cavity. In this way a flow of hydraulic fluid through this flow path cannot be directed into an opposite opening of another flow path.

In an embodiment of the invention a wall section of the cavity is arranged opposite to each opening of the flow path. Thus, there is no opening of a flow path directly opposite an opening of another flow path. Thus, it is not possible that the flow of hydraulic fluid can favour one opening of the flow paths over others with the consequence that the fluid is forced to flow to the outlet of the housing in a more laminar manner.

In an embodiment of the invention the valve seat element is allowed to rotate in the chamber. The valve seat element is not fixed against rotation.

In an embodiment of the invention the channel arrangement comprises a number of bores in the valve seat element, wherein the flow paths extend through the bores. The bores form a defined flow path in which the flow of the hydraulic fluid is as laminar as possible.

In an embodiment of the invention the valve seat element comprises for each bore a flattened section in a circumferential outer wall of the valve seat element and the bore extends from the respective flattened section. The flattened section forms a border of a kind of inlet area for the bore, in which the fluid can spread.

In an embodiment of the invention in circumferential direction each flattened section extends over more than twice the largest diameter of the respective channel. This means that the gap between the valve seat element and the housing is large enough to allow a spreading of the fluid contributing to a laminar flow of the fluid.

In an embodiment of the invention the valve seat element, the valve element and the biasing means form a unit that can be handled together. The valve seat element, the valve element and the biasing means, for example, a spring, can be mounted to form the unit, wherein the unit is then inserted into the chamber of the housing. In an embodiment of the invention the valve element comprises a stem penetrating the valve seat element. This is a simple way to keep the three elements valve seat element, valve element and biasing means together.

A preferred embodiment of the invention will now be described with reference to the drawing, in which:

Fig. 1 shows a schematic sectional view of a shock-valve,

Fig. 2 shows a sectional view along line ll-ll of Fig. 1 ,

Fig. 3 shows a sectional view of a unit of valve seat element, valve element and biasing means,

Fig. 4 shows a perspective view of this unit,

Fig. 5 shows a flow situation in a conventional shock-valve, and

Fig. 6 shows the flow situation in a shock-valve according to the present invention.

Fig. 1 schematically shows a shock-valve 1 having a housing 2. The housing comprises an inlet 3 opening into a chamber 4. The shock-valve 1 comprises furthermore an outlet which is not visible in Fig. 1 .

A unit 5 comprising a valve seat element 6, a valve element 7 and biasing means 8 in form of a spring is arranged in the chamber 4 of the housing 2. The valve seat element 6 forms a valve element section. The biasing means 8 can be in form of a spring. The valve element 7 is connected to a stem 9. The stem 9 comprises an outer thread 10 at an end remote from the valve element 7. A nut 11 is threaded onto the outer thread 10. The biasing element 8 is pretensioned between the nut 11 and the valve seat element 6. A distance D between the nut 11 and the valve seat element 6 determines the force with which the biasing element 8 presses the valve element 7 against the valve seat element 6.

The valve seat element 6 comprises a valve seat 12. The valve element 7 cooperates with the valve seat 12. In the condition shown in Fig. 1 and 3, the valve element 7 contacts the valve seat 12 and the shock-valve 1 of Fig. 1 is closed.

The chamber 4 is sealed to the outside by means of a plug 13 which can be threaded into the housing 2. The valve seat element 6 is pressed against a step 14 of the housing 2 by the pressure at the inlet 3 of the chamber 4. Furthermore, the unit 5 is kept seated between the plugl 3 and the step 14 of the housing 2 by means of a spring 22. This spring 22 has a conical form, i.e. it comprises a diameter which increases from the nut 11 towards the plugl 3. The spring 22 provides a small compression between the plugl 3 and the step 14. It aids assembly due to the interference fit between the spring 22 and the nut 11 .

The valve seat element 6 comprises an odd number of bores 15, distributed evenly in circumferential direction. Each bore 15 forms a channel, so that the bores 15 together form a channel arrangement. The channel arrangement defines a number of flow paths from the chamber 4 to the valve seat 12. To this end the valve seat element comprises a cavity 16 through which the stem 9 of the valve element 7 is guided. The cavity 16 comprises a central axis 17 and the flow paths through the bores 15 are directed towards the central axis 17. The valve seat 12 is formed at an edge of the cavity 16. Since the bores 15 are evenly distributed in circumferential direction, a wall section 18 of the cavity is arranged opposite to the openings of the bores 15 into the cavity 16. In other words, it is not possible that a flow coming from one bore enters directly the opening of another bore. To the contrary, it hits the wall section 18 of the circumferential wall of the cavity 16.

As mentioned above, the valve seat element 6 is not mechanically fixed in the housing 2 but only by the force of the conical spring 22 and by the pressure in the chamber 4. There is a small gap 21 between the valve seat element 6 and the housing 2 in radial direction (related to the central axis 17). This means also that the valve seat element 6 can freely rotate in the chamber 4.

As can be seen in Fig. 2 and 4, the valve seat element 6 comprises for each bore 15 a flattened section 19 of a circumferential outer wall of the valve seat element 6 and the bore 15 extends from the respective flattened section 19. In other words, a space 20 is formed between the valve seat element 6 and the housing 2 in which the hydraulic fluid coming from the chamber 4 can spread before entering the bore 15. The flattened section extends in circumferential direction over more than twice the largest diameter of the bore 15.

The shock-valve operates as follows:

Hydraulic fluid entering the chamber 4 via the inlet 3 produces a hydraulic pressure in the chamber 4. This hydraulic pressure presses the valve seat element 6 against the step 14 in the housing 2 producing a sufficient tightness, so that a leakage through the shock-valve 1 is avoided. The biasing means 8 press the valve element 7 against the valve seat 12 of the valve seat element 6 so that the shock-valve 1 is closed. The fluid from the chamber 4 propagates through the bores 15 into the cavity 16. The pressure of the fluid in the cavity 16 acts on the valve element 7. When the force onto the valve element 7 exceeds the force produced by the biasing means 8, the valve element 7 is moved away from the valve seat 12 of the valve seat element 6 and the shock-valve opens until the pressure has been released to an acceptable magnitude. Thereafter, the biasing means 8 move the valve element 7 back to contact the valve seat 12.

The technical effect of the odd number of flow paths is illustrated with reference to Fig. 5 and 6.

Fig. 5 shows the flow situation in a conventional shock-valve. Fig. 5a shows a sectional view corresponding to the line ll-ll of Fig. 1 . Fig. 5b shows a view perpendicular to the view of Fig. 5a.

It can be seen that a flow 23 (shown as an arrow) passing bore 15a can directly enter an opposite bore 15b. When, on the other hand, a similar flow flows in opposite direction through bore 15b, this produces noise when these two flows meet.

Fig. 6 shows the situation in the shock-valve 1 according to the present invention. Fig. 6a shows a sectional view corresponding to the line ll-ll of Fig. 1. Fig. 6b shows a view perpendicular to the view of Fig. 6a. A flow 23 flowing through bore 15 cannot enter an opposite bore, but hits against a wall section 18 of the circumferential wall of the cavity 16. Thus, flows of different bores 15 do not meet each other in opposing directions, but always meet under an angle which dramatically reduces the noise produced.

Instead of the five bores 15 forming five flow channels, another odd number of flow channels can be used, for example three or seven flow channels. The flow through the bores 15 is forced to flow to the outlet in a more laminar manner.