Patent Description:
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.

A shock valve according to the preamble of claim <NUM> is known from <CIT>.

<CIT> 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.

<CIT> discloses a hydraulic pressure relief valve and <CIT> teaches a proportional valve for controlling a gaseous medium. Further, <CIT> describes a valve seat assembly of an electronic expansion valve and a manufacturing method of valve seat assembly. Another expansion valve is known from <CIT>.

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 according to claim <NUM>.

It comprises 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, wherein the valve seat section is formed in a valve seat element arranged between the inlet and the outlet. The channel arrangement forms an odd number of flow paths larger than two. The channel arrangement comprises a number of bores in the valve seat element, wherein the flow paths extend through the bores, wherein the shock-valve is configured such that fluid from the chamber can propagate through the bores into a cavity, wherein a pressure of the fluid in the cavity acts on the valve element and when a force onto the valve element exceeds a force produced by the biasing means, the valve element is moved away from the valve seat of the valve seat element, wherein the shock-valve opens until the pressure has been released to an acceptable magnitude, wherein the biasing means move the valve element back to contact the valve seat thereafter.

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 the 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.

According to 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> schematically shows a shock-valve <NUM> having a housing <NUM>. The housing comprises an inlet <NUM> opening into a chamber <NUM>. The shock-valve <NUM> comprises furthermore an outlet which is not visible in <FIG>.

A unit <NUM> comprising a valve seat element <NUM>, a valve element <NUM> and biasing means <NUM> in form of a spring is arranged in the chamber <NUM> of the housing <NUM>. The valve seat element <NUM> forms a valve element section. The biasing means <NUM> can be in form of a spring.

The valve element <NUM> is connected to a stem <NUM>. The stem <NUM> comprises an outer thread <NUM> at an end remote from the valve element <NUM>. A nut <NUM> is threaded onto the outer thread <NUM>. The biasing element <NUM> is pretensioned between the nut <NUM> and the valve seat element <NUM>. A distance D between the nut <NUM> and the valve seat element <NUM> determines the force with which the biasing element <NUM> presses the valve element <NUM> against the valve seat element <NUM>.

The valve seat element <NUM> comprises a valve seat <NUM>. The valve element <NUM> cooperates with the valve seat <NUM>. In the condition shown in <FIG>, the valve element <NUM> contacts the valve seat <NUM> and the shock-valve <NUM> of <FIG> is closed.

The chamber <NUM> is sealed to the outside by means of a plug <NUM> which can be threaded into the housing <NUM>. The valve seat element <NUM> is pressed against a step <NUM> of the housing <NUM> by the pressure at the inlet <NUM> of the chamber <NUM>. Furthermore, the unit <NUM> is kept seated between the plug13 and the step <NUM> of the housing <NUM> by means of a spring <NUM>. This spring <NUM> has a conical form, i.e. it comprises a diameter which increases from the nut <NUM> towards the plug13. The spring <NUM> provides a small compression between the plug13 and the step <NUM>. It aids assembly due to the interference fit between the spring <NUM> and the nut <NUM>.

The valve seat element <NUM> comprises an odd number of bores <NUM>, distributed evenly in circumferential direction. Each bore <NUM> forms a channel, so that the bores <NUM> together form a channel arrangement. The channel arrangement defines a number of flow paths from the chamber <NUM> to the valve seat <NUM>. To this end the valve seat element comprises a cavity <NUM> through which the stem <NUM> of the valve element <NUM> is guided. The cavity <NUM> comprises a central axis <NUM> and the flow paths through the bores <NUM> are directed towards the central axis <NUM>. The valve seat <NUM> is formed at an edge of the cavity <NUM>.

Since the bores <NUM> are evenly distributed in circumferential direction, a wall section <NUM> of the cavity is arranged opposite to the openings of the bores <NUM> into the cavity <NUM>. 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 <NUM> of the circumferential wall of the cavity <NUM>.

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

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

The shock-valve operates as follows:
Hydraulic fluid entering the chamber <NUM> via the inlet <NUM> produces a hydraulic pressure in the chamber <NUM>. This hydraulic pressure presses the valve seat element <NUM> against the step <NUM> in the housing <NUM> producing a sufficient tightness, so that a leakage through the shock-valve <NUM> is avoided. The biasing means <NUM> press the valve element <NUM> against the valve seat <NUM> of the valve seat element <NUM> so that the shock-valve <NUM> is closed. The fluid from the chamber <NUM> propagates through the bores <NUM> into the cavity <NUM>. The pressure of the fluid in the cavity <NUM> acts on the valve element <NUM>. When the force onto the valve element <NUM> exceeds the force produced by the biasing means <NUM>, the valve element <NUM> is moved away from the valve seat <NUM> of the valve seat element <NUM> and the shock-valve opens until the pressure has been released to an acceptable magnitude. Thereafter, the biasing means <NUM> move the valve element <NUM> back to contact the valve seat <NUM>.

The technical effect of the odd number of flow paths is illustrated with reference to <FIG>.

<FIG> shows the flow situation in a conventional shock-valve. <FIG> shows a sectional view corresponding to the line II-II of <FIG>. <FIG> shows a view perpendicular to the view of <FIG>.

It can be seen that a flow <NUM> (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> shows the situation in the shock-valve <NUM> according to the present invention. <FIG> shows a sectional view corresponding to the line II-II of <FIG>. <FIG> shows a view perpendicular to the view of <FIG>. A flow <NUM> flowing through bore <NUM> cannot enter an opposite bore, but hits against a wall section <NUM> of the circumferential wall of the cavity <NUM>. Thus, flows of different bores <NUM> do not meet each other in opposing directions, but always meet under an angle which dramatically reduces the noise produced.

Claim 1:
Shock-valve (<NUM>) comprising a housing (<NUM>) having an inlet (<NUM>) connected to a chamber (<NUM>) and an outlet, a valve seat section having a valve seat (<NUM>) and being arranged in the housing (<NUM>), a valve element (<NUM>) cooperating with the valve seat (<NUM>), and biasing means (<NUM>) acting on the valve element (<NUM>) in a direction towards the valve seat (<NUM>), wherein a channel arrangement extends from the chamber (<NUM>) to the valve seat (<NUM>), wherein the valve seat section is formed in a valve seat element (<NUM>) arranged between the inlet (<NUM>) and the outlet, characterized in that the channel arrangement forms an odd number of flow paths larger than two,
wherein the channel arrangement comprises a number of bores (<NUM>) in the valve seat element (<NUM>), wherein the flow paths extend through the bores (<NUM>), wherein the shock-valve (<NUM>) is configured such that fluid from the chamber (<NUM>) can propagate through the bores (<NUM>) into a cavity (<NUM>), wherein a pressure of the fluid in the cavity (<NUM>) acts on the valve element (<NUM>) and when a force onto the valve element (<NUM>) exceeds a force produced by the biasing means (<NUM>), the valve element (<NUM>) is moved away from the valve seat (<NUM>) of the valve seat element (<NUM>), wherein the shock-valve (<NUM>) opens until the pressure has been released to an acceptable magnitude, wherein the biasing means (<NUM>) move the valve element (<NUM>) back to contact the valve seat (<NUM>) thereafter.