Patent Description:
Such a valve arrangement is used to control a hydraulic consumer, like a hydraulic motor or a hydraulic actuator.

<CIT> relates to an electrohydraulic proportional directional control valve.

The valve arrangement can be remotely controlled by supplying a pilot pressure to the pressure chamber. The pressure in the pressure chamber drives the spool in its lengthwise direction. Depending on the position of the spool in the housing the flow path is established allowing hydraulic fluid to flow from the supply port to one of the working ports of the book port arrangement. This flow path has a certain flow resistance which depends also on the position of the spool within the housing. In a neutral position there is no flow path from the supply port to the working port arrangement.

When the hydraulic arrangement is used in connection with a lifting device, like a crane, the hydraulic motor is used to lift or lower a load or to actuate other parts of the crane, like a rotational drive. In this and in other cases, several safety requirements must be fulfilled.

It is an object of the invention to show a simple way to achieve a safety functionality of a hydraulic arrangement.

This object is solved with the hydraulic arrangement having the features of claim <NUM>. The housing comprises a pilot pressure relief port connected to the return port via a shut-off valve and the spool after a predetermined stroke opens a connection between the pressure chamber and the pilot pressure relief port.

In this way it is possible to establish a mode of operation in which the flow of hydraulic fluid from the supply port to one of the working ports is limited. This limitation can simply be achieved by opening the shut-off valve. When the shut-off valve is opened and the spool in the housing has been moved by the predetermined stroke, the hydraulic fluid producing the pilot pressure in the pressure chamber is released to the return port, so that the pressure in the pressure chamber cannot further increase and cannot drive the spool further. This is in particular the case when a restoring spring acts on the spool against the force of the pilot pressure in the pressure chamber. However, when full flow is desired, the shut-off valve is closed, so that the pilot pressure can build up in the pressure chamber and the stroke of the spool within the housing is no longer restricted.

Accordingly, the hydraulic arrangement includes a safe limited flow function. The safety functionality is implemented in the form of a safe limited flow. The safe limited flow function is controlled via the shut-off valve. The full flow is only allowed while the shut-off calve is closed.

For example, the hydraulic arrangement can be used to control a hydraulic consumer, like a hydraulic motor or a hydraulic actuator; e.g. in connection with a lifting device, like a crane, where the hydraulic motor is used to lift or lower a load and/or to actuate other parts of the crane, like a rotational drive. According to another aspect, the hydraulic arrangement can be used in connection with a hydraulic steering device. For the hydraulic steering device, the safety functionality requirements are very important as well.

The pilot pressure relief port is connected to a pilot pressure relief chamber. In this case the pilot pressure relief chamber can be connected to the return port. This simplifies the construction.

In an embodiment of the invention an area of a connection between the pressure chamber and the pilot pressure relief chamber increases gradually after the predetermined stroke of the spool. This means that the pilot pressure in the pressure chamber is not suddenly lowered to the pressure at the return port but decreases only with an increasing stroke of the spool, so that the movement of the spool is not abruptly interrupted. This increases the comfort for the user of a hydraulic consumer, for example, when the hydraulic consumer is a motor rotating an upper part of an excavator with respect to a lower part.

In an embodiment of the invention the shut-off valve comprises actuating means actuating the shut-off valve. This means that the shut-off valve can be remotely controlled. The direct access of an operator to the shut-off valve is not required.

In an embodiment of the invention the actuating means are in form of a solenoid. The shut-off valve can be activated electrically. Thus, an auxiliary energy can be used which is available in most cases.

In an embodiment of the invention the actuating means are connected to a condition sensor arrangement sensing at least a working condition of the hydraulic arrangement and the actuating means activate the shut-off valve depending on the at least one working condition of the hydraulic arrangement. In this case the flow of hydraulic fluid to the working port and to the motor or consumer connected to the working port can be adapted to the working condition of the hydraulic arrangement. If, for example, the working port is connected to parts of a crane or an excavator, the speed of movement of these parts should be adapted to the load handled by the crane or excavator. When the load is heavy, the movement speed should be low to avoid dangerous situations. When the hydraulic arrangement is part of the hydraulic steering of the vehicle, the steering speed can be adapted to the driving speed of the vehicle.

The spool is movable in two directions opposite to each other, wherein a pressure chamber is provided for each direction of stroke, and the spool after a predetermined stroke in one direction opens a connection between one of the pressure chambers and the pilot pressure relief chamber and the spool after a predetermined stroke in the other direction opens a connection between the other of the pressure chambers and the pilot pressure relief chamber. The valve can thus control the operation of the motor or consumer connected to the working port arrangement in two directions. Safety can be achieved for both directions.

In an embodiment of the invention the predetermined stroke is the same for both directions. Thus, the same behavior can be achieved for both directions of operation.

In an embodiment of the invention the shut-off valve is open in an inactivated condition. Thus, when no auxiliary energy is available to actuate the shut-off valve, the shut-off valve is in a condition in which the flow through the hydraulic arrangement is limited. For example, the shut-off valve may be biased to (automatically) open, e.g. mechanically biased when the shut-off vale is not activated. In one embodiment, the shut-off valve is spring-biased to open. The actuating means may be configured to close the shut-off valve (against the bias) if the shut-off valve is in an activated condition, e.g. being electrically activated.

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

<FIG> shows schematically a hydraulic diagram of a valve arrangement <NUM>. The valve arrangement <NUM> comprises a supply port P, a return port T, a working port arrangement having two working ports L, R, and a valve <NUM>. The valve <NUM> controls the flow of hydraulic fluid from the supply port P to one of the working ports L, R. To this end the valve <NUM> comprises a spool <NUM> which is arranged in a housing <NUM> and can be moved in the lengthwise direction within the housing <NUM>. The spool <NUM> and the housing <NUM> together form variable orifices or bleeds which are schematically indicated in the spool <NUM> shown in <FIG>. Depending on the position of the spool <NUM> in the housing <NUM> these orifices or bleeds are opened or closed to form a flow path between the supply port P and the working port arrangement L, R or not. When orifices are open, hydraulic fluid can flow from the supply port P to one of the working ports L, R. When the orifices are closed such the flow is interrupted.

The position of the spool <NUM> within the housing <NUM> determines which of the working ports L, R is supplied with hydraulic fluid from the supply port P. Furthermore, the position of the spool <NUM> in the housing <NUM> determines the size of the flow of the hydraulic fluid. The larger the stroke of the spool <NUM> out of the neutral position the larger the area of the orifices and the larger the flow of fluid.

The spool <NUM> is held or pretensioned in the position by means of springs <NUM>, <NUM> which are equally dimensioned and act on to the spool <NUM> with the same force. The housing <NUM> is provided on both sides of the spool <NUM> in the longitudinal direction with a pressure chamber <NUM>, <NUM>. The pressure chambers <NUM>, <NUM> are connected to the source of the pilot pressure, as it is known in the art. When a left pilot pressure <NUM> in pressure chamber <NUM> is larger than a right pilot pressure <NUM> in the pressure chamber <NUM> the spool <NUM> is moved to the right to allow supply of hydraulic fluid to the left working port L ("left stroke"). When the right pilot pressure <NUM> in pressure chamber <NUM> is larger than the left pilot pressure <NUM> in pressure chamber <NUM>, the spool <NUM> is moved to the left to allow supply of hydraulic fluid to the right working port R ("right stroke").

Briefly spoken, maximum flow is adjusted when the spool <NUM> has been moved by the maximum left stroke <NUM> (<FIG>, in order to supply hydraulic fluid to the left working port L) or by the maximum right stroke <NUM> (in order to supply hydraulic fluid to the right working port R).

The housing <NUM> is provided with a pressure relief chamber <NUM>. The pressure relief chamber <NUM> is connected to the return port T by means of pressure relief port <NUM> and a shut-off valve <NUM>. The shut-off valve <NUM> is provided with actuating means <NUM>, in the present embodiment in form of the solenoid.

When the actuating means <NUM> are not activated, the shut-off the valve <NUM> is open and directly connects the pressure relief chamber <NUM> to the return port T. When the actuating means <NUM> are activated, for example, when the solenoid is provided with an electric current, the shut-off valve <NUM> is moved in a position, in which the connection between the pressure relief chamber <NUM> and the return port T is interrupted.

The pressure relief chamber <NUM> is closed by the spool <NUM> when the spool <NUM> is in the neutral position. This means that there is no connection between the pressure chambers <NUM>, <NUM> and the pressure relief port <NUM>. The pressure relief chamber <NUM> remains closed during a first part of a stroke of the spool <NUM>. This is indicated by a minimum left stroke <NUM> and a minimum right stroke <NUM>. During the minimum left stroke <NUM> and the minimum right stroke <NUM> the pressure in the pressure chambers <NUM>, <NUM> is exclusively determined by the pilot pressures <NUM>, <NUM> mentioned above.

However, when the spool <NUM> should be moved more than the minimum left stroke <NUM> and the minimum right stroke <NUM>, this is only possible when the shut-off valve <NUM> is closed. When the shut-off valve <NUM> is open, as shown in <FIG>, there is a connection between the respective pressure chamber <NUM>, <NUM> and the pressure relief port <NUM> via the pressure relief chamber <NUM> and the hydraulic fluid producing this pressure in the respective pressure chamber <NUM>, <NUM> is released to the pressure relief chamber <NUM> and from there to the return port T.

As is shown in <FIG>, a size or area of a connection between the respective pressure chamber <NUM> and the pressure relief chamber <NUM> increases with the stroke of the spool <NUM>, i.e., there is no abrupt lowering of the pressure in the respective pressure <NUM>, <NUM>.

The stroke of the spool <NUM> until a connection between the respective pressure chamber <NUM>, <NUM> and the pressure relief chamber <NUM> is established is the same for both moving directions of the spool <NUM>.

When the shut-off valve <NUM> is closed, there is no possibility for the hydraulic fluid in the respective pressure chambers <NUM>, <NUM> to flow out of the pressure relief chamber <NUM> to the return port T. In this case, hydraulic fluid supplied to the respective pressure chamber <NUM>, <NUM> moves the spool <NUM> further, so that the maximum left stroke <NUM> or the maximum right stroke <NUM> can be achieved. It should be noted that spool <NUM> can be positioned in any position between neutral and maximum stroke <NUM>, <NUM> (when the shut-off valve <NUM> is closed) or between neutral and minimum stroke <NUM>, <NUM> (when the shut-off valve <NUM> is open).

<FIG> shows, how the valve <NUM> is arranged within the hydraulic arrangement <NUM>. The pressure port P is connected to the valve <NUM> via a priority valve <NUM>. Means for generating the controlled pilot pressures <NUM>, <NUM> actuating the spool <NUM> are not shown but known in the art. Lines <NUM>, <NUM> are shown connecting the respective pressure chambers <NUM>, <NUM> to the shut-off valve <NUM> when the spool <NUM> is moved more than the minimum stroke <NUM>, <NUM>. As illustrated in connection with <FIG>, there may be a variable orifice between the respective pressure chamber <NUM>, <NUM> and the shut-off valve <NUM>. However, this is only an option and therefore not shown in <FIG>.

The hydraulic arrangement can include a status sensor means <NUM>. The status sensor means <NUM> is configured to provide information whether the flow limitation is enabled or not. For example, the status sensor means <NUM> may be coupled to the shut-off valve <NUM> and configured to detect whether the shut-off valve <NUM> is open or closed. In this embodiment, the status sensor means <NUM> is coupled to the actuating means <NUM>. It may determine whether the shut-off valve is activated (closed) by the actuating means <NUM> or not activated (i.e. the shut-off valve <NUM> is open).

Claim 1:
Hydraulic arrangement (<NUM>) comprising a supply port (P), a return port (T), a working port arrangement (L, R), and a valve (<NUM>) controlling a supply of hydraulic fluid from the supply port (P) to the working port arrangement (L, R), wherein the valve (<NUM>) comprises a housing (<NUM>) and a spool (<NUM>) movable in lengthwise direction in the housing (<NUM>) and forming together with the housing (<NUM>) at least one flow path the resistance of which depends on the position of the spool (<NUM>) in the housing (<NUM>), and the spool (<NUM>) is actuated by a hydraulic pilot pressure (<NUM>, <NUM>) in a pressure chamber (<NUM>, <NUM>), wherein the housing (<NUM>) comprises a pilot pressure relief port (<NUM>) connected to the return port (T) via a shut-off valve (<NUM>) and the spool (<NUM>) after a predetermined stroke (<NUM>, <NUM>) opens a connection between the pressure chamber (<NUM>, <NUM>) and the pilot pressure relief port (<NUM>), wherein the housing (<NUM>) is provided with a pilot pressure relief chamber (<NUM>), wherein the pilot pressure relief port (<NUM>) is connected to the pilot pressure relief chamber (<NUM>), wherein the spool (<NUM>) is movable in two directions opposite to each other, wherein a pressure chamber (<NUM>, <NUM>) is provided for each direction of stroke, and the spool (<NUM>) after a predetermined stroke (<NUM>) in one direction opens a connection between one of the pressure chambers (<NUM>, <NUM>) and the pilot pressure relief chamber (<NUM>), characterized in that the spool (<NUM>) after a predetermined stroke (<NUM>) in the other direction opens a connection between the other of the pressure chambers (<NUM>, <NUM>) and the pilot pressure relief chamber (<NUM>).