GB2264996A - Pressurised-fluid valve assembly - Google Patents

Abstract

A valve assembly for attachment to a hydraulic system for the control of fluid under pressure comprises inlet and exhaust ports 11, 12 for fluid under pressure, first and second control ports 13, 14 for connection to a hydraulic device and a switching valve selectively connecting the inlet and exhaust ports respectively with the first and second control ports. The conduit to each control port includes a spring-biassed valve. A piston 56 reciprocates in response to fluid pressure to open that conduit which is to be connected to tank, the other valve being moved off its seat by fluid pressure alone. <IMAGE>

Description

PRESSURISED FLUID VALVE The present invention relates to pressurised-fluid valves and particularly, but not exclusively, to such valves used in the supply of oil under pressure to a hydraulic ram or jack.

Hydraulic rams or jacks can support large weights in critical positions. With existing valves a sudden reduction in oil pressure, caused for example by a malfunction of the pump or a split hose, would cause the weight suddenly to collapse with undesirable results.

Even in a correctly operating system there is often some seepage resulting in unwanted reduction of the support.

The object of the invention is to mitigate this problem.

According to the present invention there is provided a valve having supply-side inlet and exhaust ports for fluid under pressure, control ports for conveying to and from a device to be attached to the valve, conduit means connecting the supply-side ports selectively with respective ones of the control ports and a selector valve to determine the passage of fluid between the said ports, wherein there is provided second valve means biassed to close the conduit means to both control ports and operable to open on application of a fluid pressure above a predetermined value.

Advantageously the second valve means comprises a respective one-way valve in the conduit to each control port each openable by pressure in a direction from the supply-side towards the respective control port and an actuator operable by fluid pressure to open a selected one of the one-way valves to allow fluid exhaust to take place through the said one-way valve.

Preferably the selector valve includes a position which interconnects the inlet directly with the outlet via conduits in the selector valve. The selector valve may be biassed to this position.

According to a second aspect of the invention there is provided a valve for attachment to a hydraulic system for the control of the fluid under pressure, the valve comprising inlet and exhaust ports for fluid under pressure, first and second control ports for attachment to a hydraulic device and conduits connecting the inlet and exhaust ports respectively with the first and second control ports wherein the valve includes means biassed to close both conduits and to open both conduits on the application of fluid pressure above a predetermined value to allow fluid to flow through the control ports.

This valve may be attached to an existing hydraulic system to provide a fail safe control.

Preferably the means biassed to close both conduits comprises a pair of one-way valves directed towards one another with an actuator arranged therebetween, the actuator being adapted to open one one-way valve when pressure is applied to through the first supply-side port and the other one-way valve when pressure is applied to the other supply-side port.

The present invention will now be described,by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross section view of a valve according to the invention in which the selector valves are set for pressurised fluid to lift a device connected to the valve, Figure 2 is a cross-section of the valve of Figure 1 in which the selector valves are set for pressurised fluid to lower a device connected to the valve, Figure 3 is a cross section of the valve of Figure 1 in which the settings are shown and the fluid passage charted in the event of a reduction in fluid pressure, Figure 4 is an end view on A-A of Figure 3, Figure 5 is a section on B-B of Figure 3, Figure 6 is a section on C-C of Figure 3, and Figure 7 is an end view on D-D of Figure 3.

The illustrated valve is adapted to be located in the fluid line for example between a hydraulic pump and a ram or jack (not shown). The valve may of course be used with any fluid under pressure, although oil is preferred, and any suitable device. Four connections are made to the valve, the inlet from the pump is connected to a supply-side inlet port 11 and the exhaust to a supply-side exhaust port 12. The supply-side ports 11,12 are selectively connected to control ports 13 and 14 depending on whether the jack is to be lifted or lowered.

The valve is made in three pieces and held together by bolts passing through bores 10. All left and right hand indications hereafter will refer to the drawings as seen. The left hand piece houses the inlet and outlet ports 11 and 12 and conduits from ports 11,12 interconnecting ports 11,12 with ports and channels on the right hand face of the left hand piece, which ports and channels are shown in Figure 5. The inlet port 11 is connected by conduits 16a,16b to two ports 17 and 18.

The exhaust port 12 is connected by conduit 20 to port 22 and thence via channel 24 (see Figure 5) to port 26.

The channel 24 is surrounded by a seal 26 located in a groove in the right hand face of the left hand piece.

The central piece has a ported outer member 21 defining a cylinder in which is mounted a selector valve 30 having three operating annuli 25,27,29 and three operating lands. The valve 30 is sealed to the cylinder by O-rings 31 located in respective grooves one at each end of the valve. The selector valve 30 moves within the outer member 21 so as to connect selectively the ports and channels in the outer member. The left hand side of the outer member 21 has five ports 32a,b,c,d,e, positioned as shown in Figure 2. The right hand side of the central outer member 21 is shown in Figure 6. In particular it defines two channels 34 and 36. Each channel 34,36 is surrounded by a respective seal 35,37 located in a respective groove in the central piece.

The right hand piece, which may be used on its own with other hydraulic systems, comprises a second outer member 42 carrying the ports 13 and 14 on the right hand side as well as port 46 (first supply-side port to the right-hand piece) in fluid connection with the channel 34 and port 47 ( second supply-side port for the righthand piece) in fluid connection with the channel 36. The outer member 42 houses two one-way valves 48,52 screw threaded one into each end of a cylindrical bore and facing towards one another with a valve actuator or shuttle 56 therebetween. Each one way valve has a respective seated ball 49,50 resiliently biassed by a respective compression spring 53 to close a respective opening 51,54. Port 46 is in flow communication with port 13 via one way valve 48 and conduit 61. Port 47 is in flow communication with the port 14 via one way valve 52 and conduit 62. The openings 51 and 54 are disposed in the right-hand piece facing one another and the floating secondary actuator 56 having opposed protrusions 58, 60 is located between the openings slideably mounted in the bore. The actuator 56 is shuttled between the openings by- fluid pressure between three positions i) to open the valve 48 (Figure 2) ii) to open the valve 52 (Figure 1) iii) to leave both valves closed with the balls firmly against their respective seatings.

Other ports formed during manufacture but not required are blocked off with plugs.

The operation of the valve is as follows: In the pressurised mode (Figure 1) the selector valve 30 is in the lowest position allowing the direct access for the pressurised fluid through passage 16a, port 32c in the central piece 21, annulus 25, to channel 34 and port 46. The fluid pressure acts both to lift the ball 50 from its seating to open the valve and to urge the actuator downwardly so that the protrusion 60 pushes against the ball 49 to open the valve 52. In this position the pressurised fluid is free to flow to the control port 13 and exhaust from the control port 14.

The passage for the exhaust fluid is via the valve 52 (the ball having been lifted from the seating by the protrusion 60) the port 47, the channel 36, annulus 29 port 22, passage 20 and outlet 12.

To retract the jack the flow through the jack is reversed. Thus the pressurised fluid is applied to control port 14. To create a passage for this flow the selector valve 30 is raised to the position shown in Figure 2. This creates a passage from port 11, through conduit 16b, port 18, annulus 27, channel 36, port 47, valve 52, conduit 62 and port 14. The valve 52 is opened by the pressure of the fluid, which pressure also acts to urge the actuator upwardly so that protrusion 58 pushes the ball 50 from its seat to open the valve 48.

The passage for the exhausting fluid is as follows: port 13, valve 48 via the seating opened by the protrusion 58, port 46, channel 34, annulus 25, port 32a, port 26, channel 24, port 22, passage 20 to port 12. Lands on the selector valve 30 block off the other alternatives.

In the event that the pressure drops below a particular value at which the valve is set the pressure becomes insufficient either to move the balls of the valves 48, 52 against the resilient bias or to move the floating actuator enough to open either valve. When the selector valve returns to the intermediate position shown in Figure 3 ports 18 and 22 are interconnected by annuli 27 and 29 and channel 36 so that any fluid can circulate harmlessly around the valve and exhaust without access to the jack. Meanwhile the high pressure required to support the jack is retained by blocking all access to or exhaust from the ports 13 and 14 by means of the one way valves. Due to the strong one-way valve mitigating against any fluid seepage an improved support is obtained in these circumstances. Thus the jack remains in position until the supply of fluid pressure at the correct pressure is restored.

The position shown in Figure 3 is also the idle position which is adopted when the jack is not being used and the selector valve is biassed to this position.

The selector valve is operated by means of a springloaded twist grip which contains two cam surfaces.

Twisting of the grip in one direction pushes the valve down to pressurise the device and in the other direction pushes the valve up to release the pressure from the device. If the twist grip is released it returns automatically to the neutral idle position.

Claims (7)

1. A valve having supply side inlet and exhaust ports for fluid under pressure, control ports for conveying fluid to and from a device to be attached to the valve, conduit means connecting the supply-side ports selectively with respective ones of the control ports and a selector valve to determine the passage of fluid between the said ports, wherein there is provided second valve means biassed to close the conduit means to both control ports and operable to open on application of a fluid pressure above a predetermined value.

2. A valve according to claim 1 wherein the selector valve means comprises a respective one-way valve in the conduit to each control port each openable by pressure in a direction from the supply-side towards the respective control port and an actuator operable by fluid pressure to open a selected one of the one-way valves to allow fluid exhaust to take place through the said one-way valve.

3. A valve according to claim 1 or 2 wherein the selector valve includes a position which interconnects the inlet directly with the outlet via conduits in the selector valve.

4. A valve according to 3 wherein the selector valve is biassed to the said position.

5. A valve for attachment to a hydraulic system for the control of fluid under pressure, the valve comprising inlet and exhaust ports for fluid under pressure, first and second controls ports for attachment to a hydraulic device and conduits connecting the inlet and exhaust ports respectively with the first and second control ports wherein the valve includes means biassed to close both conduits1 but adapted to open either conduit on the application of fluid pressure above a predetermined value to allow fluid to flow through the control ports.

6. A valve according to claim 5 wherein the means biassed to close both conduits comprises a pair of oneway valves directed towards one another with an actuator arranged therebetween, the actuator being adapted to open one one-way valve when pressure is applied to the first supply side port and the other one-way valve when pressure is applied to the other supply-side port.

7. A valve substantially as herein described with reference to the accompanying drawings.