GB2356915A

GB2356915A - Magnetic venting valve with roll-over mechanism

Info

Publication number: GB2356915A
Application number: GB9927610A
Authority: GB
Inventors: Graham Platt
Original assignee: ENVIROTECH PRODUCTS Ltd
Current assignee: ENVIROTECH PRODUCTS Ltd
Priority date: 1999-11-23
Filing date: 1999-11-23
Publication date: 2001-06-06
Also published as: GB0008299D0; GB9927610D0

Abstract

A pressure release valve for a container (e.g. a fuel tank) has a roll-over mechanism and comprises a housing 101 and pressure relief valve having a plunger 102 held on a seat 104 by permanent magnets 126 until the pressure differential on the plunger is sufficient to overcome the force of the magnets. The magnetic force is preferably adjustable. The plunger 102 preferably carries a further plunger having a seal plate 106 pressed onto a seat in the plunger 102 by spring 124 and which allows air into the container when vacuum exists in it. The further plunger may be used in conjunction with a connecting nozzle to drain the container. A closure plate 103 may be urged towards a seat in the housing by movement of a pivot plate 111 about a fulcrum defined by a universal joint comprising a ball 110 and socket, in response to movement of a pendulum 105. The socket is preferably defined by mutually facing recesses in a pair of plates 108,109. The plate 103 is normally urged away from its seat, preferably by a spring 125, such that the plate is returned after it has been urged onto its seat by the pendulum and pivot plate.

Description

2356915 PRESSURE RELEASE VALVE The present invention relates to a pressure

release valve.

Conventionally, pressure release valves are used in conjunction with fluid that readily evaporates and which may, in the absence of a pressure relief valve, result in a dangerous build-up of pressure. If the vapour is, for example, highly flammable or corrosive, an explosion involving such vapour would be clearly dangerous.

Rather than continuously venting potentially hazardous vapour into the atmosphere, pressure release valves are arranged to vent vapour only when the pressure has reached a predetermined pressure.

It can be appreciated that in some circumstances such as, for example, in the case of an overturned petrol tanker, the valves are arranged to assume a closed position to avoid spilling petrol or other hazardous f luids. It is known to use an inertial mass or pendulum to close the pressure release valve in such circumstances. A valve having such a mode of operation is conventionally said to incorporate a roll-over mechanism. As the pendulum deviates from the vertical, the valve closes and ceases to act as a pressure release mechanism. As the pendulum moves toward the vertical, the valve opens and the valve continues to act as a pressure release mechanism.

Such a valve would be actuated and therefore become closed when a tanker either climbs or descends a steep hill. Further, the valve must be capable of operating correctly if the tanker in which the valve is used is 2 subjected to a 2g load in the direction of travel, a lg load at right angles to the direction of travel or a lg load vertically upwards or a 2g load vertically downwards a bump in the road. It can be appreciated that under such circumstances there is a risk of inadvertently closing the valve when the pressure inside the tanker is high but not sufficiently high to instigate venting or during venting. The high pressure can prevent the valve from returning to the open position once the tanker is no longer inclined relative to the vertical.

It is an object of the present invention to mitigate at least some of the problems of the prior art.

Accordingly, a first aspect of the present invention provides a pressure relief valve for venting a fluid from a movable container comprising an inertially actuable roll-over mechanism arranged, in a first position, to urge a closure member towards a corresponding seat to form a fluid tight seal, and means for urging the closure member away from the seat to allow venting such that the fluid tight seal can be broken when the inertially actuable roll-over mechanism is in a second position.

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which:

figure la and lb illustrate a cross-sectional view of a pressure relief valve having a roll-over mechanism according to an embodiment of the present invention; and figure 2 illustrates in greater detail an embodiment of the valve body.

Referring to figure la and lb there is shown a pressure relief valve assembly 100 comprising a roll-over 3 mechanism. The valve assembly 100 comprises a valve body 101 housing a valve plunger 102 that is slidingly movable along a longitudinal axis within a neck of the valve body 101. The valve plunger 102 has a circular shoulder that sits, in a closed position, on a corresponding valve seat 104. Referring to figure 2, it can be seen that the valve body comprises a plurality of vent holes that communicate between the exterior and interior of the valve to allow vapour to be vented. The vent holes have axes that are co-linear with radii of the valve body, that is, they are perpendicular to the valve longitudinal axis.

The valve assembly uses permanent magnets 126 that are arranged to urge the valve plunger 102 against the valve seat 104. The permanent magnets 126 may be disposed within, on or form part of the valve seat 104 or within, on or form part of the circular shoulder of the valve plunger 102. The valve assembly uses the non linear force characteristics of the magnets to urge the valve assembly towards the closed position even though the vapour pressure may still be slightly above the predetermined pressure. The magnets are arranged to ensure that there is magnetic attraction between the valve seat and valve plunger.

An embodiment provides a valve plunger comprising compressed spring 124 that cooperates with a seal plate 106 and a circlip 112 to seal a channel in the valve plunger from the exterior of the valve to the interior.

Preferably, the channel is used either to allow air to flow into the container if a vacuum exists within the container. However, an embodiment may use the channel to allow fluid to be drained from the container by connecting an extraction nozzle (not shown) to the valve 4 assembly which has an appropriately shaped and sized plunger to displace the seal plate.

An embodiment is provided in which the seal plate and the spring are mounted on a central spindle. The degree of compression of the spring can be set by appropriate positioning of the seal plate or a reaction plate on the spindle.

When the pressure within a container (not shown) in which the valve assembly 100 is used, exceeds a predetermined level, for example a pressure in the range of not less that 20 millibars and not more than 120 millibars, the valve plunger 102 is urged away from the valve seat 104 into an open state. In the open state, the vapour within the container is vented thereby relieving the pressure within the container.

The predetermined pressure level at which venting occurs can be established manually by adjusting a number of adjuster screws 119 that are positioned circumferentially around the body of the valve plunger at substantially the same radius. The adjuster screws 119 control the distance and hence the magnitude of the magnetic force of attraction between the permanent magnets and an opposing face of the valve seat by protruding beyond the base of the valve plunger. It will be appreciated that the magnetic force of attraction diminishes in a non-linear manner with distance. The adjuster screws 119, once set at a selected position, corresponding to a desired pressure level at which venting should occur, are locked into position by corresponding locking screws 120. The locking screws are arranged to abut firmly against the adjuster screws 119 to hold the latter in position.

Although the above embodiment has the magnets arranged at substantially the same radius, an embodiment can be realised in which the magnets are positioned at different radii. In an alternative embodiment, the permanent magnets can be carried on the ends of the adjuster screws 119.

A closure plate 103 is arranged to be urged towards internal shoulders of a cylindrical cavity of the valve body 101 by movement of pivot plate 111 about a fulcrum.

The pivot plate 111 pivots about ball 110 of a ball and socket joint in response to movement of a ball weight or pendulum 105 about the axis of the valve assembly. The socket is formed by a pair of retainer plates 108 and 109 having mutually facing recesses that form a complementary socket for the ball. The retainer plates are coupled together using a number of screws 121 and kept in place by a circlip 113. The retainer plates comprise a number of holes through which vapour can flow to alleviate any vacuum that may otherwise result due to movement of the closure plate 103. The pivot plate 111 is coupled to a pivot stem of the ball 110 using a screw 122.

The closure plate 103 has a dependent skirt, that slides snugly along an inner wall of the' cylindrical cavity, and a closure member comprising an 0-ring 118 is mounted on a head of the closure plate 103. The 0-ring 118 when urged against the internal shoulders of the cylindrical cavity forms a fluid tight seal around the opening formed by the neck of the valve body 101. The skirt ensures that the 0-ring is substantially concentric with the neck of the valve body 101.

The internal shoulders of the cylindrical cavity carry means for urging the closure plate 103 away from 6 the opening formed by the neck of the valve body 101 to break the fluid tight seal. Preferably, the means for urging the closure plate 103 away from the opening formed by the neck comprises a leaf spring, wave spring or coil spring. Alternatively, the means for urging the closure plate 103 away from the neck can be carried by the closure plate 103 and arranged to act against the internal shoulders of the cavity. The mass of the closure plate 103 and the reaction of the means for urging the closure plate 103 away from the neck are such that even under a high pressure, that is, a pressure above the predetermined pressure at which the valve assembly should ordinarily vent vapour, that pressure is insufficient to keep the 0-ring 118 urged against the internal shoulders and hence the valve assembly in a closed state when the pivot plate ceases to urge the closure plate towards the neck. Therefore, when the axis of the pendulum is substantially co-linear with the axis of the valve assembly, the closure plate 103 is pushed away from the internal shoulders of the cavity so the valve can continue to vent vapour safely.

Preferably, a wire gauze 127 is retained within an outlet of the valve assembly. The wire gauze 127 reduces the risk of fire or an explosion within the container if the vented vapour is flammable.

A fluid tight seal between the valve assembly and a container (not shown) is realised using an 0-ring 117.

Similarly, a fluid tight seal between the valve plunger 102 and the valve seat 104 is realised using an 0-ring 116. A further fluid tight seal between the plate seal 106 and an internal circular shoulder of the valve plunger 102 is realised using an 0ring 115.

7 Referring to figure 2 there is shown in third angle projection front, end and sectional views together with respective dimensions of an embodiment of a valve body according to the present invention. These views show more clearly the holes in the valve body via which vapour can be vented.

Advantageously, the valve plunger 102 can be removed from the valve assembly for calibration and/or testing.

The pressure at which the valve plunger 102 is lifted from the valve seat 104 can be set by varying the proximity of the magnets to the valve seat. This ensures that the valve plunger, which is a relatively small component, can be swiftly tested and calibrated.

Furthermore, due to the non-linear characteristics of the permanent magnet, the valve plunger 103 is moved between the closed position and an open position such that the flow area through which vapour can be vented is significantly greater than the flow area of a corresponding spring based valve plunger at a given pressure. In an embodiment, the valve assembly can be either closed or substantially fully open. It will be appreciated that in prior art valve assemblies the available f low area through which vapour can be vented is proportional to the degree of extension or compression of a spring. In contrast, the flow area is not dependent upon spring characteristics.

It will be appreciated that the term fluid encompasses at least one of gases, vapours and liquids.

Although the above embodiment is arranged to vent vapour or fluid via radially directed valve body holes and a longitudinal valve opening, the present invention 8 is not limited thereto. An embodiment can be realised in which the venting is substantially longitudinally. The substantially longitudinal venting can be achieved by ensuring that the closure plate has through-holes via which fluid can flow having passed through the holes in the retainer plates.

9

Claims

1 A pressure relief valve for venting a fluid from a container comprising an inertially actuable roll over mechanism arranged, in a first position, to urge a closure member towards a corresponding seat to form a fluid tight seal, and means for urging the closure member away from the seat to allow ve nting such that the f luid tight seal can be broken when the inertially actuable rollover mechanism is in a second position.

2. A pressure relief valve as claimed in claim 1, in which the means for urging the closure member away from the seat comprises at least one of a leaf spring, wave spring or coil spring.

3. A pressure relief valve as claimed in any preceding claim, in which the inertially actuable roll-over mechanism comprises a ball and socket joint that co operate and a pivot plate that co-operate to urge the pivot plate against the closure member.

4. A pressure relief valve as claimed in claim 3, in which the socket is formed using two retainer plates having mutually facing recesses for receiving the ball.

5. A pressure relief valve as claimed in any preceding claim, in which the valve plunger comprises drainage means, preferably disposed wholly or at least partially within the valve plunger, for urging the closure member away from the seat such that the fluid tight seal can be broken.

6. A pressure relief valve as claimed in claim 5, in which the drainage means comprises a moveable sealing member that is urged against internal shoulders of an aperture of the valve plunger to form a further fluid tight seal.

7. A pressure relief valve as claimed in claim 6, in which the moveable sealing member comprises an adjustment means for setting the force with which the sealing means is urged towards the internal shoulders.

8. A pressure relief valve as claimed in either of claims 6 or 7, in which the moveable sealing meniber can be urged away from the internal shoulders such that the further fluid tight seal can be broken to allow fluid to flow through the aperture.

9. A pressure relief valve substantially as described herein with reference to and/or as illustrated in the accompany drawing.

10. A method for venting vapour in a pressure relief valve having a roll-over mechanism, the method comprising the steps of urging a closure member away from a corresponding seat to thereby break a fluid tight seal after the actuation of the roll-over mechanism.

11. A method for venting vapour in a pressure relief valve substantially as described herein with reference to and/or as illustrated in the accompanying drawing.

12. A pressure release valve comprising a moveable portion and a fixed portion, said valve allowing fluid to flow therethrough when the moveable portion adopts a first disposition with respect to the fixed portion, and preventing fluid to flow when in a second disposition, said moveable portion being displaced relative to the fixed portion when there is a pressure differential across the valve, characterised in that one or other of the portions is provided with magnetic means which magnetically attracts the alternate portion, such magnetic attraction there between being sufficient to prevent relative displacement of the portions when the pressure differential is below the predetermined level.

13. A pressure release valve as claimed in claim 12 in which the moveable portion comprises a moveable plunger and the fixed portion comprises a fixed seat having at least partial ferro magnetic characteristics, the plunger being provided with magnets therein or being magnetised so as to magnetically attract the seat.

14. A roll over mechanism for a pressure release valve, the valve having a moveable sealing means which is free to move towards and away from a pressure surface within the valve, a sealing means creating a seal with the pressure surface when adjacent therewith which prevents fluid escape through the valve, characterised in that the roll-over mechanism comprises pendulum means which communicates with the sealing means to urge the same towards and ultimately against the pressure surface as gravity acts on the pendulum means to deflect the same as the valve rotates about an axis parallel with any 12 axis about which the pendulum means can swing.

15. A roll-over mechanism as claimed in claim 14, in which the degree of displacement of the sealing means towards the pressure surface is dependent on the degree of deflection of the pendulum means and therefore with the angle through which the valve is rotated.

16. A roll-over mechanism as claimed in either of claims 14 or 15, in which the pendulum means includes a profiled end on one side of a pivot about which the pendulum means swings there beneath, the sealing means resting on the said profiled end which urges is the sealing means against the pressure surface as it rotates above the pivot with the pendulum means.

17. A roll-over mechanism as claimed in claim 16, in which the profiled end is at least partially arcuate.

18. A roll-over mechanism as claimed in any of claims 14 to 17, in which the sealing means is provided with an annular or 0-ring seal on the surface of a sealing means adjacent the pressure surface, which is also preferably annular.

19. A roll-over mechanism as claimed in any of claims 14 to 18, in which the pendulum means is provided with universal joint means in order that said pendulum means can rotate about a plurality of different axes as the valve is rotated about an axis parallel to any of the said plurality of axes.

20. A fluid storage tank comprising a pressure relief 13 valve as claimed in any preceding claim.

21. A moveable fluid storage tank comprising a pressure relief valve as claimed in any of claims 1 to 19.

22. A road tanker comprising a fluid storage tank as claimed in claim 21.