GB2400165A

GB2400165A - Torsionally frangible release valve for gas container

Info

Publication number: GB2400165A
Application number: GB0307411A
Authority: GB
Inventors: Paul Davies; Keith Butler
Original assignee: Leafield Marine Ltd
Current assignee: Leafield Marine Ltd
Priority date: 2003-03-31
Filing date: 2003-03-31
Publication date: 2004-10-06
Anticipated expiration: 2023-03-31
Also published as: GB2400165B; GB0307411D0

Abstract

A release valve, suitable for use on a pressurised fluid container, comprises a frangible release element 30, breakable under a torsional force. Also disclosed is a release valve with helical support element, and a flexible inlet duct (80, fig.3) with a weighted end (88,fig.3). The first valve mechanism described above may be used to inflate a life raft from a gas container 70. A mechanism to trigger the frangible release element, may comprise a pull handle 66 whose linear action is translated to an internal rotary action by a system of gears, such as gear 50, which may also amplify the linear force applied to the handle 66. The mechanism may be taken apart and certain elements, such as 26, 28,30, replaced after the mechanism has been fired so that the device can be re-used.

Description

A RELEASE VALVE

This invention relates to a release valve for a fluid under pressure and is particularly, although not exclusively, concerned with a release valve for releasing a gas for inflating an inflatable article suchas a life raft.

Inflatable life rafts and similar articles are filled for use from a gas container, such as a bottle or cylinder, which contains the inflation gas. A common inflation gas is carbon dioxide, stored in the container at a pressure high enough to liquefy the gas at normal temperatures. It is also common to include in the cylinder or bottle a propellant gas, such as nitrogen, to speed up the flow of carbon dioxide to the inflatable life raft. Consequently, the cylinders or bottles commonly contain liquefied carbon dioxide, having a free surface above which there is a pocket of nitrogen.

Release valves for inflatable life rafts and similar articles need to be capable of withstanding the pressure applied by the contents of the container, without leakage, for long periods of time, and yet work reliably to release the gas when required. Many such valves are operated by means of a lanyard or ripcord.

It is important for the pulling force required on the lanyard to open the valve to remain below a predetermined threshold so that a user will have no difficulty inflating the life raft when required.

Many known release valves, for example that shown in GB 2291172, employ a diaphragm to prevent flow until inflation is required. Pulling of the lanyard actuates a mechanism which punctures the diaphragm to allow the contents of the container to flow to the inflatable article. The piercing of a diaphragm is inherently unpredictable, and occasionally the aperture formed is so small as to restrict flow out of the container so resulting in undesirably slow inflation of the inflatable article. Also, piercing may cause a piece of the diaphragm to become detached, and the detached portion can cause blockages or flow restrictions in the flow path to the inflatable article.

US 3892253 discloses a release valve having a release element including an integral frangible cap which, to open the valve, is sheared off by a linear movement.

The linear movement may be achieved by an explosive charge or the release of a compressed spring, or manually by turning a handle which acts through a screwthread. However, if the valve is operated manually, operation must be continued after the cap has been detached in order to move it out of the way of the flow passage to enable full flow of inflation gas to the inflatable article. This is undesirable, since, in an emergency situation, there is a danger that the user will stop operating the valve as soon as flow is detected. Also, the valve has a significant dimension transverse to the length of the container, which means that it projects laterally beyond the container.

Another disadvantage is that the friction losses in the screwthread negate its mechanical advantage, with the result that substantial torque needs to be applied to the handle to break the cap.

According to the present invention, there is provided a release valve for a fluid under pressure, comprising a flow passage and a release element which closes the flow passage, the release element being breakable under torsion to separate into two portions to permit flow through the flow passage, the valve also comprising an actuating device for applying torsion to the release element.

There may be a defined breakage region between the two portions of the release element, and this defined breakage region may be a weakened region, for example a groove extending circumferentially around the release element.

In a preferred embodiment, the release element has a release passageway which, in use, communicates at one end with a source of the fluid under pressure and is closed at the other end, breakage of the release element into the two components causing opening of the release passageway between its ends so as to permit flow.

It is desirable for the release valve to open if the pressure of the fluid exceeds a predetermined threshold, for example in the event of increased temperature, such as may occur in the event of fire.

In order to achieve this, the closed end of the release passageway may be closed by a rupturable partition which will rupture, to release the fluid, when the predetermined threshold pressure is reached. The partition may be retained in the release element by a removable securing ring.

The flow passage may comprise a chamber disposed between upstream and downstream portions of the flow passage, with respect to the direction of flow of the fluid when the release element is broken. With this construction, the release element is preferably positioned so that the breakage under torsion occurs at a region of the release element situated within the chamber. The downstream portion of the flow passage may extend transversely of the upstream portion, so that torsion may be applied to the release element about an axis which is generally aligned with the upstream portion. One of the portions of the release element may be fitted in a gas-tight manner within the upstream portion of the flow passage, with the actuating device then preferably engaging the other portion of the release element. This other portion is preferably supported in such a way as to be movable away from the portion fitted to the upstream portion of the flow passage, so as to permit full flow through the flow passage upon breakage of the release element.

The portion of the release element engaged by the actuating device may comprise a non-circular spigot received within a complementary recess in the actuating device so that rotation of the actuating device applies torsion to the release element. The actuating device is preferably mounted for rotation in a body of the valve, and may be rotatable by operation of an actuating element having a linear movement such as a lanyard. A torque multiplication arrangement, such as a planetary gear arrangement, may be provided between the actuating element and the actuating device. For example, the actuating element may be operable to rotate a sun gear of the planetary gear arrangement while the actuating device may be connected to a planet carrier of the planetary gear arrangement.

The flow passage may be provided with a flexible inlet duct configured so that, in use, the inlet end of the inlet duct remains situated in a lower region of a container for the fluid, when the container is horizontal and is rotated about its lengthwise axis.

This measure ensures that, where the container contains a mixture of liquid and gas, such as liquefied carbon dioxide and nitrogen gas, the inlet end of the inlet duct will always be immersed in the liquid when the container lies horizontally.

In a preferred embodiment, the inlet duct comprises a helical support element disposed within an impermeable flexible cover which communicates at one end with the flow passage. The inlet duct may be weighted, for example at the inlet end, in order to promote adequate flexing.

In accordance with another aspect of the present invention, there is provided a release valve for mounting on a storage container for a fluid under pressure, the release valve having an inlet duct which, in use, extends into the container, the inlet duct comprising a flexible helical support element disposed within a flexible substantially impermeable cover, the inlet duct being provided with a weight which causes the inlet duct to deflect under gravity.

The helical support element may be in the form of a spring, and preferably a close-coiled spring to provide the required flexibility. The cover may be substantially non-self-supporting, that is to say it will not maintain a cylindrical shape, without the support of the spring, when subjected to the pressure prevailing within the container. The cover may be made from a polymer such as a silicone rubber, and is preferably a loose fit over the spring.

The weight may be provided at the inlet end of the inlet duct, and may be formed to provide the inlet to the duct.

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a sectioned view of a release valve; Figure 2 is a top view of the valve with parts omitted; Figure 3 is a diagrammatic view of a cylinder to which the release valve is fitted.

The valve shown in Figure 1 comprises a main body 2 and a cap 4. The cap 4 fits over the main body 2 and includes integral clamping components 6 having holes 8 which receive bolts (not shown) engaging grooves 10 in the main body 2 to secure the cap 4 to the main body 2.

The main body 2 defines a flow passage comprising an upstream portion 12, a chamber 14 and an downstream portion 16. The flow passage is closed by a release element 18 which is screwed into a threaded region of the upstream portion 12. The release element 18 has an enlarged hexagonal head 20, for use in fitting the release element 18 to the main body 2. The head 20 has a part-spherical sealing surface 22 which engages a conical seat 24 formed in the main body 2 at the transition between the upstream portion 12 and the chamber 14.

The release element 18 comprises two portions, namely a first portion 26 which includes the head 20 and is fitted in the upstream portion 12, and a second portion 28. The two portions are, before use of the valve to release gas, interconnected at a weakened region of the release element 18, this weakened region being defined by a circumferential groove 30. This groove 30 is situated within the chamber 14.

A central bore 32 runs through the release element 18.

At its lower end, this bore 32 opens into the upstream portion 12 of the flow passage, and at its upper end it opens into a screw threaded counter bore 34 in the second portion 28 of the release element 18. A securing ring 36, itself having a central passage 38, is secured in the counter bore 34, and a partition 40 is trapped between the securing ring 36 and the end of the counter bore 34 so as to prevent communication between the central bore 32 of the release element 18 and the passage 38 of the securing ring 36.

The second portion 28 of the release element 18 has a non-circular, for example hexagonal, outer periphery which is received in a complementary recess in an actuating device 42. The actuating device 42 has a spigot 44 which is supported for rotation in a retaining element 46 which is screwed into the main body 2. The free end of the spigot 44 is splined and thus rotationally fixed to a planet carrier 48 carrying planet wheels 50 (only one shown in Figure 1). The planet wheels 50 engage a toothed spigot 52, serving as a sun gear, which projects from a drive element 54 mounted for rotation in the cap 4. The drive element 54 has a groove 56 extending circumferentially part of the way around it. A cylindrical bore 58 intersects the groove 56 and receives an enlarged end fitting 60 of an actuating element in the form of a lanyard 62.

The lanyard passes along the groove 56 and through an opening 64 in the cap 4. Outside the cap 4, the lanyard is formed into a loop 66 to serve as an attachment point for a rope or other element to be grasped by hand to actuate the valve. The loop 66 is secured by means of a moulded-on plug 68 having a part- spherical shape seating in a complementary part of the opening 64 to provide a seal between the interior and exterior of the cap 4.

As shown in Figure 1, the valve is fitted to the opening of a gas cylinder 70 by means of a tapered threaded connection 72 between the cylinder 70 and the body 2. Beneath the threaded connection 72, the body 2 has a spigot 74 projecting into the cylinder 70. The spigot 74 has a screwthreaded portion 76 connected to the rest of the body 2 by a neck 78. A pick-up tube 80 is fitted over the spigot 74 and is secured by a tie 82 at the neck 78. The tube 80 comprises a thin-walled flexible, non-selfsupporting cover 84 of a polymer such as silicone rubber, within which is a helical support 86 in the form of a close-coiled spring of high flexibility. The cover 84 is a loose fit over the spring 86, so that the coils of the spring 86 can move freely within the cover 84. The coils of the spring 86 engage the screwthread 76 to assist in retaining the tube 80 on the spigot 74. The spring 86 stops short of the neck 78, so that only the cover 84 is gripped by the tie 82. The other end of the tube 80 is shown in Figure 3. An inlet fitting 88 is secured to the tube by a tie 90 in a similar manner to that described above. The fitting 88 may be made of metal and have a substantial mass to ensure flexing of the tube 80 as will be described below.

The body 2 has a screw threaded spigot 74, through which the downstream portion 16 of the flow passage extends, for connection to an inflatable device such as a life raft.

For use, the cylinder 70 is charged with an appropriate inflating gas, possibly in liquefied form, such as liquefied carbon dioxide and a relatively small proportion, for example 4%, of gaseous nitrogen to act as a propellant. The spigot 74 is connected to a deflated life raft. Since the head 20 of the release element 18 makes sealing contact with the seat 24, and since the diaphragm 40 prevents flow through the central bore 32, any leakage of the contents of the cylinder 70 is prevented. In addition, seals are provided between other components of the valve both to prevent leakage of gas after the life raft has been inflated and to prevent dirt and other contaminants from entering the interior of the valve.

If the life raft is to be inflated, the lanyard 62 is pulled by means of the loop 66. Optionally, a locking device may be provided to prevent accidental actuation of the valve, and this locking device may be removed or released before the lanyard 62 is pulled. Pulling of the lanyard 62 causes rotation of the drive element 54 which, through the planetary gear arrangement comprising the spigot 52, the planet gears 50 and the planet carrier 48, causes rotation of the actuating device 42 so as to turn the second portion 28 of the release element 18. Since the first portion 26 of the release element 18 is securely fitted to the body 2, rotation of the second portion 28 will apply torsion to the release element 18 which eventually will cause the release element 18 to break at the weakening formed by the groove 30. It will be appreciated that the drive element 54 serves to convert the linear motion of the lanyard 62 into rotation of the spigot 52. In a preferred embodiment, the planetary gear arrangement comprising the spigot 52, the planet gears 50 and the planet carrier 48 may provide a torque multiplication of 6.75:1, which means that a pulling force on the lanyard 62 of 75 N or less, well within the required maximum force of 150 N. is sufficient to break the release element 18 at the groove 30.

When broken, the release element 18 separates into the two portions 26 and 28, allowing gas to flow through the central bore 32 into the chamber 14 and through the downstream portion 16 of the flow passage into the inflatable life raft. This flow of gas impels the second portion 28 into the recess in the operating element 42 so as to leave the exit of the central bore 32 fully open. This enables the inflating gas to flow rapidly through the flow path constituted by the upstream portion 12, the chamber 14 and the downstream portion 16, so rapidly inflating the life raft.

Furthermore, breakage of the release element 18 occurs with no broken-off fragment being produced which could potentially cause blockage of the flow path downstream of the chamber 14.

If, before opening the valve, the pressure within the cylinder 70 exceeds a predetermined value, the resulting pressure difference across the diaphragm 40 will cause it to rupture, allowing the contents of the cylinder 70 to escape through the central bore 32 and the passageway 38 in the bung 36, so as to avoid explosive bursting of cylinder 70. The escaping gas can flow through the clearance between the second portion 28 and the actuating device 42 to the chamber 14 and thence through the downstream portion 16 of the flow passage to the life raft or other inflatable product.

Of course, this measure will cause inflation of the life raft if the cylinder 70 is subjected to overpressure, for example as a result of a fire causing heating of the container 70. If such inflation would be undesirable in such circumstances, for example on board an aircraft, means can be provided to vent to atmosphere the gas passing through the passageway 38 after rupture of the diaphragm 40.

Once the valve has been opened by breakage of the release element 18, the release element 18 must be replaced before the valve can be re-used. This is achieved by removing the cap 4 by releasing the bolts passing through the holes 8. The cap 4 takes with it the planetary gear arrangement comprising the drive element 54, the planet gears 50 and the planet carrier 48. Subsequently, the retaining element 46, which is screwed into the body 2, is removed, this element 46 taking with it the actuating device 44. This enables the broken-off second portion 28 to be removed and discarded, and provides access to the hexagonal head of the first portion 20. The first portion 20 can thus be unscrewed from the first portion 12 of the flow passage and replaced by a new release element 18. In order to recharge the container 70, the release element 18 is initially screwed only partially into the body 2, leaving two transverse bores 72 exposed to the chamber 14. A special fitting (not shown) may be screwed into the body 2 in place of the retaining element 46, to provide a gas-tight seal while enabling operation of a tool to engage the hexagonal head 20 of the first portion 26. While the transverse bores 74 are exposed to the chamber 14, the container 70 is charged through the spigot 74. When fully charged, the release element 18 is screwed fully into the first portion 12 of the flow passage until the conical surface 22 makes sealing engagement with the seat 24. The retaining element 46 with the actuating device 42 is then replaced, followed by the cap and components retained within it. The spigot 74 can then be attached to the inflatable life raft or other product for re-use.

The flexible nature of the pick-up tube 80 ensures that its inlet end is always in the lower region of the cylinder 70 when the cylinder lies with its longitudinal axis horizontal. As a consequence of this, the inlet end is always submerged in the liquid component (e.g. CO2) of the contents of the cylinder 70, so that this liquid component will be discharged first when the release valve is opened. As shown in Figure 3 in dashed outline, the tube 80 will flex so that the inlet fitting 88 will lie against the side wall of the cylinder if the cylinder is laid on its side.

Claims

1. A release valve for a fluid under pressure, comprising a flow passage and a release element which closes the flow passage, the release element being breakable under torsion to separate into two portions to permit flow through the flow passage, the valve also comprising an actuating device for applying torsion to the release element.

2. A release valve as claimed in claim 1, in which the portions of the release element are connected together at a breakage region.

3. A release valve as claimed in claim 2, in which the breakage region is defined by a weakened portion of the release element.

4. A release valve as claimed in claim 3, in which the weakened region is defined by a groove extending circumferentially around the release element.

5. A release valve as claimed in any one of the preceding claims, in which the release element comprises a release passageway which communicates at one end with a source of the fluid under pressure and is closed at the other end, breakage of the release elements severing the release passageway between its ends to permit flow through the release passageway.

6. A release valve as claimed in claim 5 when appendant to any one of claims 2 to 4, in which the release passageway extends through the breakage region.

7. A release valve as claimed in claim 5 or 6, in which the release passageway is closed at its said other end by a rupturable partition.

8. A release valve as claimed in claim 7, in which the rupturable partition is retained in the release element by a removable securing ring.

9. A release valve as claimed in any one of the preceding claims, in which the flow passage comprises upstream and downstream portions which communicate with each other through a chamber, breakage of the release element occurring at a region in the chamber.

10. A release valve as claimed in claim 9, in which the downstream portion of the flow passage extends transversely of the upstream portion.

11. A release valve as claimed in claim 8 or 9, in which one portion of the release element sealingly closes the upstream portion of the flow passage.

12. A release valve as claimed in claim 11, in which the actuating device engages the other portion of the release element.

13. A release valve as claimed in claim 12, in which, after breakage, the other portion of the release element is movable away from the said one portion of the release element.

14. A release valve as claimed in claim 12 or 13, in which the said other portion comprises a non-circular spigot engaged within a complementary recess in the actuating device.

15. A release valve as claimed in any one of the preceding claims, in which the actuating device is rotatable within a body of the valve.

16. A release valve as claimed in claim 15, in which the actuating device is rotatable by operation of an actuating element.

17. A release valve as claimed in claim 16, in which conversion means is provided for converting linear movement of the actuating element into rotation of the actuating device.

18. A release valve as claimed in claim 16 or 17, in which a torque multiplication arrangement is provided between the actuating element and the actuating device.

19. A release valve as claimed in claim 18, in which the torque multiplication arrangement comprises a planetary gear arrangement.

20. A release valve as claimed in claim 19, in which the actuating element is operable to rotate a sun gear of the planetary gear arrangement, the actuating device being connected to a planet carrier of the planetary gear arrangement.

21. A release valve as claimed in any one of the preceding claims, in which the flow passage communicates with a flexible inlet duct.

22. A release valve as claimed in claim 20, in which the inlet duct comprises a helical support element disposed within a flexible cover, the inlet duct being weighted so as to deflect under gravity.

23. A release valve for mounting on a storage container for a fluid under pressure, the release valve having a flexible inlet duct which, in use, extends into the container, the inlet duct comprising a helical support element disposed within a flexible cover, the inlet duct being weighted so as to deflect under gravity.

24. A release valve as claimed in claim 22 or 23, in which the helical support element comprises a spring.

25. A release valve as claimed in any one of claims 22 to 24, in which the cover is substantially non-self- supporting.

26. A release valve as claimed in any one of claims 22 to 25, in which the cover is formed from a polymer.

27. A release valve as claimed in any one of claims 22 to 26, in which the inlet duct is weighted by means of a weight provided at the free end of the inlet duct.

28. A release valve as claimed in any one of claims 22 to 27, in which the weight provides an inlet to the inlet duct.

29. A storage container as claimed in claim 30 when appendant to claim 20, in which the flexibility of the inlet duct is such that it is displaceable under gravity laterally of its lengthwise direction into contact with the wall of the container in all directions extending transversely of the lengthwise direction of the inlet duct.

29. A release valve substantially as described herein with reference to, and as shown in, the accompanying drawings.

30. A storage container for a fluid under pressure, provided with a release valve in accordance with any one of the preceding claims.

31. A storage container as claimed in claim 30 when appendant to claim 21 or 22, in which the flexibility of the inlet duct is such that it is displaceable under gravity laterally of its lengthwise direction into contact with the wall of the container in all directions extending transversely of the lengthwise direction of the inlet duct.

- - . . . ..

. . ..

Amendments to the claims have been filed as follows

1. A release valve for a fluid under pressure, comprising a flow passage and a release element comprising two portions which are separable from each other by breakage of the release element under torsion, one portion of the release element being disposed in the flow passage and having a release passageway which is closed by the other portion before breakage of the release element, the other portion, after breakage of the release element, being displaceable away from the said one portion to enable flow through the release passageway, the valve also comprising an actuating device for applying torsion to the release element.

5. A release valve as claimed in any one of the preceding claims, in which the release passageway, in use, communicates at one end with a source of the fluid under pressure and is closed at the other end, breakage of the release elements severing the release passageway between its ends to permit flow through the release passageway.

- By- e. . me. me: À À . . À À À . Àe. .. .4, 6. A release valve as claimed in claim 5 when appendant to any one of claims 2 to 4, in which the release passageway extends through the breakage region.

11. A release valve as claimed in claim 8 or 9, in which one portion of the release element is sealingly engaged within the upstream portion of the flow passage.

13. A release valve as claimed in claim 12, in which the said other portion comprises a non-circular spigot engaged within a complementary recess in the actuating device. _ f \

e À e À 14. A release valve as claimed in any one of the preceding claims, in which the actuating device is rotatable within a body of the valve.

15. A release valve as claimed in claim 14, in which the actuating device is rotatable by operation of an actuating element.

16. A release valve as claimed in claim 15, in which conversion means is provided for converting linear movement of the actuating element into rotation of the actuating device.

17. A release valve as claimed in claim 15 or 16, in which a torque multiplication arrangement is provided between the actuating element and the actuating device.

18. A release valve as claimed in claim 17, in which the torque multiplication arrangement comprises a planetary gear arrangement.

19. A release valve as claimed in claim 18, in which the actuating element is operable to rotate a sun gear of the planetary gear arrangement, the actuating device being connected to a planet carrier of the planetary gear arrangement.

20. A release valve as claimed in any one of the preceding claims, in which the flow passage communicates with a flexible inlet duct.

21. A release valve as claimed in claim 20, in which the inlet duct comprises a helical support element disposed within a flexible cover, the inlet duct being weighted so as to deflect under gravity.

À e e e e.

t1 À e À À e -e eve Àee À 22. A release valve as claimed in claim 21, in which the helical support element comprises a spring.

23. A release valve as claimed in claims 21 or 22, in which the cover is substantially non-self-supporting.

24. A release valve as claimed in any one of claims 21 to 23, in which the cover is formed from a polymer.

25. A release valve as claimed in any one of claims 21 to 23, in which the inlet duct is weighted by means of a weight provided at the free end of the inlet duct.

26. A release valve as claimed in any one of claims 21 to 25, in which the weight provides an inlet to the inlet duct.

27. A release valve substantially as described herein with reference to, and as shown in, the accompanying drawings.

28. A storage container for a fluid under pressure, provided with a release valve in accordance with any one of the preceding claims.