GB2504533A

GB2504533A - Shock wave protection valve

Info

Publication number: GB2504533A
Application number: GB201213751A
Authority: GB
Inventors: Michael George Christopher Garland
Original assignee: Bioquell UK Ltd
Current assignee: Bioquell UK Ltd
Priority date: 2012-08-02
Filing date: 2012-08-02
Publication date: 2014-02-05
Anticipated expiration: 2032-08-02
Also published as: WO2014020301A1; GB2504533B; GB201213751D0

Abstract

A valve for protecting an enclosure from a shock wave which causes a transient increase in pressure comprises a duct 11, a valve seat 21, a valve plate 30 supported by at least one spring 31 and at least one frangible support 32. When the frangible support 32 is fractured, the valve plate 30 moves into contact with the valve seat 21 and forms a seal to close off the duct 11. The dimensions and material properties of the frangible support 32 are selected such that it fractures when a shock wave contacts the valve plate 30.

Description

VALVE FOR PROTECTING AN ENCLOSURE FROM SHOCK WAVES

This invention is directed towards a valve for protecting an enclosure from shock waves.

Enclosures, including shelters, vehicles, buildings, tunnels and the like, may be adapted to protect occupants or other contents located within from the effects of explosions, such as the release of harmful gases. Typically, the internal volume of the enclosure is fluidly connected with the surrounding atmosphere by a ventilation system. For example, a pump may be located within an inlet duct to draw air from the surrounding atmcsphere into the internal volume. An cutlet duct may enable air to exit the internal volume to equalise the pressure therein. Alternatively, a higher than atmospheric pressure may be maintained within the enclosure to prevent air from the surrounding atmosphere entering the internal volume.

However, explosions typically generate transient increases in pressure, such as pressure or shock waves. A wave of high pressure may travel through the ventilation system and into the internal volume of the enclosure. In doing so, the high pressure may cause harm to the occupants and/or damage to the contents of the enclosure and also to the ventilation system itself. Various arrangements of the ventilation system have been proposed to provide protection from such damage. In particular, valves have been developed which close off the ventilation ducts when a high pressure differential is developed across the valve. Such valves are commonly known as blast valves.

US-A-2873662 discloses a flap valve for protecting the inner space of a shelter from sudden increases in pressure of the outside air. A horizontal duct is located through a vertical wall. A plate is suspended over the opening of the duct by a chain attached to the wall above the duct. Springs are attached between the plate and the duct opening to hold the flap in an open position. When a blast occurs, the impact of the high pressure air will force the plate to cover the duct opening and thereby close the valve. However, such a valve is not suitable for protecting a vertical duct in a horizontal wall.

GB-A-963411 discloses a valve for protecting a ventilation shaft of an air-raid shelter in the event of an explosion. The valve comprises a valve plate which is suspended by springs in between two valve seats. Ihe valve seats are in the form of gratings to enable air flow through the valve. When an explosion pressure wave strikes the valve, the valve plate will be forced over a valve seat and the valve will thereby close. Once the pressure differential from the pressure wave has passed, the valve plate will return to its central position and the valve will thereby open.

Neither of the blast valves disclosed in US-A-2873662 and GB-A-963411 are suitable for use on enclosures which are exposed to external vibrations during normal use, for example vehicles, buildings in earthquake zones, aircraft and the like. Since the valve plates are suspended by springs, they are prone to oscillate as the enclosure is forced to vibrate. Each of the valve plates will have a resonant frequency at which the oscillations of the valve plate will reach a maximum displacement. At this displacement, or even at a lower displacement, the valve plate may shut the valve and therefore incorrectly restrict air flcw to cr from the enclcsure. In particular, if the valve is covering an inlet valve with a pump drawing air into the enclosure, the valve plate may be incorrectly held in the closed position by the negative pressure generated by the pump.

The resonant freguenoy will be proportional to the stiffness of the springs and, therefore, the spring stiffness may be adjusted to ensure that the resonant frequency is not within the frequency range of any expected external vibrations. However, as the spring stiffness is increased, a delay between the impact of the high pressure wave on the valve plate and the shutting of the valve increases. The minimum pressure at which the valve will shut will also increase. In addition, adjusting the spring stiffness may not be suitable when the enclosure is exposed to vibrations having a large bandwidth. In particular, vehicles are exposed to vibrations having a large bandwidth and high amplitudes as they travel across rough terrain and the like.

Components of enclosures must be able to continue to function under such vibration conditions. The United Kingdom Ministry of Defence's Defence Standard 00-35 specifies vibration conditions materiel is expected to resist. For example, in Test Ml for testing materiel of light tracked vehicles, spectral density curves are provided over a frequency range of 5 Hz to 2000 Hz and a power spectral density range of 0.0005 g2/Hz to 1 g2/Hz.

It is one objective of the present invention to improve upon the existing valve arrangements and overcome the aforementioned problems.

The invention therefore provides a valve for protecting an enclosure from a shock wave which causes a transient increase in pressure, said valve comprising; a duct; a valve seat; a valve plate supported by at least one spring and at least one frangible support; wherein, when the at least one frangible support is fractured, the valve plate is movable into contact with the valve seat and forms a seal therewith to close off the duct.

The invention further provides an enclosure comprising at least one of the aforementioned valve.

The invention further provides a method of preventing a wave of high pressure from entering an enclosure, said enclosure comprising; an internal volume; and at least one of the aforementioned valve; wherein, when a wave of a predetermined minimum pressure contacts the valve plate, the frangible supports break and the valve plate moves Into contact with the valve seat to form a seal therewith.

By way cf example only, embodiments of a valve of the present Invention are now described with reference to, and as show In, the accompanying drawings.

Figure 1 is a perspective view of an embodiment of a valve of the present Invention; Figure 2 is a cross-sectional perspective view of the valve shown in Figure 1; and Figure 3 is a cross-sectional side elevation of the valve shown in Figures 1 and 2.

The present invention is generally directed towards a valve suitable for protecting an enclosure from a shock wave which causes a transient increase in pressure. The valve is operable to remain open when exposed to external vibrations within a pre-defined vibration spectrum and to close upon being subjected to a transient increase in pressure.

The enclosure surrounds an internal volume which is to be protected, and preferably sealed off for a temporary period, from the surrounding environment. The enclosure may be of any suitable type, for example a stationary or movable shelter. In one embodiment the enclosure is a vehicle. In particular, the enclosure may be a military vehicle such as a patrol vehicle, a tank, an armoured personnel carrier, a command vehicle, an infantry fighting vehicle, an all terrain vehicle or the like.

The valve controls the communication of fluid, in particular air, in between the internal volume of the enclosure and the atmosphere surrounding the enclosure. The valve is ideally located in one or more inlet and/or outlet duct(s) of a ventilation system operable to control the environment of the internal volume of the enclosure. For example, the ventilation system may regulate the air flow between the surrounding atmosphere and internal volume, the humidity, pressure or temperature of the internal volume and the like.

In one arrangement, the valve is located in an inlet duct of a ventilation system, and a pump is prcvided in the inlet duct to draw air from the surrounding atmosphere and direct it into the internal volume. In another arrangement, the ventilation system maintains the internal volume at a pressure higher than the surrounding atmosphere to prevent hazardous gases from entering the enclosure.

Figures 1, 2 and 3 illustrate cne embodiment cf a valve according to the present inventicn. The valve 10 comprises a duct 11, which comprises a wall 12 surrounding a central passageway 13. In the embodiment shown, the duct 11 is formed from a first secticn 14 which is ccnnected tc a second section 15. The first and second sections 14, 15 preferably have a circular cross-section and the internal and external diameters of the first section 14 are larger than the internal and external diameters of the second section 14 respectively. An annular shoulder 16 is provided in the outer surface of the wall 12 between the first end of the first section 14 and the first end of the second section 14. A plurality of annularly spaced ribs 17 may be provided between the second section 14 and the outer side of the annular shoulder 16.

The other (second) end of the first section 14 defines an opening 18, which allows for fluid communication between the inside of the duct 11 and the surrounding atmosphere when the valve 10 is open. The other (second) end of the second section 14 (not shown) allows for fluid communication between the inside of the duct 11 and other parts of the ventilation system and/ or the internal volume of the enclosure.

In other embodiments, the duct 11 may have any suitable configuration. For example it may comprise a single wall section with a continuous internal and external diameter, it may be of any other suitable cross-sectional shape, for example square, rectangular, oval and the like. The duct 11 may be formed from one of more parts and each part may be removable for replacement or maintenance. For example, the first section 14 and the valve 10 components attached thereto (see below) may form one part, and the second section 14 and annular shoulder 16 may form a second part, with the first part being removable. The duct 11 may be formed from any suitable material, such as aluminium, steel or plastic.

An annular plate 20 is connected to the inner surface of the wall 12 of the duct 11. A valve seat 21 comprises an annular ridge projecting from the inner diameter of the annular plate 20 towards the opening 18. The diameter of the valve seat 21 is smaller than the diameter of the duct 11.

In the embodiment shown, the annular plate 20 and valve seat 21 are provided in the duct 11 where the annular shoulder 16 is formed and, therefore, separate the inner volume of the first section 14 from the inner volume of the second section 14. However, the annular plate 20 and valve seat 21 may be provided at any position along the length of the duct 11.

Furthermore, the valve seat 21 may have any other suitable design.

A valve plate 30 is also mounted within the internal diameter of the duct 11 and is movable into contact with the valve seat 21. The valve plate 30 may be mounted in proximity to, but at a distance from, the valve seat 21 by mounting means. Alternatively, the valve plate 30 is attached to the valve 10 by hinging means and at least a part of the valve plate 30 is mounted in proximity to, but at a distance from, the valve seat 21 by mounting means. The valve plate 30 may be located in an open position such that a space exists between at least a part of the valve plate 30 and the valve seat 21 and fluid is able to move through this space.

The mounting means may comprise one or more springs 31 and one or more frangible supports 32. In the embodiment shown, the valve plate 30 is circular and has a diameter larger than the diameter of the valve seat 21, but which is smaller than the internal diameter of the duct 11. The valve plate 30 may comprise a circular plate 33 formed from a material with a relatively low weight, for example an aluminium or magnesium alloy. A sealing means 34 may be provided on one side of the circular plate 33 for forming a seal with the valve seat 21. The sealing means 34 may be a plate and may be formed of any type of suitable material, including polyethylene and ethylene propylene diene monomer (EPDM) rubber.

One or more annularly spaced plate fixing means 35 may be provided on the valve plate 30 and one or more annularly spaced duct fixing means 37 may be provided around the inside of the wall 12 of the duct 11. Each of the mounting means 31, 32 is attached to a duct fixing means 37 and a plate fixing means 35, thereby supporting the valve plate 30 inside the duct 11. A plurality of support ribs 39 may extend from the centre of the valve plate 30 to the plate fixing means 35.

The duct fixing means 37 may comprise ribs protruding inwardly from and along the length of the inside of the wall 12 of the duct 11. One or more bores 40 may he provided in the ribs, and an end of each of the one or more springs 31 and one or more frangible supports 32 is fixedly attached within each bore 40. Alternatively, and as shown in Figures 1 to 3, fastening means 41, such as a screw, may be inserted into each bore 40, which may be threaded, and the end of each spring 31 or frangible support 32 is attached to the duct fixing means 37 by the fastening means 41.

The plate fixing means 35 may comprise a hole 42 for receiving the mounting means 31, 32. Alternatively, fastening means 43 may be provided and the mounting means 31, 32 are secured to the valve plate 30 by the fastening means 43.

The frangible supports 32 are operable to support and maintain the valve plate 30 in an open position (for example, the position shown in the Figures), wherein a space exists between at least part of the valve plate 30 and at least a part of the valve seat 21. The frangible supports 32 are operable to not fail when the valve 10 Is exposed to external vibrations within a predefined vibration spectrum, but to fail when a rapid transient increase in pressure contacts the valve plate 30.

-10 -The predefined vibration spectrum may be adapted to reflect the typical operating conditions to which the enclosure comprising the valve 10 is exposed. The vibrations forming the spectrum may have any form, including random, harmonic, periodic and transient, and the characteristics, including the waveform, frequency, wavelength, wavespeed and amplitude, of the vibrations may vary over time. For example, the vibrations may have a substantially Caussian distribution in the time domain.

In one embodiment, the vibration spectrum is a spectral density curve over a freguency range of 5 Hz to 2000 Hz and a power spectral density (POD) range of 0.0005 g2/Hz to 1 g2/Hz. The vibration spectrum may comprise one or more narrow bandwidth spectrums superimposed upon a wide bandwidth spectrum and the POD of the narrow bandwidth spectrums may be higher than that of the wide bandwidth spectrum. In particular, the POD range of the wide bandwidth spectrum may be between 0.0005 g2/Hz and 0.015 g2/Hz and that of the narrow bandwidth spectrum may be between 0.125 g2/Hz and 1 g2/Hz. Each narrow bandwidth spectra may have a bandwidth of between 5 Hz and 15 Hz and the wide bandwidth spectrum may have a bandwidth of 1995 Hz.

Alternatively, the vibration spectrum may comprise a pulse, representing a shock which the valve is expected to withstand during typical operating conditions of the enclosure. The pulse may have any form, such as sinusoidal, half sinusoidal, square, trapezoidal, sawtooth, damped sinusoidal. For example, the spectrum may comprise a half sine pulse with a duration of 6 ms and a maximum amplitude of 100 g.

-11 -The transient increase in pressure is a substantially abrupt increase (i.e. an impulse increase) in localised pressure of fluid within or adjacent to the valve 10 and/or valve plate 30. In particular, the transient increase in pressure is caused by a pressure wave or a shcck wave (i.e. a pressure wave travelling at a supersonic velocity) . For one embodiment of the present invention, experimentation has shown that, including a factcr of safety, the frangible supports 32 should fracture and the valve plate 30 form a seal with the valve seat 21 when a transient increase in pressure results in a pressure of approximately 14500 N/m2 contacting the valve plate 30. This value will vary for embodiments of the invention in which there are, for example, different diameters of valve plate 30, dimensions of the valve 10, weights of the valve plate 30, material properties of frangible suppcrts 32 and/or the like. A factor of safety may be added such that the frangible supports 32 will not fail unless the stress imposed upon them is substantially greater than the maximum stress resulting from the predefined vibration spectrum.

Therefore, the fracture strength of the frangible supports 32 is above the stress imposed by the external vibrations, but below the stress imposed by a transient increase in pressure contacting the valve plate 30.

Preferably, the frangible supports 32 are formed from a material with a relatively high bending stiffness, a relatively high modulus of elasticity and relatively little plastic deformation prior to fracture such that failure of the frangible supports 32 occurs rapidly. Suitable materials include glass and ceramics.

-12 -In the embodiment shown, the frangible supports 32 are solid cylinders. However, the cross-sectional shape and length of the frangible suppcrts 32 are selected to ensure rapid failure. The cross-sectional shape may, for example, be square or annular. An increase in the length of the frangible support 32 reduces the force required to achieve the bending moment at which the frangible support 32 will fail and, therefore, a lower force will be required to cause the frangible support 32 to fail.

The springs 31 are selected to have a sufficiently low stiffness to enable the valve plate 30 to move upon contact with a transient increase in pressure and to form a seal with the valve seat 21. The springs 31 may also be selected to be sufficiently stiff to enable the springs 31 to suspend the valve plate 30 in the open position. Therefore, if the frangible supports 32 are broken or not in place, the springs 31 suspend the valve plate 30 in a substantially similar position as would be the case if the frangible supports 32 were in place.

In the embodiment shown, the valve 10 comprises three springs 31, three frangible supports 32, six plate fixing means 35 and six duct fixing means 37. However, the number of springs 31, frangible supports 32, plate and duct fixing means 35, 37 may be varied. The number is selected to ensure that the frangible supports 32 and springs 31 function as described above.

The valve 10 has three main operational states. In the open and secured state, the frangible supports 32 and -13 -springs 31 support the valve plate 30 in the open position such that fluid can flow in cr out through the valve 10. In particular, this is due to the diameter of the valve plate being smaller than the internal diameter of the duct 11 and/or the internal diameter formed between the ridges of the duct fixing means 37. Therefore, fluid can flow from the surrounding atmosphere, in between the valve plate 30, valve seat 21 and duct 11, and into the internal volume or vice-versa.

When a transient increase in pressure contacts the valve plate 30, a large pressure differential will be formed across it. The frangible supports 32 will break as a result of this pressure differential and the valve plate 30 will move into contact with the valve seat 21. A seal is therefore formed between the valve seat 21 and valve plate 30, and this is the closed state of the valve 10. The seal will substantially prevent the transient increase in pressure from travelling past the valve seat 21.

Furthermore, the external diameters of the valve plate 30 and valve seat 21, the internal diameter of the duct 11 and the distance the duct fixing means 37 protrude into the duct 11 are selected to ensure that, when the valve plate 30 is in contact with the valve seat 21, a seal is formed.

Once the transient increase in pressure has passed, the energy stored in the springs 31 will move the valve plate 30 back to its original position. This is the open and unsecured state, as the frangible supports 32 are now broken, fluid can again flow through the valve 10.

-14 -One or more valves 10 may be provided to communicate air between the internal volume of an enclosure and the surrounding environment. When the enolosure is exposed to an external oscillatory force, and the vibrations are within a predefined vibration spectrum, the frangible supports 32 will maintain the valve 10 in the open and secure state and thereby prevent any unintentional closing of the valve 10.

When a transient increase in pressure contacts the valve plate 30, the frangible supports 32 will break and the valve 10 will rapidly move to the closed state. As a result, the ventilation system, and/or the enclosure occupants and/or equipment, will be protected from potential damage resulting from the transient increase in pressure. Once the transient increase in pressure has passed, the valve 10 will return to the open and unsecured state such that air can be communicated between the internal volume of the enclosure and the surrounding environment. The frangible supports 32 may then be manually replaced such that the valve 10 may be reused.

Claims

-15 -CLAIJYIS: 1. A valve for protecting an enclosure from a shock wave which causes a transient increase in pressure, said valve comprising; a duct; a valve seat; a valve plate supported by at least one spring and at least one frangible support; wherein, when the at least one frangible support is fractured, the valve plate is movable into contact with the valve seat and forms a seal therewith to close off the duct.
2. A valve as claimed in claim 1 wherein the at least one frangible support is configured to fracture when a shock wave contacts the valve plate.
3. A valve as claimed in claim 2 wherein the at least one frangible support is configured to fracture when the shock wave results in a pressure of approximately 14500 N/m2 contacting the valve plate 30.
4. A valve as claimed in any one of the preceding claims wherein the at least one spring is biased to separate the valve plate from the valve seat.
5. A valve as claimed in any one of the preceding claims wherein the at least one frangible support is configured to not fail when the valve is exposed to external vibrations within a predefined vibration spectrum.
6. A valve as claimed in claim 5 wherein the vibration spectrum is a spectral density curve with a freguency range -16 -of 5 Hz to 2000 Hz and a power spectral density range of 0.0005 g2/Hz to 1 g2/Hz.
7. A valve as claimed in any one of the preceding claims wherein one ends of the at least one spring and at least one frangible support are attached to the valve plate and other ends of the at least one spring and at least one frangible support are attached to the duct.
8. A valve as claimed in any one of the preceding claims wherein the at least one frangible support is replaceable.
9. A valve as claimed in any one of the preceding claims wherein the diameter of the duct is greater than the diameter of the valve plate, and the diameter of the valve plate is greater than the diameter of the valve seat.
10. A valve as claimed in any one of the preceding claims further comprising; an annular plate connected to an inner wall of the duct; and an annular ridge projecting from the inner diameter of the annular ring, said annular ridge forming the valve seat.
11. A valve as claimed in any one of the preceding claims wherein the valve seat and valve plate are each located inside the duct.
12. A valve as claimed in any one of the preceding claims wherein the valve plate comprises; a circular plate; and -17 -a sealing means provided on one side of the circular plate; wherein said sealing means is operable to form a seal with the valve seat.
13. An enclosure comprising at least one valve as claimed in any one of the preceding claims.
14. An enclosure as claimed in claim 13 wherein the at least one valve is operable to seal an internal volume of the enclosure from an environment surrounding the enclosure.
15. An enclosure as claimed in claim 13 or claim 14 wherein the enclosure is a vehicle.
16. An enclosure as claimed in any one of claims 13 to 15 wherein the enclosure further comprises a ventilation system for communicating fluid between an internal volume of the enclosure and an environment surrounding the enclosure; and the at least one valve is provided within the ventilation system.
17. A method of preventing a wave of high pressure from entering an enclosure, said enclosure comprising; an internal volume; and at least one valve as claimed in any one of claims 1 to 12; wherein, when a wave of a predetermined minimum pressure contacts the valve plate, the frangible supports break and the valve plate moves into contact with the valve seat to form a seal therewith.-18 -
18. A method as claimed in claim 17 wherein after the wave of high pressure has passed the at least one spring returns the valve plate to a distance from the valve seat.Amended claims have been filed as follows:-CLAIJYIS: 1. A valve for protecting an enclosure from a shock wave which causes a transient increase in pressure, said valve comprising; a duct; a valve seat; a valve plate supported by at least one spring and at least one frangible support; wherein, when the at least one frangible support is fractured, the valve plate is movable into contact with the valve seat and forms a seal therewith to close off the duct; and wherein the dimensions and material properties of the at least one frangible support are selected such that the at least one frangible support fractures when a shook wave 0 contacts the valve plate.2. A valve as claimed in claim 1 wherein the dimensions and material properties of the at least one frangible support are selected such that the at least one frangible support fractures when the shock wave results in a pressure of approximately 14500 N/m2 contacting the valve plate 30.3. A valve as claimed in any one of the preceding claims wherein the at least one spring is biased to separate the valve plate from the valve seat.4. A valve as claimed in any one of the preceding claims wherein the dimensions and material properties of the at least one frangible support are selected such that the at least one frangible support does not fail when the valve is exposed to external vibrations within a predefined vibration spectrum.5. A valve as claimed in claim 4 wherein the vibration spectrum is a spectral density curve with a frequency range of 5 Hz to 2000 Hz and a power spectral density range of 0.0005 g2/Hz to 1 g2/Hz.6. A valve as claimed in any one of the preceding claims wherein one ends of the at least one spring and at least one frangible support are attaohed to the valve plate and other ends of the at least one spring and at least one frangible support are attached to the duct.7. A valve as claimed in any one of the preceding claims 0 wherein the diameter of the duct is greater than the diameter of the valve plate, and the diameter of the valve plate is greater than the diameter of the valve seat.8. A valve as claimed in any one of the preceding claims further comprising; an annular plate connected to an inner wall of the duct; and an annular ridge projecting from the inner diameter of the annular ring, said annular ridge forming the valve seat.9. A valve as claimed in any one of the preceding claims wherein the valve seat and valve plate are each located inside the duct.10. A valve as claimed in any one of the preceding claims wherein the valve plate comprises; a circular plate; and a sealing means provided on one side of the circular plate; wherein said sealing means is operable to form a seal with the valve seat.11. An enclosure comprising at least one valve as claimed in any one of the preceding claims.12. An enclosure as claimed in claim 11 wherein the at least one valve is located in between an internal volume of the enclosure from an environment surrounding the enclosure.13. An enclosure as claimed in claim 11 or claim 12 wherein the enclosure is a vehicle. r14. An enclosure as claimed in any one of claims 11 to 13 wherein the enclosure further comprises a ventilation system for communicating fluid between an internal volume of the enclosure and an environment surrounding the enclosure; and the at least one valve is prcvided within the ventilation system.15. A method of preventing a wave of high pressure from entering an enclosure, said enclosure comprising; an internal volume; and at least one valve as claimed in any one of claims 1 to 10; wherein, when a wave of a predetermined minimum pressure contacts the valve plate, the frangible supports break and the valve plate moves into contact with the valve seat to form a seal therewith.16. A method as claimed in claim 15 wherein after the wave of high pressure has passed the at least one spring returns the valve plate to a distance from the valve seat. r a)