GB2349084A

GB2349084A - Fire Extinguisher

Info

Publication number: GB2349084A
Application number: GB9907000A
Authority: GB
Inventors: David Laurence Melton
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-03-27
Filing date: 1999-03-27
Publication date: 2000-10-25
Anticipated expiration: 2019-03-27
Also published as: GB9907000D0; GB2349084B

Abstract

The extinguisher 10 has two enclosures 10a, 10b one being within the other. Each enclosure is bounded at least in part by walls of heat softenable material and both contain a pressurised fire extinguishing fluid 16a, 16b. Under high external temperature conditions, the outer enclosure wall softens and is then ruptured by the fluid pressure thus releasing the fire extinguishant. If the external temperature continues to increase, the inner enclosure wall similarly ruptures to release extinguishing fluid. The enclosures are typically in the form of flexible nylon tubing. Also claimed is a temperature detector where each of the enclosures contain a pressurised fluid and there is a means in each enclosure responsive to a change in pressure.

Description

A TEMPERATURE DETECTOR This invention relates to apparatus for detecting a temperature rise and automatically responding to the temperature rise in two stages, in particular for use with a fire extinguishing system.

There are many situations where a temperature rise may cause damage or develop into a fire. In such situations it is desirable to detect the temperature rise and respond by applying an extinguishant or a fire extinguishing medium to halt the temperature rise or extinguish the fire, the terms"extinguishant"and"fire extinguishing medium"being used interchangeably in this specification.

This can be achieved automatically with many fire extinguishing systems, where a rise in temperature above a predetermined threshold activates a fire extinguisher which must then be turned off manually. However, such fire extinguishing systems may apply more extinguishant than is necessary, which, in the case of water, may cause damage to equipment unnecessarily.

According to a first aspect of the present invention, there is provided a temperature detector comprising two enclosures, one substantially within the other, where each enclosure is bounded at least in part by walls of heatsoftenable material, and where both enclosures contain a fluid fire extinguishing medium under pressure.

When a temperature rise occurs close to the wall of the outer enclosure, the wall will soften. Above a threshold temperature, the pressure of the fire extinguishing medium acting on the inside of the wall will cause the wall to rupture, burst or otherwise fail, thereby releasing the fire extinguishing medium held in the outer enclosure which is then expelled by the internal pressure onto the source of the temperature rise.

The release of the extinguishant from the outer enclosure will have a cooling effect, but if the temperature is not attenuated or keeps rising, for example if a fire develops which is not extinguished by the extinguishant from the outer enclosure, the wall of the inner enclosure will subsequently heat up and burst, releasing further extinguishant to help ensure the temperature rise is reversed or a fire is extinguished. This arrangement ensures that the inner enclosure will only release the extinguishant within it if the extinguishant released from the outer enclosure was insufficient, hence helping to minimise the unnecessary use of extinguishant.

The extinguishant in each enclosure may be the same substance, for example a gas such as a halon or a mixture of halons. Alternatively, a different substance could be employed in the inner enclosure, such as water for example, which is readily available under pressure from the mains supply.

The wall thickness, wall material and internal pressure of each enclosure may be chosen so that each enclosure fails at a pre set temperature. For example, the outer enclosure may be set to fail at a relatively low temperature in response to minor overheating, whereas the inner enclosure may be set to fail at a higher temperature. Alternatively, both enclosures may be set to fail at the same temperature, the shielding effect provided by the outer enclosure ensuring that it fails before the inner enclosure.

The walls of the enclosures may be formed integrally with the casing of an item of equipment made by injection moulding. However, in a preferred embodiment, a wall of each enclosure is formed by a flexible tube, with one tube residing within the other tube. The tubes may then be arranged to follow any suitable path which comes close to the main areas where a fire or overheating is most likely to occur. For example, the tubes may be inserted into the casing of electrical equipment and wound around the component parts.

If a fire or overheating occurs, a tube will fail closest to the hottest point along its path, so that the extinguishant released will automatically be directed to the region where it is needed most.

The tubes may be made from a thermoplastic material, such as nylon, provided the tube walls are sufficiently thick to withstand the pressure within the tubes.

One or both enclosures may be connected to a pressurised vessel containing a fire extinguishant, such as a conventional extinguisher cylinder, for example. The capacity and content of the pressurised vessel connected to each enclosure may be chosen to provide a two stage response, so that initially when the outer enclosure has failed, only a small amount of extinguishant is released, whereas when the inner enclosure has failed, a much larger quantity of extinguishant is released.

According to a second aspect of the invention, there is provided a temperature detector comprising two enclosures, one substantially within the other, wherein each enclosure is bounded at least in part by walls of heat-softenable material, and wherein both enclosures contain a fluid medium under pressure, the detector including means responsive to a change in pressure within the inner enclosure and means responsive to a change in pressure within the outer enclosure.

When either the outer or inner enclosure fails due to an excessive increase in temperature, the release of fluid medium will cause a pressure drop in the respective enclosure which will be sensed by the respective pressure responsive means.

The pressure may simply be displayed as a pressure reading, but preferably the pressure responsive means produce a first response when a pressure drop occurs in the outer enclosure, and a second response when a pressure drop occurs in the inner enclosure. Since the outer enclosure will fail before the inner enclosure, the first response will occur after an initial rise in temperature, and the second response will occur if the temperature rise has not been attenuated.

A first or second response may be to operate a valve and/or an electrical switch, either mechanically by causing the physical displacement of a component part, or electrically by producing an electrical or electronic signal.

The first and second response may be different so that, for example, the first response may be to disconnect an electrical circuit from an electrical supply, and the second response may be to open a valve to a fire extinguishing device.

In order to warn an operator that an excessive temperature rise has occurred, a first warning signal may be produced in response to a pressure drop in the outer enclosure, the warning signal being either a visual warning or an audible alarm. Similarly, a second warning signal may be produced in response to a pressure drop in the inner enclosure to warn the operator that the temperature rise has not been attenuated.

The first or second warning signal may also be produced in combination with another form of response, such as the operation of a valve for example.

The features described in the first aspect of the invention may also be applied, mutatis mutandis, to the second aspect of the invention. For example, a wall of each enclosure in the second aspect of the invention may comprise a flexible tube, with the one tube residing within the other tube, the fluid medium contained in each tube having fire extinguishing properties.

In a preferred embodiment of the second aspect of the invention, one or both of the enclosures may communicate with a self closing water valve which is normally held closed by the pressure within the enclosure (s) and the mains water pressure but which will open when the corresponding enclosure bursts. The valve can be used to control the flow of water to fire sprinklers or any other fire extinguisher device.

If the enclosures are formed from flexible tubes, the tubes can conveniently be positioned close to the places where a fire is most likely to start, thereby acting as local temperature sensors, so that a local temperature rise above a critical temperature will cause the failure of a tube which will in turn cause the self closing water valve to open.

The outer enclosure may communicate with the self closing valve via a normally open float valve connected between the outer enclosure and the self closing valve, the float valve being orientated such that following the failure of the outer enclosure, water entering the self closing valve causes a float in the float valve to move into a closed position, thereby cutting off the point of failure in the outer enclosure.

This arrangement allows the self closing valve to refill with water and consequently causes the valve to close, with the result that following a failure of the outer enclosure, the self closing valve is only open for a limited period. This may be desirable if only a small fire has occurred, where the application of a fire extinguisher for a limited period is sufficient.

However, if for example a fire has not been fully extinguished, the inner enclosure will eventually fail.

Therefore, the inner enclosure may be connected to the self closing valve directly, such that failure of the inner enclosure will cause the self closing valve to remain permanently open, and guarantee that the fire is extinguished.

Although water is the preferred extinguishant with the self closing valve having a float valve, any pressurised source of fire extinguishing liquid may be used as an alternative to the mains water supply.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic cross sectional view of a temperature detector according to the invention.

Figure 2 is a view according to Figure 1, where an outer tube has ruptured.

Figure 3 is a view according to Figure 2, where both an inner and outer tube have ruptured.

Figure 4 illustrates a use of the temperature detector inside the casing of electrical equipment.

Figure 5 illustrates a use of the temperature detector with a self closing water valve.

Figure 6 illustrates a use of the temperature detector as in Figure 5, but where the outer tube communicates with the water valve via a float valve.

Figure 1 shows a length of tubing 10 with an inner tube lOa which lies within an outer tube lOb. The inner tube lOa is bounded at one end by a seal and at the other end is in communication with a vessel 14a, the vessel and tube together forming an inner enclosure which contains a fire extinguishant 16a under pressure. In a similar fashion, the outer tube lOb is bounded at one end by a seal and at the other end is in communication with a vessel 14b, the vessel and tube together forming an inner enclosure which contains a fire extinguishant 16b under pressure.

In Figure 2 a fire 12 adjacent to part of the tubing 10 has caused the outer tube lOb to soften, which, aided by the pressure within the tube, has resulted in a local rupture of the tube close to the fire. Consequently the extinguishant 16b in the tube lOb is released in the vicinity of the fire.

If the fire is extinguished in time by the extinguishant 16b which was contained in the outer enclosure, the inner tube 10a will remain closed and the extinguishant 16a within the inner enclosure will be retained. If however the fire is fierce enough to rupture the inner tube 10a, then further extinguishant 16a from the inner enclose will be released on the fire, as is shown in Figure 3.

The volume and pressure of the pressurised vessels can be chosen to determine the relative amounts of extinguishant available from each enclosure. In general, the amount of extinguishant available in the inner enclosure will be larger than that in the outer enclosure to ensure that even a severe fire is extinguished completely.

Each enclose may contain a different extinguishant. For example, an effective but potentially damaging extinguishant such as water can be contained in the inner enclosure, whilst a less damaging but more expensive extinguishant is contained in the outer enclosure. In this way the potential damage to equipment in extinguishing a fire is minimised, since the content of the inner enclosure is only released if the content of the outer enclosure has failed to extinguish the fire.

This inner enclosure will normally contain a larger quantity of extinguishant than the outer enclosure, to ensure that a fire is extinguished.

Figure 4 illustrates a possible use for the invention shown in Figure 1 with an item of electrical equipment.

The electrical equipment shown here has a casing 20 with walls 20a, 20b, and 20c (a side wall and the top wall are omitted here for clarity) and a base 22 containing four printed circuit board cards 24. The flexible tubing 10 with an outer and inner tube lOa and lOb respectively is wound around and in between the boards 24 inside the casing 20.

The inner and outer sections of tubes lOa and lOb each form a separate enclosure and are respectively connected to pressurised vessels 14a and 14b respectively as in Figure 1. Here, the pressure vessels are conventional gas cylinders.

Pressure meters 32a and 32b are connected to the inner and outer enclosures of the inner and outer tubes lOa and lOb respectively, and an alarm 34 is connected to pressure meter 32b of the outer enclosure.

Since the tubing 10 is flexible, it can easily be arranged to follow any particular path though the apparatus. If a fire or local overheating occurs due to a defective component for example, the outer tube lOb will rupture close to the defective component and release the extinguishant contained in the outer tube lOb and cylinder 14b, thereby providing a cooling effect.

The resulting drop in pressure in the outer tube is sensed by the pressure meter 14b which activates the alarm 34 to indicate that a fault or a fire has occurred. The alarm can be connected to an electrical switch device which disconnects the electrical equipment from the mains electrical supply.

If a fire begins which is not extinguished by the release of extinguishing material from the outer tube lOb, the inner tube 10a will rupture and release further extinguishant, thus helping ensure that the fire is extinguished.

Figure 5 shows how a self closing water valve 40 can be operated by the pressure in an inner tube 10a, the inner tube 10a residing within an outer tube lOb.

The self closing valve 40 has an inlet 48 and an outlet 50, communication between the inlet and outlet being controlled by a diaphragm 46, shown here in the closed position. The inlet 48 is connected to the mains water supply (not shown), and the outlet 50 could, for example, be connected to a sprinkler device for extinguishing a fire.

The diaphragm 46 divides the valve 40 into two regions, a first valve region 42 and a second valve region 44, the two regions 42 and 44 being located on opposite sides of the diaphragm 46. A bleed valve 56 in the diaphragm 46 communicates between the valve regions 42 and 44, and ensures that when the inner tube 10a has not burst or ruptured, both valve regions 42 and 44 are at the same pressure.

The inner tube 10a communicates directly with the self closing valve 40 whereas in the present embodiment the outer tube lOb is sealed at both ends and forms a separate enclosure which contains an extinguishant under pressure.

However, the outer tubing could also be connected to a pressurised vessel containing an extinguishant.

If the outer tube lOb bursts in response to a temperature rise, the extinguishant contained within the tube lOb will be released, which will have a cooling effect and may prevent any further rise in temperature. However, if the extinguishant contained in the outer tube lOb is insufficient and the temperature rise continues or develops into a fire, the inner tube lOa will also burst.

The space formed by the inner tube lOa and valve regions 42 and 44 contains a gaseous medium under pressure, the pressure of the gaseous medium being greater or equal to the mains water pressure, so that water from the mains supply cannot enter the water valve 40. Hence when the water valve 40 is in the closed position as shown in Figure 5, there is a net gas pressure in the second valve region 44 acting on the diaphragm 46 over the area of the outlet 50. This pressure ensures that the diaphragm 46 remains firmly pressed into contact against the outlet 50 and keeps the water valve 40 in the closed position, thereby maintaining the gas pressure in the water valve 40 and preventing the flow of water.

A burst in the inner tube lOa causes the gas pressure in the tube lOa and hence also the gas pressure in the second valve region 44 to drop to atmospheric pressure. This allows pressurised water to enter the first valve region 42 which forces the diaphragm away from the outlet 50 and into an open position where water may flow through the water valve 40.

After the inner tube lOa has burst, the water valve 40 will remain in the open position so that for example a sprinkler system controlled by the water valve 40 will apply water over a fire or the source of a temperature rise until the water supply is disconnected.

Because the inner tube lOa will only burst if the extinguishant released from the outer tube lOb was insufficient to halt or reverse the rise in temperature, this arrangement helps prevent the water valve 40 opening unnecessary in response to a temperature rise.

If the water valve 40 is used to control a sprinkler system, the tubing 10 can be placed close to where overheating is most likely to occur, thereby acting as a remote temperature sensor to detect overheating and provide an initial response before causing the water valve 40 to open and activate the sprinkler.

In an alternative embodiment shown in Figure 6, both the outer enclosure lOb and the inner enclosure 10a communicate with the water valve 40, the outer enclosure lOb communicating with the water valve 40 via a float valve 52 having a float 54.

The space formed by the valve regions 42,44; the inner and outer tubes 10a, lOb ; and the float valve 52 contains a gaseous medium under pressure which prevents water entering the valve when the inner and outer tubes remain airtight. As in the previous embodiment, the diaphragm 46 is in the closed position, thereby allowing the gas pressure to be maintained.

Since the float valve 52 is empty of water, the float 54 lies at the bottom of the float valve such that the float valve 52 is open. Hence when the outer tube lOb is punctured or bursts, the gas pressure in the valve 40 drops. This allows water into the valve region 42, which forces the diaphragm 46 into an open position where water can flow through the outlet 50, to a fire sprinkler device for example.

Over a period of time, water in the first valve region 42 will flow through the bleed valve 56 into the second valve region 44 on the other side of the diaphragm 46, where it can enter the float valve 52.

As the float valve 52 fills with water, the float 54 rises towards the top of the float valve 52 where it closes the communication between the float valve and the outer tube lOb. Pressure can then build up in the second valve regions 44, which, together with the flow of water in the vicinity of the outlet 50, causes the diaphragm to move back into the closed position shown in Figure 6.

Thus a burst in the outer tube lOb will cause the water valve 40 to open for a limited period of time determined by the fill time of the float valve 52. This limited period during which the water valve 40 is open may be sufficient to respond adequately to a temperature rise or extinguish a fire. However, if the fire or temperature rise persists, then the inner tube lOa will burst, which will cause a permanent loss of pressure in valve region 44 so that the water valve remains open until it is re set manually at the appropriate time.

The above embodiment represents a two stage detection and response to a temperature rise or fire, first by opening the water valve 40 for a limited period, and then, only if necessary, opening the water valve again until an operator deems it safe to disconnect the water supply and re set the water valve 40.

It will be apparent that the invention provides simple and reliable apparatus for detecting and responding to a rise in temperature in two stages. Since the apparatus can be purely mechanical, it can continue to be effective even where there has been a disruption of the mains power supply.

Claims

Claims 1. A fire extinguisher comprising two enclosures, one substantially within the other, where each enclosure is bounded at least in part by walls of heat-softenable material, and where both enclosures contain a fire extinguishing fluid under pressure.
2. A fire extinguisher as claimed in Claim 1, where the extinguishant in each enclosure is the same substance.
3. A fire extinguisher as claimed in Claim 1, where the extinguishant in one enclosure is different from the extinguishant in the other enclosure.
4. A fire extinguisher as claimed in any preceding claim, wherein the extinguishant in one enclosure is water.
5. A fire extinguisher as claimed in any preceding claim, wherein the wall thickness, wall material and internal pressure of each enclosure are chosen so that each enclosure fails at a pre set temperature.
6. A fire extinguisher as claimed in Claim 5, wherein the outer enclosure is set to fail at a relatively low temperature and the inner enclosure is set to fail at a higher temperature.
7. A fire extinguisher as claimed in Claim 5, wherein the wall material of both enclosures is set to fail at the same temperature, the shielding effect provided by the outer enclosure ensuring that it fails before the inner enclosure.
8. A fire extinguisher as claimed in any preceding claim, wherein the walls of the enclosures are formed integrally with the casing of an item of equipment made by injection moulding.
9. A fire extinguisher as claimed in any one of Claims 1 to 7, wherein a wall of each enclosure is formed by a flexible tube, with one tube residing within the other tube.
10. A fire extinguisher as claimed in Claim 9, wherein the tubes are arranged to follow any suitable path which comes close to the main areas where a fire or overheating is most likely to occur.
11. A fire extinguisher as claimed in Claim 9 or Claim 10, wherein the tubes are made from a thermoplastic material sufficiently thick to withstand the pressure within the tubes.
12. A fire extinguisher as claimed in any preceding claim, wherein one or both enclosures is/are connected to a pressurised vessel containing a fire extinguishant.
13. A fire extinguisher as claimed in Claim 12, wherein the capacity and content of the pressurised vessel connected to each enclosure is chosen to provide a two stage response, so that initially when the outer enclosure has failed, only a small amount of extinguishant is released, whereas when the inner enclosure has failed, a much larger quantity of extinguishant is released.
14. A temperature detector comprising two enclosures, one substantially within the other, wherein each enclosure is bounded at least in part by walls of heat-softenable material, and wherein both enclosures contain a fluid medium under pressure, the detector including means responsive to a change in pressure within the inner enclosure and means responsive to a change in pressure within the outer enclosure.
15. A temperature detector as claimed in Claim 14, wherein the pressure is displayed as a pressure reading.
16. A temperature detector as claimed in Claim 14, wherein the pressure responsive means produce a first response when a pressure drop occurs in the outer enclosure, and a second response when a pressure drop occurs in the inner enclosure.
17. A temperature detector as claimed in Claim 16, wherein one of the two responses is to operate a valve and/or an electrical switch, either mechanically by causing the physical displacement of a component part, or electrically by producing an electrical or electronic signal.
18. A temperature detector as claimed in Claim 16 or Claim 17, wherein the first and second responses are different.
19. A temperature detector as claimed in any one of Claims 14 to 18, wherein a first warning signal is produced in response to a pressure drop in the outer enclosure, the warning signal being either a visual warning or an audible alarm.
20. A temperature detector as claimed in Claim 19, wherein a second warning signal is produced in response to a pressure drop in the inner enclosure.
21. A temperature detector as claimed in Claim 14, wherein one or both of the enclosures communicates with a self closing water valve which is normally held closed by the pressure within the enclosure (s) and the mains water pressure but which will open when the corresponding enclosure bursts.
22. A temperature detector as claimed in Claim 21, wherein the valve is used to control the flow of water to fire sprinklers or any other fire extinguisher device.
23. A temperature detector as claimed in Claim 21 or Claim 22, wherein the outer enclosure communicates with the self closing valve via a normally open float valve connected between the outer enclosure and the self closing valve, the float valve being orientated such that following the failure of the outer enclosure, water entering the self closing valve causes a float in the float valve to move into a closed position, thereby cutting off the point of failure in the outer enclosure.
24. A temperature detector as claimed in Claim 14, wherein the inner enclosure is connected to the self closing valve directly, such that failure of the inner enclosure will cause the self closing valve to remain permanently open, and guarantee that the fire is extinguished.
25. A fire extinguisher, substantially as herein described with reference to the accompanying drawings.
26. A temperature detector substantially as herein described with reference to the accompanying drawings.