GB2388775A

GB2388775A - Fire extinguisher

Info

Publication number: GB2388775A
Application number: GB0212019A
Authority: GB
Inventors: Keith Larke
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-05-24
Filing date: 2002-05-24
Publication date: 2003-11-26
Also published as: GB0212019D0

Abstract

A fire extinguisher (10) has a container (11) which is partially filled with a means for extinguishing a fire. A pressurising means is distributed within the container (11), whereby opening a seal in a release means (13) releases the pressurising means from the container (11), the release entraining the extinguishing means. The release means (13) includes an eductor tube (33) which is operably linked at a first end to the release means (13). The second end is in the extinguishing means, such that the extinguishing means separates the internal volume of the eductor tube (33) from the free volume of the container (11). One or more holes (36) in the wall of the eductor tube (33) links the free volume of the container (11) with the internal volume of the eductor tube (33). The extinguishing means is sodium bicarbonate, ammonium sulphate phosphate with nitrogen being the pressurising means.

Description

AN IMPROVED FIRE EXTINGUISHER

Field of the Invention

The present invention relates to a fire extinguisher and in particular to an extinguisher providing an enhanced means of monitoring its internal pressure Background of the Invention

The public is increasingly aware of the dangers associated with and the likelihood of outbreak of fires. Companies also, faced with increasin, claims for damages, as a result of accidents caused by fires are also faced with increasing costs As a result of these factors the presence of fire extinguishers in the house, car, 10 workplace etc. is becoming increasingly common. A number of different types of extinguishers are available to deal with different types of fire, such as carbonaceous, flammable liquid, electrical etc. One feature that each of the types of extinguishers has in common is that a pressurised system needs to be present to propel the actual fire extinguishing material out of the extinguisher to the place 15 where the extinguishing material is required. The provision of sufficient pressure can be achieved in a number of ways, for example, having a high pressure within the extinguisher body itself or including a canister of material which material when released from the canister expands rapidly thereby increasing the pressure in the extinguisher body and expelling the extinguishing material.

20 Whatever the type of extinguisher it is advisable, and, in some cases required by law, that the fire extinguisher be checked to ensure that the pressure within the extinguisher is sufficiently high. Some fire extinguishers have a gas pressure gauge incorporated which gives a reading of the internal pressure. Others require

-2 a gauge to be fixed to the outlet and the valves in the extinguisher to be opened to release a small amount of pressurising means to enable a measurement taken. The extinguisher is then sealed up again.

Unfortunately, for powder extinguishers, of the type in which the entire internal 5 volume is under pressure, difficulties arise due to the release of an amount of powder during the testing. Some of the powder released is deposited in the closure valves and can either cause a gap7 as the valve cannot shut properly, or abrade the seal, again resulting in release of pressure from within the extinguisher.

If, before the following pressure check the pressure drops to a level where it is 10 insufficient to expel the powder onto a fire, then the extinguisher will be useless and could prove fatal if relied upon in an emergency.

It is an object of the present invention to seek to address the above problems Summary of the Invention

According to the invention, there is provided a fire extinguisher, the fire 15 extinguisher including a container to hold a means for extinguishing a fire, the container including a free volume said volume being free of the extinguishing means, a pressurising means distributed within the container, a release means to open a seal and release the pressurising means from the 20 container said release entraining the extinguishing means.

the release means including an eductor tube operably linked at a first end to the release means and having the second end in a volume occupied by the extinguishing means such that the extinguishin, means separates the internal free volume in the eductor tube from the free volume of the container, wherein the said 25 free volumes are linked together by a linkage means The pressure within the extinguisher can be determined without release of the extinguishing means so

reducing impairment of the effectiveness of the seal Preferably, the linkage means is one or more holes in the wall of the eductor tube.

Advantageously, the extinguishing means is selected from sodium bicarbonate, ammonium sulphate or ammonium phosphate 5 The pressurizing means is preferably nitrogen and particularly oxygen free nitrogen. According to a further aspect of the invention there is provided a conventional powder fire extinguisher having an eductor tube, wherein the wall of the eductor defines an aperture, the aperture being above the inuse level of the powder 10 Brief Description of the Drawings

The invention will now be described with reference to the accompanying drawings which show by way of example one embodiment of a fire extinguisher In the drawings: Figure I is a side view of a fire extinguisher, 15 Figure 2 is a section through the fire extinguisher with release means removed, and Figure 3 illustrates the internal mechanism of the release means Detailed Description of the Invention

Figure I shows the external appearance of a fire extinguisher 10 The 20 extinguisher 10 has a cylindrical body 11 in which an extinguishing medium is maintained under pressure The cylindrical body 11 narrows at one end to define a neck 12. The neck 12 co-operates with a valve assembly 13 to form a seal, two elements being threadably connected.

( -4 The external surface of the body 11 has a number of areas 14 on which information such as the type of extinguisher, use instructions hazard warning information etc. can be displayed. In order for the body I I to have sufficient strength to withstand the internal pressures the body is formed from carbon steel 5 having a carbon content of 0.08% into which manganese to a level of 0.45 /0 has been added. In addition the steel also contains - sulphur (0.03%), phosphorus (0 03%) and aluminium (0 02%). Typically the body will be produced as two sections which are flash welded together along the line 15 in Figure 2.

Turning now to the valve assembly 13 shown in more detail in Figure 3. In order 10 to contain and maintain the pressure within the container body 10, a breakable valve seal 30, formed from a resilient nitrilo-rubber, engages the outer neck assembly 31 of the valve assembly 13 To maintain the seal, a carbon steel spring 32 urges the valve seal 30 against the neck assembly seal 31. To ensure that a good seal is maintained, a nitrilo-rubber O-ring seal is included 15 An eductor tube 33 has a first end in the lower portion of the container body 10.

This ensures that when the pressure within the container is released by operation of the valve assembly, then all of the extinguishing powder is forced out, as the powder is entranced in the flow of pressurising mechanism. A typical pressurising mechanism is oxygen free nitrogen, although carbon dioxide can also 20 be used. A pressure (at 20C) of 1015bar is acceptable, although around 13.5 bar is common A coupling member 34 couples the eductor tube 33 to the outer neck assembly 33.

The coupling member 34 also provides a seat for the spring 32.

In order to utilise the extinguisher 10, the first handle 16 is lifted from the body I I 2S breaking the safety seal 17 The second handle 18 is then compressed towards the first handle 16. The valve seal 30 is forced downwards against the spring 32. The pressure from the pressurising medium within the container body forces the medium up the eductor tube 33 and through the space formed between the valve seal 30 and the assembly 31. As the medium leaves. powder is entrained and also 30 exits the container. The medium and the powder are forced out through the valve

-s- body 35 and can then be directed to the appropriate area to extinguish a fire. The powder is typically selected from one or more of sodium bicarbonate, ammonium phosphate and ammonium sulphate. Sodium bicarbonate is particularly preferred as it breaks down at temperature to form carbon dioxide However, the 5 composition of the powder will be determined by the type of fire being extinguished, for example carbonaceous, electrical, flammable liquid etc. The extinguisher includes a further feature, namely a hole 36 in the wall of the eductor tube 33. The hole 36 is typically the size of a pinhole and positioned so that it lies above the normal level of the powder within the container, the normal 10 level being indicated by the broken line 37 in Figure 2 The hole 36 enables a measurement of the pressure within the container body 10 to be made without damage being caused to the seals In order to make a measurement, a pressure gauge (not illustrated) is attached to the end of the valve body 35 The seal formed by the valve seal 30 is broken as described above The 15 pressure within the body 11 enters the extra volume within the valve body 35 and acts on the pressure gauge As the extra volume is small, very little pressure is lost from within the container body 11. The reading is taken and the valve seal 30 re engaged with the assembly 31 As the pressure in the valve body is equalised by pressurizing medium drawn 20 from above the powder, no powder is entrained during the measurement procedure as would be the case if the medium had to force its way through the powder The seals do not thereby come into contact with the powder during the measurement and the seals are not therefore impaired by residual powder on the surfaces of the various elements making up the seal 25 In addition to the above, a number of modifications can be included within the fire extinguisher without departing from the scope of the invention Further holes can be provided at other locations within the wall of the eductor tube. Should the pressure test be conducted under mix-used conditions, such as the extinguisher being tipped up on its side, a single hole might become blocked. The additional 30 holes if suitably positioned, ensure that at least one hole will remain unblocked

/ -6 lt will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the invention

Claims

( -7 Oaims 1. A fire extinguisher, including a container holding a charge

of extinguishing material, the container enclosing a free volume said volume being free of the extinguishing material in a 5 storage or standby mode; a pressurising medium distributed within the container, a release means to open a seal and release the pressurizing means from the container said release entraining the extinguishing material; the release means including an eductor tube operably linked at a first end 10 to the seal and having the second end within the charge of extinguishing material the extinguishing material thereby separating the free volume from the seal, wherein the eductor tube includes a linkage means linking the free volume to the release means.
2. A fire extinguisher according to Claim 1, wherein the linkage means

15 permits passage of the pressurising medium but not the extinguishing material.
3. A fire extinguisher according to Claim I or Claim 2, wherein the linkage means is one or more holes in the wall of the eductor tube.
4. A fire extinguisher according to any preceding claim, wherein the 20 extinguishing means is selected from sodium bicarbonate. ammonium sulphate or ammonium phosphate.
5. A fire extinguisher according to any preceding claim, wherein the pressurising medium is nitrogen.

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6. A fire extinguisher according to Claim 5, wherein the nitrogen is oxygen free.
7. A powder fire extinguisher having an eductor tube' wherein the wall of the eductor defines an aperture, the aperture being above the in-use level of 5 the powder.
8. A fire extinguisher substantially as herein described with reference to and as illustrated in the accompanying diagrams.