GB2084014A - Fire extinguishers - Google Patents

Abstract

A device for providing a simple indication of the serviceability of gas cartridge-operated fire extinguishers. An indicating piston 9 in a housing 10 is attached to a plunger 15 sensitive to the pressure within the headspace in the extinguisher body 2. If this pressure should rise to a first predetermined value, indicative of the leakage of propellant from the gas cartridge, the piston will be shifted up to a shoulder 14 on the inside surface of the housing 10, so that a first indication (such as "CO2 LEAK") on the piston becomes visible through a viewing window 13. Furthermore, if the headspace pressure reaches a second predetermined value, indicative of the total discharge of the gas cartridge when the extinguisher is used, the piston will be shifted further, past the shoulder 14, so that a second indication (such as "USED") on the piston becomes visible through the window 13. A frictional bearing is provided on the plunger 15 so as to prevent the piston being reset to its lower position after use without first dismantling the extinguisher. <IMAGE>

Description

SPECIFICATION Fire extinguishers The present invention relates to fire extinguishers and more particularly to gas cartridgeoperated fire extinguishers. By this term is meant fire extinguishers of the type in which a sealed cartridge of pressurised propellant gas in disposed within the extinguishant-containing body of the apparatus, the propellant thus normally being kept separate from the extinguishant and the body chamber remaining unpressurised. In use of such an extinguisher the propellant is relased into the body chamber (usually by breaking a frangible seal on the cartridge by means of a suitable operating mechanism), to pressurise the extinguishant and force it out of the body for discharge towards the fire.

At present it is different to test simply and satisfactorily the serviceability of such fire extinguishers in terms of the state of charge of the gas cartridge.

Generally this requires the dismantling of the apparatus to remove the cartridge, which is then weighed and its weight compared with that when installed or at the previous service call, to ensure that no leakage has occured. Failures of cartridgeoperated fire extinguishers when required at the outbreak of a faire are believed to be mostly due to haphazard servicing or the incidence of relatively small leaks from the gas cartridge over several months between servicing.

The present invention seeks to alleiviate these problems by providing a gas cartridge-operated fire extinguisher with means whereby the state of charge of the gas cartridge can be continuously signalled in a simple but effective manner, to give an immediate visual indication of the serviceability of the apparatus.

Accordingly the invention resides in a gas cartridge-operated fire extinguisher equipped with a status indicator assembly comprising an indicating member slidably borne within a housing externally of the extinguisher body chamber and an elongate pressure-sensing member extending from the indicating member sealingly into the body chamber whereby the distal end of that member is subject to fluid pressure within said chamber, and arranged such that an increase of fluid pressure within the body chamber to a predetermined value causes the pressure-sensing member to liftthe indicating member unidirectionally and substantially stepwise relative to the housing to a position in which a specified portion of the indicating member is visible relative to a viewing part of said housing.

With a fire extinguisher according to the invention, in the event of leakage from the gas cartridge into the body chamber the pressure therein will increase and when the predetermined value of pressure is attained the specified portion of the indicating member-which can bear markings indicative of a leakage condition - will appear relative to the viewing part of the housing. The unserviceability or at least questionable serviceability of the extinguisher will thus be apparentfrom simple visual inspection by the owner or any other person looking at the apparatus and need not await a service call and dismantlement of the extinguisher.

In a preferred embodiment it is also arranged that an increase of fluid pressure within the body chamberto a predetermined value higher than the first causes the pressure-sensing member to shift the indicating member unidirectionally and substantially stepwise relative to the housing to a second position in which a second specified portion of the indicating member is visible relative to said viewing part. In this arrangement the second portion of the indicating member can appear relative to the view ing part to give an indication of the used condition of the apparatus when the extinguisher is operated, it being understood that operation involves pressurising the body chamber to a value far higher than that which is indicative of a simple leak.

The term "unidirectionally and substantially stepwise" refers to the characteristic that significant movement of the indicating member does not occur prior to the attainment of the appropriate chamber pressure and that under normal conditions the indicating member will be held in the appropriate indicating position after it has been shifted even if the chamber pressure should thereafter decrease. This is of advantage eg in ensuring that a "leakage" indication remains even if the chamber pressure should subsequently dissipate through further leakage out of that chamber, and in ensuring that a "used" indication remains (in embodiments providing this function) after the chamber has been exhausted - preferably access to the indicating member for resetting the same being obtained only by dismantling the apparatus.

A cartridge-operated fire extinguisher in accordance with the invention will now be more particularly described, by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a partly cut-away elevation of the head portion of the extinguisher; Figure 2 is a sectional view to an enlarged scale, of the indicator assembly of the extinguisher, in a first condition; and Figure 3 is a view similar to Figure 2 with the indicator assembly in a second condition.

Referring to Figure 1, the extinguisher has a main body shell 1 defining a chamber 2 which contains a fire extinguishant such as water, foam solution or powder. A cap 3 is screwed and sealed to the top of the shell to close the chamber 2, and supports a squeeze-grip operating mechanism comprising a pivoted lever 4 and a fixed carrying handle 5. The lever4 is connected to a piercer (not shown) within a tubularfitting 6 carried by the cap 3, whereby squeezing the lever 4towards the handle 5 causes the pierces to break a frangible seal on a pressurised propellant gas cartridge 7, in known manner.The cartridge 7 is screwed into the lower end of the fit ting 6 and when pierced releases its gas, typically carbon dioxide, into the chamber 2 to pressurise the extinguishant and force it from the body through a dip tube (not shown) within the chamber 2 and a discharge hose 8 attached to a nozzle mounted on the cap 3. A valve (not shown) which normally closes the outlet from the extinguisher is also controlled by the lever 4. The extinguisher also comprises a status indicator assembly which is more clearly shown in Figures 2 and 3.

The indicator assembly includes an indicator member 9, which for convenience will be termed herein a "piston", slidably borne within a housing 10 mounted on the cap 3 to one side of the lever 4 and fitting 6. The piston 9 is a plastics moulding having an order, flexible skirt portion 11 with a lip 12 engaging the inner surface ofthe housing 10. Indicia exemplified as "CO2 LEAK" and "USED" ere inscribed on the outer surface of the piston 9, one above the other. The housing 10 is made of essentiallytransparent plastics material but has a bevelled or frosted outer surface except at a viewing window 12 (Figure 1). This viewing window (which is provided at the bevel indicated by the chain lines in Figures 2 and 3) permits clear observation of the indicia on the piston 9 in appropriate circumstances, as will be explained below.The inner surface ofthe housing adjacent to the top of the viewing window 13, is provided with a shoulder indicated at 14; in Figure 3 the lipped upper end 12 of the piston is shown in engagement with this shoulder.

An operating plunger 15 connected to the piston 9 extends through a passageway 16 in the cap 3 into the headspace within the chamber 2 and is provided with one or more "O" ring seals 17. A washer 18 which is an interference fit on the plunger 15 is held in position by a screwed boss 19. A circlip 20 is fixedly mounted on the plunger 15 towards its lower end.

The fire extinguisher is assembled with the indicator piston 9 initially in its lowermost position, as shown in Figure 2, so that there is no indicating sign in view in the viewing window 13. If any carbon dioxide leaks from the cartridge 7 into the chamber 2, the pressure therein builds up above the atmospheric pressure which pertains on initial assembly. When this pressure reaches a first predetermined value, the force generated on the lower end surface of the plunger 15 becomes sufficient to overcome the resistance to movement caused by the friction ofthe '0' ring seal and the washer 18 (if any) and the piston 9 moves upwards until it reaches the position shown in Figure 3, in which the indication ''C02 LEAK" appears in the viewing window 13.

If the extinguisher is operated the chamber 2 is, of course, pressurised by the full contents ofthe cartridge 7. When this increased pressure, acting on the plunger 15, reaches a second predetermined value it oyercomes the upward resistance to movement of the piston 9 relative to the housing 10 caused by the lipped end 12 of the piston abutting the shoulder 14, and the piston skirt 11 flexes to pass the shoulder. At this time, the indicated "USED" moved into position opposite the viewing window 13. Further upward movement of the piston is restrained by the circlip 20 on the plunger 15 abutting the boss 19.

It will be noted that the movement of the piston 9 is unidirectional under the action of pressure changes in the chamber 2, in an upwards only direction, as described. The indicator will operate in other than a vertical plane if desired and still provide unidirectional movement. The '0' ring seal(s) 17 provide sufficient resistance to prevent casual movement even, say, when the indicator is placed in a horizontal plane, and will retain the "USED" indication in place afterthe extinguisher is exhausted. The indicator cannot be reset without dismantling the extinguisher and provide a clear outward indication at all times of the condition of the extinguisher. It is no longer necessary, as is the case with earlier extinguishers, to dismantle the extingusher to determine its state.

The housing 10 is shown slightly tapered (for ease of moulding) but this is not necessary; the housing could be parallel-sided.

In the described embodiment, the housing 10 apart from the window 13 is effectively translucent such that the indication signs on the piston 9 are visible to some extent at all times but generally only clearly visible when opposite the viewing window.

To some extent this tends to reassure the owner that the indicator has not moved but is capable of indicating a faulty or used condition if one should occur.

However, the housing may be arranged to be completely opaque except at the viewing window 13, or the housing could be completely transparent and inscribed with a simple line, arrow or other distinctive marking so that the line, arrow or whatever becomes in effect a "viewing part" for the piston indicia in determining the condition of the extinguisher. Preferably, the viewing part is not formed as an aperture, although it could be if otherwise preferred, because if the aperture provided access to the piston the indicator could be reset from outside the extinguisher which would normally be unsatisfactory.

In one embodiment ofthe invention, the diameter of the plunger 15 is approximately 3mm and the chamber 2 has a capacity of 9 litres. The first predetermined pressure value is arranged to be about 10% of the pressure in the cartridge 7 and the second predetermined value is arranged to be 85% ofthat pressure. It will be appreciated that such dimensions and values can be readily altered together with the material and design of the '0' ring seal(s) 7 to meet any operating requirements or statutory regulations.

It will be noted that other forms of seal can be used instead of the '0' ring 17. However, where a nitrile material especially is used, it is preferred to prevent at least in major part contact between the carbon dioxide and the '0' ring. If this is not done, there can be reduced to the extent where the functional be reduced to the extent whene the functional characteristics of the seal are significantly changed.

In the embodiment described, the piston 9 moves to the position shown in Figure 3 whenever the pressure in the chamber 2 rises to about the 10% value or above. The piston moves again only when the pres sure exceeds the 85% value. Thus the piston moves in stepped fashion as the pressure in the chamber 2 increases. The lower pressure value is determined by the resistance to movement caused by the '0' ring seal(s) 17 and diameterofthe plunger 15, and the upper pressure value is determined by the shape of the outer surface of the piston 9 and its flexibility as well as the change of internal dimensions of the housing 10.

It will be appreciated that this stepped movement could be provided by other means. For example, the lower pressure value may be controlled by another stepped change in inner diameter of the housing 10, arranged to provide less resistance to movement than the shoulder 14, positioned near the base ofthe housing. Also, the upper value could be alternatively provided by suitably increasing the diameter of the plunger 15 step-wise towards its base such that much more force was required to urge the increased diameter portion through the '0' ring(s) 17. In that case pressure in the chamber 2 at the 10% value moves the piston 9 to indicate "CO2 LEAK", where it remains until the pressure increases to such an extent that the increased diameter portion of the plunger 15 is forced to enter the '0' ring seal(s) and beyond.In such an arrangement, the two same conditions of the extinguisher are indicated correspondingly, and the operation of the indicator remains unidirectional as before, there being no forces acting to return the plunger toward the chamber 2 sufficient to overcome the resistance caused by the '0' ring seal(s).

It will be noted that the piston 9 may be extended to show "FULL" above "CO2 LEAK" if desired. In that case until there is a "10%" leak, the viewing part shows "FULL".

Whereas the embodiment described provides separate indications "CO2 LEAK" and "USED", other embodiments may combine these indications and show only one indication, say "LEAK/USED". As either 'LEAK or 'USED' conditions will normally require replacement of the gas cartridge or at least dismantling of the extinguisher, it may be sufficient to have only a single or combined indication. In such a case, the indicator may be formed with a housing without a stepped inner diameter and the "LEAK/USED" condition arranged to show up whenever the pressure in the chamber 2 reaches the 10% level; this will happen if either there is a significant leak or the extingisher is used.

Claims (6)

1. A gas cartridge-operated fire extinguisher equipped with a status indicator assembly compris-ing an indicating memberslidably borne within a housing externally of the body chamber and an elongate pressure-sensing member extending from the indicating member sealingly into the body chamber whereby the distal end of that member is subject to fluid pressure within. said chamber, and arranged such that an increase of fluid pressure within the body chamber to a predetermined value causes the pressure-sensing member to shift the indicating member unidirectionally and substantially stepwise relative to the housing to a position in which a specified portion of the indicating member is visible relative to a viewing part of said housing.

2. A fire extinguisher according to claim 1 and arranged such that an increase of fluid pressure within the body chamber to a second predetermined value higher than the first causes the pressuresensing memberto shift the indicating member unidirectionally and substantially stepwise relative to the housing to a second position in which a second specified portion of the indicating member is visible relative to said viewing part.

3. Afire extinguisher according to claim 1 or claim 2 wherein movement of the indicating member prior to the attainment of the or at least one of said predetermined values of pressure is restrained at least in substantial part by friction between the pressure-sensing member and means whereby that member is sealed in relation to said chamber.

4. Afire extinguisher according to claim 1 or claim 2 wherein movement of the indicating member prior to the attainment of the or at least one of said predetermined values of pressure is restrained at least in substantial part by the engagement of a peripheral portion ofthat member with an abutment on the internal surface of the housing.

5. A fire-extinguisher according to claim 4 wherein the indicating member is diametrally compressible to pass said abutment when the appropriate value of pressure is attained.

6. Agas cartridge-operated fire extinguisher substantially as hereinbefore described with reference to the accompanying drawings.