GB2420280A

GB2420280A - Fire extinguisher with an integrally sealed unit

Info

Publication number: GB2420280A
Application number: GB0522604A
Authority: GB
Inventors: Roger Carr
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-11-23
Filing date: 2005-11-07
Publication date: 2006-05-24
Anticipated expiration: 2025-11-07
Also published as: GB0425682D0; GB0522604D0; GB2420280B

Abstract

There is provided a fire extinguisher comprising a metal outer body (10) and an inner bottle (14) made of plastics material, a neck portion (36) of the bottle (14) engaging with a neck portion (32) of the outer body (10) and a cap (40) being permanently sealed over and to both the neck portions. This results in integral sealing of the bottle (14), ensuring that substances contained within the bottle (14). The bottle (14) is blow-moulded from polymer plastics material, with the internal surface of the bottle and cap coated with "nylon 66". This ensures that the bottle (14) is non-leaching of gaseous contents and with the metal outer body (10) encasing the plastics material, deterioration of plastics material from light is also prevented. To assess the condition of the inner body and whether contents have been compromised, a pressure gauge (15) is positioned on the metal outer body (10) and extends through a small aperture in the metal body to connect with the outer surface of the bottle (14). The pressure gauge is responsive to any deflection of the bottle (14). The fire extinguisher further comprises a piercing mechanism 48 for piercing the cap and breaking the seal when discharge is required. The cap is permanently sealed by any suitable method including plastics interference weld or by adhering the cap and incorporates a siphon tube 42 extending down into the inner body.

Description

Title: Fire Extinguisher with an Integrally Sealed Unit

Field of the Invention

This invention relates to a fire extinguisher with an integrally sealed unit for containing fire-fighting substances and a method for manufacturing a fire extinguisher with such an integrally sealed unit.

Background to the Invention

Fire extinguishers with integrally sealed units containing powder are appropriate for certain types of fire, for example those caused by petrol, solvents and electrical equipment.

Integrally sealed units reduce the need for ongoing maintenance of a fire extinguisher given that the powder contents within the unit are permanently sealed from the atmosphere before release. However developing integrally sealed units for other types of fire-fighting substances is problematic due to problems with seals and maintaining the integrity of the unit and its contents.

It is an aim of the present invention to provide a fire extinguisher with an integrally sealed unit suitable for use with any type of substance used for extinguishing fires.

Summary of the Invention

In accordance with the present invention, there is provided a fire extinguisher comprising a metal outer body and an inner body made of plastics material, each body having a neck portion, wherein the neck portion of the inner body engages with the neck portion of the outer body and a cap is permanently sealed over and to both the neck portions. This results in integral sealing of the inner body, ensuring that substances contained within the inner body are sealed from the atmosphere. In particular, gaseous contents cannot become de-pressurised due to leakage. This reduces ongoing maintenance costs substantially as there is no need to replace the unit containing the fire-fighting substance as there is no degradation or leakage of the fire-fighting substance.

Preferably the irmer body is blow-moulded from polymer plastics material with its internal surface coated with nylon 66. The nylon 66 is usually adhered to the body by a layer of adhesive. The cap used to seal the bodies will similarly be made from polymer plastics material coated with nylon 66. This ensures that the inner body is non-leaching of gaseous contents and with the metal outer body encasing the plastics material, deterioration of plastics material from light is also prevented.

Typically the blow-moulded inner body will be of any thickness sufficient to resist the pressures of gas required for effective fire-extinguishing. Thus the body will be of sufficient thickness to withstand a usual gas pressure of 12 bar, and test bar pressures of between 25-52 bar.

The neck portion of the metal outer body may he threaded internally and externally, with a complementary screw thread on the outer surface of the neck portion of the inner body securing to the internal thread and the cap securing to the external thread. This is particularly suitable where the metal body has a base portion which is only secured in place after the inner body is inserted in the outer body and secured thereto.

Preferably the fire extinguisher further comprises a piercing mechanism for piercing the cap and breaking the seal when discharge is required. The piercing mechanism provides a conduit by which the contents of the inner body can be discharged through a hose.

The cap may incorporate a siphon tube extending down into the inner body to assist with discharge of gas upon operation of the fire extinguisher.

The cap may he permanently sealed by any suitable method, including a plastics interference weld or by adhering the cap.

To assess the condition of the inner body and whether contents have been compromised, the fire extinguisher may further comprise a pressure gauge positioned on the metal outer body and extending through a small aperture in the metal body to connect with the outer surface of the inner body. The pressure gauge is responsive to any deflection of the inner body. When the inner body is filled with highly-pressurised gas, as is the case before discharge, the gauge will not be able to depress the surface of the inner body and the pressure gauge will show that the integrity of the inner body is uncompromised. If for any reason contents have leaked or been discharged from the inner body, then the inner body can be deflected by any suitable force, for example, such as that exerted by the pressure gauge.

Typically the pressure gauge will be a diaphragm gauge, with a rod urged against the inner body by a biasing spring. As the pressure gauge has no contact with the fire extinguishing materials within the inner body, and therefore the integrity of the inner body as a sealed unit is not affected, the pressure gauge provides a readily visible means of checking the integrity of the inner body and its contents, without needing to access the inner body by removing it from the metal outer body. This avoids the need for maintenance for periods of, say, 10 years which reduces ongoing maintenance costs substantially.

If the inner body splits, the pressurised contents will be retained at pressure by the metal outer body. This represents a possible safety risk as the outer body may corrode and explode under pressure. Thus desirably the outer body incorporates a small aperture in which a bung is pushfitted, the bung being ejected from the aperture if pressure within the outer body is sufficient. This provides a more controlled release of pressure which does not involve rupturing of the outer body.

The inner body may be provided with a shaped recess in its base for receiving a key or the like to help screw the neck portion of the inner body into engagement with the neck portion of the outer body.

Typically the fire extinguisher will further comprise a head cap, which will incorporate the piercing mechanism as aforesaid. The head cap and piercing mechanism may, if required, be detachable from the sealed unit of outer and inner body, so as to allow checking of discharge apertures associated with the head cap, for example such as provided by a discharge hose.

In accordance with another aspect of the invention, there is also provided a method of welding a fire extinguisher, and in particular of welding a metal base onto a fire extinguisher having an inner plastics body, the method of welding comprising retaining water or other similar non-flammable liquid within a base and spraying the metal outer body with water as the base is welded to the outer body. This has proved very successful in preventing any impairment of the plastics bottle whilst welding is conducted.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a fire extinguisher in accordance with the present invention; and Figure 2 is a sectional view through the fire extinguisher.

Description

A fire extinguisher in accordance with the present invention is shown in Figure 1. The fire extinguisher comprises a steel canister 10, a release mechanism 12 and a plastics container 14 or bottle (not shown) in communication with the release mechanism 12. The container 14 is capable of withstanding high pressures and is filled with fire controlling chemicals or water under pressure. A diaphragm pressure gauge 15 is attached to the steel canister 10 and touches the inner bottle through a gauge hole behind the gauge. The release mechanism 12 comprises a valve 16 operated by a two pronged handle 18, the handle maintained in an open and inactive position when not in use by means of a locking pin 20, and an outlet nozzle 22 to which a hose is normally attached. The release mechanism also includes a bracket 24 for attaching the fire extinguisher to a support 26. Other types of release mechanism are possible, as those skilled in the art will appreciate. An optional seating washer 28 is colour-coded to indicate the contents of the fire extinguisher. A plastics ring 30 is fitted around the lower end of the canister, this being used for securing a dispensing hose (not shown) connected to the outlet nozzle 22.

A sectional view through the extinguisher is shown in Figure 2. The outer metal canister is of an inverted u-shaped cross section with a central neck 32 having an internally threaded portion 33 and an externally threaded portion 34. The canister 10 is typically formed as one integral unit by drawing and pressing sheet steel.

The plastics container or bottle 14 has a neck portion 36 with another thread which screws into the thread 33 to secure the bottle 14 to the canister 10. The bottle is typically made from polymer plastics material with a coating of "nylon 66" adhered to the internal surface so that the bottle is non-leaching of gas, so preventing the contents of the container from escaping. The blow-moulded plastics bottle 14 has a complementary shape to that of the internal surface of the canister 10 and is arranged to have a tight fit with the canister.

However there is a slight clearance between the canister and bottle as a result of internal ridging of the canister inherent in the manufacturing process associated with the canister.

The bottle 14 has a recess 38 in its bottom surface which receives a complimentary shaped key to assist with screwing the bottle 14 into position.

The bottle 14 is hermetically sealed by a cap 40 made of the same plastics material as the bottle. The cap is either screwed onto and adhered to thread 34 to form an airtight seal, or more preferably a plastic interference weld is made. The cap 40 has a coating of "nylon 66" on its innermost surface to ensure non-leaching of the bottle contents. A siphon tube 42 is held beneath the cap 40 by "o" rings and extends down into the base of the bottle 14, with a filter 44 at the end of the tube.

A head cap 46 carrying the release mechanism 12 is secured over the cap 40 such that a piercing element 48 forming part of valve 16 is suspended directly over the portion of the cap 40 carrying the siphon tube 42. The piercing element 48 is typically a hollow spike which, upon operation of the handle 18, is urged down into and through the cap 40 to break the seal and allow release of contents of the bottle 14 up through the siphon tube 42 and out through the discharge nozzle.

A separate metal base 50, in the form of a shallow disc with down-turned edges and which forms a tight fit with the internal surface of the canister 10, is welded to the open end of the canister 10 so as to ensure that the bottle 14 is fully encased by metal. This prevents degradation of the plastics bottle from light and also is an important safety feature helping to contain the bottle and its contents if there should be an inadvertent discharge due to, for example, the bottle being punctured.

Welding the base plate 50 to the canister 10 using conventional welding techniques would melt the inner plastics bottle 14. To overcome this problem, during welding the extinguisher is inverted so that the base plate is uppermost and water or other non- flammable liquid is placed into the dished surface of the base plate. Welding then takes place as water is gently sprayed around the site of the weld, and in this way, the heat associated with the welding is absorbed by the water and not transferred through the remainder of the metal canister to melt the bottle 14. The base is typically around 2mm thick, and its strength can he improved by a series of ridges or corrugations. After welding, the canister is painted to provide an improved appearance.

A diaphragm pressure gauge 15 is adhered to the external surface of the metal canister 10 and through a small hole in the canister 10, a rod and biasing spring associated with the gauge extend to touch the outer wall of the container 14. The spring strength is selected dependent on the thickness of the bottle 14. The pressure gauge is responsive to any deflection of the bottle 14. When the bottle 14 is filled with highlypressurised gas, the gauge will not be able to depress the surface of the bottle 14 and the pressure gauge will show that the pressure of the contents within the bottle is appropriate for discharge. If for any reason contents have leaked from the bottle 14, then the bottle can be deflected by the force exerted by the rod and biasing spring, and will register on the externally viewable gauge. The gauge thus provides a way of assessing the integrity of the pressure of the inner container without the need to interfere with the integrally sealed unit formed by the canister 10, bottle 14 and cap 40.

To improve the appearance of the fire extinguisher, a ring 30 with a hose clip is pushed over and down the canister 10 until it forms an interference fit with the canister over the region where the plate 50 is secured.

Typically on assembly, the metal canister 10 has a small gauge hole drilled into it prior to screw fitting of the bottle 14 to thread 33. The pressurised contents of the container 14, such as water or gas such as C02, are introduced into the container 14 and in the same process the cap 40 sealed over and to the neck portions of both the canister 10 and the bottle 14 so as to provide an integrally sealed unit. The head cap 46 with the release mechanism 12 is secured over the top of the cap 40.

The extinguisher is then inverted to have the base plate 50 welded into position as described above. The pressure gauge is adhered to the outermost surface of canister 10 so as to partially project through the gauge hole to contact the outer surface of the canister 14.

The metal canister 10, where appropriate, has a second hole drilled into it prior to assembly. A bung is push-fitted into this hole and if the bottle 14 splits, the hung will be ejected to release pressurised contents in a more controlled manner than, for example, a corroded outer body simply rupturing.

The contents of the bottle 14 are water, foam, gas, or powder and the bottles are of any of the capacities usually covered, for example for liquid chemicals and water 1, 2, 3, 4, 6, 9, 12 litres.

The integral sealing of the container 14 ensures that the extinguisher has a long shelf life of at least 10 years without a complex service being needed. The provision of an integrally sealed unit has advantages in that the main extinguisher unit can simply be sent through the post if required and maintenance checks are peripheral, just requiring a visual check that the pressure gauge registers the correct pressure.

The manufacture of such a fire extinguisher is simpler than for current extinguishers, improving manufacturing efficiency and reducing cost. The use of a non-leaching bottle integrally sealed with a non-leaching cap results in a vastly improved shelf life of typically around 10 years.

Claims

1495.00/C Claims 1. A fire extinguisher comprising a metal outer body and

an inner body made of plastics material, each body having a neck portion, wherein the neck portion of the inner body engages with the neck portion of the outer body and a cap is permanently sealed over and to both the neck portions.

2. A fire extinguisher according to claim 1, wherein the inner body is blow-moulded from polymer plastics material with its internal surface coated with nylon 66.

3. A fire extinguisher according to claim 2, wherein the blow-moulded inner body is of sufficient thickness to withstand a usual gas pressure of 12 bar, and test bar pressures of between 25-52 bar.

4. A fire extinguisher according to any of the preceding claims, wherein the neck portion of the metal outer body is threaded internally and externally, with a complementary screw thread on the outer surface of the neck portion of the inner body securing to the internal thread and the cap securing to the external thread.

5. A fire extinguisher according to any of the preceding claims, wherein the fire extinguisher further comprises a piercing mechanism for piercing the cap and breaking the seal when discharge is required.

6. A fire extinguisher according to any of the preceding claims, wherein the cap incorporates a siphon tube extending down into the inner body to assist with discharge of gas upon operation of the fire extinguisher.

7. A fire extinguisher according to any of the preceding claims, wherein the cap is permanently sealed by any suitable method, including a plastics interference weld or by adhering the cap.

8. A fire extinguisher according to any of the preceding claims, further comprising a pressure gauge positioned on the metal outer body and extending through a small aperture in the metal body to connect with the outer surface of the inner body.

9. A fire extinguisher according to any of the preceding claims, wherein the outer body incorporates a small aperture in which a hung is pushfitted, the bung being ejected from the aperture if pressure within the outer body is sufficient.

10. A fire extinguisher according to any of the preceding claims, wherein the inner body is provided with a shaped recess in its base for receiving a key or the like to help screw the neck portion of the inner body into engagement with the neck portion of the outer body.

11. A method of welding a fire extinguisher comprising retaining water or other similar non-flammable liquid within a base and spraying a metal outer body with water as the base is welded to the outer body.

12. A fire extinguisher and method of welding a fire extinguisher substantially as herein described with reference to and as illustrated in the accompanying drawings.