GB2469913A

GB2469913A - Fire extinguisher

Info

Publication number: GB2469913A
Application number: GB1006916A
Authority: GB
Inventors: Roger Carr
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-04-27
Filing date: 2010-04-26
Publication date: 2010-11-03
Also published as: GB0907127D0; GB201006916D0; GB0914935D0

Abstract

A fire-extinguisher comprising an outer casing 10, typically of metal or other protective material, surrounding an inner container 12 for retaining fire-fighting substances, wherein the inner container 12 is substantially rigid with a deformable region to allow the volume of the inner container to be expanded to fill an inner volume defined by the outer casing. The deformable region 31 is deformable in response to pressure to reduce the volume of the container 12. The deformable region may comprise a lower part of the container or a concertina wall. The base of the inner container may comprise integrally formed depressions for fingers and a neck portion having an external helical thread interrupted with vertical channels. Also included is a method of manufacturing a fire extinguisher comprising placing a plastics container within a casing, reducing the volume of the plastics container, welding a base to the casing and increasing the volume of the plastics container.

Description

Title: Improved Fire Extinguisher

Field of the invention

This invention relates to a fire extinguisher with an inner container for retaining fire-s fighting substances.

Background to the invention

Fire extinguishers with inner containers made of plastics material are known, see for example GB 2398494. The use of plastics containers within an outer metal casing io improves the operational lifespan of the fire extinguisher as the fire-fighting substances are contained within the inner plastics container and cannot corrode the metal casing. However the plastics container is often damaged during manufacture of fire-extinguishers due to heat used in welding the metal casing. Protection coatings, i.e. liners, can be applied to the internal surface of the outer metal casing. However is due to small pin holes, the metal soon becomes corroded.

Summary of the invention

In accordance with the present invention, there is provided a fire-extinguisher comprising an outer casing, typically of metal, fibreglass or other protective material, surrounding an inner container for retaining fire-fighting substances, wherein the inner container is substantially rigid with a deformable region to allow the volume of the inner container to be expanded to fill an inner volume defined by the outer casing.

By having a semi-rigid or rigid inner container whose volume can be adjusted, it is easier to weld a base to the outer casing to seal the casing. When welding takes place, the inner container has a reduced volume and does not fill the inner volume, the inner container is thus spaced sufficiently far from the welding heat source so as not to be damaged by the heat source. Once welding has finished, the inner container is expanded by deformation occurring in the deformable region such that the inner container then fills the inner volume of the outer casing.

Preferably the deformable region is responsive to pressure, to reduce the volume of the inner container. The pressure is typically externally applied by means of a plunger, push rod or piston.

I

Preferably the deformable region is expandable by pressurised gas, such as air under pressure. This allows the inner container to be expanded to fill the inner volume.

s The deformable region may comprise a tower part of the container responsive to pressure at room temperature to reduce the volume of the container, thereby to ensure the inner container is displaced from a region where welding is to occur. The deformation is typically temporary with the inner container restoring to its original volume as pressurised substances are introduced into the container.

The deformable region may be formed by a concertina wall, with the concertina wall deformed and expanded under application of pressure until the volume of the inner container matches the inner volume defined by the outer casing. In particularly preferred embodiments, the deformable region is deformed as pressure of typically 6 bar is applied whilst material forming the inner container is in a flux state at high temperature.

Preferably the inner container is formed from plastics material, and more preferably is formed from blow-molded plastics material. The use of blow molding allows consistent production of a container with a concertina wall with the appropriate dimensions to fill the internal volume of the outer casing when fully expanded.

The inner container preferably has a thickness in the range 5mm to 0.5mm, more preferably in the range 2mm to 1mm so as to be resistant to puncturing from a siphon tube through which fire-fighting substances leave the inner container.

Depressions for receiving fingers are preferably integrally formed in a base of the inner container. The depressions allow the inner container to be easily held as it is secured within the outer casing.

Preferably the inner container further comprises a neck and collar portion, the neck portion having an external helical thread interrupted with vertical channels. The neck is secured in position with regard to a neck portion of the outer casing, either by a locking ring arrangement or by the neck portion of the outer casing having a co-operating internal thread. The vertical channels allow air from the region between the outer casing and inner container to be expelled as the inner container expands to match the inner volume of the outer casing. There can also be a small aperture or hole s in the outer casing to allow for venting.

The invention also lies in a method of manufacturing a fire extinguisher comprising placing a plastics container within a casing, reducing the volume of the plastics container, typically by applying an external pressure, welding a base to the casing and io increasing the volume of the plastics container, typically by inflating under pressure.

The invention will now be described, by way of example, and with reference to the accompanying drawings in which: Figure 1 is a sectional view of a partially assembled fire-extinguisher in accordance is with the present invention showing an inner container; Figure 2 is a detailed sectional view of the inner container; Figure 3(a) is a detailed sectional view of the neck of the inner container and Figure 3(b) is a plan view of the neck from above; Figure 4 shows an alternative embodiment; and Figure 5 shows an exemplary fire extinguisher incorporating the inner container.

Description

Figure 1 shows a partially assembled cylindrical fire-extinguisher in accordance with the present invention comprising an outer casing 10, an inner plastics container 12 and a welded metal base plate 14. The casing 10 is made of heat sealable material, typically metal, although fibreglass or other protective material may be used, and has an internally and externally threaded neck 16, into the internal thread of which has been screwed the inner plastics container 12 which has a complementary externally threaded neck portion 18.

One embodiment of inner container 12 is shown in more detail with reference to Figures 2, 3(a) and 3(b) and comprises a rigid neck and shoulder portion 18, 20, a concertina wall 22 and a curved base 24 with finger-shaped recesses 26 which allow the inner container 12 to be held securely as it is twisted to secure into the internal thread of the casing 10. The neck portion 18 of the inner container 12 is formed with vertical channels 28 within the thread as can be seen in detail in Figures 3(a) and 3(b) and which allow air to pass upwards out of the volume 30 between the outer metal casing 10 and inner container 12. The container 12 has a wall thickness of around 1.5mm and if exposed to too much heat, for example from a welding process, will be damaged due to the plastics material melting.

The inner container 12 is made from plastics material blow-molded to give a thickness io of around 1.5mm. Of preference, high density polyethylene (HDPE) material, polymers or polypropylene are used.

After the inner container 12 has been screwed into position, the metal base plate 14 is welded to the metal casing 10 as seen in Figure 1. There is a space of approximately is 5cm between the base of the container 12 and the base plate 14 and when water-cooled welding occurs at point A, the inner container 12 is sufficiently far from the base plate 14 that it is not damaged by the welding process. After welding has taken place, the combined unit of casing 10, inner container 12 and base plate 14 is placed in a paint oven for the outer metal surface to be painted. After painting, air pressure of around 6 bar is introduced through neck portion 18 and the inside of the inner container 12 is blown to fit the inner wall of the casing 10.

As the inner container expands and elongates, air passes from the gap 30 between the container 12 and the casing 10 up and out of the vertical channels 28.

In another embodiment shown in Figure 4, the inner container 12 is moulded with dimensions complementary to the internal volume of the inner wall of casing 10, as shown by the dotted line 12' so that the container substantially fills the internal volume of the casing 10. The inner container is screwed into position within the casing 10 and pressure applied to base 31, typically by a piston or plunger, to compress the container temporarily and force deformable base 31 and lower part of the container 12 upwards away from where the base plate 14 is to be welded to the casing 10. The base plate 14 is then able to be welded to the casing 10 around diameter A without heat damaging the container 12 which has been displaced away from the area where welding is taking place.

After welding, the container is restored to its full volume, typically by expanding the deformable region 31 under an internally applied pressure.

Fire-controlling chemicals or water under pressure are introduced into the inner container and a release mechanism 32 attached, one of which is shown by way of example in Figure 5, so as to produce a completed fire extinguisher. As will be io appreciated by those skilled in the art, a variety of different types of release mechanisms incorporating nozzles and handles exist. With such a fire extinguisher, all the pressurised fire-fighting substances are contained within a rigid plastics container which does not corrode: even if there is corrosion of the outer metal casing, this will not lead to dangerous release of substances under pressure due to the small is hole in the outer casing.

Claims

Claims 1. A fire-extinguisher comprising an outer casing surrounding an inner container for retaining fire-fighting substances, wherein the inner container is substantially rigid s with a deformable region to allow the volume of the inner container to be expanded to fill an inner volume defined by the outer casing.
2. A fire-extinguisher according to claim 1, wherein the deformable region is deformable in response to pressure.
3. A fire-extinguisher according to claim 1 or claim 2, wherein the deformable region comprises a lower part of the container, responsive to pressure to reduce the volume of the container.is
4. A fire-extinguisher according to claim 1 or claim 2, wherein the deformable region is formed by a concertina wall.
5. A fire-extinguisher according to any of the preceding claims, wherein the inner container is formed from plastics material.
6. A fire-extinguisher according to any of the preceding claims, wherein the inner container has a thickness in the range 5mm to 0.5mm.
7. A fire-extinguisher according to any of the preceding claims, wherein the inner container has a base with integrally formed depressions for receiving fingers.
8. A fire-extinguisher according to any of the preceding claims, wherein the inner container further comprises a neck and collar portion, the neck portion having an external helical thread interrupted with vertical channels.
9. A method of manufacturing a fire extinguisher comprising placing a plastics container within a casing, reducing the volume of the plastics container, welding a base to the casing and increasing the volume of the plastics container.
10. A fire-extinguisher substantially as herein described with reference to and as illustrated in the accompanying drawings.