GB1568467A - Fire extinguishers - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO FIRE EXTINGUISHERS (71) We, THOMAS GLOVER & CO.

LIMITED, a British Company of Hathershaw, Oldham OL8 3DX, England, do hereby declare the invention for which we pray that a Patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: The present invention relates to fire extinguishers. Conventionally, fire extinguishers are put into operation by piercing or opening the seal of an auxiliary pressure container or gas cartridge so that the pressure of the released gas then serves to expel the extinguishant medium therefrom.

The actual rate of release of the expellant gas and the consequent rate of rise of pressure inside the extinguisher is not critical for extinguishers with liquid extinguishants where the expellant gas remains in the ullage space above the liquid until all the extinguishant has been expelled. However, for extinguishers with particulate extinguishants, such as dry powders, the extinguishant discharge consists of a mixture of powder particles transported in a stream of escaping expellant gas. The efficiency of this transportation is dependent on the pressure of the expellant gas. Too low a pressure allows the gas to escape through the powder without transporting an effective proportion of powder particles and results in a thin and incomplete discharge from the extinguisher.

It is, therefore, important to reach a working pressure inside the extinguisher high enough to ensure that the expellant gas and powder particles travel together to produce an effective extinguishant discharge and to leave the least possible residue of powder in the extinguisher.

The object of the present invention is to provide a fire extinguisher in which, on activation, a working pressure can be achieved before discharge of the extinguishant therefrom occurs.

According to the present invention there is provided a fire extinguisher comprising an outlet for discharge of an extinguishant medium therefrom on activation of the fire extinguisher, the outlet being obturated by a frangible diaphragm of predetermined bursting characteristics whereby no discharge of the extinguishant medium from the extinguisher takes place after the extinguisher has been activated to release the extinguishant medium until the extinguishant medium has built up a working pressure within the extinguisher sufficient to burst the diaphragm and thereby open the outlet passage.

An example of the present invention will now be described with reference to the accompanying drawing which shows a part sectional view of an extinguishant outlet nozzle of a fire extinguisher according to the invention.

A fire extinguisher comprises a container (not shown) in which is held a fire extinguishant medium and an operating head (not shown) which seals the container and which comprises an operating mechanism whereby the extinguisher may be activated. Such an operating head and fire extinguisher is the subject of our co-pending United Kingdom Patent Application No. 16429/78 (Serial No. 1567895) of 26th April, 1978. The extinguisher additionally comprises an outlet for discharge of the extinguishant medium therefrom on activation.

The outlet comprises at least partially a flexible hose 1 for directing the flow of extinguishant medium where desired. The free end of the hose 1 is secured to a ferrule 2 which is connected to an adaptor 3. Screwfitted into the adaptor 3 is a spreader discharge nozzle 4 for the extinguish ant medium. The adaptor 3 comprises a substantially cylindrical member which has an interior shoulder to provide a seating for a frangible diaphragm 5. The diaphragm 5 is clamped in position within the adaptor 3 by an annular washer 6 and the end 7 of the spreader nozzle 4 which screws into the adaptor 3. The outlet bore 8 for discharge of the extinguishant medium is, therefore, obturated by the diaphragm 5.

The frangible diaphragm 5 may be made, for example, of a metallic foil, plastics material or graphite and has known bursting characteristics which correspond to the particular working pressure of the extinguishant medium. The minimum working pressure of any extinguishant medium can be found by experiment by those skilled in the art and in this way the characteristics of the diaphragm 5 can be specified.

In use, on activation of the fire extinguisher no discharge of the extinguishant medium takes place until the correct working pressure has been built up. Thereafter, the pressure is sufficient to burst the diaphragm 5 and allow extinguishant flow through the nozzle 4.

It will be appreciated that a frangible diaphragm arrangement as described above may be incorporated in a fire extinguisher container any form of extinguishant medium.

However, the arrangement is particularly appropriate for use with a dry powdered or particulate extinguishant medium which on activation is fluidised by a pressurised gas. In this latter case, use of the diaphragm arrangement ensures proper mixing and therefore fluidisation of the gas with the extinguishant proper before discharge.

WHAT WE CLAIM IS: 1. A fire extinguisher comprising an outlet for discharge of an extinguishant medium therefrom on activation of the fire extinguisher, the outlet being obturated by a frangible diaphragm of predetermined bursting characteristics whereby no discharge of the extinguishant medium from the extinguisher takes place after the extingisher has been activated to release the extinguishant medium until the extinguishant medium has built up a working pressure within the extinguisher sufficient to burst the diaphragm and thereby open the outlet passage.

2. An extinguisher as claimed in claim 1, in which the outlet comprises at least partially a flexible discharge hose.

3. An extinguisher as claimed in claim 2, in which the frangible diaphragm is located between a free end of the hose and a discharge nozzle attached to said free end.

4. An extinguisher as claimed in any one of claims 1 to 3, in which the frangible diaphragm comprises a metallic foil, plastics material or graphite.

5. A fire extinguisher substantially as hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. an annular washer 6 and the end 7 of the spreader nozzle 4 which screws into the adaptor 3. The outlet bore 8 for discharge of the extinguishant medium is, therefore, obturated by the diaphragm 5. The frangible diaphragm 5 may be made, for example, of a metallic foil, plastics material or graphite and has known bursting characteristics which correspond to the particular working pressure of the extinguishant medium. The minimum working pressure of any extinguishant medium can be found by experiment by those skilled in the art and in this way the characteristics of the diaphragm 5 can be specified. In use, on activation of the fire extinguisher no discharge of the extinguishant medium takes place until the correct working pressure has been built up. Thereafter, the pressure is sufficient to burst the diaphragm 5 and allow extinguishant flow through the nozzle 4. It will be appreciated that a frangible diaphragm arrangement as described above may be incorporated in a fire extinguisher container any form of extinguishant medium. However, the arrangement is particularly appropriate for use with a dry powdered or particulate extinguishant medium which on activation is fluidised by a pressurised gas. In this latter case, use of the diaphragm arrangement ensures proper mixing and therefore fluidisation of the gas with the extinguishant proper before discharge. WHAT WE CLAIM IS:

1. A fire extinguisher comprising an outlet for discharge of an extinguishant medium therefrom on activation of the fire extinguisher, the outlet being obturated by a frangible diaphragm of predetermined bursting characteristics whereby no discharge of the extinguishant medium from the extinguisher takes place after the extingisher has been activated to release the extinguishant medium until the extinguishant medium has built up a working pressure within the extinguisher sufficient to burst the diaphragm and thereby open the outlet passage.

2. An extinguisher as claimed in claim 1, in which the outlet comprises at least partially a flexible discharge hose.

3. An extinguisher as claimed in claim 2, in which the frangible diaphragm is located between a free end of the hose and a discharge nozzle attached to said free end.

4. An extinguisher as claimed in any one of claims 1 to 3, in which the frangible diaphragm comprises a metallic foil, plastics material or graphite.

5. A fire extinguisher substantially as hereinbefore described with reference to the accompanying drawing.