GB2450625A

GB2450625A - Discharge valve for powder-type fire extinguisher

Info

Publication number: GB2450625A
Application number: GB0811757A
Authority: GB
Inventors: Roger Carr
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-06-28
Filing date: 2008-06-27
Publication date: 2008-12-31
Anticipated expiration: 2028-06-27
Also published as: GB0811757D0; GB0805541D0; GB2450625B; GB0712527D0

Abstract

A discharge valve comprises a reversibly deformable element 38 responsive to pressure of gas from the gas canister so as to expand. In particular the discharge valve is used in a fire extinguisher of the powder type comprising a powder-containing chamber 12 communicating with a discharge path 22, 52 leading to an outlet nozzle, a gas canister 16)and a discharge valve 20, wherein the discharge valve comprises a reversibly deformable element 38 responsive to pressure of gas from the gas canister so as to expand and temporarily block the discharge path 22, 52. In this way, sufficient time is allowed for fluidisation of powder within the chamber by the gas before discharge from the extinguisher occurs. The reversibly deformable element is responsive to gas pressures in the range 750-600psi, more preferably 750-650psi. The discharge valve further comprises a flap valve 30, 34 in communication with both the reversibly deformable element to allow gas pressure to act on is the element, and with the chamber. As gas passes through the flap valve, movement of the flap valve occurs producing a mechanical agitation of powder within the chamber, as well as agitation by flow of gas.

Description

Title: Discharge Valve for Powder-type Fire Extinguisher

Field of the invention

This invention relates to a discharge valve for a powder-type fire extinguisher.

Background to the invention

Discharge valves for powder-type fire extinguishers are described in GB 2,148,114 and GB 2,408,684. When compressed gas is released from a gas canister to discharge powder from within a fire extinguisher, the discharge valve delays the exit of the gas io to ensure the powder is in fully fluidised form from mixing with the gas before dischsrge occurs.

With discharge valves as described in GB 2,148,114 and GB 2,408,684, some of the powder remains in the fire extinguisher even after the discharge. It is an aim of the is present invention to provide an improved discharge valve which reduces the amount of powder remaining within the extinguisher after discharge.

Summary of the invention

In accordance with one aspect of the present invention, there is provided a fire extinguisher of the powder type comprising a powder-containing chamber communicating with a discharge path leading to an outlet nozzle, a gas canister and a discharge valve, wherein the discharge valve comprises a reversibly deformable element responsive to pressure of gas from the gas canister so as to expand and temporarily block the discharge path In this way, sufficient time is allowed for fluidisation of powder within the chamber by the gas before discharge from the extinguisher occurs.

The invention also lies in a discharge valve for use in a fire extinguisher, the discharge valve comprising a reversibly deformable element responsive to pressure of gas from a gas canister so as to expand and thus temporarily block a discharge path from an extinguisher.

Preferably the reversibly deforinable element comprises a sealed inflatable element with a central passageway into which gas may flow to inflate the element. The element may be in the form of a sack or a sealed tube.

s The reversibly deformable element may be responsive to gas pressures in the range 750-600psi, more preferably 750-65Opsi, and more preferably 750-700psi, expanding to block the discharge path when gas is initially released from the canister and contracting to its original size to free the discharge path as pressure reduces.

io The discharge valve may further comprise a flap valve in communication with both the reversibly deformable element to allow gas pressure to act on the element, and with the chamber. As gas passes through the flap valve, movement of the flap valve occurs producing a mechanical agitation of powder within the chamber, as well as agitation by flow of gas. Is

Preferably the discharge valve is positioned within a siphon tube communicating with the outlet nozzle.

The invention will now be described, by way of example, with reference to the following drawings in which: Figure 1 is a schematic cross-section through a fire extinguisher incorporating a discharge valve in accordance with the present invention; Figure 2 is a detailed cross-section of the discharge valve; Figure 3 is a sectional view along Ill-HI of Figure 2.

Figure 4 is a schematic cross-section through a fire extinguisher incorporating a second embodiment of the discharge valve; and Figure 5 is a detailed cross-section of the second embodiment.

Description

Figure 1 shows a schematic of an extinguisher head cap 10 for fitting onto a cylindrical fire extinguisher body with a chamber 12 containing powder 14 for use in extinguishing fires. Some of the elements are shown to an enlarged scale for viewing ease.

A generally cylindrical siphon tube comprising housing 18 and tube 19 screws into the head fitting 10 and extends down into the chamber 12, with the two sections of the siphon tube joined together by a discharge valve 20. A helical tube 22 communicates with chamber 24 directly above the gas canister 16 and extends into the top of the discharge valve 20, such that when the gas canister 16 is punctured by a firing mechanism, gas released from the canister 16 will pass along tube 22 to reach the discharge valve 20. Gas passes from the discharge valve 20 into chamber 12 to agitate the powder 14 and generate a homogenous fluid mix which passes up through tube 19 and housing 18 to be discharged from a nozzle of the extinguisher.

Figure 2 shows the discharge valve 20 and gas canister 16 in more detail. Helical tube 22 is shown entering the top of the discharge valve 20. The discharge valve 20 comprises a cylindrical collar 30 with internal passageways 32 along which gas can is travel, secured to housing 18 and tube 19 by rubber sleeve 34 held in place by a circular clip 36, and a elastomer tube 38 sealed at one end with a central passage 40 within the tube 38 communicating with the gas passageways 32 formed in the collar 30. The collar 30 and sleeve 34 together form a flap valve.

In operation, puncturing of the compressed gas cylinder 16 by the firing mechanism causes gas to be forced along tube 22 typically at a pressure of 750 psi. The gas reaches the discharge valve 20 and passes along internal passageways 32 as shown in Figures 2 and 3. The gas is at high pressure and when it passes up through passageways 32, it causes the tube 38 to inflate and expand, elastically deforming to fill the cross-sectional area of the distal end of housing 18, as shown by the dashed lines 42. This blocks the end of housing 18 and prevents any gas from flowing up housing 18 to be discharged. Instead, the gas passes out of the discharge valve 20 and into the powder within chamber 12, shown schematically by arrow 44. As the gas escapes from an aperture 46 formed between collar 30 and sleeve 34, the sleeve 34 vibrates, producing a mechanical agitation to the powder as well as the agitation produced by the gas itself.

As the gas flows into the powder, the pressure in the chamber 12 builds up, with the gas agitating the powder to create a homogenous fluidised gas powder mix. When the pressure of gas on tube 38 reduces as a result of most of the gas having passed into chamber 12, tube 38 will spring back to its original size, so clearing a path for the s pressuiised gas powder mix to travel up into housing 18. The tube 38 provides a temporary closure which is responsive to gas pressure and prevents gas passing up the siphon tube 18, 19 until sufficient time for agitation of the powder has elapsed. The tube 38 will provide approximately a four second delay before discharge occurs, by when 99 percent of the powder within the chamber 12 is in fluidised form and ready to be discharged.

A second embodiment of the discharge valve is shown in Figures 4 and 5 and this operates on the same principle as the valve shown in Figures 1-3. Discharge of gas from canister 16 passes along fluffer tube 50 causing the tube 38 to inflate and so is block tube 52 which conununicates with the discharge nozzle. The only passageway remaining open to the gas is that along tube 54 into the powder 14 held within the canister. The high pressure gas agitates the powder 14 producing a fluidised gas powder mix. As this occurs, the pressure of gas on tube 38 decreases and once the gas pressure has reduced due to the gas being distributed throughout the powder, the tube 38 deflates back to its original size, so clearing the discharge path along tube 52 and allowing the fluidised gas powder mix out of the discharge nozzle.

In the embodiment shown in Figures 4 and 5, the narrow tube 54 has two holes 56, 56' drilled at its distal end with a rubber sleeve 58 placed over the end of this tube to cover the holes, the rubber sleeve 58 held in place with a crimping ring 60. The arrangement of the holes with rubber sleeve acts as a one-way valve, allowing gas to pass out through the holes, under the rubber sleeve and into the mixture, but preventing powder mix going into the holes and so blocking the exit of gas. This arrangement is simpler than the helical tube shown in Figures 1-3 as it relies on a straight length of tubing and the discharge path of the gas is simplified.

Claims

Claims 1. A fire extinguisher of the powder type comprising a

powder-containing chamber communicating with a discharge path leading to an outlet nozzle, a gas canister and a discharge valve, wherein the discharge valve comprises a reversibly deformable element responsive to s pressure of gas from the gas canister so as to expand and temporarily biock the discharge path.
2. A fire extinguisher according to claim 1, wherein the reversibly deformable element comprises a sealed inflatable element with a central passageway into which gas flows to inflate the element.
3. A fire extinguisher according to claim 2, wherein the element is in the form of a sack or a sealed tube.
4. A fire extinguisher according to any of the preceding claims, wherein the reversibly deformable element is responsive to gas pressures in the range 750-600psi, expanding to block the discharge path when gas is initially released from the canister and contracting to its original size to free the discharge path as pressure reduces.
5. A fire extinguisher according to any of the preceding claims, wherein the discharge valve further comprises a flap valve in communication with both the reversibly deformable element to allow gas pressure to act on the element, and with the chamber.
6. A fire extinguisher according to any of the preceding claims, wherein the discharge valve is positioned within a siphon tube communicating with the outlet nozzle.
7. A discharge valve for use in a fire extinguisher, the discharge valve comprising a reversibly deformable element responsive to pressure of gas from a gas canister so as to expand.
8. A discharge valve according to claim 7, wherein the reversibly deformable element comprises a sealed inflatable element with a central passageway for receiving gas.
9. A discharge valve according to claim 7 or claim 8, wherein the element is in the form of a sack or sealed tube.
10. A discharge valve according to any of claims 7 to 9, the reversibly deformable element is responsive to gas pressures in the range 750-600psi.
11. A fire extinguisher of the powder type substantially as herein described with reference to and as illustrated in the accompanying drawings.

io
12. A discharge valve for use in a fire extinguisher substantially as herein described with reference to and as illustrated in the accompanying drawings.