GB2250435A

GB2250435A - Nozzle for discharging liquid fire extinguishant

Info

Publication number: GB2250435A
Application number: GB9026628A
Authority: GB
Inventors: David Nicholas Ball; Simon John Davies
Original assignee: Kidde Graviner Ltd
Current assignee: Kidde Graviner Ltd
Priority date: 1990-12-07
Filing date: 1990-12-07
Publication date: 1992-06-10
Also published as: GB9026628D0; WO1992010238A1

Abstract

A nozzle for discharging liquid fire extinguishant has a temperature-responsive control element (29, 30) for controlling a flow of extinguishant from the nozzle in response to ambient temperature. The nozzle has a restrictor (28) for partially blocking an outlet orifice (22) of the nozzle which is operatively coupled to the temperature-responsive element (29, 30) which may be a gas-filled bellows (29) or a bi-metallic strip or disc (30). A valve for use with a nozzle for discharging liquid fire extinguishant has a coil spring (53) made from shape memory effect metal which controls the position of a valve member (45) in response to ambient temperature.

Description

NOZZLE FOR DISCHARGING LIOUID FIRE EXTINGUISHANT This invention relates to a nozzle for discharging liquid fire extinguishant, especially, though not exclusively, a nozzle for discharging water.

Such nozzles have particular, though not exclusive, application in water spray systems installed, for example, in the passenger cabins of aircraft.

According to the invention, there is provided a nozzle for discharging liquid fire extingishant, incorporating means for controlling the flow of the extingishant from the nozzle in response to the ambient temperature.

Preferably, the extingishant is water.

In one embodiment of the invention, the temperatureresponsive controlfneans comprises a material that blocks the inlet orifice or orifices of the nozzle, the material being selected to melts at a predetermined ambient temperature whereby to -permit a flow of extingishant from the nozzle. The material may, for example, be a wax.

In a further embodiment of the invention, the temperatureresponsive control means comprises a material that blocks the inlet orifice or orifices of the nozzle, the material being selected to become soluble in water, or to soften in the presence of water, at a predetermined ambient temperature, whereby to permit a flow of extinguishant from the nozzle.

This form of temperature-responsive control means suffers from the drawback that its operation is irreversible; that is to say, the flow of extingishant, permitted by the melting of said material, cannot be reduced or terminated in response to a subsequent fall of ambient temperature.

Therefore, in a preferred embodiment of the nozzle, the temperature responsive control means is arranged to vary the flow of extingishant over a range of flow rate.

By this means, the nozzle can discharge the extinguishant at a relatively high flow rate when the ambient temperature is high, as when a fire in the vicinity of the nozzle is at its height, and the flow rate can be gradually reduced, possibly to zero, in response to the fall of ambient temperature that occurs when the fire is brought under control.

This form of temperature-responsive control means enables efficient utilization of the available extingishant and is especially beneficial if the supply of extinguishant is limited, as in the case of an aircraft water supply system having an on-board water supply vessel.

The temperature-responsive control means may be effective to vary the flow of extinguishant from the nozzle over a continuous range of flow rate and, to that end, the control means may comprise a restrictor arranged to block an outlet orifice of the nozzle to a variable extent in dependence on the ambient temperature. The control means may include a temperature responsive member arranged to displace the restrictor with respect to the orifice, and the temperature responsive member may, for example, be a gas-filled bellows, or a bi-metallic strip, operatively connected to the restrictor.

In another embodiment of the invention, the control means is effective to vary the flow of extingishant between two or more discrete flow rates - for example, a high flow rate and a low flow rate or a high flow rate and zero. In this case, the temperature responsive member, operatively coupled to the restrictor, could be a bi-metallic strip, or an element made from memory metal, that can switch between two stable positions at a predetermined ambient temperature; that is to say, a first stable position (corresponding to the low flow rate or zero) and a second stable position (corresponding to the high flow rate). In order to achieve a greater variety of different flow rates several such strips or elements, each responsive to a respective predetermined ambient temperature, could be used.

The temperature responsive member may be located within the body of the nozzle. However, in some operational situations it may be preferable to locate the temperature responsive member outside the nozzle body so as to be in more intimate contact with the ambient air.

Embodiments of the invention are now described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a longitudinal cross-section view through a water discharge nozzle in accordance with the invention; Figure 2 shows a longitudinal cross-sectional view through another water discharge nozzle according to the invention; and Figure 3 shows a longitudinal cross-sectional view through a yet further example of a water discharge nozzle according to the invention.

Figure 1 shows a water discharge nozzle having a simple open/closed operation.

The nozzle comprises a cylindrical housing 10 connected to a water supply inlet 11 and having an end wall 12 formed with several outlet orifices 13. In the closed condition of the nozzle each outlet orifice is blocked by a solid mass 14 of material that prevents water from being discharged by the nozzle. The material blocking the outlet orifices 13 is chosen to have a relatively low melting temperature (typically in the range 400 - 0 80 C) and is preferably a wax i.e. a solid having a relatively low melting temperature typically comprising saturated paraffinic hydrocarbons. Other waxes may be used e.g. those based on natural esters or on poly(ethylene oxides).

In the event of a fire, the ambient temperature will rise causing the wax to melt and the nozzle to assume the open condition thereby allowing water to be discharged. More than one type of wax may be used to block the several orifices of a single nozzle so that the flow rate is progressively increased if the temperature continues to rise. This form of nozzle has the disadvantage that its operation is irreversible - the flow rate cannot be reduced or terminated in response to a subsequent fall of ambient temperature.

The nozzle shown in Figure 2 enables the flow of water to be varied over a continuous range of flow rate in response to changes of ambient temperature.

Referring to the drawing, the nozzle comprises a nozzle body 20 having an inlet 21 and an outlet orifice 22 provided in an end wall 23 of the nozzle body.

In use, water flows around a cylindrical valve member 24 and exits the outlet orifice as a spray. The valve member has a helical, ribbed formation on its exterior surface for inducing swirling as the water approaches the outlet orifice, creating a spray in the form of a hollow cone.

The valve member has an axial shaft 25 located in a cylindrical socket 26 of a circumferentially-apertured support member 27 and is also formed with a restrictor in the form of a pip 28 which is arranged to be in axial alignment with the outlet orifice so as to be capable of at least partially blocking the outlet orifice.

The nozzle has a temperature responsive element in the form of a sealed, gas-filled bellows 29 which is mounted on the support member 27 and connected to the support shaft of the valve member, as shown. In operation of the nozzle, the bellows can expand and contract (as indicated by arrow A) in response to a respective rise and fall of ambient temperature whereby to vary the axial position of the restrictor in the outlet nozzle and exercise control over the flow of water through the nozzle. If desired, the pip 28 could be suitably profiled to obtain a desired variation of flow rate as a function of the ambient temperature.

In the embodiment of Figure 3, the temperature responsive element is a bi-metal strip 30, or alternatively an element made from memory metal, that can switch between two stable positions only at a predetermined ambient temperature - a first position I (shown in solid outline) and a second position II (shown in broken outline). This causes a corresponding change in the axial position of the restrictor enabling the nozzle to switch between a high flow rate (corresponding to position I) and a low flow rate (corresponding to position II). In order to achieve a greater variety of different flow rates several such strips, or elements, each responsive to a respective predetermined ambient temperature, could be used.

It may be advantageous in some conditions to configure such a nozzle so that the temperature responsive element is located outside the nozzle body so that it is in better thermal contact with the ambient air and is less affected by the presence of water within the nozzle.

In the case of a water spray system for aircraft, it is known that the effectiveness of the spray is to wet combustible material adjacent to where the fire is gaining ingress thereby to prevent the spread of an external or localised fire.

It will be appreciated that the discharge nozzles described with reference to the drawings are merely exemplary of the nozzle systems that could be devised in accordance with the present invention.

Claims

1. A nozzle for discharging liquid fire extinguishant, incorporating means for controlling a flow of extinguishant from the nozzle in response to the ambient temperature.

2. A nozzle as claimed in claim 1, wherein the temperature-responsive control means comprises a material that blocks the outlet orifice or orifices of the nozzle, the material being selected to melt at a predetermined ambient temperature whereby to permit a flow of extinguishant from the nozzle.

3. A nozzle as claimed in claim 2, wherein the material is a wax.

4. A nozzle as claimed in claim 1, wherein the temperature-responsive control means is arranged to vary the flow of extinguishant over a range of flow rate.

5. A nozzle as claimed in claim 4, wherein the temperature-responsive control means is effective to vary the flow of extinguishant over a continuous range of flow rate.

6. A nozzle as claimed in claim 5, wherein the temperature-responsive control means comprises a restrictor arranged to block an outlet orifice of the nozzle to a variable extent in dependence on the ambient temperature.

7. A nozzle as claimed in claim 6, wherein the temperature-responsive control means includes a temperature-responsive member arranged to displace the restrictor with respect to the outlet orifice in dependence on the ambient temperature.

8. A nozzle as claimed in claim 7, wherein the temperature-responsive member is a gas-filled bellows, or a bi-metal strip, operatively coupled to the restrictor.

9. A nozzle as claimed in claim 4, wherein the control means is effective to vary the flow of extinguishant between two or more discrete flow rates.

10. A nozzle as claimed in claim 9, wherein the control means comprises a restrictor arranged to block an outlet orifice of the nozzle to a variable extent in dependence on the ambient temperature.

11. A nozzle as claimed in claim 10, wherein the temperature-responsive control means includes a temperature-responsive member arranged to displace the restrictor with respect to the outlet orifice in dependence on the ambient temperature.

12. A nozzle as claimed in claim 11, wherein the temperature-responsive member is a bi-metallic strip, or an element made from a memory metal, operatively coupled to the restrictor.

13. A nozzle as claimed in any preceding claim for discharging water.

14. A nozzle as claimed in any preceding claim, wherein the minimum flow rate is zero.

15. A nozzle as claimed in any one of claims 4 to 14, wherein the temperature responsive means is located external to the nozzle body.

16. A water spray system incorporating one or more nozzles as claimed in any preceding claim.

17. A water spray system as claimed in claim 16 for use in an aircraft.

18. A nozzle substantially as herein described with reference to the accompanying drawings.