GB2571067A - A fire sensor, apparatus and system - Google Patents

Abstract

A fire sensor comprises at least one fibre (4, figure 8) having an electromagnetic property changeable upon contact with fire, and detection means for measuring said property. The sensor may include a layer (3) of such fibers (4, 5) arranged to cross each other at intersections (6), each fibre being individually connectible to the detection means. The fibres may have a non-conductive core material doped in a conducting agent which may itself comprise a nano material. The nano material may comprise a graphene-based doping agent, and this agent may comprise graphene oxide. The changeable electromagnetic property may be electrical resistance or surface magnetism. The sensor may include a substrate to which the fibre is attached. The substrate may comprise a thermal insulation blanket, or a fire seal. A fire sensing apparatus comprising the above sensor is also claimed, wherein detection means comprises transmission and receiving means for a test signal. An aircraft fire alarm system and an aircraft comprising said fire sensor are also claimed.

Description

The present invention relates to a fire sensor, apparatus and system adapted to deter the spread of fire.

BACKGROUND TO THE INVENTION

It is known to provide a fire resistant material such as a fire resistant blanket to deter the spread of fire in an environment. It is also known to provide fire seals to prevent the spread of fire from a fire zone on a vehicle or in other environments. On aircraft, in particular, various fire zones are difficult to monitor for fire, critical to prevent the spread of fire or both.

An example of an area which has been found susceptible to fires and where it is both difficult and expensive to monitor for fire is the cabin attic area of an aircraft. The area is hidden from view and thermal insulation blankets/films can bum undetected until a large area is damaged or until the burning area falls within the detection range of fire/smoke detectors.

Fire and smoke detectors and the complex network of wiring harness required for these add considerable unwanted weight and complexity to the aircraft.

Examples of areas on the aircraft where it is critical to prevent the spread of fire are engines, pylon ribs with fuel lines, pylon to engine interfaces and pylon to wing interfaces. In such areas, fire seals are used to prevent the spread of fire.

It is an object of the invention to provide a fire sensor which will reduce the difficulties associated with the prior art.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a fire sensor including a fibre, said fibre having an electromagnetic property changeable upon contact with fire and being connectible to detection means to detect any said change in electromagnetic property, whereby a change in electromagnetic property detected in the fibre will indicate a fire at a location of that fibre.

The fire sensor may include a layer of said fibres arranged to cross one another at intersections, said fibres being individually connectible to said detection means to detect any said change in electromagnetic property, whereby a said change in electromagnetic property detected at an intersection of two fibres will be indicative of a fire at the location of that intersection.

The at least one fibre may comprise a non-conductive core material which is preferably doped in a conducting agent. The conducting agent may comprise a nano material which may comprise a graphene-based doping agent. The graphene-based doping agent may comprise graphene oxide.

The core material is preferably non-flammable and may conveniently comprise a glass fibre or a polyvinyl fluoride fibre.

A said changeable electromagnetic property may conveniently comprise one of the group: electrical resistance and surface magnetism but may comprise any suitable electromagnetic property.

The fire sensor may include a substrate to which the at least one fibre is attached.

For any desired environment but for aircraft and other vehicles in particular, the substrate may comprise a thermal insulation blanket or a fire seal.

The fire seal may comprise elastomeric material including a layer of fire resistant reinforcement. Additionally, friction combatting lubricant may be added to promote easy sliding of the seal.

According to a second aspect of the invention, there is provided fire sensing apparatus including a fire sensor according to the first aspect and detection means, said detection means including transmission means to send a test signal to a first end of the at least one fibre of the fire sensor, receiving means to receive the test signal from a second end of the at least one fibre and analysing means to analyse the received signal and thereby detect any change in electromagnetic property of said at least one fibre.

The analyzing means may be adapted to detect any change in electromagnetic property of said at least one fibre by comparing a said received test signal with a stored test signal corresponding to an unbumt fibre and then indicating a fire if said test signal varies from said stored signal in a predetermined manner.

The apparatus may include display means to display the location of a detected fire for an observer.

According to a third aspect of the invention, there is provided an aircraft fire alarm system including fire sensing apparatus according to the second aspect and an alarm. The fire alarm system may include a fire control system including fire extinguishing means.

According to a fourth aspect of the invention, there is provided an aircraft including fire sensing apparatus according to the second aspect or a fire alarm system according to the third aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example only, with reference to the following drawings in which:Figure 1 is a schematic representation of a fire sensor according to the invention in the form of a thermal insulation blanket;

Figures 2(a) and 2(b) are a schematic representations of a fire sensor according to the invention in the form of two configurations of fire seal;

Figures 3a, 3b and 3c show an aircraft engine splitter seal in position;

Figure 4 is a graph showing normalized change in electrical resistance against fabric length or width for a fire sensor according to the invention;

Figure 5 shows schematically a fire sensing system according to the invention in use for active fire control;

Figure 6 shows schematically the fire sensing system of Figure 5 with a decision tree used by the controller shown in Figure 5;

Figure 7 shows, schematically, sensor connections on a microchip used to indicate flame position on the fire sensor, and

Figure 8 shows schematically orthogonal fibres of a fire sensor according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Figures 1 and 8 show a fire sensor according to the invention in the form of a thermal insulation blanket 1. The blanket 1 comprises a conventional layer 2 of glass fibre matting and a fire detection layer 3 according to the invention of graphene oxide doped glass fibres 4, 5 passing in orthogonal directions. The fibres 4, 5 have intersections 6 which are used to pinpoint locations of any fire detected on the sensor. It should be understood that the intersections 6 allow no electrical contact between fibres 4, 5 but merely represent positions on the sensor at which fire is deemed to exist if the two fibres 4, 5 form an intersection there. Connections are made from fibre ends 7, 8, 9, 10 to separate detection means incorporated into a controller 11 (see Figs. 5 and 6). From the fire detection layer 3 extend nominal connections 12 to the controller 11. Such connections 12 will, in practice, include connections from all fibres 4, 5 in the fire detection layer 3.

On an aircraft, in practice, such fire sensors on thermal insulation blankets will be deployed in a cabin attic area and will thus provide a fire retardant effect via the blanket and fire warning via the fire sensor which is co-extensive with the blanket.

Referring to Figures 2(a) and 2(b), there are shown, in section, two versions of a fire seal 13, 14, according to the invention. Fire seal 13 is a flat sheet in form and comprises a layer 15 of elastomeric material, here it is silicone rubber filled with high temperature stabilizing additives, two conventional layers 16, 17 of fire resistant reinforcement, for example, meta aramid, and two fire detection layers 18, 19 according to the invention. The fire detection layers 18, 19 comprise graphene oxide doped glass fabric, the glass being non-conductive by nature, and the outer fire detection layer 19 is treated with siloxane oil to reduce surface friction and may include intumescent particles (not shown here) to act as a first layer of fire containment. The graphene oxide has been chemically treated to improve its flame retardant properties.

In this example, the chemical treatment includes the addition of intumescent materials and foaming materials to the layer 19. Such treatment is carried out by techniques such as critical drying and chemical ageing.

Figure 2(b) shows an alternative configuration of fire seal in the form of a lip seal

14. Lip seal 14 is similar in configuration to the seal 22 shown in Figures 3(a), 3(b) and 3(c), discussed below.

An example of such a fire seal in use is shown in Figures 3(a), 3(b) and 3(c). Here, there is shown an aircraft engine pylon 21 on which is mounted an annular engine splitter fire seal 22 according to the invention. The fire seal 22 is manufactured according to the principles explained with reference to Figures 2(a) and 2(b), although the details of the different layers are not shown. In use, curved portion 23 of the seal 22 bears against engine component 24 and creates a fire break.

Referring now to Figure 4, there is shown a graph representing a signal sent to and received from a fire sensor according to the invention. The graph plots Sensing Fabric Length or Width against Normalized Change in Electrical Resistance. The lower trace, labelled “Normal signal”, represents a test signal sent and received from multiple fibres across the fabric length or width. The fire sensor may be a thermal insulation blanket or a fire seal.

The upper trace, labelled “Fire detecting signal”, represents a test signal sent to the same fabric. The shift in signal, as shown in the upper trace, indicates where the fire has been detected in that fabric. It will be seen that the upper trace is virtually identical with the lower trace until the ‘fire detected’ part of the signal, encircled, takes over. As the graph plots distance along or across the fabric, it is possible to determine where in the fabric the fire is detected.

In practice, the test signal received from the fibre can also be compared with a stored signal for that fibre or a similar fibre. Any difference above a given threshold can be used to determine the existence of a fire in the fibre or the presence of some other anomaly, such as a break in the fibre. This system may be used for continuous monitoring of fibres/fabric and also for calibration of the apparatus.

A similar comparison can be made between test signals sent to adjacent fabrics/ fire blankets in order to determine whether a detected fire has spread to the adjoining fabric as well.

Turning now to Figure 7, this shows, schematically, sensor connections on a microchip used to indicate presence or absence of a flame on the fire sensor. Each of the 100 diagrams in the grid represents a test signal received from a single fibre of a fire sensor according to the invention. The fibres represented show identical test signals received save for those encircled which show no signal or a modified signal, according to the specific design of the apparatus or system. The locations of those fibres with no signal or a modified signal will indicate where a fire exists in the fabric.

By this means, the fire sensor, fire sensing apparatus and fire sensing system of the invention can detect where a fire is located on a single fabric or on a series of fabrics on an aircraft. In addition, flame propagation either travelling through various fibre intersections 6 (see Figure 8) or from one fabric to the next can be detected, according to the invention.

Figure 5 shows schematically a fire sensing system according to the invention in use for active fire control. Central to the system is a controller 1 lof which further detail appears in Figure 6. The controller 11 is connected to a fire seal 13 and fire extinguishers 25, distributed throughout the aircraft in order selectively to extinguish flames wherever detected by the fire sensors, according to the invention. In addition, the controller 11 is connected to a crew warning system 26, an engine fire control system 27, an aircraft fire control system 28 and an aircraft flight management system 29. In operation, when a fire is detected by the controller 11 in a fire sensor such as the fire seal 13, it communicates with the flight management system 29, the aircraft fire control system 28, the engine fire control system 27 and an aircraft air system (not shown) to give and receive information relating to the general state of the aircraft and to the fire(s) detected. The controller 11 then selectively activates the appropriate number of fire extinguishers 25 to dowse the fire. Extinguishing is stopped once the fire sensors no longer indicate the presence of a fire to the controller 11. In addition, the controller sends a continuously updating alert to the crew 26 as to the current state of the fire(s).

Figure 6 shows detail of the decision-making used in the controller 11 when a fire is detected in one of the fire blankets 1.

The embodiments described herein are respective non-limiting examples of how the present invention and aspects of the present invention may be implemented. Any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined by the accompanying claims.

The word “or” as used herein is to be taken to mean “and/or” unless explicitly stated otherwise.

Claims (19)

1. A fire sensor including at least one fibre, said fibre having an electromagnetic property changeable upon contact with fire and being connectible to detection means to detect any said change in electromagnetic property, whereby a change in electromagnetic property detected in the fibre will indicate a fire at a location of that fibre.

2. A fire sensor according to claim 1, including a layer of said fibres arranged to cross one another at intersections, said fibres being individually connectible to said detection means to detect any said change in electromagnetic property, whereby a said change in electromagnetic property detected at an intersection of two fibres will be indicative of a fire at the location of that intersection.

3. A fire sensor according to claim 1 or 2, in which the at least one fibre comprises a non-conductive core material doped in a conducting agent.

4. A fire sensor according to claim 3, in which the conducting agent comprises a nano material.

5. A fire sensor according to claim 4, in which the nano material comprises a graphenebased doping agent.

6. A fire sensor according to claim 5, in which the graphene-based doping agent comprises graphene oxide.

7. A fire sensor according to any of claims 3 to 6, in which the core material is nonflammable.

8. A fire sensor according to any preceding claim, in which a said changeable electromagnetic property comprises one of the group: electrical resistance and surface magnetism.

9. A fire sensor according to any preceding claim, including a substrate to which the at least one fibre is attached.

10. A fire sensor according to claim 9, in which the substrate comprises a thermal insulation blanket.

11. A fire sensor according to claim 9, in which the substrate comprises a fire seal.

12. A fire sensor according to claim 11, in which the fire seal comprises elastomeric material including a layer of fire resistant reinforcement.

13. Fire sensing apparatus including a fire sensor according to any preceding claim and detection means, said detection means including transmission means to send a test signal to a first end of the at least one fibre of the fire sensor, receiving means to receive the test signal from a second end of the at least one fibre and analysing means to analyse the received signal and thereby detect any change in electromagnetic property of said at least one fibre.

14. Fire sensing apparatus according to claim 13, in which the analyzing means is adapted to detect any change in electromagnetic property of said at least one fibre by comparing a said received test signal with a stored test signal corresponding to an unburnt fibre and then indicating a fire if said test signal varies from said stored signal in a predetermined manner.

15. Fire sensing apparatus according to claim 14, including display means to display the location of a detected fire.

16. An aircraft fire alarm system including fire sensing apparatus according to claim 13, 14 or 15 and an alarm.

17. An aircraft fire alarm system according to claim 16, including fire extinguishing means.

18. An aircraft including fire sensing apparatus according to any of claims 13 to 15.

19. An aircraft including a fire alarm system according to claim 16 or 17.

Intellectual Property Office