Patent Publication Number: US-2019184217-A1

Title: Fire sensor, apparatus and system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Indian Patent Application No. 201741044614 filed Dec. 12, 2017, the entire disclosure of which is incorporated by reference herein. 
     TECHNICAL FIELD 
     The disclosure herein relates to a fire sensor, apparatus and system to deter the spread of fire. 
     BACKGROUND 
     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 burn 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 disclosure herein to provide a fire sensor which will reduce the difficulties associated with the prior art. 
     SUMMARY 
     According to a first aspect of the disclosure herein, there is provided a fire sensor including a fiber, the fiber having an electromagnetic property changeable upon contact with fire and being connectible to a detector to detect any the change in electromagnetic property, whereby a change in electromagnetic property detected in the fiber will indicate a fire at a location of that fiber. 
     The fire sensor may include a layer of the fibers arranged to cross one another at intersections, the fibers being individually connectible to the detector to detect any the change in electromagnetic property, whereby a the change in electromagnetic property detected at an intersection of two fibers will be indicative of a fire at the location of that intersection. 
     The at least one fiber 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 fiber or a polyvinyl fluoride fiber. 
     A changeable electromagnetic property may conveniently comprise one of the group consisting of 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 fiber 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 disclosure herein, there is provided fire sensing apparatus including a fire sensor according to the first aspect and a detector, the detector including a transmitter to send a test signal to a first end of the at least one fiber of the fire sensor, a receiver to receive the test signal from a second end of the at least one fiber and an analyzer to analyze the received signal and thereby detect any change in electromagnetic property of the at least one fiber. 
     The analyzer may be adapted or configured to detect any change in electromagnetic property of the at least one fiber by comparing a received test signal with a stored test signal corresponding to an unburnt fiber and then indicating a fire if the test signal varies from the stored signal in a predetermined manner. 
     The apparatus may include a display to display the location of a detected fire for an observer. 
     According to a third aspect of the disclosure herein, 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 one or more fire extinguisher(s), device or system. 
     According to a fourth aspect of the disclosure herein, 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 disclosure herein will now be described, by way of example only, with reference to the following, example drawings, in which: 
         FIG. 1  is a schematic representation of a fire sensor according to the disclosure herein in the form of a thermal insulation blanket; 
         FIGS. 2A and 2B  are schematic representations of a fire sensor according to the disclosure herein in the form of two configurations of fire seal; 
         FIGS. 3A, 3B and 3C  show an aircraft engine splitter seal in position; 
         FIG. 4  is a graph showing normalized change in electrical resistance against fabric length or width for a fire sensor according to the disclosure herein; 
         FIG. 5  shows schematically a fire sensing system according to the disclosure herein in use for active fire control; 
         FIG. 6  shows schematically the fire sensing system of  FIG. 5  with a decision tree used by the controller shown in  FIG. 5 ; 
         FIG. 7  shows, schematically, sensor connections on a microchip used to indicate flame position on the fire sensor; and 
         FIG. 8  shows schematically orthogonal fibers of a fire sensor according to the disclosure herein. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 and 8  show a fire sensor according to the disclosure herein in the form of a thermal insulation blanket  1 . The blanket  1  comprises a conventional layer  2  of glass fiber matting and a fire detection layer  3  according to the disclosure herein of graphene oxide doped glass fibers  4 ,  5  passing in orthogonal directions. The fibers  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 fibers  4 ,  5  but merely represent positions on the sensor at which fire is deemed to exist if the two fibers  4 ,  5  form an intersection there. Connections are made from fiber ends  7 ,  8 ,  9 ,  10  to separate the detector 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 fibers  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  FIGS. 2A and 2B , there are shown, in section, two versions of a fire seal  13 ,  14 , according to the disclosure herein. 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 disclosure herein. 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. 
       FIG. 2B  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  FIGS. 3A, 3B and 3C , discussed below. 
     An example of such a fire seal in use is shown in  FIGS. 3A, 3B and 3C . Here, there is shown an aircraft engine pylon  21  on which is mounted an annular engine splitter fire seal  22  according to the disclosure herein. The fire seal  22  is manufactured according to the principles explained with reference to  FIGS. 2A and 2B , 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  FIG. 4 , there is shown a graph representing a signal sent to and received from a fire sensor according to the disclosure herein. 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 fibers 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 fiber can also be compared with a stored signal for that fiber or a similar fiber. Any difference above a given threshold can be used to determine the existence of a fire in the fiber or the presence of some other anomaly, such as a break in the fiber. This system may be used for continuous monitoring of fibers/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  FIG. 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 fiber of a fire sensor according to the disclosure herein. The fibers 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 fibers with no signal or a modified signal will indicate where a fire exists in the fabric. 
     By this, the fire sensor, fire sensing apparatus and fire sensing system of the disclosure herein 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 fiber intersections  6  (see  FIG. 8 ) or from one fabric to the next can be detected, according to the disclosure herein. 
       FIG. 5  shows schematically a fire sensing system according to the disclosure herein in use for active fire control. Central to the system is a controller  11  of which further detail appears in  FIG. 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 disclosure herein. 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). 
       FIG. 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 disclosure herein and aspects of the disclosure herein 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 disclosure herein, which is defined by the accompanying claims. 
     The subject matter disclosed herein can be implemented in software in combination with hardware and/or firmware. For example, the subject matter described herein can be implemented in software executed by a processor or processing unit. In one exemplary implementation, the subject matter described herein can be implemented using a computer readable medium having stored thereon computer executable instructions that when executed by a processor of a computer control the computer to perform steps. Exemplary computer readable mediums suitable for implementing the subject matter described herein include non-transitory devices, such as disk memory devices, chip memory devices, programmable logic devices, and application specific integrated circuits. In addition, a computer readable medium that implements the subject matter described herein can be located on a single device or computing platform or can be distributed across multiple devices or computing platforms. 
     While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a”, “an” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.