Abstract:
A device for attaching overheating detection cords, in particular to a pipe for hot gases drawn from the engine of an aircraft, including a bracket with slots into which the cords, surrounded by silicone coils, are placed. Overhanging portions on the edges of the slots and flanges projecting from the base of the slots hold the coils against accidental extraction forces.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of French patent application No. 14 50623 filed on Jan. 24, 2014, the entire disclosure of which is incorporated by reference herein. 
     BACKGROUND 
     The present disclosure relates to a detection-cord attachment device, in particular for an overheating and leak detection system in an aircraft. 
     Such systems, often abbreviated to OHDS (overheating detection system), are used to detect and locate local temperature increases (overheating) due to accidental leaks in gas pipes carrying hot gases taken from the engines of the aircraft to other parts of the aircraft. The detection cords are mounted on attachment devices provided along the gas pipes. 
     In a known design, the attachment devices include brackets for thermal-detection cords (for example eutectic cords) provided with slots into which the cords, surrounded by a coil of isolating material (such as silicone), are placed, and closings (collars, clamps or attachment clips) that are subsequently closed on the brackets and screwed down such as to clamp the cords and hold same in the slots. The flexible silicone coils absorb the deformations caused by clamping and isolate thermal-detection cords from the metal elements of the attachment device. 
       FIG. 1  shows an existing example of an overheating detection system in which a pressurized stream of hot gas is drawn from the jet engines  1  via pipes  2  extending along the wings and the fuselage, before being carried to the actuators  3 . The valves  4  installed on the pipes  2  regulate the gas flow rates in the pipes  2 . These valves also enable certain portions of the pipes  2  to be isolated in the event of a gas leak. The overheating detection system includes cords  5 , arranged in loops, that extend along the pipes  2 . An electrical signal runs through the cords  5 . The cords  5  are eutectic cords comprising a core (water+salt mix) designed or configured to melt when they come into contact with the hot gas leaking out of the pipes  2 . The modification of the structure of the core of the cord  5  locally modifies (at the location of the leak) the electrical resistance of the cord and therefore the electrical signal running through the cord. This modification is detected, thereby identifying the zone. 
       FIG. 2  shows that the cords  5  are attached close to the pipes  2  by attachment devices  6  arranged in places. In practice, the pipes  2  are covered with isolating glass wool to prevent heat losses and an outer metal cover, or a flexible isolation sleeve on the connections between pipes  2 . This cover or this sleeve is provided with ventilation holes  7  through which the gas leaking from the pipes  2  can escape. Placing the cords  5  in front of the ventilation holes  7  enables leaks to be detected. 
     In a conventional design, shown in  FIG. 3 , the attachment devices  6  are mounted on metal butterfly brackets  8  installed on the outside of the pipes  2 , the isolating lining  9  of same and the metal cover  10  of same. The attachment devices  6  each include a bracket  11  mounted on the metal butterfly bracket  8  using a bolt  12  and a spacer  13  holding the bracket  11  at a given distance from the metal butterfly bracket  8  and from the duct  2 . The bracket  11  includes a lower cradle  14  designed or configured to include two slots  16  opening out onto the side opposite the pipe  2 . The cords  5  are placed in the slots  16 , and the slots  16  of a given bracket  11  receive two portions of cords  5 . To effect clamping, these portions of cords  5  are surrounded by flexible coils  15 , and it is these coils  15  that are clamped. Closings  17  are used for this purpose, articulated at the sides of the cradle  14  using hinges  18  and held in place using attachment screws  19 . The drawbacks of this attachment device  6  are a degree of complexity of the bracket  11  and the need to use attachment screws  19  to clamp the cords  5 . A tool is therefore required for clamping. 
     Such devices present assembly issues, in particular installing the coils with the required degree of precision, or reaching some of the brackets with the tools required to clamp the closings in restricted or difficult-to-access areas, such that the attachment devices are not always properly closed, and support points can become detached, and in any case the complexity of the assembly makes assembly relatively slow and difficult, even when it is completed successfully. 
     It is intended to improve such attachment devices by replacing the known bracket with another, such as to guarantee precise mounting of the cords in less time and without using tools to install the cords fitted with coils. 
     SUMMARY 
     In general terms, the subject matter disclosed herein relates to a device for attaching longitudinal detection cords in slots including coils surrounding portions of the cords, a bracket containing slots for receiving the coils, the slots passing through the whole of the bracket between two extremities and including one opening, extending from one side of the bracket, between the two extremities, the brackets including a holder for holding the coils in the slots, the holder including projections located on a wall of the slots, and overhanging stops located on opposing edges of the opening of the slots and overhanging the slots. 
     The coils are thus inserted into the slots, taking advantage of the flexibility of same, which enables them to be deformed to enable such insertion; and they are then held against extraction movement, through the openings of the slots, by overhanging stops on the edges of the slots, and against translational movement, by the projections. Consequently, no tools are required. The brackets, which may be one-piece, are simple and cheap to manufacture, and they may be very light. They may therefore be made of any material that can be cast, and weigh only a few grams. 
     The overhanging portions may include opposing pairs on opposing edges of the opening of the slot; or groups of three, a first stop being located on one of the edges and the two other stops being located on another of the edges on either side of the first stop. 
     The projections may be flanges extending over a back face of the slots and opposing sides of the slots located at the end sections of the slots to form stops for the coils, or be distributed along the slots in order to compress the coils and to prevent the translational movement of same by friction. 
     Some of the brackets may be simple brackets containing a single coil of a single cord or several cords in parallel, or they may contain several coils of a single cord separated by a coil-less length of cord also contained in the slot. These latter brackets may notably include elbow brackets causing the cord to curve in a precise shape and guaranteeing a precise position for the elbow. 
     Another aspect of the subject matter disclosed herein is a pipe for drawing hot gases from an engine of an aircraft comprising a wall with at least one vent, characterized in that it includes, on the wall, a plurality of the devices described above, each bracket being attached to the pipe, on the wall and opposite a vent and the cords being designed or configured to detect overheating as a result of leaks of the hot gases. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The different aspects, features and advantages of the subject matter disclosed herein are described below using the following figures, which illustrate different embodiments of same: 
         FIG. 1  illustrates an OHDS system; 
         FIG. 2  illustrates a fragment of this system; 
         FIG. 3  illustrates a known attachment device; 
         FIGS. 4, 5 and 6  illustrate a first embodiment of the subject matter disclosed herein; 
         FIGS. 7 and 8  illustrate a second embodiment of the subject matter disclosed herein; 
         FIGS. 9 and 10  illustrate a third embodiment of the subject matter disclosed herein; 
         FIG. 11  illustrates a fourth embodiment of the subject matter disclosed herein; and 
         FIG. 12  illustrates a fifth embodiment of the subject matter disclosed herein. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 4, 5 and 6  below illustrate a first embodiment of the subject matter disclosed herein. The bracket  11  in the prior-art embodiment is replaced by a one-piece bracket  20  including two slots  21  that open out onto the side opposite the pipe  2  and that have a generally U-shaped section, with the parallel sides connecting to a back face via a curve matching the curve of the coils  15 . The edges  22  and  23  of the slots  21  are provided, at certain points, with an overhanging stop  24  and  25 . In the example illustrated, there is an overhanging stop on each of the edges  22  and  23  of each slot  21 , and it is located at the center of these edges  22  and  23 . A moderate effort during assembly, exerting pressure on the coils  15 , is sufficient to insert same in the slots  21 , through the overhanging stops  24  and  25 . As clearly shown in  FIG. 5 , the overhanging stops  24  and  25  cover a portion of the coils  15  when they are installed in the slots  21 , thereby preventing same from being extracted when the attachment device according to the subject matter disclosed herein is in use. 
     The slots  21  also include flanges  26 , for example two flanges, projecting in an arc from the base of the slots  21  to locally compress the coils  15  and prevent the translational movement of same along the slots  21 . The flanges  26  and the overhanging stops  24  and  25  therefore hold the coils  15  in place, preventing all foreseeable movement of same, unless a deliberate effort is applied to extract same from the slots  21 . The flanges  26  may be placed beneath the extremities of the overhanging stops  24  and  25 , as shown, in order to properly clamp the coils  15 . 
       FIG. 6  shows the assembly of the bracket  20  on the metal butterfly bracket  8  by a bolt  27 . A spacer similar to the spacer  13 , but not shown here, can also be provided between the bracket  20  and the metal butterfly bracket  8 . 
     A second embodiment is described using  FIGS. 7 and 8 , in which the bracket is indicated with reference sign  32 . It differs from the first embodiment in that the overhanging stops  24  of one of the edges  22  of each of the slots  21  are replaced by a pair of overhanging portions  30  and  31  on this edge  22 . The overhanging stops  30  and  31  are positioned on either side of the overhanging stop  25 , which remains on the other edge  23  of each of the slots  21 . In this embodiment, the flanges  26  can, in general, advantageously be placed beneath the overhanging stops  24 ,  25 ,  30  or  31  or beneath the extremities of same. 
     The overhanging stops  24 ,  25 ,  30  or  31  shown here are lips with a curved contour that are wider in the center than at the extremities. 
     A variant of the two embodiments is illustrated in  FIGS. 9 and 10 . The bracket  11  in the first embodiment described is marked in this case with reference sign  28  and is different from the previous one in that the flanges  26  are replaced by semi-circular projections at the two extremities of the slots  21 ; the stops  29  prevent the movement of the coils  15 , the length of which therefore corresponds to the distance between the stops  29  on each of the slots  21 , such an arrangement making it possible to position the coils  15  more precisely and also to hold them more firmly than with the friction forces used in the embodiment described above. 
     A third embodiment is described using  FIG. 11 ; the bracket  40  is still one-piece and is strip-shaped with two slots  41  similar to the slots  21  described above. Each of the slots  41  is provided with a holder for holding the coils  15 , such as overhanging portions  24 ,  25 ,  30 ,  31 , and flanges  26 , located approximately beneath these overhanging portions, in sufficient number to enable same to receive several coils  15 , specifically four in the embodiment shown. 
     A fourth embodiment is described using  FIG. 12 . The bracket  33  is elbow shaped and includes two end portions  34  and  35 , each of which is similar to the one in one of the preceding embodiments, and an intermediate rounded portion  36 . These end portions  34  and  35  contain a coil  15  in each of the slots of same, and the intermediate portions of the cords  5  extend in the rounded portion  36  from one coil  15  to the next. The rounded portion  36  includes slots  37  that extend the slots from the end portions  34  and  35  to contain these intermediate portions. In order to prevent the weight of this more voluminous bracket  36  from increasing, it is advantageous that the slots  37  be hollowed out at the base, since they are not required to support the cords  5 . The center  38  of the rounded portion between the slots  37  can also be hollowed out. A similar layout may be adapted for the embodiment in  FIG. 11 . One of the end portions  34  has a central hole  39  to receive the attachment bolt, such as  27 . This layout enables the cords  5  to be given very precisely shaped and positioned elbows, since the positions of the flexible coils  15  on either side of this elbow are perfectly defined. 
     Although individual attachment devices such as the ones in the first two embodiments may be preferred, on account of their lighter weight and ease-of-use, attachment devices that guide longer portions of the cords may also be used since fewer metal butterfly brackets  8  are required to hold same on the pipes  2 . 
     In the third and fourth embodiments, it is advantageous that the base of the slots  41 , if not hollowed out as shown in  FIG. 12 , be provided with ventilation holes  42  (shown only in part) to enable the gases leaking from the pipes  2  to reach the portions of the cords  5  not covered by a coil  15 , thereby enabling leaks to be detected. 
     While at least one exemplary embodiment of the present disclosure has been shown and described, 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 the disclosure described herein. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, and the terms “a” or “one” do not exclude a plural number. Furthermore, characteristics or steps which have been described with reference to one of the above exemplary embodiments may also be used in combination with other characteristics or steps of other exemplary embodiments described above.