Patent Publication Number: US-2017370469-A1

Title: Conductive sealant member

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from U.S. provisional application No. 62/109,792 filed Jan. 30, 2015, the entire contents of which are incorporated by reference herein. 
    
    
     FIELD OF THE APPLICATION 
     The application relates generally to electrical grounding and moisture sealing in aircraft and, more particularly, to a conductive sealant for sealing a connection between two aircraft components while allowing conductivity at the connection. 
     BACKGROUND OF THE ART 
     A known way to provide electrical protection for aircraft wires and wire bundles is to position the wires near a grounded, electrically conductive substrate. Typically, the substrate is made from metal, such as a metallic fuselage skin, because metal materials are excellent conductors. In addition, metal materials function well to protect electrical signals in wires from being influenced by EM and RF interference. 
     When the fuselage skin is made of a material which is not sufficiently conductive (e.g. composite material), the wires may be placed adjacent a ground plane under floor panels to offer the adequate protection to the wires against the EM and RF interference, for example because of space requirements. Aircraft floor panels containing a ground plane typically include a metal to metal connection with the supporting floor beams to provide a bonding interface in order for the ground plane to be effective. The floor beam/floor panel interfaces usually require sealing to prevent water or other fluids from leaking under the floor panels, such as to mitigate the risks of corrosion. 
     One known method of floor panel assembly includes providing seals at the floor beam/floor panel interfaces and grounding the floor panels through metal brackets interconnecting the floor beams and floor panels on each side of the sealed connection. However, installation or replacement of such brackets may be difficult and/or time consuming, and/or the brackets may be damaged during installation and maintenance. 
     Other sealingly connected elements of aircraft also require conduction therebetween, for example for grounding purposes. 
     SUMMARY OF THE APPLICATION 
     In one aspect, there is provided a sealing member for a connection between two aircraft components, the sealing member comprising: a body having first and second opposed contact surfaces each contacting a respective one of the two aircraft components, and first and second opposed side surfaces extending between and interconnecting the contact surfaces, the body having a thickness defined between the contact surfaces and a width defined between the side surfaces, the body including: a conductive portion extending across the thickness of the body and defining part of each of the contact surfaces, the conductive portion extending along the width of the body from a first location to a second location, the first and second locations being inwardly spaced with respect to the first and second side surfaces; a first sealing portion extending across the thickness of the body and defining the first side surface, the first sealing portion extending along the width of the body from the first side surface to the conductive portion, the first sealing portion defining part of each of the contact surfaces from the first side surface to the conductive portion; and a second sealing portion extending across the thickness of the body and defining the second side surface, the second sealing portion extending along the width of the body from the second side surface to the conductive portion, the second sealing portion defining part of each of the contact surfaces from the second side surface to the conductive portion; wherein the conductive portion is more conductive than the first and second sealing portions; and wherein the first and second sealing portions are made of a sealing material. 
     In a particular embodiment, the contact surfaces are covered by an adhesive. The adhesive may be releasably engaged to a respective backing paper covering each contact surface. 
     In another aspect, there is provided a sealed component assembly within an aircraft, comprising: first and second components each having a surface, the surfaces of the first and second components facing one another; a sealing member extending between the facing surfaces of the first and second components, the sealing member including a conductive portion sandwiched between first and second sealing portions, with: the first and second sealing portions extending between and in contact with the facing surfaces of the first and second components, the first and second sealing portions being made of a sealing material; and the conductive portion in contact with conductive regions of the facing surfaces of the first and second components and defining an electrical connection therebetween, the conductive portion being more conductive than the first and second sealing portions. 
     In a particular embodiment, the first and second components are connected by fasteners extending through one or both of the first and second sealing portions. 
     In a particular embodiment, the first component is a floor panel with a ground plane defining the conductive surface of the floor panel, and the second component is a floor beam supporting the floor panel. 
     In a further aspect, there is provided a grounded floor assembly for an aircraft, the assembly comprising: a floor panel having a bottom surface; a conductive floor beam supporting and connected to the floor panel; a sealing member between the floor panel and the floor beam, the sealing member including a conductive portion sandwiched between first and second sealing portions; wherein: the first and second sealing portions extend between and in contact with the bottom surface of the floor panel and a surface of the floor beam, the first and second sealing portions being made of a sealing material; and the conductive portion extends in contact with conductive regions of the bottom surface of the floor panel and the surface of the floor beam and defines an electrical connection therebetween, the conductive portion being more conductive than the first and second sealing portions. 
     In a particular embodiment, the floor panel and floor beam are connected by fasteners extending through one or both of the first and second sealing portions. 
     In a particular embodiment, the assembly further comprises an adhesive between the sealing member and the bottom surface of the floor panel, and/or between the sealing member and the surface of the floor beam. 
     In a particular embodiment of any of the above, the conductive portion has a resistivity of at most 10 −6  Ω·m. 
     In a particular embodiment of any of the above, the first and second sealing portions have a resistivity of at least 10 6  Ω·m. 
     In a particular embodiment of any of the above, the conductive portion and the first and second side portions include a common base material. The conductive portion may include conductive fillers within the base material that form a conductive path between contact surfaces of the conductive portion. The conductive fillers may include at least one of a mesh material, fibers, nanoparticles and powders. 
     In a particular embodiment of any of the above, the conductive portion includes metal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference is now made to the accompanying figures in which: 
         FIG. 1  is a schematic tridimensional view of an aircraft; 
         FIG. 2  is a schematic cross-sectional view of the fuselage of an aircraft such as shown in  FIG. 1 ; 
         FIG. 3  is a schematic top plan view of a floor panel attached to a floor beam with a conductive sealing member therebetween, in accordance with a particular embodiment; 
         FIG. 4  is a schematic cross-sectional view of the panel, beam and conductive sealing member of  FIG. 3 , in accordance with a particular embodiment; and 
         FIG. 5  is a schematic top plan view of a conductive sealant, in accordance with a particular embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings and more particularly to  FIG. 1 , an aircraft is shown at  1 , and is generally described to illustrate some components for reference purposes in the present disclosure. The aircraft  1  has a fuselage  2  having a fore end at which a cockpit is located, and an aft end supporting a tail assembly, with the cabin generally located between the cockpit and the tail assembly. The tail assembly comprises a vertical stabilizer  3  with a rudder, and horizontal stabilizers  4  with elevators. The tail assembly has a fuselage-mounted tail, but other configurations may also be used for the aircraft  1 , such as cruciform, T-tail, etc. Wings  5  project laterally from the fuselage. The aircraft  1  has engines  6  supported by the wings  5 , although the engines  6  could also be mounted to the fuselage  2 . The aircraft  1  is shown as a jet-engine aircraft, but may also be a propeller aircraft. 
       FIG. 2  is a schematic cross-section of the aircraft fuselage  2 . The floor includes a plurality of floor panels  10  supported by floor beams  12 , which are spaced from one another and extend along the longitudinal axis of the aircraft  1 . Cross beams (not shown) extend laterally between the sides of the fuselage  2  and connect the floor beams  12  together to form a checkerboard lattice under the floor within the cabin of the aircraft  1 . 
     The aircraft  1  includes wire bundles  14 , for example to transfer power to one or more of the operational components within the aircraft  1 , to transmit electrical signals that are processed by one or more of the devices on the aircraft  1 , etc. It is desirable to provide shielding so that the wires in the wire bundles  14  are insulated (or isolated) from EM and RF influences, which may impact upon the performance and/or operation of the wires in the wire bundles  14  in addition to interfering with one or more components on board the aircraft  1 . 
     The floor beams  12  are conductive, for example made from metal such as aluminum or an aluminum alloy, and provide some degree of grounding and protection against EM and RF interference. To provide protection to the wire bundles  14  that are spaced from the floor beams  12  at a distance greater than the protective distance established by the floor beams  12 , the aircraft  1  includes ground planes  16  that are positioned beneath the floor, for example forming the bottom surface of the floor panels  10 , positioned above and adjacent to the wire bundles  14 . The ground planes  16  are made from a conductive material, for example made from metal such as aluminum or an aluminum alloy. The wire bundles  14  are positioned sufficiently close to the ground planes  16  so that they benefit from the electrical protection established by the ground planes  16 . The ground planes  16  may define part or the entire bottom surface of the floor panels  10 . 
     In a particular embodiment, the floor panels  10  are removably connected to the floor beams  12 , thereby providing access to the wire bundles  14  positioned thereunder. 
     In a particular embodiment, the floor panels  10  are made of material having a relatively low conductivity when compared to metal, for example composite material, and the ground plane  16  at the bottom surface of each panel  10  is formed by a thin layer of conductive material (for example, with a thickness of approximately 0.01 inch or 0.254 mm; a thicker or thinner ground plane is also possible) and may include a plurality of holes cut therethrough. The presence of holes within the ground plane  16  may help to reduce the weight of the aircraft  1 . Alternately, each ground plane  16  may be continuous as shown, i.e. without any holes defined therein; such a configuration may help to improve the shielding protection provided to the adjacent wire bundles  14 . In a particular embodiment, each ground plane  16  is provided in the form of a metal foil affixed to the floor panel  10  to define the bottom surface thereof. 
     Conduction is required between the bottom surface (ground plane  16 ) of the floor panel  10  and the contacting surface of the floor beam  12 , to provide for proper shielding of the adjacent wire bundles  14 . Moreover, metal to metal interfaces need to be sealed from moisture (spilled liquids, condensation, etc.) which could promote corrosion at the interface. The connection between the floor panel ground plane  16  and the floor beam  12  is thus sealed by a conductive sealing member  20  received between the floor panel  10  and the floor beam  12 , as shown in  FIGS. 3-4 . 
     Referring to  FIGS. 3-5 , the sealing member  20  includes a conductive portion  22  sandwiched between first and second sealing portions  24 ,  26 . The sealing portions  24 ,  26  are made of a fluid-tight or sealing material (i.e. material preventing the passing of fluid therethrough), for example a silicon-based material; alternate materials are also possible, including, but not limited to, suitable polymer-based, plastic-based and elastomer-based materials. In a particular embodiment, the two sealing portions  24 ,  26  are made of different sealing materials from one another. The conductive portion  22  is more conductive than the sealing portions  24 ,  26 , and sufficiently conductive to form an adequate electrical connection between the ground plane  16  and the floor beam  12 . The conductive portion  22  can be made of, or can include, for example a suitable metal; alternate materials are also possible. In a particular embodiment, the conductive and sealing portions  22 ,  24 ,  26  are made of a common base material having suitable sealing properties, for example a silicon-based sealing material, and the conductive portion  22  further includes conductive fillers, for example in the form of conductive mesh, conductive fibers, conductive nanoparticles or conductive powder. 
     In a particular embodiment, the conductive portion  22  has a resistivity of at most 10 −6  Ω·m. In a particular embodiment, the sealing portions  24 ,  26  are considered to be non-conductive, with a resistivity of at least 10 6  Ω·m. 
     Referring particularly to  FIG. 4 , the sealing portions  24 ,  26  extend between and in contact with facing surfaces of both the ground plane  16  and the top surface  28  of the floor beam  12 , to prevent moisture from reaching the conductive portion  22 . The conductive portion  22  extends between and in contact with the ground plane  16  and the top surface  28  of the floor beam  12 , to define the electrical connection therebetween. It is understood that the facing surfaces of the ground plane  16  and of the floor beam  12  contacting the sealing member  20  are conductive at least along the region contacting the conductive portion  22  of the sealing member  20 . In a particular embodiment, the floor beam  12  is treated to remove any coating/paint from the top surface  22 , at least along the region thereof which will contact the conductive portion  22 . Accordingly, the ground plane  16  is suitably grounded via the network of supports defined by the floor beams  12  and the cross beams (among other components in the aircraft  1 ). 
     It is understood that the facing surfaces contacting the sealing member  20  may also be conductive in the regions contacting the sealing portions  24 ,  26 ; alternately, one or both of the facing surfaces may be non-conductive or less conductive (e.g. coated, painted) in the regions contacting the sealing portions  24 ,  26 , as long as both facing surfaces are conductive in the region contacting the conductive portion to ensure conduction therebetween. 
     In a particular embodiment, abutting sealing members  20  are provided in contact with the ground plane  16  to form a closed perimeter around the entire periphery of each floor panel  10 , along the connections to the floor beams  12  and cross-beams supporting the floor panel  10 . Each floor panel  10  is thus connected to its supporting structure in a fluid-tight matter. Sealing members  20  may also overlap at junctions between floor beams  12  and cross-beams. 
     As can be seen more clearly in  FIG. 4 , the sealing member  20  shown thus has a body with two opposed contact surfaces  30 , for contacting the facing surfaces of the connected elements defining the connection to be sealed. The sealing member  20  also includes opposed side surfaces  32  extending between and interconnecting the contact surfaces  30 . The conductive portion  22  extends across the thickness t of the body to define part of each of its contact surfaces  30 , and extends along the width w of the body between two locations a, b inwardly spaced from the side surfaces  32 . In embodiments where conduction is provided through fillers, the fillers are configured and disposed to define conductive path(s) between the contact surfaces  30 . 
     In use, the side surfaces  32  are susceptible to being exposed to moisture. The two sealing portions  24 ,  26  thus each define one of the side surfaces  32  of the body, and extend along the width w of the body from the respective side surface  32  to the conductive portion  22 , so that the sealing portions  24 ,  26  insulate the conductive portion  22  from moisture contacting the side surfaces  32 . The sealing portions  24 ,  26  also extend across the thickness t of the body and define the contact surfaces  30  between the respective side surface  32  and the conductive portion  22 , so that the sealing portions  24 ,  26  act to prevent moisture from reaching the part of the contact surfaces  30  defined by the conductive portion  22 . The interface between the facing surfaces of the connected elements and the conductive portion  22  is thus sealed on each side by the sealing portions  24 ,  26 . 
     The conductive portion  22  may be centered with respect to the width w of the body, such that both sealing portions  24 ,  26  have a same dimension along the width w of the body (see  FIG. 4 ) or alternately, the conductive portion  22  may be defined closer to one of the side surfaces  32  than to the other, so that one of the sealing portions  24  has a greater dimension along the width w of the body than the other sealing portion  26  (see  FIGS. 3 and 5 ). The conductive portion  22  may be provided as a continuous line as shown, or in a plurality of spaced apart segments (e.g. dotted line) each forming a respective part of the two opposed contact surfaces  30 , and each spaced from the side surfaces  32  by the sealing portions  24 ,  26 . The configuration of the conductive portion  22  is selected so that the total area of the part(s) of the contact surfaces  30  defined by the conductive portion  22  and in contact with conductive regions of the facing surfaces is sufficient to fulfill the grounding need of the particular application, based on the level of current that is expected to circulate between the elements electrically connected through the sealing member  20 , and on the conductivity of the conductive portion  22 . Determination of the sufficient contact area is within the skill of the person of the art and will not be described therein. 
     In a particular embodiment, one or both of the contact surfaces  30  of the sealing member  20  may be covered by an adhesive releasably engaged to a respective backing paper  40  covering the contact surface(s)  30 , such that the sealing member  20  is provided in a ready-to-apply tape form. In another embodiment, the material of the sealing member  20  itself includes adhesive properties, such that the contact surfaces  30  are adhesive without the need to apply a separate adhesive material thereto. The backing paper  40  is removed and the adhesive covered surface(s)  30  of the sealing member  20  can be engaged to an element to be sealed. 
     In a particular embodiment and with reference to  FIG. 3 , the floor panel  10  and floor beams  12  are interconnected by removable fasteners  34  extending through one or both of the sealing portions  24 ,  26 . In a particular embodiment, the sealing portion(s)  24 ,  26  is/are not predrilled prior to the insertion of the fasteners  34 , so that the sealing material of the sealing portion(s)  24 ,  26  may be more closely engaged to the fasteners  34 , to reduce the risks of leaks through the fastener holes. In the embodiment shown, the floor beam  12  includes protuberances  36  for receiving the fasteners  34 ; other configurations are also possible, including, but not limited to, a floor beam having a constant cross-section along its length. In a particular embodiment, the fasteners  34  may extend through the conductive portion  22  as well. 
     In a particular embodiment and with reference to  FIG. 4 , additional sealing material  38  may be provided between the top surfaces of adjacent ones of the floor panels  10 , to reduce the risk of moisture above the floor panels  10  reaching the connection between the floor panel  10  and floor beam  12 . 
     Although the sealing member  20  has been described as used in the connection between floor panels  10  and floor beams  12 , it can also be used in any connection between components having conductive (e.g. metal) surfaces that need to be in electrical contact with one another, with the conductive interface requiring sealing from the environment. Examples of such alternate applications include, but are not limited to, the sealing of antennas connected to the fuselage, access panels on the fuselage or on the wings, shelves in avionics bays, and any connection of elements where conductivity is required therebetween for grounding or lightning strike protection. The sealing member  20  may be particularly, although not exclusively, adapted for sealing assemblies where one or the two components need to be removable. 
     Although the sealing member  20  has been depicted with an elongated rectangular body, it is understood that a variety of alternate shapes are also possible, depending on the shape of the conductive surfaces that need to be in electrical contact with one another and sealed from the environment. The sealing portions and conductive portion may thus have various shapes, with the sealing portions extending between exposed side surfaces of the sealing member and the conductive portion to prevent moisture in contact with the exposed side surfaces from reaching the conductive portion. 
     Modifications and improvements to the above-described embodiments of the present invention may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting. The scope of the present invention is therefore intended to be limited solely by the scope of the appended claims.