Patent Publication Number: US-2007114791-A1

Title: Lightweight firewall protection

Description:
TECHNICAL FIELD  
      The present invention relates to an aircraft firewall and, more particularly, to a feed through system configured to substantially seal one side of the firewall from the other.  
     BACKGROUND  
      Aircraft typically include firewalls that isolate fire zones from non-fire zones, or one fire zone from another fire zone. Each zone includes one or more systems, such as, for example, engine, electrical, pneumatic, and/or hydraulic systems, that cooperate with each other for the operation of the aircraft. Often, the firewall includes openings formed therein that allow system connection equipment, such as ducting, piping and/or wires to extend therethrough to connect the systems to each other. In some cases, gaps may be present between the system connection equipment and firewall, which, in the unlikely event of a fire, may provide a space through which flames may travel. As a result, specialized firewall fittings may need to be included between the equipment and firewall to prevent the flames from traveling from one side of the firewall to the other.  
      Several types of firewall fittings currently exist. One type of fitting uses a bulkhead connector that has an opening therethrough. The connector is disposed in the firewall opening and the system connection equipment is extended through the bulkhead connector opening. Sealant is injected between the system connection equipment and bulkhead connector to isolate the zones from one another. Another type of fitting uses a fireproof, reinforced silicone rubber boot that can be used to surround structural tubing that extends through the firewall. Still other types of fittings include the use of close tolerance fitting, single purpose penetration ducting or flanged connections at the firewall.  
      Although the above-mentioned firewall fittings are adequate for preventing flames from traveling through the firewall, they suffer from certain drawbacks. In particular, many of the fittings include a number of components that together are relatively heavy and may undesirably increase aircraft weight. Additionally, some of the fittings may be relatively costly to implement. Moreover, many of the fittings rigidly attach the system connection equipment to the firewall, which may unnecessarily increase the load on the fitting and/or firewall.  
      Thus, there is a need for a feed through system that is relatively lightweight and inexpensive to implement. Additionally, it is desirable for the system to provide a floating interface between the firewall and system connection equipment.  
     BRIEF SUMMARY  
      The present invention provides a kit for a firewall penetration system for use between a firewall and a penetrating member. The kit comprises two annular plates and a compressible seal. The first annular plate has an outer and an inner radial wall and an axial wall coupled therebetween, the axial wall extending axially away from the outer radial wall, and the inner radial wall extending radially inwardly from the axial wall, the inner radial wall having an inner peripheral edge defining an opening through which the penetrating member may extend. The second annular plate has an outer section, an inner section, and an inner peripheral edge, the outer section configured to couple to the first annular plate outer radial wall, the inner section configured to define a seal cavity with the first annular plate axial wall and inner radial wall when the first and second annular plates are coupled together, and the inner peripheral edge defining an opening. The compressible seal is configured to be disposed in the seal cavity, and has a bulb and a leg extending therefrom.  
      In another embodiment, and by way of example only, a firewall penetration system is provided that is disposed between a firewall and a penetrating member. The system includes two annular plates, a seal cavity, and a compressible seal. The first annular plate has a first section and a second section, each section including an outer radial wall, an inner radial wall and an axial wall coupled therebetween, the axial wall extending axially away from the outer radial wall, the inner radial wall extending radially inwardly from the axial wall, the inner radial wall having an inner peripheral edge defining a first space within which the penetrating member is at least partially disposed. The second annular plate has a first section and a second section, each section including an outer section, an inner section, and an inner peripheral edge, the outer section coupled to the first annular plate outer radial wall, and the inner peripheral edge defining a second space within which the penetrating member is at least partially disposed. The seal cavity is defined by the second annular plate inner section, the first annular plate axial wall, and first annular plate inner radial wall. The compressible seal is disposed in the cavity, and has ends that are joined together such that a ring is formed.  
      Other independent features and advantages of the preferred system will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a cross section view of an exemplary feed through system installed between a firewall and duct;  
       FIG. 2  is a close up view of a section of the feed through system depicted in  FIG. 1 ;  
       FIG. 3  is the feed through system depicted in  FIG. 2 a  disassembled state; and  
       FIG. 4  is the feed through system depicted in  FIG. 2  in an assembled state. 
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT  
      The following detailed description of the invention is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description of the invention.  
      Turning now to  FIG. 1 , an exemplary feed through system  100  is shown mounted between a firewall  102  and a duct  104 . The feed through system  100  allows the duct  104  to extend through an opening  106  in the firewall  102  while minimizing fluid flow communication between a first section  108  on one side of the firewall  102  and a second section  110  on another side of the firewall  102 . It will be appreciated that the duct  104  may alternatively be any one of numerous other components that may need to extend through the firewall opening  106 , such as, for example, piping, wires, structural tubing, and any other penetrating member. Depicted more clearly in  FIG. 2 , the opening  106  is sufficiently sized to allow at least a portion of the feed through system  100  to be disposed therein.  
       FIG. 2  is a close up view of the feed through system  100 , which includes a clamshell plate  114 , a cover plate  116 , and a compressible seal  118 . The clamshell plate  114  is configured to provide a space within which the compressible seal  118  may be disposed and to protect the compressible seal  118  from direct flame impingement in the unlikely event of a fire. In this regard, the clamshell plate  114  is constructed of fireproof material, such as, fiber reinforced plastic composite, for example graphite-bismaleimide. Other suitable fireproof materials may alternatively be used.  
      The clamshell plate  114  is generally annular and includes an outer radial wall  120 , an inner radial wall  122 , and an axial wall  124  extending therebetween. The outer radial wall  120  includes a plurality of fastener openings  126 , one of which is shown in  FIG. 2 . The fastener openings  126  are disposed in a pattern such that at least selected ones correspond to one or more spaced apart firewall fastener openings  128 , and each is configured to receive fasteners  130  for mounting the clamshell plate  114  to the firewall  102 . The axial wall  124  extends axially away from the outer radial wall  120  and preferably has a length that is sufficient to accommodate a width of the compressible seal  118 . Additionally, the axial wall  124  has an outer diameter that is smaller than the diameter of the firewall opening  106  so that at least a portion of the clamshell plate  114  can extend therethrough. The axial wall  124  may also include one or more openings  129  for mounting the compressible seal  118 , as described below. The inner radial wall  122  extends radially inwardly from the axial wall  124 . Additionally, the inner radial wall  122  has an inner peripheral edge  132  that defines a duct opening  134 . The duct opening  134  is sufficiently sized to allow the duct  104  to extend therethrough.  
      The cover plate  116  is preferably configured as an annular plate having an outer section  138  and an inner section  140  and is configured to mount the clamshell plate  114  to the firewall  102 . Similar to the clamshell plate  114 , the cover plate  116  is constructed of fireproof material, for example a fiber reinforced plastic composite such as graphite-bismaleimide. The outer section  138  includes a plurality of fastener openings  142 , one of which is shown in  FIG. 2 . The fastener openings  142  are disposed in a pattern such that at least selected ones correspond to one or more of the clamshell plate and firewall fastener openings  126 ,  128 . In an alternate embodiment, the clamshell plate  114  and cover plate  116  are welded or otherwise coupled together. The inner section  140  of the cover plate  116  has an inner peripheral edge  143  that defines a duct opening  144  that is sized to allow the duct  104  to extend therethrough.  
      The compressible seal  118  is used to further isolate the first and second sections  108 ,  110  from each other and is disposed in a seal cavity  146  formed between the clamshell plate  114 , the cover plate  116 , and the duct  104 . Preferably, the compressible seal  118  includes at least one bulb  148  and a leg  150  that extends therefrom. The bulb  148  preferably has a circular cross section and is appropriately sized to indirectly seal gaps formed between the clamshell plate inner peripheral surface  132 , cover plate inner peripheral edge  143 , and the duct  104  when the feed through system  100  is mounted to the firewall  102 .  
      At least a portion of the bulb  148  is made of a non-flammable material capable of withstanding temperatures over 2000° F. without melting. In one exemplary embodiment, the compressible seal  118  includes an inner component  152  and an outer component  154 . Preferably, the inner component  152  is capable of operating while exposed to temperatures greater than 2000° F. The outer component  154  is capable of operating while exposed to temperatures lower than 2000° F. and to withstand exposure to temperatures above 2000° F. Any one or more suitable materials may be used in the manufacturing of the components  152 ,  154 . For example, the inner component  152  may be a polycrystalline fiber tube and the outer component  154  may be a woven glass fiber fabric wrapped therearound. It will be appreciated that the fiber tube may be configured to provide a desired resiliency.  
      The leg  150  extends from the bulb  148  and is used to attach the seal  118  to the clamshell plate axial wall  124 . In one embodiment, as shown in  FIG. 2 , the leg  150  is formed from an extension of the outer component  154 , and, for example, may be woven glass fiber fabric. The leg  150  is preferably riveted or otherwise secured to the axial wall  124 .  
      In an alternate embodiment, the compressible seal  118  is a dual bulb seal and includes a second bulb  156  (shown in phantom in  FIG. 2 ) that is formed on an end of the leg  150 . As shown in  FIG. 2 , the second bulb  156  may be a pilot bulb that is used to assist in the installation of the compressible seal  118 . In such case, the second bulb  156  may be constructed of a different material than the first bulb  148 , such as aramid cord and the like. Alternatively, the second bulb  156  may be configured to act as a redundant seal and thus, may be similar in size to the first bulb  148 .  
      It will be appreciated that each of the components of the system  100  may either be unitary pieces, or alternatively, may comprise multiple pieces for easier mounting to the firewall  102 . For example, as shown in  FIGS. 3 and 4 , the clamshell plate  114 , cover plate  116 , and compressible seal  118  may each include two or more sections that each form arcs or semicircles. When the system  100  is fully assembled, the sections of the clamshell plate  114  are preferably offset relative to the sections of the cover plate  116 , and the sections of the cover plate  116  are preferably offset relative to the sections of the compressible seal  118 , as shown in  FIG. 3 . Consequently, a tortuous path is provided for heat or flames through the firewall  104 .  
      To further minimize the travel of fire through the firewall  104 , gaskets may be included between the clamshell plate  114  and cover plate  116  interface and/or between the firewall  102  and the clamshell plate  114  interface. Moreover, ends of each section of the compressible seal  118  may be stitched together, bonded together using a silicone adhesive, or otherwise joined. In one exemplary embodiment, a shape memory material is coupled to the seal  118  that is capable of causing the seal  118  to have a desired predetermined cross-sectional shape, for example, circular or ovular, when exposed to a predetermined temperature.  
      A feed through system has now been provided that is fireproof and relatively lightweight. Additionally, the system includes few parts and is relatively simple to implement. Moreover, the use of the compressible seal  118  and provision of the gaps defined by the diametrical differences between the inner peripheral edges  143 ,  132  and the duct  104  provide a floating interface between the firewall  102  and the duct  104 .  
      While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.