Abstract:
A low profile pass-through electrical connector is designed for aerospace applications. The connector allows voltage and current to pass-thru a conductive wing surface, while maintaining a low profile height for aerodynamic performance considerations. Examples of applications of the electrical connector include power for thin film heaters and communication antennae applications.

Description:
RELATED APPLICATION 
       [0001]    This application claims priority to U.S. provisional patent application Ser. No. 61/654,787, filed 1 Jun. 2012. 
     
    
     STATEMENT OF GOVERNMENT INTEREST 
       [0002]    This work was conducted with funding from the U.S. government through Contract No. CON00008573. The government has certain rights in the invention. 
     
    
     SUMMARY OF THE INVENTION 
       [0003]    The present invention is directed toward a low profile pass-thru connector for passing electrical voltage and current through a conductive wing surface, which are typically made of carbon fiber or aluminum. Preferably, the connector maintains a low profile height with respect to the wing surface, to maintain the wing&#39;s aerodynamic performance. The pass-thru connector may provide power to thin film heaters used for anti-icing/de-icing purposes, and can alternatively (or in combination) be utilized for other purposes such as communication antennas. Thin film heaters may require high electrical currents, so the pas s-thru connector must have sufficient cross-sectional area where it travels through the wing to prevent overheating. It also should make a transition to a thin conductive (preferably copper) strip conductor to interface with the thin film heaters. This thin copper strip does not overheat with high current use because the airflow during flight keeps it cool due to forced convection. In one variant, the total thickness of the thin film heater cannot be more than 0.020 inches (0.51 mm), and to this end, the thin copper leads for this application are preferably 0.005 inches (0.013 mm) thick or less. 
         [0004]    The invention includes any of the designs described herein including generalizations of these designs, portions of each design, as well as combinations of the designs. The invention also includes methods of making conductive assemblies and/or flying vehicles comprising the conductive assemblies. The invention also includes methods of using a heating element or antenna comprising using any of the conductive assemblies and/or flying vehicles described herein; for example, a method of deicing or heating an aerodynamic surface, or powering an antenna on an aerodynamic surface, comprising passing an electric current through any of the pass-through conductors described herein. Any of the inventive aspects can be described as forming a finished conductive assembly without solder. A nonlimiting list of the inventive concepts includes any of the following aspects. 
         [0005]    In one aspect, the invention provides a conductive assembly, comprising: a heating element or antenna; an electrically conductive pin that is electrically connected to the heating element or antenna; a mating socket that is adapted to mate with the conductive pin; and an electrically insulating sleeve disposed around the circumference of the pin and/or mating socket. 
         [0006]    In another aspect, the invention provides a flying vehicle (that is, a missile or manned or unmanned aircraft) comprising the conductive assembly disposed on an aerodynamic surface (preferably a wing) wherein the heating element or antenna is disposed on the exterior surface of the flying vehicle and the electrically conducting pin and mating socket form an electrical pathway from the exterior of the flying vehicle to the interior (for example, from the surface of a wing to the interior of the wing). In some preferred embodiments, there is no solder on the conductive pin. In some preferred embodiments, the electrically insulating sleeve comprises a threaded polymer and the pin is a screw-type pin that is adapted to screw through the threaded polymer. 
         [0007]    The invention also includes a method of making a conductive assembly or flying vehicle comprising any of the assembly steps described herein. In some embodiments, a conductive assembly comprising a heating element (in some embodiments, a plurality of heating elements) or an antenna and having one or (usually) more conductive pins is pressed through aperture(s) formed by an electrically insulating sleeve(s) that is (are) disposed in and pass through the surface of an airfoil. The electrically conductive pin(s) mate with a socket(s) to form an electrical pathway through the airfoil surface. In some preferred embodiments, no solder is required to install the conductive assembly on the airfoil surface. 
         [0008]    In another aspect, the invention provides a method of conducting electricity from the inside to the outside of an airfoil (or vice versa), that comprises passing electricity through the electrically conductive pin. In a preferred embodiment, this method is conducted while a fluid passes over the surface of the airfoil at a velocity of at least 200 mph (320 km). This condition would typically be encountered during flight but would not be experienced by a structure on the ground. 
         [0009]    In a further aspect, the invention provides a flying vehicle comprising an airfoil (such as a wing) comprising a conductive wire passing from the inside of the airfoil to the outside of the airfoil and an insulating sleeve disposed around the conductive wire. Preferably, the insulating sleeve is fit by compression into the airfoil. In some embodiments, the conductive wire is a screw that has a flat head that conforms to the surface of the airfoil. 
         [0010]    In yet another aspect, the invention provides a conductive assembly, comprising: a heating element or antenna; an aerodynamic surface; a connector base forming a pathway through the aerodynamic surface; a floating center disposed inside the connector base; and an electrical conductor disposed within the floating center. The invention also includes a flying vehicle comprising this conductive assembly, the corresponding methods of making these assemblies, and the corresponding methods of using the heating elements or antennas. The floating element can be loose and able to move in the x and y directions while remaining immobile in the z-direction; in this case, the assembly is typically an intermediate structure. The intermediate structure can be treated with an adhesive that secures the copper conductor (or other strip conductor) and/or the heating element and/or the antenna; the adhesive also secures the floating center so that is no longer floating. The connector base is typically cylindrical. The connector base and floating center preferably have the same length. The connector base may have a rim that retains a cylindrical floating center or an eyelet in the airfoil surface can retain the floating center. In preferred embodiments, a snap ring (also called a retainer ring) prevents the floating center from moving up through the airfoil surface and preferably immobilizes the floating center in the z direction (that is, the direction normal to the airfoil surface). Preferably, a retaining ring is disposed around and at the top part (that is, the part nearest the airfoil surface) of the floating center. In one embodiment, the retainer ring is a cut circle that snaps into place; this ring may have a c-shape that acts as a spring by pressing against the rim of the connector base. Typically, the floating center contains a socket. The socket can complete the electrical connection from the interior of an airfoil to a heater element or antenna on the surface of the airfoil. As with other aspects of the invention, the heater element or antenna can be plugged into (or removed from) the socket in the floating center. In some embodiments, the top portion of the connector base and the floating center form a groove that can be filled by an adhesive that anchors the floating center and may also secure the heating element or antenna to the airfoil surface. Desirably, the connector base and floating center are electrically insulating. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIGS. 1-3  illustrate a low profile pass-through electrical connector comprising an electrically conductive pin passing through a non-conductive sheath. 
           [0012]      FIGS. 4-6  illustrate a low profile pass-through electrical connector in which a copper lead is sandwiched between a steel screw and an insulating sleeve. 
           [0013]      FIGS. 7-9  illustrate a low profile pass-through electrical connector in which the use of a conductive screw avoids the use of solder to fasten the conductive lead. 
           [0014]      FIGS. 10-13  illustrate a low profile pass-through electrical connector comprising a pin and socket. 
           [0015]      FIG. 14  illustrates an assembly comprising multiple thin film heaters stacked in close proximity. 
           [0016]      FIGS. 15-18  show photographs of low profile pass-through electrical connectors. 
           [0017]      FIG. 19  illustrates a floating pass through connecter (far right), connector base (far left), and floating center (center). 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    While various embodiments of the present invention are described herein, it should be understood that they have been presented by way of example only, and are not intended to limit the invention. 
         [0019]    In one embodiment, the invention provides a low profile pass-through electrical connector that connects or is adapted for connecting an electrical conductor on a outer surface of a plane wing to conductors in the interior of the plane wing, comprising: a conductive pin (e.g., a brass pin of 12-14 gauge); a non-conducting vented fastener for receiving the pin; a captive nut configured to thread around the fastener in the interior of the wing; a non-conductive sheath; a micro-jack connector press fit into the non-conductive sheath; and a wire. 
         [0020]    Referring to  FIGS. 1-3 , a low profile pass-through electrical connector  10  comprises: a conductive brass pin  15  of 12-14 gauge; a ¼-20 size (¼ inch diameter, 20 threads per inch; 0.64 cm diameter, 8 threads per cm) non-conducting vented fastener  20  that has been modified for fitment of a brass conductor; a captive nut  25 ; a micro-jack connector  30 , press fit into the non-conductive sheath; a non-conductive sheath  35 ; and a wire  40 .  FIG. 2  illustrates a cutaway view of the assembled pass through connector, with a solder joint  23  where the thin copper lead  24  connects to the head of the 12-gauge pin.  FIG. 3  is a bottom view of the pass through connector assembly. 
         [0021]    In another embodiment, referring to  FIGS. 4-6 , a low profile pass through electrical connector  45  comprises: a number  10 , 100-degree ( 25/64 inch, 0.99 cm nominal diameter, 100-degree is the angle formed by the tapered screw head) flat-head stainless steel screw  50 ; a wide flange nylon insulating sleeve  55 ; a wide nylon insulating washer  60 ; a copper ring terminal with solder flange  65 ; and a captive nut  70 .  FIG. 4  is an exploded view and  FIG. 5  is a cutaway view of an assembled connector. The thin copper lead  52  is sandwiched between the head of the screw and the nylon sleeve in this concept to complete the electrical connection. This obviates the need for a solder joint. 
         [0022]    In a further variant, referring to  FIGS. 7-9 , a low profile pass through electrical connector  100  comprises a copper lead  105  that has been cut with an eyelet shaped feature  110  on one end. This eyelet shape is then swaged into a countersink shape. The countersunk eyelet provides for a large contact area for the thin copper lead. 
         [0023]      FIGS. 7-9  illustrate a compression connection without the need for any solder connections. This design uses a polymer insulating insert  114 , made from a material such as Noryl™, that is fastened to the wing surface by means of a threaded nut  111 . The head of the insert has a countersink shape, which allows it to mount flush to the wing surface with a countersunk hole in the wing. The inside of the insert  114  is also threaded, and a conductive screw  88  (such as aluminum) is threaded into it as the pass-thru conductor. The screw also has a countersunk head, which sandwiches the countersink shape of the swaged copper lead  92  into the head of the insulating insert.  FIG. 7  is a top view,  FIG. 8  is a cutaway view and  FIG. 9  is a close-up cutaway showing the compression fit. 
         [0024]    In another example, referring to  FIGS. 10-13 , the low profile pass-through electrical connection comprises:
         155 —a flattened conductive lead (preferably copper).     160 —conductive pin.     165 —electrically insulating sleeve.     170 —conductive socket for mating with the conductive pin.     175 —electrical power wire.       
 
         [0030]      FIGS. 10-13  illustrate a mated pin and socket connection. MIL-SPEC (United States military specifications) pins and sockets improve the shock- and vibration-resistance of the connection. The mated pin  160  and socket  170  connection uses a comparatively smaller area, allowing a greater density of connections to be made. This can improve the performance of the thin film heater by allowing a higher resolution of individual heater control. A conductive wire (such as wire  40 ) can be connected to socket  170  by crimping or soldering. Typically, the socket  170  is potted in place. A preferred potting compound is an epoxy that produces a seal that is air and water tight. As can be seen in the drawings, on the airfoil-surface-facing side of socket  170  there is a hollow receptacle for receiving the conductive pin  160 . Preferably, surfaces for electrical connections are gold plated. The thin film heater  195  can be removed and replaced without having to undo any internal wiring connections since the socket is fastened to the insert. 
         [0031]      FIG. 10  illustrates a mating receptacle in an exploded view.  FIG. 11  is an exploded cutaway view, and  FIG. 12  is an illustration of a mated pin and socket cutaway.  FIG. 13  shows a cutaway of the complete thin film heater assembly, including the wing section  162 . 
         [0032]      FIG. 14  illustrates a heater and pass-thru assembly  196  illustrating multiple thin film heaters  198  can be stacked in close proximity using a tiled approach with a pass-thru connector design. 
         [0033]      FIGS. 15-18  illustrate example embodiments of the low profile pass through electrical connection comprising a mated pin and socket connection. 
         [0034]      FIG. 15  is a photograph of insert receptacle assemblies installed in a wing surface. 
         [0035]      FIG. 16  is a photograph of thin film heaters with a pin mating interface. 
         [0036]      FIG. 17  is a photograph illustrating a mating of pin with insert receptacle. 
         [0037]      FIG. 18  is a photograph of an inside of a wing showing pass-thru receptacle wiring. 
         [0038]    The floating pass through connector is illustrated in  FIG. 19 . The illustrated floating pass through connector  102  is comprised of  4  main parts: the connector base  104 , the floating center  106 , the socket (not visible in  FIG. 19 ), and the snap ring  108 . The interior of floating center  106  can be identical to the interior of electrically insulating sleeve  165 . Similarly, the socket is inserted into the floating center and potted in-place with an electrical wire. The connector base  104  is epoxied in-place into the wing surface. The floating center  106  is then installed into the connector base, and is held in place by the snap ring (also called a retainer ring). The floating center can move laterally in the X and Y-plane, but the snap ring prevents it from moving axially. Once a thin-film heater is applied onto the wing surface, the epoxy used to apply the heater fills the groove  110  where the snap ring resides. This solidifies the connector, adds structural strength, and prevents movement in the future. The floating aspect only needs to be utilized during the assembly phase; however, the part may still be termed as a floating center after fixing in place by an adhesive. 
         [0039]    This floating design allows for the connector to tolerate an additional 0.020″ inch (0.5 mm) of tolerance from the pin connection without causing the thin film plastic heater to stretch or wrinkle. This is especially important when installing several connector into a wing surface as maintaining the hole position tolerance is very challenging. The connector design maintains its flush surface mount properties to ensure aerodynamic performance. A vibration test has been performed on this connector design without any failures.