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 
     This application claims priority to U.S. provisional patent application Ser. No. 61/654,787, filed 1 Jun. 2012. 
    
    
     STATEMENT OF GOVERNMENT INTEREST 
     The work was conducted with funding from the U.S. government through Contract No. FA8650-09-D-5601. The government has certain rights in the invention. 
    
    
     SUMMARY OF THE INVENTION 
     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. However, 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. 
     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. A nonlimiting list of the inventive concepts includes: 
     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. 
     In another aspect, the invention provides a flying vehicle (such as 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. 
     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. 
     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. 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1-3  illustrate a low profile pass-through electrical connector comprising an electrically conductive pin passing through a non-conductive sheath. 
         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. 
         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. 
         FIGS. 10-13  illustrate a low profile pass-through electrical connector comprising a pin and socket. 
         FIG. 14  illustrates an assembly comprising multiple thin film heaters stacked in close proximity. 
         FIGS. 15-18  show photographs of low profile pass-through electrical connectors. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In one embodiment, the invention provides a low profile pass-through electrical connector that connects or is adapted for connecting an electrical conductor on an 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. 
     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. 
     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. 
     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. 
       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  11 . The head of the insert has a countersink shape  112 , 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. 
     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.   

       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. Lastly, 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. 
       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. 
       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. 
       FIGS. 15-18  illustrate example embodiments of the low profile pass through electrical connection comprising a mated pin and socket connection. 
       FIG. 15  is a photograph of insert receptacle assemblies installed in a wing surface. 
       FIG. 16  is a photograph of thin film heaters with a pin mating interface. 
       FIG. 17  illustrates a mating of pin with insert receptacle. 
       FIG. 18  is a photograph of an inside of a wing showing pass-thru receptacle wiring. 
     While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and are not intended to limit the invention.