Abstract:
The conductive rivet designed to connect the first and second conducting surfaces of circuit board through an aperture in the board. The rivet includes a conical member with an associated insulating washer associated on one side of circuit board. A T-shaped rivet and cooperating insulating sleeve are designed to contact the opposite side of the circuit board and provide a thermal conduction path via tail on the T-shaped rivet to the conical member on the opposing side.

Description:
GOVERNMENT INTEREST 
   This invention can be made used and licensed by the United Sates for Governmental Purposes without payment to me of any royalty. 

   BACKGROUND OF THE INVENTION 
   In one aspect this invention relates to fasteners for attaching items to a substrate. In a further aspect, this invention relates to coated, metallic circuit cards and means to conduct current from one surface coating to the opposite face and not diminish any thermal transfer. 
   Heat is a particularly destructive condition for circuit card components. In certain applications, particularly in military vehicles and more especially combat vehicles, there is severely limited space for air flow and the vehicles are also subjected to extreme environmental heat under many combat conditions. Failure of a particular card can result in mission failure and death to vehicle users. To combat this problem, the military may use specialized metallic circuit cards that are engineered to enhance heat dissipation. Such cards have insulating layers on each face or surface to isolate the circuit trails from the metallic cards. However, enhanced heat dissipation along the card is of lessened value unless it is possible to further dissipate the heat from the card to the vehicle body in which the card is mounted. 
   Generally the cards are mounted to a vehicle by means of threaded fasteners or rivets. While such devices are frequently made of metal and provide some heat transfer it is also necessary to electrically insulate the fastener or current feed through from the metallic circuit board substrate in order isolate the electrical circuits on the board&#39;s surface. 
   SUMMARY OF THE INVENTION 
   The improved rivet structure of the present invention provides improved electrical conductivity between the surfaces of a metallic circuit card while at the same time electrically isolating the rivet from the metallic circuit card substrate. The rivet structure has a conical member formed with an outer annular member. The annular member has a plurality of circumferentially placed projections that extend from the annular member. 
   A segmented disc is attached to the inner surface of the annular member at the disc&#39;s periphery. The segmented disc is formed so the segments project at an angle to a plane defined by the annular member, the free ends of the segments converging near the center of the conical structure so as to define an aperture that is coaxially aligned with the axis of the annular member. By virtue of the angle between the segments and the plane of the annular disc, the free ends of the segments are disposed in and located on a plane spaced from the plane of the annular member on the side of the annular member opposite the circumferentially placed projections. The resulting structure is frusto-conical in shape. 
   The rivet structure of this invention has an associated insulating washer that is adapted to fit within the volume defined by the frusto-conical structure of the segmented disc. The washer is formed as an annulus of insulating material and has an aperture complimentary to an associated aperture formed in the circuit board to which the rivet structure is to be attached. The outer diameter of the insulating washer is adapted to fit within the inner diameter of the annular member and has a thickness that will not prevent the circumferential projections of the conical structure from contacting the surface of the circuit board. 
   The insulating rivet of this invention has an insulating sleeve with an outer diameter complimentary to an aperture in the circuit board the insulating sleeve having a head on one end to hold the insulating sleeve in place. The insulating sleeve is inserted in the circuit board so the head also provides an insulating surface on the side of the circuit board opposite the insulating washer. The insulating sleeve in combination with the insulating washer on the opposite side of the circuit board will protect the electrical equipment mounted on the board from short circuits or other electrical drain due to the use of the conductive rivet. 
   The final element in the conducting rivet of this invention is a tubular T-shaped rivet. The tubular rivet has a head and a leg with a second plurality of circumferentially extending projections extending from the head portion of the tubular rivet. The second plurality of projections extends in the direction of and is coaxially aligned with the leg of the T-shaped rivet. The outer diameter of the T-shaped rivet&#39;s leg is complimentary to the inner bore of the insulating sleeve and the aperture defined by the segmented discs so when the T-shaped rivet is inserted among the free end of the segments, they will grip the outer surface of the leg. This securely holds the various parts of the rivet in place with the first and second plurality of projections in contact with the conductive surfaces on the circuit board. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     In the accompanying drawing: 
       FIG. 1 , is an exploded view of one insulating rivet construction according to this invention; 
       FIG. 2 , is a side view, in section, of the rivet of  FIG. 1  assembled on a circuit board with the segments fixed into place by expansion of the leg of the rivet; and 
       FIG. 3  is a side view of a second embodiment of this invention with a solid stud formed as part of the rivet structure. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to the accompanying drawing in which like numerals refer to like parts and initially  FIG. 1 , the rivet structure of this invention  10  has a conical structure designated generally  12  formed with an outer annular member  14 . Annular member  14  has a first plurality of projections  16  which are spaced equidistant from each other about the periphery of the conical structure  12 . Projections  16  are formed so that they will make good electrical and heat conductivity contact with a conductive surface  17  on circuit board  18  when the conical structure  12  is brought into contact with the conductive surface. 
   The conical structure  12  has a segmented disc generally  20  formed as shown from a plurality of segments  22 , there being six segments in the structure shown. The segments  22  are joined together at their outer diameter to the inner diameter of the annular member  14 . The segments  22  project at an angle to a plane defined by the annular member  14 , to form frustoconical structure with the free ends  24 , of segments  22 , defining an aperture at the center of segmented disc  20 . The aperture formed by free ends  24  of segments  22  is of a size to allow the free ends to engage a leg  26  of a tubular T-shaped rivet,  28 , which will be further discussed hereinafter. 
   An insulating washer  30 , formed of an insulating material, is positioned so as to fit within annular member  12 . The insulating washer  30  will be chosen from a suitable class of polymeric insulating materials or otherwise suitable materials which will protect the circuit board surface or prevent unwanted electrical contact with any residual electrically conducting chips, debris, etc. formed when making the aperture in the electrically conductive circuit card  17  from making contact with segments  22 . The outer diameter of the washer  30  fits within the inner diameter of annular member  14  and the diameter of aperture  34  is sized to allow leg  26  of the T-shaped rivet  28  to pass through and engage the free ends  22  of segments  24 . 
   The insulating rivet structure  10  of the present invention has an insulating sleeve  40  with a head  42  and tail  44 . The tail  44  is chosen to fit snugly within an aperture  46  formed in circuit board  18 . The insulating sleeve  40  when inserted into aperture  46  will extend through the circuit board  18  and be held in position the head  42 . 
   A final element in the conducting rivet of this invention is the T-shaped rivet  28  which has a head  48  and a second plurality of circumferentially disposed projections  50  which extend outward from the head  48 . The plurality of second projections  50  extend in the direction of and are coaxially aligned with leg  28  of the T-shaped rivet. The outer circumference of leg  28  is complimentary to the inner diameter of insulating sleeve  40  and also complimentary with the aperture formed by the free ends  24  of segmented disc  20 . 
   Referring to  FIG. 2 , the conducting rivet structure  10  is assembled by placing the insulating sleeve  40  within aperture  46  of circuit board  18 . The insulating washer  30  can be placed over that portion of tail  44  of insulating sleeve  40  that extends beyond the circuit board as shown. This provides a complete insulating structure which slightly overlaps the aperture  46  on both sides of circuit board  18  to protect the conductive surfaces  17  from stray electrical and heat transmission and ensure that the rivet becomes the sole means of heat and electrical conduction between the two surfaces  17 . The T-shaped rivet  28  has its leg  26  inserted longitudinally through the bore of insulating sleeve  40  and will extend beyond the tail  44  of the insulating sleeve  42 . The conical structure  12  will be placed over that portion of leg  26  which extends beyond the insulating washer with the base of the frustoconical structure being located adjacent surface  18  of the circuit board. As the conical disc is forced downward into contact with the surface  17  of circuit board  18  projections  16  will contact the conductive surface  17  of the circuit board and the free ends  24  of the segments will simultaneously grasp and contact the outer surface of leg  26 . The result will be that the projections  16 ,  50  are firmly in contact and engaging both sides of the circuit board and a sound thermal and electrical connection will be made between the opposed surfaces  17  of the circuit board  18 . 
   As a variation, the T-shaped rivet  28  may have a conductive stud  60  formed as part of the head  48 , this variation being disclosed in Figure three. This stud  60  is preferably disposed on the surface of head  48  opposite the second plurality of projections  50 . This provides an additional connection to the rivet  10  for heat dissipation. This stud  60  may also be used to attach components or parasitic circuit cards. 
   Various alterations to this invention will become apparent to those skilled in the art without departing from Scope and spirit of this invention. It is understood that this invention is limited only by the appended claims.