Patent Publication Number: US-6902413-B1

Title: High retention connection

Description:
BACKGROUND ART 
   1. Field of the Invention 
   The invention relates to a connection between a spark ignition coil and a spark plug head. More particularly, the invention relates to a spark plug connector having a multi-point contact system having an increased spring force interface. 
   2. Description of the Related Art 
   Electrical connections between high voltage terminals and spark plug heads are well known in the art. Typically, a high voltage lead wire extends from a central high voltage source coil assembly. The lead wire contains a high voltage metal sheath with an insulating coating. The metal conductor sheath is connected to a connector usually formed of a stamped sheet metal which forms an encircling clamp that snaps on to the spark plug head. This arrangement provides little tolerance when assembling the connection. The orientation between the metal conductor sheath and the spark plug head must be substantially identical for the connection to occur. 
   It is also known to employ a spring within an electrical connection of a spark plug head. These spring designs are complex, costly and do not reliably provide a positive attachment of the spring to the high voltage terminal. These complex designs also require complicated techniques and specialized tools to assemble. 
   U.S. Pat. 6,358,071, having common inventorship and ownership, discloses a spring that provides an electrical connection for a spark plug head and a high voltage terminal. The spring has contact legs which are slightly compressed by the walls of a connector. These contact legs are leaf springs. While this configuration is simple, the force required to insert the spark plug head into the connector is great. Therefore, a need exists for having a simple spring connection for a spark plug head within a high voltage terminal into which the spark plug is easily inserted and, at the same time, maintain a high retention force on the spark plug head so it is not easily dislodged from the high voltage terminal. 
   SUMMARY OF THE INVENTION 
   An electrical spring connection assembly electrically connects a conducting case, having a predetermined case diameter, and a spark plug. The electrical spring connection assembly includes a base having a securing aperture for receiving a portion of the conducting case therein. The base fixedly secures the electrical spring connection assembly within the conducting case. The electrical spring connection assembly also includes a leaf spring portion that extends radially out from the base for receiving the spark plug therein. The leaf spring portion creates a receiving force the spark plug must overcome to be positioned within the electrical spring connection assembly. The electrical spring connection assembly also includes a beam spring extending out from the leaf spring portion. The beam spring portion creates a retention force to retain the spark plug within the electrical spring connection assembly. The retention force is greater than the receiving force. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Advantages of the invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
       FIG. 1  is a cross-sectional side view of a spark plug, a conducting case and a pencil ignition coil case partially cut away; 
       FIG. 2  is an exploded perspective view of one embodiment of the invention being inserted into a conducting case terminal; and 
       FIG. 3  is a cross-sectional side view of the invention inserted into a conducting case with a spark plug head shown in two positions being inserted therein. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to the Figures, one embodiment of the invention, an electrical spring connection assembly, is generally indicated at  10 . The electrical spring connection assembly  10  is used to electrically connect a high voltage terminal (not shown) within a pencil ignition coil case  12  to a spark plug  14  having a spark plug head  16 . Intermediate the pencil ignition coil case  12  and the spark plug head  16  is a conducting case  18 . The conducting case  18  defines a cylindrical cavity  20  having a predetermined case diameter  22  (FIG.  3 ). The conducting case  18  also includes a recess  24  for receiving a portion of the high voltage terminal that is housed within the pencil ignition coil case  12 . The conducting case  18  also includes a flange  26  to properly position and retain the conducting case  18  with respect to the pencil ignition coil case  12 . 
   The pencil ignition coil case  12  also includes a connector portion  28  having a plurality of barbs  30  extending out therefrom. The barbs  30  secure the connector portion  28  and, hence, the pencil ignition coil case  12  to an insulating boot  32 . The insulating boot  32  surrounds the spark plug head  16  and engages a ceramic insulating portion  34  of the spark plug  14 . 
   The electrical spring connection assembly  10  includes a base  36 . The base  36  includes a securing aperture  38  for receiving the recess  24  of the conducting case  18  therein. This allows the electrical spring connection assembly  10  to be fixedly secured to the conducting case  18 . The electrical spring connection assembly  10  also includes a leaf spring portion  40  that extends radially out from the base  36 . The leaf spring portion  40  receives the spark plug  14  therein. The leaf spring portion  40  includes a bend  42  that extends between the leaf spring portion  40  and the base  36 . The bend  42  does not engage the conducting case  18 . More specifically, the bend  42  defines a bend diameter  44  that is less than the predetermined case diameter  22  of the high voltage terminal  18 . This allows the leaf spring portion  40  to move relative to the cylindrical cavity  20  during insertion of the spark plug head  16  and to the electrical spring connection assembly  10 . The leaf spring portion  40  creates an engagement force  45  that must be overcome to insert the spark plug head  16  therein. 
   The electrical spring connection assembly  10  also includes a beam spring portion  46  that extends out from the leaf spring portion  40 . The beam spring portion  46  extends from the leaf spring portion  40  out to the conducting case  18 . In the embodiment shown, the leaf spring portion  40  and the beam spring portion  46  create an arm  48 . There are a plurality of arms  48  that are included in the electrical spring connection assembly  10 . While any number of arms  48  greater than two would effectively allow the electrical spring connection assembly  10  to operate, there are four arms  48  shown in the Figures. 
   Each of the plurality of arms  48  extends out to a distal end  50 . It is the distal end  50  that engages the conducting case  18 . The length of the plurality of arms  48  extends over the spark plug  14  only as far as the connector portion  28 . This allows the electrical spring connection assembly  10  to be mounted onto the spark plug head  16  off-axis by seven degrees. It should be appreciated that other embodiments may increase the misalignment up to fifteen degrees. 
   Because the beam spring portion  46  extends down to the distal end  50  of each of the plurality of arms  48 , the beam spring portion  46  creates a retention force  51  to retain the spark plug  14  within the electrical spring connection assembly. This retention force is greater than the engagement force  45  of the leaf spring portion  40 . 
   Intermediate the leaf spring portion  40  and the beam spring portion  46  of each of the plurality of arms  48  is a detent  52 . It is the detent  52  that delineates the leaf spring portion  40  from the beam spring portion  46 . In addition, it is the detent  52  that matingly engages the spark plug head  16  of the spark plug  14  and abuts thereagainst to create the retention force  51 . 
   When assembling the electrical spring connection assembly  10  and the conducting case  18 , the cylindrical cavity  20  has a bottom edge  54  ( FIG. 2 ) that is straight. Once the electrical spring connection assembly  10  is inserted into the cylindrical cavity  20 , the bottom edge  54  is curled around the distal ends  50  of each of the plurality of arms  48 . This secures the electrical spring connection assembly  10  inside the conducting case  18  and further increases the retention force by preventing the distal ends  50  of the arms  48  from moving laterally or longitudinally, thus creating a strong beam spring portion  46 . 
   The invention has been described in an illustrative manner. It is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation. 
   Many modifications and variations of the invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the invention may be practiced other than as specifically described.