Ignition coil adapter for a distributorless ignition system
BACKGROUND OF THE INVENTION 
     The present invention relates to electrical adapters for distributorless ignition systems; more particularly, the present invention relates to an adapter for use between a spark plug cable and a high output terminal of a distributorless ignition system. 
     Prior art automotive ignition systems relied upon a distributor to deliver energy to spark plugs at given intervals. In a distributorless ignition system, the timing function is computerized and each spark plug is attached to a separate high energy output terminal which delivers energy at the proper interval, eliminating the need for a distributor. 
     Typically, the distributorless ignition system (D.I.S.) includes multiple terminals, each of which include a cup-shaped electrode and a tower extending upward from the electrode. The spark plug cable must be connected to the high output terminal to deliver energy to the spark plug located at the opposite end of the spark plug cable. The connection means between the cable and the terminal must provide an electrical as well as a water-tight mechanical connection. Prior art adapters designed for connecting the spark plug cable to the high output terminal of a D.I.S. include the device disclosed in U.S. Pat. No. 4,790,767 to Sturdevan. The device described in this patent is a cap-like arrangement with an annular recess that fits over the top of the tower to effect a water-tight seal. Mechanical connection is made with levered dogs which grip a flange formed at the outside of the tower. Electrical connection in the device described in U.S. Pat. No. 4,790,767 is by a terminal which fits within the cupshaped electrode of the D.I.S. 
     One disadvantage of the adapter disclosed in U.S. Pat. No. 4,790,767 is its reliance on the external shape of the tower for a proper connection and water-tight seal. While present distributorless systems like those utilized by Ford Motor Company include a flanged tower, future D.I.S. designs may not have flanged towers and may require internal connections and sealing. Additionally, as space becomes more important in automotive designing, future distributorless systems may require the output terminals to be spaced closer together making it impracticable to use an adapter which grips the outside of the tower. 
     There is a need, therefore, for an adapter for a distributorless ignition system which does not utilize the outside perimeter of the tower for mechanical connection or water-tight sealing. 
     There is a further need, therefore, for an adapter for a distributorless ignition system which requires less space than those presently available. 
     SUMMARY OF THE INVENTION 
     The present invention is an adapter which provides a watertight, mechanical and electrical connection between a spark plug cable and the high energy output terminal of distributorless ignition systems. It does not utilize the outside perimeter of the tower and it requires less space than those adapters presently available. The ignition system includes a cup-shaped electrode and a tower extending upward from the electrode. The adapter includes an electrode extension which expands into the cup-shaped electrode at one end and is connected to the spark plug cable at the opposite end. The extension is held within a rubber insert which is pressfit into the tower at one end and a boot at the opposite end, providing an internal water-tight seal within the adapter. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1 is a side view, in section of the adapter that is the subject of the present invention; 
     FIG. 2 is a section view depicting the terminal connection between the spark plug cable and the cap; 
     FIG. 3 is a detailed view depicting the expanding means in a non-energized position; 
     FIG. 4 is a detailed view depicting the expanding means in an energized position; 
     FIG. 5 is a section view showing a second embodiment of the invention; and 
     FIG. 6 is a section view showing a third embodiment of the invention. 
    
    
     DESCRIPTION OF A PREFERRED EMBODIMENT 
     The present invention can best be appreciated by reference to the Figures. FIG. 1 is view in section of a high voltage output terminal 20 of a distributorless ignition system with the adapter 30 of the present invention. The output terminal 20 is exemplary of the current D.I.S. utilized by the Ford Motor Company and consists of a cup-shaped electrode 25 and a dielectric tower 35 which extends up from the electrode 25. The tower 35 and electrode 25 are component parts of module 22. Also included in the module 22 is a coil (not shown) for each electrode or pair of electrodes. In a typical system, at least one module containing several towers, electrodes and coils will be located in the engine compartment of the automobile. Tower 35 acts to provide an entrance to the electrode 25 with a series of increasingly smaller inside diameters 40. The exterior of tower 35 includes a circular flange 37. 
     Electrical connection between the cup-shaped electrode 25 and the spark plug cable 66 is through an electrode extension 45 which acts to extend the cup-shaped electrode 25. The electrode extension 45 is made of an electrically conductive material and is anchored at the bottom of electrode 25 by expanding means. In the preferred embodiment the extension 45 includes a cylindrical body 80 having slots 82 (FIGS. 3 and 4) extending upward from its bottom end. Extension 45 also has a threaded shaft 85 running its length. At the bottom end, the shaft 85 forms a cone-shaped head 90. The larger diameter of the cone-shaped head 90 extends partially from the end of extension body 80. At the upper end of threaded shaft 85 is a cap 50 which is slotted at 91 to allow the cap 50 to be turned with a screwdriver. 
     The cylindrical body 80 is held in compression between the cap 50 and the cone-shaped head 90 of shaft 85. As ca 50 is turned in a clockwise motion on threaded shaft 85, tabs 87 on the sides of cone-shaped head 90 contact slots 82 and prevent the rotation of shaft 85. FIG. 3 depicts the expanding means of the extension 45 in the non-energized position. As shown in FIG. 3, the tabs 87 on cone 90 have slipped into slots 82, but the bottom of cone 90 still extends from extension body 80. 
     FIG. 4 depicts the expansion means in the energized, anchored position. As the cap 50 is rotated clockwise, cone-shaped head 90 is pulled into the end of body 80, spreading body 80 along slots 82. By forcing body 80 into the inside walls 83 of cupshaped electrode 25, the extension 45 is anchored within electrode 25. 
     Cap 50 could be fitted with a means for locking the extension 45 in the energized position. For example, a lock washer could be utilized between cap 50 and the top surface of body 80, preventing shaft 85 from moving once cone-shaped head 90 has been pulled into body 80. Additionally, locking ears could be formed on the bottom surface of cap 50 or the top surface of body 80 to lock the cap 50 in place after energizing. Additions of the foregoing sort are contemplated as an aspect of the invention. 
     Water-proofing is accomplished by an elastomer insert 70 which is designed to fit around and support the electrode extension 45 in a coaxial relationship. The outer, bottom portion of insert 70 forms progressively smaller diameters 72 which are slightly larger than inside diameters 40 of tower 35, allowing a press-fit between insert 70 and tower 35. In the preferred embodiment, there is a sealing ridge 71 (FIG. 1) formed in the largest diameter of insert 70 to further effect a water-tight seal. At its upper end, insert 70 fits into elastomer boot 65. The upper portion of insert 70 is slightly greater in diameter than the inside diameter of boot 65, allowing a press-fit between the insert 70 and boot 65. In the preferred embodiment, the inside diameter of boot 65 includes a series of ridges 68 which ar designed to further seal the boot 65 and insert 70 surfaces. 
     The adapter can be supplied with a spark plug cable 66 with an attached terminal 67 and boot 65. The electrode extension 45 is 15 supplied already inserted into the insert 70. The extension and insert assembly is then placed in the high output terminal 20 of the D.I.S. with the insert 70 sealing the tower 35 and the coneshaped head 90 extending into the cup-shaped electrode 25. The cap 50 at the top of extension 45 is then turned forcing the coneshaped head 90 into body 80, thereby expanding the body 80 and anchoring extension 45. Thereafter, the boot 65 containing the spark plug cable 66 and terminal 67 are placed over cap 50, making an electrical and mechanical connection between ca 50 and spark plug terminal 67 (FIG. 2). A water-tight seal is simultaneously made between the surfaces of the insert 70 and boot 65 (FIG. 1). 
     One variation of the preferred embodiment, depicted in FIG. 5, includes a separate cone-shaped member 100 which has internal threads 101. As in the first embodiment, the extension 110 has a body 115 with slots (not shown) in the lower end and a center shaft 120. However, the bottom portion 103 of the shaft 120 is threaded. To utilize the adapter, cone 100 is first placed into the cupshaped electrode 25 in a press-fit relation. Thereafter, the shaft 120 is threaded into the cone 100, pulling it into the body 115 of the extension 110 and expanding the body 115 into the walls of cupshaped electrode 25. While the electrode extension 4 and anchoring means 90 described and depicted is the preferred embodiment, one skilled in the art will appreciate that the method of anchoring the electrode extension 45 to the cup-shaped electrode 25 could vary and still be within the scope of the invention. For example, as depicted in FIG. 6, the extension body 150 could be solid with a threaded bottom portion 152 having an outside diameter slightly larger than the inside diameter of cup-shaped electrode 25. The extension 150 could then be threaded into electrode, forming threads within the interior of the electrode cup 25. 
     In yet another alternative embodiment (not shown) the electrode extension consists of three pieces of metal giving the appearance of a round rod with a threaded cap on one end. The rodlike assembly includes a center section and two outer sections. The end of the center section opposite the threaded cap is tapered to reduce the cross-section at that end. The two outer sections have a matching but reverse taper. The ends of the outer sections opposite the taper are threaded to accept a portion of the threaded cap. The center section is longer than the outer sections, has no threads and has a shaft-like extension which fits into the threaded cap allowing the cap to rotate. When first assembled the threepiece assembly has essentially the same diameter throughout its length which allows it to be inserted in a hole of slightly larger diameter. When the cap is turned, the two outer sections move up or down along the center section, depending on the direction the cap is turned and whether right-hand or left-hand threads are used. When the cap is turned to cause the outer sections to move into the threaded cap, the tapers cause the outer sections at the opposite end to move outward, increasing the diameter of the unthreaded end of the assembly thereby anchoring the assembly against the walls of the cup-shaped electrode 25. 
     In the forgoing embodiments, the cap 50 is provided with a slot 91 for a regular screwdriver. However, one skilled in the art will realize that the cap 50 could be shaped for use with any type of screw driver or wrench and still be in the purview of the invention. Additionally, the threads could be left or righthanded, requiring rotation in either direction to anchor the extension within the cup-shaped electrode. 
     At its upper end, extension 45 is electrically and mechanically connected to spark plug cable 60. In the preferred embodiment, as depicted in FIG. 2, the extension 45 is connected to the cable by a standard female spark plug terminal which fits over cap 50. However, the connection could be made any number of ways. For example, the top of the extension 45 could form a female member and the terminal could be a male member. Also, while the elastomer boot 65 is shown in the preferred embodiment as forming a 90 degree angle, those skilled in the art will appreciate that the boot 65 could form any angle or even be straight and still preform the same function and be within the scope of the invention. 
     While the adapter of the present invention has been described by reference to its preferred embodiment, it will be understood that other various embodiments of the device and method of the present invention may be possible by reference to the specification and the appended claims. Such additional embodiments shall be included within the scope of the appended claims.