Spark plug
United States Patent Felt Apr. 22, 1975 SPARK PLUG Prinurrv Examiner-John Kominski 75 l t Ath E.Flt,Pl&#39; th.M l 1 or r ur e lch Assistant E.\&#39;aminerDarwm R. Hostetter [73] Ass1gnee: Ethyl Corporation, R1chmond. Va. Armrney. Agent. or Firm-Donald L. Johnson; Robert 122 Filed: 01:1. 11, 1973 21 A 1. N 40 ,664 l 1 pp 0 5 57 ABSTRACT An air gap spark plug having improved resistance to fouling is described. A single electrode is used with improved results over two electrodes. A method of operating an internal combustion engine and other devices which utilize a hydrocarbon fuel is also disclosed.  
 US. Cl. 313/141 Int. Cl. H0lt 13/32 Field of Search 313/141 References Cited UNITED STATES PATENTS 9/1953 Johnson 313/141 4 Claims 3 Drawing Figures SPARK PLUG BACKGROUND OF THE INVENTION This invention is directed to an air gap spark plug and its use in an internal combustion engine or other device.  
  Spark plugs having air gaps are known in the art. This type spark plug is commonly used in gasoline fueled combustion engines to provide a spark. It is characterized in that the spark is generated across an air gap between the primary electrode and the secondary or ground electrode. Ordinarily, the primary electrode runs through the center of the spark plug. Depending on the relationship of the ground electrode to the primary electrode, this spark may be generated in a direction either substantially perpendicular to or substantially parallel with the long axis of the primary electrode.  
 The spark characteristics of either type of plug are subject to change as deposits form on or bridge the electrodes or other parts of the spark plug during the course of their use in initiating the combustion of fuel in an engine or other device. Deposits can build up to a point where the spark plug will not produce a spark as required. This tendency to build up a deposit on a spark plug is generally referred to as fouling. Gapbridging is a specific type of fouling. which is of special concern for certain fuel/additive combinations.  
  An air gap spark plug of the type where the spark is generated in a direction substantially perpendicular to the primary electrode, which is centrally located in the spark plug is disclosed. This spark plug features an improved single ground electrode configuration. This spark plug is considerably more resistant to gapbridging than spark plugs of conventional multigap configuration.  
 SUMMARY OF THE INVENTION An air gap spark plug suitable for providing a spark to ignite fuel in a combustion chamber features a novel ground electrode configuration which improves resistance to fouling and especially, gap-bridging; a method of improving the operation of an internal combustion engine which burns a fuel containing an organo metallic additive, by using the aforesaid improved air gap spark plug.  
 DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal partial section view of an air gap spark plug of the present invention.  
  FIG. 2 is an end view of said FIG. 1 spark plug to A---A&#39;. FIG. 3 is an end view of a conventional twin electrode, parallel gap spark plug having substantially the same upper construction as that shown in FIG. 1.  
 &#39; DESCRIPTION OF PREFERRED EMBODIMENTS An embodiment of this invention is an air gap spark plug featuring a novel ground electrode configuration. The preferred embodiment is an air gap spark plug suitable for supplying a spark to ignite fuel in a combustion chamber which consists essentially of:  
 a. a center electrode,  
 b. an insulator having a central passageway running longitudinally therethrough to receive said center electrode,  
 c. a metal shell enclosing a portion of said insulator,  
 the lower end of said shell 1. extending beyond said insulator and 2. having a single ground electrode extending therefrom in a plane which is substantially parallel to the long axis of said center electrode,  
 d. said center electrode extending beyond the lower end of said shell at least a sufficient distance to define an air gap between the side, and not the end, of said ground electrode and said center electrode, said air gap being no lower than the distal end of said center electrode,  
 thus providing an air gap for a spark to be generated between said center electrode and the side of said ground electrode, in a direction substantially perpendicular to the long axis of said center electrode Another preferred embodiment is the spark plug described above wherein said ground electrode tip (i.e., the unattached end) extends only as far as the farther edge of said center electrode. In a more preferred embodiment said center electrode is cylindrical.  
  These and other embodiments of the invention will be fully elucidated by considering the illustrations presented in FIGS. 1 and 2; and FIG. 3 which illustrates a conventional two ground electrode construction. In all the drawings, the same numbers are used to identify the same part in each of the figures.  
  FIG. I is a longitudinal partial section view of an air gap spark plug of the present invention. In FIG. 1, the spark plug comprises a center electrode 1 which is positioned in the central passageway 2 which runs longitudinally through the insulator 3. A metal shell 4 encloses a portion of the insulator 3. The lower end of the shell 4 has a ground electrode 5 which extends from the shell 4 in a plane substantially parallel to the long axis of said center electrode 1.  
  The center electrode 1 also extends beyond the lower end of said insulator 3 and said shell 4. An air gap 6 is thus defined between the side In of said center electrode l at its distal end and the side 50 of the ground electrode 5. It is across this gap that a spark is generated when the center electrode 1 and the ground electrode 5 are in circuit with an ignition source. Any suitable ignition source can be used.  
  The center electrode 1 is shown to extend beyond the end of said shell 4 a distance 1b. Although this center electrode 1 must so extend, the exact distance of this extension can be varied to fit the needs of the ignition system, the fuel to be burned, the combustion chamber shape, the particular combustion device it is utilized in, and the like.  
  In addition, FIG. 1 also shows a conventional terminal 7 which extends through and outside the insulator 3 and is in contact with the center electrode 1; this terminal 7 provides a means of engaging a conventional wire conductor (not shown) from an ignition source (not shown). FIG. 1 also illustrates that the center electrode l is held in place in the passageway 2 in the insulator 3 by means of a pressed powder seal 8; the same means is used to hold the insulator 3 within the metal shell 4. The spacer 9 also illustrate a conventional means for holding the insulator 3 away from the outer shell 4. These means of mounting and holding the essential elements of the spark plug of FIG. 1 are used for illustrative purposes; and other conventional or art recognized means of accomplishing the same purpose in the spark plug assembly can be used.  
  FIG. 2 is an end view of the FIG. 1 spark plug to the A-A&#39; plane. It illustrates the configuration and placement of the ground electrode 5. The ground electrode 5 contacts the shell 4 along said shells periphery at 40. The air gap 6 runs between the side 50 of said ground electrode and the side of said center electrode 1. The tip (or free end) 5b of said ground electrode extends no further than the farther edge of said center electrode I. The ground electrode 5 may be slightly shorter than shown in FIG. 2 provided it is long enough to define an air gap between its side and the center electrode side. A ground electrode substantially longer than shown may be less efficient.  
  The materials used in fabricating the insulator. center electrode, outer shell. and other portions of the spark plug of the present invention are not of critical importance. These elements of the spark plug can be made of any materials which have suitable physical and electrical properties. Furthermore, although only one upper spark plug body construction is illustrated, this is not meant to be limiting. In other words, any spark plug body construction having an outer metal shell and an insulator separating a center electrode from the shell can be utilized. For example, the center electrode may have a second air gap in series with the primary air gap.  
  FIG. 3 is an end view of a spark plug tip of conventional design having two parallel, side gap ground electrodes (7 and 8). It is not encompassed by nor meant to illustrate the present invention. Its purpose is to illustrate how the present spark plug configuration differs from the conventional configuration. The upper portion of the FIG. 3 spark plug is the same as that illustrated in FIG. 1.  
  The spark plug of the present invention is especially useful to provide a spark in a reciprocating, spark ignition. internal combustion engine which is fueled with a suitable hydrocarbon fuel. Suitable fuels include hydrocarbons boiling in the gasoline range, liquefied normally gaseous hydrocarbons such as propane, butane, methane, and the like. or gaseous hydrocarbons such as methane, natural gas, and the like. These fuels may contain additives such as antiknock agents, phosphorus containing deposit modifiers, antioxidants, blending agents, carburetor detergents, intake valve deposit suppressors metal deactivators, anti-icers, dyes, and the like. Thus, another embodiment of this invention is a method of operating a spark ignition, internal combustion engine by providing each combustion chamber (cylinder) with a fuel containing an organometallic antiknock agent, sufficient air for combustion and igniting the air/fuel charge with a spark provided by an air gap of the present invention whereby time to misfire is substantially increased. An especially preferred embodiment of this method is accomplished by utilizing a fuel containing a tetrahydrocarbyllead, such as tetraethyllead, tetramethyllead, and the like, or a cyclopentadienyl compound of iron, manganese, or nickel. or an ironcarbonyl such as ironpentacarbonyl, in antiknock quantities. A most preferred embodiment of this method utilizes a fuel containing an antiknock quantity of (methylcyclopentadienyl)manganese tricarbonyl.  
  An outstanding feature of the present single spark plug construction is that it is substantially more resistant to gap-bridging than a multigap spark plug of comparable design. This improved resistance to gapbridging was demonstrated in a comparative engine test. This test involved road operation of a multicylinder internal combustion engine-powered automobile until plug misfire was unacceptable. Misfire indicates that the spark plug has gap-bridged and is either not sparking at all or that it is sparking in such a manner that proper ignition of the fuel/air mixture is not occurring.  
  This test was first run with the engine provided with the spark plugs substantially as illustrated in FIG. 1 and then with the engine provided with spark plugs substantially as illustrated by FIG. 3. The fuel used in both cases was a commercial base gasoline containing about 0.5 grams of manganese as (methylcyclopentadienyl)- manganese tricarbonyl. The data obtained was reported as number of miles to unacceptable misfire. The following table contains this data.  
 TABLE Multi-Cylinder Engine Road Test Evaluation The data clearly shows the unexpected superiority of the single gap spark plug of the present invention compared to the conventional twin gap spark plug.  
 Claims to the invention follow.  
 I claim:  
  1. An air gap spark plug suitable for supplying a spark to ignite fuel in a combustion chamber which consists essentially of a. a center electrode,  
 b. an insulator having a central passageway running longitudinally therethrough to receive said center electrode,  
 c. a metal shell enclosing a portion of said insulator,  
 the lower end of said shell 1. extending beyond said insulator and 2. having a single ground electrode extending therefrom in a plane which is substantially parallel to the long axis of said center electrode,  
 d. said center electrode extending beyond the lower end of said shell at least a sufficient distance to define an air gap between the side, and not the end, of said ground electrode and said center electrode, said air gap being no lower than the distal end of said center electrode,  
 thus providing an air gap for a spark to be generated between said center electrode and the side of said ground electrode, in a direction substantially perpendicular to the long axis of said center electrode.  
  2. The spark plug of claim 1 wherein the unattached end of said ground electrode extends no further than the farther edge of said center electrode.  
 3. The spark plug of claim 2 wherein said center electrode is cylindrical.  
 4. The spark plug of claim 3 wherein said air gap is adjustable.