Patent Publication Number: US-3878418-A

Title: Igniter plug

Description:
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 United States Patent 11 1 Meyer [451 Apr. 15, 1975 1 IGNITER PLUG [75] Inventor: Helmut P. Meyer, Sidney, NY.  
 [73] Assignee: The Bendix Corporation, Southfield,  
 Mich.  
 [22] Filed: Jan. 28, 1974 [21] Appl. No.: 437,258  
 [52] US. Cl. 313/118; 313/137; 313/141; 313/143 [51] Int. Cl. H011 13/20 [58] Field of Search 313/141-145, 313/118,137; 123/169 P, 169 PA, 169 E2 [56] References Cited UNITED STATES PATENTS 1,037,307 9/1912 Pierrel 313/143 X 1,192,003 7/1916 Schmidt 313/141 1,452,054 4/1923 Propst 313/141 X 1,540,137 6/1925 Lautenschlager 313/141 X 2,693,082 11/1954 Arthur 313/143 X 3,745,400 7/1973 Meyer 1. 313/144 Primary ExaminerAlfred L. Brody Attorney, Agent, or FirmRaymond J. Eifler [57] ABSTRACT An igniter plug for a turbine engine which has increased life and improved ignition capabilities. The igniter plug is characterized by an angled end portion which extends into a combustion chamber of a turbine engine. The angled end of the plug fits the contour of the combustion chamber, to permit freer flow of gases past the plug tip while at the same time allowing maximum projection and exposure of the spark into the combustible mixture.  
 3 Claims, 1 Drawing Figure IGNITER PLU;  
 BACKGROUND OF THE INVENTION This invention relates to a spark discharge device for igniting combustible materials and more particularly to an improved igniter plug for igniting fuel in a turbine or jet engine. This invention is most particularly related to the novel configuration of the electrical discharge end of the igniter plug that ignites combustible gases.  
  lgniter plugs generally comprise a metal shell or body that has a flange or other mounting means for mounting the igniter plug in a ttlrbine engine. the shell constituting one electrode of the igniter plug. A central electrode passes through the shell and is supported by an insulator which surrounds the central electrode and which is fitted into an opening in the metal shell. A copper packing ring or bushing is then provided between the insulator and the shell in order to seal the opening in the body. through which the insulator extends. against escape of gases. One example of a prior art igniter plug may he found in U.S. Pat. No. 3.745.400 entitled lgniter Plug issued July l0. 1973 to H. P. Meyer. hereby expressly incorporated by reference.  
  The igniter plug is mounted so that the discharge end that supplies the electric discharge to ignite the fuel extends into the combustion chamber of the engine. Because of the extremely high temperatures encountered during combustion of the gases and the impingement of the rapidly flowing gases on the spark plug. the discharge end of the spark plug wears away until the spark plug is no longer capable of igniting fuel in the engine.  
 SUMMARY OF THE INVENTION This invention provides an improved igniter plug for turbine or jet engines that has an increased life span and is more effective in igniting fuel in the engine.  
  The invention is an igniter plug characterized by an angled surface at the discharge end of the igniter plug.  
  In one embodiment of the invention. the igniter plug comprises an inner elongated electrode (30) having a front portion (32). a rear portion and a central axis. a forward elongated insulator (80) disposed around the forward portion of said electrode (30): an intermediate elongated insulator (40) disposed around at least a rear portion of the electrode (30). the intermediate insulator (40) having a front portion and a rear portion; an outer elongated metal shell disposed around the electrode and electrically isolated therefrom by the forward (80) and intermediate (40) insulators. metal shell (20) having a rear portion that has an opening therein and a front end portion (23) arranged to provide a spark gap with the end of the front portion (32) of the electrode the improvement wherein the front end of the spark plug terminates in an angled surface comprising: the front portion of the inner elongated electrode (30) which terminates in a first angled surface one end of the forward elongated insulator (80) which terminates in an angled surface (85) parallel to the first angled surface (35 and the forward end of the front end portion of the metal shell (20) which terminates in an angled surface (25) parallel to the first angled surface (35).  
  Accordingly. it is an object of this invention to provide an igniter plug that has an increased life span.  
  It is another object of this invention to provide an igniter plug that provides a more effective electrical discharge to ignite the fuel in a turbine or jet engine.  
  it is a further object of this invention to provide an igniter plug having an angled surface at the electric arc discharge end of the plug to improve the performance of the plug.  
  The above and other objects and features of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings and claims which form a part of the specification. Further. the use of numerals in any portion ofthe specification is for the purpose of facilitating an understanding of the invention and is not intended to limit the scope of the invention to the specific embodiments referenced.  
 DETAILED DESCRIPTION OF THE DRAWING The single FlGURE illustrates an igniter plug incorporating the objects of this invention.  
  The igniter plug comprises an elongated central electrode 30; an outer metal shell 20 which forms the second electrode; a forward insulator and a rear insulator 40.  
  The central electrode 30 is generally comprised of an electrically conducting material so that when an electric potential is applied across the central electrode 30 and the outer shell electrode Zll. an arc discharge may be formed between the tip 32 of the inner electrode 30 and the surrounding portion 23 of the shell electrode 20. The end portion of the electrode 30 from which the spark discharge occurs is a cylindrically shaped end portion 32 that is of a much larger diameter than the rest of the electrode which contains therein one or more passages 3| for the passage of gas to cool the tip of the electrode 30 during operation. The end portion 32 of the electrode 30 terminates in an angled surface 35. makes an angle of about 30 with the central axis of the inner electrode 30. Coaxially disposed around the central electrode 30 is a ceramic insulator 40 which electrically isolates the central electrode 30 from the outer shell electrode 20. To prevent any gases from escaping through the rear end of the spark plug (not shown). the rear end of the spark plug is sealed so that no gases may escape.  
  A second forward ceramic insulator 80. having a shoulder 81. is also positioned within the shell 20 to prevent radial and axial movement of the control electrode 30 that might result in contact between the control electrode 30 and the shell electrode 20. hence preventing electrical short circuits. The insulator 80 has a rear portion and a front portion having an angled end surface that makes an angle of about 30 with the central axis of the electrode 30. The angled end surface 85 therefore provides an end surface having an inclination of about 30 to the main axis of the insulator and parallel with the end surface 35 of the electrode 30.  
  The outer shell 20 includes a mounting flange (not shown] for mounting the igniter plug to a turbine engine: intake and exhaust ports 21 and 22 for allowing the entrance and exit of engine gases into the igniter plug to cool the electrode 30&#39;. and a forward shell portion or cap 23 that is welded to the shell 20. The front portion of the shell includes an angled surface 25 that is parallel to the angled surface 35 of the inner electrode 30; and an opening that forms the discharge surface of the shell that together with the angled surface 35 of the control electrode 30 forms the discharge gap which when energized ignites the fuel. This cap 23 also has an internal angled surface 26 which mates with the angled surface 86 of the forward insulator 80. When assembling the igniter plug. the last two pieces added to the assembly are the forward ceramic insulator 80 and then the shell cap 23 which is welded to shell 20 to retain the forward insulator in a position that isolates the central electrode 30 from the outer electrode 23. The shell 23 and the insulator 80 are now in 360 mated contact between surfaces 86 and 26. The cap 23 and insulator 80 are axially assembled with the same case as symmetrical parts. but provide an igniter with an inclined end surface.  
  The igniter plug shown in its operating position wherein it extends through the outer wall 2 ofthe cornbustion chamber so that it is generally flush with the inner wall I of the combustion chamber of the engine. It is the inventor&#39;s belief that the angled or oblique end portion of the igniter plug which extends into the combustion chamber increases the effectiveness of the igniter plug and increases its life. Preferably. the igniter plug is mounted so that the end surface 25 of the shell 20 is flush with the wall 2 of a combustion chamber.  
  While a preferred embodiment of the invention has been disclosed. it will be apparent to those skilled in the art that changes may be made to the invention as set forth in the appended claims and. in some cases. certain features of the invention may be used to advantage without corresponding use of other features. Accordingly. it is intended that the illustrative and descriptive materials herein be used to illustrate the principles of the invention and not to limit the scope thereof.  
 Having described the invention. what is claimed is:  
  T. ln combination with a spark plug of the type having an inner elongated electrode having a front portion. a rear portion. and a central axis; a forward elongated insulator disposed around the forward portion of said electrode; an intermediate elongated insulator disposed around at least the rear portion of said electrode; an outer elongated metal shell disposed around the electrode and electrically isolated therefrom by the forward and intermediate insulators. said metal shell having a front end portion arranged to provide a spark gap with the end of the front portion of said electrode. the improvement wherein the front end of said spark plug terminates in an angled surface comprising:  
 the front portion of said inner elongated electrode which terminates in a first angled surface;  
 one end of the forward elongated insulator which terminates in an angled surface parallel to said first angled surface; and  
 the forward end of the front end portion of said metal shell which terminates in an angled surface parallel to said first angled surface.  
  2. The combination recited in claim 1 wherein the parallel angled surfaces are about 30 from a plane that is perpendicular to the central axis of said inner elongated electrode.  
  3. A spark plug comprising an inner elongated electrode having a cylindrically shaped front portion and a central axis; an elongated insulator means disposed around at least a portion of the electrode: an outer elongated metal shell disposed around the electrode and insulator means and electrically isolated from the electrode by said insulator means. said metal shell having an annular front portion arranged around the inner electrode to provide an annular spark gap with the end of the front portion of said electrode. and wherein the front end of said metal shell is equidistant at all adjacent points between the end of the inner electrode and the end of said metal shell the front end of said elongated electrode and the front end of said metal shell terminates in angled surfaces which are parallel to each other. with the front end of said metal shell extending beyond the adjacent front end of said inner electrode. l