US2814665A

US2814665A - Connector for igniter plug

Info

Publication number: US2814665A
Authority: US
Publication date: 1957-11-26
Anticipated expiration: 1974-11-26

Description

1957 w. A. BYCHINSKY 2,814,665

CONNECTOR FOR IGNITER PLUG Filed -Nov. 6, 1952 (IUNNECTUR FOR IGNITER PLUG Wilfred A. Bychinsky, Ann Arbor, Mich., assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application November 6, 1952, Serial No. 319,145

2 Claims. (Cl. 174-88) This invention relates to an electrical connector and more particularly to an electrical connector especially suited for use with an igniter plug in an internal combustion engine ignition system. The qualities of the electrical connector structure of this invention which render it especially suitable for use in an ignition harness as a lead for a sparking plug are its very high heat resistance, its resistance to deterioration andbreakage and its ability to provide for the expansion and contraction which results from the wire temperature ranges to which such connectors are subjected.

The particular problem for which my invention provides a solution is that which arises because of the very high temperatures encountered adjacent internal combustion engines due to the large amounts of heat given off during their operation. Thus, my invention is particularly suited for use on jet or gas turbine engines or gas turbine engine afterburners wherein extremely high temperatures are generated.

The ignition harness or spark plug connector structure immediately adjacent the internal combustion engine is subjected to very high temperatures during the period of engine operation but at the same time is also subjected to lower temperatures during the periods of. the engines idleness. Because of this wide temperature differential, it is essential that the conductor not only have a high heat resistance but also that it be such as' to allow it to expand and contract without damage and without breaking the electrical connection. At the same time, it is just as important that the connector structure have a certain amount of flexibility and have a high resistance to shock and vibration. Lastly, it is essential that adequate electrical insulation be provided to prevent short circuiting or flash over of the high voltage current being conducted to the igniter plug. On conventional reciprocating type internal combustion engines which operate at relatively low temperatures, the insulation for the spark plug conductors generally consists of some elastic material such as rubber or the like, this material having sufficient heat resistance to withstand the temperaturesv encountered and at the same time providing the amount of flexibility, shock resistance and insulation required. Such insulation material does not, however, have suflicient heat resistance for use on turbine engines or turbine engine afterburners operating at relatively high temperatures, and it has therefore been proposed to use ceramic as the igniter plug connector insulating material. Ceramics, however, have relatively little flexibility and shock resistance and are particularly subject to breakage. Moreover, continuous ceramic insulation is impractical not only because of its low shock resistance and tendency to break but also because of its rigidity. On the other hand, discontinuous ceramic insulation requires the use of some suitable supporting casing of a highly heat resistantmaterial such as metal, and when such structure is used, the good insulating qualities of the ceramic are lost because of the spaces which necessarily result between adjacentv pieces of the ceramic insulation.

'nited States Patent 2,814,665 Patented Nov. 26, 1957 It is an object of this invention to provide an igniter plug connector structure which is adequately insulated, has high heat resistance, high resistance to shock and breakage and which allows for expansion and contraction caused by wide temperature diiferentials. Another ob-. ject of the invention is to provide an igniter plug connector structure which utilizes ceramic insulation and thereby has a high heat resistance but which, at the same time, has sufficient flexibility and shock resistance to prevent breakage and failure due to shock and engine vibration.

These and other objects are carried out in accordance with the invention by the provision of a connector structure having a series of aligned tubular ceramic insulator members retained within a metal sleeve supporting member, each of said insulator members having a metal contact within its central bore and intermediate its ends, and conductor members covered with a ceramic insulation positioned within the insulator members to establish the electrical connection, the conductors and insulator members being arranged in staggered relationship. By means of such structure, the metallic conducting path is provided with a discontinuous ceramic covering which furnishes electrical insulation as adequate as though the ceramic were continuous but at the same time aflord the flexibility and shock resistance required. The connector structure of this invention may be straight or may be in the form of an elbow, the latter form being that required for most installations because of the limited space available adjacent the turbine engine or afterburner to which the igniter is connected.

The invention, its objects and advantages will appear more clearly and precisely from the following description of preferred embodiments as well as in the accompanying drawing in which:

Figure 1 represents an igniter plug installation in a gas turbine engine afterburner and shows the connector structure of this invention in its environment;

Figure 2 is a cross-sectional view of one embodiment of the invention;

Figure 3 is a bottom view of the igniter plug shown in Figure 1 but drawn to larger scale; and

Figure 4 is a cross-sectional view of another embodiment of the invention.

Referring now to the drawing, Figure 1 shows an igniter plug 6 mounted on the wall 8 of a gas turbine engine afterburner by means of a mounting pad 10. A fuel inlet pipe 12 is shown extending through the afterburner Wall to direct a combustible charge into the afterburner adjacent the spark gap of the igniter plug.

The igniter plug 6 consists of a center electrode 14 surrounded by an insulator 16 which in turn is surrounded and supported by a metal shell 18. A ground electrode 20 extends from the base of the shell into spaced relationship with the end of the center electrode 14 to form a spark gap therewith. The upper end of the igniter plug has secured thereto a connector 22 embodying the present invention, this connector establishing electrical contact between the center electrode of the igniter plug and the source of the electrical energy of the ignition system.

With reference now to Figure 2, the connector comprises a metal supporting jacket 24, the interior of which is lined with a plurality of aligned tubular insulator mem bers 26 and 28 through which extends in staggered relationship therewith a series of inner insulator members 29 and 30 of smaller diameter and carrying conductors 32 and 34 in electrical contact with each other to furnish a conducting path to the igniter plug 6.

For purposes of illustration the connector structure is shown as including only two outer insulator members and two inner insulator members and conductors; however, it is obvious that either end of the connector can be lengthened by the use of additional insulator and conductor members arranged in the same relationship as that shown and described.

In the particular embodiment shown by Figure 2, the metal supporting jacket is constructed in sections 36 and 38 secured together and to the igniter plug 6 by means of threaded joints 4i and 42 respectively. Welded joints are used at 44, 46 and 43 to secure the various parts of the individual metal sections 36 and 38 together. The tubular insulator member 28 is fixedly secured within the metal jacket by means of an external annular shoulder 50 which engages an annular groove 52 on the interior of the metal jacket. Gaskets, either of a metal such as copper or nickel or of a heat resistant cement composition such, for example, as a mixture of sodium silicate and asbestos is placed between the edges of the shoulder 50 and the groove as shown at 54 and 55. In the embodiment shown, the connector is in the form of an elbow and thus the tubular insulator member 26 which is positioned at the connector elbow is also of an angular shape. This insulator member is retained within the jacket by means of an annular shoulder 56 which is held between the end wall 58 and the shoulder 60 of the jacket section 36 by a metal gasket 62 and a gasket 64 either of metal or of a heat resistant sealing composition of the type heretofore described.

The tubular insulator member 28 is provided with an internal annular shoulder 66 which supports a contact plug 68 for establishing electrical connection between the end of the insulated conducting member 34 and the next in line conducting member (not shown) which would be positioned in the outer insulator bore shown at 70. The plug 63 is retained within the insulator member by means of a pair of opposed flanges which engage opposite sides of the shoulder 66. In the case of the insulator member 26, a contact plug consisting of a metal block 76 threadedly engaged by a screw member 78, the head of which abuts an internal shoulder of the insulator member serves to establish electrical contact between the ends of adjacent ends of the conductors 32 and 34.

In the embodiment shown, the inner insulators 29 and 30 are in the form of a ceramic coating on the respective conductors 32 and 34. Each of these conductors is provided with flanges at either end in order to retain the ceramic coating and metal conductor as a unit and in order to ai'ford a larger electrical contact area.

To provide the necessary heat and shock resistance and flexibility needed, the electrical contacts within the tubular insulators 26 and 28 are made resilient by the use of spiral metal springs 88 and 90, one of these springs being interposed between one side of each of the contact plugs 68 and 76 and the adjacent end of the respective conductors 32 and 34.

The terminal portion of most of the commonly used igniter plugs for aircraft reciprocating or gas turbine engines is the same or similar to that shown by Figure 2 and consists of a ceramic sleeve 91, which is usually the top of the igniter plug insulator, at the bottom of which is located the electrical contact 92 for the igniter plug centerwire. The outer metal shell 18 of the plug concentrically surrounds the ceramic sleeve and is threaded as shown at 94 for the reception of the connector structure. The connectors of this invention are adapted for use with such a spark plug design, the lower end 96 of the tubular insulator member 26 being substantially of the same dimensions as the top of the ceramic sleeve 91 and the inner insulator-conductor member being sized to fit into the sleeve 91 and make electrical connection with the contact 92, the same staggered relationship being established between the outer insulator 26, the ceramic sleeve 91 and the inner insulator 29 as is established be tween inner and outer insulators in the main body of the connector.

In order to obtain maximum electrical insulation from the amount of ceramic used, it is preferable to locate the contact plugs 68 and 76 as close as possible to the midpoint of the outer insulators since, in this manner, the distance of the air path from the conductors 32 and 34 to the metal sleeve 24 is at a maximum for the lengths of insulator members used.

When the entire connector and igniter plug are assembled as shown and described, the spaces between outer insulators are intermediate the breaks in the inner insulation adjacent the contact plugs 68 and 76. The lengths of the inner and outer insulators are, of course, sufficient to prevent a shorting-out over the air path from the conductors to the metal sleeve. Thus, while a discontinuous ceramic insulation is usd, it has the excellent insulating qualities of a continuous ceramic body.

As stated previously, additional inner and outer insulators arranged in staggered relationship can be used to lengthen the connector. Electric connection with the free end of the connector may be made by a conventional elastomer insulated conductor which is adapted to fit into the bore of the last-in-line outer insulator and make contact with its metal center plug. This latter connection, may of course, be located away from the high heat zone of the engine.

The threaded joint connector jacket shown in Fig. 2 is somewhat advantageous in that it allows for easy assembly and disassembly. However, it has been found that the use of such threaded joints in ignition harness has undesirable effects on radio reception and transmission and from this standpoint, the screw jointed sleeve structure shown by Figure 2 is disadvantageous.

In order to eliminate such radio interference, in the preferred embodiment shown by Figure 4, the metal supporting jacket is a one piece unit, the various portions of the jacket being jointed by welds as shown at 112 and 114. Likewise, the jacket 110 is welded to the outer shell 116 of the igniter plug so as to eliminate the threaded joint at this point. Thus, with the structure shown by Figure 4, the only screw joint used is that at the free end 118 of the connector, this joint being used to connect the ignition lead to the connector. While Figure 4 shows only two series of inner and outer insulators, it is to be understood that additional series could be added if a longer connector is desired. The outer insulators 120 and 122, inner insulators 124 and 126, conducting members 128 and 13!),

contact plugs

132 and 134 and

spring members

136 and 138 are substantially the same in construction and location as those shown by Figure 2 and described with reference thereto. In order to impart additional strength to the connector, a metal brace member 140 having one end welded to the sleeve 110 and the other welded to the shell 116 of the igniter plug may be used.

The connectors of this invention employing inner and outer insulators arranged in staggered relationship so that the break in the outer insulation is midway between the breaks in the inner insulation and vice versa afford means for utilizing all of the advantages of ceramic insulation but at the same time provide the necessary shock resistance and flexibility.

It is to be understood that, although the invention has been described with specific reference to particular embodiments thereof, it is not to be so limited since changes and alterations therein may be made which are within the full intended scope of this invention as defined by the appended claims.

I claim:

1. An electrical connector for an igniter comprising a metal jacket, a plurality of tubular ceramic insulators within and secured to said jacket, each of said insulators having an electrical contact positioned within its bore intermediate the extremities thereof, a plurality of elongated conducting members within said tubular insulators, each of said conductors having a sleeve of insulating .5 material fixedly secured thereto and extending between two of said contacts, and a resilient conducting member interposed between one end of each of said conducting members and the contact adjacent thereto to establish a conducting path from a source of electrical energy to the igniter.

2. In combination with an igniter plug having a terminal portion including a ceramic sleeve insulator surrounded by a metal shell and an electrical contact within said sleeve; a connector comprising an elbow-shaped metal jacket secured to said metal shell to form an extension thereof, a plurality of tubular ceramic insulators fixedly secured Within said jacket to form a discontinuous elbow-shaped extension to said ceramic sleeve insulator,

each of said tubular insulators having a resilient electri- 15 ,87

References Cited in the file of this patent UNITED STATES PATENTS 2,008,573 Blount July 16, 1935 2,081,503 Nowosielski May 25, 1937 2,173,766 Ramsay Sept. 19, 1939 Paulson Oct. 10, 1944