US2733385A

US2733385A - bychinsky

Info

Publication number: US2733385A
Authority: US
Publication date: 1956-01-31
Anticipated expiration: 1973-01-31

Description

Jan. 31, 1956 w. A. BYCHINSKY IGNITER PLUGS 2 Sheets-Sheet 1 Filed May 21, 1952 3nvenf0r W 9 m (Ittornegs 2 Sheets-Sheet 2 3 11 men for Kai/hm @Zfiyclzhsy (Ittornegs Jan. 31, 1956 w. A. BYCHINSKY IGNITER PLUGS Filed May 21, 1952 m a 8 a m a M W M 8 5 i i 3 8 M w I m mqw 4 6 III 252 IGNITER PLUGS Wilfred A. Bychinsky, Ann Arbor, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application May 21, 1952, Serial No. 289,158 6 Claims. (Cl. 317-83) This invention relates to spark plugs and, more particularly, to spark plugs especially suitable for use with high voltages as igniters in jet engine burners.

it often occurs that the fuel mixture which is fed into jet engine burners is quite poor and ditficult to ignite, perhaps because the mixture is too lean or too rich or because the fuel is not completely vaporized. This is particularly true when operation is at high altitude under which conditions it is often quite diflicult to ignite and to maintain ignited the fuel mixture which is blown into the burner at high speed. it is well known that an igniter having a spark gap which is considerably larger than the ordinary is effective to cause a more complete ignition of the fuel mixtures and is therefore beneficial for increasing the eificiency of the burner. An increase in the size of the spark gap demands the use of a much higher voltage than that usually used and thus increases the problem of electrical insulation in the igniter. If a conventional ground return type plug is redesigned by widening the spark gap and providing the extra amount of insulation required by the application or" higher voltages, various difiiculties which are inherent in such a design preclude efficient and satisfactory operation. The problem of adequately cooling the igniter becomes more ditficult when increased amounts of electrical insulation are used. Also, larger and more complex insulators must be manufactured. Such a system likewise increases the problems of electrically insulating the entire ignition wiring system since the entire voltage load is carried by a single circuit.

It is an object of this invention to provide an igniter having a larger than ordinary spark gap to operate at high voltage, but which avoids the problem of high tension insulation. Another object of the invention is the provisic-n of an igniter plug which is designed to operate at high voltages and which has adequate cooling means, both for the electrical insulator and supporting members and for the electrodes.

These and other objects are carried out by the provision of an igniter having a spark gap formed between a pair of air conducting hollow electrodes, each of the electrodes being insulated from ground by a pair of vertically arranged insulators the structure of which cooperates with the insulator supporting shell to provide for the passage of cooling air through the electrode and insulators, the igniter operating in conjunction with a two-coil ignition system.

Other objects and advantages will appear more clearly from the following description of specific embodiments of the invention and from the accompanying drawings in which Figure l is a side view of one embodiment of the invention with one half of the igniter shown in section; Figure 1A is an enlarged cross-sectional view of the upper portion of the electrode shown in Figure 1; Figure 2 is bottom view of the embodiment shown in Figure 1; Figure 3 is a view taken on the line 33 of Figure 1; Figure 4 is a view taken on the line 44 of Figure 1; Figure 5 is a side view with parts broken away of another embodiment tinite rates Patent nice 2,733,385 Patented Jan. 31, 1956 of the invention, and Figure 6 is a bottom view of the modification shown in Figure 5 Referring now to the drawings, Figure 1 shows an igniter consisting of two units 3 and 10 mounted side by side in parallel spaced relationship on a mounting plate or pad 12. With the exception that the electrodes are bent in opposite directions as hereinafter discussed, these units are identical and thus the description and reference numerals hereinafter used are applicable to either of the units except as specified otherwise.

Each of the units includes a metal outer shell 14, a pair of vertically arranged

insulators

16 and 18, and an electrode 2%. Mounted on the top of and concentrically with the shell is a metal shield 22 externally threaded at 24 for The shield 22 is secured to the shell by soldering or brazing and by means of the metal ring 26 which is brazed or soldered both to the shell in and to the shield 22. The shield and shell may of course be integral so long as means is provided for assembly of the insulators and electrode therein.

The lower insulator 16, which has a center bore 28 with an upper end of enlarged diameter, a lower sleeve portion which extends below the shell 14, and an external annular shoulder 34-, is supported in the shell 14 by a support ring so which in turn is held in the shell by means of the indentation 38 provided thereon.

In the particular embodiment shown, the shell 14 consists of sheet metal and thus the support ring 36 and indentation 33 provide a convenient means for supporting the insulator 16. However, it is to be understood that the shell 14 can be made of machined cast metal in which case the ring 36 can be made integral therewith, thus making unnecessary the indentation 38.

Pressed against the top of the shoulder 34 is an annular shaped spacer member 49 mounted concentrically with the shell 14. A pair of metal gaskets seal between the lower oortion of the shoulder 34 and the support ring 36 and between the upper portion of the shoulder 34 and the spacer member The shell 1 the ring as, the spacer 4t and also the gaskets and are all made of some heat-resistant metal such, for example. as stainless steel.

The upper insulator 18 is somewhat similar in construc tion to the lower insulator in that it is provided with a center bore 46 having ameter and an extrenal annular shoulder 59. The upper portion 48 of sage is provided therebetween. The function of this opening will be hereinafter discussed. The lower edge of the shoulder 50 rests against the upper edge of the spacer member 40 and the insulator is secured in position by means of the shield 22, the lower edge 56 of which abuts and holds pressed against the shoulder 56 a gasket 58 made of copper or some other suitable metal. A gasket oil, of some heat-resistant metal such as nickel, forms a seal between the spacer 40 and the shoulder 50.

Mounted in the centerbores of the two vertically arranged

insulators

16 and 18 is the tubular electrode 20 having a hollow center 62 and a pair of cooling air entrance slots 64. The electrode is made of a heat-resistant metal or metal alloy such, for example, as Chromel or Inconel.

The lower end 66 of the electrode 20 of unit 8 is bent at an angle of about inwardly (to the left as shown) toward the electrode of unit 10, and the lower end 68 of the electrode of unit 10 is also bent at an angle of about 90 inwardly (to the right as shown) toward the electrode of unit 8. Thus, to this extent the two units difler.

As can best be seen in Figure 1A, the top of the electrode 20 is provided with a cap 7% having a shank 72 which extends into the hollow center of the electrode 24 and is secured thereto by brazing and by pressing a circumferential portion of the electrode inwardly to engage a groove '74 provided in the shank. A slotted head portion '76 of the cap 70 cooperates with a shoulder 78 in the bore of the upper insulator to maintain the electrode vertically positioned. It is preferable to provide a sealing composition, such as silicate cement 80, between the electrode and cap assembly and the bore of the insulator. For the purpose of supplying this cement, a diagonally upwardly (as shown) extending hole 82 is provided in the electrode and cap assembly. After the electrode and cap assembly is positioned in the upper insulator, the sealing composition, such as a silicate cement, is forced through the hollow center 62 of the electrode 26 through the hole 82 and into the space between the electrode-cap assembly and the wall of the centerbore 46 of the upper insulator. When the cement oozes out from the bottom of the upper insulator there is assurance that the entire space has been filled. The hole 82 is cut upwardly and diagonally at an angle of about 45 in order to insure that the cement will be forced upwardly between the cap 70 and the insulator centerbore shoulder 7 8. The cement 80 provides a mechanical support of the electrode and also serves to seal the structure.

A conductive glass seal 84 which has a screw-shaped partially bored electrical contact 86 embedded therein forms a bond with the walls of the insulator bore and with the top of the cap 70 to form a gas-tight seal and an electrical path. Electrical contact with the ignition current is made through the contact 86. The seal 84 may be of any suitable composition such, for example, as a mixture of glass and copper or nickel powder.

In order to maintain the electrode concentrically positioned in the lower insulator bore, radially extending circumterentially spaced lugs 88 of sufiicient size to contact the insulator inner wall are provided on at least one axial portion of the electrode. It will be noted that this structure serves to maintain the centerwire concentric but at the same time allows a free passage for cooling air beween the electrode and the insulator. Other means could of course be used in place of the lugs 88 to assure that the electrode remains centered in the lower insulator bore while at the same time permitting the free passage of cooling air.

The spark plug shell is provided with a pair of vertically arranged openings 9% and 92. The lower opening 92 allows cooling air to reach the bottom 32 of the lower insulator and also the lower portion of the shell 14 thus cooling the lower portions of the shell and lower insulator. The upper opening 9d, which is aligned with a similar opening 94 in the spacer member 40, provides cooling air for the upper as well as the lower insulator and for the electrode. The air flows through the openings 9i) and 94 over the top of the lower insulator 16 and against the upper insulator 18, through the passage 54 and the slots or openings 64 and into the center 62 of the hollow electrode 29 where it is led to spark gap 96. Also, some of the air entering the opening M) will flow between the lower insulator and the electrode past the lugs 88. Thus, the air entering the opening 90 effects the cooling of the entire length of the electrode as well as the firing tip thereof. As can be seen from the drawing, the air flowing through the electrode of unit 8 will be directed against the end of the electrode of unit and vice versa.

The mounting pad 12, which is welded or brazed to the metal shells of the units 3 and 10, is provided with a plurality of holes 93 for the reception of screws or rivets to secure the igniter to a wall of the burner. A suitable air duct, not shown, is provided in the burner to lead the air ii to the openings and 92 in the shells of the units 8 and 10.

The igniter is used with a grounded center tap double secondary ignition system, one coil supplying unit 8 and the other, of opposite polarity, supplying unit 10. in this manner, voltages in the order of 40,009 volts and higher can be used, no part of the circuit being required to carry more than one-half of the total voltage. Spark gaps of /2 and larger may be used without the use of a circuit and igniter made bulky, expensive and inelficient by way of large amounts of insulation.

Figure 5 shows a modification consisting of a single unit having a straight electrode. Except that the electrode is straight as shown at 1% rather than bent, and that the mounting pad 1&2 supports a single unit rather than a pair, the igniter unit is identical to the units 3 and iii shown in Figure 1. Thus, except for these dilferences, the numerals used for identification of the structure of Figure 5 are the same as those used in conjunction with units 8 and 10 of Figure 1, and the description of these units previously given is applicable to Figure 5.

For use of the embodiments shown by Figure 5, two of the units shown are individually mounted on a wall of the afterburner in such a way that the ends of the respective electrodes form a spark gap of the desired size. Generally it is preferable to mount the individual units on diametrically opposing Walls of the burner so that the air emitted by the end of each electrode will be eiiective in cooling the end of the electrode of the other unit. Of course, if the units are mounted on the burner walls so as to be at an angle to each other, the ends of the electrodes can be bent the desired amount to direct cooling air into the spark gap.

Separate air ducts are employed to lead cooling air to each of the units and just as in the case of the previously described embodiment, a grounded center-tap ignition system is used with each pair of units.

By means of the igniters of this invention, a long spark, that is, a spark on the order of /2 or more can be obtained by the use of high voltages but without the use of large amounts of electrical insulation. At the same time, adequate cooling means for the entire assembly is provided by the use of the novel double insulator structure the air passage structure described.

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 the invention as defined by the appended claims.

I claim:

1. An igniter unit comprising a hollow electrode, an upper insulator and a lower insulator surrounding said electrode, a metal shell surrounding and supporting said insulators and means for cooling said unit, said means comprising an opening through said shell adjacent said lower insulator to allow cooling air to circulate past said lower insulator and a second opening through said shell adjacent said upper insulator to allow cooling air to circulate past said upper insulator and through said hollow electrode.

2. An igniter comprising a pair of units, each of said units including a metal shell, upper and lower centerbored insulators in said shell, said upper insulator extending into the centerbore of said lower insulator and leaving passage between said upper and said lower insulators for the circulation of air, a hollow electrode mounted in the centerbores of said insulators, said electrode having an opening adjacent said passage to allow cooling air to circulate through said electrode, an opening through said shell adjacent said passage to allow air to circulate past said upper insulator and into said passage, and a lower opening through said shell to allow air to circulate past said lower insulator, said units being mounted together in parallel spaced relationship, the end of the electrode of each of said units being bent at and toward the end of the electrode of the other of said. units to provide a spark gap and to direct air against the electrode of the other of said units.

3. In an igniter unit, an elongated electrode, an upper insulator and a lower insulator surrounding said electrode, each of said insulators being provided with an annular shoulder, a sheet metal shell surrounding said insulators, and means for supporting said insulators in said shell, said means comprising an interior shoulder indented in the wall of said shell cooperative with said lower insulator shoulder for supporting said lower insulator and a spacer ring concentrically positioned in said shell between said lower insulator shoulder and said upper insulator shoulder for supporting said upper insulator.

4. An igniter comprising a metal shell having upper and lower openings therethrough, upper and lower insulators with vertically aligned centerbores mounted in said shell, an electrode in said upper insulator centerbore and extending through said lower insulator centerbore, an annular passage between said upper and said lower in sulators and communicating with a passage between said electrode and said lower insulator, a plurality of radially extending lugs on said electrode to maintain said elec trode concentric with said lower insulator centerbore, said upper opening through said metal shell being adjacent said annular passage to allow cooling air to pass between said electrode and said lower insulator and said lower opening through said metal shell allowing cooling air to pass between said lower insulator and said shell, and means for sealing and securing the upper end of said elec trode in said upper insulator centerbore said means comprising a conductive glass seal bonded to the walls of said upper insulator centerbore and in electrical contact with said electrode and a silicate cement between said electrode and the walls of said upper insulator centerbore.

5. An igniter comprising a metal shell having upper and lower openings therethrough, upper and lower insulators having vertically aligned centerbores mounted in said shell, said upper insulator extending into the centerbore of said lower insulator, an annular passage between said upper insulator and said lower insulator adjacent the upper opening through said shell, a tubular electrode sealed into the centerbore of said upper insulator and extending concentrically through the centerbore of said lower insulator, said electrode having an air passage through the wall thereof adjacent said first mentioned passage, said upper opening allowing air to circulate past said upper insulator and through said electrode and said lower opening allowing air to circulate past said lower insulator to cool said unit.

6. An igniter comprising a pair of units, each of said units including a metal shell, upper and lower ccnterbored insulators in said shell, said upper insulator extending into the centerbore of said lower insulator and leaving a passage between said upper and said lower insulators for the circulation of air, a hollow electrode mounted in the centerbores of said insulators, said electrode having an opening adjacent said passage to allow cooling air to circulate through said electrode, an upper opening through said shell adjacent said passage to allow air to circulate past said upper insulator and into said passage, and a lower opening through said shell to allow air to circulate past said lower insulator, said units being separately mounted in spaced relationship to provide a spark gap between the electrode of one of said units and the electrode of the other of said units.

References Cited in the file of this patent UNITED STATES PATENTS