US2325024A

US2325024A - Spark plug cooling means

Info

Publication number: US2325024A
Application number: US390061A
Authority: US
Inventors: Paul G Andres
Original assignee: Bowes Seal Fast Corp
Current assignee: Bowes Seal Fast Corp
Priority date: 1941-04-24
Filing date: 1941-04-24
Publication date: 1943-07-27
Anticipated expiration: 1960-07-27

Description

July 27, 1943. P. 5. ANDRES SPARK PLUG COOLING MEANS Filed April 24, 1941 iwm O P EN 0 fi w m. 4 am, m i Y E Patented July 27, 1943 SPARK PLUG COOLING MEANS Paul G. Andres, Oak Park, Ill., assignor to Bowcs Seal Fast Corporation, Indianapolis, Ind., a corporation of Indiana Application April 24, 1941, Serial No. 390,061

Claims.

This invention relates to spark plugs of the type employed in automotive practice for engine ignition. With the advent of the high compression, high speed engines and particularly under the heavy duty imposed on aviation engines, small details in construction of spark plugs have come to involve major problems and have been found to vitally affect the durability and life of the plugs. Furthermore, due to several factors, one of which is reduction in weight per horsepower output of the engines, spark plugs have been reduced in dimensions in order to fit within the limited spaces permitted, and yet are required to give a higher degree of reliable performance than heretofore.

It has been found that a major problem involved in the design of a reliable spark plug is that of dissipation or rather distribution of heat. It is possible for the nose of the porcelain insulator of the commonly provided central electrode to run too hot and it is also equally possible for that nose to run too cold. Again it has been found that in the spark plug commonly employed heretofore, the gap between the shell electrode and the central insulated electrode will vary considerably due to temperature changes. In these prior constructions of spark plugs, it has been the usual practice to employ a round shell electrode welded or otherwise secured by one end to the lowermost end of the shell and then bend that electrode around and under the central electrode. This meant that the shell electrode at all times had a bend in it which would cause the gap between it and the central electrode to vary on account of subsequent relieving of stresses under expansion and contraction. Furthermore, there was no possibility of making a fixed gap dimension in manufacture of the plug since the exposed shell electrode was subject to being shifted under storage and transportation conditions due to impact.

A further difficulty found to exist in these prior types of spark plugs is that in order to place the shell electrode at the proper position in relation to the wall of the combustion chamber, it was necessary to provide a supporting shell normally less than the length of the threaded hole into which the shell was threaded. This reduced length of shell in relation to the length of the threaded hole, of course, reduced the area of contact between the shell and the water surrounded part of the engine through which the threaded hole was provided, meaning that the rate of heat dissipation was reduced.

Also what may now see to be a simple solution of heat transfer has been discovered to be of utmost importance, and a solution also offering an additional advantage over and above the accelerated heat dissipation. This solution relates to the seating of a highly heat conductive gasket around the shell of the plug to be compressed between it and the engine wall not only to seal against escape of gases but also to form a quick heat dissipating zone. This gasket becomes in effect an integral part of the shell so that when the spark plug is removed from the engine, the gasket is not left down in a well as is the usual case but is withdrawn with the spark plug so that upon replacing the plug, there is no possibility remaining of a new gasket being placed over an old gasket down in that well, a situation which would affect the positioning of the electrodes of the plug.

It is the primary purpose of my invention to overcome the difficulties above enumerated in a very simple and readily constructed mechanism as will hereinafter be set forth. Other important objects and advantages of the invention will become apparent to those versed in the art in the description which is made in reference to the accompanying drawing, in which Fig. 1 is a view in side elevation of a spark plug embodying the invention and shown in a mounted position;

Fig. 2, a view in end elevation of the nose of the plug, on a greatly enlarged scale; and

Fig. 3, a central diametrical section on the line 3-3 in Fig. 2 through the threaded end of the plug.

Like characters of reference indicate like parts in the several views in the drawing.

The spark plug, generally designated by the numeral ID, has the usual porcelain insulator Ii sealably mounted in the metallic shell I2 from which extends a threaded end portion l3 to be screw-threadedly entered into a hole provided in an engine head or wall 14, The invention herein set forth involves primarily the lower part of the plug Ill.

The threaded end I3 is given a length in every instance which will carry it entirely through the bore in the wall l4 so that this end I3 will always have the greatest possible area of contact through its threaded surface with the surface of the bore within which it is carried.

The lower end of this portion i3 carries a short straight electrode bar l5, herein shown as I rectangular in cross sect on. The lower end of to receive therein the nose of the insulator II) so as to receive the outer end of the bar I5 therein preferably by a forced fit, following which the bar I5 is electrically welded to the portion I3. The bar I5 extends horizontally, in reference to the drawing herein, across under the lower end of the central electrode I6 that projects beyond the lower end of the insulator I I, Fig. 3. Thus it is to be seen that there is no bend whatsoever in the bar I5, and furthermore, the under side of this bar I5 is flush with the terminating end of the shell portion I3. To all intents and purposes, the electrode bar I5 becomes an integral part of the shell end I3. The spacing between the lower end of the central electrode I6 and the bar I5 may be predetermined and fixed in manufacturing. Since the bar I5 extends within the bore within the end portion I3, there is very little likelihood of its spacing from the electrode I5 being changed accidentally.

At the upper end of the threaded portion I3, the shell is given an outwardly extending tapered shoulder I! from which extends upwardly a short cylindrical surface I8. The diameter of this surface I8 is made to be slightly greater than the normal internal diameter of the sealing gasket I9. This gasket I9, while it may take any desired form, is herein shown as of the usual type which consists of a sheet of copper folded over on itself and finished in the form of a ring.

The threaded end plug portion I3 is entered through the gasket I9 and screw-threadedly engaged in the bore through the wall I4. By drawing the plug I down snugly, the inclined or beveled surface II will be carried through the gasket I9 tending first to center it around the plug and then tending to expand the gasket so that continued downward travel of the plug will eventually force the gasket I9 up and around the cylindrical surface I8 to have the gasket I9 eventually come against the flat seat 20 provided around the plug.

The gasket I9, of course, resists expansion under this action and is forcibly carried onto the surface I9 with the result that the gasket is snugly fitted against the fiat face 20 in intimate contact therewith and is given an even greater intimate contact with the surface l8. In fact,

practice shows that it is quite difficult to remove the gasket I9 from this seated position since the gasket becomes in effect a fixed part of the plug.

Now in service, a plug constructed as above described will have the gap between the end of the electrode I6 and the top side of the shell electrode I positioned substantially in the plane of the inner side of the wall I4 and at the same time the threaded portion I3 will be carried down to that inside face of the wall I4. This means that heat arising from combustion of gases causing the spark plug to be heated thereby is prevented from unduly heating the lower end of the plug by reason of the fact that heat received by the electrode I5 is rapidly conducted into the threaded portion I3 without having to travel through or around bends therein and begins to be dissipated at, the very lowest part of the threaded end of the plug which, as above indicated, is at the inner face of the wall I4. The wall I4 is, of course, as indicated in Fig. 1, covered over by water and this water space extends up and around the part through which the threaded portion I3 extends. Further, as the heat is transmitted along the threaded portion I3, it is further and more quickly dissipated through the gasket I9 at t e top of the water-jacketed part so as to aid in preventing travel of the heat upwardly into the larger mass of metal of the shell I2. In other words there is a cool ring interposed between the lower threaded portion I3 and the upper mass of the shell. This ring, as above indicated, is automatically placed in position and into effect simply by screwing the plug into operating position on the engine.

This heat control and travel is obtained without, in the present instance, affecting the heat control of the nose of the porcelain insulator II. In other words the electrode I5 and its supporting shell portion I3 may have the temperatures thereof effectively controlled independently of the temperature of the electrode I6 and its supporting insulator I I.

While I have herein shown and described my invention in the one precise form, it is obvious that structural changes may be employed without departing from the spirit of the invention and I therefore do not desire to be limited to that precise form beyond the limitations as may be imposed by the following claims.

I claim:

1. For an engine having a water jacketed wall through which extends a spark plug receiving bore, a spark plug having a metallic shell; a central insulator carried thereby; a central electrode carried by the insulator; a lower shell end portion threaded exteriorly and having. an internal bore receiving said central electrode therein, said end portion extending below the lower end of said electrode; a straight shell electrode bar having one end inserted within a slot in and integrally united with said portion to extend in a straight transverse direction into the bore of said portion to leave a spark gap between it and said central electrode; and means forming a rapid heat dissipation zone around the upper end of said lower shell portion; whereby heat may be dissipated with minimum travel through said shell electrode to said wall and limited in upward travel in said shell by said zone.

2. For an engine having a water jacketed wall through which extends a spark plug receiving bore, a spark plug having a metallic shell; a central insulator carried thereby; a central electrode carried by the insulator; a lower shell end portion threaded exteriorly and having an internal bore receiving said central electrode therein, said end portion extending below th lower end of said electrode; a straight shell electrode bar having one end inserted within a slot in and integrally united with said portion to extend in a straight transverse direction into the bore of said portion to leave a spark gap between it and said central electrode; and means forming a rapid heat dissipation zone around the upper end of said lower shell portion; whereby heat may be dissipated with minimum travel through said shell electrode to said wall and limited in upward travel in said shell by said zone; said heat dissipating zone means comprising a high heat conducting collar intimately attached to said shell to be compressively held against said wall by said plug.

3. For an engine having a water jacketed wall through which extends a spark plug receiving bore, a spark plug having a metallic shell; a central insulator carried thereby; a central electrode carried by the insulator; a lower shell end portion threaded exteriorly and having an internal bore receiving said central electrode therein, said end portion extending below the lower end of said electrode; a straight shell electrode bar having one end inserted within a slot in and integrally united with said portion to extend in a straight transverse direction into the bore of said portion to leave a spark gap between it and said central electrode; and means forming a rapid heat dissipation zone around the upper end of said lower shell portion; whereby heat may be dissipated with minimum travel through said shell electrode to said wall and limited in upward travel in said shell by said zone, said insulator being spaced within and from the wall of said threaded portion throughout its length.

4. For an engine having a water jacketed wall through which extends a spark plug receiving bore, a spark plug having a metallic shell; a central insulator carried thereby; a central electrode carried by the insulator; a lower shell end portion threaded exteriorly and having an internal bore receiving said central electrode therein, said end portion extending below the lower end of said electrode; a straight shell electrode bar having one end inserted within a slot in and integrally united with said portion to extend in a, straight transverse direction into the bore of said portion to leave a spark gap between it and said central electrode; and means forming a rapid heat dissipation zone around the upper end of said lower shell portion; whereby heat may be dissipated with minimum travel through said shell electrode to said wall and limited in upward travel in said shell by said zone; said shell electrode being rigid and of sufficient cross-sectional area to resist bending under temperature changes.

5. For an engine having a water jacketed wall through which extends a spark plug receiving bore, a spark plug having a metallic shell; a central insulator carried thereby; a central electrode carried by the insulator; a lower shell end portion threaded exteriorly and having an internal bore receiving said central electrode therein, said end portion extending below the lower end of said electrode; a straight shell electrode bar having one end inserted within a slot in and integrally united with said portion to extend in a straight transverse direction into the bore of said portion to leave a spark gap between it and said central electrode; and means forming a rapid heat dissipation zone around the upper end of said lower shell portion; whereby heat may be dissipated with minimum travel through said shell electrode to said wall and limited in upward travel in said shell by said zone; said shell electrode being confined within said lower shell por- :7

tion.

6. For an engine having a water jacketed wall through which extends a spark plug receiving bore, a spark plug having a metallic shell; a central insulator carried thereby; a central electrode carried by the insulator; a lower shell end portion threaded exteriorly and having an internal bore receiving said central electrode therein, said end portion extending below the lower end of said electrode; a straight shell electrode bar having one end inserted within a slot in and integrally united with said portion to extend in a straight transverse direction into the bore of said portion to leave a spark gap between it and said central electrode; and means forming a rapid heat dissipation zone around the upper end of said lower shell portion; whereby heat may be dissipated with minimum travel through said shell electrode to said wall and limited in upward travel in said shell by said zone; said shell electrode being confined within said lower shell portion, the under side of the shell electrode being in a plane of the lower end of that shell portion.

'7. For an engine having a water jacketed wall through which extends a spark plug receiving bore, a spark plug having a metallic shell; a central insulator carried thereby; a central electrode carried by the insulator; a lower shell end portion threaded exteriorly and having an internal bore receiving said central electrode therein, said end portion extending below the lower end of said electrode; a straight shell electrode bar having one end integrally united with said portion to extend in a straight transverse direction into the bore of said portion to leave a spark gap between it and said central electrode; and means forming a rapid heat dissipation zone around the upper end of said lower shell portion; whereby heat may be dissipated with minimum travel through said shell electrode to said wall and limited in upward travel in said shell by said zone; said electrode shell consisting of a flat bar welded by its said end within a rectangular slot in the shell portion.

8. For an engine having a water jacketed wall through which extends a spark plug receiving bore, a spark plug having a metallic shell; a central insulator carried thereby; a central electrode carried by the insulator; a hollow, threaded, lower shell end portion extending below the lower end of said electrode; a straight shell electrode bar having one end inserted within a slot in and integrally united with said portion to extend in a straight transverse direction into said portion to leave a spark gap between it and said central electrode; and means forming a rapid heat dissipation zone around the upper end of said lower shell portion; whereby heat may be dissipated with minimum travel through said shell electrode to said wall and limited in upward travel in said shell by said zone; said shell electrode being confined within said lower shell portion, the under side of the shell electrode being in a plane of the lower end of that shell portion; said central electrode terminating by its lower end above said shell electrode.

9. In a spark plug having a metallic shell, a central insulator carried thereby, an electrode extending axially through the insulator, the combination of a lower threaded end shell portion; an electrode extending from the shell portion to form a spark gap between it and said central electrode; an upwardly and outwardly flaring shoulder at the upper end of said threaded portion terminating by a maximum diameter substantially equal to at least the external diameter of said threaded end portion; a cylindrical area extending upwardly from said shoulder and having a diameter at least equal to that of said maximum shoulder diameter; a gasket compressing seat carried by said shell portion at the upper end of said cylindrical area, said seat extending outwardly from said cylindrical area in a plane substantially normal to the plug axis; a ring-like metallic gasket initially having a minimum internal diameter less than that of said cylindrical area; said gasket being elastically stretched around said cylindrical area and frictionally engaged therewith below said seat.

10. In a spark plug having a metallic shell, a central insulator carried thereby, an electrode extending axially through the insulator, the combination of a lower threaded end shell portion; an electrode extending from the shell portion to form a spark gap between it and said central electrode; an upwardly and outwardly flaring shoulder at the upper end of said threaded portion terminating by a maximum diameter substantially equal to at least the external diameter of said threaded end portion; a cylindrical area ex-- tending upwardly from said shoulder and having a diameter at least equal to that of said maximum shoulder diameter; a gasket compressing seat carried by said shell portion at the upper end of said cylindrical area, said seat extending outwardly from said cylindrical area in a plane substantially normal to the plug axis; a ring-like metallic gasket initially having a minimum internal diameter less than that of said cylindrical area: said gasket being elastically stretched around said cylindrical area and frictionally engaged therewith below said seat; said gasket being formed of a high heat conducting material and its external diameter being limited substantially to that of said seat, the upper face of said gasket being limited in elevation to that of said 10 seat.

PAUL G. ANDRES.