US2327220A - Spark plug - Google Patents

Description

Patented Aug. 17, 1943 SPARK PLUG George F. Buddies, Chicago, Ill.

No Drawing. Application July 24, 1940, Serial No. 347,144

7 Claims.

The present invention relates to improvements in spark plugs and it particularly relates to improvements in spark plugs as may be utilized in connection with automotive engines.

Although the present invention will be specifically described in its application to spark plugs and spark plug constructions, it is to be understood it has a broader application to the treatment and construction of spark producing apparatus, which may be placed in contact with a fuel or combustible mixture containing dispersed therein metallic compounds, particularly lead compounds.

It has been found that in the operation of automotive engines, particularly automobile engines, that the presence of lead tetraethyl, as well as other lead or heavy metal compounds for antideposit thereon, so as to eliminate and avoid said knock purposes, tends to result in the deposition of a film of metallic lead or other conductive materials upon or around the sparking points or the ceramic materials of spark plugs.

This accumulation of metallic materials tends to give rise to a condition which will not assure satisfactory and correctly timed explosion of the mixture.

It has been found that increasing deposits of metallic lead and lead oxide upon the points of the spark plug weaken the spark intensity at the gap between the electrodes to such a degree that there speedily results sluggish motor operation with frequent missing of firing in the cylinders and with a final elimination of the spark.

Not only do these metal deposits tend to arise from the lead alkyls which may be present in the fuel, but it appears that they also sometimes arise from the cast iron or aluminum which may be used either for the cylinder walls or pistons of the internal combustion engine when small amounts of these materials are volatilized or thrown into the fuel gas mixture in colloidal form during operation of the vehicle.

In an effort to overcome this tendency for deposition upon the points of the spark plug, various aliphatic or aromatic halogen compounds have been utilized, such as for example ethylene dibromide or chlorbenzenes or naphthalenes, but it is found that this disadvantageously affects the explosion and does not give maximum economy with maximum power generation as would be desired. Moreover, these halogenated hydrocarbons, such as ethylene dibromide, must frequently be added in amounts equal to the lead tetraethyl.

Moreover, these compounds are quite expensive and greatly increase the cost of the fuel and it cannot be included in many instances where metallic deposit.

Another object of the present invention is to provide an improved spark plug construction which will render unnecessary the inclusion of halogenated aliphatic or aromatic hydrocarbons, such as ethylene dibromide, in fuel mixtures and which at the same time will give most satisfactory operating characteristics with assurance that there will be a substantial absence of metallic deposit upon the spark plug terminals.

It is among the further objects of the present invention to provide an improved spark plug construction which will altogether avoid the tendency toward sluggish firing and weakening of the spark intensity, together with frequent missing of firing, which occurs with fuels containing substantial amounts of lead tetraethyl as an anti-knock agent, without the addition of ethylene dibromide {or other expensive addition agents to the fuel mixture.

Still further objects and advantages will appear from the more detailed description set forth below, it being understood, however, that this more detailed description is given by way of illustration, since various changes therein may be made by those skilled in the art without departing from the scope and spirit of the invention.

It has now been found that the above objects; may be most satisfactory accomplished by placing in or in close contact with the points of a spark plug, certain types of metal coatings or surfacings, particularly chromium and less desirably nickel and/0r cobalt or other inert metals electro-positive to lead.

It is also possible to include less preferably metals electro-positive to iron and aluminum, but generally the metals should be electro-positive to lead. The thickness of coating should generally be about a thousandths of an inch. In some cases it has been not only possible to use the metal but; the ores of the metal or minerals containing the metal may be employed.

Alloys of chromium and nickel may be em ployed, if desired, but most satisfactory results have been obtained with chromium.

The chromium surfacing may be placed upon the spark plug points in various manners, as by plating or in the form of a fine powder, which is pressed into the surface of the points, or if desired, the molten metal in combination with other metals, such as for example combinations of chromium and nickel, may be sprayed or otherwise applied to the points.

In applying a chromium surface to steel electrodes, it is most important that a close junction be made, which will prevent peeling or chipping or loss of the chromium surface due to the different thermal expansion properties of the chromium and steel. 1

As a general rule the surface of the points should first be thoroughly cleaned before application of the chromium surfacing and this may be conveniently done by sand blasting or rubbing such points with emery until they are highly polished.

Where electro-plating is employed, it is usually found most desirable first to plate a very thin layer of a chromium-nickel alloy and then to finish up with a substantially pure chromium plate.

It is found that this combination will take care of the difference in thermal expansion of the chromium and steel and will result in the treated points having long durability.

Apparently the chromium or chromium nickel has a catalytic or electro-displacement effect in respect to the lead or lead oxide depositions and if desired, other durable metals, more electropositive than chromium, may be employed.

For example, among the metals that may be employed are vanadium, tungsten, uranium, molybdenum and so forth, and these metals may be used either in the form of the metals or in the form of the alloys.

It has also been found that these various mettals, such as chromium, may be incorporated in the shell or even in an insulated manner in the ceramic material of the sprak plug where an electrical contact can be obtained instead of being p aced upon the points.

For example, these metals may be incorporated in the sillimanite or even upon or into mica or porcelain forming part of the spark plug con-' struction.

Often these materials may be oxidized before being placed into electrical contact with the points or after deposition upon the spark plug on or in electrical communication with the points.

These metals may either be deposited upon the ceramic body of the spark plugs or actually formed in the ceramic throughout the body thereof.

It is to be understood that many alternatives and varying constructions may be made pursuant to the broad aspects of the present invention, as above pointed out, and it is intended to cover and include all such alternatives and variations as come within the scope of the appended claims.

What I claim is:

l. A spark plug construction for use with fuels containing lead alkyls comprising points having an undercoat of an alloy of nickel and chromium and an overcoat of chromium.

2. A spark plug construction for use with fuels containing lead alkyls comprising points having an undercoat of an alloy of nickel and chromium and an overcoat of chromium, said overcoat being positioned directly opposite the insulator surface of said plug.

3. A spark plug construction for use with fuels containing lead alkyls comprising the exposed portion thereof coated with alloy of nickel and chromium.

4. A spark plug construction for use with fuels containing lead alkyls, comprising a coating of chromium which has an underlayer of a chromium alloy to cause an electro-displacement effeet in respect to lead deposits.

5. .A spark plug construction for use with fuels having metal compound distributed therein and comprising electrolytically plated chromium surfaces in proximity to the electrode of the insulator, thereby causing an electro-displacement effect in respect to metal deposits on the insulator surface during fuel combustion.

6. A spark plug insulator construction for use with fuels containing metal compounds in solution therein, having incorporated in and exposed at the surface of the insulator a material containing a hard metal electro-positive to that in the fuel and causing an electro-displacement effect of metallic decomposition of the fuel.

'7. A spark plug construction for use with fuels containing tetraethyl lead gasoline anti-knock fluid, comprising a material containing metal selected from the chromium group, disposed in proximity to the insulator surface and spread over an area which is wide relative to that of the points of the spark plug and causing an electrodisplacement effect of metallic films on the insulator, thereby to avoid diminution of the spark intensity or interruption thereof.

GEORGE F. RUDDIES.