US2833950A

US2833950A - Spark plug

Info

Publication number: US2833950A
Application number: US545489A
Authority: US
Inventors: Jr Arthur C Hastings
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-11-07
Filing date: 1955-11-07
Publication date: 1958-05-06
Anticipated expiration: 1975-05-06

Description

M 6, 5 A. c. HASTINGS, JR 2,833,950

SPARK PLUG Filed Nov. '7, 1955 INlfENTOR. Arthur C. Hostin gs Jr.

A TTORNE Y.

United States Patent SPARK PLUG Arthur C. Hastings, Jr., Toronto, Ontario, Canada Application November 7, 1955, Serial No. 545,439

3 Claims. (Cl. 313137) This invention relates to a spark plug for internal combustion engines.

One object of the invention is to provide a novel construction of spark plug for internal combustion engines having improved operating characteristics as compared with conventional spark plugs now on the market and which may be economically manufactured in a simple, rapid and practical manner.

A further object of the invention is to provide a novel and improved spark plug of a construction which imparts to the plug a substantially wider heat range than conventional spark plugs and which enables the plug to be run at high speed without preignition and with minimum fouling during starting and while the engine is idling.

A still further object of the invention is to provide a novel construction of spark plug which may be run in cool engines without fouling and in hot engines without preignition, thus enabling the dealer to stock one plug instead of a range of plugs.

With these general objects in view and such others as may hereinafter appear, the invention consists in the constructions of spark plug hereinafter described and particularly defined in the claims at the end of this specification.

In the drawings illustrating the present invention:

Fig. 1 is a sectional view of a spark plug embodying the present invention;

Fig. 2 is a sectional view of a modified form of the present spark plug;

Fig. 3 is a sectional view of a further modified form of the present spark plug;

Fig. 4 is a plan view of the spark plug illustrated in Fig. 3;

Fig. 5 is a cross sectional view taken on the line 5-5 of Fig. 3; and

Fig. 6 is a cross sectional view of another spark plug embodying the invention.

The invention contemplates a novel structure of spark plug in which several important advantageous structural and operating characteristics are imparted to the plug including a much wider heating range than comparable conventional spark plugs and to impart to the plug the ability to run satisfactorily at high engine speeds without preignition and to run with minimum fouling during starting and while the engine is idling. Experience with the present plug has demonstrated its ability to run satisfactorily in cool engines without fouling and in hot engines without preignition, and these advantages enable a dealer to stock a single plug instead of a wide range of plugs as is now the general practice.

in general the present improved spark plug, which may take various forms, embodies a center electrode mounted in an insulating body portion and preferably connected at its upper end to a terminal member to which the usual wiring connection may be made. As illustrated in Fig. 1, 10 represents the central metal electrode or firice ing pin which is extended through and insulated along a major portion of its length by a tubular insulating member 12 of suitable insulating material capable of withstanding the high temperatures encountered in the operation of the plug and which may and preferably will comprise the thin walled heat resistant ceramic tube or sleeve 12. The upper portion of the electrode 10 and tubular insulating member 12 are preferably imbedded within an elongated body 14 of insulating material, such as a ceramic sleeve or suitable resinous plastic as, for example, a semirigid plastic manufactured under the trade names Silastic, nylon, or any of 'the silicone plastics. In practice the electrode 10 and thin walled tubular insulating member 12 may be molded within a cylindrical sleeve member 14 or may be secured therein by any suitable heat resistant cement, such as any of the pressure sensitive silicone adhesives now on the market. A metal terminal 16 is preferably molded into or otherwise secured in the upper end of the sleeve member 14 to provide suitable connection to the electrode 10, as shown. The exposed upper portion of the terminal 16 is provided with threads 18 to enable a suitable connecting member 20 to be secured thereto in order that a lead wire may be electrically connected to the central electrode or firing pin 10. The insulating body 14 is secured within the upper portion of a metal housing 22, the lower end of which is hollow and provided with external threads adapted to enable the member to be screwed into the usual threaded openings in the cylinder wall or head of the internal combustion engine. The lower end of the central electrode 10 is preferably headed, as shown, and serves to afford an abutment against which the lower end of the insulating tube 12 may rest, and the housing 22 may be provided with an outer electrode 24 of L-shape, as shown in Figs. 1, 2, 3 and 6. The threaded lower end of the housing 22 is hollow and forms an open ended chamber into which the lower end portion of the insulating tube 12 and central electrode 10 project terminating substantially in the plane of the lower end of the housing, as illustrated, and in a position to form the usual spark gap between the inner and outer electrodes. The thinness of the walls of the tube 12 and the dimensions of the center electrode are preferably such as to provide a relatively large annular chamber surrounding the projecting end portion of the central electrode unit, thus forming a gas scavenging chamber of maximum volume for any given dimension of the threaded lower end of the housing. This structure is embodied in all of the spark plugs forming the subject matter of the present invention and contributes to the improved operation of the present plug. The fact that the portion of the central electrode unit which projects into the hollow scavenging chamber of the lower end of the metal housing is insulated by a heat resisting insulating tube having relatively thin walls imparts to the plug the ability of rapidly heating and cooling during and between each operation of the plug. In other words the thinness of the wall of the tube 12 contributes to enabling the projecting portion of the central electrode unit to become extremely hot at the instant of explosion, minimizing the formation of carbon thereon, and after the explosion has taken place the same cools extremely rapidly below the point where preignition would occur. The relatively large scavenging chamber surrounding this portion of the central electrode unit assists in affording opportunity for turbulence of the gases, and this effect also appears to contribute to the maintenance of the electrodes in clean, unfouling condition. In addition, the said scavenging chamber is preferably closed at its top by a relatively plane ceiling which may be domed and is provided, in the embodiments of Figs. 1, 2, and 3 by structural detail 22' of housing 22.

3 and is. further provided, inthe embodiment of Fig. 6, by. the lower end 14. or the insulating. body 145 In practice the preferred range of wall thicknesses of the projecting portion of the insulating tube may vary from: .0257 to 050 In. the various forms of plugs illustratedin Figs. 1, 2,3 and 6 various methods have been illustrated for securing the central electrode unit tothehousing unit; For exple in Fig. 1- the upper plastic body 14- may be provided with an enlargedilower end and the parts secured to the housing by the engagement of a nut with the flanged lower end of the plastic member. In Fig: 2 the upper end of theplastic body 14 may be provided with a socket into which the lead wire may be forced toestablish a connection with the central electrode at its upper end. In Fig. 3 I have illustrated.- a typical form of structure in which the plastic body 1=4-ismolded around the flanged upper end of the housing. In" Fig. 6' I have illustrated a structure in which the insulating body 14 may be of porcelain, and the tube 12 isarranged to project into asuitable socket in the lower end of the porcelain body 14 and secured therein by a suitable high temperature cement or adhesive, such as Silastic cement, or by silver chloride, or otherwise. The housing may take various forms to enclose andbe secured-to the porcelain member 14. The principal advantages of the present structures of sparkv plug include the relatively wide-heat range possessed by this type of plug enabling the dealer to stock a single size which will operate satisfactorily in various engines for which a widerange of conventional spark plugs having. different heat ranges have heretofore been used. Experience has demonstrated that thepresent plugs fire satisfactorily at high engine speed Without preignition and at the same time minimize fouling when the engine is operating at idling speeds, and during starting the plugs may berun in cool engines without fouling andin hot engines without preignitibn- While the preferred embodiments of the invention" have been illustrated-and described, it will be understood that the invention may be embodied in other forms within the scope of the following claims.

Having thus described the;- invention, what is claimed 1s:

1. A spark plug comprising a hollow metal housing adapted for installation in an internal combustion engine and having walls providing a lower chamber, said chamber having an open mouth; at; its. bottom and a substantially plane ceiling at its top, which meets and merges with said housing walls; a'thin-walled ceramic tube proiecting n a d ower chambe h o hsai l s; an insulating body disposed, hermetically engaged and held by said housing above said chamber, supporting said ceramic tube in said. chamber; a; metal rod contained within said tube with both of 'its ends projecting therefrom, and an electrode carried by said housing forming a spark gap with one end of said metal rod at the mouth of said lower chamber; said insulating body having an opening imparting: accessibility to the other end of said metal rod and having also a socket accommodating the upper end" of said-ceramic tube and within which said ceramic tube'is integrallybonded" to said insulating body above said-lower chamber.

2, A spark plugas defined in claim 1 wherein the cross-sectional area of said ceramic tube at the said ceiling is at least as small as the cross-sectional area of any'other portion t-hereofwithin the said lower chamber.

3: A-spark plug as defined in claim 1 wherein the said-ceramic tube is-of substantially uniform cross-sectional area'and'cont'our' throughout that portion thereof which is disposed within said' lower chamber.

References Cited in the file of this patent UNITED- IATES. PATENTS- 1,346',759'-' Meyer v July 13, 1920 1 ,370,789 Delano Mar. 8, 1921 2,651,298 Brinson Sept. 8, 1953 2,672,577 Thies Mar. 16, 1954