US1477522A - Spark plug - Google Patents

Description

Patented Dec. 11, 1923.-

UNITED STATES ROBERT JAMES RUTHS, OF BALTIMORE, MARYLAND.

SPARK PLUG.

Application filed January 16, 1922. Serial No. 529,703.

T 0 all whom 2'6 may concern:

Be it known that 1, ROBERT J AMES Burns, a citizen of the United States, residing at Baltimore, State of Maryland, have invented certain new and useful Improvements in Spark Plugs, of which the following is a specification.

This invention relates to spark plugs of the type used in automobile and other internal combustion engines.

More particularly the invention relates to a multiple gap spark plug which, on account of the number of spark gaps in the plug, is preferably termed a sextet spark plug.

in the design of spark plugs for internal combustion engines a number of factors of the engine design have an important bearing on spark plug design. The advance in the design of internal combustion engines has now reached a point where such factors as the revolutions per minute, compression ratio, piston speed, displacement, relative locations of the spark plug and the inlet and exhaust ports, amount of lubrication, temperature and the like, have all been determined for conditions of highest efficiency to such an extent that radical departures are seldom made from the recognized standards.

One principal object of the present invention is to provide an improved general construction of spark plug especially designed to meet the substantially fixed conditions now existing in the factors of internal combustion engine design above noted.

The spark plugs commonly used in internal combustion engines employing the jump spark system of ignition are subject to many ills. At present the chief of these is the fouling of the plugs with carbon and oil, which are deposited on the surface of the insulation between the electrodes thus forming a conducting path for the current. The voltage required for a spark plug having a 0.5 millimeter gap (approximately 0.02 inch) is in the neighborhood of 6000 volts. The resistance of insulation between the electrodes is frequently lowered to such an extent by the carbon and oil deposits above referred to that the current will all follow the path thus formed and no spark will be produced at the gap. It has been found that under these conditions modifications of the ignition system involving one or more so called subsidiary gaps in the high tension circuit will, to a certain extent, decrease the liability of the short circuiting above described and thus will cause the spark plug to function with somewhat higher efficiency. In the majority of cases such subsidiary gaps have been introduced in the connection between the high tension terminal of the magne-to or coil and the terminal on the insulated electrode of the spark plug. Such a subsidiary gap is termed a series gap and in its original form as frequently used by automobile racing drivers consists of a block of wood fastened to a spark plug with the high tension terminal secured on it in such fashion that a gap will exist between the terminal and the insulated electrode of the plug. Another form consists of a gap at the central point of the distributor and is known in France, where it is principally used, as a carbolyseur.

A second important object of the present invention is to so improve the construction of a spark plug that a series of gaps of improved character and effectiveness will be formed by the manner in which the plug itself is designed and constructed.

Readings taken with a direct-current ammeter in series with a clean spark plug have shown that the presence of a series gap or gaps reduces the current as indicated by the instrument. The oscillograph, however, shows that the presence of the series gap or gaps has no other effect than to decrease the duration of the discharge between the electrodes of the plug. This is due to the, higher sustaining voltage, made necessary to maintain current flow across the combination of series and plug gaps, on account of which the current is interrupted sooner than would be the case with a single gap requiring a lower sustaining voltage than such combination. Thus an arrangement of series gaps does affect the value of the current while it is flowing. Consequently the indication or reading of a direct current ammeter in the circuit will be decreased by the presence of series gaps. Experiments also show that the use of series gaps does not cause a large drain of current as has been sometimes stated but that on the contrary, series gaps have but little or no effect on the consumption of current in the different parts of the ignition circuits. Furthermore, other experimental evidence shows that it may be concluded that a modification of jumpspark ignition systems by the addition of a prop erly designed and operated gap or gaps in series with each plug gap will remedy effectively the greater part of the trouble now experienced from fouling and that gaps formed in the plug itself are more effective than those in elsewhere.

A third important object of the present invention is to provide an improved spark plug having an improved-arrangement of spark gaps in series, the construction being such that the spark gaps effectively reduce the evils from carbon and oil deposition and also increase the effectiveness of the ignition of the explosive mixture in the engine cylinder.

A fourth important object of the invention is to provide an improved construction of spark plug wherein a thorough cracking of the lubricating oil in the vicinity of the spark gaps as well as a thorough mixing thereof will take place.

A fifth important object of the invention is to provide an improved construction of spark plug wherein the explosive mixture in the vicinity of the spark gaps will be under higher pressure than the explosive mixture in the body of the cylinder.

A sixth important object of the invention is to provide a spark plug having an improved arrangement of umbrella like guard for preventing short circuiting by water or oil on the exterior of the plug. a

With the above and other objects in view the invention consists in general of certain novel details of construction and combina tions of parts hereinafter fully described, illustrated in the accompanying drawings, and specifically claimed.

In the accompanying drawings, like char acters of reference indicate like parts in the several views, and

Figure 1 is an assembly view of the improved spark plug, one half of the view be ing in elevation and the other half being a vertical section.

' Figure 2 is a top plan view of the improved plug.

Figure 3. is a bottom plan view thereof.

Figure d is a top plan'view of the gap block used herewith.

Figure 5'is a vertical median section of such a gap block.

Figure 6 is a bottom plan view thereof.

In the embodiment of the invention herein illustrated there is provided a body or shell 10 which is preferably constructed of carefully selected and tested carbon steel heattreated to insure proper tensile strength,

the proper hardness to assure good surfaces for tight ]O1IltS,' and the proper freedom from injurious physical changes from the heat variations obta ning under service conditions. This shell provided wlth a hexagonal body for permitting the plug to be screwed into place by the use of the usual wrenchand this body is provided with apiurality of spaced peripheral grooves 11. The lower part of the shell is reduced and threaded as at 12 in the usual manner and between the body and threaded portion of the shell is an inclined shoulder 13 so arranged as to form an inverted frusto-conical face at the upper end of the screw threaded portion. This shell has a bore or opening extendin therethrough from top to bottom and opposite the threaded portion 12 the bore has a cylindrical wall 14; terminating below in an internally threaded portion 15. Above the cylindrical portion the bore has a frusto-conical wall 16 the base of which is of slightly less diameter than the cylindrical portion of the bore so that a narrow shoulder 17 is formed between these two portions. Above the frusto-conical portion is a cylindrical portion 18 being slightly larger than the upper end of the frustoconical portion. The bore finally terminates at its upper end in a shallow cylindrical p01 tion 19.

lVithin the frusto-conical portion of the shell bore and extending above and below the same is the main or middle insulating section or sleeve 20. The central portion of this sleeve has a frusto-conical exterior 21 so dimensioned as to fit closely on the frustoconical wall 16. The upper end 22 of this sleeve is also frusto-conical in shape but the base angle of this portion is more acute than that of the body so that the taper is greater. Below the lower frusto-conical portion the sleeve becomes cylindrical exteriorly as shown at 28. The upper end of this sleeve terminates about on a level with the upper end of the. portion 18 of the shell bore so as to provide a V-shaped channel around the sleeve portion 22. Through this sleeve extends an axial bore having a relatively small upper end and a relatively large lower end 2 l'between which and the upper end there is a frusto-conical portion26.

Extending through this sleeve bore is a spark plug spindle having a body portion 27 terminating at its lower end in a head 28-, the shoulder between the head and the body being frusto-conical to fit the frusto-conical portion of the sleeve bore, the body and head being slightly smaller in diameter. than the portions of the bore wherein they fit so that a filling of suitable cement may be used as shown at 29. This spindle is made from an especially selected alloy wire having the properties of ability to maintain a high yield point and tensile strength under high temperatures, non-'oxidization under such high temperatures, and asurface resistant to the deposition of carbon.

Mounted on the spindle above the sleeve is a second or upper insulating sleeve '30 having a frusto-conical body merging below into a cylindrical portion 31 of the proper size to fit within the shell bore portion 19 and rest on the shoulder between that portion and the portion 18 of said shell bore. From the flat underside of this cylindrical portion 31 depends an annular rib or skirt 32 which is of the proper V-shaped cross section to enter the V-sha-ped trough or channel at the upper end of the shell 10, space being left for thecement 29.

Mounted on the spindle 27 and resting on the upper end of the insulating sleeve is a combination retaining washer and umbrella or drip guard, the washer being a flat perforated disk 33 from the periphery of which depends a flange or skirt 34 of the reversely curved form commonly known as a cyma recta so that the upper part of thls skirt fits snugly on the upper end of the sleeve while the lower part is well spaced from said sleeve. Thus the umbrella protects the upper porcelain from oil or moisture and from accidental injury by the usual socket wrench when applying the plug to an The upper end of the spindle is threaded as at 35 and on the lower part of this threaded portion is a retaining nut having a lower polygonal wrench receiving portion 36 and an upper round portion 37. This nut is screwed down tightly on the washer 33 and by its action, in connection with the spindle head 28 draws the parts 10, 20, 30, and 33 securely together so that they are rigidly held against all movement, this action being assisted by the cement between the several parts.

Above the nut 37 is a terminal nut consisting of a lower rounded portion 38 and an upper knurled portion 39 connected by a neck 40 so that a groove is provided between the portions 38 and 39. The parts 37 and 38 combine when screwed to engage each other, from a flattened ball. By means of this construction and the provision of the two nuts, one having a groove, the plug can be used with any of the usual types of terminals such as those known as the ball, Rajah, or flat terminals. The upper end of the spindle projects but slightly above the terminal nut and in this upper end is formed a screw slit kerf 41 so that the spindle may be held from rotation when tightening the retaining nut.

Within the lower portion of the shell is a third or bottom insulator in the form of a sleeve having a cylindrical upper portion 42 and a reduced cylindrical lower portion 43. This third sleeve may be termed the electrode carrier. The bore 44 of this sleeve is of a form similar to the well known Venturi tube and extending transversely across this bore 44 are a series of electrodes 45. Between adjacent el ctrodes 45 are other electrodes 46 arranged at right angles to the electrodes 45. Each of the electrodes 45 and 46 is inserted through an opening 47 in one side of the sleeve and extends diametrically through the bore to terminate in. a pocket 48 on the opposite side of the sleeve after insertion of the electrodes the outer ends of the openings 47 are plugged with cement 49. These electrodes, as well as those to be hereinafter selected and tested I1011f81101l5 alloy offering maximum resistance to burning, pitting, corrosion or oxidation under any motor operating conditions.

At the lowermost end of the plug there is provided an assembling thimble consisting of a segmento-spherical diaphragm 50 provided with a peripheral annular flange 51 threaded exteriorly to engage in the thread ed lower end of the shell. This thimble is provided with a centrally disposed opening wherein is mounted a lower terminal electrode 52 which is surrounded by a series of openings 53 constituting flame openings or passages. Firmly fixed in the lower end of the spindle is an upper terminal electrode 53 which is thus in axial alinement with the shell and the electrode 52. Cement- 54 is also used between the shell and thimble and the electrode carrier. It is to be noted that the electrodes 45 and 46 are substantially in the form of flat rods rectangular in cross section and that the adjacent ends of the electrodes 52 and 53 are also fiat. A cylinder gasket 55 is also provided as shown.

The general principle of this spark plug where used in a gasoline engine is as follows :At the beginning of the compression stroke of the piston, the cylinder is filled with a vapor consisting of gasoline and lubricating oil suspended in air. This vapor is compressed and forced into the shell through the openings 53 in. the thimble. These holes restrict the flow of the mixture somewhat sothat the pressure at this tune does not quite keep pace with the pressure in the cylinder outside the shell. In passing through the holes the globules of gasoline and oil are thoroughly cracked up by the heat of the thimble and mixed by the velocity of the vapor caused by the restricted area of the holes. A further turbulence is created when this vapor comes in contact with the electrodes 45 and 46. The shell thus contains a mixture practically equivalent to a homogeneous gas which, from contact with the large surface areas of the plugs interior absorbs heat and thus reduces the temperature of the plug. As the vapor rises in temperature it naturally increases in pressure from its tendency to expand. Just previous to the passage of the spark the increase in pressure due to this action is such that the pressure and temperature within the plug is greater than the pressure and temperature in the cylinder. It is to be noted that the density of the explosive mixture at the upper spark gap is slightly less than that below by reason of a small. pro

ously than a rich one thus causing a rapid V flame propagation within the plug result ing in four distinct flashes of flame into the cyllnder giving a complete and extremely rapid ignition of the entire power charge in The fire w thin the plug is said cylinder. extremely-shortlived resulting in a clean plug due to complete combustion and a comsleeve and the exterlor of the plug, and a paratively cool plug because it is not subected to a slow burning back fire during the entire expansion stroke of the piston as occurs in the ordinary spark plug having I its spark gap at-the tips. Moreoveiydue to the lean mixture at the upperspark gap oil is not deposited around the upper elec trode and consequently carbon deposits cannot occur.

The porcelain'which'is preferably used in this spark plug is alsoof peculiar character being without free quartz and containing no'feldspathic flux, the latter being replaced by silicates of the type MgOAl O 2SiO or MgOAl O etSiO and the elimination of free quartz being effected by the substitution of such substances as highly calcined kaolin or alumina.

There has thus been provided a simple eflicient device of the kind described and for the purposes specified.

Having thus described the invention, what is claimed as new, is:-

1. A spark plug provided withan insulating sleeve having a boreforming an ignitlon chamber, means to afford IGSlZllCtGCl' port communication between said bore and the exterior of said plug, electrodes extending into said chamber and other electrodes extending transversely across the chamber in spaced relation between the first .rnenport communication between said bore and the exterior of said plug, and a series of spaced electrodes arranged within said chamber supported from the side walls of lating sleeve having bore forming an ignition chamber, means to afford restricted port communication between said bore and "theexterior of said plug, and a series of electrodes Within said chamber supported from the side walls thereof and arranged to provide a series of spark gaps arranged within the chamber in alinement axially with the plug.

4. A spark plug including a shell having longitudinal bore, an insulating sleeve secured in the upper part of said shell, :an electrode supported Within said sleeve at the lower end thereof, a second insulating sleeve forming an electrode carrier and having an axial bore, auxiliary electrodes supported by the second sleeve and extending transversely of the bore thereof, a thimble screwed in said shell below the second sleeve to hold the same in position and having a series of perforations therein constituting passages between the bore of the second terminal electrode mounted centrally on the thimble and extending towards'the lowermost'auxiliary electrode.

5. In aspark plug of the class described, an electrode carrier sleeve of insulating material having an axial bore, diametrically disposed electrode rods extending transverse y across said bore in spaced relation, and a shell supporting the sleeve and having a sparking electrode in spaced relationto the terminal electrodes of the electrode rods extending transversely of the sleeve.

6. In a spark plug of the class described, an electrode carrier sleeveof insulating material having an axial bore constricted cen trally of its length to constitute substantially a Venturi tube, diametrically disposed electrode rods'extending transversely across said bore in spaced relation, and a shell supporting the sleeve and having a sparking electrode in spaced relation to the terminal electrodes of the electrode rods extending transversely of the sleeve.

7. In a spark plug of the class described, an electrode carrier sleeve of insulating material having an axialv bore, diametrically disposed electrode rods extending transvcrsely across said bore in spaced relation,

said, rods being disposed in two sets with the rods of one setalternating with the rods of. the other set and at right angles thereto,

and a shell supporting the sleeve and having a sparking electrode in spaced relation to the terminal electrodes of the electrode rods extending transversely of the sleeve.

8. In a spark plug of the class described, an electrode carrier sleeve of insulating material having an axial bore constituted contrally of its length toconstitute' substantially a Venturi tube, diametrically disposed electrode rods extending transversely across said bore in spaced relation, said rods being disposed in two sets with the rods ofmone set alternating with the rods of the other set and at right anglesthereto, and a shellsupporting the sleeve and having. a sparking electrode in spaced relation to the terminal electrodes of the elctrode rods extending transversely of the sleeve.

9. In a spark plug of the class described, an electrode carrier sleeve of insulating material having an axial bore, diametrically disposed electrode rods extending transversely across said bore in spaced relation, each of said rods extending through a radially disposed opening in the wall of the sleeve and into a radially disposed pocket in the wall opposite the opening, the outer end of each opening being filled with a plug of insulating cement, and a shell supporting the sleeve and having a sparking electrode in spaced relation to the terminal electrodes of the electrode rods extending transversely of the sleeve.

10. In a spark plug of the class described, an electrode carrier sleeve of insulating material having an axial bore constricted centrally of its length to constitute substantially a Venturi tube, diametrically disposed electrode rods extending transversely across said bore in spaced relation, each: 01 said rods extending through a radially disposed opening in the wall of the sleeve and into a radially disposed pocket in the wall oppo site the opening, the outer end of each opening being filled with a plug of insulating cement, and a shell supporting the sleeve and having a sparking electrode in spaced relation to the terminal electrodes of the electrode rods extending transversely of the sleeve.

11. In a spark plug of the class described, an electrode carrier sleeve of insulating material having an axial bore, diametrically disposed electrode rods extending transversely across said bore in spaced relation, said rods being disposed in two sets with the rods of one set alternating with the rods of the other set and at right angles thereto, each of said rods extending through a radially disposed opening in the wall of the sleeve and into a radially disposed pocket in the wall opposite the opening, the outer end of each opening'being filled with a plug of insulating cement, and a shell supporting the sleeve and having a sparking electrode in spaced relation to the terminal electrodes of the electrode rods extending transversely of the sleeve. p

12. In a spark plug ol the class described, an electrode carrier sleeve of insulating material having an axial bore constituted oentrally of its length to constitute substantially a Venturi tube, diametrically disposed electrode rods extending transversely across said bore in spaced relation, said rods being disposed in two sets with the rods of one set alternating with the rods of the other set and at right angles thereto, each of said rods extending through a radially disposed opening in the wall of the sleeve and into a radially disposed pocket in the wall opposite the opening, the outer end of each opening being filled with a plug of insulating cement, and a shell supporting the sleeve and having a sparking electrode in spaced relation to the terminal electrodes of the electrode rods extending transversely of the sleeve.

13. In a spark plug, a shell having a centrally disposed bore, the middle portion of said bore being frusto-co-nical in shape and the bore being cylindrical above the frusto-conical portion thereof, an. insulating sleeve mounted in said shell and having a frusto-conical portion fitting the frustoconical portion of the shell bore, said sleeve extending above the frusto-conical portion of said shell bore whereby to provide a V-shaped channel between the upper ends of the sleeve and shell, a second insulating sleeve resting on the shell above the first sleeve and having a depending rib V-shaped in cross section and entering said channel, means to force said sleeves toward each other and hold them firmly in relation to the shell, and electrodes supported in spaced relation by the shell and sleeve holding means.

14. In a spark plug, a shell having a centrally disposed bore, the middle portion of said bore being frusto-conical in shape and the bore being cylindrical above the frustoconical portion thereof, an insulating sleeve mounted in said shell and having a frustoconical portion fitting the frusto-conical portion of the shell bore, said sleeve extending above the frusto-conical portion of said shell bore whereby to provide a V-shaped channel between the upper ends of the sleeve and shell, a second insulating sleeve resting on the shell above the first sleeve and having a depending rib V-shaped in cross section and entering said channel, means to force said sleeves toward each other and hold them firmly in relation to the shell, said means comprising a spindle extending through said sleeves and having a head on its lower end, and a nut screwed on the upper end of: said spindle, and electrodes supported in spaced relation by the shell and sleeve holding means.

In testimony whereof I aflix 1n signature.

ROBERT JAMES UTHS.

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