US3320461A - Self-renewable spark plug construction - Google Patents

Description

May 16, 1967 J. F'EINS SELF-RENEWABLE SPARK PLUG CONSTRUCTION 3 Sheets-Sheet 1 Filed Jan. 27, 1965 INVENTOR FIE/N8 AUG/(NE 5 l/ll/l/r/ III I r r 1 JOJEPH May 16, 1967 J. FEINS 3,320,461

SELF-RENEWABLE SPARK PLUG CONSTRUCTION Filed Jan. 27, 1965 5 Sheets-Sheet 3 f 75* v \5 r 1.5;

, a K z 5W INVENTOR d JosEPH FE/Ms BY ATTDRNE 5.

corporation of Delaware Filed Jan. 27, 1965, Ser. No. 428,429 2 Claims. (Cl. 313-125) This invention concerns an improved, self-renewable spark plug of simplified construction.

Spark plugs conventionally used in internal combustion engines of automobiles and other automotive vehicles as well as in stationary apparatus such as pumps, electric generators, and the like, have a number of important shortcomings. The conventional type of spark plugs in general use employs a center electrode spaced from a ground electrode attached to the cylindrical shell of the plug. This structure requires that a radial ground electrode be welded to the shell of the plug. This is costly in material and labor; also the ground electrode is an element where operational failure often occurs. The center electrode is attached to a long wire which extends axially through the plug from the center electrode at one end to the nose tip at the other end. Installation of this wire requires a number of complex operations; the wire uses costly material; and the several connections of the wire at opposite ends are subject to breakage resulting in operational failure of the plug.

Complex, critical processes are required to force a sealing cement into the center of the plug between the center electrode and an outer cylindrical or conical porcelain insulator. This requires high baking temperatures in a furnace which in itself introduces several difficulties. The insulator may come out of the process with fine cracks which later lead to operational failure of the plug. Also it is very difficult to maintain the few thousandths of an inch clearance between wire and insulator allowed for expansion of parts. This clearance is often non-uniform and not enough resulting in fracture of the insulator due to thermal shock. Sometimes thermal shock results in small internal fissures in the porcelain insulator. These fissures accumulate carbon and metallic salts and carry electric current causing partial or complete short circuiting of the plug electrodes, reducing operational efficiency or stopping operation altogether.

The conventional spark plug has a very high voltage applied to the nose tip or terminal. Since the distance from the nose tip to the grounded engine head to which the ground electrode is connected, is very short, arcing or flashover frequently occurs, particularly when the porcelain insulator becomes wet or moist, or even if the ambient humidity is high. This results in operational failure of the engine in which the spark plug is installed. Rubber jackets provided at the insulator do not solve this problem since the jackets themselves act as conductive paths for arcing and fiashover when the jackets become wet or damp. Another difficulty encountered in conventional spark plugs is known as corona discharge. This involves current leakage along the surface of the porcelain insulator, particularly when it becomes coated with grease, dirt and moisture. Other dimculties in conventional spark plugs are caused by the fact that the large mass of the plug absorbs heat rapidly leaving the small tip of the central electrode cold. This causes fouling of the electrode, misfiring, and the disparity in temperatures causes thermal shock during which the insulator is fractured or cracked. Another problem encountered in conventional spark plugs arises from the central location of the gap between center and ground electrodes. This gap is located in alignment with the path of greatest explosive United States Patent force in the engine cylinder. This results in a high rate of erosion of the electrodes, oil fouling and carbon collection. Also a condition known as flame arrest occurs which is most undesirable. Due to the conditions men'- tioned and others which exist, conventional spark plugs must be frequently removed, cleaned and regapped which involves a laborious, expensive, time consuming process. Furthermore the spark plugs must be replaced frequently due to progressive failure, which imposes a great economic burden on engine users. Between times of servicing and replacement, faulty operating spark plugs cause hard starting of engines, poor fuel economy, loss of engine power and overall degradation of engine efficiency.

The present invention is directed at overcoming the above and other difficulties and disadvantages in conventional spark plugs, and does so with a spark plug which is simpler in construction and more economical to manufacture. According to the invention, a spark plug is provided which has a cylindrical porcelain insulator housing in which is a short axially located electrode. The electrode is rotatable in the housing. The electrode is seated in the housing under a spring bias which results in an effective, leakproof seal with the housing. The tip of the center electrode extends radially outward to the rim of the metal shell supporting the procelain housing. This rim serves as the ground electrode, so that the gap between electrodes is off-center. The center electrode may be made of a hard, fouling-resistant material such as phosphor bronze or other equally effective alloy. The rim of the metal shell can be made of softer material. Periodically, the center electrode can be rotated through a small angle so that a fresh part of the rim of the shell is exposed to the center electrode. This renews the gap between the electrodes. The entire circumference of the rim of the shell is available for use, thus the useful life of the spark plug may equal or exceed life of the engine in which it is installed. The new spark plug has a number of other advantages which are described below.

It is an object of the invention to provide a spark plug with grounded metal shell and with an internal, rotatable center electrode having a radially extending tip disposed near the rim of the grounded metal shell to define an off-center gap.

A further object is to provide a spark plug as described, wherein the center electrode is seated in a porcelain insulator housing under spring bias which effects a complete metal-to-porcelain seal without physical attachment between the electrode and jacket.

Another object is to provide a spark plug as described, wherein the gap is between center and ground electrodes can be renewed by rotating the center electrode, and this can be done while the spark plug is in place in an engine cylinder and in operation, so that the effect of electrode rotation can be observed under actual operating conditions of the engine.

Other objects are to provide a spark plug as described in which a high voltage cable can be detachably engaged on a terminal lug located inside the porcelain housing; in which a ceramic spacer can be installed between the lug and end of the cable to serve as a capacitative dielectric for intensifying the voltage applied to the center electrode; in which the spark plug can be fired continuously under conditions of high humidity and even under water; in which current leakage along the porcelain housing is prevented; in which savings of material and labor are effected in manufacturing, installation and servicing.

For further comprehension of the invention, and of the objects and advantages thereof, reference will be had to the following description and accompanying drawings, and to the appended claims in which the various novel features of the invention are more particularly set forth.

In the accompanying drawings forming a material part of this disclosure:

FIGURE 1 is a side elevational view of a spark plug assembly embodying the invention, the spark plug being shown mounted on a wall of an engine cylinder,

FIG. 2 is an enlarged bottom view taken on line 22 of FIG. 1,

FIG. 3 is a reduced central longitudinal view taken on line 33 of FIG. 3,

FIG. 4 is an exploded perspective view of parts of the spark plug assembly,

FIG. 5 is an enlarged sectional View of the spark plug shown with a tool in position for adjustably rotating the center electrode,

FIG. 6 is an enlarged central longitudinal sectional view of another spark plug assembly showing a modification of the invention,

FIG. 7 is a side elevational view on a reduced scale of the spark plug of FIG. 6,

FIG. 8 is an enlarged perspective view of the center electrode employed in the spark plug of FIGS. 6, 7,

FIG. 9 is a perspective view of an adapter tool which can be used in association with a spark plug to adjust the same while the spark plug is in operating condition,

FIG. 10 is a central longitudinal sectional view showing the adapter tool of FIG. 9 in operative association with a spark plug,

FIG. 11 is a perspective view of a ceramic spacer disk,

FIG. 12 is an enlarged fragmentary, central longitudinal sectional view of a spark plug assembly employing the spacer disk of FIG. 11.

Referring first to FIGS. 1 to 5 there is shown a spark plug assembly including a spark plug to which is detachably connected an insulated cable 22 having a single central electric Wire conductor 24. The conductor terminates at a cylindrical spring clip 25 which detachably engages on a knob 26 of a terminal lug 28 of the spark plug 20.

The spark plug 20 includes a ceramic insulator housing 30 having a long cylindrical body 32. The upper end of body 32 is open. The housing has a short integral conical tip 34. Integrally joining the tip 34 and body 32 is a cylindrical flange 36 having an annular rim or seat 38 at its upper end. A short tapered transition section 39 joins flange 36 and tip 34.

Body 32 has a central bore 40 terminating at a flat circular seat 42 near the lower end of the body. A narrow central bore 44 communicates with bore 40 and terminates at seat 42; see FIGS. 3 and 5. Extending axially through bore 40 is metal stem 45 of electrode 46. The electrode has an annular flange 48 at its lower end which abuts the free narrow end of tip 34. Extending radially outwardly of the stern and flange is an electrode tip 50. Tip 50 is slightly spaced by a gap G1 from beveled rim 52 of cylindrical metal shell 54. The metal shell has an externally threaded lower portion 55 which screws into a threaded hole 56 in electrically grounded wall 58 of an engine cylinder. Shell 54 has an internal cylindrical bore 60 which is radially spaced from insulator tip 34. An intermediate section 62 of the central bore of the shell is conical and receives a conical, soft metal washer 64 in which seats tapered section 39 of housing 30. The upper wider cylindrical section 65 of the central bore of the shell is internally threaded and receives externally threaded portion 66 of a locknut 70. The locknut has an annular flat bottom end which seats on the annular seat 38 of insulator 30 thus holding the insulator immovable in the metal shell 54. Shell 54 has a polygonal head 57 to receive a wrench for seating the shell securely in the cylinder wall 58.

The upper end 72 of the stem 45 is threaded and securely screwed into threaded hole '74 in the bottom of terminal lug 28. The lug has a bottom circular flange 75. A coil spring 76 is coaxial with the upper part of stem 45. The upper end of the spring bears against the underside of flange 75. The lower end of the spring bears on the seat 42 at the bottom of bore 40. The knob 26 of the lug may have a slot 77 to receive blade 78 of the screwdriver 80. If desired this slot may be formed as a polygonal recess or aperture to receive a hexagonal wrench, an Allen-head screw screwdriver, a Phillips-head screwdriver, etc.

It will be apparent that the coil spring 76 biases the electrode 46 axially upward in the housing 30 so that flange 48 abuts the bottom end of tip 34. This holds electrode tip 50 properly spaced from the rim 52 of shell 54- which is relatively fixed with respect to the housing 30. The electrode 46 is rotatable in the housing 30 and can even be moved axially downward if pressure is exerted on the top of terminal lug 28.

By the structure described, fouling of the gap G1 can be cleared by pushing the electrode down axially which will break any debris connecting tip 50 and rim 52. Furthermore the electrode can be rotated so that a fresh unfouled part of the rim 52 is exposed to electrode tip 50. The entire 360 circumference of the rim 52 is available for this purpose. To effect rotation and axial movement of the electrode 46, the cable 22 can be quickly pulled off the terminal lug 28 and out of body 32 of the insulator housing 30 so that tool 80 can be inserted as shown in FIG. 5. A slight turn of a few degrees will be suflicient to locate tip 50 at an unfouled part of rim 52.

Insulated handle 82 is located outside the housing while shaft 83 of the tool extends axially down the body 32 for conveniently turning electrode 46.

The lower end of a rubber sleeve or nipple 85 can be engaged on the upper end of body 32 in an air-tight and liquid-tight sealing relationship. The upper end 86 of the nipple can engage the outside of cable 22 in a similar air-tight and liquid-tight seal; see FIG. 3. This com= pletely isolates the central electrode 46 from the exterior of the plug 20 outside of the engine cylinder and makes it possible for the spark plug to operate in damp or wet conditions and even under Water.

FIGS. 68 illustrate another spark plug 20a embodying a modification of the invention, in which parts corresponding to those of spark plug 20 are identically numbered. Electrode 46a has two radial tips 50a, 50b of unequal lengths. Longer tip 50a is spaced from rim 52 of shell 54 by gap G1 located in the axial or longitudinal direc tion of the spark plug. Shorter tip 50b is spaced from the wall or bore 60 inside of the shell to define gap located in the radial or transverse direction of the spark plug. The two cooperating longitudinal and radial gaps insure posi tive operation of the spark plug even under the most diffi= cult operating conditions.

The lower end 89 of bore 44 in tip 34 of housing 30a may be flared to receive flaring lower end 90 of stem 45a just above flange 48a; see FIGS. 6 and 8. This flange may have a circumferential wall 92 which rotatably engages the end of housing tip 34 and insures that electrode tips 50a, 50b are held from moving radially with respect to shell 54.

FIG. 9 shows an adapter tool which can be used for adjusting the rotatable electrode in one of spark plugs 20 or 20a while the plug is in operating condition in the engine cylinder. The tool has a metal blade 102 at the end of long metal shank 104. An annular flange 106 surrounds the shank just above the blade and facilitates location of slot 77 by the blade since the flange centers the tool in the insulator housing 30. The tool has an insulated, hollow cylindrical handle 108 to which the upper part of shank 104 is secured. The handle and shank are non-rotatably fixed with respect to each other by keys 107. The upper end of shank 104 extends through the bottom wall 110 of the handle 108 and is externally threaded. A terminal lug is secured on the end 105 of shank 104 in handle 108. The lug has an internally threaded bore 122 which receives the end 105 of shank 104. A knob 124 is formed at the upper end of lug 120;

The spring clip 25 of cable 22 snaps on knob 124 so that there is a direct electrical path from wire 24 through clip 25, terminal lug 120, shank 104, terminal lug 28 and stem 45 to electrode tip 50.

While a high voltage is applied to wire 24, and the engine in which the spark plug is installed is operating, the handle 108 can be turned and can be repeatedly axially advanced and retracted as spring 76 contracts and expands. Operation of the engine can be continuously observed while the electrode 46 or 45a is being manipulated until optimum operation of the spark plug is obtained. Then the adapter tool 100 can be removed and cable 22 can be reconnected to the terminal lug 28.

Some engines develop a tendency to burn oil. This is caused by seepage of oil into the engine cylinder passed loosely fitting piston rings or poorly fitting valves. The burned oil causes fouling of the electrodes in the conventional spark plug. In the present spark plug it is possible to burn off the debris fouling the gaps G1, G1 or G2 by employing a ceramic spacer shown in FIGS. 11 and 12. This spacer has a threaded stud 152 which screws into the threaded hole 74 in lug 28. The spacer has a flat circular disk 154 against which bears the upper end of spring 76. In disk 154 is a threaded hole 156 which receives the upper threaded end 72 of stem 4-5 or 45a.

In this capacitative arrangement, the spacer 15% serves as a dielectric element between terminal lug 28 and. stem 45. When a pulsating voltage is applied to wire 24 the voltage builds up inside the air space S surrounding the spacer 150. When the voltage is maximum a spark discharge of maximum energy content takes place causing a fat spark between electrode elements 50 and 52 in the engine cylinder. While the time duration of the spark is less than if the spacer 150 were absent, the current flows at a higher magnitude causing efiective burnout or clearance of the fouling condition. Spacers having different thickness of thicknesses of disk 154 can be used depending on the design parameters of the engine cylinder. The electrode 46 or 46a can be rotatably adjusted and axially moved in the same way as previously mentioned even through the spacer 159 is present.

The spark plugs and 20a described embody a number of unique and desirable features. It will be noted that only one centrally located electrode is provided, one centrally located and the other attached to the rim of the shell and extending radially inward of the shell. The centrally located electrode in the present invention is rotatable as well as being axially movable, while in conventional spark plugs the center electrode is fixed in position. The seating of the center electrode is leakproof since it is maintained under spring tension. There is no danger of fracture of the insulator due to different rates of expansion of the insulator and electrode since the electrode is not fused or attached to the insulator. The structure is not subject to thermal shock encountered in conventional spark plugs. The resetting of the central electrode is accomplished by a slight turn without need for disassembly of the spark plug from the engine. Servicing time and labor are saved in performing the adjustment of the cen tral electrode, since the spark plug does not have to be removed. The length of the spark plugs life is lengthened because the entire 360 circumference of the beveled rim of the metal shell is available for use as a return or ground electrode. This efifects better ionization of gas in the gap between electrodes to facilitate internal combustion in the engine cylinder. Since the ground electrode has many times the mass of the electrode in the conventional spark plug, its useful life is greatly lengthened and it is almost indestructible in normal use. The large mass of metal in contact with the engine block surrounded by coolant pulls heat from the ground electrode which is the shell itself. This results in material reduction in erosion. The rim of shell 54 need not be made of a noble or precious metal to derive the advantages inherent in the invention.

The center electrode tip 50 or tips 50a, Stlb can be made of superior, corrosion resistant metal while the rims" of the metal shell can be a erodable, sacrificial metal. This will favor the center electrode which is preferable since the available circuference of the rim 42 of shell 54 is so very much larger than the diameter of tip 50.

A further advantage derived from the present invention is the prevention of arcing and fiashover. It will be noted that the terminal lug 28 is located at the bottom of the deep well in bore 40 of the insulator housing 30. The electrical path from terminal lug 28 up the inside of bore 40 and then down the outside of body 32 is too long for leakage current to traverse even under the most adverse operating conditions. This length of path is three or more times as long as the path between nose tip and engine head in a conventional spark plug installation. The value of this feature is especially appreciated in marine engines and in engines operating in high ambient conditions of high humidity. Since the hollow plug stays cool, preignition is prevented. Fouling due to excessive oil burning can be cleared by use of the ceramic spacer. The spring seating of the electrode accommodates to slight irregularities in insulator and electrode structure to keep a perfect seal against gas leakage. The simplified structure of the spark plug makes it possible to manufacture it at lower cost so that cost to the user is ultimately reduced, servicing time and costs are saved, and need for replacement is reduced or eliminated entirely.

The provision of an adapter tool to permit adjustment while the spark plug is in use with engine operating is a further desirable advantage of the invention.

While I have illustrated and described the preferred embodiments of the invention, it is to be understood that I do not limit myself to the precise constructions herein disclosed and that various changes and modifications may be made within the scope of the invention as defined in the appended claims.

Having thus described the invention, what I claim as new, and desire to secure by United States Letters Patent is:

1. A spark plug for an internal combustion engine, comprising an insulated housing having a cylindrical body with a wide cylindrical bore therein open at one end, said housing having an opposite end portion formed with a narrow axial bore therein communicating with the cylindrical bore, said cylindrical bore having a fiat seat defined at its junction with the narrow bore, an electrode having an electrically conductive stem extending through said narrow bore and rotatably disposed therein, one end of the stem extending into the wide bore, a flange on the other end of the stem bearing against the free other end of the housing and sealing said narrow bore, first and second electrode tips extending radially from said stem adjacent said flange outside of said housing, a terminal lug for a high voltage cable engaged on the one end of said stem in the wide bore, and a spring partially compressed and located between said seat and said lug urging the stern upwardly in the narrow bore and holding said flange against the free other end of the housing, said terminal lug having means engageable by a tool inserted in the wide bore for turning the electrode to adjust the radial positions of said electrode tip circumferentially with respect to said housing, a metal shell mountable in a metal wall of an engine cylinder, said shell having a central bore formed with a seat receiving the other end of said housing in a fixed non-rotatable position, said shell having a rim at one end of the central bore therein, the first electrode tip being longer than the second electrode tip, the first electrode tip being spaced by a gap from said rim longitudinally of the shell, the second electrode tip being spaced by another gap from the central bore of the shell near said rim, whereby fresh portions of said rim and central bore are exposed to the electrode tips in each rotational position thereof circumferentially of the rim.

2. A spark plug for an internal combustion engine,

comprising an insulated housing having a cylindrical body with a wide cylindrical bore therein open at one end, said housing having an opposite end portion formed with a narrow axial bore therein communicating With the cylindrical bore, said cylindrical bore having a flat seat defined at its junction with the narrow bore, an electrode having an electrically conductive stem extending through said narrow bore and rotatably disposed therein, one end of the stem extending into the wide bore, a flange on the other end of the stem bearing against the free other end of the housing and sealing said narrow bore, first and second electrode tips extending radially from said stem adjacent said flange outside of said housing, a terminal lug for a high voltage cable engaged on the one end of said stem in the wide bore, and a spring partially compressed and located between said seat and said lug urging the stem upwardly in the narrow bore and holding said flange against the free other end of the housing, said terminal lug having means engageable by a tool inserted in the wide bore for turning the electrode to adjust the radial positions of said electrode tip circumferentially with respect to said housing, a metal shell mountable in a metal wall of an engine cylinder, said shell having a central bore formed with a seat receiving the other end of said housing in a fixed non-rotatable position, said shell having a rim at one end of the central bore therein, the first electrode tip being longer than the second electrode tip, the first electrode tip being spaced by a gap from said rim longitudinally of the shell, the second electrode tip being spaced by another gap from the central bore of the shell near said rim, whereby fresh portions of said rim and central bore are exposed to the electrode tips in each rotational position thereof circumferentially of the rim, said shell having an internally threaded portion, and a locknut engaged in said internally threaded portion and holding said housing immovable with respect to the shell.

References Cited by the Examiner UNITED STATES PATENTS 1,403,448 1/ 1922 Ryder 3 l3125 2,626,595 1/1953 Berstler 3 l3125 2,685,872 8/1954 Berstler 3 13l25 D. I. GALVIN, Primary Examiner.

Claims (1)

1. A SPARK PLUG FOR AN INTERNAL COMBUSTION ENGINE, COMPRISING AN INSULATED HOUSING HAVING A CYLINDRICAL BODY WITH A WIDE CYLINDRICAL BORE THEREIN OPEN AT ONE END, SAID HOUSING HAVING AN OPPOSITE END PORTION FORMED WITH A NARROW AXIAL BORE THEREIN COMMUNICATING WITH THE CYLINDRICAL BORE, SAID CYLINDRICAL BORE HAVING A FLAT SEAT DEFINED AT ITS JUNCTION WITH THE NARROW BORE, AN ELECTRODE HAVING AN ELECTRICALLY CONDUCTIVE STEM EXTENDING THROUGH SAID NARROW BORE AND ROTATABLY DISPOSED THEREIN, ONE END OF THE STEM EXTENDING INTO THE WIDE BORE, A FLANGE ON THE OTHER END OF THE STEM BEARING AGAINST THE FREE OTHER END OF THE HOUSING AND SEALING SAID NARROW BORE, FIRST AND SECOND ELECTRODE TIPS EXTENDING RADIALLY FROM SAID STEM ADJACENT SAID FLANGE OUTSIDE OF SAID HOUSING, A TERMINAL LUG FOR A HIGH VOLTAGE CABLE ENGAGED ON THE ONE END OF SAID STEM IN THE WIDE BORE, AND A SPRING PARTIALLY COMPRESSED AND LOCATED BETWEEN SAID SEAT AND SAID LUG URGING THE STEM UPWARDLY IN THE NARROW BORE AND HOLDING SAID FLANGE AGAINST THE FREE OTHER END OF THE HOUSING, SAID TERMINAL LUG HAVING MEANS ENGAGEABLE BY A TOOL INSERTED IN THE WIDE BORE FOR TURNING THE ELECTRODE TO ADJUST THE RADIAL POSITIONS OF SAID ELECTRODE TIP CIRCUMFERENTIALLY WITH RESPECT TO SAID HOUSING, A METAL SHELL MOUNTABLE IN A METAL WALL OF AN ENGINE CYLINDER, SAID SHELL HAVING A CENTRAL BORE FORMED WITH A SEAT RECEIVING THE OTHER END OF SAID HOUSING IN A FIXED NON-ROTATABLE POSITION, SAID SHELL HAVING A RIM AT ONE END OF THE CENTRAL BORE THEREIN, THE FIRST ELECTRODE TIP BEING LONGER THAN THE SECOND ELECTRODE TIP, THE FIRST ELECTRODE TIP BEING SPACED BY A GAP FROM SAID RIM LONGITUDINALLY OF THE SHELL, THE SECOND ELECTRODE TIP BEING SPACED BY ANOTHER GAP FROM THE CENTRAL BORE OF THE SHELL NEAR SAID RIM, WHEREBY FRESH PORTIONS OF SAID RIM AND CENTRAL BORE ARE EXPOSED TO THE ELECTRODE TIPS IN EACH ROTATIONAL POSITION THEREOF CIRCUMFERENTIALLY OF THE RIM.

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