US1314129A - crowther - Google Patents

Description

H. M. CROWTHER.

, SPARK PLUG. APPL'ICATION FILED HIL? I5. |918,

` Patentd Aug. 26,1919.

III

INVEN ron Y HENRY M. Caowr/m? 3, /J/. 11 Alsl A r r'vs.

HENRY M. CBOWTHER, 0F KING-MAN, ARIZONA.

SPARK-PLUG.

Specification of Letters Patent.

Patented Aug. 26, 1919.

Application led July 15, 1918. Serial No. 245,034.

To all whom it may concern:

Be it known that I, HENRY M. Cnow'rrriin, a citizen of the United States residing at Kingman, in the county of Mohave and State of Arizona, have invented new and useful Improvements in Spark- Plugs, of which the following is a specification.

My object is to make a self-cleaning spark plug and my invention consists of the novel features herein shown, described and claimed.

Figure 1 is a vertical central sectional detail of a self-cleaning spark plug embodying the principles of my invention.

Fig. 2 is a bottom plan view looking in the direction indicated by the arrow 2 in Fig. 1.

Fig. 3 is a perspective of the heater serving asa return terminal.

The insulating core 1 is preferably formed of porcelain or other strong, har refractory, non conducting material, and comprises the upper (fzylindrical portion 2, the annularretainintg ange 3 extending around the lower end o the upper cylindrical portion 2, the lower cylindrical portion 4 extending downwardly from the annular .retaining ilange 3; said portions 2 and 4 being substantialll the same diameter; the reduced cylin rical portion 5 extending downwardly from the cylindrical portion 4 and havin a rounded lower end 6 and an enlarge central bore 7 and a shoulder 8 at the top of the central bore 7, and the clrcular tapered shank 9 extending upwardly trom the upper cylindrical portion 2; there being a central bearing` bore 10 extending from the shoulder 8 upwardly through the lower c lindrical portion 4, the retainin ange 3, t e upper cylindrical portion 2 an the tapered shank 9, and there being a flat upper face 11 at the upper end of the shank 9.

The conductor feed rod 12 is inserted upwardly through the enlarged bore 7 and through the bearing bore 10 and lits the bore 10; there being a chamber 13 around the rod 12in the bore 7 and there being a stop 14 fixed upon the rod to engage the shoulder 8 and hold the rod so that the lower end 15 will proj ect slightly beyond the rounded end 6.

A cap 16 ts against the flat face 11 and around the upper end of the tapered shank 9 and has a central opening through which the rod 12 extends. A bindin post nut 17 is screwed upon the upper en of the rod -12 against the cap 16 to draw the stop 14 against the shoulder 8 and hold the parts tight. A second binding post nut 18 is screwed upon the rod 12 against the first nut 17 and serves as a jam-nut, said second biliding post nut having a neck 19 to receive the feed conductor.

The heater 20 is preferably stamped from good sheet copper and comprises a cylindrical portion 21 slightl larger in diameter than the lower cylin rical portion 4, the flaring retaining flange 22 extending from the upper edge of the cylindrical portion 21, the cy indrical foraminous portion 23 extending downwardly from the portion 21, and the rounded foraminous ortion 24 extending downwardly froin t e portion 23 and having a central circular opening 25. A cushion 26 of asbestos paper or the like is placed around the lower cylindrical portioin 4 of the insulating core, a similar cushion 27 is placed against the inclined lower face 28 of the retaining liange 3, and the heater 20 is inserted upwardly around the cushion 26 against the cushion 27; there being a chamber 29 within the heater around the reduced cylindrical portion 5 and an extension chamber 30 within the heater around the rounded lower end 6 of the insulating core, and the lower end 15 of the conductor feed rod 12 bein centrally located in the opening 25, sai lower end 15 serving as the' feed terminal of the spark gap 31, and the edge of the heater around the opening 25 serving as the return terminal for t e spark gap.

The metal case 32 has a hexagonal upper end 33 forming a wrench seat and said upper end has an internal screw-thread 34. An externally screw-threaded nipple 35 extends downwardly from the upper end 33, said nipple being reduced in size relative to the upper end 33 and the threads 36 upon the nipple being adapted for screwing into the head of the engine cylinder. An internal inclined shoulder 37 is formed at the bottom of the threads 34 and a bore 38 extends through the nipple 35 to the shoulder 37. The metal case 32 is inserted upwardly around the heater 20, the cylindrical portion 21 0f the heater iitting tightly in the bore 38, and the flange 22 fitting closely against the shoulder 37. The lower end of the bore 38 is enlarged to form the chamber 39 around the foraminous portion 23 within the lower `end of the nipple 35.

A cushion 40 of asbestos paper or the like is placed around the upper cylindrical portion 2 and a similarpacking 41 is placed against the upper face of the flan e 3, and a gland 42 is screwed down into tie threads 34 around the cushion 40 and against the cushion 41 to draw the casing 32 tightly against the cushion 27 and hold the parts together. A hexagon head 43 forms a Wrench seat upon the upper end of the gland 42.

The trouble with the best spark plugs heretofore made hasbeen that the insulating cores will become coated with smoke, lamp black, or carbon, from poor combustion of the explosive mixture, and this coating forms more or less of an electric conductor to carry theelectricity from the central feed rod along the surface of the insulating core to the casing. In this type of spark plugs the casing forms the return side of the spark gap. In order that a spark plug shall Work satisfactorily it is necessary that the entire force of the electric current pass through the spark gap and any leakage of the current duc to the smoke deposit upon the insulatin core will reduce the Vpower and certainty of the spark. It is not necessary that a full short circuit be established between the fd rod and the casing to ruin the efliciency of the spark plug. Any continuous layer of soot or smoke or carbon, all of which may be called lamp black, extending from the feed rod 12 along the 'exposed face of the insulating core l to the casing 32 reduces the efficiency of the spark to the extent of the current Which Will leak through this layer oflanip black, and any effective gap or breakin this layer of lamp black vvi'l'l stop the leak, although the other parts may be loaded with lamp black.A

v"While the heater 20 serves as the return side ofthe spark gap, the object of the particular construction shovvnand described is to burnthe lamp black from the' exposed face of the insulatin core and break the circuit of electricity t rough the lamp black from the feedI rod 12 tothe casing 3 The chambers 29 and 30 are substantially of even thickness between the heater 20 andV the face of the insulatin core. The material of the heater 20 arou'n these chambers is exposed to the flash of the exploding fuel mixture in the 'engine and this material should be of high`degree of fusibility soithat Will stand a temperature rising tothe verge "of red-hotness or incandescence for an indefinite time, and the material should be of high'conductivity, absorption and radiation so that it will readily become heated to vth'erdeslred extent and readily give off the heat to lower theteinperature so that at'thetime 'of the explG'Sive flash the heater Will be almost or quite 'red-hot and. lwill retain this 'temperature for an instant andthen cool sliilicie'ntly so that it' will not ign-imite next narge.

The explosive mixture Will enter the chambers 29 and v3() and at the time of the explosion there will be a flash inside of the heater as Well as outside and the heat will circulate freely through the opening 25 and through the perforations in theforaminous portions 23 and 24 and at the time of the explosion and immediately following the explosion the heater Will be hot enough to urn the lamp black from the surface of the portions 5 and 6 of the insulatin core. At this time the lamp black is backs by the rc fractory,V non-heat-conducting, non-heat-absorbing insulating core Iand is faced by an clement of high conductivity, hi absorption, and rapid radiation, and t e heat of this element, the heater 20, in close prox imity to the lamp black; the lam black being a perfect absorber of heat; W1 linstantly ignite and burn the lamp black, thereby keeping the insulating core clean around the lower end of the bore 7, thereby making a break in the lamp black coating and preventing a short circuit or leakage of the electric current.

At the present time I consider copper the best medium for the heater 20. The lower end of the heater may be erforated more" or less as desired. The'thic' ness of the copper may be varied to some extent but I consider that it should be comparatively thin so that it Ywill readily heat and so that the temperature will uctuate rapidly as the engine operates.

The heater 20 presents a very large surface both inside and out for contact with the flash and the absorption of heat.

The lamp black deposit upon the inner and outer surfaces of the heater duringthe period of poor combustion will ignite and burn when thecombustion improves and the burning of this lamp black 'will assist in heatingi the heater and assist in burning the lamp b ack from the insulating core.

T e layer of lam black as deposited is porous'and more or less saturated withoxyen and whileit will not ignite and burn rom theii'ash ofthe explosion it will read` ily burn in the presence of a hot element where the heat continues for a short time after the flash has gone. The element of time seems to be necessary to the burning ofI the lamp black. l V

Various changes may be made in the details of construction without departing from the spirit of my invention as claimed.

Iclaim: l I

1.' The'combination with a spark lug, of means entirely inclosing the exposedp end of the insulatin core for `breaking thecontinutyrdffthe amp biack epositfonfthe insulating'cierre` j,

2. 'l hecomliination with a spark plug, :of heat absorbing andradiatin'g means `entirely inclosingthe exposed end ofthe insulating core for breaking the continuity of the lamp black deposit on the insulating core.

3. The combination with a spark plug, of a heater entirely inclosing the exposed end of the insulating core and 1n position to burn the lamp black from the insulating core.

4. The combination with a spark plug, of an element entirely inclosing the exposed end of the insulating core and in position to be heated by the explosive flash and in position to burn the lamp black from the insulating core to break the continuity of the lamp black deposit.

5. The combination with a spark plug having an insulating core, a feed rod extending through the insulating core, and a casing for mounting the insulating core, of an element entirely inclosing the exposed end of the insulating core and in position to be heat-- ed by the explosive flash and in position to burn the lamp black from the exposed inner end of the insulating core.

6. The combination with a spark plu having an insulating core, a feed rod exten ing through the insulating core, and a casing for mounting the insulating core, of a heater connected to the casing and entirely surrounding the exposed inner end of the insulating core and forming the return side of the spark gap; said heater being adapted to burn the lamp black deposit to break the continuity thereof.

7. The combination with a spark plug having an insulating core, a feed rod extending through the insulating core and forming one side of the spark gap, and a casing for mounting the insulating core, of a heater connected to the casing and entirely surrounding the exposed inner end of the insulating core and formin the other side of the spark gap; said heatergbeing spaced from the insulating core and being adapted to absorb, conduct and radiate heat from the flash of the explosion to burn and break the continuity of the lamp black deposit upon the insulating core.

8. A spark plug comprising a cylindrical non-conductor having a reduced lower portion terminating in a semi-spherical head, a circular retaining flange intermediate its length and integral therewith, an inner conductor passing through the axis of the nonconductor, an outer conductor comprising a thimble shaped perforated thin shell, said shell being a good thermal conductor, said shell having a circular end flange, means for locking said ilange in position against said retaining flange,` said shell being perforated at its lower end and being slightly spaced in parallel relation from the non-conductor, there being a spark gap formed by an aperture at the center of the lower end of said shell through which the inner conductor projects.

9. A spark plug comprising an inner and an ,outer conductor, a non-conductor interposed therebetween, said non-conductor having a cylindrical lower portion terminating in a semi-spherical head, the outer conductor comprising a perforated thin shell of metal, said shell being a good thermal conductor and slightly spaced in parallel relation from the non-conductor and provided with a spark gap consisting of an aperture at the apex of the shell through which the inner conductor projects.

10. A spark plug comprising an inner and an outer conductor, a non-conductor interposed therebetween, said non-conductor having a lower portion terminating in a head, the outer conductor comprising a perforated thin shell of metal, said shell being a goed thermal conductor and slightly spaced in parallel relation from the nonconductor and provided with a spark gap consisting of an aperture at the apex of the shell through which the inner conductor projects.

In testimony whereof I have signed my name to this specification.

HENRY M. CROWTHER.

Copies of this patent may be obtained for ve cents each, by addressing the Commissioner of Patents, Washington, D. C.

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