US1842834A - Aviation plug - Google Patents

Description

Jan. 26, 1932. c. E. LEONARD 1,842,834

Q AvIA'rIoN PLUG Filed Nov. 21, 1928 ATTORNEY which prevents gas leakage under high as Patented Jan. 26, 1932 UNITED. STATES PATENT OFFICE.

CALEB E. LEONARD, OF MIAMI, FLORIDA, ASSIGNOR TO LEONARD SPARK PLUG COM- PANY, INCORPORATED, OF ST. PETERSBURG, FLORIDA, A CORPORATION OF FLORIDA AVIATION PLUG 'My invention relates to ignition plugs for internal combustion engines, and its general object is to provide a structure which is exceptionally durable and efficient under the severeconditions imposed by service in a high-pressure, or airplane cylinder, as well as under less severe conditions.

, More particular objects are: To effectively radiate the heat from the central electrode; to provide an improved gas tight connection of the insulator or insulators in the shell,

well .as ordinary pressures; and to provide a new and improved main electrode assembly.

in carrying out one of the principal objects above stated, namely, the cooling of the main or central electrode, I provide an outer or upper electrode member which is tubular and provided an opening to atmosphere, together with aheat conducting and radiating element within such tubular electrode which is in heat conductive connection with the main electrode and which rapidly conveys therefrom to the chamber of the tubular electrode, this heat being dissipated therefrom to atmosphere.

The stated features reduce strains upon the insulators, such as are ordinarily occasioned by undue heating and expansion of the central electrode, and increase the durability and eiiiciency of the plug invarious other ways.

, The present invention is similar in some respects to that disclosed in my companion application, executed on even date herewith; but in the present case the general object is to adapt the plug for even more severe service, such as in airplane engines, where the pressure and heating effects may be extreme. To withstand these stresses and provide electrical and mechanical efficiency, long life and dependability, I provide a lower insulating member of highly refractory material,

such asquartz, and an upper insulator which has more mechanical elasticity and is therefore better able to withstand mechanical stresses, such, for example, as laminated mica.

in connection with the following detail description of the accompanying drawings, which shows one preferred embodiment. After considering this example, skilled persons will understand that many variations .trode members, some parts being in section.

Fig. 4 is a side elevation of the lower, or quartz, insulator.

The shell 1 may be of ordinary construction, except as hereinafter specified. It is formed at an intermediate part of its length with a sealing chamber having a cylindrical wall 2 terminating in a horizontal bottom shoulder 3. Above this chamber the shell is internally threaded as at 4:- The lower insulator 5, which is preferably of highly refractory material, such, for example, as quartz (or fused quartz), has oppositely. ar ranged or tapering outer conical surfaces 6, the bases of the cones abutting at the line 7. A short upper portion of this insulator is cylindrical, as at '8. This insulator is secured and sealed in the shell by identical upper and lower gaskets 9 of compressible material such as copper, arranged 1n rela tively reversed positions, and having inner conical surfaces cooperating with the cone surface 6, and outer cylindrical surfaces cooperating with the cylindrical wall of the sealing chamber. The gaskets are compressed to form a perfectly gas-tlght seai, by a ring nut- 10 having an external thread engaging the shell thread 4 and having its lower end formed to engage the upper gasket and so to compress both of the gaskets. This nut or screw ring has in its upper face, sockets 11 to receive a spanner or other suitable tool to tighten it in position.

The upper or outer insulator 12, which is preferably of laminated mlca, or other material better able to resist mechanical shocks, is preferably assembled as a unit with, the

central electrode structure, so that the updiair'i eter inserted with a.tight press fit in the lower end of a conducting sleeve 14, which may in some cases be of highly conductive material, such as brass or copper, or may, if

desired, be of other metal. The sleeve 14 is desirably enclosed in a tubular wrapping 15 of mica to reduce electrical and gas leak effects, the laminations of the main laminated body 12 being internally ,diametered to fit above the sleeve. The laminations of the main body are compressed between a nut 16 engaging. a thread 17 on the upper end of the sleeve 14, and'a metal washer 18 in threaded engagement with the lower end of sleeve 14. Washer 18 preferably rests on a compressible gasket 19 which, in turn, is seated on an internal transverse shoulder 20 of the lower insulator. At its lower .end, the upper insulator has an extension 12, entering the cylindrical bore of the lower insulator, and

1 having its lower end engaging the upper face of washer 18. t v

The upper insulator 12'is desirably formed with a shoulder -at 21, and a compressible gasket 22 is located between this and the upper end of the locking or screw ring 10 to form a gas-tightjlseal. Below shoulder 21 the insulator 12 as a cylindrical surface 23 of the same diameter as surface 8 of the lower insulator and desirably an insulating sleeve 24 of micais wrapped about these surfaces, fitting within the inner bore of the screw ring 10. a

A heat radiating rod or wire 30, which is preferably of small diameter and made' of a highly conductive material, such as brass,

copper or bronze, but otherwise may be ofot er material, is inserted with a tight press fit in a hole in the upper end of the main or lower electrode 13, and this radiating mem.-

ber preferably extends through a'greater part of the length of the sleeve14, which is open at its upper end and acts 'as a radiating chamber. Desirably rod 30 is of waved or sinuous formation to increase its effective radiating length.

Desirably a shoulder is formed as at? 35,

. Fig. 1, in the upper insulator'a short distance above bushing 25, thus reducing or preventing spark-jumping from the shell or bushing to the central electrode structure.

The central structure, including the upper tor 12, by which shoulder 21 is located down on the compressible gasket 22, the lower end of the bushing also seating against this gasket.

An suitable lower or grounded electrode may e provided. Preferably this is in the form of a strip or block 40 bridging the lower or sparking chamber 41 of the shell and secured positively against any loosening or falling out by having its ends engaged in undercut sockets, or an annular channel 42 in the shell bore. The actual sparking element is a raised member 43 on the upper face of the block, in properly spaced relation to the lower end of the main electrode 13.

The central electrode structure, including the members 14, 18, 13 and 30, is, as above explained, a practically unitary structure, the part-s being in tight heat conducting contact. In operation, therefore, heat is rapid- 'ly conducted away from the lower electrode entire central structure, except the lower insulator 5, may be removed as a unit and replaced, by the removal of the bushing.

In some cases the adjacent edges of gaskets 9 may approximately or closely meet, when compressed, to increase the tightness of the gas seal at this point.

Also, the main electrode 13, sleeve 14, and disc (or nut) 18, may be. welded together, for greater mechanical strength and to increase heat-conductivity.

v I claim 1. In a spark plug, a central struc re comprising an insulator, a metal sleev therein open to atmosphere at its upper end, and a lower electrode tightly engaged in the lower lower electrode tightly engaged in the'lower end of the sleeve, and a radiating rod of waved formation and of small diameter in conductive connection with the upper end of the lower insulator and extending upwardly within the sleeve whereby heat is conducted from the electrode and dissipated to air within the sleeveand so to atmosphere.

'3. In a spark plug, a substantially unitary central electrode structure comprising a sleeve open to atmosphere at its outward end, and an electrode tightly inserted in one end thereof, and a radiating wire tightl inserted in the electrode and extending within the sleeve.

4. In a spark-plug, in combination with the shell and insulator, acentral electrode structure comprising a lower, solid electrode portion and an upper tubular conducting portion having close heat conducting connec- Io tion to the lower portion and open to atmosphere at its upper end, and a radiating rod of smaller diameter than said tubular portion and located therein and having close heat conductive connection tothe lower electrode portion.

5. In a spark plug, in combination with the shell and insulator, a central electrode structure comprising a lower, solid electrode portion and an upper tubular conducting portionhaving close' heat conducting connection to the lower portion and open to atmosphere at its upper end, and a radiating rod of smaller diameter than said tubular portion and located therein and having close heat conductive connection to the lower electrode portion, the radiating rod being in sinuous formation. I

6. In a spark plug,.in combination with the shell and insulator, a central electrode structure comprising a lower, solid electrode portion andan upper tubular conducting portion having close heat conducting connection to the lower portion andopen to atmosphere at its upper end, and a radiating rod of smaller diameter than said tubular portion and located therein and having close heat conductive connection to the lower electrode portion, said radiating rod extending through a large part of the length of said tubular portion. y

'In testimony whereof I aflix my signature.-

CALEB E. LEONARD.

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