US2212725A - Spark plug temperature control - Google Patents

Description

Aug 27, '3940. P. G. ANDRES 2,212,725

SPARK PLUG TEMPERATURE CONTROL Filed Aug. 18, 1939 rIl# lili i Patented Aug. 27, 1940 UNITED STATES PATENT OFFICE Paul G. Andres, Indian Bowes Seal-Fast Ind.

Application August 18,

l Claims.

This invention relates to spark plugs such as are employed upon internal combustion engines and relates particularly to means for controlling temperatures of the central insulator when used s in engines of diierent plug heat requirements.

An important object of the invention is to provide not only an eicient heat control of the insulator but to do so without having to employ more than two packing gaskets, both being located up above the usual threaded end of the plug Where large diameter shoulders may be had in order to provide the necessary cushion seal.

A still further important object of the invention is to provide an insulating contacting member that may be varied in length along the shank or' the insulator in accordance with the heat requirements, the contacting member being shortened where the nose of the insulating member is to operate at a relatively high temperature and lengthened Where the temperature of the nose is to be reduced. This contacting member is made out of a high heat conducting metal and is intended to operate to transfer heat laterally or radially from the shank of the insulator to this encircling conducting member and then permit the heat to be conducted along that conducting member to the outer metal shell which supports the insulating member. The entire idea is to regulate the temperature of the lower end of the shank of the insulator which is exposed, principally across its nose, to the heat of combustion within the cylinder of the engine.

A still further important object of the invention is to provide an automatic heat control means whereby the temperature of the lower end of the insulating member is automatically changed in accordance with the heat generated within the engine cylinder, the temperature of the insulating member being reduced as the heat in the cylinder increases.

lt is well known that spark plugs must be designed to meet diierent heat conditions. For example, a spark plug having an insulator operating at a relatively cool temperature due to dissipation of heat from the insulator will foul by collecting oil when the engine temperature is relatively low, a condition encountered in warming up the average automobile engine or when a car is driven at slow speeds as in city driving. Another condition may arise where the insulator does not dissipate heat sufficiently fast to prevent its becoming damaged by overheating under excessive cylinder combustion temperatures, such as when a car is driven at high speeds on a highway, and in racing cars, or even in heavy duty apolis, Ind., assigner to Corporation, Indianapolis,

1939, Serial N0. 290,866

Cl. 12S-169) trucks. There are intermediate conditions also that must be taken care of in order to get the best performance of the spark plug.

These and other objects and advantages of the invention will become apparent to those 5 versed in the art in the followingI description of the invention as illustrated in the accompanying drawing, in which Fig. 1 is a top plan view of a plug of conventional type to which the invention is applied;

Fig. 2, a central longitudinal section through the plug;

Fig. 3, a side elevation in partial, longitudinal, central section of a plug having a modied form of insulator;

Fig. 4, a similar view illustrating a modified form of insulator heat control member;

Fig. 5, a side elevation of a plug in partial, longitudinal section showing a still further modied form; and

Fig. 6, a view in perspective of a skirted gasket as employed in Fig. 3.

Like characters of reference indicate like parts throughout the several views in the drawing.

Referring rst to that iorm as illustrated in Fig. 2, the conventional metallic shell lll is em- L ployed an'd formed to have a shoulder l l below which is a threaded portion l2 formed to engage within the threaded bore of the cylinder and to carry the shoulder li down against a sealing gasket (not shown) in order to form a gas-tight iit with the cylinder head, all in the usual and well known manner. The shell i@ is provided with the usual inturned annular shoulder it to carry a gasket lll thereon. A ceramic insulator l5 is formed in the conventional manner to have a shank il extending centrally through the gasket ifi downwardly into the bore provided: through the threaded end portion ii?.

The upper part or the insulator i5 carries an upper shoulder it therearound against which a sealing gasket i@ is pressed by means of the screw-threaded ierrule @il screw-threadedly engaging internally of the upper end of the shell i@ whereby a centrally enlarged portion oi the insulator i5 is compressively gripped between the shell shoulder i3 and the ferrule 23 by means of the intervening gaskets lil and ld respectively. t is to be noted thatboth of the gaskets i4 and i@ are well spaced above the threaded portion l2 and hence are in a cooler part of the shell. The two gaskets lil and i9 are, of course, employed for the usual purpose of cushioning and sealing the insulator it within the shell l to prevent escape of gases outwardly through the shell past 55 Awith the shell I0.

the insulator. The gasket I3 is formed in any suitable manner, the nature of which per se does not enter into the invention.

From the gasket Iii is carried a metal skirt 2I, here shown as being conical in shape to be in close proximity and preferably in immediate contact with the conical shank I1 of the insulator I5. It is to be noted that the lower end of this skirt I1 is shown in Fig. 2 as being carried down into the bore within the threaded portion I2 of the shell. That is to say, the lower end of theV skirt 2| is brought down in close proximity to the nose 22 of the insulator I5, this nose, of course, being normally the hottest portion of the insulator.

When the'plug is in use, the nose 22 becomes heated. The insulator I5, being made out of a ceramic material, is inherently a very poor heat conductor and, therefore, the insulator normally has quite a range of temperatures between its extreme upper and outer end and the nose 22. This means that considerable strain is set up in the insulator itself. By placing the gaskets I4 and I9 in the upper portion of the shell I0 or at least in that portion above the shoulder II and spacing the gaskets to be relatively close one to the other axially along the insulator I5, permits that insulator to be gripped between zones having substantially the same temperatures or at least with but slight temperature difference. 'This alone permits the obtaining 'of a good seal.

Furthermore by use of the skirt 2I, heat is transferred laterally from the extremely heated nose 22 into this metal skirt. Being a good conductor, heat will be carried along the skirt up to the gasket I4 which is in intimate contact Through this intimate contact, the heat carried up the skirt 2l is rapidly conducted to the shelll I0 and thus dissipated into that body where the heat may be radiated v into the atmosphere from the upper portion of the shell and also conducted through the threaded portion into the water-cooled cylinder head,

it being understood, of course, that the shell I0 itself constitutes a relatively considerable mass of metal that is heat conducting.

The skirt 2I, if made of copper, may have its lower end oxidized when subjected to the heat This fact is of of combustion in the cylinder. considerable advantage in that the copper oxide is normally a poor heat conductorl and, therefore, heat of combustion would not be transmitted to any great extent directly up the skirt 2I by reason of the presence of this lower oxide end. This would limit largely the function of -the skirt 2I to the conducting of heat laterally initially from the shank II and then upwardly to the shell IIJ. f

It is obvious from `the foregoing description of the skirt 2|, that the rate of heat conduction from the shank I1 may be varied by changing the axial length of the skirt 2 I. That is, if the skirt is made longer, the nose 22 willl be maintained at a lower temperature whereas if the skirt 2| is made shorter, the nose 22 will be permitted to assume a higher temperature; The exact position of the termination of the nose 22 within the threaded portion I2 may vary and is not to be considered as being limited by the positions indicated in the accompanying draw- Referring now to that form of the invention as shown in Fig-3, the insulator I5 is shown as having a cylindrically formed shank 23 in place of the conical shank I'I shown in Fig. 2. In this form, the gasket I4 will have a cylindrically extending skirt 24 brought into close contact with the shank 23. While in both Figs. 2 and 3, a slight clearance is indicated as being between the skirt and the shell I0, this clearance isextremely small and is provided merely to permit expansion of the shank of the insulator without limitation thereof as might cause f'racturing of that ceramic material. Normally this clearance will substantially disappear when the plugs are in use so that to all intents and purposes, there will be conduction of heat radially not only from Y the insulator shank to the surrounding metallic skirt but also directly from the skirt into the shell without all of the heat having to be transmitted upwardly to the gasket I4 and with little or no air gap between the skirt and the shell.

Referring now to Fig. 4, the same type insulator I5 with the cylindrical shank 23 is indicated. In this form, however, the skirt extending from the gasket I4 is shown as comprising a plurality of individual bands 25, here shown as three in number, although this number may be Varied in accordance with the length of the shank 23 and also in accordance with the temperature desired to be maintained at the nose 22. In any event, these bands 25 are employed as a simple means of obtaining the desired skirt length. Where a short length is required, the bands may be omitted entirely or simply one or two bands employed. Where the length is to be increased, more bands are used. The bands are placed around the shank 23 in compressive engagement therewith and pressed into abutment one band with another so as to obtain the continuityof heat conduction required.

In Fig. 5 there is indicated a further modified form of structure in that the skirt is divided into a plurality of individual tongues 26, each having its upper end engaged with the annular gasket I4. These tongues 26 may be made out of. any suitable heat conducting metal. However, where an automatically controlled temperature range within the shank 23 of' the insulator I5 is desired, each of these tongues 26 is preferably made of bimetal wherein initial contact of each tongue 26 is had with the upper end of the shank'23 adjacent the shoulder I6 of the insulator. This permits rapid heating of the shank upon starting of the engine in which the Aplug is used. As the temperature of the engine increases, the tongues 26 will curl or bend toward the shank 23 to increase the area of contact therewith. Thus it is to be seen that as the temperature of the shank 23 increases, there will be an increasing area of contact of the tongues 26 with that shank until the maximum area of the tongues is reached to obtain the maximum heat conduction from the. shank. It is, of course, understood, that the tongues 26 are so positioned relative to the shank 23 and in reference to the metals employed that the desired bending of' the individual tongues 26 is secured. In other words, the form as shown in Fig. 5 gives an automatic thermostat control of the rate of transfer of heat from the insulator to the shell.

In further reference to the bimetal tongues 26 shown in Fig. 5, these tongues may be so positioned relative to their direction of bending under application of heat that the lower free ends may be maintained in contact with the wall of the bore `through the shell IIJ and to operate under a buckling action to force areas above the lower ends into increasing contact with the shank 23 as the temperature at the nose 22 tends to increase.

'While I have herein shown and described my invention in the several forms as now best known to me, it is obvious that structure variations may be employed, particularly in the shapes of the shanks of the insulator, the particular construction of the insulator gaskets, materials employed in the heat conducting skirts, and the like, all without departing from the spirit of the invention and I, therefore, do not desire to be limited to those specific forms beyond the limitations as may be required by the following claims.

I claim:

1. In a spark plug having a metallic shell, an insulator sealed in a .bore of the shell by a lower gasket, and an insulator shank extending below the gasket in spaced relation from the wall of said bore, a heat-conducting skirt extending from contact with said shell at said gasket about said shank within the space between the shank and the wall of said bore, said skirt serving to conduct heat from said shank to said shell, said skirt being formed of a plurality of bimetal members arranged to bend under temperature changes toward and away from said shank whereby the contact length of skirt with the shank will automatically vary to increase with increase in temperature.

2. In a spark plug having a metallicshell with a bore therethrough, an insulator sealed in said bore by means of a heat conducting gasket and having a shank extending from the gasket a distance therebeyond freely along said bore, and a heat conducting skirt extending from said gasket a distance alonggand around said shank, and relatively poor heat-conducting means on the lower end of said skirt substantially limiting heat transfer thereto to lateral flow from said shank to the skirt.

3. In a spark plug having a metallic shell with a bore therethrough, an insulator sealed in said bore by means of a heat conducting gasket and having a shank extending on through the gasket a distance therebeyond freely along said bore, and a heat conducting skirt integrally extending from said gasket a distance along and around said shank, a part of said skirt at least consisting of metallic bands successively contacting one with another and encircling and compressively engaging said shank, the number of bands being varied to give a skirt length in accordance with the shank temperature desired.

4. In a spark plug having a metallic shell and an insulator carried in a bore of the shell, means for securing a complete, gas tight seal about an intermediate part of the insulator Within an upper relatively cool zone of the shell, and heat transfer means about the insulator below said seal for conducting heat to said shell, said heat transfer means consisting of a metallic member conforming to the shape of and closely fitting along an initial upper length of said shank and having a portion in direct contact with the shell,

and means for varying the shank contacting length of the metallic member below said shank upper length in accordance with the rate of heat transfer required.

5. In a spark plug having a metallic shell and an insulator carried in a bore of the shell, means for securing a complete, gas tight seal about an intermediate part of the insulator within an upper relatively cool zone of the shell, and heat transfer means about theinsulator below said seal for conducting heat to said shell, said heat transfer means consisting of a metallic member conforming to the shape of and closely fitting along said shank and having a portion in direct contact with the shell, and means automatically varying the shank contacting length of the metallic member. in accordance with the rate of required heat transfer.

6. In a spark plug having a metallic shell with a lower threaded end portion, an external cylinder seal gasket shoulder about the shell at the upper end of said threaded portion, a bore through the shell, and a shoulder in the bore above said threaded portion, the combination with an insulator in the shell bore having an intermediate enlarged portion above said bore shoulder and a shank portion extending past the bore shoulder freely into said threaded portion, of a sealing gasket interposed between said bore shoulder and said insulator enlarged portion forming a lowermost gas seal along the insulator with said shell, and a skirt extending from the gasket along said shank for selective heat transfer therefrom to the shell in accordance with the relative lengths of the skirt andl the shank, said skirt consisting of a plurality of bimetal portions arranged to go into and out of contact with the shank upon predetermined temperature fluctuations.

7. For a spark plug, an insulator sealing gasket comprising a seat annulus and an annular iinlike metallic skirt extending axially therefrom.

8. For a spark plug, an insulator sealing gasket comprising a seat annulus and an annular finlike metallic skirt extending axially therefrom having a variable effective diameter in accordance with heat changes.

9. For a. spark plug having an insulator, a

gasket receiving shoulder therearound and a shank extending from said shoulder,` a collar surrounding the shank having an internal diameter permitting the collar to be placed in juxtaposition with said shoulder, and a slotted metallic skirt extending from said collar about said shank.

10. For a spark plug having an insulator, a gasket receiving shoulder therearound and a shank extending from said shoulder, a collar surrounding the shank having an internal diameter permitting the collar to be placed in juxtaposition with said shoulder, and a slotted skirt extending from said collar about said shank, said skirt being formed of bimetal deforming subject to temperature changes.

PAUL G. ANDRES.

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