US2305208A - Ignition of internal combustion engines - Google Patents

Description

Dec. 15, 1942. E. M. TRAMMELL, sR., ETAL 0 IGNITION OF INTERNAL COMBUSTION ENGINE Filed July 25, 1941 2 Sheets-Sheet l FIG.1. l6

- INVENTORS EARL M.-TRAMMELL, SR. EARL M.TRAMME| L, JR.

ATTORNEY E. M. TRAMMELL, $R., ETAL IGNITION OF INTERNAL COMBUSTION ENGINE Filed July '25, 1941 -Dec. 15, 1942. 2,305,208

2 sheets-sheet 2 INVENTORS EARL M.TRAMME| L ,SR. EARL M.TRAMMELL,JR.

AT TOR NEY conditions generally, become paramount.

Patented Dec. 15, 1942 IGNITION or INTERNAL COMBUSTION ENGINES Earl M. Trammell, Sr., and Earl M. Trammell,

In, St. Louis, Mo., assignors of one-third to Irving J. McGuire, Dolgeville, N. Y.

Application July 25, 1941, Serial No. 403,974

.15 Claims.

This invention relates to improvements in ignition of internal combustion engines, and more particularly to methods of and means for improving conditions of electric ignition of compressed fuel-air charges in internal combustion engines.

Considerable design effort has heretofore been devoted to attempts to control the conditions of incipient burning of fuel in internal combustion engines, particularly in engines of compressionignition types, as well as some others. It is also appreciated that various designs of head and combustion chamber construction have been evolved in electrically ignited engines and others, for the purposes of supposedly controlling conditions of flame propagation and trends of travel of burning fuel. These efforts have assumed an increased importance due to the prevalent tendency toward higher compression ratios in gasoline engines, wherein the problems of controlling detonation, controlling the expansion ratio of the burning charge, and of improving electric ignition The present invention may be stated as broadly directed toward improvement of the factors mentioned.

Probably the most important objective of present improvements, considered from a structural point of view, is attained in an improved design, shaping and arrangement of parts of an electric igniter or spark plug, such that, when certain parts adjacent the zone of actual ignition, are disposed in a rapidly moving fluid stream, for example, of mixture partly compressed in the cylinder, the movement of such stream in the region of the igniting arc, results in a reduction of pressure head, accompanied by increase in velocity head of the gas particles in the immediate region of first burning. This may be regarded as the paramount objective of present developments, since numerous physical agencies may be employed in the cylinder, for attaining the desired jet or stream of rapidly moving gas particles.

Among the several additional objects of the invention may be stated the improved combustion of an electrically ignited charge, by a novel method and. means for directing an ignited stream of gas mixture at a high velocity, into a centralized nal combustion engine, by a localized modifica- 55 tion of pressure in the immediate region of ignition, preferably in the main combustion space.

A further object of the invention is attained in an improved method of and agencies for effecting a physical direction of a defined portion of the charge, first into the region of ignition, and thence depthwise into the remainder of the charge, in a manner to produce a more efiicient combustion of the whole charge with a minimization of detonation.

Expressed in terms of operational results attained, the present developments enable an increase in engine compression ratio, without any comparable increase in detonation, or conversely expressed, enable a reduction of detonation, in high compression engines equipped with the present improvements, when compared with similarengines not so equipped.

A still further object of the invention is attained in a more gradual and a more desirable direction of propagation of flame from the zone of ignition and incipient burning, throughout the mass of compressed combustible mixture.

An additional important object of the invention is attained by establishing, through a novel form of cylinder-and-piston construction in conjunction with novel form of electrical igniter, a directional flow of a high velocity stream of the combustible mixture, and the direction of such stream, just, before,\ during and just after the time of igniti 'n,\ina fixed relation with respect to the electrodes of the igniter, such as a spark plug of special design.

Somewhat ancillary to the foregoing objects,

the present improvements importantly attain a definite physical, as distinguished from a chemical control of direction of flame propagation, such as often attempted heretofore by preliminary combustion of a portion of the charge, as in certain Diesel engines.

The foregoing and numerous other objects will be more clearly understood as to the manner and degree of their attainment, from the following detailed description of certain preferred embodiments of the invention, particularlywhen considered in connection with the accompanying drawings, in which:

Fig. 1 is a fragmentary section in a plane parallel to the axis of the cylinder, of the cylinder, piston and head structure of one cylinder of an engine to which the improvements are applied;

Fig. 2 is a fragmentary sectional view taken along line 22 of Fig. 1; Fig. 3 is a fragmentary section through the ignition zone and a portion of the combustion chamber of the cylinder of I suitable for use in and as a part of an engine embodying present improvements; Fig. 5 is an end elevation of the igniter or plug shown by Fig. 4; Fig. 6' is a sectional elevation taken in an axial plane, showing the upper portion of the cylinder, head, spark plugs and piston of one cylinder of an air cooled engine of a type suitable, for example, for aircraft use, and to which the present improvements have been applied; Fig. 7 is a fragmentary sectional elevation of the structure shown by Fig. 6, and as viewed along line 1-1 of Fig. 6, and Fig. 8 is a sectional elevation showing portions of the cylinder or head structure, piston'and igniter of the modified embodiment, and as viewed along line 8-8 of Fig. 6.

Referring now by characters of reference to the drawings, and first to the embodiment identifled with Figs. 1 through 5, only the elements necessary for adequate illustration of present improvements have been included in the drawings since the remaining elements of the engine are or may be of more or less conventional design. The structure illustrated includes the upper portion of a cylinder, the cylinder wall or liner element being indicated at l5, serving operatively to house the piston indicated generally at Hi, the latter being preferably of a design particularly adapted for present improvements, as will later more clearly appear. The cylinder i5 is provided with cooling liquid jackets, the chambered portions of which are indicated at l1, and a detachable head structure is mounted, through an intervening gasket 2 I, on the cylinder proper. Preferably two or more valves, generally indicated at 22, cooper ate with seats 23 for the admission, for example, of a carbureted gasoline-air mixture and for the timed exhaust of burnt gases, as will be readily understood. By preference the cylinder head 20 is provided with chambered portions 24, 25, 26 for the circulation of a cooling liquid, which, as may be desired, is in communication with that within the spaces of the cylinder and adapted for circulation as by the usual rotary pump or the like (not shown).

Threaded into the head 20 is an electric igniter such as a spark plug indicated generally at 30, and consisting for example, 3|, a porcelain or other insulating body 32, and a. terminal for the reception of the high tension ignition lead (not shown). The special features of construction of the plug will be later described.

.Referring now briefly to the elements of design for defining and physically directing a high velocity stream of mixture across the region of ignition of the charge, it will be noted that the piston I5, as best appears from Fig. 2, is provided with an undercut or shouldered portion 33 at one side of and slightly below its upper or outer margin. This undercut portion serves in operation to engage and cooperate with a fixed bridge or inset 34, formed by preference of a metal having high heat-resisting properties such as tool steel, stainless steel or the like, and fixed in position across this zone of the cylinder. In form the element 34 as shown. is of a generally rectangular shaping, except that its outer face is of a somewhat arcuate contour, this surface being indicated at 35 (Fig. -2). As will also best appear from Fig.2, the cylinder wall or liner i5 is provided with a recess portion 36 which constitutes a hollow lateral extension of the liner l5 and the inside surface 31 ofwhich conforms cl ly to the surface 35. The

of the usual metal shell projection 36 considered as a whole is of a trend axially of the cylinder and so, in a vertical cylinder, would be of vertical trend.

In the upper portion of the liner l5, it will appear that the hollow formation 38 is extended outwardly, and again inwardly toward the head, being constructed to constitute an arcuate nozzlelike formation 40 (Fig. 1), the latter opening into the combustion chamber immediately adjacent to the ignition region as defined by the plug electrodes hereinafter more particularly described. The nozzle 40 is formed by and between the conformed upper part of portion 36, and a small, preferably rectangularly notched portion in the element 34, the preferred shaping of the recess or notch resulting in nozzle 40, being best shown by the section of Fig. 2.

In the construction of the cylinder, the insert 34 may be assembled to the cylinder in any suitable manner as by welding, or by the provision of integral studs (not shown) on the block 34, engaging apertures in the adjacent upper peripheral portions of the cylinder, andbeing deformed into holding engagement therewith. The holding expedients are not illustrated, since it is felt that either mode of attachment of the insert 34 to the cylinder will be readily understandable.

It is a preference with the present improvementsto utilize a combustion chamber which is of substantial depth and which, by preference, is substantially coextensive in transverse area with the full face of the piston. Although the major principles of the present improvements may be practiced with other forms of piston deviating considerably from those shown, it is a preference in the arrangement of Fig. 1, to provide the piston head or face 42 with a central recess defined by a depressed piston head portion 43 of partly spherical contour. Y

Referring now to a special form of plug or igniter designed to function efficiently for ignition of the defined high velocity stream of mixture resulting from features heretofore described, or otherwise created, the threaded inner end 44 of the plug is or may be of itself of conventional construction provided with the usual external threads, engaging companion threads (not shown) in the head portion 20. The plug connector terminal is in electrical communication with a central electrode 45 and the latter is surrounded, down to a zone just short of its inner end, with a preferably frusto-conical body of insulating material such as the porcelain or mica 46. It will be understood of course that the high tension lead from the distributor of the ignition source, such as a magneto or battery ignition system, is in electrical circuit with the upper terminal, and therethrough, with the central electrode 45 of the plug.

By preference the electrode 45 has metallically secured thereto a small rectangular center plug electrode 41, the shaping of which best appears 'from Fig. 5, and arranged in line with the electrode 45,- but suitably spaced therefrom to form a spark gap or plurality thereof, are a pair of grounded plug electrodes 50 and 5|.

As will appear from Fig. 5, the electrodes 50, 41 and 5| are of generally block-like form, and of unusual width, and by great-preference, the outer surfaces of the electrodes 50 and 5|, or alternate y the adjacent portions of the shell 44, are given a smooth and convex contouring, or streamlined shaping, each of these surface portions approximating by preference, the nose portion of a streamlined object. This shaping is done for the specific purpose of disposing the row of electrodes 50, 41 and directly in, and in line with the defined trend of the high velocity stream of mixture expelled from the nozzle formation 40, above described in connection with Figs. 1 and 2.

It will have appeared from the description of the arrangement and shaping of the electrodes or adjacent spark plug portions that when a high velocity fluid stream is projected across the inner end of the plug, the stream so projected, will be divided, but with a minimum of turbulence or frontal resistance, by the streamlined nose surfaces of either the electrode 50 or the electrode 5| depending upon exact placement of the plug in the cylinder, and for which provision is made as will later appear. The result of this division of the high velocity stream of mixture by the plug elements, is the creation of a cavitation effect within both of the spaces indicated at 52 between the ad jacent electrodes. Otherwise explained, the pressure head component of total pressure otherwise existing because of cylinder compression, in the region of the plug and elsewhere, is in the latterregion converted in substantial part to a velocity head, thus effectively reducing momentary static pressures in the immediate region of the plug electrodes. Since the relation of electrical resistance to arcing, in respect to gaseous pressures, is well known, it will be obvious that the reduction of pressure head in the zones 52 between the electrodes, will operate to attain a number of advantages. For example, with an ignition coil of a given step-up ratio and number of turns of secondary winding, constant inductance, etc., the gap between igniter electrodes may be increased with certainty of ignition because of reduced gas pressure across the gap. There being thus permitted a greater spark gap, a measurable increase in fuel economy will result.

Incidentto the movement of the defined stream of the mixture across the electrodes prior to and at the time of ignition, there results the further obvious advantage of self-cleaning of the plug electrodes and a lessened tendency to fouling thereof due, for example, to carbon accumulation.

It will have appeared from the foregoing description of eflect of movement of the high velocity stream of mixture across the electrodes, that the cavitation effect resulting in the zones 52 approximates what is sometimes popularly referred to as a venturi action. Since, however, the relation between pressure head and velocity head is more accurately expressed by the well known Bernoullitheorem, and since the situation existing in the region of the ignitor is thereby ac- I countedfor, or by a corollary of such theorem, this'conditio'n and the effect attained is, for convenience,-referred to as 'a Bernoulli effect.

' As thus far described, the three aligned elements of the plug or igniter, viz. 50, 41 and 5|, have been referred to as electrodes, since, depending upon the.relative spacing of these elements, the ignition spark may occur in either of the zones 52, necessarily across the gap of least resistance. It is, however, important to consider that it is not necessary to utilize, solely, the electrodes as agencies forattaining the Bernoulli effect in the region of ignition. For example, by spacing'the center electrode 41 somewhat more closely to element than to element 5|, ignition will invariably take place by arcing between electrodes 41 and 50. Underthese conditions element 5| ceases efiectively its function as a plug electrode, and may be regarded solely as a physical agency, when presented nearest the point of origin of the fluid jet-forming agencies such as channel 40, and under such conditions element 5| serves solely the purpose of a deflector. It is accordingly distinctly within the purview of the present developments, to employ a deflector element to attain the described cavitation effect in the region of the ignition are, by means other than the electrodes themselves. In the example just described, one of the outside elements (50 or 5| according to location of the plug in the cylinder) serves this purpose.

There should be mentioned for completeness a fact which will clearly appear from the drawings and foregoing description, namely, the preference for such an arrangement of spark plug, plug electrodes and stream deflecting agencies, that the spark discharge occurs in a direction along or parallel to the trend or defined direction of the high speed jet of mixture heretofore described. It is to be noted as one of the advantages of the special form of plug described, that when the plug is properly oriented in the cylinder as by indicia for this purpose, hereinafter described, the arc and moving jet of fluid will be characterized by about the same direction. This feature is of some advantage over the conditions prevailing were a conventional plug to be used, and the engine provided with a suitable form of jet-deflecting agency either on or near the plug. In the latter arrangement, the direction of the jet would be normal or at right angles to the line of spark discharge, and hence would exhibit a marked snufling tendency, which is not noticeable with present improvements.

Proceeding now to a more complete discussion of the preferred agencies by which the high velocity stream of mixture is caused to move across the electrodes as described, it may be noted that the relation between the insert 34, channel or nozzle 40 and element 36 is such that, as the piston I6 is moved upwardly on its compression stroke, (assuming for example the improvements to be embodied in a four cycle engine) there will be a certain portion of the fluid mixture under compression, entrapped in the space between shoulder 33 and the shouldered under portion of bridge 34, during such outward or upward movement of the piston toward the cylinder head. As soon, however, as the piston approaches its top center position or more advanced firing position as desired, thus bringing the shoulder 33 and bridge 34 together, the portion of the charge entrapped therebetween will thereupon be released and expelled into and through the channel 40, and because of the previous confinement of this charge portion and the relatively small sectional area of the passage formed by the nozzle structure, this stream, which is of a width only slightly greater than that of the plug electrodes 50, 41 and, will be expelled at high velocity in a line with and just ahead of this row ofelectrodes. From this it will be seen that the described jet-forming structure of the cylinder and piston or one thereof, coacts with the igniter, at the time of ignition, to attain a high-velocity stream of burning mixture, the rate of projection of which is at least equal to linear piston speed, and may be of greater speed because of some separate initial compression of the small charge entrapped just before its release.

There will now be considered the effect on ignition and the subsequent complete burning of the charge confined in the main portion of the clearance between the piston and head, as attained by the piercing action of the defined stream of now-ignited combustible mixture. In

most if not all engines of prevailing type equipped Accordingly, in the absence of some physical,

means serving to define a trend of movement of the first-kindled burning particles, there can exist no defined trend ordirection of flame propagation. According to the best information available it appears that in the prevailing absence of any specific physical agency for determining such trend, burning will first take place peripherally or perimetrally of the combustion chamber, often first in the relatively shallow portions thereof, thus resulting in undesirable detonation effects. In the utilization of present improvements it will appear from the location of the jet or nozzleforming elements in relation to both piston and head, that the high-velocity stream of initially burning charge is propelled definitely toward the center, and preferably also the deepest portion of the clearance or combustion chamber. Thus, as far as is known to applicants, there is created for the first time a positive control by a distinctly physical agency, of trend of flame propagation. The movement of the stream emanating from the nozzle-forming elements 40 and 4|, being inwardly and approximately diametrally of the combustion chamber, the initially kindled particles of mixture projected as they are at high velocity directly to a central zone of the whole combustible mass, will result thereafter in a flame extension from the center or deepest'portion of the charge outwardly, with reasonable uniformity, toward the marginal portions of the confined charge. By the time, however, that the outermost portions of the charge have been completely fired, some recession of .the piston and hence some expansion has taken place in a manner to render crank angles more favorable for continued expansion without detonation, and with a minimum'heat loss by wiping action of flame on the cooled upper cylinder walls.

From the foregoing it will have appeared that the present improvements serve to attain a definite physical control of trend and manner of fiame propagation through the whole. mass of charge, and that in utilization of the present developments, by controlling the more intense early burning stage of the charge so that it is kept in or near the center of the mass of mixture instead of the flame predominantly wiping the inside perimetral combustion "chamber surfaces. This older and prevailing practice results in deleterious effects on metal surfaces and lubrication, and causes relatively higher heat losses to the jacket or ribs, which effects are all markedly minimized according to the present design.

In order to minimize or obviate any destructive tendency of localized heating effects in the region of the nozzle-forming elements, such as might. otherwise occur during expansion of the charge on the working stroke of the piston, it is preferred to provide a relatively thin wall section 53 (Fig. 1) in the region of the passage 40. This relatively thin wall separating the nozzle from the cooling jacket fiuid in this zone, facilitates heat transfer with a locally augmented cooling effect in such manner that any tendency toward an accentuated heating effect in this region will not damage the metal parts even over a long period of operation.

Itwillbenotedthatthereareanumberof structural possibilities, varying from the few selected embodiments, for producing the high velocity stream of mixture across the igniter electrodes and projecting the stream into the center of the charge of fuel mixture. It will be apparent that the nozzle-forming structure may be constituted either solely by special construction of the piston, or solely by a particular conformity of the cylinder wall element, or by both of such cooperating members.

As an example of an embodiment of the present improvements in an engine of somewhat different type, such as an air cooled aircraft engine, Figs. 6, 7 and 8 will be found supplementally instructive. The function and principles of operation are or may be similar to those set forth above in connection with the structure of Figs. 1 through 5, but it may be noted for completeness that in the modified form the cylinder structure indicated at is provided with an integral head portion indicated generally at H, both cylinder and head being provided with preferably integral cooling ribs or fins 62 on the cylinder, and 63 on the head. In this arrangement a piston 64 may be provided with a relatively fiat top or head 85, since the cylinder head ii is substantially arched or domed to provide a deepened central portion of the combustion space defined between the piston and head ii. In the latter are operatively seated, inlet and exhaust valves designated generally at 66 and GLand cooperating respectively with seats and H.

Although dual ignition or in fact any desired reasonable number of igniter elements may be employed in either of the embodimentsillustrated, or others, dual ignition is shown as embodied in the air cooled cylinder, the two plugs being each indicated at 30, since they are or may be similar to the single plug Iii in the embodiment of Fig, 1. The construction and arrangement of electrodes are or may be as heretofore described. In the modified form of Figs. 6, 7 and 8, the igniters 30 are disposed diametrally opposite each other, and in a vertical cylinder would be arranged horizontally in a zone in or near the juncture of the head and cylinder body. In this zone, the cylinder structure is undercut or recessed somewhat as indicated at 12, the recesses I2 terminating inwardly in a shoulder 13 just below the plug recess. The piston I4 is provided with similarly shaped, cooperating shoulders l4.

Each of the recesses 12 is in this case, formed in a projection 15, (Fig. 8) extending inwardly" of the normal cylinder wall, and each of these recesses is formed as a channel of a trend axially of the cylinder, 1. e., a vertical trend in a vertical cylinder. The projections 15 are individually provided with a planar, inwardly presented face 16, with which cooperates a companion planar face 11 on the piston 84, the mating plane between the surfaces I6 and I1 chordwise intersecting the cylinder space. It will have appeared from the structure just described, that the eflect in operation is closely similar to that attained in the structure of Fig. 1. except for the fact, obviously, of the provision of two sets of agencies in diametrally opposite zones of the cylinder for simultaneously collecting, compressing, confining and then sharply injecting the high speed jets of compressed fuel mixture, each jet being projected at high velocity across the ignition zone of the adjacent plug 30.

It will appear that, in the arrangement of Fig. 6, as the piston moves upwardly on its compression stroke, portions of the charge will be entrapped at opposite sides of the cylinder, in each of the channels 12 and between the cooperating shoulders 13 and H. Just before the piston attains top center position, or optionally, some other lower point in piston travel'at which ignition occurs, the charge collected between parts 13 and 14 and in the nozzle-forming passage 12,

will be forcibly delivered across the electrodes of the igniters 30, thence by the curved upper surface of the recess 12 indicated particularly at 80 (Fig. 6) these high velocity, now-ignited charge streams will be propelled depthwise, diametrally and more or less directly to the center of the burning mass, all with results and advantages heretofore described.

Since it is of course desirable to be assured of the correct alignment of the igniter electrodes, and other parts, in keeping with the trends or directioning of streams of igniting charge, it is desirable to provide both the plug and the adjacent exterior elements of the cylinder or head with suitable indicia by which the correct position of the plug in the cylinder is assured. Such indicia may for convenience consist of suitable arrows, pointers, or other provisions, such for example "as the arrow 8| on the shell of the plug, and projection 82 (Fig. 6), on the cylinder or head casting. In the manufacture of the plug,

the arrow 8| will of course be located on theshell of the plug in such manner that when brought to register with the projection 82, the electrodes will be suitably aligned with the nozzle-forming elements of the cylinder.

It will have appeared that the foregoing embodiments of the invention serve to attain each and all of the several advantages and objects hereinabove-specifically stated, as well as those implied from the more detailed description.

Although the present disclosure has described the invention by detailed reference to specific structural embodiments, the description is to be understood merely as illustrative, and not as limiting the invention, since various changes may be made in the parts, their combinations and the manner of their utilization without departing from the full intended scope of the invention as defined by the claims.

We claim:

1. The described method of operating an internal combustion engine provided with an electrical igniting agency in a combustion chamber, which consists in projecting a defined ignitable fluid stream across the igniting agency and parallel to the course of the ignition discharge, thence substantially directly into approximately the central portion of the combustion space, substantially at the time of'ignition, and in reducing the pressure head of the fluid in the immediate region of ignition at the time of ignition discharge.

2. The described method of operating an internal combustion engine of piston-and-cylinder type provided with an electrical igniting agency in a combustion chamber, which consists in entrapping within the cylinder, a portion of the cylinder charge, and thereafter projecting said entrapped portion of fluid at a substantial velocity across the igniter and therebeyond, to a zone substantially inwardly of the wall portions defining the clearance, firing the charge by an arc, and so directioning the arc that resistance thereto by the charge, is' minimized by the said stream of projected fluid.

3. The described method of igniting a charge of combustible fluids in an internal combustion engine of piston-and-cylinder type, which consists in projecting a relatively high-velocity, nonturbulent stream of the combustible fluids along such'a course that substantially the highest velocity portion of said stream traverses a zone of electric ignition igniting said stream by an arc of fixed direction approximately paralleling said high velocity stream portion, thence impelling said stream into a zone substantially centrally and transversely of the combustion chamber.

4. The described method of operating an internal combustion engine of piston-and-cylinder type provided with electric ignition, which consists in projecting a jet of gas substantially diametrally of the medial portion of the combustion chamber and s0 directioning the jet of gas that its stream is of substantially rectilinear trend, and igniting the charge of combustiblefiuid in the cylinder by an electric discharge, and imparting a definite trend to the ignition are so that it occurs along a path parallel to and distinctly within the said jet of gas.

5. The method recited by claim 4, further characterized by the step of causing said electric discharge for ignition purposes, in a zone close to the point of projection of the jet of gas into the combustion space.

6. The described method of operating an internal combustion engine of piston-and-cylindertype equipped with electric ignition, which consists in confining a minor portion of the cylinder charge between the piston and cylinder during the compression stroke of the piston, projecting said confined portion in the form of a jet, into a substantially intermediate zone of the cylinder charge while undergoing compression, in utilizing the velocity head of said fluid jet to create a Bernoulli efiect between the ignition electrodes during the period of ignition and in causing an electrical ignition discharge substantially parallel to said fluid jet in the region of the electrodes.

7. The described method of operating an electrically ignited internal combustion engine of piston-ancl-cylinder type, which consists in confining a relatively minor portion of the compression charge within the cylinder, between the piston and cylinder during a compression stroke of the engine, projecting said confined portion of the charge in the form of a relatively high velocity jet directed to the central zone of the combustion space, and in igniting the substantially compressed cylinder charge, by an electric discharge, and causing said discharge to occur in a direction along rather than across said jet, as in a portion of reduced pressure within the projected fluid jet.

8. In an internal combustion engine, a cylinder, a piston operable therein, means formed by adjacent coacting portions of the cylinder and piston to entrap arelatively minor portion of the cylinder charge and to expel said entrapped charge portion in jet form into the combustion space, an ignition member in the path of expulsion of said entrapped charge, and means associated with the ignition member for dividing said jet in the immediate region, and at the time of the igniting arc, said member and means being arranged to establish the igniting arc in substantially a coaxial relation to the jet, whereby said jet promotes, rather than exhibits any tendency to snuff the ignition arc.

9. In an internal combustion engine, a cylinder, a piston operable therein, means formed by adjacent coacting portions of the cylinder and piston to entrap a relatively minorportion of igniter being fixedly so located with respect to the means aforesaid, that the electrodes are substantially aligned with the jet resulting from expulsion of said entrapped charge.

10. In an internal combustion engine including a cylinder and a piston operable therein, means 10 for impelling a relatively minor portion of a partly compressed cylinder fluid, in a defined stream at a substantial velocity, said means being so located and directioned as to impel said stream substantially medially of the combustion space,

an electric igniter, and an element in the region of the igniter, formed to create, in coaction with said stream, and with low turbulence, a relatively reduced pressure head in the region of ignition, said igniter and element being arranged to establish a substantial coincidence of the line of ignition arc with the source of said stream in the region of ignition.

11. In an internal combustion engine including a cylinder and a piston operable therein, 5

means for impelling a relatively minor portion of a partly compressed cylinder fluid, in a defined stream at'a velocity substantially equal to the then-prevailing linear velocity of the piston,

said means serving to impel said stream substantially medially of the combustion spacefiand an electric igniter, including a pair of electrodes spaced along the course of said stream, at least one of said electrodes being formed in part of a tapered cross section, whereby to create a region of relatively reduced local pressure in the immediate region of the electrodes and at the time of ignition,

12. An electric igniter for an internal combustion engine, the igniter having an element adapted to extend into the combustion space of the engine, and shaped to provide a portion of tapered cross section, whereby when disposed in a high velocity jet of fluid in the cylinder, said element serves to reduce the pressure head in the region in which ignition occurs.

13. In an internal combustion engine, a cylinder, a piston operable therein, an electric igniter including a pair of electrodes, means for causing a stream of ignitible mixture to move across the nfiion of the electrodes and generally parallel to the direction of discharge at the time of ignition, an element of streamline section arranged substantially in the line of said stream, adapted under the influence of the stream, to modify the fluid pressure head in the region of the electrodes at the time of ignition, and means on an exterior portion of the igniter, enabling location of the igniter in the cylinder to preserve a constant relation between the direction of said mixture stream and the igniter electrodes.

14. An electric igniter for an internal combustion engine, and including a pair of electrodes between which ignition sparking occurs, one of said electrodes being of tapered section and so shaped as to minimize resistance thereof to a flow of fluid in the direction of ignition arc, whereby when the igniter is disposed in a high velocity jet of fluid undergoing compressiom-said electrode serves to reduce the pressure head in the region of ignition,

15. A spark plugfor internal combustion engines, including a pair of electrodes normally adapted to extend into the combustion space of the engine, the plug being so formed as, when energized, to provide an igniting arc of'deflnite direction or trend with respect to predetermined portions of the combustion space of the engine, and indicia provided so as to be visible exteriorly of the plug, for directionally positioning the plug into the combustion space of the engine.

EARL M. TRAMMELL, an. EARL M. 'rasmmm, JR.

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