US2075232A - Method and means for scavenging - Google Patents

Description

March 30, 1937. sc N E 2,075,232

METHOD AND MEANS FOR SCAVENGING I Filed Oct. 2 1', 1952 5 Sheets-Sheet 1 Snnentor ((ttorneg March 30, 1937. scHNElDER 2,075,232

' V I METHOD AND MEANS FOR SCAVENGING 'Filed 061:. 24, 1952 3 Sheets-Sheet 2 (Ittorneg March 30, 1937. .H. SCHNEIDER 2,075,232

METHOD AND MEANS FOR SGAVENGING Filed Oct. 24, 1952 5-SheetS-Sheet :s

inventor HH/VRICH fem/H05 By I ' g Y ('(ttomeg Patented Mar. 30, 1937 ME'rnoi') AND MEANS FOR SCAVENGING Heinrich Schneider, Beloit, Wis., assignor'to Fairbanks, Morse & 00., Chicago, 11]., a corporation of Illinois Application October 24, 1932, Serial No. 639,307

25 Claims.-

In older prevailing forms of scavenging systems for two-cycle internal combustion engines, it is usual to arrange the scavenging ports in such a manner that an air stream issuing from any one port, clears the products of combustion, or exhaust gases, from only a single portion of the cylinder chamber, and similarly, the scavenging i air streams issuing from the remaining ports,

each clears only an indefinite, fragmentary pore tion of the chamber. With such older arrangements, it is difficult to obtain a thorough coalescence of the individual scavenging air streams, with a resulting poor coaction of such streams, since, as generally occurs, the individual streams 1., tend to interfere with each other, and to produce a turbulent condition withinthe cylinder chamber, resulting in an undesirable admixture of the exhaust gases with the incoming scavenging streams, thus rendering the scavenging proc- 30 ess imperfect and only partially effective. In the older, prevailing scavenging systems, a venturi or throat of the scavenging stream, has usually been located at some point outside of the port, and outside of the cylinder chamber. There- 95 fore, the air stream expanded immediately upon being directed into the cylinder chamber, resulting in an immediate decrease in velocity and, consequently, an increase in pressure. Thus, a high pressure region is'usually formed in the :10 inner or lower portion of the cylinder chamber in a zone immediately adjacent the scavenging air intake ports, preventing an orderly upward movement, either of the individual air streams, or of any resultant stream, thus causing a partial loss of the incoming scavenging air through the exhaust ports, an objectionable mixing of the incoming air with the exhaust gases in the cylinder, and hence an incomplete scavenging process. g

.m In the older forms of scavenging systems, the ports themselves usually constitute the only stream-forming or -shaping means outside of the cylinder, being in communication with a common scavenging air supply chamber or mani- 5 fold, and inthe usual constructions, the length of any supply conduit ismerely the thickness of the cylinder wall. Such types of scavenging port supply passages or' nozzles are entirely inefiective as stream-forming and -directing means, since so an air stream cannot be properly shaped and directed within such relatively short length of passage or nozzle. Furthermore, the port passages or nozzles of many of the older types of engines, besides being objectionably short, are 55' of uniform cross-sectional area throughout their length, and it is evident that with such a. construction it is practically impossible to alter the velocity of the air stream passing therethrough, as a result of which, the velocity of the air stream is substantially reduced immediately upon its 5 entrance into the cylinder. Thus, with the older forms of port nozzles it will be apparent that the individual streams entered the cylinder chamber in a more or less haphazard manner,

resultingin turbulence within the chamber, in- 10 complete clearing of exhaust gases therefrom, and mixture-of a portion of the exhaust gases with the incoming scavenging air. Such mixing continuesthroughout the scavenging stroke of the engine, serving to contaminate the scavenging air remaining in the cylinder at the end of the scavenging stroke for subsequent compression. Such a condition causes ineflicient combustion and consequently a substantial reduction in power developed per stroke of the engine.

It has been found from experience-that in order to obtain a positive and efiective cylinder scavenging action, it is essential to unite the individual air streams proceeding from each of the ports, so as to form a coalescent body of positive and. evenly rising layers of air, along and. adjacent a wall portion of the cylinder on the side opposite the exhaustports. Furthermore, such an upstream within the cylinder must remain substantially stable and uniform, irrespective of fluctuation in air supply pressures, such as may normally occur due tovarying speed of the engine. Since it is intended to have the upstream thus formed, control all other air currents within the cylinder, it is essential that this stream be more-positive in its action and movement than any other stream in the chamber. It

is, therefore, an object of the present invention to provide an improved scavenging system which 40 will attain the above noted advantages.

A further object is to provide an improved method of scavenging engine cylinders, which consists in uniting the individual scavenging air streams from the various ports, into an upstream constituting a stable, columnar body of air having a comparatively high velocity, and which is of a relatively small cross-sectional area on the scavenging port side of the cylinder, the crosssectional area of the bodyaof air being substan- 5o tially maintained until it attains a zone near the outer or head end of the cylinder, where it is permitted to dissipate a substantial part of its velocity into pressure, to form a relatively high pressure, low velocity downstream along the exhaust port side of the cylinder chamber. The latter stream is of comparatively larger crosssectional area, and occupies substantially all of the remaining cross-sectional area of the cylinder chamber not filled by the upstream. The

two opposite streams, together filling the cylinder, thus insure thorough sweeping and complete displacement of the exhaust gases from the cylinder. chamber.

A still further object is attained by an improved arrangement of port passages or. nozzles, in which each port nomle is formed of gradually, uniformly decreasing cross-sectional area, the maximum sectional'area of the node being 10- cated at the intake end of the nomle, and the minimum cross-sectional area being substantially the area of the ort. By this provision, the air stream passing through'the port nozzle, gradually increases its velocity as it approaches theport,

and as a result a. relatively high velocity air stream is projected a considerable distance into the cylinder chamber before its velocity is dissi- Another object is attained by aniimproved arrangement of port nozzles in which the margins of each nozzle, or the dividing walls between adjacent nozzles, consist of plane portions, the planes and axes of which are directed toward, and intersect at or near a point lying in an axial plane 3 of symmetry of the cylinder, such point of intersection being disposed adjacentthewall of the cylinder opposite the exhaust ports, and about midway of the dead center positions of the piston. The arrangement is further such that the streamlines of the several port nozzles or passages,

being lines each connecting the centers of the various cross sections of a port nozzle, are so directed as to approach, closely, the point of intersection of the port wall planes. By this provision, the air streams passing through the several nozzles, are directed positively toward a common point, and it is thus evident that there will result at this point, a coalescence of the various individual scavenging streams. An additional object is attained by an improved I arrangement of port nozzles in which the side or dividing walls of each port nozzle are each inclined with respect to a longitudinal planeof symmetry of the cylinder, the angle of inclination being different for each dividing wall on one side of the plane of symmetry; Since the lateral port margins are formed byj-the intersection of the dividing walls with the cylinder bore, each port is shaped substantially in the'form of an irregular four-sided polygon, or rectangle.

A still further object is attained in an improved arrangement of intake and exhaust ports for an internal combustion engine, in which the'neighboring margins of the adjacent exhaust and scavenging ports are increasingly spaced from each other, from the inner. end toward the head and of each port. By this'proyision, the tendency of air leakage from each end scavenging. port, over to the adjacent'exhaust ports, is minimized.

Further objects and advantages will appear from the following detailed description of parts and the accompanying drawings, in which: Fig. l is a longitudinal sectional elevation of a preferred form of engine cylinder of the two-cycle typ to which the present improvements are applied; Fig. 2 is a section taken along line 2-2 of Fig. I; Fig. 3 is a section taken along line H in Fig. 1; Fig. 4 is a development of the improved form of cylinder illustrated in Fig. l, and Fig. 5 75 int diagrammatic transverse section through the aovaaaa cylinder, showing, on a greatly reduced scale, the

relative-sectional areas, or fronts, of the high velocity and low velocity scaveng ng characterizing the present scavenging method.

. Referring to the drawings by characters of reference, the numeral 10 designates, generally, a preferred form of engine cylinder, of port scavenging type, which is, by preference, provided with a bore ii forming the internal cylindrical surface .of the cylinder, and in which is operable a piston 12. Air-for scavenging the cylinderv chamber II of exhaust gases is, by preference, supplied under. pressure through a conduit ll,-

from any suitable source (not shown), to an air reservoir or supply manifold II, which is, by preference, extended circumferentially about the inner end of the cylinder structure. scavenging port nozzles or conduits l6, II and II are, by

preference, formed by side or dividing walls I, 2|, 2i and 22, respectively, in the cylinderbody, each port nozzle including the entire conduit or passage which extends from the cylinder bore ii to a line which is indicated at 23-22 (Figs. 1 and 4) or to a point where the nozzle joins. the common air supply chamber or manifold ii. The intersection of each of the port nozzles J6, II and It with the cylinder bore forms scavenging Ports 24, 25 and 26 respectively, and in like manner the intersection of theport'nomie dividing wallswith the cylinder bore, forms port sides or bridging portions 21, 20, 2s and a. It will be readily seen that the port nozzles,'ports, dividing 'walls and port sides are arranged symmetrically oneach side of a plane indicated at Jl-Si in broken lines (Figs. 2 and 4), such plane extending lon-- gitudinally of the cylinder, and preferably including the cylinder axis. While the symmetrical arrangement of ports is preferable, the number thereof may be greater or less than the number shown. V I

Exhaust port nozzles '32 and 23 are, by-preference, formed, in part, by side walls 34, 35 "and 38,

respectively, the exhaust port nozzles serving to connect the cylinder with a -common exhaust chamber or conduit 31. The intersection of the exhaust port nozzles 32 and 33 with the cylinder bore, forms exhaust ports 38 and 32, respectively'. It will be noted that the exhaust port nozzles, ports and side walls.are shown as arranged symmetrically on opposite sides of. the plane 3i-4l of cylinder symmetry. 7

For best results, it is necessary that the individual scavenging streams issuing from the air,

port nozzles, unite within an area indicated at ll (Fig. 5) in a transverse plane which is preferably located substantially midway of the dead center positions of the piston. It'ls evident, therefore,

that the streamlines, of the several port nomles,

each of which may be regarded as an imaginary line connecting the centers of all the various cross sections of the nozzle. andproduced into the cylinder chamber, most desirably intersect. in .a point indicated at 42, which lies-within the zone or area I, and in or near theplane of symmetry ll-Jl. Furthermore, the steamlines must each be angularly positioned with respectto the plane of symmetry, the streamline of the port nomle It being inclined to a greater extent than either the .s'treamline of the port nozzle H,- or that of the port nozzle it, (see Fig. 4).

' In Fig. 4, the cylinder bore ii is shown developed' in a plane indicated at "-llin which the scavenging ports, exhaust ports, and associated port nozzles are symmetricallyarrangedon each side ofthe planedl-Il. podtion of.

the port nozzle walls I9, 20 and 2| are determined by planes 3|, 44, 45 and 46, respectively, the plane 3l.3l bisecting the dividing wall l9, with the streamline plane of the port nozzle I6 lying midway between planes 3| and 44, and similarly with the streamline planes of the port nozzles l1 and I8. It will be evident that the planes 44, 45 and 46 intersect substantially at the point 42 within the zone 4|. From Fig. 4 it will be apparent that the side walls of each port nozzle are increasingly spaced from each other as the nozzle approaches the common supply chamber or manifold l4, and consequently a gradually decreasing cross sectional-area of nozzle is presented to the stream moving therethrough, for a purpose hereinafter appearing.

In constructing the cylinder, the portinozzles ,are, by preference, so formed that each is of a spiral trend about the cylinder bore, and as a 4 result the streamline determined by the shape of each port nozzle is constantly but gradually varying in a direction tangential of the cylinder, and substantially maintains the same curved course, toward the area 4| within the cylinder chamber. The end port nozzles l8 are, by preference, formed with a greater spiral trend, than the inner port nozzles, and as shown in the figures, the outer port nozzles are extended under the exhaust ports.- Therefore, since the scavenging air supply is introduced through the conduit M, which is immediately adjacent the exhaust ports, it will be seen that the scavenging air streams are continually being directed to the area or 'zone of coalescence 4| in the chamber. As above noted, the intersection of the dividing walls with the cylinder bore forms the bridging portions of the ports, and since the port nozzle walls vary in inclination with respect to an axial cylinder plane, theintake ports 24, 25 and 26 are each 40 of an irregular four sided polygonal or trapezoidal form, and further, no two intake ports on one side of the plane of symmetry 3l3l are alike. Such an arrangement is of particular advantage in minimizing loss of scavenging air issuingfrom the scavenging ports 26 by shortcircuiting through the adjacent exhaust ports 38, since it is apparent that the adjacent sides of these ports, are increasingly spaced from each other in a direction extending from the bottom of the port to the top thereof. The arrangement of the inlet ports 26 with respect to the adjacent exhaust ports 38 is of particular importance near the beginning of the scavenging stroke at which time, the piston, I2 is about to uncover these ports. Further movement of the piston, in its downward stroke uncovers aportion of the scavenging ports, and at such time, the issuing air streams have not assumed a definite path of movement within the cylinder chamber. Also at the same time, the'adjacent sides of these ports are in their maximum spaced relation, such that a minimum loss of the scavenging air occurs. Further piston movement gradually decreases the distance between the adjacent side walls of these ports, but as the inlet ports are thus uncovered, the airstreams issuing therefrom assume a definite form and path of movement within the cylinder, and since the streamlines of the port nozzles l8 are directed toward the area 4| which is within the cylinder on the side opposite the exhaust ports, itis evident that loss of scavenging air is minimized.

It has been found from experience and through the use of stream-viaualizing-devices, that by the tain its minimum cross section until attaining the described arrangement of ports and port nozzles, the individual streams issuing from the various ports coalesce within the area 4| in the cylinder chamber. A smooth and non-turbulent uniting'of the air streams is effectedby directing 5 all the port nozzle streamlines so as to intersect alongthe plane of symmetry and within the zone 4|. It has been found that the area 4| is approximately equal to the combined areas of the scavenging ports 24, 25 and 26, and since this area is formed substantially within the outermost half or two thirds of the cylinder chamber length, it is evident that the'individual scavenging air streams entering the cylinder chamber, do not expand before reaching this area. Such a condition is produced, in part, by the particular formation of the port nozzles, in that each port nozzle is constructed with a gradually decreasing cross-sectional area, in the direction of the port and so the air stream passing therethrough, gradually increases in velocity until a comparatively high velocity is obtained at the port. This velocity of introduction is such that the stream continues to becompacted, and so does not at- 5 zone 4|. It is evident that this high velocity stream thus continues beyond the ports, in unbroken form, into the cylinder chamber, since practically no expansion of the individual streams is apparent at the time of coalescence. The union of the individual streams within the area 4|, results in the formation of an unbroken upstream or column of scavenging air, all parts of which are moving at the same, comparatively high velocity, which is evidenced by the fact that the-cross sectional area of this upstream, at a point adjacent the cylinder head 41, is substantially equal to the area-indicated at-4I, thus negativing any substantial expansion until the columnar stream reaches a zone close to the cylinder head.

It is apparent that in order to unite air streams of high velocity without causing appreciable turbulenceor lossin velocity, the direction of movement, and the velocity of the individual streams must be practically the same. In the present disclosure, the velocities of the uniting streams are practically uniform, since the ports are all of substantially the same area. Also, due to the slight convergence of the streamlines, the direction of movement of any one stream is prac-- tically the sameas the direction of movement of its neighboring stream, at the point where such streams unite or blend. Therefore, an orderly blending of the various individual air streams will result in a stable and comparatively high velocity upstream, the sectional area of the upstream being practically equal to the combined area of the scavenging ports, it being noted that the venturi throat of each individual stream is located at some point along the path of this upstream within the cylinder, and not at the ports. This upstream, once formed, practically maintains its velocity until the stream reaches the cylinder head 41. The head is formed, by preference, of substantially dome shape, avoiding preferably all sharp bends',.edges,' and abruptly angulate surfaces. This construction results'in a minimum upsetting effect on the, upstream as the head is deflectingly engaged there- The upstream, upon reaching-a zone adjacent the cylinder head, expands and forms a high pressure region under the head, which causes a downward movement of the air toward the exhaust ports.

As this expansion takes place, the downstream, as a consequence, occupies the remaining cross 5 sectional area of the cylinder, and since the area of the downstream is-substantially larger than the area ll of the upstream, it is evident that the velocity of the downstream is considerably less than that of the upstream. By this arrangement, a high pressure region is formed substantially under the cylinder head, and not, as in older prevailing scavenging systems, in the vicinity of the intake ports. Such a condition aids in forming a downstream of relatively high pressure, which pressure is, however, not sumcient to interfere with the movement of the upstream, which because of its high velocity and columnar characteristics, exhibits little tendency toward leakage into the downstream. The downstream thus being of integral aspect, presents a solid front, and causes an orderly movement of the exhaust gases through the exhaust ports. The combined cross sectional area of the upstream and downstream substantially equals the cross-sectional area of the cylinder chamber, and therefore thorough scavenging results, leaving no gas fllled pockets or voids, unswept by the fresh air streams.

With the described improved arrangement of ports and port nozzles, it will be apparent that the various streamlines may be arranged to intersect along any point or restricted area along the plane of symmetry other than the point 42, the desirable condition being that they intersect in some defined, restricted area. It will further be apparent that in order to insure theintended path of movement of the individual air stream within the cylinder it is essential that the streamlines contain as few bends or curves as possible. It may be noted that the port nozzles 01 passages are each importantly characterized by an absence of internal corners or abruptly angularly related surfaces. The curvature of streamlines defined by the nozzles is, desirably,

4,5 on as greata radius or radii as space conditions will permit. In constructing the cylinder in the form of a casting, the cores resulting in the nozzles or passages are carefully prepared and carefully removed so as to avoid any internal o projections or protuberances of any nature. This structural caution precludes any turbulence which might otherwise result in an upsetting effect on the air stream, either within the nozzle or beyond the port. It results, therefore, that the energy of each air stream is entirely reflected in a distinctly linear velocity characterized byan almost complete absence of eddies within the stream. The course of each .stream is thus definite, even though the air pressure of the-source, within the manifold, may vary within wide. limits. 7 4

It will also be noted, as a structural feature of importance, that each of the port passages or nomles is of substantial length. Particularly is 65 this ,of advantage, as in the preferred practice,

where high air pressures and velocities are employed, since-in such case only a minimum period of time is available for shaping the air stream in its course through the passage or nozzle. It appears as a minimum requirement that the length of the passage be considerably in excess of the greatest dimension of the port. A much more dependable shaping of the individual air streams has been foimd to result from the improved form of ports herein described, as well .as the increased length and novel trend of the several port passages or nozzles.

While the foregoing description of a specific embodimentof the invention is based on a structurein whichthepartsarecastasanintegral unit, the assembly may be formed as a part of a cylinder liner, which includes, integrally with the cylinder wall structure. the air nomles or passages cast exterlorly thereon.

The foregoing description has been predicated.

for example, of the inner end of the cylinder I having reference to the lower end of a vertical cylinder on the crank end thereof, while references to the outer or upper end refer to the head end of the cylinder. The terms of description are therefore not to be understood as restrictive in a directional sense.

It will, of course, be understood that the present detailed description of parts and the accompanying drawings relate to only a single preferred executional embodiment and practice of the inv'ention, and that substantial alterations and modifications may be made without departing from the spirit and full intended scope of the invention, as defined by the claims.

Iclaim:--. I 1. The herein described method of scavenging a two cycle internal combustion engine, which consists in introducing a plurality of non-intersecting jets of air near one end of the cylinder, in causing said jets gradually to converge to result in a unified stream of scavenging air at a point somewhat beyond one end of the cylinder, increasing the velocity of the jets, at least to the zone of their convergence and causing a -movement of said stream toward the opposite end of the cylinder and in a direction substantially parallel to the cylinder axis; in so defining and shar ng the stream externally o1 the cylinder so as to restrict the expansion of such stream during its movement to the opposite end, sothat it presents a front of substantially less than onehalf the sectional area of the cylinder-until the stream attains a zone adjacent the opposite end of the cylinder; in reducing the velocityof the stream within the said zone, and in moving said stream at a reduced velocity from said zone .toward and adjacent to the first said end of the resultant stream in proceeding from said zone; 'in confining the resultant stream to a region of substantially segmental form,--and of a trans-.

versearea less thanhalfthatotthe cylinder, incausimsaidresultantureamto expand ha.

zoneadiacenttheouterendofthecylinder,md

n Willem resultant strem to a point adjacent the inner end of the cylinder, at a pressure substantially greater than that. of the said resultant stream.

3. The herein described method of scavenging '5 a two cycle ,internal combustion engine which less than one-half the sectional area of the cylin-v der, and to a segmental region at one side of the cylinder axis, in thereafter reducing the velocity of said stream by deflection and expansion thereof near the outer end of the cylinder, and in directing the said stream in an opposite direction, after expansion, parallel to the cylinderaxis, andiso that said expanded stream presents a front of an area substantially greater than one-half the sectional area of the cylinder.

4, A step in the described method of scavenging a two cycle internal combustion engine, which consists in introducing a plurality of streams of scavenging air, each at a point close to one end of the cylinder, in increasing the linear velocity of said streams as they are impelled internally of the cylinder and beyond the points of introduction, and in causing coalescence of said streams within the cylinder at a point substantially remote from the points'of introduction, and without diminution of velocity.

5. In combination with the cylinder and piston of a two cycle internal combustion engine, a

plurality 'of scavenging air inlet ports and port nozzles connected thereto, and extending there from beyond the cylinder wall and beyond the zone of the ports, in a direction toward the crank 40 end of the cylinder, the ports being disposed near the inner end of the cylinder, said nozzles being formed to direct streams of air within and toward the outer end of the cylinder, the ports and nozzles each being constructed to constrict the stream of air after issue from said port; andthe ports and nozzlesbeing of such shape and trend as to efiect their smooth and gradual convergence and produce within the cylinder, 2. single resultant outwardly moving column of air resulting from coalescence of the streams from said ports, and to restrict said air column to a sectional area not substantially greater than the combined areas of said and substantially less than one-half the transverse sectional area of the cylinder.

6. In a'two cycle internal combustion engine including a cylinder and 'piston, a "band of scavenging air ports located near the inner end 0f the cylinder, each port being defined by lateral rectilinear margins, the planes of said'margins of the intake ports outermost of the band, being inclined with respect to the axis of the cylinder, such angle of inclination being less as to the ports lying inwardly of the ends of said band, a port nozzle 01'' passage for each of said ports, the passages extending from a point outside the cylinder wall to the connected port, and sloped or inclined proportionately to the margins of the associated port, each nozzle or passage being of gradually reduced sectional area from its intake to the associated port, the slope ofnozzles and ports being such'thatthe streams. therefrom substantially agree in direction throughout the length of the'cylinder between the port band and the cylinder head.

'7. In an internal combustion engine of two of all parts of said stream between the zone of its' introduction, and the outer end of the cylinder, confining said stream to a front of substantially cycle type including a cylinder and piston,- a band of scavenging air ports disposed about the innerend of the cylinder, symmetrically with respect to an axial plane; a plurality of said ports being defined by rectilinear lateral margins of differinginclination with respect to such plane, the margins of the ports, of greater inclination, being progressively more remote from said plane of symmetry, and port nozzles communicating with the ports, said nozzles extending through and beyond the cylinder wall, and the axes of the nozzles diiiering in slope conformably to the inclinations of the said port margins.

8.v The herein described method of scavenging a two cycle internal combustion engine, which consists in introducing a plurality of streams of scavenging air to a cylinder, and so directing the streams 'that they meet within the cylinder, each stream at substantially less than a right angle to each of the-others encountered thereby',. so

that thestreams coalesce in non-bucking relation, in so shaping and directing said streams asto confine them to a region substantially at one side of the cylinder axis, and tocause their coalescence into a substantially unified homoge-,

nous resultant stream, in a zone substantially region, and at least until attaining the said zone of coalescence.

9. The described method of scavenging a two cycle internal combustion engine, which consists in introducing a plurality of individual air streams, and forming therefrom ,in a zone nearer the inner end of the cylinder, a columnar air stream of substantially solid front, and of a sec tional area substantially less than one-half that of a cylinder section, in increasing the velocity of the individual air streams between the points of their introduction and said zone of formation of the columnar air stream, and' so restricting their difiusion and expansion, in confining said columnar stream to a segmental space at one side of the cylinder axis,'in moving both said,

individual streams and the resulting columnar of the length of the cylinder, and in maintaining a substantially uniform .velocity and generally corresponding direction of all parts of said stream, until contact thereof with the cylinder head structure.

10. In an internal combustion engine of two cycle type including a cylinder and piston, a band of scavenging air ports arranged about the inner end of the cylinder and symmetrically with respect to an axial plane through the cylinder, each of said ports'being of irregular polygonal shape, and sloped, in the plane of the cylinderwall, toward said axial plane, and each of said ports on a given side of said plane of symmetry,

beingof a shape and slope different from each 7 other port on' the same side of said plane, the

ports being of progressively greater slope at greater distances from said plane.

11. In an internal combustion engine or" two cycle type including a piston and cylinder, a plurality of port nozzles and communicating ports for scavenging air; each directed into the cylinder near the inner end thereof, a source of air underpressure communicating with the inlet ends of the nozzles, each nozzle being of difier-ing sectional area between its inlet end and the port, and the associated port being of smaller sectional area than otherparts of the nozzle, the nozzles being located and shaped to define streams which under pressure adjacent :the cylinder,," a pluralityof air conduits directedi-ror'n said source and v ing or gradually reducedsectional' areabetween i the receiving end-and said port, the port end of I each conduit-being formed to co'nstrict the 'air stream after emergence and at points substane tially within the cylinder and each conduit being iormed to define astream whose center" line is curved about and along the cylinder:

13. In an internal combustion engine "of two 'cycle type including a cylinder and piston adapted 'to operate therein, a plurality o f.i n let ports arranged in a band along a transverse plane near the inner end oi thecylinder, acondultjor each of said ports directed thereto from a source or scavenging air, each 01' said conduits characterized by gradual changes in trends and being so iormed that the major, portion of the streamline therethroug'h lies ina plane curved on a substantial radius and intersecting the cylinder chamberat only a slightangle at the corresponding port,

the slope of the streamlines varying only slightly, Y

, each from the others, "whereby to avoid crossing until the streams port band. e a V 14. In an internal'combustlon-engine oi. two

' cycle type'including-a cylinderand piston ,'.a plnairfpassages directed from, a sourceor. air underpr'essure and terminating rality of scavenging in a band of ports near the inner end ofthe cylinder, said ports' being symmetrically arranged' about the cylinder with respect to an axial plane therethrough, said'passages being arrangedwith their axes sloped along the cylinder wall, .and' the slope oi the axes of said passages, being progrest, sively less,in proceeding from the endmost ports I toward said plane of symmetry.-' .n

. 15. In an internal combustion engine -of two cycle type including a cylinder and piston, a pluraiity of scavenging air ports arranged aboutthe v cylinder'in a zone'near its inner end, an airsupply passage communicating witheach oi said ports, a plurality 01' said passages each being formed to define a stream therein, and gradually tcalter the course of said stream between the in-- let oi the passage, and its discharge through the associated port; said passages being relatively convergent to only a degree so slight that their produced axes cannotlntersect near the port 7 zone, and each passage being so shaped that the trend of streamline therethrough. varies, substan- 0 tially uniiormly, in radial, axial an'd'tangential directions, between the inlet of the passage and its' associated'port.

16. In an internal combustion engine of two cycle ty'pe includinga cylinder and -piston. 8.

-- 5 group of'scavenging air'inlet and exhaust. ports disposed near the innerend oi. the cylinder, a port passage for each inlet port, extending exteriorly of the port ina directioniurther toward the in ner end oi the cylinder, each ofsaid passages 7 being of spiral trend-and directed about the cylinder towardthe exhaust sidether'eoi', the said passagesbeing' of such slope that no two of their produced axes can intersect in the region oi'said port group. v I 7 17. In an internal combustion engine 0! two in each or said intake ports and each being of a,

said exhaust ports, the

10 te minating in said ports} said conduits each .bel ght y out 0! par l lism, a d a l the of being Ill are substantially beyond .the

"therethrough lie, in greater cycle type including a cylinder and piston, a

band oi. scavenging air ports disposed about a portion 01 the inner end of the cylinder, exhaust ports spaced from the intake ports and located on one side oithe cylinder, a nozzle. terminating substantially spiral" trend, directed around the cylinder and toward the side thereof occupied by adjacent-nozzles being located with their produced axes out oi. intersecting relation in the vicinity oi the air port band.

18. In an internal combustion engine of two cycle type including a cylinder and piston,a band of intake ports disposed near the inner end 01' the 13 cylinder, port nozzles extending downwardly and divergently away from said ports and a plurality I of. plane elements formed integrally with the pylinder structure .and constituting partitions between adjacent port nozzles, said partitions being divergently disposed in adirection longitudinally of the cylinder, and their produced axes being out of intersecting relation in the vicinity or the port band.

ports intersected by said plane, Passages com- I municating with said ports, all of those leading to the air portszjbein'g characterized bystream' lines whichare out of intersecting relation inthe 1' -vicini tyoisaidcylinder plane, the adiacent air inlet and exhaust passages being-oi such trend "N that the streamlines thereof, diverge both longiw tudinallyand transversely oi the cylinder.

- '20,I-n an internalcombustion-engine OfxtWO cycle time including a cylinder and -p iston,' .a row ,of scavenging air intake po ts. 8 fi rt nozzle for a each oi. said air ports, a plurality or exhaust 40 ports, the intake and exhaust ports being disposed ne'ar'a common plane transverse oi the cylinder, the nozzles 01, those intake ports adjacent the exhaust portsbeing sloped to underlie the 7 adjacent exhaust ports,-and'all oi'the port noz- 45 z les having inlet openings distributedatsub- ,stantially .equal intervals about the cylinder, "in Y a zone remote from said plane or the ports. 3 '21. In an internal'coznbustion engine oi two cycle type, ascavenging air manii'old'oi' substan- 0 tiallyannular' form,-extending about an .inner portion of the cylinder','exhaust passages from the cylinder, disposed outwardly of the said manhiold, an intake-or supply connection to said mani-- V fold on theexhaust side of the cylinder, an ex- 55 -haust' connection adjacent the intake connection, air ports in the cylinder beyond said manifold. vand a passage from the manifold to each 0! said 22., In an internal combustion engine includo0v ing a cylinder and piston, a source 01 scavenging air, a plurality or conduits leading from said source to thecylinder, and each'terminating in a port. inthe cylinder wall near the inner and ot.

I the cylinder,'said conduits and ports each being 05 so shaped that the center lines or the streams part, .in a curved plane extending along the cylinder such that each-said center line intersects the wall at i the port at an angle sufllciently slight with respect. to the plane ofthe cylinder wall that the streams substantially agree in direction, and none thereof 'is appreciably altered in course by the cylinder wan r 23 In an combustion engine oi'two cycle type, a cylinder, a. piston operable therein,

a plurality of scavenging air intake ports arranged in a group near the inner end of the cylinder, and

adapted to be controlled by the piston, air passages each communicating with one of said ports, and extending divergently beyond the port zone toward the crank end of the cylinder, the passages and ports being arranged to consolidate a plurality of streams of scavenging air in a zone intermediate the length of the cylinder, but to maintain all of such streams out of intersecting relation prior to reaching the said zone of consolidation, and to direct the resultant stream toward the outer end of the cylinder, and a head structure presenting a domed air deflecting surface toward the interior of the cylinder, and adapted to contact with said air stream, said surface being characterized by a regular and substantial curvature. 24. In an internal combustion engine of two cycle type including a cylinder and piston, a group of scavenging air inlet ports disposed near the inner end of the cylinder, tubular passages opening into the said ports,- the adjacent pas-' t sages being of divergent trend away from said ports, said passages having their inlet openings.

distributed substantially about the circumference of the cylinder, and located substantially beyond the zone of said ports, the tubular passages being angularly so related that their stream lines are in non-intersecting relation in the zone of the ports, and a manifold adapted to contain a supply of air under pressure, and communicating with the inlets of the several air passages.

25. In an internal combustion engine of two conduit further being so formed that the streamline therethrough lies in a curved plane substantially in wrapped relation to the cylinder, but intersecting the cylinder chamber at only a slight angle to the plane of the cylinder wall at the corresponding port, the curved planes of said stream lines being non-coincident.

HEINRICH SCHNEIDER. I

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