US2814281A - Two-cycle engine - Google Patents

Description

Nov. 26, 1957 w. HOLT 2,814,281

TWO-CYCLE ENGINE Filed May 21, 1954 3 Sheets-Sheet 1 FIG. I.

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M n a w a W 21570 Naif/VENT d fig Z mil mw m MM m m A. Z L MB 360 (Barron cewre'k) 180 (rap CENTER) United States Patent TWO-CYCLE-ENGINE William Holt, Kearny, N. 1., as'si'gnor of one-half to Andrew 'F; Stanier, Passaic,'N;'J.

Application May 21, 1954, Serial No. 431,475 J 12 Claims. (Cl. 123-71) My invention relates to internal-combustion engines" and in particular to these-called two-cycle engine.

In spiteof the many improvements madefromiirne to" time in the two-cycle engine, certain inherent limitations continue to plague the designer and seriously to' impair achievement of what I consider to beoptimum operating efiiciency; One of these limitations is that,in the'absence of a supercharger or its equivalent, intake'air or intake combustible mixture is at very much reduced pressure at the time 'whenthe valving mechanism'opens to commenceadrn'ission of combustible mixture into the working cylinder. This results in some delay in fillingthe'volume in Which' combustion is to'take place; and, because the' compression stroke has already started by the time combustible mixture is first admitted to the cylinder, there is little or'no opportunity to achieved optimumcompre'ssio'n before firing.

Accordingly, it is an object of the inventionto provide It is another specific object to provide means other than a supercharger for supplying pressurized intake gasesv to the Working cylinder as soon as the inlet valve is opened.

Further specific objects 'reside'in the provision of means which may inherently avoid inadvertentrun-ning of'the engine in the reverse direction, and in the provision of an improved valve construction for two-cycle engines.

Other objects and further'features of novelty'and invention will be pointed out or will occur to those skilled in the art from a reading of the following specification in conjunction with the accompanying drawings. In said drawings, which show, for illustrative purposes only, preferred forms of the invention:

Fig. 1 is a'vertical' sectional view through a two-cycle engine incorporating 'featuresof the invention;

Fig. 2 is a series of graphsshowing,ion the same reference cycle, a number of separate functional'cycles in the valve and other mechanism of Fig. 1;

Fig. 3 is an enlarged'fragmentary view in perspective of one of the valves in the engine of Fig; 1;.-

Fig. 4 is a view in perspective and partly broken away, illustrating" a part insertablyrernovably; in the crankcase of 'theengineof'Fig; l; V

Fig. 5"is an enlarged fragmentary sectional view showing a modification of apart of the engine of Fig 1;

Figs. 6 and'7 are sectional views taken, respectively, in the 'planes 5'5"and 6"6r-of Fig, 5;

Fig.1,8 is a simplifiedverticalsectional view illustrating fuelcontrol mechanism for parts illustrated in Fig.5 and Fig. 9'isa graphicaldiagram similartoFigrl ancl'illust trating, on the same cyclical scale as Fig, 2, the additional functions performedwit h' the structure of Fig, 5;

Briefly stated, my invention comprises means for im- Z,8l4,28i Patented Nov. 26, 1957 proving the efficiency of a two-cycle engine by providing, without resort to superchargers, compressed air or combustible-gas mixture for immediateintroduction into the working cylinder as soon as the inlet port thereto is open; in the caseof admitting compressedair directly, I provide novel fuel-injection means. By quickly introducing the charge in this manner, it is possible to assure maximum charging of the working cylinder and-at the same time to make available a greater fraction of the compression stroke to be devoted to strictly compressional purposes.

Asfurther' features, I provide means for increasing the compression ratio for the handling of scavenging air, so as more efficiently to flush the cylinder between. working strokes, and thereby to' provide greater combustion efliciency. I also provide improved valving mechanisms par ticularly adaptable to two-cycle engines, and means. for avoidingiinadvertent operation of the engine in'the reverse direction;

Referring to Fig. 1 of the drawings, my invention is shown inapplication to a two-cycle engine comprising a block '10, containing two cylinders 11-12, cooperating with separate working and compressional surfaces 1314 of piston means 15. Piston means 15'may be'connected in driving relation with an output shaft, as by means of a connecting rod 17'fastened to' crankshaft 16 between counterweigh ts 1819, and connected to the piston means 15 by wrist pin 20. Seal rings 1115 carried by cylinder 11 and piston 15 may serve to isolate the working and compressional volumes 11-12.

The lower end of theworkingcylinder 11 may be pro vided with a number of exhaust ports 21 communicating (through means not shown) to the outside, and with similar ports diametrically opposed to those shown at 21 for admission of'scavenger air delivered from the crankcase 22 during a down or working stroke of the piston means 15, in the usual manner.

Valving means 23 on one side of the piston may control the supply of air or air-fuel mixture for combustion, and valving means 24 on the other side of piston 15 'may control the admission of scavenger air to the crankcase; valving means 24 may also serve a by-pass valving function to be described below in greater detail. Both valve means23"24 are'preferably driven directly fromthe crankshaft 16, as by geared connections 25-26.

It is:characteristic of two-cycle engines that they may be driven equally well in opposite directions. Of'course,

there is usually only one desired direction, and, to avoid inadvertent driving in the wrong direction, I provide lostmotion connections between the crankshaft '16" and the respective valve means 2324. In the form shown, thelost motions are angular, and they take place between the valves 2324'and the hubsfor the respective valvegears 26; pins 27'28 in these hubs may travel in slots"29 30 in the respective'valves 23'24 throughout the angular lost motion involved in each case. that the'extent of lost motion providedxby slots 29-30 is suflicien-t to disrupt the valve-timing" cycle for: any attempted running of the engine in reverse, while permittingproper valve timingfor the design direction of rotation.

In accordance with a feature of the invention', I provide for preliminary compression and storage of intake air or of intake air-fuel mixture (depending upon the opera tion of the engine), prior to introduction'of such air or pistons operating in in-phase relation--that is, both pis-" tonsgo through their compression stroke at the same time. The piston provided by surface 13 operates in the working cylinderll, and this performs the conventional twocycle operations; but the auxiliary piston provided by the.

It will be understood compression surface 14 is used for my novel purposes. Both pistons preferably have substantially the same area as shown, so as to displace similar volumes.

In the form shown, I provide a chamber 30 for accommodation of the air or gas mixture to be stored in compression, in readiness for pressurized release into the working cylinder 11. This chamber 30 may conveniently be carried by a moving part of the valve means 23. The chamber 30 is shown defined between bulkheads 31-32 sealed within the elongated tube 33 from which the valving means 23 is formed, and, in order that the chamber 30 may both release and receive compressed gases during a single compression stroke of the piston means 15, I provide two ports 34-35 (see Fig. 3) in the wall 33 of valve means 23, for cooperation with a port 36 forming part of the engine block and communicating with the intake compression volume 12. The spacing between bulkheads 31-32 is preferably such as to define a,substantially more restricted volume of chamber 30 than is represented by the displacement volume 12 of the auxiliary cylinder, thus permitting storage in chamber 30 at substantially elevated pressure.

The bulkheads 31-32 serve the additional function of isolating the compressed-gas storage function from other intake-valve functions occurring within the same structure 23. Thus, in the volume of valve means 23 beneath bulkhead 32, inlet air or air-fuel mixture may be admitted at port 37 and passed by way of rotor ports 38-39 to an inlet port 40 communicating with the compression volume 12.

On the other side of the engine, I provide the further valve means 24, also driven in one-to-one relation with the crankshaft 16 but serving the function of by-passing compressed combustible air or air-fuel mixture, for timed admission to the working cylinder 11, as at inlet port 41. The valving means 24 may thus consist basically of an elongated tubular rotor 42, with such internal partitions and ports as necessary to accomplish the desired functions.

I prefer that a minimum volume of unburned gases shall be contained within the passage which connects compression cylinder 12 with working cylinder 11, and I therefore have provided more restricted means 43 for channeling the flow of the unburned mixture. The means 43 is shown as a bent pipe or tube fitted to the valve rotor 42 at an inlet port 44 and an outlet port 45. The inlet port 44 may cooperate with outlet port 46 at the top of the compression cylinder 12, and the outlet port 45 may cooperate with the inlet port 41 to the working cylinder 11.

As was the case with the valving means 23, the valving means 24 may perform a dual function, as in the additional control of scavenge-air intake to the crankcase 22. In the form shown, scavenge air enters the engine block at a stationary port 48 and passes through the rotor 42 of valve means 24 by way of control ports 49-50, for discharge at port 51 into the crankcase. The scavenge air is introduced by suction during the compression phase of the piston 15, and valve means 49-50 seals off the influx of scavenge air before the working stroke is substantially under way. The working stroke serves to compress the scavenge air in the crankcase, and, when the piston 13 nears the end of the working stroke, scavenge and exhaust ports 21 are opened to permit the cylinder 11 to be flushed with clean compressed air in readiness for the next working cycle.

The compression ratio characterizing treatment of the scavenge air is preferably as high as possible consistent with the displacement dimensions of any particular engine, and, in accordance with a further feature of the invention, I provide means whereby this ratio may be increased for any particular engine. The compression ratio for scavenge air may be improved by holding to a minimum the free undisplaced volume within the crankcase 22. Naturally, some space is required for accommodation of the moving parts, but such space as is not required for this purpose may, in accordance with the invention, be substantially eliminated by employment of a suitably designed removable insert, as illustrated in Fig. 4. The insert of Fig. 4 is shown formed of two parts representing conjugate halves 53-54 of a filler block capable of fitting in substantially all the undisplaced volume of the crankcase 22; in order that the showing in Fig. 1 may be kept simple, the filler blocks 53-54 are shown only in Fig. 4.

The filler block-s 53-54 will be seen to include an u per generally cylindrical portion 55, internally excavated to accommodate the connecting rod 17 and its movement, and externally contoured to fit within a substantial part of the lower space 56 inside the piston 15. Lower portions, as at 57, may be excavated or recessed to accommodate the valve gears 25 and parts of the crankshaft 16, but the net result will be substantially to reduce the undisplaced volume of the crankcase. It will be understood that the filler blocks 53-54 may be provided with sufiicient clearance or passages (not shown) to accommodate the influx and exhaust of scavenge air, so as not to impair the flow of scavenge air. Also, it will be understood that the structural features of any particular filler block 53-54 may be such as to be self-retaining within the crankcase after the crankshaft and other parts. have been assembled to the engine.

Quite aside from the functional improvements resulting from the general structure thus far described, further features of the invention reside in the structure of the rotary valves 23-24 themselves. Each of these valves preferably rides in close clearance relation with the stator or engine block bore in which it is fitted, but, to enhance the sealing effectiveness between stationary and moving parts of the valves, I employ a combination of axially spaced circumferential sealing means and of angularly spaced longitudinal sealing means, as best illustrated in Fig. 3, for the case of valve means 23. Each of the cir- I cumferential sealing means may be a ring 60, preferably formed with an axial discontinuity for engagement with a suitable abutment on rotor 33, so as to permit the ring 60 to be carried for rotation with the valve. In the preferred forms shown, the discontinuity is formed by developing the ring 60 as a helix, relying upon one or both overlapping ends of the helix to define the discontinuity, as at 61-62. Thus, at each circumferential sealing, the tube 33 may be externally grooved for accommodation of the seal ring 60 and formed with end abutments 63-64 to locate the ends of the ring and to assure positive rotation of the ring 60.

It will be understood that, because the ring 60 is carried for rotation with the valve, there is a constant tendency to maintain peripheral sealing through the action of centrifugal force. Referring to Fig. 1, and in the case of the valving means 23, three circumferential rings 60 suffice to isolate the intake air or air-fuel flow (via ports 37-38-39-40) from the flow accompanying excessgas storage functions in chamber 30 (via ports 34-35- 36). Further isolation and sealing effectiveness may be promoted by longitudinally extending vanes 67-68 accommodated in longitudinal grooves at angularly spaced locations on the periphery of the rotor 33. The vanes 67-68 may extend as short lengths between adjacent circumferential seals 60, but in the small broken-away part of Fig. 3 I indicate my preference that each such vane (68) shall be continuous for the full length, or substantially the full length, of the valve, with small local recesses, as at 69, to accommodate each circumferential seal 60, as will be understood; in Fig. 1, the longitudinal seal vanes havebeen shown by dotted outlines 68-68 for valves 23-24, but it will be understood that the outline is merely suggestive because the proper angular location of such vanes in Fig. 1 would unnecessarily complicate the showing of Fig. 1. The valve 24, with its seals 60-67-68, may thus be self-retaining in assembled relation prior to assembly in the engine block.

For many purposes, the described seals and close tolertion ofthe valve.- However, I indicatein-Fig. 1=my.

preference for positive axial location of the valve structure,-as by a shoulder 70 formedintegrally with the rotor 33 at the topend thereof, and supported in-suitable bearings, such as bushing 71 and thrust washers 72-73. At the-lower or drive end of the valve, a similar but perhaps more elongated bushing 73 may provide an adequate bearing.

The seals and bearings provided for the valve means 24 may generally resemble those described for the valve 23, except as necessary to suit the particular requirements of valve 24. Valve 24 is shown with a large diameter head 75 on the rotor 42, so that combustible gas may be -introduced as close as possible to the working cylinder 11; and, of course, to promote sealing at this location, double circumferential seals 76 are preferably provided in the head 75.

My improved engine construction will perhaps be better understood from a description of a typical cycle of operation, with particular reference to the graph of Fig. 2. In this operation, I contemplate carburetion prior to admission in port 37, so that the engine handles an air-fuel mixture. Thus, gas-mixture intake takes place under the control of ports 37-38-39-40 into the volume 12 during a down or working stroke of the main piston 13; 1 have shown this function taking place during the interval extending from after top center to NY after bottom center. The full opening of the gas-intake valve may be achieved quickly with a relatively narrow angle opening for the moving ports 38-39; for the case depicted, this angle is 15 about the valve axis, meaning that, to produce the effective 180 opening indicated in Fig. 2 for the intake valve 38-39, the stationary ports communicating with the rotor openings 38-39 are 150 wide.

Aftera down stroke of the piston 13, a full charge of mixture will have been sucked into the compression volume 12 and, as the piston commences its up stroke, the control port 34 briefly opens and closes to admit from storage chamber the previously-compressed and stored charge of combustible mixture, thereby quickly elevating the pressure of mixture in the compression volume 12 just prior to the supply of suchmixture to the working cylinder 11. As soon as valve 34 closes after the bottom center), the gas-bypass valve 44-45 will open so as to discharge compressed unburned gas immediately into the inlet port 41 for the cylinder 11. This function preferably commences just before the exhaust ports 21 are closed up, so that, by the time the exhaust ports have been closed, the combustible gas will be flowing into the cylinder under pressure and in substantial volume. The effective angle of the gas-bypass valve 44-45 will depend upon the extent to which it is desired to have cylinder 13 perform a pure-compression function, but while piston 13 is compressing so is piston 14, so that compression is in reality taking place even while the gas-bypass valve 34-35 is still open.

I have shown the gas-bypass valve 44-45 as closing preferably 45 before top center, so that pure compression within cylinder 11 (due to piston 13) may take place during the remainder of the compression stroke.

Now, in accordance with the invention, and by virtue ofthe storage chamber 30 and valve means 34-35 associated therewith, I utilize this remaining part of the compression stroke to pass the still-compressing combustible mixture from compression volume 12 to thestorage-chamber 30. This flow will be controlled by port 35 in cooperation with stationary port 36, and is shownterminating substantially at andpreferably justafter topv center .soas to hold the charge of combustible mixture in-chamber 30, in readiness for instant discharge,

fired by plug 78, in'the conventional manner,"before or after top center ,edepending ;upon' the desired'operation." The dinng mayrbe under-the control of conventional-elem tric timing means synchronized-with crankshaft rotation;

as -will be understood; By enabling greater compression i of combustible-'mixture,--I also enable operation "with': relatively; advanced spark, thereby promoting combustion efliciency.

During: the compressionstroke described in detail above,-it will beunderstood that valve means 49-50 will have been open -to admit scavenge airto the crank case 22. Valve '49-50 will havebeen closed "at sub-' stantiallytop-center, so that compression of scavengeairmay 'takeplace during-the working stroke, and, of course, assoon -as--'the-scavenge and exhaust'ports' 21 are exposed by piston- 13 toward theend of the working; stroke, thecompressed scavenge air'will be available -to insureeflicient flushing :of burned gases from the cylinder- In'the modification of Fig. 5, I illustrate how th prinbustible mixture-to the engine.

the excess-gasstorage features of the engine of Fig; l

maybe utillzed in l ig. 5 for the supply of air to bemixed' withthe injected fuel.

Compressed air is' thusava'ilableto the'mechanismof Fig.5 through the'tube'or passage 43', forminglan in ternal restrictive passage within the rotor 42" of the valve' means 24. The gas-injector head to which such air supply l'is vmade available may comprise cooperating :rotor andstatorparts -81, received within: the samespace as accommodated by the head 75'in the description of t Fig. l. The rotor may comprise essentially an annular manifold 82, With a radial passage 83 continuouslycommunicating with the compressed-air supply pipe 43', and

anoutlet-air passage 84 radially communicates with manifold 82; outlet passage 84 cooperates with stationary port 41, permanently aligned with and therefore elfectively part of the port 41, already described as the inlet for cylinder 11.

Injected fuel may be introduced through aninclined nozzle 85 fixed to the rotor '80 and having its discharge end located preferably in the middle of the discharge cross-section of the air-outlet passage 84, so that, whenever valve 41-84 is open, the blast of available compressed air will induce speedy injection and atomizing of fuel, through an action which is in part aspirating. For the supply of fuel, the stator 81 may be provided with an internal passage 86 (see Fig. 7) opening at one angular location on the top or distributor surface 87 of the stator 81, and at a radius to register with the base of the nozzle 85 for such one angular location.

Fuel may be available from conventional pumping or throttling control means, and I have shown, in Fig. 8, a simple control in which the rate of fuel flow is governed by greater or less spilling (for return to the fuel supply) of a more or less continuous flow of fuel in a supply pipe 88, connected to pumping means (not shown). The pipe 88 may communicate with a small chamber 89 having outlet passage 90 'to the engine, and available to the described injector at the port 86. For controlled flows of 1 fuel, a spillway may employ a vertically displaceable pipe 91 having a throttling cut-out orifice 92 near the bottom of the chamber 89; spilled fuel will flow in line ber 89, desired fuel flow may be availablein line '90 to 1 port 86.

In operation, the port 86 for nozzle 85 will beopened" by registration with nozzle 85, preferablyas soon as valve 41-84 admits compressed air to the cylinder 11. By this means a quick shot of raw fuel may be induced into the cylinder 11 and atomized with greatest efiiciency as the piston 13 proceeds with its compression stroke.

If desired, the nozzle may be flushed of fuel between injection operations, and I prefer that this flushing take place while the valve 4184 is still open. In the form shown, I accomplish flushing by providing a plurality of air-supply ports 93 manifolded to each other and opening on the top surface 87 of the stator, for successive registration with the nozzle 85 and with rotor air opening 95 after the nozzle has received its fuel-injection charge. By employing a plurality of openings 93, rather than a single opening, I assure a succession of transient air blasts for flushing the nozzle 85, thus promoting complete discharge of any fuel in the injector. The preferred timing of air supply to cylinder inlet 41, of fuel injection, and of nozzle flushing, are all clearly set forth in the graph of Fig. 9.

It will be seen that I have described an improved two-cycle engine construction featuring a relatively simple organization of parts, as compared with existing engines, and yet promoting superior operating efliciency. My engine has been described as being adaptable with little modification either to the conventional carbureted supply of air-fuel mixtures or to fuel injection immediately adjacent the working cylinder. My invention makes possible extreme ruggedness and long life by virtue of the elimination of reciprocating parts, except of course for reciprocation of the piston in the cylinder, and I have provided means for avoiding inadvertent reverse-running of the engine.

-While I have described my invention in detailfor the preferred forms shown, it will be understood that modifications may be made within the scope of the invention as defined in the claims which follow.

I claim:

1. In an internal combustion engine of the character indicated, a first cylinder, a piston including a first cylindrical portion riding said cylinder and a second cylindrical portion of a diameter greater than said first cylindrical portion, a second cylinder guiding said second cylindrical portion, whereby a working volume is established by displacement of said piston in one of said cylinders and whereby a compression volume is established by displacement of said piston in the other of said cylinders, intake and exhaust ports for each of said cylinders, first valving means connecting the exhaust of one of said cylinders to the intake of the other, a compressed-gas storage chamber, second valving means connecting said storage chamber to the intake port of said one cylinder, the connection through said second valving means being the only connection to said storage chamber, whereby stored compressed gas in said chamber is releasable only to said one cylinder and timing means controlling said respective valving means to open and shut in alternation during the compression stroke of said piston.

2. In an internal-combustion engine of the character indicated, a first cylinder, a piston including a first cylindrical portion riding said cylinder and a cylindrical portion of a diameter greater than said first cylindrical portion, a second cylinder guiding said second cylindrical portion, whereby a working volume is established by displacement of said piston in one of said cylinders and whereby a compression volume is established by displacement of said piston in the other of said cylinders, a crankshaft connected to said piston, intake and exhaust ports for each of said cylinders, first valving means connecting the exhaust of one of said cylinders to the intake of the other, a compressed-gas storage chamber, second valving means connecting said storage means to the intake of said one cylinder; and timing means synchronized with rotation of said crankshaft and controlling, first, the opening and the closing of said second valving means, whereby stored compressed gas in said storage chamber maybe released to said one cylinder, then the opening and closing of said first valving means wherebypressurized gas is by-passed from said one cylinder to said other cylinder, and then a second opening and closing of said second valving means, all'substantially during a single compression stroke of said piston,whereby com pressed gas may be stored in said chamber during that part of the compression stroke after which a charge of combustible gas has been delivered to the workingvol- E ume, and whereby the stored gas may be keptat pressure in readiness for delivery to said working volume immediately upon opening the valving means between said cylinders. Y

3. In an internal-combustion engine of the character indicated, a working cylinder, a compression cylinder, piston means including working and compression surfaces guided for displacement in each of said cylinders,

means interconnecting said working and compression' parts of said piston means in in-phase relation, whereby compressional strokes of both parts of said piston means are concurrent in both said cylinders, a gas intake for said engine, intake and exhaust ports for each cylinder, first valving means connecting the exhaust of one cylinder to the intake of the other cylinder, a compressed-gas storage chamber, second valving means connecting said storage chamber to the intake of said one cylinder, and timing means controlling said respective valving means to open and shut in alternation during a compression stroke of said piston means, said second valving means being connected to admit stored compressed gas from said storage chamber to said compression cylinder substantially coincidentally with connection of said gas intake to said compression cylinder, whereby compression may commence at a pressure level greater than would be the case if dependence for intake gas were placed solely and directly on said gas intake.

4. An engine according to claim 3, in which the volume of said storage chamber is less than the displacement volume of said compression surface.

5. In a two-cycle engine, a working cylinder, a compression cylinder, a piston including working and compression surfaces slidable in said respective cylinders, a crankshaft, a connecting rod connecting said piston to said crankshaft, intake and exhaust ports for said cylinders, first valving means connecting the exhaust of said compression cylinder to the intake of said working cylinder, a compressed-gas storage chamber, second valving means connecting said chamber to said compression cylinder, and geared connections from said crankshaft to said first and second valving means, said geared connections including a lost-motion linkage such that said first and second valving means operate in alternation during the upstroke of said piston for one direction of crankshaft rotation, said alternation being such as to connect said compression cylinder first to said storage chamber, then to said working cylinder, and then to said storage chamber, all during said upstroke, said lost-motion connection being such that for the other direction of crankshaft rotation said order of alternation is not obtained.

6. In a two-cycle engine, a cylinder comprising axially spaced working and compression sections of different diameters, a piston with working and compression areas on parts riding said respective diameters of said cylinder, thereby defining two displacement volumes, a crankshaft, a connecting rod coupling said crankshaft to said piston, a compressed-gas storage chamber, intake-valve means controlling admission of combustible gas to said storage chamber and to one of said volumes, a geared connection between said valve means and said crankshaft, said valve means providing first and second open-andclose cycles to said storage chamber for a full cycle of said piston, said valve means also providing a single openand-close cycle for intake of air or combustible gas to said one cylinder for said cycle of said piston, both openand-close cycles of said valve means for said storage chamber being timed during the compression stroke of said piston, and the cycle of said valve means being timed for intake during the Working stroke of said piston.

7. An engine according to claim 6, in which said geared connection includes a lost motion, whereby the specified relationships obtain for one direction of crankshaft rotation but do not obtain for the other direction of crankshaft rotation.

8. In a two-cycle engine of the character indicated, a two-diameter piston and spaced Working and compression cylinders guiding the respective diameters of said piston so as to define a working volume in one of said cylinders and a compression volume in the other of said cylinders, an output shaft, means connecting said piston in driving relation with said output shaft, inlet and exhaust ports for both cylinders, a storage chamber and rotary-valve means geared to said output shaft and connecting the outlet of said compression cylinder to the inlet of said working cylinder during an intermediate part of the upstroke of said piston, said rotary-valve means further connecting said storage chamber only to said compression cylinder and during the upstroke of said piston, said storage-chamber connection occurring at both the beginning and at the end of said upstroke.

9. An engine according to claim 8, in which said geared connection includes a lost motion, whereby the specified relationships obtain for one direction of crankshaft rotation but do not obtain for the other direction of crankshaft rotation.

10. In a two-cycle engine of the character indicated, a two-diameter piston defining working and compression surfaces at axially spaced locations, axially spaced cylinders guiding the respective working and compression surfaces of said piston, two elongated tubular rotary valves, each of said valves being on an opposite side of said cylinders and each of said valves having its axis of rotation substantially parallel to the axis of said piston, a crankshaft driven by said piston, gear means connecting said crankshaft in one-to-one driving relation with said valves, a compressed-gas storage chamber in one of said valves, there being two ports for said one valve in communication with said compressed-gas storage chamher, and both said ports being so disposed as to open and close once during the compression stroke of said piston.

11.An engine according to claim 10, in which the other of said valves includes a by-pass connection communicating from one of said cylinders to the other and being timed with relation to said first valve to establish said by-pass connection only essentially in a time interval between successive openings and closings of said compressed-gas storage chamber during said compression stroke of said piston.

12. An engine according to claim 10, in which said second valve includes a scavenge-air opening to the crankcase beneath said piston, said opening being established during the compression stroke of said piston, whereby scavenge air is induced into said crankcase, said second valve means being closed during the working stroke of said piston, whereby scavenge air may be compressed for discharge into the working cylinder toward the end of the working stroke of said piston.

References Cited in the file of this patent UNITED STATES PATENTS 1,115,481 Bachle et a1. Nov. 3, 1914 1,132,357 Koelzer Mar. 16, 1915 1,166,939 Russell Jan. 4, 1916 1,253,599 Hogan Jan. 15, 1918 1,539,041 Crawford May 26, 1925 1,633,851 Durr June 28, 1927 1,635,963 Seifert July 12, 1927 1,705,062 Mantle Mar. 12, 1929 1,722,201 Crary July 23, 1929 2,058,526 Tanner Oct. 27, 1936 2,089,582 Seifert Aug. 10, 1937 2,183,116 Coates Dec. 12, 1939 2,440,726 Probst May 4, 1948 2,474,879 Winfield July 5, 1949 2,587,842 Hall Mar. 4, 1952

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