US2093433A - Internal combustion engine - Google Patents

Description

Sept. 21, 1937. A. E. GREENE INTERNAL COMBUSTION ENGINE 5 Sheets-Sheet 1 Filed June 9, 1933 Sept. 21, 1937. A. E. GREENE INTERNAL COMBUSTION ENGINE Filed June 9, 1953- 5 Sheets-Sheet 2 INVENTOR WE-QM 1. OWVD EM ATTORNEYS m Q a kmw.

p 1937. A. E. GREENE INTERNAL COMBUS T ION ENGINE 5 Sheets-Sheet 5 Filed June 9, 1953 INVENTOR ATTORNEYS Sept. 21, 1937. A. E. GREENE INTERNAL COMBUSTION ENGINE Filed June 9, 1933 5 Sheets-Sheet 4 P3 MI INVENTOR 7 BY P W %J ,A

ATTORN EYG Sept. 21, 1937.

A. E. GREENE INTERNAL COMBUSTION ENGINE Filed June 9, 1953 5 Sheets-Sheet 5 INVENTOR adr gg v I B ATTORN EYS Patented Sept. 21, 1937 UNITED STATES PATENT OFFICE' INTERNAL COMBUSTION ENGINE Ambrose E. Greene, Berkeley, Calif.; Catharine De Motte Greene administratrix for Ambrose E. Greene, deceased Application June 9, 1933, Serial No. 675,070

,72 Claims.

contemplates the provision of engines of simple.

construction capable of highly efficient operation with a wide variety of fluid fuels. The invention also contemplates the provision of an improved fuel induction system for internal combustion engines. The invention further contemplates the provision of an improved method for lubricating step pistons. A further object of the invention is to provide an improved engine of the type in which opposed pistons act in each cylinder.

While many of the features of the invention are of broad application, all are particularly suitable for use in internal combustion engines of the type in which opposed pistons act in each cylinder. Therefore, the novel features of the invention will be disCt-ssed and described hereinafter with reference to their employment in.

engines of thetype in which opposed pistons act in each cylinder. It is to be understood that the following discussion and description are provided for purposes of illustration and not for purposes of limitation, and the appended claims are to be accorded all reasonable interpretations not inconsistent with the terminology employei. therein.

Engines of the general class in which opposed pistons act in each cylindenpossess certain bvious features of advantage over engines in which only a single piston. acts in each cylinder. Among these advantages are the reduction of frame stresses; reductionof main crank shaft bearing loads; more favorable dynamic characteristics, including the possibility of perfect balancing of both reciprocating and rotating parts; desirable shape of combustion chambers; reduction in water-jacketed area; improved scavenging of twostroke-cycle engines, because scavenging air and exhaust ports can encircle and be located at opposite ends of the cylinder.

It has been proposed to employ opposed pistons in each'cylinder of engines of the two following types:

(1) Single cylinder engines or engines of the type in which several cylinders are all disposed on one side of a crank shaft serving them all wih their axes at right angles to the axis of the crank shaft;- and (2) Engines of the type in which cylinders are disposed in axial alignment on opposite sides of a crank shaft with two connecting rods extending to a wrist pin on one side of the crank shaft and controlling the movement of a pair of outer pistons, and one connecting rod extending to a wrist pin on the opposite side of the crank shaft and contrelling the movement of a pair of. inner pistons. A

In spite of the many advantages which may be obtained'through the use of the opposed-piston principle'in engine design and operation, opposed piston engines of thetype proposed heretofore 'are not widely used because of certain inherent disadvantages which limit their application and make them compare unfavorably with engines having but a single piston in each cylinder. Thus, single cylinder engines and engines of the type in which several cylinders are all disposed on. one side of a crank shaft can not be perfectly, balanced, because'the connecting rods serving inertia forces will not be balanced. The magnitude of these unbalanced forces is increased, as compared with single-piston engines of the same cylinder arrangement, because of the greater weight of the reciprocating parts of the opposed piston engine, which in turn is due to the additional elements needed to connect the outer piston with thecrank shaft. Thes'e increased reciprocating weights have the further disadvantage of producing increased inertia pressures and consequently increased loads on wrist pin and crank pin bearings.

Opposed piston'engines of the type in which cylinders are disposed in axial. alignment on opposite sides of a crank shaft can be perfectly balanced and can be so constructed that the bearing loads due to inertia of the reciprocating parts are diminished by opposing gas pressures acting on the pistons. The enginesof this type proposed heretofore have been provided with sleeve pistons or reciprocating power cylinders which have their outer ends closed to serve as the outer pistons of each cylinder, while theirinner ends are open to receive the inner piston of each cylinder.

The use of these reciprocating cylinders imposes several difiiculties and disadvantages of such seriousness that they have not been adopted for commercial use. They must be lubricated inside and outside; they double the rubbing velocity of the inner piston, which greatly reduces the life of the engine; they must be cooled themselves and must also serve to cool the inner piston, so that the heat extraction from the inner piston must take place through two oil films and through boththe wall of the reciprocating cylinder and the wall of the outer stationary cylinder. The reciprocating cylinder is itself exposed to the hot gases of combustion, and it is further burdened with conducting heat from its outer end.

Heretofore, designers of engines having opposed cylinders and opposed-pistons in each cylinder have encountered a further difficulty in providing straight-line connecting elements between either the inner pair or the outer pair of pistons of opposite cylinders. In designing such engines they have usually employed twoor three-throw crank shafts, and they have resorted to large bores with relatively very short strokes,

so that the connecting means could clear the tically-impossible to construct a serviceable engine with straight-line connecting elements between the inner pistons, and in which said elements are spaced far enough apart to clear the crank pins, arms and connecting'rods of a threethrow crank shaft operating between them.

If a two-throw crank shaft is used in such an engine, it is obviously impossible to avoid either a bending the connecting rods or off-setting them with respect to the forces acting through them in line with the cylinder axis. Curving'the connecting rods (I now refer to connecting rods between pistons and crank shafts) results in producing bending moments in them, with consequent flexure; and the alternative of off-setting the rods with respect-to the axis of the cylinders, causes tilting of the pistons within the cylinders and consequent rapid wear of both pistons and cylinders. Three-throw crank'shafts, in such engines, must either incur the objections just stated for a two-throw shaft, or else the center throw must act so that the'ce'nter of its connecting rod is in the same plane as the axis of the cylinders, and theother two throws must be equally spaced on opposite sides of the said plane. Any of these constructions encounter the aforementioned impossibility of providing straight-line connecting elements between the inner pistons in combination with feasible relations between bore, stroke and bearing areas.

I have developed an opposed-piston type of engine which possesses all of the aforementioned advantageous features of engines employing this principle and few, if any, of the undesirablefeatures of the heretofore proposed engines of the opposed-piston type. The engine of my invention comprises spaced, axially aligned cylinders, and two pistons mounted for reciprocatingmovement within the opposite end portions of each cylinder. v

The preferred form of engine of my invention comprises two axially aligned cylinders disposed on opposite sides of a crank shaft. Two pistons lost by being mixed with the scavenging air.

are mounted for reciprocating movement in each cylinder, one Within the inner end portion of the cylinder and one within the outer end portion of the cylinder. The pistons in the adjacent end portions of the cylinders (the inner pistons) are rigidly connected to each other, and the pistons in the opposite end portions of the cylinders (the outer pistons) are rigidly connected together. The inner pistons and outer pistons are units extending between the cylinders and mounted'for reciprocating movement in opposite directions.

I have overcome the disadvantages resulting from failure to provide connecting straight-line elements in engines of the type proposed heretofore by employing a form of crank shaft which provides two throws for operating a pair of outer pistons, and two throws for operating a pair of inner pistons; and which provides a clearance space, between the two throws which serve the inner pistons, through which the straight-line connecting elements between the inner pistons can pass. This arrangement contributes to a more favorable bore-stroke relationship; avoids bending moments in either connecting rods or connecting elements between the inner pistons; avoids non-concentric loading of pistons; and reduces weight and bearing loads.

In the preferred form of engine of my invention, I employ step or differential pistons which serve the dual purpose of power pistons and pumping pistons for providing scavenging air, and I provide simple and efiicient means for lubricating such pistons. Efforts to lubricate step pistons by means of oil-splash or oil-mist produced in the engine crank cases have been largely unsuccessful heretofore. If the step piston is used with the large diameter toward the crank case, it is diflicult to get sufficient oil past the large end to lubricate the smaller portion which serves as a, power piston. Or, if this should be accomplished, it must be done by allowing oilto get past the large end of the piston and into the scavenging pump chamber, whereupon, of course, most of it is blown by the scavenging air into the power cylinder and burned or wasted. Engines heretofore designed with a step piston in the outer end of a cylinder have never, so far as I am aware, provided means of conveying oil-,

laden crank case atmosphere to said piston in a manner to provide sufficient lubrication for its rubbing surfaces, and without mixing said oil with the scavenging air, and with provision of means for returning all excess oil to the crank case. I accomplish this by circulating high velocity currents of atmosphere between the crank case and. the step pistons in the outer ends of the cylinders. These currents of air, carrying atomized oil, do not reach the chamber in which scavenging air is compressed, so that no oil is It would be possible to obtain fair lubricating oil economy in such an engine, if the step pistons were lubricated by direct forced-feed of oil to their rubbing surfaces in measured volumes per stroke, but this would require additional apparatus at increased cost, and would not be as simple, positive or economical as my entirely automatic system.

The apparatus of my invention for supplying fuel to the engine cylinders may include a precombustion chamber communicating with the interior of the combustion chamber of each cylinder and provided with ignition means. The pre-combustion chambers are connected by means of suitable conduits to a source of supply of fuel. In the preferred form of apparatus, a vaporizing or atomizing device is included in the fuel supply line. The arrangement is such that hot gases may flow from the combustion chambers through the vaporizing or atomizing device and provide the energy required to effect vaporization or atomization and injection of the fuel. By employing pre-combustion chambers having restricted ports leading to the cylinders and by employing combustion gases for injecting the fuel into the pre-combustion chambers, I can employ high compression pressures without causing pre-ignition and without causing detonation.

When oil is to be employed, I prefer to provide atomizers having small cylindrical atomizing chambers and substantially parallel tangential inlet and outlet passages for gas under pressure on opposite sides of the chamber. This arrangement of passages causes entering liquid to be guided in a circular path of travel during the course of which it must pass over the. lip defining the inner edge of the outlet passage.

The invention will be better understood from a consideration of the following description in conjunction with the accompanying drawings in which is shown a preferred embodiment of the complete apparatus of my invention, and, in which Fig. 1 is a sectional elevation, taken substantially along the line of Fig. 2, of an engine of my invention;

Fig. 2 is a sectional plan view of the engine illustrated in Fig. 1, taken substantially along the line 22 of Fig. 1;

Fig, 3 is a section taken substantially along the line ,33 of Fig. 1;

Fig. 4 is a section taken substantially the line 4-4 of Fig. 1;

Fig. 5 is a section taken substantially the line 55 of Fig. 2; I

Fig. 6 is a section taken substantially the line 66 of Fig. 2;

Fig. 7 is a diagrammatic plan view of an engine of the type illustrated in Figs. 1 to 6;

Fig. 8 is a diagrammatic illustration of the relative positions of the crank pins of the crank shaft illustrated in Fig. 7;

Figs. 9 and 10 are diagrammatic illustrations similar to those shown in Figs. 7 and 8 but showing different relative positions of the crank pins and pistons;

Fig. 11 is a section of apre-combustion chamber of the engine illustrated in Figs. 1 to 6;

along along along Fig. 12 is a plan view of the pre-combustion' chamber illustrated in Fig. 11;

Fig. 13 is a section of a single-chamber atomizer or vaporizer of the invention, taken substantially along line |3|3 of Fig. 14;

Fig. 14 is a section taken substantially along line |4-|4 of Fig. 13;

Fig. 15 is a section taken substantially along the', line |5--.|5 of Fig. 14;

Fig. 16 is a section of a duplex or double chamber atomizer or vaporizer of the invention, taken substantially along the line |6--|6 of Fig. 17;

Fig. 17 is a section taken substantially along 7 the line |1 |1 of Fig, 16;

Fig. 18 is a diagrammatic illustration similar to that shown in Fig. 9, but showing a modified fuel system; and

Fig. 19 is a sectional view of the atomizer included in the modified fuel system shown in Fig. 18.

The engine illustrated in the drawings is a two-cycle internal combustion engine comprisportions of which are enlarged. The large-diameter end portions of the step pistons 23 and 26 are enclosed in cylindrical casings 21 and 30 which communicate with the outer end portions of the cylinders and 2| and which serve as scavenging pump cylinders, the large-diameter end portions of the outer pistons serving as pistons for the scavenging pumps.

The outer pistons 23 and. 26 are-rigidly connected together and to a cross-head 3| by means of straight-line tie rods 32. The outer pistons 23 and 26 are spaced apart and maintained in fixed positions relatively to each other and to the cross-head 3| by means of tubes 33 and 34 which surround or encase the tie rods and extend between and engage the pistons and the crosshead.

The cross-head 3| is in the form of a ring, and it has an external diameter greater than the internal diameter of the cylinder 2|. The outer surface of the cross-head is smooth,.and the cross-head is so mounted that its outer surface engages the smooth inner surface of a cylindrical casing 35 which communicates with the inner portion of the cylinder 2|, A similar cylindrical The crank casing 38 is associated with the inner portion of I the cylinder 2|].

The inner pistons 24 and 25 are rigidly connected together by means of straight-line tie rods 36 which are shown as formed integrally with the pistons but which may be of any suitable construction.

A wrist pin 31 is mounted on the annular crosshead 3| with its aXis extending parallel with the axis of the crank shaft 22 and at right angles to the common. axis of the cylinders 20 and 2|. Two similar connecting rods 4|! and 4| connect the wrist pin 31 with two outer, spaced but axially aligned crank pins of the crank shaft 22.

A wrist pin 42 is mounted on the piston 24 with its axis extending parallel with the axis of the crank shaft '22 and at right angles tothe common axis of the cylinders 29 and 2 Two similar connecting rods 43 and 44 connect the wrist pin 42 with two inner, spaced but axially alignedcrank pins of the crank shaft 22.

The inner crank pins and outer-crank pins are spaced apart angularly but all are in the same circle. The axes of the wrist pins 31 and 42 and the crank shaft 22 and the common axis of the cylinders 20 and 2| all lie in the same horizontal plane. Y

The crank shaft 22 is soconstructed as to provide a clearance space between two of its cheeks The inner ends of the similar casings 35 and 38'associated with the inner ends of the cylinders 20 and 2| are spaced horizontally from each other, and from the crank shaft 22. A central casing section 45 forms a supporting structure for the engine and provides support for bearings 46 and 41 in which the opposite end portions of the crank shaft are supported for rotation. The

\ central casing section and the similar casings 35 and 38 cooperate toprovide a crank case which may be sealed to prevent dust from entering. A flywheel 50 is mounted on one end the crank shaft.

The cylinders 20 and 2| are provided with exhaustxports and 52 adjacent their inner ends which communicate with exhaust manifolds 53 and 54 and with inlet-or transfer ports 55 and 56 adjacent their outer ends. The scavenging pump cylinders 21 and 30 are enclosed by rectangular casings 51 and 60, the outer closed ends of which form cylinder heads for the scavenging pump cylinders. The inlet ports 55 and 56 communicate with the interiors of the scavenging pump cylinders through the triangular passages 6| and 62 formed between the rectangular casings 51 and 60 and the scavenging pump cylinders 21 and 30 on one side, which triangular passages communicate in turn with annular passages 58 and 59. On the other side, ports 63 and 64 provide means of communication between the atmosphere and the interior of the scavenging pump cylinder through intake manifolds 65 and 66.

The cylinders 20 and 2| are provided with cooling water jackets 61 and 10. The water jacket 61 surrounding the cylinder 20 comprises three annular chambers 1|, 12 and 13, chambers 1| and 12 being separated by the walls defining the annular air inlet passage 56, and chambers 12 and 13 being separated by the walls defining the substantially annular exhaust passage 14. The three chambers comprising the water jacket surrounding the cylinder 20 are connected by means of suitable conduits which provide for the circulation of water therebetween. Thus, (Figs. 3 and 4) con-duits. or passages 15 at the sides and conduits or passages 16 at the top and bottom provide means of communication between chambers 1| and 12. Similarly, a relatively large upper passage 11 and a relatively small lower passage 80 provide means of communication between chambers 12 and 13.

The water jacket surrounding the cylinder 2| comprises three annular chambers BI, 82 and 83 corresponding to the chambers 1|, 12 and 13 comprising the water jacket 61. The chambers 8| and 82 are separated by the walls defining the annular air inlet passage 59, and chambers 82 and 83 are separated by the walls defining a substantially annular exhaust passage 84 similar to the exhaust passage 14 associated with the cylinder 20.- Passages or conduits 85 and 86 similar to the passages and 16 provide means of communication between the chambers 8| and 82 and passages or conduits 81 and 90 similar to the passages 11 and 80 provide means of communication between the chambers 82 and 83.

Suitable means (not shown), which may include a pump and a radiator, are provided for circulating the water through the water jackets.

Each of cylinders and 2| has associated therewith conduits or passages through which oil laden atmosphere may pass from the crank case to the cylinder in which the large diameter portion of the step piston associated therewith is confined. Thus, conduits 9! are mounted within and portion of at the sides of the water jacket 61 surrounding the cylinder 20, and conduits 92 are mounted within and at the top and bottom of the water jacket 61. The conduits 9| and 92 are open at their ends, and they extend from the cylindrical casing 38 associated with the inner end portion of the cylinder 20 to the cylindrical casing 21 in which the large-diameter portion of the step piston 23 is confined. The upper conduits serve the double function of casings for the tie rods 32 and conduits for the flow of oil-laden atmosphere from the crank case to the step pistons.

The water jacket 10 is provided with conduits 93 and 94, similar in construction and function to the conduits 9| and 92, respectively. The conduits 93 and 94 are open at their ends, and they extend from the cylindrical casing 35 associated with the inner end portion of the cylinder 20 to the cylindrical casing 30in which the large-diameter portion of the step piston 26 is confined.

Any suitable apparatus may be provided for supplying fuel to the engine hereinbefore described.

The apparatus shown in the drawings for providing fuel to the engine comprises two similar pre-combustion chambers 95 and 96 which communicate with the interiors of the cylinders 20 and 2|, respectively, and a fuel atomizer or vaporizer 91 .(Figs. '7 and 9). The atomizer or vaporizer 91 is connected to both pre-combustion chambers by means of conduits I00 and IOI.

An additional atomizer I02 is shown suitably connected directly to the power cylinders 20 and 2| by means of conduits I03 and I04. The atomizer I02 and its associated conduits may be employed alone or in conjunction with the atomizer 91 and thepre- combustion chambers 95 and 96.

The details of the pre-combustion chamber are shown in Figs. 11 and 12. The main chamber of the pre-combustion chamber comprises a cylindrical outer or upper portion I05 and a frusto-conical inner or lower portion. I06. A threaded tubular element I01 forms a continuation of the frusto-conical, portion of the main chamber. The height H of the main chamber is somewhat less than the internal diameter of the cylindrical portion. A conduit or passage I|0 having a threaded, outwardly projecting end portion for connection with a conduit leading to the vaporizer or atomizer communicates with the interior of the main chamber in such a manner that fluid entering the main chamber is directed against a wall of the conical portion of the main chamber along a line normal thereto. The conduit M0 for introducing the vaporized or atomized fuel into the main chamber is surrounded by a water-cooling chamber |I2 having threaded outlets H3 and M4 for connection to a water circulating system (not shown). A spark plug II5, connected to a high tension ignition system (not shown) of the type commonly employed on gasoline engines is mounted in a threaded opening in the end wall of the cylindrical portion of the main chamber with its spaced tips disposed adjacent the point at which the entering stream of atomized or vaporized fuel strikes the wall of thefrusto-conical portion of the main chamber.

The details of the atomizers or Vaporizers 91 and I02 are shown in Figs. 13 to 15. The main body of the atomizer is a metal block 6 having a centrally disposed cylindrical atomizing or vaporizing cavity or chamber 1 therein. Substantially parallel tangential inlet and outlet passages I20 and I2I communicating with the interior of the cylindrical chamber are provided in 'opposite side portions of the block and on opposite sides of the axis of the cylindrical chamber. The outer portion of each passage is cylindrical and the inner portion is defined by two surfaces lying in parallel planes and two surfaces lying in planes diverging toward the cylindrical chamber. The width of the inner end of each passage is substantially equal to the length of the cylindrical chamber. Conduits II 8 and I I9, corresponding to the conduits I00 and IOI extending between the atomizer 91 and the pre- ' combustionchambers 95 and 96 or corresponding to the conduits I03 and I04 associated with the atomizer I02 of the apparatus illustrated diagrammaticallyin Fig. '7, are provided for conducting vaporizing or atomizing gas from a suitable source to the vaporizer or atomizer and for conducting the vaporized or atomized fuel from the vaporizer or atomizer to its points 'of use. The vaporizing or atomizing chamber II1 may be of any suitable size. I have obtained good results by employing chambers having internal diameters varying from about A; inch to about inch.

For introducing liquid fuel into the cylindrical chamber II1, a valve block I22 having relatively small inner and outer passages I23 and I24'communicating with a larger central cavity I25 is mounted in one side portion of the main body I I 6 with the inner passage. I23 in axial alignment with the cylindrical chamber H1. The flow of fuel into the cylindrical chamber I I1 through the inner passage I23 is controlled by means of a needle valve I26 suitably mounted for adjustable positioning axially in an opening in the opposite side portion of the main body. A ball I21, normally held in engagement with the inner peripheral edge of the outer passage I24 within the valve block cavity I25 by means of a spring I30, forms a check valve for preventing the back flow of gases from the cylindrical chamber H1 in the main body II6. A tube or conduit I3I communicates with the outer passage I24 and a source of supply of liquid fuel (not shown).

A duplex or double-chamber atomizer or vaporizer is shown in Figs. 16 and 1'1. The duplex atomizer comprises a main body I32 having oppo-.

sitely disposed, axially aligned cylindrical atomizing or vaporizing chambers I33 and I34 therein. The inner surfaces of the vaporizing chambers I33 and I34 are grooved circumferentially to facilitatepicking up of the oil by the high velocity gas streams. Tangential inlet and outlet passages I35 and I36 having their axes forming a right angle communicate with the interior of the cylindrical vaporizing or atomizing chamber I34 through a common opening in the wall of the chamber. Conduits I31 and I40 communicate with the passages I35 and I36 and serve to conduct vaporizing or atomizing gas from a suitable source to the vaporizer or atomizer and to conduct the vaporized or atomized fuel from the vaporizer or atomizer to its points of use. Similar inlet and outlet passages are associated in a similar manner with the vaporizing or atomizing chamber I33, and conduits similar to the conduits I31 and I40 are associated with such passages.

Liquid fuel is introduced into both vaporizing or atomizing chambers I33 and I34 through a common passage MI in the main body I32. The common passage communicates with passages I42 and I43 which are in axial alignment with the atomizing and vaporizing chambers I33 and I34. The fuel is introduced into the common passage through a'valve block I 44, having relatively small inner and outer passages I45 and I46 communicating with a larger central cavity of a spring I53 forms a check valve for prevent-.

ing the back flow of gases from the vaporizing or atomizing chambers I33 and I34 through the common passage I4I.

In the modified apparatus shown in Fig. 18, similar tubes I54 and I55 connect the atomizer I62 with the precombustion chambers 95 and 96, respectively, and are provided with check valves I56 and I51, respectively, located at or near their precombustion chamber ends. The check valves. I56 and I51 permit fluid flow from the atomizer I62 through the tubes I54 or I55 to either precombustion chamber, but prevent flow in the opposite direction through either tube.

Similar tubes I58 and I59 connect the atomizer I 62 with the main combustion chambers of cylinders 20 and 2|, respectively, and are provided with check valves 159A and I60, respectively, located at or near their. atomizer ends. These check valves serve to permit flow through either tube into theatomizer and prevent flow from the atomizer into either tube. may be introduced into the atomizer chamber in any suitable manner, as, for example, through the axially arranged passage I68. I

The atomizer I62, shown in detail in Fig. 19,

Liquid fuel provides tangential outlet passages I63 and I64 leading from the chamber I61 -to the tubes I 54 and I55, respectively. Other tangential inlet passages I65 and I 66 communicate with the in-.

terior of the atomizing chamber and with the check valves I59A and I60, respectively, and through them with their respective tubes I58 and I59. The 'check valves I 56 and- I51, shown diagrammatically in Fig. 18, are similar to the check valves I59 and I60 which are shown in detail in Fig. 19, but are arranged to permit flow in the direction away from the atomizing chamber and not into it, whereas check valves I59 and I 0 permit flow into the atomizing chamber and n t away from it.

The mode of operation of the apparatus illuss trated in the drawings will be clear from a con"- sideration of the following description. When the crank shaft of the engine illustrated in Figs, 1' to 8, inclusive, .is rotated in either direction, the pistons 25 and 26 will move away from each other, and the pistons 23 and 24 will move toward each other. The outer end of the piston 26 will close the ports 64, compress airin the outer end ports 63 and cause air to be forced from the inner end portion of the scavenging pump cylinder 21 through the passages 9| and 92 into the crank case. Uponfurther movement, the ports 63 will be opened into the outer end portion of the scav enging pump cylinder 21, relieving the vacuum therein, and the piston 25 will open the exhaust ports 52 just prior to the time when the piston .26 opens the transfer ports 56 and permits compressed air from the outer end portion of the scavenging pump cylinder 30 to flow to the interior of the power cylinder 2|. Rotation of the crank shaft through the succeeding 180 will cause each of the operations just described to be repeated in the opposite cylinders.

It will be seen that if, during the compression stroke in either power cylinder (20 or 2|) fuel should be injected by suitable means to form a combustible mixture, and if, at the proper time, this fuel charge should be ignited, combustion and expansion will take place and power will be developed.

It has been shown that during the operation of the engine, alternate suction and compression takes place in the inner end portions of the scavenging pump cylinders 21 and 30. This action causes atmosphere from the crank case to be carriedv back and forth through the passages 9|, 92, 93 and 94. I provide forced feed lubrication to the crank shaft and crank pin bearings, by suitable conventional means which are not shown in the drawings. This forced feed lubrication produces, as is well known, a mist of lubricating oil in the crank case, and it is obvious that this mist will be carried, in the manner just explained, out to the inner end portions of the scavenging pump cyliders. Proper relationships should be established between the aggregate areas of the passages 9|, 92, 93 and 94 and the volumes of air caused to pass through them during each stroke of ,the engine, so that the velocity through the passages, will be high enough to support and transfer, at minimum engine speeds, a sufiiciency of oil. It will be further observed that the oil v thus carried, impinges against the inner end walls of the large-diameter portions of the step pistons 23 and 26 and is distributed by turbulence to lubricate all rubbing surfaces of said pistons without becoming mixed with the scavenging air which is being pumped by the opposite sides of said pistonsi Figs. 9 and 10 illustrate a modified arrangement of the engine in which the two pairs of crank pins have their axes in the same circle,

but spaced more and/or less than 180 apart therein. With this arrangement, the engine will function properly when rotation is in one direction only. For the arrangement and crank positioning shown in Figs. 9 and 10, the correct direction of rotation is indicated by the arrow in Fig. 10. In the position of parts shown in Fig. 9,

the piston 24 is seen to have completed its outward or power stroke and to have started on its compression stroke; whereas the piston 23, in the same cylinder, has just completed its outward or power stroke. ,In other words, the piston 24 is several degrees of crank shaft rotation in advance of the piston 23. Thus, the exhaust port 5| was opened by the piston 24 before the transfer port 55 was opened by the piston 23, and the exhaust port 5| has been closed by the piston 24 while the transfer port 55 is yet open. Therefore, compressed air from the outer end portion of the scavenging cylinder 21 will continue to flow into the power cylinder 20 after the exhaust port ciprocating parts.

5| is closed, and in this way the powder cylinder 20 can be filled with air under greater pressure at the beginning of the compression stroke therein, than is possible with a crank shaft having pairs of throws or pins 180 apart. Engine capacity may thus be increased with a sacrifice of perfect balance.

Following are some of the advantages permitted by engine designs embodying my invention:

(1) Perfect balance of all rotating and re- This is accomplished by making both groups of oppositely moving reciprocating elements equal to each other in weight, and by providing oppositely disposed and identically proportioned and weighted pairs of connecting rods, all of which always assume at the same time the same angle with respect to the axes of the cylinders; and by controlling one group of re- (2) Forces acting on the crank pin bearings due to either combustion, inertia or centrifugal pressures, act always as pure couples and thus do not produce radial loads on the main bearings.

(3) Forces acting on the crank pin and wrist pin bearings due to combustion in the power cylinder, are diminished during the first, part of every power stroke by inertia of the reciprocating parts; and the loads on the same bearings due to inertia of the reciprocating parts are diminished during the latter part of every power stroke by. compression pressure between the opposed pistons in the opposite cylinder. Thus, bearing loads, are diminished and the turningefiort is more uniform.

(4) scavenging pump displacements are provided in excess of the combined displacement plus clearance space of the power cylinders they serve, which insures clean scavenging and full charges of air."

In the operation of engines of the typ illustrated in the drawings with oil, employing atomizers of the type illustrated in Figs. 13, 14 and 15, the tangential passages I20 and I2I of the atomizer or vaporizer may be operatively connected with the interiors of the power cylinders 20 and 2| by means of the conduits H8. and H9.

The oil is introduced into the vaporizing or tion gases flowing alternately from the power cylinders 20 and 2| through the conduits H8 and 9 (corresponding to conduits I00 and IN or I03 and I04), and the resulting atomized or vaporized product flows alternately to the interiors of the power cylinders 20 and 2| or to the interiors of the cylinders 20 and 2| through the pre-combustion chambers and 96.

During the course of a typical operation,-oil of say 27 B. enters the atomizing or vaporizing chamber II I which has become heated by the hot gases from the cylinders to a temperature ranging upward of 300 F. (about C.), and the viscosity is reduced to between 3 and 5 Engler (15 to 1'? sec. Saybolt). This reduction in viscosity renders the oil much easier to atomize, probably because it reduces the surface tension.

The hot gases passing through the atomizer from one cylinder to the other, pick up the oil and revolve it at an extremely high velocity in the cylindrical chamber II! from which it escapes in a highly atomized state and is carried with the hot gases through the tube H8 or H9 into the combustion chamber of the engine.

The rapid revolution of the oil in the cylindrical chamber produces great pressure on the oil due to centrifugal force, and'this pressure tends-to overcome the surface tension so that the oil can be blown off the edge or lip of the outlet port I20 or 12! of the atomizer in the form of drops so small that they appear as a mist or gas in the atmosphere which floats upward and does not seem to come down. It appears that successful atomization is largely a matter of overcoming surface tension, and, to accomplish atomization, I use the heat of the gases from the combustion chamber of the engine to reduce the surface tension and the kinetic energy of the high-velocity gas-flow to produce pressure on the oil due to centrifugal force. The angular velocity imparted to the oil gives it a tendency to pass the outlet opening from the atomizing chamber without going out through the outlet, and a portion of the oil, at the beginning of the process, goes on around and around the chamber and is spread by centrifugal force on the inner surface of the bore and reaches the outlet lip in a thin film, or perhaps a series of films moving at different velocities, and this film is broken up by the out-rushing gases into tiny particles as it leaves the lip of the outlet port. The tubes associated with the atomizer, as Well as the atomizer body, become heated by the gases, so that the oil is-not ,only atomized but it is at least partially vaporized before it reaches the engine cylinder.

I prefer to control the temperature "of the tubes associated with the atomizer, or keep it low enough to prevent pyrogenic decomposition of the fuel, or to avoid cracking it until after it reaches. the combustion chamber. This 'avoids the formation of carbon deposits in the tubes, and I have found that copper tubes are better for this purpose than tubes made of other materials. Without any special provision' for cooling, ,copper tubes of a certain. size and wall thickness remain free from carbon, while'identical tubes made of steel or brass become choked. The

tubes get hottest at points near the combustion chambers, and I have found that it is desirable, whensusing tubes larger than inside diameter, to provide additional radiating surface, as by finning the tubes, for a portion of their length near their combustion chamber ends, and

to insulate them to prevent heat transfer to the atmosphere for a portion of their length near the atomizer. This maintains more uniform temperatures' throughout the length of each tube and increases the temperature of the gases reaching the atomizer. It is also desirable to insulate the body of the atomizer, allowing only enough heat to be radiated from the body to keep itscylinder which is compressing. As this stroke nears completion in each cylinder, the rising compression pressure in one cylinder will first equal and then exceed the falling combustion pressure in the opposite cylinder, and at this point the direction 'of flow through the tubes and atomizer will be reversed and this reverse flow will be accelerated by the rapid rise in pressure due to combustion in the cylinder which has just completed its'compression stroke. Thus, the cylinders alternate in charging each other withatomized fuel, the atomizer functioning identically with gas flow in either direction.

I have found that with compression ratios which are usual in gasoline engines, the compression pressure in one cylinder does not sufliciently exceed the gas pressure in the opposite cylinder to overcome the inertia of the gas in the tubes and cause a reverse flow of any appreciable volume of gas and fuel until afterignition takes place in one cylinder and the exhaust and inlet ports open in the opposite cylinder. Even after the pressure differences in the two cylinders reach a maximum, which is approximately at the end of the stroke, with ports open in one cylinder and maximum combustion pressure in the other, there is a lag, due to inertia and friction in the tubes and back pressure or resistance caused by centrifugal force and turbulence in the atomizer, so that no measurable amount of fuel ever enters a cylinder dur-' ing the time that the ports are open which would cause unburned fuel to be carried out the exhaust ports. I provide a safeguard against this possible Waste of fuel which is particularly suitable for use in the operation of engines which must operate for considerable periods of time at very low speed. For such conditions I preferably provide two atomizers and two sets of tubes (as illustrated in Figs. 7 and 9), one set carrying fuel to. pre-combustion chambers and one set carrying fuel to the -i'nain cylinders of the engine. I position the tubes of the latter. set so that they penetrate the cylinder walls atpoints which are cov-' ered by the pistons in each cylinder during the time that the ports are open in the opposite cylinder, and thus no fuel can be injected directly. into a cylinder during the time that its ports are open. I find that fuel injected into pre-combustion chambers is never carried out through the exhaust ports.

Fuel may be supplied to the -atomizer under constant pressure, which need not exceed onetenth of the maximum pressure resulting from combustion in the cylinders, or it may be supplied by a displacement pump, or metering pump, which forces into the atomizer chamber a measured quantity of fuel'oil during the compression stroke of each opposite cylinder. sure fuel supply is preferable because a very simple and cheap pump, such as a gear pump, may be used. However, a metering pump of any suitable or well known construction can be used to supply individual atomizers of a plurality of pairs of cylinders with approximately equal quantities of fuel per cycle per cylinder; and, it is to be noted, such pumps will function with more nearly identical equal volumes of discharge per cylinder, when operating in connection with this low-pressure system, than they do when used for injecting under pressures of from 2000 to 9000 lbs. per

square inch, as is done in Diesel type engines.

Instead of employing two-way atomizers, it is possible to employ pn e-way atomjgers, cross connected by tubes to the prewombristfifihambers Constant presand/or the cylinders In this case, however, it will be necessary to employ check valves, to limit flow of gas through each atomizing device to one direction. The duplex atomizer of Figs. 16 and I! can also be used in place of the two atomizers 91 and I02.

A suitable fuel system including a one-way atomizer is shown in Figs. 18 and 19. When, in the operation of apparatus of the type shown in Figs. 18 and 19, the pressure in the cylinder 2| exceeds the pressure in the cylinder 20, gas will flow through the tube I59, the atomizer I62 and the tube I54 into thepre-combustion chamber 95;

and during this phase there will be no flow through either of the other two tubes of the system. Then, when the pressure in cylinder 20 exceeds the pressure in cylinder 2|, gas will flow through the tube I58, the atomizer I62 and the tube I55 into the pre-combustion chamber 96; and during this phase, there will be no flow through either tube I54 or I60. Thus, I have provided two sets of tubes each of which carries gases from the main combustion chamber of one cylinder of the engine through a common atomizing chamber to the pre-combustion chamber of the opposite cylinder, and this flow is in one direction only in each set of tubes.

I have found that a residuum of fuel will remain in the tubes I54 and I55 following the injection period, and an object of the arrangement just described is to prevent this fuel from being directly exposed 'to the intensely hot gases of,

combustion until after such gases have been cooled sufficiently so that they will not effect pyrogenic decomposition of the fuel and consequent deposition of carbon in the tubes. This adequate cooling of the gas products of combusto the atomizer before such gases can come intocontact with any fuel. A considerable cooling of the gases takes place during passage through the tubes I58 or I59, due to heat dissipation through the tube walls, and a further cooling is effected by expansion of the gases into the atomizing chamber. Remaining heat'in the gases is employed in vaporizing and atomizing the fuel.

The provision of precombustion chambers the complete combination of my invention permits the use of higher compression pressures acting upon combustible mixtures of fuel and air without causing pre-ignition and without causing detonation. In the operation of apparatus provided with pre -combustion chambers, the major portion of the fuel is injected into the 'precombustion chambers by means of gases diverted from the cylinders of the engine. which last enter either precombustion chamber during the injection period are burned gases, being products of combustion in the opposite cylinder.

The precombustion chamber is so shaped and the flow of said gases which carry the fuel charge into it is so directed that practically the entire fuel charge is retained within the pre-combus tion chamber during the entire compression stroke. At the beginning of the compression stroke, the pre-combustion chamber is entirely The gases r shown and described, in conjunction with the 5 engine of my invention, I find that I can use much higher compression pressures, without causing ignition due to the heat of compression, than would be possible in an engine which did, not

- embody these features and which similarly. had

fuel present in the combustion chamber during all or a major part of the compression stroke. This is true whether my engine is operated on gasoline or heavier oils, and it permits exact timing of ignition by means of a spark plug located in the-pre-combustion chamber, and brings about increased engine efficiency and capacity bypermitting a higher compression ratio.

Detonation is caused by exceedingly rapid flame spread in a combustible mixture and by compression waves which travel through the mixture in advance of the flame sphere and bring the mixture adiabatically to the ignition temperature. I avoid detonation by using burned gases to shield the fuel charge in a relatively small pre-combustion chamber so that, even though the compression temperature and pressure exceeds the usual detonation point for the fuel used, the mixture lacks suflicient air to permit ignition, except as the result of a spark, or to support rapid flame The fuel ejected from the pre- I propagation. combustion chamber into the main cylinder by means of the pressure generated by this inccmplete combustion, will not cause detonation in the cylinder because the rate of flame spread in mixture ahead of the flame which could be caused 40 to detonate by the advancing compression waves. As a matter of fact, I find that with a certain pre-combustion chamber, and a compression pressure of 165 lb. ga., and using ordinary gasoline as fuel, ignition can not beproduced even with a spark until just about the end of the compression stroke; and no detonations occur. Increasing the compression pressure with this same precombustion chamber will cause a sufficient amount of air to enter the chamber at an earlier time in 5 the compression stroke and will thus permit advancing the spark to produce earlier ignition.

These objects and characteristics of my precombustion chamber are realized in greater or less degree regardless of whether the entire 'fuel 5 charge is introduced into the pre-combustion chamber, or entirely into the main cylinder, or partly into both, provided thespark plug is located in the pre-combustion chamber, because in any of thesecases only a small amount of fuel is burned in the pre-combustion chamber and it serves to provide a pilot flame causing a more uniform rate of flame spread in the main charge. A still further advantage of my pre combustion chamber is that it protects the spark plug. It 5 is a fact well known to experimenters that the burning of heavy oil in an engine using spark ignition usually results in spark plug trouble. The character of this trouble varies from fouling with oil or soft carbon to coking with hard carbon and to burning out of the plugs, and one or all of these difiiculties appears when heavy oil is burned in ordinary engines with ordinary placem t or positioning of the spark plug. One reason for this is imperfect atomization and distribution i of the fuel charge, but even with my atomizing and vaporizing system, which seemingly produces completev and perfect burning of the fuel, the

trouble still persists unless the spark plug" is shielded from the main combustion" space, and I have found that placing the plug in a small chamber separated fromthe main combustion space, and communicating therewith by means of a constricted passage, eliminates the difficulty. 7 A further feature of advantage in my fuel burning system, considered as a whole, in a pre-w ferred embodiment, including a two cylinder, two

cycle, engine, with cylinders firing at different under idling or light-load conditions is accom- I plished in my'engine by isolating a small fuel charge in a precombustion chamber with sum--v cient air to support its combustion. Thus I can burn the smallamount of fuel required for idling operation, whereas, if this small fuel charge was distributed throughout, the entire air charge, as

,in ordinary gasoline two-cycle engines, either the mixture would be too lean to be ignited, or the air charge would be restricted or reduced to such an extent that scavenging would be incomplete.

' With engines depending upon a hot surface for igniting the fuel, the difficulty encountered is to. maintain a sufllciently hot surface when the engine is burning a small amount of fuel, and to '4 avoid over-heating the surface when the engine is operating at full load and speed.

When the engine is cold it should be started on a light hydro-carbon fraction, such as gasoline, in place of Diesel oil. Thus in practice, the oil line connected to atomizer Hi can lead to a twoway valve, so that it can be placedin communication with either a supply of gasoline under pressure, or a supply of Diesel oil.- After the engine has been started in operation this valveis turned to supplyDiesel oil.

While my fuel system has been specifically shown and described in its application to two-- cylinder two-cycle engines, it is obviously applicable to other engines. der four-cycle engine, it is possible to provide tubes for conducting gases from the combustion chamber of each cylinder to a common atomizer, a check valve being provided in each tube, preferably nearits atomizer end, which prevents flow in the opposite directiom Another tube may communicate with the atomizer and with the interior of a manifold which conductsthe air to all of the cylinders of the engine for supporting combustidn. By these means regulatable quantities of, fuel vapor and atomized fuel may. be injected into the air stream in the manifold each time combustion takes place in any cylinder of the engine. a

If my fuel system be applied to a conventional multiple-cylinder four-cycle engine, and if the fuel-partly vaporized and partly atomized--be sprayed into the inlet air stream in the manifold, it is theniessential, or most desirable, if not essential, that the air stream in the manifold shall move at high velocity. If the velocity falls below about 50 ft. per second, the vaporized portion of the fuel charge will more rapidly, or in greater quantity,.condense 'on the walls of the ft. per. sec. at maximum power,; It follows Thus, in a multiple-cylinmanifold, and the atomized portions of the charge will tend to coalesce, producing largerfuel globules and less opportunity for the fuel to com-- tact and combine with the atoms of oxygen in the air charge. conduit through whiclrair is supplied to the cylinders be restricted only sufflciently to maintaina minimum velocity of about 50 ft; per sec. and, preferably, a mean velocity of app oximately 125 that the ,usual' practice ingasoline engines of throttling the air supply which, of course, reduces its velocity through the manifold, should not be resorted to under this system in order to operlate the engine at lowespeed and low power outi put. If,-on the other hand, a sufflcient amount of j fuel is introducedto the air'stream of an ordinary gasoline engine to operate the engine at idling speed and no power output, and if the weight of air per cycle per cylinder is not especially restricted, then the ratio of air to 'fuel will not be in, such proportion as to produce a combustible mixture-too lean--and the charge i will not be ignited by the spark. By my system, I, I provide an air supply to all cylinders with the least possible restriction consistent with .maintaining a velocity of not less than about 50 ft.

per sec. at idling speed, and I tlienprovide a precombustion chamber communicating with the interior of the cylinder through a restricted passage, and ignition means associated withthe precom- I bustion chamber. 1 have found that by these 7 means an air-fuel ratio, which would be too lean in fuel to be ignitible in an ordinary gasoline enginecombustion chamberjcan be ignited and .completely burned if the said precombustion chamber is employed. The reason for this is that the precombustion chamber-such as described herein-is not scavenged and remains, during the exhaust phase of the cycle, filled with products of combustion, and thus, at the end of the compression stroke, the ratio of air'to'fiiel within the precombustion chamber is in a proportion of less air to more fuel-because a portion of the space is occupied by inert gases-'than that which obtains, or would obtain, within the main cylinder v or main combustion spaceof a similar engine operating without; the precombustion chamber. Thus a mixture of air and fuel, with the fuel proportion too small to form an ignitible mixture will, when compressed and partly driven into a, precombustion chamber previously occupied by burned gases, formwithin the said precombustion chamber a mixture which can be ignited by the ignition means within said precombustion chamber. v a.

1. Apparatus of the class described comprising a crank shaft, spaced, axially aligned cylinders disposed on opposite sides of the crankshaft, two pistons mounted for reciprocating movement,

within the opposite end portions of each cylinder,

means rigidly connecting the inner pistons and the outer pistons to form inner and outer piston units, and one or more connecth) ipivo'tally attached to each piston unit and two or more crank pins of the crank shaft.

"2. Apparatus of the class described comprising a crank shaft, spaced, axiallyjall'gned cylinders disposed on opposite sides of the crank shaft, two pistons mounted for reciprocating movement'in opposite directions within the opposite endportions of each cylinder, means rigidly connecting the inner pistons and the outer pistons to form inner and outer piston units, and one or more Thus, it is desirable that the 5 connecting rods pivotally attached to each piston unit and to two or more crank pins of the crank shaft.

3. The combination with a power unit comprising spaced, axially aligned cylinders and two piston units mounted for reciprocating movement within said cylinders, of a four-throw crank shaft disposed between said cylinders, and means for operatively connecting two crank pins with each piston unit.

4. Apparatus of the class described comprising spaced, axially aligned cylinders, two pistons mounted within the opposite end portions of each cylinder, means separately connecting the pistons mounted within the adjacent end portions of the cylinders and the pistons mounted within the opposite end portions of the cylinders to provide two reciprocable units, a four-throw crank shaft disposed between the cylinders, and means for connecting two crank pins with each reciprocable unit.

5. Apparatus of the class described comprising a crank shaft, a pair of spaced, axially aligned cylinders, pistons mounted within the adjacent end portions of said cylinders, step pistons mounted within the opposite end portions of said cylinders, and means separately connecting the pistons mounted within the adjacent end portions of the cylinders and the step pistons to provide two reciprocable units, said means connecting the pistons mounted in adjacent end portions of the cylinders comprising at least two straight-line elements spaced apart a distance not substantially exceeding the throw of the crank shaft.

6. Apparatus of the class described comprising a crank shaft, a crank case surrounding the crank shaft, a power cylinder disposed adjacent the crank shaft with its longitudinal axis normal to the axis of the crankshaft, interior of said power cylinder being isolated during normal operation from communication with the interior of the crank case, a step piston mounted within the portion of the power cylinder remote from the crank shaft with its large-diameter portion disposed outwardly, means connecting the piston with a crank pin on the crankshaft, an enlarged cylinder surrounding the large-diameter portion of the step piston and attached to and communicating with the power cylinder, and one or more passages communicating with the interior of the crank case and the interior of the cylinder surrounding the large-diameter portion of the step piston adjacent its point of attachment to the power cylinder.

'7. Apparatus of the class described comprising a crank shaft, a crankcase surrounding the crank shaft, a power cylinder associated with the crank case, interior of said power cylinder being isolated during normal operation from communication with the interior of the crank case, a piston mounted within the portion of the power cylinder adjacent the crank case, a step piston mounted within the opposite end portion of the power cylinder with its large-diameter portion disposed outwardly, means separately connecting each piston with a crank pin on the crank shaft, an enlarged cylinder surrounding the large-diameter portion of the step piston and attached to and communicating with the power cylinder, and one or more passages communicating with the interior of the crank case and the interior of the cylinder surrounding the large-diameter portion of the step piston adjacent its point of attachment to the power cylinder.

8.. Apparatus of the class described comprising a crank shaft, a crank case surrounding the crank shaft, spaced, axially aligned power cylinders associated with the crank case, interior of said power cylinder being isolated during normal operation from communication with the interior of the crank case, a piston mounted within the end portion of each power cylinder adjacent the crank case, a step piston mounted within the opposite end portion of each power cylinder with its largediameter portion disposed outwardly, means connecting the pistons with crank pins on the crank shaft, enlarged cylinders surrounding the largediameter portions of the step pistons and attached to and communicating with the power cylinders, and one or more passages communicating with the interior of the crank case and the interior of the cylinder surrounding the largediameter portion of each step piston adjacent its point of attachment to the power cylinder with which it is associated.

9. Apparatus of the class described comprising a crank shaft, a crank case surrounding the crank shaft, spaced, axially aligned power cylinders communicating with the crank case, a piston mounted within the end portion of each power cylinder adjacent the crank case, a step piston mounted within the opposite end portion of each power cylinder with its large-diameter portion disposed outwardly, means rigidly connecting the inner pistons and the step pistons to'form' inner and outer piston units, one or more connecting rods pivotally attached to each piston unit and to two or more crank pins on the crank shaft, enlarged cylinders surrounding the large-diameter portions of the step pistons and attached to and communicating with the power cylinders, and one or more passages communicating with the interior 0f the crank case and the interior of the cylinder surrounding the large-diameter portion of each step piston adjacent its point of attachment to the power cylinder with which it is associated.

10. Apparatus of the class described comprising a four-throw crank shaft, a crank case surrounding the crank shaft, spaced, axially aligned power cylinders communicating with the crank case, a piston mounted within the end portion of each power cylinder adjacent the crank case, a step piston mounted within the opposite end portion of each power cylinder with its large-diameter portion disposed outwardly, means rigidly connecting the inner pistons and the step pistons to form inner and outer piston units, means operatively connecting two crank pins on the crank shaft with each piston unit, enlarged cylinders surrounding the large-diameter portions of the step pistons and attached to and communicating with the power cylinders, and one or more passages communicating with the interior of the crank case and the interior of the cylinder surrounding the large-diameter portion of each step piston adjacent its point of attachment to the I cylinders and communicating .with the'power cylinders and with the atmosphere, one or more passages communicating with the interior of the crank case and the interior of the scavenging pump cylinder surrounding the large-diameter portion of each step piston adjacent its point of attachmentto the power cylinder with which it is associated, ,and one or more passages communicating with the outer end portion of each scavengingpump cylinder and with the interior of the adjacent power 'cylinder.

12. Apparatus of the class described comprising a crank shaft, a crank case surrounding the crank shaft, spaced, axially aligned power cylinders communicating with the crank case, a piston mounted within the end portion of each power cylinder adjacent the crank case, a step piston mounted within the opposite end-portion of each power cylinder with its large-diameter portion disposed outwardly, means rigidly connecting the inner pistons and the step pistons to form inner and outer piston units, one or more connecting rods pivotally attached to each piston unit and to two or more crank pins on the crank shaft, scavenging pump cylinders surrounding the large-diameter portions of the step pistons attached to the power cylinders and communicating with the power cylinders and with the atmosphere, one or more passages communicating with the interior of the crank case and the in terior of the-scavenging pump cylinder surrounding the large-diameter portion of 'each step piston adjacent its point of attachment to the power cylinder with which it is associated, and one or more passages communicating with the outer end portion of each scavenging pump cylinder power cylinders communicating with the crank.

and with the interior of the adjacent power cylinder. ,o 1

13. Apparatus of the class described comprising a four-throw crankshaft, a crank case surrounding the crank shaft, spaced, axially aligned case, a piston mounted within the end portion of each power cylinder adjacent the crank case, a step piston mounted within the opposite end portion of eachpow'er cylinder with its largediameter portion disposed outwardly, means rigidly connecting the inner pistons and the step pistons to form inner and outer piston units, means operatively connecting two crank pins on the crank shaft-with each piston unit, scavenging pump cylinders surrounding the large-diameter portions of the step pistons attached to the q which it is associated, and one or more passages communicating with the outer end portion of each scavenging pump cylinder and with the interior of the adjacent power cylinder.

14. Apparatus of the class described comprising a crank shaft, a crank case surrounding the crank shaft, spaced, axially aligned power cylinders communicating with the crank case, a

piston mounted within the end portion of each power cylinder adjacent the crank case, a step piston mounted within the opposite end portion of each power cylinder with its large-diameter portion disposed. outwardly, means connecting the pistons'with crank pins on the crank shaft,

enlarged cylinders surrounding the large-diameter portions of thest'ep pistons and attached to and communicating with the power cylinders, one or more passages communicating with the interior of the crank case and the interior of the cylinder surrounding the large-diameter portion 5 of each steppiston adjacent its point of attachment to the power cylinder with which it is associated, and means for delivering fuel to each power cylinder including a pre-combustion chamber having a restricted inlet passage com- 10 municating with the interior of the power cylinder and having ignition means associated therewith.

15. "Apparatus of the'class described comprising a crank shaft, a crank case surrounding the 15 crank shaft spaced, axially aligned power cylinders communicating with the crank case, a piston mounted within the end portion of each power cylinderadjacent the crank case, a step piston mounted within the opposite end portion 20 of each power cylinderwith its large-diameter portion disposed outwardly, means rigidly con- 'the interior ofkcthe crank case and the interior of the cylinder surrounding the large-diameter portion of each step piston adjacent its point of attachment to the power cylinder with which it is associated, and means for delivering fuel to 35 each power cylinder including a pro-combustion chamber having a restricted inlet passage communicating with the interior of the power.cylin-' der and having ignition means, associated therewith.

16. Apparatus of the, class described comprising a four-throw crankshaft, a crank case surrounding the crank shaft, spaced, axially aligned power cylinders communicatingwith the crank case 'a piston mounted within the end portion 5 of ch power cylinder adjacent the crank case, a step piston mounted within the opposite end portion of each, power cylinder with its largediameter portion disposed outwardly, means rigidly connecting the inner pistons andthe step 50 pistons to form inner and outer-piston units,

means operatively connecting two crank pins on the crank shaft with each piston unit, enlarged cylinders surrounding the large diameter p'ortions of the step pistons and attached to and 5 communicating with the power cylinders, one or a restricted inlet passage communicating.- with the interior of the power cylindenand having ig- 65 nition means associated therewith.

17.- Apparatus of the class described comprising a crank shaft, a crank case surrounding the crank shaft, spaced, axially aligned power cylin ders communicating with the crank case, a piston mounted within the end portion of each power cylinder adjacent, the crank case, a step piston mounted within the opposite end portion of each power cylinder with its large-diameter portion disposed outwardly, means connecting thepistons .75

with crank pins on the crank shaft, scavenging pump cylinders surrounding the large-diameter portions of the step pistons attached to the power cylinders and communicating with the power cylinders and with the atmosphere, one 'or more passages communicating with the interior of the crank case and the interior of the scavenging pump cylinder surrounding the large-diameter portion of each step piston adjacent its point of attachment to the power cylinder with which it is associated, one or more passages communicating with the outer end portion of each scavenging pump cylinder and with the interior of the adjacent power cylinder, and means for delivering fuel to each power cylinder including a pre-combustion chamber having a restricted inlet pas sage communicating with the interior of the power cylinder and having ignition means associated therewith.

18. Apparatus of the class described comprising a crank shaft, a. crank case surrounding the crank shaft, spaced, axially aligned power cylinders communicating with the crank case, a piston mounted within the end portion of each power cylinder adjacentthe crank case, a step piston mounted within the opposite end portion of each power cylinder with its large-diameter portion disposed outwardly; means rigidly connecting the inner pistons and the step pistons to form inner and outer piston units, one or more connecting rods pivotally attached to each piston unit and to two or more crank pins on the crank shaft, scavenging pump cylinders surrounding the large-diameter portions of the step pistons attached tothe power cylinders and communicating'withthe power cylinders and with the atmosphere, one or more passages communicating with the interior of the crank case and the interior of the scavenging pump cylindersurrounding the large-diameter portion of each step piston adjacent its point of attachment to the power cylinder with which it is associated, one or more passages communicating with the outer end portion of each scavenging pumpfcylinder and withv the interior of the adjacent power cylinder, and means for delivering fuel to each power cylinder including a precombustion chamber having a restricted inlet passage communicating with the interior of the power cylinder and having ignition means associated therewith.

19. Apparatus of the class described comprising a four-throw crank shaft, a crankcase surrounding the crank shaft, spaced, axially aligned power cylinders communicating with the crank case, a piston mounted within the end portion of each power cylinder adjacent the crank case, a step piston mounted within the opposite end portion of each power cylinder with its largedianieter portion disposed outwardly, means rigidly connecting the inner pistonsand the step pistons to form inner and outer piston units, means operatively connecting two crank pins on the crank shaft with each piston unit, scavenging pump cylinders surrounding the largediameter portions of the step pistons attached to the power cylinders and communicating with the power cylinders and with the atmosphere, one or more passages communicating with the interior of the crank case and the interior of the scavenging pump cylinder surrounding the large-diameter portion of each step piston adjacent its point of attachment to the power cylinder with which it is associated, one or more passages communicating with the outer end portion of each scavenging pump cylinder and with the interior of the adjacent power cylinder, and means for delivering fuel to each power cylinder including a pre-combustion chamber having a restricted inlet passage communicating with the interior of the power cylinder and having ignition means associated therewith.

20. Apparatus of the class described comprising a crank shaft, a crank case surrounding the crank shaft, spaced, axially aligned power cylinders communicating with the crank case, a piston mounted within the end portion of each 'power cylinder adjacent the crank case, a step piston mounted within the opposite end portion of each power cylinder with its large-diameter portion disposed outwardly, means connecting the pistons with crank pins on the crank shaft, enlarged cylinders surrounding the large-diameter portions of the step pistons and attached to and communicating with the power cylinders, one or more passages communicating with the interior of the crankcase and the interior of the cylinder surrounding the large-diameter portion of each step piston adjacent its point of attachment to the power cylinder with which it is associated, and means for delivering fuel to each power cylinder including a source of supply of liquid fuel, a cylindrical atomizing chamber provided with tangentially arranged inlet and outlet passages, conduits. connecting the tangential inlet and outlet passages with the interiors of the power cylinders, and a conduit for introducing liquid fuel from the source of supply axially into the cylindrical atomizing chamber.

21. Apparatus of the class described comprising a crank shaft, a crank case surrounding the crank shaft, spaced, axially aligned power cylinders communicating with the crank case, a piston mounted within the end portion of each power cylinder adjacent the crank case, a step piston mounted within the opposite end portion of each power cylinder with its large-diameter portion disposed outwardly, means rigidly connecting the inner pistons and the step pistons to form inner and outer piston units, one or more connecting rods pivotally attached to each piston unit and to two or more crank pins on the crank shaft, enlarged cylinders surrounding "the large-diameter portions of the step pistons and attached to and communicating with the power cylinders, one or more passages communicating with the interior of the crank case and the interior of the cylinder surrounding the large-diameter portionof each step' piston adjacent its point of attachment to the power cylinder with which it is associated, and means for delivering fuel to each power cylinder including a source of supply of liquid fuel, a cylindrical atomizing chamber provided with tangentially arranged inlet and outletv passages, conduits connecting the tangential inlet and butlet passages with the interiors of the power cylinders, and a conduit for introducing liquid fuel from the source of supply axially into the cylindrical atomizing chamber.

22. Apparatus of the class described comprising a four-throw crank shaft, a crank case surrounding the crank shaft, spaced, axially aligned power cylinders communicating with the crank case, a piston mounted within the end portion of each power cylinder adjacent the crank case, a step piston mounted within the opposite end portion of each power cylinder with its large-cliameter portion disposed outwardly, means rigidly connecting the inner pistons and the step pistons to form inner and outer piston units, means operatively connecting two crank pins on thei V v crankshaft with each piston unit, enlarged cylinders surrounding the large-diameter portionsof the step pistons and attached to and communicating with the power cylinders, one or more passages communicating with the interior of the crank case and the interior of the cylinder surrounding the large-diameter portion of. each step piston adjacent its point of attachment to the power cylinder with which it is associated, and means for delivering fuel to each power cylinder including a source of supply of liquid fuel, a cylindrical atomizing chamber provided with tangentially arranged inlet and outlet passages, conduits connecting the tangential inlet and outlet passages with the interiors'of the power cylinders, and a conduit for introducing liquid fuel from the source of supply axially into the cylindrical atomizing chamber.

23. Apparatus of the class described compris- I ing a crank shaft a crank case surrounding the crank shaft, spaced, axially aligned power cylin-1 ders communicating with the crank case, a piston mounted within the end portion of each power cylinder adjacent the crank case, a step piston mounted within the opposite end portion of each power cylinder with its large-diameter portion disposed outwardly, means connecting the pistons with crank pins on the crank shaft, scavenging pump cylinders surrounding the large-diameter portions of the step pistons attached to the power cylinders and communicating with the power" cylinders and with the atmosphere, one or more passages communicating with the interior of the F crank case and, the interior of the scavenging pump cylinder surrounding the large-diameter portion of each step piston adjacent its point of attachment to the power cylinder with .which it is associated,'one or more passages communicating with the outer end portion'of each scav- 40 enging pump cylinder and with the interior of the adjacent power cylinder, and means for deizing chamber provided with tangentially ar- {i5 ranged inlet and outlet passages, conduits connecting the tangential inlet and outlet passages with the interiors of the power cylinders, and a conduit for introducing liquid fuel from the source of supply axially into the cylindrical 60 atomizing chamber.

24 Apparatus of the class described comprising a crank shaft, a crank case surrounding the crank shaft, spaced axially aligned power cylinders communicating with the crank case, a pis- 65 ton mounted within the end portion of each power cylinder adjacent the crank case, a steppiston mounted within the opposite end portion of each power cylinder with its large-diameter portion disposed outwardly, means rigidly connectt0 ing the inner pistons and the step pistons to form inner and outer piston units, one or more connecting rods pivotally attached to each piston unit and to two or more crank pins on the crank shaft, scavenging pump cylinders surrounding (15 the large-diameter portions of the step pistons attached to the power cylinders and communicating with the power cylinders and with the at- I mosphere one or more passages communicating with the interior of the crank case and the inte- 70 rior of the scavenging pump cylinder surrounding the large-diameter portion of each step-pis-- ton adjacent its point of attachment to the power cylinder with which it is associated, one or more passages communicating with the outer end por- 75 tion of each scavenging pump cylinder. and with the interior of the adjacent power cylinder, and means for delivering fuel to each power cylinder including a source of supply of liquid fuel, a cylindrical atomizing chamber provided with tangentially arranged inlet and outlet passages, conduits connecting the tangential inlet and outlet passages with the interiors of the power cyling a four-throw crank shaft, a crank case sur-' rounding the crank shaft, spaced, axially aligned power cylinders communicating with the crank case, a piston mounted within the end portion of each power cylinder adjacent the crank case,-

the crank shaftwith each piston unit, scavenging pump cylinders surrounding the large-diameter portions of the step pistons attached to the power cylinders and communicating with the power cylinders and with the atmosphere, one or .more passages communicating with the interior of the crank case and the interior of the scavenging pump cylinder surrounding the large-diameter portion of each 'step' piston adjacent its point of attachment to the power cylinder with.

delivering fuel to each power cylinder including a source of supply of liquid fuel, a cylindrical atomizing chamber provided with tangentially arranged inlet and outlet passages, conduits connecting the tangential inlet and outlet passages with the interiors of the power cylinders, and a conduit for introducing liquid fuel from,the-

source of supply axially into the cylindrical atomizing chamber.

26. Apparatus of the class described comprising a crank shaft, a crank case surrounding the crank shaft, spaced, axially aligned power cylinders communicating with the crank case, a

piston mounted within the end portion of each power cylinder adjacent the crank case, a step piston mounted within the opposite end portion of each power cylinder with its large-diameter portion disposed outwardly, means connecting the pistons witli crank. pins on the crank shaft, enlarged cylinders surrounding the large-diameter portions of the step pistons and attached to and communicating with the power cylinders, one or more passages communicating with ,the interior of the crank case and the interior of the cylinder surrounding the large-diameter portion of each step piston adjacent its point of attachment to the power cylinder with which it is associated, a pre-combustion chamber communicating with the interior of each powercylinder through a restricted passage, ignition means associated with each pre-combustion chamber, source of supply of liquid fuel, two cylindrical atomizing chamatomizing chamber with the interiors of the power cylinders, and means for introducing liquid fuel from the source of supply axially into the cylindrical atomizing chambers.

27. Apparatus of the class described compris ing a crank shaft, a crank case surrounding the crank shaft, spaced, axiallyaligned power cylinders communicating with the crank case, a piston mounted. within the end portion of each power cylinder adjacent the crank case, a step piston mounted within the opposite end portion of each power cylinder with its large-diameter portion disposed outwardly, means rigidly connecting the inner pistons and the step pistons to form inner and outer piston units, .one or more connecting rods pivotally attached to each piston unit and to two or more crank pins on the crank shaft, enlarged cylinders surrounding the large-diameter portions of the step pistons and attached to and communicating with the power cylinders, one or more passages communicating with the interior of the crank case and the interior of the cylinder surrounding the largediameter portion of each step piston adjacent its point of attachment to the power cylinder with which it is associated, a pre-combustion chamber communicating with the interior of each power cylinder through a restricted passage, ignition means associated with each precombustion chamber, source of supply of liquid fuel, two cylindrical atomizing chambers provided with tangentially arranged inlet and outlet passages, conduits connecting the tangential inlet and outlet passages of one atomizing chamber with the interiors of the pre-combustion chambers, conduits connecting the tangential inlet and outlet passages of the other atomizing chamber with the interiors of the power cylinders, and means for introducing liquid fuel from the source of supply axially into the cylindrical atomizing chambers.

28. Apparatus of the class described comprising a four-throw crank shaft, a crank case surrounding the crank shaft, spaced, axially aligned power cylinders communicating with the crank case, a piston mounted within the end portion of each power cylinder adjacent the crank case, a step piston mounted within the opposite end portion of each power cylinder with its largediameter portion disposed outwardly, means rigidly connecting-the inner pistons and the step pistons to form inner and..outer piston units, means operatively connecting two crank pins on the crank shaft with each piston unit, enlarged cylinders surrounding the large-diameter portions of the step pistons and attached to and communicating with the power cylinders, one or more passages communicating with the interior of the crank case and the interior of the cylinder surrounding the large-diameter portion of each step piston adjacent its point of attachment to I the power cylinder with which it is associated, a

pre-combustion chamber communicating with the interior of each power cylinder through a restricted passage, ignition means associated with each pre-combustion chamber, source of supply of liquid fuel, twocylindrical atomizing chambers provided with tangentially arranged inlet and outlet passages, conduits connecting the tangential inlet and outlet passagesof one atomizing chamber with the interiors of the pre-combustion chambers, conduits connecting the tangential inlet and outlet passages of the other atomizing chamber with the interiors of the power cylinders, and means for introdu g quid fuel from the source of supply axially into the cylindrical atomizing chambers.

29. Apparatus of the class described comprising a crank shaft, a crank case surrounding the crank shaft, spaced, axially aligned power cylinders communicating with the crank case, a

piston mounted within the end portion of each power cylinder adjacent the crank case, a step piston mounted within the opposite end portion of each power cylinder with its large-diameter portion disposed outwardly, means connecting the pistons with crank pins on the crank shaft,

' scavenging pump cylinders surrounding the largediameter portions of the step pistons attached to the power cylinders and communicating with the power cylinders and with the atmosphere,

one or more passages communicating with the interior of the crank case and the interior of the scavenging pump cylinder surrounding the largediameter portion of each step piston adjacent its point of attachment to the power cylinder with which it is associated, one or more passages communicating with the outer end portion of each scavenging pump cylinder and with the interior of the adjacent power cylinder, a pre-combustion chamber communicating with the interior of each power cylinder through a restricted passage, ignition means associated withveach precombustion chamber, source of supply of liquid fuel, two cylindrical atomizing chambers propower" cylinder adjacent the crank case, a step, piston mounted withinthe opposite end portion.

of each power cylinder with its large-diameter portion disposed outwardly, means rigidly connecting the inner pistons and the step pistons to form inner and outer piston units, one or more connecting rods pivotally attached to each piston unit and to two or more crank pins on the crank interiors of the pre-combustion' shaft, scavenging pump cylinders surrounding the large-diameter portions of the step pistons attached to the power cylinders and communicating with the power cylinders and with the atmosphere, one or more passages communicating with the interior of the crank case and the interior of the scavenging pump cylinder surrounding the large-diameter portion of each step piston adjacent its point of attachment to the power cylinder with which it is associated, one or more passages communicating with the outer end portion of each scavenging pump cylinder and with the interior of the adjacent power cylinder, a pre-combustion chamber communicating with the interior of each power cylinder through a restricted passage, ignition means associated with each pre-combustion chamber, source ,of supply of liquid fuel, two cylindrical atomizing chambers provided with tangentially arranged inlet and outlet passages, conduits connecting the tangential inlet and outlet passages of one atomizing chamber with the interiors of the pre-combustion chambers, conduits connecting the. tangential in-. let and outlet passages of the other atomizing chamber with the interiors of the power cylinders,

' and means for introducing liquid fuel from the source of supply axially into the cylindrical atomizing chambers.

31. Apparatus'of the class described comprising a four throw crank shaft, a crank case surrounding the crank shaft, spaced, axially aligned power cylinders communicating with the crank case, a piston mounted within the end portion of each power cylinder adjacent the crank case, a step piston mounted within the opposite end portion of each power cylinder with itslargediameter portion disposed outwardly, means rigidly connecting therinner pistons'and the step pistons to form inner and outer piston units,

means operatively connecting two crank pins on the crank shaft with each piston unit, scavenging pump cylinders surroundingthe large-diameter portions of the step pistons attached to the power cylinders and communicating with the power cylinders and with the atmosphere, one or more passages communicating with the interior of the crank case and the interior of the scavenging pump cylinder surrounding the large-diameter ,portion of each step piston adjacent its point of means associated with each pre-combustion chamber, source ,of. supply of .liquid fuel, two cylindrical-atomizing chambers provided with tangentiallyarranged inlet and outlet passages, conduits connecting "the tangential inlet and outlet passagesbf. one atomizing chamber with the interiors of the pre-combustion hamber's, conduits connecting the tangential inlet and outlet passages of the other atomizing chamber with the interiors of the power cylinders, .and means for introducing liquid fuel from the source of supply v axially into the cylindrical atomizing chambers.

32. An atomizing device for liquid fuels com-v, prising a cylindrical atomizing chamber having a circumferentially grooved inner-surface and provided with tangentially arranged inlet and outlet passages. x

33. An atomizing device for liquid fuels comprising a cylindrical atomizing chamber having a circuniferentially grooved inner surface and provided with tangentially-arrangedinlet and outlet passages, and means for introducing liquid fuel axially into the atomizing chamber.

34. An atomizing device for liquid fuels comprising a cylindrical atomizing chamber provided withangularly arranged tangential inlet and outlet passages communicating with the interior of the chamber through a common opening in a wall thereof. U h

35. An atomizing device for liquid fuels comprising a cylindrical atomizing chamber provided with angularly arranged tangential inlet and outlet passages communicating with the interior of the chamber through a common opening in a wall thereof, and means for introducing liquid fuel axially into the atomizing chamber.

3d. In the operation of an engine provided with a crank shaft, a crank case, a power cylinder, a step piston mounted for reciprocating movement within the portion of the power, cylinder remote from the crank shaft and operatively connected to a crank pin on the crank shaft, and a scavenging pump cylinder surrounding the large diameter portion of the step piston and provided with an air outlet port in one end portion thereof, theimprovement which comprises circulating high velocity currents of oil-laden crank case atmosphere between the crankcase and the end portion of the scavenging 'pumpcylinder opposite the end portion in which the air outlet port is located, thereby to lubricate the rubbing surfaces of the step piston without mixing the lubricating oil with the scavenging air.

37. The combination with a multiple cylinder internal combustion engine of a pre-combustion chamber-communicating with the interior of a cylinder through a restricted passage, ignition means associated with the pre-combustion chamber, a source of fuel, and conduits connecting the source of fuel with the pre-combustion chamber and with another cylinder to permit the use of combustion (gases from said cylinder for in;

jecting fuel directly into the pre-combustion chamber. 1

38. The combination with a'two cylinder internal combustion engine of a pre-combustion chamber associated with each cylinder and communicating with the interior thereof through a restrictedpassage, ignition means associated with each pre-combustion chamber, a source of fuel, and a conduit connecting the source of fuel with each pre-combustion chamber to permit the use of combustion gases from each cylinder for injecting fuel directly into the! pre-combustion chamber associated with the other cylinder 39. The combination with a two cylinder internal combustion engine of a pre-combustion chamber associated with each cylinder and communicating with the interior thereof through a restricted passage, ignition means associated with each pre-combustion chamber, a source of liquid fuel, an atomizer, means connecting the source, of liquid fuel with the atomizer, and a conduit connecting the atomizer with each pre-combustion chamber to permit the use of combustion gases from each cylinder for atomizing the liquid fuel and injecting the atomized fuel directly into the' -pre-combustion chamber associated with the other chamber associated with each cylinder and communicating with the interior thereof through a restricted passage, ignition means associated with each pre-combustion chamber, a source of liquid fuel, a cylindrical atomizing chamber provided with tangentially arranged inlet and outlet passages, means connecting the source ofliquid fuel with the atomizing chamber, and a conduit connecting a tangential passage with each pre-combustion chamber to permit the use of combustiongases from each cylinder 'for atomizing the liquid fuel and injecting the atomized fuel into the precofnbustionchamber associated with the other cylinder.

41. The combination with a two cylinder internal combustion engine of a pre-combustion chamber associated with each cylinder and communicating with the interior thereof through a restricted passage, ignition means associated with each pre-combustion chamber, a cylindrical atomizing chamber provided with tangentially arranged inlet and outlet passages, means for introducing liquid fuel axially into the atomizing chamber, and a conduit connecting a tangential

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