US2001533A

US2001533A - Internal combustion engine

Info

Publication number: US2001533A
Application number: US379772A
Authority: US
Inventors: Herbert W Houston
Original assignee: Individual
Current assignee: Individual
Priority date: 1929-07-20
Filing date: 1929-07-20
Publication date: 1935-05-14
Anticipated expiration: 1952-05-14

Description

May 14, 1935. H. W'N I- iOUSTON- fi fi INTERNAL COMBUSTI ON ENGINE Filed July 20, 1929 4 Sheets-Sheet l 4 r row/ 5 K May 14, 1935. H. w. HOUSTON INTERNAL COMBUSTION ENGINE Filed July 20, 1929 4 Sheets-Sheet 2 R m mm &

al'ili B0 M9 v o o w ning-g v Q m K Ou I'- m r M A H a Q 0 May 14, 1935. H. w. HOUSTON INTERNAL COMBUSTION ENGINE mamas I Filed July 20, 1929 Sheets-Sheet 3 May 14,1935,

H. W. HOUSTON 20015533 INTERNAL COMBUSTION ENGINE Flled July 20, 1929 4 Sheets-Sheet 4 /4a #6 /52 A50 I 7 4m) .6. 2 OH T 1 NW f v r Z o we Patented May 14, i935 UNITED STATES PATENT OFFICE INTERNAL COMBUSTION ENGINE Herbert W. Houston, North Hollywood, Calif. Application July 20, 1929, Serial No. 319,772 15 Claims. (01. lea-58) My invention relates to internal-combustion engines and in particular to a cam engine which finds special utility in the field of air transportation. My invention is particularly adapted to two-cycle engines and in this connection will be explained in the ensuing description, but it should be understood that certain features of my invention are adapted to other types of engines.

It is an object of my invention to provide a twocycle engine which is more efficient than certain present engines, thus adapting it ,to aircraft use. I prefer to accomplish this object by providing atwo-cycle engine in which the scavenging of the spent gases from the cylinders is more efiicient, thus increasing the overall efilciency.

One way in which the scavenging of the spent gases may be made more eflicient is by holding the piston in a retracted position for a greater length of time thus allowing the fresh air to more completely expel the spent gases from the cylinder.

It is another object of my invention to provide a two-cycle engine which is operable by a cam-operating means in which the shape of the cam may be designed so that the piston is held in a retracted position for a material length of time whereby better scavenging of the burned gases is secured.

Another way in which a better scavenging action may be secured is by introducing into the cylinder, air which has been highly compressed, thus more completely blowing out the spent gases in the cylinder.

It is a further object of my invention to provide a two-cycle engine of the above type which employs a novel method of compressing air on the retracted stroke of the piston so as to secure a better scavenging action.

It is another object of my invention to provide a novel method of securing for the air to be compressed an initial pressure which is'slightly above atmospheric, thus securing a supercharging effect.

My invention also relates to Diesel engines. Diesel engines are ordinarily operated by compressing a quantity of air in a cylinder to a high pressure and a high temperature, and introducing a charge of fuel into the compressed air, the fuel being ignited by contact with the high temperature of the air and burning to provide a high pressure of gases in the. cylinder which in expanding moves a piston in the cylinder and provides the power. The speed of ordinary Diesel engines is limited due-to the fact that the fuel used is relatively slow-burning and the pressure and the temperature. in the cylinder during expansion must be maintained at sufiiciently high values to support combustion of the fuel. This means that the piston must not be retracted in the cylinder at such a rate that the burning gases are cooled sufliciently to stop combustion.

It is also an object of my invention to provide a Diesel engine in which the shaft speed thereof may be greatly increased without retracting the piston in the cylinder at such a rate as to stop combustion of the fuel.

It is also an object of my-invention to provide an engine in which the duration of the expansion stroke is relatively long as compared to the other strokes of the cycle.

It is another object of my invention to provide a. two-cycle Diesel cam engine with increased speed and efficiency.

It is also an object of my invention to provide a novel injector for injecting fuel into an engine so as to mix the fuel with the air in the cylinder as the fuel is injected.

It is also an object of my invention to provide a novel type of fuel pump for an engine which may be adjusted to pump a definite charge of fuel into the cylinder. 25

Further objects of my invention reside in the particular details of construction as will be explained in the ensuing description.

In the attached drawings I have illustrated a preferred form of my invention, but it should.v be understood that I am not limited to the form shown therein. In the drawings:

Fig. 1 is an end view of a portion of my invention showing the arrangement of the parts, certain of the parts being in section. 35

Fig. 2 is a partial sectional view taken on the line 2-2 of Fig. 1, showing a side elevation of my device.

Fig. 3 is a sectional view taken as indicated by the line 3-4 of Fig. 2 showing a fuel pump of my invention.

Fig. 4 is a section taken on the line 4-4 of Fig. 3.

Fig. 5 is a fragmentary view of a fuel injector shown in Fig. 2. 45

Fig. 6 is an alternative form of fuel injector.

Fig. 7 is a development of the fuel pump assembly and its associated cams.

Fig. 8 is a development of the main cam showing the positions of the pistons.

Fig. 9 represents indicator diagrams illustrating the operation of my engine as compared with other types of engines. I

In the present applicationI have shown certain features of construction that are shown and ex- 55 device (not shown).

plained in detail in my co-pending application entitled Variable stroke cam engine, Serial No. 320,579, filed November 20, 1928, Patent No. 1,810,- 017 issued June 16, 1931. For a complete detailed explanation of these features, reference should be had to the application supra.

Referring to Fig. 2, my engine consists of a supporting structure indicated by the numeral I, which consists of a circular rear crank case member I2 and a forward web structure I3 which are held in spaced relationship by studs or cross-head guides l4. Formed in the forward web structure I3 is a plurality of openings IS, the openings I5 being grouped around the center ofthe web struc-- ture I3 and positioned between and in alternate relationship with the several cross-head guides I4. Adjacent the forward web structure l3 and extending in the direction of the rear crank case member I2 is a cylindrical member I6 which has cupped portions II that are received by the openings I5, the member I6 being secured to the web structure I3 by attaching bolts 2| which pass through the web structure I3 and into flanges 20 around the cupped portions ll. Secured to the cylindrical member I6 and to the rear crank case member I2 is a perimetric dust plate 24 which excludes dust from the interior of the crank case thus formed and retains lubrication therein.

A sleeve 25 extends rearwardly from the center of the forward web structure I3 and is provided with a central bore 26 which is axially parallel with the cross-head guides I4. In the" forward end of the sleeve 25 is a counterbore 21 which receives the outer race of a bearing 28. In axial alignment with the bore 26 is a bore 30 in the rear crank case member I2, which bore 30 receives the outer race of a bearing 3|.

Joumaled by the inner races of the bearings 28 and 3| is a main shaft 32, the forward end of which extends outside the engine and may be connected to a propeller. or other power-taking Around the shaft 32 to the rear of the sleeve 25 is a thrust bearing 34, a forward race of which contacts the rear end of the sleeve 25, and a rear race of which contacts a hub 35 of a drive cam 36, the hub 35 being rigidly keyed to the shaft 32 and being clamped in position by a nut 31 which is threaded on the shaft 32. The cam 36 has cam faces 36 which are shaped in a manner to be hereinafter described and is provided withan annular rearward projecting skirt 39. Positioned between the projecting skirt 39 and the rear crank case member I2 is a double thrust bearing 39a, the bearing 39a having a double race so as to reduce the ball speed thereof in a manner described in my application supra.

Secured to the forward web structure I3 in abutting relationship with one of the cupped portions I1 is a cylinder member 40 which is separated only by a gasket 4| fromthe cupped portion and cooperates therewith to form a continuous cylinder 42 which is closed at the forward end by a cylinder head 43 and at the rear end by a wall 44 formed at the rear of each of the cupped portions H. The cylinder member 46 is provided with a flange 46 through which the bolts 2| are passed for securing the cylinder member 40 to the forward web structure I3 and for clamping the gasket 4| between the abutting edges of each of. the cupped portions l1 and the cylinder members 40. A piston 50 is slidable in the cylinder 42 to a forward or advanced position and to a rear or retracted position and divides the cylinder 42 into a forward power-producing chamber 5|,and a rear air compression chamber 52. Intake passages 53 are formed through the walls of the cylindrical member I6 and communicate between the compression chamber'52 and a chamber 54 I by an intake valve disc 63 which rests there-,

against by the action of a spring 64 to form an intake valve.

When my motor is used with a propeller, the mouth 60 of the horn 56 is in the air stream -of the propeller which is attached at the forward end of the shaft 42 so that the air-compression chamber 52 receives air through the intake valve at a pressure slightly greater than atmospheric. The air thus received into the compression chamber 52 is adapted to be compressed therein by the piston 50 as the piston 50 moves from an advanced to a retracted position. When the piston 50 is retracted so that the top of the piston uncovers a mouth 61 of a by-pass port 66 the compressed air is discharged through this port. This allows the compressed gas to pass from the compression chamber 52 to the power-producing chamber through an exhaust port 10 formed through the walls of the cylinder member 40 opposite the mouth 61 of the by-pass port 66. The'piston 50 provides extending legs 1| which always close the mouth 61 of the by-pass port 66 and the exhaust port Ill except when the piston 50 is man extreme retracted position, the legs II being of such length that they do not prevent entrance of the air from the compression chamber 52 to the-by-pass port 66 when the piston 50 is in a retracted position. This permits communication between the compression chamber 52 and'the power-producing chamber 5| when the piston 50 is in a fully retracted position. I

I have described only one of my cylinder assemblies, but have shown my engine as having six such assemblies, it being understod that more or fewer may be used as desired. I

The piston 50 is moved into the retracted and advanced positions by a piston rod 12 which is threadedly attached to the piston 50 and extends rearwardly through a central opening I3inasleeve I4 which is formed on the wall 44 and projects forwardly into the cylinder 42. Packing I6 is provided between the walls of the opening 13 and the piston rod 12 so' as to form a hermetically tight joint therebetween. The rearward end of the piston rod I2 is provided with cross-head arms (not shown) which slidably contact the cross-head guides I4 and are guided thereby. Inner;,races of bearings 18 and 19 are carried by pins 8|! and 8| formed on the rearward .endof co-pending application supra.-

-.. It should be noted that I positionthe openings I5 in the forward web structure I3 so that sumfor each of the cylinders 42 and to operate the fuel pump once for every revolution of the shaft 32 so as to. inject fuel into the cylinder 42 at the correct time. However, it should be understood that I am not confined to this arrangement as it is possible to provide only one fuel pump and have this fuel pump operated so as to inject fuel into each of the cylinders at the proper time. Where a fuel pump is provided for each of the cylinders as is shown in the attached drawings, I provide a forwardly projecting cylinder 85 which is formed on the forward web structure I3 and which threadedly supports an adjusting nut 86, the adjusting nut 86 being rotatable on a cylindrical body Bl between a rear shoulder 88 and a forward attaching nut 89. The cylindrical body 81 surrounds the shaft 32 and is keyed to the sleeve 85 as indicated by the'numeral 99, so that as the adjusting nut 86 is turned, a relative motion occurs between the adjusting nut 86 and the body 81, and the body 81 is moved along the shaft 32.

In the body 87 are the fuel pumps 84 of my invention, each of which consists of a hole bored through the body 81 between the cylinder member 49 and the shaft 32 and providing. a cylinder 92 in which is slidable a piston 93 which provides a pumping chamber 94 in the cylinder 92 forward of the piston 93. The rear end of the piston 93 extends through a counterbore 95 and a fluidtight joint is formed therebetween by a packing member 96 which is retained in place by a nut 91 threaded in the counterbore 95. A spring 98 is compressed between the nut 91 and a collar I99 formed on the rear end of the piston 93 and normally tends to move the piston 93 in a rearward direction, the piston 93 being retained in the cylinder '92 by a retaining nut I9I threaded in the counterbore 95.

Secured to the shaft 32 to the rear of the body 81 is a cam plate I92 having a fuel pump cam I93 which has a single hump and which engages a roller I94 on the rear end of the piston 93 so as to move the piston 93 forwardly and backwardly once for each revolution of the shaft 32. As the piston 93 is moved rearwardly in the cylinder 92, a charge of fuel is drawn into the pumping chamber 94 from a fuel tank (not shown) through an inlet pipe I96 in which is a check valve I 91. As the piston 93 is moved forwardly, the fuel in the pumping chamber 94 is forced outwardly through a discharge outlet, and outlet pipe I98,,,pasta check valve I99, and is injected into the powerproducing chamber 5| through an injector H9. The fuel continues to be injected into the powerproducing chamber 5| until communication is established between the pumping chamber 94 and the fuel tank through a by-pass opening I I2 which permits the fuel in the pumping chamber 94 to return to the fuel tank instead of being forcedin a valve seat formed by a counterbore I I! in the body 81. i

Threaded in the counterbore H1 is a nut H8 .containing a spring H9 which normally forces a pin I29 into contact with the valve head H6 so as to normally maintain the valve I I3 in a seated position. The valve H3 is operated by a valve cam I22 formed on the cam plate I92 which engages a roller I23 on the rear end of the piston rod I I5 so as to open and close the valve H3. When the valve H3 is opened, communication is established between a chamber I24 formed in the counterbore H1 between the valve head H6 and the nut H8, and a chamber I25 formed by the walls of the guide-opening H4, and an annular groove I26 formed on the valve rod H5 to the rear of the valve head H6. The chamber I24 is in communication with the by-pass opening H2 so that when the valve H3 is opened fuel may pass from the fuel pump, through the by-pass opening H2, to the chamber I24 past the valve H3, into the chamber I25, and out through the outlet opening I21 which communicates between the chamber I25 and the fuel tank.

It should be noted that by turning the adjusting nut 86 so as to move the body 8'! in a forward direction the roller I23 on the by-pass valve H3 is contacted by the valve cam I22 at a later time which means that fuel is injected into the cylinder 42 by the fuel pump for a greater length of time. As the adjusting nut 86 is turned so that the body 81 is moved in a rearward direction the roller I23 contacts the valve cam I22 at an earlier time which causes fuel to be injected into the cylinder 42 for a shorter period of time and a smaller charge. is thus injected into the cylinder 42. The adjusting nut 86 thus provides a means for adjusting both the duration of injecting fuel 7 into the cylinder 42 and the amount of fuel injected therein.

It will be noted by referring to Fig. '7 that I proportion the size of the parts of my pump and by-pass valve so that the roller I94 on the pump is always in contact with the cam I93 even when the body 81 is moved to its extreme forward position, while the roller I 23 on the by-pass valve does not contact the cam I22 except when'operated thereby. This provides for changing the opening of the by-pass valve so as to pump to the cylinder 42 a smaller charge of fuel when the body 81 is moved forward and a greater charge of fuel when the body 81 is moved backward.

The fuel which is pumped by the fuel pumps 84 is injected through the injector H9 as explained before. In order to thoroughly mix the fuel which is injected into the cylinder with theair which is in the cylinder and thus provide better combustion, I provide a novel type of injector which is shown in enlarged form in Fig. 5. The injector H9 consists of an injector body I28 which is threaded in a flanged nut I 29 threadedly inserted in the cylinder head 43. The outlet pipe I98 of the fuel pump communicates with an opening I39 in the flanged nut I 29 and the discharge end of the opening I39 is formed into a nozzle I3I which nozzle I3I directs the fuel through a restricted throat I32 of an opening I33 formed in the body I28. Surrounding the opening I33 and parallel therewith is a plurality of air openings I34 which admit air to a central opening I35 around the nozzle I 3| so that air is drawn through the throat I 32 as the fuel is injected therethrough, which intimately mixes the air and the fuel.

I prefer to provide the forward end of the piston 5|! with a conical projection I36 positioned opposite the opening I32 so that as the mixture of air and fuel is injected into the cylinder 42 the mixture will be deflected by the conical projection I 36 and directed toward the walls of the, cylinder 42 so as to distribute the mixture evenly therein.

In the operation of my engine, the cam 36 moves the piston 50 from a retracted position to an advanced position which causes air to be drawn into the compression space'52 through the intake valve, the air being drawn in at a pressure slightly above atmospheric, as heretofore explained. As the piston 5|) is moved from an advanced position to a retracted position the air in the compression space 52 is compressed, and when the mouth of the port 61 is uncovered the air in the compression space 52 is forced out through the by-pass port 66 to the power-producing chamber 5| and exerts a scavenging action on any spent gases therein. As the piston 50 is again moved from a retracted to an advanced position the air in the power-producing chamber 5| is compressed and at the correct time, determined by the timing of the engine, fuel pumped by the fuel-pump 84 is injected through the injector I III into the powerproducing chamber 5|. The fuel is ignited by contact with the high temperature of the air in the power-producing chamber 5| and burns to produce a greater gas pressure therein, which pressure forces the piston 50 from an advanced position to a retracted position to permit expansion of the gases. I

Each time the piston 50 is moved from a retracted to an advanced position to define a compression stroke, air is drawn into the compression chamber 52 and the air in the power-producing chamber 5| is compressed, and each time that the piston is moved from an advanced position to a retracted position to define an expansion stroke, air is compressed in the, compression chamber 52 and expansion of the gases in the chamber 5| occurs. While the piston is in a retracted position the air which has been compressed in the compression chamber 52 exerts a scavenging action and exhausts the spent gases from the power-producing chamber 5|. This is a well known cycle of operation for a two-cycle engine.

As yet I have not desqribed the paricular contour of the cam surface 38 which moves the piston 50 in order to define the above strokes, but before describing this contour'it is advisable to point out some of the limitations of the present crank type engines. All intemal-combustion engines in which a piston is reciprocated by a crank on a crank shaft are limited to a piston motion in which the piston has a compression and an expansion stroke of the same duration. This limits the shaft speed of 9. Diesel engine to a speed determined by the maximum speed at which the piston may be retracted in the cylinder, as explained before, it being necessary to with-.

" draw the'piston in the cylinder at a sufiiciently slow rate of speed that the pressure in the cylinder will not be decreased sufficiently to cool the burning gases therein below the combustion point.

In a crank type engine of the two-cycle type, the piston is retained in the retracted position for a very short period of time due to the substantially harmonic motion of the piston andthus incomplete scavenging of the gases in the cylinder results.

In a cam engine of the type described above, the cam may be so designed as to give to the piston any required movement. Thus it is possible to design the cam so that the piston will be moved with a relatively quick compression stroke, a slow power stroke, and may be left in the retracted position for a sumcient length of time to secure a greater efilciency in scavenging the gases.

In Fig. 8 I have illustrated the development of a cam which is designed to impart to a piston a movement as defined above. In this figure I represent the bearings I9 by circles I40 and the bearings 18 by circles I. The bearings 19 and I8 are shown by the circles I40 and I4I as moved to a plurality of .equally spaced positions I42, I43, I44, I45, I46 and I41. The contours of the forward and rear surfaces 38 of the cam 36 which engage the bearings 19 and I8 are represented by the lines I50 and I5I.

When the bearings "I3 and 18 are in a position I42 represented by circles I40 and I, the piston 50 is in the extremely retracted position, and as the bearings 19 and I8 move through the successive positions the piston is moved to an extremely advanced position which position is shown as being between positions I44 and I45 and re-.

turned to a retracted position to define a complete cycle. 7

As the piston '50 is directly connected by the piston rod 12 to the bearings I5 and I8, the

motion of the bearings 19 and I8 is directly trans mitted to the piston and the motion of the piston,

is therefore the same as the motion of these bearings. I have accordingly drawn a line I52 through the centers of the circles I40 in the various positions and this line I52 can therefore be considered as being indicative of the movement of the piston 50, and the piston 50 will therefore be referred to as having a motion corresponding to this line. When the piston 50 is moved from the position I42 and reaches a position indicated by a position I54, intermediate the positions I42 and I43, the top of the piston 50 covers the mouth 61 of the by-pass port 66 and the compression stroke begins. The compression stroke continues during approximately of rotation of the shaft 32 oruntil a position I55 is reached which is intermediate the positions I43 and I44. At this time fuel is introduced into the cylinder in a manner previously explained and the power of the expansion stroke commences. The expansion stroke continues during 170 and through positions |44, I45 and I46 until a position I56 is reached which is intermediate positions I46 and I41, at which position the forward end of the piston 50 uncovers the mouth 61 of the by-pass port 66 and the air which has been compressed in the compression chamber 52 is by-passed into the power-producing chamber 5| and theexhaust interval commences, this interval ending when the piston again closes the mouth 61.

I design the cam 36 so that the piston is held in a retracted position between the positions I56 and I54 for of rotation of the shaft 32 which is for the purpose of more completely scavenging the gases from the cylinder. It will thus be seen that a complete cycle of operation for the piston is accomplished for every revolution of the shaft 32. The set of operating conditions outlined above provides a cam having a contour as indicated in Fig. 8. Another set of operating condi-' required set of operating conditions, it being only necessary to-ascertain what operating conditions Various other contours may be given to the cam so as to. secure any are wanted and design the cam to give the required movement to the piston 50.

In Fig. 9 I have illustrated some indicator diagrams suchas could be obtained with different cams, these diagrams being compared with indicator diagrams of various other types of engines. Diagrams A and B are diagrams such as can be obtained by a cam engine of my design having different shapes of cams. Diagram C is an indicator diagram of another type of Diesel engine, diagram D is taken from a conventional gasoline engine, and diagram E from a conventional steam engine.

It is a well known fact that the area enclosed by the lines of an indicator diagram is representative of the power which is provided by the combustion of the gases in the cylinder. The amount of power available at the shaft of the engine being determined by the mechanical efliciency of the engine, those engines of equal mechanical efliciency provide the greatest shaft horse-power which have the greatest area enclosed by the lines of the indicator diagram.

It will be noted from a study of the diagrams shown in Fig. 9 that the lengthening out of the time for the expansion stroke is of considerable advantage-in providing a much larger area in an indicator diagram. Another advantage of having a long power stroke is that with the same shaft speed of Diesel engine, a cam type engine having a long power or expansion stroke is able to use a cheaper and longer burning oil than a conventional engine of the crank type having a uniform time for the compression and expansion strokes.

It will be noted that the placing of the mouth of the intake valve in the air stream of the propeller provides an initial pressure on the air in the air-compression chamber, and the provision of a smaller space in which the air is compressed during the expansion stroke provides a much higher pressure for the air and this 'air is therefore better able to scavenge the gasesfrom the cylinder.

The use of the deflector wall68 is efiective in distributing the incoming air toward the top of the cylinder 42 so as to better scavenge the gases therefrom and the maintaining of the piston 50 in a retracted position for a longer period of time provides a better scavenging action for the gases. The use of the injector I III of my invention is responsible for a more complete mixture of the fuel with .the air in the cylinder 42 which secures more complete combustion of the gases.

Although I haveexplained and illustrated the pump of my invention as being used to pump fuel to the cylinder, I am not limited to this use as my pump has utility in other ways. For example, my pump is also useful in pumping lubricating oil to the moving parts of the engine and in other capacities.

In Fig. 6 I have shown an alternative form of injector which operates on the same principle as the form shown in Fig. 5 but which has certain advantages with different fuels. In the form of the injector shown in Fig. 6 a. nozzle I6!) is formed on the flanged nut I29 which is similar to the nozzle I3I with the exception that the nozzle I60 extends a short distance into the cylinder 42. An injector body I6I is threaded into the flanged nut I29 and is provided with an opening I62 in alignment with the opening through the nozzle I60 and which has a throat I63. Air openings I64 through the injector body I6I permit air to enter to a central opening I65 in the insuch contour on the head of the piston 50 being particularly advantageous with the alternative form of my injector.

It should be clear that certain features of my invention are not limited to the particular form of two-cycle Diesel engine which I have explained in this description but may be applied to various other engines. If it is desired to make a gasoline engine in place of 2. Diesel engine, the

main shaft 32 may be made hollow and the combustible gases taken into the engine through the hollow shaft. A jacket surrounding openings in the shaft and communicating with the air-compression chamber permits introduction of the combustible gases into the cylinder 42. A similar arrangement is explained in my co-pending application' supra. This and other modifications can be made without departing from the spirit of my invention as defined by the appended claims.

I claim as my invention:

1. In an engine, the combinationof: a main shaft, walls defining a cylinder axially parallel with said shaft; a piston slidable in said cylinder to an advanced position and to a retracted position; and means for controlling the movement of said piston, said means moving said piston from a retracted position to an advanced position to define a compression stroke, moving said piston from an advanced position to a retracted position to define an expansion stroke, and holding said piston in a retracted position to define an exhausting interval, said expansion stroke occurring during a longer interval of time than said compression stroke, and said exhausting interval being of approximately equal duration to said compression cycle.

2. In an engine, the combination of: a main shaft, a cylinder mounted with its longitudinal axis parallel with said shaft; a piston slidable in said cylinder and adapted to be reciprocated therein with a power and a compression stroke;

' and means for controlling the movement of said piston and for holding said piston stationary during a substantial portion of the operating cycle to provide a prolonged exhaust interval.

3. In an engine, the combination of: a main shaft, a cylinder mounted with its longitudinal axis parallel with said shaft; a piston slidable in said cylinder through successive compression and power strokes; and means for controlling the movement of said piston and for positively holding said piston stationary for a substantial length of time between the end of a power stroke and the beginning of a succeeding compression stroke to provide a prolonged exhaust interval.

4.. In a cam-engine, the combination of a main shaft, a cylinder mounted with its longitudinal tively hold said piston stationary at the end of a power stroke thereof and during a substantial portion of the operating cycle to provide a prolonged exhaust interval.

' 6. In a cam-engine, the combination of: a main shaft, a cylinder mounted with its longitudinal axis parallel with said shaft; a piston slidable in said cylinder through successivepower and compression strokes; and a cam on said shaft and.

connected with said piston for controlling the movement of said piston, said cam having a dwell extending throughout a sufflcient portion of the cam cycle to hold said piston stationary for a substantial length of time between the end of a power stroke and the beginning of a succeeding compression stroke to provide a prolonged exhaust interval. v h

7. In a cam-engine, the combination of: a main shaft, a cylinder mounted with its longitudinal axis parallel with said shaft; a piston slidable in said cylinder; and a cam for controlling the movement of said piston, said cam having a power portion cooperating with said piston during an expansion stroke thereof; a compression portion for moving said piston through a compression stroke, and an intermediate exhaust portion having a dwell extending throughoutv a suflicient portion of the cam cycle to hold said piston stationary a substantial length of time between the end of an expansion stroke and the beginning of a compression stroke to provide a prolonged exhaust period.

8. A cam-engine as defined in claim '7 in which the compression portion of said cam extends throughout a sufllcient portion of the cam cycle to provide a relatively quick compression stroke of the piston and in which the expansion portion of said cam extends throughout a sufficient portion of the cam cycle to provide a relatively slow expansion stroke of said piston.

9. A cam-engine as defined in claim '7 in which the extent of the expansion portion of the cam in the cam cycle is approximately twice that of the compression portion of said cam.

, 10. A cam-engine as defined in claim 7 in which the extent of the exhaust portion of the cam in in the cam cycle is approximately equal to that of the compression portion of said cam.

11. In a two-cycle internal-combustion engine, the combination of: a main shaft, a cylinder axially parallel with said shaft and having an exhaust port and an intake port; a piston slidable in said cylinder through successive compression and power strokes and adapted to open said ports at the end of a power stroke and to close said ports at the beginning of a succeeding compression stroke; and means including an operative connection between said piston and said shaft, for controlling the movement of said piston and for positively holding said piston stationary for a substantial length of time between the end of said power stroke and the beginning of the succeeding compression stroke and while said ports are open so as to provide a prolonged scavenging interval.

12. In a two-cycle internal-combustion camengine, the combination of: a main shaft, a cylinder axially parallel with said shaft and having an exhaust port and an intake port; a piston slidablein said cylinder; and a cam for controlling the movement of saidpiston, said cam having a dwell extending throughout a sufficient portion of the cam cycle to hold said piston stationary while said ports are open and during a substantial portion of the operating cycle to provide a prolonged scavenging interval.

13. In a two-cycle internal-combustion camengine, the combination of a main shaft, a cylinder having an exhaust port and an intake port; a piston slidable in said cylinder through successive compression and power strokes in a path parallel with said shaft and adapted to open said ports at the endof a power stroke and to close said ports at the beginning of a succeeding compression stroke; and a cam for controlling the movement of said piston and having a dwell extending throughout a sufficient portion of the cam cycle to positively hold said piston stationary for a substantial length of time between the end of a power stroke and the beginning of a succeeding compression stroke to provide a prolonged scavenging interval.

14. In a two-cycle internal-combustion camengine, the combination of: a crank shaft, a cylinder having an exhaust port and an intake port; a piston slidable in said cylinder parallel with said shaft through successive compression and power strokes and adapted to open said ports at the end of a power stroke and. to close said ports at the beginning of a succeeding compression stroke; and a cam for controlling the movement of said piston, said cam having a power portion cooperating with said piston during an expansion stroke thereof, a compression portion for moving said piston through a compression stroke, and an intermediate exhaust portion having a dwell extending throughout a sufllcient portion of the cam cycle to hold said piston stationary for a substantial length of time between the end of a power stroke and the beginning of a succeeding compression stroke to provide a prolonged scavening interval.

15. An engine as defined in claim 13 in which the power portion of the cam extends throughout a relatively large portion of the cam cycle, in which the compression portion of said cam extends throughout a substantially smaller portion of the cam cycle, and in which the exhaust. portion of said cam extends throughout a portion of the cam cycle approximately equal to the extent of the compression portion of said cam.

HERBERT W. HOUSTON.