US3810450A - Stuffer for two-cycle engines - Google Patents

Abstract

In two-cycle internal combustion engines where the mixture of gas and air is introduced from the carburetor to the crankcase, and thereafter flows from the crankcase to the combustion cylinder, a stuffer is provided surrounding the inlet from the carburetor to the crankcase in a manner which does not interfere with flow into the crankcase, the stuffer extends into the crankcase and surrounds a part of the crankshaft and its counterweights in a manner so as to not interfere with the operation of the crankshaft while at the same time reducing the volumetric area of the crankcase. The stuffer is particularly useful in a two-cycle engine equipped with a back pressure producing muffler or exhaust constriction.

Description

Waited [States Patent [191 Woodhouse [451 May 14, 1974 1 1 STUFFLER FOR TWO-CYCLE ENGINES [75] Inventor: John C. Woodhouse, Cheyenne,

Wyo.

[73] Assignee: Robert F. Deike, Cheyenne, Wyo. [22] .Filed: Aug. 29, 1972 [21] Appl. No.: 284,636

[52] 11.8. C1.... 123/73 A, 123/73. R, 123/73 V [51] Int. Cl. F02b 33/04 [58] Field of Search 123/73 R, 73 A, 73 V, 73 S,

123/73 AC, 73 AF [56] References Cited I UNITED STATES PATENTS 1,385,250 7/1921 Gernandt 123/73 R 3,008,459 11/1961 Kaufman 123/73 V 3,042,013 7/1962 Nelson .l 123/73 V FOREIGN PATENTS OR APPLICATIONS 133,070 6/1942 Sweden 123/73 V Canada 123/73 V Primary Examiner-Laurence M. Goodridge Assistant Examiner-Tony Argenbright Attorney, Agent, or Firm-Hill, Sherman, Meroni,

Gross & Simpson 57 ABSTRACT In two-cycle internal combustion engines where the mixture of gas and air is introduced from the carburetor to the crankcase, and thereafter flows from the crankcase to the combustion cylinder, a stuffer is pro-- .vided surrounding the inlet from the carburetor to the crankcase in a manner which does not interfere with flow into the crankcase, the stuffer extends into the crankcase and surrounds a part of the crankshaft and its counterweights in a manner so as to not interfere with the operation of the crankshaft while at the same time reducing the volumetric area of the crankcase. The stuffer is particularly useful in a two-cycle engine equipped with a back pressure producing muffler or exhaust constriction.

4 Claims, 10 Drawing Figures PATENTEDMAY 14 m4 3810.450

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to internal combustion engines and more particularly to a volumetric reduction insert for crankcases of two-cycle engines equipped with exhaust dampers.

2. Prior Art Twocycle internal combustion engines are provided for a wide range of uses. However, such engines are usually of small displacement and are constructed as economically as possible.

To a large extent, this has resulted in the production of extremely noisy two-cycle engines. Recent noise control legislation has required modification of existing engines to reduce operational noise. The greatest sourceof operational noise is the engine exhaust. Thus, one common step for the reduction of noise is the provision of a muffler or damper to control exhaust noise levels. 7 A

Most effective mufflers or dampers produce a back pressure in the exhaust manifold. This back pressure reduces the ability of the cylinders to evacuate themselves. This probelm is more acute in two-cycle engines than in four-cycle engines, inasmuch as the exhaust must flow from the cylinder rather than being pumped from the cylinder by action of the piston. Thus, where a back pressure is provided by a muffling device, the cylinder or cylinders do not properly exhaust themselves. This back pressure further continues to exist in the cylinder to the point when the piston has opened the inlet ports. With the resultant high pressure in the cylinder, flow of new fuel and air from the inlet into the cylinder is restricted.

Thus, the majority of two-cycle engines which have been retrofitted with muffling devices have experienced noticeable power losses. A typical type of twocycle engine ports the carburetor to the crankcase area below the reciprocating piston, thus when the piston rises, a low pressure is provided in the crankcase due to the enlarged displacement. This low pressure aids in flowing the mixed fuel and air from the carburetor into the crankcase. Thereafter, as the piston descends during the power stroke, the volume of the crankcase area is reduced and the mixture therein is forced through a conduit or intake manifold to the intake port to the cylinder. Thus, the volumetric changes that occur naturally in the crankcase are utilized to aid in the flow of new fuel to the cylinder.

It has been determined previously that by reducing the crankcase area through the provision of fillers or stuffers, that increased compression of the fuel mixture in the crankcase can be provided. See for example the U. S. Pat No. to I. H. Spencer, 1,552,515, issued Sept. 8, 1925 and the U. S. Pat. No. to Larson, 3,604,403, issued Sept. 14, 1971.

Such fillers or stuffers have normally been provided above the crankshaft with their major body portion extending upwardly into the lower end of the cylinder below the piston. These devices, therefore, are of limited use in that they require that the engine have a considerable cavity space above the crankcase and below the piston. Where there is not such a large cavity, the stuffers must be complexly contoured to be free of adverse influence on the piston and piston rod.

It would therefore be an advance in the art if a device for reducing the volume of the crankcase could be provided which was not positioned above the crankcase and which did not extend into the area below the piston in the cylinder.

SUMMARY OF THE INVENTION My invention provides for a volume reducing stuffer for positioning in the crankcase of a two-cycle engine. l have, however, located my stuffer below the crankshaft in the area of the crankcase which forms an inlet forthe carburetor/A common engine construction in two-cycle engines is to mount the carburetor directly to the crankcase housing. While this can be done at other areas, one specific location has been at the bottom of the crankcase below the crankshaft. In order to allow for assembly of the crankshaft and counterweights, piston and rod, etc., as well as to provide clearance for the revolving crankshaft and rod connections, the bottommost area of the crankcase housing is relatively large. Operating clearances do not require this large area. However, because it'is difficult to produce rounded internal cavities, the walls at the bottom of the crankcase are normally as far apart as is required for internal clearances further into the crankcase. Thus, a large area is defined by the walls. It is common to mount the carburetor directly at the bottom of the crankcase and to port the carburetor into the crankcase area through reed valves. Because of the presence of the reed valves, it has not heretofore been suggested to reduce the area in the bottom of the crankcase through the provision of a stuffer. l have, however, provided a stuffer in this area which has internal clearances for the reed valves and a centrally disposed opening extending through the stuffer to provide a conduit between the reed valves to the carburetor and the central crankcase area.

Further, I have coupled my stuffer with a novel damper for the engine exhaust. My damper is unique in that it provides a spirally wound laminate of sheet metal, spun glass and screen received in a cup-shaped housing. The exhaust is ported to the center of the spiral and is exhausted from the periphery of the housing. Thus, the damper provides no blockage in that the exhaust gases are free to follow the spiral path which is not blocked by walls. This allows for a free flow through the damper while at the same time reducing the degree of noise through absorption by the spun glass layer and as a result of the narrow spiral path. I

This type of dampener is effective in reducing noise to acceptable levels while at the same time providing an acceptable level of back pressure.

It is therefore an object of this invention to provide improvements for two-cycle engines.

It is a further and more specific object of this invention to provide an improvement for a two-cycle engine which increases the low pressure suction from the carburetor and the compression of fuel to the cylinder.

It is another object of this invention to provide a volumetric reducing stuffer for the crankcase of a twocycle internal combustion engine, the stuffer received around the intake from the carburetor to the crankcase.

It is another and more important object of this invention to provide a stuffer for a two-cycle internal combustion engine, the stuffer received in the bottom of the crankcase below the crankshaft and around the inlets from the carburetor.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantages of the invention will be readily apparent from the following description of certain preferred embodiments thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure, and in which:

FIG. 1 is a plan view of a two-cycle engine equipped with the improvements of this invention;

FIG. 2 is a perspective view of the stuffer of this invention;

FIG. 3 is a plan view of the stuffer of this invention received in place over the carburetor openings;

FIG. 4 is a cross-sectional view of the engine of FIG. 1 illustrating the placement of the stuffer in the crankcase;

FIG. 5 is a cross-sectional view with parts broken away to show underlying parts of the damper of this invention;

FIG. 6 is a view of the damper of FIG. 5 taken along the lines VI-VI;

FIG. 7 is a fragmentary exploded perspective view of the spirally wound laminate of the damper of this invention;

FIG. 8 is a diagrammatic view illustrating the working of the damper of this invention; I

FIG. 9 is a part sectional view of the stuffer of this invention received in place adjacent the carburetor opening indicated by the lines IX-IX of FIG. 3; and

FIG. 10 is a view similar to FIG. 9 taken along the lines X-X of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a two-cycle internal combustion engine 10. The engine includes a combustion cylinder portion 11, a crankcase portion 12, and a carburetor 13 which are positioned in line. The engine is illustrated with these components being related horizontally in stacked relation with the crankcase portion 12 intermediate the combustion chamber portion 11 and the carburetor 13. On the top 14 of the crankcase portion is a starter 15 and magneto assembly 16 while on the bottom 17 of the crankcase as illustrated is a power takeoff 18.

As best shown in FIG. 4, the combustion cylinder portion 11 consists of a housing 20 which defines an open cylinder 21 with a piston 22 disposed therein for reciprocating movement. The housing 20 is integral with the crankcase portion 12 which receives a crankshaft 23 which has a piston rod 24 attached thereto and which has counterweights 25 attached thereto opposite the attachment point 26 of the piston rod to the crankshaft. Because both the weights 25 and the attachment point 26 are offset from the center 27 of the crankshaft, the area 28 of the crankshaft portion 12 has to be sufficiently large to allow rotation of the crankshaft weights and the piston rod attachment point as well as to allow insertion of the components into the housing. This dimension is normally greater in a plane normal to the plane of the crankshaft than is the dimension of the housing 20 in the area of the combustion cylinder portion. Therefore, the housing portion 20a for the crankshaft extends outwardly as is illustrated in FIG. 4 and continues to the bottom 29 of the crankcase. While the bottom portions of the crankcase could be rounded as are the top portions at 30, economies of manufacturing and assembly require that the bottom of the crankcase be as wide as the widest portion.

To round the bottom of the crankcase to conform with the minimum dimensions allowable with respect to the orbit path of the weights and piston rod attachment would require that the interior dimension of the crankcase portion 12 be greater than the top or bottom dimensions and of the bottom opening to the crankcase. This would create numerous difficulties in casting and machining the housing.

For these reasons, the bottom of the crankcase at the point of attachment of the carburetor is considerably larger than internal clearances require. I have therefore provided a stuffer 35 which fits into the end 29 of the crankcase. The stuffer has a base portion 36 which overlies the flanged end 29 of the crankcase and a main body portion 37 which projects into the interior 38 of the crankcase. The main body portion is substantially rectangular and has ribs 39 extending up side walls 40 of the body portion. The ribs 39 are received in grooves 41 in the side walls of the crankcase housing which are provided to give clearance to the attachment point 26 of the piston rod to the crankshaft in those engines where the attachment point 26, because of the clamp 42 at the end of the piston rod, projects radially outwardly beyond the weights 25. The other two side walls 43 are dimensioned to mate with corresponding side wall portions of the crankcase housing. The top surface 44 of the body 37 is arcuately curved from the end wall 40 to the other end wall 40 so that the central portion 45 intermediate the end walls 39 has a height from the base 36 less than the height of the walls 40. Internal grooves 48 in the top 44 may be provided aligned with the ribs 39 to provide clearance for the bracket 42. The remainder of the wall 44 is shaped to provide minimum clearance for the crankshaft and weights.

The carburetor I3 is attached to the underside of the base 36 whereby the base 36 is enclamped between the flanged end 29 of the crankcase and the carburetor 13. The carburetor 13 ports a mixture of fuel and air into the crankcase through passageways 50 in the body of the carburetor portion 13. The passageways 50 communicate to the crankcase through reed valves 51. A limiter 52 limits the degree of opening of the valves into the crankcase area. The stuffer 35 has a cloverleaf opening 55 therethrough from the wall 44. The cloverleaf opening 55 is dimensioned to receive the limiter 52 of the carburetor opening as illustrated in FIG. 3 wherein a four-pronged limiter 52 is received into the bottom of the cloverleaf opening 55. The opening 55 extends entirely through the stuffer 35 and communicates the carburetor passageways 50 to the interior of the crankcase. As best illustrated in FIG. 9, the wall of the carburetor through which the openings 50 project may have recesses 61 therein. In that case, the undersurface 62 of the base 36 of the stuffer will have corresponding projections 64 thereon extending into the recesses 61.

It can thus be seen from the above that my stuffer is received into the crankcase and overlies the carburetor connection to the crankcase. The stuffer has ports therethrough communicating the crankcase to the carburetor and has a body portion extending into the crankcase with a curved top wall dimensioned to provide clearance with the moving parts within the crankcase while at the same time having a body thickness sufficient to take up unnecessary volume clearances interior of the crankcase.

74. A conduit 78 extends from the exhaust outlet to the central portion of the bottom wall 74 and communicates with a port 79 through the bottom wall 74 to the interior of the housing. The cap 75 may be retained on the housing'by a bolt 80 passing through the housing. Disposed interiorly of the housing is a spirally wound laminate 90best illustrated in FIG. 6. The laminate as shown in FIG. 7 consists of three layers. The first layer is a sheetmetal layer 91. The second layer is a layer of sound damping material such as spun glass 92 or the like. The-layer 92 is positioned atop the sheet metal layer 91 and a third layer of wire or the like material screen 93 is positioned atop the layer 92. The laminate of the three layers is spirally wound with clearance between adjacent windings and is inserted into the cupshaped housing. The winding is preferably approximately as long as the cup-shaped housing and has an outer diameter extending at the end to the inner diameter of the housing. Exhaust ports 95 through the housing beyond the end 96 of the outermost winding provide an exit path for gases.

Exhaust gases enter the cup-shaped housing through the conduit 78 and the port 79 to the central space radially interiorly of the innermost winding of 'the laminate. Thereafter, the exhaust gases follow a spiral path as defined by the windings to the end 96 of the windings. Thereafter, the gases will pass through the ports 95 to the ambient atmosphere.

The damper works as follows. The screen 93 and metal backing 91 will deflect the sound waves into the spun-glass absorbing layer 92. Thus, as shown in FIG. 8, as high-decibel sound 100 enters the spiral wind, the sound waves are deflected into the absorbing material of the layer 92 and are absorbed by the layer and curved throughout the length of the spiral. The sound then exits the housing as a low-decibel sound 101. By 1 providing a space between adjacent windings, the gases are never blocked but are free to flow between the ad-. jacent windings in the spiral.

The spiral path forced upon the gases forces a back pressure into the two-cycle engine. The gas pressure in the two-cycle engine would normally have a disadvantageous effect upon the performance of the engine, resulting in a reduced horsepower output. l-lowevendue j to the provision of the stuffer 35, this disadvantage is overcome. The stuffer increases both the compression and suction in the crankcase caused by reciprocal movement of the piston. The increased suction causes a greater flow of fuel mixture from the carburetor into the crankcase. The increased compression causes a Y greater flow of the fuel from the crankcase to the cylinder. The increased compression acts to offset the in creased back pressure interior of the cylinder. The combination of the back pressure producing damper and the stuffer results in a further advantage in that a portion of the fuel combusted in a previous stroke of the engine will be retained by the back pressure within the cylinder. Thus, a greater economy is provided in that partially unbumt fuel remaining within thev cylinder after combustion is not exhuasted totally and is retained for mixture with the new fuel and air mixture for additional combustion. Thus, the power represented by such unbumt fuel is more thoroughly utilized, resulting in a more efficient engine. At the same time, the exhaust from the engine is cleaner, containing fewer unburnt hydrocarbons.

ln a modification of the damper illustrated in FIGS.

5 and 6, l have applied end caps to the ends of a spiral wind of the illustrated laminate so that the outermost layer of the laminate forms the peripheral wall of the damper with the metal backing layer 91 forming the outside periphery. One of the end caps is then ported at the center to provide the equivalent of the port 79 and is connected to the conduit 78 to the exhaust opening in the engine. In this modification, the outlet from the damper is the end 96 of the spiral wind.

It will therefore be appreciated from the above that my invention-provides a stufi'er for receipt into the crankcase of a two-cycle engine, the stuffer' being received entirely within the crankcase portion of the engine in that no portion of the stuffer extends upward into the cylinder portion of the engine. That is, the stuffer does not extend out of the crankcase in the direction' of the cylinder. Further, the stuffer surrounds the intake from the carburetor to the crankcase and has ports therethrough providing communication betweenthe carburetor and the crankcase. Additionally, my invention discloses a novel damperor'muffler to be used in connection with the stuffer. Thev damper provides sound absorption for high decibel sound emissions from the engine. Additionally, the damper provides a desirable back pressure to the engine, which back pressure is compensated for by the stuffer.

Although the teachings of my invention have herein been discussed with reference to specific theories and embodiments and although illustrative means for accomplishing explained results have been described, itis to be understood thatthese are by way of illustration only and that others may wish to utilize my invention in different designs or applications.

I claim as my invention:

1. In a two-cycle engine having a cylinder, a crankcase extending from one end of the cylinder, a carburetor mounted on the crankcase, a piston reciprocably mounted in the cylinder, a counterweighted crankshaft in the crankcase, a piston rod joining the piston and crankshaft, the counterweight portion and the piston rod attachment portion of the crankshaft being oppositedly offset from the center of rotation of the crankshaft and the crankcase having opposed recesses receiving said counterweight and attachment portions, the improvement of a stuffer in the crankcase filling the crankcase space between the carburetor and the crankshaft without interfering with the operation of the piston, piston rod and crankshaft, said stuffer having a flange between the crankcase and the carburetor, a body portion projecting from said flange filling both opposed crankcase recesses below the center line of the crankshaft and shaped to provide operating clearance for the counterweight and attachment portions of the crankshaft and having a port through the bottom of the body portion and the flange communicating with the carburetor and the crankcase and a reed valve controlling flow from the carburetor through the port to the crankcase.

2. A stuffer for a two-cycle engine which comprises a member having a flat flange adapted to be mounted between the carburetor and crankcase of a two-cycle engine, a body extending from one face of said flange having opposed side walls with external ribs adapted to fill recesses in the crankshaft for receiving the counterweight and piston rod attachment portions of the crankshaft of a two-cycle engine at a level below the center line of the crankshaft, said side walls having grooves affording clearance for the counterweight and piston rod attachment portions of the crankshaft, said stuffer having a central port through the flange and body portions thereof, a reed valve overlying'the port, and a reed valve limiting member secured to the stufier controlling the extent of opening of the reed valve.

3. The two-cycle engine assembly of claim 1 wherein the port of the stuffer has a clover-leaf shape, the reed valve has a conforming shape and a single screw attaches the reed valve to the stuffer.

4. The stufi'er of claim 2 wherein the port has four lobes, the reed valve and the limiter are x-shaped overlying the port lobes and a central bolt unites the limiter and the reed valve to the stuffer.

Claims (4)

1. In a two-cycle engine having a cylinder, a crankcase extending from one end of the cylinder, a carburetor mounted on the crankcase, a piston reciprocably mounted in the cylinder, a counterweighted crankshaft in the crankcase, a piston rod joining the piston and crankshaft, the counterweight portion and the piston rod attachment portion of the crankshaft being oppositedly offset from the center of rotation of the crankshaft and the crankcase having opposed recesses receiving said counterweight and attachment portions, the improvement of a stuffer in the crankcase filling the crankcase space between the carburetor and the crankshaft without interfering with the operation of the piston, piston rod and crankshaft, said stuffer having a flange between the crankcase and the carburetor, a body portion projecting from said flange filling both opposed crankcase recesses below the center line of the crankshaft and shaped to provide operating clearance for the counterweight and attachment portions of the crankshaft and having a port through the bottom of the body portion and the flange communicating with the carburetor and the crankcase and a reed valve controlling flow from the carburetor through the port to the crankcase.

2. A stuffer for a two-cycle engine which comprises a member having a flat flange adapted to be mounted between the carburetor and crankcase of a two-cycle engine, a body extending from one face of said flange having opposed side walls with external ribs adapted to fill recesses in the crankshaft for receiving the counterweight and piston rod attachment portions of the crankshaft of a two-cycle engine at a level below the center line of the crankshaft, said side walls having grooves affording clearance for the counterweight and piston rod attachment portions of the crankshaft, said stuffer having a central port through the flange and body portions thereof, a reed valve overlying the port, and a reed valve limiting member secured to the stuffer controlling the extent of opening of the reed valve.

3. The two-cycle engine assembly of claim 1 wherein the port of the stuffer has a clover-leaf shape, the reed valve has a conforming shape and a single screw attaches the reed valve to the stuffer.

4. The stuffer of claim 2 wherein the port has four lobes, the reed valve and the limiter are x-shaped overlying the port lobes and a central bolt unites the limiter and the reed valve to the stuffer.

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