CA1075609A - Engine valving and porting including piston porting - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A two-cycle crankcase compression internal com-bustion engine having extended and specially positioned intake porting including porting in the piston skirt, to-gether with reed-type intake valves, with the porting and valves arranged to improve various of the operating charac-teristics of the engine.

Description

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ENGINE VALVING AND PORTING
INCLUDING PISTON PORTING

The present invention has the general objective of improvlng the performance, power output, flexibility, repsonse and fuel economy of internal combustion engines, especially two-cycle, variable speed, crankcase compression engines as used, for example, on motorcyc:Les.
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A. Summary of the Invention : :

In considering some of the major general objectives of the invention it is first noted that performance character-istics of engines and especially of two-cycle engines are determined in large part by the fuel intake capabilities, which are in turn governed by the total cross-sectional area of the intake passages, the duration of the intake, the :
portion of the cycle during which intake occurs, and the ~ responsiveness of the action of the intake valves. With - these features in mind the present invention provides novel arrangements and interrelationships of intake porting and reed valves which mutually contribute to an increase in the cross-sectional intake flow area for the fuel, to an ex-tension of the portion of the cycle during which intake of fuel occurs, and to increased responsiveness or sensitivity of the intake valves.

According to one aspect o~ the present invention there is provided a fuel intake system for a variable speed ~;l two cycle crankcase compression internal combustion engine having a piston working in a cylinder with transfer porting :~

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extended between the compression and the intake sides of the piston and with an intake port adaptec7 to communicate with the cylinder at the intake s.ide of the piston when the piston is positioned to block the transfer porting, and having a fuel intake chamber for receiving fuel from a supply source and for delivering the fuel to the intake port, a :~ ported valve seat presented downstream of the fuel flow through the intake chamber, a primary reed valve coverina said seat and the valve port therein, said primary reed being supported throughout substantially its entire periphery by said seat and being sufficiently flexible to open the port under the influence of decrease in pressure in the intake chamber incident to high speed engine operation but being sufficiently rigid to remain closed under the influence of decrease in pressure in the intake chamber incident to low speed engine opexation, . .
said primary reed having a.secondary valve port therethrough of smaller size than the por-t through the valve~seat, and a secondary reed valve covering the secondary port and being sufficiently flexible to open the secondary port under the influence of decrease in pressure in the intake chamber incident to engine operation either at said high speed or at said low speed.

According to another aspect of the invention; a variable speed two-cycle crankcase compression internal com-25 bustion engine comprises a cylinder, a piston working inthe cylinder, a crankcase having a crank space below the cylinder, a combustion chamber above the piston and a fuel :~

flow space immediately below the piston but above the crank ~la-~: , space even in bottom dead center position of the piston, fuel intake porting and passage means for supplying fuèl to the engine and including fuel intake porting in the cy-linder wall confronting the bottom dead center position of the piston and being of sufficient exial climension to supply fuel to said fuel space immediately below the piston through-out at least a substantial part of the upward stroke of the piston and further including a fuel tract approaching the cylinder in the region of said intake porting above said fuel space, a fuel transfer system having transfer porting through the cy].inder wall above the piston in bottom dead center position and comprising passage means provid.ing uninter-rupted intercommunication between said transfer porting and said tract, a passage providing uninterrupted intercommunica-tion between said fuel flow space and said fuel tract through-out the cycle of the engine, and reed valve means in said fuel tract for controlling the fuel supply to the engine.

In another aspect such a variable speed, two-cycle, crankcase compression, internal combustion engine comprises a cylinder having a combustion chamber, a piston working in the cylinder, a crankcase, port means in the cylinder including intake porting providing communication with the .
crankcase, an intake tract in fluid communication with the .
j intake porting, valve means disposed in the intake tract ..
: 25 for controlling the flow of fluid therethrough, the port ~:~
means further including transfer porting communisating with ; the combustion chamber, and a transfer passage, one end of which commun}cates with tbe transfer portiny and. the other end of which communicates with the crankcase, below tlhe pis~on~ I
30 for conveying fluid from the crankcase to the transfer porting, ~ ~:
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the communication of the intake porting with the crankcase being independent of the transfer passage, and a region of the transfer passage intermediate its ends being in communica-tion with the intake tract downstream of the valve means and providing for flow of fluid from the intake tract directly into the transfer passage.
' In still another aspect there is provided a variable speed, two-cycle, crankcase compression internal combustion engine comprising a cylinder, a piston working in the cylinder, a crankcase having a crank space below the cylinder, a combustion chamber above the piston and a fuel flow space immediately below the piston but above the crank space even in bottom dead center position of the piston, fuel intake porting and passage means for supplying fuel to the engine and including fuel intake porting in the cylinder wall confronting the bottom dead center position of the piston and being of sufficient axial dimension to supply fuel to said fuel space immediately below the piston throughout at least a substantial part of the upward stroke of the piston and Eurther including a fuel tract approaching the cylinder in the region of said intake porting above said fuel space, ~ fuel transfer system having transfer porting through the cylinder wall above the piston in bottom dead center position and comprising passage means providing uninterrupted in~ercommunication between ~aid trans fer porting and said uel space, a fuel supply passage commu-nicating with said transfer passage means independently of said fuel space, and reed valve means controlling the flow through said supply passage.
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Various of the features of the present invention which contribute to the foregoing general objectives will be exp].ained more specifically hereinafter, followlng a brief description of the prior art in this field.

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' -ld-~5~9 t the Prior Art In two-stroke engines of the crankcase compression type9 the moving piston is utili~ed to effect ~he intake of a charge of combustible fluid into the cylinder of the en~ine and to effect the exhaust of burned gases from the cylinder of the engine. Basically~ this is accomplished by using the piston ~o uncover and cover three types of ports -an inlet port, an exhaust port, and a transfer port - formed in the walls of the cylinder~ On the up stroke of the piston, combustible fluid is drawn into the crankcase by the ascending piston and is compressed therein on the down stroke of the piston and is then transmitted by a transfer port to the oombustlon chamber of the engine. The piston uncovers both the transfer port and the exhaust port thereby effecting the intake of combustible gases and exhaust of spent gases.

At the outset, problems were encountered in the two-s~roke design because of the mixing of the incoming combus-tible charge with the out~oing exhaus~ gases, with a resulting decrease in power output and fuel economy. Efforts to solve this problem have included deflector - top pistons wherein a deflecting surface on the top of the piston directs the incoming combustible charge toward the cylinder head of the , engine to prevent the charge from being drawn out through ~; the open exhaust portO This solu~ion was displaced by later techniques of cylinder sca~enging where~n the velocity and direction of the charge issuing from the transfer ports is con~rolled and resonances or pressure pulses in the exhaust and inlet tracks are harnessed for precise control of gas flow, These techniques are dlsadvantageous from the standpoint that the resonance points ar pressure pulses are a function of engine speed and optimal conditions occur only over a

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very narrow speed range. Thus9 these efforts resulted in engines which are not flexible in terms of producing power output over a varying range of engine speeds.

Some measure of control over the above noted problems has been achieved by the use of reed valves for delivering in timed fashion, the charge of combustible fluid to the inlet port of the engine. However, such designs have utili~ed a single reed petal or flap, formed of a piece of this spring steel or a val~e assembly having a plurality of such flaps.
These single stage designs place opposing requirements on the reed petal structure which must be compromised with the result that engine response and power, particularly in the low speed range is reduced. A brief consideration of the design illustrates the problem involved. At low engine speeds, vacuum on the downstream side of the ~alve is low and to provide a valve which will operate under these conditions to time the flow of the incoming charge, it would be necessary to utilize a relatively yieldable reed pe~al, i.e. one having a low spring constant. However, such a reed petal does not provi de optimal performance a~ middle and high engine speeds because at higher engine speeds, ~he vacuum developed in the crankcase becomes greater resulting in a grester pressure differentiaL across the reed and at such press~re differentials, ~he reed petal tends to flex ~pen to or near the position of ~reatest openi~gO In addit~on, as the engine speed is increased the rate at which the crankcase is placed alternately under pressure or vacuum by the rapidly moving piston is increased. Under these conditions, the frequency of response of the reed petal tthe time required by the reed petal to Qpen and close) is exceeded and the reed petal therefore fails to provide positive control of the timing and stre~gth _3_ .... ,. . . . . . . : ~ - . .

~7S~g of the incoming cha~ge and allows the spit back of portions of the incoming charge into the carburetor. Further when the alternations in the crankcase from vacuum to positive pressure occur at intervalls which are less in time tnan the response tlme of the reed petals, the reed petal, as it is in an open position, is sub~ected to the high positive pressure developed by the descending piston. As a consequence of this, reed petal life is substantially dlminished because of the uncontrolled flexure of the reed petal as it opens and whipping of the reed petal as it closes. Reed stops have been employed to li~it 1exure of the reed petal~ but such stops limit the opening of the reed petal, thereby restrict-ing the flow of charge through the valve. Conversely ~hen a less yieldable reed petal is utilized~ i.e.~ one having a higher spring constant, low speed performance of the engine is adversely affected because the low vacuum existing on ~-the downstream side of the valve is insufficient to open the reed petal for a duratioD long enough to ins~re an adequate incoming charge. Present designs of this type are engineered to provide a compromise between low speed and hi8h speed performance so that at the mid range of speed, power o~tput is maximized but power output in the lo~ speed and high speed ranges is less than optimal.

One known attempt to solve the problems referred to hereinabove is shown in U~S. Pat. No. 2,689,552 to E~
C. KeikhaeferO In that design, a single reed petal is utili7ed to open and close an inlet port to the crankcase of a two-cycle engine~ An additional, shorter spring flap is placed ; over a port~on of the reed petal 90 that, at l~w engine RPM9 the free end of the reed petal flexes to admit an incoming charge, and at high RPM the entire reed petal flexes against .

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the actlon of ~he overlying spring to provide the timed delivery of combustible mixture to the crankcase.

In addition, engines having t~ansfer ports extending from the intake tract to the combustion side of the piston have been proposed, as in U.S. Pat. NOr 3,687,118 to K. Nomura.
As ~ill be noted, the aforementioned patent discloses the use of a reed valve assembly employing single reed petals.
In this design, the crankcase is cut off from the inlPt tract for a significant portion of the cycle~ about 90~ Thus, while advantage is taken of the additional transfer capabilities of this design arising by reason of the fact that negative pressure pulses in the exhaust port draw combustible gas to the combustion side of the piston, there is, however, a restriction in the total capability of this design because the intake tract is cut off from the crankcase during this critical portion of the engine cycle, when certain phenomena could be utilized to impro~e scavenging and performance.
Also, engines of this basic design having pistons with ports in the skirt thereof have been proposed. In these designs, such ports have been placed in the lower portion of the skirt of the piston and thus the plston still acts ~o close off the intake tract from the crankcase for a significan~ portion of the cycle. Such designs have contemplated positioning the piston ports so that communication between the inlet tract and the crankcase is cut off until almost 45 to 50 after bot~om dead center position of the piston. In such designs, when the piston ports uncover the intake port9 ~eed val~es pGsitioned in the intake tract snap open. This results in a discontinuous flo~ of combustible fluid to the engine and in the intake of lesser volumes of combustion fluid in comparison to engines utlli~ing aspects of the invention disclosed herein.

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In addition to the general objectives hereinabove referred to the invention also has other objectives including the following:

Thus~ it is another ob~ect of this invention to provide improved reed valves for the control of combustible fluids to internal combustion engines and particularly to engines of the two-stroke design.

It is an additional object of this invention to provide a valve asse~bly having lncreased life.

Further~ it is an object of this invention to provide ~wo-stroke engines having increased power output, a broader power band, and improved power characteristlcs.
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It is also an object of this invention to provide a method and means for obtaining a supercharging effec~ to increase the volume of the charge of combustible fluid intro-duced into the combustion cha~ber of an internal combustion en8ine.

It is still another object of the inventlon to provide greatly increased intake por~ing for a t~70-cycle engine and ~o provide for an increase in ~he portion of th~
cycle during which the in~ake porting is open, It is a urther objec~ of the invention to pro~7ide a port in the pistoD skirt, for delivery of fuel into the ; 25 crankc~se for co~pression therein~ w~ich skirt port is so ~ :

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located in the piston skirt as to remain open ~hen the transfer ports are open and which is so located as to provide for communicaeion between the intake chamber and the crankcase when the pist~n is positioned to block the intake porting so that there is constant communication between the intake chamber and the crankcase throughout the entire cycle of the operation of the engine.

The invention has as a further object the employment of special intake ports, herein referred to as injector ports, interconnecting the intake passage at a point ~ust downstream of the intake valve with the transfer ports, thereby providing still another channel through which intake of fuel may occur whenever the transfer ports are open. In this aspect of the invention, one e~bodiment i9 featured by the provision of injector port means which can be made in the simplest possible manner, taking the form of a cavity provided in the cylinder in position to confront an outer side portion of the piston.

How the foregoing and other ob~ects and advantages are obtained will be clear from the following description referring to the accompanying drawings in which:

Figure 1 is a sectional ViPw of a two-~ycle internal conbustion engine ha~ing intake valves and intake porting conforming with the present invention;

Figure 2 is a section of certain of the valve ports shown in Figure 17 ~ ''.
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Figure 2G is a graph showing co~parative curves representing the power output in relation to speed for conven-tlonal two-cycle engines and for engines utili~ing certain features of the invention as disclosed in F:igures 1 and 2;

~ 5 Figure 3 is a view similar ~o Figure 1 but illustra-ting a modified ~alve arrangement;

Figure 4 is a view of a cylinder showlng certain improved inlet ports and showing also an arrangement of val~es positioned as in Figure 3;

Figure 5 is an elevational view of a piston adapted for use in an arrangement according to the present invention and incorporating extended porting~ as described hereinafter;

Figures 6A, 6B, 6C~ 6D and 6E are schematic illustra-tions showing the operating sequence of an engine employing porting arrangements according to the present invention;

-Figure 7 is a graph showing the portion of the cycle during which the intake valves are open in the arrangements illustrated in Figures 1 and 3 to 6E;

Figure 8 is a graph showing comparative power curves of a prlor art arrangement in comparison with an arrangemen~
conforming with Figures 3 to 6E, and still further with curve number 3 of graph 2G;

Figures 9 and 10 are views similar to Figues 3 and 4 but illustrating the provlsion of injector ports, as hereinafter explained;

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Figure 11, on the same sheet as Figures 7 and 8, is a graph showing the power curves for two engines con-structed according to the present invention, in one of which the injector ports are utilized and the other of which the in]ector ports are not utilized; and Figures 12 and 13 are views similar to Figures 9 and 10, respectively, but illustrating the provision of a modified form of injector portsO

Turning now to the drawings, reference is first made to the embodiment illustrated in Figures 1, 2 and 2G.

Referring to Figure 1, there is shown therein a schematic representation of a two-cycle piston engine having a cylinder 12 and a piston 14.
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The cylinder 12 includes main transfer ports 16 for delivering a combustible gas from the crankcase (not shown) to the combustion side of the piston 14. As is con-ventional, combustible gases pressurized by the descending piston, flow from the crankcase through suitable conduits ~ - :
(not shown) to the main transfer ports 16.

The cylinder 12 also includes an inlet port 18 which communicates with a valve housing 20 which may be mounted on or formed integrally with the barrel of cylinder 12, and which housing defines, at least in part, the above~
mentioned intake passage or tractO

. 25 A valve assembly 27 is received in the housing 20 and may be secured therein by a readily removable cover -g- :~

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plate 24 ~hat extends over the flanges 22 of the valve assembly and which preferably includes an intake passage extension 26 for receiving a carburetor ~not shown) thereon~

Referring to Figures 1 and 2, a preferred embodiment of a type of valve is shown therein in greater detail. The valve assembly 27 can include a valve body 29 having two convergent surfaces 30 and 32 joined in an apex by a transver~e member 35. The surfaces 30 and 32 include at least one opening 34 and 36 extending through each of the surfaces 30 and 32.
While the openlng 34 and 36 could be made in the form of one continuous opening, it is preferred that at least two openings be formed in the surfaces 30 and 32 for reasons as will be hereinafter explained. It should be noted that in Figure 2 the reed petals 38 and 42 at the top are shown lS closed, but those at the bottom ase shown open~ It will be ~nd~rstood that in actual use the flexing of both sets of reed petals on both sides of the ~alve will always be substantially the same, depending upon the opera~ion condition.

As the reed petal assemblies to be hereinafter d~scribed are the same on surface 30 as on surface 32, héreinafter reference will be made only to ~he reeds disposed on surface 30, it bei~g understood that the comments so made are Pqually applicable to the assemblies on surface 32. Disposed over the opening 34 is a primary reed 38. The size and shape o the primary reed is such that peripheral surfaces thereo~
extend beyond side edges of the openings 34 so that the flow of fluid through opening 34 is substantially precluded when the reed 38 i5 urged by i~s own resilience against the surface 10-~

~7~6at9 The primary reed 38 has a vent or opening 40 for~ed therethrough. A secondary reed 42 of a size and shape suffi-cient to o~erlay vent 40 is mounted over the vent 40 by, for instance, a machine screw 44 that secures both the secondary reed 42 and the pri~ary reed 38 to the valve body 29.

The primary and secondary reeds 38 and 42 respecti~ely are both formed of a yieldable, resilient material. However, it is important that the secondary reed 42 be more yieldable than the primary reed 38 beca~se secondary reed 42 must ope~l at lower intake port pressures than primary reed 38, as will hereinafter be described. It should be understood that any thin, resilient matPrlal can be used to form the primary and secondary reeds~ A preferred material that has been used with good result is a woven glass fiber and epo~y laminate commonly identified as G~10, or example as marketed by the Formica Company. Reed assemblies of ~his material wherein ; the thickness of ~he primary reed is abou~ 0.022~ to about 00026" and wherein the thickness of the secondary reed is about 0.014" to about 0.016" have been found satisfactory.
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An arrange~ent similar ~o that described abo~e `ii is illustrated in Figure 3, which lattPr Figure is more fully described hereinafter, but with reference to which it should be no~ed that it is preferred in all of the arrangements according to the invention that the primary reeds 38 should overlie the entire opening 34, (shown in broken lines in ~ -~igure 3~, and further that the primary reeds 38 are wider and longer than the secondary reeds 420 This has the ad~antage of greatly reducin~ the mass of each secondary reed 42 making . :

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it more responsive to lower pressure differentials across the val~e assembly and more able eo work independently of the operation of primary reed 38.

In addition~ it should be noted that the vent 40 is positioned closer to the end of reed 38 ~hich is secured to the valve body 29. This allows the length of the secondary reed 42 to be kept to a minimum9 thereby resulting in a decrease in the mass of the secondary reed as heretofore noted.

Also the provision of the vent 40 reduces the mass of the primary reed 38 thereby further decreasing ine~ial effects on that reed, The decrease in mass of the prim~ry and secondary reeds, it is believed, results in lncreased reed life as it reduces overflexing and eliminates the need for reed stops. Furthermore~ when both primary and secondary reeds are open, a larger volume of char~e passes through the ~alve, in comprarison to single reed valves9 because the impedance of the pri~ary reed to flow is reduced as portions of the charge c~n flow through the vent which is opened by the more yieldable secondary reed.

By providing a plurality of openings 34 and 36 and concomitantly a plurality of primary reeds and secondary reeds~ the mass of each of the reeds ls maintained at a minimum.
This in turn reduces inertial effects on the pri~ary and secondary reeds and increases the freque~cy of response of the reeds thereby making ~he englne more responsive to changes in thro~tle settings~

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As can be seen in Figures 1 and 2 the valve body 29 includes a transverse apex ~orming member 35 formed a-t the point of convergence of surfaces 30 and 32. The member 35 has formed -thereon an aerodynamic sur~ace 37 which gives the member 35 an air foil or tear drop cross section. Thus formed, the member 35 offers minimum resistance to passage of incoming gas. In single stage reed designs as heretofore discussed the corresponding surface 37 of the apex member 35 is flat or poin-ted and presents a non-aerodynamic sub-sonic barrier to the passage of gases thereover. The flator pointed surface is required ln certain single reed designs to lift the reeds from the surfaces of the valve body -to which they were mounted, by means of the shock and turbulence created at the apex member, which, it is felt, interfers with -the timed, uniform delivery of the charge into the intake port.

Referring to Figures 1 and 2, the valve assembly as heretofore disclosed operates in the following manner.
- At very low engine speeds, the secondary reed 42 opens each time the piston 14 moves upwardly in the cylinder 12 -to uncover the inlet port 18, as the force generated by the pressure of -the combustible gas, ~or instance, air-fuel mixture from a carburetor (not shown) on the upstream side of the secondary reed 42 is sufficient to overcome the resistive force gen-, 25 erated by the relatively yieldable secondary reed. Thisallows the passage of a quantity of air-fuel mixture into , the inlet port at each stroke of the piston and provides ; a timed supply of the air-fuel mixture to the cylinder 12 a-t very low engine speed. As the engine speed increases to mid range, the pressure differential across the valve .... .
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assembly becomes great enough to cause the primary reed 38 to begin to operate, alternately opening and closing wi-th the stroke of piston 14 to deliver a timed charge of the air-fuel mixture through the opening 30 to the inlet port S 18. In the high speed range, because of -the high vacuum conditions existing at the inlet port 18 and the increased frequency at which the crankcase changes from a condition of positive pressure to a condition of vacuum, secondary reed 42 remains open, varying in posi~ion in accordance wi-th the crankshaft ro-tation, while the less yieldable primary reed 38 continues to provide a timed charge in the manner heretofore described. Thus, the system described provides valve timing throughou-t the en-tire speed range of the engine.
The blow back of the air-fuel mixture -through the opened vents 40 at high RPM is preven-ted by the restricted area o~` these vents and by the mom~ntum of the entering high veloci-- ty intake charge.

Referring again to Figure 1, the more efficient -porting involves an increase in the charge delivered to the combustion side of the piston 14, by reason of a supercharging effect at low RPM occurring through main transfer ports 16 and auxiliary transfer port 46. This supercharging effect at lvw ~PM ranges results from the low pressure wake occurring in the crankcase as the compressed charge suddenly exits from the crankcase through the main transfer ports 16 and `~ auxiliary transfer port 46. The low pressure in the crankcase is communica-ted via a port 58 in the piston (more fully described hereinafter) to the intake port 18. This in turn causes secondary reed ~2 to open early, about 45 before BDC at Iow engine speeds, delivering a charge to the auxiliary ' 7~6~

transfer por-t 46, immediately downstream from the valve assem-bly and to the inle-t port 18 and thence through the crankcase to -the -transfer ports 16. This increased charge is in turn delivered -to the compression side of -the piston, thereby improving scavenging of the exhaust gases and charging of the cylinder, which results in an increase in -the overall compression ratio of -the engine and thus an increase in the power output.

An advantage of the sys-tem herein described is that at high RPM, the flow of the air-fuel mixture into the intake port 18 is significantly more constant because the secondary reeds ~2 remain open. In sys-tems using single reeds, the flow of the air-fuel mixture is stopped and started by the opening and closing of the single reed thereby reducing the speed and uniformity of the flow of the air-fuel mixture into the intake port 18.
:~, Ano-ther advantage of the valve assembly herein disclosed is -that the secondary reeds, which opera-te at low engine pressure differentials and which have faster response times allow a more efficient porting of the cylinder and piston. Single reed petal designs require greater vacuum in the inlet port to open the reed petals and require -the plston -to close off the intake system from the crankcase so tha-t the necessary vacuum can be achieved. The foregoing ?5 is a problem occurring most frequently in larger displacement engines, for instance engines having a displacement exceeding 100 cc. As the valve assembly herein disclosed does not require the buildup of a high vacuum to operate the secondary reeds, the intake system of the engine may be ported directly -'.

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~756al9 -to the crankcase at all times to yield better flow of the air fuel mixture at low engine speeds for larger displacement ~ engines.
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Another advantage realized by the vented reed sys- ~
tem herein disclosed is increased responsiveness of the en- "
gine. This aIises from the situa-tion that when the throttle plate of the carburetor (not sho~n) is closed, the vacuum upstream from the valve assembly 27 is the sarne as the crank~
case vacuum and both reeds remain closed. But immediately upon the opening of the throttle plate in the carburetor (not shown), the vacuum upstream of the valve assembly 27 drops while the vacuum in the crankcase rearnins. The vented reeds snap open earlier and more quickly, in comparison to single reed designs, because the vented valves are respon-sive to lower pressure differentials occurring across the valve assembly and provide more area for the flow of gases with less flexing, as earlier described.
' ,' .' ~ nother advantage to -the design herein disclosed is vastly increased life of the reeds. In single stage reed designs fatigue failures of the reeds being oecurring within twenty hours of service. Attempts to eliminate this situation include the use of spring steel reed elements. While these reed elements exhibit a longer life, failure of these ele-' ments results in destruction of the engine if the steel .
reeds are drawn into the cylinder. Dual reed assemblies ofthe type herein disclosed, on the contrary, have exhibited a normal service life in excess of one year.

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Referring to ~igure 2G, there is shown therein a graph indicating the power input in relation to engine speed for an engine modified as heretofore described. The graph shows the result of tests performed on a 25 cc. two-cycle engine utilizing, in stock form, piston controlled inlet ports and exhaust expansion chambers for exhaust extraction.

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The line identified by the numeral "1" represents the results of dynamometer testing for the above engine not utilizing reed valves of the type herein disclosed and em-ploying carburetor jetting suitable for normal use at varyingspeeds and loads. As can be seen from the graph, peak power of about 22 horsepower is developed a-t a speed of about 6600 RPM and power output falls off rapidly beyond -the peak power speed.

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Line 2 shows the result of testing the engine as equipped in test l with the exception that the carburetor jet-- ting was chosen to obtain maximum dynamometer power. A maxi-mum power of about 28 horsepower was achieved at a speed of ~ ;
I approximately 6600 ~PM. Again, as with test l, there was ex-20 perienced a rapid fall off in power after the peak power point, and maximum RPM safely achievable was indicated to be about 8500 RPM. It should be pointed out that the engine as set up in test 2 was not suitable for use in application re- -quiring varying speeds as the mixture became unduly rich each time the throttle plate was closed thereby loading the cylin-der with unburned fuel.

In test 3, an engine of the type used in tests l and .! 2 but further including reed valves of the type herein ., ~7~ 9 disclosed plus auxiliary transfer por-ting of the type herein disclosed was tested. As can be seen from -the graph of test

3, power output below 5000 RPM is significantly increased, somewhere in the order of` S0% and peak power of about 29 5 horsepower was achieved at a speed of about 7300 RPM. More-over, power output beyond peak power speed ~alls off more gradually than that for the number 1 and number 2 tests.
Further, maximum engine speeds of almost ll,000 RPM were achieved.

In test 4, an engine with the same modifications as -that in number 3 and further including a carburetor with a larger venturi diameter, auxiliary transfer porting, modi-fied exhaust porting, and a modified exhaust expansion chamber was used. Peak power on this engine rose to 3~ horsepower at a speed of about 9200 RPM. Maximum engine speed was found to be in excess of 12,500 RPM.
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It should be understood in connection with the vent-ed reed valve arrangements heretofore discussed that valve assemblies having more than two reeds are contemplated accord-ing to the invention. For example, triple reed valve arrange-ments may be employed, in which even-t the secondary reeds ~; will be apertured or vented, so that the third or tertiary reeds serve to open and close the vent in the secondary reeds.
In this case, the tertiary reeds are desirably smaller and more flexible than the secondary reeds.

With further reference to Figure 3, it is pointed out tha-t the arrangement of Figure 3 is similar to that des-cribed above and that all of the parts descrlbed above are .

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also employed, bu-t the reed valve assembly is differently positioned in the valve housing 20. In effect, the reed valve assembly in Figure 3 is merely rotated 90 in the valve housing, as compared with i-ts' position in Figures 1 and 2. ;
Because of -the angular position of the valve assembly in Figure 3, the reed valves themselves occupy a different posi-tion in relation to -the porting and to the axis of the cylinder.
This is oE advantage because it allows a more predictable flow ; , pattern of combustion fluid through the system, especially during high speed engine operation. The flow is more evenly divided between the sets of reeds disposed on each side of the valve body 29 and is directed in a manner which conforms to the natural directions of the fluid flow through the engine, i.e., curved toward the sides of the crankcase where the trans-fer passages are open to the crankcase, by reason of the fluidflowing through the valve port which acts as an orifice having a fixed side and a yieldable side defined by the reeds which cause the flow to curve. By reason of the orientation of the valve assembly as shown in Figure 3, the reeds are placed closer to the par-t 46 and the flow into port 46 is smoother because the fluid does not have to flow upwardly from the reeds as in the Figure 1 embodimen-t.

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This orientation of the reed valves is also desirable because it improves cold starting of the engine, which is particularly advantageous with engines requiring manual starting.
The reason for this is that when the engine is at rest, there is no vacuum in the crankcase to operate -the reeds. Thus, at start up, the engine must be cranked to develop sufficient . , -- ' .
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~75~9 vacuum in the crankcase to cause -the reeds to open and allow the passage of the combus-tion fluid into -the engines. When the valves are positioned as shown in Figure l, the combustion fluid passing through -the bottom se-t of reeds must flow up-wardly as it enters -the valve assembly 27 so that it can exit through the vent in the primary reed 38. These factors re-quire a greater vacuum -to be developed in the crankcase in order to draw the combustion fluid through the valve assembly and this necessitates higher cranking speed at start-up. When the arrangement shown in Figure 3 is used, the only forces which must be overcome in order to draw combustion fluid through the valve assembly are the resistive forces developed by the secondary reeds. This reduces the vacuum required to draw the combustion fluid through the valve and correspondingly decreases the cranking speed or starting effort required. In some engines this difference is so great as to make it practical to manually start the engine if the valve arrangement of the invention is ; used, whereas manual starting would not be practical without the valve arrangements of the invention.

In connection with the orientation with the reed valves as shown in Figure 3, it should be kept in mind that in many installa-tions such as motorcycles and snowmobiles, the intake passage and also the engine itself is somewhat inclined in a direction so that liquid fuel would tend to flow from the carburetor through the intake passage and intake port into the cylinder. This inclination is shown in Figure 3. With the vaives oriented as in Figure 3, some liquid fuel may readily leak past the valves or may accumulate immediately upstream o~ the valves, which is in contrast with the condition when '~ :

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the orientation of the valves is as shown in Figures 1 and 2.
The arrangement of ~igure 3, par-ticularly where the intake passage and engine is inclined, is therefore of special advan-tage where easy s-tar-ting is an important factor.
:':
I-t shoulcl be noted that the foregoing benefits are achieved from orien-tation of the valve assemblies as shown ln Figure 3 with vented reeds as heretofore disclosed, and also with single reed designs. Single reed designs benefit because the single reeds are less yieldable than the vented reeds and therefore do not open as easily.

Turning now to Figures 4, 5 and 6A to 6E, a-ttention is directed to the porting employed in accordance with the present invention.

Figure 4 shows a cross-section, taken along line

4-4 of Figure 3, of a typical cylinder showing the preferred manner of mounting the valve assemblies 27 in relation to the cylinder. In this embodiment, two valve assemblies 27, are positioned vertically as discussed above with respect to Figure 3 in a housing 20 which is attached to the cylinder C.
The valve assemblies 27 are positioned so that each valve assembly is aligned with one of the intake ports 18. The use -of the two valve assemblies 27 is advantageous because it causes the flow of combustion fluid to agree with the natural flow pat-tern of the engine, and this results in a smoother, more direc 2S tional flow of combustion fluid through the engine. The com-bustion fluid flows through each of the valves 27 into an aligned inlet port lB and into -the crankcase of the engine and ` from there into the transfer passages 53 and is introduced to the ~

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, ~CI 7~609 combustion side of the piston through the transfer ports 16.
It should be noted that this is particular:Ly important in the preferred embodiment of cylinder arrangements as shown in Figures 3 and 4 because in such designs, the axes o~ the trans-fer ports 16 are angularly displaced f`rom the axis of the in-take tract by about 90 , as is shown in Figure 4. These designs require that the combustion fluid make an abrupt change in direction once inside the engine, i.e., a direction change of to either side of the engine to enter the transfer pas-sages 53, and without the arrangements as shown in Figures 3and 4, the charge has little inherent directional tendency to flow toward either side of the crankcase, and in fact does not do so until after the charge has been compressed and flow starts through the transfer passages. ~t high operating speeds, -the time during which the change in direction can occur is short and therefore -the change must occur quite rapidly.
When using the double valve assembly arrangement shown, the valve assemblies give direction to the combustion fluid streams before the streams enter the engine. This predetermining results in the combus-tion fluid stream undergoing the direction change more efficiently, rapidly, and smoothly, thereby ultima-te-ly resulting in the delivery of a larger volume charge to the combustion side of the piston.

It should be noted -that the axis of the entire inlet tract of the engine shown in Figure 4, including the valve assemblies 27 and -the intake ports 18, is positioned so that it is aligned along a radius enamating from the center of the cylinder bore and is angularly offset from the axes of the transfer ports.

There is shown in Figure 5 a pis-ton which is usable in conjunction with a cylinder such as shown in Figure 4. The 7SÇ;~9 piston 56 includes two spaced pis-ton ports 58, each of which is positioned to be aligned with one of the in-talce ports 18 of cylinder C. An important aspect of the pis-ton shown in Figure 5 is that the height of the ports 58 is grea-tly in-creased over that of prior designs. As will be hereinaftermore fully explained, this resul-ts in allowing the inlet ports 18 (and thus the inlet trac-t including -the reed valves) -to communicate with the crankcase at all times during the engine cycle. The height of -the ports 58 can be increased in designs as shown in Figures 3 and 4 both with single reed valves and with ven-ted valves as hereto~ore disclosed. This is so because the improved fluid flow resulting from the vertical placement ; causes the engine to start more easily and does not require the intake ports to be closed off from the crankcase in order -that sufficient vacuum be developed -to operate the reeds--the mode of operation,necessary in designs having horizontally orien~ted reeds. The increased heigh-t of the piston ports, and the concomitant increase in port area allows a longer induction period and thus greater charge of fuel to be inducted into -the engine and this results in higher engine outputs.

There is shown in Figures 6A-E a schematic representa-tion of the operating cycle of an engine employing vented reed valved of the type heretofore described and employing a ported piston as shown in Figure 5.
.: .
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, 25 Figure 6A shown the position of the piston 56 just .!
slightly before it reaches bottom dead center. The combustion fluid charge compressed by the~descending piston 56 has exited -from the crankcase 60 and is in-troduced via the transfer ports ;~ 16 and somewhat through auxiliary port ~6 to the combustion : -. .

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side of the piston. As described above, the rapid exi-ting of the compressed combustion fluid from the crankcase 60 causes a vacuum to be created in its wake in -the crankcase 60. This vacuum is -transmitted via the pis-ton por-t 58 to the reed valves which open allowing the introcluction of additional charge of combustion fluid through the auxiliary -transfer port 46 to the combustion side of the piston and also into the crankcase 60 through the piston port 58, resulting in extended delivery of charge through ports 16 (as shOwn by the arrows). This creates what is known as a supercharging effect in the lower RPM ranges, and results in higher engine outputs.

I`here is also a supercharging effect which occurs at high RPM. At high RPM, it will be recalled, the second-ary reeds remain open, by reason of the fact that the in- -coming charge of the air-fuel mixture is travelling at high velocity and has significant momentum, and therefore, the -charge continues to flow through the open vent in the pri-mary reed and allows the system to maintain a higher delivery rate. Also, at piston bottom dead center, typical exhaust ex-pansion chambers are supplying suction to the cylinder. At this posi:tion, the auxiliary transfer por-t 46 is open to the combus--tion side of the piston, and because of the high monentum of the incoming charge which maintains secondary reeds open at high RPM, a portion of the air-fuel mixture flows directly from the intake tract, through the port 46. Thus, this portion of the charge bypasses the crankcase at high RPM -to fill the cylinder thorougly. Any of the charge tending to escape through the exhuast port as the piston moves upwardly is now held in the cylinder by a positive reflective wave generated by a typical exhuast expansion chamber. Also, because the ~.

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secondary reeds remain open a-t high RPM ranges, there is an increase in the amount of charge drawn into the crankcase through the skir-t port 58 and a correspondingly increased flow of gases through the crankcase and to the transfer ports.

Figure 6B shows the piston as it has just closed off the transfer port 16 and auxiliary port 46. The piston is ascending, thereby creating a vacuum in the crankcase which is communicated to the reed valves via the piston port 58, thereby causing the reed valves to open further. Combustion fluid flow from the inlet port 56 and also from the auxiliary ; transfer port 46 when the piston 56 hasmoved high enough, through the piston port 58 to the crankcase. At this point, the skirt of the pis-ton has not ye-t begun opening -the intake port 18.
.

In ~igure 6C, the bottom edge of the skirt of the piston 56 has cleared the intake port. Under these conditions, the reed petals are open, combustion fluid flows beneath the ~
bottom of the piston and also through the piston part 58 in-to -the crankcase. It should be noted that combustion fluid flow-ing through auxiliary transfer port 46 is directed upwardly through the pis-ton port 58 toward the underside of -the top of piston 56. This latter flow cools the top portion of the piston. ~-. . .
j As shown in Figure 6D, the piston 56 is approaching the -top of its stroke, the bottom edge of the skirt has com-pletely opened the intake port l~, thereby allowing a great volume of combus-tion fluid to be drawn into the crankcase through the open reed valves.

~7~6~9 Figure 6E shows the piston 56 descending and clos-ing off the intake port 18. The piston is of course compress-ing the volume of combustion fluid drawn into the crankcase during the previous up stroke of the piston. A-t this time, the pressure of the fluid in the crankcase is greater than the pressure on the upstream side of the valve assembly and blow-back of the pressurized charge is prevented by the closed reeds in the lower RPM ranges and by the restricted area of the vents and the monentum of the incoming charge entering through the vents at high RPM ranges. It should be noted that -at all times through the cycle the crankcase is in communi-cation with the intake tract, either via the piston port 58, the inlet port 18, or a combination of both. This provides for the induction of larger qu~antities of combustion fluid into the engine and results in higher power and higher torque outputs.

Figure 7 is a graph based upon the type of valve and port arrangemen-ts shown in Figures 1, 3, 4, 5 and 6A to 6E, including the vertically extending porting 58 provided in the piston skirt as shown in Figure 5. In Figure 7, the graph there shown plots two curves, curve 1 represen-ting typical operating behavior of the reed petals at low intake ~velocities, i.e., engine speeds below the power peak, and curve 2 representing typlcal operating behavior o~ the reed pe-tals a-t high intake veloci-ties, i.e., engine speeds above the power peak. As has been seen, at high intake air velocities, the intake is open to at least some extend throughout the entire cycle of operation of the engine. As plotted in the graph of Figure 7, 180 re-presents the bottom dead cen-ter posi-tion of the engine cranlc, and 360 represents the top dead center position of the engine crank.

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:~7~i609 It will be noted that the vertical scale of the graph of Figure 7 represents the degree of reed valve opening, graduated at quarterly intervals from zero opening to full opening, and the lowermost quarter of th:is scale comprehends the extend of opening provided by ~he secondary reeds, it being assumed that at the one-quarter position on the graph the secondary reeds are fully open.

The graph of Figure 7, also shows that even a~ low intake air velocity, the duration of reed or valve opening is extended throughout approximately 240 of the cycle of opera-tion. This aids in maintaining relatively high output and performance at low engine RPM, un~er which condition both the primary and secondary reeds c~cle, as has been described.
~' "' The duration o~ reed opening as described above in ~`
relation to Figure 7 is greater than prior arrangements both at low as well as at high int~ke air velocity, and these condi-tions can only be achieved when the skirt porting 58 is high enough to be open whenever the piston skirt would block com-munication from the intake passage to the crankcase. In prior arrangements, where the skirt port is closed during a portion of the cycle, the commencement of opening of the valve is delayed bo ~x beyond the 180 position, i.e., bottom dead canter. Such prior arrangements ad~ersely af~ect the torque at both high and low engine RPM.
.`
It should be noted that the graphs shown in Figure 7 are representative of engines emplo~ing standard transfer port timing, i.e.~ usually not in excess of 120 duration. It has - `
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been found that when using vented reed valves as herein dis-closed, especially in conjunction with piston porting as heretofore described, that the height of the transfer ports 16, as shown in Figures 1, 3 and 6A-E, 9 and 10, can be raised to give greater transfer duration. Engines having transfer port durations of about 148 have been found to have power curves as depicted by line 4 of Figure 2G. It will be note~ that greatly increased power results at high RP~q. In addition, the height of the exhaust port can be raised t result-ing in increased scavenging time and concomitant higher engineoutputs.

Turning now to the graph of Figure 8, the graph indicated by the numeral 1 represents a prior known sinyle reed valve engine and is characterized b~ rapid drop-off of horsepower after the power peak is passed. The curve identi-fied by the numeral 2 is similar to curve 3 of Fi~ure 2G, and illustrates one arrangement or embodiment of the present inven-tion incorpoxating a vented reed valve assembly. This curve shows much less tendency for the horsepower to drop off after the pea]c is reached. In another embodiment conforming with the present invention of the kind shown in Figures 3 and 4, in which multiple pairs of reed valves are arranged and in which a pair of spacecl intake ports 18 are provided, a horse-power curve as shown by numeral 3 in Figure 8 is secured. Here it will be seen that the peak horsepower is still higher and further, that the horsepower at the higher RPM levels off, instead of dropping sharply, as in the case of curve 1 '. :.
Turning now to Figures ~ and 10, there is here shown still ano~her feature as applied to arrangements similar to ' ~8- -,.,: ,' :~75~

those illustrated in Figures 3 an~ 4. Similar parts are again iden~ified b~ the same re~erence numerals. In these Figures however, additional ports, hereiil referred to as "in-jector" ports, are provided. Two injector ports are illus-trated at 62,62. Each of these ports int:erconnects one of the intake passages 18 with one of the transfer passages 53, as is shown in Figures 9 and 10. These i.njector ports are open at all times, and serve to increase intake of fuel at the higher ~PM's, especially above 6000 or 7000 RPM.

It will be noted from Figure 9 that the longitudinal ::
axis o~ the injector ports 62 is arranged at substantially a 90 angle to the axis of the transfer passage 53. When the charge contained in the crankcase is pressurized by khe des-cendiny piston, the charge i5 caused to flow upwarclly through the transfer passages 53 to the transfer por-~s 16 at high velocity. In accordance with Bernoulli's Principle, the rapidly moving charge in the passage 53 moving past the open-ing of injector port 62 causes an eductor effect in the injec-tor por~ 62 which causes a low pressure to exist in the port 62, which low pressure is communicated to the intake tract just downstream of the reed assemblies. In this manner, a quantity of charge is drawn rom the intake tract downstream rom the valve assembly, through the port 62 and into the transfer pas-sage 53. This results in a higher density charge passing through the portion of the transfer port between the injector ~ port 6? and the transfer port 16. It is believed that injec-: tor ports can be used with beneficial results in two-cycle : engine designs having valving in the inlet tracts, for example, .-:; rotary in~ake valves. As will be noted below, in connection ::~ -2~

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with discussion of Figure 11, especially ~ood results are achieved when injector ports are used in engines having reed valves, especially vented reed valves of the type disclosed herein.

It is also preferred, as shown in Figures 9 and 10, to provide a partition or wall 64 between the two intake chan-nels 18 and the two pairs of reed valvesl thereby aiding in dixecting the intake flow through the channels 18 and into the crankcase through the porting provided in the piston skirt.
~ .
Comparative analysis of a given engine of somewhat ~
higher horsepower than that employed as the basis for the graphs of Figures 2G and ~, both with and without the in~ector ports gives horse~ower curves such ~s shown in Figure 11. Here curve 1 is a curve of an engine conforming with the arrangements of Figures 9 and 10 except for the omission of the injector ports, and curve 2 represents the same engine altered merely by add- :
ing the injector ports. It will be seen that the peak horse-power has been raised, and further, that the drop-off of horse-power after the peak is further reduced, which is important at high RPM.
', :
Figures 12 and 13 illustrate a modified form of in~
jectox port means which achieves the operational features con~
sidered above with reference to the injector ports of Figures 9 and 10, but which is additionally advantageous because of its :

simplicity in manufacture and consequent cost advantage. The -~ embodiment of Figures 12 and 13 also presents minimal flow obstruction and, consequently, maximizes the induction of in- .` ;
take fluid, and therefore affords still greater efficiency even ' ~ .
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' ... . .. . .. - ~ : .. ~

7~9 as compared with the arrangement of Figures 9 and 10. Por-tions of this modified apparatus, which correspond to the similarly functioning injector ports of Figures 9 and 10, are identified b~ similar reference numerals r but include the subscript a.
.
As is the case with the embodiment of Figures 9 and 10, two port areas which serve an injector function are provid-ed in the modified embodiment. These are shown at 62a, 62a, and each is arranged at a substantially 90~ angle to the axis of the adjacent transfer passage 53, which terminates in the transfer port 16a. As will be apreciated, the transfer port 16a is that portion of the transfer passage which lies above the upper surface of the piston P, when the latter, as shown fragmentarily in Figure 12, occupies its bottom d~ad eenter position.

In the embodiment of Figures 12 and 13 each of the injector port means 62a takes the form of a cavity recessed in the cylinder wall in a position in which its open side con~
fronts an outer side wall portion of the piston P. This cavi-ty is simpler to provide than the injector ports 62, of Figures9 and 10, which are passages completely enclosed by the metal of the cylinder and its liner. This construction facilitates casting of the cylinder. The outer side wall of piston P
provides the inner wall limit (considered radially of the cylinder) of each injector port 62a, as appears in Figure 13.
Each of the resultant enclosed cavities 62a provides one of the injector ports, and each interconnects one of the intake passa~es 18 (in the zone 62b~ with on~ of the transfer pas-~' sag~s, as (at 62c).
. . .
~ -31-7~

As described above, with reference to the earlier embodiment, the rapidly moving charge in the passa~e 5 3 f low~
ing past the open end 62c o~ in~ector port 62a causes low pres-sure to exist throughout the injector means 62a. This low pressure is communicated to the intake tract through the open passage existing in the region 62h, all with results and horsepower advantayes similar to those already d~scribed with respect to Figures 9, lQ and 11.

With the fore~oing embodiments in mind, it is here desired to point out certain additional advantages and desirable operating characteris~ics secured when employing not only the multiple reed valves herein disclosed, but also when employing various of the porting features described.

The employment of reed valves also makes possible extensive increase in the total cross-sectional area of the intake portin~, as is disclosed herein, and still further makes possible considerable increase in the total time in the ; cycle during which the valves are open, both at ~ow speed and at high speed. The employment of reed valves further makes ~ -possible extending the porting 58 in the piston skirt to the point where the intake tract is open to the crankcase when the transfer ports are open. The use of reed valves also en-ables the vertical extension of the piston skirt porting to a point such that the intake tract is constantly open to the crankcase ~hroughout the entire cycle of operation of the engine.
-:

It should be noted that many manufacturers of two-cycle engines have been reluctant to adopt reed valves as a ~

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means o controlling the flow of the cha:rge to the sylinder.
This is believed to be because prior reed valve designs have added to the complexity of the enqine design compared with piston port intake systems and have exhibited unsatisfactory service life, yet have yielded onl~ modest benefits in terms of somewhat higher power output at low ~PM. Applicant's vented reed design, alone and in combination with the porting arrangements herein disclosed, has on the other hand achieved very significant increases in power output, torque output, and power band width. It is believed that these impxovem~nts make the adoption of reed valves by engine manufacturers much more likely.

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Claims (7)

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. A fuel intake system for a variable speed two-cycle crankcase compression internal combustion engine having a piston working in a cylinder with transfer porting extended between the compression and the intake sides of the piston and with an intake port adapted to communicate with the cylin-der at the intake side of the piston when the piston is posi-tioned to block the transfer porting, a fuel intake chamber for receiving fuel from a supply source and for delivering the fuel to the intake port, a ported valve seat presented downstream of the fuel flow through the intake chamber, a primary reed valve covering said seat and the valve port there-in, said primary reed being supported throughout substantially its entire periphery by said seat and being sufficiently flex-ible to open the port under the influence of decrease in pres-sure in the intake chamber incident to high speed engine op-eration but being sufficiently rigid to remain closed under the influence of decrease in pressure in the intake chamber incident to low speed engine operation, said primary reed having a secondary valve port therethrough of smaller size than the port through the valve seat, and a secondary reed valve covering the secondary port and being sufficiently flex-ible to open the secondary port under the influence of decrease in pressure in the intake chamber incident to engine operation either at said high speed or at said low speed.

2. A reed valve assembly for controlling the flow of fluid through the intake tract of a variable speed, crankcase compression, two-cycle internal combustion engine comprising a valve body having a valve seating surface, port means in the valve seating surface for providing for the flow of fluid through the valve body, an elongate primary reed valve positioned over the port means for controlling the flow of fluid through the port means, said primary reed valve being supported throughout substantially its entire periphery by said valve seating surface and the port means having a port area extended throughout most of the length of the primary reed valve, means securing one end of the primary valve to the valve body whereby the reed is free to flex and thereby open and close the port means, secondary port means formed in the primary reed having port area ex-tended throughout most of the length of the reed and includ-ing area positioned adjacent the secured end of the reed a secondary reed positioned over the secondary port means in the primary reed, means for mounting the secondary reed on the valve body whereby the secondary reed controls the flow of fluid through the secondary port means, the secondary reed being more yieldable than the primary reed.

3. A fuel intake system for a variable speed two-cycle crankcase compression internal combustion engine having a piston working in a cylinder with transfer porting extended between the compression and the intake sides of the piston and with an intake port adapted to communicate with the cylinder at the intake side of the piston when the piston is positioned to block the transfer porting, a fuel intake chamber for receiving fuel from a supply source and for delivering the fuel to the intake port, a ported valve seat presented downstream of the fuel flow through the intake chamber, a primary reed valve covering the valve port and being formed of synthetic polymeric resin material of sufficient flexibility to open the port under the influence of decrease in pressure in the intake chamber incident to high speed engine operation but of sufficient rigidity to remain closed under the influence of decrease in pressure in the intake chamber incident to low speed engine operation, said primary reed having a secondary valve port therethrough of smaller size than the port through the valve seat, and a secondary reed valve covering the secondary port, and being formed of synthetic polymeric resin material of sufficient flexibility to open the secondary port under the influence of decrease in pressure in the intake chamber incident to engine operation either at said high speed or at said low speed.

4. A fuel intake system as in Claim 3, wherein the primary and secondary reed valves are fiber reinforced.

5. A variable speed two-cycle crankcase compression internal combustion engine comprising a cylinder, a piston working in the cylinder, a crankcase having a crank space below the cylinder, a combustion chamber above the piston and a fuel flow space immediately below the piston but above the crank space even in bottom dead center position of the piston, fuel intake porting and passage means for supplying fuel to the engine and including fuel intake porting in the cylinder wall confronting the bottom dead center position of the piston and being of sufficient axial dimension to supply fuel to said fuel space immediately below the piston throughout at least a substantial part of the upward stroke of the piston and further including a fuel tract approaching the cylinder in the region of said intake porting above said fuel space, a fuel transfer system having transfer porting through the cylinder wall above the piston in bot-tom dead center position and comprising passage means providing uninterrupted intercommunication between said transfer porting and said tract, a passage providing uninterrupted intercom-munication between said fuel flow space and said fuel tract throughout the cycle of the engine, and reed valve means in said fuel tract for controlling the fuel supply to the engine.

6. A variable speed, two-cycle, crankcase compres-sion, internal combustion engine comprising a cylinder having a combustion chamber, a piston working in the cylinder, a crankcase, port means in the cylinder including intake porting providing communication with the crankcase, an intake tract in fluid communication with the intake porting, valve means disposed in the intake tract for controlling the flow of fluid therethrough, the port means further including transfer porting communicating with the combustion chamber, and a transfer passage, one end of which communicates with the transfer porting and the other end of which communicates with the crankcase, below the piston for conveying fluid from the crankcase to the transfer porting, the communication of the intake porting with the crankcase being independent of the transfer passage, and a region of the transfer passage intermediate its ends being in communication with the intake tract downstream of the valve means and providing for flow of fluid from the intake tract directly into the transfer passage.

7. A variable speed, two-cycle, crankcase compression internal combustion engine comprising a cylinder, a piston working in the cylinder, a crankcase having a crank space below the cylinder, a combustion chamber above the piston and a fuel flow space immediately below the piston but above the crank space even in bottom dead center position of the piston, fuel intake porting and passage means for supplying fuel to the engine and including fuel intake port-ing in the cylinder wall confronting the bottom dead center position of the piston and being of sufficient axial dimension to supply fuel to said fuel space immediately below the piston throughout at least a substantial part of the upward stroke of the piston and further including a fuel tract approaching the cylinder in the region of said intake porting above said fuel space, a fuel transfer system having transfer porting through the cylinder wall above the piston in bottom dead center position and comprising passage means providing uninterrupted intercommunication between said transfer porting and said fuel space, a fuel supply passage communicating with said transfer passage means independently of said fuel space, and reed valve means controlling the flow through said supply passage.