US2779576A - Charge forming device - Google Patents

Description

Jan. 29, 1957 H. MORGENROTH CHARGE FORMING DEVICE 2 Sheets-Sheet 1 Filed June 9, 1953 INVENTOR. HENRI MORGENROTH Jan. 29, 1957 H. MORGENROTH 2,779,576

CHARGE FORMING DEVICE Filed June 9, 1953 2 Shee'ts-Sheet 2 INVENTOR.

HENRI MORGENROTH ATTORNEY United States Patent My invention relates to carburetors for internal combustion engines and has particular reference to a combination of reed valve and carburetor wherein the reed valve forms a part of the carburetor structure.

The invention is applicable to internal combustion engines particularly to two-cycle engines employing crank case compression or the equivalent as when a separate air charging pump is used. Reed valves are thin flexible plate valves which may have one end firmly attached to the valve seat, while the free portion forms the valve proper, moving and deflecting as a flap valve when a pressure differential exists. Such reed valves are used on two-cycle engines where the scavenging and charging pump is a separate pump as well as on two-cycle engines wherein the lower side of the working piston forms the pump in conjunction with the crank case. The invention is applicable to internal combustion engines which are fed by an anterior discharge carburetor. An anterior discharge carburetor is a carburetor with the fuel or fuel-foam discharge jet posterior to the air throttle. Such carburetors are used for aircraft as well as in some motorcycle carburetor designs.

It' is old and well known to juxtapose the reed valve andthe carburetor for two-cycle engines, the reed valve being disposed at the discharge end of the carburetor.

Such structures, however, generally use up a considerable space inasmuch as the barrel or passage through the carburetor is disposed at right angles to the reed valve, and the entire assembly occupies a very considerable space compared to the total bulk of small two-cycle engines.

It is a general object of the invention to combine an anterior discharge carburetor with a reed valve.

It is another object of the invention to simplify the construction and design of a two-cycle engine carburetor by combining it with a reed valve.

Still another object is to provide an inexpensive compact and reliable carburetor for two-cycle engines by combining it with a reed valve structure.

Other objects and advantages of my invention will be apparent in the following description and claims considered together with the accompanying drawings in which:

" Fig. l is a longitudinal sectional view through a combined carburetor and reed valve embodying my invention,

Fig. 2 is a view along the line 11-11 of Fig. 1,

Fig. 3 is an outline view of an engine embodying my novel structure showing the relationship of parts,

Fig, 4 is a sectional view through a modified form of :my combined carburetor and reed valve, and

Fig. 5 is a view along the line V-V of Fig. 4.

h Fig. 6 is a view in full section through a modified form of my invention wherein the throttle valve is a plate valve and the fuel discharges into the airstream as a rich airfuel mixture; and

Fig. 7 is a view along the line VII-VII of Fig. 6.

Referring to Fig. 3 there is illustrated an engine E having a crank case A to which is secured a carburetor B. A piston P operates within the engine structure and may act as a pump for the air intake to the crankcase A or a separate charging pump may be used. Fuel may be disposed in a tank T which may feed a float chamber or bowl D which, in turn, supplies fuel to the carburetor B.

Referring to Figs. 1 and 2 the crankcase A may have side walls 6 upon which may be disposed a carburetor body 5 to seal off the inlet opening of the crankcase. The carburetor body may have an air passage 8 therethrough which may connect with the interior chamber 1 of the crankcase A and these two cavities may be intermittently connected by a reed valve assembly C. The bottom of the carburetor B may form a valve seat 3 upon which may seat a reed or flexible plate 2 the downward movement of which may be limited by an inflexible reed guard 12. The plate 2 and guard 12 may be secured to the carburetor body 5 by means of screws 13. The upper end of passage 8 is the intake end and the lower end is the discharge end, and this lower end may be formed as a groove in the body 5.

Referring now to the details of the carburetor, the body 5 may have formed therein two fuel or fuel-foam discharge apertures 10 and 11. Also, the discharge aperture may admit a rich mixture as disclosed in my United States Patent 2,638,330 granted May 12, 1953. These discharge openings generally speaking may be alternative in their use and both are shown in one figure of the drawings for purposes of illustration and not necessarily utilitarian design.

The carburetor passage 8 may be controlled by a throttle valve 7 which may be of any desired design, for example, the conventional butterfly valve. Posterior to this throttle valve 7 the passage 8 is shaped particularly in accordance with my invention and it will be noted from a comparison of both Figs. 1 and 2 that the region designated by the dimension arrow 9 constitutes a restricted area or region with respect to the upstream and downstream portions immediately adjoining it. The bottom edge of this constricted region 9 is formed by the reed valve 2 which normally is seated against the valve face 3. This restricted area 9 accordingly is, in fact, a venturi giving rise to the usual low pressure area in response to air flow at this region so that it is suitable for the use of a fuel jet. It will be noted that the jet 10 is positioned at this most constricted part so that it may function in the usual fashion of carburetor jets positioned at a venturi.

The alternative fuel jet 11 operates effectively at all speeds. There is suflicient air flow between the valve face 3 and the plate 2 to create a low pressure condition due to the restriction of the air passage as the air escapes around the edges of the plate valve 2. The jet 1]. under these conditions will then be in a low pressure area akin to a venturi action and accordingly can function in much the same manner as a conventional fuel jet.

Considering now the operation of the fuel jet 10 the engine E or a separate charging pump may be started, drawing air through the carburetor passage 8 under the control of the butterfly 7. On the intake pumping stroke of the piston P (or upon starting a separate pump) the air will flow through the passage 8 unseating the valve 2 and hence flow into the crankcase passage 1 (or separate pump intake). The region 9 being a constricted part of the passage will create a venturi action causing fuel or fuel-foam to flow out of the jet 10. The air accordingly will be carbureted and the crankcase A will be filled with carbureted air mixture ready for use in the combustion chamber of the engine. When the piston P starts its charging and scavenging stroke, pressure differential seats the reed valve and the carburetor becomes momentarily inactive. The throttle valve 7 controls the volume of air flowing through the carburetor and hence controls engine speed.

The operation of the alternative fuel jet or aperture arrows v11 is similar to that for jet 10. This embodiment of the invention used the fuel discharge lll positioned close to the edge of the valve seat 3 on which the reed valve 2 comes to rest in its closed position. This is a high speed area where consequently suction is existing, While this point does not show the better aerodynamics of a venturi it is nevertheless useful for this purpose, a pressure drop is created at this point, and consequently it can be made useful for fuel metering purposes for interior discharge carburetors. The characteristic of this arrangement is the same as if one wall of an aerodynamically formed venturi is formed by the reed valve, namely, one wall of the restriction is formed by the reed valve. The air at the point of the discharge 11 is speeded up and squeezed through a slot-shaped opening formed on one side by the valve seat 3 and on the other side by the reed valve 2. The configuration of this slot has to be such as to create sufficient suction for metering purposes. This means that the reed valve preferably is not too large, or it must not open too far, or a combination of both. Of course, if the valve .seat edge is used as a true venturi throat and the fuel is metered to the point ll, then other forms of reed valve bodies than those shown in Figs. 1 and 2 can be used. Ordinary reed valve designs could be used provided their opening area is restricted as explained before and provided that the air flow is properly directed towards the reed valve opening so as to create the maximum of suction at this point.

Illustrated in Figs. 4 and 5 is a modification of my invention wherein the reed valve constitutes a part of the passage of the carburetor for the entire length of the passage. Accordingly, there may be secured to the walls 6 of the crankcase A a carburetor housing 20 having a groove 21 formed therein. Secured to the underside of the housing 20 may be a reed valve 22 backed up by a reed guard 23. Both may be secured to the housing 26 in any suitable manner, as by screws 24. The housing 20 may be secured by suitable means such as screws 26, and a gasket 27 may be interposed between the housing 20 and the crankcase walls 6. In this connection it should be noted that the reed 22 may be extended to the outer face of the housing 20.

The groove 21 and the reed 22 together form a carburetor passage designated generally by the numeral 28 and there may be disposed in this passage 28 an air control valve 29 of any type, for example, a butterfly valve. A constriction is formed in the groove 21 at the region 31 to thereby form a venturi in the passage 2% A fuel jet 32 may communicate with the passage at this point. An alternative fuel jet 33 may be disposed adjacent the most interior end of the passage 28. In Fig. 4 the left end of passage 28 is the intake end and the right end is the discharge end.

The operation of the carburetor of Figs. 4 and 5 is similar to that of Figs. 1 and 2. When the fuel jet 32 is operated the venturi action in the region 31 causes a metering of fuel from the jet 32. When it is desired to use the metering action of the air flow between the groove 28 and the reed valve 22, then the jet 33 may be used. The air valve 2? may be used to control total air flow and hence power output of the engine.

As used in this specification the word jet is synonomous with fuel discharge opening or aperture. The word jet is used in its sense as a nozzle or outlet opening and not in the sense of a controlled flow or metered device.

Referring to Figs. 6 and 7 there is illustrated a carburetor body 43 secured to the crankcase A by suitable means such as bolts or screws 41. The body 4 may have an air passage 42 therein which is intermittently communicated with the crankcase by a reed 43 backed by a guard 44 and both secured by suitable means such as a fastener 46. The conduit formed by the walls of the passage or groove 42 and the reed valve 43 may have a region of maximum constriction as at 47 wherein a .venout is formed. A fuel discharge opening 48 may com- 4 municate with the air passage 42 a this region 47 and .a smaller fuel discharge opening 49 may communicate also with passage 42 downstream or posterior to passage 48.

Disposed on the top of body 40 may be a valve plate 51 mounted for sliding pivotal action in a thin space 52 formed between the body 40 and a cap 53. The valve plate 51 may be secured to a shaft 54 journaled for rotation in the cap 53, permitting the valve plate to swing from one extreme to the other in space 52 (Fig. 7). Formed in cap 53 may be apertures or passages 42a, 45in and 49a registering with the passages 42, 48 and 49 respectively. The valve plate may have a close fit in its space 52 to limit leakage between the passages 42a, 48a and 49a.

The passage 48a may have a venturi formed therein at which point a fuel discharge opening 56 may be provided supplied by a conduit 57. The passage 49a may be constricted by a screw 58 and a fuel conduit 59 may discharge into this passage posterior to the screw. The passages aha and 49a act as rich mixture carburetors and the resultant rich mixture is metered by the air passage venturi 47. The air flow through these rich mixture carburetors may be carefully regulated and tailored by means of specially configurated apertures 42b, 48b and 49b formed therein, giving rise to variant flow and control according to any preselected pattern. The rich mixture carburetor of passage 49a is especially effective at low and idle speeds.

The operation of the charge forming device of Figs. 6 and 7 is that the rich mixture is diluted at the venturi 47 to form a desired air-fuel mixture when the reed valve 43 is open. When the reed valve is closed the charge forming device is ineffective.

l have discovered that passage friction gives rise to an apparent constriction which causes a low pressure area. This low pressure varies with the volume of air flow and can be used as a metering device in the same manner as a venturi especially with highly sensitive fuel feeding mechanism, for example, the rich mixture carburetor disclosed in my said Patent 2,638,330. Such friction takes place in a plain passage wherein a reed forms part of the passage.

It can be seen from the drawings that the venturi is arranged in such a way as to be substantially parallel to the reed valve. This arrangement serves two functions. First it gives a very nicely streamlined flow, which does not force as sharp bends in the air or mixture stream as usually found in induction systems with the carburetor discharging in a vertical axis towards the reed valve. The second purpose is to eliminate a separate casting for the reed valve seat thus saving both on manufacturing cost and the size of the combined apparatus. It can be .seen that one wall of the venturi throat is formed by the reed valve proper. The slight amount of opening at the carburetor throat of course increases the size of the throatsomewhat, but this opening being always the same, it is easy to compensate for it by proper selection of the fuel meters orifice. Another a n g f thi fo mat on of on wall of the venturi by the reed valve is in manufacture with the die casting method. Here an -accurately formed venturi throat can easily be cast without the use ,of slides or without the need for further machining.

With regard to Figs. 1 and 2 it is not necessary that fuel outlet 11 be positioned at the point of greatest deflection of the valve reed 2. All that is required to obtain a ven ri-like met ring act on i a c ns riction in the air stream. The reed valve 2 constricts the air all about its entire end. A metering action occurs therefore in a U- shaped region around the entire end of the reed 2 as viewed in Fig. 2. It would be practical therefore to place the fuel outlet at any point outwardly from about the region 9.

Frequently a number of reed valves are u ed to control th induction system of two cycle engines- These may be arranged separately or combined as for instance in the form of a star. The invention as illustrated in Figs. 1 and 2 can also be used in conjunction with such multiple finger reed valves. It is merely necessary to form at least one of these reed valves according to the before given description while the others can maintain their conven tional form and shape.

It is to be understood that other forms of execution are possible as would be apparent to persons skilled in the art.

I claim:

1. A carburetor comprising: a housing having a passage formed therein with an intake end and a discharge end, at least the discharge end of which is an open groove; a venturi constriction formed in the open groove creating part of a venturi whereat the groove cross sectional area is less than the groove portions immediately posterior and anterior; a reed valve positioned over the discharge end of said groove and opposite said groove constriction to form part of and to complete the venturi and to form part of the passage walls at, and to normally close ofi, the groove portion of said passage; a fuel discharge aperture in said housing at a low pressure area in said passage created by said venturi; and an air valve in said passage anterior to said fuel discharge aperture.

2. A carburetor comprising: a housing having a passage formed therein with an intake end and a discharge end, at least the discharge end of which is an open groove; a venturi constriction formed in the open groove dis charge end of said passage to form part of a venturi and having a lesser cross sectional groove area than the groove portions immediately anterior and posterior to the venturi to create a first area of constriction; a reed valve positioned over the discharge end of said groove and opposite the venturi constriction to form part of the passage walls and to complete the venturi at the first area of constriction, and said reed valve having its greatest deflection at the extreme discharge end of said passage whereby a second area of constriction is created when said reed val e is open; a fuel discharge opening communicating with the passage in at least one of said areas of constriction; and on air valve for said passage anterior to both of said areas of constriction.

3. A carburetor as defined in claim 2 wherein a fuel opening is located at each area of constriction.

4. A carburetor as defined in claim 2 wherein a fuel opening is located at the first area of constriction.

5. A carburetor as defined in claim 2 wherein a fuel discharge opening is located at the second area of constriction.

6. A carburetor as defined in claim 2 wherein the entire intake end of the passage is defined by said housing.

7. A carburetor as defined in claim 2 wherein the entire passage is an open groove and the reed valve completes the passage.

References Cited in the file of this patent UNITED STATES PATENTS 1,307,665 Guider June 24, 1919 2,442,217 Smith May 25, 1948 2,459,594 Smith Jan. 18, 1949

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