US 3191618 A
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Description (OCR text may contain errors)
June 29, 1965 C.- D, McK|M 3,191,618
cURvED SEAT REED VALVE Filed Oct. 29, '1962 from/sys United States Patent O 3,191,618 CURVED SEAT REED VALVE Carrol D. McKim, 791 34th Ave., San Francisco, Calif. Filed Oct. 29, 1962, Ser. No. 233,581 3 Claims. (Cl. IS7-525.3)
The present invention relates to valves, and pertains more particularly to a curved seat reed valve.
Reed valves are Widely used in industry where a light weight, quick acting, demand type of valve is desired, for example, in certain types of pumps, small gasoline engines, particularly of the two cycle type, and other uses well known to those familiar with valves.
One particularly important field of use for such valves is in small, high performance, two cycle engines of the type used in small racing vehicles known as karts In engines used to drive these karts, reed valves are used to control the passage of the fuel-air mixture from the carburetor into the crankcase. When the engine is operating at extremely high r.p.m., however, even these conventional reed valves have a tendency to either float, or to flutter from bounce in closing, and when either of these conditions occur the power and eiliciency of the engine drops oi sharply.
The present invention consists in providing a valve reed seated on a curved seat, the curvature of the seat conforming to a naturally flexed condition of the reed.
Another object of the invention is to provide a reed valve wherein the reed is ilexed to curved condition and is seated on a seat which conforms substantially to the normal curvature of the reed in such liexed condition. Another object of the invention is to provide an improved, curved seat, reed valve.
These, and other objects and advantages of the invention, will be apparent from the following-description and the accompanying drawings, wherein:
. FIG. 1 is a view, partly in side elevation and partly in medial section, of a reed valve assembly embodying the present invention and mounted on the crankcase-cylinder block of a two cycle engine.
FIG. 2 is a sectional view taken along line 2-2 of FIG. 1, a portion of the engine block being broken away to the plane of the valve block.
FIG. 3 is an enlarged, perspective view of the valve reed shown in FIGS. 1 and 2 as it would appear when firmly gripped at one end thereof, and with its other end supported by a T-shaped bar to flex the valve reed to a curved condition corresponding to that shown in FIGS. 1 and 2, the normal, iiat, unstressed condition of the valve reed being shown in broken lines.
FIG. 4 is a plan View somewhat similar to FIG. 2, but showing a modified, double port form of the invention.
FIG. 5 is a sectional view taken along line 5-5 of FIG. 4.
Referring briefly to the form of the invention shown in FIGS. 1-3, a valve A comprises a valve block 10 mounted over the intake port 11 of a generally conventional, air cooled, two-cycle engine block B. The latter consists of unitary engine cylinder portion 12 and crankcase portion 13. A valve reed 14, of spring sheet material, such as, for example, shim stock, secured by an anchor bar 15 and screws 17 to a curved seat 18 formed on the inner or engine side of the valve block 10.
The curvature of this seat 18 conforms to the normally exed condition of the valve reed 14 when the latter is exed laterally from its normally straight position as shown in FIG. 3. The valve reed thus bears throughout its length against the valve seat, with the seating bias at the free end of the reed as great as, or greater than, that throughout the remainder of the reed. Thus, the reed tends to seat quickly, effectively, and without float or bounce after each opening thereof. This provides greatly increased etti- 3,191,618 Patented June 29, 1965 ciency, particularly at high speeds, over a reed valve seated on a conventional tiat seat.
Referring to the drawings in greater detail, the illustrated unitary crankcase and cylinder block B is conventional, and requires no detailed explanation for one familiar with this type of engine. The usual intake port 11 is provided in a side of the engine block B, and the valve block 10, and a usual carburetor mounting pad 19 are attached to the engine block B over this intake port by bolts 20. Sealing gaskets 21 and 21a seal the joints between the carburetor mounting pad 19 and the valve block 10, and between the latter and the engine block B, respectively.
A conventional carburetor C is mounted on the carburetor mounting pad 19, and is secured thereto by studs 22 and nuts 23. The carburetor is sealed to its mounting pad 19 by a gasket 24. The usual throat 25 (broken lines, FIG. l) of the carburetor C registers with aligned passages 26 through the carburetor mounting pad 19, and 27 through the valve block 10. The latter, as mentioned previously herein, registers with the intake port 11 in the engine block B.
The curved valve seat 18, which is an important feature of the present invention, is formed on the inner or engine side of the valve block 10, and is curved to conform to the normal curvature of a valve reed 14 to be used therewith when said reed is securely clamped to one end of the seat 14 by the transverse mounting bar 15 and screws 17.
The curved shape of the valve seat 18 is determined by the normal curvature of the valve reed 14 when the mounting end portion 27 (FIG. 3) thereof is gripped securely between the bar 15 and a suitable support pad 28, and the other or free end 29 of the reed is flexed laterally a required amount as by the head of a T-shaped member 30 bearing for free universal pivotal movement on a point 31 formed on the lower end of its stem 32. Thus the T- shaped member 30 is free for tilting movement in any direction about its supporting point 31, and the reed 14 in FIG. 1 is in a normally exed condition.
The normally flexed curvature of the convex side of the reed 14 thus found is reproduced on the valve seat 18. The reproduction may be performed in any desired way, a number of which ways are well within the knowledge and capability of a skilled machinist or other artisan. For example, a mold may be made thereof in plaster of Paris or other suitable molding material, and the shape thus provided may be reproduced in metal as by machining or casting to provide the seat 13 of FIGS. l and 2.
The stiffness of the valve A, i.e., its resistance to opening and its tendency to close rapidly, may be increased by: (l) increasing the iiexure or curvature of the valve seat, and therefore the initial or seated curvature of the valve reed; (2) increasing the thickness of the reed; or (3) employing stiffer material from which to make the reed.
When a valve embodying the present invention is to be used for an extremely high speed engine, for example, one which will turn at a speed of the order of ten or twelve thousand revolutions per minute, a thin reed and a substantial curvature of the valve seat would be desired, since this would insure full and rapid opening, and quick and complete closing ofthe valve, and would tend to eliminate oat and bounce. For a more modest speed, for example tive or six thousand r.p.m., the curvature of the valve seat may be reduced to provide freer and fuller opening of the valve at such lower speeds.
Aside from the advantages explained previously herein,
' the operation of the valve A is in general similar to that valve reed 14, the valve opens, and remains open until the difference in these pressures is reduced sufficiently to allow the spring bias of the reed 14 to return it to its seat. When the pressure within the crankcase 13 is greater than that on the outer side of the valve, the reed 14 is urged thereby t0- ward its seated condition.
In the modified form of the invention shown in FIGS. 4 and 5, a double ended valve reed 35 controls double in-V let ports 33 and 34:, formed in a valve block 36. The valve reed 35 is secured medially of its length between the ports 33 and 34 by a transverse mounting bar 37 and screws 38. As in the form of the invention shown in FIGS. l and 2, the valve seat 39 conforms to the normal curvature of the reed 35 when the latter is flexed as shown. The operation' and other features and advantages of the double ended reed Valve shown in FIGS. 4 and 5 are in general similar to those of the single reed valve A shown in FIGS. l and 2, and the operation of the valve shown in FIGS. 4 and 5 will be obvious to one who has read the explanation pertaining to the form of the invention shown in FIGS. 1 3. Y
The invention provides a simple and effective reed valve,
and one which has been found to increase the efficiency and power of a two cycle engine, particularly at high rpm., and also insures ellicient performance at intermediate and lower speeds, due to its full and rapid opening and highly effective closing action, and the absence of a tendency to bounce, flutter or float.
hile I have illustrated and described a preferred embodiment of the present invention, and one modified form thereof, it will be understood, however, that various changes and modifications may be made in the details thereof without departing from the scope of the invention as set forth in the appended claims. Having thus described the invention, what I claim as new and desire to protect by Letters Patent is dened in the following claims. Y
l. A reed valve comprising:
a valve reed of thin, normally flat, single thickness,
springy, sheet material, which, when relieved of external stresses will lie flat, lbut which is flexed lengthwise thereof to define a curve determined by the normal ilexure of the reed when the latter is xedly held at one end thereof, and the other end thereof is offset laterally and without torque a selected distance from a plane tangent to the iixedly held end of the reed when so held by a force applied transversely to the other end of the reed,
a valve seat having a valve opening therein and curved to conform to the convex side of the thus flexed valve reed,
a valve mounting surface co-extensive with the valve seat and laterally adjacent the valve opening therein, and
means xedly securing such xedly held end of the valve reed onto the valve mounting surface, thereby flexing the normally flat valve reed into conforming relation with the valve seat throughout the length of the reed.
2. A reed valve comprising:
a valve reed of thin normally llat, single thickness,
springy, sheet material, which, when relieved of external stresses will lie flat,
a valve seat having a valve opening therein and curved to conform to a selected, transversely flexed condition of the valve reed to be mounted thereon,
a'valve mounting surface co-extensive with the valve seat and laterally adjacent the opening therein,
and means securing a portion of the valve reed remote from the flexed end thereof onto said valve mounting surface, thereby transversely flexing the reed into said transversely flexed condition for conforming relation and overall contact with the valve seat. 3. The method of providing a substantially uniformly flexed reed valve structure which comprises shaping a valve seat to conform to the curve defined by a thin, normally llat, springy valve reed of uniform thickness when rigidly held at one end thereof and deflected transversely to the normal plane of the valve reed bya laterally directed force applied to the free endv of the reed, and then mounting one end portion of a thin, normally ilat valve reed of uniform thickness on a surface adjacent to and co-extensive with one end of the valve seat and drawing the thus applied end of the valve down closely to the mounting surface to thereby flex the normally flat valve reed into overall, substantially uniformly flexed conformity with the valve seat.
References Cited bythe Examiner UNITED STATES PATENTS WILLIAM F. ODEA, Primary Examiner.