US3286728A - Slot type reed valve - Google Patents

Description

Nov. 22, 1966 D. K. STEPHENSON SLOT TYPE REED VALVE Filed March 27, 1963 INVENTOR.

W, M24 m ATTORNEY? United States Pfltfiflt F Filed Mar. 27, 1963, Ser. No. 268,362 2 Claims. 01. 131-s2s.s

The invention relates to reed valves. Generally speaking, a reed valve is a form of check valve comprising a flexible valve leaf or reed member mounted at one side of a port. and operated by pressure differential to and from engagement with a seat to control flow'through the port. In moving from its open position to its closed pOSltion, the reed member does not pivot upon a fixed axis but upon an axiswhich progressively approaches the port.

The invention seeks to attain increased reed member life by reducing as far as possible such stress loading as occurs during operation. More particularly, increased reed member life is attained in accordance with the invention by means providing for the elimination of, or at least a reduction in, reed member failure by reason of the formation of cracks or fissures extending inwardly from the periphery of the reed member. Such failure is believed to be occasioned by fatigue resulting from repeated heavy stress loading. 7

Reed valves are employed in many areas, including combustion air-intake arrangements in engines such as chain saw engines and outboard motor engines, which engines often operate at rates as high as 4,800 cycles per minute and sometimes at higher speeds. While the pressure conditions causing reed valve operation are generally not very high, it is common for the reed member to dish into the port after closure of the valve. Such dishing generally involves curvature about more than one axis and raisin-g of at least a portion of the reed periphery from the seat and into an area of less magnitudethan that which it occupied when flat. Such action creates a fluted or undulating configuration along the reed member periphery. As a result, it is believed that relatively heavy stresses are created, particularly in the form ofstress waves along the periphery of the reed.

Reduction of the maximum stress loading occurring during each cycle can be obtained in accordance with the invention in several ways which, when combined, cooperate to provide optimum reduction in the maximum stress experienced during. each operationalcycle.

A very significant contribution to maximum stress reduction can be obtained by limiting the amount or extent of lap between the periphery of the reed member and its associated seat. In this regard, the lesser the amount of lap, the lesser the extent to which the reed member periphery is raisable from the valve seat in response to dishing of the reed member into the port. Such lap is desirably limited to within a range from about .045 inch to about .010 inch. The lower figure represents a practical limit from the viewpoint of manufacturing tolerance and effective operation. Use of a lap of about .020 inch has been found to provide a significant increase in reed member life, as compared with conventional valves in least .065 inch and is commonly substantially in excess of .065 inch. which the lap between the reed member and the seat isat Limitation of lap between the reedrnernber andthe seat surrounding the port has also been found to result in an increased amount of wear along the periphery of the reed member, at least during initial operation of the reed valve. As fatigue is considered, at least initially, to be a surface condition, it is possible that the rate of wear is faster, when a limited lap is employed, than the rate of development of fatigue in the wearing surface. It isialso "ice possible that such wear serves to work harden the lapping surface of the reed member and thereby inhibit the development of a fatigue in the wearing surface.

Reduction in valve'member stress can also be obtained in accordance with the invention by formation of the reed member and its associated port and seat so as to limit reed member fiexure, when the reed member is in portclosing position, either by substantially preventing dishing, or by substantially limiting such dishing to fiexure about a single axis. Prevention of reed member dishing or fiexure, when the reed member is seated, can be obtained by formation of the port with a seat which, with respect to the reed member, is convexly curved about a single axis extending parallel to the axis about which the reed member flexes to close the port. Consequently, during progressive closing of the port, the reed member assumes a curvature which serves to rigidify it against curvature about more than one axis, therefore tending to preclude displacement or dishing inwardly of the port. Alternatively, the reed member can be preformed to provide rigidity against fiexure about more than one axis.

Limitation of dishing to curvature about a single axis can be obtained in large measure by formation of the port so that all or a substantial portion of the edge of the port lies in the surface of an imaginary curved surface, such as for example, a cylindrical or hyperbolic surface, which surface is concave with respect to the reed member. One arrangement for accomplishing this result employs an elongated port configuration with at least one rectilinear edge which extends lengthwise of the port and which tends to serve to establish reed member fiexure about a single axis parallel to said edges along the major part of the length of the port inwardly of the ends of the port. With this configuration, reed member flexure can be limitedat the ends of the port-closing portion to curvature about a single axis by forming the end edges of the port so as to lie in an imaginary curved surface which includes said rectilinear edge. For best results, the edge of the port opposite to said rectilinear edges also lies in said imaginary curved surface.

Increased stress reduction can also be obtained in accordance with the invention by reduction in impact occurring incident to seating of the reed member. Reduction in impact can be obtained either by reducing the reed valve velocity at the time of impact or by extending the time interval of impact.

Reduction in reed member velocity at the time of impact can be obtained by limiting the area of the reed member which is subject to the pressure differential causing reed member travel relative to its seat. One arrangement for attaining this result is to limit lap. Another arrangement includes provision for porting the reed member in the area between its hinged connection to the rigid member and the adjacent edge of the controlled port. Such limitation of lap and porting of thereed member 1 serve to reduce the over-all reed member area subject to the action of any pressure differential. Consequently, the applied force and resultant velocity relative to the valve seat is also reduced. Reduction in impact stress can also be obtained by providing resiliency in the valve seat so as to lengthen the time interval of impact. Resilient seats can also be used to assist in obtaining single-axis flexure.

Other objects and advantages of the invention will become known by reference to the following description and accompanying drawings.

In the drawings:

FIGURE 1 is a partially broken away elevational view of a reed valve in accordance with the invention;

FIGURE 1a is an enlarged sectional view of a portion of the reed valve shown in FIGURE 1, showing the disposition of the reed member relative to the reed plate during gas flow through the reed valve;

FIGURE lb is a view similar to FIGURE la, showing the relation of the reed member to the reed plate immediately upon engagement of the reed member with the reed plate and just prior to disengagement of the reed member from the plate;

FIGURE 10 is a view similar to FIGURES la and lb, showing the disposition of the reed member when seated against the port in the reed plate and flexed inwardly of the port;

FIGURE 2 is an exploded perspective view of the reed valve shown in FIGURE 1;

FIGURE 3 is a sectional view taken along line 3-3 of FIGURE 1;

FIGURE 4 is a fragmentary sectional view of a modified form of reed plate;

FIGURE 5 is a fragmentary elevational view of a reed valve embodying the reed plate shown in FIGURE 4;

FIGURE 6 is a fragmentary sectional View of another modified reed plate;

FIGURE 7 is a fragmentary elevational view of a reed valve embodying the reed plate shown in FIGURE 6;

i in less remote relation to theboundary line 24. At its ends, the port is defined by end or side edges' 29 and 31 which are generally parallel to each other, which are substantially normal to thelengthwise edges 25 and 27, and which merge through small radii, indicated at 33, into the outer and innerlengthwise edges 25 and 27, respectively.

Use of an elongated port, as disclosed above, serves to limit flexure of theportion 20 of the reed member inwardly of theport 17, when the reed member is seated against the plate in port-closing relation thereto, to curvature about only one axis along a major portion of the length of the port inwardly of theend edges 29 and 31 of the port. Such flexing of the port-closingportion 20 of the reed member inwardly of theport 17 is believed to be primarily caused by momentum of the reed member, but is also believed to be due in part to the existing pressure difl'erential.

Flexure of the port-closing portion 20 of thereed member 19 adjacent to theend edges 29 and 31 of theport 17 can be substantially limited to curvature about. the single axis mentioned immediately above by various means.

Specifically, as shown in FIGURES 4 through 7, the valve FIGURE 8 is a fragmentary sectional view of still an- 7 other modified reed plate;

FIGURE 9 is a fragmentary elevational view of a reed valve incorporating the reed plate shown in FIGURE 8;

FIGURE 10 is an enlarged fragmentary view of still another modified reed valve; and

FIGURE 11 is a fragmentary sectional view of still another modified reed valve. a

The reed valve 11 shown in FIGURE 1 of the drawings is exemplary of various arrangements and configurations that can be used in accordance with the invention. The reed valve 11 includes a rigid member orplate 15 having therein a port oraperture 17, a relatively flexible valve leaf orreed member 19 which is fixed to theplate 15 and includes a port-closingportion 20 movable relative to theplate 15 to open and close theport 17, together with aleaf stop 21 which is fixed to theplate 15 and which serves to limit opening movement of thereed member 19 away from theplate 15. Theleaf stop 21 can be fabri cated of any rigid material, such as for example, brass or steel, and can be of various configurations.

While various arrangements can be used to unite thereed member 19 and theleaf stop 21 to theplate 15, the disclosed construction utilizes a series of laterally. aligned screws 23 which can serve to establish an area of permanent engagement between thereed member 19 and theplate 15. During movement between its open and closed positions, thereed member 19 flexes relative to the area of permanent engagement about an axis which progressively moves from the boundary line of the area of permanent engagement toward the outer or free end of the reed member until closure of the reed member against theplate 15 is complete. theleaf stop 21 is fabricated and assembled to the reed plate so as to establish aboundary line 24 limiting the area of permanent engagement of thereed member 19 with theplate 15. Preferably, theboundary line 24 is essentially rectilinear.

Theplate 15 can be formed in various ways, as for instance, by aluminum die casting. Suitable arrangements not material to the invention can be provided for securing theplate 15 about an opening in a housing, such as a crankcase, which housing is subject to cyclical pressure variation above and below a pressure condition exterior to the housing.

Theport 17 is elongated in generally parallel relation to theboundary line 24 of permanent engagement. The port includes an outerrectilinear edge 25 which extends lengthwise of theport 17 in remote, generally parallel relation to theboundary line 24. Theport 17 also includes a second or innerrectilinear edge 27 extending in parallel, opposed relation to the outerrectilinear edge 25 In the disclosed construction,

seat portions at the margins of theplate 15 at the end edges 29 and 31 can be concavely dished with respect to the plane of the plate so as to conform generally to the curvature of the port-closingportion 20 of thereed member 19 about the before-mentioned axis when flexure of thelengthwise edges 25 and 27. The curvature of therecesses 35 corresponds to the curvature of the central part of the reed member port-closingportion 20 when the flexure of the reedmember inwardly of the port is at its normal maximum, thereby permitting flexure of the end parts 20a of the port-closing portion in substantially like manner to the flexure of the central part 20b of the reed member port-closing portion.

In the embodiment shown in FIGURES 6 and 7, thereed plate 15 is provided with a concavely dishedrecess 37 which includesmarginal portions 39 and 41 of the feed plate extending along therespective edges 25 and 27, as wellasmarginal portions 43 of the reed plate at the ends of theport 17. Preferably, theouter edge 45 of the recess 39 terminates in the area where the outer edge of thereed member 19 initially engages thereed plate 15 during port-closing operation and before flexure of the reed member inwardly of the port.

Limitation of reed member flexure at the ends of the port-closingportion 20 curvature about a single axis extending lengthwise of the port-closing portion can alternatively. or additionally be obtained by using resilient in-- serts at the ends of theport 17. Such inserts can be a fabricate of materials such as nylon to permit conformance of the lapped margins of the inserts to the tendency of the port-closingportion 20 of thereed member 19 toward flexure about a single longitudinally extending axis of curvature. a

More specifically, in the embodiment shown in FIG-URES 8 and 9, thereed plate 15 is recessed about each of the ends of theport 17 to provide a seat 47 receiving aresilient insert 49 capable of conforming to the tendency of the port-closingportion 20 toward flexure about a single lengthwise axis. In the embodiment shown in FIG-URE 10, the reed plate is recessed around the entirety a resilient insert 53.-

In general, if ports having outlines other than the illustrated, generally rectagula-r outlines are employed, the valve seats or edges defining such ports preferably should encourage reed flexure about a single axis when the reed member is seated against the reed plate in port-closing relation thereto. Such seats or port edges therefore should lie in the surface of an imaginary curved surface having an axis and radius corresponding to the axis and radius of curvature of the reed member under a condition of normal maximum flexure inwardly of the port.

Stress reduction can also be obtained by preventing fiexure of the reed memberinto the port. More specifically, in the embodiment shown in FIGURE 11, the reed member is induced by the reed plate during progressive closure of the port, to assume a curvature about a single axis, which curvature is concave with respect to the reed plate. Such concave curvature tends to rigidify the reed member so as to prevent subsequent curvature about axes other than said single axis and thereby prevent the creation of peripheral stress waves such as are believed to occur during reed member flexure about more than one axis.

Still more particularly, in FIGURE 11, the plate is provided with a valve seat which extends about the port and which, with respect to thereed member 19, presents a convexly curved surface 75. During closure of thereed member 19 against the seat, the reed member assumes the curved configuration of the surface 75, thereby rigidifying thereed member 19 against buckling or dishing into the port, and thereby avoiding the creation, along the periphery of the reed member, of stress waves such as are believed to commonly occur in response to dishing or bending about more than one axis. Alternatively, thereed member 19 can be preformed with a curved configuration complementary to that of the reed plate seat surface 75, or the reed plate can be flat and the reed member preformed with a configuration which, with respect to the fiat reed plate seat, is concavely curved, thereby rigidifying the reed member against flexure into the port.

In the illustrated embodiment, means are also provided in thereed plate 15 for eliminating, or at least substantially reducing, adhesion between the reed member and the reed plate due to accumulated oil on the contacting surfaces thereof between theline 24 and theport 17. Such means includes, in theplate 15, one or more grooves, recesses, or chanels 55 which extend across thereed plate 15 between theiner port edge 27 and theboundary line 24 of permanent engagement between the reed member and the plate, thereby reducing the area of contact between the reed member and the reed plate, in the area between theport 17 and theboundary line 24. Thegroove 55a adjacent to theline 24 also provides a space for collecting any grit or foreign material which may enter between the reed member and the reed plate, without affecting progressive port-closing and portopening flexure of the reed member.

Reduction in impact stress can also be achieved by lengthening the time interval of impact through the provision of a resilient margin or insert around all or a part of theport 17, such as theinserts 49 and 53 already mentioned. Such resilient margins can also be used, as explained above, to permit reed member flexure about a single axis, particularly if the end portions of the resilient margins are fabricated to be of greater yieldability than the lengthwise margins.

Thereed member 19 is fabricated of resiliently flexible material, such as stainless steel, and, in the disclosed construction, is generally of rectangular configuration, including the port-closingportion 20 and a series of spaced, generally parallel legs orsegments 59 which extend from the port-closingportion 20 and are secured to thereed plate 15 by thescrews 23. The port-closingportion 20 of the reed member includes anouter edge 61 and side edges 63 and 65, and is dimensioned so that when thereed member 19 is assembled to theplate 15, the outer and side edges 61,

63, and 65, respectively, lap the seat area at the margin of theplate 15 along the port edges 25, 29, and 31 by an amount within a range of from about .010 to about .045 inch, preferably about .020 inch. Limitation of the lap to the above range lessens the area of thereed member 19 subject to the effect of cyclical pressure variation, thereby tending to reduce reed valve velocity and consequent reed member stress. Such limitation of lap also lessens the extent to which the outer and side edges 35, 37, and 39 of the reed member are dispiaceable from the plane of thereed plate 15 adjacent to theport 17 when the port is closed. This feature is especially important in instances where reed member flexure is not confined to curvature about a single axis.

The construction of thereed member 19 also serves to limit impact velocity by the provision of the open area orcutouts 58 which define the before-mentionedlegs 59. As thecutouts 58 extend from at least theboundary line 24 of permanent engagement between the reed member and the plate to adjacent theedge 27 of theport 17, the total reed member area subject to reaction to any pressure differential, during opening and closing reed member movement, is thereby reduced.

Various of the features of the invention are set forth in the following claims.

What is claimed is:

1. A reed valve including a reed plate having therein means defining a port and a seat extending from and surrounding said port, a reed member subject to curvature upon port closing operation and including a port clos ing portion, and means securing said reed member to said reed plate for movement of said port closing portion rela tive to said reed plate to and from a position of engagement with said seat, said reed member overlapping said seat by an amount less than about .045 inch along a portion of said seat which is most remote from said reed member securing means, said port being elongated and including a rectilinear edge at the intersection of said port and said remote portion of said seat, said edge extending lengthwise of said port, and said seat having end portions including resilient means surrounding at least a portion of said port and permitting displacement of the surface of said end portions.

2. A reed valve including a reed plate having therein means defining a port and a seat extending from and surrounding said port, a reed member including a port closing portion subject to curvature upon port closing operation, and means securing said reed member to said reed plate for movement of said port closing portion relative to said reed plate to and from a position of engagement with said seat, said reed member overlapping said seat by an amount less than about .045 inch along a portion of said seat which is most remote from said reed member securing means, said seat being fabricated of resilient material to afford conformance of the surface of said material to the curvature of the part of said port closing portion engaged against said seat.

References (Iited by the Examiner UNITED STATES PATENTS 978,152 12/1910 Gutermuth 137525.5 1,029,726 6/1912 Sprado 137517 1,299,762 4/1919 Nelson 137525.3 2,001,885 5/1935 Ohmart l37525.5 X 2,224,494 12/1940 White 137527 2,616,403 11/1952 Kiekhaefer 137525.3 X 2,639,699 5/1953 Kiekhaefer 12373 2,798,505 7/1957 Kehler 137516.11 2,851,054 9/1958 Campbell 251368 X 2,885,178 5/1959 Mott 251-368 3,016,914 1/1962 Keithahn 137-527 X 3,191,618 6/1965 McKim 137-5253 WILLIAM F. ODEA, Primary Examiner.

D. ZOBKIW, Assistant Examiner.

Claims (1)

1. A REED VALVE INCLUDING A REED PLATE HAVING THEREIN MEANS DEFINING A PORT AND A SHEET EXTENDING FROM AND SURROUNDING SAID PORT, A REED MEMBER SUBJECT TO CURVATURE UPON PORT CLOSING OPERATION AN INCLUDING A PORT CLOSING PORTION, AND MEANS SECURING SAID REED MEMBER TO SAID REED PLATE FOR MOVEMENT OF SAID PORT CLOSING PORTION RELATIVE TO SAID REED PLATE TO AND FROM A POSITION OF ENGAGEMENT WITH SAID SEAT, SAID REED MEMBER OVERLAPPING SAID SEAT BY AN AMOUNT LESS THAN ABOUT ABOUT .045 INCH ALONG A PORTION OF SAID SEAT WHICH IS MOST REMOTE FROM SAID REED MEMBER SECURING MEANS, SAID PORT BEING ELONGATED AND INCLUDING A RECTILINEAR EDGE AT THE INTERSECTION OF SAID PORT AND SAID REMOTE PORTION OF SAID SEAT, SAID EDGE EXTENDING LENGTHWISE OF SAID PORT, AND SAID SEAT HAVING END PORTIONS INCLUDING RESILIENT MEANS SURROUNDING AT LEAST A PORTION OF SAID PORT AND PERMITTING DISPLACEMENT OF THE SURFACE OF SAID END PORTIONS.

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