CA2058629A1 - Butterfly-type check valve - Google Patents

Abstract

A butterfly-type check valve (30) employs a secondary check valve (38) that is carried on the valve plate (36). The valve plate (36) is revolvable and translatable relative to the pivot shaft (34). In operation, the check valve (30) opens in response to a change in aerodynamic forces which act on the valve plate (36), the change being effected as a response to the opening of the secondary check valve (38). As the valve plate (36) rotates to an open position, its revolutionary movement relative to the shaft (34) changes the location of pivot points (40) relative to the surface (62) of the plate. This changes the areas (42, 44) of the surface (62) on both sides of the pivot points (40) so that the aerodynamic forces cause the valve (30) to open still further.

Description

W~J 'Jliiiii~b~ ; r~ ~ ~ ? ~j ?~T/~ssoio3i~2 BUTTERFLY-T~PE CHECg VALYE -TECHNIC~L ~IELD

The pres2nt invention rela~es-generally to check valves. More specifically, the invention relates to check 5 valves which are operable to open in response to flow through a pilot valve, and which comprise a plate-like main valve member which is secured to a shaft in such manner that the va~ve member is revolvable and translatable relative to the shaft.

Th~ in~en~ion employs ~arious aspects of the teaching contained in U.S. Patent Application Serial No.
374,~97 entitled "Butterfly Valves With Actuators Carried On Valve Plate", which was filed on June 30, 1989. ~The dis-clo~ure thereof i6 incorporated herein.by referenee.
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BACKGROUND OF THE INVENTION
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FIG. 1 of the accompanying drawing~ schematically illustrate~ a-conventional.bu~teri.ly valve arrangement 10 in which a butterfly pla~e 12 posi~ioned in a duct 14 is .: rotated about.an axis.defined by~a`spindle or shaft 16 in - 20 order-to vary.~the ra~e-à~ which-.fluid-flows through the -.. duct. ~Typically; the pla~e 12 is.rota~ed via ~orque applied . ~.. by.an e~ternal.actuator-..18~through thè shaft:l6.:

.. . . A iseries o:arrows 20 generally~illù~tratés the .static.-pres~ure~profil~ re~ulting from the aerodynamic or .25 -hydrodynamic forces~acting on-the~but~erfly!plate 12.. The overall effect of~the ætatic pre~sure may be repre~ented by . a-center..of.pressure-(indicated..by`-the-arrow~22)~which tends to force ~he~pl~e 12~to.the.:cloged;posi~ion~.~xThis~orce .mNst be~..counteredsor overcome by.energy sùpplled`~o the `: :

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, ,, , ., : --_, _ actuator 18 in order to retain the position of the plate 12 or further open the valve 10.
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As a general matter, in order to lower the externally-supplied energy required to match or exceed the hydrodynamic force~ acting on the plate 12, the center of pressure 22 sho~ld be favorably altered in relation to the axis of rotation. That is, either ~he center of pressure 22 should be aligned with or moved closer ~o the shaft 16, or ~he shaft should be aligned with or moved closer to the center of pressure.

. The abo~e-referenced application teaches, among o~her ~hings, that if in the design of a butterfly valve one provides for relative ~ransla~ional movement between the .-- shaft 16 and-the plate 12, then the bulk of the energy required to torque the plate can be provided by the aero-dynamic forees acting thereon. The present invention employs this and other ~eaching contained in said applica-tion to provide a butter1y-type chec~ valve.
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:. " i ;`~ DISCIl)SURE OF TEE: INVE~TION

.20 ,~ ~ !The invention `is:a butterfly-type check valve.
- The salient fea~ures of the invention in its broadest aspect .`' '. ,t' are ~wo. .The first is.that the butterfly plate is secured to;the shaft in ~such manner that.the:plate is c~pable of revo'lu~ionary movement rel~tive to the shaft, whereby the ., 25 .re~ol~tionary movement-effec~s translation of the plate rela~ive to ith`e shaftO .The seeond -is ~he provision of a secondary check -valve~- or. pilo~. ~alve carried -on the plate .
he importance of..the pilot valve is that it provides a ,means for, initially opening the check valve in response to ,3 . 30 ~.laerodyna3lic .forces which might othérwi~e tend ~o keep the ~3,~ butterfly plate in a . closed position~ ~~, The importance of the , .
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first feature is that as the plate revolves and translates relative to the shaf~, it also translates relati~e to a pivot line about which the plate can turn. Thus, the posi~ion of the pivot line relative to the plate varies with the angle of rotation of the.plate. The advantages theireby provided are better understood by reference to the following description, which includes the appended claims and accompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustra~ion o a conven-tional butterfly valve arrangementO

FIG. 2('a)-2~d) schematically illustrate the operation of a butterfly-type check valve in accordance with the invention.--.
FIG. 3 is a croc~-sectional view of ~he preferred embodiment of the invention and is taken along line 3-3 of FIG. 4.

~. ~ FIG. 4 is a.g~nerally el.evational, partially ..~. . cross-sectional view taken along l.ine.~-4 of FIG. 3.

20 ~ ~ . . FIG. 5~is a cross-sectional view as in FIG. 3 and ~ illu~tra~es the check valve in an:open.position~
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^.BEST MODE FOR CARRYING OUT. T~E INV~NTION

.:''':!~' `'`":`' ::" '~i' ~ FIGS. 2A through,~2D schematically~illustrate the ; . ... principles.on which the check valve o the invention oper-., . ~
..,;...~,~25 ate8. In.FIG. 2A,-~the~valve 30 is shown in:a clo3ed posi-,~ ,r..~tion..t The.~desired direction.of/fluid flow,(indicated by arr~ 32) is from left to right. The valve 30 comprises a . . : : .
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, . v shaft 34 defining a longitudinal axis 35, a plate-like ~alve rnember 36 (hereinafter "plate") that is secured to the shaft in such manner that the plate is capable of revolutionary and translational movement relative to the shaft, and a pilot valve 38 secured to and carried by the plate. Ini-tially, with the pilot valve 38''closed, the center of pressure 22 associated'wi~h `t~e aerodynamic forces acting on ~he plate 14 is aligned wi~h the pivot point 40 about which the plate turns, as is illus~rated in FIG. 2A ~The pivot line 40 can be viewed as extending into the sheet in a direction parallel to both ~he axis 35 and the plate 36).
As fluid pressure forces the pilot valve 38 open, the center of pressure 22 mov~s upward, as is illustrated in FIG. 2B.
In response to the change in aerodynamic forces, the plate 36 rotates in a clockwise direction, as is illustrated in FIG. 2C. As the plate 36 rotates, it also undergoes revolu-tionary movement rela~ive to the shaft 34. This revolutionary movement effects translational movement of the plate rela-tive to the shaft. Thus, in FIG. 2A, the area ~indicated in ~0 single dimension-by arrows 42'and 44) of the plate 36 is the same on each side of the pivot linls 40. However, in FIG.
2C, the area 42 above the pivot line 40 is greater than the area 44 below the pivot line.` Assisted by the fact ~hat the aerodynamic.forces can act on a g'reater-area 42 above 2S the pi.vot line 40, ~he valve 30 will continue to open until : the center of pressure;22 is-again aligned with the pivot line 40, as is illustra~ed in FIG.'~2D.; The':'downward movement of ~he eenter of pressure 22 may be attributable to .a mlmber of actor~,c: Onè su'ch :factor'may be flow restric-tion by the shat 34. ~nother is that the aerodynamic '. :;forces~.acting-~against-~thè^edge of thP plate 36 become more :influential~:asith~:plate moves to:h'igher'angles'of rotation .(angles.of;ro~at~on being-lndicated generally'by'~'the`:curved arrow 45).' Yet another'i~''the aero~ynamié forcè"acting on ' : ' ' ' .
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, - the gating mechaniæm 47 of the pilot valv~ 38. If fluid flow is reversed as indieated by ~he dashed arrow 46, the pilot valve 38 is forced æhut and the aerodynamic forces, assisted by the fact that the area 42 i~ greater than the area 44, rotate the pla~e 36 to the closed position indi-cated by FIG. 2A.

Referring now ~o FIGSo 3 and 4 a shaft 34 is formed from two axially-extending components to accommodate rigid securement of two spaced pinion gears 48, 50 to the shaft, and to provide for installation of a tubular sleeve 52. The sleeve 52 surrounds a centrally-disposed, recessed portion 54 of the shaft 34 and is freely rotatable there-about via bearings 56. A plate 36 has ~wo rectangular recesses (not shown) into which two rack gears 58, 60 are 15 -positioned and rigidly ~ecured to the plate. The plate 36 is provided with a ~uitable rim seal-(not shown~ and is positioned parallel to the shaf~ 34`such that the latter equally bisects the plate and the rack gears 58, 60 engage the pinion gears 48, 50. To minimize binding, the gears 48, 50, 58,~60 and recesses are dimen~i.oned to ensure that the : contac~ po~nts:between the gears are nominally flu~h with the surface 62 of the plate 36. ~ generally C-shap~d bracke~ 64 envelops the haft 34 and ~ welded at its ends ~ - to tha plate.36'....1-The bracket 64 is'dimenæioned;~o accom-modate the expected ran~e of transl~tional movemènt of ~he plate 36 relative to the shaft 34, and to ensure that its : dis~al;inner~surface:66 abuts.the~ou~er ~urface of the ~- sleeve 52 . ? .: The:pla~e 36.has a.hole 68 formed therethrough.
A:reed, hinged--flap 7Q,--or functionally similar-gating - ,:. 30 device;is;~sec~red~to thè.~plate 3S so that i~:eovers the hole 68. ?The flap~70 and hole 68 cooperate~to form the ~ :~pilot valve ~38.~iThe pilot valve 38:.is-e~sentially;a-æecond-ary eheck valve and unc~ion~ to effec~ a change in thP

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locatiun of the center o pressure 22 tFIG. 2) so ~hat the check valve 30 opens when flow proeeeds in the desired direc~ion 32. A stop 72 secured to the flap 70 limits movemen~ so that the flap can close when flow proceeds in the opposite direction 46. The shaft 3~t iS rigidly secured to a duet 74 so tha~ it extends-transversely across an elongate flow path 7~ which ~s de~ined by the duct, and does not rotate about its axis 35 (FIG. 2~.

In operation~ when flow proceet~ in the desired direction 32, pressure exerted by the fluid on the flap 70 causes ~he pilot valve 38 to open, thus permitting flow through ~he pilot valve. This effectively moves the center of pressure 22 above the pivot line 40 tFIG. 2 _ in the illustrated embodiment the pivot line is defined by the poin~s of con~act between-the rack and pinion gears 48, 50, 58, SO~. Consequently, the plate 36 rotates clockwi~e as viewed in FIGS. 3 and 5.
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Since the axis of rotation of the plate 36 is not coincident with the axis 35 ~FIG. 2) of the ~haft 34, ; 20- rotation is accompanied by revolutionary movement of the .plate relatlve to the axis 35,.which in turn is accompanied by tran~lational movement of the pla~e relative to the a~is -.~ 35. In ffect,-this can bè viewed as a rolling motion of - ~ .the plate 36 around the shaft 340 ^ . .-25 ` r ~ In the.simplest form of the invention, the plate ~,~t~ '~ ', "` '-`! -' 36~would abu~-~he::sha~.34^along a pivot`line^40 ~FIG. 2)~- ~ extending acro~s..the plate. ~However,:it is desirable to ensure;that for a:particular ~ngle~o rota~ion of thè plate .~: . -36, there is a repeatablej p~rticular degrèe of transla-~ 30 ~ional movement of the pla~e relative to the shaft 34.

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~ i ilJii4h3 ~ ''`. n~ P(~ lX~ l X2 Accordingly, the illustrated embodiment incorporates mechan-ical timing means in ~he form o rack and pinion gears 48, 50, 58, 60 which prevent slippage between the plate 36 and the shaft 34. As an alternative to the illustrated timing means, one could employ an arrangement in which three strips of a flexible material are wound around the shaft 34 and suitably secured to both the shaft and the plate 36. Two outer strips would be wound in one direction and a central strip would be wound in an opposl~e direction. Such an arrangement would be similar in operation to that of a reel-type window shade.

Returning now ~o the operation of the check valve 30 and referring to FIGS. 2 9 3, 4, and 5, as the pla~e 36 rotates clockwise the teeth of the rack gears 58, 50 sequen-~ially engage the teeth of the pinion gears 48, 50, thuspreventing slippage as the pivot line 40 moves clockwise around the stationary shaft 34 and dow~ward along the plate 36. The area 42 above the pivot line 40 increases with increasing angles of rotation 45 until an angle is reached at which the center of pressure 22 i~ again aligned with ~he pivot line 40.. A test.has demons~rated that for a plate 36 with no protrusion ~such as the flap 70), a "fully -. open" angle of rotation 45 of slightly less than ninety - .. degrees:can be achieved.-~
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~-- ;25.~ ,;.The-effect of.the flap J0 on the fully-open angle ha~lnotJbeen determined. However,~a number of possibilities - ~-are,contemplated,for either minimizing ~hi effect or pro- :
viding a particular fully-open anglP in a given design.
These include opening the flap 70 from the opposite side of the hole 58 (i~e. as vie~ed in FIG. 5 the flap would open downwardly instead of upwardly), appropriately dimensioning the flap andtor the ~top 72; using a very thin reed instead .. ~

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of the fl~p; and in applieations whPre thP plate 36 i6 sufficiently thickt securing the flap to the plat~ inside the hole.

When flow proceeds in the opposite direction 46, aerodynamic forces act to close the flap 70. The center of pressure associated with these forces ~s 80 located relative to the pivot line 40 that the closing torque applied to the plate 36 is e~en greater than would ob~ain if the pivot line were centered relative to the plate.
Consequently, the plate 36 is quickly rotated in a counterclockwise direction, with the rack gears 58, 60 rolling around the pinion gears 48, 50, until it reache~
the closed position indicated by FIG. 3. -If the plate 36 transitorily overshoots the closed posi~ion, ~he lower area 44 is made transitorily greater ~han the upper area 42 and the ~erodynamic forces act to return the plate~to the closed position. Conversely~ if the plate 36 for any reason transitorily rotates in a clockwise direc~ion while flow is proceeding from right to left, the upper area 42 is made transitorily greater than th~e lower area 44, and again ~the plate 36 i8 returned;to thei`closed position.:

. The reader shoult understand that the foregoing text and accompanylng drawings.are not intended to restrict the scope of the invention to specific details which are 25 ~ancillary to the teaching contained herein. Ar~ordingly, the-invention ~hould~be construed as broadly i as ;'is con~
. te!~t wi~h the following claims`and-theiir equivalent~.

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Claims (8)

WHAT IS CLAIMED IS:

1. A check valve,characterized in that the check valve comprises in combination:
a duct defining a flow path for fluid;
a shaft supported across said duct and extending across said flow path;
a plate-like member having a hole formed there-through; said member being secured to said shaft in such manner that said member is revolvable and translatable relative to said shaft; and a secondary check valve carried upon said member for permitting flow through said hole in one direction and substantially preventing flow through said hole in an opposite direction, whereby in operation said check valve opens in response to a change in forces exerted by said fluid on said member, said change occurring when said secondary check valve is opened in response to forces exerted thereon by said fluid.

2. The invention of Claim 1 further comprising a pinion gear secured to said shaft and a rack gear secured to said member and engaging said pinion gear.

3. The invention of Claim 1 further comprising a tubular sleeve surrounding a centrally disposed portion of said shaft and being freely rotatable about said portion.

4. The invention of Claim 1 wherein said shaft is rigidly secured to said duct.

5. The invention of Claim 1 wherein said secondary check valve comprises a second plate-like member movably secured to said plate-like member.

6. The invention of Claim 1 wherein said member contacts said shaft along a pivot line parallel to said axis, said revolutionary movement of said member effecting revolutionary movement of said pivot line relative to said axis.

7. The invention of Claim 6 further comprising a rack gear secured to said member and a pinion gear secured to said shaft and engaging said rack gear for inhibiting slippage during said revolutionary movement.

8. The invention of Claim 7 wherein said shaft is secured to said duct so that said shaft cannot rotate about said axis.