Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BIDIRECTIONAL ~VE SEAI
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8ACKGROUND O:F THE INVEMTION
This invention relates to a valve seal, and
more particularly to a bidirectional valve seal
in which pressure in the fluid line makes sealing
more effective.
Tne prior art shows many types o~ seals ~or
butterfly valves. Perhaps the simplest seal uses
a solid resilient member. In one form, the resilient
member is captured in the v21ve body and has an
--- 10 annular surface that seals against the valve disc.
U.S. patents 3,591,133 to Miles et al; 3,608,861
to Helman et al; 3,997,142 to Broadway; 4,114,856
to MacAfee et al; and 4,210,313 to Chester; and
British Patent 1,203,029 ~o Jarrett show such
sealing arrangements. A variation of that approach
mounts the solid resilient member to the disc and
an annular sur~ace on the resilient member seals
against the valve body. U.S. patents 3,658,292
to Takigawa and 4,15~,426 to Santy et al disclose
such seals.
~ nother seal uses a sealing member similax to
those discussed above, except that the member has
an annular cavity rather than being solid. Within
the annular cavity is another separate resilient
member. The outer me~ber may be of a material
relati~ely impervious to the media carried through
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01 - 2 -
02 the valve and the inner member provides the
03 resistance to deformation that optimizes sealing.
04 U.S. patent 3,563,510 to Priese shows that type of
05 seal, in which a rubber or elastomeric o-ring or a
06 helically wound, round-wire spring, comprises the
07 inner member. Another variation of that approach
08 uses a flat-wire spring as the resilient inner
09 member held between two legs of the outer member
clamped in the valve body. The two legs of the
11 outer member have a spacing member between them that
12 provides a bearing surface to resist radially
13 outward movement of the inner member when the disc
14 closes. That type of seal is incorporated in valves
sold by the Duriron Company, Inc. of Cookeville,
16 Tennessee under the name BIG MAX*.
17 A third type of seal uses a sealing
18 member that "floats" in a cavity in the valve body
19 and has a backing member in the cavity to urge the
floating member radially inwardly against the valve
21 disc. ~.S. patents 3,282,558 to Swain; 3,497,178 to
22 Priese: 3,642,248 to Benware: 3,986,699 to Wucik,
23 Jr. et al 4,088,299 to Maciulaitis et al 4,113,268
24 to Simmons et al: 4,130,285 to Whittaker: 4,165,859
to Maciulaitis et al and 4,194,749 to Bonafous
26 disclose seals that use that approach. Those
27 patents disclose various devices as the backing
28 member. For example, in one embodiment of Benware's
29 seal, an 0-ring deforms in cross-section when system
pressure enters the cavity and wedges against the
31 sealing member to urge it radially inwardly against
32 the valve disc. It is known that the seal shown in
33 Benware has also used a flat-wire spring backing
34 member. The flat-wire spring provides resistance to
the radially outward urging of the floating member
36 by reacting against the bottom of the cavity, thus
37 holding the floating member against the disc. The
38 seal shown in the Bonafous patent functions in a
39 similar manner, but uses a round-wire instead of a
flat-wire spring. The Benware patent, and o-ther of those
41 *Trade mark
patents such as the ~hittaker patent, also show
a garter spring as the backing member The
garter spring creates hoop compression in the
sealing member to urge it against the valve disc
and thus generally creates a sealing action different
from that created by a backing member that is resilient
in cross-section.
A final type of seal uses a sealing member
having one leg held in the val~7e body. The sealing
member and the valve body define a cavity. Generally,
although not always, the cavity has a backing member
in it. U.S. patents 2,g88,320 to Kent; 3,260,496 to
Borcherdt; 3,734,457 -to Roos; 4,005,848 to Eggleston;
and 4,044,994 to Priese, and the"Series 206 Valves"
made by Royal Industries of Santa Ana, California, show
embodiments of that approach. The Kent '320 and Priese
'994 patents show a round-wire gar-ter spring that creates
hoop compression in the disc to urge the sealing member
radially inwardly. The Roos patent uses flat metal
hoops for the same purpose. The Eggleston patent
uses a round-wire garter spring in the cavity as a
fulcr~m about which the sealing member can bend under
system pressure. In that way, the sealing member is
urged against the valve disc.
The typical structure for holding annular seals,
like those used for butterfly valves, in place includes
a retaining ring held against a valve body. The seal
is disposed in an annular slot formed by the valve
body and retaining ring. The valve body includes
flanges for connectïng the valve to flanges on the
fluid line.
In the prior art, the retaining ring is held
against the valve body by bolts d-isposed axially
through the valve body and retaining ring. An example
of such an arrangement is shown in the ~roadway patent.
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01 - 4 -
02 With that configuration, the heads of the bol~s must
03 be recessed into the axial face of the retaining ring
04 because the flanges on the fluid line bear directly
05 against the axial face of the retaining ring.
06 In general, the present invention is a valve
07 seal having an annular valve body which defines an
08 axially extending valve chamber, a valve closure
09 member which is movable in the valve chamber between
open and closed positions, and an annular retaining
11 ring which is secured to the valve body and whic'n
12 defines therewith an annular slot having a
13 circumferential inwardly-facing axially-ex-tending
14 shoulder. The valve seal is comprised of an annula
elastomeric valve seating member having a generally
16 U-shaped cross section defining generally radially
17 outwardly extending first and second legs which are
18 connected by a generally inwardly-facing
19 axially-extending bight portion, the bight portion
including a radially disposed inwardly Eacing annular
21 sealing surface for sealing cooperation with the valve
22 closure member. The invention further includes
23 anchor apparatus, extending radially outward from the
24 first leg, for flexibly and rotatably anchoring the
seating member between the valve body and the
26 retaining ring and in the annular slot, the seating
27 member having an axial cross section relative to the
28 axial cross section of the slot so as to divide the
29 slot into first and second axial sides each in fluid
pressure communication with the valve chamber, whereby
31 the seating member is free to rotate about the anchor
32 apparatus relative to the limits of the slot. The
33 legs and bight portion of the valve seating member
34 define an open annular groove which is bounded
generally axially by the legs and generally radially
36 inwardly by the bight portion, the annular groove
37 being open generally radially outwardly to the
01 - 4a -
02 shoulder in the slot. In addition, the invention is
03 comprised of a plurality of circular wound helically
04 connected resilient elements which are disposed within
05 the groove and which are in substantial radial
06 alignment with the sealing surface, each of the
07 resilient elements having a sufficiently large
08 circumference so as ko have peripheral sectors which
09 simultaneously bear against the first leg and the
second leg and the bight portion and the shoulder,
11 whereby that sector o-f any one resilient element which
12 bears against the bight portion of the seating member
13 resists outward displacement of the seating member,
14 urges the seating surface against the closure member
when the valve is closed, and when displaced outwardly
16 produces an expansive reaction force in the adjacent
17 resilient elements which is directed generally
18 inwardly towards the seating member.
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Another aspect of the present invention comprises
attachment means for holding -the retaining ring to the
valve body. The attachment means comprises a radially
extending threaded hole through the body and a conical
blind hole in the retaining ring aligned with the
radially extending threaded hole. A screw with a
conical end is accepted in the radially extending
threaded hole in the body for cooperation with the
blind hole to urge the retaining ring a~ially toward
the valve body.
BRIEF DESCRIPTION OF THE DRAWINGS
_
Figure 1 is a sectional view of a butterfly
valve, taken axially along the valve shaft, incor-
porating the present invention.
Figure 2 is a sectional view of the butterfly
valve taken along lines II-II in Figure 1.
Figure 3 is a detailed view of the valve seal of
the present invention when the valve is open.
Figure 4 demonstrates the interference fit
between the valve disc, shown in dotted lines, and
the seal of the present invention, shown in the position
it assumes when the valve is open.
Figure 5 is a detail of an open-helical, flat-
wire spring back-up member used in the preferred
embodiment of the present invention.
Figure 6 is a detail showing the relative
positions of the valve parts and seal of the present
invention when the valve disc is closed and, in solid
lines, when there is no system pressure and, in dotted
lines, when system pressure is from right to left
in Figure 6.
Figure 7 is a detail of the relative positions
of the valve parts and seal of the present invention
when the valve disc is closed and system pressure is
from left to right as viewed in Pigure 7.
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DETAILED DESCRIPTION OF
EMBODIL~ENTS OF THE INVENTIO~I
Figures 1 and 2 show a butterfly valve 10.
The butterfly valve 10 includes a valve body 12 that
S defines a valve chamber 14. The valve body 12 has
a shaft 16 mounted therein for rotation. A disc 18
is mounted -to the shaft 16 by pins 19 or other
suitable fasteners. The disc 18 functions as a valve
closure member that opens and closes by rotation
of the shaft 16, as is illustrated in Figure 2.
Figure 2 illustrates the double-offset used
in such valves. First the plane of the disc 18 is
offset axially from the center line of the valve
shaft 16. Second, the valve shaft 16 is offset very
slightly (up or down as seen in Figure 2) from the
center line of the valve chamber 14. The first offset
moves the valve disc 18 clear of its seal for all open
positions. But for the first offset, the portions
of the seal where the valve disc mo~lnts to the
valve body would be subject to rubbing and excessive
wear. The second offset causes the final portion
of the travel of the valve disc 18, as it approaches
the closed position, to be axial of the valve chamber
14. This double-offset geometry is familiar to those
skilled in the art and is particularly advantageous
with the seal of the present invention. A stop 20
limits rotation and defines the closed position of
the valve disc 18. The stop 20 is cast into the valve
body 12 and then machined to provide precise positioning
of the valve disc 18 in its closed position.
As Figure 1 shows, the shaft 16 is mounted in
bosses 21, and seals and packing 22 prevent leakage
from the valve chamber 14 around the shaft 16. The
bosses 21 form an integral part of the valve body 12.
The valve body also includes circumferentially extending
mounting faces 24. The mounting faces 24 include holes
therethrough (not shown) for mounting the valve body
to the flanges of pipes P that form the fluid line.
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A retaining ring 26 fits into an annular groove
in one face of the valve body 12. The retaining ring 26
holds in place a valve seal 100 that forms one aspect of
the p~esent invention. The valve seal 100 cooperates
with the valve disc 18 when the valve disc is closed
to prevent flow through the fluid line.
Figure 3 shows the relation of the valve body
~ 12, the retaining ring 26 and the various attachment
means. Figure 3 is a sectional view taken radially
at a circumferential location away from the bosses
21.
The valve ,seal 100 comprises an annular valve
seating member 102 made of a relatively hard, yet
flexible, material such as TEFLON synthetic resin
polymer. The seating member 102 is U-shaped with
two legs 104, 106 and a bight portion 108 connecting
them. The bight portion'108 includes an extension
110 that projects radially inwardly. The extension
110 terminates in an annular sealing surface 112
that cooperates with the outer surface of the valve
dlsc 18. As the dotted lines in Figure4 show, the
valve seating member 102 forms an interference fit
with the valve disc 18 when the valve disc is in its
closed position. The valve seal 100 also comprises
an annular, cross-sectionally compressible back-
up member 114. The valve body 12 and retaining
ring 26 form an annular slot 116 in which the valve
seal 100 fits.
One leg 104 of the valve s~ating member 102
forms an anchor means 118 that is captured between
the valve body 12 and the retaining ring 26 to hold
the valve s,eating member 102 in the slo-t 116. The
valve body 12 has serrations on the axial face
where -the leg 104 is captured between the valve body
12 and the retaining ring 26. The axial distance
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~etween the valve body 12 and the retaining ring 26
where the leg is captured is less ~han the axial
thickness of the leg 104. The retaining ring 26
includes a lip 120 that further decreases the axial
distance between the valve body 12 and the retaining
ring 26. When the retaining ring 26 is pressed
axially against the valve body 12, the lip 120 causes
cold flow of the leg 104 radially outwardly of the
lip 120 and aids ~he cold flow of the leg 104 into
the serrations. The seating member is thus held
securely in the slo~ 116 and the leg 104 acts as a
secondary seal to ensure that there is no flow
across the seal 100.
The principal force clamping the retaining
ring 26 axially against ~he valve body 12 is provided
by axial compression occurring when the valve body
12 is clamped between the pipes P. ~owever, it is
necessary to hold the valve body 12 and the retaining
ring 26 in the proper relative positions with the
seal 100 in its proper place prior to insertion
of the valve in the fluid line. The retaining ring
attachment means performs that task.
Pre-assembling positioning is accomplished by
set screws 200, the axes of which are disposed
radially. A plurality of threaded radially
extending holes 202 spaced equally around the
circumference of the valve body 12 accept the set
screws 200. The retaining ring 26 includes a like
plurality of blind conical holes 204 aligned with the
threaded radial holes 202. The set screws 200 have
conical ends 206 tha-t cooperate with the inclined
sides of the blind holes 204 to urge the retaining
ring 26 axially to the right as viewed in Figure 3
as the set screws 200 are screwed radially into the
3~ holes 204. This retaining ring attachment means,
instead of the axial holes through the retaining
ring 26 used in the prior art, enables easier
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01 - 9 -
02 preliminary assembly of the valve body 12 and
03 retaining ring 26. And by e]iminating the axial
04 holes through the retaining ring 26, it removes a
05 potential source of leakage. Although this
06 arrangement can include any number of such
07 attachment means, four has been found to yield
08 acceptable results.
09 Figures 3 and 4 show the seal 100 in the
position it assumes when the valve is open. The
11 annular slot 116 formed by the valve body 12 and the
12 retaining ring 26 is generally similar in
13 cross-sectional shape to the shape of the annular
14 seating member 102. The annular slot 116 narrows
axially to a circumferentially extending opening.
16 The radial extension 110 of the bight 108 projects
17 through that opening into the valve chamber 14. The
18 seating member 102 divides the slot 116 into a first
19 axial side 122 and a second axial side 124, both of
which are in fluid communication with the valve
21 chamber 14.
22 The slot 116 includes a radially
23 inwardly facing shoulder 126 which, with the legs
24 104 and 106 and the bight portion 108, defines an
annular cavity 128. The annular cavity 128 is
26 substantially aligned radially with the annular
27 sealing surface 112. The radially inwardly facing
28 walls of the cavity 128 formed by the seating member
29 102 are circular in cross-section and conform to the
outer surface of the back-up member 114. The cavity
31 128 is in fluid pressure communication with the
32 second axial side 124 of the slot. The annular
33 sealing surface 112 has a face 130 at one axial side
34 of the sealing surface 112.
Figure 5 shows in detail a portion of
36 the preferred cross-sectionally compressible back-up
37 member 114. The back-up member 114 comprises a
38 helically wound metallic "flat wire" spring
39 element. Stainless steel or HASTELOY* is the
preferred material because of their resistance to
41 deterioration by a wide variety of media. The pitch
42 of the spring
43 *Trade mark
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! is greater than the width of the flat wire so that
i~ there are spaces between adjacent sections of wire.
Such an "open-helical" confiyuration enables fluid
to flow freely around and through the back-up member
114 and thus transmit fluid pressure therethro;~gh.
i When the cross-section of the back-up member 114 is
! compressed in one direction, it will cause an expansive
reaction force perpendicular to the compressive force.
A "flat wire" spring, that is, one formed of a s~rip
of spring material rectangular in cross-section,
more readily than other cross-sections transforms
such a compressive force into an e~pansive reactio~
force perpendicular thereto.
The operation of the valve seal of the present
invention is best seen by reference to Figures 6 and
7. Figure 6 shows, in solid lines, the position of the
valve seal when the valve disc 18 is closed but no
system pressure is present. A comparison of Figure 3
or 4 with Figure 6 shows that the seating member 102
moved slightly axially by rotation about the leg 104
as the disc 18 closed. The outer peripheral surface
of the disc 18 contacts the annular sealing surface
112 and the seating member 102 rotates toward the
second axial side 124 of ~he slot 116. The annular
cavity 128 and the cross-section or the back-up member
114 is slightly compressed in a generally radial direction
relative to the valve body. The back-up member lla
resists that compression and creates a generally radial
reaction force against the shoulder 126 and the inside
of the bight portion 108 that forces tne valve seating
member 102 toward the disc 18. The interference rit
between the annular sealing surface 112 and the disc
surface 18, in addition to the generally radial force
exerted by the back-up member 114 in reaction to its
compression, form the static component of the sealing
force that holds the annular sealing surface 112
against the disc 18.
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As Figure 2 illustrates, a certain circumferential
portion of the periphery of the valve disc 18 approaches
the annular seating member 102 from left to right as
viewed in Figure 6. The double offset described
above, tne radius R and the flat sealing face F formed
on the valve disc 18 and a face 132 on the annular
sealing surface 112 combine to cause the disc 18 to
approach the seating member 102 at an advantageous
angle w'nich a-ds in seating the face F of the valve
disc against the face 130 of the annular sealing
surface 112 (see Figure 6) around the entire periphery
of the valve disc 18. Ideally, when the valve disc has
closed completely, the annular seating member 102 has
rotated just far enough to allow a very small passageway
between the leg 106 and the second axial side 124 of
the annular slot 116 to provide pressure communication
between the valve chamber 14 and the annular cavity
128.
Fluid pressure adds a dynamic component to the
sealing force regardless of which side of the disc
is pressurized when the valve is closed. Figure 6
shows in dotted lines the position assumed by the
annular seating member 102 and the valve disc 18
when the valve is pressurized from the right side as
shown in Figure 6. As the pressure on the right
side of the disc 18 builds, manufacturing tolerances and
wear that inevitably leave clearance between the valve
shaft 18 and the bearings and packing 22 (see Figure 1),
and deflection of the disc 18 because of the pressure
against it, allow axial movement to the left of the
disc 18. The annular seating member 102 rotates to
tne left with the axial movement of the valve disc
18 until the leg 106 contacts the wall on the second
axial side of the annular slot 116. The back-up
member 114 resists that rotation and thus urges the
annular sealing surface 112 and the-valve disc sealing
face F together.
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If the pressure is high enough, it will also
push on the surface of the leg 104 facing the first
axial side 122 of the slo~ 116 and axially compress
the back-up member 114. The dotted line position of
the leg 104 as sho~n in Figure 6 is exaggerated to
illustrate this aspect of the operation of the valve
seal. In any event, as the leg 104 continues to move
generally axially under the influence of the pressure
in the valve cha~er 14 and the first axial side 122,
the axial dimension of the annular cavity 128 is
reduced. The back-up member 114 creates a generally
radial reaction force that acts between the annular
shoulder 126 and the annular seating member 102 to
force the annular sealing surface 112 radially
inwardly against the valve disc 18.
Figure 7 shows the position of the annular
seating member 102 and the valve disc when the valve
is pressurized from left to right. Pressure forces
the valve disc 18 to the right because of the clearances
and deflection already mentioned. The annular
seating member 102 rotates to the right with the disc
18. Because the disc 18 rotated the seating member 102
to the left upon closing, the counterrotation caused by
pressuri~ation from the left acts against that original
rotation. The counterrotation of the annular seating
member 102 in effect wedges the annular sealing
surface 112 against the sealing face F of the valve
disc 18. The counterrotation also exposes the
annular cavity 128 to system pressure by opening the
passageway at the second axial side 124 of the slot
116. The system pressure thus urges further counter-
rotation of the annular seating member 102 and also
creates a generally radially inward force on the interior
of the annular cavity 128 that urges together the sealing
face F of the valve disc 18 and the annular sealing
surface 112.
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Thus, the valve seal of the present invention
provides a static sealing component that preloads
the seal in the absence of system pressure and a
dynamic component regardless o~ the direction in
which system pressure acts on the valve disc. Known
prior art valve seals are believed to perform less
effectively under a system pressure in one direction
than they perform for a system pressure in the other
direction. One of the reasons, it is believed, is
because the known prior art seals do not allow
for the inevitable axial movement of the valve disc
under pressure. The present invention, however,
per~orms very effectively regardless of the direction
of system pressure.
As Figure 7 illustrates, the size of the passageway
at the second side 124 of the slot 116 without system
pressure is not critical. The axial movement of the
disc when system pressure acts to the right will tend
to open the passageway because the annular seating member
102 rotates under those conditions. The open-helical,
- flat-wire structure of the back-up member 114 has been
found to be the most advantageous configuration. For
e~ample, although a round-wire spring would work, it
has been found that each coil of the spring provides
insufficient bearing surface between the TEFLOM annular
seating member and the spring and the TEFLON cold-flows
between the coils. A solid back-up member that deLorms
in cross-section, such as an O-ring, can also be used
but is the least advantageous choice because it will
not allow system pressure to enter the entire annular
cavity 128 when pressurization is from left to right
(see Figure 7).
Although certain specific embodiments of the
present invention and modifications thereto have been
described, those skilled in the art will recognize
other modifications that can be made within the
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spirit of the invention. For example, the present
invention may be used with other types of valves and
is not limited to use with a butterfly valve like
that shown herein. Thus, it is intended that the
above description be illus~rative only of the preferred
embodiments of the present invention, the scope of which
is defined solely by the appended claims.
