Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
This invention relates to the valve art and more
paticularly to ball valves.
The invention is particularly applicable to a new and
improved seat assembly and ball valve of the type having a
so-called floating ball and will be described with reference
thereto. However, it will become readily apparent to those
skilled in the art that the invention is capable of broader
applications and could be adapted for use in other types and
styles of valves.
., ,,~, . . . .... .
4- Typical ball valve constructions in commercial use
employ annular seats or seat rings formed of a resilient and
deformable plastic. A pair of such seat rings are positioned
in engagement with and on opposite sides of the ball member
about the valve body inlet and outlet openings. Normally, the
seats are designed to engage the ball with narrow band or line
contact and to flex slightly under loads. The ball itself is
mounted for a slight amount of free movement or shifting
axially of the seat when the ball is in a valve closed position
under fluid pressure conditions. Such shifting causes the ball
to act aglainst and flex the downstream seat ring to enhance its
~5 sealing engagement with the ball. The amount of such flexin~
varies in accordance with the fluid pressure involved.
With increasing fluid pressure and resultant
downstream shifting of the ball, thé ball is moving away from
the upstream seat. The ball contact with the upstream seat may
or may not be broken, depending upon the pressure and/or seat
--2--
113387~7
design. Some designs intentionally seal at the upstream seat
while others deliberately prevent an upstream seal and do all
the sealing on the downstream seat. Moreover, some ball valve
designs utilize spring biasing means for continuously urging
the opposed seat rings toward each other and into sealing
engagement with the ball.
Small ball valves, that is, valves of l" and under,
and low pressure ball valves are usually made with end loaded
seats and a floating ball as described above. This is typical
of small ball valve designs for two primary reasons. The
shut-off pressure acts on the total seal dia~eter, either the
outer diameter of contact between the ball and downstream seat
or the outside diameter of the inlet seat. The total force
tfluid pressure x area) must be carried by the ball. With a
floating type ball, all the force is applied to the downstream
seat and since the seat comprises an annulus of a smaller area,
seat stress is always greater than the fluid pressure. At very
high fluid pressures, the seal force crushes ordinary plastic
type seats. Also, as the valve size increases, the ball force
increases as a function of the square of the seal diameter
whereas the annular seat does not increase in area at the same
rate. Therefore, alternative valve constructions must be
employed to overcome these problems. To that end, large ball
valves, that is, valves over 2" and high pressure ball valves
2~ are usually constructed with a trunnion supported ball. The
valve seats float and are pressure activated to seal against
the ball. Large valves must have a trunnion mounted ball to
avoid overstressing of the seat even at low pressures.
Existing valve designs have taken the approach of
minimizing the seat area by sealing on the downstream seat
`` 1133877
only. This reduces the effective area to considerably less
than the full outside diameter of the inlet seat. However, if
identical seats are used both upstream and downstream, this
requires that the seat be designed to leak with upstream
pressure, but seal with downstream pressure. Tnis has two
disadvantages. First, to not seal as an inlet, there must be a
way for pressure to bypass the inlet seat. This means the
downstream seat must have two dynamic seals, i.e., one against
the ball and another to seal the bypass. Usually, this
involves an additional mechanism for sealing the seat against
the downstream flange or fitting. Obviously, the use of two
seal points provides a less reliable arrangement than a single
seal. Second, if the inlet seat is bypassed, it cannot apply
any force to the ball to hold it against the downstream seat at
low pressure. The weight of the ball causes it to fall below
the seat centerline and allows fluid leakage at low pressure.
This problem becomes more significant with larger valves
because the weight of the ball increases with the cube of the
size. Thus, a valve having a floating ball should have seats
which are firmly held against the ball without system pressure
so that a seal is formed regardless of how low the pressure may
be. As noted above, this has been accomplished by placing a
disc spring behind each seat. This feature not only provides a
low pressure seal, but also assures an upstream seal at high
seat loads.
An upstream seal, however, creates a second problem
which also becomes more pronounced as valve size increases.
While the valve is being opened, this seat must span the hole
or fluid opening through the ball. With a small ball and
opening, the seat is quite rigid when loaded as a beam in
3877
bending and can easily bridge the gap. As the valve size and
opening increase, the section modulus of the seat does not
proportionately increase to retain the same stiffness. Thus,
the seat may deflect further into the ball opening. Similarly,
the outside diameter of the seat ring is normally supported
only by a shoulder in the valve body. The area of the seat
and, therefore, the force acting on it, increases as the square
of the diameter. Since the supporting shoulder is usually
quite narrow and its area is more closely related to the seat
circumference, the supporting shoulder only increases in a
linear fashion. Here also, the problem becomes more pronounced
as the valve size increases.
It has, therefore, been desired to develop a ball
valve and seat assembly which facilitate use of a floating ball
in connection with higher system pressures than have heretofore
been possible. Such a design would, in many cases, eliminate
the necessity for utilizing trunnion mounted balls. Trunnion
mountings are not considered practical unless the valve is
quite large because their use substantially increases the size,
complexity and cost of the valve.
The present invention contemplates a new and improved
construction which overcomes all of the above referred to
problems and others and provides a new and improved ball valve
and seat assembly construction which produce increased pressure
capabilities for a floating ball type of ball valve and wherein
the seats may be formed from a wide variety of materials to
suit a wide range of operating conditions or parameters.
BRIEF DESCRIPTION OF THE INVENTION
Generally, the present invention contemplates a new
and improved ball valve and seat assembly wherein the seat ring
--5--
1133877
assembly is flexible in one direction of travel and generally
rigid in the opposite direction. A pair of such assemblies are
disposed on opposite sides of a ball member and continuously
urged toward the ball for maintaining it properly positioned in
the valve body and providing valve sealing regardless of how
low the fluid system pressure may be. When the valve is
closed, the system pressure moves or shifts the ball downstream
toward the downstream seat assembly so that it is further
deflected against an associated disc spring. The upstream seat
ring is simultaneously urged toward continued engagement with
the ball by a disc spring operably associated therewith. In
response to some system fluid pressure, the disc spring
associated with the downstream seat assembly is fully deflected
and the ball is moved away from engagement by the upstream seat
assembly.
More specifically, the subject invention is
particularly applicable to use in a valve of the type having a
generally cylindrical passageway, a ball member disposed in the
passageway and mounted for selective rotation therein between
valve opened and closed positions. The ball member is
shiftabi~ generally axially of the passageway at least when the
valve is in the closed position under fluid pressure
conditions. Annular seat rings are disposed in the passageway
on opposite sides of the ball member between the ball member
and an associated valve body shoulder with annular disc sprin~s
_ disposed between each shoulder and the associated seat ring.
These disc springs continuously urge the seat rings toward
sealing engagement with the ball member. Each seat r ing has a
first continuous surface facing the ball member and a second
surface facing an associated shoulder of the valve body with a
1133877
disc spring interposed between each seat ring second surface
and its associated shoulder. Each disc spring has a generally
frusto-conical configuration in its unstressed condition with
its smaller diameter end pointing toward the ball member. The
components are dimensioned so that when the ball member, seat
rings and disc springs are assembled between the valve body
shoulders, the seat ring first surfaces engage the surface of
the ball member with the seat rings being flexed slightly
outward of each other. The frusto-conical disc springs, in
turn, are partially stressed toward a flattened configuration
for continuously urging the seat ring first surfaces toward
engagement with the ball member. When the ball member is
axially shifted in the passageway toward one of the valve body
shoulders in response to fluid pressure acting thereon when the
valve is closed, the seat ring associated with the one shoulder
is further flexed toward the one shoulder with the first
surface thereof remaining in engagement with the ball member
and the disc spring associated with the one shoulder is further
stressed toward a flattened configuration. The other seat ring
is flexed toward the ball member in the direction of shifting
thereof under the influence of its associated disc spring in
order that the other seat ring first surface will be urged
toward continued contact with the ball member.
In accordance with another aspect of the invention,
the seat ring associated with the one shoulder may be flexed by
shifting movement of the ball member in engagement with the
seat ring first surface to a position where the associated disc
spring is stressed to a substantially flattened configuration.
In that condition, the ball member has been moved away from
contact by the first surface of the other seat ring. In the
~3387~7
preferred arrangement of the invention, the seat rings
experience rotational type of flexure in response to engagement
with and/or shifting of the ball.
According to another aspect of the present invention,
a pair of reinforcing rings are also included in the passageway
on opposite sides of the ball member axially inward of the seat
rings. Each reinforcing ring includes means for locating it in
a desired axial position in the passageway, a first surface
facing an associated one of the valve body shoulders and a
second surface generally facing the ball member in a spaced
relationship therefrom. The first surface provides a rigid
bearing surface for the associated seat ring to prevent seat
ring distortion and displacement in the passageway. The
provision of a rigid bearing surface is of significant value
for the upstream seat ring-when the valve is closed and exposed
to elevated system pressures and when the valve is moved from a
closed to an open position under such elevated pressures.
According to a limited aspect of the present
invention, the reinforcing rings are positively located in the
valve body passageway by engagement with the end walls of
passageway counterbores. In one case, the reinforcing rings
may include radially outward extending flanges which engage the
counterbore end walls. Alternately, the inner end walls of the
reinforcing rings may engage the counterbore end walls.
2~ In accordance with another more limited aspect of the
invention, each seat ring second surface further includes a
relief groove extending therearound. Such grooves facilitate
ease of flexure in the seat rings during valve operation under
fluid pressu.e conditions.
3Q
--8--
11338~7
The principal object of the invention is the provision
of a new and improved ball valve and seat assembly which allow
higher pressure ratings to be obtained from a floating ball
type of ball valve.
Another object of the present invention is the
provision of such a ball valve and seat assembly which will
effect valve sealing even at very low fluid system pressures.
Still another object of the invention is the provision
of a new and improved ball valve and seat assembly which
permits the seat rings to be formed or constructed from a wide
variety of materials.
A further object of the present invention is the
provision of a new and improved ball valve and seat assembly
wherein the seat rings are flexible in one direction of axial
ball movement and generally rigid in the opposite direction.
Still other objects and advantages of the invention
will become apparent to those skilled in the art upon a reading
and understanding of the following specification.
BRIEF DESCRIPTION OF THE DRAWINGS
Tbe nvention may take physical form in certain parts
and arrangements of parts, preferred and alternative
embodiments of which will be described in detail in this
specification and illustrated in the accompanying drawings
which form a part hereof and ~herein:
: FIGURE 1 is a cross-sectional view through a ball
valve which incorporates the preferred embodiment of the
invention thereinto;
FIGURE 2 is a cross-sectional view of the preferred
seat assembly construction shown just prior to valve make-up
~13387'7
an~ with the ball member removed for ease of illustration;
FIGURE 3 is a slightly enlarged view of a portion of
the valve of FIGURE 1 showing the ball in the valve opened
position under a no-load condition;
FIGURE 4 is an enlarged cross-sectional view of a
portion of a seat assembly when the valve is in the opened
position of FIGURE 3;
FIGURE 5 is a view similar to FIGURE 3 with the ball
member in the valve closed position under the influence of an
elevated fluid pressure condition;
FIGURE 6 is an enlarged cross-sectional view showing a
portion of the upstream seat assembly when the valve is in the
closed position of FIGURE 5;
FIGURE 7 is an enlarged cross-sectional view of a
portion of the downstream seat assembly when the valve is in
the closed position of FIGURE 5; and,
FIGURE 8 is a cross-sectional view similar to FIGURE 2
snowing a seat assembly which includes various alternative
design features.
DESCRIPTION OF PREFERRED AND ALTERNATIVE EMBODIMENTS
Referring now to the drawings wherein the showings are
for purposes of illustrating preferred and alternative
embodiments of tne invention only and not for purposes of
limiting the same, FIGU~E 1 shows a ball valve A having a pair
of opposed seat assem~lies B disposed on opposite sides of a
floating type spherical ball member C.
More particularly, and with reference to FIGURES 1 and
3, ball valve A includes a body or housing generally designated
10 having a main or central body section 12 and opposed end
--10--
~3387~7
flttings 14,16. Seat assemblies B and ball C are centrally
mounted within main body section 12 with the ball member being
arranged for selective rotation by a stem and actuating handle
assembly generally designated 18.
The details of all portions of the valve illustrated
in FIGURES 1 and 3, except for the ball and seat ring
assemblies, may be modified as desired and~or necessary to
accommodate different types or styles of ball valve
constructions. In general, however, and for purposes of
describing the subject invention, the valve body includes a
generally cylindrical central passageway or axially extending
fluid flow opening 20 which is only slightly larger in diameter
than ball C. Each of end fittings 14,16 is releasably
connected to central body section 12 by a plurality of
longitudinally extending tie bolts generally designated 22
(FIGURE 1). The end fittings are also provided with internal
threaas 24,26 or any other convenient means to accommodate
connecting the valve to an associated fluid system or piping.
The stem and actuating handle assembly 1~ as
illustrated includes a stem member 30 having a lower end 32
shaped as shown for sliding receipt in a slot or groove 34
included in the upper end of ball C. This arrangement allows
the ball to be rotated between valve opened and closed
positions while at the same time permitting the ball to have
some freedom of ~ovement for shifting axially in valve body
passageway 20 when the valve is in a closed position.
Stem member 30 extends outwardly through an opening 36
in central body section 12. Suitable packing rings 33,40 and
42 are positioned in opening 36 and sealingly engage the
opening and stem member 30. As shown, lower packing ring 42
1133877
rests upon an inwardly extending flange 44 formed within
opening 36. A split thrust washer 46 is positioned below
fiange 44 and is clamped thereto by an outwardly extending
shoulder or flange 48 formed at the base of stem member 30.
The stem is held in position by a packing gland 50 and a
packing nut 52. As shown in FIGURE 1, tightening of packing
nut 52 applies pressure to packing rings 38,40,42 to assure a
fluid tight seal about the stem.
Although it is possible to actuate the valve stem by
1~ many different types of actuators, including both manual or
automatic, a handle member 54 has been shown. This handle is
releasably secured to stem member 30 by a nut 56 which clamps
the handle to the top of packing nut 52. Cooperating flats
58,60 are advantageously formed in the handle opening and on
the exterior of the stem outer end for properly positioning the
handle on the stem. Moreover, the position of the handle and,
in turn, the position of ball member C are limited by depending
stop members 60,62 carried by handle 54. These stop members
engage suitable surfaces on central body section 12 to provide
fixed stops for the valve in the full opened and full closed
positions.
With continued reference to both FIGURES 1 and 3, the
ball seat arrangement utilized in the subject invention
includes a pair of seat ring assemblies B disposed on opposite
sides of bali member C. As shown, the seat ring assemblies are
clampingly maintained in position on opposite sides of the ball
adjacent opposite ends of the central body section passageway
or opening 20. In the preferred embodiment here under
discussion, the seat ring assemblies are located substantially
equidistantly on diametrically opposite sides of the axis of
il3387~7
rotation of the ball member. While the seat ring assemblies
could be maintained in position by many different or
alternative arrangements, they are shown in the preferred
embodiment as being located by shoulders 70,72 defined by end
S faces 74,76 of end fittings 14~16, respectively. The inward
limit of movement of the seat ring assemblies is defined by a
pair of shoulders 78,80 which are formed by the inner end walls
of counterbores extending inwardly of valve body passageway or
opening 20. Still further, a seal is provided between central
body section 12 and end fittings 14,16 by means of O-rings
82,84 which are received in second counterbores 86,88,
respectively. Each O-ring is disposed about the outer
circumference or outer peripheral surface of a portion of the
associated seat ring assembly B.
The structural details of ball valve A described
hereinabove are with reference to the preferred valve
construction. It will be readily apparent to those skilled in
the art, however, that modifications may readily be made
thereto to accommodate particular operational needs and/or
requirements. Such changes are not deemed to affect the
overall intent or scope of the present invention as will be
describtd in detail hereinafter.
With reference to FIGURE 2, description will be made
of the s~ecific details of seat assemblies B. FIGU~E 2 shows a
cross-sectional view of the seat assembly disposed at end
fitting 14, it being appreciated that the other assembly is
identical thereto unless otherwise specifically noted. Also,
ball member C has been deleted for ease of understandin~ and
appreciating the seat assembly construction.
-13-
113387'7
Each seat assembly is preferably comprised of three
components, i.e., a reinforcing ring 100, a seat ring 102 and a
frusto-conical disc spring 104. Reinforcing ring 100 has an
annular configuration and is desirably constructed from a rigid
material such as steel or other suitable metal. In FIGURE 2,
reinforcing ring 100 is shown as including a first continuous
surface or end face 110 which faces the associated shoulder 70
of end fitting 14. A second continuous surface 112 faces
generally toward the ball member (not shown) but is dimensioned
to be spaced therefrom in order to prevent any contact or
interference therewith. A radially outward extending flange
114 is configured and dimensioned to engage shoulder 78 in
cent~al body section passageway 20 to establish a positive
forwardmost or home position for the reinforcing ring. The
outer circumference or peripheral surface 116 of ring 100 is
closely disposed to the side wall of passageway 20.
Referring still to FIGURE 2, it will be seen that seat
ring 102 also comprises an annular or ring-like member having a
central opening therethrough. A first continuous ball engaging
surface 120 initially has a generally frusto-conical
conformation concentric with the seat ring itself. A seat ring
second surface 122 generally faces the associated shoulder 70
of end fitting 14. A third surface 124 faces reinforcing ring
first continuous surface 110 and is conveniently stepped as at
area 12~ radially inward from outer peripheral surface 12B.
This stepped area is dimensioned and configured to be received
over a portion of the reinforcing ring and engage first
continuous surface 110 thereof. As will become more readi~y
apparent, surface 110 acts as a bearing surface to provide
rigid support for the upstream seat ring during exposure to
fluid pressure.
-14-
~13387'7
A flange or lip 130 extends axially outward of surface
122 generally at outer peripheral surface 128. This lip or
flange is preferably continuous about the seat ring and so
located that its radial inner surface generally corresponds to
the outside diameter of conical disc spring 104. Flange or lip
130 is beveled at the radial outermost area thereof and is
rolied over the radial outer edge of the disc spring in the
manner shown. While not necessary, this arrangement
advantageously maintains the seat ring and disc spring together
as a sub-assembly.
In the preferred arrangement of the invention, seat
rings 102 are constructed from a resilient plastic material
such as polytetrafluoroethylene or the like. It should be
readily appreciated, however, that other types of materials
such as acetal resins and the like could also be advantageously
utilized. The particular material chosen will, to some extent.
be dependent upon the operating conditions to which the valve
is to be subjected. Moreover, various design modifications may
be incorporated into the seat assembly components as will be
described hereinafter with reference to FIGURE 8.
Frusto-conical disc spring 104 includes an outer end
140 and an inner end 142. The diameter at the outer end is
such that a disc spring may be received within the cylindrical
cavity defined by the inner wall of seat ring axial flange 130
and second surface 122. The inner diameter of the spring at
end 142 is substantially equal to the diameter of the opening
through the seat ring.
The spring is selected so that its force is sufficient
under partial deflection to continuously urge the seat ring
tcward ~he ball and toward bearing engagement with surface 110
11338~q
of reinforcing ring 100. The spring must aiso allow stressing
or compression thereof toward a flattened condition to
accommodate ball shifting in engagement with seat ring first
surface 12~. In the preferred embodiment here under
discusslon, seat ring second surface 122 is configured so as to
partially stress disc spring 104 when the seat ring and disc
spring are joined as a sub-assembly. Such stressing is
approximately equal to one half of the distance from the free
state toward the fully stressed or substantially flattened
configuration. However, it should be appreciated that this
stressing is not necessary to satisfactory operation of seat
assemblies B and the presence or absence thereof is a function
of the relative dimensional characteristics between seat ring
second surface 122 and disc spring 104.
Disc spring 104 advantageously accommodates generally
rotational flexure of the seat ring at least until the spring
has been moved to a substantially flattened condition. Such
operation provides for improved valve sealing results in a
manner to be described. Dependin~ upon the type, size and
~0 style of ball valve involved, conical disc springs 104 may be
advantageously constructed from a number of different metals
which have spring properties falling within an acceptable range.
Referring to FIGURES 3-7, description will hereinafter
be made with reference to operation of the new ball valve and
seat assembly. FIGURE 3 shows the valve in a fully assembled
valve opened position (no load fluid pressure condition). In
this position, the two seat assemblies B have been shifted from
the unstressed condition shown in FIGURE 2 to a partially
stressed condition. Sizing of ball member C, seat assemblies B
and shoulders 70,72 are such as to provide this relationship at
ball valve assembly or make-up.
-16-
~33877
More particularly, and with continued reference to
FIGURE 3 as well as with reference to FIGURE 4, the seat
assemblies are moved such that opposed seat rings 102 are
slightly rotatably flexed away from each other generally about
their outer peripheries and against disc springs 104 in
response to engagement between seat ring first surfaces 120 and
ball member C. This action slightly compresses the associated
disc springs toward a flattened condition. In the position of
FIGURE 3, the disc springs are preferably deflected through
approximately half of their remaining travel~ In addition to
positioning the ball member, this spring deflection assures a
seal force between the two seat rings and ball at first
surfaces 120 regardless of how low the system pressure may be.
It also assures that the seat ring disposed adjacent the valve
inlet will form a seal with the overall seat load being
dependent upon the area of the seat ring outside diameter.
FIGURE 4 shows an enlarged partial view of the
downstream seat assembly B which is disposed at end fitting 14
when the valve is in the opened position of FIGURE 3. In this
valve position, the upstream seat assembly associated with end
fitting 1~ assumes a substantially identical relationship. As
there shown, frusto-conical seat ring first or ball engaging
surface 120 is in sealing engagement with the surface of the
ball member C. The ball slightly deforms a portion of surface
120 so that at least that portion has a concave spherical
conformation. Simultaneously, seat ring 102 is rotatably
flexed against disc spring 104 so as to slightly compress the
disc spring. Because of the rotational flexing in seat ring
102, the surface of seat ring stepped area 126 is moved away
from a contacting relationship with reinforcing ring first
surface 11~.
~133877
FIGURE 5 shows the valve in a closed position under
elevated fluid pressure conditions with the direction of fluid
flow being designated by arrow P adjacent the valve inlet.
Depending upon the system pressure, the ball is forced to shift
axially of passageway 20 in the direction of fluid flow toward
the outlet or downstream seat assembly. As a result of this
shifting, the seat ring of the upstream seat assembly will be
moved back toward its original unstressed conformation as shown
in FIGURE 6 under the influence of the associated disc spring
104. Thus, the upstream seat ring is rotatably flexed or
shifted toward the ball as the Dall moves downstream. At the
same time, the outlet seat ring is further shifted or rotatably
flexed downstream as shown in FIGURE 7 to further compress its
associated disc spring. Up to this point, both seat rings are
approximately equally flexible with deflection occurring across
the full annulus of the seat from the outside diameter to the
inside diameter.
Once the inlet seat deflects back to its original
unstressed condition, it changes from a flexible to a much more
rigid member. In this condition, the surface of seat ring
stepped area 126 bears against first surface 110 of the
associat:ed reinforcing ring (FIGU~E 6). The aforementioned
bearing engagement virtually stops the inlet seat from any
further movement toward the ball as the system pressure
continues to increase. Conversely, the downstream seat ring
assembly remains flexible and continues to rotatably flex until
the associated disc spring is moved to its su~stantially fully
flattened configuration (FIGURE 7).
As the downstream seat ring is rotatably flexed, and
with the seat ring constructed from polytetrafluoroethylene or
-18-
1133877
the like, ball member C further deforms first or ball engaging
surface 120 thereof so that an increasing surface portion
assumes a concave spherical conformation. In the preferred
structural arrangement here described, substantially all of
first surface 120 will matingly engage the ball member when the
downstream disc spring is fully stressed. This relationship is
shown in FIGURE 7. A lesser amount of deformation in first
surface 120 would be present in those cases where the seat ring
is constructed from harder materials such as acetal resins and
the like. When ball member C has shifted an amount to
substantially fully deflect the downstream disc spring, the
ball memDer is moved away from all contact by ball engaging
surface 120 of the upstream seat ring. A gap x (FIGURES 5 and
6) is formed therebetween and no sealing whatsoever occurs on
the upstream side of the ball.
This result minimizes downstream seat loading and wear
as well as reducing the turning torque required to rotate ball
member C back to the valve opened position. Within the
predetermined operational li~,its of the valve, ball engaging
surface 120 of the downstream seat ring will not generally be
substantially further deformed due to system pressures from the
conformation generally shown in FIGURE 7. Substantial further
deformation could undesirably cause the downstream seat ring to
break down and/or be completely destroyed.
Reinforcing ring 100 associated with the upstream seat
assembly prevents failure of the associated seat ring 102 by
providing a large bearing surface so that the bearing stress
will only be approximately 1 1~2 to 2 times the fluid system
pressure. This bearing stress is well within the capabilities
of most plastic materials utilized in constructing ball valve
--19--
1~3387~7
seat rings. ~oreover, and as the valve approaches the opening
point, i.e., when the ball C is rotated from the position shown
in FIGURE 5 back to the position shown in FIGURE 3, only seat
ring ball engaging surface 120 must span the ball opening.
This greatly reduces the unsupported area and length of the
span. First surface 110 of the reinforcing ring also provides
support substantially across the entire span of upstream seat
ring third surface 124. The combined effect of support across
the ball opening and a wide bearing shoulder at seat ring
stepped area 126 prevents the upstream or inlet seat ring from
distorting. It is essential to prevent such distortion in
order to preclude subsequent damage to the downstream seat
ring. When an unsupported upstream seat ring deforms into the
ball opening, it forms a bulge in a sector of the seat ring.
This bulge, in turn, pushes the ball member off center and
forces it to cut or distort the downstream seat. Such
downstream seat ring distortion causes it to leak at both high
and low pressures.
The ball valve A with seat assemblies B described in
detail hereinabove is deemed to provide a substantial
improvement over those arrangements previously known in the
art. The subject design permits the seat assemblies to be
flexible and deflect when acting as a downstream seat but to be
rigid when acting as an upstream seat. The assemblies are
spring loaded at initial assembly to facilitate sealing at low
pressures. The seat ring and ball movements are proportioned
to release the upstream seat ring from sealing against the ball
at high pressures. The upstream seat is supported by a
reinforcing ring during valve opening to prevent distortion.
Also, this reinforcing ring provides a large bearing support
-20-
1~3387'7
area to prevent the upstream seat ring from shearing at the
valve body shoulder or being otherwise displaced from its
proper location within the valve.
FIGURE 8 shows a number of design modifications or
features which may be advantageously incorporated into seat
assemblies B. Such modifications accommodate component
machining and valve use as will become apparent. Moreover, the
modifications may be individually adopted to use and are not
dependent on each other for successful seat assembly
operation. For ease of illustrating these alternative design
features, like components are identified by like numerals with
a primed (') suffix and new components are identified by new
numerals.
In FIGURE 8, counterbore end wall 78' extends further
inwardly into main valve body section 12' and the radially
outward extending flange is not included on reinforcing ring
100'. Thus, the inner end face or wall 150 of the reinforcing
ring abuts counterbore end wall 78' to positively establish an
axial innermost or home position therefor.
In addition, third surface 124' of seat ring 102' does
not include a stepped area as shown and described above with
reference to the preferred embodiment. Rather, the seat ring
third surface is continuous over the annular extent thereof and
is adapted to directly engage reinforcing ring first surface
110'.
The above two modifications are primarily production
oriented. That is, each eliminates a machining step which is
otherwise required for reinforcing ring 100' and seat ring 102'.
With continued reference to FIGURE 8, seat ring first
or ball engaging surface 120' also has a slightly modified
11338~7
conformation. As shown, the ball engaging surface is designed
to have a concave spherical surface concentric with the
longltudinal axis of the seat ring itself and a radius equal to
the radius of the ball member. Thus, when the valve is
S initially assembled, surface 120' will substantially matingly
engage the ball member surface and will remain in such
substantial mating engagement during rotational flexure of the
seat ring.
It is also possible witnin the broad aspects
contemplated for the invention that first or ball engaging
surface 1~0' may have other radii of curvature, both larger and
smaller than the radius of the ball member. Moreover, in some
cases it may be desirable to configure the body of seat ring
r~ *
102' so that in the free state thereof such as is shown in
FIGURE 8, ball engaging surface 120' is rotated slightly
outward of the seat ring central opening. With this type of
structure, the loci of the radius for surface 120' will form a
circle concentric with the seat ring longitudinal axis. The
aforementioned possible alterations for the seat ring ball
engaging surface do not in any way depart from the overall
intent or scope of the invention.
Finally, with regard to FIGURE 8, a groove 1~0 is
included in second surface 122' of seat ring 102'. This groove
extends inwardly into the seat ring body between the inner and
outer diameters thereof, is continuous and extends around the
entirety of second surface 122'. Groove 160 is particularly
desirable for use with harder seat ring materials such as
acetal resins and the like to increase flexi~ility and ~etter
accommoàate the desired rotational flexure thereof as
previously described. In addition to the particular groove
1~33877
configuration shown, other shapes and/or sizes therefor may be
utilized to accommodate still other types of seat ring
materials and/or valve parameters. Still further, groove 160
may also be incorporated into seat rings constructed from
softer materials if desired to accommodate a particular valve
application or design.
Other modifications not specifically shown in the
drawings may be readily incorporated into seat ring assemblies
B without in any way departing from the overall invention. For
example, it is possible to form axial flange 130 of seat ring
- - 102 at the inside diameter thereof as opposed to the preferred
. ;. .,~ ,. ~,
position at the outside diameter. Another example resides in
the specific orientation of seat ring second surface 122. As
~-~wy~ = -shown--in the-drawings, this surface tapers inwardly into-tbe
seat ring body from the outside diameter toward the inside
diameter. This taper angle may be varied as deemed necessary
ana/or second surface 122 may be disposed normal to the seat
ring axis so as to be generally parallel to the associated
valve body shoulder. It may also be desirable to slightly
modify the relative dimensional characteristics between the
seat rings, reinforcing rings and disc springs to accommodate
particular operational requirements.
Still further, and in some applications of the valve,
it would be possible to entirely eliminate use of reinforcing
rings 100 in seat assemblies B. In that case, forward or
inward movement of the seat rings into valve body passageway 20
would be limited by, for example, engagement of the seat ring
third surfaces with the end wa~ls of the passageway
counterbores. However, elimination of the reinforcing rings
will reduce the pressure ratings attributable to the valve due
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113387'7
to increased potential for upstream seat ring displacement
and/or distortion which could result in damage to the
downstream seat. This could be compensated to some extent by
modifying the dimensional relationships between other of the
remaining components. Nevertheless, the advantageous
relationships between the ball member seat rings and disc
springs as described above would still be obtained during valve
use.
The invention has been described with reference to
preferred and alternative embodiments. Obviously,
modifications and alterations will occur to others upon the
reading and understanding of this specification. It is our
intention to include all such modifications and alterations
--- insofar as they come within the scope of the appended claims or
the equivalents thereof.
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