End entry ball valve with seal wear compensation and force isolated seal

In an end entry ball valve assembly, a bifurcated seal carrier comprised of an annular seal support member and back-up member, is received in at least one end opening. The seal support member includes an axially facing end wall and a radially facing guide wall. The back-up member is slidably received in the opening and presents a recess defined by an axially facing support wall and a radially facing guide wall respectively adjacent the end wall and guide wall of the seal support member. An annular, resilient biasing and sealing ring is disposed, in a radially tensioned and axially compressed condition, in a groove disposed in at least one of those axially facing walls at a location radially inwardly of the guide walls. The ring biases the seal support member and a seal carried thereby toward the valve ball and seals against fluid flow between the axially facing walls. The seal support member is dimensioned for limited radial centering movement in the receiving recess without direct compressive resistance by the biasing and sealing ring. Longitudinal loads on the back-up member are isolated from the valve ball.

BACKGROUND OF THE INVENTION 
This invention relates generally to ball valves. More particularly, this 
invention relates to thermoplastic ball valves of the end entry type. 
End entry type ball valves have well recognized advantages from the 
standpoint of manufacturing and assembly. In known thermoplastic end entry 
ball valves, such as the type shown in U.S. Pat. No. 3,550,902, additional 
advantages are offered by the provision for adjusting the parts of the 
assembly when wear occurs upon the seals. 
While compensation for wear is desirable, control over the contact 
relationship between the seal member and ball is also an important factor. 
This relationship can be affected by operating conditions as well as by 
assembly operations. 
For example, external forces generated by thermal expansion or contraction, 
piping misalignment, and initial positioning of the seal member can all, 
in the absence of precision tolerances, materially affect the sealing 
relationship. With thermally induced expansion, the seal members can be 
pushed very tightly against the valve ball, and perhaps result in 
undesirably high operating forces and/or marring of the ball. Thermally 
induced contraction can result in loss of the seal. Excessive tightening 
of the seal member against the ball during assembly or misalignment of the 
desired assembled relationship of the seal member and ball can lead to 
permanent deformation of the seal member itself and other undesirable 
problems. 
OBJECTS AND SUMMARY OF PREFERRED FORMS OF THE INVENTION 
It is a general object of the present invention to provide a novel ball 
valve that retains the manufacturing and assembly advantages of end entry 
design while providing compensation for wear upon the seals and 
establishing control over the contact relationship between a seal member 
and the ball. 
It is a particular object of the present invention to provide such a novel 
ball valve of the thermoplastic type. 
It is a further object of the present invention to provide such a novel 
ball valve wherein contact between the seal member and the ball is 
controlled by isolating longitudinal forces resulting from operating 
conditions and induced by assembly. 
It is another object of the present invention to provide such a novel ball 
valve wherein contact between the seal member and the ball is controlled 
by providing for self-adjusting alignment of the seal member with respect 
to the ball. 
Preferred embodiments of the invention intended to accomplish the foregoing 
and other objects comprise an end entry ball assembly including a 
thermoplastic valve body presenting first and second open ends and 
operable to be connected in fluid communicating relationship to conduits. 
The valve body includes a valve chamber between the first and second ends 
and a stem receiving passage communicating with the valve chamber. A 
thermoplastic valve ball is positioned in the valve chamber. The valve 
ball is operable to rotate in the chamber between a flow permitting 
position and a flow blocking position. A thermoplastic stem extends 
through the stem receiving passage and is engageable with the valve ball 
to rotate the ball between the flow permitting and flow blocking 
positions. 
The opening of at least one end of the valve body is sufficiently enlarged 
for insertion of the valve ball means into said valve chamber. A 
thermoplastic, bifurcated seal carrier is received in at least one end of 
the valve body. The bifurcated seal carrier includes an annular seal 
support member and a back-up member. 
An end connector operable to couple the ball valve assembly to a conduit at 
that end of the valve body is operable to transmit longitudinal loads to 
the back-up member. Means on the valve body isolates longitudinal loads on 
the back-up member from the valve ball. 
In one preferred form of the invention the end connector and the back-up 
member are integral, and the load isolating means comprises a radially 
extending flange of the end connector which is solvent welded against an 
abutment surface of the valve body. 
In another preferred form of the invention, the back-up member may be 
integral or separate from the end connector, but in either case it 
includes a leading portion of smaller external diameter and a trailing 
portion of enlarged external diameter to define a stepped abutment 
surface. The load isolating means comprises an internal shoulder of the 
valve body which is cooperable with the stepped abutment surface to 
isolate the longitudinal loads. An interiorly threaded union nut, 
engageable with exterior threads of the valve body means and a flange of 
the end connector, is operable to impose longitudinal loads on the end 
connector. An annular member seals between the leading portion of said 
back-up member and the valve body forward of the abutment surface. 
The annular seal support member carrier an annular thermoplastic seal 
member engaged with the valve ball. The seal support member includes an 
axially facing end wall and a radially facing guide wall. 
The back-up member is slidably receivable in the opening of one end of the 
valve body. The back-up member in that location presents a seal support 
member receiving recess defined by an axially facing support wall adjacent 
the axially facing end wall of the seal support member and a radial facing 
guide wall adjacent the radially facing guide wall of the seal support 
member. 
An annular retaining groove is disposed in at least one of the axially 
facing walls. The retaining groove is located radially inwardly from the 
radially facing guide walls of the support member and the back-up member. 
An annular, resilient biasing and sealing ring is disposed in the retaining 
groove in axially compressed condition. The ring generally axially biases 
the seal support member and the seal carried thereby toward the valve ball 
and seals against flow between the axially facing walls of the annular 
seal support member and the recess. The ring, in its relaxed condition, 
has an internal diameter smaller than the internal diameter of said groove 
and is received therein in tensioned condition. 
The seal support member is dimensioned for limited radial centering 
movement in the receiving recess without direct compressive resistance by 
the resilient biasing and sealing ring. 
Other objects and advantages of the present invention will become apparent 
from the subsequent detailed description of preferred embodiments in 
conjunction with the accompanying drawings in which:

DETAILED DESCRIPTION 
Depicted in FIG. 1 is an end entry ball valve assembly 20 constructed in 
accordance with a preferred embodiment of the present invention. The ball 
valve assembly 20 is adapted for connection in general longitudinal 
alignment with a pair of fluid conduits (not shown) by means of 
conventional end connectors 22, 24. The end connectors are respectively 
provided with generally radially outwardly extending flanges 26, 28. Each 
flange 26, 28 has a substantially radial face 30, 32 and a frustoconical 
surface 34, 36 which tapers radially inwardly and away from the radial 
face 30, 32. 
The ball valve assembly 20 includes an open-ended, main valve body portion 
38 which is fabricated of a corrosion-resistant thermoplastic material 
such as polyvinylchloride (hereinafter PVC). The main valve body portion 
includes a generally cylindrical external surface 40 which extends from a 
first generally radial end face 42 to a second generally radial end face 
44. Each end of the external surface 40 is provided with an externally 
threaded end portion 46, 48. Union nuts 50, 52 cooperate with the threaded 
end portions 46, 48. 
The substantially identical union nuts 50, 52 each include a cylindrical 
portion 54 that is internally threaded for connection to the corresponding 
threaded end portion 46, 48 of the main valve body portion 38. Extending 
radially inwardly from one end of the cylindrical portion 54 is a flange 
56 which presents a central opening 58 adapted to slide longitudinally on 
the outer circumference of the corresponding end connectors 22, 24. 
The flanges 56 (FIG. 1) each include an internal frustoconical surface 60 
that tapers radially inwardly and away from the main valve body portion 38 
so that it corresponds to the adjacent one of frustoconical surfaces 34, 
36 of the end connector flanges 26, 28. Accordingly, when the union nuts 
50 are tightened onto the main valve body portion 38, the radially 
extending flange 56 imposes longitudinal forces on the end connectors 22, 
24. 
The open-ended, main valve body portion 38 is provided with a 
longitudinally extending passage 62 which extends therethrough from the 
first radial end face 42 to the second generally radial end face 44. The 
illustrated longitudinally extending passage 62 includes a plurality of 
axially extending, generally cylindrical sections of diverse diameters. 
One axial section positioned generally centrally of the main valve body 
portion 38 is radially large enough to define a valve chamber 64. In the 
illustrated valve, the valve chamber 64 is essentially the same diameter 
as a section of the passage 62 which extends toward one end 42 of the main 
valve body portion 38. An axially, inwardly extending counterbore, 
indicated at 66, is provided at that end for a purpose hereinafter 
discussed. In any event, it will be appreciated that the opening of at 
least one end of the main body portion 38 is sufficiently enlarged for 
endwise insertion of the apertured valve member 70 into the valve chamber 
64. 
The counterbore, indicated at 66, defines an internal shoulder 68 spaced 
from the first end 42 of the main body portion 38 by a predetermined axial 
distance. If desired, this structure could be duplicated adjacent the 
other end 44 of the main body portion 38. However, in the illustrated 
valve, provision is made for end entry of the valve member 70 at only one 
end 42 and part of the bifurcated seal carrier structure (described more 
fully below) is integral with the main body portion 38 at the other end 
44. 
A stem receiving opening 72, with an axis substantially perpendicular to 
the longitudinal axis of the longitudinal passage 62 through the main body 
portion 38, extends laterally through a generally central section of the 
main body portion 38 into communication with the valve chamber 64. An 
outwardly projecting collar 76 integral with the main body portion 76 may 
provide additional lateral support for a valve stem assembly received in 
the opening 72. 
The valve ball 70 positioned within the valve chamber 64 is preferably a 
thermoplastic ball. The external surface 80 of the valve ball 78 may be 
essentially entirely spherical, as illustrated, and is preferably 
spherical at least at the portion adapted to provide a sealing surface. 
The valve ball 70 is provided with a generally cylindrical central bore 82 
having a generally circular cross section (see FIG. 3) and is rotatable 
about a rotational axis 84 which is substantially perpendicular to the 
axis 86 of the bore or flow passage 82. 
The external surface 80 of the valve ball 78 has a nominal diameter which 
is less than the nominal diameter of the valve chamber 64. In this manner, 
the main valve body 38 will not interfere with the valve ball 70 during 
rotation about the axis 84 between its flow permitting position of FIG. 1 
and its flow blocking position of FIG. 4. 
A groove 88, which is generally perpendicular to both the ball rotational 
axis 84 and to the bore axis 86, is provided in the ball 70 at a location 
where it does not interfere with the sealing portion of the external ball 
surface 80. The groove 88 may have a dovetail cross-sectional 
configuration and is adapted to receive a correspondingly configured end 
portion 90 of a thermoplastic valve stem 92 in a conventional manner. The 
cylindrical external surface of the valve stem assembly 92 may be provided 
with an annular groove 96 that receives a suitable conventional O-ring 98. 
In this manner a fluid seal is effected between the lateral opening 72 and 
the valve stem 92. 
With continued reference to FIG. 1, it will be appreciated that a 
bifurcated seal carrier assembly 100 is slidably received in the ball 
entry end of the main valve body portion 38. The bifurcated seal assembly 
100 includes an annular thermoplastic seal support member 104 and a 
thermoplastic back-up member 102. 
The back-up member 102 includes a longitudinal bore 106 having a diameter 
substantially equivalent to the diameter of the valve ball throughbore 82. 
The seal support member 104 and the seal carried thereby have similarly 
dimensioned bores. In this manner, the fluid passing through the main 
valve body portion 38 is substantially unrestricted by the presence of the 
seal carrier assemblies, the seals and the valve ball 70. 
A leading portion 110 of the back-up member has a smaller external diameter 
and a trailing portion 108 has an enlarged external diameter to define a 
stepped abutment surface 112. The internal shoulder 68 of the main body 
portion 38 cooperates with the stepped abutment surface 112 to isolate 
longitudinal loads on the back-up member 102 from the valve ball 70. 
The back-up member 102 is provided with a circumferential groove 118 that 
receives a peripheral seal member, such as a suitable conventional O-ring 
120, to prevent fluid from leaking between the back-up member 102 and the 
main valve body portion 38. Preferably the O-ring 120 is positioned 
forward of the shoulder 112 so that fluid pressure in the valve chamber 64 
is confined to act only on the smallest annulus area of the back-up member 
102. 
At the leading end of the reduced section 110 of the back-up member 102 an 
annular receiving recess 122 for the seal support member 104 is presented. 
This recess is defined by an axially facing support wall 113 and a 
radially facing guide wall 114. The annular seal support member 104 
includes an axially facing end wall 124 and a radially facing guide wall 
125 respectively adjacent the support wall and guide wall of the back-up 
member 102. The seal support member is, however, dimensioned for limited 
radial centering movement in the receiving recess 122. Thus, the back-up 
member 102 provides for axial movement of the seal support member 104 
while allowing for radial centering adjustment of the seal support member 
104. 
An annular retaining groove 126 is disposed in at least one of the axially 
facing walls 113 and 124 of the seal support member 104 and the back-up 
member 102 at a location radially inwardly of the radially facing guide 
walls 114 and 125. In the illustrated valve, the groove 126 is disposed 
entirely in the axially facing wall 113 of the back-up member 102. An 
annular, resilient sealing and biasing member 128 is received in the 
groove 126. The sealing and biasing member provides a fluid seal between 
the axially facing walls of the back-up member 102 and the seal support 
member 104. In addition, the sealing and biasing member 128 causes an 
axial force biasing the seal support member 104 and the seal carried 
thereby toward the valve ball 70. 
The sealing and biasing member 128 preferably comprises a suitable 
conventional O-ring fabricated from "VITON" and having a cross-sectional 
diameter in its relaxed condition which exceeds the axial depth of the 
annular groove 126 (see phantom lines of FIG. 2). In this manner, the 
O-ring is in a compressed state when the seal support member 104 and the 
back-up member 102 are positioned in the valve assemby 20. Preferably, the 
O-ring 128, in its relaxed condition, has an internal diameter smaller 
than the internal diameter of the groove 126 so that it is also received 
therein in a radially tensioned condition. This enhances the sealing 
action of the O-ring 128. 
The seal support member 104 includes a seal receiving recess 130 facing the 
valve ball 70. An annular seal member 138 is received therein on the side 
of the seal support member 104 opposite the axially facing wall 124 on 
which the biasing ring 128 acts. 
As will be appreciated, the axial dimensions of the reduced section 110 and 
enlarged section 108 of the back-up member 102 and those of the seal 
support member 104, its receiving recess 122 and the ball seal 138 are 
preferably such that when the union nut 50 is tightened to produce 
abutment of the stepped abutment surface 68 and the shoulder 112, the 
axial faces 113 and 124 of the back-up member 102 and seal support member 
104 are in engagement, the ball seal 138 is loaded against the ball 70 at 
a predetermined acceptable level, and the biasing ring 128 is axially 
compressed. Should wear of the ball seal 138 occur, the axially compressed 
biasing ring 128 will act, over a predetermined expected wear range, on 
the seal support member 104 to urge it axially toward the ball 110 so as 
to compensate for the wear. The initial compression of the biasing ring 
128 is such that over the expected range of ball seal wear, the biasing 
ring 128 is capable of imposing an acceptably high load in the ball seal 
138 against the ball at a level of the order of that imposed by the 
initial assembly conditions. The same is true over the expected range of 
loss of seal load attributable to thermal contraction for which the 
biasing ring 128 may also compensate. However, the load of the ball seal 
138 against the ball is prevented from being excessive, whether through 
assembly forces or thermal expansion, because of the load isolation 
established through the cooperation of the stepped abutment surface 68 and 
the shoulder 111. 
As previously mentioned, the seal support member 104 is dimensioned to have 
limited clearance in the receiving recess 122 of the back-up member 104. 
This clearance permits limited radial movement to allow the ball seal 138 
to center itself on the ball 70. Such self-centering action aids in 
avoiding marring or excessive wear of the ball. Of particular significance 
in this regard is the fact that the biasing ring 128 is so located that it 
does not impose direct compressive resistance to this centering movement. 
As earlier noted, the groove 126 for the biasing ring is disposed radially 
inwardly of the radially facing guide walls 114 and 125 of the back-up 
member 102 and seal support member 104. The retaining groove 126 can be 
located in either or both of the axially facing walls 113, 124 of those 
members as long as it is arranged so that direct compressive resistance to 
centering movement is not offered by the biasing ring 128. 
The ball seal member 138, usually referred to as a seat, is preferably 
fabricated from polytetrafluoroethylene to make use of its highly 
desirable low friction characteristics. As may be seen in FIG. 2, the ball 
seal 138 includes a relatively narrow, generally radial end face 140. This 
face 140 faces the valve ball without contacting it. Parallel to and 
axially spaced from the narrow face 140 is a relatively wide radial end 
face 142. The relatively wide radial end face 142 may be supported in 
axial abutment with the axially facing bottom surface 144 of the seal 
receiving recess 130 defined by the seal support member 104. 
The annular seal member 138 has an axial length exceeding the predetermined 
length of the radially facing sidewall 136 of the seal receiving recess 
130. A first, preferably major, portion 146 of the external sidewall of 
the annular seal member 138 is radially supported in sealing contact with 
the cylindrical sidewall 136 of the seal receiving recess 130. The leading 
annular lip portion 148 of the external sidewall of the annular member 138 
extends beyond the front end surface 130 of the seal support member 104 
and is radially unsupported. In this fashion, the portion of the seal 
member 138 that projects beyond the seal support member 104 is permitted 
to deflect radially outwardly. 
The internal peripheral surface or sidewall 150 of the seal 138 has a 
diameter substantially the same as the diameter of the bore 135 through 
the seal support member 104. A frustoconical surface 152 of the seal 
member 138 extends from a leading edge 154 common with the narrow front 
radial surface 140 to an edge 155 common with the internal sidewall 150. 
It is this frustoconical surface 152 that against which the valve ball is 
sealed. The frustoconical surface 152 spans at least part of the radially 
supported portion of the seal as well as the entire radially unsupported 
portion. 
During final assembly (see FIG. 3), the valve ball 70 initially is 
contacted by the seal member 138 along a contact circle defined by relaxed 
contact of the frustoconical surface 152, at or adjacent its leading edge 
154, with the sealing surface 80 of the ball. A conical surface, tangent 
to the spherical surface 80 of the ball along that contact circle has a 
cone half-angle .theta..sub.t. As will be appreciated, the cone half-angle 
.theta. of the frustoconical surface 152 is less than the cone angle 
.theta..sub.t of that tangent cone. 
As the union 50, associated with the end connector 28, is tightened, the 
axial force imparted results in responsive radially outward deflection of 
the leading, unsupported lip portion of the seal 138 to establish 
substantial surface contact with the sealing surface of the ball. With the 
ball 70 oriented in the "closed" position of FIGS. 3 and 4, the ball 70 
can move axially relative to the stem 92 by reason of the longitudinally 
extending orientation of the dovetailed groove 88. Thus, a similar radial 
outward deflection of the leading unsupported portion of the seal 138' 
(FIG. 1) on the other side of the ball is induced. At the same time, the 
ball is substantially centered so that its central transverse axis 84 is 
brought into alignment with the rotational axis 156 of the stem (compare 
(FIGS. 3 and 4). 
In the final assembled position (FIG. 4), with the unsupported portions of 
the seals 138 and 138' deflected and in somewhat resilient surface contact 
with the ball, the ball 70 also makes contact with the radially supported 
portions of the seals preferably at the juncture with the unsupported 
portions. By reason of the radial support, cold flow of the seal material 
is essentially avoided. By reason of the flexure of the radially 
unsupported lip portions of the seals, potential marring of the ball 
through edge contact is militated against. Simultaneously, the earlier 
noted substantial degree of surface contact between the ball and seals is 
provided. As such, an improved sealing relationship which can withstand a 
fairly high contact force useful for maintaining the seal is established 
while the possibility of ball marring is minimized and the expense of 
conforming the seal surface of the ball surface during manufacture is not 
encountered. 
In the illustrated valve of FIG. 1, seal adjustment and force isolation is 
also provided on the side of the ball opposite from that shown in FIGS. 3 
and 4. However, the back-up member 102' of the bifurcated seal carrier is 
integral with the main valve body portion 38 and the valve can thus be 
conveniently used as a shutoff mechanism at the end of a flowline. Because 
of the fixed nature of the back-up member, no seal is required between 
that back-up member 102' and the main body portion as in the case of the 
O-ring seal 120 between the back-up member 102 and the main body portion 
at the other end of the valve. 
The seal support member 104' associated with the fixed back-up member 102' 
is identical in structure to the seal support member 104 associated with 
the movable back-up member 102, so it need not be described in detail. The 
same is true of the associated biasing O-ring 128' and the valve ball seal 
138' which correspond to the similarly numbered members already described 
in connection with the entry end of the valve. 
It will, however, be apparent that many advantages of the present invention 
can be realized without incorporating such structure at the "closed" (i.e. 
nonentry end) of the valve. It will also be apparent that provision may be 
made for valve ball entry at the second end, either with or without 
structure duplicating that described in connection with the entry end 
(i.e., with or without provision for seal adjustment and centering, etc. 
according to the present invention). Moreover, although the illustrated 
valve is of the dropout type where the valving section can be removed or 
inserted without disturbing the associated pipe ends (not shown), it will 
be appreciated that this need not be the case, and the present invention 
embraces a situation where the end connectors are integral with the 
back-up members of the bifurcated seal carrier at either or both ends of 
the valve. In such instances, of course, the illustrated seals 162 located 
in grooves at the outer ends of the back-up members would not be employed. 
Other variations are also envisioned. 
Turning now to FIG. 5, a further embodiment of a thermoplastic end entry 
ball valve assembly 20a according to the present invention will be seen. 
In that embodiment the end connector 166 at one end of the valve is 
integral with the main valve body 38a, and no provision is made for 
compensating for adjustment of the ball seal 138a at that end. 
At the other end, the end connector 24a is integral with the back-up member 
102a of the bifurcated seal carrier. The back-up member 102a has an 
external diameter substantially equal to the internal diameter of the 
entry opening in the main body 38a of the valve at that end, and neither 
are stepped as in the embodiment of FIG. 1. Force isolation is provided by 
the abutment of an enlarged flange 28a of the end connector with the end 
wall 42a of the main valve body. The end connector is permanently fixed in 
any suitable manner, such as by solvent, vibration or heat welding, to the 
main valve body at that location, which, of course, will preclude further 
access to the interior. 
The ball 70a, stem 92a, seal support member 104a, the seal 138a carried 
thereby, and the biasing O-ring 128a function as the correspondingly 
numbered members described in connection with FIG. 1. 
Although the invention has been described in conjunction with preferred 
forms thereof, it will be appreciated by those skilled in the art that 
additions, deletions, substitutions and modifications not specifically 
described may be made without departing from the spirit and scope of the 
invention as defined in the appended claims.