Patent Publication Number: US-6217003-B1

Title: Valve assembly having floating retainer rings

Description:
This is a divisional of application Ser. No. 09/006,513, filed on Jan. 13, 1998 now U.S. Pat. No. 6,029,948. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a valve assembly, and more particularly to a valve assembly having a valve member rotatably positioned within a valve housing by retaining ring assemblies that include floating retainer rings. 
     BACKGROUND 
     Valve assemblies, such as ball valve assemblies, are well known and have been used for a variety of applications. Such ball valve assemblies commonly include a ball valve that is securely, but rotatably positioned within a housing by a seating or retaining member. Traditionally, the valve assembly and the piping to which the valve assembly is connected have been made of steel or other metal material, but recently thermoplastic piping has become increasingly popular. Thermoplastic piping is desirable for various reasons such as reduced cost, the non-corrosive nature of thermoplastics, and the fact that thermoplastic parts have a longer useful life than do their metal counterparts. Further, thermoplastic piping is easier to install and repair, since adjoining sections of pipe can quickly and easily be butt-welded together. Thus, it is now desirable to also have thermoplastic valve assemblies for use in conjunction with thermoplastic piping. 
     Designing thermoplastic valve assemblies is more complicated, however, due to the fact that thermoplastic materials tend to expand and contract with variations in both temperature and pressure. The rate and amount of expansion and contraction will depend on various factors, such as the particular type of thermoplastic used, the coefficient of thermal expansion of the thermoplastic, and the physical dimensions of the element. Accordingly, in a thermoplastic valve assembly, the relatively thin thermoplastic housing will typically expand in diameter more rapidly as temperature increases than will other elements of the valve assembly, such as the ball valve or seating member. Thus, during normal operation the physical relationship or the physical “fit” between the various elements of the valve assembly may change. For example, due to their differing shapes and masses, the housing will typically expand radially at a rate greater than that of the ball valve. Under such circumstances, it is difficult to ensure that the fluid seals between the ball valve and the surrounding housing remain intact, since the seating member may expand at a different rate, or if it is physically secured to another element such as the housing, it may move with that element In addition, in the case of a thermoplastic ball valve, the ball itself, due to its shape, will be particularly subject to thermal or pressure deformation in the areas surrounding its inlet and outlet openings, known as the “lip” regions, since the material thickness is lowest in this area. Deformation of these lip areas will cause flaring that will affect both fluid flow through the valve and the integrity of the ball valve itself. Further, flaring of the lip areas will also prevent the valve from opening and closing properly. Thus, in a thermoplastic ball valve assembly it is also important to maintain the positioning and the structural integrity of the ball valve under all operating conditions. 
     Known thermoplastic ball valve assemblies, such as that shown in FIG. 1, have provided a thermoplastic housing  100 , with thermoplastic seating members  101  that are positioned within a recess or groove  102  in the housing itself, and thus are physically secured to the housing. Such a configuration does not solve the problems described above, since the movement of the housing (such as by expansion) directly corresponds to movement of the seating members. Thus, as the housing expands, the seating member that is secured to the housing tends to move with it, being drawn away from the ball valve. As described above, this has the disadvantage of affecting the fluid seals between these elements, and also decreases the ability of the seating member to ensure the proper positioning and the physical integrity of the ball valve, particularly around the lip areas, under all operating conditions. 
     Thus, known thermoplastic ball valve assemblies have been unable to account for large variations in temperature or pressure, and therefore, have been limited to applications involving relatively mild operating conditions, i.e., uses under which temperature and/or pressure variations are relatively insubstantial. These devices are simply unsuitable for many applications in which thermoplastic piping is otherwise desirable, such as the water market, where operating conditions as well as testing requirements are much more severe. 
     SUMMARY OF THE INVENTION 
     Accordingly, a need currently exists for a valve assembly that includes floating retainer rings that both maintain their physical “fit” in relation to the valve member, and that ensure the structural integrity of the valve member during all normal operating conditions, including operating conditions under which large variations in temperature and/or pressure can be expected. Further, a need currently exists for such a valve assembly that can be made of thermoplastic materials. 
     In accordance with the present invention, a valve assembly is provided that comprises a valve housing having a fluid passageway extending therethrough. The fluid passageway includes an inlet portion, the cross-section of which is defined by a substantially annular inlet surface; an outlet portion, the cross-section of which is defined by a substantially annular outlet surface; and an inner chamber portion that is positioned between and adjacent to the inlet and outlet portions and has an inlet end and an outlet end. The inner chamber portion is defined by a substantially annular inner chamber surface, an inlet wall, and an outlet wall. The inlet wall extends inwardly from the inner chamber surface to the inlet surface, and the outlet wall extends inwardly from the inner chamber surface to the outlet surface. A valve member is located within the inner chamber portion of the fluid passageway, and is movable between a closed position in which the fluid passageway is blocked, and an open position in which the fluid passageway is not blocked. 
     The valve assembly further includes first and second substantially annular retainer ring assemblies located within the inner chamber portion of the fluid passageway for rotatably positioning the valve member within the inner chamber portion. The first retainer ring provides a first fluid seal between the valve member and the inner chamber surface at the first end of the inner chamber portion, and the second retainer ring provides a second fluid seal between the valve member and the inner chamber surface at the second end of the inner chamber portion. The first and second retainer ring assemblies each include a floating retainer ring and a plurality of sealing members. The floating retainer rings are spaced apart from and movable relative to the inner chamber surface and the inlet and outlet walls. A first one of the plurality of sealing members of the first and second retainer ring assemblies forms a fluid seal between the respective floating retainer ring and the inner chamber surface; a second one of the sealing members of the first retainer ring assembly forms a fluid seal between the floating retainer ring of the first retainer ring assembly and the inner wall; a second one of the sealing members of the second retainer ring assembly forms a fluid seal between the floating retainer ring of the second retainer ring assembly and the outer wall; and a third one of the sealing members of the first and second retainer ring assemblies forms a fluid seal between the respective floating retainer ring and the valve member. 
     In one embodiment of the present invention the valve housing has a coefficient of thermal expansion, and the first and second floating retainer rings have a coefficient of thermal expansion that is lower than that of the valve housing. Further, the sealing members are sufficiently compressed so that the first and second fluid seals are maintained if the valve housing expands during normal operation of the valve assembly. 
     In yet another embodiment of the present invention, the valve assembly includes a similarly configured valve housing having a fluid passageway extending through it, and a valve member located within the inner chamber portion of the fluid passageway that is movable between a closed position in which the fluid passageway is blocked, and an open position in which the fluid passageway is not blocked. The inner chamber surface includes a threaded portion at the outlet end of the inner chamber portion. The valve assembly also includes first and second substantially annular retainer ring assemblies located within the inner chamber portion of the fluid passageway for rotatably positioning the valve member within the inner chamber portion. The first retainer ring assembly provides a first fluid seal between the valve member and the inner chamber surface at the first end of the inner chamber portion, and the second retainer ring assembly provides a second fluid seal between the valve member and the inner chamber surface at the second end of the inner chamber portion. 
     This alternate embodiment further includes a substantially annular securing ring positioned within the inner chamber portion of the fluid passageway. The securing ring has a hole through it, a threaded outer edge, an outer side, and an inner side. The outer edge is threadably engaged with the threaded portion of the inner chamber surface, and the outer side is substantially aligned with and substantially complementary to the outer wall. 
     First and second retainer ring assemblies of the valve assembly each have a floating retainer ring and a plurality of sealing rings. The floating retainer rings are spaced apart from and movable relative to the valve member, and relative to the inner chamber surface and the said inlet and outlet walls. A first one of the plurality of sealing rings of the first and second retainer ring assemblies forms a fluid seal between the respective floating retainer ring and the inner chamber surface; a second one of the plurality of sealing rings of the first retainer ring assembly forms a fluid seal between the first floating retainer ring and the inner wall; a second one of the plurality of sealing rings of the second retainer ring assembly forms a fluid seal between the second floating retainer ring and the outer side of said securing ring; and a third one of the plurality of sealing rings of the first and second retainer ring assemblies forms a fluid seal between the respective floating retainer ring and the valve member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings in which like reference numbers indicate like features wherein: 
     FIG. 1 illustrates a prior art thermoplastic ball valve assembly; 
     FIG. 2 is an exterior view of one embodiment of a valve assembly according to the present invention; 
     FIG. 3 is a cross-sectional view of the valve assembly of FIG. 2, taken along line A—A; 
     FIG. 4 illustrates a ball valve that forms part of the valve assembly; 
     FIG. 5 a  illustrates one embodiment of a floating retainer ring that forms part of the valve assembly; 
     FIG. 5 b  is a cross-sectional view of a portion of a floating retainer ring; and 
     FIG. 6 is a cross-sectional view of another embodiment of a valve assembly according to the present invention that includes a securing ring. 
    
    
     DETAILED DESCRIPTION 
     FIG. 2 is an exterior view of one embodiment of a valve assembly according to the present invention, and FIG. 3 is a cross-sectional view of the valve assembly of FIG. 2 taken along line A—A. The valve assembly  300  includes a valve housing  301  having a fluid passageway  302  extending through it that lies along a central axis a—a. The fluid passageway  302  includes an inlet portion  303 , the cross-section of which is defined by the substantially annular inlet surface  304  of the valve housing, and an outlet portion  305 , the cross-section of which is defined by the substantially annular outlet surface  306  of the valve housing  301 . Both the inlet and outlet portions of the fluid passageway have a first inlet end  310 ,  311  and a second outlet end  312 ,  313 . The fluid passageway  302  further includes an inner chamber portion  307  that is positioned between and adjacent to the inlet and outlet portions, which is defined by the substantially annular inner chamber surface  308  of the valve housing, and the inner wall  315  and outer wall  316  of the valve housing. The inner chamber portion  307  also has a first inlet end  320  and a second outlet end  321 . 
     The inner wall  315  extends inwardly from the inner chamber surface  308  to the inlet surface  304  at the outlet end  312  of the inlet portion of the fluid passageway so as to form a substantially continuous surface. Likewise, the outer wall  316  extends inwardly from the inner chamber surface  308  to the outlet surface  306  of the outlet portion  305  of the fluid passageway so as to form a substantially continuous surface. 
     Although the inner  315  and outer  316  walls, as shown in FIG. 3, are substantially perpendicular to the inner chamber surface  308 , other configurations, such as angled walls or walls having multiple surfaces, are also possible. Similarly, the diameters of the inlet and outlet portions D 1 , D 2  of the fluid passageway may be substantially the same, and substantially constant along the length of the inlet and outlet portions as shown in FIG. 3, but may also differ from one another, or vary along the length of the respective portions. 
     Within the inner chamber portion  307  is a valve member, such as a ball valve  325 . The ball valve  325 , shown separately in FIG. 4, is substantially spherical in shape, has an outer ball valve surface  400 , and a valve hole  401  extending through it that is concentric with a central axis; b—b. The valve hole  401  has an inlet end  402  and an outlet end  403 . Extending from the ball valve is a stem  330  (FIG. 3) that extends through an aperture  331  in the valve housing to the exterior of the valve housing. The stem cooperates with a handle  332  that is located outside the valve housing  301 . In the embodiment shown in FIG. 3, the stem is engaged with the ball valve by means of an enlarged portion  335  that cooperates or mates with a similarly shaped groove  402  in the ball valve  325  (FIG.  4 ). Thus, when the stem  330  is rotated by means of the handle  332 , the ball valve will also rotate between open and closed positions. As will be described in more detail below, the ball valve is rotatably positioned with the inner chamber portion  307  of the fluid passageway so that in the closed position the outer surface  400  of the ball valve completely obstructs the fluid passageway, thereby preventing fluid that is flowing through the fluid passageway from passing from the inlet portion  303  to the outlet portion  305  of the fluid passageway. In the open position, the ball valve is rotated so that the valve hole  401  is oriented such that fluid flow between the inlet portion  303  and the outlet portion  305  of the fluid passageway is not entirely obstructed. In a fully open position, the valve hole  401  is oriented so that its central axis b—b is substantially parallel to the central axis a—a of the fluid passageway  302 . In a partially open position, the central axis b—b will be at an angle relative to the central axis of the fluid passageway. 
     The ball valve also includes an inlet lip region  405  and an outlet lip region  406  (FIGS. 3 and 4) that surrounds the valve hole  401  at its inlet  402  and outlet  403  ends. The thickness of the ball valve material in these lip regions is substantially less than that of other regions, as can be readily seen in FIGS. 3 and 4. Thus, the lip regions are particularly subject to deformation at elevated temperatures and/or pressures, and tend to flare out when so deformed if not otherwise restrained. According to the present invention, these lip regions are restrained from flaring by the retainer ring assemblies described below. 
     As stated, the ball valve is positioned within the inner chamber  307  of the fluid passageway  302 . It is securely, but rotatably held in place by first  440  and second  441  substantially annular retainer ring assemblies. The first retainer ring assembly  440  is positioned within the first inlet end  320  of the inner chamber portion  307  of the fluid passageway, and forms a fluid seal between the ball valve  325  and the inner chamber surface  308  that substantially prevents any fluid that is flowing through the fluid passageway from reaching the inner chamber surface. Likewise, the second fluid retainer ring assembly  441  is positioned within the second outlet end  321  of the inner chamber portion  307  of the fluid passageway, and forms a fluid seal between the ball valve  325  and the inner chamber surface  308  on the downstream or outlet end  321  of the inner chamber portion  307 . 
     The first and second retainer ring assemblies each further comprise substantially annular first  353  and second  354  floating retainer rings respectively, and a plurality of sealing members  351 . The floating retainer rings  353 ,  354  shown in FIG. 3 are shown in greater detail in FIGS. 5 a  and  5   b.  The floating retainer rings are substantially annular in shape and have a substantial annular hole  501  therethrough that is concentric with a central axis c—c. The floating retainer rings further include at least a first outer ring surface  503 , a second side ring surface  504 , and a third valve surface  505 . When positioned within the valve housing  301 , the central axis c—c is substantially coincident with the central axis a—a of the fluid passageway, and the first outer ring surface  503  of each floating retainer ring is substantially aligned with and substantially complementary to a respective portion of the inner chamber surface  308  of the valve housing  301 . Similarly, the second side ring surface  504  of the first floating retainer ring  353  is substantially complementary to the inner wall  315 , and the second side surface of the second floating retainer ring  354  is substantially aligned with and substantially complementary to the outer wall  316 . The third valve surface  505  of each floating retainer ring is substantially aligned with and substantially complementary to a respective portion of the outer surface  400  of the ball valve  325 . 
     The three surfaces of the floating retainer rings are substantially aligned with the corresponding surfaces of the valve housing  301  and the ball valve  325  as described above, but awe also slightly spaced apart from these corresponding surfaces, as shown in FIG.  3 . Positioned between and cooperating with the floating retainer rings and each of the corresponding surfaces is at least one sealing member, such as an O-ring. These O-rings are of a sufficient size to form a fluid seal between the respective members. In the embodiment of the present invention shown in FIG. 3, the inner  315  and outer  316  walls have a substantially annular recess or groove  360 ,  361  therein; the inner chamber surface  308  has a first  362  and second  363  substantially annular recess or groove therein; and the third valve surface  505  of each of the floating retainer rings also has a substantially annular recess or groove  506  therein. These recesses or grooves are sized and positioned so that an O-ring may be positioned partially within the groove, but yet also protrude from the groove, as shown in FIG.  3 . For example, the first retainer ring assembly  440  includes a first O-ring  370  that fits partially within and protrudes from the first inner chamber surface recess  362 . It protrudes from the groove so that it also communicates with the first outer ring surface  503  of the first floating retainer ring  353 . A second O-ring  371  similarly is positioned partially within the inner wall recess  360  and communicates with the second side ring surface  504  of the first floating retainer ring, and a third O-ring  372  is positioned partially within the third valve surface recess  506  of the first floating retainer ring  353  and communicates with the outer surface of the ball valve  400 . The first, second and third O-rings  373 ,  374 ,  375  of the second floating retainer ring assembly  441  are similarly positioned partially within the corresponding recesses, and communicate with the corresponding surfaces. 
     In the configuration described above, the floating retainer rings are “floating” in that they are not secured to or integral with either the ball valve or the valve housing, and therefore, may independently move relative to each of these members. The “floating” nature of the floating retainer rings is particularly advantageous in a thermoplastic valve assembly, when various members of the valve assembly move relative to one another when expanding or contracting in response to variations in temperature or pressure. According to one embodiment of the present invention, the valve housing  301  is comprised of a thermoplastic material, preferably polyethylene. The ball valve and the floating retainer rings are also comprised of a thermoplastic material, preferably polypropylene, which may be glass filled for added strength if desired. The thermoplastic material selected for the floating retainer rings has a coefficient of thermal expansion such that the floating retainer rings will remain substantially free from expansion or contraction under normal operating conditions. Thus, because the ball valve (also polypropylene) and the floating retainer rings substantially retain their shape and size, the valve surface  505  of the floating retainer rings  350  and the corresponding outer surface  400  of the ball valve  325  will remain substantially complementary during all normal operating conditions. 
     Although the floating retainer rings  350  and the ball valve  325  do not substantially expand or contract during normal operation, typically a valve housing comprised of polyethylene will undergo a certain amount of expansion, particularly when used for applications having more severe operating conditions, such as in the water market. To account for this variation, the O-rings are sized sufficiently so as to maintain a seal between the valve housing and the floating retainer rings, both of which have different coefficients of thermal expansion. The O-rings are sufficiently compressed so that when the valve housing expands, the O-rings will expand to ensure that the fluid seal is always maintained between the surfaces of the floating retainer rings and the corresponding surfaces of the ball valve or valve housing. To serve this purpose the O-rings maybe comprised of EPDM or Buna N. 
     As is readily apparent from the above description, the valve assembly of the present invention is advantageous because the floating retainer rings are “floating”, rather than integral or otherwise secured to the valve housing. Thus, the floating retainer rings may at all times move independent of these members to maintain the proper orientation and the proper complementary fit to the corresponding surfaces, rather than moving with another member as that other member expands or contracts. Thus, in conjunction with the compressed O-rings that will expand sufficiently to ensure that a fluid seal is maintained, the floating retainer rings ensure that the ball valve is properly positioned and its physical integrity sufficiently preserved at all times. With regard to the latter feature, it can be seen in FIG. 3 that the third O-ring  371 ,  375  of the first and second retainer ring assemblies is positioned adjacent the inlet  405  and outlet  406  lip regions of the ball valve  325  respectively, thereby assuring the structural integrity of the hip regions by preventing flaring of these regions. Because the floating retainer rings are floating rather than physically secured to another member such as the housing, the physical relationship between the ball valve and the floating retainer rings is maintained during expansion and contraction, as described above, and the proper positioning of the O-rings against the lip regions will also be maintained. 
     In an alternate embodiment shown in FIG. 6, the valve assembly  300  also includes a securing ring  600  that is positioned within the inner chamber portion  307  of the fluid passageway  302 . The securing ring  600  is substantially annular in shape, and has a hole  601  therethrough that is substantially equal in diameter to that of the outlet portion  305  of the fluid passageway  302 . In this embodiment, the inner chamber surface  308  includes a threaded portion  605  at the second outlet end  321  of the inner chamber portion  307 , and the securing ring  600  has a threaded outer edge  602  that is threadably engageable with the threaded portion  605  of the inner chamber surface  308 . The securing ring  600  also includes an inner side edge  606  and an outer side edge  607 . The securing ring  600  is positioned between the second retainer ring assembly  441  and the outer wall  316 , such that the second side ring surface  504  of the second floating retainer ring  354  is substantially aligned with and substantially complementary to the inner side edge  606  of the securing ring  600  rather than the outer wall  316 , and the outer side edge  607  of the securing ring  600  is substantially aligned with and substantially complementary to the outer wall  316 . Further, the second O-ring  374  of the second retainer ring assembly  441  that cooperates with the second side ring surface  504  also cooperates with the inner side edge  606  of the securing ring  600  rather than the outer wall  316 , and is positioned partially within and protruding from a substantially annular groove  608  in the inner side edge of the securing ring. 
     According to the above-described embodiment, a valve assembly according to the present invention may be assembled in the following manner. The first and second O-rings  370 ,  371  of the first retainer ring assembly  440  are inserted into the respective recesses in the inner chamber surface  308  and the inner wall  315 . The first floating retainer ring  353 , along with the third O-ring  371  are inserted next, followed by the ball valve  325 . Subsequently, the first O-ring of the second retainer ring assembly  441 , and the second floating retainer ring  354  along with the third O-ring  375  of the second retainer ring assembly  441  are inserted. The securing ring along with the second O-ring  374  of the second retainer ring assembly  441  are then inserted by threadably securing the threaded outer edge  602  of the securing ring to the threaded position  605  of the inner chamber surface. Finally, the remaining section of the valve housing  301  that surrounds and encloses the outer portion  305  of the fluid passageway  302  is secured to the rest of the valve housing by means of welding, bolting or the like. 
     Accordingly, a valve assembly is provided having floating retainer rings that ensure the proper positioning and operation of a ball valve within the pipe housing. The above-described configurations of the valve assembly are particularly suited for valve assemblies that are made of thermoplastic materials, and increase the range of applications for which thermoplastic valves may be used. 
     Other modifications of the invention described above will be obvious to those skilled in the art, and it is intended that the scope of the invention be limited only as set forth in the appended claims.