Valves and valve actuation – With means to increase head and seat contact pressure – Seat pressed to valve
Reexamination Certificate
1999-12-21
2001-04-17
Shaver, Kevin (Department: 3754)
Valves and valve actuation
With means to increase head and seat contact pressure
Seat pressed to valve
C251S192000, C251S314000
Reexamination Certificate
active
06217003
ABSTRACT:
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 t
Baker & Botts L.L.P.
Keasel Eric
Shaver Kevin
LandOfFree
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