Patent Publication Number: US-11047483-B2

Title: Valve with self-aligning stem tip

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims is a continuation of U.S. patent application Ser. No. 15/603,530, filed on May 24, 2017, titled “VALVE WITH SELF-ALIGNING STEM TIP” which claims priority to and all benefit of U.S. Provisional Patent Application Ser. No. 62/341,160, filed on May 25, 2016, for VALVE WITH SELF-ALIGNING STEM TIP, the entire disclosures of which are incorporated by reference. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     The inventions relate to flow valves. The inventions more particularly relate to valves that utilize stem sealing subassemblies, including, for example, bellows valves. 
     SUMMARY OF THE DISCLOSURE 
     An exemplary aspect of the present application relates to a valve closure subassembly having a stem tip that is angularly adjustable with respect to the valve stem to accommodate misalignment of an annular sealing portion of the stem tip with an annular valve seat against which the stem tip seals. 
     In an exemplary embodiment, a valve includes a valve body and a valve closure subassembly assembled with the valve body. The valve body includes a central passage, an annular valve seat having a first central axis extending along the central passage, a first end passage that extends from the central passage to a first fluid port, and a second end passage that extends from the central passage to a second fluid port. The valve closure subassembly includes a valve stem extending along the first central axis and a stem tip attached to the valve stem by a stem connector and including an annular seal portion having a second central axis. The valve stem is axially movable from an open position permitting fluid flow between the first fluid port and the second fluid port to a closed position in which an annular seal portion of the stem tip engages the annular valve seat when a closing force is applied to the valve stem. When the first central axis is misaligned with the second central axis, the stem tip is pivotable about the valve stem to effect angular adjustment of the annular seal portion of the stem tip into uniform sealing engagement with the annular valve seat when the closing force is applied to the valve stem. The stem connector is configured to resist pivoting movement of the stem tip when the valve stem is in the open position. 
     In another exemplary embodiment, a valve closure subassembly includes a valve stem extending along a first central axis and a stem tip attached to the valve stem by a stem connector and including an annular seal portion having a second central axis. The stem tip is pivotable about the valve stem to effect angular adjustment of the second central axis with respect to the first central axis. The stem connector is configured to resist pivoting movement of the stem tip when a lesser pivoting torque (i.e., less than a closing force applied to the stem tip, for example, up to about 1 in-lb, up to about 5 in-lbs, or up to about 10 in-lbs) is applied to the stem tip. 
     In another exemplary embodiment, a valve closure subassembly includes a support ring for attachment to a valve body, a valve stem extending through a central passage of the support ring along a first central axis, a stem tip attached to the valve stem, and a hollow extensible member having a first end directly attached to the stem tip and a second end directly attached to the support ring. The valve stem is axially movable with respect to the support ring. The stem tip includes an annular seal portion having a second central axis, wherein the stem tip is pivotable about the valve stem to effect angular adjustment of the second central axis with respect to the first central axis. 
     In another exemplary embodiment, a valve closure subassembly includes a stem tip including a socket and an annular seal portion, a valve stem including a ball joint received in the socket for pivoting movement of the stem tip about the valve stem, and a retainer assembled with the stem tip and including a flexible ball retaining portion that engages the valve stem to resist pivoting movement of the stem tip. 
     These and other inventive concepts and embodiments are fully described hereinbelow, and will be readily understood by those skilled in the art from the following detailed description of the exemplary embodiments in view of the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross sectional view of a valve assembly in accordance with an exemplary embodiment, shown with the stem tip sealing portion misaligned with the valve seat; 
         FIG. 2  is a schematic cross-sectional view of the valve assembly of  FIG. 1 , shown in the closed position with the stem tip adjusted for uniform sealing engagement between the stem tip sealing portion and the valve seat; 
         FIG. 3  is a perspective view of a valve assembly in accordance with another exemplary embodiment; 
         FIG. 4  is a cross-sectional side view of the valve assembly of  FIG. 3 , shown in the open condition; 
         FIG. 5  is an enlarged partial cross-sectional side view of the valve assembly of  FIG. 3 , shown with the stem tip sealing portion misaligned with the valve seat; 
         FIG. 6  is an enlarged partial cross-sectional side view of the valve assembly of  FIG. 3 , shown in the closed position with the stem tip adjusted for uniform sealing engagement between the stem tip sealing portion and the valve seat; 
         FIG. 7  is an exploded perspective view of the valve assembly of  FIG. 3 ; 
         FIG. 8  is a schematic cross sectional view of a valve assembly in accordance with another exemplary embodiment, shown with the stem tip sealing portion misaligned with the valve seat; and 
         FIG. 9  is a schematic cross-sectional view of the valve assembly of  FIG. 8 , shown in the closed position with the stem tip adjusted for uniform sealing engagement between the stem tip sealing portion and the valve seat. 
     
    
    
     DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     The exemplary embodiments described herein are directed to a bellows valve, and to a bellows valve in combination with an actuator assembly, however, many different valve designs and configurations may be used as appropriate for particular applications, including, for example, other valves having stem sealing arrangements. Use of the terms axial and radial are referenced to a longitudinal axis, such as for example, a central axis as noted on the drawings. As described herein, the longitudinal axis may be the central longitudinal axis of the valve seat, the valve stem, or the sealing portion of the stem tip. 
     Valves utilizing stem sealing arrangements commonly include a flow path defining valve body having a central passage surrounded by an annular valve seat, and a valve stem disposed in the central passage and axially movable to engage an annular sealing portion of the valve stem (typically but not necessarily on an endmost stem tip) with the annular valve seat in a closed position. Angular or central axis misalignment of the valve stem sealing portion with respect to the annular valve seat may result in non-uniform or partial engagement, leakage, increased closing force required to effect a seal, and undesired wear and/or seal surface particle generation. 
     An inventive concept presented herein provides a valve design that accounts for or accommodates an axial or angular misalignment between an annular sealing portion of a stem tip of a stem sealing valve subassembly (e.g., a bellows valve subassembly) and an annular valve seat of a flow path defining valve body with which the stem closure subassembly is assembled. In one such embodiment, a valve closure subassembly includes a valve stem and a stem tip attached to the valve stem by a stem connector that permits or provides for pivoting or swiveling movement of the stem tip with respect to the valve stem, while axially fixing the stem tip on the valve stem (i.e., holding the stem tip axially rigid). 
       FIGS. 1 and 2  schematically illustrate a valve  10  having a valve body  20  assembled with a valve closure subassembly  30 . The valve body  20  includes a central passage  21  and an annular valve seat  25  surrounding the central passage and having a central axis X 1  that extends along the central passage. A first end passage  23  extends from the central passage  21  to a first fluid port  23   a  (e.g., a conduit fitting connection), and a second end passage  24  extends from the central passage to a second fluid port  24   a.    
     The valve closure subassembly  30  includes a valve stem  31  disposed in the central passage  21 , extending along the central axis X 1 , and a stem tip  32  attached to an end portion  31   a  of the valve stem  31  by a stem connector, shown schematically at  40 . An actuator  50  is assembled with the valve body  20  and is operable to axially move the valve stem  31  between an open position, in which the stem tip is spaced apart from the valve seat  25  to permit fluid flow between the first and second fluid ports  23   a ,  24   a , and a closed position, in which an annular sealing portion  35  of the stem tip  32  seals against the valve seat  25  to block flow between the first and second fluid ports  23   a ,  24   a.    
     While the exemplary stem tip  32  is preferably axially fixed with respect to the valve stem  31 , to accommodate misalignment of the valve stem  31  with respect to the central axis X 1  of the valve seat  25  (e.g., due to orientation of the valve stem or variances in the valve seat surface), the exemplary stem connector  40  is movable or adjustable to permit pivoting or swiveling movement of the stem tip  32  with respect to the valve stem  31 . This pivoting or swiveling movement provides for reorientation or adjustment of the misaligned stem tip  32  during valve closure, such that a central axis X 2  of the sealing portion  35  is aligned with or substantially coaxial with the central axis X 1  of the valve seat  25  when the valve stem  31  is in the closed position. The stem connector  40  may be integral with or assembled with either or both of the valve stem  31  and the stem tip  32 , and may take a variety of forms, including, for example, a joint or a deformable connection, as discussed in greater detail below. 
     When a closing force is applied to the misaligned valve stem  31  by the actuator  50 , initial non-uniform engagement between the sealing portion  35  and the valve seat  25  on one side (at S in  FIG. 1 ) applies a pivoting force or torque to this side portion S of the stem tip  32 , thereby pivoting the stem tip and bringing the sealing portion central axis X 2  into alignment with the valve seat central axis X 1  for uniform sealing engagement between the sealing portion  35  and the valve seat  25  ( FIG. 2 ). 
     While a stem tip may be permitted to freely swivel on a valve stem, such an arrangement may result in subsequent misalignment of the stem tip when the valve is opened (e.g., due to fluid forces against the stem tip, or forces applied by other valve components, such as a bellows), thereby requiring repeated re-alignment of the stem tip upon each valve closure and undesirable repetitive movement. According to another inventive aspect of the present application, the stem connector  40  attaching the stem tip  32  to the valve stem  31  may be configured to resist further pivoting movement of the stem tip as a result of lesser torque forces applied to the stem tip, as may be experienced when the valve stem is in the open position. In such an arrangement, pivoting adjustment of the stem tip may be limited to valve closure when there is seat-seal misalignment, for example, upon initial closure of the valve, or subsequent to valve component wear or other conditions that may result in seat-seal misalignment during the life of the valve. 
     Accordingly, the stem connector  40  may be configured to resist pivoting adjustment of the stem tip  32  when the stem tip is exposed to lesser (e.g., open valve) torque forces, while permitting pivoting adjustment of the misaligned stem tip when the stem tip is exposed to relatively greater normal closing forces, as applied by the actuator  50 . In other exemplary embodiments, the stem connector may be configured to resist pivoting adjustment when the stem tip is exposed to normal valve closing forces, instead requiring an increased closing force to be applied to a valve stem with a misaligned stem tip to effect an angular adjustment. In some such embodiment, this increased closing force may be applied only during initial valve assembly, or by a non-standard (e.g., use of increased pneumatic pressure to an actuator port) operation of the valve actuator. 
     Many different configurations may be utilized to provide a resistance to movement or adjustment of the stem connector that is sufficient to prevent pivoting or swiveling movement of the stem tip when the valve is in the open condition, while still permitting pivoting movement of the stem tip into seat-seal alignment upon valve closure. As one example, a joint connector between the valve stem and stem tip may be provided with a press fit, friction fit, clamping engagement, or spring biased retention to resist pivoting movement due to lesser torque forces (e.g., torque forces up to about 1 in-lb, or up to about 5 in-lbs, or up to about 10 in-lbs). 
     With reference to  FIGS. 3-7 , an exemplary embodiment of a valve assembly  100  includes a valve body  120 , a valve closure subassembly  130  at least partially disposed in central passage  121  of the valve body, and a valve actuator  150  assembled with the valve body and operable to move the valve closure subassembly  130  between open and closed positions to open and close the valve  100 . In the illustrated embodiment, the valve actuator  150  is a pneumatic actuator, operated by applying a pressurized gas to an actuation port  151  of the actuator. Alternatively, the actuator may be a manual actuator, for example with a lever or knob, or an electromagnetic actuator or a hydraulic actuator or any other type of actuator that produces a linear or axial motion to open and close the valve  100 . 
     The valve body  120  includes an annular valve seat  125  surrounding the central passage  121  and having a central axis X 1  that extends along the central passage. A first end passage  123  extends from the central passage  121  to a first fluid port  123   a  (e.g., a conduit fitting connection), and a second end passage  124  extends from the central passage to a second fluid port  124   a . As shown, the first and second fluid ports  123   a ,  124   a  may be disposed on a common lower surface of the valve body  120 . As such, this configuration is what is generally and commonly known as a surface mount configuration. However, other porting configurations may be used, for example as schematically shown in the first embodiment herein. Mounting bolts (not shown) may be used to attach a surface mount fluid component to an underlying substrate or manifold (not shown) as is known. 
     The valve closure subassembly  130  includes a valve stem  131  disposed in the central passage  121 , extending along the central axis X 1 , and a stem tip  132  attached to an end portion  131   a  ( FIGS. 5 and 6 ) of the valve stem  131  by a stem connector  140 . The stem tip  132  includes an annular sealing portion  135  disposed on an end surface of the stem tip for engagement with the annular valve seat  125 . As shown, the sealing portion  135  may include a sealing insert staked or otherwise retained in a groove in the stem tip  132 , and may be provided in a material selected to effectively seal against the annular valve seat  125 , such as, for example, perfluoroalkoxy (PFA) polymer, polytetrafluoroehtylene (PTFE), polyetheretherketone (PEEK), metals (e.g., 316 stainless steel), ceramics, (e.g., aluminum oxide, sapphire, ruby, or alumina). The annular valve seat  125  may, but need not, form a substantially planar surface perpendicular to the central axis X 1  of the valve seat. In other embodiments (not shown), the annular valve seat may include an insert staked or otherwise retained in a groove in the valve body, and the stem tip sealing portion may, but need not, form a substantially planar surface perpendicular to the central axis of the annular sealing portion. In still other embodiments (not shown), the valve seat and stem tip sealing portion may include complementary shaped frustoconical surfaces. 
     As used herein, a stem connector may include a variety of configurations and arrangements. In one embodiment, a stem connector includes a pivotable or swiveling joint connection between the valve stem and stem tip. As one example, a stem connector may include a ball joint disposed on one of the valve stem and the stem tip, and a socket disposed on the other of the valve stem and the stem tip. In the illustrated embodiment of  FIGS. 3-7 , the valve stem  131  includes a ball joint  141  and the stem tip  132  includes a socket  142  that receives the ball joint  141  for pivoting or swiveling movement of the stem tip  132  on the ball joint. As used herein, a “ball” or “ball joint” need not be a spherical component, and may include other shapes and contours selected to permit pivoting or swiveling movement within a socket. 
     The ball and socket joint may be configured to axially fix the stem tip on the valve stem. Additionally or alternatively, the ball and socket joint may provide resistance to movement or adjustment of the socket  142  on the ball joint  141  that is sufficient to prevent pivoting or swiveling movement of the stem tip  132  when the valve  100  is in the open condition, while still permitting pivoting movement of a misaligned stem tip  132  into seat-seal alignment upon valve closure. As one example, the ball joint  141  and socket  142  may be provided with a press fit or friction fit, such that the contacting surfaces of the ball joint and socket provide resistance to pivoting or swiveling movement of the stem tip when the stem tip is exposed to the lesser torque forces that may be experienced when the valve is in the open condition (e.g., pressurized fluid flow, biasing force from the bellows). This friction may be increased or enhanced, for example, by use of compressible materials (e.g., polymers, metallic foams) or high friction surfaces. For example, the outer surface of the ball joint and/or the inner surface of the socket may be knurled or splined to increase frictional resistance to pivoting movement. As another example, a compressible coating or bushing between the ball joint and socket may provide an increased grip and resulting resistance to pivoting movement. In such examples, the friction or gripping engagement may be selected to prevent pivoting movement when exposed to lesser (open valve) torque forces (e.g., torque forces up to 1 in-lb, up to 5 in-lbs, or up to 10 in-lbs), while permitting pivoting movement when exposed to greater (valve closing) torque forces (e.g., torque forces greater than 1 in-lb, greater than 5 in-lbs, or greater than 10 in-lbs). 
     According to another aspect of the present application, resistance to pivoting or swiveling movement of a valve stem tip may be increased or controlled by a retainer or retaining member assembled with one of the valve stem and the stem tip for biasing engagement of the pivoting joint (e.g., engagement of the ball joint in a ball and socket joint). As one example, a retaining ring may be secured or assembled with or adjacent to a socket portion of a ball and socket joint, such that a base portion of the ball joint extends through an aperture in the retaining ring. An inner periphery (e.g., a web, tab, flange, etc.) of the retaining ring engages the ball joint. The inner periphery of the retaining ring is configured to be rigid enough to resist or prevent pivoting or swiveling movement of the ball joint in the socket when the stem tip is exposed to lesser, open valve forces, but flexible enough to permit pivoting or swiveling adjustment of a misaligned stem tip during valve closure. 
     In the illustrated embodiment, the stem tip  132  includes a recessed shoulder portion or counterbore  144  outward of and surrounding the socket  142 , and a retaining ring  145  press fit into the counterbore  144 . An inner periphery or web portion  146  of the retaining ring  145  engages a base portion  141   a  (e.g., a spherical surface or cylindrical neck extending from the ball) of the ball joint  141  to resist pivoting or swiveling movement of the ball joint  141  in the socket  142 . The resistance provided by the retaining ring  145  may be controlled or selected based on the material of the ring (e.g., flexibility or elasticity), the thickness of the web portion  146 , or the amount of surface contact between the web portion and the ball joint base portion (e.g., uniform circumferential engagement, or intermittent/discrete engagement, such as by spaced tabs). As the retaining ring  145  provides for retention of the ball joint  141  in the socket  142  and for resistance to pivoting movement, the ball joint  141  may be loosely received in the socket  142 . In other embodiments, the ball joint may be retained in the socket with a press fit or friction fit, to provide further resistance to pivoting beyond that provided by the retainer. 
     When a closing force is applied by the actuator  150  to a valve stem  131  having a stem tip  132  that is misaligned with respect to the valve seat  125 , as shown (and exaggerated for clarity) in  FIG. 5 , initial non-uniform engagement between the sealing portion  135  and the valve seat  125  on one side (at S in  FIG. 5 ) applies a pivoting force or torque to this side S of the stem tip  132 , thereby pivoting the ball joint  141  within the socket  142  (and against the retaining ring  145 ), to bring the sealing portion central axis X 2  into alignment with the valve seat central axis X 1  for uniform sealing engagement between the sealing portion  135  and the valve seat  125  ( FIG. 2 ). When the valve is subsequently opened, the biasing engagement of the retaining ring web portion  146  against the base portion  141   a  of the ball joint  141  prevents further pivoting movement of the stem tip  132  on the valve stem  131  when the stem tip is exposed to lesser torque forces (e.g., pressurized system fluid, biasing force of the attached bellows). 
     In the exemplary embodiment illustrated herein, the valve closure subassembly  130  includes a hollow extensible member (e.g., a bellows  137 , as shown) surrounding the valve stem  131  and having a first end  137   a  attached (e.g., welded or otherwise sealingly attached) to the stem tip  132  and a second end  137   b  attached to the valve body  120 . While the bellows  137  may be directly attached to the valve body, in the illustrated embodiment, the second end  137   b  of the bellows is directly attached (e.g., welded or otherwise sealingly attached) to a support ring  138  assembled with the valve body  120 , as discussed in greater detail below. The bellows  137  extends and contracts axially as the valve stem  131  is moved between the open and closed positions (i.e., in response to operation of the actuator  150 ), to maintain a fluid tight seal enclosure around the valve stem, thereby maintaining the valve stem and the stem-actuator connection as non-wetted components. The terms “hollow extensible member” and “bellows,” as used herein, are intended to be construed broadly, and to include a conventional or traditional bellows design or alternative bellows designs, for example a series of conical elements or springs or other elements that form a hollow extensible member. Bellows valves find particular use for high purity, high flow rate applications, but the inventions may additionally or alternatively be used in valves for many other types of applications, including, for example, valves having wetted valve stems (i.e., without a bellows or other sealing enclosure surrounding the stem). 
     According to another aspect of the present application, the pivoting resistance function of the stem connector may additionally or alternatively be provided by the bellows connection between the valve stem and the stem tip. In one such embodiment, at least a portion of the bellows may be plastically deformable, such that when a closing force is applied to the misaligned valve stem, initial non-uniform engagement between the sealing portion and the valve seat on one side applies a pivoting force or torque sufficient to plastically deform the plastically deformable portion of the bellows, thereby pivoting the ball joint within the socket for uniform sealing engagement between the sealing portion and the valve seat. The plastically deformed portion of the bellows may be rigid enough to resist further plastic deformation when exposed to lesser torque forces (e.g., the open valve forces described above). 
     Still other plastically deformable components or configurations may provide resistant pivoting of the stem tip on the valve stem. In one such embodiment, as schematically shown in  FIGS. 8 and 9 , a valve  200  includes a valve body  220  assembled with a valve closure subassembly  230  having a valve stem  231  and a stem tip  232  attached to an end portion  231   a  of the valve stem  231  by a plastically deformable stem connector  240 . An actuator  250  is assembled with the valve body  220  and is operable to axially move the valve stem  231  between an open position, in which the stem tip is spaced apart from the valve seat  225  and a closed position, in which an annular sealing portion  235  of the stem tip  232  seals against the valve seat  225 . To accommodate misalignment of the valve stem  231  with respect to the central axis X 1  of the valve seat  225 , the stem connector  240  is a plastically deformable shaft configured to bend to provide for pivoting or swiveling movement of the stem tip  232  with respect to the valve stem  231 , to orient the stem tip  232  such that a central axis X 2  of the sealing portion  235  is aligned with or substantially coaxial with the central axis X 1  of the valve seat  225  when the valve stem  231  is in the closed position. The shaft  240  may be integral with the valve stem  231  and the stem tip  232 , as shown, or may be otherwise attached to the valve stem and stem tip. 
     When a closing force is applied to the misaligned valve stem  231  by the actuator  250 , initial non-uniform engagement between the sealing portion  235  and the valve seat  225  on one side (at S in  FIG. 8 ) applies a pivoting force or torque to this side portion S of the stem tip  232 , thereby bending the shaft  240  to pivot the stem tip and bring the sealing portion central axis X 2  into alignment with the valve seat central axis X 1  for uniform sealing engagement between the sealing portion  235  and the valve seat  225  ( FIG. 9 ). 
     Referring back to the embodiment of  FIGS. 3-7 , the bellows  137  may also sealingly enclose a biasing member  160 , for example, a spring. The biasing member  160  may be captured between a spring guide or upper bushing  161  and a lower bushing  162 , and held in compression by a threaded member  163  that may be screwed onto an upper end of the valve stem  131 . The lower bushing  162  is supported by a radially inward flange  138   a  on the support ring  138 . The compressed biasing member  160  applies an upward force on the valve stem  131  so that the valve  100  in this embodiment is a normally open valve (disregarding for the moment operation of the actuator  150 ). Many other designs may be used to provide the normally open functionality, and alternatively the valve  100  may be designed as a normally closed valve. The biasing member  160  also causes the bellows  137  to compress longitudinally when the valve stem  131  is moved upward (as viewed in  FIG. 4 .) 
     The valve body  120  may be machined or otherwise formed with a valve cavity wall  122  (valve cavity  122  for short herein), a portion of which may be cylindrical or may be generally cylindrical in shape, although alternatively other geometries may be used as needed. The valve closure subassembly  130  is at least partially received in the valve cavity  122 . An adapter  165  is partially disposed within the valve cavity  122 . The adapter  165  may be shaped generally as a cylinder to be received in the valve cavity  122 . Alternative geometry shapes may be used, it being preferred for convenience but not required that the adapter  165  generally conform to the shape of the valve cavity  122  (herein the adapter  165  may also be referred to as a cylinder adapter  165  for embodiments having generally cylindrical shapes for the adapter  165  and the valve cavity portion that receives the adapter). The adapter  165  thus has a smaller outside diameter than the diameter of the valve cavity  122  and a larger inside diameter than the outside diameter of the bellows  137 . 
     A bonnet nut  166  may be joined with the valve body  120  using a threaded connection or other suitable means. The adapter  165  is captured and compressively axially loaded between an upper flange  138   b  of the support ring  138  and a support surface  126  of the valve body  120  when the bonnet nut  166  is tightened down. A fluid tight body seal is made between a lower surface  165   a  of the cylinder adapter  165  and the support surface  126 , and a fluid tight subassembly seal is made between an upper surface  165   b  of the cylinder adapter  165  and the upper flange  138   b  of the support ring  138 . To facilitate the subassembly seal and the body seal, the adapter  165  may include on the upper surface  165   b  an upper annular bead that forms a compression face seal with the upper flange  138   b , and the adapter  165  may include on the lower surface  165   a  a lower annular bead that forms a compression face seal with the support surface  126 . Therefore, after the bonnet nut  166  is tightened down onto the valve body  120 , the adapter  165  in combination with the valve body  120  and the support ring  138  subdivides or partitions the valve cavity  122  to provide a sealed fluid flow cavity (when the valve  100  is installed or plumbed with inlet and outlet fittings or connections attached.) The sealed fluid flow cavity provides a fluid tight flow path between the first flow passageway  123  and the second flow passageway  124  when the valve  100  is in an open position and a sealed flow cavity when the valve  100  is in a closed position. 
     The adapter  165  in effect allows for the valve body  120  to be machined with a larger valve cavity  122  than could otherwise be provided if the adapter  165  were not used. As noted above, by larger valve cavity is meant that dimensionally either the diameter of the valve cavity can be made larger for machining the flow passageways or a shallower or shorter longitudinal length, or both if so desired. In the embodiment of  FIGS. 3-7 , the adapter  165  allows for a larger inside diameter of the valve cavity  122  to facilitate machining. In the second embodiment described below, an adapter may be used that provides for an axially or longitudinally shorter valve body to facilitate machining. 
     The lower bushing  162  serves to help center the valve closure element or valve stem  131 . The valve stem  131  may for example be a floating valve stem as depicted in  FIGS. 4-6 , meaning that the valve stem  131  is not tied or mechanically connected to the actuator  150 . Rather, the valve stem  131  upper end simply contacts a drive member  152  of the actuator  150 . The lower bushing  162  helps maintain alignment and self-centering of the valve stem  131  so as to form an effective closing seal when the valve  100  is in the closed position. 
     The pneumatically operated actuator assembly  150  ( FIG. 4 ) may include a piston assembly  155  that is disposed in an actuator housing  153 . The actuator  150  may be mounted to the valve  100  by a threaded connection with the bonnet nut  166 . As shown, the actuator housing  153  may be a multi-piece housing or alternatively a single piece housing. In the exemplary embodiment, two pistons may be used but alternatively a single piston actuator may be used or more than two pistons may be used as needed. A spring  156  biases the piston assembly  155  downward against the force of the biasing member  160 . The piston assembly  155  optionally may drive a drive member  152 , for example in the form of an actuator stem  152  that contacts an upper end of the valve closure subassembly  130 , for example, an upper surface of the threaded member  163 . The spring  156  may be stronger than the biasing member  160  so that with no air pressure applied to the actuator  150 , the valve  100  is in a closed position and the bellows  137  is longitudinally extended. When pressurized air is supplied to the pneumatically operated actuator assembly  150 , the air pressure moves the piston assembly  155  against the force of the spring  156 , thereby allowing the biasing member  160  to longitudinally compress the bellows  137  to lift the valve stem  131 , thereby opening the valve  100 . Alternatively, the actuator  150  may be configured so that application of pressurized air to the piston assembly  155  closes the valve  100  to provide a normally open valve. The same functionalities may alternatively be achieved with manual actuators or other actuator designs. 
     Note that an additional benefit of the adapter concept is that the adapter in effect decouples the valve body from the bellows. In other words, the bellows and the adapter preferably are not welded to each other nor to the valve body. The use of a compression seal or other mechanical seal means (mechanical as distinguished from a welded connection) between the adapter and the valve body as well as between the adapter and the valve member subassembly allows for easy installation of the valve member subassembly into the valve body, and also the adapter and the valve member subassembly to be removed easily and replaced if so needed for maintenance or repair. Alternatively, the adapter may be welded at one end to the valve member subassembly to form a single piece component and then installed with a single compression seal for the body seal. In either scenario, different adapters having different dimensions such as diameter or longitudinal length may be used to accommodate different bellows designs while still fitting into a particular or common valve body. This means that a single valve body size may be used with different bellows sizes by use with an appropriately sized adapter. Moreover, a particular bellows design may be used in differently sized valve bodies by providing different adapters as needed. 
     The inventive aspects and concepts have been described with reference to the exemplary embodiments. Modification and alterations will occur to others upon a reading and understanding of this specification. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.