Abstract:
Example apparatus include load relieving stem connectors. An example apparatus includes a connector housing including an internal cavity therein, a load relieving body disposed in the internal cavity, and a shaft coupled to the load relieving body. In the example apparatus, the shaft is to rotate the load relieving body between a first position and a second position.

Description:
RELATED APPLICATION 
     This patent arises as a divisional of U.S. application Ser. No. 11/314,620, which was filed on Dec. 21, 2005 and is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     This disclosure relates generally to assemblies for coupling shafts or rods and, more specifically, to a load relieving stem connector and method for coupling, for example, an actuator rod to a control valve stem. 
     BACKGROUND 
     Control valves are typically operated by an actuator, such as a pneumatic actuator, an electric actuator, a hydraulic actuator, etc. The actuator is typically coupled to the control valve and provides the force to move a valve plug to control a fluid flowing through the control valve. For instance, in a pneumatic actuator, increasing or decreasing air pressure moves a diaphragm, which in turn moves an actuator rod that is attached to the center of the diaphragm along the longitudinal axis of an actuator housing. Thus, changes in the air pressure correspond directly to changes in the axial position of the actuator rod. 
     The actuator rod may be attached to a valve stem that protrudes from the valve body. By mechanically coupling the actuator rod to the valve stem via a valve stem connector, the position of the attached valve plug can be determined by the actuator rod to control the fluid flowing through the valve. Typically, the valve stem connector consists of a single, rigid, connector that includes two threaded cavities for receiving externally threaded ends of the actuator rod and valve stem. However, known valve stem connectors may suffer from certain manufacturing disadvantages and design limitations. 
       FIGS. 1 and 2  show a cross-sectional view of one example of a typical valve assembly  100  that includes a valve stem connector  102  mechanically fastening an actuator rod  104  to a valve stem  106 . The actuator rod  104  is housed in an actuator  108 , for example, a pneumatic actuator, and when a supplied air pressure to the actuator  108  changes, the actuator rod  104  moves along a longitudinal axis A-A. The valve stem connector  102  couples the axial motion supplied by the actuator rod  104  through the valve stem  106  to a valve plug  110 , which is located in a valve body  120 , to allow the valve plug  110  to be positioned relative to a valve seat  112 . For example, when the valve plug  110  is positioned away from the valve seat  112 , fluid can flow from a valve inlet  114  to a valve outlet  116  as indicated by the arrows shown. 
     As shown in greater detail in  FIG. 2 , the illustrated valve stem connector  102  includes two connector portions  118   a - b  that are fastened by bolts  122   a - b  to form a rigid connector. The valve stem connector  102  has a threaded upper cavity  124  that includes a plurality of threads  126  to threadingly engage the actuator rod  104 . Similarly, the valve stem connector  102  has a threaded lower cavity  128  that includes a plurality of threads  130  to threadingly engage the valve stem  106 . The actuator rod  104  and the valve stem  106  are joined when the upper threads  126  and the lower threads  130  mechanically engage corresponding external threads  132  and  134  ( FIG. 1 ) on the actuator rod  104  and the valve stem  106 , respectively. In this example, because the actuator rod  104  and the valve stem  106  have different diameters, the upper cavity  124  and the lower cavity  128  are connected via a tapered internal surface  136 . 
     To complete the valve assembly  100 , the actuator rod  104  and the valve stem  106  are threaded in counter-rotating directions into the cavities  124  and  128 , respectively, until the desired length is achieved so that the valve stem  106  and the plug  110  properly interact with the valve seat  112 . Axial adjustment of the actuator rod  104  and the valve stem  106  is typically limited by the minimum number of threads that must be engaged to create a secure and safe mechanical connection. Finally, the bolts  122   a - b  may be tightened to create additional compressive load between the threads  126 ,  130 ,  132 , and  134  to securably fasten the actuator rod  104  to the valve stem rod  106 . 
     As mentioned above, in a pneumatically controlled valve assembly, a diaphragm (not shown) is coupled to the actuator rod  104 , the position of which is controlled by the pressure on one side of the diaphragm and one or more springs on the opposite side of the diaphragm. By controlling the pressure in the space above the diaphragm, a direct-acting actuator is created. By controlling the pressure below the diaphragm, a reverse-acting actuator  104  is created. Movement of the diaphragm and, thus, the actuator rod  104  causes the valve stem  106  to open and close the valve plug  110  relative to the valve seat  112  to control the fluid flow through the valve body  120 . 
     SUMMARY 
     In accordance with one example, an apparatus for operatively connecting an actuator rod to a valve stem includes a connector housing having an outer surface and an inner surface where the inner surface defines an internal cavity. The apparatus further includes an actuator rod passage extending from the outer surface into the internal cavity that is adapted to receive at least a portion of the actuator rod and a valve stem passage extending from the outer surface into the internal cavity that is adapted to receive at least a portion of the valve stem. The apparatus also includes a load relieving body disposed within the internal cavity between the actuator rod passage and the valve stem passage. 
     In accordance with another example, an apparatus for coupling shafts includes a connector housing including a first portion and a second portion. Each of the first and second portions includes first and second angled surfaces adapted to engage ends of first and second shafts when the first portion is removably coupled to the second portion. The apparatus also includes one of a wedge, a cam, or a tapered rod configured to be coupled to at least one of the first or second housing portions between the first and second shaft ends and further configured to be adjustable to cause the angled surfaces to securely engage the ends of the first and second shafts. 
     In accordance with yet another example, an apparatus for coupling shafts includes first means for coupling a first shaft end to a second shaft end and second means for coupling the first shaft end to the second shaft end and for coupling to the first means for coupling. The apparatus further includes means for adjustably moving the first and second shaft ends to securably engage the first and second means for coupling. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a known valve stem connector incorporated into a control valve assembly. 
         FIG. 2  is an exploded view of the known valve stem connector shown in  FIG. 1 . 
         FIG. 3  is a cross-sectional view of an example valve assembly with an example valve stem connector. 
         FIG. 4  is an exploded view of the valve stem connector of  FIG. 3 . 
         FIG. 5  is a cross-sectional view of the example valve stem connector of  FIG. 4 . 
         FIG. 6  is an exploded view of an alternative example valve stem connector. 
         FIG. 7  is a cross-sectional view of the example valve stem connector of  FIG. 6 . 
         FIG. 8  is an exploded view of another alternative example valve stem connector. 
         FIG. 9  is cross-sectional view of the example valve stem connector of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings,  FIG. 3  shows an example control valve  300 . The valve  300  includes a diaphragm  302  located inside a diaphragm casing  304 . Above the diaphragm  302  is a plate  306  that is coupled to actuator springs  308  and an actuator rod  310 . The actuator rod  310  extends from the diaphragm casing  304  through a yoke  312  where the actuator rod  310  is coupled to a valve stem  314 . The valve stem  314  extends through the yoke  312  into a valve body  316  and is coupled to a plug  318 . The plug  318  engages a valve seat  320  when the valve is closed, which blocks the flow of process fluid from an inlet  322  to an outlet  324 . 
     To increase pressure in the diaphragm casing  304 , a fluid such as, for example, air, is forced into the casing  304  under the diaphragm  302  through a port  326 . The example diaphragm casing  304  includes an upper casing  305  and a lower casing  307 . In the illustrated example, the port  326  is associated with the lower casing  307 . In alternative examples, the port  326  may be associated with the upper casing  305  and the springs  308  may be located between the plate  306  and the lower casing  307 . The air forced through the port  324  increases the pressure and moves the diaphragm  302  and plate  306  upward, which compresses the springs  308 . As the plate  306  and the diaphragm  302  move upward, the actuator rod  310  and the valve stem  314  also move up along the B-B axis. The lifting of the valve stem  314  lifts the plug  318  from the valve seat  320 , which allows a process fluid to flow from the inlet  322  past the plug  318  to the outlet  324  of the valve body  316 . 
     In this embodiment, the apparatus for operatively connecting the actuator rod  310  to the valve stem  314  is a valve stem connector  328 , which is shown in greater detail in  FIGS. 4 and 5 . The valve stem connector  328  includes a connector housing formed in this example by two portions  330 ,  332  each having an outer surface  400  and an inner surface  402 , where the inner surfaces  402  cooperate to define an internal cavity  369 . The top portion of the internal cavity  369  forms an actuator rod passage  372  ( FIG. 5 ) that extends from the outer surface  400  into the internal cavity  369  and is adapted to receive at least a portion of the actuator rod  310 . The bottom portion of the internal cavity  369  forms a valve stem passage  374  that extends from the outer surface  400  into the internal cavity  369  and is adapted to receive at least a portion of the valve stem  314 . The valve stem connector  328  also includes a load relieving body in this example formed by cooperating wedges  338 ,  348  disposed within the internal cavity  369  between the actuator rod passage  372  and the valve stem passage  374 . Further, the wedges  338 ,  348  form a surface  352  configured to contact an end  370  of the valve stem  314 , and an opposing surface  340  configured to contact an end  366  of the actuator rod  310 . 
     As noted, the example valve stem connector  328  includes a first connector portion or housing  330  and a second connector portion or housing  332 . The first connector portion  330  has a first upper sloped wall  334  and a first lower sloped wall  336 . The first connector portion  330  also has a first generally wedge-shaped projection  338  extending radially outward from the outer surface  402  into the internal cavity  369 . The first wedge  338  has a first substantially flat surface  340  and a first angled surface  342  shown best in  FIG. 5 . Likewise, the second connector portion  332  has a second upper sloped wall  344  and a second lower sloped wall  346 . The second connector portion  332  also has a second generally wedge-shaped projection  348 , but the second wedge  348  of the second connector portion  332  is complementary to the first wedge  338  of the first connector portion  330  such that the wedges  338 ,  348  engage to form a load relieving body with substantially co-planar surfaces. The second wedge  348  also has non-coplanar surfaces, i.e., a second angled surface  350  above a second substantially flat surface  352 . 
     As shown in  FIG. 4 , the first connector portion  330  has a first aperture  353  and a second aperture  354 . The second connector portion  332  has a third aperture  356  and a fourth aperture  358 . To releasably join the first connector portion  330  and the second connector portion  332 , a first bolt  360  is inserted through the first aperture  353  and the third aperture  356 , and a second bolt  362  is inserted through the second aperture  354  and the fourth aperture  358 . Though the illustrated example uses bolts  360 ,  362  to join the connector portions  330 ,  332 , any known mechanical fastener may also be used. Furthermore, though two fasteners  360 ,  362  are shown, any number of fasteners may be used, e.g., 1, 3, 4, etc. In addition, the apertures  353 ,  354 ,  356 ,  358  may be angled such that the fasteners  360 ,  362  may only be secured when the apertures  353 ,  354 ,  356 ,  358  are properly aligned, thereby ensuring that the connector portions  330 ,  332  are oriented so that the wedges  338 ,  348  complement each other and function properly. 
     Returning to  FIG. 5 , the actuator rod  310  has a first undercut  364  adjacent to and acutely angled with respect to a first mating surface  366 . Similarly, the valve stem  314  has a second undercut  368  adjacent to and acutely angled with respect to a second mating surface  370 . As the connector portions  330 ,  332  are joined and as the bolts  360 ,  362  are tightened in the apertures  353 ,  354 ,  356 ,  358 , the wedges  338 ,  348  make contact with each other. As the union between the two connector portions  330 ,  332  further tightens, the angled surfaces  342 ,  350  slide along each other. Concurrently, the upper sloped walls  334 ,  344  engage the undercut  364  of the actuator rod  310 , while the lower sloped walls  336 ,  346  engage the undercut  368  of the valve stem  314 . As the sloped walls  334 ,  336 ,  344 ,  346  engage the undercuts  364 ,  368 , the actuator rod  310  and the valve stem  314  become coupled, and ultimately the first mating surface  366  of the actuator rod  310  at least partially contacts the first substantially flat surface  340  of the first wedge  338 . Similarly, the second mating surface  370  of the valve stem  314  at least partially contacts the second substantially flat surface  352  of the second wedge  348 . 
     The actuator rod  310  and the valve stem  314  may vary in length based on manufacturing tolerances. The wedges  338 ,  348  in the valve stem connector assembly  328  accommodate varying lengths of actuator rods and valve stems without requiring additional or separate components so the valve  300  will function properly. For example, if one or both of the actuator rod  310  and/or the valve stem  314  are on the longer side of the manufacturing tolerances, the angled surfaces  342 ,  350  engage each other less (i.e., have a smaller engagement or contact surface area) and the connector portions  330 ,  332  do not need to be tightened as much to create a secure connection. If one or both of the actuator rod  310  and/or the valve stem  314  are on the shorter side, the angled surfaces  342 ,  350  engage each other more, and the connector portions  330 ,  332  are tightened closer to one other for a secure connection. Accordingly, the valve stem connector  328  can accommodate a variety of lengths of actuator rods  310  and/or valve stems  314  by, in effect, lengthening or shortening the overall length of the actuator rod  310  and/or valve stem. 
     The ability of the stem connector  328  to lengthen or shorten the overall length of the actuator rod  310  and/or valve stem  314  is also particularly beneficial for relieving spring load and/or compressing the actuator springs  308  as needed for maintenance. For example, when the actuator rod  310  and the valve stem  314  need to be separated such as, for example, when the valve  300  needs maintenance during an outage, the stem connector  328  is disassembled. In this example, the bolts  360 ,  362  are removed, and the two connector portions  330 ,  332  and, thus, the wedges  338 ,  348  are separated. Then, the distance between the two mating surfaces  366 ,  370  is no longer occupied by the wedges  338 ,  348 . Consequently, the load experience by the actuator rod  310  and the valve stem  314  is relieved, the actuator rod  310  and the valve stem  314  are no longer coupled, and the actuator rod  310  and the valve stem  314  can be moved independently of each other. This allows the valve stem  314  and the plug  318  to be removed from the valve seat  320  manually (i.e., without the need for power or air to compress the springs  308  and lift the actuator rod  310 ). Essentially, the first wedge  338  and the second wedge  348  form a load relieving body that relieves the load in the springs  308  so the actuator rod  310  can freely disassociate from the valve stem  314 . Without the spring load exerting a downward force, the valve stem  314  and the plug  318  can be moved away from the valve seat  320 . As a result, the valve  300  may be disassembled during unanticipated outages without damage. 
     In addition to accommodating manufacturing tolerances with respect to the length of the actuator rod  310  and the length of the valve stem  314 , the stem connector  328  can accommodate axial misalignment of the actuator rod  310  and the valve stem  314 . Both connector portions  330 ,  348  are positioned to enclose or surround the ends of the actuator rod  310  and the valve stem  314 . The stem connector  328 , when fully assembled, forms the internal cavity  369 , as described above, which includes the actuator rod passage  372  and the valve stem passage  374 . The actuator rod passage  372  has a diameter larger than the diameter of the first undercut  364 . Similarly, the valve stem passage  374  has a diameter larger than the diameter of the second undercut  368 . The resulting gaps accommodate axial misalignment between the actuator rod  310  and the valve stem  314 . The actuator rod  310  and/or the valve stem  314  may be shifted to the left and/or the right within the internal cavity  369  without affecting the performance of the valve  300 . The internal cavity  369  may be sized to accommodate various magnitudes of axial misalignment. 
       FIGS. 6 and 7  illustrate an alternative example stem connector  600 . The valve stem connector  600  includes a connector housing formed in this example by two portions  602 ,  604  each having an outer surface  700  and an inner surface  702 , where the inner surfaces  702  cooperate to define an internal cavity  704 . The top portion of the internal cavity  704  forms an actuator rod passage  706  that extends from the outer surface  700  into the internal cavity  704  that is adapted to receive at least a portion of the actuator rod  310 , and the bottom portion of the internal cavity  704  forms a valve stem passage  708  that extends from the outer surface  700  into the internal cavity  704  that is adapted to receive at least a portion of the valve stem  314 . The valve stem connector  600  also includes a load relieving body  608  disposed within the internal cavity  704  between the actuator rod passage  706  and the valve stem passage  708 . The load relieving body  608  has a surface  614  configured to contact an end  370  of the valve stem  314  and an end  366  of the actuator rod  310 . 
     The connector portion  604  has an opening  606  through which the load relieving body or projection  608  is inserted. The projection  608  has a head  610  that can be manipulated by a wrench, pliers or other tool to adjustably insert or remove the projection  608  into/from the opening  606 . The projection  608  further has a body section  612  that traverses the connector portion  604 . In the illustrated example, the body section  612  has threads that engage threads in the opening  606 . The projection  608  ends in the surface or angled structure  614  creating a tapered rod, which may be generally wedge-shaped, conically shaped, or any other combination of shapes with a sloping, rounded or curved surface. The angled structure  614  engages the mating surfaces  366 ,  370  of the actuator rod  310  and the valve stem  314 , respectively, as described above. 
     As the projection  608  is inserted further into the connector portion  604 , a greater thickness of the wedge  614  is inserted between the actuator rod  310  and the valve stem  314 . Because the projection  608  may be inserted into the valve stem connector  600  to varying degrees to create a full assembly, this example can accommodate manufacturing tolerances in the lengths of the actuator rod  310  and the valve stem  314  and can, in effect, lengthen or shorten the actuator rod  310  and/or valve stem  314 , similar to the stem connector  328  described above. For example, if the actuator rod  310  and/or the valve stem  312  are on the long side of their respective tolerances, they will be closer to one another (i.e., the gap  616  will be smaller). When the gap  616  is smaller, the projection  608  need not be inserted as far into the stem connector  600  for a secure fit. If the actuator rod  310  and/or the valve stem  312  are on the short side of their respective tolerances, they will be further from one another (i.e., the gap  616  will be larger). When the gap  616  is larger, the projection  608  may be inserted more deeply into the stem connector  600  for a secure fit. 
     The connector portions  602 ,  604  each have passages  706 ,  708  and sloped walls similar to those described above in connection with the stem connector  328 . The passages  706 ,  708  with the plurality of sloped walls engage the rods  310 ,  314  and guide the rods  310 ,  314  toward the wedge surface  614  and into alignment with each other. Accordingly, the stem connector  600  accommodates axial misalignment of the actuator rod  310  and the valve stem  314  by virtue of the sloped walls and the passages  706 ,  708 . 
     The stem connector  600  may be manually disassembled by removing the projection  608  and separating the connector portions  602 ,  604 . Removing the projection  608  relieves the spring load and allows the actuator rod  310  and the valve stem  314  to be mechanically decoupled and, if needed, to be moved independently of each other. This allows the valve stem  314  and the plug  318  to be removed from the valve seat  320  manually (i.e., without the need for power or air to compress the springs  308  and lift the actuator rod  310 ). As a result, the valve  300  may be disassembled during unanticipated outages without damage. 
     In an alternative example (not shown), the projection  608  may be integrally formed in one of the connector portions  602 ,  604  and disposed in the internal cavity  704 . In this alternative example, the stem connector  600  is assembled and tightened by bolts  618 , which run through apertures  620  in a similar manner as described above in connection with the stem connector  328 . 
       FIGS. 8 and 9  illustrate a third example stem connector  800 . The valve stem connector  800  includes a connector housing formed in this example by two portions  802 ,  804 , each having an outer surface  900  and an inner surface  902 , where the inner surfaces  902  cooperate to define an internal cavity  810 . The top portion of the internal cavity  810  forms an actuator rod passage  904  that extends from the outer surface  900  into the internal cavity  810  that is adapted to receive at least a portion of the actuator rod  310 , and the bottom portion of the internal cavity  810  forms a valve stem passage  906  that extends from the outer surface  900  into the internal cavity  810  that is adapted to receive at least a portion of the valve stem  314 . The valve stem connector  328  also includes a load relieving body  812  disposed within the internal cavity  810  between the actuator rod passage  904  and the valve stem passage  906 . Further, the load relieving body  812  has a surface  813  configured to contact an end  370  of the valve stem  314 , and an end  366  of the actuator rod  310 . 
     Both of the connector portions  802 ,  804  have apertures  806  through which bolts  808  are inserted to releasably connect the two connector portions  802 ,  804 . Though bolts  808  are illustrated in  FIG. 9 , any known removable mechanical fastener may be used. Further, although four apertures  806  and two bolts  808  are shown, any number of apertures and bolts can be used, e.g., 1, 2, 3, 4, etc. 
     When the two portions  802 ,  804  are connected, the internal cavity  810  is formed therebetween. The cavity  810  is sized to accommodate the actuator rod  310  and the valve stem  314 . As stated above, the cavity  810  includes spring load relieving structure or a cam  812 . In the illustrated example, the cam  812  is ellipsoidal and has an open center  814  in which a shaft  816  is inserted. In the illustrated example, the shaft  816  is a hex shaft, but any shaft that can be manipulated by a wrench, pliers or other tool may be used. 
     When the shaft  816  is rotated, the cam  812  is also rotated, and rotation of the cam  812 , in effect, lengthens or shortens the actuator rod  310  and/or valve stem  314 . When the cam  812  is rotated so that the major axis of the ellipsoid, the C-C axis is oriented as shown in  FIG. 9 , the surface  813  of the cam  812  engages the mating surfaces  366 ,  370  of the actuator rod  310  and valve stem  314 , respectively, and the actuator rod  310  and valve stem  314  are at their longest lengths. To disassemble the stem connector  800 , the cam  312  is turned so that the minor axis of the ellipsoid, the D-D axis, is aligned with the axes of the actuator rod  310  and the stem connector  314 , and the actuator rod  310  and valve stem  314  are at their shortest lengths. In fact, in this position, the spring load is relieved and there is enough slack between the actuator rod  310  and the valve stem  314  so that valve  300  can be disassembled manually (i.e., without the need for power or air). This allows the valve  300  to be disassembled during unanticipated outages. 
     As described above, rotation of the cam  812  lengthens or shortens the actuator rod  310  and/or the valve stem  314 , which enables the stem connector  800  to accommodate manufacturing tolerances in the lengths of the actuator rod  310  and the valve stem  314 . The distance between the mating surfaces  366 ,  370  of the actuator rod  310  and the valve stem  314 , respectively, varies as a function of the position of the cam  812 . For example, when the cam  812  is positioned so that the C-C axis is aligned with the axis of the actuator rod  310  and the valve stem  314  ( FIG. 8 ), the distance between the actuator rod  310  and the valve stem  314  is the greatest. When the cam  812  is positioned such that the D-D axis is aligned with the actuator rod  310  and the valve stem  314 , the distance between the actuator rod  310  and the valve stem  314  is the shortest. To fully engage the mating surfaces  366 ,  370 , the position of the cam  812  between the D-D axis and the C-C axis will vary depending on the lengths of the actuator rod  310  and/or the valve stem  314  relative to their manufacturing tolerances. Additionally, the stem connector  800  can accommodate axial misalignments in a manner similar to the stem connector  328  described above. 
     Although certain example apparatus and articles of manufacture have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all apparatus and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.