Abstract:
Methods and apparatus for adjusting a spring load in an actuator are described. An example actuator includes a housing and a plate. Further, the example actuator includes one or more springs disposed in the housing to apply a force to the plate. Additionally, the example actuator includes a spring load adjuster having a collar extending through and movably engaged to the plate to enable an adjustment of the position of the collar relative to the plate to change a load provided by the one or more springs.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    The present disclosure relates generally to actuators and, more particularly, to methods and apparatus for adjusting a spring load in an actuator. 
       BACKGROUND 
       [0002]    Control valves are commonly used in systems to control the flow of a fluid (e.g., a gas, a liquid, etc.) or any other substance through pipes and/or vessels to which they are connected. A control valve is typically composed of one or more inlets and outlets, and includes a flow control element or member (e.g., a valve gate, a piston, a valve plug, a closure member, etc.) that operates to control fluid flow through apertures that fluidly couple the inlet(s) to the outlet(s). A flow control member is typically coupled to a valve bonnet assembly that is mechanically coupled (e.g., bolted, clamped, threaded into, etc.) to the valve body. Typically, the flow control member is configured to engage a sealing structure (e.g., a seat ring) that encompasses a flow path through the valve. 
         [0003]    An actuator is typically coupled to the valve bonnet and includes an actuator stem that engages a valve stem to produce a torque and/or a thrust on the flow control member to control fluid flow through the valve. Actuators often include one or more springs that apply a biasing force to the actuator stem to move the flow control member to, for example, an open or closed condition in the absence of a control signal. The loading force provided by the spring(s) determines the position of the actuator stem and, thus, the position of any flow control member operatively coupled thereto for a given control signal. Additionally, for a given input or control signal, the spring load is set to achieve a target valve seat load when the valve is in a closed position and a target valve back seat load when the valve is in an open position. 
         [0004]    When the valve actuator is manufactured, the spring(s) may be selected based on theoretical spring performance. However, due to manufacturing tolerances relating to springs and/or spring housing components, actual spring performance often deviates from theoretical spring performance, which may result in valve seat loads that are too low or too high. Insufficient or excessive valve seat loads can lead to improper valve operation. Depending on the deviation from the theoretical spring performance, the spring load can be increased or decreased in an attempt to achieve the target valve seat load and the target valve back seat load. 
         [0005]    In some known actuators, to adjust for the discrepancy between the actual spring performance and the desired target or theoretical spring performance, it is necessary to disassemble the actuator to adjust the spring load by either adding or removing shims and/or spacers and then reassembling the actuator. After the actuator is reassembled, the actuator can be retested to determine if the actual spring performance provides the desired target valve seat load and the target valve back seat load. If not, the laborious process of disassembling the actuator to adjust the spring load must be repeated. Further, because shims and/or spacers are typically manufactured in specialized assembly shops in an other location from where the actuators are assembled and tested and an other location from where the actuators are installed, the customers or other users may not have the proper resources (e.g., proper tools, trained employees, etc.) to manufacture the shims and/or spacers to properly adjust the spring load. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  shows an enlarged cross-sectional view of a known actuator. 
           [0007]      FIG. 2  shows an enlarged cross-sectional view of a portion of an example actuator including an example spring load adjuster. 
           [0008]      FIG. 3  shows a cross-sectional view of the example actuator including the example spring load adjuster of  FIG. 2 . 
           [0009]      FIG. 4  shows a top view of the example actuator including the example spring load adjuster of  FIG. 2 . 
           [0010]      FIG. 5  shows an enlarged cross-sectional view of an alternative example actuator including an alternative example spring load adjuster. 
           [0011]      FIG. 6  shows a top view of the alternative example actuator including the alternative example spring load adjuster of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Certain examples are shown in the above-identified figures and described in detail below. In describing these examples, like or identical reference numbers are used to identify common or similar elements. The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale or in schematic for clarity. 
         [0013]    The example apparatus and methods described herein may be used to adjust a spring load in an actuator. One example actuator described herein includes an example spring load adjuster, a housing, a plurality of tie rods, a first plate and a second plate. The housing may be positioned between the first plate and the second plate. The tie rods may be positioned substantially parallel to the exterior of the housing and may be coupled to the first plate and the second plate. In some examples, the spring load adjuster may include a collar that is at least partially concentric with an aperture in the first plate, adjusters, and locking devices. A rim of the collar may engage at least one of a plurality of springs (i.e., a biasing element), which may be contained in the housing. 
         [0014]    In one example actuator, the example spring load adjuster may be coupled to the first plate via at least one or more adjusters. Further, the spring load adjuster may include one or more locking devices that may engage a face of the first plate. To adjust the spring load, the locking devices may be loosened and the one or more adjusters may be adjusted. Adjusting the one or more adjusters changes the distance between the spring load adjuster and the first plate and, thus, changes the spring load as described in greater detail below. The adjuster(s) may be used to make a substantially continuous adjustment to the spring load. The collar may be substantially locked (i.e., fixed) into place relative to the first plate by engaging at least one of the locking devices with the first plate. Engaging at least one of the locking devices with the first plate may prevent vibration, caused by operating conditions, from loosening the adjusters. 
         [0015]    In an alternative example actuator, an alternative example spring load adjuster includes a collar with a threaded exterior surface to engage a threaded aperture of a first plate of the actuator. Further, the spring load adjuster may include one or more locking devices to engage a face of the first plate to substantially lock or fix the collar relative to the first plate. To adjust the spring load, the one or more locking devices are loosened and the collar is rotated. Rotating the collar changes the distance between a flange of the collar and the first plate and, thus, changes the spring load as described in greater detail below. Again, the collar may be used to make a substantially continuous adjustment to the spring load. The collar may be substantially locked (i.e., fixed) into place relative to the first plate by engaging at least one of the one or more locking devices with the first plate. 
         [0016]      FIG. 1  shows an enlarged cross-sectional view of a known actuator  2 .  FIG. 1  depicts the relationship between a spring housing  4 , an outboard plate  6 , and an inboard plate  8 . The spring housing  4  is positioned between the outboard plate  6  and the inboard plate  8 . 
         [0017]    The spring housing  4  contains a plurality of disc springs  10  and a plunger  12 . The plurality of disc springs  10  are substantially coaxial relative to the central axis of the spring housing  4 . Each of the plurality of disc springs  10  includes a respective one of a plurality of an apertures (not shown). A face of the springs  10  engages a face  14  of the plunger  12 . Further, a face of at least one of the springs  10  engages a face  16  of at least one of a plurality of spacers or shims  18 . The plunger  14  has a cylindrical portion  20  and a flange  22 . The cylindrical portion  20  of the plunger  14  is at least partially surrounded by the apertures of the springs  10 . The plunger  14  is operatively coupled to an adapter  24  via a piston rod  26  and other actuator components (not shown) contained in a hydraulic cylinder  28 . An end of a valve stem  30  may be operatively coupled to the actuator  2  via the adapter  24 . 
         [0018]    As pressure (e.g., hydraulic pressure) changes within the hydraulic cylinder  28 , the springs  10  compress or expand and the plunger  14  and the adapter  24  move to a designated position. The springs  10  provide a spring load and, when the adapter  24  is coupled to the stem of a valve, are configured to provide a valve seat load in a valve closed position and a valve back seat load in a valve open position for various pressures. It may be necessary to adjust the spring load of the actuator  2  of  FIG. 1  to achieve target or desired load values when the actual spring load deviates from a theoretical desired load. To adjust the spring load, it is necessary to disassemble the actuator  2 , add or remove shims or spacers  18 , and then reassemble the actuator  2 . After the actuator  2  is reassembled, the actuator  2  can be retested to determine if the actual spring performance provides the target valve seat loads. If the target values are not attained after the adjustment, the disassembly process may be repeated. In addition, the shims or spacers  18  are typically manufactured in an other location from where the actuators are assembled and tested and an other location from where the actuators are installed and, thus, the customer, the field technician, etc. may not have the proper resources (e.g., proper tools, trained employees, etc.) to manufacture the shims or spacers  18  and/or to otherwise adjust the spring load. 
         [0019]      FIG. 2  shows an enlarged cross-sectional view of a portion of an example actuator  200  including an example spring load adjuster  202 ;  FIG. 3  shows a cross-sectional view of the example actuator  200  including the spring load adjuster  202  of  FIG. 2 ; and  FIG. 4  shows a top view of the example actuator  200  including the example spring load adjuster  202  of  FIG. 2 . The example actuator  200  may be coupled to any suitable valve (not shown) such as, for example, any valve requiring a biasing spring for fail-safe operation, a ball valve, a butterfly valve, a sliding stem valve, a plug valve, etc. Further, while the example actuator  200  is illustrated as a spring-extend actuator, the example actuator  200  is not limited to the specific examples described herein. For example, the example actuator  200  may be a spring-retract actuator, etc. 
         [0020]    The example actuator  200  may also include a housing  204 , a plurality of tie rods  206 , a first plate  208 , and a second plate  302  ( FIG. 3 ). The housing  204  may be, for example, a spring housing and may be positioned between the first plate  208  and the second plate  302  ( FIG. 3 ). Each of the plurality of tie rods  206  may be coupled at one of its ends to the first plate  208  and at the other of its ends to the second plate  302  ( FIG. 3 ). At least one of the plurality of tie rods  206  may be positioned substantially parallel to the housing  204 . Any number of tie rods  206  (e.g., 1, 3, 4, 5, 6, etc.) may be used. The first plate  208  may include an aperture  210  that may be, for example, positioned substantially in the center of the first plate  208 . The spring load adjuster  202  may include a movable collar  212  that may extend through the first plate  208 . The collar  212  may be comprised of a cylindrical portion or sleeve  213  and a flange  214  at an opening  215 . The collar  212  may slidingly engage the aperture  210  of the first plate  208 . A rim  216  of the collar  212  may engage a washer  217  (e.g., a hardened washer, etc.) and may be coaxial relative to the washer  217 . The flange  214  may be substantially parallel to a face  218  of the first plate  208 .  FIG. 3  clearly depicts the relationship between the housing  204 , the plurality of tie rods  206 , the first plate  208 , the second plate  302 , and the collar  212 . 
         [0021]    The spring load adjuster  202  may include one or more adjusters  219  to couple the collar  212  to the first plate  208 . The plurality of adjusters  219  may be implemented using any suitable adjuster such as, for example, pull down screws, pins, studs, or any other device to change or adjust the position of the collar  212  relative to the first plate  208  as described in greater detail below. Each of the plurality of adjusters  219  may have a threaded portion that engages a threaded portion of the collar  212  and/or the first plate  208 . Further, the spring load adjuster  202  may include one or more locking devices  220  that may engage the face  218  of the first plate  208 . The locking devices  220  may be implemented using any suitable locking device such as, for example, jacking screws, retaining screws, or any other device(s) to fasten, retain, or fix the position of the collar  212  relative to the first plate  208  in at least in one direction as described below. The locking devices  220  may have a threaded portion to engage a threaded portion of the collar  212 . Further, the locking devices  220  may extend through the collar  212  and engage and/or drive against the first plate  208 .  FIG. 4  depicts the relationship between the plurality of adjusters  219 , the locking devices  220 , and the collar  214 . Although eight adjusters  219  are shown in the illustrated examples, any number of adjusters (e.g., 1, 2, 3, 4, 5, etc.) may be included instead. Further, although four locking devices  220  are shown in the illustrated examples, any number of locking devices (e.g., 1, 2, 3, 4, 5, etc.) may be included instead. Further, the adjusters  219  and the locking devices  220  may be arranged at varying distances relative to and at various angles about the longitudinal axis of the actuator  200 . 
         [0022]    Turning to  FIG. 2 , the housing  204  may include a plunger  222  and one or more springs  224 . The plurality of springs  224  may be annular and may be substantially coaxial relative to the housing  204 . The springs  224  may be substantially concentric relative to at least a portion of the plunger  222 , and an exterior surface  225  of the plunger  222  may act as a guide for the springs  224 . The plunger  222  may have a cylindrical portion or sleeve  226  and a flange  306  ( FIG. 3 ). Further, at least one of the springs  224  may be housed within the housing  204 , and one or more of the springs  224  may include an aperture that surrounds at least a portion of the plunger  222 . The example springs  224  may be implemented using a plurality of Belleville-type disc springs stacked in a series arrangement, though any suitable spring(s) such as, for example, a plurality of coil springs in a parallel-arrangement, a plurality of coil springs in a nested-spring arrangement, a single coil spring, etc. may be used instead. 
         [0023]    A face of at least one of the springs  224  engages a face of the washer  217 , and a face of at least another one of the springs  224  (where there are at least two springs) or another face of the at least one spring  224  (where there is one spring) engages a face  304  ( FIG. 3 ) of the plunger  222 , etc. The springs  224  provide a spring load that may be configured to achieve a target or desired valve seat load in a valve closed position and a target or desired valve back seat load in a valve open position (i.e., target load values). When the actuator  200  is manufactured, depending on the design specifications and/or target load values, the spring(s)  224  may be selected based on a theoretical spring performance (i.e., how the spring(s)  224  should theoretically perform in the actuator  200 ). However, due to manufacturing tolerances, actual spring performance (i.e. how the spring(s)  224  actually perform in the actuator  200  when the actuator  200  is assembled) may deviate from the theoretical spring performance and, as a result, the spring load may need to be adjusted to substantially achieve the target load values or desired spring load(s). 
         [0024]    To adjust the spring load of the example actuator  200 , the locking devices  220  may be loosened (e.g., the locking devices  220  may be rotated to disengage from the first plate  208 ) and the plurality of adjusters  219  may be adjusted (e.g., turned or rotated). In this example, when the locking devices  220  are loosened and the adjusters  219  are adjusted, the collar  212  may be moved relative to (e.g., toward or away from) the first plate  208 . More specifically, the collar  212  may be moved by rotating, twisting, pulling, sliding or otherwise moving the collar  212  relative to the first plate  208 . The spring load adjuster  202  may be adjusted by any means such as, for example, by hand, with a tool, etc. The adjusters  219  may be adjusted to continuously move the collar  212  to a desired position relative to the first plate  208  where the desired position may correspond to the target load values. In the example of  FIG. 2 , as the plurality of adjusters  219  are tightened, the flange  214  of the collar  212  is continuously moved toward the first plate  208  and the rim  216  of the collar  212  is continuously moved away from the first plate  208  to compress the spring(s)  224  and, thus, increase the spring load. On the other hand, loosening the plurality of adjusters  219  allows the flange  214  to continuously move away from the first plate  208  and the rim  216  and the washer  217  to continuously move toward the first plate  208 , which allows the spring(s)  224  to expand and the spring load to decrease. 
         [0025]    The collar  212  may be substantially locked (i.e., substantially secured) in a desired adjustment position by tightening at least one of the plurality of locking devices  220  so that the locking devices  220  engage the first plate  208  and fix (e.g., retain, restrict, etc.) the collar  212  relative to the first plate  208  in at least one direction. In this example, the position of the locking devices  220  determines how close the flange  214  of the collar  212  may move toward the first plate  208 . In some example implementations, movement of the adjusters  219  when the locking devices  220  do not engage the first plate  208  and the adjusters  219  are coupled to the collar  212  and the first plate  208  makes a continuous adjustment of the position of the collar  212  relative to the plate  208  that affects a continuous setting of the spring load provided by the springs  224 . The continuous adjustment and/or the continuous setting may be implemented via, for example, a plurality of incremental changes, a plurality of incremental adjustments, a plurality of fine adjustments, etc. At least one of the plurality of adjusters  219  and/or at least one of the plurality of locking devices  220  may be externally accessible (i.e., accessible from the exterior of the actuator  200 ) to enable adjustment of the spring load without disassembly of the actuator  200 . 
         [0026]    If one or more of the adjusters  219  is coupled to the collar  212  and the first plate  208 , the spring load may not substantially decrease or substantially increase even if other of the adjusters  219  and/or the locking devices  220  are loose (i.e. do not engage the first plate  220 ). 
         [0027]      FIG. 5  shows an enlarged cross-sectional view of a portion of an alternative example actuator  500  including an alternative example spring load adjuster  502 , and  FIG. 6  is a top view of the example actuator  500  including the example spring load adjuster  502  of  FIG. 5 . The example actuator  500  may be coupled to any suitable valve (not shown) such as, for example, any valve requiring a biasing spring for fail-safe operation, a ball valve, a butterfly valve, a sliding stem valve, a plug valve, etc. Further, while the example actuator  500  is illustrated as a spring-extend actuator, the example actuator  500  is not limited to the specific examples described herein, for example, the example actuator  500  may be a spring-retract actuator (not shown), etc. The housing  204  of  FIG. 5  may include a structure similar to the structure described above in the example actuator  200  of  FIGS. 2 and 3 . Reference numbers in  FIG. 5  that are the same as those used in  FIGS. 2 and 3  correspond to structures that are similar or identical to those described in connection with  FIGS. 2 and 3 . 
         [0028]    The example actuator  500  may also include a housing  204 , a plurality of tie rods  206 , a first plate  506 , and a second plate  302  ( FIG. 3 ). The first plate  506  may include a threaded aperture  508  that may be, for example, positioned substantially in the center of the first plate  506 . The spring load adjuster  502  may include a movable collar  510  that may extend through the first plate  506 . The collar  510  may be comprised of a cylindrical portion or sleeve  512  and a flange  514  at an opening  516 . The collar  510  also includes a threaded exterior surface  518  that engages a threaded aperture  508  of the first plate  506 , which together act as an adjuster. 
         [0029]    The spring load adjuster  502  may include one or more locking devices  520  that may engage the face  522  of the first plate  506 . The locking devices  520  may be implemented using any suitable locking device such as, for example, jacking screws, retaining screws, or any other device(s) to fasten, retain, or fix the position of the collar  510  relative to the first plate  506  in at least one direction as described below. The locking devices  520  may have a threaded portion to engage a threaded portion of the collar  510 . Further, the locking devices  520  may extend through the collar  510  and engage and/or drive against the first plate  506 .  FIG. 6  depicts the relationship between the plurality of locking devices  520  and the collar  514 . Although two locking devices  520  are shown in the illustrated example, any number of locking devices (e.g., 1, 2, 3, 4, 5, etc.) may be included instead. Further, the locking devices  520  may be arranged at varying distances relative to and at various angles about the center of the actuator  500 . 
         [0030]    Turning to  FIG. 5 , to adjust the spring load of the example actuator  500 , the locking devices  520  may be loosened (e.g., the locking devices  520  may be rotated to disengage from the first plate  506 ) and the collar  510  may be adjusted (e.g., turned or rotated) relative to the first plate  506 . The spring load adjuster  502  may be adjusted by any means such as, for example, by hand, with a tool, etc. Adjusting the collar  510  may move the collar  510  relative to the first plate  506  to a desired position relative to the first plate  506 , where the desired position may correspond to the target spring load values. In the example of  FIG. 5 , as the collar  510  is tightened (e.g., rotated clockwise), the flange  514  of the collar  510  is continuously moved toward to the first plate  506  and the rim  524  of the collar  510  is continuously moved away from the first plate  506  to compress the spring(s)  224  and, thus, increase the spring load. On the other hand, loosening the collar  510  allows the flange  514  to move away from the first plate  506  and a rim  524  and the washer  217  to move toward the first plate  506 , which allows the spring(s)  224  to expand and the spring load to decrease. 
         [0031]    The collar  510  may be substantially locked (i.e., substantially secured) into a desired adjustment position by tightening at least one of the plurality of locking devices  520  so that the locking devices  520  engage the first plate  506  and fix the collar  510  relative to the first plate  506  in at least in one direction. In this example, the position of the locking devices  520  determines how close the flange  514  of the collar  510  may move toward the first plate  506 . In some example implementations, movement (e.g., rotation) of the collar  510  when the locking devices  520  do not engage the first plate  506  makes a continuous adjustment of the position of the collar  510  relative to the first plate  506  that affects a continuous setting of the spring load provided by the springs  224 . The continuous adjustment and/or the continuous setting may be implemented via, for example, a plurality of incremental changes, a plurality of incremental adjustments, a plurality of fine adjustments, etc. At least one of the plurality of locking devices  520  and/or the collar  510  may be externally accessible (i.e., accessible from the exterior of the actuator  500 ) to enable adjustment of the spring load without disassembly of the actuator  500 . 
         [0032]    The example apparatus and methods described herein can be used to adjust a spring load in an actuator. The examples described herein may save time and simplify the assembly and testing of an actuator. The described examples may enable a person to adjust a spring load of an actuator without disassembling the actuator to access the spring(s) and without having to add/or remove shims, spacers or any other components including custom or specially made parts. Further, the locking devices described herein may ensure that inadvertent adjustment of the actuator spring load does not occur. 
         [0033]    Although certain methods, apparatus, and articles of manufacture have been described herein, the scope of coverage of this patent is not limited thereto. To the contrary, this patent covers all methods, apparatus, and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.