Abstract:
An attenuating device that is configured to replace motion converters in conventional control valve assemblies. The attenuating device can generate an output displacement in response to a position of a plug relative to a seat in the valve assembly. In one embodiment, the attenuating device comprises a spring assembly with a pair of spring members, disposed in series, and configured to assume a deflection that reduces the displacement of the plug to a smaller displacement that is useful to position a target member of a sensor. This embodiment, however, forgoes the mechanisms of conventional devices in lieu of components that are amenable to compact design. In this way, the attenuating device can substantially fit within the existing structure of the valve assembly, and, in one construction, the attenuating device is disposed in the actuator of the valve assembly.

Description:
BACKGROUND 
     The subject matter disclosed herein relates to improvements in valve technology with particular discussion about embodiments of a modulating device that generates an output that relates to displacement of components in a valve assembly. 
     Valve assemblies like control valves can regulate flow of a process fluid in a process line. In their broadest configuration, these valve assemblies have a valve component with a plug (or moving element) that moves relative to a seat (or stationary element). This configuration also includes an actuator component that utilizes pneumatic signals (or flow of working fluid) to change the position of the plug. The actuator component can have a diaphragm (or actuating element) and a stem element that couples the diaphragm with the plug. During operation, the pneumatic signals cause movement of the diaphragm to set the position of the plug, often in accordance with signals that originate from a process control system. These signals instruct operation of the valve assembly to define an amount of process fluid that flows through the valve assembly and, thus, maintain operating conditions across the process line. 
     Operating conditions in many processes are sensitive to even small deviations in the amount of process fluid that flows through the valve assembly. This feature warrants construction of the valve assembly in a manner that can accurately and repeatability position the plug relative to the seat. Often, the valve assembly incorporates a valve positioner and a sensor, or like device, that measures the relative movement of the actuator (or its constituent components). This sensor provides feedback to the valve positioner about displacement of the plug relative to the seat. The valve positioner can use this feedback to regulate the pneumatic signals, which in turn operates the actuator to position the plug relative to the seat to within some reasonable operating tolerances or thresholds. 
     Most facilities with process lines allocate only a finite amount of power for operation of the valve assembly. This power constraint can influence design choices, namely for sensors and other electronics that are found on the valve assembly. For example, designs for the valve assembly may incorporate sensors (e.g., Hall Effect sensors) that consume less power than other sensors. These low power sensors often have an operating range (or detecting range) that is narrow relative to these other sensors that consume more power. 
     Unfortunately, the position of the plug relative to the seat may require movement of the actuator that exceeds the operating range of these low power sensors. Conventional designs for a valve assembly address this problem with a motion converter that reduces the relative movement of the actuator to motion that “fits” within the operating range of the sensor. Examples of the motion converter include linkages, lever arms, and/or cam-follower mechanisms, each of which can convert linear movement of the actuator to rotary displacement that fits within the operating range of the sensor. However, these mechanisms add cost and complexity to the valve assembly and, in many cases, are susceptible to defects in operation, wear, and damage due to dirt (and debris) and vibrations that prevail in and around the process line. 
     BRIEF DESCRIPTION OF THE INVENTION 
     This disclosure describes embodiments of an attenuating device to replace these motion converters. As discussed more below, these embodiments can generate an output displacement that is proportionally less than displacement necessary to move the plug. The embodiments, however, forgo the mechanisms of conventional devices in lieu of components that are amenable to compact design. In this way, the attenuating device can substantially fit within the existing structure of the valve assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference is now made briefly to the accompanying drawings, in which: 
         FIG. 1  depicts a schematic diagram of an exemplary embodiment of a modulating device; 
         FIG. 2  depicts a perspective view of a valve assembly that can incorporate a attenuating device, e.g., the modulating device of  FIG. 1 ; 
         FIG. 3  depicts a detail view of the valve assembly of  FIG. 2  that illustrates a elevation, cross-section of the attenuating device; 
         FIG. 4  depicts a schematic diagram of an exemplary embodiment of a attenuating device with resilient members in the form of linear springs disposed in series; 
         FIG. 5  depicts a schematic diagram of the attenuating device of  FIG. 4  in several configurations to illustrate one implementation to attenuating motion in a valve assembly; 
         FIG. 6  depicts a schematic diagram of an exemplary embodiment of an attenuating device with resilient members in the form of a linear spring and a coils spring; and 
         FIG. 7  depicts a schematic diagram of the attenuating device of  FIG. 6  in several configurations to illustrate one implementation to attenuating motion in a valve assembly. 
     
    
    
     Where applicable like reference characters designate identical or corresponding components and units throughout the several views, which are not to scale unless otherwise indicated. 
     DETAILED DESCRIPTION 
       FIG. 1  depicts a schematic diagram of an exemplary embodiment of an attenuating device  100 . This embodiment resides in an operating envelope  102  that generally bounds all of the components of the valve assembly  104 . The operating envelope  102  provides a hypothetical boundary that defines a volume of space about the valve assembly  104 . For purposes of example, this volume can have a value that is about 10% larger than the volume of the valve assembly  104 . As noted herein, the attenuating device  100  is also configured to fit inside of this volume along with all of the components of the valve assembly  104 . These components may include a valve component  106  with an actuator  108  and a valve  110  with a plug  112  that moves relative to a seat  114 . The valve assembly  104  can also include a valve positioner  116  that couples with a sensor member  118  to provide feedback about operation of the valve  110 . The sensor member  118  can have a target member  120  that moves relative to a sensor  122 . The valve positioner  116  couples with the actuator  108  to provide a pneumatic signal in response to a signal from the sensor member  118 . In use, the actuator  108  regulates the position of the plug  112  relative to the seat  114 , effectively defining an amount of process fluid that can flow through the valve component  106 . 
     The attenuating device  100  is configured to mechanically convey the position of the plug  112  to the sensor member  118 . As shown in  FIG. 1 , the attenuating device  100  may utilize a structure with one or more actuating members (e.g., a first actuating member  124  and a second actuating member  126 ) and an attenuating assembly  128 , shown here interposed between the actuating members  124 ,  126 . The attenuating device  100  can couple with the valve component  106  and/or the target member  120 , either directly and/or through one or more intermediary components (e.g., a first intermediary component  130  and a second intermediary component  132 ). During operation, the first actuating member  124  moves (e.g., by a first displacement  134 ) in response to travel or motion of the valve component  106  (e.g., the valve stem, the actuator, the plug, etc.). The second actuating member  126  moves (e.g., by a second displacement  136 ), for example, in response to movement of the first actuating member  124 . The second displacement  136  can change the position of the target member  120 , thereby relaying the position of the plug  112  to the sensor member  118 . In one example, the sensor member  118  can generate a measured value for the position of the plug  112  at a first distance from the seat  114 , wherein the second displacement  136  corresponds with the measured value. 
     The components of the attenuating device  100  can be configured to provide structure that can accommodate large (or long) displacements necessary to appropriately position the plug  112  relative to the seat  114 . Each of the actuating members  124 ,  126  can be configured for motive action (e.g., translation, rotation, etc.) that is useful to move the target member  120 . In one example, this motive action embodies linear translation along an axis. The attenuating assembly  128  can be configured with an attenuating characteristic that regulates displacement  134 ,  136  of the actuating members  124 ,  126 . This attenuating characteristic relates to properties of the members of the attenuating assembly  128 . As noted in the examples below, these members may embody springs and like resilient members. Such resilient members may exhibit a spring constant suitable to regulate movement. This spring constant defines the attenuating characteristic of the attenuating assembly  128  to relate a value for the first displacement  134  to a value for the second displacement  136 . This disclosure does, however, contemplates the use of other types of devices (e.g., hydraulic cylinders) that can serve to regulate displacement  134 ,  136 . These devices may have properties (e.g., surface area, volume, etc.) that also define the attenuating characteristic of the assembly  128 , as contemplated herein. 
     The attenuating characteristic of the assembly  128  can maintain the relationship between the first displacement  134  and the second displacement  136 , but result in much smaller magnitude for the second displacement  136  relative to the first displacement. For example, in one configuration the second displacement  136  is different from the first displacement  134 , and, often, the second displacement  136  is less than and/or proportionally less than the first displacement  134 . This feature can configure the valve assembly  104  to accommodate translation of components within the valve component  106  that is necessary to move the plug  112 , but that would otherwise outstrip the operating range of the sensor  122 . However, unlike conventional valves, use of the attenuating assembly  128  can configure the attenuating device  100  to fit on the valve assembly  104  in a manner that does not extend outside of the operating envelope  102 . In one implementation, the attenuating device  100  is configured to fit substantially within a housing and/or a casing that encloses the working components of the actuator  108 . This feature offers improved performance as between conventional motion converters that are likely to extend, at least, outside of the operating envelope  102  in order to appropriately reduce displacement of, e.g., the actuator  108  that moves the plug  112  into position relative to the seat  114 . 
       FIGS. 2 and 3  illustrate an exemplary embodiment of an attenuating device  200  that is configured to attenuate displacement during operation of the valve assembly  202 .  FIG. 2  is a perspective view of the valve assembly  202 .  FIG. 3  is a detail view of an elevation, cross-section of the valve assembly  202  that shows one implementation of the attenuating device  200 . The valve assembly  202  in  FIG. 3  has several parts removed for clarity. 
     In  FIG. 2 , the valve component  204  embodies a control valve  238  with a fluid coupling  240  with a body  242  that has a pair of inlet/outlets (e.g., a first inlet/outlet  244  and a second inlet/outlet  246 ). The fluid coupling  240  can also have a valve (e.g., valve  110  of  FIG. 1 ) that resides in the body  242  and is thus not shown in the diagram of  FIG. 2 . As noted herein, the valve can be configured with a plug (e.g., plug  112  of  FIG. 1 ) and a seat (e.g., plug  114  of  FIG. 1 ) that work in combination to regulate flow of process fluid between the inlet/outlets  244 ,  246 . The actuator  208  can include an actuating member  248  is configured to couple with a valve stem  250  that is configured to move the plug on the valve. In one implementation, the valve positioner  216  couples with a network system  252  via a network  254  that can transfer data, information, and signals by way of wired protocols (e.g., 4-20 mA, Foundation Fieldbus, etc.) and/or wireless protocols, many of which find use in a plant or factory automation environment. The network  254  facilitates communication between the valve positioner  216 , a process control system  256 , a terminal  258 , and/or an external server  260 . As also shown in  FIG. 2 , the actuating member  248  includes a housing  262  with one or more housing members (e.g., a first housing member  264  and a second housing member  266 ). 
     The attenuating device  200  can be disposed within the housing  262  to reduce the overall footprint of the control valve  238 . In the present example of  FIG. 2 , the second actuating member  226  extends through the first housing member  264  to convey the change in position of the plug (not shown). Other embodiments of the attenuating device  200  may reside in different parts of the valve assembly  202 . The attenuating device  200  may couple with the exterior structure of the valve assembly  202 , for example, to provide feedback as to the position and/or displacement of the valve stem  250 , which couples with the plug (not shown). 
       FIG. 3  depicts one configuration for the attenuating device  200  that can reside in the housing  262 . In this configuration, the actuating member  248  also has a moving element, shown here as a diaphragm member  268  that couples with the valve stem  250 . The attenuating device  200  has a body member  270  with a first end  272  and a second end  274 . The attenuating assembly  228  can include one or more attenuating members (e.g., a first attenuating member  276  and a second attenuating member  278 ). At the first end  272 , the first actuating member  276  can include an input member  280  that extends to and, in one example, couples with the diaphragm member  268 . The second attenuating member  278 , found at the second end  274 , has an output member  282  that extends from the second end  274  through the housing  262  (here, through the first housing member  264 ). As also shown in  FIG. 3 , the actuating member  248  can include one or more seal members (e.g., a first seal member  284  and a second seal member  286 ) that configure the valve component  204  to maintain pressure inside of the housing  248 . 
     Use of the attenuating device  200  can avoid the need for extraneous structure to extend outside the operating envelope  202  ( FIG. 2 ) of the valve component  204 . The body member  270  (and the attenuating members  276 ,  278 ) can be configured to fit within the interior cavity of the housing  262 . During operation, movement of the diaphragm member  268  can cause the input member  280  to actuate from a first position to a second position that is spaced apart from the first position by the first displacement  234 . The input member  280  can interface with the attenuating assembly  228  to cause the output member  282  to change position, e.g., from a third position to a fourth position that is spaced apart from the third position by the second displacement  236 . In one implementation, displacement of the input member  280  can actuate one or more of the attenuating members  276 ,  278 . The input member  280  can actuate the first attenuating member  276 , for example, which in turn actuates the second attenuating member  278  to cause the output member  282  to change position, e.g., from the third position to the fourth position. 
     Construction of the attenuating members  276 ,  278  can utilize devices that facilitate the utility of the attenuating device  200  in a form factor that fits the operating envelope  202  as noted herein. As noted above, these devices can assign, or prescribe, the attenuating characteristic, which in turn defines the degree to which the displacement of the output member  282  is changed (e.g., reduced) relative to the displacement of the input member  280 . Examples of the devices can embody actuators that operate, often in combination, so that the second displacement  236  is proportionally less than the first displacement  234 . The actuators may utilizes one or more spring elements of varying mechanical properties, one or more piston actuators of varying size and stroke, hydraulic actuators that pass fluid between one or more fluid chambers of varying area, volume, and the like. The discussion that follows below describes configurations of actuators that are useful to attenuate movement, e.g., of the input member  280  and the output member  282 . However, this disclosure does contemplate other configurations of actuators, and related construction and assembly, as possibly desirable for use to attenuate movement as noted herein. 
       FIG. 4  illustrates a schematic diagram of a cross-section of an exemplary embodiment of an attenuating device  300  to illustrate details for one construction of the attenuating assembly  328 . The attenuating members  376 ,  378  can comprise one or more spring members (e.g., a first spring member  388  and a second spring member  390 ), disposed in series (or, also, “end-to-end”). The attenuating members  380 ,  382  can have a base element  392  and a shaft element  394 , the combination of which can translate along a central axis  396 . 
     Each of the spring members  388 ,  390  can be configured with physical characteristics that can help attenuate displacement of the members  380 ,  382 . These characteristics include spring constant (also “spring rate”), wherein the spring constant for each of the spring members  388 ,  390  is selected to obtain a deflection for the attenuating assembly  328  that attenuates the displacement as desired. In the example of  FIG. 4 , each of the spring members  388 ,  390  embodies a linear coil spring (e.g., tension or compression). During operation, movement of the input member  380  will deflect the first spring member  388 , causing the first spring member  388  to generate a force in accordance with Equation (1) below,
 
F 1 =k 1 d 1 ,  Equation (1)
 
wherein F 1  is the force, k 1  is the spring constant for the first spring member, and d 1  is a first deflection of the first spring member. The interface member  398  can transfer the force F 1  to the second spring member  390 , which in turn will deflect an amount in accordance with Equation (2) below,
 
                       d   2     =       F   1       k   2         ,           Equation   ⁢           ⁢     (   2   )                 
wherein F 1  is the force, k 2  is the spring constant for the second spring member, and d 2  is a second deflection of the second spring member. The relationship between the spring members can be tuned using the spring constants to vary the amount and/or extent of deflection and, thus, vary the displacement of the output member  382  relative to the displacement of the input member  380 . Notably, as the second spring constant k 2  becomes much larger than the first spring range k 1 , the second spring member will generate a opposing force that is much larger (and in the opposite direction of) the force F 1  of the first spring member. This feature maintains the second displacement at the output member  382  much less relative to the first displacement at the input member  380 .
 
       FIG. 5  depicts diagrams of an exemplary embodiment of the attenuating device  300  that demonstrates several configurations of the device during operation. Some parts of the attenuating device  300  are removed for clarity. In  FIG. 5 , the attenuating device  300  is shown in a first configuration A, typical of operation of the valve component with one or more components in a first position. The attenuating device  300  in also shown in a second configuration B with the first resilient member  388  ( FIG. 4 ) having a first deflection d 1  under a load L. The second configuration B can generate the force F 1 , noted above. The second configuration B can reflect the configuration of the attenuating device  300  in response to a change in position of the plug on the valve component. The attenuating device  300  is also shown in a third configuration C with the second spring member  390  ( FIG. 4 ) having a second deflection d 2  that generates an opposing force F 2 . In the third configuration C, each of the members  380 ,  382  ( FIG. 4 ) are in position to reflect the change in position of the plug that, as noted herein, correspond with displacements  334 ,  336 . The third configuration C may occur in response to the first spring member  388  ( FIG. 4 ) reaching the end (or near the end) of deflection d 1 . In use, the third configuration C may reflect the configuration of the attenuating device  300  in response to a change in position of the plug on the valve component (e.g., from the first position to a second position). 
       FIG. 6  depicts a schematic diagram of an exemplary embodiment of an attenuating device  400  to illustrate details for another construction of the attenuating assembly  428 . In this construction, the output member  482  operates as a pivot arm with a pivot P. The first spring member  488  embodies a linear coil spring. On the other hand, the second spring member  490  embodies a torsion spring (or like resilient element that generates spring force by torsion and/or twisting). 
       FIG. 7  depicts diagrams of an exemplary embodiment of an attenuating device  400  that demonstrates several configurations of the device during operation. In  FIG. 7 , the attenuating device  400  is shown in a first configuration A, typical of operation of the valve component with one or more components in a first position. The attenuating device  400  in also shown in a second configuration B with the first resilient member  488  ( FIG. 6 ) having a first deflection d 1  under a load L. The second configuration B can generate the force F 1 , noted above. The attenuating device  400  is also shown in a third configuration C in which the second spring member  490  ( FIG. 6 ) will have a second, angular displacement (e.g., displacement d 2 ). This angular displacement will generate an opposing, torsion force F 2 . In the third configuration C, each of the members  480 ,  482  ( FIG. 6 ) are in position to reflect the change in position of the plug. The third configuration C may occur in response to the first spring member  488  ( FIG. 6 ) reaching the end (or near the end) of deflection d 1 . In use, the third configuration C can reflect the configuration of the attenuating device  400  in response to a change in position of the plug on the valve component (e.g., from the first position to a second position). 
     As used herein, an element or function recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural said elements or functions, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the claimed invention should not be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.