Abstract:
Apparatus for increasing stiffness in a seal are disclosed. A disclosed apparatus includes a first flexible member having a curved sealing surface and a second flexible member adjacent to a retainer side of the first flexible member. The second flexible member is configured to increase a stiffness of the first flexible member in one of a plurality of flow directions.

Description:
TECHNICAL FIELD  
       [0001]     The present disclosure pertains to seals and, more particularly, to an apparatus for increasing stiffness in a seal.  
       BACKGROUND  
       [0002]     Typically, it is necessary to control the transmission of fluids in industrial processes, such as oil and gas pipeline distribution systems, chemical processing plants, etc. In some process control systems, process fluid control devices, such as butterfly valves, provide a means to control the transmission of the fluids and, in particular, may provide shut-off capabilities in a forward fluid flow direction and a reverse fluid flow direction. Although many process fluid control devices provide shut-off capabilities in both forward and reverse flow directions, these process fluid control devices may not provide the same degree of shut-off in both flow directions. For example, a butterfly valve may provide shut-off capabilities for up to a 300 psi pressure drop in a forward flow direction but may only provide shut-off capabilities for up to a 100 psi pressure drop in a reverse flow direction.  
         [0003]     Process fluid control devices may not provide equal shut-off capabilities in both fluid flow directions due to mechanical tolerances in the construction of the process fluid control device and the design of the process fluid control device. In a forward flow direction, a movable flow control member used to control and/or stop fluid flow through the process fluid control device (e.g., a disk of a butterfly valve or any other mechanical element used to control and/or stop fluid flow) may have tapered edges so that the diameter at one end of the movable flow control member is larger than the diameter of the flow control member at an opposite end. The movable flow control member may be coupled to the process fluid control device so that the end of the movable flow control member having the larger diameter is configured to prevent a sealing member from flexing too far the in the forward fluid flow direction. In particular, in response to fluid pressure in the forward flow direction, the increasing diameter of the movable flow control member allows the sealing member to flex and maintain contact with the outer surface (e.g., the tapered edge) of the movable flow control member. In a reverse flow direction, the amount the sealing member flexes in the reverse flow direction may be too large to maintain contact with the tapered edge of the movable flow control member. As a result, a fluid seal between the sealing member and the movable flow control member may be compromised (e.g., broken) and fluid is allowed to pass by the movable flow control member.  
       SUMMARY  
       [0004]     In accordance with one example, a sealing apparatus includes a first flexible member comprising a curved sealing surface and a second flexible member adjacent to a retainer side of the first flexible member. The second flexible member is configured to increase a stiffness of the first flexible member in one of a plurality of flow directions.  
         [0005]     In accordance with another example, a sealing device includes a clamping portion configured to be rigidly coupled to a body of a process fluid control device. The sealing device also includes a flexible portion that extends from the clamping portion and has a curved sealing surface configured to seal against a movable flow control member associated with the process fluid control device. The flexible portion is configured to have a first stiffness in a first flow direction and a second stiffness in a second flow direction. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a cross-sectional view of a portion of a known butterfly valve.  
         [0007]      FIG. 2   a  is an enlarged cross-sectional view of a portion of the known sealing structure used in  FIG. 1 .  
         [0008]      FIG. 2   b  is an enlarged cross-sectional view of the portion of the known sealing structure of  FIG. 2   a  as fluid pressure is applied to the sealing structure in a reverse flow direction.  
         [0009]      FIG. 3  is a cross-sectional view of a first apparatus that increases the stiffness of a seal in a reverse flow direction.  
         [0010]      FIG. 4  is a plan view of the first apparatus depicted in  FIG. 3 .  
         [0011]      FIG. 5  is a cross-sectional view of a second apparatus that increases the stiffness of a seal in a reverse flow direction.  
         [0012]      FIG. 6  is a plan view the second apparatus depicted in  FIG. 5 .  
         [0013]      FIG. 7  is a cross-sectional view of a third apparatus that increases the stiffness of a seal in a reverse flow direction.  
     
    
     DETAILED DESCRIPTION  
       [0014]      FIG. 1  is a cross-sectional view of a portion of a known butterfly valve  100 . The butterfly valve  100  shown in  FIG. 1  may, for example, be used to control the flow and/or pressure of a fluid, such as natural gas, oil, water, etc. in high temperature environments. Thus, the butterfly valve  100  may be made of materials such as, for example, stainless steel, that can withstand such environments.  
         [0015]     As shown in  FIG. 1 , the butterfly valve  100  has a disk  102  (e.g., a movable flow control member) at which a relatively high pressure fluid may be presented. The butterfly valve  100  also includes a valve body  104  and a sealing structure  106  coupled to the valve body  104 . The sealing structure  106  includes a seal retainer  108  and a sealing ring  110  and is configured to form a fluid seal between the disk  102  and the sealing ring  110 .  
         [0016]     The disk  102  may be eccentrically mounted to the valve  100  via a shaft  112  that is offset from the center line of the valve body  104 . The disk  102  is securely attached to the shaft  112 . In operation, when fluid passes through the valve  100 , the disk  102  and the shaft  112  rotate within the valve  100  so that a tapered edge  114  of the disk  102  is spaced from the sealing ring  110  (e.g., in an open position). The disk  102  may also be rotated to a closed position (e.g., the tapered edge  114  of the disk  102  is brought into contact with the sealing ring  110 ) to form a fluid seal with the sealing structure  106  to prevent process fluid from passing through the butterfly valve  100 . The eccentrically mounted disk  102  may be configured to provide an approximately linear flow characteristic and, thus, may be used for on/off and/or throttling control applications.  
         [0017]      FIG. 2   a  is an enlarged cross-sectional view of a portion of the sealing structure  106  of  FIG. 1 . The sealing structure  106  is configured to form a seal with the disk  102  to prevent the flow of the fluid in a forward flow direction  116  and/or a reverse flow direction  118 . A fluid seal is formed between the disk  102  and the sealing structure  106  when the disk  102  is rotated to a closed position and contacts a curved sealing surface  120  of the sealing ring  110 . The sealing ring  110  may be made of a flexible material (e.g., stainless steel) suitable for use in high temperature applications such as those described above. The sealing ring  110  may have an inner diameter  121  ( FIG. 1 ) approximately equal to the average diameter of the disk  102 . As shown in  FIG. 2   a , a flexible portion  122  of the sealing ring  110  is disposed between a seal support  124  and the seal retainer  108 .  
         [0018]     In operation, when the disk  102  is closed (i.e., is in contact with the curved sealing surface  120 ) and fluid pressure is applied to the disk  102  in the forward flow direction  116 , the sealing ring  110  is flexed in the forward flow direction  116  until the sealing ring  110  abuts or contacts the tapered edge  114  of the disk  102  and/or the seal support  124 . As pressure increases, the fluid seal is not compromised or broken because the flexible portion  122  of the sealing ring  110  is supported by or drives against of the tapered edge  114  of the disk  102  and towards the larger diameter end of the disk  102 .  
         [0019]      FIG. 2   b  is an enlarged cross-sectional view of the sealing structure  106  of  FIG. 1  depicting a reverse flow pressure drop within the body of the butterfly valve  100  (e.g., the condition in which the disk  102  is closed and fluid pressure is applied in the reverse flow direction  118 , thereby flexing the flexible portion  122  of the sealing ring  110  in the reverse flow direction  118 ). As the fluid pressure increases, the fluid seal may ultimately be compromised or broken because the flexible portion  122  of the sealing ring  110  flexes away from the disk  102  as shown in  FIG. 2   b  and, thus, is not supported by the tapered edge  114  of the disk  102 . As can be appreciated from  FIG. 2 , the tapered edge  114  of the disk  102  does not support the flexible portion  122  of the sealing ring  110  in the reverse flow direction  118  because the diameter of the disk  102  decreases in the reverse flow direction  118 .  
         [0020]      FIG. 3  illustrates a cross-sectional view of a first sealing structure  300  that increases the stiffness of a sealing ring  302  in a reverse flow direction  304 . As depicted in  FIG. 3 , the sealing structure  300  includes a seal retainer  306  and a seal support  308  that are similar to the seal retainer  108  and the seal support  124  of  FIG. 2   a . Additionally, the sealing ring  302  includes a flexible portion  310 , a curved sealing surface  312 , a tip portion  314 , and a disk  316  configured to form a fluid seal against the curved sealing surface  312 .  
         [0021]     In contrast to the sealing structure  106  of  FIG. 1 , the sealing structure  300  includes an example flexible member  318  adjacent to the retainer side of the sealing ring  302 . The flexible member  318  is configured to increase the stiffness of the sealing ring  302  (i.e., functions as a seal stiffener) in the reverse flow direction  304  and is further configured to not interfere with the functionality of the sealing structure  300  in a forward flow direction  320  (e.g., the stiffness of the sealing ring  302  is not affected by the flexible member  318  in the forward flow direction  320 ). As shown in  FIG. 3 , the example flexible member  318  or seal stiffener  318  is disposed between the seal retainer  306  and the sealing ring  302 . In some examples, the seal stiffener  318  may not be fastened to the seal retainer  306  and/or the sealing ring  302 . For example, the seal stiffener  318  may be captured or clamped between, but not permanently fixed to, the sealing ring  302  and seal retainer  306 . As a result, the flexible portion  310  is configured to have one stiffness in the forward flow direction  320  and another or different stiffness in the reverse flow direction  304 .  
         [0022]     One with ordinary skill in the art will readily appreciate that a variety of different materials may be used to implement the seal stiffener  318 . For example, the seal stiffener  318  may be composed of a similar material to the material used to form the sealing ring  302  and/or may be made of a material that has relatively improved wear and/or corrosion resistance than that of the sealing ring  302 . Alternatively, the seal stiffener  318  may also be composed of a material that has less wear resistance than that of the sealing ring  302  because the seal stiffener  318  does not maintain sliding contact with the sealing ring  302 .  
         [0023]      FIG. 4  illustrates a plan view of the seal stiffener  318 . The seal stiffener  318  may have a washer-like shape with an inner diameter  352  equal to the inner diameter of the sealing ring  302 . The seal stiffener  318  may have an outer diameter  354  that is large enough so that the seal stiffener  318  is securely captured between a clamping portion (e.g., the seal retainer  306 ) and the sealing ring  302 . The seal stiffener  318  may be substantially planar or may have a contoured profile. The contoured profile may be formed by bends  356  and  358 . Additionally, the seal stiffener  318  may be configured to interfere with abrasive media making contact with the sealing ring  302 , thereby functioning as a shield to protect the curved sealing surface  312  from abrasive media.  
         [0024]     Alternatively, the seal stiffener  318  may have a plurality of flexible cantilevered members, each of which may have one end captured between the sealing ring  302  and the seal retainer  306  and another end extending to at least the tip portion  314  of the sealing ring  302 . The plurality of cantilevered members may be uniformly spaced around the circumference of the sealing ring  302  and/or may be spaced around the circumference of the sealing ring  302  in any desired configuration so that the plurality of cantilevered members substantially uniformly increase the stiffness of the entire sealing ring  302  in the reverse flow direction  304 .  
         [0025]     Returning to  FIG. 3 , as fluid pressure in the reverse flow direction  304  is applied to the disk  316  in the closed position, the sealing ring  302  is flexed in the reverse flow direction  304  until the tip portion  314  abuts or contacts the seal stiffener  318 . In this manner, the seal stiffener  318  acts as a flexible support for the tip portion  314  of the sealing ring  310 . As a result, the seal stiffener  318  increases the stiffness of the flexible portion  310  in the reverse flow direction to prevent the sealing ring  302  from flexing too far so that the fluid seal between a tapered edge  322  of the disk  316  and the curved sealing surface  312  is not compromised or broken.  
         [0026]      FIG. 5  illustrates a cross-sectional view of another example sealing structure  400  that increases the stiffness of a sealing ring  402  in a reverse flow direction  404 . As depicted in  FIG. 5 , the sealing structure  400  includes a seal retainer  406  and a seal support  408  that are similar to the seal retainer  108  and the seal support  124  of  FIG. 2   a . Additionally, the sealing ring  402  includes a flexible portion  410 , a curved sealing surface  412 , a tip portion  414 , and a disk  416  configured to form a fluid seal against the curved sealing surface  412 .  
         [0027]     In contrast to the sealing structure  106  of  FIG. 1 , the sealing structure  400  includes a flexible member  418  adjacent to the retainer side of the sealing ring  402 . Similar to the example flexible member  318  of  FIG. 3 , the example flexible member  418  is configured to increase the stiffness of the sealing ring  402  (i.e., functions as a seal stiffener) in the reverse flow direction  404  and to not interfere with the functionality of the sealing structure  400  in a forward flow direction  420 . As depicted in  FIG. 5 , the example flexible member  418  or seal stiffener  418  may be disposed between the seal retainer  406  and the sealing ring  402 . Preferably, the seal stiffener  418  is not fastened or permanently joined to the seal retainer  406  and/or at least the flexible portion  410  the sealing ring  402  so that it does not interfere with the functionality of the sealing structure  400  in the forward flow direction  420 . As a result, the flexible portion  410  is configured to have one stiffness in the forward flow direction  420  and another or different stiffness in the reverse flow direction  404 .  
         [0028]     The example seal stiffener  418  may be composed of a material similar to that used to form the sealing ring  402  and/or may be made of a material that has relatively improved wear and/or corrosion resistance than that of the material used to form the sealing ring  402 . Alternatively, the seal stiffener  418  may be composed of a material that has similar or less wear resistance than that of the sealing ring  402  because the seal stiffener  418  does not maintain sliding contact with the sealing ring  402 .  
         [0029]     The seal stiffener  418  may have an overall shape similar to that of a washer but is not planar. As depicted in  FIG. 6 , the seal stiffener  418  may have an outer diameter  452  that is similar to the outer diameter  354  of the seal stiffener  318  of  FIG. 4 , but which does not extend to the tip portion  414  of the sealing ring  402 . Instead, the example seal stiffener  418  is contoured to have a bend  422  to follow the contour of the sealing ring  402  and, as a result, the seal stiffener  418  has a non-planar geometry. Thus, the example seal stiffener  418  is configured to increase the thickness of a portion of the sealing ring  402  and/or the flexible portion  410 . For example, as shown in  FIG. 5 , the seal stiffener  418  does not extend along the full length of the flexible portion  410  but, rather, extends along a portion of the flexible portion  410 .  
         [0030]     Similar to the seal stiffener  318  of  FIG. 3 , the seal stiffener  418  may also be composed of a plurality of flexible cantilevered members, each of which may have one end captured between the sealing ring  402  and the seal retainer  406  and another end contoured to have the bend  422  similar to that used with the example sealing ring  402 . The plurality of cantilevered members may be uniformly spaced around the circumference of the sealing ring  402  and/or may be spaced around the circumference of the sealing ring  402  in any desired configuration so that the plurality of cantilevered members uniformly increase the stiffness of the entire sealing ring  402  in the reverse flow direction  404 .  
         [0031]     Similar to the sealing structure  300  of  FIG. 3 , as fluid pressure in the reverse flow direction  404  is applied to the disk  416  in the closed position, the flexible portion  410  of the sealing ring  402  is flexed in the reverse flow direction  404 . The seal stiffener  418  increases the stiffness of the flexible portion  410  by supporting the flexible portion  410  (e.g., at or near the bend  422 ). By supporting the flexible portion  410 , the fluid seal between a tapered edge  424  of the disk  416  and the curved sealing surface  412  is not broken due to the increased fluid pressure in the reverse flow direction  404 . More specifically, the seal stiffener  418  significantly increases the stiffness of the flexible portion  410  in the reverse flow direction  404 , thereby substantially decreasing the degree to which the curved sealing surface  412  can travel along the tapered edge  424  of the disk  416  toward the smaller diameter end of the disk  416 .  
         [0032]      FIG. 7  illustrates a cross-sectional view of a yet another sealing structure  500  that increases the stiffness of a sealing ring  502  in a reverse flow direction  504 . As depicted in  FIG. 7 , the sealing structure  500  includes a seal retainer  506  and a seal support  508  that are similar to the seal retainer  108  and the seal support  124  of  FIG. 2   a . Additionally, the sealing ring  502  includes a flexible portion  510 , a curved sealing surface  512 , a tip portion  514 , and a disk  516  configured to form a fluid seal against the curved sealing surface  512 .  
         [0033]     Unlike the example sealing structure  300  of  FIG. 3  and the example sealing structure  400  of  FIG. 5 , the example sealing structure  500  of  FIG. 7  includes a compressible cylindrical member  518  configured to rest in an annular cavity or recess, a trough, a well, or a channel between the seal retainer  506  and the curved sealing surface  512 . For ease of discussion, the annular cavity, the trough, the well, or the channel will be herein referred to as the annular recess  520 . For example, the compressible cylindrical member  518  may be a helical spring. The compressible cylindrical member  518  may be fastened to the annular recess  520  of the curved sealing surface  512 . The placement of the compressible cylindrical member  518  prevents the compressible cylindrical member  518  from affecting the stiffness of the sealing ring  502  in a forward flow direction  522 .  
         [0034]     The compressible cylindrical member  518  may be composed of a similar material as the sealing ring  502  and/or may be made of a material that has relatively improved wear and/or corrosion resistance than that of the material used to form the sealing ring  502 . Alternatively, the seal stiffener  518  may be composed of a material that has similar or less wear resistance than that of the sealing ring  502  because the seal stiffener  518  does not maintain sliding contact with the sealing ring  502 . The compressible cylindrical member  518  may also have a length so that the compressible cylindrical member  518  rests in the annular recess  520  formed by the curved sealing surface  512 .  
         [0035]     Alternatively, the compressible cylindrical member  518  may be composed of a plurality of helical springs disposed along the annular recess  520  of the sealing ring  502 . Such a plurality of helical springs may be placed in the annular recess  520  of the curved sealing surface  512  and disposed uniformly along the annular recess  520 . Alternatively, such a plurality of helical springs may be placed in any configuration that substantially uniformly increase the stiffness of the entire sealing ring  502  in the reverse flow direction  504 .  
         [0036]     As fluid pressure in the reverse flow direction  504  is applied to the disk  502  in the closed position, a seal is formed between the disk  502  and the curved sealing surface  512 . As the reverse flow fluid pressure increases, the flexible portion  510  increasingly flexes in the reverse flow direction  504  until the compressible cylindrical member  518  is compressed against the seal retainer  506 , thereby preventing the tip portion  514  of the sealing ring  502  from abutting or contacting the seal retainer  506 . In this manner, the compressible cylindrical member  518  prevents the fluid seal between a tapered edge  524  of the disk  516  and the curved sealing surface  512  from being compromised or broken.  
         [0037]     Although certain methods, 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 apparatuses, methods and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.