Abstract:
Exemplary embodiments are directed to rotary shear valves which include a stator, a rotor defining a cavity extending at least partially therethrough, and a bladder. The rotor is rotatably mounted relative to the stator to create at least one fluidic path therebetween. The bladder comprises a polymer disposed inside the cavity. Exemplary embodiments are also directed to methods of operating a rotary shear valve.

Description:
RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Application No. 61/740,836, filing date Dec. 21, 2012, which is incorporated herein by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates to rotary shear valves and associated methods and, in particular, to rotary selector valves, which include an internal bladder and, in some embodiments, include a diaphragm. 
       BACKGROUND 
       [0003]    Rotary valves are generally used in process industries for directing fluids from one or more sources to one or more destinations in a repeatable or cyclic process. For example, CO 2  based chromatography systems or UHPLC systems can generally utilize rotary shear valves which include a rotor and a stator as the two interacting sealing surfaces to alter the flow path directions of mobile phase constituents (e.g., solvents, modifiers, and the like) within the valve. Current high pressure chromatography shear valves typically employ a stator comprising a metallic element and a rotor device composed of a polymer material that forms a fluid-tight seal at a rotor/stator interface. While this combination has been found useful, it can be limited in pressure rating and/or valve lifetime. 
         [0004]    Rotor materials can include high strength and solvent resistant polymers, such as polyether ether ketone (PEEK) or polyimide. However, both PEEK and polyimide have compressive strength limitations that can prevent the valve from safely operating above 20,000 psi. To increase the operating conditions of the valve beyond 20,000 psi, higher strength materials, such as stainless steels, have been considered. In particular, stainless steels have a significantly higher modulus than polymers, e.g., approximately 28 million psi versus approximately 2 million psi. However, the higher modulus can make it more difficult to achieve uniform contact stresses for the sealing surface between the rotor and stator. In particular, uniform contact stresses are important to allow for uniform wear and to seal the fluidic paths. 
       SUMMARY 
       [0005]    In general, embodiments of the present disclosure are directed to rotary shear valves that create substantially uniform contact stresses between the rotor and stator, thereby promoting uniform wear and sealing of the fluidic paths. Specifically, the exemplary rotary shear valves utilize a three piece design including a diaphragm and bladder which allows for more uniform contact stresses between the rotor and stator and allows operation of the valve beyond 20,000 psi. 
         [0006]    In accordance with embodiments of the present disclosure, exemplary rotary shear valves are provided that include a rotor, a stator and a bladder. The rotor defines a cavity extending at least partially therethrough and is rotatably mounted relative to the stator to create at least one fluidic path therebetween. The bladder comprises a polymer disposed inside the cavity. 
         [0007]    The rotor generally includes at least one rotor groove and the stator includes at least one stator port for the at least one fluidic path. The polymer forming the bladder can be a low compressive yield strength polymer and generally exhibits fluid-like properties under a compressive stress. The bladder can be disposed inside the cavity such that, when compressed, the bladder substantially distributes contact stresses in at least two directions between the rotor and the stator. The exemplary rotary shear valves can include at least one diaphragm coupled to the rotor. The diaphragm can be, e.g., an integrated diaphragm, a separate diaphragm, and the like. The separate diaphragm can be coupled to the rotor using at least one of, e.g., electron beam welding, laser beam welding, friction welding, and the like. The integrated diaphragm is coupled to the rotor by being formed from a portion of the rotor. The exemplary rotary shear valves can include at least one relief slot for increased flexure of the integrated diaphragm. 
         [0008]    The stator can define a flat stator face and at least one of the rotor and the at least one diaphragm can define a flat face complementary to the flat stator face. The diaphragm can be fabricated from at least one of, e.g., a stainless steel alloy, a UNS S21800 steel, an MP35N alloy, a cobalt alloy, a nickel alloy, and the like. The stator can be fabricated from at least one of, e.g., a titanium alloy, a 316 stainless steel, an MP35N alloy, and the like. The stator can include a coating, e.g., a diamond-like coating, and in some embodiments, a nanofilm diamond-like coating (e.g., having a thickness of 5,000 nm or less). The polymer can be at least one of, e.g., a polytetrafluoroethylene (PTFE), an ultra-high-molecular-weight polyethylene (UHMWPE), and the like. 
         [0009]    The exemplary rotary shear valves can include a spacer disposed at least partially inside the cavity which transmits a load into the bladder. The spacer can be fabricated from, e.g., a 316 stainless steel, and the like. The bladder can transmit the load into at least one of the rotor and at least one diaphragm through uniform contact stresses. That is, in some embodiments the bladder transmits the load into the rotor. In certain embodiments, the bladder transmits the load in both the rotor and a first diaphragm. In other embodiments, the bladder transmits the load into the rotor, and two or more diaphragms. In some embodiments, the uniform contact stress reduces wear of at least one of the rotor, the stator, the bladder, and the at least one diaphragm. In certain embodiments, the uniform contact stress seals the at least one fluidic path. In embodiments, the uniform contact stress seals the at least one fluidic path as well as reduces wear of one or more of the rotor, stator, bladder, and at least one diaphragm. 
         [0010]    In accordance with embodiments of the present disclosure, exemplary methods of operating a rotary shear valve are provided that include providing a valve body that includes a rotor, a stator and a bladder. The exemplary methods generally include providing a stator and providing a rotor defining a cavity extending at least partially therethrough rotatably mounted relative to the stator to create at least one fluidic path therebetween. The exemplary methods include positioning a bladder comprising a polymer inside the cavity of the rotor. The exemplary methods further include transmitting a compressive stress into the bladder. Transmitting the compressive stress into the bladder generally distributes contact stresses between the rotor and the stator. 
         [0011]    In general, the exemplary methods include providing at least one diaphragm coupled to the rotor and providing a spacer disposed at least partially inside the cavity. The exemplary methods can include transmitting a compressive stress into the bladder via the spacer such that the bladder exhibits fluid-like properties and substantially distributes the compressive stress in at least two directions. The exemplary methods can include transmitting the compressive stress into at least one of the rotor and the at least one diaphragm via the bladder through uniform contact stresses. 
         [0012]    The above exemplary embodiments in accordance with the present disclosure provide many advantages. For example, one or more embodiments described herein create substantially uniform contact stresses between the rotor and stator to promote uniform wear and/or sealing of the fluidic paths. As a result, the exemplary rotary shear valves can be implemented in a variety of operating conditions, including those beyond about 20,000 psi. 
         [0013]    Other advantages and features will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    To assist those of skill in the art in making and using the disclosed rotary shear valves and associated methods, reference is made to the accompanying figures (which are not necessarily to scale), wherein: 
           [0015]      FIG. 1  shows a side view of a rotary shear valve of the prior art; 
           [0016]      FIG. 2  shows a cross-sectional view of an exemplary rotary shear valve; 
           [0017]      FIG. 3  shows a cross-sectional view of an exemplary rotary shear valve with an integrated diaphragm; 
           [0018]      FIG. 4  shows a cross-sectional view of an exemplary rotary shear valve with two separate diaphragms; 
           [0019]      FIG. 5  shows a cross-sectional view of an exemplary rotary shear valve with an integrated diaphragm and a separate diaphragm; and 
           [0020]      FIG. 6  shows a cross-sectional view of an exemplary rotary shear valve with an integrated diaphragm. 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0021]    With reference to  FIG. 1 , a traditional rotary shear valve  10  is illustrated with a one-piece rotor  12  and a stator  14  having a sealing surface  16 . A preload  18  of, e.g., approximately 650 lbs, can generally be applied to the rotor  12  to maintain contact between the rotor  12  and the stator  14  at the sealing surface  16 . However, due to the one-piece rotor  12  in contact with the flat sealing surface  16  of the stator  14 , the traditional rotary shear valve  10  can exhibit non-uniform contact stresses  20  at the sealing surface  16 . In particular, the contact stresses  20  can generally be lowest at the center and gradually increase from the center in the direction of the edges of the stator  14  sealing surface  16 . As discussed above, the non-uniform contact stresses  20  at the sealing surface  16  between the rotor  12  and the stator  14  can cause non-uniform wear of the rotor  12  and/or the stator  14  and can fail to properly seal the fluidic paths  22  between the rotor  12  and stator  14 . 
         [0022]    The relationship between stress and strain can be determined by utilizing Hooke&#39;s Law as shown by Equation 1 below: 
         [0000]      σ= E×ε   (1)
 
         [0000]    where σ represents stress, E represents Young&#39;s Modulus and ε represents strain. As an example, a traditional rotor  12  may have a thickness of approximately 0.140 inches, a modulus of approximately 28 million psi for a stainless steel, a rotor thickness variation of approximately 0.000050 inches, and a stress of approximately 10,000 psi. To fluidically seal at approximately 25,000 psi, the contact stresses  20  must exceed the fluid pressure and be near approximately 28,000 psi. Having a potentially 10,000 psi variation in contact stresses  20  can lead to uneven and excessive wear of the rotor  12 . 
         [0023]    Turning now to  FIG. 2 , a cross-sectional view of an exemplary (i.e., in accordance with an embodiment of the present technology) rotary shear valve  100 , e.g., a rotary selector valve such as a rotary injector valve with three rotor grooves, a rotary vent valve with two rotor grooves, and a rotary column selection valve with one radial groove, is provided which includes a three-piece rotor  102  and a stator  104 . The rotor  102  and the stator  104  can be aligned along a central vertical axis A 1 . The rotor  102  and the stator  104  can further rotate relative to each other about the central vertical axis A 1 . The rotor  102  generally defines a rotor groove (not shown) and the stator  104  generally defines at least one stator port  105  for creation of fluidic paths between the rotor  102  and stator  104 . In some embodiments, the stator  104  can be fabricated from, e.g., a titanium alloy, a 316 stainless steel, an MP35N alloy, and the like. In some embodiments, the stator  104  can include a coating, e.g., a nanofilm diamond-like coating (DLC), and the like. The material of fabrication for the stator  104 , e.g., a titanium alloy with a modulus of approximately 14,000,000 psi, and the like, can exhibit a lower modulus and be more compliant or compatible with the material of fabrication for the rotor  102  to improve the sealing capability against the rotor  102 . The coating on the stator  104  generally reduces the amount of friction between the stator  104  and other components of the rotary shear valve  100 . In some embodiments, the stator  104  can be fabricated from a material containing iron content and the DLC coating can act to prevent the iron content from rusting after being exposed due to wear. 
         [0024]    The rotary shear valve  100  includes a ram shaft  110  including a shaft  109  and a shaft/rotor interface  111 . The shaft  109  can extend from the shaft/rotor interface  111  along the central vertical axis A 1  and engage with a mechanism configured to rotatably drive the shaft  109  about the central vertical axis A 1 . The shaft/rotor interface  111  can include two or more apertures  113  configured and dimensioned to receive pins  112  for engaging complementary apertures  115  in the rotor  102 . When inserted in the respective apertures, the pins  112  can detachably interlock the ram shaft  110  with the rotor  102 . Thus, as the ram shaft  110  axially rotates about the central vertical axis A 1 , the pins  112  engage the apertures  115  in the rotor  102  to simultaneously axially rotate the rotor  102  relative to the stator  104 . 
         [0025]    In some embodiments, the ram shaft  110  can include a cavity  117 , e.g., a groove, centrally positioned on the face of the shaft/rotor interface  111  adjacent to the rotor  102 . The cavity  117  can be configured to receive a ball bearing  114  for supporting the rotor  102 . The ball bearing  114  can define a substantially circular top face for mating relative to the complementary cavity  117  surface and a substantially planar bottom face for mating relative to the rotor  102  or components of the rotor  102 . In some embodiments, the cavity  117  can further include a grease well  116  configured and dimensioned to receive a lubricant for lubricating the contact area in the cavity  117  between the ball bearing  114  and the shaft/rotor interface  111  of the ram shaft  110 . In some embodiments, a spacer  120  can be positioned between the substantially planar bottom face of the ball bearing  114  and the components of the rotor  102 . The spacer  120  can be fabricated from, e.g., a 316 stainless steel, and the like. In some exemplary embodiments, the spacer  120  can be fabricated from alternative heat-treated stainless steel materials in order to strengthen the spacer  120  for transfer of forces against a bladder  126 . The rotary shear valve  100  assembly can be surrounded by a bushing  118 . 
         [0026]    The exemplary three-piece rotor  102  generally includes a rotor body  122  which defines a cavity  124  axially centered along the central vertical axis A 1 . The cavity  124  can extend at least partially through the rotor body  122 . In some embodiments, the cavity  124  can be configured as substantially cylindrical. However, it should be understood that in some embodiments, the cavity  124  can be configured in a variety of shapes. In the exemplary embodiment illustrated in  FIG. 2 , the rotor body  122  defines cavity  124  extending through the entire rotor  102 , e.g., extending from a top surface to the bottom surface of the rotor body  122  along the central vertical axis A 1 . 
         [0027]    In some embodiments, the rotor  102  can be fabricated from a non-stainless steel material to reduce or prevent rust formation and can have a thickness of, e.g., approximately 0.140 inches. Steel alloys generally include a significant percentage of iron. As the rotor  102  begins to wear due to interaction with the stator  104 , the passive chromium oxide layer of stainless steel materials which provides corrosion resistance can be penetrated. Once penetrated, the iron underneath the layer, if exposed to air and/or water, can begin to rust. Rust can thereby enter the chromatographic mobile phase (e.g., CO 2  flowstream), a contamination which cannot be tolerated. Thus, in some embodiments, the rotor  102  can be fabricated from a non-stainless steel material, e.g., a cobalt alloy, a nickel alloy, and the like, with no iron content to reduce or prevent rust formation. 
         [0028]    The cavity  124  of the rotor body  122  can be configured and dimensioned to receive a bladder  126  therein. For example,  FIG. 2  illustrates the rotor  102  including the bladder  126  positioned within the cavity  124  such that the bladder  126  does not extend outside of the cavity  124 . The bladder  126  can be fabricated from a low compressive yield strength polymer, e.g., a polytetrafluoroethylene (PTFE), an ultra-high-molecular-weight polyethylene (UHMWPE), and the like. As will be discussed in greater detail below, upon transmission of a compression stress against the bladder  126  with the bearing  114  and/or the spacer  120 , the bladder  126  can exhibit substantially fluid-like properties. 
         [0029]    In the exemplary embodiment of  FIG. 2 , the rotor  102  includes a diaphragm  128 , e.g., a separate membrane, coupled to the bottom surface of the rotor body  122  by coupling means such as welding, e.g., electron beam welding, laser beam welding, friction welding and the like, with or without filler materials. The diaphragm  128  can be fabricated from a metal material, e.g., a stainless steel alloy, a UNS S21800 steel, an MP35N alloy, a cobalt alloy, a nickel alloy, and the like. The diaphragm  128  can act to hermetically seal the rotor  102  such that the fully-constrained compliant backing, e.g., the bladder  126 , can be contained therein. Thus, when the diaphragm  128  has been secured to the rotor body  122 , the rotor body  122  and the diaphragm  128  can essentially become integral parts. It should be understood that the coupling means for securing or coupling the diaphragm  128  to the rotor body  122  should be sufficiently strong to resist the torque created by the rotating ram shaft  110  between the stator  104  substrate and the rotor  102 . 
         [0030]    A preload  108 , e.g., a compressive stress, axially applied to a shaft/rotor interface  111  of the ram shaft  110  in a direction parallel to the central vertical axis A 1  can transfer through the ball bearing  114  (into the optional spacer  120 ) and further into the bladder  126 . Upon transmission of the preload  108  against the bladder  126 , the bladder  126  can exhibit substantially fluid-like properties within the cavity  124 . The bladder  126  can thereby evenly transfer the compressive forces from the preload  108  against the inner walls of the cavity  124 , the spacer  120  and the diaphragm  128 . Further, the compressive forces of the preload  108  can be evenly distributed by the diaphragm  128  against the sealing surface  106  of the stator  104 . The alignment of the ram shaft  110 , the ball bearing  114 , the spacer  120  and the diaphragm  128  along the central vertical axis A 1  ensures a self-aligned loading and transfer of the preload  108 . 
         [0031]    In some embodiments, the diaphragm  128  can measure approximately 0.024 inches in thickness. In some exemplary embodiments, the diaphragm  128  thickness can be thinner or thicker than 0.024 inches. In general, the diaphragm  128  is sized to adequately absorb and uniformly transfer the compressive forces created by the bladder  126  against the sealing surface  106  of the stator  102 . In particular, during operating conditions of the rotary shear valve  100 , the pressure applied against the bladder  126  can cause the bladder  126  to yield and exhibit substantially fluid-like properties such that the bladder  126  substantially evenly distributes the forces against the inner walls of the cavity  124 , the spacer  120  and the diaphragm  128 . As would be understood by those of ordinary skill in the art, since the bladder  126  is fully constrained within the cavity  124  of the rotor  102  at all surfaces, (e.g., by the spacer  120 , the walls of the cavity  124  and the diaphragm  128 ) substantially all of the stresses created by the preload  108  can be sustained. Substantially uniform stresses are therefore applied to the thin diaphragm  128  and further transferred against the sealing surface  106  of the stator  104 . 
         [0032]    The uniform stresses distributed by the bladder  126  against the diaphragm  128  ensure that, rather than increasing from the center to the edges of the sealing surface  106 , the contact stresses are uniformly distributed along the sealing surface  106 . In some embodiments, the uniform contact stresses promote even wear of the rotor  102  and/or the stator  104 . In some embodiments, the uniform contact stresses create the desired sealing pressure of the fluidic paths at the sealing surface  106 . In some embodiments, the sealing surface  106 , e.g., the sealing interface, can be substantially flat or planar rather than having a complex form in order to uniformly mate with the rotor  102  and/or the diaphragm  128  and to simplify the manufacturing process of the stator  104 . In some exemplary embodiments, the sealing surface  106  diameter can be approximately 0.170 inches and can withstand, e.g., approximately 25,000 psi, 28,000 psi, and the like, in contact stresses. 
         [0033]      FIG. 3  illustrates an exemplary assembly of a stator  104  of  FIG. 2  with an exemplary embodiment of a rotor  202 . The rotor  202  and the stator  104  can be aligned along the central vertical axis A 2 . The rotor  202  can include a rotor body  222  which defines a cavity  224  passing only partially therethrough, e.g., passing from the top surface of the rotor body  222  and extending only partially through the rotor body  222  in the direction of the bottom surface of the rotor body  222  along the central vertical axis A 2 . It should be understood that in some embodiments, the cavity  224  can pass from the bottom surface of the rotor body  222  and extend only partially through the rotor body  222  in the direction of the top surface of the rotor body  222  along the central vertical axis A 2 . In particular, the cavity  224  can extend partially through the rotor body  222  such that an integrated diaphragm  232  is formed at either the top and/or bottom surface of the rotor body  222 . The integrated diaphragm  232  can be configured to function substantially similarly to the separate diaphragm  128  discussed with respect to the embodiment of  FIG. 2 . Thus, rather than coupling the diaphragm  128  to the rotor  102  such that the diaphragm  128  is substantially integral with the rotor  102 , the integrated diaphragm  232  can be formed from the rotor body  222  by creating a cavity  224  partially therethrough. 
         [0034]    Similar to the rotor  102  of  FIG. 2 , in some embodiments, the rotor  202  can include a spacer  220  which transfers a preload  208  against the bladder  226  which is disposed in the cavity  224  and positioned against the integrated diaphragm  232 . The fluid-like property of the bladder  226  upon application of the compressive preload  208  forces from the spacer  220  allows the bladder  226  to evenly distribute the preload  208  force against the inner surfaces of the cavity  224 , the spacer  220  and the integrated diaphragm  232 . The diaphragm  232 , in turn, evenly transfers the compressive forces against the sealing surface  106  of the stator  104 . Substantially uniform contact stresses  230  are thereby created between the diaphragm  232  and the sealing surface  106  of the stator  104 . In particular, the integrated diaphragm  232  can be dimensioned such that the bladder  226  can evenly transmit the preload  208  forces through the integrated diaphragm  232  and against the sealing surface  106 . For example, the integrated diaphragm  232  can have a thickness of approximately 0.024 inches. However, it should be understood that the thickness of the integrated diaphragm  232  can be dimensioned greater or less than 0.024 inches in other embodiments such that the integrated diaphragm  232  is capable of evenly transferring the compressive forces imparted upon the diaphragm  232  by the bladder  226 . 
         [0035]    With reference to  FIG. 4 , an exemplary rotor  302  having a cavity  324  extending through the entire rotor body  322  is provided. In particular, the cavity  324  can centrally extend from the top surface to the bottom surface of the rotor body  322  along the central vertical axis A 3 . The rotor  302  includes two separate diaphragms  328   a  and  328   b  coupled to the rotor body  322  at the cavity  324  openings such that the two diaphragms  328   a  and  328   b  are essentially integral with the rotor body  322 . In some embodiments, the rotor body  322  can include a circumferential step or groove surrounding the cavity  324  openings configured and dimensioned to receive one of the two diaphragms  328   a  and  328   b . The bladder  326  can be disposed and sealed within the cavity  324  between the two diaphragms  328   a  and  328   b  by coupling the diaphragms  328   a  and  328   b  to the top and bottom surfaces of the rotor body  322 . Although illustrated as being offset from the planar surface of the rotor body  322 , in some embodiments, one or both of the diaphragms  328   a  and  328   b  can be substantially aligned and planar with the surface of the rotor body  322 . 
         [0036]    In some embodiments, the top diaphragm  328   a  can be positioned against the planar bottom surface of the ball bearing  114  and/or a spacer  120  of  FIG. 2  such that a preload, e.g., a compressive force, can be transferred into the bladder  326  and the bottom diaphragm  328   b . In particular, the top diaphragm  328   a  can receive the preload and transfer the preload to the bladder  326  contained within the cavity  324 . As discussed previously, the fluid-like property of the bladder  326  during operating conditions, e.g., application of a compressive stress against the bladder  326 , results in substantially uniform forces being transmitted to the inner walls of the cavity  324  and the two diaphragms  328   a  and  328   b . Substantially uniform contact stresses are thereby created by the bottom diaphragm  328   b  against the sealing surface of the stator  104 . 
         [0037]    With reference to  FIG. 5 , an exemplary rotor  402  having a cavity  424  extending partially through the rotor body  422  is provided. In particular, the cavity  424  can centrally and partially extend from the bottom surface of the rotor body  422  in the direction of the top surface of the rotor body  422  along the central vertical axis A 4 . In particular, the partially extending cavity  424  can form an integrated diaphragm  432  in top surface of the rotor body  422 . The cavity  424  opening at the bottom surface of the rotor body  422  can include a circumferential step or groove configured and dimensioned to receive a separate diaphragm  428  for coupling to the rotor body  422 . A bladder  426  can be positioned and sealed within the cavity  424  between the integrated diaphragm  432  and the separate diaphragm  428 . Although illustrated as being offset from the planar surface of the rotor body  422 , in some embodiments, the separate diaphragm  428  can be substantially aligned and planar with the surface of the rotor body  422 . 
         [0038]    In some exemplary embodiments, the integrated diaphragm  432  can include a relief slot  434  or groove circumferentially surrounding the integrated diaphragm  432  about the central vertical axis A 4  to allow for increased flexure of the integrated diaphragm  432  (as indicated by the dashed lines), thereby permitting additional and/or improved transmission of preload forces to the bladder  426 . For example, the relief slot  434  can increase the flexibility of the integrated diaphragm  432  such that the integrated diaphragm  432  can bend in the direction of the bladder  426  to more effectively transfer preload forces applied to the rotor  402 . 
         [0039]      FIG. 6  illustrates an exemplary rotor  502  having a cavity  524  extending partially through the rotor body  522 . In particular, the cavity  524  can centrally and partially extend from the top surface of the rotor body  522  in the direction of the bottom surface of the rotor body  522  along the central vertical axis A 5 . In particular, the partially extending cavity  524  can form an integrated diaphragm  532  along the bottom surface of the rotor body  522 . A bladder  526  can be disposed within the cavity  524  and positioned against the integrated diaphragm  532 . A spacer  520  can be positioned at least partially within the cavity  524  and against the bladder  526  to transfer a preload to the bladder  526 , the integrated diaphragm  532  and the sealing surface of the stator. Translation of the spacer  520  along the central vertical axis A 5  can be aligned by partially translating the spacer  520  within the cavity  524  as a preload is applied to maintain a substantially even distribution of preload forces against the bladder  526 . 
         [0040]    In operation, the valves discussed herein are configured to receive a compressive stress into a bladder positioned within a cavity such that the bladder distributes substantially uniform contact stresses between the rotor and the stator. The substantially uniform contact stresses created between the rotor and the stator promote uniform wear and sealing of the fluidic paths. The substantially uniform contact stresses between the rotor and the stator also allow operation of the valve beyond 20,000 psi. 
         [0041]    While exemplary embodiments have been described herein, it is expressly noted that these embodiments should not be construed as limiting, but rather that additions and modifications to what is expressly described herein also are included within the scope of the invention. Moreover, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations, even if such combinations or permutations are not made express herein, without departing from the spirit and scope of the invention.