Patent Publication Number: US-2023138406-A1

Title: Rotary valve with compensation element to compensate for axial misalignment

Description:
RELATED APPLICATIONS 
     The present application claims the benefit of German patent application No. 10 2021 128 649.2, filed on Nov. 3, 2021, which is hereby incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to flow elements, particularly for HPLC applications. 
     BACKGROUND ART 
     In high performance liquid chromatography (HPLC), a liquid must be conveyed at typically very precisely controlled flow rates (e.g., in the range of nanoliters to milliliters per minute) and at a high pressure (typically 20-100 MPa and beyond, currently up to about 200 MPa), taking into account the respective compressibility. For liquid separation in an HPLC system, a mobile phase, which—in operation—comprises a sample liquid with components to be separated, is driven through a stationary phase (such as a chromatographic column) in order to separate different components of the sample in this way. In doing so, the composition of the mobile phase can be constant over time (isocratic mode) or vary (e.g. in the so-called gradient mode). 
     Valves are frequently used in liquid chromatography to either enable or interrupt flow paths, e.g. of the mobile phase. Typically, rotary valves (shear valves) are used, in which a rotor can be moved in rotation relative to a stator in order to switch corresponding flow paths. At the high pressures common in HPLC in the range of 100 MPa and more, a suitable fluidic seal is required especially between the stator and rotor. For this purpose, the rotor and stator are usually subjected to a high axial contact pressing force in order to achieve the fluidic seal. Mechanical tolerances, wear and other influencing variables can counteract the fluidic seal. 
     DE102012107378A1 describes a switching valve for liquid chromatography with a compensation element for acting on the rotor to transmit an axial contact pressing force to the stator. The compensation element comprises a bending area which allows elastic bending deformation in such a way that even if the rotor wobbles, it is subjected to the full surface pressure. 
     SUMMARY 
     It is an object of the present disclosure to improve the fluidic sealing of a rotary valve, especially for HPLC applications. 
     One embodiment relates to a valve, preferably in a high performance chromatography system for separating components of a sample liquid introduced into a mobile phase. The valve comprises a rotor and a stator, wherein a flow path can be established or inhibited by a rotational movement of the rotor relative to the stator. The valve further comprises a compensation element which is axially arranged together with the rotor and the stator, and which, in an operating state of the valve, effects an axial pressing of the rotor against the stator. The compensation element comprises at least one spherical surface to compensate for axial misalignment between the rotor and the stator. The compensation element can thus form one or more bearing points that can roll spherically on each other. The compensation element may thus have one or more pivot points to counteract and preferably compensate for the axial misalignment between the rotor and the stator. The compensation element can further also reduce or compensate for lateral misalignment, for example of the rotor, for example by the compensation element allowing tilting in the axial direction. 
     In one embodiment, the compensation element comprises one or more pivot points, each formed by a spherical surface. 
     In one embodiment, the pivot point or pivot points each comprise a bearing location where two of the spherical surfaces roll on each other. 
     In one embodiment, the compensation element comprises two spherical surfaces, so that in case of an axial misalignment between the rotor and the stator, the spherical surfaces can move against each other to compensate for the axial misalignment. 
     In one embodiment, the compensation element is configured to compensate for a lateral offset of the rotor relative to the stator. 
     In one embodiment, the compensation element is arranged together with the rotor and the stator axially in the direction of an axis of rotation of the rotor. 
     In one embodiment, the compensation element is configured such that in the operating state of the valve, an axial force acts on the at least one spherical surface to cause the axial pressing of the rotor with respect to the stator. 
     In one embodiment, the valve comprises a drive for moving the rotor. 
     In one embodiment, the drive comprises a rotatable shaft that can in particular be driven by a motor. 
     In one embodiment, the compensation element is arranged axially between the drive and the rotor or the stator. 
     In one embodiment, the compensation element is arranged axially between a housing of the valve and the stator. Preferably, the compensation element acts axially on a first side of the stator, the drive acts via the rotor on a second side, and the second side is arranged axially opposite to the first side. 
     In one embodiment, the compensation element comprises a first end and a second end axially disposed in opposite directions in the operating state of the valve, wherein the first end comprises a first spherical surface such that the compensation element can tilt axially at the first spherical surface to compensate for the axial misalignment between the rotor and the stator. 
     In one embodiment, the second end of the compensation element comprises a second spherical surface such that the compensation element can tilt at the second spherical surface to compensate for the axial misalignment between the rotor and the stator, wherein in particular a direction of lift-off at the second spherical surface is opposite to a direction of lift-off at the first spherical surface. 
     In one embodiment, the compensation element has an elongated shape in the axial direction. 
     In one embodiment, the compensation element comprises at least one ball joint with at least one spherical surface, in particular two ball joints at axially opposite ends of the compensation element. 
     In one embodiment, by a relative movement of the rotor with respect to the stator, a first effective surface of the rotor can be brought into contact or connection with a second effective surface of the stator and a flow path can be established or inhibited. 
     In one embodiment, the valve is a high pressure switching valve for high performance liquid chromatography. 
     In one embodiment, the valve comprises a housing in which one or more of the rotor, the stator, the drive, and the compensation element are disposed. 
     In one embodiment, the stator comprises a plurality of connection ports, each for being able to provide a fluidic coupling. 
     In one embodiment, the rotor cooperates with the stator in predetermined switching positions defined by associated angular positions to fluidically connect or disconnect predetermined connection ports. 
     In one embodiment, the rotor is rotatably mounted by means of, in particular in a disposed bearing and pressing device, and is subjected to a predetermined pressing force in the direction of the stator. 
     In one embodiment, the bearing and pressing device comprises the compensation element that acts on the rotor to transmit the pressing force. 
     In one embodiment, the compensation element comprises a head portion that acts on the rotor with an application surface. 
     In one embodiment, the compensation element comprises a foot portion with which the compensation element is supported against a unit of the bearing and pressing device that generates the pressing force or against an element of the bearing and pressing device that transmits the pressing force. 
     In one embodiment, the compensation element is configured in such a way that the application surface of the head region impacts the rotor over the entire surface, even during wobbling movements of the rotor, in any angular position of the rotor, and a substantially uniform pressure distribution is thereby generated in the plane of contact between the rotor and the stator. 
     In one embodiment, the compensation element is formed as a rod-shaped element, and it is in particular made of steel or ceramic. 
     In one embodiment, the rotor is axially fixed within the valve and the stator is configured such that it can elastically align with respect to the rotor. 
     In one embodiment, the stator is axially fixed within the valve and the rotor is configured such that it can elastically align with respect to the rotor. 
     In one embodiment, the rotor comprises a first effective surface and the stator comprises a second effective surface. By a relative movement of the rotor relative to the stator, the first effective surface can be brought into contact or connection with the second effective surface and a flow path can be established or inhibited. The stator comprises an elastic region to compensate for an axial angle between the rotor and the stator so that the first effective surface and the second effective surface can be aligned parallel to each other. 
     In one embodiment, the stator comprises an outer region and an inner region, the inner region comprises the second effective area, and the outer region is connected to the inner region via the elastic region so that the inner region is elastically movable relative to the outer region through the elastic region. 
     In one embodiment, the outer portion is fixed with respect to the rotor and the inner portion can elastically align with respect to the rotor. 
     In one embodiment, the elastic region comprises one or more webs, each of which is connected to the outer region on one side and to the inner region on the opposite side, such that the inner region can tilt with respect to the outer region. 
     One embodiment relates to a high performance chromatography system comprising a pump for moving a mobile phase, a stationary phase for separating components of a sample liquid introduced into the mobile phase, and a valve according to any of the previously mentioned embodiments for establishing or inhibiting a flow path of the mobile phase. 
     One embodiment relates to a method, in particular in a high performance chromatography system, for separating components of a sample liquid introduced into a mobile phase. The method relates to a valve comprising a rotor and a stator, wherein a flow path can be established or inhibited by rotational movement of the rotor relative to the stator. The method comprises compensating for an axial misalignment between the rotor and the stator by forming a pivot point on at least one spherical surface. 
     Embodiments of the present disclosure can be carried out on the basis of many of the known HPLC systems, such as the Agilent Infinity Series 1290, 1260, 1220, and 1200 systems from the applicant Agilent Technologies, Inc., see www.agilent.com. 
     A pure solvent or a mixture of different solvents can be used as mobile phase (or eluent). The mobile phase can be chosen such as to minimize the retention time (response time) of liquid components of interest and/or the amount of mobile phase for conducting the chromatography. The mobile phase can also be chosen such that specific components are effectively separated. It may comprise an organic solvent, such as methanol or acetonitrile, which is often diluted with water. For a gradient operation, water and an organic solvent (or other solvents commonly used in HPLC) are often varied in their mixing ratio over time. 
     One or more of the methods explained above may be controlled, supported or executed in whole or in part by software when running on a data processing system, such as a computer or workstation. The software may be stored on a data carrier in the process or for this purpose. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure is further explained below with reference to the drawings, wherein like reference characters refer to like or functionally like or similar features. 
         FIG.  1    shows an example of a liquid separation system according to embodiments of the present disclosure, as used, for example, in HPLC. 
         FIG.  2    shows an example of a valve, as it can for example be used in a sample injector of a liquid separation system, according to an embodiment of the present disclosure. 
         FIG.  3    shows schematically and in sectional view an example of a valve according to another embodiment of the present disclosure. 
         FIG.  4 A  is a schematic cross-sectional view of an example of a valve according to another embodiment of the present disclosure. 
         FIG.  4 B  illustrates exemplarily and schematically an alternative embodiment of a compensation element of a valve compared to  FIG.  4 A . 
         FIG.  5    shows an example of an elastic stator in sectional view (top) and schematic top view (bottom), such as may be utilized in the valve illustrated in  FIG.  4 A , according to an embodiment of the present disclosure. 
         FIG.  6    shows schematically and in sectional view an example of a valve according to another embodiment of the present disclosure. 
         FIG.  7    shows schematically and in sectional view an example of a valve according to another embodiment of the present disclosure. 
         FIG.  8    shows schematically and in sectional view an example of a valve according to another embodiment of the present disclosure. 
         FIG.  9    shows schematically and in sectional view an example of a valve according to another embodiment of the present disclosure. 
         FIG.  10    shows schematically and in sectional view an example of a valve according to another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Specifically,  FIG.  1    shows a general illustration of a liquid separation system  10 . A pump  20  receives a mobile phase from a solvent supply  25 , typically via a degasser  27 , which degasses the mobile phase and thereby reduces the amount of dissolved gases in the mobile phase. The pump  20  drives the mobile phase through a separation device  30  (such as a chromatographic column), which has a stationary phase. A sample device (or sample injector)  40  may be provided between the pump  20  and the separation device  30  to deliver a sample fluid into the mobile phase. A fluidic conduit between the pump  20  and the sample injector  40  shall be denoted by a reference numeral  41 , and a fluidic conduit between the sample injector  40  and the separation device  30  shall be denoted by a reference numeral  42 . The stationary phase of the separation device  30  is adapted to separate components of the sample fluid. A detector  50  detects separated components of the sample fluid, and a fractioning device  60  may be provided to output the separated components. 
     The mobile phase may comprise only one solvent or a mixture of different solvents. The mixing can be done at low pressure and upstream of the pump  20 , so that the pump  20  already conveys the mixed solvent as mobile phase. Alternatively, the pump  20  may comprise individual pump units, each pump unit conveying one solvent or solvent mixture at a time, so that the mixing of the mobile phase (as then seen by the separation device  30 ) occurs at high pressure and downstream of the pump  20 . The composition (mixture) of the mobile phase may be kept constant over time (isocratic mode) or varied over time in a so-called gradient mode. 
     A data processing unit  70 , which may be a conventional personal computer or a workstation, may be coupled to one or more of the devices in the fluid separation system  10 , as indicated by the dashed arrows, to receive information and/or to control the operation of the system or individual components therein. 
       FIG.  2    shows an example of a valve  200 , such as it may be used in the sample injector  40 , e.g. for injecting the sample fluid into the mobile phase. Such injectors including switchable valves are sufficiently known in the prior art, such as from WO2010139359A1, US20160334031A1 or US2017343520A1, all of the same applicant. The first two documents show the injector in a so-called flow-through configuration, in which a sample loop containing the sample fluid is connected between the pump and the separation device during injection. The third document, on the other hand, describes an injector in the so-called feed-injection configuration, in which the sample fluid is pressed or forced into the mobile phase between the pump and the separation device by means of a T-coupling, so that a sample flow containing the sample fluid is added to the flow of the mobile phase. 
     The valve  200  exemplarily shown in  FIG.  2    is a so-called rotary valve, in which a rotor  210  and a stator  220  rotate relative to each other, wherein the rotor  210  is typically being rotated with respect to the stator  220 . Both the rotor  210  and the stator  220  may thereby have so-called ports in them, each presenting an open end to a respective flow path that may be connected to the valve  200  via respective ports  230 A,  230 B, etc. Furthermore, both rotor  210  and stator  220  can comprise corresponding connecting elements (e.g. recesses such as notches, grooves etc.) which can fluidically connect one or more ports with each other by relative movement of rotor  210  and stator  220 . This is shown only schematically in  FIG.  2    and is sufficiently known in the prior art, e.g. from the documents mentioned above. It is also known that so-called translation valves can be used as an alternative to rotary valves, in which a translational movement is performed instead of a rotational movement. 
     In the exemplary embodiment of  FIG.  2   , the valve  200  further shows a drive  240  for moving the rotor  210 , for example a rotatable shaft that may be driven by a motor, for example. The drive  240  may be fixedly connected to the rotor  210  or may even be an integral part thereof. The drive  240  together with the rotor  210  is preferably elastically/resiliently pressed against the stator  220 , e.g. by means of a spring assembly  250 . Rotor  210 , drive  240  and spring assembly  250  may be arranged in a housing  260 . The stator  220  together with the connections  230  may preferably be arranged in a valve head  270 , which may be connected to the housing  260 , for example by means of a screw connection  270 . 
     For example, the valve  200  may be connected such that the fluidic conduit  41  is connected to the port  230 A and the fluidic conduit  42  is connected to the port  230 B. By suitable design of the rotor  210  and the stator  220 , in particular by design of suitable connecting elements, a desired functionality in the fluidic coupling between the fluidic conduits  41  and  42  can be designed, as is sufficiently known in the prior art. 
     In order to bring about fluidic tightness, e.g. in the fluid path between the conduits  41  and  42 , between the rotor  210  and the stator  220 , in the prior art an appropriate dimensioning of the spring assembly  250  or another static biasing mechanism is usually proposed so that the rotor  210  presses axially against the stator  220  with a desired sealing force F (i.e. in the direction of the sealing force F). A sealing force F that is too low can result in leakage (in particular between rotor  210  and stator  220 ), while a sealing force F that is too high can result in increased wear (in particular of the friction components between rotor  210  and stator  220 ). 
       FIG.  3    shows schematically and in sectional view an embodiment of a valve  300 , which essentially corresponds to the valve  200  shown in  FIG.  2   , so that reference numerals are used accordingly. The housing  260  (not shown in  FIG.  3   ) contains the rotor  210 , which abuts against the stator  220  and can be driven in rotation by the drive  240 . A bearing (not shown in  FIG.  3   ), e.g. an axial thrust bearing, can support the drive  240  in axial direction. 
     The valve  300  further comprises a compensation element  310  to accomplish an axial pressing of the rotor  210  with respect to the stator  220 . For this purpose, the compensation element  310  is arranged together with the rotor  210  and the stator  220  in the axial direction of the valve  300 , where axial is to be understood with respect to an axis of rotation of the valve  300 . In order to be able to compensate for an axial misalignment or offset between the rotor  210  and the stator  220 , the compensation element  310  comprises at least one spherical surface  320 , which will be discussed in more detail below. 
     In the embodiment according to  FIG.  3   , the compensation element  310  is arranged in an axial recess or cavity  340  of the drive  240 , wherein one or more preferably elastic elements  350 , such as the O-rings  350 A and  350 B shown in  FIG.  3   , may be arranged radially between the compensation element  310  and a surface of the axial cavity  340  to support and position the compensation element  310  within the axial cavity  340 . The resilient elements  350  may also facilitate mounting of the valve  300 , in particular the compensation element  310  within the drive  240 . 
     In the embodiment according to  FIG.  3   , the compensation element  310  comprises an elongated base body  360  extending substantially in the axial direction. The elongated base body  360 , which may be a cylinder for example, comprises a spherical surface  320 A at its upper (with respect to the embodiment in  FIG.  3   ) end face and a spherical surface  320 B at its lower end face. 
     In the initial example shown in  FIG.  3   , a further spherical surface  320 C is shown extending along an axial end face of a spacer element  370  and facing the spherical surface  320 A. This spacer element  370  can be associated (spatially) with either the compensation element  310  or, in this case, the stator  210  and interacts functionally with the compensation element  310 . 
     Furthermore, one or more drivers  380 A,  380 B, etc. can be arranged between the drive  240  and the rotor  210 , which are inserted loosely between the drive  240  and the rotor  210 , for example as pins, and which effect transmission of a rotational movement of the drive  240  to the rotor  210  in the sense of an inhibitor or a locking mechanism, preferably without thereby firmly coupling the rotor  210  (in particular axially) with respect to the drive  240 . Accordingly, other mechanical designs are also possible in the transfer and transmission of the rotational movement. 
     In the schematically illustrated embodiment example according to  FIG.  3   , the compensation element  310  is designed and arranged or fastened in the valve  300  in such a way that an axial angular offset between stator  220  and rotor  210  can be compensated at least to a certain degree and thus the effective surfaces of stator  220  and rotor  210  lie parallel opposite or flat against each other, as shown in  FIG.  3   . 
     In the embodiment shown in  FIG.  3   , the compensation element  310  forms two bearing locations  390 , namely a first bearing location  390 A and a second bearing location  390 B. The first bearing position  390 A is formed by the spherical surface  320 B, which can roll off with respect to an axial end surface  395  of the axial recess  340 . The second bearing position  390 B is formed by the two adjacent spherical surfaces  320 A and  320 C, which can roll on each other. 
     In the example shown in  FIG.  3   , the stator  220  is intentionally shown at an exaggerated axial angle relative to the drive  240 , e.g., due to or caused by appropriate tolerances, abrasion, and/or a less than optimal assembly. The compensation element  310  may tilt relative to the axis of rotation of the drive  240  at the first bearing location  390 A, squeezing the upper O-ring  350 A on the right and the lower O-ring  350 B on the left (each in the drawing representation shown in  FIG.  3   ). The spacer element  370  is tilted at the second bearing location  390 B relative to the compensation element  310 , so that as a result the active surfaces of rotor  210  and of stator  220  are flat opposite to each other and pressed against each other. The drivers  380  allow such tilting of the rotor  210  relative to the drive  240 . 
     In addition to compensating for any axial angular misalignment between rotor  210  and stator  220 , both bearing locations  390 A and  390 B also allow no or little lateral radial misalignment between rotor  210  and stator  220  to result from such axial angular misalignment. 
     The number and positioning of the spherical surfaces  320  is not limited or fixed according to the exemplary embodiment according to  FIG.  3   . For example, the axial end face  395  could also be designed as a spherical surface. Alternatively, only a single spherical surface  320  could also be sufficient to achieve an axial compensation between rotor  210  and stator  220 , in which case a lateral radial offset or misalignment between rotor  210  and stator  220  may result. 
       FIG.  4 A  illustrates schematically and in sectional view another embodiment of a valve  300  substantially corresponding to the one shown in  FIG.  3   . The stator  220  is fixedly connected to the housing  260 , e.g. by means of appropriate mechanical fasteners. An optional thrust bearing  240 L supports the drive  240  in the axial direction. The housing  260  may be of one-piece construction or of multiple-piece construction, such as two-piece construction for simplified assembly, as shown in  FIG.  4 A . 
     Furthermore, in the embodiment shown in  FIG.  4 A , the stator  220  is elastic in that it can elastically align itself axially and/or radially with respect to the rotor  210  despite being rigidly connected to the housing  260 , as is deliberately exaggerated in  FIG.  4 A . To this end, in the exemplary embodiment shown in  FIG.  4 A , the stator  220  is configured to include an elastic region  400  located between a mounting region  405  and an abutment region  410 . The attachment region  405  represents the region where the stator  220  is attached relative to the housing  260 . Preferably, and as exemplarily shown in  FIG.  4 A , fluidic connection points for fluidic coupling of the stator are located in or within the mounting region  405 . The abutment region  410  represents the area in which the stator  260  is in contact with the rotor  210 , i.e. in which the effective area of the stator  220  required for the valve function is located. 
     The compensation element  310  in the exemplary embodiment according to  FIG.  4 A  is formed by a spherical body  420 , an upper shell  425  and a lower shell  430 . Preferably, both the upper shell  425  and the lower shell  430  are designed with a spherical surface in their surface/side opposite or adjacent to the spherical body  420 , preferably concave, e.g. with a radius corresponding to or (in particular slightly) larger than that of the spherical body  420 . 
     The upper shell  425  or the lower shell  430  can also be firmly (integrally) connected to the spherical body  420 , e.g. by a suitable forming or bonding (e.g. soldering, welding, gluing, etc.). Correspondingly, the other shell  425 / 430  that is not fixedly connected to the spherical body  420  can then also be designed in such a way that its surface/side opposite the spherical body  420  does not have a spherical surface, but is designed to be planar, for example. In such an exemplary embodiment, the compensation element  310  then comprises only one spherical surface, namely that of the spherical body  420 , which is opposite or in contact with the shell  425 / 430  (which is not fixedly connected to the spherical body  420 ). The up to three elements of the compensation element  310  in the embodiment according to  FIG.  4 A  can also be appropriately pre-assembled and/or held together, for example, by means of a rubber hose, in order to accomplish a simplified assembly. 
     In the embodiment according to  FIG.  4 A , an axial pressing mechanism  435  (e.g., a corresponding screw mechanism, as exemplarily shown) preferably connected to the housing  260  may further be provided to position the compensation element  310  axially relative to the stator  220  and, for example, to bias or press the stator  220  axially tightly relative to the rotor  210 . Further or alternatively, an axial spring element may also be implemented to accomplish an elastic (resilient) axial bias. Accordingly, an elasticity of the housing  260  may also be utilized. 
     When operating the valve  300 , an axial angular misalignment, for example, between the rotor  210  and the housing  260 , as exemplarily shown in  FIG.  4 A , can be at least partially compensated for and offset (at least in part) by the compensation element  310  in that the at least one spherical surface forms a bearing location in which the spherical surface can roll. For example, if both the upper shell  425  and the lower shell  430  are rotatable relative to the spherical body  420 , i.e., with spherical surfaces both between the spherical body  420  and the upper shell  425  and between the spherical body  420  and the lower shell  430 , the lower shell  430  can roll relative to the upper shell  425  and compensate for the axial angular misalignment. The same also applies if, for example, only the upper shell  425  or only the lower shell  430  is designed to be movable relative to the spherical body  420 . 
     In addition to compensating for an axial angular misalignment between rotor  210  and stator  220 , the one or more bearing locations  390 A and  390 B further allow for no or little lateral radial misalignment between rotor  210  and stator  220  to result from such axial angular misalignment. 
     In contrast to the embodiment according to  FIG.  3   , in which the compensation element  310  comprises an elongated base body  360  so that the elongated base body  360  can tilt, the compensation element  310  according to  FIG.  4 A  can be designed and arranged in such a way that a pure rotation about the spherical center of the spherical body  420  takes place. Conversely, the body  420  can also be designed not as a sphere but, for example, as an axially elongated body in order to achieve a corresponding tilting. 
       FIG.  4 B  illustrates exemplarily and schematically an alternative embodiment of the compensation element  310  compared to  FIG.  4 A . At least one of the shells  425  or  430 , which are concave in  FIG.  4 B , is convex in  FIG.  4 B  as shell  425 A with a spherical surface  427 A. Accordingly, the spherical body  420  is replaced, for example, by a cylinder  420 A having a concave recess  422 A that cooperates with the spherical surface  427 A of the shell  425 A. Opposite to the spherical surface  427 A, the shell  425 A may comprise a preferably planar surface  428 A, which in turn may correspondingly abut against another planar surface, for example of the contact pressure mechanism  435  or of the stator  220 . 
     In  FIG.  4 B , only one axial side of the cylinder  420 A is designed and shown schematically, namely the concave recess  422 A. The axially opposite side of the cylinder  420 A can also have a concave recess, for example, or be flat, for example, according to the respective application. 
       FIG.  5    shows—isolated from the valve  300 —an embodiment of the elastic stator  220  used in  FIG.  4 A  in sectional view (top) and schematic top view (bottom). A plurality of ports  500  are centrally formed in the abutment region  410  of the stator  220 . The ports  500  each provide an open end to a respective flow path and cooperate with corresponding connecting elements (such as grooves) of the stator  210  to interconnect respective flow paths. 
     The abutment region  410  (with the ports  500 ) is designed as a flexible region, which is achieved in the exemplary embodiment according to  FIG.  5    by two recesses  510  and  515 . The two recesses  510  and  515  allow—to a certain degree—a twisting (in particular a tilting) of the abutment region  410 , so that it lies as flat as possible against the rotor  210 , even in case of a twisting or tilting of the stator  220  against the rotor  210 . 
     The stator  220  further comprises external ports  520 , exemplarily shown in the exemplary embodiments of  FIGS.  4  and  5   , which may correspond, for example, to the ports  230  in  FIG.  2   , i.e., and which may serve for external fluidic contacting of the stator  220 . 
     The stator  220  in the exemplary embodiment according to  FIG.  5    may further comprise mounting holes (not shown in more detail here) or the like for mechanically coupling and/or fixing the stator  220  e.g. with respect to the housing  260 . 
     In addition to the abutment region  410 , which includes the ports  500 , the stator  220  comprises the mounting region  405  (which may be formed as a ring, as shown here) and two webs  540 A and  540 B, each of which extends between and is connected to the abutment region  410  and the mounting region  405 . Only one web or more than the two webs  540  shown here may also be implemented, and of course these webs  540  may have a different shape than the one that is shown here. Preferably, fluidic connections between the ports  500  and connections (interface ports)  520  in the mounting region  405  may be guided in these webs  540 . 
     Due to the webs  540 , the abutment region  410  is elastically movable relative to the (outer) mounting region  405  and is thus pronounced as a flexible area, so that the abutment region  410  can move relative to the mounting region  405 , in particular in the axial direction (of the valve  300 ). Furthermore, this flexible structure also allows the abutment region  410  to be twisted/tilted relative to the mounting region  405 , i.e. the surface of the abutment region  410  that is in contact with the rotor  210  can be angled/tilted relative to the surface in which the mounting region  405  is located. 
     Preferably, the plurality of ports  500  are centrally located in the abutment region  410  of the stator  220 . The ports  500  each provide an open end to a respective flow path and cooperate with corresponding connecting elements (such as grooves) of the stator  210  to interconnect corresponding flow paths. The abutment region  410  (with the ports  500 ) is pronounced as a flexible region by the two recesses  510  and  515 . The two recesses  510  and  515  allow—to a certain extent—tilting of the abutment region  410 , so that the abutment region  410  lies as flat as possible against the rotor  210 , even in case of tilting or canting of the stator  220  relative to the rotor  210 . 
     In  FIG.  5    above, the stator  220  is shown with no force applied, i.e., in a sort of resting position. As deliberately exaggerated in  FIG.  4 A , the stator  220  can elastically deform in the event of an axial angular misalignment (e.g. between the rotor  210  and the housing  260 , as exemplarily shown in  FIG.  4 A ) to compensate for such an axial angular misalignment. 
     The stator  220  shown in  FIGS.  4  and  5    can preferably be implemented with microfluidic structures, preferably based on interconnected metal layers, also referred to as metal microfluidic or MMF structures. In one exemplary embodiment (not shown in detail here), the stator  220  is constructed from a plurality of metal layers (e.g., four metal layers or more), each of which has preferably been tightly bonded together by diffusion bonding. One or more fluidic channels may be formed by suitable recesses in the metal layers and flowed through by a fluid, such as the mobile phase. Such channels can also be at least partially surrounded by ceramic inserts, which are inserted, for example, as bonding auxiliaries during the bonding process, and preferably serve the manufacturing process to prevent or reduce subsidence of the geometry. 
       FIG.  6    shows schematically and in sectional view another embodiment of the valve  300 . In contrast to the embodiment according to  FIG.  4 A  but corresponding to the embodiment according to  FIG.  3   , the compensation element  310  in  FIG.  6    comprises an elongated body  600 . In addition, the compensation element  310  comprises a ball  610  and a shell  620 . Furthermore, an optional elastic spring element  630  is implemented between the contact pressure mechanism  435  and the compensation element  310  in order to be able to achieve a resiliently elastic axial contact pressure of the stator  220  relative to the rotor  210 . 
     By implementing one or more spherical surfaces, one or more bearing locations of the compensation element  310  can be achieved. For example, (referring to  FIG.  4 A ) a bearing location may be implemented between the ball  610  and the shell  620  and/or between the ball  610  and the elongated body  600 . Accordingly, an end face  640  of the elongated body  600  opposite the ball  610  in the axial direction may also comprise a spherical surface and, together with the resilient spring element  630 , form a further bearing point. It can be seen that several bearing points allow further degrees of freedom in a compensation of an axial angular displacement. 
     In one embodiment, the body  600  is configured to perform axial length variation. For example, the body  600  may be implemented as or include a piezo element such that when an appropriate electrical signal is applied (which is indicated by the wires  650 A and  650 B shown in  FIG.  6   ), the body  600  can expand or contract in the axial direction. Other materials known in the prior art, such as electroactive polymers and the like, may be used instead of a piezo element. Such variation of the axial expansion of the body  600  may be used, for example, to vary an axial contact pressure of the rotor  210  relative to the stator  220  during a switching operation of the valve  300 , for example, by reducing the contact pressure before, during, and/or after the switching operation. Such a reduction of the contact pressure can, for example, reduce or even completely prevent wear of the valve  300 , in particular an abrasion of the rotor  210  with respect to the stator  220 . 
       FIG.  7    shows, in accordance with the illustration of  FIG.  3   , a further embodiment of the valve  300 . In contrast to the embodiment according to  FIG.  3   , the compensation element  310  in  FIG.  7    comprises one or more spherical joints (each with one or more spherical surfaces). 
     In the exemplary embodiment shown in  FIG.  7   , the compensation element  310  again comprises an elongated base body  700  and an upper pressing element  710  and a lower pressing element  720 . The upper pressing element  710  abuts against the rotor  210 , while the lower pressing element  720  rests within the axial recess  340  of the drive  240  and is preferably held therein accordingly. A first ball joint  730 A is arranged between the upper pressing element  710  and the elongated base body  700 , and a second ball joint  730 B is arranged on the axially opposite side between the elongated base body  700  and the lower pressing element  720 . Each of the ball joints  730  may comprise one or more spherical surfaces, which may correspondingly cooperate with each other and may form one or more bearing points. Accordingly, an axial angular misalignment between the rotor  210  and the drive  240 , as again exaggeratedly illustrated here, may be compensated for without compromising an axial preload of the drive  240  relative to the rotor  210  and thus relative to the stator  220 . 
     The exemplary embodiment of the compensation element  310  shown in  FIG.  7    can preferably also be designed as an assembly, e.g. by pressing corresponding balls of the ball joints  730  into corresponding recesses of the base body  700  and/or the pressing elements  710 / 720 . 
       FIG.  8    schematically shows a further embodiment in which the compensation element  310  is formed by the drive  240  or is a part thereof. The drive  240  is formed, at least in a region adjacent to the rotor  210 , as a rotatable shaft comprising a spherical surface  320 A on its end face opposite to the rotor  210 . In one operating state of the valve  300 , the drive  240  axially urges the rotor  210  against the stator  220  with the spherical surface  320 A abutting against the rotor  210 . An axial rotational motion of the drive  240  is thus transmitted to the rotor  210 , allowing the rotor  210  to be rotated in an axial direction and relative to the stator  220 . The drive  240  may preferably be fixedly clamped at its end opposite the spherical surface  320 A (not shown in  FIG.  8   ) or may be part of a rotatable motor, as is sufficiently known in the prior art. 
       FIG.  9    shows a further embodiment according to that in  FIG.  8   , whereby the representation corresponds to  FIG.  2   , so that what has been said about  FIG.  2    applies here accordingly. In the partial representation of  FIG.  9   , only the left-hand part of the representation in  FIG.  2    is shown for the sake of clarity. According to the representation in  FIG.  8   , the shaft of the drive  240  comprises a spherical surface  320 A on its side adjacent to the rotor  210 , so that the drive  240  forms the compensation element  310 . The radius of this spherical surface  320 A can be selected in such a way that only a slight curvature results in relation to the flat contact surface of the rotor  210 . 
       FIG.  10    shows a further embodiment and corresponds in its representation to  FIG.  9   . In contrast to the embodiment according to  FIG.  9   , the embodiment of  FIG.  10    comprises a compensation element  310  separate from the drive  240 , which can preferably lie in an axial recess  1000  of a shaft of the drive  240 , as shown in  FIG.  10   . The compensation element  310  comprises a spherical surface  320 A that is axially opposite the drive  240 , or that abuts the side of the axial recess  1000  that is in the direction of the rotor  210 . An end face  1010  axially opposite the spherical surface  320 A, which abuts the rotor  210  during operation of the valve  300  and rotationally entrains the rotor  210 , is preferably flat, so that the end face  1010  abuts the rotor  210  in a planar manner. In a further embodiment not shown here, the end face  1010  may also have a spherical surface  320 , for example corresponding to the illustration shown in  FIG.  3   . The compensation element  310  of the embodiment shown in  FIG.  10    may be radially retained and/or positioned with respect to the lateral transformations of the recess  1000  by a corresponding elastic element  350 , corresponding to the embodiment shown in  FIG.  3   . Preferably, the elastic element  350  is formed by an O-ring, although several O-rings may also be used.