Abstract:
Disclosed is a rotary valve  1  comprising a stator  20  and a rotor  40  generally in rotary sliding engagement with the said stator about a valve axis RA, the stator including a plurality of fluid ports  22, 26, 28 , the rotor  40  being operable to selectively fluidically interconnect two or more of said ports during its rotary sliding engagement. The valve further includes an actuator ( 70 ) for disengagement of the rotor from the stator to enable efficient cleaning of the valve interconnections.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a filing under 35 U.S.C. 371 of international application number PCT/EP2014/071583, filed Oct. 8, 2014, which claims priority to Great Britain application number 1319276.0, filed Oct. 31, 2013, the entire disclosures of each of which are hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to the cleaning of rotary valves of the type that control fluid flow, particularly, but not exclusively, fluid flow in laboratory or bio-processing equipment such as chromatographic equipment, and more specifically to valves for directing fluid flow along a desired path, selected from a set of such paths. 
     BACKGROUND OF THE INVENTION 
     Rotary valves are commonly used in devices for controlling fluid flow. A typical type of valve, for example used in laboratory equipment of moderate sizes such as a liquid chromatography system (LCS), is a rotary selection valve employed to select an appropriate fluid path from a number of paths and thus to redirect fluid from one fluid path to another fluid path. 
     Generally, a rotary valve has a stationary body, herein called a stator, which co-operates with a rotating body, herein called a rotor. 
     In commercially available LCS rotary valves, the stator is provided with a number of inlet and outlet ports. The ports are in fluid communication with a corresponding set of orifices on an inner stator face, via bores in the stator. The inner stator face is an inner surface of the stator that is in generally fluid tight abutment with an inner rotor face of the rotor. The rotor is typically formed as a disc and the inner rotor face is pressed against the inner stator face in rotating co-operation. The inner rotor face is provided with one or more grooves which interconnect different stator orifices depending on the rotary position of the rotor with respect to the stator. 
     Rotary valves can be designed to withstand high pressures (such as pressures above 30 MPa). They can be made from a range of materials, such as stainless steel, high performance polymeric materials and ceramics. 
     The number of inlets/outlets as well as the design of grooves in the rotator or the stator reflects the intended use of a specific rotary valve. 
     A common type of multi-purpose valve has one inlet port (typically placed in the rotary axis of the valve) and a number of outlet ports that are placed around the inlet port. The rotor has a single, radially extending groove that has one end in the rotary axis, thereby always in fluid communication with the inlet, while the other end can be in fluid communication with any one of the outlets depending on the angular position of the rotor with respect to the stator. Such a valve is useful to direct a flow from the inlet to any of the outlets, one at a time. Other arrangements of fluid paths are known also. 
     Whilst these valves function very well, small amounts of leakage are possible between the abutting rotor and stator faces, which manifests itself as growths of bacteria and other microorganisms, usually around the orifices on the stator where the leakage has taken place. This in turn leads to contamination in the fluid paths as the rotor moves between selected angular positions. For highly sensitive laboratory equipment, this contamination is not acceptable, and so the valve has to be dismantled and cleaned regularly, which takes time and renders the equipment inoperable during cleaning. 
     One attempt to address the above issue is described in, as yet unpublished, application PCT/EP2013/058752, which provides improved rotary selection valve that requires less cleaning and is thus more convenient to use. That invention consists in a rotary selection valve, the valve comprising a stator and a rotor, said stator and rotor each having complementary abutment surfaces for allowing generally fluid tight relative rotation between the stator and the rotor about a rotational axis, said stator or rotor comprising at least one connection port in fluid communication with an associated orifice at said stator or rotor abutment surface, that invention being characterised in that said stator and/or said rotor further comprises a fluid recess extending radially beyond said associated orifice or orifices and open to the complementary abutment surfaces. 
     Thereby, the inventor observed that arrangement allows easier cleaning or sanitisation of the valve, because bacteria or other microorganisms cannot pass radially beyond the fluid recesses described above. The valve can be cleaned by automated means and need not be dismantled so frequently. 
     However the same inventor has realised that an even better system is possible which cleans the whole internal valve assembly including the complementary abutment faces mentioned above, which system can be readily automated. Embodiments of the present invention address this realisation. 
     The invention provides rotary valve according to claim  1  having preferred features defined by claims dependent on claim  1 . The invention provides also a method as defined by claim  9  having preferred features define in subsequent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be put into effect in numerous ways, illustrative embodiments of which are described below with reference to the drawings, wherein: 
         FIG. 1  shows a sectional view of part of a first rotary valve; 
         FIG. 2  shows a sectional view of the valve shown in  FIG. 1 , but in a different orientation; 
         FIG. 3  shows a sectional view of part of a second rotary valve; and 
         FIG. 4  shows a sectional view of the valve shown in  FIG. 3 , but in a different orientation. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , a rotary valve  1  is illustrated schematically, showing only the main parts. The valve  1  includes a housing  10 , a stator  20 , a rotor  40  and a drive shaft  60 , for connection to an electric motor  12 , for example the d.c. motor shown or a stepper motor or other rotary drive (not shown). The drive will in practice include a means (not shown) for recognizing the angular position of the rotor. Manual operation of the valve is possible also. The rotor  40  is rotatable with respect to the stator  20  about a rotary axis RA of the valve, as a result of the rotary motion of the motor  12  and drive shaft  60 . 
     The stator  20  is fixed with respect to the housing  10  and is provided with ports  22 ,  26  and  28 . Ports  22 ,  26  and  28  are visible in  FIG. 1  but more than three ports will generally be provided. The ports allow selective fluid communication between a source and any components with which the valve is to co-operate. The ports may be situated on any suitable position on the exterior surface of the stator. The ports are provided with means to connect capillaries or tubing, such as threaded recesses. Other connections are known in the art. Via fluid communication channels, the ports  22 ,  26  and  28  are in fluid communication with a corresponding set of orifices  21 ,  24  and  27  on the end face  30  of the stator  20 , i.e. the surface of the stator  20  that during operation engages with the rotor  40 . 
     The rotor  40  is typically formed as a disc and has a rotor end face  50 , i.e. the surface pressed against the inner stator face  30  during operation. The faces  30  and  50  are complementary such that they provide generally fluid tight engagement. Most conveniently these faces are flat, but other complementary shapes are possible, for example they may be matched part-spherical or conical shapes. The inner rotor face  30  too is provided with one or more fluid communication channels, in the present case form of a groove  32  in the end face  30 . 
     In use the rotor  40  can be rotated about axis RA by means of the motor  12  and shaft  60  such that the orifice  21  which remains always in communication with the groove  32 , is selectively caused to communicate with either orifice  24  or orifice  27 , or, in practice other circumferentially arranged orifices not shown. Thus various stator outlet ports can be made to communicate selectively with the central inlet port  22 . 
     The foregoing detailed description describes elements of a rotary valve which are generally conventional. However, with additional reference to  FIG. 2 , the valve of the present invention includes an actuator  70 , the function of which is disengage the rotor  40  from the stator  20 , by moving the rotor  20  with linear movement away from the stator  20  towards the left when looking at  FIG. 1 , and thereby to provide a washing cavity  90  which allows washing fluid, typically sodium hydroxide, to circulate over the entire surfaces  30  and  50 , and in turn to clean those faces and the respective orifices  21 ,  24  and  27 . To prevent excess volumes of cleaning fluid being used, a cylindrical bellows seal  80  is connected between the stator  20  and the housing  10 , and circumstances orifices  21 ,  24  and  27 . An additional O ring seal  82  is provided between the rotor  40  and the housing  10  to prevent cleaning fluid from passing beyond the rotor  40  toward the motor  12 . 
     In more detail the actuator  70  comprises an actuator motor  14  (for example another d.c. motor or stepper motor) and a cam  16 . The cam  16  rotates 180 degrees about an axis RB which is generally perpendicular to the axis RA, in order to act upon a thrust bearing  18  attached to the shaft  60  at its radially inner region, which in turn causes said linear movement of the shaft  60  and rotor  40  from the position shown in  FIG. 1  to the position shown in  FIG. 2 . Cleaning fluid is then pumped through the cavity  90  via port  28  in this case. When cleaning complete, the motor  14  is driving a further 180 degrees, a return spring  23  forces the shaft  60  and thereby the rotor  40  back into engagement with the stator  20 , typically with a force of 1000-1500N. 
       FIGS. 3 and 4  show a valve  100  similar to that shown in  FIGS. 1 and 2 , with the differences described below. 
     In this instance the bellows seal  80  and O ring seal  82  are replaced by a single conical bellows seal  84  which at its radially outer region is compressed between the stator  20  and the housing  10 , and at its radially inner region provides a rotatable seal around the rotor  40 . Further the stator  20  includes a dedicated cleaning fluid inlet port  23  and outlet port  25  which in this instance are not part of the selective interconnections of the remaining valve ports. 
     The valve  100  operates in the same manner as valve  10 , although the volume of cleaning fluid required is less. The actuator  70  again moves the rotor to the left in the drawing, as shown in  FIG. 4  to produce a cleaning cavity  190 . It will be noted that the inlet port  23  has a respective orifice  29  at the inner stator face which is close to the lowermost extent of the cleaning cavity  190 , to act as drain for any trapped cleaning fluid. As can be seen best in  FIG. 3 , the inlet orifice  29  and an outlet orifice  31  associated with the outlet port  26  are located radially outside the area which the rotor engages. This means that the port  23  is in fluid communication with the port  25  even when the rotor and stator are engaged. Further, this means that a supply of cleaning fluid can be pumped through the ports when the valve is operating in its conventional fluid path switch mode. This cleansing during normal operation of the valve can be useful in preventing growth of microorganisms, for example in extended operations of the valve and its associated equipment. 
     It will be evident that both valves ( 1 ,  100 ) can be operated to provide automatic cleansing, for example at the end of operations and initiated automatically by a control signal, or can be manually selectively operated to be cleaned. There is no need to disassemble the valves and a convenient but efficient cleansing cycle can be achieved with this arrangement. 
     Although two embodiments have been described and illustrated, it will be apparent to the skilled addressee that additions, omissions and modifications are possible to those embodiments without departing from the scope of the invention claimed. For example, the actuator  70  shown could be modified, such that the motor  12  withdraws the rotor during a portion of its rotation, for example by using a cam rotatable about the axis RA which acts on a follower in the housing, only duration said portion of its rotation. Other arrangements are possible, for example in which the stator moves away from the rotor, or in which both the rotor and the stator move to achieve disengagement. 
     Whilst 3, and 5 port stators have been illustrated, it will be apparent that other numbers of ports could be employed. Although a bellows seal has been used, any flexible seal will suffice, or the seal could be omitted if the volume of cleaning fluid used is not important.