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.
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 claims 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.
The invention can be put into effect in numerous ways, illustrative embodiments of which are described below with reference to the drawings, wherein:
Referring to
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
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
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
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
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.
Number | Date | Country | Kind |
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1319276.0 | Oct 2013 | GB | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2014/071583 | 10/8/2014 | WO | 00 |