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Rotary Pinch Valve (patented 2007) - Partner/Applications Wanted

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- Patented Rotary Pinch Valve – - - Suitable for a Plurality of Flexible Tubes - - - Seeking Partners and Applications – Interested parties please reply to : rotarypinchvalve@hotmail.com Date : May 14 2009 Message : Please find attached herein, a patented description and photos of a Rotary Pinch Valve for which a partner and applications are sought. The current PCT patent application has a priority date of October 2007 and is due for national phase expenditure in approximately March 2010. Consequently a partner and applications are sought to help cover these costs by that time. The rotary pinch valve described herein may have application as a sequence valve where a relatively large number of valves (pinch) need to open and close over a processing cycle. This may be in medical, laboratory, and biochemical fields but also in other non specific areas where this multiple valving solution may make economic, processes which are not otherwise so. This is due to the low cost , low space requirement and easy repair /replacement of tubing. The patented rotary pinch valve is described in attached photographs and patented description. Photos of a prototype valve which is capable of handling 16 tubes is shown herein, This prototype appears to work in a satisfactory manner. Please address any enquiries to rotarypinchvalve@hotmail.com ------------------------------------------ A ROTARY PINCH VALVE Field of the Invention The present invention relates to a rotary pinch valve housing a plurality of flexible tubes. Background to the Invention Pinch valves are well known devices for controlling flow in flexible tubing. Therein a pinch member acts to pinch a flexible tube and so interrupts flow in the flexible tube. Pinch valve apparatus featuring a plurality of tubes are also known, some of which rely on a rotary mechanism to open and close the tubes. However such rotary pinch valves housing a plurality of tubes, are often more amenable to manual, discrete settings and have limitations on the number of tubes that can effectively be handled. Other devices may be complex requiring microcomputer controllers. There is a requirement for a rotary pinch valve that is suited to sequencing of flows for an automated processing cycle. Summary of the Invention According to the present invention, there is provided a rotary pinch valve comprising a rotor, a stator, at least one rigid backing member and a plurality of movable members suitable for a plurality of flexible tubes. The rotor may comprise a single essentially circular cam disk. The rotor may comprise a plurality of essentially circular cam disks separated from each other by cam spacer disk(s) and arranged as an essentially cylindrical whole. The essentially cylindrical whole of the rotor may comprise separate laminar cam disks and spacer disks held together by fastener(s) or comprise an essentially continuous piece of rigid material. The stator may comprise at least one stator pinch disk. The stator may comprise a plurality of stator pinch disks separated from one another by a stator spacer disk(s) and arranged into an aligned whole. The aligned whole of the stator may comprise separate laminar disks held together by fastener(s) or comprise an essentially continuous piece of rigid material. A cam disk and its matching stator pinch disk may be in the same pinch plane. A cam spacer disk and a stator spacer disk may be in the same plane. The stator may be essentially cylindrical. The stator may be truncated. The stator may comprise at least one removable end plate so as to allow loading of the essentially cylindrical rotor. The rotor and stator may have a means for being maintained in proper relative axial position. The rotor when loaded may be maintained in proper axial position by the removable end plate. At least one pinch slot may be located in a stator pinch disk. The stator may have matching alignment holes at axially opposite ends of the stator for positioning the plurality of flexible tubes. The alignment holes of the stator may be separated by alignment gaps. A removable end plate may have alignment holes for positioning the flexible tubes separated by alignment gaps. The plurality of flexible tubes may be aligned along the stator parallel to the axis of the rotary pinch valve. A particular flexible tube may be aligned to pass over at least one pinch slot. A pinch slot may comprise at least one spring compression base. Pinch slots may be staggered around the circumference of the stator as well as along its axial length. The at least one rigid backing member may comprise a single rigid piece suitable as a backing member for the plurality of flexible tubes. The single rigid piece may be removable from or rotatable about the stator. The at least one rigid backing member may comprise a plurality of individual rigid backing members, one for each pinch slot and its associated particular flexible tube. An individual rigid backing member may be positioned over a particular pinch slot. A rigid backing member may be rigidly attached to the stator. An individual rigid backing member may be rigidly attached to the stator by a strut(s). An individual rigid backing member may be rigidly attached to the stator by radial struts or substantially radial struts. A particular individual rigid backing member may be removable from the radial struts or rotatable around them, so as to facilitate loading new flexible tubing and/or movable members. A movable member may comprise a curved surface for mating with a cam disk and a pinching surface for pinching a particular flexible tube. A movable member may comprise lateral protrusions. A movable member may comprise a pinching surface with rounded edges to avoid cutting the flexible tube. A movable member may be positioned in any pinch slot of the stator The rotary pinch valve may comprise a spring mechanism for acting on any particular movable member so as to ensure appropriate positioning of that particular movable member relative to its particular cam disk. The spring mechanism may comprise a pair of springs acting on a spring compression base(s) associated with a pinch slot of the stator and lateral protrusions associated with a movable member. The spring mechanism may comprise at least one short elastically deformable sleeve more resilient than a particular flexible tube which fits over a particular flexible tube in the vicinity of the pinch slot The stator may comprise aligners to prevent lateral movement of any particular flexible tube and thereby allow the particular flexible tube to be pinched by a compact sized movable member the width of which is essentially the width of a pinched flexible tube. Aligners for a particular flexible tube may be placed upstream or downstream of the pinch slot associated with a particular flexible tube and preferably at a distance where the particular flexible tube always exhibits an unpinched diameter and preferably as close to the pinch slot as possible. Aligners may be incorporated into a stator spacer disk. Aligners and radial or substantially radial struts for any particular flexible tube may be placed within a passage which is in axial alignment with an alignment gap in the end plate. Radial or substantially radial struts associated with an individual rigid backing member may encompass at least three flexible tubes. A pinched flexible tube may be axially adjacent to two adjacent flexible tubes that are not exhibiting a pinched diameter within that same pinch plane. A pinch slot may extend laterally within the pinch plane across an axial passage associated with its associated flexible tube and also across both adjoining axial passages associated with the aligners of that flexible tube, preferably fully across both adjoining axial passages associated with the aligners of that flexible tube. A flexible tube when pinched may spread its width into the axially aligned passage occupied by its aligners, preferably fully into the axially aligned passage occupied by its aligners. Alignment gaps may be sized such that the pinched flexible tube and/or its associated extended movable member when in the pinched condition almost touch the unpinched flexible tubes either side of it within the same pinch plane. Any of the movable members or springs or flexible tubes may be loaded into the rotary pinch valve from an external position. Movable members and/or springs may be loaded into the rotary pinch valve from an external position after the rotor has been placed in the stator and preferably with the end plate fixed. The stator may comprise a plurality of indentations upstream or downstream of a pinch slot for the purpose of externally loading a plurality of movable members into their pinch slots. The shape of the indentations may approximate the shape of the bottom of a movable member. The stator may comprise a plurality of removable indentation filling pieces for filling the indentations after the plurality of movable members have been loaded into their pinch slots. Movable members may be loaded into the stator from an external position by placing the movable member in an indentation in the stator and sliding the movable member axially and under the individual rigid backing member so that the pinching surface of the movable member is substantially flush with the pinching surface of the individual rigid backing member and then with the movable member being loaded into the pinch slot. Where springs within a pinch slot are used the movable member when slid under the individual rigid backing member so as to be substantially flush with it may have its lateral protrusions fit just under the spring compression base(s). Where no springs within a pinch slot are used a spring compression base(s)is not necessary but the lateral protrusions of the movable member may be maintained for alignment purposes and the movable member may be advanced into the stator by the distance taken by the flexible tube. Where springs within a pinch slot are used the springs may be then added to act on the movable member and the indentation filled with a solid indentation filling piece of material so as to act as a backing surface for maintaining the springs and/or the movable member in correct alignment. Movable members with or without their associated springs may be loaded into the stator from an external position by removal from the stator or rotation within the pinch plane or otherwise of a latching piece comprised of an individual rigid backing member, radial or substantially radial strut(s) and spring compression base(s) and subsequently latching the latching piece to the stator. An individual rigid backing member as an individual piece may be removable from or rotatable about its associated radial or substantially radial strut(s) The stator may be assembled about the rotor from a number a laminar stator pinch disks alternating with laminar stator spacer disks and with the movable members with or without associated springs, loaded with each appropriate laminar stator pinch disk. At least one pinch valve may be located along the axial length of a flexible tube. The rotary pinch valve may be programmable by providing a means to rotate and fix any cam disk relative to another cam disk. A means to rotate any cam disk relative to another cam disk may comprise laminar cam disks and laminar cam spacer disks being detachable and having matching bolt holes or male and female accommodations at regular angular intervals. The plurality of flexible tubes may be of different diameter. A change of valve state as from open to closed and closed to open is abrupt, as from five to fifteen rotational degrees of the rotor. The rotor may rotate within or about the stator with a close clearance. The rotor may be driven by a rotating mechanism such as a geared electric motor or stepper motor. Any of the cam disks may act on a particular movable member positioned within a pinch slot in the same pinch plane of the stator so as pinch a particular flexible tube against a rigid backing member so as to open and close the particular flexible tube in a desired manner. Brief Description of the Drawings Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an overall view of the rotary pinch valve but showing the apparatus to pinch but one flexible tube. Figure 2 is an exploded view of the curved surface of the rotary pinch valve stator indicting pinch slots staggered around the circumference as well along the axial length of the stator. Figure 3 is an overall view of the essentially cylindrical rotor comprised of alternating cam disks and cam spacer disks. Figure 4 shows an example of the cross section of two possible cam disks of the rotor. Figure 5 is a view through a particular pinch plane outlining the pinch mechanism. Figure 6 is a view of a cross section of the stator showing aligners for flexible tube positioning Figure 7 is a view of a movable member ready to be loaded via an indentation into a pinch slot of the stator in association with springs. Figure 8 is a view of a movable member loaded via an indentation into a pinch slot of the stator in association with springs. Figure 9 is a view of a movable member ready to be loaded via an indentation into a pinch slot of the stator without springs. Figure 10 is a view of a movable member loaded via an indentation into a pinch slot of the stator without springs. Figure 11 is a partially exploded view of a rigid backing member as an individual piece rotatable about a modified radial strut. Figure 12 is a view of a particular cam disk of the rotor comprising bolt holes so as to allow programming of the rotary pinch valve. Detailed Description of Embodiments Embodiments of the present invention relate to a rotary pinch valve housing a plurality of flexible tubes. The rotary pinch valve of the present invention may be adapted to discrete settings, where rotation is stopped either manually or by other means, after the rotating mechanism has passed through a particular angulation. However the rotary pinch valve of this invention is more particularly applicable where it is desired to produce fluid flow through a plurality of tubes in a particular sequence so as effect an automated processing outcome in a piece of equipment or other such use and preferably where the rotation is driven by an essentially constant speed device such as by an electric motor. As such, the rotary mechanism of the rotary pinch valve, will usually be a rotating cam surface. The full processing cycle will normally be defined by an angular rotation of 360 degrees of the rotating mechanism of the rotary pinch valve. Patents US 3,506,032, US 3,918,490, US 4,282,902, US 5,113.906 indicate rotary pinch valves featuring a plurality of flexible tubes. However, these rotary pinch valves are intended for devices requiring essentially discrete positioning, such as manual laboratory apparatus, where the rotation is halted once a desired position has been reached. Furthermore the angle of rotation of the rotating mechanism, to induce a change of valve state from open to closed or vice versa is rather large, as indicated by the cam surfaces shown in the figures of the above patents. This large angle of rotation to induce a change of valve state is not a problem where three or four discrete positions are required for such apparatus, as may be achieved manually or even by a stepper motor. However for an automated device driven by a constant speed motor it is often desirable that a change of valve state, as from open to closed or closed to open, occur over as small an angle as possible. This allows as much of the angular cycle and as a consequence time, to be devoted to flow through the respective tubes so as to enact their function. Angular rotation and thus time devoted to a change of valve state is effectively wasted time. This can become especially important as the number of flexible tubes increase, together with the requirement, for example, for some valves to shut before others close. Patents US 4,457,339 and US 4,694,861 describe two further rotary pinch valves designed for a plurality of tubes, again mainly for a laboratory setting, driven by stepper motors and intended to be easily reprogrammable. US 4,457,339 has a limitation on the number of tubes capable of being handled as noted by US 4,469,861, which itself, while being highly programmable, is a complex and expensive device requiring a microcomputer controller. The rotary pinch valve of the present invention therefore seeks to provide a rotary pinch valve suitable for a plurality of tubes, as might be required by an item of equipment requiring a particular sequencing of flows to be enacted for an automated cycle and preferably using a constant speed driver or a stepper motor. Such a valve has advantage in terms of cost and simplicity where an essentially fixed flow regime is to be enacted over a large number of cycles without the need to reprogram for varied flow regimes. While the rotary pinch valve of the present invention may be designed to be reprogrammed, this is mechanical in nature and possibly time consuming and is where the rotary pinch valves of the prior art as noted above may be more applicable. Now a particular embodiment of the rotary pinch valve of the present invention is shown in Figure 1. Therein the rotary pinch valve 1 comprises a rotor 2 a stator 3 and a plurality of flexible tubes 4 aligned parallel to the axis 5 of the rotary pinch valve 1. The stator 3 further comprises for each particular flexible tube 6, a pinch slot 9 and a rigid backing member 10 supported by radial struts 11. A movable member 12 is located within the pinch slot 9 and when activated moves to pinch the particular flexible tube 6 against the rigid backing member 10. Figure 1 shows, for illustration, but one such pinch slot 9, movable member 12 and rigid backing member 10 for a particular flexible tube 6. However each aligned flexible tube of the plurality of flexible tubes 4 will require its own pinch slot, movable member and rigid backing member. Consequently a plurality of pinch slots are staggered around the circumference of the stator 3 as well as along its axial length, one variation of which is shown in Figure 2. A particular flexible tube 6 also has flexible tubes 7 and 8 either side of it except for a particular flexible tube at the periphery. Referring now to Figure 1 the stator 3 also comprises an end plate 13 with alignment holes 14 which are separated by alignment gaps 15. This is matched by a similar set of alignment holes 16 and alignment gaps 17 at the other end of the stator 3. The stator 3 also comprises an internal cylindrical annulus 18 into which the essentially cylindrical rotor 2 is placed with a close tolerance. The end plate 13 is removable from the stator 3 so as to allow the essentially cylindrical rotor 2 to be fitted into the internal cylindrical annulus 18. The diameter of the hole 19 in the end plate 13 is less than the diameter of essentially cylindrical rotor 2. The end plate 13 when fixed in place therefore maintains the rotor 2 in axial position. Referring now to Figure 3 and Figure 4 the rotor 2 comprises essentially circular cam disks 20 each with a particular cam surface 21 separated by cam spacer disks 23 and held together in an essentially cylindrical whole. Each cam disk 20 of the rotor 2 interfaces with a particular pinch slot 9 and movable member 12 all of which are within in a particular pinch plane 22 so as to act on a particular flexible tube 6. The cam spacer disks 23 are placed between consecutive cam disks 20 such that, given the tolerances available, a particular movable member 12 is acted upon by only the intended cam disk 20 in its pinch plane 22 and is not acted upon by an unintended adjoining cam disk. The cam spacer disks 23 therefore may have a radius equal to or less than the smaller radius of the cam disk 20. The pinch slots 9 in the stator 3 are also effectively placed to mate with the corresponding cam disk 20 and so take account of the cam spacer disks 23 in the rotor 2. Referring now to Figure 5 there is shown a cross section through a particular pinch plane 22 so as indicate the pinch mechanism. Therein the movable member 12 is shown to be acted upon by a pair of springs 24 which are supported by a spring compression base 25 associated with the stator 3 within the pinch plane 22. The springs 24 are also supported at their other end by lateral protrusions 29 of the movable member 12. The springs 24 are to return the movable member 12 to a position corresponding to an open state for the particular flexible tube 6, when allowed to by the rotating cam disk 20. The natural resiliency of the tubing may be sufficient to return the movable member 12 back to the open position, in which case the springs 24, the spring compression base 25 and lateral protrusions 29 may not be required. This is especially true under conditions when the flexible tube carries fluid under pressure. However where the fluid is under vacuum the springs 24 may be preferable. Also shown in Figure 5 are the radial struts 11 which support the rigid backing member 10. These radial struts 11 encompass and align within the pinch plane 22 the flexible tubes 7 and 8 either side of the particular flexible tube 6 which is acted upon by a particular movable member 12. Its is noted from Figure 5 there is a space between the particular flexible tube 6, and adjoining flexible tubes 7 and 8 at an axial position where none are pinched. This space corresponds to the alignment gap 15 between the alignment holes 14 in the end plate 13. However by appropriate selection of the alignment gap 15 this space between the particular flexible tube 6 and adjoining flexible tubes 7 and 8 may diminish almost completely when the particular flexible tube 6 is pinched by the movable member 12 and so spreads its width. Also by ensuring the adjoining flexible tubes 7 and 8 are pinched a suitable distance along the axial length of the stator 3 to where the pinched particular flexible tube 6 has returned to its unpinched diameter either upstream or downstream, it follows that any flexible tube of the plurality of flexible tubes 4 where pinched within a pinch plane 22 will be axially adjacent to two flexible tubes which are exhibiting an unpinched diameter within that same pinch plane 22. Consequently the rotary pinch valve 1 can be made to be compact with a distance between adjoining unpinched flexible tubes being essentially half of the difference between the pinched and unpinched width of the particular flexible tube 6. This does not take into account the slight curvature of the surface of the stator 3 on which the plurality of flexible tubes is placed. Furthermore referring now to Figure 6 there is shown a cross section through the stator 3 which indicates aligners 26 for the particular flexible tube 6. These aligners 26 which are not shown in Figure 1 are to avoid the particular flexible tube 6 moving laterally. This essentially fixed lateral position allows the particular flexible tube 6 to be pinched by a compact sized movable member 12 the long edge of which in the pinch plane 22 is approximately the same length as the pinched width of the particular flexible tube 6. The aligners 26 are placed at an appropriate short distance upstream and downstream of the pinch slot 9 where the particular pinched flexible tube 6 returns to its unpinched diameter. Furthermore the aligners 26 for the particular flexible tube 6 are axially aligned in the gap between the unpinched flexible tubes 6 and 7 as well as the gap between flexible tubes 6 and 8 as shown in Figure 6. The particular flexible tube 6 is also axially aligned by the alignment hole 14 in the end plate 13 as well as by the radial strut corresponding with the rigid backing member of another flexible tube It follows that there is a series of passages parallel with the axis 5 of the stator 3 and in line with the alignment gaps 15 where aligners 26 and radial struts 11 associated with any pinch slot 9 may be placed. This equally leaves a separate series of parallel passages down the stator 3 in line with the alignment holes 14 for unimpeded passage of the plurality of flexible tubes 4. Furthermore a pinch slot 9 may have an exposed long edge within a pinch plane 22 that extends across the axial passage of its particular flexible tube 6 and preferably fully or almost fully into the adjoining axial passages of the two aligners 26 of that particular flexible tube 6. This exposed long edge of the pinch slot 9 is also essentially the same length as the long edge of the pinching surface of movable member 12 and is chosen to be essentially the same length as the pinched width of a particular flexible tube 6. Consequently by proper selection of the alignment gaps 15 as shown previously not only the particular flexible tube 6 but also the movable member 12 may almost touch the adjacent unpinched flexible tubes 7 and 8 when the movable member 12 is extended to pinch a particular flexible tube 6. In other embodiments the radial struts 11 may encompass more than three adjoining flexible tubes or less than three adjoining flexible tubes such as for peripheral flexible tubes. Furthermore the radial struts 11 need not be fully radial but rather project appropriately outward from the stator 3. Also the pinching surface of the movable member 12 as shown in Figure 1 is rectangular. In other embodiments the long pinching edges of this pinching surface may be rounded so as to minimize cutting or shearing of a particular flexible tube 6. Referring now to Figures 4 and 5 it is noted the curved surface of the movable member 12 interfaces with the curved surface of the cam disk 20. This is designed to deliver an abrupt change in valve state over as small an angle of rotation as possible. The design of optimal interfacing cam surfaces to achieve such an abrupt change would be known to those skilled in the art. However a cam angle approximating 45 degrees on the cam surface 21 which may also be curved at the outer edge so as to avoid a point, together with a curved surface approximating a semicircle for the bottom of the movable member 12 is determined to deliver such an abrupt change. It may be that more abrupt changes are possible as with greater angles than 45 degrees and with other curved surfaces on the movable member 12 such as elliptical section shapes. It is desirable that the change of valve state from fully open to fully closed or vice versa can occur over as small a rotational angle as possible as from 5 to 15 degrees, for example. However this is ultimately dependent on the movement required of the movable member 12 which is itself dependent on the diameter and wall thickness of the particular flexible tube 6 as well as on the diameter of the rotor 2 which is itself a function of the physical space allocated to the rotary pinch valve 1. This is to be clearly contrasted, however, with other known rotary pinch valves as noted above, where no emphasis has been placed on minimizing angular rotation of the rotor of the rotary pinch valve so as to induce a change of valve state. Referring now again to Figure 1 it is noted that the stator 3 of the rotary pinch valve 1 is truncated. That is it is not cylindrical and has flat sides. However in another embodiment the stator 3 may be fully cylindrical thereby allowing the plurality of flexible tubes 4 to be placed fully around its circumference. However by close spacing a given number of flexible tubes of a certain diameter around the full circumference, depending on the number of tubes and their diameter, the diameter of the rotor 2 may become excessively small. This could negatively influence the change of valve state sensitivity of the valve which is effectively proportional to the diameter of the rotor 2. By truncating the stator 3, the diameter of the rotor 2 is maximized for a given number of flexible tubes of given diameter and physical spatial depth, in which to physically fit the rotary pinch valve 1 corresponding to the truncated width of the rotary pinch valve 1. The larger the diameter of the rotor 2 the smaller the angle that is required for a change of valve state, other factors remaining equal. Referring also to Figure 1 it is noted the cam surface of the rotor 2 is internal to the stator 3. However in another embodiment it may also be external to the stator and rotate around the stator. Referring again to Figure 1 a desirable feature of the rotary pinch valve 1 is the external access to the plurality of flexible tubes 4 which facilitates loading and replacing ruptured tubing. It is similarly desirable to be able to externally load the movable members 12 and/or their associated springs 24 into the respective pinch slots 9 from the outside of the rotary pinch valve 1 as loading from within the cylindrical annulus 18 presents handling difficulties. The loading of the movable member 12 and/or associated springs 24 into the stator 3 is preferably done after the rotor 2 has been placed inside the stator 3 and before the plurality of flexible tubes 4 are threaded into the stator 3. This may be done by a number of means. Referring to Figure 5 but also to Figures 8 and Figure 9 one means is to have an indentation 27 either upstream or downstream of the pinch slot 9. The indentation 27 therefore will be associated with a different pinch plane(s) to that of pinch slot 9. Thereby the movable member 12 may be loaded into the indentation 27 and slid axially and under the rigid backing member 10, at which stage the flat pinching surface of the movable member 12 will be flush with the bottom of the rigid backing member 10 (Figure 8). Also the lateral protrusions 29 of the movable member 12 may preferably fit just under the spring compression base 25. The movable member 12 may then be lowered into pinch slot 9 (Figure 9). The springs 24 may then be loaded possibly with a tool whereafter an indentation filling piece (not shown) may be fixed in the axial upstream or downstream indentation 27, especially in the instance where springs 24 are utilized, so as to provide a backing surface for the springs 24 and also for the movable member 12. However where no springs 24 are utilized, an indentation filling piece may not be required, as the movable member 12 will be held in correct alignment by the stator 3 as the movable member 12 is advanced into the stator 3 over the loading position, by a distance equivalent to that taken up by the flexible tube 6. Such a condition is shown by comparison of Figure 10 and 11. Figure 10 shows the movable member 12 ready to be loaded into the pinch slot 9 and Figure 11 shows the movable member 12 loaded into the pinch slot 9. The movable member 12 is prevented from wobbling axially by the axial width of the movable member 12 fitting into the pinch slot 9 with close tolerance. Also while no springs 24 or spring compression base 25 are utilized in this embodiment the lateral protrusions 29 of the movable member 12 are preferably maintained and so effectively increase the effective length of the movable member 12 loaded into the stator 3 when a particular flexible tube 6 is pinched. This increased effective length loaded into the stator 3 also acts to keep the movable member 12 properly aligned in the pinched condition. In another embodiment not shown in the Figures, the rigid backing member 10 and radial struts 11 together with the spring compression base 25 may be made into a single latching piece (not shown) which latches into attachments on the stator 3. This latching may be by a number of means including pin like fasteners through holes in the latching piece and mating holes in the stator 3 or via circlips, for example. Thereby the said latching piece may be fitted and removed from the stator as required. When the said latching piece is removed the movable member 12 and springs 24 may be loaded into the pinch slot 9 from above and the latching piece then attached to the stator 3. In this embodiment the indentation 27 will not be necessary. In a variation, the abovementioned latching piece latches at only one point in the stator 3 and is rotatable within the pinch plane 22 about another point on the stator 3. Unlatching the rotatable latching piece thereby allows the movable member 12 and springs 24 to be loaded in the pinch slot 9 whereafter the latching piece is rotated to latch into the stator 3. Another desirable feature of the rotary pinch valve is that ruptured tubes may be removed when desired. It may be that a particular flexible tube 6 is in the closed position when the motor has stopped with the movable member 12 protruding from the stator 3 as indicated in Figure 1 and it is not practical to restart the motor. With the rigid baking member 10 in a permanent fixed position relative to the radial struts 11 the pinched flexible tube 6 will therefore be difficult to remove as will loading of a new flexible tube. However if the rigid backing member 10 is removable from the radial struts 11 or rotatable around them, then a ruptured particular flexible tube 6 can be removed and a new particular flexible tube 6 placed in position over the protruding movable member 12 and then the rigid backing member 10 may be compressed into position. This may be achieved with the rigid backing member 10 being a part of the aforementioned latching piece or with the rigid backing member 10 being removable or rotatable as a separate individual piece. For example, the radial struts 11 may also be made to flex such as by spring steel within the pinch plane 22, so that a mating rigid backing member 10 as an individual piece may be fitted into and removed from the radial struts 11 by flexing the radial struts 11. The rigid backing member 10 as an individual piece may also rotate and latch in the pinch plane 22 in a similar manner to the aforementioned latching piece with the exception that it rotates about and latches into the radial struts 11. In a further variation, the rigid backing member 10 as an individual piece is rotatable about a modified radial strut 30 but in a plane at right angles to the pinch plane 22 or substantially at right angles to the pinch plane. This is shown in a partially exploded view in Figure 12. The modified radial strut 30 has a cylindrical end 31 which may act as a bearing about which the rigid backing member 10 as an individual piece may rotate. The rigid backing member 10 as an individual piece may be held in the pinch position above the pinch slot 9 by a torsional spring 32, for example, fitted about the cylindrical end 31 and in elastic contact with the rigid backing member 10 as an individual piece. At its other end the rigid backing member 10 as an individual piece has a mating surface or other means of attachment with the other modified radial strut 33. The torsional spring 32 may be extended and relaxed for loading and unloading the movable member 12 or a ruptured particular flexible tube 6. In another embodiment indicating how the movable member 12 and springs 24 may be loaded into the rotary pinch valve 1, the stator 3 may be consist of a number of laminations comprising consecutive laminar stator pinch disks with the cross section as shown in Figure 5 alternating with laminar stator spacer disks with a cross section as shown in Figure 6. These may be individually loaded over the rotor 2 with a movable member 12 and springs 24 added for each laminar stator pinch disk until the whole stator 3 is assembled about the rotor 2. In yet another embodiment, not shown in the Figures, the natural resiliency of a particular flexible tube 6 may be enhanced by fitting over a particular flexible tube 6 a short, essentially cylindrical, close fitting elastically deformable sleeve of a material preferably more resilient than the particular flexible tube 6 itself. This short flexible sleeve would be fitted around the flexible tube in the vicinity of the pinch slot 9 and preferably between the upstream and downstream aligners 26. This close fitting sleeve may be held in axial position, over and above its frictional association with the particular flexible tube 6, by physical interaction with a component of the stator 3 such as the rigid backing member 10 or movable member 12, whether by small mating indentations or otherwise. This embodiment acts as an alternative for providing the necessary spring action to ensure the full design movement of the movable member 12. While slightly adding to the effective diameter of a particular flexible tube 6, it avoids the need for the pair of springs 24 and their associated loading into the stator 3. In another embodiment more than one pinch valve is located along the axial alignment of an alignment hole 14. For example it is possible to have two pinch slots in axial alignment along an alignment hole 14 and thereby create a three way valve with the common junction between the two pinch slots. This also may serve to reduce the overall size of the rotary pinch valve 1 for a given number of valves. Figure 1 shows an individual rigid backing member 10 for a particular pinch slot 9. The rigid backing member 10 is attached to the stator 3 by radial struts 11. However in another embodiment a single backing member is used for all the flexible tubes on one side of the rotary pinch valve 1. Such a backing member may be a full piece of curved but rigid sheet material, for example, which can be either slid axially or rotated into place using the stator 3 alone or together with the end plate 13 for anchoring. In such an instance the flexible tubing which transverses the stator 3, as is visible from the outside the rotary pinch valve 1 as shown in Figure 1, would not be able to be seen. The said one piece of curved but rigid sheet material would then comprise the totality of backing members on that side of the rotary pinch valve. In yet another embodiment the curved but rigid piece of sheet material is not a full continuous piece but yet still one piece such that material suitable for a rigid backing member is located strategically above the pinch slot 9. In this case a portion of the flexible tubes which transverse the stator 3 would be visible from the outside of the rotary pinch valve 1. In another embodiment the rotary pinch valve 1 may be made programmable by incorporating a mechanism which allows any one cam disk 20 to be rotatable to another fixed position relative to all other cam disks in the rotor 2. This may be achieved for example by having bolt holes 28 in the cam disks 20 and cam spacer disks 23 of the rotor 2 at regular angular intervals as shown in Figure 7 for a cam disk 20 only. In this embodiment the rotor 2 would be comprised of various cam disks 20 and cam spacer disks 23 held together by bolts (not shown). Any particular cam disk 20 may be removed from the bolts and rotated to another angular position and then replaced on the bolts and assembled into a rotor 2. Alternatively the cam disks 20 and cam spacer disks 23 may be held together by accommodating male and female fittings possibly also in association with a bolt(s). For example the cam spacer disks 23 of the rotor 2 may have male pin like protrusions which slide into female accommodations on the cam disks 20 of the rotor 2. These male and female fittings would be on a similar angular basis as the bolt holes thereby allowing the rotor 2 to be disassembled and cam disks 20 rotated to appropriate positions whereafter the disks are reassembled into the essentially cylindrical whole rotor 2 and placed in the stator 3. While the embodiment shown in Figure 1 has flexible tubes of equal diameter, in another embodiment the rotary pinch valve has flexible tubes of varying diameter. In a further embodiment, where a plurality of flexible tubes of equal diameter have an identical on/off duration for a cycle but at different times of the cycle, a plurality of flexible tubes may be associated with a single stator pinch disk. This is because the fixed cam profile of the cam disk delivers the same on/off program to each flexible tube but with a time delay. In this embodiment, a single stator pinch disk may have a plurality of pinch slots and associated movable members and rigid backing members suitable for the plurality of flexible tubes rather than a single pinch slot 9 for a single particular flexible tube 6 as was the case for the previous embodiments. In this embodiment also the stator may comprise just a single stator pinch disk so as to house a plurality of flexible tubes and the rotor may comprise a single cam disk. In the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. It is to be clearly understood that although prior art publications(s) are referred to herein, this reference does not constitute an admission that any of these documents forms part of the common general knowledge in the art in Australia or in any other country.