FILTERING APPARATUS COMPRISING AN INTEGRATED FLOW REDUCER, AND METHOD FOR COMPLETELY IMBIBING A FILTER MEMBRANE

Abstract

A filtration device, in particular a disposable filtration device, has a flow path in which a filter element and an integrated flow reducer are arranged one behind the other. The flow reducer is adapted to be brought to a first operating position, which permits a defined first volume flow rate, and at least to a second operating position, which permits a defined second volume flow rate which is smaller than the first volume flow rate.

Claims

1. A filtration device comprising a flow path in which a filter element and a flow reducer are arranged one behind the other, the flow reducer being adapted to be brought to a first operating position, which permits a defined first volume flow rate, and at least to a second operating position, which permits a defined second volume flow rate which is smaller than the first volume flow rate, wherein the ratio between the second volume flow rate and the first volume flow rate is between 0.05 and 0.9.

2. The filtration device according to claim 1, characterized in that the filtration device is a disposable filtration device.

3. The filtration device according to claim 1, characterized in that the flow reducer is integrated in the filtration device.

4. The filtration device according to claim 1, characterized in that the flow reducer consists entirely of materials that are sterilizable.

5. The filtration device according to claim 1, characterized in that the ratio between the second volume flow rate and the first volume flow rate is between 0.05 and 0.5.

6. The filtration device according to claim 1, characterized by an adjustable control element, which in the first operating position of the flow reducer assumes a defined first position, in which it exposes a first effective flow cross-section, and in the second operating position of the flow reducer assumes a defined second position, in which it exposes a second effective flow cross-section, which is smaller than the first effective flow cross-section.

7. The filtration device according to claim 6, characterized by a control device by means of which the control element can be moved to the first position and to the second position in an automated manner.

8. The filtration device according to claim 6, characterized in that the control element can assume further defined positions in addition to the first and second positions.

9. The filtration device according to claim 6, characterized in that the control element is adapted to be moved to the defined positions by means of a sliding mechanism or a rotating mechanism.

10. The filtration device according to claim 6, characterized in that the defined positions of the control element are configured as detent positions.

11. The filtration device according to claim 10, characterized in that the control element is adapted to be transferred to the detent positions by means of a pretensioned actuating element.

12. The filtration device according to claim 9, characterized by a protective covering which surrounds the sliding or rotating mechanism and, if required, the actuating element, the protective covering.

13. The filtration device according to claim 6, characterized in that the control element comprises an orifice plate having a passage opening, which can be inserted into a pipe section of the flow reducer.

14. The filtration device according to claim 6, characterized in that the control element comprises a body movable in a pipe section of the flow reducer and having a passage that is oriented in the flow direction in the first position of the control element and substantially transversely to the flow direction in the second position of the control element.

15. The filtration device according to claim 14, characterized in that the body and the passage the control element in the second position provide sickle-shaped passage ducts.

16. The filtration device according to claim 6, characterized in that the control element is a disk which is rotatable in a pipe section of the flow reducer and has an outside diameter that is smaller than the inside diameter of the pipe section by a defined dimension and/or has an outer contour that has one or more recesses extending from the outside inwards.

17. The filtration device according to claim 6, characterized in that the control element includes orifice plate sections which cooperate with orifice plate sections at an outlet opening of the flow reducer.

18. The filtration device according to claim 16, characterized in that in the first position of the control element, the orifice plate sections are superimposed to the greatest possible extent so that free intermediate spaces are left, and in that in the second position of the control element, the orifice plate sections cover the free intermediate spaces to the greatest possible extent, with a defined free flow passage being left.

19. The filtration device according to claim 6, characterized in that the flow reducer includes a pipe section that is divided into two partial sections and has mouths that are opposite each other, and in that the control element comprises an axially displaceable cone which in the first position of the control element dips less far into the mouth of one of the partial sections than in the second position of the control element.

20. The filtration device according to claim 19, characterized in that the cone is attached to an axially positionable sleeve which connects the two partial sections to each other.

21. The filtration device according to claim 20, characterized in that the sleeve has an internal thread which engages with an external thread on one of the partial sections.

22. The filtration device according to claim 21, characterized in that the sleeve is firmly connected to the other partial section.

23. The filtration device according to claim 20, characterized in that the cone is held to the sleeve by struts, between which free intermediate spaces are left.

24. The filtration device according to claim 6, characterized in that the flow reducer includes a pipe section which is in the form of a flexible hose, and in that the control element in the second position reduces the effective flow cross-section of the hose by a specific degree.

25. The filtration device according to claim 24, characterized in that the control element is a hose clamp having two clamp sections which are adapted to be deflected relative to each other and which engage the outer wall of the hose.

26. The filtration device according to claim 25, characterized in that the clamp sections are connected to each other by means of a joint.

27. The filtration device according to claim 24, characterized in that the control element is in the form of a bendable articulated rail having two substantially rigid collar sections and an articulated joint located therebetween, the two collar sections each surrounding a partial section of the pipe section.

28. The filtration device according to claim 6, characterized in that the control element comprises movable flaps which are arranged in a pipe section of the flow reducer and are adapted to be deflected by means of a force field generated outside the pipe section.

29. The filtration device according to claim 28, characterized by a force field generator arranged outside the pipe section.

30. The filtration device according to claim 28, characterized in that the flaps are fitted to a wall of the pipe section by means of joints.

31. The filtration device according to claim 28, characterized in that the deflection of the flaps is limited by flap stops.

32. The filtration device according to claim 6, characterized in that a pipe section of the flow reducer comprises a main pipe section having a first valve as the control element and a bypass pipe section for bypassing the first valve, the flow cross-section of the bypass pipe section being smaller than the flow cross-section of the main pipe section.

33. The filtration device according to claim 32, characterized in that the first valve is adapted to fully open and fully close the main pipe section.

34. The filtration device according to claim 32, characterized in that a second valve is provided in the bypass pipe section.

35. The filtration device according to claim 34, characterized in that the first valve and/or the second valve is/are adapted to assume a plurality of positions in which different flow cross-sections are exposed.

36. A method of completely wetting a filter membrane in a filtration device according to claim 1 within the scope of a flushing process, characterized in that the flow reducer is in the second operating position, which permits a defined second volume flow rate, which is smaller than the first volume flow rate, so that the flushing of the filter element is effected with a reduced volume in order to completely wet the filter membrane, wherein the flow reducer is brought to the first operating position after the flushing process for carrying out a filtration process.

37. The method according to claim 36, characterized in that the complete wetting of the filter membrane is performed while saving flushing medium by 10 to 95% in comparison with the complete wetting without pressure reduction.

Description

[0046] Further features and advantages of the invention will be apparent from the description below and from the accompanying drawings, to which reference is made and in which:

[0047] FIG. 1a schematically shows a first embodiment of a flow reducer for a filtration device according to the invention in a first operating position, viewed in the flow direction;

[0048] FIG. 1b schematically shows the flow reducer from FIG. 1a in a second operating position;

[0049] FIG. 2a schematically shows a second embodiment of a flow reducer for a filtration device according to the invention in a second operating position in a perspective view;

[0050] FIG. 2b schematically shows the flow reducer from FIG. 2a in a first operating position, viewed in the flow direction;

[0051] FIG. 2c schematically shows the flow reducer from FIG. 2a in the second operating position, viewed in the flow direction;

[0052] FIG. 2d schematically shows the control element of the flow reducer from FIG. 2a in a perspective view;

[0053] FIG. 3a schematically shows a third embodiment of a flow reducer for a filtration device according to the invention in a second operating position in a perspective view;

[0054] FIG. 3b schematically shows the flow reducer from FIG. 3a in a first operating position, viewed in the flow direction;

[0055] FIG. 3c schematically shows the flow reducer from FIG. 3a in the second operating position, viewed in the flow direction;

[0056] FIG. 3d schematically shows the control element of the flow reducer from FIG. 3a in a perspective view;

[0057] FIG. 4a schematically shows a fourth embodiment of a flow reducer for a filtration device according to the invention in a second operating position in a perspective view;

[0058] FIG. 4b schematically shows the flow reducer from FIG. 4a in a first operating position, viewed in the flow direction;

[0059] FIG. 4c schematically shows the flow reducer from FIG. 4a in the second operating position, viewed in the flow direction;

[0060] FIG. 4d schematically shows the control element of the flow reducer from FIG. 4a in perspective front and rear views;

[0061] FIG. 5a schematically shows a fifth embodiment of a flow reducer for a filtration device according to the invention in a first operating position in a partly transparent side view;

[0062] FIG. 5b schematically shows the flow reducer from FIG. 5a in the first operating position, viewed in the flow direction;

[0063] FIG. 6a schematically shows a sixth embodiment of a flow reducer for a filtration device according to the invention in a first operating position in a partly sectional side view;

[0064] FIG. 6b schematically shows the flow reducer from FIG. 6a in a second operating position;

[0065] FIG. 7 schematically shows a seventh embodiment of a flow reducer for a filtration device according to the invention in a second operating position in a partly sectional side view;

[0066] FIG. 8a schematically shows an eighth embodiment of a flow reducer for a filtration device according to the invention in a first operating position in a side view;

[0067] FIG. 8b schematically shows the flow reducer from FIG. 8a in a second operating position; and

[0068] FIG. 9 schematically shows a ninth embodiment of a flow reducer for a filtration device according to the invention in a side view.

[0069] All of the embodiments described below of a flow reducer 10 for a filtration device have in common that they can replace a previously commonly used separate control valve of a filter means of the filtration device for setting a defined back pressure during flushing of the filter means.

[0070] The flow reducer 10 is arranged in the same flow path as the filter means and downstream thereof and is firmly integrated in the filtration device. In particular with a view to the preferred use of the flow reducer 10 in a disposable filtration device, the flow reducer 10 is made entirely from sterilizable materials. This means that the entire disposable filtration device, inclusive of the flow reducer 10, can be sterilized before or after packaging the filtration device, if necessary together with the packaging material, for example by gamma rays, superheated steam or autoclaving.

[0071] The flow reducer 10 can change between a first operating position, which exposes or opens a defined first effective flow cross-section, and a second operating position, which exposes or opens a defined second effective flow cross-section, which is markedly smaller than the first effective flow cross-section. To flush the filter means, the flow reducer 10 is brought to the second operating position with a reduced flow cross-section, so that the volume flow through the flow reducer 10 is reduced. Thus, the pressure with which the flushing medium is pressed through the filter means is opposed by a defined back pressure. For example, a flushing pressure of 2.5 bar may be specified, and the flow reducer 10, in its second operating position, opposes this pressure with a back pressure of 2 bar, so that the filter means is ultimately wetted with the flushing medium at a resulting pressure of 0.5 bar.

[0072] The back pressure is obtained by the selective reduction of the volume flow rate. The ratio between the volume flow rate during flushing operation and the volume flow rate during filtration operation as intended is between 0.05 and 0.9, preferably between 0.05 and 0.5, more preferably between 0.05 and 0.15.

[0073] In most cases, filter means include a dedicated inlet and a dedicated outlet, between which at least one filter membrane is arranged. Here, the terms inlet and outlet refer to the filtration operation as intended. For the flushing operation, however, a possible reverse feed is to be included here in principle as well, i.e. an intake of the flushing medium through the outlet and an outflow through the inlet.

[0074] Changing between the two operating positions of the flow reducer 10 does not require any components to be added or removed, and no connections or disconnections need to be made. The sterility of the flow reducer 10 is not impaired by the changeover.

[0075] FIGS. 1a and 1b illustrate a first embodiment of such a flow reducer 10 for a filtration device including at least one filter means. The flow reducer 10 is arranged downstream of the filter means and comprises a pipe section 12 having a defined flow cross-section, which is usually dictated by the inside diameter. The medium which was previously pressed through the filter means flows through the pipe section 12.

[0076] The flow reducer 10 further comprises a control element 14, here in the form of an orifice plate 16 having a passage opening 18. The control element 14 can be moved between a defined first position shown in FIG. 1a and a defined second position shown in FIG. 1b.

[0077] In the first position, the medium flowing through the pipe section 12 can pass unobstructed to the greatest possible extent. The control element 14 protrudes at most slightly into the pipe section 12 and reduces the flow cross-section of the pipe section 12 only insignificantly or not at all at this point.

[0078] In the second position, the control element 14 has been completely inserted into the pipe section 12 and extends substantially across the entire flow cross-sectionwith the exception of the small passage opening 18 having a defined cross-section.

[0079] Basically, further positions of the control element 14 may be provided, in particular intermediate positions with an effective flow cross-section that is reduced in relation to the first position, but increased in relation to the second position.

[0080] The defined positions of the control element 14 are detent positions, which are provided by a detent/sliding mechanism. The detent/sliding mechanism includes an actuating element 20, in this case a type of pushbutton, which is coupled to the control element 14 and is pretensioned by means of a spring element. By manually actuating the pushbutton, the control element 14 can be transferred from the first detent position (FIG. 1a) to the second detent position (FIG. 1b). By another actuation, the control element 14 will optionally return to the first detent position, etc.

[0081] In principlejust as with all of the embodiments described belowan automated actuation of the control element 14 or the actuating element 20 in connection with a control device is also possible.

[0082] A protective covering 22, for example made from a deformable and sterilizable elastomer, surrounds the detent/sliding mechanism inclusive of the actuating element 20. The protective covering 22 serves as an external sterile barrier and protects the inside of the flow reducer 10 from possible contamination.

[0083] In the first operating position of the flow reducer 10, in which the control element 14 assumes its first position, the filter means can be used as intended for filtration at a specified medium pressure, i.e. without substantial back pressure.

[0084] In the second operating position of the flow reducer 10, in which the control element 14 assumes its second position, the control element 14 blocks the major part of the flow cross-section in the pipe section 12. The medium can now only flow through the small passage opening 18 in the orifice plate 16. Due to the now significantly reduced effective flow cross-section and the reduced volume flow rate caused by this, a defined back pressure is built up in the pipe section 12. In this second operating position of the flow reducer 10 the flushing process takes place.

[0085] Preferably, the flow reducer 10 is delivered in the second operating position (flushing position), to be then transferred to the first operating position (filtration position) in one single step after flushing.

[0086] When describing the following embodiments of the flow reducer 10, the general principles described above are applicable in the same way. Therefore, only the design differences will be discussed.

[0087] For instance, in the second embodiment shown in FIGS. 2a to 2d, the control element 14 is designed differently and the sliding mechanism is replaced by a rotating mechanism which is basically similar to that of a stop valve.

[0088] The control element 14 shown separately in FIG. 2d has a substantially cylindrical contour here. The otherwise solid body 24 of the control element 14 has a passage 26 which is also substantially cylindrical and the axis of which is perpendicular to the axis of the cylindrical body 24. The body 24 and/or the passage 26 may basically also be shaped differently, e.g. conically.

[0089] The control element 14 is received in a matching socket 28 in the pipe section 12 of the flow reducer 10; the control element 14 can rotate in this socket about the axis of the body 24. To rotate the control element 14, an actuating element 20 is provided again, in this case a kind of T-handle, which is connected with the body 24 of the control element 14.

[0090] The socket 28 in the pipe section 12 and the body 24 and the passage 26 of the control element 14 are matched to one another such that in a first position of the control element 14, which is shown in FIG. 2b, the axis of the passage 26 is parallel to the axis of the pipe section 12 (flow direction). In this position, the medium can flow through the passage 26 of the control element 14 without hindrance, since the diameter of the passage 26 transverse to the flow direction substantially corresponds to the diameter of the pipe section 12, so that the flow path in the pipe section 12 is completely open.

[0091] In the second position, shown in FIGS. 2a and 2c, the control element 14 is rotated through 90. In this position the body 24 of the control element 14 blocks the flow path for the most part. Only the two remaining passage ducts 30, which are sickle-shaped when viewed in the direction of flow, allow a significantly reduced defined volume flow rate through the pipe section 12.

[0092] As in the embodiment described above, further positions of the control element 14, in particular intermediate positions, may basically also be provided, and the defined positions of the control element 14 may be configured as detent positions. This also applies to all further embodiments.

[0093] The third embodiment of the flow reducer 10 as shown in FIGS. 3a to 3d is very similar to the second embodiment. Here the body 24 of the control element 14 is in the form of a disk having a defined thickness. The outside diameter of the body 24 is smaller than the inside diameter of the pipe section 12 by a defined dimension, and/or the outer contour of the body 24 is adapted such that one or more recesses extend from the outside inwards.

[0094] For enabling the maximum possible flow, the control element 14 is rotated, with the aid of the actuating element 20 (T-handle), to the first position shown in FIG. 3b, in which the cylinder axis of the body 24 is transverse to the direction of flow, so that the control element 14 only slightly affects the flow through the pipe section 12.

[0095] For the flushing operation, the control element 14 is rotated to the position shown in FIG. 3c, in which the cylinder axis of the body 24 is oriented parallel to the direction of flow. A defined flow rate is obtained by the outside diameter which is smaller in comparison with the inside of the pipe section 12 or by the recess(es), whereby a free annular channel or one or more differently shaped channels are produced around the body 24, through which the medium can flow.

[0096] In the fourth embodiment shown in FIGS. 4a to 4d, provision is also made for a rotatable control element 14. Here, the control element 14 has a substantially hollow cylindrical design, but includes orifice plate sections 32 projecting inwards.

[0097] A cover 34 of the flow reducer 10 is matched to the control element 14 and has an outlet opening which is likewise partly covered by orifice plate sections 36.

[0098] The control element 14 can be rotated (e.g. through 90) from the first position shown in FIG. 4b, in which the orifice plate sections 32, 36 of the control element 14 and of the cover 34 are superimposed to the greatest possible extent (filtration operation of the filter means), to the second position shown in FIG. 4c, in which the orifice plate sections 32 of the control element 14 cover the free intermediate spaces 38 between the orifice plate sections 36 of the cover 34 to the greatest possible extent (flushing operation), and vice versa. In the second position, a defined small free flow passage 40in the illustrated exemplary embodiment a central flow passage 40remains at all events to maintain a reduced volume flow rate.

[0099] This embodiment can be manufactured with comparatively few components.

[0100] FIGS. 5a and 5b show a fifth embodiment of the flow reducer 10.

[0101] Here, the pipe section 12 of the flow reducer 10 is subdivided into two partial sections 42, 44 located opposite each other on the front sides. The first partial section 42 is firmly connected to an axially projecting sleeve 46. The projecting part of the sleeve 46 is provided with an internal thread 48, which engages an external thread 50 of the second partial section 44. By rotating the sleeve 46, this allows one partial section 42 to be moved in the axial direction towards or away from the other partial section 44, depending on the direction of rotation. The sleeve 46 provides a sterile barrier to the inside of the sleeve by sealing the thread flight. This ensures that the transition between the two partial sections 42, 44 is sealed, regardless of the axial position of the sleeve 46, and that there is no risk of contamination.

[0102] As can be seen in particular from FIG. 5b, the sleeve 46 has a control element 14 in the form of a cone (needle) arranged therein, the tip 52 of which points towards the second partial section 44 of the pipe section 12. The control element 14 is held here by a four-point retaining device with struts 54, which leaves intermediate spaces 56 open when viewed in the flow direction.

[0103] In a first position of the control element 14, it does not protrude at all or only to a comparatively small degree into the free mouth of the second partial section 44. The medium can flow largely unobstructed from the first partial section 42 into the sleeve 46 and there through the intermediate spaces 56 into the second partial section 44. This position corresponds to the intended filtration operation of the filter means.

[0104] For the flushing operation, the control element 14 is shifted towards the second partial section 44 (to the left in FIG. 5a) by a defined amount by rotating the sleeve 46. The control element 14, which now dips far into the mouth of the second partial section 44, minimizes the effective flow cross-section such that a desired back pressure is built up.

[0105] FIGS. 6a and 6b illustrate a sixth embodiment of the flow reducer 10. The pipe section 12 of the flow reducer 10 is formed as a flexible hose here. A control element 14 in the form of a hose clamp engages the outer wall 58 of the hose on two opposite sides. The hose clamp has two clamp sections 60, 62, which are connected to each other by means of a joint 64. The hose clamp can be angled in a defined manner by means of a catch mechanism in the joint 64.

[0106] In the first position shown in FIG. 6a (filtration operation of the filter means), the flow cross-section of the pipe section 12 is virtually unimpaired. In the second position shown in FIG. 6b (flushing operation), one of the clamp sections 60 is swiveled towards the other clamp section 62 by a specific clamping angle . The clamping achieved in this way reduces the effective flow cross-section of the pipe section 12 at the clamping point, thereby inducing the desired reduction in flow.

[0107] FIG. 7 shows a seventh embodiment of the flow reducer 10. Similar to the sixth embodiment described above, the pipe section 12 of the flow reducer 10 is in the form of a flexible hose. The desired defined change in the effective flow cross-section to permit a normal filtration operation of the filter means with a large volume flow rate and a flushing operation with a distinctly reduced volume flow rate is effected here by means of a control element 14 in the form of a bendable articulated rail.

[0108] The articulated rail is constructed in the nature of a knee orthosis having two substantially rigid collar sections 66, 68 and an articulated joint 70 positioned therebetween. The two collar sections 66, 68 each surround a partial section of the pipe section 12. With the aid of the articulated joint 70, the flexible pipe section 12 can be bent or folded by a specific angle , as a result of which the effective flow cross-section is reduced by a certain degree. The two folding positions and any further positions that may be provided, in particular intermediate positions, are preferably configured as detent positions.

[0109] In the eighth embodiment shown in FIGS. 8a and 8b, a control element 14 in the form of movable flaps 72, 74 is provided in the pipe section 12 of the flow reducer 10, the flaps being fitted to the wall 80 of the pipe section 12 by means of joints 76, 78. The effective flow cross-section can be influenced by a deflection of the flaps 72, 74. The flaps 72, 74 are adapted to be deflected by a force field 82 which penetrates the wall 80 of the pipe section 12. The force field 82 is produced, for example, by electromagnetic interaction with the aid of a force field generator 84 arranged outside the pipe section 12.

[0110] A force field 82 of sufficient strength is generated to achieve a defined narrowing of the effective flow cross-section starting from the first operating position of the flow reducer 10 as shown in FIG. 8a. The flaps 72, 74 are deflected by a predetermined amount. The deflection can be limited by flap stops, for example. The narrowing results in a flow resistance increased by a defined amount, which corresponds to the second operating position of the flow reducer 10.

[0111] No additional seals etc. are required for this embodiment, since the movable components of the control element 14 are arranged within the pipe section 12 and the application of force is not mechanical, but contactless.

[0112] A ninth embodiment of the flow reducer 10 is shown in FIG. 9. The pipe section 12 of the flow reducer 10 here comprises a main pipe section 86 having a control element 14 in the form of a first valve 88 and a bypass pipe section 90 for bypassing the first valve 88. The bypass pipe section 90 has a flow cross-section that is significantly smaller compared with that of the main pipe section 86 and optionally includes a second valve 92.

[0113] According to a first variant of this embodiment, the first valve 88 in the main pipe section 86 is used as a pure shut-off valve. During normal filtration operation of the filter means, the first valve 88 is fully open, and during flushing operation it is fully closed. In this case, the medium can only flow through the bypass pipe section 90, which results in a reduced flow through the flow reducer 10, accompanied by a corresponding increase in pressure (back pressure). The degree of flow reduction is defined by the flow cross-section and the length of the bypass pipe section 90. Optionally, the resulting flow can be varied by the second valve 92 in the bypass pipe section 90.

[0114] In a second variant of the ninth embodiment, the flow through the main pipe section 86 can be varied by means of the first valve 88. This means that the first valve 88 can assume one or more intermediate positions so that the resulting flow through the flow reducer 10 and the pressure can be adjusted over a selectable range. The different valve positions are configured as detent positions in order to allow reproducible settings. The second valve 92, which is possibly provided, may also be designed such that it can assume one or more intermediate positions, which are preferably configured as defined detent positions. This provides even more adjustment options.

[0115] The above-described embodiments of a flow reducer 10 for a filtration device are exemplary and should therefore not be understood as being limiting. For example, certain features of the various embodiments can be combined with each other.

LIST OF REFERENCE NUMBERS

[0116] 10 flow reducer [0117] 12 pipe section [0118] 14 control element [0119] 16 orifice plate [0120] 18 passage opening [0121] 20 actuating element [0122] 22 protective covering [0123] 24 body [0124] 26 passage [0125] 28 socket [0126] 30 passage ducts [0127] 32 orifice plate sections [0128] 34 cover [0129] 36 orifice plate sections [0130] 38 intermediate spaces [0131] 40 flow passage [0132] 42 first partial section [0133] 44 second partial section [0134] 46 sleeve [0135] 48 internal thread [0136] 50 external thread [0137] 52 tip [0138] 54 struts [0139] 56 intermediate spaces [0140] 58 outer wall [0141] 60 first clamp section [0142] 62 second clamp section [0143] 64 joint [0144] 66 first collar section [0145] 68 second collar section [0146] 70 articulated joint [0147] 72 first flap [0148] 74 second flap [0149] 76 first joint [0150] 78 second joint [0151] 80 wall [0152] 82 force field [0153] 84 force field generator [0154] 86 main pipe section [0155] 88 first valve [0156] 90 bypass pipe section [0157] 92 second valve