CA2338497A1 - Regulator valve - Google Patents
Regulator valve Download PDFInfo
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- CA2338497A1 CA2338497A1 CA 2338497 CA2338497A CA2338497A1 CA 2338497 A1 CA2338497 A1 CA 2338497A1 CA 2338497 CA2338497 CA 2338497 CA 2338497 A CA2338497 A CA 2338497A CA 2338497 A1 CA2338497 A1 CA 2338497A1
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- fluid line
- upstream
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- vessel
- pressure
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D16/00—Control of fluid pressure
- G05D16/04—Control of fluid pressure without auxiliary power
- G05D16/06—Control of fluid pressure without auxiliary power the sensing element being a flexible membrane, yielding to pressure, e.g. diaphragm, bellows, capsule
- G05D16/0611—Control of fluid pressure without auxiliary power the sensing element being a flexible membrane, yielding to pressure, e.g. diaphragm, bellows, capsule the sensing element being deformable, e.g. Bourdon tube
- G05D16/0613—Control of fluid pressure without auxiliary power the sensing element being a flexible membrane, yielding to pressure, e.g. diaphragm, bellows, capsule the sensing element being deformable, e.g. Bourdon tube the deformable sensing element acting as a throttling member
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- Fluid Mechanics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Automation & Control Theory (AREA)
- External Artificial Organs (AREA)
Abstract
The present invention provides a regulator valve for use in a fluid line, the regulator valve having a deformable conduit connectable to the fluid line to form thereby a portion of the fluid line, a vessel enclosing the conduit, the vessel having an interior volume external to the conduit connectable to be in fluid communication with the fluid line upstream or downstream of the vessel, wherein pressure in the fluid line regulates pressure in the interior volume and hence the pressure difference between pressure internal to the conduit and pressure in the interior volume of the vessel, so that the pressure difference and thereby the effective cross-sectional area of the conduit varies according to upstream or downstream pressure respectively within the fluid line.
Description
REGULATOR VALVE
The present invention relates to a flow-rate or pressure-drop limiting valve, of particular but by no means exclusive application with a shunt such as a hydrocephalus shunt.
Existing shunts for draining excess fluid in the body commonly include valves to regulate the rate of flow, either by attempting to impose a maximum pressure drop over the length of the shunt or a maximum flow-rate, though in some cases also employing a pressure release valve to initiate outflow when the fluid pressure rises above some predetermined threshold. Hydrocephalus (enlargement of part or all of the cerebrospinal fluid spaces within the cranium, resulting from a blockage to the cerebrospinal fluid (CSF) pathways in the head), for example, is commonly treated by surgical subcutaneous implantation of a shunt - a small-diameter catheter - to lead cerebrospinal fluid from the head to another space in the body, most commonly the peritoneal cavity. Because this arrangement puts the ventricles in hydraulic communication with unnaturally distant fluid spaces, an important part of the shunt is a valve, serving both to prevent backflow under unusual postures, and to limit the CSF drainage in the face of considerable hydrostatic fluid colunui suction after the manner of a siphon when the patient is upright. (The flow is usually constrained to be one-way, typically by means of a simple valve in series with but separate from the flow-regulating valve elements.) However, limiting the drainage by means of existing devices remains problematic, despite the development and commercialisation of a large variety of different valve devices. When the patient is upright, siphoning can lead to the overdrainage of the ventricles, which has been associated with various neurological complications (subdural CSF collections, slit ventricles syndrome, craniosynostosis, and loculation of the ventricles).
Overdrainage can also cause obstruction of the catheter inlet in the ventricles, which can become permanent and usually requires surgical shunt revision. The valuing parts of the existing devices are typically wholly contained in what amounts to a local dilatation of the catheter with maximum dimensions of the order of 5 mm diameter and 30 mm length. For functional reasons this is located as proximally as possible, subcutaneously at the back of the neck. As small, flat, soft and smooth a device as possible is desirable to avoid skin erosion.
After noting that the vast majority of the more than 400 valves designed before 1990 showed inaccuracy, long-term drift, safety problems and unphysiological flow properties, a recent study (Aschoff, A., Oikonomou, J., Hashemi, B., Kremer, P. and Kunze, S.) reported that the majority of new valves designed in the 1990s also showed inaccuracy, long-term drift, safety deficits and hydraulic mismanagement.
Existing devices to limit drainage include so-called pressure-regulating and flow-regulating valves. An ideal pressure-drop regulator would provide a constant pressure drop (Op) irrespective of flow-rate (Q), while an ideal flow-rate regulator would provide a constant (maximum) flow-rate independent of the pressure drop. Miniature existing devices achieve these ideals only very approximately, owing to a combination of fundamental constraints, design drawbacks and problems in manufacture.
Pressure-drop regulation is used in many current valves.
However, this is actually inappropriate in principle, as pressure-drop regulation does not deal with the relatively massive increases in flow-rate consequent upon the greater hydrostatic pressure drop when the patient stands.
The present invention relates to a flow-rate or pressure-drop limiting valve, of particular but by no means exclusive application with a shunt such as a hydrocephalus shunt.
Existing shunts for draining excess fluid in the body commonly include valves to regulate the rate of flow, either by attempting to impose a maximum pressure drop over the length of the shunt or a maximum flow-rate, though in some cases also employing a pressure release valve to initiate outflow when the fluid pressure rises above some predetermined threshold. Hydrocephalus (enlargement of part or all of the cerebrospinal fluid spaces within the cranium, resulting from a blockage to the cerebrospinal fluid (CSF) pathways in the head), for example, is commonly treated by surgical subcutaneous implantation of a shunt - a small-diameter catheter - to lead cerebrospinal fluid from the head to another space in the body, most commonly the peritoneal cavity. Because this arrangement puts the ventricles in hydraulic communication with unnaturally distant fluid spaces, an important part of the shunt is a valve, serving both to prevent backflow under unusual postures, and to limit the CSF drainage in the face of considerable hydrostatic fluid colunui suction after the manner of a siphon when the patient is upright. (The flow is usually constrained to be one-way, typically by means of a simple valve in series with but separate from the flow-regulating valve elements.) However, limiting the drainage by means of existing devices remains problematic, despite the development and commercialisation of a large variety of different valve devices. When the patient is upright, siphoning can lead to the overdrainage of the ventricles, which has been associated with various neurological complications (subdural CSF collections, slit ventricles syndrome, craniosynostosis, and loculation of the ventricles).
Overdrainage can also cause obstruction of the catheter inlet in the ventricles, which can become permanent and usually requires surgical shunt revision. The valuing parts of the existing devices are typically wholly contained in what amounts to a local dilatation of the catheter with maximum dimensions of the order of 5 mm diameter and 30 mm length. For functional reasons this is located as proximally as possible, subcutaneously at the back of the neck. As small, flat, soft and smooth a device as possible is desirable to avoid skin erosion.
After noting that the vast majority of the more than 400 valves designed before 1990 showed inaccuracy, long-term drift, safety problems and unphysiological flow properties, a recent study (Aschoff, A., Oikonomou, J., Hashemi, B., Kremer, P. and Kunze, S.) reported that the majority of new valves designed in the 1990s also showed inaccuracy, long-term drift, safety deficits and hydraulic mismanagement.
Existing devices to limit drainage include so-called pressure-regulating and flow-regulating valves. An ideal pressure-drop regulator would provide a constant pressure drop (Op) irrespective of flow-rate (Q), while an ideal flow-rate regulator would provide a constant (maximum) flow-rate independent of the pressure drop. Miniature existing devices achieve these ideals only very approximately, owing to a combination of fundamental constraints, design drawbacks and problems in manufacture.
Pressure-drop regulation is used in many current valves.
However, this is actually inappropriate in principle, as pressure-drop regulation does not deal with the relatively massive increases in flow-rate consequent upon the greater hydrostatic pressure drop when the patient stands.
Pressure-drop regulation has nevertheless been advocated, because of the physician's ignorance of the patient's CSF
production rate. So-called programmable pressure-drop regulators allow external readjustment of the pressure drop offered by the implanted device, but do not overcome this inherent problem.
One existing flow-rate regulator comprises an anti-siphon device 2 (illustrated schematically in section in figure 1) comprising a toroidal chamber 4, orifice 6 (above inner wall 8 of chamber 4) and diaphragm 10. Toroidal chamber 4 also has one or more inlets (not shown), in its outer wall 12 or base 14. The external pressure on diaphragm 10 is atmospheric, while the pressure within chamber 4 - during normal use - is atmospheric or somewhat higher. Under these conditions fluid flows 16 out of the device 2 via orifice 6. However, should siphoning occur, downstream pressure and therefore the pressure within chamber 4 drops (while the external pressure on diaphragm 10 remains atmospheric), pushing diaphragm 10 downwards and thereby reducing the size of orifice 6. Flow 16 is consequently reduced and, if the pressure drop is sufficiently great, stopped altogether.
However, this regulator is vulnerable to variations in external pressure, such as produced by the weight of the recumbent patient's body. Further, its operation assumes that atmospheric pressure will indeed be exerted on diaphragm 10. This may be so generally, but only if suitably soft tissues within the patient's body rest against diaphragm 10, thereby transmitting external, atmospheric pressure to the diaphragm. This is by no means certain, however: stiffer fibrous tissue may, under some conditions, resist atmospheric pressure and - if located against the diaphragm 10 - alter the performance of the anti-siphon device 2.
production rate. So-called programmable pressure-drop regulators allow external readjustment of the pressure drop offered by the implanted device, but do not overcome this inherent problem.
One existing flow-rate regulator comprises an anti-siphon device 2 (illustrated schematically in section in figure 1) comprising a toroidal chamber 4, orifice 6 (above inner wall 8 of chamber 4) and diaphragm 10. Toroidal chamber 4 also has one or more inlets (not shown), in its outer wall 12 or base 14. The external pressure on diaphragm 10 is atmospheric, while the pressure within chamber 4 - during normal use - is atmospheric or somewhat higher. Under these conditions fluid flows 16 out of the device 2 via orifice 6. However, should siphoning occur, downstream pressure and therefore the pressure within chamber 4 drops (while the external pressure on diaphragm 10 remains atmospheric), pushing diaphragm 10 downwards and thereby reducing the size of orifice 6. Flow 16 is consequently reduced and, if the pressure drop is sufficiently great, stopped altogether.
However, this regulator is vulnerable to variations in external pressure, such as produced by the weight of the recumbent patient's body. Further, its operation assumes that atmospheric pressure will indeed be exerted on diaphragm 10. This may be so generally, but only if suitably soft tissues within the patient's body rest against diaphragm 10, thereby transmitting external, atmospheric pressure to the diaphragm. This is by no means certain, however: stiffer fibrous tissue may, under some conditions, resist atmospheric pressure and - if located against the diaphragm 10 - alter the performance of the anti-siphon device 2.
An alternative class of devices utilises gravity to change the valve resistance or opening pressure. However those that use ball weights malfunction when the valve is shaken by normal locomotion, and another device works only when the patient goes direct from upright to supine, and not in any other orientation. Anti-siphon devices are also sometimes used in series with pressure-regulating and other types of shunt valve. This increases the complexity of the implanted system, and thereby the likelihood of a malfunction.
It is an object of the present invention, therefore, to provide a regulator valve that can be employed to regulate flow-rate or pressure drop by employing a conduit located in a pressure-regulating external vessel or container.
The present invention provides, in a first aspect, a regulator valve for use in a fluid line, said regulator valve having:
a deformable conduit connectable to said fluid line to form thereby a portion of said fluid line;
a vessel enclosing said conduit, said vessel having an interior volume external to said conduit connectable to be in fluid comanunication with said fluid line upstream or downstream of said vessel;
wherein pressure in said fluid line regulates pressure in said interior volume and hence the pressure difference between pressure internal to said conduit and pressure in said interior volume of said vessel, so that said pressure difference and thereby the effective cross-sectional area of said conduit varies according to upstream or downstream pressure respectively within said fluid line.
Thus, the conduit will respond to the fluid pressure within the fluid line and either reduce or increase in effective cross-sectional area according to that pressure, therefore regulating fluid flow or pressure through the conduit and hence the fluid line.
If the interior volume is in fluid communication with the fluid line upstream, the characteristics are those of a flow-rate regulator. If the interior volume is in fluid communication with the fluid line downstream, the characteristics are those of a pressure-drop regulator.
Preferably the regulator valve includes an upstream duct to connect said interior volume of said vessel to be in fluid communication with said fluid line upstream of said vessel, wherein said conduit is collapsible (and preferably a collapsible tube).
It will be understood that a collapsible conduit (such a collapsible tube) could be regarded also as dilatable, in that - after collapsing - the conduit may return to its previously uncollapsed state under suitable pressure conditions. However, the term "collapsible" in the expressions "collapsible conduit", "collapsible tube", etc. is intended to suggest that, in its relaxed state, the conduit or tube is uncollapsed, and collapses in response to a finite but negative transmural pressure (i.e. where the pressure external to the conduit is greater than that internal to the conduit). Similarly, a dilatable conduit would be one that is undilated in its rest state, possibly in the form of an essentially flat tube, which dilates under conditions of finite, positive transmural pressure.
Preferably said upstream duct includes an upstream occluder so that said upstream duct can be closed, such as during implantation.
Preferably the regulator valve includes an adjustable flow resistor between said conduit and the point at which said upstream duct joins said fluid line, so that different levels of flow-rate regulation can be set.
In one embodiment the regulator valve includes a downstream duct to connect said interior volume of said vessel to be in fluid communication with said fluid line downstream of said vessel, in which case the conduit is preferably dilatable by large boundary deformation.
That is, the conduit preferably deforms by simply altering in shape (such as from essentially flat to elliptical or circular in cross-section). Many materials (e. g. latex) may have a reasonable degree of intrinsic elasticity, but nevertheless be employed simply to deform rather than stretch. Indeed, it is envisaged that, in physiological pressure regimes, dilatation through wall bending rather than stretching will be by far the dominant effect.
Preferably said downstream duct includes a downstream occluder so that said downstream duct can be closed, such as during implantation.
Preferably the regulator valve includes an adjustable flow resistor between said conduit and the point at which said downstream duct joins said fluid line, so that the constancy of pressure-drop regulation can be set.
In another embodiment, the regulator valve includes an upstream duct and a downstream duct to connect said interior volume of said vessel to be in fluid comanunication with said fluid line upstream and downstream, respectively, of said vessel, and either said upstream duct includes an upstream occluder or said downstream duct includes a downstream occluder.
In one particular embodiment, the regulator valve includes an upstream duct and a downstream duct to connect said interior volume of said vessel to be in fluid communication with said fluid line upstream and downstream, respectively, of said vessel, and said upstream duct includes an upstream occluder and said downstream duct includes a downstream occluder.
This would allow the regulator valve to be used with the vessel's interior volume connected either upstream or downstream. Even if the regulator valve is employed with the vessel's interior volume connected upstream, for example, it may be useful to provide the downstream duct and occluderso that the interior volume can be flushed periodically.
Preferably the regulator valve includes an adjustable upstream flow resistor between said conduit and the point at which said upstream duct joins said fluid line, so that different levels of flow-rate regulation can be set, or an adjustable downstream flow resistor between said conduit and the point at which said downstream duct joins said fluid line, so that the constancy of pressure-drop regulation can be set, or both.
The present invention also provides a fluid line including a regulator valve as described above.
The present invention also provides a shunt including a fluid line with a regulator valve as described above.
In a second broad aspect, the present invention provides a fluid line, having:
a deformable segment, variable in effective cross-sectional area when deformed;
a vessel enclosing said deformable segment, said vessel having an interior volume external to said deformable segment in fluid communication with said fluid line external to and upstream or downstream of said vessel;
whereby pressure within said interior volume exerted on said deformable segment, and therefore the cross-sectional area of said deformable segment, is regulated according to upstream or downstream pressure, respectively, within said fluid line.
In another broad aspect, the present invention provides a method of regulating fluid flow in a fluid line, involving:
providing in said fluid line a deformable segment that is variable in effective cross-sectional area when deformed;
enclosing said deformable segment in a vessel having an interior volume external to said deformable segment in fluid communication with said fluid line external to and upstream or downstream of said vessel;
whereby pressure within said interior volume exerted on said deformable segment, and therefore the cross-sectional area of said deformable segment, is regulated according to upstream or downstream pressure, respectively, within said fluid line.
In order that the present invention may be more clearly ascertained, embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which:
Figure la is a schematic view of a prior art antisiphon device;
Figure 1b is a schematic view of the prior art antisiphon device of figure la in a condition of reduced internal pressure;
Figure 2a is a schematic view of a shunt regulator valve according to an embodiment of the present invention;
Figure 2b is a schematic view of the shunt regulator valve of figure 2a under conditions of reduced transmural pressure;
_ g _ Figure 3 is a schematic view of a shunt regulator valve according to further embodiment of the present invention;
Figure 4 is a plot of measured pressure drop as a function of flow-rate for a variety of upstream flow resistances, obtained with the shunt regulator valve of figure 3 and a mixture of water and glycerine;
Figure 5 is a plot of measured pressure drop as a function of flow-rate at a fixed upstream flow resistance, illustrating hysteresis in this relationship, obtained with the shunt regulator valve of figure 3;
Figure 6 is a plot of measured pressure drop as a function of flow-rate for a variety of upstream flow resistances, obtained with the shunt regulator valve of figure 3 and water;
Figure 7 is a plot of a simulation of the shunt valve principle of the present invention where the vessel is in fluid communication with the fluid line upstream of the container, depicted as pressure drop (in arbitrary units) along the collapsible tube versus flow-rate; and Figure 8 is a plot of a simulation of the shunt valve principle of the present invention where the vessel is in fluid communication with the fluid line downstream of the container, depicted as pressure drop (in arbitrary units) along the dilatable tube versus flow-rate.
A shunt regulator valve according to a first embodiment of the present invention is illustrated schematically at 20, attached to a fluid line 22, in figure 2a. The fluid line 22 has upstream and downstream portions 22a and 22b respectively.
The regulator valve 20 includes a deformable conduit in the form of a small-diameter collapsible tube 24 (which forms in effect a part of fluid line 22a,22b) located inside a vessel in the form of container 26 which is effectively rigid at the pressures likely to be encountered in the envisaged physiological environment.
The regulator valve 20 also includes upstream and downstream ducts 28a and 28b, respectively, joining the interior volume 30 of container 26 to the respective upstream and downstream portions 22a and 22b of the fluid line. Each of upstream and downstream ducts 28a and 28b has an occluder 32a and 32b respectively, so that the ducts 28a,28b can be opened or closed as desired. The interior volume 30 may thus be rendered in fluid communication with the fluid line 22 either upstream or downstream, or both, depending on the settings of the occluders 32a and 32b.
When the upstream occluder 32a is open and the downstream occluder 32b is closed, the pressure in the external volume 30 of container 26 reflects the pressure of fluid entering the collapsible tube 24 upstream 24a; when the downstream occluder 32b is open and the upstream occluder 32a is closed the pressure in the external volume 30 of container 26 reflects the pressure of fluid leaving the collapsible tube 24 downstream 24b. In the former case, the characteristics of the valve 20 will approach flow-rate regulation. Means might be included to prevent both occluders 32a and 32b being open or closed simultaneously unless specifically required temporarily, such as to allow CSF to flush out the normally stagnant contents of the container 26.
In figures 2a and 2b (and indeed in figure 3), occluders 32a and 32b are shown as rotary taps for the purposes of the schematic only.
Figure 2b illustrates the regulator valve 20 of figure 2a in conditions in which upstream occluder 32a is open and downstream occluder 32b is closed, and the downstream pressure has dropped owing to siphoning effects. The pressure within the collapsible tube 24 drops as a result of the lower downstream pressure, while the pressure within the internal volume 30 of the container 26 remains relatively constant; the pressure difference or transmural pressure (which is thereby negative) causes the collapsible tube 24 to constrict, thereby reducing fluid flow and maintaining the upstream pressure.
Since the hydrostatic variation of pressure inside and outside the collapsible tube 24 is the same irrespective of orientation, the profile of tube illustrated in figure 2b reflects only a streamwise diminution of pressure within tube 24 owing to viscous flow. As a result, the operation of the whole device is independent of orientation.
A further embodiment of the present invention provides a shunt regulator valve 40 identical in most respects to valve 20 of figures 2a and 2b, but additionally provided with adjustable upstream and downstream flow resistors 42a and 42b as shown schematically in figure 3. Upstream flow resistor 42a is located in fluid line 22 between the container 26 and the junction of upstream duct 28a with the fluid line 22. Upstream flow resistor 42a permits the setting of different levels of flow-rate regulation when the valve 40 is employed with upstream occluder 32a open and downstream occluder 32b closed.
Downstream flow resistor 42b is located in fluid line 22 between the container 26 and the junction of downstream duct 28b with the fluid line 22. Downstream flow resistor 42b permits the setting of different degrees of constancy of pressure-rate regulation when the valve 40 is employed with upstream occluder 32a closed and downstream occluder 32b open.
This flexibility may be desirable as a further level of programanability in such a regulator valve, though the simplicity of valves without flow resistors may be preferred in some applications. In this latter case, the regulator valve would have its characteristics selected at manufacture, by specification of the resistance (or simply length) of the sections of conduit between the junctions to the occluders and the collapsible-tube mountings.
Example 1 An over-sized regulator valve (viz. in the context of a hydrocephalus shunt) of the type shown in figure 3 was constructed and tested in a series of trials, at a variety of flow resistances (set by means of an upstream flow resistor 42a) to simulate different flow-rates. The results, though obtained in an over-sized prototype, are referrable to a hydrocephalus shunt as the trials were conducted with water: glycerine (51~ by weight glycerine);
by the principle of scaling, the behaviour of the over-sized regulator valve with a viscous fluid is comparable to that of a miniature tube with the less viscous CSF
(which has properties similar to water). The temperature was carefully measured in all the trials because fluid viscosity is a strong function of temperature and is one of the quantities used in converting from measured flow-rate to the scaling parameter, Reynolds number or Re.
The collapsible tube employed was a latex rubber tube of nominal inside diameter 6.25 mm and measured wall thickness 0.268 mm, mounted between rigid pipes 281.5 mm apart. The water:glycerine fluid was propelled by an upstream head from an overflowing reservoir. Pressures entering, leaving and surrounding the collapsible tube were measured by means of disposable blood-pressure transducers. For each of the flow-limitation curves, a different value of the resistance just upstream of the collapsible tube was set by means of a micrometer-controlled flow resistor 42a (see figure 3).
The results are plotted as pressure drop Op (mm HZO) versus Reynolds number in figure 4, where the pressure drop Op is the pressure of fluid entering 44a the collapsible tube 24 minus the pressure of fluid leaving 44b the collapsible tube 24. The curves correspond, from left to right, to progressively higher micrometer settings M2, corresponding to progressively lesser flow resistances, as indicated above the upper end of each curve.
Figure 4 indicates flow-rate limitation where the curves turn parallel to the ordinate; the flow-rate, which is proportional to the Reynolds number, is then approximately constant despite variations in the pressure drop Op along the tube 24. (It should be noted that, for a hydrocephalus shunt, Reynolds numbers of between 1 and 25 are most likely to be encountered.) Thus the downstream pressure can be very low, implying a large pressure drop along the tube, without significant increase in the flow-rate.
Figure 5 is a plot of the M2 = 2.30 mm trial shown in figure 4. However, whereas only the results for the progressive reduction of ~p are shown in figure 4 (though data for the progressive raising of 0p were also obtained), figure 5 includes the results from both progressively raising Op over the experimental range and progressively lowering the pressure difference 0p over the same range. While some hysteresis is apparent, the desired flow-rate regulation was still observed.
Example 2 Another set of trials was performed with the same apparatus used in Example 1, but with water (rather than water: glycerine) in order to access much higher Reynolds numbers. The results are shown in figure 6, though with Op plotted against flow-rate Q (mL/s); again, each curve corresponds to a different flow resistance (indicated by micrometer setting M2), where a lower micrometer reading corresponds to a higher resistance.
The figure at the top of each curve is the Reynolds number when oscillations broke out (viz. when the next point above the topmost one plotted was attempted). This figure approximates the Reynolds number applying to the vertical section of each curve, i.e. the flow-rate did not change a great deal When oscillations started. The device would not oscillate below Re = 140 (bearing in mind that the Reynolds numbers of physiological interest are approximately 1 <_ Re <_ 25).
A simulation of the behaviour of the regulator valve (such as valve 20 of figure 2a, with upstream occluder 32a open and downstream occluder 32b closed) was performed, where the position of the junction between the upstream duct and the fluid line Was varied. The simulation assumed that the container (such as container 26 in figure 2a) Was in fluid coxmnunication with the fluid line upstream and not downstream. The results are plotted in figure 7 as pressure drop ~p over the length of the collapsible tube (in arbitrary units) versus flow-rate Q. The parameter xpg (indicated above each curve) represents the distance along the fluid line upstream of the collapsible tube at which this junction is located; the reservoir (representing the source of CSF) is two units upstream from the collapsible tube. Flow-rate limitation normally requires that the external pressure pe be held equal to or at a constant offset from the upstream pressure; this situation would pertain at xpe = 2. At the other extreme (i.e. xpg = 0), pe would be constant, With no flow limitation.
As may be seen in figure 7, the curves corresponding to 1 <_ xpe <_ 1.9 demonstrate flow-rate regulation, but the curve corresponding to xpe = 0.3 ceases to provide this function for ~p > 50.
Finally, a simulation was performed of the behaviour of a regulator valve such as valve 20 of figure 2a, but with upstream occluder 32a closed and downstream occluder 32b open (so that the container would be in fluid communication with the fluid line downstream and not upstream), and with collapsible tube 24 replaced by a dilatable tube. The dilatable tube would appear - in its relaxed state - much as the collapsible tube 24 in its collapsed state (such as in figure 2b) though almost completely flat, and in its dilated state much as the collapsible tube 24 in its relaxed state (such as in figure 2a). The dilatable tube required 20 units of positive transmural pressure to go from collapsed to dilated. In this simulation the position of the junction between the downstream duct and the fluid line was varied.
The results are plotted in figure 8 as pressure drop Op over the length of the collapsible tube (in arbitrary units) versus flow-rate Q. In this figure, the parameter xpg (indicated beside each curve) represents the distance of this junction downstream along the fluid line from the dilatable tube. Hence, xpg = 0 would correspond to having the junction at the downstream end of the dilatable tube, and xpg = 2 to having the junction 2 units downstream of the downstream end of the dilatable tube. The constant-pressure exit of the fluid line is two units downstream from the downstream end of the dilatable tube.
Pressure-drop limitation (indicated by the levelling out of the curves) is clearly visible. However, changing xpg, the position of the junction in the downstream line, does not change the level at which pressure-drop limitation sets in, only the slope of the curve once limited. The level is set by the positive transmural pressure (the degree to which the pressure in the container outside the dilatable tube exceeds that inside the tube) that is required to dilate the dilatable tube. That level is a property of the deformable tube. Consequently, in this embodiment the level is generally more conveniently selected at implantation, rather than 'programmed' from outside the skin after implantation.
Just as, in figure 7, it is apparent that flow-rate regulation ceases for xpe = 0.3 and Op > 50, it would be expected that, for excessively high values of xpg and flow-rate, pressure-drop regulation would also break down.
Indeed, the curves corresponding to xpg = 1.3 and xpe = 1.7 (which, above Q ~ 10, are indistinguishable) show this effect for Q > 10 and Q > 7.5 respectively.
In conclusion, while existing valves have drawbacks in some aspect of their performance, the present invention -employing a deformable conduit, not previously applied to shunt valve design - makes it possible to alleviate the relatively coamnon problem of over-drainage with change in patient posture. The embodiments described above provide an improved passive (as opposed to actively controlled) valve utilising soft materials, such as silicone rubber.
The device makes use of a natural flow- or pressure-control principle that is ideally adapted to this application, where it is the descent of downstream pressure which gives rise to the need for regulation. The valve is 'programmable' in the sense that that term is employed in this field, i.e. adjustable through the intact skin by the physician, and is expected to be relatively cheap to manufacture.
A further advantage over an existing device (such as that illustrated in figure 1) is that, according to the present invention, resistance is developed along the length of the deformable conduit, not merely across the lip of an orifice. The latter requiring a very small orifice, which makes that orifice susceptible to blockage and imposes greater demands on manufacturing tolerances. The _ 17 _ deformable conduit (and particularly the collapsible tube), however, distributes the resistance over a greater distance and therefore need not be so small; consequently it is less susceptible to blockage.
Modifications within the spirit and scope of the invention may readily be effected by persons skilled in the art. It is to be understood, therefore, that this invention is not limited to the particular embodiments described by way of example hereinabove.
It is an object of the present invention, therefore, to provide a regulator valve that can be employed to regulate flow-rate or pressure drop by employing a conduit located in a pressure-regulating external vessel or container.
The present invention provides, in a first aspect, a regulator valve for use in a fluid line, said regulator valve having:
a deformable conduit connectable to said fluid line to form thereby a portion of said fluid line;
a vessel enclosing said conduit, said vessel having an interior volume external to said conduit connectable to be in fluid comanunication with said fluid line upstream or downstream of said vessel;
wherein pressure in said fluid line regulates pressure in said interior volume and hence the pressure difference between pressure internal to said conduit and pressure in said interior volume of said vessel, so that said pressure difference and thereby the effective cross-sectional area of said conduit varies according to upstream or downstream pressure respectively within said fluid line.
Thus, the conduit will respond to the fluid pressure within the fluid line and either reduce or increase in effective cross-sectional area according to that pressure, therefore regulating fluid flow or pressure through the conduit and hence the fluid line.
If the interior volume is in fluid communication with the fluid line upstream, the characteristics are those of a flow-rate regulator. If the interior volume is in fluid communication with the fluid line downstream, the characteristics are those of a pressure-drop regulator.
Preferably the regulator valve includes an upstream duct to connect said interior volume of said vessel to be in fluid communication with said fluid line upstream of said vessel, wherein said conduit is collapsible (and preferably a collapsible tube).
It will be understood that a collapsible conduit (such a collapsible tube) could be regarded also as dilatable, in that - after collapsing - the conduit may return to its previously uncollapsed state under suitable pressure conditions. However, the term "collapsible" in the expressions "collapsible conduit", "collapsible tube", etc. is intended to suggest that, in its relaxed state, the conduit or tube is uncollapsed, and collapses in response to a finite but negative transmural pressure (i.e. where the pressure external to the conduit is greater than that internal to the conduit). Similarly, a dilatable conduit would be one that is undilated in its rest state, possibly in the form of an essentially flat tube, which dilates under conditions of finite, positive transmural pressure.
Preferably said upstream duct includes an upstream occluder so that said upstream duct can be closed, such as during implantation.
Preferably the regulator valve includes an adjustable flow resistor between said conduit and the point at which said upstream duct joins said fluid line, so that different levels of flow-rate regulation can be set.
In one embodiment the regulator valve includes a downstream duct to connect said interior volume of said vessel to be in fluid communication with said fluid line downstream of said vessel, in which case the conduit is preferably dilatable by large boundary deformation.
That is, the conduit preferably deforms by simply altering in shape (such as from essentially flat to elliptical or circular in cross-section). Many materials (e. g. latex) may have a reasonable degree of intrinsic elasticity, but nevertheless be employed simply to deform rather than stretch. Indeed, it is envisaged that, in physiological pressure regimes, dilatation through wall bending rather than stretching will be by far the dominant effect.
Preferably said downstream duct includes a downstream occluder so that said downstream duct can be closed, such as during implantation.
Preferably the regulator valve includes an adjustable flow resistor between said conduit and the point at which said downstream duct joins said fluid line, so that the constancy of pressure-drop regulation can be set.
In another embodiment, the regulator valve includes an upstream duct and a downstream duct to connect said interior volume of said vessel to be in fluid comanunication with said fluid line upstream and downstream, respectively, of said vessel, and either said upstream duct includes an upstream occluder or said downstream duct includes a downstream occluder.
In one particular embodiment, the regulator valve includes an upstream duct and a downstream duct to connect said interior volume of said vessel to be in fluid communication with said fluid line upstream and downstream, respectively, of said vessel, and said upstream duct includes an upstream occluder and said downstream duct includes a downstream occluder.
This would allow the regulator valve to be used with the vessel's interior volume connected either upstream or downstream. Even if the regulator valve is employed with the vessel's interior volume connected upstream, for example, it may be useful to provide the downstream duct and occluderso that the interior volume can be flushed periodically.
Preferably the regulator valve includes an adjustable upstream flow resistor between said conduit and the point at which said upstream duct joins said fluid line, so that different levels of flow-rate regulation can be set, or an adjustable downstream flow resistor between said conduit and the point at which said downstream duct joins said fluid line, so that the constancy of pressure-drop regulation can be set, or both.
The present invention also provides a fluid line including a regulator valve as described above.
The present invention also provides a shunt including a fluid line with a regulator valve as described above.
In a second broad aspect, the present invention provides a fluid line, having:
a deformable segment, variable in effective cross-sectional area when deformed;
a vessel enclosing said deformable segment, said vessel having an interior volume external to said deformable segment in fluid communication with said fluid line external to and upstream or downstream of said vessel;
whereby pressure within said interior volume exerted on said deformable segment, and therefore the cross-sectional area of said deformable segment, is regulated according to upstream or downstream pressure, respectively, within said fluid line.
In another broad aspect, the present invention provides a method of regulating fluid flow in a fluid line, involving:
providing in said fluid line a deformable segment that is variable in effective cross-sectional area when deformed;
enclosing said deformable segment in a vessel having an interior volume external to said deformable segment in fluid communication with said fluid line external to and upstream or downstream of said vessel;
whereby pressure within said interior volume exerted on said deformable segment, and therefore the cross-sectional area of said deformable segment, is regulated according to upstream or downstream pressure, respectively, within said fluid line.
In order that the present invention may be more clearly ascertained, embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which:
Figure la is a schematic view of a prior art antisiphon device;
Figure 1b is a schematic view of the prior art antisiphon device of figure la in a condition of reduced internal pressure;
Figure 2a is a schematic view of a shunt regulator valve according to an embodiment of the present invention;
Figure 2b is a schematic view of the shunt regulator valve of figure 2a under conditions of reduced transmural pressure;
_ g _ Figure 3 is a schematic view of a shunt regulator valve according to further embodiment of the present invention;
Figure 4 is a plot of measured pressure drop as a function of flow-rate for a variety of upstream flow resistances, obtained with the shunt regulator valve of figure 3 and a mixture of water and glycerine;
Figure 5 is a plot of measured pressure drop as a function of flow-rate at a fixed upstream flow resistance, illustrating hysteresis in this relationship, obtained with the shunt regulator valve of figure 3;
Figure 6 is a plot of measured pressure drop as a function of flow-rate for a variety of upstream flow resistances, obtained with the shunt regulator valve of figure 3 and water;
Figure 7 is a plot of a simulation of the shunt valve principle of the present invention where the vessel is in fluid communication with the fluid line upstream of the container, depicted as pressure drop (in arbitrary units) along the collapsible tube versus flow-rate; and Figure 8 is a plot of a simulation of the shunt valve principle of the present invention where the vessel is in fluid communication with the fluid line downstream of the container, depicted as pressure drop (in arbitrary units) along the dilatable tube versus flow-rate.
A shunt regulator valve according to a first embodiment of the present invention is illustrated schematically at 20, attached to a fluid line 22, in figure 2a. The fluid line 22 has upstream and downstream portions 22a and 22b respectively.
The regulator valve 20 includes a deformable conduit in the form of a small-diameter collapsible tube 24 (which forms in effect a part of fluid line 22a,22b) located inside a vessel in the form of container 26 which is effectively rigid at the pressures likely to be encountered in the envisaged physiological environment.
The regulator valve 20 also includes upstream and downstream ducts 28a and 28b, respectively, joining the interior volume 30 of container 26 to the respective upstream and downstream portions 22a and 22b of the fluid line. Each of upstream and downstream ducts 28a and 28b has an occluder 32a and 32b respectively, so that the ducts 28a,28b can be opened or closed as desired. The interior volume 30 may thus be rendered in fluid communication with the fluid line 22 either upstream or downstream, or both, depending on the settings of the occluders 32a and 32b.
When the upstream occluder 32a is open and the downstream occluder 32b is closed, the pressure in the external volume 30 of container 26 reflects the pressure of fluid entering the collapsible tube 24 upstream 24a; when the downstream occluder 32b is open and the upstream occluder 32a is closed the pressure in the external volume 30 of container 26 reflects the pressure of fluid leaving the collapsible tube 24 downstream 24b. In the former case, the characteristics of the valve 20 will approach flow-rate regulation. Means might be included to prevent both occluders 32a and 32b being open or closed simultaneously unless specifically required temporarily, such as to allow CSF to flush out the normally stagnant contents of the container 26.
In figures 2a and 2b (and indeed in figure 3), occluders 32a and 32b are shown as rotary taps for the purposes of the schematic only.
Figure 2b illustrates the regulator valve 20 of figure 2a in conditions in which upstream occluder 32a is open and downstream occluder 32b is closed, and the downstream pressure has dropped owing to siphoning effects. The pressure within the collapsible tube 24 drops as a result of the lower downstream pressure, while the pressure within the internal volume 30 of the container 26 remains relatively constant; the pressure difference or transmural pressure (which is thereby negative) causes the collapsible tube 24 to constrict, thereby reducing fluid flow and maintaining the upstream pressure.
Since the hydrostatic variation of pressure inside and outside the collapsible tube 24 is the same irrespective of orientation, the profile of tube illustrated in figure 2b reflects only a streamwise diminution of pressure within tube 24 owing to viscous flow. As a result, the operation of the whole device is independent of orientation.
A further embodiment of the present invention provides a shunt regulator valve 40 identical in most respects to valve 20 of figures 2a and 2b, but additionally provided with adjustable upstream and downstream flow resistors 42a and 42b as shown schematically in figure 3. Upstream flow resistor 42a is located in fluid line 22 between the container 26 and the junction of upstream duct 28a with the fluid line 22. Upstream flow resistor 42a permits the setting of different levels of flow-rate regulation when the valve 40 is employed with upstream occluder 32a open and downstream occluder 32b closed.
Downstream flow resistor 42b is located in fluid line 22 between the container 26 and the junction of downstream duct 28b with the fluid line 22. Downstream flow resistor 42b permits the setting of different degrees of constancy of pressure-rate regulation when the valve 40 is employed with upstream occluder 32a closed and downstream occluder 32b open.
This flexibility may be desirable as a further level of programanability in such a regulator valve, though the simplicity of valves without flow resistors may be preferred in some applications. In this latter case, the regulator valve would have its characteristics selected at manufacture, by specification of the resistance (or simply length) of the sections of conduit between the junctions to the occluders and the collapsible-tube mountings.
Example 1 An over-sized regulator valve (viz. in the context of a hydrocephalus shunt) of the type shown in figure 3 was constructed and tested in a series of trials, at a variety of flow resistances (set by means of an upstream flow resistor 42a) to simulate different flow-rates. The results, though obtained in an over-sized prototype, are referrable to a hydrocephalus shunt as the trials were conducted with water: glycerine (51~ by weight glycerine);
by the principle of scaling, the behaviour of the over-sized regulator valve with a viscous fluid is comparable to that of a miniature tube with the less viscous CSF
(which has properties similar to water). The temperature was carefully measured in all the trials because fluid viscosity is a strong function of temperature and is one of the quantities used in converting from measured flow-rate to the scaling parameter, Reynolds number or Re.
The collapsible tube employed was a latex rubber tube of nominal inside diameter 6.25 mm and measured wall thickness 0.268 mm, mounted between rigid pipes 281.5 mm apart. The water:glycerine fluid was propelled by an upstream head from an overflowing reservoir. Pressures entering, leaving and surrounding the collapsible tube were measured by means of disposable blood-pressure transducers. For each of the flow-limitation curves, a different value of the resistance just upstream of the collapsible tube was set by means of a micrometer-controlled flow resistor 42a (see figure 3).
The results are plotted as pressure drop Op (mm HZO) versus Reynolds number in figure 4, where the pressure drop Op is the pressure of fluid entering 44a the collapsible tube 24 minus the pressure of fluid leaving 44b the collapsible tube 24. The curves correspond, from left to right, to progressively higher micrometer settings M2, corresponding to progressively lesser flow resistances, as indicated above the upper end of each curve.
Figure 4 indicates flow-rate limitation where the curves turn parallel to the ordinate; the flow-rate, which is proportional to the Reynolds number, is then approximately constant despite variations in the pressure drop Op along the tube 24. (It should be noted that, for a hydrocephalus shunt, Reynolds numbers of between 1 and 25 are most likely to be encountered.) Thus the downstream pressure can be very low, implying a large pressure drop along the tube, without significant increase in the flow-rate.
Figure 5 is a plot of the M2 = 2.30 mm trial shown in figure 4. However, whereas only the results for the progressive reduction of ~p are shown in figure 4 (though data for the progressive raising of 0p were also obtained), figure 5 includes the results from both progressively raising Op over the experimental range and progressively lowering the pressure difference 0p over the same range. While some hysteresis is apparent, the desired flow-rate regulation was still observed.
Example 2 Another set of trials was performed with the same apparatus used in Example 1, but with water (rather than water: glycerine) in order to access much higher Reynolds numbers. The results are shown in figure 6, though with Op plotted against flow-rate Q (mL/s); again, each curve corresponds to a different flow resistance (indicated by micrometer setting M2), where a lower micrometer reading corresponds to a higher resistance.
The figure at the top of each curve is the Reynolds number when oscillations broke out (viz. when the next point above the topmost one plotted was attempted). This figure approximates the Reynolds number applying to the vertical section of each curve, i.e. the flow-rate did not change a great deal When oscillations started. The device would not oscillate below Re = 140 (bearing in mind that the Reynolds numbers of physiological interest are approximately 1 <_ Re <_ 25).
A simulation of the behaviour of the regulator valve (such as valve 20 of figure 2a, with upstream occluder 32a open and downstream occluder 32b closed) was performed, where the position of the junction between the upstream duct and the fluid line Was varied. The simulation assumed that the container (such as container 26 in figure 2a) Was in fluid coxmnunication with the fluid line upstream and not downstream. The results are plotted in figure 7 as pressure drop ~p over the length of the collapsible tube (in arbitrary units) versus flow-rate Q. The parameter xpg (indicated above each curve) represents the distance along the fluid line upstream of the collapsible tube at which this junction is located; the reservoir (representing the source of CSF) is two units upstream from the collapsible tube. Flow-rate limitation normally requires that the external pressure pe be held equal to or at a constant offset from the upstream pressure; this situation would pertain at xpe = 2. At the other extreme (i.e. xpg = 0), pe would be constant, With no flow limitation.
As may be seen in figure 7, the curves corresponding to 1 <_ xpe <_ 1.9 demonstrate flow-rate regulation, but the curve corresponding to xpe = 0.3 ceases to provide this function for ~p > 50.
Finally, a simulation was performed of the behaviour of a regulator valve such as valve 20 of figure 2a, but with upstream occluder 32a closed and downstream occluder 32b open (so that the container would be in fluid communication with the fluid line downstream and not upstream), and with collapsible tube 24 replaced by a dilatable tube. The dilatable tube would appear - in its relaxed state - much as the collapsible tube 24 in its collapsed state (such as in figure 2b) though almost completely flat, and in its dilated state much as the collapsible tube 24 in its relaxed state (such as in figure 2a). The dilatable tube required 20 units of positive transmural pressure to go from collapsed to dilated. In this simulation the position of the junction between the downstream duct and the fluid line was varied.
The results are plotted in figure 8 as pressure drop Op over the length of the collapsible tube (in arbitrary units) versus flow-rate Q. In this figure, the parameter xpg (indicated beside each curve) represents the distance of this junction downstream along the fluid line from the dilatable tube. Hence, xpg = 0 would correspond to having the junction at the downstream end of the dilatable tube, and xpg = 2 to having the junction 2 units downstream of the downstream end of the dilatable tube. The constant-pressure exit of the fluid line is two units downstream from the downstream end of the dilatable tube.
Pressure-drop limitation (indicated by the levelling out of the curves) is clearly visible. However, changing xpg, the position of the junction in the downstream line, does not change the level at which pressure-drop limitation sets in, only the slope of the curve once limited. The level is set by the positive transmural pressure (the degree to which the pressure in the container outside the dilatable tube exceeds that inside the tube) that is required to dilate the dilatable tube. That level is a property of the deformable tube. Consequently, in this embodiment the level is generally more conveniently selected at implantation, rather than 'programmed' from outside the skin after implantation.
Just as, in figure 7, it is apparent that flow-rate regulation ceases for xpe = 0.3 and Op > 50, it would be expected that, for excessively high values of xpg and flow-rate, pressure-drop regulation would also break down.
Indeed, the curves corresponding to xpg = 1.3 and xpe = 1.7 (which, above Q ~ 10, are indistinguishable) show this effect for Q > 10 and Q > 7.5 respectively.
In conclusion, while existing valves have drawbacks in some aspect of their performance, the present invention -employing a deformable conduit, not previously applied to shunt valve design - makes it possible to alleviate the relatively coamnon problem of over-drainage with change in patient posture. The embodiments described above provide an improved passive (as opposed to actively controlled) valve utilising soft materials, such as silicone rubber.
The device makes use of a natural flow- or pressure-control principle that is ideally adapted to this application, where it is the descent of downstream pressure which gives rise to the need for regulation. The valve is 'programmable' in the sense that that term is employed in this field, i.e. adjustable through the intact skin by the physician, and is expected to be relatively cheap to manufacture.
A further advantage over an existing device (such as that illustrated in figure 1) is that, according to the present invention, resistance is developed along the length of the deformable conduit, not merely across the lip of an orifice. The latter requiring a very small orifice, which makes that orifice susceptible to blockage and imposes greater demands on manufacturing tolerances. The _ 17 _ deformable conduit (and particularly the collapsible tube), however, distributes the resistance over a greater distance and therefore need not be so small; consequently it is less susceptible to blockage.
Modifications within the spirit and scope of the invention may readily be effected by persons skilled in the art. It is to be understood, therefore, that this invention is not limited to the particular embodiments described by way of example hereinabove.
Claims (19)
1. A regulator valve for use in a fluid line, said regulator valve having:
a deformable conduit connectable to said fluid line to form thereby a portion of said fluid line;
a vessel enclosing said conduit, said vessel having an interior volume external to said conduit connectable to be in fluid communication with said fluid line upstream or downstream of said vessel;
wherein pressure in said fluid line regulates pressure in said interior volume and hence the pressure difference between pressure internal to said conduit and pressure in said interior volume of said vessel, so that said pressure difference and thereby the effective cross-sectional area of said conduit varies according to upstream or downstream pressure respectively within said fluid line.
a deformable conduit connectable to said fluid line to form thereby a portion of said fluid line;
a vessel enclosing said conduit, said vessel having an interior volume external to said conduit connectable to be in fluid communication with said fluid line upstream or downstream of said vessel;
wherein pressure in said fluid line regulates pressure in said interior volume and hence the pressure difference between pressure internal to said conduit and pressure in said interior volume of said vessel, so that said pressure difference and thereby the effective cross-sectional area of said conduit varies according to upstream or downstream pressure respectively within said fluid line.
2. A regulator valve as claimed in claim 1, including an upstream duct to connect said interior volume of said vessel to be in fluid communication with said fluid line upstream of said vessel, wherein said conduit is collapsible.
3. A regulator valve as claimed in claim 2, wherein said conduit is a collapsible tube.
4. A regulator valve as claimed in either claim 2 or 3, wherein said upstream duct includes an upstream occluder so that said upstream duct can be closed.
5. A regulator valve as claimed in any one of claims 2 to 4, including an adjustable flow resistor between said conduit and the point at which said upstream duct joins said fluid line, so that different levels of flow-rate regulation can be set.
6. A regulator valve as claimed in claim 1, including a downstream duct to connect said interior volume of said vessel to be in fluid communication with said fluid line downstream of said vessel.
7. A regulator valve as claimed in claim 6, wherein said conduit is dilatable by large boundary deformation.
8. A regulator valve as claimed in either claim 6 or 7, wherein said downstream duct includes a downstream occluder so that said downstream duct can be closed.
9. A regulator valve as claimed in any one of claims 6 to 8, including an adjustable flow resistor between said conduit and the point at which said downstream duct joins said fluid line, so that the constancy of pressure-drop regulation can be set.
10. A regulator valve as claimed in claim 1, including an upstream duct and a downstream duct to connect said interior volume of said vessel to be in fluid communication with said fluid line upstream and downstream, respectively, of said vessel, and either said upstream duct includes an upstream occluder or said downstream duct includes a downstream occluder.
11. A regulator valve as claimed in claim 1, including an upstream duct and a downstream duct to connect said interior volume of said vessel to be in fluid communication with said fluid line upstream and downstream, respectively, of said vessel, and said upstream duct includes an upstream occluder and said downstream duct includes a downstream occluder.
12. A regulator valve as claimed in claim 11, including an adjustable upstream flow resistor between said conduit and the point at which said upstream duct joins said fluid line, so that different levels of flow-rate regulation can be set, or an adjustable downstream flow resistor between said conduit and the point at which said downstream duct joins said fluid line, so that the constancy of pressure-drop regulation can be set, or both.
13. A fluid line including a regulator valve as claimed in any one of the preceding claims.
14. A shunt including a fluid line with a regulator valve, said fluid line as claimed in claim 13.
15. A fluid line, having:
a deformable segment, variable in effective cross-sectional area when deformed;
a vessel enclosing said deformable segment, said vessel having an interior volume external to said deformable segment in fluid communication with said fluid line external to and upstream or downstream of said vessel;
whereby pressure within said interior volume exerted on said deformable segment, and therefore the cross-sectional area of said deformable segment, is regulated according to upstream or downstream pressure, respectively, within said fluid line.
a deformable segment, variable in effective cross-sectional area when deformed;
a vessel enclosing said deformable segment, said vessel having an interior volume external to said deformable segment in fluid communication with said fluid line external to and upstream or downstream of said vessel;
whereby pressure within said interior volume exerted on said deformable segment, and therefore the cross-sectional area of said deformable segment, is regulated according to upstream or downstream pressure, respectively, within said fluid line.
16. A fluid line as claimed in claim 15, including an upstream duct to connect said interior volume of said vessel to be in fluid communication with said fluid line upstream of said vessel, wherein said deformable segment is collapsible.
17. A method of regulating fluid flow in a fluid line, involving:
providing in said fluid line a deformable segment that is variable in effective cross-sectional area when deformed;
enclosing said deformable segment in a vessel having an interior volume external to said deformable segment in fluid communication with said fluid line external to and upstream or downstream of said vessel;
whereby pressure within said interior volume exerted on said deformable segment, and therefore the cross-sectional area of said deformable segment, is regulated according to upstream or downstream pressure, respectively, within said fluid line.
providing in said fluid line a deformable segment that is variable in effective cross-sectional area when deformed;
enclosing said deformable segment in a vessel having an interior volume external to said deformable segment in fluid communication with said fluid line external to and upstream or downstream of said vessel;
whereby pressure within said interior volume exerted on said deformable segment, and therefore the cross-sectional area of said deformable segment, is regulated according to upstream or downstream pressure, respectively, within said fluid line.
18. A method as claimed in claim 17, including establishing said interior volume to be in fluid communication with said fluid line upstream of said vessel, wherein said deformable segment is collapsible.
19. A method as claimed in claim 17, including establishing said interior volume to be in fluid communication with said fluid line downstream of said vessel, wherein said deformable segment is dilatable by large boundary deformation.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2338497 CA2338497A1 (en) | 2001-02-27 | 2001-02-27 | Regulator valve |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2338497 CA2338497A1 (en) | 2001-02-27 | 2001-02-27 | Regulator valve |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2338497A1 true CA2338497A1 (en) | 2002-08-27 |
Family
ID=4168445
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2338497 Abandoned CA2338497A1 (en) | 2001-02-27 | 2001-02-27 | Regulator valve |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2338497A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2371759A1 (en) | 2010-03-29 | 2011-10-05 | Anheuser-Busch InBev S.A. | Beverage dispensing apparatus comprising self-regulated flow control means |
-
2001
- 2001-02-27 CA CA 2338497 patent/CA2338497A1/en not_active Abandoned
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2371759A1 (en) | 2010-03-29 | 2011-10-05 | Anheuser-Busch InBev S.A. | Beverage dispensing apparatus comprising self-regulated flow control means |
| WO2011120883A1 (en) | 2010-03-29 | 2011-10-06 | Anheuser-Busch Inbev Nv | Beverage dispensing apparatus comprising self-regulated flow control means |
| US8839993B2 (en) | 2010-03-29 | 2014-09-23 | Anheuser-Busch Inbev Nv | Beverage dispensing apparatus comprising self-regulated flow control means |
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