WO2011131790A1

WO2011131790A1 - Fluid dispensing device and method for emptying a collapsible reservoir

Info

Publication number: WO2011131790A1
Application number: PCT/EP2011/056496
Authority: WO
Inventors: Olivier Fuchs; Raymond Campagnolo
Original assignee: Commissariat à l'énergie atomique et aux énergies alternatives
Priority date: 2010-04-23
Filing date: 2011-04-22
Publication date: 2011-10-27
Also published as: FR2959224A1

Abstract

The invention relates to a method for emptying a collapsible reservoir (1), such that it is possible to detect when said tank (1) has finished emptying. For this purpose, the invention consists in measuring the pressure of the fluid in an outlet duct (3) that is fluidically connected to the reservoir (1) and stopping the reservoir from being emptied when the value of a parameter, which depends on the pressure of the fluid or its derivative and is obtained from the pressure measured, reaches a reference value, said reference value having been calculated in an adaptive manner according to a plurality of successive pressure measurements.

Description

DEVICE FOR DISPENSING A FLUID AND METHOD FOR DRAINING A RESERVOIR

collapsible

DESCRIPTION

TECHNICAL AREA

The present invention relates to the general field of the emptying of a collapsible reservoir (collapsible reservoir, in English), comprising walls, including at least one flexible wall, delimiting an interior volume of reservoir. It also relates to a device for dispensing a fluid of interest contained in such a tank.

STATE OF THE PRIOR ART

It is common practice to use devices for dispensing or injecting a fluid from a collapable reservoir containing said fluid.

A collabable reservoir is a flexible and sealed reservoir, comprising walls, including at least one flexible wall, defining an interior reservoir volume. The flexible wall is able to deform freely under stress, so that the internal volume remains substantially equal to the volume of the fluid that it contains.

The internal volume of the reservoir can be fluidly connected to a pump through a fluid outlet conduit. Thus, the actuation of the pump causes the emptying of the tank, causing the decrease of its internal volume, by deformation of the flexible wall, as the volume of the fluid still present in the tank decreases.

During the emptying, the pressure of the fluid in the reservoir remains substantially equal to the external pressure, that is to say to the pressure of the medium in which the reservoir is placed, insofar as the internal volume of the reservoir adapts substantially continuously to the volume of fluid remaining. Also, before emptying the tank or during emptying, the pressure difference across the flexible wall is relatively small, typically less than a few tens of millibars.

Collabable tanks thus have the advantage of imposing only a low pressure resistance at the inlet of the pump, independently of the pressure drop relative to the outlet duct. The energy required for the pump to empty the tank is then minimized.

However, it is particularly important to detect, when draining a collabable tank, the moment when the tank becomes empty or almost empty. Detection means are generally provided which inform the user of the need to stop the pump and / or to change the reservoir.

Also, in the absence of change of the tank or stoppage of the pump by the user, it continues to operate despite the total emptying of the tank. The risk is then important that a malfunction occurs, such as a heating of the pump, or a degradation of the fluid circuit. The European patent application EP-0 965 423 describes an example of a device for dispensing a fluid of interest from a collapable reservoir, comprising means for detecting the substantially empty nature of said reservoir.

The dispensing device according to this document comprises a collabable reservoir whose interior volume is fluidly connected to a peristaltic pump by an outlet duct. The pump is then fluidly connected to a fluid dispensing conduit.

The means for detecting the substantially empty nature of the reservoir comprise a capacitive fluid level sensor disposed near a vertical rigid wall delimiting the internal volume of the reservoir.

Actuation of the peristaltic pump causes fluid flow from the reservoir into the outlet conduit and into the dispensing conduit.

As the tank empties, the fluid level in the tank decreases continuously. When the sensor detects that the fluid level reaches a threshold level, an audible or light signal is emitted which informs the user that the reservoir becomes substantially empty. The pump can be stopped, or the tank replaced.

However, this example of a device for dispensing a fluid of interest has a number of disadvantages.

Indeed, the capacitive sensor requires that the fluid of interest to be dispensed is electrically conductor, so as to allow the creation of a capacitance to be measured between the conductive fluid and the capacitive sensor. This type of detection means can not be used regardless of the electrical properties of the fluid of interest.

In addition, the walls of the reservoir must be made of a material that is compatible with the capacitive measurement of the fluid level, so as not to disturb the measurements made.

Furthermore, this sensor is necessarily arranged vertically, near an equally vertical wall of the tank, in order to detect the level, or height, of the fluid contained in the tank. It can therefore not be arranged horizontally, nor can it be used with a collabable tank whose interior volume would be delimited only by one or more flexible walls (s).

STATEMENT OF THE INVENTION

The object of the invention is to present a method of emptying a collapsible reservoir, at least partially overcoming the aforementioned drawbacks relating to the example of the prior art.

In order to do this, the object of the invention is a method of emptying a collapsible reservoir, said reservoir comprising walls, of which at least one flexible wall, defining an interior volume of the reservoir, said internal volume of the reservoir being filled with a fluid of interest and fluidly connected to a pump via an outlet duct.

According to the invention, the method comprises the steps according to which: a flow of the fluid of interest from the reservoir in the outlet duct is generated by actuation of the pump, causing a decrease in the internal volume of the tank by deformation of the at least one flexible wall. ;

a plurality of pressure measurements of the fluid of interest are made in the outlet duct;

a value of a parameter, which is a function of the pressure of said fluid of interest or of its derivative, is obtained from the pressure thus measured, and said value thus obtained is compared with a reference value, the reference value having been previously calculated from said plurality of successive measurements of the pressure;

- It stops the emptying of the tank, when said value of the parameter reaches the reference value.

By collabable reservoir is meant a flexible and sealed reservoir, having walls, including at least one flexible wall, defining an internal reservoir volume, so that the reservoir internal volume remains substantially equal to the volume of the fluid that it contains.

It should be noted that the terms "flexible" and "flexible" are considered synonymous here. They reflect the fact that the reservoir and the wall (s) considered (s) are likely to deform freely under stress. Preferably, the deformation is in the elastic regime, so that the reservoir and the wall or walls (s) can present their original shape again. According to the invention, the actuation of the pump causes the emptying of the reservoir and thus 1 / flow of the fluid of interest in the outlet duct. The flexible wall or walls of the tank then deforms so that the internal volume of the tank is substantially continuously adapted to the volume of fluid of interest still present in the tank.

When the reservoir becomes substantially empty, the pressure of the fluid of interest in the outlet conduit decreases abruptly. When the value of a parameter, which is a function of the pressure of the fluid or its derivative, obtained from the measured pressure, reaches a reference value, it can be deduced that the reservoir is substantially empty and the pump can then be stopped.

The parameter may be an increasing function of fluid pressure or its derivative. The value of the parameter can reach the reference value when it is less than or equal to it.

The parameter can be a decreasing function of the fluid pressure or its derivative. The value of the parameter can reach the reference value when it is greater than or equal to this value.

By derivative of the pressure is meant the time derivative of the pressure of the fluid of interest in the outlet duct.

The substantially empty nature of the reservoir reflects the fact that the fluid volume of interest possibly contained in the reservoir is negligible vis-à-vis the volume of fluid initially present. It should be noted that in the case of a tank only provided with rigid walls, the internal volume of the tank can not adapt to the volume of the fluid. Also, the pressure of the fluid of interest in the outlet duct decreases continuously as the reservoir is drained, and does not show a sharp decrease when the reservoir becomes substantially empty.

The pressure measured in the outlet duct may be the absolute pressure of the fluid of interest or the relative pressure of the fluid of interest relative to a substantially constant external pressure of a fluid surrounding the reservoir. Relative pressure means the absolute pressure of the fluid minus the external pressure. The external pressure may be the atmospheric pressure at the dispensing device.

Said parameter is preferably chosen from the pressure of the fluid of interest in the outlet duct and the time derivative of said pressure.

According to the first embodiment of

According to the invention, said parameter is the pressure of the fluid of interest in the outlet duct.

According to a second embodiment of

According to the invention, said parameter is an average pressure of the fluid of interest in the outlet duct obtained from at least a part of the plurality of successive measurements of the pressure.

According to a third embodiment of

According to the invention, said parameter is a time derivative of an average pressure of the fluid of interest in the outlet duct, said average pressure being obtained from at least a part of the plurality of successive measurements of the pressure.

The previously calculated reference value is advantageously equal to an average pressure of the fluid of interest in the outlet duct to which is subtracted the associated standard deviation weighted by a strictly positive predetermined x coefficient, the mean pressure and the difference between type being calculated from at least a portion of said plurality of successive measurements of the pressure.

The previously calculated reference value may also be equal to an average pressure of the fluid of interest in the outlet duct to which is subtracted a constant initial value of the pressure of the fluid in the weighted outlet duct by a predetermined positive positive coefficient y and less than 1, the average pressure being calculated from at least a portion of said plurality of successive measurements of the pressure.

The invention also relates to a device for dispensing a fluid of interest comprising a collapsible reservoir comprising walls, at least one flexible wall of which defines an internal volume of the reservoir, said internal volume of the reservoir being filled with the fluid of interest, a pump fluidly connected to the interior of the tank through an outlet conduit, and pump control means connected to said pump to control the operation thereof. According to the invention,. the dispensing device comprises pressure measuring means able to measure the pressure of the fluid of interest in the outlet duct; calculating means capable of obtaining a value of a parameter, which is a function of the pressure of said fluid of interest or its derivative, from the measured pressure, said calculation means being furthermore suitable for calculating a reference value at from a plurality of successive measurements of said pressure; and control means adapted to compare said value of the parameter thus obtained with said reference value, and to send an end of drain signal when said value of the parameter has reached the reference value.

The measuring means may comprise a pressure sensor connected to the outlet duct for measuring the pressure of the fluid in said duct.

The calculating means may be connected to said pressure sensor for receiving a pressure value from the pressure sensor. They can obtain a value of the parameter from the pressure thus measured.

The control means may be electrically connected to the calculation means for receiving from said means a value of said parameter and said reference value, and are able to compare said value of said parameter with said reference value.

The control means may be electrically connected to said control means of the pump, for transmitting said end of drain signal to said control means.

Other advantages and features of the invention will become apparent in the detailed non-limiting description below.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of nonlimiting examples, with reference to the accompanying drawings, in which:

Figure 1 is a schematic view of a dispensing device of a fluid of interest according to a first embodiment of the invention, when the tank is being drained;

Figure 2 is a schematic view of the dispensing device shown in Figure 1, the collapsible reservoir being substantially empty;

FIG. 3 illustrates an example of time evolution of the pressure of the fluid of interest in the outlet duct, and the comparison thereof with a constant reference value;

Figure 4 is a schematic view of a dispensing device according to a variant of the first embodiment, wherein the internal volume of the collapsible reservoir is entirely delimited by a flexible wall;

FIG. 5 illustrates, with reference to the second and third embodiments of the invention, a temporal evolution of the pressure of the fluid of interest in the output duct, as well as the time evolution of a reference value;

FIG. 6 is a schematic view of a device for dispensing a fluid of interest according to a fourth embodiment of the invention, in which the means for measuring and analyzing the pressure comprise a pressure sensor at threshold;

FIGS. 7A and 7B are a schematic view of a part of a device for dispensing a fluid of interest according to another embodiment of the invention, in which the reservoir is placed in a hermetically sealed enclosure. ; and

FIG. 8 illustrates, with reference to the embodiment of FIGS. 7A and 7B, a time evolution of the pressure of the fluid of interest in the outlet duct, as well as the time evolution of the external pressure.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

In Figure 1 is shown schematically a device for dispensing a fluid of interest according to a first embodiment, comprising a collabable reservoir 1.

The tank 1 comprises walls, including at least one flexible wall 2, defining an interior volume of the tank, filled with the fluid to be dispensed.

The internal volume of the tank is fluidly connected to a pump 10 via an outlet pipe 3. The outlet duct 3 may be a tube or a tube. channel, allowing the flow of the fluid of interest within it.

The pump 10 can then be connected fluidly to a conduit for dispensing the fluid of interest.

Control means 30 of the pump are electrically connected thereto, and make it possible to control its operation.

The dispensing device further comprises means 21 for measuring the pressure of the fluid in the outlet duct 3, calculation means 22 and control means 23.

Said measuring means 21 are adapted to measure the pressure of the fluid of interest in the outlet duct 3.

The calculation means 22 are adapted to obtain the value of a parameter, which is a function of the pressure of the fluid in the outlet duct or of its derivative, from the measured pressure.

Finally, the control means 23 are adapted to compare said value thus obtained with a reference value, and to send an end of drain signal when said value of the parameter reaches the reference value.

According to the first embodiment of the invention, the measuring means 21 comprise a pressure sensor 21, making it possible to measure the pressure of the fluid of interest in the outlet duct 3, between the tank 1 and the pump 10. The pressure measured may be the absolute pressure of the fluid, or the relative pressure of the fluid relative to a substantially constant external pressure of the surrounding atmosphere.

The calculation means 22 are electrically connected to the pressure sensor 21 to receive therefrom, during the emptying of the tank, a plurality of successive values for measuring the pressure.

From the measured pressure, the calculation means 22 obtain a value of a parameter, which is a function of the pressure of the fluid in the outlet duct or its derivative.

According to the first embodiment of the invention, said parameter is the pressure of the fluid of interest in the outlet duct 3. Also, the value of the parameter coincides with the value of the measured pressure.

The calculation means 22 also include means for storing a reference value. The reference value here is a constant pressure value. This value may be predetermined arbitrarily or established by experimental tests.

The control means 23 are electrically connected to the calculation means 22 and receive therefrom the value of said parameter and the reference value. They ensure the comparison between said two received values.

To ensure these various functions, the calculation means 22 and the control means 23 may comprise, in a conventional manner, a microprocessor, at least one random access memory and at least one read-only memory or memory card.

The reference value can be determined and entered into a memory of the calculation means 22 in advance. It can also be calculated automatically by the calculation means 22, based on at least one pressure measurement of the fluid of interest in the conduit. output 3 before the emptying of the tank 1 is initiated.

It should be noted that, in the case of a collapsible reservoir, the initial pressure of the fluid before emptying is substantially equal to the atmospheric external pressure of the fluid surrounding the reservoir 1.

Thus, in the case of a measurement of the absolute pressure of the fluid of interest by the pressure sensor 21, the reference value may be less than or equal to 3Pi / 4, Pi / 2 or even Pi / 10, where Pi is the initial absolute pressure of the fluid of interest in the outlet pipe 3, this pressure value being substantially equal to the atmospheric external pressure P _e .

In the case of a measurement of the relative pressure of the fluid of interest by the pressure sensor 21 vis-à-vis the external pressure P _e , the reference value may be less than or equal to 3P _e / 4-P _e , P _e / 2-P _e , or even P _e / 10-P _e .

Depending on the result of this comparison, the control means 23 may emit an end of drain signal. This signal indicates that the tank collabable is substantially empty and the emptying must be stopped.

Preferably, the control means 23 are electrically connected to the control means 30 of the pump 10. The end of emptying signal can then be an electrical signal transmitted to the control means 30 so that they ensure the stopping of the Draining the Tank 1. The operation of the fluid dispensing device of interest according to the first embodiment is now described with reference to Figures 1 to 3.

The reservoir 1 is initially filled with a fluid of interest to be dispensed. The internal volume of the reservoir 1 is substantially equal to the volume of the fluid present.

The emptying of the tank 1 is initiated by actuation of the pump 10, which results in a flow of the fluid of interest from the interior volume of the tank through the outlet duct 3.

As the volume of the fluid in the reservoir 1 decreases, the internal volume of the reservoir also decreases by deformation of the flexible wall 2, to ensure a substantial equality between the two volumes.

The pressure sensor 21 carries out successive measurements of the pressure of the fluid of interest, between the tank 1 and the pump 10, in the outlet duct 3. Each value of the measured pressure is transmitted to the calculation means 22, which transmit to the control means 23 the value of the measured pressure and the reference value. These compare these two received values.

FIG. 3 illustrates the temporal evolution, during emptying of the tank 1, of the relative pressure of the fluid of interest in the outlet pipe 3 with respect to an external pressure of the atmosphere surrounding the tank 1.

The curve of FIG. 3 shows that the pressure of the fluid in the duct 3 is substantially constant, and a few millibar lower than said external pressure. It is indeed a property of collabable tanks to have a substantially constant fluid pressure during emptying, due to the substantially continuous adaptation of the internal volume of the reservoir to the volume of the fluid still present therein, by deformation of the flexible wall 2.

It should be noted that, during the emptying, the pressure of the fluid in the tank is substantially identical to the pressure of the fluid in the outlet duct 3, with a coefficient substantially equal to the pressure drop associated with said duct 3.

At the end of emptying (FIG. 2), the tank 1 becomes substantially empty, insofar as the volume of the fluid possibly present in the tank is substantially negligible with respect to the initial volume of fluid. As shown in FIG. 3, the value of the pressure of the fluid of interest in the outlet duct 3 then shows a sharp decrease, for t> 230 min.

This phenomenon can be explained by the fact that the flexible wall 2, strongly deformed, is placed substantially against the outlet of the tank 1 opening on the outlet duct 3, which obstructs said duct 3. It then behaves as a closed valve, which strongly limits or even stops the flow of the fluid of interest in the outlet duct 3. Insofar as the fluid of interest present in the outlet duct 3 remains subjected to a flow force exerted by the pump 10, it is subjected to a mechanical stress which generates said observed abrupt decrease in its pressure.

When the measured pressure reaches the reference value, for example of the order of -40 mbar (FIG. 3), the control means 23 send an electrical end-of-drain signal to the control means 30 which stop the pump 10. Draining tank 1 is stopped before the pump 1 or another element of the fluidic circuit (conduit, fluidic connector element) undergoes any degradation. Thus, the moment when the tank becomes substantially empty is detected and the drain stopped. The pump is thus protected from any heating which can be detrimental.

In addition, it is possible to dispense any type of fluid, whether it is electrically conductive or insulating. The measurement of pressure, especially during the Sudden decrease of the latter at the end of emptying, is indeed independent of the electrical properties of the fluid dispensed.

Moreover, the measuring means 21 ensure the measurement of the pressure in the outlet duct 3, and not in the tank 1.

Also, any type of collabable tank can be used, that the walls defining the internal volume of the tank are partly or entirely flexible.

By way of illustration, FIG. 4 illustrates an example of a collapsible reservoir emptied whose interior volume is entirely delimited by a flexible wall 2.

Any type of material, compatible with the fluid of interest, can be used for said walls of the tank without this disturbing the measurement of the pressure in the outlet duct 3, performed by the pressure measuring means 21.

It should also be noted that the tank 1 and the outlet duct 3 can each be arranged in any vertical, horizontal or inclined orientation, without the measurement of the pressure in the outlet duct 3 being affected.

The flexible wall 2 of the tank 1 can be made in different ways, for example from a stack of layers of different materials, assembled to each other. The layers may comprise at least one layer, preferably two layers, of a thermoplastic material with adequate mechanical properties.

Between two layers of thermoplastic material may be disposed a layer of a material ensuring in particular the sealing vis-à-vis the fluid of interest. This material may be inorganic, such as A 10 _x , Al _x O _y N _z , SiO _x , SiO _x N _y , SiN, _: .

It is also possible to use organic materials, in combination or not with the layers of thermoplastic material, such as polyvinyl chloride (PVC), cycloolefin copolymer (COC), polypropylene (PP) or polychlorotrifluoroethylene (PCTFE).

The tank 1 can have any type of capacity. When the device is miniaturized, the reservoir can have a capacity of the order of a few tenths of a milliliter to a few hundred milliliters. Preferably, the reservoir has a capacity of the order of a few milliliters.

The outlet duct 3 may have an inside diameter making it possible to limit the associated pressure drop. By way of example, the diameter may be of the order of a few hundred microns to a few millimeters.

The pump 10 advantageously induces a laminar flow in the outlet duct 3, thus making it possible to obtain a controlled dispensing of the fluid of interest, and to allow precise pressure measurements to be made in the outlet duct 3. The flow generated by the pump 10 in the outlet duct 3 can be of the order of a few microliters per minute at. a few milliliters per second.

The pressure sensor may be piezoelectric or piezoresistive, with a strain gauge, with a differential transformer, with a capacitive effect in the case of a fluid of electrically conductive interest, or with a surface acoustic wave.

As a variant of the first embodiment of the invention, the end-of-discharge signal may, alternatively or in addition to the electrical signal sent by the control means 23, be a light or sound signal intended for a user, so that it stops the emptying of said tank.

The user can then stop the emptying of the tank by stopping the pump.

In the case where the dispensing device has a plurality of collapsible containers each connected in parallel to the outlet duct via, for example, a multi-way valve, the user can also stop the emptying of the tank in question. actuating the multi-way valve, so as to fluidly connect a second collapsible reservoir with said pump. Thus, the emptying of the first tank is stopped without the pump being stopped.

It should be noted that, in the preceding case where the dispensing device comprises a plurality of collapsible containers, the control means 23 can send an electrical signal to control of the multi-channel valve, so that it puts in fluidic connection a second collabable reservoir with said outlet conduit 3 when the end of emptying the first tank is detected. The manual intervention of a user is then avoided.

Alternatively to the use of a constant reference value as described in the first embodiment of the invention, the reference value may vary as a function of time.

The reference value is preferably defined so that ^one between two sufficiently distant times, its evolution over time is lower than that of said function parameter of the pressure of the fluid or its derivative. Sufficiently distant means 10 to 100 times the sampling period of the pressure measurements, this period being defined as the time between two successive pressure measurements.

Thus, according to a variant of the first embodiment, the calculation means 22 calculate a mean pressure from at least a portion of the pressure values measured by the sensor 21, as well as the associated difference -type σ .

The average pressure can be calculated from all the measured pressure values, or from a given number of the most recent measured pressure values. In the latter case, the average pressure is a sliding average of the measured pressure values.

The calculation means 22 then determine the reference value V _ref such that V _ref = - χ * σ, where x is a strictly positive coefficient, x may be greater than or equal to 1, and preferably greater than or equal to 2.

Figure 5 shows the time evolution of the fluid pressure in the outlet duct 3 as well as that of the reference value. When the measured pressure reaches the reference value, the control means 23 send an end of idange signal intended to stop the emptying of the tank 1.

This variant has the advantage of being fully automatable, insofar as it does not depend on external pressure measurements or on adjustment coefficients. In addition, it is not necessary to perform a prior calibration step of the dispensing device, which may be useful or necessary when determining an optimum constant reference value.

Of course, other expressions of a time dependent reference value are possible. Thus, the reference value can be calculated by the calculation means 22 from an average pressure obtained as above, and from a constant pressure value. This constant pressure value may be the initial pressure of the fluid of interest in the outlet duct 3, obtained before the start of the emptying. It may also be the external pressure P _e of the surrounding fluid.

Thus, when the pressure measured by the sensor 21 is the absolute pressure, the reference value may be such that: V _ref = - y * Pi, where is an average pressure calculated from at least a part of the pressure values measured by the sensor 21, Pi is the initial absolute pressure of the fluid of interest, ie before the initialization of the emptying, in the outlet duct 3, and y is a strictly positive coefficient, less than or equal to at 1, preferably less than or equal to 1/2.

Alternatively, when the pressure measured by the sensor 21 is the relative pressure with respect to the external pressure P _e of the fluid surrounding the tank 1, the reference value can be defined such that V _ref - - y * P _e .

Alternatively, it is possible to determine a pressure difference ΔΡ between the initial pressure P ₁ and a measured pressure P ₁ at a predetermined time t 1. P ± is the initial absolute pressure of the fluid of interest, ie before the initialization of the emptying, in the outlet duct 3. The reference value can then be equal to V _ref = Pi - ζ * ΔΡ, where z is a positive real greater than 1. This reference value will only be used for pressure measurements carried out at times t after t = tl

According to a second embodiment of the invention, said parameter, which is a function of the measured pressure or of its derivative, is an average pressure calculated from at least a part of the measured pressure values. The average pressure can be calculated from the set of measured pressure values, or be a running average obtained at from the most recent measured pressure values.

The reference value may be constant, previously stored in the memory of the calculation means 22.

As previously described, when the value of the average pressure reaches the predetermined reference value, the control means 23 send an end of drain signal.

The dispensing device according to this second embodiment comprises elements identical or similar to those described with reference to the first embodiment or its variants, and has a similar operation.

According to a third embodiment of the invention, said parameter function of the measured pressure or of its derivative is the time derivative r _t of a mean pressure calculated from at least a part of the values measured pressure. The average pressure can be calculated from the set of measured pressure values, or be a sliding average obtained from the most recent measurements of the pressure. In this respect, the mean sliding average pressure can be obtained by recursive low-pass filtering. For example, the average pressure (t _N ) at the time of measurement t _N can be obtained by the following relation: (t _N ) = a * (t _N _i) + (l ~ oo) * P (t _N ), where a is a forgetting factor. The reference value can be constant, and previously stored in the memory of the calculation means 22.

As described above, when the value of the time derivative r of the average pressure reaches. predetermined reference value, the control means 23 send an end of emptying signal.

The dispensing device according to this third embodiment comprises elements identical or similar to those described with reference to the second embodiment, and has a similar operation.

However, in order to prevent the end of discharge detection criterion from being verified too early, in particular during the transient regime of the initiation of emptying (see FIGS. 3 and 5, for t <5 min), the control means 23 can compare the value of the time derivative 9 _t with the reference value when a safety time has passed. In the examples of Figures 3 and 5, this safety time can be set to 10 min.

A calibration step may therefore be necessary when the operating parameters of the dispensing device according to this embodiment are changed, for example when the flow rate of the fluid of interest in the outlet duct is changed, the physical parameters (density, viscosity) of the fluid, the internal diameter of the duct 3, or even the technical characteristics (capacity, diameter of the outlet orifice) of the tank 1. A fourth embodiment of the invention is illustrated in FIG. 6, where the measurement means 21, the calculation means 22 and the control means

23 comprise a threshold pressure sensor 24, and no longer a pressure sensor 21 on the one hand and calculation means 22 and control 23 on the other hand.

The threshold pressure sensor 24 measures the pressure of the fluid of interest in the outlet duct 3, and compares the measured pressure with a so-called threshold value.

The reference value is here constant and previously determined.

When the value of the measured pressure reaches the reference value, the threshold pressure sensor

24 emits an end of drain signal.

As described above, the end of discharge signal may be an electrical signal transmitted to the control means 30 of the pump 10 (FIG. 6), and / or a light or sound signal intended for a user of the device according to the invention.

According to another embodiment described with reference to FIGS. 7A, 7B and 8, the tank 1 is placed in a hermetically sealed enclosure 4 with rigid walls.

The reference numerals identical to those of FIGS. 1 and 2 denote identical or similar elements.

As shown in Figures 7A and 7B, the tank 1 and the chamber 4 has common rigid walls. Alternatively, the tank 1 and the enclosure 4 may not have rigid walls common. This can be the case when the tank 1 has an interior volume entirely delimited by a flexible wall, as represented in FIG. 3. Whatever the type of tank 1, this one communicates fluidly directly with the outlet duct 3.

The external pressure P _e is here the pressure of the surrounding fluid at least partly the tank 1. It corresponds to the pressure of the fluid present in the space defined between the tank 1 and the chamber 4.

Thus, during the emptying of the tank, the external pressure P _e to the tank 1 decreases continuously as and when the drain, as shown in Figure 8 (curve dashed lines). The pressure P measured in the outlet channel 3 is shown in solid lines. It is found that during the emptying, the pressure difference | P _e -P | on either side of the flexible wall 2 is substantially constant, here of the order of 20 mbar.

As previously described, the measured pressure decreases sharply when the reservoir is substantially empty.

The detection of the moment when the reservoir becomes substantially empty can be carried out in a manner similar to what has been previously described, and is therefore not repeated here.

Of course, various modifications may be made by those skilled in the art to the invention which has just been described, solely as non-limiting examples.

Claims

Ρ37247, λνο 2011/131790 PCT / EP2011 / 056496 CLAIMS

1. A method of emptying a collabable reservoir (1), said reservoir (1) having walls,

At least one flexible wall (2) defining an internal volume of the reservoir, said internal volume of the reservoir being filled with a fluid of interest and fluidly connected to a pump (10) via an outlet pipe (3), characterized in that

10 - it generates, by actuation of said pump

(10), a flow of the fluid of interest from the reservoir (10) into the outlet conduit (3), causing a decrease in the interior volume of the reservoir by deformation of the at least one flexible wall (2);

a plurality of successive pressure measurements of the fluid of interest are made in the outlet duct (3);

a value of a parameter, which is a function of the pressure of said fluid of interest or its derivative, is obtained from the pressure thus measured, and said value thus obtained is compared with a reference value, the reference value having been previously calculated from said plurality of successive measurements of the pressure;

the emptying of the tank (1) is stopped when said value of the parameter reaches the reference value.

30

2. Draining method according to claim 1, characterized in that said parameter is chosen from SP37247, _wo 20H / 131790 PCT / EP2011 / 056496

29

the pressure of the fluid of interest in the outlet duct (3) and the time derivative of said pressure.

3. Draining method according to claim 1 or 2, characterized in that said parameter is the pressure of the fluid of interest in the outlet duct (3).

4. Draining method according to claim 1, characterized in that said parameter is a mean pressure () of the fluid of interest in the outlet duct (3) obtained from at least a part of the plurality successive measures of pressure.

5. A method drain according to claim 1, characterized in that said parameter is a time derivative (O _t ) of a medium pressure () of the fluid of interest in the outlet duct (3) said average pressure () being obtained from at least a part of the plurality of successive measurements of the pressure.

6. Draining method according to claim 3, characterized in that the previously calculated reference value is equal to an average pressure.

() of the fluid of interest in the outlet duct (3) to which is subtracted the associated standard deviation (σ) weighted by a predetermined positive x coefficient, the average pressure () and the standard deviation (σ) being calculated from at least a portion of said plurality of successive measurements of the pressure. SP37247 _/ , WO 2011/131790 PCT / EP2011 / 056496

30

7. Draining method according to claim 3, characterized in that the reference value previously calculated is equal to a mean pressure () of the fluid of interest in the outlet duct (3) to which is subtracted a constant initial value of the pressure (Pi, P _e ) of the fluid in the tie duct (3) weighted by a coefficient, y predetermined positive positive and less than 1, the average pressure () being calculated from at least a part of said plurality of successive measurements of the pressure.

8. Device for dispensing a fluid of interest comprising a collabable reservoir (1) having walls, of which at least one flexible wall (2), defining an interior volume of the reservoir, said internal volume of the reservoir being filled with the fluid of interest a pump (10) fluidly connected to the interior of the tank through an outlet pipe (3), and pump control means (30) connected to said pump (10) for controlling the operation thereof;

characterized in that it comprises pressure measuring means (21) able to measure the pressure of the fluid of interest in the outlet duct (3); calculation means (22) capable of obtaining a value of a parameter, which is a function of the pressure of said fluid of interest or its derivative, from the measured pressure, said calculation means being furthermore suitable for calculating a value reference from a plurality of measurements successive of said pressure; and control means (23) adapted to compare said value of the parameter thus obtained with said reference value, and to send an end-of-drain signal when said parameter value reaches the reference value.

9. Dispensing device according to claim 8, characterized in that the measuring means (21) comprise a pressure sensor (21) connected to the outlet duct (3) for measuring the pressure of the fluid in said duct (3).

10. Dispensing device according to claim 8 or 9, characterized in that the calculation means (22) are connected to said pressure sensor (21) for receiving pressure sensor. (21) a measured value of pressure, and are able to obtain a value of the parameter from the pressure thus measured.

11. Dispensing device according to the claim

10, characterized in that the control means (23) are electrically connected to the calculation means (22) for receiving from said means (22) a value of said parameter and said reference value, and are able to compare said value of said parameter with said reference value.

12. Dispensing device according to claim 10, characterized in that the control means (23) are electrically connected to said control means (30) of the pump (10) for transmitting said end of drain signal to said control means (30).