FR2835912A1 - Differential volumetric doser for small quantities of liquid product has hollow body and piston with sections of different diameters - Google Patents

Abstract

The doser, comprising a hollow body (1) with a cylindrical dosing chamber (2) having feed and outlet channels (7, 8) and an inner piston (3), has the upper zone of the body and piston made with a smaller diameter than the dosing zone (2) and lower part (9) of the piston. The wall of the upper zone also has two lengthwise grooves (15, 16) extending from the feed and outlet channels towards the dosing chamber and designed to interact with a distribution groove (11) in the upper part (10) of the piston.

Description

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DIFFERENTIAL VOLUMETRIC DOSING DEVICE.

The invention relates to a differential volumetric metering device, in particular intended to deliver a determined and dosed quantity of liquid, very particularly for volumes typically between the microliter and the milliliter.

Many industrial sectors require the implementation of precise dosing and in a small quantity of liquid, especially in the fields of the pharmaceutical, cosmetic, chemical and also food industry.

In order to carry out the metering of small quantities of liquid, a device has been proposed in particular implementing the principle of metering by means of a piston with alternating stroke within a cylindrical chamber, the stroke of the piston being well heard depending on the volume to be dosed. In fact, the determination of the volume to be metered is a function either of the length of the piston stroke within the cylindrical chamber, or of the diameter of said metering chamber.

However, it is observed that if the stroke of the piston is reduced too much, this imposes a kinematics of the piston or of the quasi-perfect cylindrical chamber, and which does not exhibit any derivation over time. In fact, experience shows that there are problems of reproducibility and therefore of precision in terms of the quantities dosed and delivered.

If on the contrary we choose to reduce the diameter of the chamber and therefore of the piston, we observe that below a diameter of a value typically close to six millimeters, the cost of manufacturing the corresponding material increases drastically, and moreover , the device is very fragile, incompatible with a good number of applications.

Among these different devices, one of them implements a piston provided on its periphery with a longitudinal distribution groove, said piston sliding in a hollow cylinder defining the metering chamber. The implementation of this type of device, taking into account the degree of precision in the production of the elements, makes it possible to dispense with any seal. The ascent of the piston in the cylinder causes the suction of the liquid to be metered from a pipe opening into the body of the cylinder. At the end of the upward stroke, the piston is rotated by a determined angle, for example 180 degrees, in order to match said groove with

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 another pipe, also opening into the cylinder body, and located in a position diametrically opposite to the intake pipe.

The downward stroke of the piston induces the ejection of the liquid from the peripheral groove in this delivery or ejection pipe. At the end of the stroke, the piston is again rotated by an angle of 180 degrees, and the described cycle begins again.

If this particular architecture makes it possible to satisfy the requirements in terms of dosage, it nevertheless has the following drawbacks. First of all, an impurity at the level of the groove can induce alteration or even blockage of the suction or the ejection of the liquid contained therein. In addition, such impurity can cause premature wear of the piston or cylinder. Finally, for certain applications, pharmaceutical or agrifood in particular, this type of device is subjected to severe hygiene and sterility conditions, therefore requiring the use of easily decontaminable organs. The presence of a groove as well as intake and exhaust pipes induces relatively rapid contamination of the piston, and consequently decontamination made more difficult, due to the existence of angles, recesses, intersections.

When it comes to dosing very small quantities of liquids, typically micron or submicron, the phenomenon of inertia and the use of piezoelectric quartz are used. This dosing principle is used in particular in inkjet printers. However, such a principle cannot be implemented for dosages of a greater quantity between the micro and the milliliter.

Indeed, the nano or pico dosage, implements submultiples of the micro dosage. To obtain a microdose, it will be necessary to add nano or pico-doses, which consequently causes an addition of errors.

In addition to this dosing function, the industry is also demanding a simultaneous washing and sterilization function for this type of device, without involving any dismantling of the components.

Among the washing and decontamination devices of a known dosing system, one of them uses a pump provided with a cleaning chamber attached to the piston cylinder, and inducing the injection of cleaning solvents hot and / or cold and pressurized vapors. However, as long as there is no restlessness,

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 experience shows that this cleaning system is relatively ineffective, especially when this washing phase occurs after the dosing of relatively high viscosity fluid.

There has been described in document FR-A-2 797 046 of the Applicant, a device bringing together the two functions, dosing and washing respectively. This device therefore makes it possible to offer respectively the possibility of dosing quantities of liquids substantially between the microliter and the milliliter, and the possibility of cleaning and sterilization on the spot, called by the profession according to the expression CIP / SIP for cleaning. in place / sterilization in place basically comprises: - a hollow body, defining a cylindrical metering chamber at the level of which respectively leads a supply and delivery pipe for ejecting the liquid to be metered; said hollow body is extended at one of its ends by a secondary chamber coaxial with the metering chamber, but of a diameter less than the internal diameter of the metering chamber; - A cylindrical piston, the external diameter of which corresponds to the clearance close to the internal diameter of the metering chamber, and capable of sliding within the latter, the piston being provided at its periphery with a longitudinal distribution groove capable of come opposite the orifice opening, respectively of the supply and delivery or ejection pipe; said piston is extended by a part coaxial with the latter, also of external diameter less than the external diameter of said piston, and corresponding to the clearance close to that of said secondary chamber.

 This piston is capable of being animated by an upward and downward translational movement within said hollow body, simultaneously or not with a rotational movement.

According to this document, the metering chamber is surmounted at its other end by a washing chamber, also coaxial, with an internal diameter slightly greater than the external diameter of the piston, and provided with a perforated peripheral partition at the level of which is conveyed by a pipe a washing fluid, said pipe being closable, in particular during the dosing phases, by means of a valve.

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 If this device thus satisfactorily ensures the dosing and washing functions, on the other hand, it has the following drawback. During the washing phase, a large part of the piston is retracted out of the washing chamber.

In other words, this emerging part is not cleaned during said washing phase. What is more, during its reintroduction to carry out the dosing phases, this uncleaned external zone is liable to introduce impurities, microparticles, dust, etc. which may prove to be prohibitive in the context of the volumetric dosing sought, in view, in particular, of subsequent analyzes, in addition to generating wear phenomena of the type of those mentioned above.

The present invention aims to overcome this drawback. To do this, it partly takes up the architecture of the aforementioned device. It is characterized in that the actual metering is carried out in the upper part of the hollow body, and in that during the washing step, the piston is fully inserted within said hollow body, so that all of the piston undergoes the washing and cleaning stage.

To this end, the metering chamber has a smaller diameter than the washing chamber, the corresponding portions of the piston having, apart from play, complementary diameters.

Thus, the longitudinal distribution groove is located at the periphery of the zone of the piston having the smallest diameter.

The manner in which the invention can be implemented and the advantages which ensue therefrom will emerge more clearly from the example of embodiment which follows, given by way of indication and without limitation in support of the appended figures.

Figure 1 is a schematic representation in longitudinal section of the metering device according to the invention, shown in the intermediate metering position.

Figure 2 is a schematic representation similar to Figure 1, but showing the metering device in the washing or sterilization position.

Figures 3 to 7 are schematic representations similar to Figures 1 and 2, showing the different stages of positioning the piston relative to the hollow body during a metering phase.

FIG. 1 therefore represents a view in longitudinal section of the volumetric metering device according to the invention, in the metering position.

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 Basically, this metering device is based on the principle of actuation of a piston within a cylinder, said cylinder defining the metering chamber.

More precisely, the cylinder is defined by a hollow body (1) defining a metering chamber (2).

Within this hollow body (1), a piston (3) translates in an upward or downward movement, said piston being also capable of performing a rotational movement. In order not to unnecessarily overload the figures, the member ensuring the translation and the rotation of the piston has not been shown.

As can be seen in Figures 1 and 2, the hollow cylindrical body (1) defines two zones of different diameter, respectively an upper zone (4), hereinafter designated as participating in the washing chamber , and a lower zone (5), of larger diameter and more specifically designated for metering, in particular in cooperation with the part (10) of the piston (3).

Thus, in the upper zone (4), there are two pipes, respectively supply (7) and discharge or ejection (8) of the liquid to be dosed. These two pipes open at the same height, but in the example described, form an angle of 1800 between them. Specific pipes are likely to be fitted at these pipes, and are fixed at their respective ends by a fixing nut, according to a principle known per se.

The piston (3) proper has different portions.

First of all, it has a lower end portion (9), the diameter of which corresponds to the clearance, to the diameter of the zone (5) of the cylindrical body (1). This portion (9) is extended by the zone (10), more particularly used for metering, and has a diameter less than the diameter of the zone (10). In addition, this zone (10) first of all has an outside diameter corresponding to the clearance close to the internal diameter of the upper zone (4) of the hollow cylinder. In addition, this portion (10) has at its periphery a longitudinal groove or groove (11), the operation of which will be described in more detail later.

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This zone (10) is extended by an upper zone (12) of slightly smaller diameter with respect to the zone (10), and has the sole function of transmitting the movement of translation and rotation to the entire piston. This zone (12) is extended by a zone (13), of larger diameter corresponding substantially to the diameter of the upper end of the hollow cylinder, and intended to cooperate with an O-ring (14), in order to ensure sealing during the entire washing period, as can be seen in Figure 2.

In addition, the wall of the zone (4) of the cylindrical body has downstream, respectively, supply (7) and discharge (8) pipes for the liquid to be metered, also a longitudinal groove, respectively (15) and ( 16), intended to be positioned facing the longitudinal groove (11), which is provided with the part (10) of the piston during the dosing phases.

Thus, since the volume of these respective grooves (15) and (16) is known and clearly defined, and moreover, that the respective diameter of the part (5) of the cylindrical body (1) and the diameter of the part (10) of the piston (3) is also clearly defined, the volume generated at the metering chamber (2) becomes perfectly defined and reproducible as a function of the stroke imparted to the piston during the metering phase.

Finally, the cylindrical body (1) is provided with a shoulder (17), intended to cooperate with the part (9) of the piston (3), so as to limit its upward stroke.

There will be described briefly in relation to FIGS. 3 to 7, the mode of operation of the metering device according to the invention.

Thus in Figure 3, the piston (3) is located at the maximum of its upward stroke. In this configuration, the longitudinal groove (11) with which it is provided, is positioned facing the supply pipe (7) of the liquid to be metered. On the other hand, the ejection pipe (8) is closed by the zone (10) of the piston.

During its downward stroke, (Figure 4) there is suction of the liquid to be dosed, within the metering chamber for a volume depending on the diameter of the area (5) of the cylindrical body (1), the diameter of the part (10) of the piston, and of the height of the downward stroke of said piston.

It is observed that throughout this stroke, the liquid can always be sucked in, passing respectively through the groove (15) located directly above the supply pipe (7) of the liquid to be dosed, then through the channel (11 ) with which the piston is provided

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 level (see figure 4). We can observe in Figure 4, in black, the volume occupied by the liquid to be dosed, volume as already said, clearly defined as a function, on the one hand, of the respective diameters of the metering chamber (5), of the part ( 10) of the piston and of the height of the stroke of said piston.

When the desired dosing volume is reached, the downward stroke of the piston is stopped, and the piston is rotated by 180 (FIG. 5), so as to make the groove (11) of the piston coincide with the groove ( 16) which is provided with the wall of the chamber (4) of the cylindrical body. As a corollary, the pipe (7) for supplying the liquid is blocked by said piston.

The latter then undergoes an upward translation, so as to expel the liquid contained in the metering chamber (5), rising by the two grooves respectively (11) and (16), at the level of the evacuation pipe and ejection (8), until the piston reaches the maximum possible of its upward stroke.

A new rotation of the piston (FIG. 7) from 1800 in the example described, allows the cycle to be restarted, by repositioning the groove (11) with regard to the supply line for the liquid to be dosed (7).

It can be observed that during this entire dosing period, the lower end of the dosing chamber (5), which is extended by a discharge pipe (18), is closed by the portion (9) of the piston (3 ).

As a corollary, the upper end of the zone (4) of the cylindrical body is closed by the portion (10) of said piston.

In fact, the upper end of the hollow body (1) is also provided with a pipe (19) for supplying a washing fluid, in accordance with another characteristic of the present invention.

Thus, between two successive dosages, in particular of different compounds, a washing and sterilization phase can be carried out, in particular of the dosing chamber, but also of the piston, in addition to the supply (7) and evacuation pipes. (8) liquid to be dosed.

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 Thus in washing mode, the piston is inserted in maximum downward travel inside the cylindrical body (1), as shown in FIG. 2.

In this configuration, it is observed that the periphery of the entire piston, with the exception of its upper part (13) closing off said cylindrical body (1), is no longer in contact with any of the guide walls formed by the hollow body (1).

The cleaning fluid, in particular steam, hot water, alcohol, solvent, etc., is introduced through said pipe (19), within the total volume thus defined in the washing chamber and the dosing chamber, then collected by the pipe. main evacuation (18), but also by the pipes (7) and (8).

In doing so, the entire outer surface of the piston and its groove (11) undergoes this cleaning phase. For this purpose, it can be emphasized that the lower end of the zone (5) of the cylindrical body (1) has an internal diameter slightly greater than the external diameter of the end portion (9) of the piston (3).

The structure of the device also allows agitation of the washing or cleaning fluid during the washing phase. To this end, the main evacuation pipe (18) of the washing fluid is provided respectively, and the pipe (19), for introducing said fluid, with a shut-off valve, respectively (20) and (21). , intended to close the corresponding pipes.

Thus, when the fluid has been introduced into the chambers (2,4, 5), it is possible to carry out different translations of the piston (3). Taking into account on the one hand, the correspondence of the respective diameters to the clearance near the zone (10) of the piston (3) and of the chamber (4), and on the other hand the correspondence of the respective diameters to the clearance near the zone (9) of the piston (3) and of the chamber (5), the translation of said piston induces a depression within the respective volume of each of the two chambers (4,5), causing rapid displacement of the washing fluid at within it, and in contact with the piston, as soon as the valves (20) and (21) are closed. It creates in fact a vigorous agitation of the washing fluid inside the volume defined by said chambers, thus allowing, by the mechanical effect thus generated, to clean the impurities in situ, optimizing the washing function.

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The repetition of several washing and stirring cycles makes it possible to achieve a complete and effective washing or cleaning both of the chambers and of the piston. A sterilization phase can then be carried out, if necessary, which essentially consists in subjecting the device to a flow of steam under pressure at 130 ° C. for a determined period, defined by the standards in force, in order to achieve effective sterilization.

It is therefore understandable the advantage of the metering device according to the present invention.

First of all, in addition to the high precision of the differential volumetric metering resulting from its operating principle, and from the washing function also available, we note the possibility of carrying out an integral washing of the piston, without generating an exit from the latter. out of the cylindrical body (1) and therefore avoiding the introduction inside the cylindrical body, and in particular of the metering chamber, of any particle, dust, etc. capable of distorting the measurements or even of clogging the pipes supply and outlet of the liquid to be dosed.

Note also the optimization of the accuracy by reducing the dead volumes.

Claims (4)

 CLAIMS 1. Differential volumetric metering device, comprising: a hollow body (1), defining a cylindrical metering chamber (2), surmounted by a zone (4) at the level of which a drain pipe opens at the same height respectively supply (7) and ejection (8) of a liquid to be dosed; * a cylindrical piston (3), comprising several coaxial, respectively lower (9), and intermediate (10) parts, the respective diameters of which correspond to the clearance close to the internal diameter of the metering chamber (2) and of the zone (4 ) of the cylindrical body, said piston having at the periphery of its part (10) a longitudinal distribution groove (11), capable of coming to be positioned opposite respectively the arrival of the supply pipe (7) and the departure of the line (8) of the liquid to be dosed, said piston also being capable of being driven in an upward and downward translational movement within said hollow body (1), simultaneously or not with a rotational movement, characterized: * in that the internal diameter of the area (4) of the hollow body (1) is less than the diameter of the metering area (2) of said body; in that the external diameter of the part (10) of the piston (3) is less than the external diameter of the part (9) of said piston; and in that the wall of said zone (4) is provided with two longitudinal grooves, respectively (15) and (16), extending from the opening zone of the supply (7) and ejection (8) pipes. ) of the liquid to be dosed in the direction of the metering chamber (2), and intended to cooperate with the distribution groove (11) of the part (10) of the piston (3). 2. differential volumetric metering device according to claim 1, characterized in that the cylindrical body (1) is provided with a shoulder (17), intended to cooperate with the part (9) of the piston (3), so to limit its upward stroke. 3. Differential volumetric metering device according to one of claims 1 and 2, characterized in that the zone (4) of the cylindrical body (1) has, in the vicinity of its upper end, a pipe for supplying a washing and / or sterilization fluid, and in that the zone (5) said body has in the vicinity of its lower end a discharge pipe of said fluid. <Desc / Clms Page number 11> 4. Differential volumetric metering device according to claim 3, characterized in that the vicinity of the lower end of the zone (5) of the hollow body (1) has an internal diameter slightly greater than the external diameter of the part (9) piston (3), so that when the piston is fully retracted inside the hollow body (1), the washing fluid can come into contact with the entire peripheral surface of said piston.