FR2844593A1 - Differential volumetric doser comprises hollow body and piston with sections of different diameters and groove along upper body section wall - Google Patents

Abstract

The differential doser, comprising a hollow body (1) with a cylindrical dosing chamber (2) an inner piston (3) that can perform a reciprocating and rotary motion, has the inner diameter of the upper section (11) of the body smaller than the diameter of the dosing chamber, and the outer diameter of the piston's intermediate section (10) greater than that of its upper section (9). The inner wall of the body's upper section has a lengthwise groove (4) extending from the entry point of a feed channel (6) for the dosed liquid to the upper end of the section defining an accumulation and acceleration chamber (7) connected to an ejection channel (8) and designed to co-operate with a distribution groove (5).

Description

DIFFERENTIAL VOLUMETRIC DOSING DEVICE

  The invention relates to a differential volumetric metering device with accelerating chamber, in particular intended to deliver a determined and metered quantity of liquid, very particularly for volumes typically between one tenth of a microliter and a hundred microliters.

  Many industrial sectors require the implementation of precise metering and in small quantities of liquid, especially in the field of pharmaceutical industry, medical analysis, food industry, and related activities.

  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 15 depending on the volume to be dosed. In fact, the determination of the volume to be dosed 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

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

many 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 an angle determined by the positioning angle of the pipes of the pump, for example by degrees, in order to match said groove with another pipe, also opening into the body of the cylinder, and located in diametrically position

  opposite 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 again undergoes a new rotation by an angle equal to the angle previously

  cited, 1800 in the example described, and the cycle described 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, in particular pharmaceutical or agrifood, this type of device is subject 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 with inkjet printers. However, such a principle cannot be exploited for dosages of 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 of this type of device, without involving a

  any disassembly of the constituent parts.

  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, insofar as there is no agitation, experience has shown that this cleaning system is relatively ineffective, in particular when this washing phase occurs after the dosing of

relatively high viscosity.

  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 comprised 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 opens respectively a supply and delivery or ejection pipe 'of 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 coming opposite the orifice opening, respectively of the supply and delivery or ejection pipe; said piston is extended by a part coaxial therewith, 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 document FR-A-2 797 046, 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 peripheral partition perforated at level from which a washing fluid is conveyed by a pipe, said pipe being closable, in particular during the dosing phases, by means of a valve. This device thus ensures

  satisfactory dosing and washing functions.

  If this device allows very precise doses to be made between the microliter and the milliliter, it does not allow correct ejection of the dose after a certain distance from the dosing tube for volumes between the microliter and the hundred microliters. Indeed, the pressure drops, whatever their origins (surface tensions, roughness, singular pressure drops ...) for such reduced quantities, absorb the dynamics of the ejection.

  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 metering chamber is doubled at the end of the pump by a so-called liquid accelerator chamber. This architecture can be used with or without the bedroom

cleaning as needed.

  More specifically, the metering device according to the invention comprises: * a hollow body, defining a cylindrical metering chamber, surmounted by an upper zone at the level of which open respectively a supply pipe and a delivery pipe or ejection of a liquid to be dosed; has a cylindrical piston, comprising several coaxial, respectively upper, and intermediate parts, the respective diameters of which correspond to the clearance close to the internal diameters of the metering chamber and of the upper zone of the cylindrical body, said piston having at the periphery of its upper part a longitudinal distribution groove, capable of coming to be positioned opposite the arrival of the supply line for the liquid to be metered, said piston 25 being moreover capable of being driven in an upward and downward translational movement within said hollow body, simultaneously or not simultaneously with

a rotational movement.

  It is characterized: * in that the internal diameter of the upper zone of the hollow body is less than the diameter of the metering zone of said body; * in that the external diameter of the intermediate part of the piston is greater than the external diameter of the upper part of said piston; * in that the internal wall of said upper zone of the hollow body is provided with a longitudinal groove, extending substantially from the level at which the liquid feed metering pipe opens out towards the end of the upper zone of the hollow body, defining at this level an accumulation chamber for the liquid to be metered, said groove being intended to cooperate with the distribution groove of the upper part of the piston; and in that the line for delivering or ejecting the liquid to be dosed

  emerges at the level of the accumulation chamber.

  The accelerating chamber is therefore in communication with the metering chamber s proper by a set of grooves located on the piston and the cylinder or hollow body. The dose ejection nozzle is therefore offset at the end of the metering device, in direct communication with the accelerating chamber. Thus, the longitudinal distribution grooves are located at the level of the

  periphery of the zone of the piston and of the cylinder 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 device

  dosing device according to the invention, shown in the intermediate dosing position.

  FIG. 2 is a schematic representation similar to FIG. 1, but showing the metering device with a cleaning chamber whose operation is identical to that described in document FR-A2 797 046 of the Applicant, this

  device will therefore not be described in this document.

  Figures 3 to 6 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.

  Figures 7 to 9 are schematic representations, illustrating in cross section of the device according to the invention, different configurations of the

operation of it.

  Figures 10 to 12 are schematic representations similar to Figures 7 to 9 of a variant of the invention.

  FIG. 1 therefore represents a view in longitudinal section of the metering device

  volumetric according to the invention, in the metering position.

  Basically, this dosing 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 moreover capable of carrying out a rotational movement. In order not to unnecessarily overload the figures, the organ

  ensuring the translation and rotation of the piston has not been shown.

  As can be seen in Figures 1 and 2, the hollow cylindrical body 10 (1) definesZ two zones of different diameter, respectively an upper zone

  (11), and a lower zone (12), of larger diameter.

  One thus observes in the upper zone (11), a pipe (6) for supplying the liquid to be dosed and a pipe (8) for delivering or ejecting said liquid. According to a characteristic of the invention, this pipe (8) for delivering or ejecting the liquid to be dosed opens out at the upper end of the upper zone (11) of the hollow body. In the example described, this pipe (8) is even oriented in the main direction of the metering device. 20

  According to the invention, the upper zone (11) of the hollow body (1) also comprises a groove for discharging (4) the metered liquid extending between the level of opening of the supply line (6) of the liquid to be metering, and the upper end of said zone (11). This upper end defines an accumulation chamber, also referred to in the following description as the acceleration chamber for the liquid to be metered.

  As can be seen in Figures 1 and 2 for example, the respective locations of the level of opening of the supply line of the liquid to be dosed (6) and the groove (4) form a angle of 180, this angle can be considerably reduced. It will be noted that the reduction of this angle allows a significant gain in operating cadence, and in addition the establishment of a set of

  additional grooves described in relation to Figures 7 to 12.

  The purpose of these additional grooves is to rapidly prime the metering device according to the invention, by putting the various pipes and chambers thereof into direct communication.

  The accelerating chamber (7) is defined by the upper end of the upper zone (11) of the hollow body (1), and by a plug in the form of an adjusted conical part (13), according to a principle known per se. In order to ensure the ejection of the dose from the accelerating chamber, the conical stopper integrates the pipe (8) for delivering 5 or ejecting the metered liquid, advantageously placed at the highest point, thus promoting priming in liquid. of the device avoiding any accumulation

air in the upper part.

  Thus, specific pipes are likely to be connected to the 1o pipes. The piping fastener was deliberately not

  shown so as not to unnecessarily overload the figures.

  The piston (3) proper has different portions.

  First of all, it has an intermediate portion (10), the diameter of which corresponds to the clearance, to the diameter of the zone (12) of the cylindrical body (1). This portion (10) is extended by an upper zone (9), having a diameter less than the diameter of the zone (10). In addition, this zone (9) has first of all an outside diameter corresponding to the clearance close to the internal diameter of the upper zone (11) of the hollow cylinder. In addition, this portion (9) has at its periphery a longitudinal groove or groove (5), the operation of which will be described in more detail later. The intermediate zone (10) is extended by a lower extreme zone (18) of smaller diameter than the zone (10), and has the sole function of transmitting the movement of translation and rotation to the whole of the piston. This zone (18) is itself extended by a zone (14), not shown in detail, which constitutes

  the member for fixing the piston to its means for driving in rotation and translation.

  Thus, as soon as the respective diameter of the part (12) of the cylindrical body (1) and the respective diameters of the parts (9) and (10) of the piston (3) are known and clearly defined, the volume generated at the metering chamber (2) becomes perfectly defined and reproducible as a function of the difference in the sections of the aforementioned diameters and the stroke imparted to the piston during the metering phase. 35 It will be described in relation to FIGS. 3 to 6, 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 its defined and known position, called the reference. In this configuration, the longitudinal groove (5) with which it is provided, is positioned with regard to the place of opening of the supply pipe (6) of the liquid to be metered. On the other hand, the ejection groove (4) is closed by the upper zone (9) of the piston (3). During its downward stroke, (FIG. 4) there is suction of the liquid to be metered, within the metering chamber (2) for a volume which depends on the diameter of the zone (12) of the cylindrical body (1), the diameters parts (9 and 10) of the piston, and the height of the downward stroke of said piston. At the same time, it is easily observed that the accelerating chamber (7) is filled at the same time as the metering chamber (2), with the liquid contained in the ejection piping (8) of the dose of liquid. In other words, during the aspiration phase of the liquid to be metered at the level of the metering chamber (2), the liquid contained in the delivery and ejection pipe of said liquid and in the piping is corollary aspiration. associated with it (not shown), thus constituting a "dead" volume accumulated at

  level of the accelerating or accumulation chamber (7).

  It is observed that throughout this stroke, the liquid can always be aspirated by passing respectively through the supply line (6) of the liquid to be dosed, then by

  the channel (5) with which the piston is provided at this level (see FIG. 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 (2), of the parts (9 and 10) the piston and the height of the stroke of said piston.

  On the other hand, it can be observed that throughout this stroke, the liquid can always be sucked through respectively the delivery and ejection pipe (8) located in the extension of the accelerating chamber (7). The volume 30 in the accelerating chamber is defined by the diameter of the upper zone (11) of the

  cylindrical body and the stroke made by the piston.

  When the desired metering volume is reached in the metering chamber (2), the downward stroke of the piston is stopped, and said piston is rotated by a value equal to the angle formed between the delivery line. supply (6) of the liquid and the ejection groove (4) towards the accelerating chamber, 1800 in our example (FIG. 5), so as to make the groove (5) of the piston reconcile with the groove (4) of which is provided with the wall of the upper zone (11) of the cylindrical body. As a corollary, the

  supply line (6) of the liquid to be metered is closed by said piston.

  The latter then undergoes an upward translation, so as to expel the liquid 5 contained in the metering chamber (2), rising by the two grooves respectively (5) and (4), then in communication, at the level of the accelerating chamber (7), which itself drives out the metered liquid added to the accelerator volume through the ejection pipe (8), until the piston reaches the maximum possible of its upward stroke, the portion (19) of the piston located to the area 10 of junction of the upper (9) and intermediate (10) areas coming to a stop at a defined and repetitive position (20) given by the drive system, therefore at a

  distance defined as reference position and reproducible at each cycle.

  A new rotation of the piston (FIG. 3) from 1800 in the example described, makes it possible to restart the cycle, by repositioning the groove (5) with regard to the pipe.

supply (6) of the liquid to be dosed.

  It can also be observed that during this entire dosing period, the lower end of the dosing chamber (2), which is open towards the outside, is closed off by the portion 10) of the piston (3) .

  The previously described cycle therefore exposes the operating principle of the accelerating chamber. Indeed, for dosages of a very small volume, the major difficulty for the ejection of a dose is the lack of kinetic energy at the level of the ejection site, directly related to the volumes in movement in the

  piping and pressure losses related to these same piping. Thus it is observed that the larger the volume in displacement, the easier it is to eject the desired dose.

  However, the present system proposes to move, for each piston movement, a volume called the accelerator which will not be ejected and will therefore only serve as a kinetic energy supply to eject the metered volume coming from the metering chamber.

  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 dosing resulting from its operating principle, we note the interest of the function of the

accelerator volume.

  Note also the washing function also available, and already described in relation to document FR-A-2 797 046, the content of which is incorporated into the present description by reference, and in relation to the references (15, 16 and 17 ) of the figure

2.

  Illustrated in relation to Figures 7 to 9, an advanced version of the invention. The various possible configurations of the upper region (9) of the piston (3) within the upper region (11) of the piston are shown in particular at the cross sections passing through the metering liquid supply pipe (6). cylindrical hollow body 10.

  Thus, within FIG. 7, the groove (5) of the piston (3) is positioned opposite the supply pipe (6) of the liquid to be metered, the metering device therefore being in the suction configuration. The liquid to be dosed is therefore routed towards the metering chamber (2). As a corollary, the ejection groove (4) is closed by said

upper zone (9) of the piston.

  Within FIG. 8, the piston has made a rotation of 900 relative to its position in FIG. 7, inducing on the one hand, the closure of the supply line 20 (6) of the liquid to be metered, and on the other hand, the communication of the metering chamber (2) with the ejection groove (4), by means of an additional groove (21), formed at the level of the upper zone (9) of the piston (3), and extending along the same length and the same direction as the groove (5). We are therefore in the position for evacuating the contents of the metering chamber (2) in the direction of the accelerating chamber (7), and as a corollary towards the ejection or delivery pipe (8).

  Finally, the configuration of FIG. 9 is new compared to the preceding description. It is intended to allow rapid priming or purging of the metering arrangement according to the invention. According to this configuration, the piston has

  rotated 180 relative to its orientation in Figure 8.

  According to this configuration, one of the grooves (21) of the upper zone (9) of the piston (3) is in communication with the supply line (6) of the liquid to be metered, the piston being in maximum upward travel, so at its reference position (volume

minimum death).

  As a corollary, the second groove (5) of the piston is found directly above a second groove (22), formed in the upper zone (11) of the hollow body, said second groove (22), offset by 90 relative to the ejection groove (4), and having the same characteristics in terms of length and orientation as the groove (4). The liquid can therefore fill the entire metering device by simple flow to the ejection nozzle, no pump movement is necessary for this operation. This configuration allows rapid filling of the circuit. The advantage of this priming process is clearly seen in the case of pumps intended to produce very low doses of the order of microliter up to a hundred microliters. In fact, on a conventional system, priming is carried out by dosing cycles in maximum stroke of the pump. However, on a microdosing pump, the maximum dose may represent only a very small fraction of the total volume of the dosing circuit. In this case, it is necessary to carry out a very large number of cycles before the complete circuit is started, and therefore requires a long start.

  before being able to start production dosages.

  In addition, a continuous flow of liquid during priming makes it possible to drain any air bubbles which may have remained stuck to the walls of the hydraulic circuit.

  On a conventional pump with a low metering volume, the low volumes set

  work do not allow to take off the air bubbles resident in the circuit.

  FIGS. 10 to 12 illustrate a variant of the previous configuration, in which the upper part (9) of the piston (3) always has two grooves (5,

  21), but this time offset from each other by an angle of about 120, the upper zone (11) of the hollow body (1) having only one ejection groove (4). This embodiment simplifies the manufacture of the device, and as a corollary to reduce the costs. Its operating mode is broadly identical.

Claims (6)

  1. Differential volumetric metering device, comprising: * a hollow body (1), defining a cylindrical metering chamber (2), surmounted by an upper zone (11) at the level of which respectively lead a supply pipe ( 6) and a delivery or ejection pipe (8) of a liquid to be dosed; ò a cylindrical piston (3), comprising several coaxial, respectively upper (9) and intermediate (10) parts, the respective diameters of which correspond to the clearance close to the internal diameters of the metering chamber (2) and of the zone ( 11) of the cylindrical body, said piston having at the periphery of its upper part (9) a longitudinal distribution groove (5), capable of coming to be positioned opposite the arrival of the liquid supply pipe (6) 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 rotary movement, characterized: * in that the internal diameter the upper zone (11) of the hollow body (1) is less than the diameter of the metering chamber (2) of said body; a in that the external diameter of the intermediate part (10) of the piston (3) is greater than the external diameter of the part (9) of said piston; * in that the wall of said upper zone (11) is provided with a longitudinal groove (4), extending substantially from the level of opening of the supply pipe (6) of the liquid to be metered in the direction of the upper end of the upper zone (11) of the hollow body (1), defining an accumulation and acceleration chamber (7) of the liquid to be metered, and intended to cooperate with the distribution groove (5) of the upper part (9) of the piston (3);   * and in that the delivery or ejection pipe (8) of the liquid to be metered 30 opens at the level of the accumulation and acceleration chamber (7).   2. Differential volumetric metering device according to claim 1, characterized in that the delivery or ejection pipe (8) of the liquid to be metered is oriented in the main direction of the metering device. 35   3. Differential volumetric metering device according to one of claims 1 and   2, characterized in that the upper zone (9) of the piston (3) has additional grooves (21), oriented in the same direction and extending along the   same distance as the distribution groove (5).   4. Differential volumetric metering device according to claim 3, characterized in that the upper zone (9) of the piston (3) has an additional groove (21), positioned at 900 relative to the distribution groove (5). 5. differential volumetric metering device according to claim 4, characterized in that the upper zone (11) of the hollow body (1) has an additional groove (22), oriented in the same direction and extending by the same distance as the ejection groove (4), and oriented 90 relative to it 6. differential volumetric metering device according to claim 3,   characterized in that the upper zone (9) of the piston (3) has an additional groove (21), positioned at 120 relative to the distribution groove 20 (5).