METHOD FOR DOSING SUGGESTION UNITS AND USE OF A DOSING VALVE IN A CALIBRATION DEVICE FOR A CAPACITIVE MEASURING SYSTEM

Description

[0001] The invention relates to a method for dosing dosage units by means of a dosing device including a calibration device, as well as the use of a dosing valve in the calibration device.

[0002] In the pharmaceutical sector, for example, precise and repeatable dosing of dosage units is crucial to ensure that the patient receives exactly the intended amount of active ingredient. Solid dosage forms can be tablets, powder quantities or pellets contained in push-in capsules. Any other dosage form, whether solid or liquid, can also be considered. Such dosage units are usually dosed volumetrically, with a specific target mass being achieved using a specific measured volume and the density of the material. Ultimately, however, it is not the volume that counts, but the mass of the individual dosage units actually achieved during dosing. Density fluctuations in the material, incomplete filling or emptying of the volumetric measuring chamber, or similar factors can lead to undesirable fluctuations in the target mass.Reliable process control is therefore necessary, especially for critical active ingredients.

[0003] To monitor the proper flow of the dosing process, EP 3 279 618 B1 describes a mass determination of the individual, previously measured dosage units using a capacitive measuring system. For calibrating the capacitive measuring system, a calibration device is provided in which a test specimen is moved back and forth between two end positions along a guide section in the measuring channel of the capacitive measuring system by means of a corresponding drive mechanism. The test specimen acts as a test standard, with the corresponding measurement result of the capacitive measuring system being used as the calibration value.

[0004] The design and calibration procedure have proven themselves, at least during the initial calibration at the machine's manufacturing plant. However, the problem is that dosage units of very different masses are dosed and filled. While the capacitive measuring system can cover a wide measurement range, it is difficult to maintain the required measurement accuracy across the entire measurement range. Calibration should therefore be performed as close as possible to the respective target mass to achieve high accuracy. According to the described state of the art, this requires the availability of a large number of test specimens with different masses, some of which may be only a few milligrams. Such test specimens are difficult and expensive to obtain, as well as difficult to handle.A change in the target mass often requires recalibration, which then no longer takes place at the machine's manufacturing plant but rather at its operating site. Practice has also shown that recalibration is required from time to time during ongoing production. Calibration using the aforementioned state-of-the-art technology is complex and costly. Furthermore, it is difficult for the machine operator to manage, requiring the involvement of dedicated service personnel.

[0005] The use of solid test specimens for calibration is also known from EP 2 030 895 A1. US 2019 / 0151840 A1, DE 10 2010 035 599 A1, WO 98 / 04358 A1, and US 2013 / 0099023 A1 disclose ways to generate drops with a defined volume using dosing valves.

[0006] The invention is further based on the object of specifying a dosing method which is particularly suitable for large-scale production and by means of which different target masses of the dosage units can be reliably and repeatedly maintained.

[0007] This object is achieved by a method having the features of claim 1.

[0008] The invention is also based on the object of providing a simplified calibration device.

[0009] This object is achieved by using a dosing valve having the features of claim 6.

[0010] The invention is based on the fundamental idea of ​​dispensing with a supply of prepared solid test specimens of varying masses during calibration. Instead, a test specimen adapted to the respective calibration scenario is created as a liquid subset of a defined volume only during the execution of the calibration routine. This liquid subset is then passed through the measuring channel as the test specimen. According to the invention, a conventional dosing valve is used in the calibration device, allowing liquid subsets of very precisely measured volumes to be generated as test specimens. The test liquid, selected with regard to its dielectric properties, is also clearly defined with regard to its specific gravity, so that an equally precisely defined mass can be derived from the exact volume.The dosing valve not only allows the generation of precisely measured liquid portions, but can also deliver them with the desired accuracy over a wide volume or mass range with the required precision. Overall, according to the invention, the required test specimens can be easily generated and used directly on demand, in the required size. The complex procurement and storage of solid test specimens of various sizes is eliminated. The device itself is also simple and cost-effective. Furthermore, its operation is so easy that the calibration routine can be performed on-site by operating personnel, even under clean room conditions.

[0011] Dosing valves of various designs are considered within the scope of the invention. The dosing valve preferably comprises a piezo actuator and a fluid reservoir. This combination combines clearly defined closing and opening times with short delivery paths for the test fluid. This creates a precise profile of the fluid delivery over time, resulting in an equally precise and reproducible quantity or droplet size.

[0012] In an advantageous development, the fluid reservoir has a pressure connection for supplying an overpressure. This overpressure allows for a uniform and clearly defined discharge velocity of the fluid, which is essentially independent of the fill level of the test fluid in the fluid reservoir. A quasi-constant discharge pressure can be set and maintained.

[0013] In a preferred embodiment, several calibration measurements are performed, with a different amount of overpressure being applied to the liquid reservoir during different calibration measurements to expel partial amounts of liquid at different speeds. This allows the sensitivity of the sensor to varying flow rates to be tested. This can be particularly useful if the dosing device tends to decrease in its discharge speed during operation or to fluctuate generally.

[0014] In an advantageous further development, the geometry of the liquid portion is recorded using a camera. The volume is derived from the recorded geometry, and from this, together with the density of the liquid used, the mass of the liquid portion is determined. This allows the dosing valve to be monitored and checked for the requested and actually dispensed liquid portion.

[0015] In a preferred embodiment of the method, a single partial amount of liquid is ejected from the dosing valve during a single calibration measurement. This is particularly advantageous if, during subsequent regular dosing operations, corresponding individual amounts of the dosage forms are to be measured, for example, as powder plugs or the like. The individual partial amount of liquid can be adjusted as closely as possible to the individual amount to be dosed, thereby achieving a very precise calibration in this case.

[0016] In an advantageous variant, a sequence of several partial quantities of liquid is ejected from the dosing valve during a single calibration measurement. This is particularly advantageous if, during subsequent regular dosing operations, several partial quantities of the dosage forms, for example, pellets or the like, are to be measured. The sequence of several partial quantities of liquid can be adjusted as closely as possible in terms of number and individual quantity to the number of partial quantities to be dosed, thus resulting in a very precise calibration in this case.

[0017] An embodiment of the invention is described in more detail below with reference to the drawings. They show: Fig. 1 in a schematic overview of a dosing device according to the invention for dosing dosage units with a capacitive measuring system and an associated calibration device using a single liquid portion as a test body, Fig. 2 the Fig. 1 calibrated dosing device in regular dosing operation in conjunction with a capacitive mass test of the individual dosage units, and Fig. 3 a variant of the Fig. 1 described calibration procedure using a sequence of several immediately consecutive liquid portions.

[0018] The Fig. 1 und 2 show a schematic sectional view of the dosing device in two different configurations. The dosing device according to the invention comprises, in addition to a schematically indicated dosing unit 16 ( Fig. 2 ), a capacitive measuring system 1 and a calibration device 2 ( Fig. 1 ) for the capacitive measuring system 1. The dosing device is designed to dispense, in particular, solid pharmaceutical dosage units 9 ( Fig. 2 ), to check the actual mass of a single dosage unit 9 and to transfer it to a target container 17. The pharmaceutical dosage units 9 mentioned can be tablets, pellets, compressed powder plugs or the like. However, within the scope of the invention, liquid dosage units 9 from this or other areas, such as eye drops, can also be provided. In addition to pharmaceutical dosage units 9, those from the area of ​​food supplements, from the area of ​​care products or the like are also considered. The target container 17 ( Fig. 2 ) blister packs, plug-in capsules or the like, but also intermediate containers for further processing, for example, come into consideration.

[0019] First, Fig. 2 Reference is made to FIG. 1, in which the dosing device is shown in its usual operating configuration. In the dosing unit 16, which is only schematically indicated, a measured partial quantity, for example, of a powder or granulate, is dosed, particularly volumetrically, to form a schematically indicated dosage unit 9. This dosage unit 9 can be blown out of the dosing unit 16 toward the target container 17. Alternatively or additionally, the force of gravity can be used to allow the dosage unit 9 to fall from the dosing unit 16 into the target container 17.

[0020] For 100% in-process control, the individual dosage units 9 pass through the measuring section of the capacitive measuring system 1 mentioned above on their way from the dosing unit 16 to the target container 17. For this purpose, the capacitive measuring system 1 comprises a base body 10 with at least one measuring channel 8 formed therein, here oriented vertically in the direction of weight. Located in the measuring channel 8 is the measuring section of a schematically indicated capacitive measuring sensor 14, which is connected to an evaluation unit 15. As a result of a calibration of the capacitive measuring system 1, which is described further below, the mass of each individual dosage unit 9 can be determined with high precision and repeatability in the evaluation unit 15 based on the measurement signal recorded by the capacitive measuring sensor 14 and generated by the passage of the dosage unit 9.

[0021] Optionally, a further measuring channel 8' with a further capacitive measuring sensor 14' can be arranged parallel to measuring channel 8. This additional measuring channel 8' is used as a compensation channel to compensate for, for example, atmospheric changes, so that the latter have no influence on the determined measurement result. Furthermore, it should be noted that, for the sake of simplicity, only one pair of measuring channels 8, 8' with capacitive measuring sensors 14, 14' is shown here. In practice, a multi-row dosing unit 16 with, for example, twelve adjacent dosing outlets is used. Accordingly, a corresponding number of measuring channels 8 and, if necessary, also additional measuring channels 8' are formed in the base body 10 of the capacitive measuring system 1.

[0022] In order to be able to make a reliable statement about the actually achieved mass of each individual dosage unit 9 from the measurement result of the capacitive measuring system 1, the invention provides a calibration device 2 and an associated calibration method for calibrating the capacitive measuring system 1, as can be seen from the schematic representation according to Fig. 1 For a better overview, the capacitive measuring system 1 is shown here, omitting the dosing unit 16 and the target container 17. Fig. 2 in interaction with the calibration device 2.

[0023] The calibration device 2 comprises a metering valve 21 and an indicated mounting frame 30, by means of which the metering valve 21 is aligned with the associated measuring channel 8 and held in position. The term "metering valve" chosen here encompasses valves that, by means of electrical control, dispense a defined partial quantity 22 of liquid through an outlet nozzle 27 according to an arrow 28. According to the invention, such a known metering valve 21 is used in the calibration device 2 in such a way that at least one partial quantity 22 of liquid of a defined volume is ejected therefrom in a manner described in more detail below and passed as test specimen 3 through the associated measuring channel 8.

[0024] In the preferred embodiment shown, the metering valve 21 comprises a piezo actuator 23 and a fluid reservoir 24, wherein the fluid reservoir 24 has a pressure connection 25 for supplying excess pressure. In the present case, a metering valve 21 in the form of a so-called jet metering valve with a piezo actuator 23 in the form of a commercially available PICO Pµlse® from Nordson EFD is selected.

[0025] The liquid reservoir 24 contains a test liquid, from which individual liquid portions 22 are extracted to form the aforementioned test specimens 3. For this purpose, the applied overpressure pushes the liquid through the piezo actuator 23, on the underside of which, facing the measuring channel 8, is an outlet nozzle 27. The metering valve 21 or its piezo actuator 23 is controlled by a schematically indicated control unit 29 such that a volumetrically defined liquid portion 22 exits the outlet nozzle 23 over a defined opening time / opening stroke. The outlet nozzle 23 is directed into the measuring channel 8, so that the exiting liquid portion 22 passes through the measuring channel 8 from top to bottom as a result of its exit velocity and assisted by the force of gravity.

[0026] The calibration of the capacitive measuring system 1 is carried out according to the invention as follows: First, at least one partial liquid quantity 22 of a defined volume is generated by means of the dosing valve 21 of the calibration device 2 and ejected according to the arrow 28. This at least one partial liquid quantity 22 is passed through the measuring channel 8 as a test specimen 3 and then optionally collected in a collecting container 26.

[0027] The resulting measurement signal of the capacitive sensor 14 is evaluated in the evaluation unit 15. It may be sufficient for a single calibration measurement according to the illustration in Fig. 1 to guide only a single partial quantity of liquid 22 as test body 3 through the measuring channel 8, whereby then only a single measuring or calibration signal is generated analogous to a regular measuring signal when filling individual quantities such as powder plugs or the like. Fig 3 . shows a variant of this approach, in which a sequence of several immediately successive liquid partial quantities 22' is ejected from the dosing valve 21 during a single calibration measurement. This then results in a corresponding sequence of several immediately successive measurement or calibration signals, analogous to regular measurement signals during the simultaneous filling of, for example, several pellets. In the remaining features and reference symbols, the embodiments according to the Fig. 1 and 3 agree.

[0028] The number of calibration measurements is selected to be high enough so that the evaluation of the associated individual measurements in the evaluation unit 15 is statistically significant. Optionally, a different amount of overpressure can be applied to the fluid reservoir 24 via the pressure connection 25 for each calibration measurement. The overpressure determines the exit velocity of the respective fluid portion 22 from the outlet nozzle 27. By varying the overpressure as mentioned above, the different fluid portions 22 are ejected at different speeds. This allows the sensitivity of the capacitive measuring system 1 with respect to the exit velocity to be tested, which allows for appropriate calibration adjustment if necessary.

[0029] In any case, test specimens 3 are used which have known dielectric properties due to their defined volume and the known properties of the test liquid. These are used as measurement standards, and the measured values ​​determined in the capacitive measuring system 1 are used for calibration. This allows calibration of the capacitive measuring sensor for almost any mass of a single dosage unit 9 ( Fig. 2 ) is possible. The dosage units 9 are finally calibrated using the dosing device according to Fig. 2 dosed and checked for properly dosed mass using the calibrated capacitive measuring system 1. Within a wide measuring range of, for example, 1 to 175 mg, defined target masses can be determined or checked with a measurement accuracy of < 0.5% RSD (relative standard deviation).

[0030] As mentioned above, in practice, a multi-row dosing unit 16 with several adjacent dosing outlets and a corresponding number of measuring channels 8 is used. Accordingly, a multi-row calibration device 2 can also be provided. However, a single calibration device 2 is preferably used, which is automatically positioned and centered sequentially over the individual measuring channels 8 with its one dosing valve 21. The capacitive measuring system (1) is then calibrated sequentially in the individual measuring channels 8.

[0031] The representation of the Fig. 1 and 3It can also be seen that the calibration device has a camera 31 for recording the geometry of the ejected liquid partial quantity 22. This is based on the fact that the outlet nozzle 27 of the dosing valve 21, with its nozzle diameter, specifies the diameter of the ejected liquid partial quantity 22. The opening time of the dosing valve and thus the delivery time is controlled via the piezo actuator 23. The length of the ejected liquid partial quantity 22 results from the opening time and the pressure-dependent delivery speed, which, in conjunction with the also known diameter, allows a volume determination and, taking the density of the liquid into account, a mass determination of the ejected liquid partial quantity 22. The geometry (diameter, length) recorded by the camera 31 can be used to check orverify, and proof of calibration accuracy can be provided.

[0032] Finally, it should be noted that the test specimen should be as close as possible in both size and mass to the product to be measured later in operation. Therefore, a calibration fluid is selected whose dielectric properties are as close as possible to the product. If water-containing liquids are to be filled and measured, water can be chosen as the calibration fluid. If a pharmaceutical powder is to be filled, a silicone oil, a mineral oil such as white oil, or the like can be chosen as the calibration fluid. In both cases, the dielectric properties of the calibration fluid are sufficiently close to the dielectric properties of the product, which contributes to accurate calibration.

Claims

1. Method for the metering of dosage units (9), in particular from the pharmaceutical field or the field of food supplements, by means of a metering installation and a calibration installation (2), wherein the metering installation has a capacitive measuring system (1), and wherein the capacitive measuring system (1) has at least one measuring channel (8) with a capacitive measuring sensor (14) for the dosage units (9), wherein the calibration installation (2) comprises a metering valve (21) which is configured to eject a liquid portion (22) of defined volume and convey it as a test body (3) through the measuring channel (8), the method comprising the following method steps: - The capacitive measuring system (1) is calibrated, by means of the calibration installation (2), by at least one calibration measurement of a test body (3), wherein at least one liquid portion (22) of defined volume is ejected by means of the metering valve (21) of the calibration installation (2), and wherein the at least one liquid portion (22) is conveyed as a test body (3) through the measuring channel (8); - The dosage units (9) are metered by means of the metering installation and are checked, in terms of correctly metered mass, by means of the calibrated capacitive measuring system (1).

2. Method according to claim 1, characterized in that a number of calibration measurements are carried out, wherein an overpressure of different extent in each case is introduced into the liquid reservoir (24) for different calibration measurements, in order to eject liquid portions (22) at a different speed.

3. Method according to claim 1 or 2, characterized in that the geometry of the liquid portion (22) is recorded by means of a camera (31), and the volume of the liquid portion (22) is deduced therefrom.

4. Method according to one of claims 1 to 3, characterized in that, in an individual calibration measurement, an individual liquid portion (22) is ejected from the metering valve (21).

5. Method according to one of claims 1 to 3, characterized in that, in an individual calibration measurement, a sequence of several liquid portions (22') immediately succeeding one another is ejected from the metering valve (21).

6. Use of a metering valve (21) in a calibration installation (2) for a capacitive measuring system (1) in a metering installation for dosage units (9), in particular from the pharmaceutical field or the field of food supplements, in order to eject at least one liquid portion (22) of defined volume and to convey it as a test body (3) through the measuring channel (8).

7. Use of a metering valve according to claim 6, characterized in that the metering valve (21) has a piezo actuator (23) and a liquid reservoir (24).

8. Use of a metering valve according to claim 7, characterized in that the liquid reservoir (24) has a pressure port (25) for the introduction of an overpressure.

9. Use of a metering valve according to one of claims 6 to 8, characterized in that the calibration installation has a camera (31) for recording the geometry of the ejected liquid portion (22).