Systems and methods for analyzing tablet coatings

Abstract

A system (1) for analyzing the coating of tablets, pills, capsules and the like for pharmaceutical and / or food applications, which may be associated with a tablet coater machine (50), comprises an exit chute (51) configured to be associated with the coater machine (50), a dome illuminator (2) arranged to illuminate a detection zone (B) of a descent plane (52) of the exit chute (51) along which the tablets (100, 101) fall by gravity, a vision means (3) associated with the dome illuminator (2) and arranged to detect images of the tablets (100, 101) moving on the descent plane (52), and a control unit (10) connected to the vision means (3) to receive images of the tablets (100, 101), configured to track the movement of each tablet (100, 101), analyze only images of selected tablets without shadows, in particular single, spaced apart tablets with their maximum extension surface exposed to the vision means (3), and assess the color uniformity of the outer surfaces of the selected tablets.

Description

[Technical field]

[0001] The present invention relates to a machine and method for coating tablets, pills and capsules for pharmaceutical and food applications, and in particular to a system that can be associated with a tablet coater machine to automatically analyze the quality of the coating applied to the tablets.Furthermore, the present invention relates to a method for analyzing tablet coatings in a tablet coater machine. [Background technology]

[0002] In the pharmaceutical and food industries, it is known to use machines and processes to apply coatings to the exterior surfaces of tablets, pills, capsules, and the like, for example to protect them from stomach acid, to protect the gastric mucosa from aggressive drugs contained in the tablet, to allow delayed release of drugs by controlling the rate at which the tablet dissolves, and to maintain the shape of the tablet or pill.

[0003] Known coater machines typically comprise a rotating drum in which a controlled atmosphere is maintained and into which the tablets to be processed are introduced. Inside the rotating drum are dispensers, such as sprayers or nebulizers, which dispense a substance, typically in liquid form, that adheres to the outer surface of the tablets and dries to form a coating. The rotating drum is equipped with angular blades or baffles, and an air flow crosses the rotating drum in such a way that the tablets are moved and mixed during rotation about the horizontal axis of the rotating drum, in particular lifted and rotated towards the center of the rotating drum, so that the tablets gradually and uniformly receive the coating substance dispensed by the sprayer.

[0004] The coating applied to the exterior surface of each tablet is dried by introducing hot air into a rotating drum and regulating both the flow and temperature of the hot air so that the drying process is carried out in a controlled manner.

[0005] So-called batch coating systems are known which involve the introduction of a specific amount of tablets (batch) inside the rotating drum of a coater machine and the subsequent removal of that specific amount of tablets after the coating process is completed.

[0006] Also known are so-called continuous flow coating systems, in which a constant (mass) flow of tablets is introduced into a first end of a rotating drum of a coater machine, passes longitudinally through the rotating drum as it rotates, and, after being coated, is continuously removed from the second end of the drum on the opposite side. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] REKalman. “A New Approach to Linear Filtering and Prediction Problems”. Journal of Basic Engineering, 1960, 82.1: 35-45 [Non-Patent Document 2] P. Jaccard. “The distribution of the flora in the alpine zone”. New Phytologist, 1912, 11.2:37-50) and Hungarian algorithm (HW Kuhn. “The Hungarian method for the assignment problem”. Naval Research Logistics Quarterly, 1955, 2.1-2:83-97) [Non-Patent Document 3] J. O'Rourke. “Finding minimal enclosing boxes”. International journal of computer & information sciences, 1985, 14.3: 183-199 [Non-Patent Document 4] J. Canny. “A Computational Approach To Edge Detection”, IEEE Transactions on Pattern Analysis and Machine Intelligence, 1986, 8.6: 679-698 [Non-Patent Document 5] “Improvement to industrial color-difference evaluation”, Wien:CIE Publication No.142-2001, Central Bureau of the CIE;2001 Summary of the Invention

[0008] In both types of coating systems, it is known that there is a need to check the quality of the coating in order to optimally adjust the process parameters, such as the average residence time of the tablets in the rotating drum, the amount of coating material dispensed per unit time, the rotation speed of the rotating drum, etc.

[0009] Coating analysis is known which allows for periodic taking of samples of coated tablets which are examined by analysing the colour of their outer surface using specialised instruments such as colourimeters, spectrophotometers, spectrophotometers etc. Measurement of the difference between the detected colour and the colour of a reference standard tablet gives an indication of the quality of the coating.

[0010] Systems are also used to assess the quality of a coating based on the change in weight of tablet samples.

[0011] However, these analytical systems are labor intensive as they require manual removal of tablet samples from the rotating drum, and they also provide very low statistical quality control of the production as only a small number of coated tablets can be removed and analyzed.

[0012] One object of the present invention is to improve known systems for analyzing coatings on coaters, particularly tablets associated with continuous flow coaters for tablets, pills, capsules, etc.

[0013] Another object is to provide a simple and inexpensive system that allows for the automatic analysis of large numbers of tablets removed from a continuous flow coater machine without operator intervention.

[0014] A further object is to achieve a system that allows for a precise and accurate assessment of the coating quality, in particular the internal and external variability index of the coating of tablets processed by a coater.

[0015] In a first aspect of the present invention there is provided a system for analysing a tablet coating according to claim 1.

[0016] In a second aspect of the present invention there is provided a method for analysing a tablet coating according to claim 7. [Brief description of the drawings]

[0017] The invention may be better understood and practiced with reference to the accompanying drawings, which illustrate exemplary and non-limiting embodiments of the invention.

[0018] [Figure 1] 1 is a schematic partial cross-sectional front view of a tablet coating machine associated with a system for analyzing tablet coatings of the present invention; FIG. [Diagram 2] 2 is a cross-sectional view taken along line II-II of FIG. 1, illustrating the system of the present invention, particularly in relation to the tablet exit chute; [Diagram 3] 1 is a cross-sectional view of a dome illuminator and visual means of the system of the present invention; [Figure 4]FIG. 13 is a close-up view of a portion of the tablet exit chute showing multiple tablets of various shapes arranged in various placement positions. [Diagram 5] Figures 5a and 5b show two elongated tablets with low and high intra-intra-intra-variability indexes, respectively. [Figure 6] Figures 6a and 6b show groups of elongated tablets with low and high external variability indices, respectively. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] 1 to 4, a system 1 of the present invention for analyzing the coating of tablets, pills, capsules and the like for pharmaceutical and / or food applications associated with a tablet coater machine 50 is generally illustrated.

[0020] The coater machine 50 is, for example, a continuous-flow machine of known type comprising a rotating drum 55 which is elongated and rotatable about an axis of rotation X, in particular a horizontal axis of rotation X, and which is provided at a first end 55a with a first opening, not shown, for feeding the tablets 100 to be coated and at an opposite second end 55b with a second opening which is connected to the outlet chute 51 of the system 1 of the invention for the coated tablets.

[0021] Inside the rotating drum 55 there are discharge means 56 arranged to discharge a substance, for example a liquid substance, which adheres to the outer surface of the tablets 100 to form a coating. The discharge means 56 comprise, for example, a number of sprayers 57 fixed to a supply duct 58 for supplying the coating substance.

[0022] In addition to the exit chute 51, the system 1 for analyzing tablet coatings includes a dome illuminator 2 positioned to illuminate a detection zone B of the descent plane 52 of the exit chute 51 into which the tablets 100 fall by gravity along an exit direction A.

[0023] The system further comprises a vision means 3 associated with the dome illuminator 2 and arranged to detect images of the tablets 100 in the detection zone B, and a control unit 10 connected to the vision means 3 to receive the images of the tablets 100. The control unit 10 is configured to track the movement of each tablet 100 and to analyse only images of selected tablets without shadows, in particular single and spaced tablets whose maximum extension surface is exposed to the vision means 3, and to assess the colour uniformity of the outer surface of the selected tablets.

[0024] In particular, the control unit 10 implements a tracking algorithm which provides the following procedure.

[0025] Considering the qth image of the tablet moving on the exit chute, acquired by the vision system 3, first each tablet 100 present in the image is identified. Then, based on the tablet's location in the qth image, a prediction is made of where the tablet will be in the q+1th image, based on physics considerations and the use of a Kalman filter (RE Kalman. "A New Approach to Linear Filtering and Prediction Problems". Journal of Basic Engineering, 1960, 82.1:35-45). Finally, after identifying each tablet 100 present in the q+1th image acquired by the visual means 3, the concept of Jaccard distance (P. Jaccard. “The distribution of the flora in the alpine zone”. New phytologist, 1912, 11.2:37-50) and the Hungarian algorithm (HW Kuhn. “The Hungarian method for the assignment problem”. Naval Research Logistics Quarterly, 1955, 2.1-2:83-97) are used to associate the new position of each tablet 100 in the q+1th image with its prediction derived from the analysis of the qth image.

[0026] By tracking the movement of each tablet, the control unit 10 is able to distinguish between tablets in each image captured by the vision system 3 and analyse the tablets separately if they are not shaded. In other words, and with particular reference to Figure 4, the control unit 10 is configured to discard and not assess the colour uniformity of the outer surface of tablets having shade or shade zones C, i.e. areas of the outer surface that are not properly and completely illuminated by the light emitted by the dome illuminator 2, for example because the tablets are overlapping, touching or tilted.

[0027] More precisely, three criteria are used to assess whether a tablet 100, 101 is properly and completely illuminated by the light emitted by the dome illuminator 2, has no shadow zones and is therefore suitable for color uniformity analysis, which may be used individually or in combination. For example, one can choose to analyze a tablet only if the conditions for fulfilling all three of the criteria are met for the tablet, or if the conditions for at least one of the criteria are met.

[0028] The first criterion is based on the assessment of the aspect ratio of the tablet under consideration, which is defined as the ratio between the length and the width of the relative oriented closing rectangle (J. O'Rourke. "Finding minimal enclosing boxes". International journal of computer & information sciences, 1985, 14.3:183-199). In particular, the color of the tablet is analyzed if the aspect ratio does not deviate excessively (the operator can define a tolerance threshold) from the value obtained by achieving the ratio between the theoretical actual dimensions corresponding to the type of tablet under consideration (round or circular 100 or elongated 101).

[0029] The second criterion instead provides that the operator provides the control unit 10 with a model image (template) of a tablet of the type under consideration (round or circular 100 or elongated 101) taken in an ideal pose, whose outer contour is identified by the Canny algorithm (J. Canny. “A Computational Approach To Edge Detection”, IEEE Transactions on Pattern Analysis and Machine Intelligence, 1986, 8.6:679-698). Subsequently, the outer contour of the tablet is also detected, the analyzability of the tablet's color is evaluated and its dissimilarity to the outer contour of the model tablet is calculated. If this index is below a tolerance threshold specified by the operator, the color of the tablet under consideration is analyzed.

[0030] The third criterion is based on the identification of edges present within the image of the tablet whose color analysability must be evaluated, also identified using the above-mentioned Canny algorithm, and the tablet's color is analyzed if, in particular, the number of pixels belonging to these edges is less than a tolerance threshold specified by the operator.

[0031] In Fig. 4, by way of example, the shaded tablets are grouped together, indicated with the reference R, and comprise round or circular tablets 100 and elongated tablets 101. In this way, the control unit 10 actually selects and evaluates the colour uniformity only of single, separate tablets whose maximum extension faces are exposed to the visual means 3, i.e. tablets whose opposite maximum extension faces land on the descent plane 52. In Fig. 4, these selected tablets are grouped together, indicated with the reference S, and comprise round or circular tablets 100 and elongated tablets 101. In this way, the visual means 3 can optimally detect a complete and illuminated image of the outer surface of the tablet 100 for which the colour uniformity analysis is to be performed.

[0032] More precisely, the control unit 10 is configured to measure the internal and external variability indexes of the colour of the tablets.

[0033] For the definition of these indices, consider a group made up of a number of tablets 100, 101 equal to N, belonging to a selection of tablets that have no shading, and in particular the images of each of the tablets acquired by the vision system 3.

[0034] M j Define j as the number of pixels belonging to the image of the tablet,

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[0035] Then, the average internal distance associated with the jth tablet

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[0036] For example, with particular reference to Figures 5a and 5b, a low intra-intra-variability index indicates that the surface of a single tablet has a high homogeneity or uniformity in color, i.e., the surface does not have areas or zones of no color and / or areas or zones of different intensity (Figure 5a). Conversely, a high intra-intra-variability index indicates that the surface of a single tablet has a low homogeneity or uniformity in color, i.e., the surface has one or more areas or zones of no color and / or areas or zones of different intensity (Figure 5b). In particular, in Figure 5a, the color is distributed with a substantially uniform intensity and is therefore shown with one type of hatching, while in Figure 5b, some of the tablets are colorless and therefore have no hatching.

[0037] In addition, the average color of the group under consideration of N tablets of types 100 and 101 belonging to the selected tablets without shading was examined and the results were compared in triplicates.

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[0038] Therefore, for the group under consideration of N tablets of types 100 and 101 belonging to the selected tablets without shading, the vector of external distances

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[0039] In this way, the external variability index for the group under consideration of N tablets of types 100 and 101 belonging to the selected tablets without shading is the vector of external distances

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[0040] For example, with particular reference to Figures 6a and 6b, a low external variability index indicates low color diversity among the surfaces of a group of tablets, i.e., high uniformity or homogeneity of the surface color (Figure 6a). Conversely, a high external variability index indicates significant color diversity among the surfaces of a group of tablets, i.e., low uniformity or homogeneity of the surface color (Figure 6b). In particular, in Figure 6a, the tablets all have the same hatching since the color is substantially uniformly distributed on the tablets, while in Figure 6b, the tablets each have a different color, so the hatching is different.

[0041] Therefore, based on the above definition, the internal variability index

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[0042] Generally, the variability index threshold below which color differences are considered negligible is equal to 3.

[0043] This threshold is experimentally derived.

[0044] Alternatively, it is possible to use the vision system 3 to analyze tablets 100 belonging to a production batch considered as a standard, i.e. a reference batch, to calculate relative internal and external variability indices considered as references, and then to compare these reference indices with the internal and external variability indices obtained for other tablets for which coating quality control is performed.

[0045] Another alternative involves analysing the evolution over time of the variability indices obtained for selected and analysed tablets 100 and detecting possible degradation in the performance of the coating process carried out by the coater machine 50 based on unexpected changes in these variability indices.

[0046] The visual means 3 comprise, for example, a camera.

[0047] With particular reference to Figure 3, the dome illuminator 2 comprises a dome-shaped vault 21, in particular having a circular bottom 22, provided with an internal reflective surface 23 and a peripheral internal flange 24. The peripheral internal flange 24 is provided at the bottom 22 and comprises a number of light sources 25, in particular of the LED type, suitable for diffusing light towards the internal reflective surface 23, which makes it possible to diffuse the light evenly downwards, i.e. towards the bottom 22. The dome vault 21 comprises an upper central opening 26, for example coaxial with the vertical axis of symmetry Z of the dome vault 21, which allows the visual means 3 to detect the image of the tablet 100 in the dome illuminator 2 in the detection zone B of the exit chute 51.

[0048] The operation of the system 1 according to the present invention for analysing the coating of tablets, pills, capsules etc. for pharmaceutical and / or food applications produced by the coater machine 50 provides that the coated tablets 100 exiting the coater machine 50 are analysed by the vision means 3 and the control unit 10 as they slide under gravity on the exit chute 51 along the exit direction A.

[0049] More precisely, the tablet 100 is illuminated at a detection zone B in the descent plane 52 of the exit chute 51 by a dome illuminator 2 configured to emit and diffuse light uniformly and homogeneously.

[0050] With this illumination, the images of the tablets 100 detected by the visual means 3 are selected by the control unit 10 which analyses only the outer surface of the selected tablet which is free of shadows, i.e. a single, separate tablet whose maximum extension surface is exposed to the visual means 3. The outer surface of the selected tablet is therefore subjected to a series of analyses, in particular to the internal variability index, in order to assess the color uniformity.

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[0051] Based on the results of this analysis, it is possible to modify the operating parameters of the coater machine 50, particularly if the value of the measured variability index deviates from the reference variability index.

[0052] To this end, the coater machine 50 comprises a processing unit 60 connected to the control unit 10 of the system 1 and arranged to modify its operating parameters on the basis of information provided by the control unit 10 regarding the colour uniformity of the outer surface of selected coated tablets. In particular, the operating parameters include the inlet flow rate of the tablets, the rotational speed of the rotating drum 55 and the flow rate of coating material dispensed by the sprayer 57 onto the tablets.

[0053] The method of the present invention for analyzing the coating of tablets, pills, capsules and the like for pharmaceutical and / or food applications in a tablet coater machine 50 equipped with an exit chute 51 for the discharge of the coated tablets 100 comprises: illuminating with a dome illuminator 2 a detection zone B of a descent plane 52 of an exit chute 51 along which a tablet 100 falls by gravity along an exit direction A; Detecting an image of a tablet 100 moving on a descent plane 52 using a vision means 3 associated with a dome illuminator 2; - analyzing only the images of selected tablets that are free of shadows, using a control unit 10 connected to the vision means 3 to receive images of the tablets 100; evaluating the color uniformity of the exterior surface of the selected tablets; Includes.

[0054] According to the method of the present invention, the selected tablets without shading include single, spaced apart tablets with their maximum extension surface exposed to the visual means 3.

[0055] The method comprises detecting an image of the tablet 100 by visual means 3 comprising, for example, a camera.

[0056] According to the method, evaluating the color uniformity of the outer surface of the selected tablets includes measuring the internal color variability index of the selected tablets 100 according to the following formula:

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[0057] Thus, the system and method of the present invention allows for the analysis of large numbers of tablets 100 at the exit from a coater 50, particularly a continuous flow type coater, simply, economically, and automatically, without operator intervention.

[0058] The visual means 3 and dome illuminator 2 associated with the exit chute 51 of the coater machine 50 actually make it possible to analyze the tablet 100 in motion, i.e., the tablet 100 descending under gravity along the exit direction A on the descent plane 52 of the exit chute 51.

[0059] Since the control unit 10 analyses only images of the tablets 100 detected by the visual means 3 that are free of shadows, i.e. images of single, separated tablets with their maximum extended surface exposed to the visual means 3, the system 1 of the present invention allows to determine the quality of the coating of the tablets 100, in particular the internal variability index of the coating of the tablets 100 processed by the coater machine 50.

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Claims

1. A system (1) for analyzing coatings of tablets, pills, capsules, etc. for pharmaceutical and / or food applications, which may be associated with a tablet coater machine (50), comprising: an exit chute (51) configured to be associated with said coater machine (50) for the discharge of the coated tablets (100, 101); a dome illuminator (2) positioned to illuminate a detection zone (B) of the descent plane (52) of the exit chute (51) along which the tablets (100, 101) fall by gravity along an exit direction (A); a vision means (3) associated with said dome illuminator (2) and arranged to detect an image of said tablet (100, 101) moving on said descent plane (52); a control unit (10) connected to at least said vision means (3) to receive images of said tablets (100, 101) and configured to track the movement of each tablet (100, 101) and to analyze only said images of selected tablets without shadows, in particular single, spaced tablets whose maximum extension surface is exposed to the vision means (3), and to evaluate the color uniformity of the outer surface of said selected tablets; A system (1) comprising:

2. The system (1) according to claim 1, wherein the visual means (3) comprises a camera.

3. The dome illuminator (2) A dome vault (21) having a base (22), in particular a circular base (22), provided with an internal reflective surface (23) and a peripheral internal flange (24) provided with a number of light sources (25), in particular of the LED type, located at said base (22) and suitable for diffusing light towards said internal reflective surface (23), The dome vault (21) is an upper central opening (26) that allows the vision means (3) to detect the image of the tablets (100, 101) within the dome illuminator (2); The system (1) according to claim 1 or 2, comprising:

4. the control unit (10) is configured to measure an intra-tablet variability index of color of the selected tablets (100, 101) according to the following formula: [0010] Where: [0025] is the average inter-color distance associated with the jth tablet in the CIELAB color space, the inter-color variability index assesses the color homogeneity of the surface of each tablet viewed individually, and The control unit (10) is configured to measure an external variability index of the color of the selected tablets (100, 101) according to the following formula: [0030] Where: [0045] 4. The system (1) according to claim 1, wherein j is a vector of color external distances associated with the jth tablet in CIELAB color space, and the external variability index evaluates the color diversity between multiple tablets.

5. A continuous coater machine (50) for coating tablets, provided with a system (1) for analyzing the coating of tablets (100, 101) according to any one of claims 1 to 4.

6. 6. A continuous coater machine (50) as claimed in claim 5, comprising a processing unit (60) connected to a control unit (10) of the system (1) and arranged to modify operating parameters of the processing of the coater machine (50) based on information provided by the control unit (10) regarding the colour uniformity of the outer surfaces of the coated tablets.

7. A method for analyzing coatings of tablets, pills, capsules and the like for pharmaceutical and / or food applications in a tablet coater machine (50) equipped with an exit chute (51) for the discharge of coated tablets (100, 101), comprising: illuminating with a dome illuminator (2) a detection zone (B) of a descent plane (52) of the exit chute (51) along which the tablets (100, 101) fall by gravity along an exit direction (A); detecting an image of the tablet (100, 101) moving on the descent plane (52) using a vision means (3) associated with the dome illuminator (2); tracking the movement of the tablets (100, 101) using a control unit (10) connected to the vision means (3) for receiving images of the tablets (100, 101) and analysing only the images of selected tablets that are free of shadows; assessing the color uniformity of the exterior surface of the selected tablets; The method includes:

8. 8. The method of claim 7, wherein the selected tablets without shading comprise a single, spaced apart tablet with its maximum extension surface exposed to the visual means (3).

9. 9. The method according to claim 7 or 8, comprising detecting the image of the tablet (100, 101) by visual means (3) comprising a camera.

10. The evaluating the color uniformity of the outer surface of the selected tablets (100, 101) comprises measuring an internal color variability index of the selected tablets (100, 101) according to the following formula: [0050] Where: [006] is the average inter-color distance associated with the jth tablet in the CIELAB color space, the inter-color variability index assesses the color homogeneity of the surface of each tablet viewed individually, and The evaluating step includes measuring the external variability index of the color of the selected tablets (100, 101) according to the respective formula: [0070] Where: [0080] 10. The method of claim 7, wherein j is a vector of external color distances associated with the jth tablet in CIELAB color space, and the external variability index measures color diversity among a plurality of tablets.

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