DEVICE FOR MAKING FILLED FOIL BAGS

Description

[0001] The invention relates to a device for producing filled foil bags with the features according to the preamble of claim 1.

[0002] In many applications, particularly in the household, foil pouches containing, for example, washing-up liquid or dishwashing detergent are increasingly used. These foil pouches are commonly made from water-soluble film materials such as PVOH (polyvinyl alcohol), which dissolves upon contact with water and releases the contents.

[0003] A typical manufacturing device for such film bags comprises plate elements with forming cavities, which can be moved to various processing stations. In a first processing station with a thermoforming unit, a base film is initially deep-drawn into the forming cavities, creating filling cavities in the base film. These filling cavities are then filled with the product in a subsequent second processing station. This is followed by a third processing station with a sealing unit. There, a top film is sealed onto the base film, forming a sealed edge that completely surrounds each filling cavity. Finally, individual film bags are cut from this sealed web and separated.

[0004] The quality of the seal is of particular importance. Even small seal defects, for example, caused by intervening filler material, can lead to product leakage, resulting in undesirable consequences such as contamination of the filling machine and potentially unusable retail packaging. US 2017 / 0030797 A1 describes the production of film pouches, whereby thermoforming, filling, and sealing are followed by camera-assisted inspection for defects, particularly in the seal seams. US 2013 / 0219996 A1 also describes a machine-based optical inspection of pouches for potential leaks. For this purpose, the pouch contents are mixed with an additive visible to the machine's optics. US 2019 / 0066288 A1 proposes, among other things, the use of a black background to increase contrast for detecting particles in film containers when inspecting them.According to JP 2001 349837 A, a foil package is illuminated with polarized light. This is intended to make inclusions between the foils more visible to the camera.

[0005] The invention is based on the objective of further developing a device mentioned at the outset in such a way that the quality of the finished sealing edge can be reliably assessed during ongoing operation.

[0006] This problem is solved by a device with the features of claim 1. According to the invention, a fourth processing station with a testing device for optical detection and quality assessment of the seal edge is arranged downstream of the third processing station with the sealing assembly. The testing device comprises an optical camera, means for increasing the contrast of the images captured by the camera, a lighting device, and an evaluation unit for the images captured by the camera.

[0007] The invention enables, in particular, 100% in-process control of whether the produced sealing edges are of sufficient quality and thus airtightness. The camera captures the sealed film webs within one or more foil pouches and takes one or more images. The contrast enhancement means that the captured image is such that a clear distinction can be made between the sealing edge, any defects in the sealing edge, and other areas of the foil pouch, such as the filling cavity and its contents. Electronic image recognition and evaluation then take place in the evaluation unit using a suitable algorithm. Based on the evaluation result, it can be determined whether the sealing edge is of sufficient quality. If not, the corresponding foil pouch can be separated and disposed of after being cut out.Overall, the desired tightness of the foil bags can be ensured with a high degree of process reliability.

[0008] In a preferred embodiment, the means for increasing contrast comprise a reflection-reducing surface on the plate elements. The reflection reduction can be achieved, for example, by matting the otherwise bare metallic surface. In particular, the reflection-reducing surface is formed by blackening the surface. In practice, it has been found that this allows for particularly good differentiation between a proper seal edge and any defects therein.

[0009] According to the invention, the means for increasing contrast comprise a polarizing filter for the illumination device and a camera configured as a polarizing camera. This is based on the understanding that films, due to their manufacturing process involving extrusion and / or blowing, have a more or less pronounced preferred direction, which becomes apparent during the sealing process. When the film surface is partially dissolved, particularly during wet sealing, this preferred direction, under certain circumstances, leads to the clear visibility of completely or insufficiently sealed areas in polarized light. The achievable contrasts are so good that a quality assessment is sometimes possible even without a costly anti-reflective coating on the plate elements.

[0010] According to the invention, the polarization direction of the polarizing filter is aligned at a polarization angle to a direction of movement of the plate elements, wherein the polarization angle lies in a range of 30° to 60° and is particularly 45°. This takes into account the fact that the film webs generally have a preferred direction determined by their longitudinal direction, which in turn corresponds to the direction of movement of the plate elements. Under these conditions, the aforementioned polarization angle leads to a significant increase in contrast and thus to the possibility of a reliable quality assessment.

[0011] In a preferred embodiment, the plate elements are provided with a marking for identifying the position of the sealing edge. This is based on the understanding that the achievable contrasts alone are not always sufficient to distinguish the sealing edge from other image parts, such as the filling cavity and the contents. However, with a suitable marking, the image can be virtually rotated and shifted to align with the actual container geometry. This allows specific image contrasts to be clearly assigned to the sealing edge under investigation, thus facilitating a reliable quality assessment.

[0012] In an advantageous embodiment, the camera is a line scan camera. One image line is oriented transversely to the direction of movement of the plate elements. The movement of the plate elements results in the construction of an image from a multitude of such image lines, achieving high image resolution. A timed interruption of the plate feed specifically for imaging is not required, which simplifies the integration of optical seal seam inspection into the rest of the manufacturing process. Parallax errors during imaging are reduced to a minimum. Furthermore, only relatively simple requirements for image illumination need to be considered, since differences in illumination intensity along the direction of movement are irrelevant.

[0013] The line scan camera captures only a single image line at a time, in rapid succession. To create a two-dimensional image from these image lines, the sequence of lines must be synchronized with the movement of the format plates. In a common design, the format plates are moved as an endless chain on a circular track by a servo motor. Such a servo motor can transmit its current position to the camera system and could thus act as an encoder for the format plate movement. However, it has been shown that the actual movement of the format plates at the camera location is not always sufficiently uniform and does not correlate with the drive movement of the servo motor. This is because various disturbances affect the plate transport. One such disturbance is the uneven stretching of the chain links in the transport chain.Secondly, the format plates are pulled through a vacuum channel, which leads to high static friction and jerky position changes during acceleration and deceleration of the transport. These effects are most pronounced in the center of the machine (total length approx. 18m), roughly where the camera is mounted.

[0014] In a preferred further development, a separate encoder is therefore arranged in the area of ​​the line scan camera for motion detection of the plate elements. This allows the aforementioned irregularities in plate movement to be taken into account, so that exact synchronization between the plate movement and the recording sequence of the line scan camera can be achieved.

[0015] The encoder installed at the aforementioned location can be equipped with a wheel that rolls on the plate elements or with other motion detection methods. However, it has been shown that under real production conditions, for example during the filling of powdered and / or liquid detergent, the format plate can become so contaminated that reliable, clean rolling cannot be guaranteed. Therefore, it is advantageous to equip the encoder with a non-contact sensor, and in particular with a laser sensor, for motion detection of the plate elements. For example, by utilizing the Doppler effect, both uneven behavior of the drive train can be taken into account and negative influences from contamination can be excluded.Precise motion detection and, consequently, precise synchronization of the line scan camera's recording sequence with the plate movement are possible even under harsh production conditions.

[0016] Alternatively, it may be advantageous to use an area scan camera. With simple means and without synchronization effort, a complete image of the area to be inspected can be obtained in a very short time.

[0017] In an advantageous embodiment, the lighting device is designed as a light bar arranged transversely to one direction of movement of the plate elements. This allows for uniform illumination, at least transversely to the aforementioned direction of movement, which is particularly desirable in combination with a line scan camera. Furthermore, the light bar also provides a good base for a polarizing filter and thus for image illumination with polarized light.

[0018] Exemplary embodiments of the invention are described in more detail below with reference to the drawing. The drawing shows: Fig. 1 shows a schematic overview of a device according to the invention for producing filled foil bags with a thermoforming arrangement, filling arrangement, sealing arrangement and optical inspection device; Fig. 2 shows a schematic top view of the arrangement according to Fig. 1 in the area of ​​the test setup with a lighting device designed as a light bar and with a line camera, Fig. 3 in a schematic top view, a device according to the Figuren 1, 2 manufactured foil bags with a circumferential sealing edge, Fig. 4 in a side view a variant of the arrangement according to the Fig. 1, 2 with a lighting device comprising a lighting dome and with an area camera, Fig. 5 in a schematic front view a variant of the light bar according to the Fig. 1, 2 with a polarizing filter placed in front of the light bar at a polarization angle of 45°, Fig. 6 shows a section of the image sensor of the line camera in a schematic perspective view. Fig. 1, 2 in an optional version as a polarization camera, and Fig. 7 in a schematic top view a section of the image sensor of the area camera according to Fig. 4 in an optional version as a polarization camera.

[0019] Fig. 1 Figure 1 shows a schematic overview of a device according to the invention for producing filled film bags 50. The film bags 50 are made from a deep-drawn base film 11 with filling cavities 13, from a filling material 14 filled into the filling cavities 13, and from a sealed top film 12. Any film material can be used within the scope of the invention. In this case, the base film 11 and the top film 12 are water-soluble films, in particular made of PVA (polyvinyl alcohol). The filling material 14 can also be freely selected within the scope of the invention. In this case, it is detergent or dishwashing liquid in powder and / or liquid form.

[0020] The device comprises a series of processing stations, a selection of which is schematically indicated here as a first processing station 1, a second processing station 2, a third processing station 3, and a fourth processing station 4. A multitude of plate elements 9 are connected to each other to form a closed chain. During operation, this chain is driven continuously and cyclically by a drive (not shown). For clarity, only a section of the upper chain segment (in the vertical direction) is shown here, which, in the image, is continuously moved sequentially from left to right in a direction of movement 25 to the various processing stations 1, 2, 3, 4. However, intermittent operation is also possible.After the foil bags are finished, the emptied plate elements 9 are returned to the starting position in a closed orbit below the upper chain section shown here, in a manner not shown, as the lower chain section.

[0021] From the combination of Fig. 2 It follows that the individual plate elements 9 each have several forming cavities 10 arranged in a matrix. For the sake of simplicity, the forming cavities are shown schematically here with a square base and rounded corners. In practice, any other base shape is chosen, whereby for each individual foil bag 50, several forming cavities 10 for several different contents 14 can be grouped together.

[0022] First, the base film 11 is laid flat onto the plate elements 9. The first processing station 1, shown here, comprises a deep-drawing assembly 5, indicated only in block representation. With this assembly, the base film 11 is heated until it plasticizes and then deep-drawn into the mold cavities 10 of the plate elements 9 using a vacuum. This creates filling cavities 13 in the base film 11. The plate elements 9, together with the deep-drawn base film 11, are then conveyed to the second processing station 2, which comprises a filling assembly 6, also indicated only in block representation. Using the filling assembly 6, measured portions of the aforementioned fill material 14 are filled into the filling cavities 13. In the subsequent processing step, the plate elements 9, together with the deep-drawn base film 11 and the filled fill material 14, pass through the third processing station 3, which includes a sealing assembly 7, also indicated only in block representation.There, the cover film 12 is moistened on its underside facing the base film 11 by means of a humidification device 26 (optional), placed on the base film 12, and then sealed there under the influence of pressure and (optional) temperature.

[0023] In this way, a web of many connected foil bags 50 is created, which are ultimately separated into ready-to-use units in a manner not shown. Such a foil bag 50 is shown schematically in a top view in Fig. 3 shown. Accordingly, the seal arrangement 7 ( Fig. 1 ) in the case of the individual still connected foil bags 50, each has a sealing edge 15 that surrounds the filling cavity 13 filled with the filling material 14, at which the cover film 12 is tightly connected to the base film 11.

[0024] According to the invention, a fourth processing station 4 follows the third processing station 3 in the direction of movement 25. This fourth processing station 4 has a testing device 8, schematically represented as a block, for optically detecting and evaluating the quality of the seal edge 15. The testing device 8 comprises an optical camera 16, which is directed towards the path of continuous foil bags 50 still located in the forming cavities 10 of the plate elements 9. The testing device 8 further comprises means for increasing the contrast of the images captured by the camera 16, a lighting device 17, and an evaluation unit 18 for the images captured by the camera 16, as described in more detail below.

[0025] The test device 8 is spatially stationary, while the chain of plate elements 9 together with the path of connected foil bags 50 still located in the forming recesses 10 of the plate elements 9 is moved past it in a continuous movement in the direction of movement 25.

[0026] Fig. 2 A schematic top view shows the arrangement according to Fig. 1 In the area of ​​the test device 8. In the illustrated embodiment, the camera 16 is designed as a line scan camera and is oriented such that, with a single snapshot, it captures a line of images of the foil bags 50 located in the mold cavities 10, extending transversely to the direction of movement 25 and thus, according to a double arrow 27, transversely across the entire width of the plate elements 9. The camera 16 generates a large number of such image lines in rapid succession. These image lines are fed into the evaluation unit 18.

[0027] In addition to camera 16, an encoder 24 for motion detection of the panel elements 9 is also connected to the evaluation unit 18. With respect to the direction of movement 25, the encoder 24 is located in the vicinity of camera 16 and is positioned vertically below the panel elements 9. The encoder 24 is equipped with a non-contact sensor, in this case a laser sensor, for motion detection of the panel elements 9 using the Doppler effect. The detected motion data is fed into the evaluation unit 18.

[0028] Due to the immediate proximity of the encoder 24 to the camera 16, the movement of the plate elements 9 detected by it corresponds exactly to the movement that results in different image lines for the spatially stationary camera 16. In the evaluation unit 18, the different image lines are synchronized with the detected movement data of the plate elements 9 in such a way that a distortion-free 2D image of the foil bags 50 located in the mold cavities 10, including their sealing edges 15, is created from the image lines. Fig. 3 ).

[0029] A quality assessment based on this, preferably also carried out automatically in the evaluation unit, in particular of the seal edges 15 ( Fig. 3 This requires uniform illumination. Since the camera records 16 image lines perpendicular to the direction of movement 25, only uniformity of illumination in this transverse direction is relevant. Consequently, the lighting device 17 is designed as a light bar 20, which is arranged perpendicular to the direction of movement 25 and spans the entire width of the plate elements 9.

[0030] As a further measure for reliable quality assessment, the means for increasing the contrast of the images captured by the camera 16, already mentioned at the beginning, are provided. For this purpose, a surface 23 of the plate elements 9 facing the camera 16 is provided with a reflection-reducing treatment. This can be a matte or satin finish instead of a bare metallic surface 23. In the illustrated embodiment, this surface 23 is completely coated, i.e., within the mold cavities 10 and also between them in the area of ​​the sealing edges 15 ( Fig. 3 ) blackened. At selected points, this blackening is reinforced by circular milling to form markings 22 for position identification of the seal edges 15 ( Fig. 3 ) in particular, in contrast to the mold recesses 10, the markings 22 are interrupted. Accordingly, they are light or metallically bright, unlike the rest of the blackening. For better readability of the drawing, in Fig. 2 A negative representation was chosen in which the light markings 22 are shown dark, and the remaining blackened areas of the surface 23 are shown light.

[0031] The markings 22 are designed such that a unique position determination is possible within all degrees of freedom of the image or plate plane. They can, for example, be a cross or another geometric figure. In this case, a pair of circular, point-like surfaces was chosen for each plate element 9. In any event, this allows the evaluation unit 18 to perform a virtual displacement of the image captured by the camera 16 in the direction of movement 25, a virtual displacement in the lateral direction perpendicular to it according to the double arrow 27, and a virtual rotation about a vertical axis perpendicular to both directions, such that the captured image is superimposed on an existing target geometry.In this way, the areas of the seal edges to be inspected can be clearly distinguished from other areas such as the areas of the mold cavities 10 with the filling cavities 13 and the filling material 14.

[0032] The images, enhanced in contrast as described above, allow for a particularly automated assessment of the quality of the sealing edges 15. Contamination trapped during sealing, especially from the contents 14, unwanted creases in the film material, or other defects in the sealing edges can be clearly identified. Correspondingly defective individual film bags can then be sorted out. In the event of an increased defect rate, the production process can also be interrupted for rectification. In any case, consequential damage caused by leaking film bags can be reliably avoided or at least reduced to a minimum.

[0033] Fig. 4 shows a side view of a variant of the arrangement according to the Fig. 1, 2 , where camera 16 is designed as an area scan camera. Unlike the line scan camera according to the Fig. 1, 2 The area camera captures a complete two-dimensional image of the path of foil bags in a single shot, which is visible both in the direction of movement 25 and perpendicular to it (double arrow 27 in Fig. 2 ) extends. An encoder 24 as in Fig. 2 This is not required here. However, for reliable image evaluation, uniform illumination of the entire image field is necessary, not only in the transverse direction (double arrow 27 in). Fig. 2 ), but also in the direction of movement 25. For this purpose, the lighting device 17 in the arrangement according to Fig. 4 an illumination dome 19 which completely covers the image area of ​​the area camera. The image area is preferably at least as large as the base area of ​​a single plate element 9.

[0034] The lighting dome 19 is equipped with light sources 28 on its edges facing the plate elements 9. These light sources are not directed directly at the plate elements 9, but rather illuminate the inside of the lighting dome 19 in the direction indicated by arrows 29. The inside of the lighting dome 19 has a surface that diffusely reflects the light from the light sources 28, thereby illuminating the upper surface of the plate elements 9 facing the camera 16 with uniform intensity.

[0035] At the upper apex of the lighting dome 19, it has an image opening 30, above which the camera 16 is mounted. Through this image opening 30, the camera takes pictures of the plate elements 9 below, with the still connected foil bags 50 contained therein.

[0036] Between the camera 16 and the image aperture 30 is a semi-transparent mirror 31, inclined at 45°. The semi-transparent mirror 31 allows the image to be captured by the camera 16 as described above. Additionally, light from another light source 32 is fed into the interior of the illumination dome 19 via the semi-transparent mirror. This compensates for the lack of reflection of light from the lower light sources 28 at the image aperture 30, resulting in an overall illumination of the image field with uniform intensity.

[0037] Unless otherwise described, the exemplary embodiment according to Fig. 4 in the remaining features and reference numerals with the embodiment according to the Fig. 1 bis 3 agree.

[0038] Another concept according to the invention for means of increasing the contrast of the images taken by the camera 16 is described in the Fig. 5 bis 7 The means for increasing contrast include a polarizing filter 21 of the illumination device 17 and the configuration of the camera 16 as a polarizing camera. From the combination of the Fig. 1, 2 This results in a variant of the arrangement shown there, in which the light strip 20 is connected to a preceding, in Fig. 5 The polarizing filter 21 is schematically indicated. The polarizing filter 21 polarizes the light emerging from the light bar 20 at a polarization angle α relative to the direction of movement 25. The polarization angle α is advantageously in a range of 30° to 60° and is approximately 45° in the preferred embodiment shown. Accordingly, the web of connected foil pouches 50 ( Fig. 1 ) illuminated with light polarized in this direction.

[0039] The after Fig. 1 Camera 16, designed as a line scan camera, is configured as a polarization camera in the variant described here. A corresponding image sensor 34 of such a line scan camera configured as a polarization camera is shown schematically in Fig. 6 The system is shown and comprises a total of four sensor strips 35, 36, 37, 38 running transversely to the direction of movement 25, each with different filters for different polarization states. A first sensor strip 35 records image components with a polarization angle α = 0°. A second sensor strip 36 records image components with a polarization angle α = 135°. A third sensor strip 37 records image components with a polarization angle α = 90°. And a fourth sensor strip 38 is equipped without a polarizing filter and records unfiltered image signals. A resulting image line can be generated from the image line signals of all four sensor strips 35, 36, 37, 38 according to their actual polarization state.

[0040] Alternatively, an area scan camera designed as a polarization camera can be used instead of the line scan camera. A corresponding image sensor 39 is shown schematically in Fig. 7 The image sensor is shown in part. Accordingly, the image sensor has 39 individual sensor pixels 40, each composed of four subpixels 41, 42, 43, 44. Each subpixel 41, 42, 43, 44 has a polarization filter with a different polarization direction in front of it. A first subpixel 41 captures image components with a polarization angle α = 0°. A second subpixel 42 captures image components with a polarization angle α = 135°. A third subpixel 43 captures image components with a polarization angle α = 90°. And a fourth subpixel 44 captures image components with a polarization angle α = 45°.

[0041] Both of the above-described variants of a polarization camera can be incorporated into a device according to the invention. Fig. 1, 2 together with polarized lighting after Fig. 5 The two foil webs 11, 12 exhibit a preferred orientation due to their manufacturing process, which influences the polarization direction of the incident and then reflected light. Image contrasts, especially in the area of ​​the seal edges 15 ( Fig. 3 ) are increased by the change in the polarization state to such an extent that defects in the seal edges become readily apparent, and that, under certain circumstances, a contrast-enhancing but costly blackening or another treatment of the surface 23 ( Fig. 2 ) can be omitted. The remaining features and reference symbols can be adopted individually or in combination without modification.

Claims

1. Apparatus for producing filled film bags (50), comprising plate elements (9) which can be conveyed to various processing stations (1, 2, 3, 4), each having at least one mould recess (10), a first processing station (1) with a deep-drawing arrangement (5) for deep-drawing a base film (11) into the mould recesses (10) of the plate elements (9) in order to form filling cavities (13) in the base film (11), a second processing station (2) with a filling arrangement (6) for filling the filling cavities (13) with a filling substance (14), and a third processing station (3) with a sealing arrangement (7) for sealing a cover film (12) onto the base film (11) while respectively forming a continuous circumferential seal edge (15) around each of the filling cavities (13), the third processing station (3) with the sealing arrangement (7) being followed by a fourth processing station (4) with a testing device (8) for optical acquisition and quality assessment of the seal edge (15), the testing device (8) comprising an optical camera (16), an illumination device (17), and an evaluation unit (18) for the images recorded by the camera (16), characterized in that the testing device (8) comprises means for increasing the contrast of the images recorded by the camera (16), in that the means for increasing the contrast comprise a polarization filter (21) of the illumination device (17) and a configuration of the camera (16) as a polarization camera, and in that a polarization direction of the polarization filter (21) is aligned at a polarization angle (α) with respect to a movement direction (25) of the plate elements (9), the polarization angle (α) lying in a range of from 30° to 60°.

2. Apparatus according to claim 1, characterized in that the means for increasing the contrast comprise a reflection-reducing surface (23) of the plate elements (9).

3. Apparatus according to claim 2, characterized in that the reflection-reducing surface (23) is formed by blackening of the surface (23).

4. Apparatus according to one of claims 1 to 3, characterized in that the polarization angle (α) is 45°.

5. Apparatus according to one of claims 1 to 4, characterized in that the plate elements (9) are provided with a marking (22) for identifying the placement of the seal edge (15).

6. Apparatus according to one of claims 1 to 5, characterized in that the camera (16) is a line scan camera.

7. Apparatus according to claim 6, characterized in that an encoder (24) for acquisition of the movement of the plate elements (9) is arranged in the region of the camera (16) embodied as a line scan camera.

8. Apparatus according to claim 7, characterized in that the encoder (24) is provided with a contactless sensor and in particular with a laser sensor for acquisition of the movement of the plate elements (9).

9. Apparatus according to one of claims 1 to 5, characterized in that the camera (16) is an area scan camera.

10. Apparatus according to one of claims 1 to 9, characterized in that the illumination device (17) is embodied as a strip light (20), which is arranged transversely with respect to a movement direction (25) of the plate elements (9).