Inspection device for converters

Abstract

The invention relates to an inspection device (42) for verifying the position of at least one coating on a blank (1) conveyed through a converter (10). The inspection device comprises a camera (49) configured to capture an image of a portion of the blank provided with a reference mark (30) comprising at least one coating. The optical axis (A) of the camera is arranged at a first angle (φ) with respect to a vertical axis (V) defined by a normal vector (N) of the surface of the blank (1). An illumination system (50) is configured to emit an incident light beam towards a measurement point (Pm) on the blank (1). The incident light beam from the illumination system is directed towards the reference mark and a specularly reflected light beam from the reference mark is captured by the camera.

Description

Technical Field

[0001] The present invention relates to a converting machine for producing packaging containers such as flat box packages or folding boxes. In particular, the present invention relates to an inspection system for detecting the position and alignment of printed colors and coatings.

Background Art

[0002] A converting machine can be configured to produce packaging containers such as flat box packages or folding boxes from a sheet substrate that is printed, cut, and scored to form blanks. These blanks can then be folded and assembled into three-dimensional boxes. The boxes are designed to be folded either manually or automatically in a folder-gluer.

[0003] When the packaging containers and boxes are provided with a printed motif including multiple colors and various coatings, it is required that each color and coating be in the exact position on the blank and that the colors and coatings be aligned with each other.

[0004] Aligning the colors, referred to as setting the print register, is often done by printing reference marks in the margins of the blank and using a camera system to capture an image of the printed reference marks. The displacement of different elements within the reference marks can then be determined. Based on this information, the printing unit in the converting machine can be adjusted either manually or automatically. However, in known systems, it is difficult to detect transparent coatings such as varnishes.

Summary of the Invention

Problems to be Solved by the Invention

[0005] In view of the above problems, it is an object of the present invention to provide an inspection device capable of detecting coatings with high accuracy. It would also be an advantage to provide an inspection device capable of additionally detecting different colors with high accuracy. [Means for solving the problem]

[0006] This objective is achieved by the inspection device according to claim 1.

[0007] According to a first aspect of the present invention, an inspection device is provided for determining the location of at least one coating on a blank being transported via a converter, the inspection device comprising a camera configured to capture an image of the location of a blank provided with a reference mark having at least one coating, The optical axis of the camera is positioned at a first angle with respect to a vertical axis defined by the normal vector of the blank surface, and the inspection device comprises a lighting system comprising a first lighting module having at least one lighting unit. The illumination unit is configured to emit incident light rays toward a measurement point on the surface of the blank, and the emitted light rays form a second angle with respect to the vertical axis, and the first and second angles are selected such that the incident light rays from the illumination unit are directed toward a reference mark and the specularly reflected light rays from the reference mark are captured by the camera.

[0008] This invention is based on the realization of making reflective coatings detectable by generating a mirror effect from a coating accepted by a camera. Depending on the angle of the optical axis, the camera can capture specularly reflected light rays, thereby enabling the detection of the reflective coating.

[0009] Specularly reflected light rays are captured by the camera when they are directed towards the camera lens's entrance pupil.

[0010] The entrance pupil is the optical opening from the blank; therefore, it is from the object side. In other words, the entrance pupil can be defined as the optical opening into the camera through which light can enter.

[0011] The surface of the blank may be a horizontal plane. Therefore, the vertical axis may coincide with the direction of gravity. The measurement point is located on the surface of the blank where printed reference marks are provided.

[0012] In the context of this application, the term "coating" means transparent, i.e., colorless. This refers to the transparent nature of the coating that makes it invisible to conventional camera systems. A reference mark may be a composite reference mark comprising multiple individual reference marks. A reference mark therefore includes at least one individual reference mark printed together with the coating. Each individual reference mark may be printed by a separate flexographic printing cylinder.

[0013] The first lighting module may be configured to illuminate a reference mark that produces specular reflection. The reference mark that produces specular reflection may include varnish.

[0014] In one embodiment, the first lighting unit of the first lighting module includes a diffusion layer. The first lighting unit further includes a plurality of light sources arranged side by side on a circuit board, the light sources being covered by the diffusion layer.

[0015] In an advantageous embodiment, the reference mark comprises at least one first individual reference mark and a second individual reference mark, and the inspection apparatus comprises a second illumination module configured to illuminate the individual reference marks, which are configured to cause diffuse reflection of light rays, the second illumination module comprising at least one illumination unit positioned at a third angle with respect to the vertical axis, the third angle being selected such that incident light rays from at least one illumination unit are directed toward the reference marks and specularly reflected light rays from the reference marks are directed toward the outside of the camera's entrance pupil.

[0016] The second individual criterion mark is printed in color. The color is printed using an opaque ink containing at least one pigment, such as a dye or pigment. The color typically produces diffuse reflection of light.

[0017] The second lighting module may comprise at least two lighting units, the first and second lighting units being positioned on opposite sides of the camera's optical axis.

[0018] The first and second lighting units preferably comprise multiple light sources arranged in a line, and are elongated in shape. The vertical spread of the lighting units is positioned perpendicular to the direction of blank transport.

[0019] The first and second illumination units can be positioned at a large angle toward the field of view on the blank. This allows light rays from both sides to be received outside the camera's entrance pupil, and uniform illumination can be achieved.

[0020] In one embodiment, the first and second illumination units comprise only light sources positioned at the tips of their elongated spreads. In this manner, the illumination units are arranged in a square around the optical axis of the camera. This provides even distribution of the illumination units around the camera. As a result, uniform illumination is provided within the camera's field of view.

[0021] The light intensity from the first and second lighting modules is adjustable. By changing the light intensity, the balance between the glare and strength of the illumination of the reference mark can be optimized to achieve accurate image capture of the reference mark.

[0022] In one embodiment, the first lighting module can be disabled. This is advantageous when the reference mark does not have a reflective coating.

[0023] In another embodiment, the second lighting module can be disabled. There is an advantage to illuminating using only the first lighting module when the blank contains color marks that have low contrast against the blank's background, but the marks exhibit different reflective properties as a background.

[0024] In a preferred embodiment, the inspection device is mounted inside the housing shroud. The inspection device may further include slide rails extending transversely to the conveyance path of the blank, and the inspection device is configured to be displaced along the slide rails. The slide rails extend vertically above or below the conveyance path of the blank.

[0025] In one embodiment, the camera is triggered by a time signal from the control unit that is emitted when the optical sensor records the detection of the front leading edge of the blank, and the time signal corresponds to the arrival time of the reference mark in the reflection illumination area of the camera's field of view. The reflection illumination area may be provided by the first illumination module.

[0026] The present invention will now be described by way of example and with reference to the embodiments shown in the accompanying drawings, where the same reference numerals are used for similar elements.

Brief Description of the Drawings

[0027] [Figure 1a] A schematic plan view of a blank suitable for producing a box is shown. [Figure 1b] A first type of detailed view of a reference mark at the edge of the blank is shown. [Figure 1c] A second type of detailed view of the reference mark is shown. [Figure 2] A schematic perspective view of a converter in the configuration of a rotary die cutter is shown. [Figure 3] A schematic view of a flexographic printing module and an inspection device according to an embodiment of the present invention is shown. [Figure 4] A schematic perspective view of an inspection device according to an embodiment of the present invention is shown. [Figure 5] An exploded view showing the inspection device of FIG. 4 is shown. [Figure 6] A schematic cross-sectional view explaining the mounting of the camera inside the inspection device is shown. [Figure 7a] A schematic cross-sectional view showing the light rays emitted from the first illumination module towards the blank is shown. [Figure 7b]A schematic cross-sectional view is shown illustrating the light rays emitted from the second lighting module onto the blank. [Figure 8] This diagram shows a schematic cross-sectional view illustrating the installation of the inspection device inside the converter. [Figure 9a] The image shown was taken using the first lighting module of the present invention. [Figure 9b] This shows an image taken without using the first lighting module of the present invention. [Modes for carrying out the invention]

[0028] Figure 1a shows an example of a blank 1 for a flat box packaging box or a folding box. The blank 1 may be produced from cardboard, paperboard, plastic, etc.

[0029] Blank 1 may be produced in a converter 10, as shown in Figure 2. The converter 10 is located within the configuration of a rotary die-cutting machine 10. At the inlet position of the converter 10, a sheet substrate 1 is placed in a supply module 14 and transported through the converter 10 in the transport direction T to undergo a series of operations in which the sheet substrate 1 is printed, cut, and folded to form Blank 1. Thus, in the context of this application, the term “blank” applies when the sheet substrate 1 is given a printed motif from at least one printing unit. The transport direction T is defined from the inlet to the outlet of the converter 10. Blank 1 is transported along a transport path P, which is defined as the trajectory of Blank 1 through the converter 10.

[0030] From the inlet of the converter 10 and downstream along the transport direction T, the converter 10 may include a pre-feeder 12, a supply module 14, a printing module 15, a die-cutting module 18, a bundle stacker module 20, and a palletizer breaker 22. Optionally, a dryer module 13 (Figure 3) is provided after the printing module 15 and configured to dry the ink before the blank 1 enters the die-cutting module 18. A main operator interface 11 may be provided near the converter 10.

[0031] As shown in Figure 3, the printing module 15 comprises a plurality of flexographic printing units 16a to 16e. Each flexographic printing unit 16 comprises a flexographic printing assembly including a flexographic printing cylinder and is configured to print individual motifs on a sheet substrate 1 in different colors or coatings. Together, the individual motifs form the final motif 2 on the blank 1. Typically, at least four flexographic printing units 16a to 16d are provided to enable printing using different colors from a large color palette.

[0032] As is most visible in Figures 1b and 1c, the reference marks 30 are printed together with the motifs 2 by the flexographic printing unit 16. Each flexographic printing unit 16 is configured to print individual reference marks 30 at the same time that individual motifs are printed on the sheet substrate 1. In this manner, composite reference marks 30 are produced by different flexographic printing units 16. The reference marks 30 are preferably located on the front leading edge 4 of the blank 1.

[0033] Optionally, an additional second reference mark 34 may be provided on the rear edge 6 of the blank 1. The reference mark 30 on the front leading edge 4 and the second reference mark 34 on the rear edge 6 facilitate the measurement of the rotational displacement of the blank 1 within the flexographic printing module 15.

[0034] As shown in Figure 1b, the reference mark 30 may include a grid 36 and a plurality of individual dot-shaped reference marks 30' placed within the grid 36. The grid 36 is typically printed by a first flexographic printing unit 16a, together with separate dot-shaped reference marks 30' of a first color. The grid 36 is provided with a predetermined height H and length L.

[0035] As the sheet substrate 1 is transported through the flexographic printing module 15, each flexographic printing unit 16 prints a dot-shaped reference mark 30' within the grid 36. When the colors and coatings are aligned and thus perfectly registered, each dot-shaped reference mark 30' is positioned in a predetermined location within the grid 36, such as the center of the grid 36.

[0036] Alternatively, as shown in Figure 1c, the grid 36 is removed, and only the dot-shaped reference marks 30' are printed by each flexographic printing unit 16. These reference marks 30 indicate the position and alignment of different colors and coatings in two dimensions by their interrelated distances in the X and Y coordinates.

[0037] As shown in Figure 3, the converter 10 includes a print quality control system 40 configured to detect the position of individual motifs and the alignment of different individual motifs transferred from each flexographic printing unit 16 onto the sheet substrate 1. The print quality control system 40 includes an inspection device 42, a control unit 44, and a memory 46.

[0038] The print quality control system 40 is configured to detect and measure the longitudinal and transverse displacements between different colors and coatings at the reference mark 30. The longitudinal displacement is in the transport direction T, and the transverse displacement is perpendicular to the transport direction T. In this manner, print registration, i.e., the position and alignment between different colors and coatings, can be determined. If the printing units 16 are not precisely registered with respect to each other, the final motif 2 will show misalignment of the individual motifs printed in different colors.

[0039] The print quality control system 40 is configured to calculate vertical and horizontal displacements and transmit correction information to the central control system 48 of the converter 10. The correction information includes adjustments required for the angular and lateral positions of the printing cylinder of the printing module 15. The converter 10 may be configured to automatically adjust the angular and lateral positions of the printing cylinder. Alternatively, the print quality control system 40 can display the correction information required for manual adjustment of the printing module 15 on the machine interface 11.

[0040] If the print quality control system 40 detects a defective blank 1 having misaligned color and coating, the central control system 48 can transmit the information to the ejection module 17 to discard the blank 1.

[0041] As is most commonly seen in Figures 4, 6, 7a, and 7b, the inspection apparatus 42 comprises an imaging system 49 and an illumination system 50. The imaging system 49 may be a camera 49 having an active pixel sensor (e.g., a CMOS sensor) with an interface protocol configured to send images to a control unit 44. The camera 49 is configured to receive light rays from blank 1 within its field of view 51.

[0042] As shown in Figure 8, the inspection device 42 can be attached to a slide rail system 45, also referred to as a "sliding rail system 45". The slide rail system 45 includes vertical slide rails 47 that extend perpendicular to the transport direction T.

[0043] Referring again to Figure 3, the optical sensor 52 may be positioned upstream of and near the camera 49 and can be configured to detect the arrival of the front leading edge 4 of the blank 1. The camera 49 is triggered by a time signal from the control unit 44, which is emitted when the optical sensor 52 records the detection of the front leading edge 4 of the blank 1.

[0044] The inspection device 42 is mounted downstream of the flexographic printing module 15. As shown in Figure 3, the inspection device 42 is positioned below the transport path P of the blank 1. However, it is also possible to position the inspection device 42 above the transport path P of the blank 1. The inspection device 42 is therefore positioned so that the field of view 51 of the lighting system 50 and camera 49 is directed toward the printing side of the blank 1. If the converter 10 is provided with a dryer module 13, the inspection device 42 may be positioned after the flexographic printing module 15 and the dryer module 13. Alternatively, the inspection device may be positioned between the flexographic printing module 15 and the dryer module 13.

[0045] As is most visible in Figures 6, 7a and 7b, the camera 49 has an optical axis A, which is a straight line passing through the geometric center of the lens 53 of the camera 49. The optical axis A is positioned at a first angle φ with respect to the direction defined by the normal vector N of the surface of the printed sheet of blank 1.

[0046] As shown in Figure 4, the lighting system 50 comprises a first lighting module 56 having at least one lighting unit 57. As best seen in Figure 7a, the light emitted from the first lighting unit 57 toward the measurement point Pm on the blank 1 forms a second angle-α with respect to the vertical axis V defined by the normal vector N of the sheet surface of the blank 1. The second angle-α is a negative angle. The measurement point Pm is preferably located at the reference mark 30.

[0047] The absolute values ​​of the second angle -α and the first angle φ may be equal. However, the first angle φ of the optical axis A is a positive angle.

[0048] In the context of this application, a positive angle results from a counterclockwise rotation from the vertical axis V. Therefore, a negative angle results from a clockwise rotation from the vertical axis V.

[0049] As shown in Figure 7a, the blank 1 having a reflective surface is illuminated by the first illumination unit 57. The second angle-α of the first illumination unit 57 is selected such that the incident light rays from the first illumination unit 57 are directed toward the reference mark 30, and the specularly reflected light rays from the reference mark 30 are directed toward the entrance pupil 55 of the camera lens 53.

[0050] Coatings such as varnish have high reflectivity, making it difficult to detect the coating without causing a "specular reflection" effect at the entrance pupil 55 of the camera lens 53. These types of coatings exhibit specular reflection when illuminated.

[0051] The first illumination unit 57 is configured to emit diffuse light rays directed toward the reference mark 30 from multiple directions. This ensures that some specularly reflected light rays are received through the entrance pupil 55 of the camera lens 53. The first illumination unit 57 comprises at least one light source 58 and a diffuser layer 59. The diffuser layer 59 is positioned on at least one light source 58. The diffuser layer 59 is configured to scatter transmitted light rays from the light source 58, providing a uniform emission surface of diffuse light. The diffuser layer 59 can be made of a light-diffusing material such as polymethyl methacrylate.

[0052] In the illustrated embodiment, the first illumination unit 57 is configured such that only light rays reflected by a portion of the field of view 51 on the blank 1 are received through the entrance pupil 55 of the camera lens 53. This portion is referred to as the reflected illumination region Ria. Therefore, the reflected illumination region Ria on the blank 1 is a smaller surface area than the field of view 51 on the blank 1. The reference mark 30 thus needs to be positioned within the reflected illumination region Ria of the field of view 51 on the blank when the image of the reflected reference mark 30 is captured by the camera 49.

[0053] The camera 49 can be triggered by a time signal from the control unit 44, which is emitted when the optical sensor 52 records the detection of the front tip edge 4 of the blank 1. The signal can be set to a time corresponding to the arrival time of the reference mark 30 in the reflective illumination area Ria of the field of view 51.

[0054] In one embodiment, the first lighting unit 57 can be extended together with a plurality of light sources 58 arranged side by side. The vertical extension of the lighting unit 57 is positioned perpendicular to the transport direction T. The vertical direction of the light sources is also positioned perpendicular to the transport direction T and coincides with the vertical extension of the reference mark 30 on the blank 1.

[0055] The light sources 58 can be arranged in one or more rows. The light sources 58 may be placed on a printed circuit board (PCB). The distance between the light sources is selected to ensure uniform illumination of the diffusion layer 59.

[0056] When the inspection device 42 is mounted on the converter 10, the camera axis A is positioned at a first angle φ with respect to the vertical axis V. The horizontal axis is defined by the printed surface on the blank 1, and the vertical axis is perpendicular to the printed surface. The first angle φ allows the camera 49 to capture specularly reflected light rays reflected obliquely from the reference mark 30. The first angle φ may be between 1° and 15°, and is preferably about 5°.

[0057] In a preferred embodiment, a second illumination module 60 is also provided. The second illumination module 60 is configured to illuminate the printed color, which undergoes diffuse reflection when illuminated with specularly reflected light.

[0058] These types of colors include, for example, water-based or solvent-based inks. Due to the diffuse reflection of light rays from the reference mark 30, the camera 49 will receive the reflected light rays at the entrance pupil 55 of the camera lens 53. The second illumination module 60 is configured to provide uniform illumination of the reference mark 30 on the blank 1.

[0059] As is best seen in Figures 4 and 7b, a reflective surface on the blank 1 illuminated by the second illumination module 60 is shown. The second illumination module 60 comprises at least one illumination unit 62, 63, 65 positioned to emit light at a third angle β with respect to a vertical axis V defined by the normal vector N of the surface of the blank 1. The third angle β is selected such that incident rays from at least one illumination unit 62, 63, 65 of the second illumination module 60 are directed toward the reference mark 30, and specularly reflected rays from the reference mark 30 are directed toward the outside of the entrance pupil 55 of the camera lens 53. This allows the camera 49 to capture a clear image of the reference mark 30 without glare. Therefore, when illuminating the reflective surface, specularly reflected rays are not received by the entrance pupil 55 of the camera lens 53. The entire field of view 51 on the blank 1 may be illuminated by the second illumination module.

[0060] At least one lighting unit 62, 63, 65 may have multiple light sources 64 that are elongated and arranged in a single row. The vertical extension of at least one lighting unit 62, 63, 65 is positioned perpendicular to the transport direction T of the blank 1.

[0061] At least one lighting unit 62, 63, 65 of the second lighting module 60 may comprise a continuous row of light sources 64 arranged at a constant distance from one another. Alternatively, at least one lighting unit 62, 63, 65 may comprise only one light source 64 located at the end of the row. In such a manner, the light sources 64 are arranged in a square around the camera 49.

[0062] In one embodiment, an additional second illumination unit 63 is positioned opposite the optical axis A of the camera 49 to the first illumination unit 62. In this manner, further improved and uniform illumination of the field of view 51 on the blank 1 can be achieved. In one embodiment, a third illumination unit 65 is further provided on at least one of the sides of the camera 49.

[0063] Each of the illumination units 62, 63, and 65 may be configured to emit light toward the blank 1 at a different third angle β. Thus, in the illustrated example in Figure 7b, there are three illumination units 62, 63, and 65, and the angles of the emitted light, respectively, may be referred to as β1, β2, and β3. These angles are selected so that the specular reflection of the light rays is directed away from the entrance pupil of the camera 49. The angles β1, β2, and β3 may all be different, as long as the reflected light rays are not received by the entrance pupil 55 of the camera 49.

[0064] The first illumination module 56 and the second illumination module 60 can be operated simultaneously, thereby allowing the camera 49 to capture one image of the reference mark 30. Alternatively, either the first illumination module 56 or the second illumination module 60 can be operated, and the image can be captured by the camera 49. In another embodiment, only one of the multiple illumination units 62, 63, 65 of the second illumination module 60 is operated.

[0065] For inks that exhibit diffuse reflection when illuminated, the first illumination module 56 may be disabled. Thus, depending on the color and reflective properties of the coating, it may be sufficient to illuminate the reference mark 30 using only the second illumination module 60. In this way, it is possible to avoid reflection from reflective surfaces on the blank. This is shown in Figure 9b, where the blank 1, when illuminated with the first illumination module 56, exhibits reflection in smooth areas unintentionally rubbed by friction in the converter 10.

[0066] The light intensity from the first and second lighting modules 56 and 60 is adjustable. This allows for the adaptation of lighting settings that depend on the characteristics of the reference mark. In particular, for reflective coatings (ink or varnish), the lighting can be calibrated to obtain detectable reflections.

[0067] As is most commonly seen in Figures 5 and 6, the camera 49 is mounted inside the outer housing shroud 70 of the inspection device 42. A cover 72 is provided on the upper surface of the housing shroud 70. The cover 72 has a transparent surface 73, such as a glass surface 73. The outer housing shroud 70 is positioned around the camera 49 and is designed to provide a sealed housing that encloses the camera 49. The level of sealing may be, for example, IP64.

[0068] The outer housing shroud 70 may comprise walls 74 having different thicknesses. The different thicknesses allow for larger transverse walls for the fasteners 71 and provide rigidity to the walls 74. The walls 74 of the housing shroud 70 may further comprise biasing portions 75 that form a first angle φ with respect to the longitudinal extension of the outer housing shroud 70. This allows the optical axis A of the camera 49 to form a first angle φ with respect to the vertical axis V. The vertical axis V coincides with the longitudinal direction of the outer housing shroud 70, and the camera 49 is thus directed through an opening 76 in the cover 72 positioned between the lighting modules 56,60.

[0069] A thermoelectric element 78 is positioned between the camera 49 and the outer housing shroud 70. The thermoelectric element 78 may be a Peltier element 78. The camera 49 comprises an optical module 49a and an electronic processing module 49b. The electronic processing module 49b comprises heat-sensitive electronic components. The camera 49 is preferably positioned within the inspection apparatus 42 such that the electronic components are located near the thermoelectric element 78. In this manner, the electronic processing module 49b is thermally connected to the thermoelectric element 78.

[0070] An isolated inner housing 80 is positioned inside the outer housing shroud 70 and is configured to surround the camera 49. The inner housing 80 may include a first housing component 80a positioned around the camera 49's electronic processing module 49b. A second housing component 80b may be positioned around the camera 49's optical module 49a. The second housing component 80b may be tubular.

[0071] The first housing component 80a may have a recess 82 into which the second housing component 80b is partially received. This allows for a modular design and access to the optical module 49a of the camera 49 without removing the first housing component 80a.

[0072] As is most clearly seen in Figure 5, the first housing component 80a comprises an isolation portion 83 and a heat conduction portion 84. The heat conduction portion 84 comprises a heat conduction plate 84, such as a metal plate. For example, the heat conduction plate 84 can be made of aluminum or silver. The thermoelectric element 78 is positioned between the heat conduction plate 84 and the outer housing shroud 70. The heat conduction plate 84 distributes and spreads cool air from the thermoelectric element 78 to the electronic processing module 49b of the camera 49. The camera is secured to the outer housing shroud 70 by at least one fastener 71. In the illustrated embodiment, multiple fasteners 71, such as four fasteners 71, connect the inner housing 80 of the camera 49 to the outer housing shroud 70.

[0073] When current is passed through both sides of the thermoelectric element 78, it generates a hot side and a cold side. Thus, the cold side of the thermoelectric element 78 is in contact with the heat conduction plate 84, and the hot side of the thermoelectric element 78 is in contact with the outer housing shroud 70. In this manner, the processing module 49b of the camera 49 is cooled, while the outer housing shroud 70 can be used to dissipate heat from the thermoelectric element 78.

[0074] As is most commonly seen in Figure 3, the inspection device 42 may be located below the vacuum conveying means 9 of the flexographic printing module 15. Alternatively, the vacuum conveying means may be located below the inspection device 42. The vacuum suction force from the vacuum conveying means 9 includes an airflow over the outer housing shroud 70 that provides heat transfer to the ambient air.

[0075] A dryer module 13 may be positioned after the flexographic printing module 15 to ensure that the ink dries before the blank 1 moves to the next module, such as a die-cutting or folding module. The dryer module 13 operates by blowing hot air onto the printed surface of the blank 1.

[0076] By integrating the aforementioned thermoelectric element 78 into the inspection apparatus 42 of the present invention, a cooling effect can be achieved to reduce the heating of the camera 49 by stray heat from the dryer. Furthermore, it is possible to obtain a dust-free environment for the camera 49.

Claims

1. An inspection device (42) for confirming the position of at least one coating on a blank (1) being transported through a converter (10), The inspection device includes a camera (49) configured to capture an image of the blank portion on which a reference mark (30) having at least one coating is provided. The optical axis (A) of the camera is positioned at a first angle (φ) with respect to a vertical axis (V) defined by the normal vector (N) of the surface of the blank (1), and the inspection device comprises a lighting system (50) which includes a first lighting module (56) having at least one lighting unit (57), The illumination unit (57) is configured to emit incident light rays toward a measurement point (Pm) on the surface of the blank (1), and the incident light rays form a second angle (-α) with respect to the vertical axis (V). The first and second angles (φ, -α) are selected such that the incident light rays from the lighting unit (57) are directed towards the reference mark and the specularly reflected light rays from the reference mark are captured by the camera. The inspection device (42) further comprises a second lighting module (60) having a plurality of lighting units (62, 63, 65), wherein the incident light rays from the plurality of lighting units (62, 63, 65) form a third angle (β1, β2, β3) that is different from each other with respect to the vertical axis (V), and the third angle (β) is selected such that the incident light rays from at least one lighting unit are directed toward the reference mark and the specularly reflected light rays from the reference mark are directed toward the outside of the entrance pupil (55) of the camera lens (53). An inspection device characterized by the following features.

2. The inspection apparatus according to claim 1, wherein the reference mark (30) comprises a plurality of individual reference marks (30'), and each individual reference mark is printed by a separate flexographic printing cylinder.

3. The inspection apparatus according to claim 1 or 2, wherein the first lighting module (56) is configured to illuminate the reference mark (30) that causes specular reflection.

4. The inspection apparatus according to claim 3, wherein the aforementioned standard mark includes varnish.

5. The inspection apparatus according to claim 1, wherein the lighting unit (57) comprises a diffusion layer (59).

6. The inspection apparatus according to claim 5, wherein the lighting unit (57) of the first lighting module comprises a plurality of light sources (58) arranged in a row on an electronic substrate, and the light sources are covered by the diffusion layer (59).

7. The inspection apparatus according to claim 2, wherein the reference mark (30) includes at least one first individual reference mark (30') and a second individual reference mark (30'), the second lighting module (60) is configured to illuminate the individual reference marks (30') which are configured to cause diffuse reflection of light rays, and the second lighting module comprises at least one lighting unit (62, 63, 64) positioned at a third angle (β) with respect to the vertical axis (V).

8. The inspection apparatus according to claim 1, wherein the second lighting module (60) comprises at least two lighting units (62, 63, 65), the first and second lighting units being positioned opposite the optical axis (A) of the camera.

9. The inspection apparatus according to claim 8, wherein the first and second lighting units are extended and comprise a plurality of light sources arranged in a row.

10. The inspection apparatus according to claim 8, wherein the first and second lighting units (62, 63, 65) are angled in opposite directions from the vertical axis (V).

11. The inspection apparatus according to claim 8, wherein the first and second lighting units comprise only light sources positioned at the tips of their elongated extensions.

12. The inspection apparatus according to claim 7, wherein the light intensity from the first and second lighting modules is adjustable.

13. The inspection apparatus according to claim 1, wherein the first lighting module is deactivatable.

14. The inspection apparatus according to claim 7, wherein the second lighting module is deactivatable.

15. The inspection device is the inspection device according to claim 1, wherein the inspection device is mounted inside the housing shroud (70).

16. The inspection device according to claim 1, further comprising a slide rail (47) extending laterally with respect to the transport path (P) of the blank, wherein the inspection device is configured to be displaced along the slide rail.

17. The inspection apparatus according to claim 1, wherein the camera is triggered by a time signal from a control unit (44) which is emitted when an optical sensor (52) records the detection of the front leading edge (4) of the blank (1), the time signal corresponding to the arrival time of the reference mark (30) in the reflective illumination area (Ria) of the field of view (51) of the camera (49), the reflective illumination area being provided by the first illumination module (56).

Images