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EP-4581352-B1 - APPARATUS AND METHOD FOR INSPECTING A SLIT ON A CAP

EP4581352B1EP 4581352 B1EP4581352 B1EP 4581352B1EP-4581352-B1

Inventors

  • BALDUCCI, MASSIMO

Dates

Publication Date
20260513
Application Date
20230831

Claims (15)

  1. An apparatus (1) for inspecting a slit made on a lateral surface (SL) of a plastic cap (T), comprising: - a conveyor (11), configured to transport the cap (T) along a path (P); - an illuminator (10), configured to illuminate the lateral surface (SL) of the cap (T) placed at an inspection position, wherein the cap (T), at the inspection position, is aligned with an inspection axis (I), the inspection axis (I) being oriented vertically and transversely to the path (P); - a plurality of cameras (12) surrounding the inspection axis (I) and configured to capture image data representing a plurality of images of the lateral surface (SL) of the cap (T) at the inspection position; - a control unit, configured to receive and process the image data to derive information relating to the slit, characterized in that the illuminator (10) includes a side wall (101) extending around the inspection axis (I) to illuminate all of the lateral surface (SL) of the cap (T) with rays that converge towards the inspection axis (I), the side wall (101) delimiting an internal space and including an inlet opening (103) and an outlet opening (104) to allow for passage of the cap into and out of the internal space, respectively.
  2. The apparatus (1) according to claim 1, comprising a collimator (113), interposed between the illuminator (10) and the inspection axis (I) and configured to collimate the light emitted by the illuminator (10) towards the inspection axis (I).
  3. The apparatus (1) according to claim 2, wherein the collimator (113) comprises a collimating grid, extending around the inspection axis (I) along the side wall (101) of the illuminator (10) to describe a cylindrical shape around the inspection axis (I) so that the rays are directed radially, perpendicularly to the inspection axis (I).
  4. The apparatus (1) according to any one of the preceding claims, wherein the side wall (101) of the illuminator (10) includes a diffuser body (110), having a ring-shaped configuration and wherein the illuminator (10) comprises: - a primary light source (111) disposed along an upper edge (110b) of the diffuser body (110), the diffuser body (110) being configured to diffuse the light from the primary light source (111) in the internal space, and - a reflective layer (112), applied on an outside surface (110e) of the diffuser body (110), facing towards the internal space to reflect the rays directed away from the inspection axis (I).
  5. The apparatus (1) according to any one of the preceding claims, comprising a top wall (102), coupled to the side wall (101) of the illuminator (10) to delimit the top of the internal space, and an additional light source (111), coupled to the top wall (102) to emit light into the internal space from above.
  6. The apparatus (1) according to any one of the preceding claims, wherein at least one of the following condition is true: i) each of the plurality of images represents a respective portion of the lateral surface (SL), imaged by a corresponding camera (12) of the plurality of cameras (12) and the control unit is programmed to derive a developed image from each of the plurality of images, where the developed image shows the lateral surface (SL) of the cap (T) represented in a plane; ii) the side wall (101) comprises a plurality of openings (114), each camera (12) being located at an opening (114) of the plurality of openings (114), iii) each camera (12) defines a capture axis (R), the capture axis (R) of each camera (12) being inclined relative to a plane that is perpendicular to the inspection axis (I).
  7. The apparatus (1) according to any one of the preceding claims, comprising a screening element (13), wherein the screening element (13) is located inside the internal space and extends in a plane (E) transverse to the inspection axis (I), is aligned with the inspection axis (I), so the cap (T) placed at the inspection position is vertically interposed between the conveyor (11) and the screening element (13), is movable vertically relative to the conveyor (11), to allow adjusting a distance between the screening element (13) and the cap (T) placed at the inspection position.
  8. The apparatus (1) according to any one of the preceding claims, comprising an upper camera (15), located above the conveyor (11) and defining a capture axis (R') oriented along the inspection axis (I) to view the cap (T) at the inspection position from above, wherein the upper camera (15) is configured to capture a control image representing a placement of the cap (T) on the conveyor (11) and wherein the control unit is connected to the upper camera (15) to receive the control image and is programmed for: - comparing the control image with reference information representing a predetermined position where the cap (T) is aligned with the inspection axis (I); - processing the image data to derive the information relating to the slit based on the comparison.
  9. The apparatus (1) according to any one of the preceding claims, comprising a position sensor configured to capture a position signal representing a placement of the cap (T) at a predetermined position upstream of the inspection zone, wherein the control unit receives the position signal and instructs the cameras (12) to capture the image data in a synchronized manner based on the position signal.
  10. A line for manufacturing plastic caps (T), comprising: - a forming machine, for manufacturing the plastic caps in continuous cycle; - an apparatus (1) for inspecting a slit made on a lateral surface (SL) of the plastic cap (T), the apparatus being according to any of the previous claims.
  11. A method for inspecting a slit made on a lateral surface (SL) of a plastic cap (T), the method comprising the following steps: - through a conveyor (11), transporting the plastic cap (T) along a path (P); - through an illuminator (10), illuminating the lateral surface (SL) of the cap (T) when the cap (T) is placed at an inspection position where it is aligned with an inspection axis (I), the inspection axis (I) being oriented vertically and transversely to the path (P); - capturing image data, by means of a plurality of cameras (12) surrounding the inspection axis (I), when the cap (T) is at the inspection position, the image data representing a plurality of images of the lateral surface (SL) of the cap (T); - through a control unit, receiving and processing the image data to derive information relating to the slit, the method being characterized in that the illuminator (10) includes a side wall (101) extending around the inspection axis (I) to illuminate all of the lateral surface (SL) of the cap (T) at the same time with rays that converge towards the inspection axis (I), the side wall (101) delimiting an internal space and including an inlet opening (103) and an outlet opening (104) to allow for passage of the cap (T) into and out of the internal space, respectively.
  12. The method according to claim 11, comprising a step, performed by a collimating grid of a collimator (113), of collimating the light emitted by the illuminator (10) towards the inspection axis (I), wherein the collimating grid is interposed between the illuminator (10) and the inspection axis (I), to collimate the light emitted by the illuminator (10) towards the inspection axis (I), and extends around the inspection axis (I) along the side wall (101) of the illuminator (10) to describe a cylindrical shape around the inspection axis (I) so that the rays are directed radially, perpendicularly to the inspection axis (I) and wherein the side wall (101) of the illuminator (10) includes a diffuser body (110), having a ring-shaped configuration and wherein the illuminator (10) comprises a primary light source (111) disposed along an upper edge (110b) of the diffuser body (110), the method comprising the following steps: - through a primary light source (111), emitting light; - through the diffuser body (110), diffusing the light from the primary light source (111) in the internal space.
  13. The method according to claim 11 to 12, wherein each camera (12) defines a capture axis (R), the capture axis (R) being inclined relative to a plane that is perpendicular to the inspection axis (I).
  14. The method according to any one of claims 11 to 13, comprising the following steps: - through an upper camera (15) located above the conveyor (11) and defining a capture axis (R') aligned with the inspection axis (I), capturing a control image representing a placement of the cap (T) on the conveyor (11) when the cap (T) is placed at the inspection position; - through the control unit, receiving the control image and comparing the control image with reference information representing a predetermined position where the cap (T) is aligned with the inspection axis (I); - through the control unit, processing and generating the information relating to the slit, based on the comparison.
  15. A method for producing plastic caps (T) in continuous cycle, comprising the following steps: - molding the caps though a forming machine; - inspecting a slit made on a lateral surface (SL) of the plastic cap (T), through a method according to any of the previous claims from 11 to 14.

Description

Technical field This invention relates to an apparatus and a method for inspecting a slit on a cap. Background art This invention addresses the technical field of the inspection of caps, specifically the inspection of slits (or recesses) on the caps. Typically, caps comprise a body and a tamper evident ring and the body is connected to the tamper evident ring by a connecting tear strip; more specifically, when a user twists the cap for the first time, the body is separated from the tamper evident ring and the tamper evident ring remains attached to the neck of the container. In other types of caps such as, for example, those known as "tethered caps", a permanent connecting zone of the tear strip does not tear and keeps the cap body attached to the tamper evident ring; thus, tethered caps are thus prevented from being lost and help reduce littering. In both traditional caps and tethered caps, the connecting strip may include a series of slits and bridges, that is to say, tearable connecting zones between the body and the tamper evident ring; alternatively, especially in the case of tethered caps, the connecting strip may include recesses, that is, narrow thickness portions which are thinner than the body and the tamper evident ring and which tear when the cap is twisted for the first time. These slits or the narrow thickness zones may be made during a step of moulding the cap (by compression, injection or both injection and compression), for example, inside the mould itself or by using movable drawers in the mould, or during a step subsequent to moulding, for example by slitting the cap using specific knives or by a material-removal process. In this field, therefore, it is important that the slits, or the recesses, be of high quality, in order to facilitate opening by the user or to prevent unwanted tearing of the connecting zone. There is therefore an ever-growing need to accurately inspect the slits or recesses before the caps are applied on the respective containers. Slitting forms an incision or a series of incisions. It is noted that this invention can be applied to the inspection of slits (or incisions) and/or recesses. Known in the prior art are technical solutions, for example, described in patent application publication document IT202000012214A1 in the name of the present Applicant, where a light source illuminates a portion of the lateral surface, and a camera next to the cap captures image data of the illuminated portion; more specifically, the cap rotates about its own axis of symmetry so as to expose different parts of its lateral surface to the camera to allow the camera to capture an image of each portion. Incorporating a solution of this kind into a cap production line reduces production speed because every cap, in order to be inspected, must be transported into the inspection apparatus and rotated to capture images of the entire surface of the cap. Other known solutions for inspecting plastic objects are described in patent application publication documents JP2017120201A, HP-H-09169392A, JP2001050898A and WO2017/196193A. JP2017120201A discloses lamps that are arranged around the cap to be inspected; HP-H-09169392A discloses a laser beam which illuminates the inside of the cap. However, a need remains for an inspection apparatus which is particularly precise and robust. Disclosure of the invention The aim of this disclosure is to provide an apparatus and a method for inspecting a slit on a cap to overcome the above mentioned disadvantages of the prior art. In particular, this disclosure has for an aim to provide an apparatus and a method for inspecting a slit on a cap and which can be easily implemented in a production line. Another aim of this disclosure is to propose an apparatus and a method for inspecting a slit and which allows obtaining an image of the lateral surface where the slits are clearly visible and creating an image with good contrast. A further aim of this disclosure is to provide an apparatus and a method for inspecting a slit and which ensures that the images obtained are realistic and natural. These aims are fully achieved by the apparatus and method of this disclosure as characterized in the appended claims. More specifically, the apparatus comprises an illuminator, configured to illuminate the cap. Preferably, the illuminator is configured to illuminate a lateral surface of the cap. More specifically, the lateral surface extends around a longitudinal axis, that is to say, like a ring around the longitudinal axis. The cap also comprises a transverse surface, that is to say, a surface connected to the lateral surface and oriented perpendicularly to the longitudinal axis. The illuminator may be configured to illuminate the transverse surface of the cap. The apparatus comprises a conveyor, configured to transport the cap along a path. The path may be partly circular and/or partly rectilinear. The path may comprise at least one substantially rectilinear portion in proximity to