System and method for analysing caps fitted by a capping machine to containers having support rings

Abstract

A system (1) for analysing caps (C) fitted by a capping machine to containers (CO) having support rings (SR), where the caps and the support rings have marks consistently oriented with respect to a start of their respective thread elements, comprises: a conveyor (2), for conveying a succession of containers (CO) with caps fitted thereto individually to an inspecting position (IP) with the container oriented along a predetermined longitudinal axis (L); an illuminator (3); a camera (4); a hypercentric or pericentric lens system positioned in front of the camera; a control unit for acquiring an image of the cap and of the support ring and programmed for processing the image to identify an angular position of the marks on the cap and on the support ring relative to the longitudinal axis.

Description

[0001] DESCRIPTION

[0002] SYSTEM AND METHOD FOR ANALYSING CAPS FITTED BY A CAPPING MACHINE TO CONTAINERS HAVING SUPPORT RINGS

[0003] Technical field

[0004] This invention relates to a system and a method for analysing caps fitted by a capping machine to containers provided with support rings, a capping machine and method for analysing caps fitted by a capping machine to containers having support rings.

[0005] Background art

[0006] The disclosure addresses the field of optical inspection systems applied to the bottling sector, with particular reference to the inspection of the tightness of plastic caps relative to the necks of the respective containers they are fitted to.

[0007] Typically, the caps are fitted by a capping machine which automatically screws each cap onto the respective container, applying a tightening torque to the cap. In some cases, the capping process may be carried out incorrectly or in an undesirable manner, with the result that the container is not correctly closed or is difficult to remove. These cap tightening defects constitute a problem for beverage suppliers. It should also be noted that, generally speaking, different caps require different tightening torques. There is therefore a need to be able to discover whether the tightening torque is the right torque to tighten the cap.

[0008] For this purpose, fiducial markers or marks are applied to the cap and support ring (also called flange) provided on the container at the height of the neck; that way, the angular position of the markers present on the neck and support ring may indicate that the cap is correctly positioned on the container. These markers are also called Pull Up Marks (PUM).

[0009] In this regard, examples of optical inspection systems used to ascertain whether a cap has been correctly tightened on a container are provided by patent documents US5321506, US6473169 and WO2014176287A1 .

[0010] US6473169 involves use of a telecentric lens. In that document it is noted that if we wanted to see both the neck of the bottle and the cap in the same image, we would have to enlarge the field of view but this would lead to undesirable reduction of the resolution; to avoid this problem, US6473169 suggests inspecting the neck and the cap at different locations on the conveying carousel (turntable).

[0011] It should be noted that a telecentric lens (or objective lens) is a special optical lens that has its entrance or exit pupil, or both, at infinity. The function of the telecentric lens is to eliminate the perspective effects for a particular framed field and distance.

[0012] Patent document WO2014176287A1 describes an optical inspection system intended to determine the angular position of the fiducial marks on the neck and support ring of the container. This system too involves acquiring two distinct images non-simultaneously and then comparing the images. Telecentric lenses are used in this case too.

[0013] The solutions proposed by these patent documents, however, have some drawbacks. First of all, they are particularly complex solutions; also, they do not guarantee the precision uniformity and reliability of the inspection in the various different possible applications.

[0014] A further example of inspection systems, a method and a device for inspecting containers with closures disposed thereon is described by patent document DE102021121489.

[0015] In particular, DE102021121489 describes a system for analysing caps applied to containers equipped with a support ring using a capping machine.

[0016] DE102021121489 provides a lighting system comprising two illuminators closed by a wall which conveys the light towards the lower diffusion wall and therefore, the light is diffused and prevents the light from coming out laterally. DE102021121489 also includes a camera and a lens system placed between the camera and the container in the inspection position. Indeed, there continues to be a need for an inspection system for checking the tightness of caps on containers which is at once simple and capable of ensuring high precision and reliability for the various different applications. In this context, it is noted that one of the problems is that inspection precision tends to depend to a considerable extent on the colour of the cap. Moreover, the precision and reliability of the inspection system tend to be particularly low in those cases where the liquid in the containers has foam in it. Indeed, the liquid or foam inside the bottle can interfere with the identification of the markers. In particular, the flange is normally made from transparent PET; for this reason, the elements under the flange may be seen as disturbances.

[0017] Another problem which reduces the reliability of prior art inspection systems is that possible defects on the flange may be confused with the markers also present on the flange.

[0018] Disclosure of the invention

[0019] This invention has for an aim to provide a system and a method for analysing caps fitted by a capping machine to containers provided with support rings to overcome the above mentioned disadvantages of the prior art.

[0020] This aim is fully achieved by the system and method of this disclosure as characterized in the appended claims.

[0021] The system according to this disclosure is intended to analyse caps fitted to containers provided with support rings (also called flanges), where the caps and the support rings have marks (or markers, also called "pull-up marks") on them. The marks are placed at predetermined locations relative to the respective threading (that is, thread elements). For example, the marks are consistently oriented with respect to a start of their respective thread elements. The caps are fitted to the containers in (by) a capping machine.

[0022] The system may comprise a conveyor for conveying a succession of containers with caps fitted thereto individually to an inspecting position, where the container is oriented along a predetermined longitudinal axis. More generally speaking, the inspection system is configured to inspect the containers preferably one at a time, at a position where they have a predetermined orientation. It should be noted that the containers are elongate along an axis and the cap fitted to each container extends around the axis of the container. At the inspecting position, the container is positioned with its axis oriented along (that is, coinciding with) the longitudinal axis.

[0023] The system comprises an illuminator, configured for illuminating the container located at the inspecting position. The illuminator is preferably configured to generate a light beam oriented along the longitudinal axis towards the cap. It should be noted that the light beam that illuminates the cap at the inspecting position may be oriented substantially along the inspection axis. Thus, the light beam from the illuminator to illuminate the cap at the inspecting position need not be light which is collimated and parallel to the inspection axis.

[0024] It is to be noted that “oriented along the longitudinal axis” is to be interpreted as “coaxially with the longitudinal axis”. Therefore, according to one aspect of the present description, the light beam is centered on the longitudinal axis and is generated along an axis coaxial with the longitudinal axis. Therefore, according to this aspect of the description, the expression “oriented along the longitudinal axis” should not be interpreted as “along a longitudinal axis parallel to the longitudinal axis”.

[0025] In one example, the longitudinal axis passes through a central point of the cap. Therefore, the illumination of the cap occurs coaxially with the longitudinal axis which corresponds to the central axis of the cap.

[0026] The system comprises a camera which is configured for viewing the container located at the inspecting position along a viewing path oriented along the longitudinal axis towards the cap. Thus, the camera is positioned above the container located at the inspecting position; the expression "above" is used to mean that the camera is proximal to the end of the container where the cap is fitted and distal to the opposite end, and is oriented coaxially with the axis of the container.

[0027] Therefore, coaxial illumination with the optical axis of the camera is provided.

[0028] In the example where the longitudinal axis is vertical and the container is oriented with the cap at the top, the camera is effectively located at a level which is higher than the container; the expression "above" as just defined, however, also applies to possible cases where the longitudinal axis has other orientations or where the bottle is oriented with the cap at the bottom.

[0029] The system also comprises a lens system, positioned in front of the camera. The lens system might be integrated in the camera or it might be external but it is important that it be positioned along the optical path of the camera, interposed between the camera and the container to be inspected. In an example, the camera is a colour camera. For example, the camera has a 25 mm lens. Other lens sizes are imaginable, however, since the size of the lens depends on the distance of the camera and the type of camera.

[0030] The system comprises a control unit. The control unit includes a processor. The control unit is connected to the camera to acquire an image of the cap and of the support ring. The control unit is programmed for processing the image to identify an angular position of the marks on the cap and on the support ring relative to the longitudinal axis. For example, the control unit might be programmed for deriving a tightening torque applied by the capping machine when it fits the cap to the container, based on the derived information regarding the angular position of the marks.

[0031] According to an aspect of this disclosure, the lens system includes a hypercentric (or pericentric) lens; that is to say, the lens system is a hypercentric (or pericentric) lens system. The expression "pericentric lens" or "hypercentric lens" (hypercentric or pericentric lens system") is used to mean a lens (or a lens system) in which the entrance pupil is located in front of the lens, in the space where the object to be viewed may be located. The result is that, in a certain region, objects distant from the lens produce larger images than objects closer to the lens, in marked contrast with the behaviour of the human eye or of a conventional camera (which are both entocentric lenses), where the greater the distance of the objects, the smaller they appear.

[0032] The geometry of a hypercentric lens can be visualized by imagining a point source of light at the center of the entrance pupil sending rays in all directions. Any point on the object will be imaged to the point on the image plane found by continuing the ray that passes through it, so the shape of the image will be the same as that of the shadow cast by the object from the imaginary point of light. So the closer an object gets to that point (the center of the entrance pupil), the larger its image will be.

[0033] A hypercentric lens (or pericentric lens) provides a convergent view of an object, making it possible to view the upper part and sides of an object in a single view.

[0034] After extensive research and experimentation, the Applicant discovered and verified that such a system, provided with a hypercentric (or pericentric) lens is particularly effective and suitable for inspecting the marks on the cap and on the support ring.

[0035] In effect, such a system allows the marks to be clearly viewed in a single view from above. The light is perpendicular to the support ring, which reflects it; this reduces or cancels the negative impact, for inspection purposes, of what is under the flange (liquids or foam).

[0036] Moreover, this approach, which involves using an axially oriented hypercentric lens (to view the cap from above) with axial illumination from above, is also robust with regard to the different colours that container caps may have.

[0037] It is also noted that such a solution is particularly simple, in the sense that it allows using a single camera to take a single image for each container and cap. This allows reducing data processing time.

[0038] It is noted that the Applicant has also developed an alternative embodiment which does not fall within the object claimed herein and is described briefly below for completeness and to better clarify the primary embodiment of the invention claimed. The alternative embodiment differs from the primary embodiment in the illuminator and the cameras (and the lenses).

[0039] In the alternative embodiment, the system comprises a plurality (for example, four) cameras, disposed laterally to the longitudinal axis, angularly spaced from each other around the longitudinal axis, and oriented transversely to and towards the longitudinal axis so as to view the object located at the inspecting position; this allows obtaining a 360- degree view of the lateral surface of the cap. The cameras are preferably colour cameras, with 35 mm lenses (if there are four, they are mounted around the object at 90° from each other). The illuminator is configured for illuminating the cap laterally; that is to say, the illuminator is configured to illuminate the cap (located at the inspecting position) radially from a plurality of angles, convergently towards the longitudinal axis. Preferably, the illuminator is configured to generate light that is collimated (radially, according to the plurality of angles, convergently towards the longitudinal axis).

[0040] Thus, the alternative solution requires a plurality of cameras and taking a plurality of images (which are processed to derive an image representing a development of the lateral surface of the cap and of the support ring). The alternative solution is therefore more complex and more expensive than the primary solution. By comparison, the alternative solution has the advantage of being usable even in those cases where the marks on the support ring are located on a face of the support ring facing towards the bottom of the bottle and where the bottle is made of a non-transparent material; in effect, in such a situation, if the bottle is viewed only from above, the marks on the support ring are not visible.

[0041] The solution comprising a plurality of cameras may be according to what is described in patent document 102022000017961 , which is in the name of the present Applicant and which is incorporated herein by reference. Continued below is the description of the primary solution.

[0042] Using a pericentric (or hypercentric) lens allows inspecting the support ring (or flange) even in the case where it is partly covered by the cap; in effect, it should be noted that depending on the type and shape of the container, the support ring may protrude to a greater or lesser extent.

[0043] Furthermore, lighting along the longitudinal axis, i.e. lighting coaxial with the longitudinal axis, particularly increases the efficiency of inspecting the marks on the bag. In particular, this lighting mode provides a highly contrasted image of the flange, in which the flange is represented in white, and the brands are represented in black. Therefore, it is possible to highlight protrusions on the flange well, thanks to the fact of illuminating the flange “in bright field” (white field and black protrusions).

[0044] The illuminator is configured to illuminate the lens system from above, along the longitudinal axis. Preferably, the illuminator is configured to illuminate the lens system exclusively from above, along the longitudinal axis. This has the advantage of preventing reflections which could lead to errors interpreting the identity of the marks in the image. Generally speaking, the fact that the illumination is exclusively from above, directed axially along the longitudinal axis, makes the system more effective and robust in identifying the marks because the direction of the light is unique and this makes it easier to compensate for any reflections when analysing the image to identify the marks.

[0045] Preferably, the illuminator includes a collimator, for collimating the light parallel to the longitudinal axis. The collimator is configured for directing to the lens system, light which is collimated parallel to the longitudinal axis. Collimating the light is advantageous because it was found that even in the presence of foam in the liquid inside the container, the light collimated from above allows clearly distinguishing the marks on the flange (a result which is not obtained with oblique light or in the presence of oblique light). According to a preferred aspect, the illuminator is configured to distribute the light beam uniformly on a top surface of the lens system. For this purpose, for example, the illuminator comprises a light source having a flat, compact shape and positioned in alignment with the longitudinal axis. In an example, the illuminator comprises a lighting panel. The lighting panel includes an array of lighting elements. The lighting elements are uniformly distributed over an entire surface of the lighting panel. The lighting panel has a surface area that is greater than or equal to a top surface of the lens system so as to evenly distribute the light beam over the top surface of the lens system.

[0046] According to a preferred aspect, the lens system is subjected to anti-reflex treatment or is provided with anti-reflex surfaces. In particular, the hypercentric lens (or the hypercentric lens system) is provided with an anti-reflex surface or subjected to anti-reflex treatment. This further reduces the probability of error identifying the marks when the image is processed.

[0047] According to a preferred aspect, the lens system includes a plurality of hypercentric lenses, cooperating together for forming a multiple-lens hypercentric lens system. This has the advantage of further reducing the risk of lens system errors.

[0048] According to a preferred aspect, the control unit is programmed to take a single image for each container with cap fitted thereto. This has the advantage of reducing the volume of data to be processed, thereby speeding up the system.

[0049] In an example, the system is integrated in a capping machine. In this context, the present disclosure provides a capping machine, configured to fit a cap to a neck of a respective bottle (or container) by generating a closing torque to tighten the cap to the neck through respective thread elements. The capping machine comprises a system for analysing the caps fitted to the containers, where the system comprises one or more of the features described in this document.

[0050] This disclosure also provides a method for analysing caps fitted by a capping machine to containers having support rings, the caps and support rings having marks consistently oriented with respect to a start of their respective thread elements.

[0051] In an example, the method comprises a step of conveying a succession of containers with caps fitted thereto to an inspecting position. Preferably, the containers with caps fitted to them are conveyed to the inspecting position individually. At the inspecting position, each container is oriented along a predetermined longitudinal axis (known to the system).

[0052] The method comprises a step of illuminating the container located at the inspecting position. For example, illumination occurs through a light beam oriented along the longitudinal axis towards the cap (that is, from above, i.e. from a position proximal to the cap and distal to the bottom of the container).

[0053] The method comprises a step of providing a lens system, positioned in front of the camera. In other words, the lens system is positioned between the camera and the container located at the inspecting position. According to an aspect of this disclosure (at least in the main embodiment), the lens system includes a hypercentric lens; that is to say, the lens system is hypercentric (or pericentric).

[0054] The method comprises a step of viewing the container located at the inspecting position, for example through a camera (preferably, a single camera). Viewing occurs along a viewing path coaxial to the longitudinal axis and directed towards the cap.

[0055] At least one image of the bottle the cap is fitted to is also taken. Preferably, for each container, a single image is taken.

[0056] The image is processed by a control (or processing) unit to identify an angular position of the marks on the cap and support ring relative to the longitudinal axis. For example, first of all, the image is processed to identify the marks on the cap and those on the support ring. Next, the relative angular position between the marks on the cap and those on the support ring is estimated or derived.

[0057] The lens system is illuminated from above, along the longitudinal axis.

[0058] Preferably, the lens system is illuminated with light collimated parallel to the longitudinal axis.

[0059] Also, preferably, the light beam is distributed uniformly on a top surface of the lens system.

[0060] This disclosure also provides a method for capping containers (for example, plastic bottles made by the blow moulding of parisons) with caps (for example, made from plastic by injection or compression moulding), where the method includes a step of optical inspection which includes, as sub-steps, the steps of the method for analysing caps fitted to containers, according to one or more of the features described in this disclosure.

[0061] It should also be noted that the Applicant, after extensive analysis and testing, has found a solution for arranging the marks on the support ring and which makes it easier to correctly identify the relative angular position between the marks on the support ring and those on the cap. This arrangement is particularly advantageous when the main embodiment of the system is adopted.

[0062] This preferred arrangement of the marks includes the following. The support ring is provided with at least one mark. In an example, the support ring is provided with a first mark and with a second mark which is angularly spaced by 180 degrees about the longitudinal axis, with respect to the first mark. The support ring is also provided with a third mark, angularly spaced from the first mark by an angle ranging between 120 and 150 degrees about the longitudinal axis. This increases the robustness of identifying the relative position between the marks on the flange and those on the cap.

[0063] Thus, this disclosure also provides a container (and a related parison) provided with a support ring, where the support ring is provided with a plurality of marks located on a face of the support ring (preferably on the face facing towards the opening of the container or of the parison) according to the arrangement described above.

[0064] Brief description of drawings

[0065] These and other features will become more apparent from the following description of a preferred embodiment, illustrated by way of non-limiting example in the accompanying drawings, in which:

[0066] - Figure 1 is a cross sectional view of a system according to this disclosure, for analysing caps fitted to containers provided with support rings;

[0067] - Figure 2 illustrates further details of the system;

[0068] - Figure 3 illustrates the lighting panel of the system.

[0069] Detailed description of preferred embodiments of the invention

[0070] With reference to the accompanying drawings, the numeral 1 denotes a system for analysing caps C fitted by a capping machine to containers CO provided with support rings SR. The caps C and the support rings SR have marks which are consistently oriented with respect to a start of their respective thread elements. The marks on the cap may be located on the bottom of the cap, on an external strip of the cap wall or on the edge of the cap wall. The system 1 comprises a conveyor 2. The conveyor 2 feeds a succession of containers CO with respective caps C fitted thereto individually to an inspecting position IP. The conveyor 2 may include a belt running along a horizontal direction, perpendicular to the vertical direction, and conveys the containers CO, with respective caps C fitted to them, individually to the inspecting position IP. Alternatively, the conveyor 2 may include a carousel which rotates about an axis of rotation to carry the containers CO to the inspecting position IP. At the inspecting position IP, the container CO is oriented along a predetermined longitudinal axis L. The support ring SR is provided with at least one mark. In an example, the support ring SR is provided with a first mark, a second mark, which is angularly spaced from the first mark by 180 degrees about the longitudinal axis, and a third mark, which is angularly spaced from the first mark by an angle ranging between 120 and 150 degrees about the longitudinal axis. The system 1 includes an illuminator 3. The illuminator 3 illuminates the container CO located at the inspecting position IP. In particular, the illuminator 3 illuminates the cap with a light beam LB oriented along the longitudinal axis L and directed towards the cap C. The illumination via the illuminator 3 occurs coaxially with the longitudinal axis L. The system includes a camera 4. The camera is configured for viewing the container CO located at the inspecting position IP. In particular, the camera 4 views the container CO along a viewing path oriented along the longitudinal axis L and directed towards the cap C. Preferably, for each container at the inspecting position, and related cap fitted thereto, the camera acquires a single image.

[0071] The camera includes an optical system 401 which comprises one or more lenses. The lens of the optical system 401 of the camera 4 is an ordinary (standard) lens with a focal length of between 10 and 50 mm.

[0072] The system 1 comprises a lens system 5. The lens system 5 is positioned in front of the camera 4. In particular, the lens system 5 is vertically aligned with the camera 4. The lens system 5 includes a hypercentric lens 501. The lens system 5 may comprise a plurality of hypercentric lenses 501. The plurality of hypercentric lenses 501 cooperate to form a multiple hypercentric lens system. Preferably, the hypercentric lens 501 is provided with an anti-reflex surface or subjected to anti-reflex treatment.

[0073] The system also comprises a collimator 6. The collimator 6 is positioned downstream of the illuminator 3 and rectifies the bundle of rays to produce a bundle of parallel rays. In particular, the bundle of rays leaving the collimator 6 is parallel to a transverse axis T, orthogonal to the longitudinal axis L.

[0074] The system 1 also comprises a beam splitter 7. In an example, the beam splitter includes a glass sheet. The beam splitter is positioned downstream of the illuminator. The beam splitter is placed between the camera and the lens system. The beam splitter is configured to direct the beams coming from the illuminator towards the lens system and towards the cap at the inspection position. The beam splitter is positioned downstream of the collimator 6. The beam splitter is positioned in such a way as to make a 45 degree angle with the transverse axis T. Thus, the bundle of rays leaving the collimator 6 is rectified towards the object through the beam splitter 7, so that the collimated light is directed onto the lens system 5 parallel to the longitudinal axis L. At the inspecting position IP, the container CO, with the respective cap fitted thereto, is vertically aligned with the lens system 5 and the camera 4. The system 1 also includes a control unit. The control unit acquires an image of the cap C and support ring SR from the camera 4 and processes the image, for example through a processing unit, to identify an angular position of the marks on the cap C and on the support ring SR relative to the longitudinal axis L.

[0075] In an example, the illuminator 3 has a lighting panel. The panel is located at a height between the camera 4 and the lens system 5. The lighting panel includes an array of lighting elements 301 (for example, LEDs), uniformly distributed over a surface of the lighting panel. The illuminator 3 therefore produces light covering the whole surface of the lighting panel and the bundle of rays is uniformly distributed over the surface of the panel. Moreover, the surface area of the lighting panel of the illuminator 3 is greater than or equal to a top surface of the lens system 5; the light from the illuminator is therefore distributed uniformly over the top surface of the lens system. In particular, the lens system includes an enclosure 502 which contains the hypercentric lens 501. The enclosure may be a cylinder. The enclosure has a top wall 502A, proximal to the camera 4, and a bottom wall 502B, distal to the camera 4. The top and bottom walls extend horizontally and are vertically aligned with the camera 4. The lighting panel has a surface area that is greater than or equal to a top surface of the lens system so as to evenly distribute the light beam over the top surface of the lens system. In particular, the surface area of the panel is greater than or equal to the area of the top surface 502A of the enclosure 502.

[0076] The illuminator therefore generates light beams which are then collimated (through the collimator 6 located downstream of the panel) and rectified, through the beam splitter 7, towards the container CO located at the inspecting position IP and along the longitudinal axis.

[0077] The beam splitter 7, the camera 4, the container CO at the inspecting position IP, and the lens system 5 are vertically aligned.

[0078] The illuminator also comprises other lighting elements downstream of the lens system 5 (between the lens system 5 and the container CO at the inspecting position IP) which illuminate the container CO positioned at the inspecting position IP. The lighting elements between the lens system 5 and the container CO at the inspecting position IP may be placed laterally to the container, hence illuminating the container with a light beam oriented obliquely with respect to the longitudinal axis L. In particular, the container CO at the inspecting position IP is illuminated along the longitudinal axis; the control unit, however, may be programmed to activate the lateral lighting elements 302 at the same time as the lighting panel. The lateral lighting elements 302 are inclined with respect to the longitudinal axis L. The lateral lighting elements 302 illuminate the walls of the cap. In an example, the container may be illuminated exclusively from above, along the longitudinal axis L. It is to be noted that the coaxial lighting with the longitudinal axis is carried out via the lighting elements 301. In particular, at the inspecting position IP, the width a of a container portion illuminated along the longitudinal axis is much smaller than a width b of the inspection system; therefore, the bundle of collimated rays entering the inspection system 5 remains collimated when the rays reach the container CO because these rays are very close to the optical axis, which is coaxial with the longitudinal axis L and which passes through a central point of the cap C. In an example, the width a of a container portion illuminated along the longitudinal axis is 28 mm and the width b of the inspection system is 50 mm. In an example, the apparatus 1 comprises a supporting cylinder 8. The supporting cylinder extends vertically along the longitudinal axis L and defines an internal space. The camera 4 may be positioned in the internal space of the supporting cylinder. The apparatus 1 may comprise a lighting ring 9 extending in a plane transverse to the longitudinal axis. The lighting ring may comprise a plurality of lighting elements 301 which, at the inspecting position, illuminate the cap from the side. The lighting ring is located at the bottom of the supporting cylinder so that, at the inspecting position, the cap C is interposed between the conveyor 2 and the lighting ring.

Claims

CLAIMS1. A system (1 ) for analysing caps (C) fitted by a capping machine to containers (CO) having support rings (SR), the caps (C) and the support rings (SR) having marks consistently oriented with respect to a start of their respective thread elements, the system comprising:- a conveyor (2), for conveying a succession of containers (CO) with respective caps (C) fitted thereto individually to an inspecting position (IP), wherein, at the inspecting position, the container (CO) is oriented along a predetermined longitudinal axis (L);- an illuminator (3), configured for illuminating the container (CO) located at the inspecting position (IP) with a light beam oriented along the longitudinal axis (L) towards the cap;- a camera (4), configured for viewing the container located at the inspecting position (IP) along a viewing path oriented along the longitudinal axis towards the cap;- a lens system (5), positioned in front of the camera (4);- a control unit, connected to the camera for acquiring an image of the cap and of the support ring and programmed for processing the image to identify an angular position of the marks on the cap and on the support ring relative to the longitudinal axis, wherein the lens system includes a hypercentric lens (501 ).

2. The system (1 ) of claim 1 , wherein the illuminator (3) is configured for illuminating the lens system (5) from above, along the longitudinal axis (L).

3. The system (1 ) of claim 2, wherein the illuminator (3) is configured for illuminating the lens system exclusively from above, along the longitudinal axis (L).

4. The system (1 ) of claim 2 or 3, wherein the illuminator (3) includes a collimator (6), for directing to the lens system, (5) light which is collimated parallel to the longitudinal axis (L).

5. The system (1 ) of claim 4, wherein the illuminator (3) comprises a lighting panel, having an array of lighting elements (301 ), uniformlydistributed over an entire surface of the lighting panel, the lighting panel having a surface area equal to or greater than a top surface of the lens system (5), so as to evenly distribute the light beam over the top surface of the lens system.

6. The system (1 ) of any of the previous claims, wherein the hypercentric lens (501 ) is provided with an anti-reflex surface or subjected to anti-reflex treatment.

7. The system (1 ) of any of the previous claims, wherein the lens system includes a plurality of hypercentric lenses (501 ), cooperating together for forming a multiple-lens hypercentric lens system.

8. The system (1 ) of any of the previous claims, wherein the control unit is programmed to take a single image for each container with cap fitted thereto.

9. The system (1 ) according to any of the previous claims, wherein the illuminator comprises a collimator (6), for collimating the light parallel to the longitudinal axis.

10. The system (1 ) according to any of the previous claims, comprising a beam splitter (7), positioned downstream of the illuminator to straighten the rays towards the cap in the inspection position.

11. A capping machine, configured for applying a cap (C) on a neck of a respective bottle (CO) by generating a closing torque for tightening the cap to the neck through respective threads, the capping machine comprising a system (1 ) for analysing the caps fitted to the containers, wherein the system is according to any of the previous claims.

12. A method for analysing caps (C) fitted by a capping machine to containers (CO) having support rings (SR), the caps (C) and support rings (SR) having marks consistently oriented with respect to a start of their respective thread elements, the method comprising the following steps:- conveying a succession of containers (CO) with caps (C) fitted thereto individually to an inspecting position (IP) wherein the container is oriented along a predetermined longitudinal axis (L);- illuminating the container (CO) located at the inspecting position (IP) with a light beam oriented along the longitudinal axis (L) towards the cap;- via a camera (4), viewing the container (CO) located at the inspecting position (IP) along a viewing path coaxial to the longitudinal axis and directed towards the cap and taking an image of the cap and of the support ring;- via a control unit, processing the image to identify an angular position of the marks on the cap and support ring relative to the longitudinal axis,- providing a lens system (5), positioned in front of the camera, wherein the lens system includes a hypercentric lens (501 ).

13. The method of claim 12, wherein the lens system (5) is illuminated from above, along the longitudinal axis (L), the lens system being interposed between the camera (4) and the container located at the inspecting position (IP).

14. The method of claim 13, wherein the lens system is illuminated with light collimated parallel to the longitudinal axis.

15. The method of claim 13 or 14, wherein the light beam is distributed uniformly on a top surface of the lens system.

16. The method of any of the previous claims from 12 to 15, wherein the hypercentric lens is subjected to an anti-reflex treatment.

17. The method of any of the previous claims from 12 to 16, wherein a single image is taken, for each container with cap fitted thereto.

18. The method of any of the previous claims from 12 to 17, wherein the support ring is provided with a first mark, a second mark, angularly spaced by 180 degrees about the longitudinal axis, with respect to the first mark; a third mark, angularly spaced by an angle ranging between 120 and 150 degrees about the longitudinal axis, with respect to the first mark.

Images