EP4114209A1 - Unit for inspection of rod-shaped articles - Google Patents

Abstract

A unit (1) for inspecting rod-shaped articles (A) of the tobacco industry comprises a first conveyor (2), a trigger device (3) and a first and a second inspection station (4a, 4b). The first conveyor (2) is configured to convey the rod-shaped articles (A) along a first conveying direction and has a plurality of peripheral seats (2a) which extend along the first conveying direction and define at least one rolling surface (2a') for each article (A). The trigger device (3) is disposed along the first conveying direction and is configured to strike each article (A), causing it to roll on the rolling surface (2a'). The first and the second inspection station (4a, 4b) are configured to detect a respective angular portions (A1, A2) of the lateral surfaces of the articles (A) respectively before and after their rolling on the respective rolling surface (2a').

Description

DESCRIPTION

UNIT FOR INSPECTION OF ROD-SHAPED ARTICLES

Technical field

This invention addresses the technical sector of production methods and systems of the tobacco industry or generically for the production of smoking or aerosol generating articles.

More specifically, this invention regards a unit for inspecting rod-shaped articles (filters, cigarettes, tubes or the like) and a related inspection method which allow assessing the quality of these articles.

Background art

In machines that make articles of the tobacco industry, the external quality of the articles is inspected normally by feeding the articles one after the other with their axes perpendicular to the feed direction along a predetermined inspection path in front of an optical inspection device situated downstream of one or more processing stations.

Typically, the inspection devices perform sampling of a limited number of sample portions of the outer surface of each article to be inspected by scanning the images of these sample portions and comparing the images with a model image to check for surface defects (for example, badly formed and/or obstructed ventilation holes, irregular gluing, incorrectly positioned and/or blurred printing or other defects detectable by optical inspection systems) and thus to determine whether the inspected article meets one or more quality requirements or whether it is unsuitable for sale and must therefore be rejected.

Prior art inspection devices comprise one or more cameras capable of capturing snapshots of the sample portions and disposed at different positions along the feed path of the articles.

In this case, the articles are processed in such a way as to expose different angular portions of their outer surfaces to the cameras. This is done by conveying the articles into suction seats having a semi-circular or circular arc cross section and, between capturing two consecutive images, transferring the articles between two tangent conveyors or rotating each article about its axis in the respective suction seat in such a way as to rotate the article so that the hidden part and the externally exposed part of it are inverted.

More specifically, it is common practice to use three cameras, each coupled with a rotary drum configured to convey the articles along the feed path. More in detail, a prior art inspection system comprises a first rotary drum (which exposes approximately 180° of the lateral surface of each article), with which two cameras are associated, and a second rotary drum (which exposes the approximate remaining 180° of each article), with which a third camera is associated.

Each camera theoretically frames an angular portion of approximately 150° of the surface of the article. In the prior art inspection system, therefore, the first two cameras capture images of two respective overlapping angular portions of the exposed part of the outer surface of each article, covering approximately 180° of it. After transferring the article to the second rotary drum, the remaining 180° portion of each article is exposed and the third camera must capture an image of the angular portion of the outer surface of the article not captured previously (the third image must have areas that overlap the two images captured previously to allow a good reconstruction of the article).

The Applicant has observed, however, that prior art inspection units have some inherent disadvantages which in some ways limit their efficiency with regard to the needs of the sector.

In particular, when the articles are rotated about their axes inside the respective seats, it is not possible, in practice, to quantify with sufficient precision the extent of the rotation which each article actually undergoes. Moreover, these systems are mechanically extremely complex and expensive. When the system involves transferring the articles from one drum to another, on the other hand, it is difficult to achieve effective control of the surface exposed for inspection, which may mean that three cameras are unable to correctly capture images of the outer surfaces of the articles. In other words, the images may not cover the full 360° of the lateral surface of each article for one or more of the following reasons: each camera captures an image covering approximately 120° and not the theoretical 150°; on being transferred from one rotary drum to another, the article undergoes an uncontrolled, unquantifiable rotation about its axis; problems of overall size (space occupied by drum/cameras and article spacing) which do not allow the cameras to be positioned completely freely.

That means the first two images usually overlap to a more than adequate extent, whereas the third image is unable to ensure a sufficiently large overlap and/or to cover the 360°.

Aim of the invention

In this context, the basic technical purpose of this invention is to provide a unit for inspecting rod-shaped articles to overcome the above mentioned disadvantages of the prior art.

More specifically, the aim of this invention is to provide a unit for inspecting rod-shaped articles capable of performing a full inspection of the outer surface of the articles in a precise and reliable manner, specifically using three cameras.

The technical purpose indicated and the aims specified are substantially achieved by a unit for inspecting rod-shaped articles comprising the technical features described in one or more of the appended claims.

Brief description of the drawings

Further features and advantages of this invention are more apparent in the indicative, hence non-limiting description of a preferred, but non-exclusive, embodiment of a unit for inspecting rod-shaped articles, as illustrated in the accompanying drawings, in which:

- Figures 1A-1 E show a sequence of operating steps performed by a unit for inspecting rod-shaped articles according to a first embodiment of the invention;

- Figures 2A-2E show a sequence of operating steps performed by a unit for inspecting rod-shaped articles according to a second embodiment of the invention;

- Figures 3A-3E show a sequence of operating steps performed by a unit for inspecting rod-shaped articles according to a third embodiment of the invention;

- Figures 4A-4E show a sequence of operating steps performed by a unit for inspecting rod-shaped articles according to a fourth embodiment of the invention;

- Figure 5 shows an enlarged detail of a portion of the unit of the invention according to any of the embodiments of Figures 1 A-1 E, 2A-2E or 3A-3E;

- Figure 6 shows a variant embodiment of the detail of Figure 5;

- Figure 7 shows an enlarged detail of a portion of the unit of the invention according to Figures 4A-4E.

Detailed description of preferred embodiments of the invention

The reference numeral 1 in the accompanying drawings denotes in its entirety a unit for inspecting rod-shaped articles A (cigarettes, filters, tubes or other articles of this shape of the tobacco industry or aerosol generating articles) according to different embodiments of the invention.

More specifically, the unit 1 is configured to receive from stations and/or working processes upstream a succession of rod-shaped articles A which may be finished products or semi-products and which must subsequently subjected to quality control to ensure their conformity to one or more quality criteria.

Depending on the result of the quality control, performed by the unit 1 , each article A is either transferred to further stations and/or working processes downstream of the unit 1 (if the quality requirements are met) or rejected, that is, moved away from the production line because it is considered unsuitable (if the quality requirements are not met).

Structurally, in all the different embodiments, the unit 1 comprises at least a first conveyor 2, a trigger device 3, a first inspection station 4a and a second inspection station 4b.

The first conveyor 2 has a plurality of seats (first seats) 2a, configured to receive respective rod-shaped articles A of the tobacco industry, and is configured to convey the rod-shaped articles A along a first conveying direction transverse to the first seats 2a.

In a preferred embodiment, as may be observed in the accompanying drawings, the first conveyor 2 is in the form of a drum and the first seats 2a are disposed circumferentially around the axis of rotation of the drum and are configured to receive and convey the articles A in such a way that the articles are disposed in parallel with the axis of rotation.

Further, the first seats 2a have, along the first conveying direction (that is to say, tangentially), an extension such as to define at least one rolling surface 2a’ for each rod-shaped article A.

More specifically, the first seats 2a extend along the conveying direction between a front abutment 2a” and a rear abutment 2a’” which delimit the rolling surface 2a’.

In other words, the first seats 2a are each configured to receive a respective article A and extend between two ends delimited by the front abutment 2a” and the rear abutment 2a’” which have, disposed and extending between them, the rolling surface 2a’ which allows controlled rolling of the articles A between one end and the other of the first seats 2a. The rolling surface has the shape of a portion of a cylindrical surface with a constant diameter around the axis of the drum 2.

The terms “front” and “rear” are used with reference to the orientation defined by the conveying direction of the drum 2.

Preferably, each first seat 2a has, along the conveying direction, an extension such as to cause an article A to rotate through an angle between 1° and 359° and preferably between 30° and 90°.

More specifically, the angle of rotation is determined as a function of the diameter of the article A, of the spacing between the seats 2a of the conveyor 2 (that is, the centre-to-centre distance of the seats 2a) and of the positioning of the inspection stations 4a, 4b (more specifically, of the angle of incidence of the cameras).

The size of the first seats 2a, and of the rolling surface 2a’ in particular, allows accurately and precisely determining the total angle of rotation of the articles A before and after their interaction with the trigger device 3.

In effect, the trigger device 3 is disposed along the first conveying direction and is configured to strike each article A, causing it to roll on the rolling surface 2a’.

In other words, as discussed in more detail below, the first conveyor 2 receives the articles A and holds them at one end of a respective first seat 2a (for example, against the front abutment 2a”) as it moves along the feed path, until it strikes the trigger device 3, which causes the article A to roll progressively along the rolling surface 2a’ until it reaches the other end of the first seat 2a (for example, the rear abutment 2a’”).

More specifically, the trigger device has a surface which confronts or is confrontable with at least one of the first seats 2a and which is disposed at a distance from it such as to come into contact with the article A and to cause it to roll.

Figures 1 A-1 E show a first embodiment of the invention, in which the trigger device 3, specifically the engagement surface thereof, has a stationary configuration comprising, for example, a trigger block 3a that defines a fixed element which the outermost surface of each article comes into contact with, causing the article to roll.

More specifically, the trigger block 3a is positioned in such a way as to define, with the first conveyor 2, a rolling channel whose height is slightly smaller than the diameter of the articles A to be conveyed so that the articles are made to roll as they move along the rolling channel.

Figures 2A-2E and 3A-3E show two further embodiments of the invention, in which the trigger device 3 defines an engagement surface that is movable in the same direction as the first conveying direction at a different speed from the first conveyor 2, specifically at a lower speed.

By way of non-limiting example, the trigger device 3 may thus comprise an entrainment element, preferably a roll or a drum 3b, as shown in Figures 2A-2E, or an entrainment belt 3c, as shown in Figures 3A-3E. In these embodiments, the trigger device 3 defines an engagement surface that is movable at a speed different from the conveying speed, in the same direction. In a situation where this speed is greater than the conveying speed of the articles A, the articles are initially in contact with the rear abutment 2a’” of the seat 2a before rolling starts and stop rolling when they come into contact with the front abutment 2a”.

To ensure that the articles A are held correctly in the first seats 2a of the first conveyor 2, as shown in the detail view of Figure 5, each first seat 2a has one or more suction orifices 10 at the front abutment 2a” (and in any case disposed in such a way as to hold an article A in position against the front abutment 2a”) and, in the same way, one or more suction orifices 20 at its rear abutment 2a’”, so that the article A can be held firmly in the specific part of the first seat 2a at all times both before and after rolling. Furthermore, to optimally control the triggering of the rolling motion of the articles A along the rolling surface 2a’, each first seat 2a may comprise at least one retaining tooth 30 (Figure 6) protruding from the bottom surface of the seat 2a and interposed between the rolling surface 2a’ and at least one between the front/rear abutment 2a”, 2a’”.

The retaining tooth also has the function of correctly holding the articles A at the respective front abutment 2a” and/or rear abutment 2a’” of the first seat 2a before and/or after interaction with the trigger device 3.

Figures 4A-4E show a different embodiment, in which the trigger device 3 is defined by a second conveyor 5 configured to receive the articles and move them away from the first conveyor 2.

Structurally, the second conveyor 5 is tangent to the first conveyor 2 and, in particular, is configured like a drum and has a plurality of seats (second seats) 5a configured to receive respective rod-shaped articles A.

The second conveyor 5 is configured to convey the articles A along a second conveying direction transverse to the second seats 5a and, in this case, too, the second seats 5a have, along the second conveying direction (that is to say, tangentially), an extension such as to define at least one rolling surface 5a’ for each rod-shaped article A.

The first conveyor 2 and the second conveyor 5 confront each other at a zone of tangency so that the rolling surfaces 2a’, 5a’ of respective seats 2a, 5a face each other and cause each article A to roll simultaneously on the rolling surfaces 2a’, 5a’ while the article A is transferred from the first seat 2a of the first conveyor 2 to the second seat 5a of the second conveyor 5. Advantageously, the second seats 5a are structurally similar, preferably identical, to the first seats 2a. In other words, the second seats 5a also extend along the conveying direction between a front abutment 5a” and a rear abutment 5a’” which delimit a respective rolling surface 5a’ and the rolling surface 5a’ is the same in length as the rolling surface 2a’ of the first seat 2a.

To promote the transfer of the articles A from the first conveyor 2 to the second conveyor 5, the first conveying direction, in the confrontation zone between the two conveyors 2, 5, is the same as the second conveying direction but the conveying speed (that is to say, the tangential speed of the two conveyors 2, 5) is different.

In addition, the spacing between the second seats 5a is different from the spacing between the first seats 2a to take the different conveying speed into account and to keep each first seat 2a and a respective second seat 5a in a condition where they confront each other at all times (as shown in particular in Figure 4C).

To ensure that the articles A are held correctly and prevented from falling off the first conveyor 2, the first seats 2a each have one or more suction orifices 20 at the rear end 2a’” and, in the same way, the second seats 5a each have one or more suction orifices 20 at the front end 5a’”, as shown in Figure 7.

That is the solution adopted because in the specific embodiment illustrated, the conveying direction of the two conveyors 2, 5, which are in the form of drums, is the same in the zone of tangency and the article A, which is initially resting against the rear abutment 2a’” of the respective first seat 2a, is made to roll forward when it engages the second conveyor 5, which is moving at a faster speed. During this interaction, the article A, which is initially resting also against the front abutment 5a” of the second seat 5a, moves progressively away from the rear abutment 2a’” of the first seat 2a and from the front abutment 5a” of the second seat 5a and stops rolling when it reaches the rear abutment 5a’” of the second seat 5a, where there is at least one rear suction orifice 20 in operation.

In a different embodiment, however, the second conveyor 5 might be moving at a slower speed and thus configured in such a way as to cause the article A to roll “backwards” in the respective first and second seats 2a, 5a. In this situation, the suction orifices are located in the front portions of the seats 2a, 5a.

Furthermore, in the same way as already discussed for the first seats 2a, the second seats 5a, too, may comprise a retaining tooth, interposed between the rolling surface 5a’ and at least one of its ends 5a”, 5a’”, to start the articles A rolling so that different outer portions of them are exposed for inspection.

Operatively, the inspection of the articles A is performed by the aforementioned first and second inspection stations 4a, 4b.

More specifically, the first inspection station 4a is disposed upstream of the trigger device 3 and configured to detect a first angular portion A1 of the outer lateral surface of each article A before rolling on the rolling surface 2a’. The second inspection station 4b, on the other hand, is disposed downstream of the trigger device 3 and is configured to detect a second angular portion A2, at least partly different from the first angular portion A1 , of the outer lateral surface of each article A after rolling on the rolling surface 2a’.

In other words, the inspection stations 4a, 4b detect the properties of the portion of the outer lateral surface of the articles A which is exposed upstream and downstream of the trigger device 3.

Preferably, the inspection stations 4a, 4b confront the same conveyor (the first conveyor 2) and are disposed on portions that are spaced from each other along the conveying direction. As shown in the accompanying drawings, the two inspection stations 4a, 4b also have (optical) detection axes which are not both directed perpendicularly to the conveying direction (that is to say, radial in the embodiment of the accompanying drawings) but are inclined at a predetermined angle so as to able to completely scan the surface to be inspected, thereby optimizing the inspection.

Thanks to the interaction between the articles A and the trigger device 3, and owing to the special shape of the first seats 2a, the lateral surface portion that is exposed and inspected by the different inspection stations 4a, 4b is at least partly different, making it possible to obtain more complete and accurate information regarding the effective conformity of the articles A that are transferred to further statins/processes downstream of the unit 1 . More specifically, thanks to this controlled rotation of the articles A, the two inspection stations 4a, 4b capture overlapping images of the article A, preferably and advantageously covering more than 180° of the outer lateral surface of each article A.

Both the first inspection station 4a and the second inspection station 4b can be made from or comprise one or more optical inspection devices, such as, for example, video cameras, picture cameras or any other device capable of obtaining images which identify and represent the outer surface of the articles A in transit in the unit 1 . Advantageously, this invention achieves the proposed aims and overcomes the disadvantages of the prior art by providing the user with a unit 1 which allows moving in a controlled and precise manner the articles to be inspected so that the portion of the lateral surface being inspected can be identified unambiguously.

Also an object of this invention is a method for inspecting rod-shaped articles of the tobacco industry which can preferably be implemented by a unit 1 comprising one or more of the technical features outlined above. Preferably, the method is carried out by performing a first inspection to inspect a first angular portion of the outer lateral surface of a rod-shaped article A.

This inspection can be performed by capturing an image or a set of images identifying and representing the first angular portion. In this circumstance, the axis or direction of inspection is not necessarily perpendicular to the instantaneous conveying direction of the article A but may be at an angle to it (angle of incidence) which is different from 90°, for example, between 60° and 80°.

After the first inspection, the article A is made to roll along a rolling surface (for example, the rolling surface 2a’ of one of the first seats 2a) in such a way that at the start and end of the rolling, the article A exposes at least partly different portions of its outer surface.

In other words, as it rolls, the article A progressively exposes for inspection a different portion of its outer lateral surface - for example, a portion of it that was originally at least partly hidden by the rolling surface it was in contact with.

After rolling has been completed, a second inspection is performed to inspect a second angular portion of the lateral surface of the article A, at least partly different from the first angular portion inspected previously. In this circumstance, too, the axis or direction of inspection is not necessarily perpendicular to the instantaneous conveying direction of the article A but may be at an angle to it (angle of incidence) which is different from 90°, for example, between 60° and 80°.

As discussed above with reference to the unit 1 , the rolling of the articles A may be facilitated by a trigger device 3 which is fixed or movable along the conveying direction.

According to a first aspect of this invention, with reference in particular to the embodiments shown in Figures 1A-1 C, 2A-2C and 3A-3C, the article A, after rolling, remains inside the first seat 2a at a position ahead or behind the position it had at the start of rolling so that, compared to the position at the start of rolling, a portion of angular surface is exposed which is at least partly different from the portion exposed at the start of rolling.

In other words, during rolling, the article A remains inside the same seat, and changes only its position along the conveying direction and the portion of its lateral surface that is exposed.

Alternatively, according to a further aspect, with reference in particular to the embodiment in Figures 4A-4D, the step of rolling is carried out during a step of transferring the article A from a first seat 2a of a first conveyor 2, preferably a rotary conveyor, to a second seat 5a of a second conveyor 5, preferably also a rotary conveyor.

More specifically, the transfer is accomplished by operating the conveyors 2, 5 in such a way that the first seats 2a move at a different speed to the second seats 5a.

Operatively, rolling is carried out while the article A is interposed between respective rolling surfaces 2a’, 5a’ of the first seat 2a and second seat 5a. To facilitate rolling of the articles A, the second seats 5a move at a higher speed, or alternatively, a lower speed, than the first seats 2a and the transfer of each article A from the first seat 2a to the second seat 5a occurs by rolling between an initial position of the article A at a rear abutment 2a’” or a front abutment 2a” of the first seat 2a, respectively, and a final position of the article A at a rear abutment 5a’” or a front abutment 5a” of the second seat 5a, respectively.

It should be noted that the process outlined above can be iterated two or more times to sequentially expose successive portions of the lateral surface of each article A until a complete, overall image can be reconstructed. For example, in an embodiment, after rolling the first time, each article can be subjected to further rolling, specifically after being transferred to a further drum, in the case of Figures 1-3, or after being transferred to a further unit comprising two similar tangent drums, in the case of the embodiment of Figures 4A-4E. After further rolling in this way, each article can expose a further portion of its outer surface to a camera to obtain a final (third) image, thereby capturing the entire outer surface. In a different embodiment, after rolling in any of the ways illustrated in Figures 1-4, the article is transferred to a further drum (for example, of traditional type, with seats of semi-circular or circular arc shape) and exposes a further portion of its outer surface to a camera to obtain a final (third) image, thereby capturing the entire outer surface. Advantageously, the method described herein allows inspecting precisely and accurately different angular portions of the articles A and, by rolling the articles, makes it possible to control, step by step, which specific portion of each is exposed for inspection.

Claims

1. A unit for inspecting rod-shaped articles (A), comprising:

- at least a first conveyor (2), specifically a drum, having a plurality of first seats (2a), configured to receive respective rod-shaped articles (A) of the tobacco industry, wherein the first conveyor (2) is configured to convey the rod-shaped articles (A) along a first conveying direction transverse to the first seats (2a) and wherein the first seats (2a) have, along the first conveying direction, an extension such as to define at least one rolling surface (2a’) for each rod-shaped article (A);

- a trigger device (3) disposed along the first conveying direction and configured to strike each article (A), causing the rolling of the article (A) on the rolling surface (2a’);

- a first inspection station (4a) disposed upstream of the trigger device (3) and configured to detect a first angular portion (A1 ) of the outer lateral surface of each article (A) before rolling on the rolling surface (2a’);

- a second inspection station (4b) disposed downstream of the trigger device (3) and configured to detect a second angular portion (A2), at least partly different from the first angular portion (A1 ), of the outer lateral surface of each article (A) after rolling on the rolling surface (2a’).

2. The unit according to claim 1 , wherein the trigger device (3) has an engagement surface, confronting or confrontable with at least one of the first seats (2a) and disposed at a distance from the first seat (2a) such as to come into contact with the article (A) and to cause a rolling of the article (A) in the first seat (2a).

3. The unit according to claim 1 or 2, wherein the trigger device (3), and specifically the engagement surface thereof, has a configuration that is stationary or movable, preferably in the same direction as the first conveying direction, at a different speed than the first conveyor (2).

4. The unit according to claim 3, wherein the first seats (2a) extend along the conveying direction between a front abutment (2a”) and a rear abutment (2a’”) which delimit the rolling surface (2a’) between them, and wherein the trigger device (3) is configured to strike each article (A) disposed in the respective first seat (2a), causing the rolling of the article (A) on the rolling surface (2a’) between a first position at which the article (A) is disposed at the front abutment (2a”) and a second position at which the article (A) is disposed at the rear abutment (2a’”).

5. The unit according to any one of the preceding claims, wherein each first seat (2a) has at least two suction orifices, specifically one at the front abutment (2a”) and one at the rear abutment (2a’”).

6. The unit according to any one of the preceding claims, wherein the trigger device (3) comprises a fixed trigger block (3a) or a movable entrainment member, preferably a roller or a drum (3b) or an entrainment belt (3c).

7. The unit according to any one of claims 1 to 4, wherein the trigger device (3) comprises a second conveyor (5), specifically a drum, configured to receive the articles (A) from the first conveyor (2) and to move them away therefrom, wherein the second conveyor (5) has a plurality of second seats (5a) configured to receive respective rod-shaped articles (A) of the tobacco industry, wherein the second conveyor (5) is configured to convey the rod shaped articles (A) along a second conveying direction transverse to the second seats (5a) and wherein the second seats (5a) have, along the second conveying direction, an extension such as to define at least one rolling surface (5a’) for each rod-shaped article (A); the first and second conveyors (2, 5) confronting each other to cause a simultaneous rolling of each article (A) on the rolling surfaces (2a’, 5a’) of the respective first and second seats (2a, 5a) during transfer of the article (A) from the first seat (2a) to the second seat (5a).

8. The unit according to claim 7, wherein the first and second conveying directions are oriented in the same way in a confrontation zone between the first and the second conveyor (5) and wherein:

- the spacing between the second seats (5a) is different from the spacing between the first seats (2a); and/or

- the second seats (5a) have a different speed than the first seats (2a) so that during the movement of the first conveyor (2) and of the second conveyor (5), each first seat (2a) confronts a second seat (5a) in the confrontation zone.

9. The unit according to claim 7 or 8, wherein each first seat (2a) has one or more suction orifices at a front abutment (2a”) or at a rear abutment (2a’”) of each first seat (2a) and wherein each second seat (5a) has one or more suction orifices at a front abutment (5a”) or at a rear abutment (5a’”) of each second seat (5a).

10. The unit according to any one of the preceding claims, wherein the first seats (2a) have, along the conveying direction, an extension such as to cause an article (A) to rotate through an angle between 1° and 359° and preferably between 30° and 90°.

11 . The unit according to any one of the preceding claims, wherein each first and/or second seat (2a, 5a) comprises at least one retaining tooth (D) interposed between the rolling surface (2a’, 5a’) and at least one front and/or rear abutment (2a”, 2a’”, 5a”, 5a’”) of the first and/or second seat (2a, 5a).

12. A method for inspecting rod-shaped articles (A) of the tobacco industry, specifically using a unit (1 ) according to any one of the preceding claims, comprising the following steps:

- performing a first inspection to inspect a first angular portion (A1 ) of the outer lateral surface of a rod-shaped article (A);

- after the first inspection, making the article (A) roll along a rolling surface (2a’, 5a’) in such a way that at the start and end of the rolling, the article (A) exposes at least partly different portions of the outer surface;

- after rolling, performing a second inspection to inspect a second angular portion (A2), at least partly different from the first angular portion (A1 ), of the outer lateral surface of the article (A).

13. The method according to claim 12, wherein the step of rolling is accomplished by striking the article (A) by means of a trigger device (3) disposed along a conveying direction of the article (A) and having an engagement surface which confronts the article (A) and which is fixed or movable along the conveying direction.

14. The method according to claim 12 or 13, wherein the article (A), after the step of rolling, remains inside the first seat (2a) at a position ahead or behind the position it had at the start of rolling so that, compared to the position at the start of rolling, a portion of angular surface is exposed which is at least partly different from the portion exposed at the start of rolling.

15. The method according to claim 12, wherein the step of rolling is carried out during a step of transferring the article (A) from a first seat (2a) of a first conveyor (2), preferably a rotary conveyor, to a second seat (5a) of a second conveyor (5), preferably a rotary conveyor, by operating the conveyors in such a way that the first seats (2a) move at a different speed than the second seats (5a), the step of rolling being carried out while the article (A) is interposed between respective rolling surfaces (2a’, 5a’) of the first seat (2a) and of the second seat (5a).