Laser marking device, installation and associated method

Abstract

Title: Laser marking device, installation and associated method The present invention relates to a device (1) for laser marking containers (2), in particular bottles or flasks made of thermoplastic material, of the type comprising at least one body (23), a shoulder (24) in the extension of said body (23) at an upper end thereof, a neck (21) in the extension of the shoulder (24), and a bottom (22) at the lower end of said body (23), said device (1) comprising at least: - a plurality of laser marking stations (3), each station (3) comprising along an optical path at least one laser marking optical head (30) equipped with a laser head unit (300) and an optical system (320) for focusing a laser beam (31) in order to generate a mark (310) at at least one marking area (20) of each container (2) to mark said area (20), said optical head (30) being connected to said apparatus (40) via an optical channel (600),- control means (4) connected to the marking stations (3) and comprising a laser processing apparatus (40) and the supply means (41) of the laser marking stations (3), - a carousel (5) with a vertical axis of rotation X driven in rotation by at least one motor relative to a frame (7) via a rolling means (70), said carousel (5) comprising at least: - a first plate (50), said first plate (50) supporting a plurality of holding members (54) for positioning said container (2) along an axis substantially parallel to the vertical axis of rotation X of said carousel (5), - a barrel (53) supporting the plurality of marking stations (3) such that each optical system (320) is located opposite a container (2) held by a holding member (54),device (1) characterized in that it comprises- dynamic focusing means (330) for adjusting the focal point as a function of the distance between said optical system (320) and said at least one marking zone (20) of the container (2). The invention also relates to an installation and a method for marking containers (2). Figure for the abstract: Figure 1,

Description

Title of the invention: Laser marking device, installation and associated method

[0001] Technical Field: The invention relates to a marking device, a marking installation, and a method for laser marking containers. State of the art

[0002] It is known to include information and decorations on containers, particularly plastic bottles. Information on a container may, for example, include the expiration date of the contents or the formula of the product contained in the container. Decorations may, for example, feature the logo of the product manufacturer.

[0003] It is well known to include this information and decorations on paper or plastic labels. The labels are stuck onto the final container after the container forming step, i.e. when the containers are formed into their final shape.

[0004] However, labeling containers has many disadvantages. Indeed, the production of labels, their printing and their gluing on the containers represents a high cost, particularly for the production of containers in large series. In addition, the label is likely to be torn off during handling of the container. The end user can then no longer access certain important information, such as the expiration date. Finally, recycling plastic containers is complicated by the presence of the label and glue. Indeed, to promote recycling, it is preferable to ensure that containers, labels, or other items are collected separately according to their different materials. However, manually removing labels from containers for separate collection can be a tedious task. Therefore, removing labels from containers is one of the factors that hinder the provision of separate collection.

[0005] For the recording of important information, methods of marking the wall of the container have already been proposed. Thus, it is known to print certain important information directly onto the wall of the container using a special ink. However, this method of marking by printing is not satisfactory because, for reasons of hygiene, the ink used for marking must dry almost instantly, and it must also remain on the surface of the wall without penetrating into the interior of the container by a migration phenomenon. As a result, the ink has a specific composition which is very expensive to manufacture. Furthermore, the use of ink also complicates the recycling processes for plastic containers.

[0006] To circumvent these problems, a marking method has also been proposed by etching the wall of the container. The etching is generally carried out using a carbon dioxide laser. Such a marking method is carried out by removing material from the wall of the container, in particular by evaporation. As a result, the wall has a locally reduced thickness. However, in the interests of economy and ecology, efforts are being made to reduce the wall thickness of containers. This makes it possible to produce a container using less plastic material than before. However, removing material from a very thin wall risks weakening the wall to the point of cracking the container at the slightest stress.

[0007] Other known laser marking devices have quality problems with respect to parts or substrates that are not flat and / or have a variable focal distance relative to the optics, as is the case for a large majority of containers. In such a case, the markings on the substrate are blurred, vary in height or spacing, and may otherwise be illegible, thus making the characters unsatisfactory to use.

[0008] Furthermore, depending on the nature or dimensions of the container, the quality of the marking becomes very random: the focal distance between the laser device and the wall of the container to be marked is not the same over the entire surface of the area to be marked. In particular, when the wall of the container is cylindrical, the marking generated is of lower quality at the periphery of the area to be marked.

[0009] To resolve these marking quality problems while remaining compatible with large-scale production of containers, the present invention proposes to provide a laser marking device making it possible to guarantee an optimal position of the marking on the container while making it possible to mark containers at a rate compatible with the productivities required in the industrial sector.

[0010] The invention advantageously proposes a laser marking device comprising dynamic focusing means to ensure quality marking on a container, without having to adjust the mechanical position of the parts of the marking station.

[0011] Thus, the invention makes it possible to adapt to different container formats without having to adjust the mechanical position of the parts of the marking station or the position of the container.

[0012] Furthermore, by using dynamic focusing means to adjust the focal point as a function of the distance between the marking station and a marking area of ​​the container, the invention makes it possible to position the text or patterns to be marked in a marking area oriented indifferently, in the desired direction, without altering the quality of the marking.

[0013] The invention firstly relates to a device for laser marking containers, in particular bottles or flasks made of thermoplastic material, of the type comprising at least one body, a shoulder in the extension of said body at an upper end thereof, a neck in the extension of the shoulder, and a bottom at the lower end of said body, said device comprising at least: - a plurality of laser marking stations, each station comprising along an optical path at least one laser marking optical head equipped with a laser head unit and an optical system for focusing a laser beam in order to generate a mark at at least one marking area of ​​each container to mark said area, said optical head being connected to said apparatus via an optical channel, - control means connected to the marking stations and comprising a laser processing device and the means for supplying the laser marking stations, - a carousel with a vertical X rotation axis driven in rotation by at least one motor relative to a frame and by means of a rolling means, the carousel comprising at least: - a first tray, the first tray supporting a plurality of holding members for positioning said container along an axis substantially parallel to the vertical axis of rotation X of said carousel, and - a barrel supporting the plurality of marking stations such that each optical system is located opposite a container held by a holding member.

[0014] The device is characterized in that it comprises dynamic focusing means for adjusting the focal point as a function of the distance between said optical system and said at least one marking zone of the container.

[0015] In embodiments, the dynamic means are arranged in the optical path between the optical channel and the optical system, preferably between the laser head unit and said optical system.

[0016] In embodiments, on the optical path, the dynamic means comprise a motorized lens, for example aligned with the laser head unit along a linear axis.

[0017] According to a possible variant, on the optical path, the dynamic means comprise a shape-changing lens.

[0018] In embodiments, the optical system consists of a 3D three-dimensional laser marking system, including said dynamic focusing means which are in the form of a focusing module for each point to be marked of the at least one marking zone of the container.

[0019] According to another possible variant, the optical head comprises a sensor for measuring the distance between the optical output and at least one marking zone of the container.

[0020] In embodiments, at least one optical head of each marking station is capable of moving the focal point of the laser beam in three directions, namely a vertical direction, a horizontal direction and a longitudinal direction relative to the at least one marking area of ​​said container.

[0021] In embodiments, each marking station comprises two optical heads, placed head to tail in each of said stations so that the optical systems of the two optical heads are superimposed in order to simultaneously mark a marking zone located in the upper part of the container and an area located in the lower part of said container.

[0022] According to a final possible variant, each marking station comprises a pulsed laser optical head whose wavelength is between 800 and 2000 nanometers.

[0023] The invention also relates to an installation comprising: - a laser marking device as described above, - a container processing station located upstream of the marking device, the processing station directly or indirectly supplying the device by means of a transfer wheel at a loading point, - a transfer wheel at an unloading point to release the marked containers directly or indirectly at a downstream conveyor.

[0024] In embodiments, the installation comprises a system for inspecting marked containers.

[0025] The invention also relates to a marking method comprising at least the following steps: - a first step consisting of carrying out a treatment on said containers, preferably filling and capping said containers, - a second step consisting of rotating said containers, preferably filled and capped, around a vertical axis around which laser marking stations are rotated, in a manner synchronized with said containers, - a step of adjusting the focal point of the laser marking stations preferably according to the dimensions and / or shape of said containers, and - a third step consisting of marking said containers during rotation.

[0026] In embodiments, the method of marking containers further comprises: - after the step of processing a container, preferably filling and capping, a step of loading the containers at a loading point, - following the marking step, an unloading step at an unloading point for said containers, each station and each container being moved respectively around said vertical axis of rotation between said loading point for said containers and said unloading point for said marked containers at at least one so-called marking zone before resuming a new cycle.

[0027] According to a possible variant, after the loading step and during the rotation step, said containers are moved vertically.

[0028] Finally, in embodiments, the marking step is carried out by a pulsed laser in the near infrared.

[0029] Brief description of the figures: The invention will be better understood thanks to the description below, which is based on possible embodiments, explained in an illustrative and in no way limiting manner, with reference to the appended figures, in which: - [Fig.l] schematically represents a perspective view of the device; - [Fig.2] represents a vertical sectional view of the device; - [Fig.3] represents a detailed view of a marking station and a container; - [Fig.4] schematically represents a detailed view of the container holding devices; - [Fig.5] schematically represents a side and detailed view of a station for applying a laser beam to a held container; - [Fig.6] schematically represents an embodiment in which the device comprises two scan heads; - [Fig.7] schematically represents an embodiment in which the device comprises a motorized lens, - [Fig.8] schematically represents an embodiment in which the device comprises a shape-changing lens, - [Fig.9] schematically represents an embodiment in which the device comprises a 3D three-dimensional laser marking system, - [Fig. 10] schematically represents a top view of the device according to the invention and in particular of the rotation of the plates; - [Fig. 11] schematically represents an installation with an inspection system - [Fig. 12] schematically represents an example of implementation of the method according to the invention.

[0030] Detailed description: In the remainder of the description, elements having an identical structure or similar functions will be designated by the same reference.

[0031] The invention firstly relates to a device 1 for laser marking containers 2, shown schematically in [Fig.l]. In the context of the invention, the container 2 is a bottle or flask. It is made of plastic. Preferably, the container is made of polyethylene terephthalate, hereinafter PET. The container 2 can therefore be rigid or semi-rigid. It is intended to contain a fluid, a liquid, powders or granules, in particular of the food or cosmetic type. The container 2 can have any type of shape, symmetrical or not. It can have a rounded section, generally circular or ovoidal in shape, or else a polygonal section, in particular rectangular or square. Preferably, said containers 2 have a rounded section, in particular generally circular.

[0032] The containers 2 have at least one body 23, a shoulder 24 in the extension of said body 23 and a bottom 22 at the end of said body 23. The body 23 of a container 2 comprises a peripheral wall 25. The wall 25 of a container 2 may be cylindrical, rectangular, or of any shape. In a normal orientation, the container 2 rests on its bottom 22 and the main direction is vertical. The bottom 22 may be generally flat, petaloid in shape or otherwise. Preferably, the containers 2 are obtained by forming from thermoplastic preforms. Such preforms are generally obtained by injection.

[0033] In the context of the invention, the container 2 has at least one marking zone 20, located on its wall. There at least one marking zone 20 is intended to receive a mark 310, produced by laser marking. The marking area 20 can be oriented such that the mark 310 is parallel to the main direction of the container 2, or orthogonal, or even have any possible orientation relative to the wall 25 of the container 2 according to its main direction.

[0034] The device 1 according to the invention comprises at least a plurality of laser marking stations 3. A laser marking station 3 comprises along an optical path at least one optical head 30 which is connected to control means 4 of the station 3. The control means 4 comprise the laser processing apparatus 40 and the power supply means 41 of the stations 3. The laser treatment apparatus 40, or laser 40, comprises a light emission source, or pump source and possibly an amplifying medium for emitting laser light in the form of a laser beam 31. According to a possible variant, the optical head 30 comprises the amplifying medium.

[0035] The optical head 30 is connected to the laser processing apparatus 40 by a network of optical fibers and electrical connections, or optical channels 600. The optical channels 600 comprise at least one optical fiber which is an optical waveguide for the laser light emitted for example by the laser processing apparatus 40. According to a possible variant, the amplifying medium is incorporated into the optical channel 600 in the form of a doped optical fiber into which the emitted light is injected towards a laser head unit 300. Station 3 controls the optical head 30 and the emission of the laser beam 31 from the control means 4.

[0036] Thus, the optical head 30 comprises a laser head unit 300 and an optical system 320, removably mounted on said laser head unit 300. Preferably, the laser head unit 300 emits a beam 31 of laser light directed in a predetermined direction.

[0037] The optical system 320 comprises at least one mirror for moving the laser beam 31 in a horizontal plane and / or in a vertical plane, and optionally a lens at the optical output 321 of the optical system 320, for focusing the light beam in the plane and at the level of at least one marking zone 20, for generating a mark 310 at the level of said at least one zone 20. By optical path is meant the path taken by the laser light from its emission from, for example, the laser processing apparatus 40 to the optical output 321 of the optical system 320 in the form of a laser beam 31. In other words, there at least one marking zone 20 corresponds to a treatment surface within which the laser beam 31 is applied in a horizontal and / or vertical direction. Depending on the type of mark 310 to be affixed, the focal point of the laser beam 31 is not necessarily located directly on the wall of the container 2, that is to say that, in a longitudinal direction relative to the at least one marking zone 20 of said container 2, the focal point of the laser beam 31 may in particular be located above the wall, directly on the wall 25, at the level of the external skin of the container 2, or inside said wall 25, for example at the level of the internal skin of said container 2, or even beyond, in a focusing zone 311.

[0038] In embodiments, the device 1 comprises a fixed lens 334, said fixed lens being able to be of the spherical type, flat field, or preferably of the type F-theta in order to keep the focal point dimension relatively constant in the plane.

[0039] According to a possible variant, the laser head unit 300 and the optical system 320 are in a single piece.

[0040] In embodiments, the control means 4 of the laser station 3 comprise a plurality of cooling units, not shown.

[0041] In the context of the invention, the laser marking on at least one zone 20 of a container 2 can be done in particular by local modification of the refractive index, and / or by local modification of the transmission index, and / or by local modification of the reflection index of the material of said container 2.

[0042] Each marking station 3 comprises at least one optical head 30 which emits and focuses the laser beam 31. According to a possible variant, said at least one optical head 30 generates the optical beam 31.

[0043] In the context of the invention, the device 1 comprises dynamic focusing means 330 for adjusting the focal point as a function of the distance between the optical system 320 and the at least one marking zone 20 of the container 2.

[0044] In embodiments, the optical head 30 comprises means (not shown) controlled to move the emitted beam 31, for example by means of mirrors movable relative to the marking zone 20 of a container 2, in the direction of the optical axis or perpendicular to it.

[0045] According to a possible variant, the optical head 30 comprises dynamic means 330 controlled to move the focal point of the emitted beam 31, for example by means of lenses movable relative to the marking zone 20 of a container 2, in the direction of the optical axis.

[0046] Indeed, depending on the format of the containers 2, that is to say depending on their dimensions and / or their shape, the curvature of the wall 25, or even depending on the mark 310 to be generated on said at least one marking zone 20, the distance between the optical output 321 and the marking zone 20 varies. Furthermore, laser marking methods require the optical focal point to be positioned very precisely relative to the marking area 20, in the focusing area 311, otherwise the mark 310 will not be generated.

[0047] Advantageously, the fact that the device 1 comprises dynamic focusing means 330 makes it possible to generate a mark 310 at the level of at least one marking zone 20 without having to adjust the mechanical position of the parts of the marking station 3.

[0048] The optical path is the path taken by the laser light at the output of the laser processing apparatus 40 to the optical output 321 in the form of a laser beam 31. The light therefore travels from the optical channel 600 to the optical output 321, passing through at least one laser marking optical head 30. Generally, the laser light passes through a laser head unit 300 and then an optical system 320 along the optical path.

[0049] In preferred embodiments, the dynamic means 330 are disposed on the optical path between the laser head unit 300 and the optical system 320.

[0050] An embodiment is illustrated in [Fig.7], in which the laser head unit 300 comprises the dynamic means 330 in the form of a motorized lens 331. The laser head unit 300 also comprises a beam expander 335 and two mirrors 333. In the illustrative example of [Fig. 7], light is emitted from a laser processing apparatus 40 and then travels through an optical channel 600 and into the laser head unit 300. The motorized lens 331 moves the focal point of the laser beam 31 along the optical axis, along a longitudinal axis relative to the marking area 20. An enlargement schematically shows the movement of the lens 331 in [Fig. 7]. For these purposes, the lens 331 comprises movable optical means which allow the focal point to be moved along a longitudinal axis relative to the laser beam 31. In the example of [Fig.7] we can see a cylindrical wall 25 of a container 2. The focal distance DI varies depending on the location of the focal point, in a focusing zone 311. Still in [Fig.7], an enlargement of the wall 25 shows that it is notably possible to move the focal point so that it is located longitudinally above the external skin of the wall 25 or inside the container 2, after the internal skin of said wall 25, within the focusing zone 311. Without adjustment, the generated marking would be of low quality in the center or at the edges of the marking area 20. In other words, the mark 310 cannot then be of a consistent quality over the entire surface of at least the marking area 20.

[0051] In possible embodiments, and as visible in [Fig.7] or 8, the dynamic means 330 are coupled to a fixed lens 334, for example of the F-Theta type, arranged at the optical output 321 of the optical system 320. The combined use of dynamic means 330, for example in the form of a motorized lens 331, and a fixed lens is particularly advantageous because it makes it possible to adjust the location of the focal point of the laser beam 31 without moving the optical head 30 or the container 2.

[0052] In embodiments, the dynamic means 330, for example in the form of a motorized lens 331, are aligned with the laser head unit 300 along a linear axis.

[0053] According to a possible variant, the dynamic means 330, for example in the form of a motorized lens 331, are arranged along an axis orthogonal or substantially orthogonal to the vertical axis of rotation X of the carousel 5.

[0054] According to another possible variant, the dynamic means 330, for example in the form of a motorized lens 331, are arranged along an axis parallel or substantially parallel to the vertical axis of rotation X of the carousel 5.

[0055] In embodiments, the dynamic means 330 comprises a shape-changing lens 332 in the optical path of the laser light. A shape-changing lens 332 allows the focus of the laser beam 31 to be adjusted without moving the entire laser station 3. For example, the curvature of the shape-changing lens 332 is adjusted by applying an electric current, which changes the focal length in a few milliseconds. In particular, the curvature of said shape-changing lens 332 can be adjusted by applying an electric current.

[0056] An example of such an embodiment is illustrated in [Fig. 8]. In this illustrative example, the shape-changing lens 332 is located between the laser head unit 300 and the optical system 320. Two mirrors 331 as well as a laser beam expander 335 are located in the optical path. In [Fig.8], an enlargement schematically shows the change in focus.

[0057] In embodiments, the optical system 320 consists of a 3D three-dimensional laser marking system, including the dynamic focusing means 330. In this case, the dynamic means 330 are in the form of a focusing module for each point 200 to be marked of the at least one marking zone 20 of a container 2. An exemplary embodiment of such a device is illustrated in [Fig.9]. Each point 200, along a longitudinal axis relative to the at least one marking zone 20, is then dynamically controlled by the focusing module as a function of the shape and dimensions of the container 2.

[0058] In other words, the use of a 3D three-dimensional marking system is particularly advantageous, since it allows total coordination of the scanning of the focal point of the laser beam 31, simultaneously horizontally, vertically and longitudinally with respect to the at least one marking area 20. The focal point of the laser beam 31 then moves longitudinally with respect to the marking area 20, so as to adjust the focus. This makes it possible to ensure uniformity of the focal point on all the points to be marked in the marking area 20, regardless of the shape or orientation of this area 20 with respect to the main direction of the container 2.

[0059] In embodiments, the optical head 30 comprises a sensor 340 for measuring the distance between the optical system 320 and the at least one marking zone 20 of the container 2. This embodiment is very advantageous because, as will be described later, it makes it possible to adjust in real time the focus of the focal point of the laser beam 31, and therefore to obtain a precise, very readable mark 310, and this on all the points of the marking zone 20.

[0060] The control means 4 comprise an electronic unit 400 for controlling the movement of the laser beam 31. The unit 400 can be configured at will to modify the mark 310 to be inscribed; for example, it is a digital control. The parameters to be modified concern, for example, the movement coordinates of the beam 31, the speed of movement of the beam 31, etc. The mark 310 may consist of characters, patterns, barcodes, etc. Typically the distance DI between the output of the beam 31 and the marking zone 20 of the container 2 may vary, depending on the shape and / or dimensions of the container 2.

[0061] The laser beam 31 can trace the mark 310 indifferently in a vector mode, that is to say by continuous tracing, or in a matrix mode, that is to say by point-by-point tracing.

[0062] Preferably, the electronic unit 400 communicates with the dynamic means 330, in order to adjust the focal point of the laser beam 31 during the production of the mark 310 on the at least one marking zone.

[0063] In embodiments, the optical head 30 comprises a pulsed laser unit 300. The unit 300 generates the laser beam 31 which is then diffused by the optical system 320. Preferably, the wavelength of the emitted laser is between 800 and 2000 nanometers (nm). In embodiments, and depending on the type of marking sought, it will also be possible to select a laser emitting a beam 31 of different wavelengths, for example of the Ytterbium, Erbium, Thulium fiber laser type, or of the Nd-YAG or Nd:YVO4 solid type. According to different possible configurations, the laser light is emitted in particular from the device 40, and / or the optical channel 600 or even from the laser unit 300. Alternatively, the Nd-YAG laser is configured to emit a laser beam 31 with a wavelength of 532 nm emitting in the visible range, more precisely in the green color.

[0064] According to yet another variant of the invention, the laser of the Nd-YAG marking station 3 is configured to emit a beam 31 at a wavelength included in the near ultraviolet, for example 355 nm. Preferably, the wavelength of the emitted laser beam 31 is therefore between 1000 and 1100 nm, or between 1500 and 1600 nm, or between 1900 and 2000 nm, depending on the type of containers 2 to be marked and / or according to the type of mark 310 to be affixed to the marking zone 20 of a container 2.

[0065] It has been observed that the “PET” wall marking areas 20 of the container 2 targeted by the laser beam 31 in the near infrared range with a suitable power and / or exposure time are subject to a phenomenon known as “foaming”. Foaming consists of melting the material and generating bubbles which expand, forming a bead on the surface, bubbles which will remain trapped during cooling. The resistance of the material is very little altered. In addition, the legibility of the mark 310 obtained is much better because the gas bubbles in the material reflect the light in a diffuse manner.

[0066] Preferably, the marking station 3 uses a laser with a pulsed operating mode to generate short pulses of a duration of less than 500 ns (nanosecond) and of peak power of the order of kW (kilowatt) to several tens of kW depending on the desired marking and by focusing the beam around the wall of the container 2, at the level of the marking zone 20.

[0067] According to other variants of the invention not shown, other types of laser can be used within the scope of the present invention. As explained previously, the laser is selected and adjusted to allow the thermoplastic material wall to be marked, on the surface or in depth, without however engraving the wall.

[0068] The device 1 according to the invention is characterized in that it comprises a carousel 5 with a vertical axis of rotation X, said carousel 5 being driven in rotation by at least one motor relative to a frame 7. A schematic view of an exemplary embodiment of the device 1 and of the carousel 5 is visible in [Fig.l].

[0069] The rotation of the carousel 5 relative to the frame 7 is done by means of a rolling means 70.

[0070] In embodiments, the carousel 5 is carried by a rotating chassis 6, rotating around the vertical axis of rotation X, in the form of an orientation ring which comprises the rolling means 70. The rolling means 70 may be, for example, produced in the form of two rings capable of being placed in relative rotation with respect to one another, each ring comprising a raceway, and the crown further comprising a rotation device consisting of rolling members or bodies (such as balls or ball bearings) interposed between the two raceways and a device for fixing the constituent elements of the crown to prevent them from becoming detached while allowing the two rings to rotate relative to each other. The rotation of the carousel 5 around the vertical axis of rotation X can then be done by connecting a ring to the frame 7, the chassis 6 of the carousel 5 being carried by the other ring. Thus, the carousel 5 can rotate relative to the frame 7. The ring connected to the frame 7 is called the fixed ring, and the other ring is called the rotating ring.

[0071] In embodiments, the frame 6 in the form of a slewing ring may comprise external teeth mounted on the rotating ring. According to a possible variant, the rotating frame 6 is in the form of a cup which is mounted on the rotating ring, for example through blind or through, smooth or tapped fixing holes. On this cup are fixed various parts of the machine, not shown, the assembly forming a carousel. By way of illustration, on a machine of the applicant, the rotating mass equipped with the organs of the device 1 (optical heads 30, control means 4, plate 50, 51, 52, barrel 53, etc.) can have a weight of the order of ten tonnes for a rotation speed of the carousel, and therefore of the rotating ring, of the order of thirty revolutions per minute. The rotating ring and thus the carousel 5 are driven in rotation by a motor, generally not directly, but via pinion and / or belt mechanisms.

[0072] In embodiments, the rotating chassis 6 is in the form of a column.

[0073] The carousel 5 of the invention comprises at least one first tray 50, or platform. The axis of rotation of the at least one tray 50 is coaxial with the axis of rotation of the carousel 5. The tray 50 can be of any shape, but is preferably circular. As visible in [Fig.2], the plate 50 supports a plurality of holding members 54 for positioning a container 2 along an axis substantially parallel to the vertical axis of rotation X of the carousel 5. In other words, a container 2 is held by a holding member 54 and is driven in rotation by the first plate 50 of the carousel 5.

[0074] As visible in [Fig.l] or 2, the carousel 5 also comprises a barrel 53.

[0075] The barrel 53 supports the plurality of marking stations 3 such that each optical system 320 is located opposite a container 2, itself held by a holding member 54. Preferably, the diameter of the barrel 53 is less than the diameter of the first plate 50 in order to facilitate the implementation of the device 1.

[0076] As can be seen schematically in [Fig. 10], the containers 2 and the optical heads 30 are both rotated along a rotation axis X vertical to the frame 7. The synchronized rotation of the marking stations 3 and the containers 2 and the vertical position of the container 2 opposite the optical system 320 of an optical head 30 is particularly advantageous. Indeed, the working distance D2 between the optical system 320 and the marking zone 20 of the container 2 is then constant or substantially constant: the containers 2 are immobilized during marking, as are the optical systems 320, and the marking produced is of high quality.

[0077] The marking stations 3, the control means 4 and the containers 2 are therefore driven in rotation in a synchronized manner relative to the frame 7. The 5 carousel also includes a 60 rotating swivel joint that supplies electricity to the 4L power sources For this purpose, the rotating joint 60 comprises a rotating electrical collector, located at the head of said rotating joint 60, which is powered by a fixed electrical cable. Conventionally, the rotating electrical collector comprises tracks, fixed or rotating, on which fingers, respectively rotating or fixed, bear elastically, the assembly being housed under a casing, not shown, which is fixed to the chassis 6 and retained by an anti-torque structure secured to the frame 7. Preferably, the barrel 53 is hollow so as to accommodate the rotating joint 60 in this hollow central part.

[0078] Thus, the invention makes it possible to mark the containers 2 during their rotation, which is extremely advantageous. It is then possible to mark containers 2 at a high rate, of the order of 8000 to 100000 markings per hour.

[0079] In embodiments, at least one optical head 30 of each marking station 3 is capable of moving the laser beam 31 in a horizontal plane and / or in a vertical plane. Preferably, the laser beam 31 is emitted in a direction orthogonal or substantially orthogonal to the vertical axis of rotation X of the carousel 5. The vertical plane corresponds to the plane which passes through the vertical axis of rotation X of the carousel 5 and the horizontal plane corresponds to the plane perpendicular to the axis of rotation X of the carousel 5.

[0080] In embodiments, the barrel 53 of the carousel 5 comprises means for vertically moving each marking station 3 or each laser head 30, so that each of said stations 3 or said laser heads 30 can move vertically along the barrel 53, for example by means of slides placed on the barrel 53 and an actuation means (not shown). This has the advantage of being able to position the optical system 320 opposite the marking zone 20 of a container 2. Indeed, the type of container 2, its dimensions, its shape, can change and it is then necessary to adjust the relative vertical positioning of the optical systems 320 and the marking zones 20, so that the optical output 321 is located opposite the at least one marking zone 20. This adjustment can be done for example automatically via an electronic control unit 400 included in the control means 4, by a mechanical cam adjusted by an operator or by means of an actuator, or even manually by the operator.

[0081] According to another possible variant, the first plate 50 and / or each holding member 54 comprises means for vertically moving a container 2. This embodiment is preferred because it is simpler to implement. In the same way, the adjustment of the vertical position of the marking zone 20 of the container 2 can be done for example automatically via an electronic control unit 400, or even by a cam. This vertical positioning is preferably carried out before marking the containers 2.

[0082] In embodiments, the carousel 5 comprises a second tray 51. The second plate 51 is called the lower plate because it is located below the first plate 50, called the upper plate. The second plate 51 is rotated in a synchronized manner with the first plate, relative to the frame 7. The second plate 51 then supports holding means 54 in the form of a plate 541, on which the bottom 22 of a container 2 rests. The container 2 is then held firmly in position from above, preferably by its neck 21, by a gripping means 540; and from below, more particularly by its bottom 22, which rests on said plate 541. This embodiment, visible in [Fig. 4], is very advantageous because it ensures that the container 2 is held in position during its rotation and therefore during its marking. In addition, the plate 541 contributes to the centering and vertical positioning assistance of the container 2.

[0083] In embodiments, the carousel 5 comprises a third plate 52, the axis of rotation of which is coaxial with the axis of rotation of the first plate 50. The third plate 52 supports the control means 4 and is preferably, but not limited to, located above the first plate 50. It is particularly advantageous to position the control means 4 on the upper part of a third plate 52 located in the upper part of the barrel 53. Indeed, this makes it possible to have a primitive displacement of the containers 2 smaller than that of the control means 4. Also, this makes it possible to avoid possible leakage problems, in cases where the containers 2 are filled before marking.

[0084] [Fig.2] shows an embodiment in which the carousel 5 comprises a first tray 50, a second tray 51 and a third tray 52. The first tray 50 supports the holding means 540, which are vertically movable, while the second tray 51 supports a plate 541, which is also vertically movable. Preferably, only the plate 541 is vertically movable. Indeed, it is preferable to position the container 2 vertically by pushing it by its bottom 22. In other words, in a preferred embodiment, only the plate 541 is actuated, or motorized, to move the container 2 vertically, the holding means 540 then performing so-called passive translations.

[0085] Two laser marking stations 3 can be seen, each comprising two optical systems 320.

[0086] Preferably, the third plate 52 is located in the upper part of the barrel 53 and supports the control means 4, and in particular the laser treatment apparatus 40 and the power supply means 41. We can also see the rotating joint 60 and optical channels 600 which connect the different elements electrically.

[0087] In the embodiment shown in [Fig.2], the different trays are connected to the barrel 53. It is also possible to connect two or three trays 50, 51, 52 together in the form of a console to be assembled on a barrel 53 of a carousel 5. Thus, according to a possible variant, the first tray 50 and the second tray 51 and / or the third tray 53 are in one piece.

[0088] In embodiments, and as seen in particular in [Fig.3], each marking station 3 comprises two optical heads 30. The two optical systems 320 can be superimposed along an axis parallel to the rotation axis X of the carousel 5 in each station 3, in order to simultaneously mark a marking zone 20a located in the upper part of the container 2 and a zone 20b located in the lower part of said container 2, in its normal orientation, that is to say when it rests on its base 22. The two optical systems 320 can also be arranged head to tail, as seen in [Fig.3].

[0089] According to another possible variant, illustrated in [Fig.6], the station 3 comprises two optical systems 320a, 320b angularly offset by an angle α on an axis orthogonal or substantially orthogonal to the vertical axis of rotation X of the carousel 5. The angle α is for example between 30 and 160° degrees. Each optical system 320a, 320b respectively carries out the marking on an area 20a, 20b. Optionally, the areas 20a and 20b can be positioned at the same height along an axis parallel to the axis of rotation X of the carousel 5. This embodiment is particularly advantageous because it makes it possible to produce a mark 310 over a larger part of the circumference of a container 2.

[0090] The invention also relates to an installation 100 for marking containers 2, comprising a laser marking device 1 as described previously.

[0091] The installation 100 also comprises a treatment station 10 for containers 2 located upstream of the device 1. The treatment station 10 directly or indirectly supplies the device 1 at the outlet of a transfer wheel 8, at a loading point 80. Such a treatment station 10 may be, for example, a filler, a capper, a blower, a labeler, or any other container processing station 2 on a packaging line.

[0092] Advantageously, the installation 100 allows a continuous supply of containers 2.

[0093] An installation 100 according to a possible embodiment is shown schematically in top view in [Fig.11]. Containers 2 circulate on a conveyor means 102 from a processing station 10, for example a filling and capping machine. Then, the containers 2 are transferred, preferably continuously, via an upstream transfer wheel 8, at a loading point 80, to the device 1 according to the invention. In particular, the containers 2 are gripped by holding members 54. The plurality of laser marking stations 3 can be seen over the entire periphery of the barrel 53 of the carousel 5. According to the variant illustrated in [Fig. 11], the installation 100 also comprises an intermediate wheel 800 between the upstream conveying means 102 and the transfer wheel 8.

[0094] The stations 3 are opposite the containers 2 held, such that the laser beam 31 can be directed towards a marking zone 20 of the containers 2, preferably orthogonally or substantially orthogonally to the axis of rotation X of the carousel 5. The direction of rotation is represented schematically by a circular arrow, which does not define the direction of rotation of said carousel 5 within the scope of the invention. In other words, the carousel 5 can rotate around its vertical axis of rotation X in one direction or the other.

[0095] During the rotation of the containers 2 in a manner synchronized with the rotation of the marking stations 3, the containers 2 are therefore marked, that is to say that a mark 310 is affixed to at least one marking zone 20 by means of a laser beam 31 emitted and diffused by the marking stations 3.

[0096] At the end of the marking, and as visible in [Fig. 11], the marked containers 2 are transferred from an unloading point 90 via a downstream transfer wheel 9. The containers 2 are for example placed on a downstream conveyor means 101.

[0097] Preferably, the unloading of the containers 2 by means of the downstream transfer wheel 9 is also carried out continuously. In other words, the installation 100 allows continuous marking of the containers 2, with a continuous supply of the containers 2 to the device 1 from a container processing station 10 until their unloading onto a downstream conveying means 101. In other words, preferably, the carousel 5 of the device 1 is driven in rotation continuously. This is particularly advantageous because it allows the marking of containers 2 to be carried out at a sustained rate.

[0098] As visible in [Fig.l 1], the installation 100 may also comprise, in embodiments, an inspection system 11. Such an inspection system 11 includes at least one camera and one control unit (not shown) to verify whether the 310 mark is compliant. In the event of non-compliance, the container 2 must be destroyed or at least rejected so as not to undergo further processing. The installation 100 may include means 110 for ejecting a container 2 whose mark 310 is not compliant. For these control purposes, in embodiments, the installation 100 comprises a central control unit 12 making it possible to enter information concerning the type of container 2, the format, the type of mark 310 to be affixed, the location of the marking zones 20, 20a, 20b, etc. According to a possible variant, the central control unit 12 communicates with the electronic unit 400 of the control means 4. In embodiments, the central control unit 12 comprises: - a database 120 in which are recorded programs for controlling the marking device 1 and possibly other container processing stations 2, said database 120 being recorded in a memory device or stored on an independent server, - a processor connected to the memory to apply the program instructions and - a communication interface connected to the processor for communication at least with the electronic unit 400 of the control means 4. According to a possible variant, the central control unit 12 comprises a calculation unit making it possible to generate instructions in real time based on the measurements taken by different sensors, for example a sensor for measuring the height of a container 2, or the sensor 340 for measuring the distance between the optical output 321 and the at least one marking zone 20 of the container 2.

[0099] In embodiments, the central control unit 12 transmits instructions to the dynamic means 330 via the electronic unit 400. The dynamic means can then adjust the focal point of the laser beam 31 in order to produce a high-quality, homogeneous mark 310 over the entire surface of the at least one marking zone 20.

[0100] In embodiments, the central control unit 12 transmits information in the form of instructions to the control means 4 via the rotating joint 60. The information transmitted relates, for example, to the at least one marking zone 20, the characteristics of the mark 310, the parameters of the marking, etc. The electronic control unit 400 acts as a slave controller to the central unit 12, called the master unit. The electronic control unit 400 is programmed to control the device 1 for the complete completion of a marking cycle, and in particular to transmit the instructions necessary for the proper execution of marking using dynamic means 330.

[0101] The central control unit 12 can also allow the direction of rotation of the carousel 5 to be set, or even its rotation speed.

[0102] The master control unit can therefore be connected to other slave controllers, to possibly operate the adjustment of the rotation speed of the transfer wheels 8, 9, or even of the conveying means 101 and 102.

[0103] The central control unit 12 can also be connected to an inspection system 11 to enable the level of conformity of the mark 310 of a container 2 to be configured. The conformity can be, for example, the readability, the positioning of the mark, etc. According to a possible variant, the inspection system 11 transmits information concerning the quality of the marking to the central control unit 12, which can then send instructions to the electronic unit 400 of the control means 4, for example aimed at correcting the height adjustment of the mark 310, the focusing carried out by the dynamic means 330, or any other parameter linked to the marking.

[0104] Advantageously, the central control unit 12 comprises various sensors, in particular speed sensors, or the sensor 340 for measuring the distance between the optical output 321 and the at least one zone 20 to be marked, the information collected from which is stored in the database 120 or transmitted to a calculation unit of the central control unit 12. For example, the database 120 of the central control unit 12 records the speed parameters of the transfer wheels 8, 9, of the carousel 5, and the information concerning the formats of containers 2 to be marked, for example their dimensions and / or their shape.

[0105] In embodiments, the central control unit 12 also transmits instructions to the electronic unit 400 in order to transmit instructions to the holding members 54 and / or to the marking stations 3 to configure the positioning of the containers 2 opposite the optical systems 320. The central control unit 12 then makes it possible to automatically manage the vertical movement of the containers 2 and / or of the marking stations 3, in particular as a function of the format of the containers 2.

[0106] In embodiments, the central control unit 12 makes it possible to configure the mark 310 to be affixed to the zones 20, 20a, 20b of a container 2.

[0107] An operator can enter the various parameters at a dedicated interface of the central control unit 12, or possibly remotely. For these purposes, the central control unit 12 may comprise a control screen for the installation 100 with a dedicated human-machine interface allowing the entry of information, for example the entry of the format of the container 2, the choice of the brand 310, etc.

[0108] The invention also relates to a method for marking containers 2 comprising at least the following steps: - a first step E1 consisting of carrying out a treatment on said containers 2, - a second step E2 consisting of rotating said containers 2 around a vertical axis around which laser marking stations 3 are rotated, in a synchronized manner with said containers 2, - a step E2' of adjusting the focal point of the laser marking stations 3, preferably according to the dimensions and / or the shape of said containers 2, and - a third step E3 consisting of marking said containers 2 during rotation.

[0109] In embodiments, the method is implemented by the device 1 of the invention as described previously. The device 1 according to the invention is therefore capable of implementing the marking method of the invention.

[0110] Preferably, the first processing step E1 is a step of filling and capping the containers 2. Indeed, it has been found that the laser marking with the laser beam 31 is of better quality (in terms of readability in particular) when the container 2 is filled. Indeed, it is generally difficult to use laser systems to mark containers 2 made of plastic, and in particular PET, because laser marking tends to degrade the container 2, due to the high power required to mark the containers 2 at high speed. This involves, for example, the formation of holes in the wall of the container 2. Advantageously, in embodiments, the method therefore consists of marking a filled container 2, preferably with liquid. This allows the liquid to quickly diffuse the heat of the transmitted laser beam 31 and to prevent degradation of the wall of said container 2. The internal integrity of the container 2 in contact with the liquid is therefore maintained while it is possible to generate a strong contrast with a lot of power to achieve a high marking rate and confine it to the external surface of the wall of said container 2. Preferably, the containers 2 are therefore filled and capped before being rotated for the purpose of marking them.

[0111] [Fig. 12] schematically shows the steps of a method according to an embodiment where the containers 2 are filled and capped during a step EL. Then, according to a possible variant, the filled and capped container 2 is transferred to the holding members 54, as visible in [Fig. 12], for example by a gripping means 540 by the neck and a plate 541.

[0112] The gripped containers 2 are then rotated, in a synchronized manner with marking stations 3. Preferably, the rotation step is done continuously, without interruption: the container 2 is placed in the trajectory of the device 1 then is grasped and rotated.

[0113] During step E3, and during their rotation, the containers 2 are marked.

[0114] The method according to the invention comprises a step E2' of adjusting the focal point. For each point of the mark 310, the device 1 adjusts the focal point simultaneously with the positioning of the laser beam 31 by the optical system 320. This step E2' of adjusting the focal point can be done after loading the containers 2, during their rotation, prior to carrying out the marking, or even during carrying out the marking, as will be described below.

[0115] In embodiments, the characteristics of the container 2, for example its shape, its dimensions, and the mark 310 are previously recorded in the database 120 of the central control unit 12. The electronic unit 400 then transmits the instructions to the dynamic means 330 and the adjustment of the focal point of the laser beam 31 is done for each point 200 of the mark 310 during the production of the mark 310. These embodiments are preferred in cases where the at least one marking zone 20 is located on a complex surface of the container 2.

[0116] In embodiments, no data has been previously recorded. The sensor 340 will then transmit the information to the central control unit 12 which, via a calculation unit, will transmit instructions to the electronic unit 400. In other words, the marking method then comprises a preliminary step of measuring the distance between the optical output 321 and at least one marking zone 20.

[0117] It is also possible to adjust the focal point of the laser beam 31 only once, prior to the marking step E3, in cases where the mark 310 and / or the marking zone 20 is of the simple type.

[0118] In other words, the step E2' of adjusting the focal point of the laser beam 31 can be done before or simultaneously with the marking step E3.

[0119] Finally, and following step E3, the containers 2 are unloaded. Preferably, the containers 2 are unloaded during rotation of the carousel 5, said carousel 5 not stopping for this unloading step.

[0120] In embodiments, the marking step E3 is performed during rotation over an angular sector less than 360 degrees around the vertical axis. In other words, each container 2 makes approximately a single convolution, more precisely less than a complete rotational turn.

[0121] In embodiments, and as schematically represented in [Fig. 11], the method comprises: - after the step El of processing the containers 2, a step El' of loading the containers at a loading point 80, - after the marking step E3, the method comprises an unloading step E4 at an unloading point 90 of the containers 2, each station 3 and each container 2 being moved respectively around said vertical rotation axis between said loading point 80 of said containers 2 and said unloading point 90 of said containers 2 marked at a so-called marking zone 20 before resuming a new cycle comprising at least steps E1 to E4.

[0122] Advantageously, after the loading step E1' and / or before the step E3, the containers 2 are moved vertically. According to a possible variant, the laser marking stations 3 are moved vertically during or after said loading step E1'. Thus, in embodiments, the containers 2 are moved vertically after their loading, in order to adjust the positioning of the at least one marking zone 20 opposite the marking stations 3, and in particular opposite the optical output 321 of an optical system 320. The containers 2 are therefore moved from an initial vertical position - or height - to a vertical marking position.

[0123] Preferably, after the loading step E1', the step of vertical movement of the containers 2 is carried out during the step E2, that is to say during the rotation of the containers 2. Indeed, preferably, the step E2 of rotation around the X axis is carried out simultaneously with all the steps of the method. The rotation step E2 therefore takes place at the same time as the different steps E1', E2', E3, E4, the rotation being carried out continuously. In other words, advantageously, there is no stoppage in the movement of the container 2.

[0124] According to another variant, the step of vertical movement of the containers 2 is carried out before step E2, that is to say before the rotation of the containers 2. Then, once the marking step E3 is completed, the containers 2 are again moved vertically to return from said vertical position to said initial position so that said containers 2 can be unloaded.

[0125] The containers 2 and / or the stations 3 can also be moved during their rotation, during the rotation step E2 and / or during the marking step E3.

[0126] In embodiments, the marking step E3 is carried out by a pulsed laser in the near infrared.

[0127] In embodiments, the marking method comprises an additional step, after the marking step E3, of inspecting the marked containers 2.

[0128] The marking method can be implemented in an installation 100 as described previously.

[0129] Thus, the invention aims at a device 1 for marking containers 2 which is particularly effective, which not only makes it possible to produce high-quality marking, but also at a high speed. It is then no longer necessary to stop the movement of the container 2 to be marked, which has a direct and favorable impact on the operating speed of the industrial line.

Claims

1. Claims Device (1) for laser marking containers (2), in particular bottles or flasks made of thermoplastic material, of the type comprising at least one body (23), a shoulder (24) in the extension of said body (23) at an upper end thereof, a neck (21) in the extension of the shoulder (24), and a bottom (22) at the lower end of said body (23), said device (1) comprising at least: - a plurality of laser marking stations (3), each station (3) comprising along an optical path at least one laser marking optical head (30) equipped with a laser head unit (300) and an optical system (320) for focusing a laser beam (31) in order to generate a mark (310) at at least one marking area (20) of each container (2) to mark said area (20), said optical head (30) being connected to said apparatus (40) via an optical channel (600),- control means (4) connected to the marking stations (3) and comprising a laser processing apparatus (40) and the supply means (41) of the laser marking stations (3), - a carousel (5) with a vertical axis of rotation X driven in rotation by at least one motor relative to a frame (7) via a rolling means (70), said carousel (5) comprising at least: - a first plate (50), said first plate (50) supporting a plurality of holding members (54) for positioning said container (2) along an axis substantially parallel to the vertical axis of rotation X of said carousel (5), - a barrel (53) supporting the plurality of marking stations (3) such that each optical system (320) is located opposite a container (2) held by a holding member (54), such that said marking stations (3),said control means (4) and said containers (2) are rotated in a synchronized manner relative to said frame (7), said containers (2) being marked during their rotation, device (1) characterized in that it comprises, - dynamic focusing means (330) for adjusting the focal point as a function of the distance between said optical system (320) and said at least one marking zone (20) of the container (2) and in that - the marking station (3) uses a laser with a pulsed operating mode to generate short pulses with a duration of less than 500ns (nanosecond) and peak power of the order of kW (kilowatt) to several tens of kW depending on the desired marking and by focusing the laser beam (31) around the wall of the container (2), at the level of the marking zone (20).

2. Device (1) according to claim 1, characterized in that the dynamic means (330) are arranged in the optical path between the optical channel (600) and the optical system (320), preferably between the laser head unit (300) and said optical system (320).

3. Device (1) according to claim 2, characterized in that, on the optical path, the dynamic means (330) comprise a motorized lens (331), for example aligned with the laser head unit (300) along a linear axis.

4. Device (1) according to claim 1 or 2, characterized in that, on the optical path, the dynamic means (330) comprise a shape-changing lens (332).

5. Device (1) according to claim 1, characterized in that the optical system (320) consists of a 3D three-dimensional laser marking system, including said dynamic focusing means (330) which are in the form of a focusing module for each point (200) to be marked from there at least one marking zone (20) of the container (2).

6. Device (1) according to any one of the preceding claims, characterized in that the optical head (30) comprises a sensor (340) for measuring the distance between the optical output (321) and at least one marking zone (20) of the container (2).

7. Device (1) according to any one of the preceding claims, characterized in that at least one optical head (30) of each marking station (3) is capable of moving the focal point of the laser beam (31) in three directions, namely a vertical direction, a horizontal direction and a longitudinal direction relative to the at least one marking zone (20) of said container (2).

8. Device (1) according to any one of the preceding claims, characterized in that each marking station (3) comprises two optical heads (30), placed head to tail in each of said stations (3) so that the optical systems (300) of the two optical heads (30) are superimposed in order to simultaneously mark an area (20a) marking located in the upper part of the container (2) and a zone (20b) located in the lower part of said container (2).

9. Device (1) according to any one of the preceding claims, characterized in that each marking station (3) comprises a pulsed laser optical head (30) whose wavelength is between 800 and 2000 nanometers.

10. Installation (100) comprising: - a laser marking device (1) according to claims 1 to 9, - a treatment station (10) for containers (2) located upstream of said device (1), said treatment station (10) directly or indirectly supplying said device 1 by means of a transfer wheel (8) at a loading point (80), - a transfer wheel (9) at an unloading point (90) for releasing said containers (2) marked directly or indirectly at a downstream conveying means (101).

11. Installation (100) according to the preceding claim, characterized in that it comprises an inspection system (11) for the marked containers (2).

12. Method for marking containers (2) comprising at least the following steps: - a first step (El) consisting of carrying out a treatment on said container (2), preferably filling and capping said containers (2), - a second step (E2) consisting of rotating said containers (2), preferably filled and capped, around a vertical axis around which laser marking stations (3) are rotated, in a manner synchronized with said containers (2), - a step (E2') of adjusting the focal point of the laser marking stations (3) preferably as a function of the dimensions and / or the shape of said containers (2), and - a third step (E3) consisting of marking said containers (2) during rotation, marking method implementing the marking device (1) according to any one of claims 1 to Q

13. id y. Method for marking containers (2) according to claim 12 further comprising: - after the step (El) of treating a container (2), preferably filling and capping, a step

14.

15. loading (ET) of containers (2) at a loading point (80), - following the marking step (E3), an unloading step (E4) at an unloading point (90) of said containers (2), each station (3) and each container (2) being moved respectively around said vertical axis of rotation between said loading point (80) of said containers (2) and said unloading point (90) of said containers (2) marked at at least one so-called marking zone (20) before resuming a new cycle comprising at least steps (El) to (E4). Method according to claim 12 or 13, characterized in that, after the loading step (El') and, during the rotation step (E2), said containers (2) are moved vertically. Method according to any one of claims 12 to 14, characterized in that the marking step (E3) is carried out by a pulsed laser in the near infrared.

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