Marking method and marked receptacle
A method for marking of a receptacle while it is moved along a conveying path, including: moving the receptacle in a marking station along the conveying path; and simultaneously marking a first surface region and a second surface region of the receptacle while it is moved in the marking station along the conveying path, using a first laser beam and a second laser beam emitted in opposite directions on both sides of the receptacle, transversally to a conveying direction of the receptacle, wherein the first and second surface regions are arranged substantially at 180° from each other with respect to a main axis of the receptacle.
1 . A method for the marking of a receptacle while it is moved along a conveying path, the method comprising:
moving the receptacle in a marking station along the conveying path in a conveying direction; and
simultaneously marking a first surface region and a second surface region of the receptacle while it is moved in the marking station along the conveying path, using a first laser beam and a second laser beam emitted in opposite directions on two sides of the receptacle, transversally to the conveying direction, wherein the first and second surface regions are arranged substantially at 180° from each other with respect to a main axis of the receptacle,
wherein the first laser beam is emitted by a first laser device and the second laser beam is emitted by a second laser device, wherein the first and second laser devices each comprise a respective laser source,
wherein each of the first and second laser beams is focused in the form of a laser spot in a focal plane corresponding to the respective surface region to be marked,
wherein, in each surface region to be marked, successive laser-marked dots, arranged in lines such that a width of each line corresponds to a diameter of one laser-marked dot, are marked by moving the laser spot produced by the respective laser beam among the first and second laser beams in the focal plane according to a scanning trajectory, wherein each laser beam among the first and second laser beams is a pulsed laser beam, with a repetition rate and a laser scanning speed adapted in such a way that, during the marking of each line of laser-marked dots in the respective surface region by moving the laser spot produced by the respective laser beam, a ratio of a length of an overlap zone between two successive positions of the laser spot to a spot diameter of the laser spot is higher than or equal to 0.15.
2 . The method according to claim 1 , wherein the first and second laser devices are controlled by a speed at which the receptacle is moved in the marking station along the conveying path and a triggering time, which is the same for both laser devices.
3 . The method according to claim 2 , wherein the triggering time for both the first laser device and the second laser device is determined by a single sensor configured to detect a position of the receptacle along the conveying path.
4 . The method according to claim 1 , wherein, for at least one of the first and second surface regions of the receptacle, a ratio of a maximum arc length of a pattern marked on said surface region, taken in a circumferential direction of the receptable, to half a circumference of the receptacle is higher than 30%.
5 . The method according to claim 1 , wherein, for each of the first and second surface regions of the receptacle, the surface region comprises a polymer resin and an additive that absorbs radiation in a given wavelength range, wherein a wavelength of each of the first and second laser beams is in the given wavelength range, wherein an energy density in a focal plane for each of the first and second laser beams avoids material ablation in the corresponding surface region of the receptacle.
6 . The method according to claim 1 , wherein each of the first and second laser beams is focused, in a focal plane corresponding to the respective surface region to be marked, in the form of a laser spot having a spot diameter in a range of between 50 μm and 150 μm.
7 . The method according to claim 1 , wherein the laser spot of each of the first and second laser beams is displaced, in a focal plane corresponding to the respective surface region to be marked, according to a scanning trajectory with a scanning speed in a range of between 2500 mm/s and 5000 mm/s.
8 . The method according to claim 1 , comprising a step of determining, for each of the first and second surface regions of marked the receptacle to be respectively by the first and second laser beams, an optimized scanning trajectory of the laser spot corresponding to an optimized marking order of characters of a pattern to be marked which minimizes a marking time of the pattern on the respective surface region.
9 . A laser-marked receptacle for use in a packaging filled with sensitive products such as food, nutraceutical products, pharmaceutical products or diagnostic products, wherein said laser-marked receptacle comprises on its outer surface two laser-marked surface regions arranged substantially at 180° from each other with respect to a main axis of the receptacle, wherein each laser-marked surface region comprises a respective marked pattern formed of a plurality of laser-marked dots resulting from a color change of material of the outer surface under the effect of a photochemical reaction induced by a laser beam, wherein, in each laser-marked surface region, the marked pattern is formed by straight and curved line segments each comprising a single row of laser-marked dots, such that a width of each line segment corresponds to a diameter of one laser-marked dot, wherein, for each line segment of each laser-marked surface region, all of the successive laser-marked dots forming the line segment are connected to each other in an overlap zone such that, for all pairs of successive laser-marked dots, a ratio of a length of the overlap zone between the two successive laser-marked dots in a longitudinal direction of the line to a diameter of each laser-marked dot is higher than or equal to 0.15, both for straight and curved line segments.
10 . The laser-marked receptacle according to claim 9 , wherein patterns marked on the two laser-marked surface regions of the laser-marked receptacle result from the color change of the material of the receptacle without material burning or material ablation.
11 . The laser-marked receptacle according to claim 9 , wherein patterns marked on the two laser-marked surface regions of the laser-marked receptacle are different from one another.
12 . The laser-marked receptacle according to claim 9 , wherein, for at least one pattern marked on a laser-marked surface region of the laser-marked receptacle, a ratio of a maximum arc length of the marked pattern in a circumferential direction of the receptable to half a circumference of the receptacle is higher than 30%.
13 . The laser-marked receptacle according to claim 9 , wherein, for each laser-marked surface region, a surface density of the laser-marked dots for the marked pattern, defined as a ratio of the number of the laser-marked dots forming the marked pattern to a surface area of the smallest circumscribing rectangle tangent to the laser-marked surface region within which the marked pattern is inscribed, is less than 300 dots/mm 2 .
14 . The laser-marked receptacle according to claim 9 , wherein, for each laser-marked surface region, the number of laser-marked dots forming the marked pattern is less than 10000.
15 . The laser-marked receptacle according to claim 9 , wherein, in each laser-marked surface region, a diameter of each laser-marked dot is in a range of between 50 μm and 150 μm.
16 . The laser-marked receptacle according to claim 9 , wherein an outer surface of the laser-marked receptacle comprises a polymeric surface comprising a polymeric resin and an additive that absorbs radiation in a given wavelength range, wherein an amount of the additive is of between 0.5 and 5 wt %.
17 . The laser-marked receptacle according to claim 9 , wherein, for each marked pattern, the length of the overlap zone between successive laser-marked dots in a longitudinal direction of the line is higher for curved line segments compared to straight line segments.
18 . An apparatus for the marking of successive receptacles in a marking station, such that in each laser-marked surface region of the laser-marked receptacles, the laser-marked dots are arranged in lines such that a width of each line corresponds to a diameter of one laser-marked dot, the apparatus comprising:
a conveyor for moving successive receptacles in the marking station along a conveying path;
a first laser device and a second laser device each comprising a respective laser source, which are located on both sides of the conveying path and configured to emit two laser beams in opposite directions, transversally to a running direction of the conveyor, wherein
the laser beam of the first laser device is focused in the form of a laser spot in a first focal plane corresponding to a first surface region of a receptacle passing in the marking station, and
the laser beam of the second laser device is focused in the form of a laser spot in a second focal plane corresponding to a second surface region of a receptacle passing in the marking station,
wherein for each receptacle, the first and second surface regions are arranged substantially at 180° from each other with respect to a main axis of the receptacle; and
a controller configured to control the first and second-laser devices as a function of a speed of the conveyor and a triggering time,
wherein, in each surface region to be marked, successive laser-marked dots, arranged in lines such that a width of each line corresponds to a diameter of one laser-marked dot, are marked by moving the laser spot produced by the respective laser beam in the focal plane according to a scanning trajectory,
wherein each laser beam is a pulsed laser beam, with a repetition rate and a laser scanning speed adapted in such a way that, during the marking of each line of laser-marked dots in the respective surface region by moving the laser spot produced by the respective laser beam, a ratio of a length of an overlap zone between two successive positions of the laser spot to a spot diameter of the laser spot is higher than or equal to 0.15.
19 . The apparatus according to claim 18 , wherein the triggering time for both laser devices is determined by a single sensor configured to detect a position of the receptacle transported by the conveyor.
20 . The apparatus according to claim 18 , wherein the triggering time for both laser devices is computed from a speed of the conveyor in the marking station and a spacing between successive receptacles transported by the conveyor.
21 . The apparatus according to claim 18 , wherein the controller is configured to control at least one laser parameter of each of the first and second laser devices selected from a group consisting of: a focal laser spot diameter, a laser average power, a laser scanning speed, a repetition rate, a pulse width, a marking direction, and a combination thereof.