FR2839668A1

FR2839668A1 - Laser engraving procedure for leather has digital signal for engraved motif converted to analog signal transmitted to pulsed laser of variable power

Info

Publication number: FR2839668A1
Application number: FR0206128A
Authority: FR
Inventors: Armand Piolat
Original assignee: Duchenaud Uniflexo
Current assignee: Duchenaud Uniflexo
Priority date: 2002-05-17
Filing date: 2002-05-17
Publication date: 2003-11-21

Abstract

The procedure for engraving a motif in a piece of natural or simulated leather (4) on a cylindrical support (2) with the aid of a laser emitter head (5) on a mobile base has the motif transcribed as a digital signal to ensure synchronization of the base and support movements. The digital signal is converted into a variable analog signal representing the quantity of material to be removed, and the analog signal is transmitted to a pulsed laser (8) delivering a beam (20) of variable power focused through a lens (22). The laser emitter head is moved parallel to the axis of rotation of the cylindrical support by a drive screw (11), and the beam is guided from the laser source to the emitter head by a series of mirrors (10). The digital signal is based on a 1 or 8-bit mode, and the analog signal varies between 0 and 10 Volts.

Description

R:\Brevets\20400\20466 doc - 18 novembrc 2002 - 22/23 La presenteR: \ Patents \ 20400 \ 20466 doc - November 18, 2002 - 22/23 This is

invention se rapporte, d'une part, a un procede de gravure d'un motif sur une piece de cuir ou simili cuir fixee sur un support mobile, a ['aide d'une tete d'emission laser monte sur une base mobile, et d'autre part, a un invention relates, on the one hand, to a method of engraving a pattern on a piece of leather or imitation leather fixed on a mobile support, using a laser emission head mounted on a mobile base, and on the other hand, has a

dispositif mettant en ceuvre ledit procede de gravure. device implementing said etching process.

Par "simili-cuir", on entend tout materiau, ou matiere, en feuille ou plaque, By "imitation leather" is meant any material, or material, in sheet or plate,

presentant visuellement ou au toucher certaines caracteristiques d'un cuir. presenting visually or to the touch certain characteristics of a leather.

Un "simili-cuir" peut etre obtenu par tout procede de synthese, de o transformation, ou autre, apparente par exemple a l'obtention de materiaux A "faux-leather" can be obtained by any process of synthesis, o transformation, or other, apparent for example in obtaining materials

plastiques composites ou non, en feuilles. composite plastics or not, in sheets.

11 est connu depuis fort longtemps de chercher a creer manuellement des motifs ornementaux sur des pieces de cuir qui peuvent etre utilisees par la suite pour It has been known for a long time to seek to manually create ornamental patterns on pieces of leather which can be used subsequently for

s realiser notamment des sacs ou encore des vetements. s especially make bags or clothing.

Le brevet US 5, 990, 444 decrit un procede de gravure automatise d'un dessin ou motif sur une piece de cuir a ['aide d'un laser delivrant un faisceau laser a US Patent 5,990,444 describes a process for automatically engraving a design on a piece of leather using a laser delivering a laser beam to

puissance continue. Dans l'un des modes de realisation presente, la piece de power continues. In one of the embodiments presented, the piece of

o cuir et le laser vent rattaches a des supports mobiles pouvant se deplacer dans des plans sensiblement paralleles. Le dessin a realiser sur la piece de cuir est transcrit en un signal numerique qui est analyse par un systeme de controle apte a commander le deplacement des deux supports mobiles. En fonction du graphisme a realiser, la poissance continue du laser est predeterminee de s fa,con a eviter la deterioration du cuir. Ce procede, qui convient pour realiser un dessin relativement simple par gravure dans une piece de cuir, presente cependant ['inconvenient de ne pas convenir lorsque l'on desire graver un motif elabore pour lequel des zones de la piece de cuir doivent etre gravees, par exemple, en degrade ou encore de fa,con a laisser de fines aretes intactes so donnant du relief au motif. En effet, compte tenu de la vitesse du deplacement de la piece par rapport au laser et du temps necessaire pour faire passer le faisceau laser de la valeur de puissance continue predeterminee a une valeur nulle, il n'est pas possible de faire varier la profondeur de gravure en jouant o leather and the wind laser attached to mobile supports which can move in substantially parallel planes. The drawing to be made on the piece of leather is transcribed into a digital signal which is analyzed by a control system capable of controlling the movement of the two mobile supports. Depending on the graphics to be produced, the continuous power of the laser is predetermined so as to avoid deterioration of the leather. This method, which is suitable for producing a relatively simple drawing by engraving in a piece of leather, has the drawback, however, of not being suitable when it is desired to engrave an elaborate pattern for which areas of the piece of leather must be engraved, for example, in degrade or in fa, con to leave fine edges intact so giving relief to the pattern. In fact, taking into account the speed of movement of the part with respect to the laser and the time necessary for the laser beam to go from the predetermined continuous power value to a zero value, it is not possible to vary the depth burning playing

alternativement sur l'ouverture et la fermeture du faisceau laser. alternately on the opening and closing of the laser beam.

La presente invention a pour but de resoudre le probleme evoque precedemment, et concerne a cet effet un procede de gravure d'un motif sur une piece de cuir ou simili cuir fixee sur un support mobile, a ['aide d'une tete d'emission laser montee sur une base mobile, ledit motif etant transcrit en un signal numerique utilise pour assurer la synchronisation des deplacements du support mobile et de la tete mobile, caracterise en ce que, i) on transforme ce signal numerique en un signal analogique variable representatif de la quantite de matiere a enlever, ii) on transmet ce signal analogique a un laser pulse apte a delivrer The purpose of the present invention is to solve the problem mentioned above, and to this end relates to a method of engraving a pattern on a piece of leather or imitation leather fixed on a mobile support, using a head. laser emission mounted on a mobile base, said pattern being transcribed into a digital signal used to synchronize the movements of the mobile support and the mobile head, characterized in that, i) this digital signal is transformed into a representative variable analog signal of the quantity of material to be removed, ii) this analog signal is transmitted to a pulsed laser capable of delivering

un faisceau laser de puissance variable. a laser beam of variable power.

Ainsi, le fait d'utiliser un laser pulse, qui peut emettre jusqu'a 10 000 impulsions par seconde, combine a un signal analogique couvrant toute la plage de puissance du laser pulse, permet une gravure particulierement fine. En effet, ce laser ayant re,cu une information extremement precise quant a la quantite de matiere a enlever en cheque point, un point devant etre compris au sens de la presente demande comme etant une zone de matiere possedant une surface minimale de l'ordre de 0, 25 um2, il est alors capable de delivrer a tout moment la puissance adequate par simple modulation du nombre d'impulsions delivrees. Dans un mode de realisation preferee, on enroule la piece de cuir autour d'un cylindre presentant un axe de rotation, et le laser pulse est apte a se deplacer Thus, the fact of using a pulse laser, which can emit up to 10,000 pulses per second, combined with an analog signal covering the entire power range of the pulse laser, allows particularly fine etching. In fact, this laser having received extremely precise information regarding the quantity of material to be removed at each point, a point to be understood in the sense of the present application as being an area of material having a minimum surface area of the order from 0.25 um2, it is then capable of delivering the adequate power at any time by simple modulation of the number of pulses delivered. In a preferred embodiment, the piece of leather is wrapped around a cylinder having an axis of rotation, and the pulsed laser is able to move

parallelement a cet axe de rotation. parallel to this axis of rotation.

o Preferentiellement, le signal numerique est realise sur la base d'un mode 1 bit ou d'un mode 8 bits. Le mode 8 bits est plus specialement prevu pour effectuer de la gravure en degrade. De plus, le signal analogique variable est o Preferably, the digital signal is produced on the basis of a 1-bit mode or an 8-bit mode. The 8-bit mode is more specifically intended for performing gradation engraving. In addition, the variable analog signal is

avantageusement compris entre O et 10 Volts. advantageously between 0 and 10 volts.

Preferentiellement, au moins une lentille est prevue de fac,on a focaliser le Preferably, at least one lens is provided so that we focus the

faisceau laser delivre par le laser pulse. laser beam delivered by the pulse laser.

La presente invention se rapporte egalement a un dispositif comprenant un support mobile, une tete d'emission laser montee sur une base mobile et apte a graver un motif sur ladite piece, et un moyen d'encodage numerique apte a o transcrire le motif en un signal numerique utilise pour assurer la synchronisation des deplacements du support mobile et de la tete d'emission laser mobile, caracterise en ce qu'il comprend: i) un moyen d'encodage analogique apte a transformer le signal numerique en un signal analogique variable representatif de la quantite de matiere a enlever, ii) un laser pulse apse, en fonction du signal analogique qu'il re,coit, a delivrer un faisceau laser de puissance variable, repris par la The present invention also relates to a device comprising a mobile support, a laser emission head mounted on a mobile base and capable of engraving a pattern on said piece, and a digital encoding means capable of transcribing the pattern into a signal. digital used to ensure synchronization of the movements of the mobile support and of the mobile laser emission head, characterized in that it comprises: i) an analog encoding means capable of transforming the digital signal into a variable analog signal representative of the quantity of material to be removed, ii) a pulsed laser capable, depending on the analog signal it receives, of delivering a laser beam of variable power, taken up by the

tete d'emission.broadcast head.

Preferentiellement, la piece de cuir est enroulee autour diun cylindre presentant un axe de rotation, et la tete mobile d'emission laser peut se deplacer Preferably, the piece of leather is wrapped around a cylinder having an axis of rotation, and the movable head of laser emission can move

parallelement a cet axe de rotation. parallel to this axis of rotation.

s Avantageusement, le signal numerique est re,cu par un moyen de controle apte a assurer la synchronisation de la rotation du cylindre et du deplacement en translation de la tete mobile d'emission laser pulse. Cette derriere est s Advantageously, the digital signal is received by a control means capable of ensuring the synchronization of the rotation of the cylinder and of the displacement in translation of the mobile head of laser pulse emission. This behind is

avantageusement montee sur une vis d'entrarnement. advantageously mounted on a drive screw.

o Preferentiellement, un jeu de miroirs est prevu pour guider le faisceau laser o Preferably, a set of mirrors is provided to guide the laser beam

depuis la source laser jusqu'a la tete d'emission. from the laser source to the transmitting head.

Avantageusement, une lentille est prevue de fa,con a focaliser le faisceau laser Advantageously, a lens is provided so as to focus the laser beam.

delivre par le laser pulse.delivered by the laser pulse.

Avantageusement encore, le signal numerique est realise sur la base d'un mode 1 bit ou d'un mode 8 bits, le signal analogique variable est compris entre O et 10 Volts, et le laser pulse possede une puissance comprise entre O et 1500 Watts. Preferentiellement encore, le faisceau laser a puissance variable est genere a o ['aide d'un melange gazeux comprenant approximativement 5% de dioxyde de Advantageously also, the digital signal is produced on the basis of a 1-bit mode or an 8-bit mode, the variable analog signal is between O and 10 Volts, and the pulse laser has a power between O and 1500 Watts . Preferably still, the variable power laser beam is generated using a gas mixture comprising approximately 5% of dioxide

carbone et 95% d'helium et d'azote en proportions equivalentes. carbon and 95% helium and nitrogen in equivalent proportions.

L'invention sera mieux comprise a ['aide de la description detaillee qui est The invention will be better understood with the aid of the detailed description which is

exposee ci-dessous en regard du dessin annexe dans lequel: set out below with regard to the accompanying drawing in which:

La figure 1 est une representation schematique d'un dispositif selon ['invention. Figure 1 is a schematic representation of a device according to the invention.

La figure 2 est une representation schematique d'un signal numerique en mode Figure 2 is a schematic representation of a digital signal in mode

1 bit correspondent au motif a graver. 1 bit corresponds to the pattern to be engraved.

La figure 3 est une vue partielle en coupe transversale d'une piece de cuir Figure 3 is a partial cross-sectional view of a piece of leather

apres gravure selon ie mode 1 bit ou 8 bit. after engraving according to the 1 bit or 8 bit mode.

Le dispositif 1 selon ['invention, tel que represente schematiquement a la figure 1, est realise a partir d'un cylindre 2 solidaire en rotation d' un mandrin 3, une piece 4 de cuir ou simili cuir a graver enroulee, reperee et fixee, et d'une tete The device 1 according to the invention, as shown diagrammatically in FIG. 1, is produced from a cylinder 2 integral in rotation with a mandrel 3, a piece 4 of leather or imitation leather to be engraved wound, located and fixed , and a head

mobile d'emission d'un faisceau laser pulse a puissance variable. mobile emitting a variable power pulsed laser beam.

Plus precisement, le mandrin 3 est apte a tourner a vitesse sensiblement o constante autour d'un axe sous l'effet d'un premier systeme d'entranement 6 lui-meme relic a un premier encodeur 14 qui renseigne continuellement un systeme de controle 7 sur le positionnement en rotation du cylindre 2. Une source laser 8 genere un faisceau laser 20 de puissance variable qui est amene jusquia la tete 5 par l'intermediaire d'un jeu de miroirs 10. Cette tete 5 est montee sur une vis d'entranement 11 et peut se mouvoir en translation parallelement a l'axe a sous l'effet d'un second systeme d'entranement 12 lui s meme associe a un second encodeur 15 qui renseigne continuellement le systeme de controle 7 sur le positionnement de la tete d'emission 5 le long de More precisely, the mandrel 3 is able to rotate at substantially constant speed around an axis under the effect of a first drive system 6 itself connected to a first encoder 14 which continuously informs a control system 7 on the rotational positioning of the cylinder 2. A laser source 8 generates a laser beam 20 of variable power which is brought up to the head 5 by means of a set of mirrors 10. This head 5 is mounted on a screw drive 11 and can move in translation parallel to the axis a under the effect of a second drive system 12 itself associated with a second encoder 15 which continuously informs the control system 7 on the positioning of the head 5 along

la vis d'entranement 11.the drive screw 11.

Plus precisement encore, la source laser 8 comporte, d'une part, des anodes et to cathodes situees dans chacun des huit tubes (non representes) generateurs du faisceau laser 20, et d'autre part, un melange gazeux circulant a grande vitesse dans ces tubes et comprenant approximativement 5% de dioxyde de carbone et % d'un melange d'helium et d'azote en proportions equivalentes. La tete d'emission 5 est munie d'une lentille 22 permettant de focaliser le faisceau laser Even more precisely, the laser source 8 comprises, on the one hand, anodes and cathodes located in each of the eight tubes (not shown) generating the laser beam 20, and on the other hand, a gas mixture circulating at high speed in these tubes and comprising approximately 5% of carbon dioxide and% of a mixture of helium and nitrogen in equivalent proportions. The transmitting head 5 is provided with a lens 22 making it possible to focus the laser beam

20 delivre par la source laser 8.20 delivered by the laser source 8.

Prealablement a la gravore proprement cite, a ['aide d'un logiciel de traitement d'image bien connu de l'homme du metier, un motif a graver sur cette piece 4 de cuir ou simili cuir est tout d'abord scanne, puis stocke sur le disque d'un o ordinateur sous la forme d'un fichier a base de donnees numeriques, qui est assimilable a un signal numerique. Ces donnees numeriques peuvent Prior to the actual engraving, using image processing software well known to those skilled in the art, a pattern to be engraved on this piece 4 of leather or imitation leather is first scanned, then stored on a computer disc as a digital file, which can be likened to a digital signal. These digital data can

egalement etre entrees directement sans utiliser de scanner. also be entered directly without using a scanner.

Au sens de la presente demande, ce motif peut consister en un dessin selon au moins deux dimensions, par exemple longueur et largeur, et eventuellement une troisieme dimension, par exemple profondeur, qu'il faut graver, eVou en un rendu visuel faisant appel a des tons degrades se traduisant par des densites Within the meaning of the present application, this pattern can consist of a design according to at least two dimensions, for example length and width, and possibly a third dimension, for example depth, which must be engraved, eVou in a visual rendering using degraded tones resulting in densities

evolutives de zones marquees, a ['aide de la tete d'emission ou gravure 5. of marked areas, using the transmission head or engraving 5.

o Ensuite, au moyen de cartes electroniques egalement connues, ce signal numerique est. d'une part, transmis au systeme de controle 7 via une entree 13 de fa,con a synchroniser les mouvements de la tete d'emission 5 et du mandrin3, par l'intermediaire de leurs systemes d'entranement 6, 12 et de leurs encodeurs respectifs 14, 15, et d'autre part, convert) en un signal numerique 1 bit ou 8 bits selon la complexite de la gravure a realiser, et parallelement en un signal numerique generant un profil de gravure en trots dimensions. A la figure 2 est represente schbmatiquement un exemple de signal numerique en mode 1 bit correspondent a un dessin en forme de E que l'on souhaite graver sur la piece 4 de cuir. Cette derriere a ete pixelisee sous la forme d'une o matrice 16 comportant des cases 17 assimilables chacune a un point. Les cases 17 portent le chiffre 0 vent destinees a rester intactes, et par consequent, o Then, by means of electronic cards also known, this digital signal is. on the one hand, transmitted to the control system 7 via an input 13 in a way, designed to synchronize the movements of the transmission head 5 and of the mandrel 3, by means of their drive systems 6, 12 and their respective encoders 14, 15, and on the other hand, converted into a 1-bit or 8-bit digital signal depending on the complexity of the etching to be performed, and in parallel into a digital signal generating an etching profile in three-dimensional trotting. In FIG. 2 is shown schematically an example of a digital signal in 1-bit mode corresponding to an E-shaped design which it is desired to engrave on the piece 4 of leather. This back has been pixelated in the form of a matrix o comprising boxes 17 each assimilable to a point. Boxes 17 carry the number 0 intended to remain intact, and therefore,

le faisceau laser 20 devra etre eteint lorsque la tete d'emission 5 les parcourra. the laser beam 20 must be extinguished when the emitting head 5 passes through them.

En revanche, dans les cases 17 portent le chiffre 1, le faisceau laser 20 devra etre actif et delivrer une puissance adequate. Comme indique precedemment, s ce signal numerique doit done etre communique, d'une part, au systeme de controle 7 afin que la gravure soit effectuee a l'endroit desire de la piece 4 de cuir, et d'autre part, au laser pulse 8 afin que celui-ci puisse generer On the other hand, in the boxes 17 carry the number 1, the laser beam 20 must be active and deliver an adequate power. As indicated above, this digital signal must therefore be communicated, on the one hand, to the control system 7 so that the engraving is carried out at the desired location of the piece of leather, and on the other hand, to the pulse laser. 8 so that it can generate

convenablement le faisceau laser 20 a puissance variable en tous points. suitably the laser beam 20 has variable power at all points.

o Pour ce faire, le signal numerique est traduit, a ['aide de cartes electroniques connues en elles-memes, en un signal analogique compris entre O et 10 volts qui permet de couvrir toute la plage de puissance du laser pulse 8, cette plage etant avantageusement comprise entre O et 1500 Watts. Ces differents niveaux de voltage vent alors convertis en niveaux de courant par l'intermediaire de cartes de regulation de courant connues de i'homme du metier. Celles-ci pilotent les electrodes situees dans chacun des huit tubes generateurs du faisceau laser 20, et l'intensite de la decharge electrique creee entre les anodes et les cathodes ionise le melange gazeux, circulant a grande vitesse dans les tubes, sous haute tension de l'ordre de 20 000 volts. Le laser pulse 8 est ainsi so apte a generer le faisceau laser 20 de puissance variable qui autorise la reproduction extremement fine du contour, du ton ou encore de la densite optique du dessin d'origine. Ce faisceau laser 20 est finalement guide grace au jeu de miroirs 10 jusqu'a la tete d'emission 5 ou il est focalise par la lentille 22 sur la piece 4 a graver. Compte tenu de cette focalisation, le faisceau laser 20 o To do this, the digital signal is translated, using electronic cards known in themselves, into an analog signal between 0 and 10 volts which makes it possible to cover the entire power range of the laser pulse 8, this range being advantageously between 0 and 1500 Watts. These different voltage levels are then converted into current levels by means of current regulation cards known to those skilled in the art. These drive the electrodes located in each of the eight tubes generating the laser beam 20, and the intensity of the electric charge created between the anodes and the cathodes ionizes the gas mixture, circulating at high speed in the tubes, under high voltage of around 20,000 volts. The pulse laser 8 is thus able to generate the laser beam 20 of variable power which allows the extremely fine reproduction of the outline, the tone or even the optical density of the original drawing. This laser beam 20 is finally guided thanks to the set of mirrors 10 to the emission head 5 where it is focused by the lens 22 on the part 4 to be engraved. Given this focus, the laser beam 20

delivre possede en section une plus grande dimension de l'ordre de 0, 1 mm. deliver has in section a larger dimension of the order of 0.1 mm.

Parallelement a cela, et de fa,con a ce que le faisceau laser 20 ainsi genere soit applique aux endroits souhaites, le systeme de controle 7 est informe des positions instantanees du cylindre 2 et de la tete d'emission 5 par le biais de leurs encodeurs 14, 15, et ce systeme de controle 7 peut alors agir sur les systemes d'entranement 6, 12 de ces derniers. Plus precisement, la tete o d'emission 5 est translatee sur la vis d'entranement 11 jusqu'a l'endroit desire et le cylindre 2 est entrane en rotation autour de l'axe A. Compte tenu de l'impossibilite de conferer au cylindre 2 une vitesse de rotation parfaitement constante, le moyen de controle 7 reajuste regulierement la vitesse de translation de la tete d'emission 5 par rapport a la vitesse de rotation du cylindre 2. Comme indique plus specialement en figure 2, le faisceau laser 20 a puissance variable balaye alors le cylindre 2 sur son perimetre en parcourant successivement des lignes notees A, B. C et D. Les zones de la piece 4 dans laquelle une gravare doit etre effectuee peuvent o done se definir comme etant chacune un assemblage de lignes paralleles situees sur le pourtour du cylindre 2 et devant etre parcourues par le faisceau laser 20 a puissance variable. II est ainsi possible de decomposer cheque cm2 At the same time, and so that the laser beam 20 thus generated is applied to the desired locations, the control system 7 is informed of the instantaneous positions of the cylinder 2 and of the emission head 5 by means of their encoders 14, 15, and this control system 7 can then act on the drive systems 6, 12 of the latter. More precisely, the emission head 5 is translated on the drive screw 11 to the desired location and the cylinder 2 is rotated about the axis A. Given the impossibility of conferring on the cylinder 2 a perfectly constant speed of rotation, the control means 7 regularly adjusts the translation speed of the emission head 5 with respect to the speed of rotation of the cylinder 2. As indicated more particularly in FIG. 2, the laser beam 20 with variable power then sweeps cylinder 2 on its perimeter by successively traversing lines noted A, B. C and D. The zones of room 4 in which a gravare must be carried out can therefore therefore be defined as each being an assembly of lines parallel located on the periphery of the cylinder 2 and to be traversed by the laser beam 20 with variable power. It is thus possible to decompose each cm2

de ces zones en un assemblage d'environ 100 lignes paralleles. of these zones in an assembly of approximately 100 parallel lines.

11 est a noter que, la gravure s'effectuant par sublimation du materiau soumis a l'energie tres elevee du faisceau laser 20, il ne reste plus apres gravure que quelques dechets sous forme de poussieres de materisu qui vent facilement evacuees par des procedes standards. Par ailleurs, sous l'effet de ce faisceau laser 20, les parties en contact peuvent changer de teinte en fonction du type so de tannins ou du type de materieux synthetiques utilises, ce qui accentue l'effet It should be noted that, the etching being carried out by sublimation of the material subjected to the very high energy of the laser beam 20, there only remains after etching a few wastes in the form of dust of material which is easily removed by standard methods. . Furthermore, under the effect of this laser beam 20, the parts in contact can change color according to the type of tannins or the type of synthetic materials used, which accentuates the effect.

de relief du cuir ou du simili cuir grave. embossed leather or serious imitation leather.

La figure 3 est une vue partielle en coupe transversale, apres gravure selon le FIG. 3 is a partial view in cross section, after etching according to the

mode 1 bit ou 8 bit, de la piece 4 possedant une epaisseur superieure a 1 mm. 1 bit or 8 bit mode, of piece 4 having a thickness greater than 1 mm.

Apres balayage du faisceau laser 20, on constate qu'un point 18 presentant une surface de l'ordre de 0, 25 um2 est reste intact. Ce point 18 correspond a la face s superieure d'une tete de point 19, dotee d'une epaisseur e d'environ 0, 1 mm, qui est raccordee a une base 20 par l'intermediaire de talus 21. La plus petite distance d mesuree entre le point 18 et la base 20 est comprise entre 0.5 et 1.3 mm. Cette base 20 comprend les zones creusees correspondent aux cases 17 portent le chiffre 1 dans la figure 2, et dans lesquelles le faisceau laser 20 a o puissance variable a ete actif. En revanche, le point 18 correspond a une case 17 portent le chiffre 0 selon la figure 2. Sur la base du signal numerique generant le profil de gravure en trots dimensions et par modulation du nombre d'impulsions constituent le faisceau laser 20, cheque talus 21 est determine automatiquement par les cartes de regulation de courant et correspond s schematiquement a la transition entre deux cases 17 voisines portent respectivement les chiffres 1 et 0. Par ailleurs, le fait de creer un talus 21 evase, autour ou de part et d'autre de cheque tete de point 19, presente l'avantage de conferer a cette derriere une meilleure tenue mecanique au fil du temps. After scanning the laser beam 20, it can be seen that a point 18 having a surface area of the order of 0.25 μm 2 has remained intact. This point 18 corresponds to the upper face of a point head 19, with a thickness e of approximately 0.1 mm, which is connected to a base 20 by means of slope 21. The shortest distance d measured between point 18 and base 20 is between 0.5 and 1.3 mm. This base 20 includes the hollow areas corresponding to the boxes 17 bear the number 1 in FIG. 2, and in which the laser beam 20 has variable power has been active. On the other hand, point 18 corresponds to a box 17 carry the number 0 according to FIG. 2. On the basis of the digital signal generating the etching profile in three-dimensional trots and by modulating the number of pulses constitute the laser beam 20, check slope 21 is determined automatically by the current regulation cards and corresponds schematically to the transition between two neighboring boxes 17 respectively bear the numbers 1 and 0. Furthermore, the fact of creating a slope 21 flares, around or on either side another check from point 19, has the advantage of giving the latter better mechanical strength over time.

Par souci de simplification, la presente description est plus specialement basee For the sake of simplification, the present description is more specifically based

sur un procede de gravure faisant appel a un signal numerique selon le mode 1 bit. Neanmoins, dans le cas ou le motif consiste en un rendu visuel comprenant des demi-tons ou degrades, le signal numerique utilise doit etre s preferentiellement realise selon le mode 8 bits. En effet, ce dernier offre 256 combinaisons numeriques qui, apres traduction en signal analogique, donnent naissance a 256 niveaux de gris ou dbgrade. ll est alors possible, aux endroits souhaites de la piece de cuir, de faire varier tres finement la densite et/ou la on an engraving process using a digital signal according to the 1-bit mode. However, in the case where the pattern consists of a visual rendering comprising semitones or degraded, the digital signal used must preferably be produced according to the 8-bit mode. Indeed, the latter offers 256 digital combinations which, after translation into an analog signal, give rise to 256 gray levels or degraded. It is then possible, at the desired locations of the piece of leather, to vary the density and / or the density very finely.

profondeur des zones marquees par le faisceau laser 20. depth of the areas marked by the laser beam 20.

Un procede de gravore selon ['invention presente par ailleurs de nombreux autres avantages. En effet, ce procede fonctionne sans necessiter de contact avec la piece a graver, et sans necessiter d'outillage specifique a chaque A gravore process according to the invention also has many other advantages. Indeed, this process works without requiring contact with the part to be engraved, and without requiring specific tools for each

nouveau motif.new pattern.

De plus, il est possible de graver des pieces de tres grandes dimensions, jusqu'a 5 m en largeur et 1, 6 m en circonference, et cela tres rapidement. Par ailleurs, la gravure peut etre realisee a differents degree de profondeur. En effet, la pulsation modulable du laser peut se faire a de trds faibles niveaux de puissance comme a de tres forts niveaux, ceci dependent du niveau de In addition, it is possible to engrave very large pieces, up to 5 m in width and 1.6 m in circumference, and this very quickly. Furthermore, the engraving can be performed at different degrees of depth. Indeed, the modular pulsation of the laser can be done at very low power levels as at very high levels, this depends on the level of

o poissance choisi par l'operateur lors du reglage des parametres de gravure. o power chosen by the operator when adjusting the engraving parameters.

Ainsi, a de faibles puissances, le laser pulse marque simplement la piece, sans lui donner veritablement de relief. A des puissances moyennes, le creux peut atteindre 1 mm de maniere constante et ceci avec une precision de l'ordre du dixieme. Enfin, a de fortes puissances, le laser peut perforer la piece de maniere tres precise pour lui donner un aspect en dentelle. De plus, il est possible de realiser sur le meme motif plusieurs profondeurs de gravure, selon un risque de decadrage maximal de l'ordre de 0, 1 mm, en effectuant plusieurs balayages a differents niveaux de puissance. Un motif comportant une zone perforce en parfait reperage avec une zone faiblement marquee peut done etre Thus, at low powers, the laser pulse simply marks the part, without giving it real relief. At medium powers, the trough can reach 1 mm in a constant manner and this with a precision of the order of a tenth. Finally, at high powers, the laser can puncture the part very precisely to give it a lacy appearance. In addition, it is possible to carry out on the same pattern several engraving depths, according to a maximum cropping risk of the order of 0.1 mm, by carrying out several scans at different power levels. A pattern comprising a perforce zone in perfect location with a weakly marked zone can therefore be

realise.realized.

Bien que ['invention ait ete decrite en liaison avec des exemples particuliers de realisation, il est bien evident qu'elle n'y est nullement limitee et qu'elle comprend tous les equivalents techniques des moyens decrits ainsi que leurs Although the invention has been described in connection with particular examples of embodiment, it is obvious that it is in no way limited thereto and that it includes all the technical equivalents of the means described as well as their

combinaisons si celles-ci entrent dans le cadre de ['invention. combinations if these are within the scope of the invention.

Claims

REVENDICATIONS s 1.- Procede de gravure diun motif sur une piece (4) de cuir ou simili cuir fixee sur un support mobile (2), a ['aide d'une tete d'emission laser (5) montee sur une base mobile, ledit motif etant transcrit en un signal numerique utilise pour assurer la synchronisation des deplacements du support mobile et de la base mobile, caracterise en ce que, i) on transforme ce signal numerique en un signal analogique variable representatif de la quantite de matiere a enlever, ii) on transmet ce signal analogique a un laser pulse (8) apte a delivrer un faisceau laser (20) de puissance variable.CLAIMS s 1.- Method of engraving a pattern on a piece (4) of leather or imitation leather fixed on a mobile support (2), using a laser emission head (5) mounted on a mobile base , said pattern being transcribed into a digital signal used to ensure synchronization of the displacements of the mobile support and of the mobile base, characterized in that, i) this digital signal is transformed into a variable analog signal representative of the quantity of material to be removed , ii) this analog signal is transmitted to a pulse laser (8) capable of delivering a laser beam (20) of variable power.

2.- Procede de gravure selon la revendication 1, caracterise en ce que l'on enroule la piece (4) autour d'un cylindre (2) presentant un axe de rotation (), et en ce que l a tete d' em i ssi on laser (5) est a pte a se dep lacer paral lelement a cet 2.- etching method according to claim 1, characterized in that the piece (4) is wound around a cylinder (2) having an axis of rotation (), and in that the head of em i if laser (5) is able to move parallel to this

axe de rotation.rotation axis.

3.- Procede de gravure selon l'une quelconque des revendications 1 ou 2, 3.- etching method according to any one of claims 1 or 2,

caracterise en ce que le signal numerique est realise sur la base d'un mode 1 characterized in that the digital signal is produced on the basis of a mode 1

bit ou d'un mode bits.bit or bit mode.

4.- Procede de gravure selon l'une quelconque des revendications 1 a 3, 4.- etching method according to any one of claims 1 to 3,

caracterise en ce que le signal analogique variable est compris entre 0 et 10 Volts. characterized in that the variable analog signal is between 0 and 10 Volts.

5.- Procede de gravure selon l'une quelconque des revendications 1 a 4, 5.- etching method according to any one of claims 1 to 4,

o caracteri se en ce qu' a u moi ns u ne lenti l le (22) est prevue de facon a focal iser le o characteristic in that a slow motion (22) is provided so as to focus the

faisceau laser (20) delivre par le laser pulse (8). laser beam (20) delivered by the pulse laser (8).

6.- Dispositif (1) comprenant un support mobile (2) destine a recevoir une piece (4) de cuir ou simili-cuir, une tete d'emission laser (5) montee sur une base mobile et apte a graver un motif sur ladite piece, et un moyen d'encodage numerique apte a transcrire le motif en un signal numerique utilise pour assurer la synchronisation des deplacements du support mobile et de la base mobile, caracterise en ce qutil comprend: i) un moyen d'encodage analogique apte a transformer le signal numerique en un signal analogique variable representatif de la o quantite de matiere a enlever, ii) un laser pulse (8) apse, en fonction du signal analogique qu'il 6.- Device (1) comprising a mobile support (2) intended to receive a piece (4) of leather or imitation leather, a laser emission head (5) mounted on a mobile base and capable of engraving a pattern on said piece, and a digital encoding means capable of transcribing the pattern into a digital signal used to synchronize the movements of the mobile support and the mobile base, characterized in that it comprises: i) an analog encoding means suitable to transform the digital signal into a variable analog signal representative of the quantity of material to be removed, ii) a pulsed laser (8) apse, as a function of the analog signal which it

rec,oit, a delivrer un faisceau laser (20) de puissance variable. rec, oit, to deliver a laser beam (20) of variable power.

7.- Dispositif (1) selon la revendication 6, caracterise en ce que la piece (4) est s enroulee autour d'un cylindre (2) presentant un axe de rotation (), et en ce que la tete d'emission (5) du laser pulse (8) peut se deplacer parallelement a cet 7.- Device (1) according to claim 6, characterized in that the piece (4) is wound around a cylinder (2) having an axis of rotation (), and in that the transmission head ( 5) the pulse laser (8) can move parallel to this

axe de rotation.rotation axis.

8.- Dispositif (1) selon la revendication 7, caracterise en ce que le signal o numerique est re,cu par un moyen de controle (7) apte a assurer la synchronisation de la rotation du cylindre (2) et du deplacement en translation 8.- Device (1) according to claim 7, characterized in that the digital signal is received, cu by a control means (7) capable of ensuring synchronization of the rotation of the cylinder (2) and the displacement in translation

de la tete d'emission (5) du laser pulse (8). of the emission head (5) of the laser pulse (8).

9.- Dispositif (1) selon la revendication 8, caracterise en ce que la tete 9.- Device (1) according to claim 8, characterized in that the head

s d'emission (5) du laser pulse est montee sur une vis d'entranement (11). s emission (5) of the pulse laser is mounted on a drive screw (11).

10.- Dispositif (1) selon la revendication 6, caracterise en ce qu'un jeu de miroirs (10) est prevu pour guider le faisceau laser (20) depuis la source laser 10.- Device (1) according to claim 6, characterized in that a set of mirrors (10) is provided for guiding the laser beam (20) from the laser source

(8) jusqu'a la tete d'emission (5).(8) to the transmission head (5).

1 1.- Dispositif (1) selon l'une quelconque des revendications 6 a 10, caracterise 1 1.- Device (1) according to any one of claims 6 to 10, characterized

en ce que le signal numerique est realise sur la base d'un mode 1 bit ou d'un in that the digital signal is produced on the basis of a 1-bit mode or a

mode 8 bits.8-bit mode.

12.- Dispositif (1) selon l'une quelconque des revendications 6 a 11, caracterise 12.- Device (1) according to any one of claims 6 to 11, characterized

en ce que le signal analogique variable est compris entre O et 10 Volts. in that the variable analog signal is between 0 and 10 Volts.

13.- Dispositif (1) selon l'une quelconque des revendications 6 a 12, caracterise 13.- Device (1) according to any one of claims 6 to 12, characterized

en ce que le laser pulse (8) possede une puissance comprise entre 0 et 1500 Watts. in that the pulse laser (8) has a power between 0 and 1500 Watts.

14.- Dispositif (1) selon l'une quelconque des revendications 6 a 13, caracterise 14.- Device (1) according to any one of claims 6 to 13, characterized

en ce qu'au moins une lentille (22) est prevue de fa,con a focaliser le faisceau in that at least one lens (22) is provided so as to focus the beam

laser (20) delivre par le laser pulse (8). laser (20) delivered by the pulse laser (8).

15.- Dispositif (1) selon la revendication 6, caracterise en ce que le faisceau laser (20) a puissance variable est genere a ['aide d'un melange gazeux comprenant approximativement 5% de dioxyde de carbone et un melange 95% 15.- Device (1) according to claim 6, characterized in that the laser beam (20) with variable power is generated using a gas mixture comprising approximately 5% carbon dioxide and a 95% mixture

d'helium et d'azote en proportions equivalentes. of helium and nitrogen in equivalent proportions.