GB2304641A

GB2304641A - System for marking articles using radiation sources

Info

Publication number: GB2304641A
Application number: GB9618559A
Authority: GB
Inventors: Alexander Paul Sator
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-09-07
Filing date: 1996-09-05
Publication date: 1997-03-26
Anticipated expiration: 2016-09-05
Also published as: DE19633510A1; GB9618559D0; DE29514319U1; GB2304641B

Description

SYSTEM FOR MARKING ARTICLES The invention refers to a system for marking printed or non-printed articles, in particular of glass, plastics, metal, paper, cardboard or the like.

In the manufacture of articles and their processing it is frequently necessary to mark the articles for identification purposes, e.g. to mark batches or the like. For example, such necessity occurs in connection with bottles which are filled with liquid or solid products, e.g. with beverages, or with products which are filled in packages, blister packings or the like, e.g. pharmaceuticals or the like. Similar situations can be encountered in connection with food products which are to be provided with a date for keeping quality. Above all, both food products or other products are concerned with an obligation to be marked whereby they can be satisfactorily identified after leaving the production facilities.

It is known to mark articles of glass by means of a TEA CO2 pulse laser by using a mask.

Instead of a pulse laser a continuous-operation laser can be used working in accordance with the vector method. Both methods are expensive and subject to distortions. Both methods require a relatively efficient laser.

TEA pulse lasers are used for a product marking where high production rates are encountered. Besides the high maintenance costs the TEA laser has the disadvantage that for each individual set of markings a separate mask is to be used. Therefore, such a marking system can be considered only if there is no alternative. Marking lasers which work with the vector method above all are used where the quality of the marking must be high, e.g. for the marking of keyboards, larger semi-conductor components and general information markings where the production rate is relatively low and a marking efficiency of a dozen signs per second is regarded as sufficient. Therefore, vector lasers are normally not used for the marking of products.

If in addition the marking has to be changed from article to article or for smaller batches, there is no possibility up to now to mark the products safely, unambiguously and unchangeably as the change of masks between individual marking steps is too time-consuming. Furthermore, the vector laser does not reach the necessary speed.

It is further known to print materials by means of an inkjet printer. Such a printer theoretically is in a position to change the marking in accordance with the production cycle. The disadvantages of conventional lasers are not existing with ink-jet printers. However, it is to be considered that the ink is a consumed material which is expensive and difficult to handle. In many cases it is additionally toxic. In the food production industry the ink undergoes specific handling provisions. For these circumstances the essential advantages of the laser marking method cannot be utilized: No secondary costs for consumed materials, no contamination of the articles to be marked with toxic materials. Under specific circumstances the marking of glass by ink by an ink-jet printer is possible or necessary, respectively (with the change of the typesetting in response to the production cycle), however, the marking results are fundamentally not resistant against abrasive wear. Finally, the maintenance costs for industrial ink-jet printers are considerable.

The prior art predominantly is discussed above in connection with articles of glass, e.g. glass bottles. However, it is understood that the same is valid for articles of metal, plastics, paper, cardboard or the like.

An object of the invention is to provide a system for the marking of articles which causes a small expense for its components and its operation which is not subject to distortions and combines the advantages of the laser applications with ink-jet printing.

With the ink jet printer the signs brought onto an article to be marked, e.g. letters, figures or the like are formed of dots which are part of a matrix consisting of dot lines and dot columns. In one system of the invention1 a plurality of controllable radiation sources is provided cyclically controlled by suitable control means. The radiation is suited to interact with the material of the article to be marked. For example, the colour of the article may change, a general evaporation of the material may occur or an ablation or a similar effect. By means of the system according to the invention an upper layer of colour of an article may be eroded dot by dot without affecting the colour layer thereunder. By this effect a contrast can be received between the lower layer of the material with the upper coloured layer.

According to an embodiment of the invention a laser is preferred as radiation source, preferably a solid-state laser using a diode laser as pump engergy source or a similar laser system which does not use consumption type material.

The system according to the invention further includes an optical means which generates a dot beam from each radiation of a radiation source. In the most simple case the beam of a laser is used, with one or a plurality of dot beams being deflected in a single plane which is perpendicular to the feed direction of the articles. In this case, the number of laser sources or of dot beams, respectively, corresponds to the number of dots in the column of the matrix.

The marking with the system according to the invention, thus, takes place by the Dot-Matrix-method. The object to be marked is moved in a horizontal plane with a speed to be determined or predetermined in the marking plane. By a corresponding pulse control of the radiation sources in response to the horizontal speed of the articles and the desired point or dot density a matrix can be generated by the radiation sources including a predetermined number of columns and lines. As mentioned, the magnitude of a matrix in the vertical plane, i.e. in the plane of the dot beams, is determined by the number of dot beams and the space of the dot beams on the article to be marked while the magni tude in the horizontal plane solely depends upon the de sired dot density and the maximum pulse rate of the laser.

It is also conceivable to split the radiation of for example only one radiation source by means of a beam splitter into a plurality of beams. The originating individual beams are separately modulated by corresponding means. Optically, these beams can be regarded as coming from individual radiation sources and can be used as described above.

In another system, a single radiation source is provided, e.g. a laser which can be cyclicly controlled by suitable control means. Also the radiation of this laser can be brought into interaction with the material of the article to be marked so that a change of the texture of the material is achieved which can be optically recognized as explained above. An optical arrangement generates a dot beam of the radiation of the radiation source. By means of a beam splitter a plurality of dot beams can be generated. The dot beam is directed to a deflection means which deflects the dot beam in a plane which extends perpendicular to the feed direction of the articles. The dot beam is deflected step by step or continuously such that the dots generated on the surface of the article have a distance from each other corresponding to the dot distance of the column of a matrix.

Also with this system according to the invention the marking in the marking plane takes place by the Dot-Matrix method. The object to be marked is fed in a horizontal plane with a speed measured or defined. By controlling the radiation source by a corresponding pulse rate which is a result of a relation between the horizontal speed and the desired dot density a matrix can be generated consisting of LxN dots. The matrix magnitude L (vertical plane) is determined by the beams pulsed and selected and separated by the deflection means. The magnitude N (horizontal plane) is solely determined by the desired dot density. The maximum number of dots per second in the marking is determined by the maximum pulse rate of the radiation source.

In the present case the pulse density is not larger than 300 dpi.

According to an embodiment of the invention a focusing means can be provided to focus the dot beams. The intensity of the radiation in the marking plane, thus, is considerably improved. Normally a more favourable effect on the material is achieved.

According to an embodiment of the first system, the dot beams of the radiation source can be directed to a segmented collection mirror which has in a vertical plane at least as many mirror surfaces as the matrix has column dots, with the mirror surfaces aligning the dot beams in a single plane, occasionally with a predetermined angle relative to each other. The collection mirror serves for the alignment of the individual beams in the vertical axis and for the alignment of the beams relative to each other if they are to have a predetermined angle relative to each other (angle offset). The angle offset determines the desired magnitude of the marking. Also for this system preferably a lens or the like is provided in order to achieve a focusing on the marking plane. It increases the intensity of the radiation in the marking plane.

For the second-mentioned system, a suitable deflection means is to be provided. This can for example include a deflection mirror which is actuated by a galvanometer.

Alternatively, a rotatingly driven polygon mirror is provided as deflection mirror. Finally, an acousto-optic deflector can be used.

With the systems according to the invention materials can be marked without consuming resources. The system according to the invention is flexible, generates markings which are non-toxic, unadulteratable and can be realized with simple technical means.

Embodiment examples of the invention are subsequently described along accompanying drawings.

Fig. 1 shows diagrammatically a system according to the invention.

Fig. 2 shows the generation of a letter by a system of Fig. 1.

Fig. 3 shows diagrammatically a possible embodiment of the system of Fig. 1.

Fig. 4 is a perspective view of enlarged details of the system of Fig. 3.

Fig. 5 shows diagrammatically another embodiment of the system of Fig. 1.

Fig. 6 shows a detail of the system of Fig. 5.

Fig. 7 shows another detail of the system of Fig. 5.

Fig. 8 is a perspective view of details of the system of Fig. 5.

In Fig. 1 a laser device 2 is diagrammatically illustrated. Details thereof are explained below. The device 2 is associated with a conveyor belt 4 which moves in the direction of the arrow with a predetermined speed v. Individual bottles 6 are placed on the belt and are to be marked by means of the laser device 2. The bottles 6 for example are made of plastics or glass. In the present case the bottles are to be marked with the letter H. A control device 8 controls the laser device 2, with the control de vice 8 receiving a signal from a speed measuring device 9 which measures the speed v of conveyor belt 4.

The marking of the bottles 6 is carried out along the Dot-Matrix method. The laser device 2 either generates a single dot beam which is deflected in a plane perpendicular to the feed direction of belt 4 by deflection means not shown. Alternatively, a corresponding number of individual dot beam lasers can be provided each generating a dot beam, with the dot beams lying in a plane extending perpendicular to the feed direction of conveyor belt 4. In the example of Fig. 2 it is taken that for example seven individual dot beams lie in a plane. Alternatively, a single laser may generate seven dots one after the other by means of the deflection means. This is for instance the case if the left column of the H is to be generated. After the left column of the H is generated, a predetermined time has expired, and the conveyor belt 4 has moved the corresponding bottle a predetermined distance. After this pulse time which results from the speed of the conveyor belt and the desired space of the dots, the transverse line of the H is generated, with only in position 4 dots being generated with a pulse width corresponding to the space between individual columns of the matrix until the right column of the H is reached which now is generated by all dots of the column which can be achieved. For the ge neration of the dots 1 to 7 of a column for instance 100 A sec. per dot, i.e. 700 S sec. per column are necessary if an individually deflectable dot beam is used.

It is understood that the bottle is marked at that moment when it has a predetermined position relative to the laser device 2. This can be obtained for example by an optical path (not shown). Alternatively, an incremental generator can be used, e.g. a shaft-encoder which determines the position of the conveyor belt 4.

As mentioned, the laser device 2 may include a number of individual dot lasers. Such a number of dot lasers, namely eight, is illustrated in Fig. 3. They are provided with the reference number 12. The switching on and off of the individual lasers 12 by the desired pulse rate takes place through the control device 11 and the control means 13 for the laser. If for example all lasers 8 are switched on a matrix column of eight dots is generated so that on bottle 6 a column of eight dots is generated, e.g. by material ablation or the like. During the next switching cycle only those lasers 12 are switched on which are necessary for the generation of the sign, e.g. only one as illustrated in Fig. 2, if only one point or dot is to be generated.

In Fig. 4 the arrangement 10 of eight lasers 12 is such that in the upper row three lasers are located side-byside, while in the medium row two lasers are provided and in the lower row three lasers again. The lasers are solidstate lasers of the type known, with the pump sources being formed by diode lasers. Each laser 12 generates a dot beam 14 directed to a reflecting mirror 16. Tkc beam 18 coming from the reflecting mirrors impinges a collection mirror 20. In a vertical plane the collection mirror 20 includes eight mirror surfaces in the form of mirror segments (not shown) which align the beams coming from the reflection mirrors in a vertical plane. The eight dot beams 22 lying in a plane may have an angle with respect to the center axis of more or less magnitude. The dot beams are directed to a lens 24 which focuses the beams on a vertical plane. The focused beams are directed to a marking plane 26, e.g. the surface of a glass container, e.g. the bottle 6 of Fig. 3.

The marking method with the system of Fig. 1 is as follows.

The marking takes place along the Dot-Matrix method. The object to be marked is moved in a horizontal plane, i.e. perpendicular to the plane of beams 22 with a defined speed or a speed to be measured. By a corresponding control of the pulse rate of the individual lasers which is a result of the relation between the horizontal speed v and the desired dot density in the horizontal plane a matrix of LxN dots is generated (with L being the number of columns and N the number of lines) (Fig. 2). The matrix magnitude L (vertical plane) is determined by the number of beams in the vertical plane which in case of Fig. 4 is eight. The magnitude N (horizontal plane) is determined by the desired dot density and the maximum pulse rate of the lasers 12.

It is also possible to reduce the number of lasers 12 and to split the laser beams by means of beam splitters into a plurality of beams (not shown). These beams are aligned in a vertical plane through a mirror. By a corresponding control of suitable modulators (not shown) each dot beam can be activated or deactivated in a vertical plane. Such modulators are known and for example can be controlled by acoustic waves.

In the embodiment of Figs. 5 and 8 a single laser 30 is provided which generates a dot beam 32 which is directed to a reflection mirror 34. The reflection mirror 34 reflects the beam to a deflection mirror 36 actuated by a galvanometer 38. Through the actuation of the deflection mirror 36 the sequential generation of seven dot beams 40 e.g. in a vertical plane takes place which are directed to a lens 42 which focuses the beams in the direction of the marking plane 44 of the article 46 to be marked. The control device 48 controls the pulse rate of laser 30 and the cycles of mirror 36.

The marking method with the system of Figs. 5 and 8 is as follows. It takes place along the Dot-Matrix method. The object to be marked, e.g. article 46, is moved in a horizontal plane with a predetermined speed through the mar king plane. By a corresponding pulse control of laser 30 with the rate of the pulses resulting from the relation between the horizontal speed of the article and the desired dot density the matrix of LxN dots is generated. The matrix magnitude L (vertical plane) is determined by the pulse-controlled and selected beams which are separated by deflection mirror 36. The magnitude N (horizontal plane) is solely determined by the desired dot density (see also Fig. 2). The maximum number of dots per second is determined by the maximum pulse rate of the radiation source.

Two examples are indicated by their essential data: (a) Magnitude of the desired Marking: 7x5 points/3 mmx2 mm Number of Signs per Second: 1000 signs/sec.

Necessary Pulse Rate of 7x5x1000 = 35 kHz the Laser: pulse rate Deflection Frequency of 5 kHz with unidirec Deflection Unit 36: tional operation (b) Magnitude of the desired Marking: 24.10 points/6 mm.4 mm Number of Signs per Second: 500 signs/sec.

Necessary Pulse Rate of the Laser: 24x10x5000 = 1.2 MHz Deflexion Frequency of 50 kHz with unidirec the Deflexion Unit: tional operation The marking takes place by interaction of the radiation with the material. Depending on the material and the intensity of the radiation a change of the colour of the material, an ablation or an evaporation of the material or a similar effect takes place. In any case, a change of the material takes place, e.g. of the texture without the use of a consumption resource as for instance ink or toner as used with conventional marking methods.

Instead of a normal deflection mirror 36 a polygon mirror 50 can be used which is rotated by suitable means cyclically. The beam 32 is then deflected in a plane for the generation of the individual dots as described. Finally, an electro-optic or acousto-optic deflection cell 52 can be provided which is controlled by an energy wave, with the deflection of beam 32 normally depending upon the amplitude of the engergy wave. Such acoustic-optic or electro-optic deflection means are known.

The above used term thermo-sensitive means an effect of the molecules of for example paper, e.g. by ionization by which a deposition of consumption resources, e.g. toner, on the radiated dot is enabled. Such a method is not used with the invention. In the method according to the invention the laser beams immediately cause a change of the material to be radiated which for example is to be recognized by optical means.

Claims

CLAIMS 1. A system for marking articles, particularly articles of glass, metal, plastics, paper, cardboard or other not necessarily thermo-sensitive material, comprising: either a single controllable radiation source or a plurality of controllable radiation sources; control means generating timing pulses for the activation and deactivation of said radiation source(s); the radiation of said source(s) being such that it interacts with the material of said articles and without consuming any additional resources causes a change of the texture of the material of said articles by a thermal or other energetic effect (ablation); optical means, forming dot beam(s) of the radiation of said source(s); either deflection means for stepwisely deflecting said dot beam from a single radiation source in response to timing pulses in a plane, with said timing pulses corresponding to the timing pulses of said control means and the length of one deflection step corresponding to the dot spaces of a column of a matrix, or said dot beams from a plurality of radiation sources being arranged in a plane and being spaced from each other when impinging on an article such that the spaces correspond to the spaces between the dots of a column of a matrix; and feed means which move the articles consecutively through the system with a given speed in a direction perpendicular to said plane of said dot beam(s), with said control means controlling said radiation source(s) during the feeding of said articles such that signs or symbols are generated on said articles which are formed of individual dots of said matrix consisting of dot columns and dot lines.
2. The system of claim 1, wherein the or each radiation source is formed by a laser.
3. The system of claim 2, wherein a solid-state laser is used with a diode laser as pumping source.
4. The system of any preceding claim, wherein a plurality of said dot beams originate from a single real radiation source and are formed by beam splitting.
5. The system of any one of claims 1 to 4, wherein there are a plurality of said dot beams and an optical means is provided focusing said dot beams on the articles to be marked.
6. The system of any one of claims 1 to 4, wherein there are a plurality of said dot beams and said dot beams are directed to a segmented collection mirror having in a vertical plane at least as many mirror surfaces as the matrix has column dots, said mirror surfaces aligning said dot beams in a plane optionally with an angle relative to each other.
7. The system of claim 6, wherein said dot beams are directed to the collection mirror through respective reflection mirrors.
8. The system of claim 6 or claim 7, wherein a collection lens is located downstream of said collection mirror.
9. The system of any one of claims 1 to 3, wherein there is a single said dot beam and a deflection mirror is provided actuated by a galvanometer.
10. The system of any one of claims 1 to 3, wherein there is a single said dot beam and a rotatingly driven polygon mirror is provided as a deflection mirror.
11. The system of any one of claims 1 to 3, wherein there is a single said dot beam and an acoustic-optic deflection cell is provided.
12. A system for marking articles substantially as hereinbefore described with reference to Figures 1 to 4, Figures 5 and 8, or Figure 5 as modified by either Figure 6 or Figure 7 of the accompanying drawings.

12. The system of any preceding claim, wherein speed measuring means are provided for measuring the feeding speed of the articles, the pulse rate of the control means determining space between adjacent matrix columns depending upon the feeding speed.

13. A system for marking articles substantially as hereinbefore described with reference to Figures 1 to 4, Figures 5 and 8, or Figure 5 as modified by either Figure 6 or Figure 7 of the accompanying drawings.

Amendments to the claims have been filed as follows 1. A system for marking movable articles which are moved along a first direction, particularly articles of glass, metal, plastics, paper, cardboard or other not necessarily thermo-sensitive material, comprising: feed means for moving the articles consecutively through the system in the first direction; speed measuring means for measuring the speed of the articles in the first direction and generating a speed signal; either a single controllable radiation source or a plurality of controllable radiation sources; control means receiving the speed signal and generating timing pulses for the activation and deactivation of said radiation source(s); the radiation of said source(s) being such that it interacts with the material of said articles and without consuming any additional resources causes a change of the texture of the material of said articles by a thermal or other energetic effect (ablation); optical means, forming dot beam(s) of the radiation of said source(s); either deflection means for stepwisely deflecting said dot beam from a single radiation source in response to timing pulses in a plane perpendicular to the first direction, with said timing pulses corresponding to the timing pulses of said control means and the length of one deflection step corresponding to the dot spaces of a column of a matrix, or said dot beams from a plurality of radiation sources being arranged in a plane perpendicular to the first direction and being spaced from each other when impinging on an article such that the spaces correspond to the spaces between the dots of a column of a matrix; and said control means controlling said radiation source(s) during the feeding of said articles and in response to the speed signal such that signs or symbols are generated on said articles which are formed of individual dots of said matrix consisting of dot columns and dot lines, the pulse time between the dots of the dot lines depending upon the speed of the articles.

2. The system of claim 1, wherein the or each radiation source is formed by a laser.

3. The system of claim 2, wherein a solid-state laser is used with a diode laser as pumping source.

4. The system of any preceding claim, wherein a plurality of said dot beams originate from a single real radiation source and are formed by beam splitting.

5. The system of any one of claims 1 to 4, wherein there are a plurality of said dot beams and an optical means is provided focusing said dot beams on the articles to be marked.

6. The system of any one of claims 1 to 4, wherein there are a plurality of said dot beams and said dot beams are directed to a segmented collection mirror having in a vertical plane at least as many mirror surfaces as the matrix has column dots, said mirror surfaces aligning said dot beams in a plane optionally with an angle relative to each other.

7. The system of claim 6, wherein said dot beams are directed to the collection mirror through respective reflection mirrors.

8. The system of claim 6 or claim 7, wherein a collection lens is located downstream of said collection mirror.

9. The system of any one of claims 1 to 3, wherein there is a single said dot beam and a deflection mirror is provided actuated by a galvanometer.

10. The system of any one of claims 1 to 3, wherein there is a single said dot beam and a rotatingly driven polygon mirror is provided as a deflection mirror.

11. The system of any one of claims 1 to 3, wherein there is a single said dot beam and an acoustic-optic deflection cell is provided.