EP2131992A1

EP2131992A1 - An apparatus for laser-processing of a packaging material web

Info

Publication number: EP2131992A1
Application number: EP07835075A
Authority: EP
Inventors: Gabor Benkö
Original assignee: Tetra Laval Holdings and Finance SA
Current assignee: Tetra Laval Holdings and Finance SA
Priority date: 2007-01-16
Filing date: 2007-10-03
Publication date: 2009-12-16
Also published as: SE530592C2; SE0700074L; CN101583458B; CN101583458A; BRPI0719401A2; EP2131992A4; WO2008088246A1

Abstract

An apparatus (201) for processing a moving web (200) of packaging material by means of a laser beam (202) in particular for cutting, etching or perforating the web (200) for forming an opening-facilitating tear perforation or prepared pouring holes in the web (200). The apparatus (201) includes an evacuation box (205) provided with inlet (212) and outlet (213) with an evacuation chamber (206) defined by the inner walls of the evacuation box (205). The evacuation chamber (206) is preferably tubular with its longitudinal axis oriented parallel with the direction of movement of the web (200) and has a first opening (209) for the incoming laser beam (202) and a second opening (210) through which the incoming laser beam (202), after passage through the chamber (206), may pass for processing of the web (200). Preferably, the first opening (209) for the incoming laser beam (202) is sealed by a laser-permeable window (209a) which may constitute a part of the evacuation box (205).

Description

An apparatus for laser-processing of a packaging material web

Technical field

The present invention relates to an apparatus for processing a web of packaging material by means of a laser beam, the apparatus comprising a laser head in communication with a laser source for generating a laser beam, as well as one or more optical control means for controlling the generated laser beam. The present invention in particular relates to such an apparatus for perforating, etching or cutting optional geometric patterns in a web of packaging material.

Background art

Packaging containers for liquid foods, e.g. milk and juice, are normally provided with an opening device or arrangement by means of which the packaging container may readily be opened when it is to be emptied of its contents. In its simplest form, an opening arrangement may be a linear perforation or a slit or cut solid line along which the packaging material is partially penetrated in order easily to be able to be torn or pulled off for exposing an emptying aperture through which the contents of the packaging container may be poured out. Another type of prior art opening arrangement has a pouring hole prepared in the planar top or upper region of the packaging container, the hole being closed by a so-called pull tab applied separately on the outside of the container and whose removal exposes the pouring hole when the packaging container is to be emptied. In yet a further prior art example, the pouring hole is closed by means of an opening arrangement of screw cap type which has a screw neck fixedly disposed on the outside of the container with external threading in mesh with a threaded screw cap.

Perforation lines which facilitate opening, as well as pouring holes themselves have traditionally been produced with the aid of mechanical punching and perforation tools which act on at least one side of a moving web of packaging material. According as laser technology has advanced, recent time has seen the steady transition towards a replacement of the mechanical punching and perforation techniques by laser technique which is a both quicker, safer and more accurate processing technique than the traditional mechanical technique. Laser technique moreover makes possible a gentler processing of the packaging material web with results which are vastly superior in terms of quality in comparison with the mechanical technique, since it does not subject the web to excessive compression forces during the processing operation. EP 0 357 841 describes a laser method for producing perforation lines and preparing pouring holes in register with a recurring printed pattern on a web of packaging material. According to EP 0 357 841, linear perforations are produced in the packaging material web by means of a moving laser beam which, with high precision, is guided along the printed pattern with the aid of optical control means, for example mirrors and lenses, for burning away packaging material in optional linear and hollow configurations.

EP 0 853 524 describes a similar laser method according to which linear perforations and preparatory pouring holes are produced in register with a recurring pattern of fold-facilitating lines (crease lines) on a web of packaging material. According to EP 0 853 524, the movable laser beam is guided along the creased pattern by means of optical control means, e.g. mirrors and lenses, in order, in a corresponding manner, to burn off packaging material in desired linear and hole configurations.

As a result of the processing of the packaging material web by the laser beam, confetti is formed, small particles and dust as well as flue gases which tend to adhere to and accompany the web in the form of impurities unless they are immediately removed from the processing region. To this end, it is known in the art to employ one or more separately provided evacuation devices, normally suction nozzles, in immediate association with the working area of the laser beam. One drawback inherent in such suction devices is that they are rapidly fouled and clogged by formed particles and dust and, as a result, require frequent operational stoppages for cleaning or replacement. Since every such cleaning operation must be carried out manually with a large labour input and considerable time consumption, every operational stoppage because of cleaning thus implies a correspondingly large production loss with a deterioration in economy and efficiency as a result. Objects of the invention

One object of the present invention is therefore to obviate the above- described drawbacks inherent in the prior art technology.

Another object of the present invention is to realise an apparatus by means of which a web of packaging material may be processed by means of a laser beam without operation needing to be stopped unnecessarily for purposes of cleaning.

Yet a further object of the present invention is to realise an apparatus for perforating, etching or cutting by means of a laser beam a packaging material web for the formation of a repeated pattern of linear perforations or prepared pouring holes, without unnecessary production loss with a deterioration in economy and poorer efficiency as a result of excessively lengthy operational stoppages for purposes of cleaning.

These and other objects will be attained according to the present invention by means of an apparatus of the type described by way of introduction which has been given the characterising features as set forth in appended Claim 1.

Expedient embodiments of the apparatus according to the present invention have further been given the characterising features as set forth in the appended subclaims.

Brief summary of the invention

According to the present invention, there will thus be realised an apparatus for processing a web of packaging material by means of a laser beam, the apparatus having a laser head in communication with a laser source for emitting a laser beam, as well as one or more optical control means for controlling the emitted laser beam during the processing. The apparatus is characterised in that it displays, between the laser head and the web, an evacuation box provided with inlet and outlet openings and with an evacuation chamber defined by the inner walls of the evacuation box, the chamber having a window facing towards the laser head, through which window the emitted laser beam may pass, and an opening facing towards the web through which the laser beam may pass for processing the web, and that the evacuation box is removably mounted in a bracket. Thanks to the removable mounting of the evacuation box in the bracket, this may rapidly and readily be removed from the bracket and be replaced by a new, on every occasion when it is time to clean the evacuation chamber without needing to stop operations for longer time than is needed for replacing the evacuation box. The removed, fouled evacuation box may thus be cleaned while the new evacuation box is in place in the bracket for continued operation. Since the actual replacement of evacuation box takes place rapidly, the time for the associated operational stoppage may thus be reduced to a minimum, whereby processing of a web using an apparatus according to the present invention may be carried out practically continuously, i.e. with in practice negligible downtime because of replacement and cleaning of an evacuation box.

In order to facilitate insertion and removal of the evacuation box on cleaning, the box may be provided with one or more handles or similar gripping devices with the aid of which the evacuation box can readily be slid into and pulled out of the bracket.

The opening of the evacuation box facing towards the packaging material web may have any optional geometric opening configuration, but is preferably dimensioned and configurated in response to the pattern which the laser beam is to cut, perforate or etch on the web. For example, when the laser beam is to perforate the web along a substantially straight line, i.e. spotwise burn wholly or partly through-going holes in the web, the evacuation box preferably displays a corresponding small opening configuration in order to reduce the risk that smoke, dust and similar fine particles adhere to and foul the web. In cases where the laser beam is to perforate the web along an arcuate line, it may for the same reasons be suitable to impart to the opening of the evacuation box an ellipsoidal configuration with the major axis of the ellipsoidal opening coinciding with the path of movement of the working laser beam on the web.

Correspondingly, the opening of the evacuation box facing towards the web displays an elongate slot-shaped opening configuration with a length dimension in the direction of movement of the web which is considerably greater than its width dimension in cases where the moving laser beam is to cut out the confetti from the web for the formation of holes preparing for emptying. As a result of the relatively large length dimension of the slot-shaped opening configuration in the direction of movement of the web, the laser beam is thereby afforded the possibility of operating on the web along a longer working area. No matter whether the opening configuration of the evacuation box towards the moving web is small, ellipsoidal or slot-shaped, it is advantageous to position the evacuation box so that the minimum distance between the evacuation box and the web is as slight as possible, but still sufficiently great to avoid direct contact between

_* the evacuation box and the web. The smaller this distance is, the smaller will also be the risk that gases, dust and similar small particles adhere on and foul the web.

The inner cavity or chamber of the evacuation box between said inlet and outlet openings is preferably cylindrical or tubular with the longitudinal axis of the tubular evacuation chamber parallel, or substantially parallel, with the direction of movement of the web in order to realise a laminar flow of fluid, e.g. air, through the evacuation chamber, whereby the proportion of removed impurities from the evacuation chamber can be increased.

Even though a through flow of fluid through the tubular evacuation chamber effectively entrains and removes a considerable quantity of pollutants, such as confetti, small material particles, dust and gases, the quantity of impurities remaining will in time progressively accumulate on the inner walls of the evacuation chamber.

In order to protect the laser head and also other optical equipment such as lenses and mirrors which are employed for controlling the laser beam from impurities, the opening of the evacuation chamber towards the laser head is preferably sealed by a window which prevents impurities from escaping from the evacuation chamber through this opening and coming into contact with the laser head.

The window is preferably a part of the evacuation box so that this may also be removed together with the evacuation box for cleaning in the same cleaning operation as the evacuation chamber. As a result of the arrangement of evacuation box and window in one and the same unit, it is thus possible to shorten even further the unavoidable downtime in connection with cleaning. Further advantages, characterising features and details of the present invention will be described in greater detail hereinbelow, with reference to the accompanying Drawings.

Brief description of the accompanying Drawings

Fig. 1 schematically shows a method of processing a moving web of packaging material by means of a laser beam in accordance with prior art technology;

Fig. 2 schematically illustrates a method of processing a moving web of packaging material by means of a laser beam using an apparatus according to a first embodiment of the present invention; and

Fig. 3 schematically illustrates a method of processing a moving web of packaging material by means of a laser beam using an apparatus according to a second embodiment of the present invention.

Detailed description of the accompanying Drawings and preferred embodiment

Thus, Fig. 1 schematically illustrates a prior art method of processing a moving web 100 of packaging material by means of a laser beam. The packaging material web 100 is unwound from a magazine reel (not shown) and led in the direction of the solid arrows by the intermediary of a bending roller 101 to a processing station at A where the laser processing of the web 100 takes place. In the illustrated example, it is assumed that the web 100 is, through this laser processing, provided with an opening-facilitating tear perforation along a substantially straight line along which packaging material is spotwise burnt off by means of a laser beam 102 directed towards the web by suitable optical equipment (not shown), for the formation of wholly or partly through-going holes in the web 100.

From the processing station A, the thus laser processed web 100 is thereafter led further by the intermediary of a bending roller 103 for rolling up or further processing and handling. In order to remove gases, dust and small particles (schematically illustrated by ghosted lines directed away from the web in the figure) which are formed in the immediate proximity of the web 100 when the laser beam 102 burns off material from the web 100, there are disposed one or more suction devices which each have their respective suction nozzles (schematically illustrated by means of two block arrows in the figure) placed close to the working area of the laser beam 102 on the web 100. One drawback inherent in such suction devices is, as has already been mentioned, that they are rapidly fouled and clogged by particles, dust and similar impurities and, as a result, require frequent operational stoppage for cleaning or replacement, before operation can be restarted once again. Since each suction device must be cleaned separately, the entire cleaning operation moreover requires both a major working input and considerable consumption of time during which operation must be kept still with the unavoidable consequence of a correspondingly great production loss and deterioration in output economy.

Fig. 2 schematically illustrates a method for corresponding laser processing of a web 200 of packaging material employing an apparatus according to the present invention carrying the generic reference numeral 201. In the same manner as previously, it is also assumed in this case that the web 200 is, as a result of the laser processing, provided with an opening-facilitating, creased, slotted or perforated indication of weakening along a substantially straight line along which packaging material is spotwise burnt off by means of a laser beam 202 directed towards to the web by suitable optical equipment (not shown), for the formation of wholly or partly through-going holes in the web 200.

The web 200 is unwound from a magazine reel ( not shown) of packaging material and led, in the direction of the solid arrows, by the intermediary of a bending roller 203 to a processing station at B where the laser processing of the web 200 employing the apparatus 201 according to the present invention takes place.

The apparatus 201 is positioned between the web 200 and a laser head 204 from which the controlled laser beam 202 is emitted, and comprises a box-shaped evacuation box 205 with an inner tubular cavity or chamber 206. The longitudinal axis of the tubular evacuation chamber 206 is substantially parallel with the direction of movement of the web 200 and displays, at its ends, an inlet and outlet opening 207 and 208, respectively, for the through-flow of fluid, e.g. air, through the chamber 206. The evacuation chamber 206 further has an opening 209 turned to face towards the laser head 204 and through which the laser beam 202 may pass, as well as an opening 210 turned to face towards the web 200 and through which the laser beam 202 may pass for processing of the web 200.

According to the invention, the evacuation box 205 is removably mounted in a bracket 211 similarly disposed between the laser head 204 and the web 200 and having, at its ends, an inlet 212 and an outlet 213 in fluid communication with a corresponding inlet opening 207 and outlet opening 208 of the evacuation chamber

206 for the through- flow of fluid, e.g. air.

In order to reduce the risk that dust, small particles and gases which are formed when the laser beam 202 processes the web 200, adheres on and fouls the processed web 200, the opening 210 in the evacuation box 205 facing towards the web 200 has only a very small hole configuration, at the same time as the distance between the evacuation box 205 and the web 200 along the entire length of the evacuation box 205 is very short, but nevertheless large enough to avoid direct contact between the evacuation box 205 and the passing web 200.

Preferably, the evacuation box 205 is provided with a handle or similar gripping device (not shown) with the aid of which the evacuation box 205 may readily be slid into and pulled out of the bracket 211 when it is time to replace a used evacuation box 205 with a new or cleaned evacuation box. From the processing station B, the thus laser processed web 200 is led further by the intermediary of a bending roller 214 for winding up or further processing and handling.

When it is time to clean the tubular evacuation chamber 206 from impurities and pollutants which have accumulated on the inner walls of the evacuation chamber 206 during the laser processing, operation is stopped only briefly while the fouled evacuation box 205, including the window 209 provided as a part of the evacuation box 205 is released and pulled out from the bracket 211 and replaced by a new evacuation box 205 which is readily slid into position in the bracket 211.

Fig. 3 schematically illustrates a method of laser processing a web 300 of packaging material employing an apparatus according to a second embodiment of the present invention which has been given the generic reference numeral 301. In this example, it is assumed that the web 300 is instead to be provided with emptying- preparatory holes of the desired size, geometric configuration and positioning and that the corresponding confetti of packaging material is thus to be cut or burnt off from the web 300 by means of a laser beam 302 directed towards the web, for the formation of said wholly or partly through-going pouring holes in the web 300. The web 300 is unwound from a magazine reel (not shown) of packaging material and led in the direction of the solid arrows by the intermediary of a bending roller 303 to a processing station at C where the laser processing of the web 300 employing the apparatus 301 according to the invention takes place.

Like the apparatus 201 in Fig. 2, the apparatus 301 is positioned between the web 300 and a laser head 304 from which the controlled laser beam 302 is emitted and guided by optical control equipment (not shown), and includes a box-shaped evacuation box 305 with a tubular chamber 306 defined by the inner walls of the evacuation box 305. The longitudinal axis of the tubular evacuation chamber 306 is substantially parallel with the direction of movement of the web 300 and displays, at its opposing ends, an inlet- and outlet opening 307 and 308, respectively, for the through-flow of fluid, e.g. air, through the evacuation chamber 306. The evacuation chamber 306 further has a window 309 turned to face towards the laser head 304 and through which the laser beam 302 may pass, as well as an opening 310 turned to face towards the web 300 and through which the laser beam 302 after passage through the evacuation chamber 306 may pass for processing of the web 300.

As is clearly apparent from Fig. 3, the opening 310 of the evacuation chamber 306 towards the web 300 has, in this example, an opening length which extends over a considerably longer working area for the laser beam 302 than in the preceding embodiment, whereby the laser beam 302 can thus follow and process the web 300 over a correspondingly longer distance than the laser beam 202 in Fig. 2. In Fig. 3, this is schematically illustrated by means of the triple laser beam 302 in order to clarify the movements of the laser beam in the plane of the web 300 throughout the entire passage of the web 300. In practice, the opening 310 may thus have a slot- shaped opening configuration with a considerably greater length than width, but where the width must nevertheless be at least as large as the corresponding geometric width dimension of the desired pouring hole, and where the length is to be sufficiently great in order that the laser beam 302 will have time at the current web speed to cut the desired number of finished holes in the web 300.

The evacuation box 305 is removably mounted in a bracket 311 which is similarly disposed between the laser head 304 and the web 300 and which, at its ends, has an inlet 312 and an outlet 313 in fluid communication with a corresponding inlet opening 307 and outlet opening 308 in the evacuation chamber 306 in order to make possible the through-flow of fluid, e.g. air, through the evacuation chamber 306 during operation.

In order to reduce the risk that dust, small particles, confetti and gases which are formed when the laser beam 302 processes the web 300, accompany and foul or damage the processed web 300, the shortest distance between the evacuation box 305 and the web 300 along the entire length of the evacuation box 305 is very short, but nevertheless sufficiently large to avoid direct contact between the evacuation box 305 and the passing web 300. Preferably, the evacuation box 305 is provided with one or more handles or similar gripping devices with the aid of which the evacuation box 305 may readily be slid into and pulled out from the bracket 311 when it is time to replace a used evacuation box with a new or cleaned evacuation box.

From the processing station C, the thus laser processed web 300 is led further by the intermediary of a bending roller 314 for winding up or further processing and handling.

When it is time to clean the tubular evacuation chamber 306 of impurities which have accumulated on the inner walls of the evacuation chamber 306 during the laser processing, operation is stopped only briefly while the fouled evacuation box 305, including the window 309 provided as a part of the evacuation box 305 is released and pulled out from the bracket 311 and replaced with a new evacuation box 305 which is readily slid into position in the bracket 311.

Industrial application The apparatus according to the present invention makes for a practically continuous processing of a web of packaging material by means of a laser beam which is intended to cut optional geometric patterns in the web. The apparatus is particularly usable in cases where a packaging material web is, on a rational industrial scale, to be provided with scored, slotted or perforated opening indications or pouring holes.

Even if the invention has been described above with particular reference to the accompanying Drawings, it should be observed that the embodiments of the apparatus according to the present invention illustrated and described in detail are not intended to limit the present invention. With the guidance of the above description, it will be obvious to a person skilled in the art that numerous different modifications and alterations are possible without departing from the inventive concept as herein disclosed. For example, it is possible, in one and the same laser processing operation, to employ a plurality of apparatuses according to the present invention adjacent one another in that case when a web of packaging material is to be provided with opening- facilitating weakening indications within a plurality of parallel longitudinal zones of the web. Alternatively, in this case use may be made of a common apparatus according to the present invention for such parallel laser processing of the web. All such obvious alterations and modifications are thus encompassed by the inventive concept as this is defined in the appended Claims.

Claims

What is claimed is:

1. An apparatus for processing a web (200; 300) of packaging material by means of laser beam (202; 302), the apparatus (201 ; 301) comprising a laser head (204; 304) in communication with a laser source for generating the laser beam (202; 302), characterised in that, between the laser head

(204; 304) and the web (200; 300), it displays an evacuation box (205; 305) with an evacuation chamber (206; 306) defined by the inner walls of the evacuation box (205; 305) and having an opening (209; 309) facing towards the laser head (204; 304) and through which the laser beam (202; 302) may pass, and an opening (210; 310) facing towards the web

(200; 300) and through which the laser beam (202; 302) may pass after passage through the evacuation chamber (206; 306) for processing of the web (200; 300), and said evacuation chamber (206; 306) having inlet- and outlet openings (207; 307 and 208; 308, respectively) for the through-flow of fluid, and that the evacuation box (205; 305) is releasably mounted in a bracket device (211 ; 311 ).

2. The apparatus as claimed in Claim 1 , characterised in that the evacuation box (205; 305) is provided with one or more handles by means of which the evacuation box (205; 305) may readily be slid into and pulled out from the bracket (211; 311).

3. The apparatus as claimed in Claim 1 or 2, characterised in that the opening (210; 310) of the evacuation box (205; 305) turned to face towards the web (200; 300) is dimensioned and configurated in response to the geometric pattern the laser beam (202; 302) is to cut, perforate or etch on the web (200; 300).

4. The apparatus as claimed in Claim 3, characterised in that the opening (210) of the evacuation box (205) turned to face towards the web (200) has a substantially circular opening configuration.

5. The apparatus as claimed in Claim 3, characterised in that the opening (310) of the evacuation box (305) turned to face towards the web (300) has an elongate slot-shaped opening configuration.

6. The apparatus as claimed in any of the preceding Claims, characterised in that the evacuation box (205; 305) is disposed at a sufficiently great distance from the web (200; 300) to avoid direct contact between the evacuation box (205; 305) and the web (200; 300).

7. The apparatus as claimed in any of the preceding Claims, characterised in that the evacuation chamber (206; 306) defined by the inner walls of the evacuation box (205; 305) is cylindrical or tubular, with the longitudinal axis of the evacuation chamber (206; 306) parallel, or substantially parallel, with the direction of movement of the web (200; 300).

8. The apparatus as claimed in any of the preceding Claims, characterised in that the opening (209; 309) of the evacuation chamber (206; 306) turned to face towards the laser head (204; 304) is sealingly covered by a protective window (209a; 309a).

9. The apparatus as claimed in Claim 8, characterised in that the protective window (209a; 309a) is a part of the evacuation box (205; 305) in order to make for the simultaneous removal of the evacuation box (205; 305) and the protective window (209a; 309a) as a releasable modular unit.

10. The apparatus as claimed in any of the preceding Claims, characterised in that the bracket (211; 31 1) has an inlet (212; 312) and outlet (213; 313) in fluid communication with said inlet opening (207; 307) and outlet opening

(208; 308), respectively, of the evacuation chamber (206; 306) in order to make for through-flow of fluid through the evacuation chamber (206; 306).