WO2001051275A1

WO2001051275A1 - A method of processing a web material for packaging pourable food products

Info

Publication number: WO2001051275A1
Application number: PCT/EP2000/013298
Authority: WO
Inventors: Jonas Hakansson
Original assignee: Tetra Laval Holdings & Finance Sa
Priority date: 2000-01-14
Filing date: 2000-12-27
Publication date: 2001-07-19
Also published as: SE0000106D0; AU2001225122A1; SE520430C2; SE0000106L

Abstract

A method of processing a web material (3) for packaging food products, including the step of laser-processing the web material (3) in order to create a register mark (14) and to perform one or more additional material structure-modifying operations such as a perforation (15) or hole; the step of printing a design (18) by successive single-colour print operations in register with the register mark (14); and the step of creating a crease pattern (24) in register with the register mark (14).

Description

A METHOD OF PROCESSING A WEB MATERIAL FOR PACKAGING POURABLE FOOD PRODUCTS.

TECHNICAL FIELD The present invention relates to a method of processing a web material for packaging pourable food products. BACKGROUND ART

Many pourable food products, such as fruit juice, pasteurized or UHT (ultra-high-temperature processed) milk, wine, tomato sauce, etc., are sold in packages made of sterilized packaging material. A typical example of such a package is the parallelepipedal package for liquid or pourable food products known as Tetra Brik Aseptic (registered trademark) , which is formed by folding and sealing a laminated web packaging material . The laminated packaging material comprises layers of fibrous material, e.g. paper, covered on both sides with thermoplastic material, e.g. polyethylene. In the case of aseptic packages, the side of the packaging material eventually contacting the food product in the package also has a layer of barrier material, such as an aluminium sheet, which in turn is covered with a layer of thermoplastic material . As is known, such packages are produced on fully automatic packaging machines, in which a continuous tube is formed from the web packaging material .

The web packaging material is loaded into the packaging machine in the form of a reel, from which it continuously unwinds and is fed to a sterilizing unit and then to a forming unit where it is longitudinally folded and sealed to form a tube. The tube is then filled with the sterilized or sterile-processed food product, is sealed by pairs of jaws and then cut at equally spaced transverse bands to form pillow packs, which are subsequently folded mechanically to form the finished, e.g. parallelepipedal, packages.

The web packaging material is produced in converting plants where a paperboard or a pre-laminated paperboard, typically including a paper layer covered on one side at least with one layer of thermoplastic material and possibly with the barrier layer and a further layer of thermoplastic material, is subjected to a plurality of successive processing operations such as: printing a repeated design pattern on one side covered with a thermoplastic layer, which is usually made in at least four successive print units, e.g. one unit for printing each colour; creasing, i.e. forming weakened lines along which the material is folded in the packaging machine to form packages; auxiliary mechanical or laser operations such as perforation or cutting; and lamination, i.e. forming a further thermoplastic layer on the printed side.

In order to assure that all discrete operations both at the converting plant and in the packaging machine are in register with one another, i.e. made at correct relative positions on the web, register indexes must be provided on the web.

According to a known processing method, this problem is solved by printing a register mark and a register code on the web at the first print unit. The register mark is used in the successive steps of the converting process to determine the actual position of the web in order to perform the successive operations, such as printing the remaining colours, creasing, and laser- processing, mechanical perforating, hole punching, etc., if any. The register code is used in the packaging machine in order to control the feed of the tube of packaging material and the forming operations thereon.

The use of a printed register mark for all successive operations implies that such operations are performed with a position error, depending on the process tolerances, which is referred to the printed mark. This means that any result of a successive operation (printed design, crease pattern, laser pattern, etc.) may have a positive or negative position error with respect to a theoretical position determined by the printed mark; the absolute value of the error is comprised within a maximum value depending on the process tolerances. In case two successive operations which have a functional impact when forming and filling packages, such as the crease pattern and the laser pattern, happen to by subjected to errors in opposite directions, the tolerance chain may produce a relative error between such operations which is up to the sum of the tolerance widths of each single operation. DISCLOSURE OF INVENTION A scope of the present invention is to provide a method of processing a web material for packaging food products which allows the overall errors due to the tolerance chain for functionally relevant dimensions to be reduced. This scope is achieved by a method according to claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention is described hereunder, by way of non-limiting example and with reference to the attached drawings, in which:

Figure 1 is a scheme of a converting plant for performing the method of the present invention; and

Figure 2 is a partial plan view of a web packaging material produced in accordance with the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to Figure 1, numeral 1 indicates as a whole a converting plant for producing reels 2 of web packaging material 3 to be used in a food product packaging machine (not shown) .

Plant 1 essentially includes an unwinder 4, in which reels 5 of raw web material are loaded, a plurality of processing stations 6, 7, 8 described hereunder in detail, and a winder 9 where reels 2 of finished web packaging material 3 are formed.

According to the present invention, the first processing station is a laser station 6 including a laser head 10 which is stationary and mirrors or lenses are moved e.g., by servo-motors, in order to deflect the laser beam. Alternatively, the laser head may be carried and moved by a controllable, high-speed positioning unit 11 such as a robot or the like, so as to produce a register mark 14 on web packaging material 3 (figure 2) , which is used to determine the actual position of the web in the successive processing stations 7, 8. Register mark 14 is repeated along web packaging material 3 at a pitch corresponding to the web length which is necessary to manufacture a package.

In laser station 6, at least a further structure- modifying laser processing operation is performed, such as a perforation 15. According to a preferred embodiment of the present invention, laser station 6 also produces a register bar code 16 on web packaging material 3, which is to be used in a packaging machine (not shown) for in-register forming operations.

A control unit 17 controls laser station 6, and in particular the motion of positioning unit 11 as a function of web speed and laser beam emission by laser head 10, as well as all the other processing stations of plant 1, as described hereunder.

The next processing station is a print station 7 including a plurality of print units 7a, 7b, 7c, 7d, per se known, each of which prints a respective colour of a repeated design pattern 18.

The position of web packaging material 3 at print station 7 is detected by a sensor 19 which reads register marks 14; web feed at print units 7a, 7b, 7c, 7d and therefore the register of the different colours successively printed, is controlled by control unit 17 in response to sensor 19.

If register bar code 16 on web packaging material 3 is not produced at laser station 6, then it may be printed at one of prints unit 7a, 7b, 7c, 7d. The following processing station is e.g., a creasing station 8 , wherein web packaging material 3 is fed between two creasing rollers 20, 21 having complementary crease profiles 22, 23 (i.e. projecting ribs on one roller and grooves on the other) which locally delaminate web packaging material 3 along predetermined lines 24 which define a crease pattern on web packaging material 3. The position of web packaging material 3 at crease station 8 is detected by a sensor 25 which reads register marks 14 ; web feed at crease station 8 , and therefore the register of the crease pattern 24, is controlled by control unit 17 in response to sensor 25.

Plant 1 may include one or more further processing units, e.g., a laminator (not shown) for producing a thermoplastic layer on the printed side and possibly on the opposite side of web material 3, and also for applying a barrier layer, where present, such as an aluminium foil layer.

According to the present invention, the method of processing web packaging material 3 performed by plant 1 includes the steps of: laser processing web packaging material 3 in order to create register mark 14, as well as to perform at least one material structure-modifying operation, and conveniently also to create register code 16; printing a design 18 by successive single-colour print operations in register with register mark 14; and creating a crease pattern 24 in register with register mark 14.

The advantages of the present invention are clear from the foregoing description. In particular, by using a laser head 10 as the first operation for the creation of the register mark 14 as well as for performing other structure-modifying operations such as making holes or perforations (which thus are perfectly in register with the register mark) , and by using the register mark to detect the web position for all subsequent operations, the overall position error between functionally relevant operations, e.g. perforation and creasing, will decrease.

If also register code 16 is made in the first operation, then also all operations carried out in the packaging machine will be free from error sum effects due to tolerance chains .

Clearly, changes may be made to the method described herein without, however, departing from the scope of the present invention as claimed.

In particular, the additional processing operation performed in laser processing station 6 may be of any kind; the number of print units may vary depending on the number of print colours; any further operations may be performed before or after creasing.

Claims

1.- A method of processing a web material (3) for packaging pourable food products, the method including a first step of creating a register mark (14) on said web material (3) , a second step of printing a design (18) by successive print operations, a third step of creating a crease pattern on said web material (3) so as to allow said web material (3) to be folded along predetermined lines (24) in a food packaging machine, and a fourth step of performing at least one further structure- modifying operation on said web material (3) , characterised in that said first and fourth steps are carried out by laser-processing said web material (3) in a laser-processing station (6) , said second and third steps being performed by using said register mark (14) created by laser processing to determine the actual position of said web material (3) .

2.- A process as claimed in claim 1, characterised by including the step of creating a register code (16) for said packaging machine on said web material (3) .

3. - A process as claimed in claim 2 , characterised in that said register code (16) is created in said first step of said method by laser processing.

4.- A process as claimed in claim 2, characterised in that said register code (16) is printed in said second step of said method.