WO2002004312A1

WO2002004312A1 - Packaging material for packaging pourable food products, and package made therefrom

Info

Publication number: WO2002004312A1
Application number: PCT/EP2000/013303
Authority: WO
Inventors: Per Gustafsson; Roberto Paltrinieri
Original assignee: Tetra Laval Holdings & Finance Sa
Priority date: 2000-07-11
Filing date: 2000-12-28
Publication date: 2002-01-17
Also published as: ES2198269T3; DE60002708D1; JP2004502607A; AU2001287657A1; PT1172299E; AU2001233670A1; EP1172299B1; WO2002004295A1; EP1172299A1; DE60002708T2; DK1172299T3; JP4965792B2; ATE240239T1

Abstract

A packaging material (4) for packaging pourable food products and having a multilayer structure having a layer of paper material (4a) covered on both sides with layers of heat-seal material. Holes (5) are formed in the paper material before it is covered with a continuous layer of barrier material (4b), e.g. aluminium, so as to obtain so-called 'preliminated' holes; the packaging material has a design (14) including first regions (15a) of a homogeneous color contrasting with the color of the holes (5); and the first regions (15a) are advantageously white or a light color.

Description

PACKAGING MATERIAL FOR PACKAGING POURABLE FOOD PRODUCTS, AND PACKAGE MADE THEREFROM

TECHNICAL FIELD

The present invention relates to a packaging material for packaging pourable food products, and to a package made from such material . BACKGROUND ART As is known, many pourable food products, such as fruit juice, wine, tomato sauce, pasteurized or long- storage (UHT) milk, etc., are packaged in packages made of sheet packaging material .

The packaging material has a multilayer structure comprising a layer of paper material covered on both sides with layers of heat-seal material, e.g. polyethylene, and, in the case of aseptic packages for long-storage products, such as UHT milk, also comprises a layer of barrier material defined, for example, by an aluminium film, which is superimposed on a layer of heat- seal plastic material and in turn covered with another layer of heat-seal plastic material eventually defining the inner face of the package contacting the food product .

To produce aseptic packages, the web of packaging material is unwound off a reel and fed through an aseptic chamber in which it is sterilized, e.g. by applying a sterilizing agent such as hydrogen peroxide, which is later vaporized by heating and/or by subjecting the packaging material to radiation of appropriate wavelength and intensity.

The sterilized web is then folded into a cylinder and sealed longitudinally to form, in known manner, a continuous, vertical, longitudinally sealed tube. The tube of packaging material, in other words, forms an extension of the aseptic chamber, and is filled continuously with the pourable food product and then fed to a forming and (transverse) sealing unit for forming the individual packages and on which pairs of jaws grip and seal the tube transversely into pillow packs .

The pillow packs are then separated by cutting the sealing portion between the packs, and are fed to a final folding station where they are folded mechanically into the shape of the finished packages .

The forming process involves folding the packaging material along crease lines formed during the material manufacturing process. The material manufacturing process typically comprises laminating steps to produce the various layers of which the material is formed; a number of printing steps to print graphics or designs periodically recur along the material with a spacing equal to the length of material used to produce each package; and a creasing step performed either on the finished material or only on a subset of material layers comprising at least the paper layer. Holes are also known to be formed in the paper layer before it is covered with a continuous layer of barrier material to form so-called "prelaminated" holes closed by the barrier material which ensures hermetic, aseptic sealing while at the same time being easily pierced. The holes in the paper layer may conveniently be formed using the same tool as for the crease lines, in which case, the barrier material is laminated afterwards.

Packaging materials with prelaminated holes are used for aseptic packages with straws or opening devices, e.g. of the type comprising a hinged lid or screw cap.

The various operations in the packaging material manufacturing process are performed using, as a register mark, an optical register code printed on the material in the course of the first printing step. The same code is normally also used on the forming machine to control feed of the material through the various work stations. More specifically, as is known, a so-called "design correcting" device acts on the packages being formed to variably "draw" the material in the feed direction and ensure performance of the mechanical forming operations matches the design on the packages.

Material manufacturing tolerances, however, may result in position errors of the optical register code with respect to the crease lines, so that frequent manual adjustment of the design correcting device (based on the optical register code) is required to prevent the forming members from interacting with the material incorrectly with respect to the crease lines .

On packaging machines using known packaging materials, the angular position of the tube of packaging material may vary, in use, with respect to the desired angular position, on account of the lateral edges of the web not being perfectly straight, and the effect produced by the pairs of jaws successively striking the tube.

As this may have negative effects on the quality of the longitudinal and transverse seals, and on the accuracy with which the packages are formed, known machines are provided with devices for manually adjusting the angular position of the tube. Such devices, however, are relatively time-consuming, and may involve shutting down the machine with consequent loss of production. Systems have also been proposed for automatically adjusting the angular position of the tube of packaging material, but call for the use of a dedicated sensor to determine the position of the longitudinal seal .

Alternatively, the packaging material may be cut into blanks, which are formed into packages on forming spindles, and the packages then filled with the food product and sealed. One example of a package of this type is the so-called "gable-top" package commonly known by the trade name Tetra Rex (registered trademark) . Position control is also desirable at later stages in the formation of packages for pourable food products, as, for example, when applying the opening device to the package, to adjust the position of the package with respect to the opening device assembly tool . In which case, the bar code is of no use by normally being located on a lateral wall of the package perpendicular to the wall in which the hole is formed. DISCLOSURE OF INVENTION It is an object of the present invention to provide a packaging material for packaging pourable food products, designed to solve the aforementioned problems, and which, in particular, provides for controlling the position of the packaging material on the package forming unit, and, for example, for easily determining the hole position on the formed package at later processing stages, as, for example, when fitting the opening device over the hole .

According to the present invention, there is provided a packaging material for packaging pourable food products and having at least one layer of paper material and at least one layer of barrier material, and comprising a number of prelaminated holes in which said layer of barrier material is whole; said packaging material having a surface design defined by graphics periodically recurring with a spacing equal to the spacing of the holes; characterized in that said design comprises first regions surrounding said holes and of a color contrasting with the color of said layer of barrier material .

The present invention therefore provides for controlling the position of the material on the forming unit and of the formed packages at other processing stages by enabling the prelaminated hole positions to be "read" reliably with no disturbance factors such as the design on the material.

More specifically, the prelaminated hole positions may be detected easily and compared with a memorized reference position to correct both the feed and angular position of the tube of packaging material on the forming unit.

Using the prelaminated holes as position detecting elements also enables both the longitudinal and angular position of the tube to be controlled using one sensor.

The present invention also provides for controlling and so adjusting the position of packages to be fitted with opening devices. BRIEF DESCRIPTION OF THE DRAWINGS

A preferred, non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which:

Figure 1 shows a portion of packaging material in accordance with the present invention;

Figure 2 shows a front view of a packaging machine featuring a device for feed adjusting the packaging material according to the present invention; Figure 3 shows a view in perspective of a station for supplying and folding the packaging material;

Figure 4 shows a schematic side view of a forming station on the Figure 2 machine; Figure 5 shows a diagram of the device for feed adjusting the packaging material according to the invention;

Figure 6 shows a diagram of an assembly for applying an opening device to the package formed using the material according to the invention;

Figure 7 shows a top plan view of a package formed using the material according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION Number 4 in Figure 1 indicates a packaging material for producing packages of pourable food products .

Packaging material 4 conveniently comprises a layer 4a of paper material; and a layer 4b of barrier material defined, for example, by a sheet of aluminium. Layers 4a and 4b are fixed to each other by an intermediate layer of thermoplastic material (not shown), e.g. polyethylene, and are covered on opposite faces with further layers of polyethylene (not shown) . Layer 4a of paper material comprises a succession of. holes 5 formed prior to laminating layer 4b; and a series of crease lines 13 (Figure 5) for assisting folding of the material when forming the packages, and which periodically recur with a spacing P equal to the distance between the holes and to the length of the portion of web 3 required to produce each package. Holes 5 and lines 13 are conveniently formed on the same fixture so that they are in register perfectly with each other.

Layer 4b is whole at holes 5 to ensure hermetic, aseptic sealing of the package until it is opened; and pull-off or other types of opening devices are later fitted over holes 5.

Material 4 also comprises a design 14 defined by a succession of graphics and conveniently comprising respective optical register codes 15.

According to the present invention, design 14 also comprises first regions 15a surrounding holes 5 (Figure 1) and of a homogeneous color contrasting with the color of second regions 15b surrounding regions 15a, and with the color of layer 4b. First regions 15a, for example, are white to enable the position of hole 5 to be read easily by an optical device.

With reference to Figures 2 to 5, number 1 indicates as a whole a packaging machine for producing packages of a pourable food product, such as pasteurized or UHT milk, fruit juice, wine, etc.

In particular, machine 1 provides for producing aseptic sealed packages of a pourable food product from a tube 2 made of packaging material 4 described above, and which in turn is formed by longitudinally folding and sealing a web 3.

Web 3 of packaging material 4 is unwound off a reel (not shown) and fed by known guide roller devices (not shown) through a known sterilizing unit (not shown) to a top aseptic chamber 6 of machine 1, which communicates with the sterilizing unit and through which web 3 is fed along a horizontal path PI. Web 3 is then diverted downwards by a roller 7 - forming part of a system of rollers, one of which is powered - and is fed downwards along a vertical path P2 extending inside a vertical chamber or tower 8.

Inside tower 8, web 3 is folded longitudinally into a cylinder to form tube 2, which has a longitudinal axis A parallel to path P2 and is sealed longitudinally by a sealing device 10 and by means of a known heat-seal strip not described in detail . Tube 2 is filled continuously with the food product by means of a known filling device 11 (not described in detail) , and is fed to a known forming unit 12 described below only as regards the parts pertinent to the present invention.

More specifically, machine 1 comprises a folding unit 9 for longitudinally folding web 3 ' to form tube 2 , and which is defined by a number of known folding assemblies 16, 17, 18 located along path P2 inside tower 8 and interacting with web 3 to fold it gradually into a cylinder and overlap the opposite lateral portions of web 3 (Figures 3 and 4) to form the tube of packaging material .

Assemblies 16, 17, 18 comprise respective numbers of substantially cylindrical folding rollers 21, 22, 23 having respective axes perpendicular to axis A, and defining polygons surrounding axis A so that the respective lateral surfaces define successive compulsory passages for web 3 of packaging material being folded. As it is fed through the passages, the web passes from an open C shape defined by folding rollers 21 of folding assembly 16, to a substantially circular shape defined by folding rollers 23 of folding assembly 18.

The axes of rollers 21, 23 of folding assemblies 16, 18 are fixed, whereas folding rollers 22 of assembly 17 are fitted to a C-shaped supporting plate 24 connected to the structure of machine 1 so as to be angularly adjustable about axis A to adjust the angular position of tube 2 being formed with respect to axis A.

The rotation of plate 24 is controlled by an actuator 25 via a transmission, e.g. a screw-nut screw, mechanism 26.

The speed at which web 3 is fed through folding assemblies 16, 17, 18 is determined by the movement of assemblies 35, 35', and is influenced by an electric motor 27 powering folding roller 7.

Once sealed longitudinally, tube 2 is fed to forming unit 12.

Unit 12 comprises a supporting structure 33 defining two vertical guides 44 arranged symmetrically with respect to a longitudinal vertical median plane α of the unit through axis A, and the respective axes of which lie in a transverse vertical median plane τ of unit 12. Axis A therefore defines the intersection of planes α and τ. Unit 12 comprises, in known manner, two forming assemblies 35, 35' movable vertically along respective guides 44 and interacting alternately with tube 2 of packaging material to grip and heat seal cross sections of the tube .

Since assemblies 35, 35' are symmetrical with respect to plane α, only one (assembly 35) is shown in detail in Figure 5 and described below. In the accompanying drawings, the corresponding parts of assemblies 35, 35' are indicated using the same reference numbers .

With reference to Figures 2 and 4, assembly 35 substantially comprises a slide 36 movable along respective guide 44; and two jaws 37 hinged at the bottom to the slide, about respective horizontal axes 38 parallel to and symmetrical with respect to plane τ, so as to open and close substantially "bookfashion" .

More specifically, each jaw 37 comprises a main control body 39, which is substantially in the form of an appropriately ribbed quadrangular plate (Figures 2 and 4) , extends along a work plane β of jaw 37 containing respective axis 38, is hinged close to its bottom side to slide 36, and comprises a respective control arm 40 projecting from a face of body 39 facing away from plane β.

Jaws 37 also comprise respective supporting arms 41, which are fitted to the top ends of respective bodies 39 of respective jaws 37, and project towards and beyond plane α, in a direction parallel to respective axes 38 and substantially along respective work planes β, so as to be located on opposite sides of tube 2.

The projecting portions of arms 41 are fitted with respective bar-shaped sealing elements 42, 43 (Figure 5) which interact with tube 2, and which may be defined, for example, by an inductor for generating current in the aluminium layer of the packaging material and Joule- effect melting the thermoplastic layer, and by a mating pad against which to grip tube 2 to the required pressure.

The reciprocating movement of slides 36 and the opening/closing movement of jaws 37 are controlled in known manner (not described) by pairs of vertical rods (not shown) in turn controlled by rotary cams or servomotors .

Jaws 37 are movable between a closed position in which respective sealing elements 42, 43 grip tube 2, and a fully-open position. At the transverse sealing step, tube 2 is heat sealed along periodically recur transverse bands 45

(Figure 5) .

Over respective sealing elements 42, 43, arms 41 of jaws 37 support respective package volume control tabs 46 having a C-shaped cross section open at the front, and which cooperate with each other, after the transverse sealing operation performed by elements 42, 43, to define a cavity of predetermined shape and volume enclosing and forming tube 2 into a rectangular-section shape.

The above forming step (Figure 5) produces "pillow" packs 47, each comprising a main portion 48 of the same shape and volume as the finished package; and transition portions 49 connecting main portion 48 to respective adjacent sealing bands 45, . and defined laterally by substantially triangular faces 50.

One of jaws 37 comprises, in known manner, two folding tabs 54 for controlling, together with folding roller 7, the longitudinal feed of tube 2 through forming unit 12.

Folding tabs 54 (Figures 4 and 5) are located on either side of tube 2 , are symmetrical with respect to axis A and adjacent to tube 2, rotate about respective axes perpendicular to plane β, and are rotated in opposite directions by a known design correcting device 51 - active at the forming step - so as to act on lateral faces 50 of transition portions 49 of the pillow packs and exert variable pull on tube 2. Device 51 comprises, for example, a variable- geometry or variable-position cam 52, shown purely schematically in Figure 5, which interacts with a cam follower 53 carried by jaw 37 and connected to tabs 54 by a transmission mechanism 55 also shown purely schematically. Examples of such a control device are illustrated in Italian Patent Application n. MI97A-002473 and in European Patent Application n. 99830715.1 filed by the present Applicant. The travel of tabs 54, and therefore the amount of pull exerted on tube 2, is adjustable, as described in detail later, on, by means of an actuator 56 acting, for example, on the position of cam 52. Actuator 25 controlling tube folding assembly 17, electric motor 27 powering folding roller 7, and actuators 56 of design correcting devices 51 of respective assemblies 35, 35' form part of a device 60 for controlling the feed of tube 2 of packaging material. In addition, device 60 also comprises a conventional first optical sensor 61 for reading the optical register code 15 printed on material 4; a second optical sensor 62 for detecting the position of holes 5; and a control unit 63 connected at the input to sensors 61, 62, and at the output to actuators 25, 56 and to motor 27.

The second optical sensor 62 is conveniently defined by a video camera, e.g. a CCD type, for "reading" the position of first regions 15a of material 4 at holes 5.

The video camera reading is assisted by the color of area 15a surrounding each hole 5 contrasting with the color of second regions 15b.

To avoid acquiring and processing an excessive amount of data, first sensor 61 is used to generate an enabling signal II, which changes state in response to detection of a code 15 and is supplied to control unit 63 to read-enable the second optical sensor. Sensor 62 is thus only read-enabled at each hole 5 or at one of every N number of holes 5, and supplies control unit 63 with signals 12 indicating the position of holes 5 and relative, for example, to a conventionally coded pixel matrix.

Control unit 63 compares the position of the detected hole 5 with a memorized reference position

(Figure 2) and calculates a longitudinal position error

El of tube 2, and a transverse position error E2 of hole

5, obviously correlated to the twist angle of tube 2.

Control unit 63 generates a signal 01 for controlling electric motor 27; signals 02 (identical) for controlling actuators 56; and a signal 03 for controlling actuator 25. Signals 01 and 02 are correlated in conventional manner with value El, and signal 03 with value E2. In actual use, the speed at which material 4 is supplied to folding assemblies 16, 17, 18 and to forming unit 12 is determined by motor 27 controlled by control unit 63. Being known and partly deducible from the above description, operation of assemblies 16, 17, 18 and forming unit 12 is not described in detail .

If the longitudinal position of tube 2 is correct, i.e. if the absolute value of El is below a predetermined threshold value, the control unit maintains a constant speed of motor 27. Conversely, in the presence of an error El, the supply speed of material 4 is corrected by control unit 63 appropriately modulating signal 01. If the resulting correction is not sufficient, in addition to motor 27, control unit 63 also acts on design correcting device 51 by appropriately adjusting, by means of signal 02, the amount of pull exerted by folding tabs 54. According to the present invention, the above controls, in themselves known, are performed on the basis of position errors of holes 5 - which, as stated, are in register to crease lines 13 - and not on the basis of optical code 15 in register to and forming part of design 14.

In a preferred embodiment of the present invention, signal II of first sensor 61 is only used to generate a "read window" in which second sensor 62 actually reads the position of material 4 based on the position of a hole 5 at a given instant, and supplies control unit 63 with a signal 12 indicating the matrix of pixels detected.'

Signal 12 is conveniently also used to calculate the transverse position error of the hole, and so correct twisting of tube 2 by means of folding assembly 17. More specifically, in response to a transverse position error E2, control unit 63 commands actuator 25, by means of signal 03, to rotate folding assembly 17 in one direction or the other depending on the error sign. This control is also performed on the basis of the position of holes 5 as opposed to optical code 15, and the hole 5 position reading is again assisted by the color of first region 15a surrounding each hole 5.

Region 15a is advantageously white or a light color, both of which contrast with the color of second regions 15b on material 4, and with the color of the aluminium barrier layer 4b covering hole 5.

Material 4 as described above is also particularly suitable for controlling the position of packages 70 made from material 4 with respect to package processing units .

For example, with reference to Figure 6, packages 70 are fed successively on a conveyor 71 to an assembly unit

72 for fitting opening devices 81 onto the packages.

Assembly unit 72 comprises a fitting assembly 76 having jaws 80 for gripping the opening device 81, and an adjusting assembly 78 for adjusting the longitudinal and transverse position of fitting assembly 76.

Assembly unit 72 also comprises a video camera 75 for reading the position of hole 5 on each package 70; and a processing and control unit 73, which receives the signals transmitted by video camera 75, compares the position of the detected hole 5 with a memorized reference position, and calculates the longitudinal and transverse position error of package 70 on conveyor 71. Processing and control unit 73 then generates an output signal for controlling adjusting assembly 78 in response to the position error of package 70.

Adjusting the position of adjusting assembly 78 provides for fitting opening device 81 correctly over hole 5 of each package 70.

In this case too, the contrasting color of first region 15a surrounding each hole 5 permits easy reading of the position of hole 5. Clearly, changes may be made to packaging material 4 as described herein without, however, departing from the scope of the invention.

Packaging material 4 may be supplied in individual blanks as opposed to a continuous web.

As regards possible applications of material 4, the hole 5 readings may also be used for reading and adjusting the transverse position of the moving web 3 of material 4. Moreover, when assembling opening devices 81, the position of packages 70 may be corrected as opposed to adjusting the position of assembly 76 for applying opening devices 81.

Claims

1) A packaging . material (4) for packaging pourable food products and having at least one layer (4a) of paper material and at least one layer (4b) of barrier material, and comprising a number of prelaminated holes (5) in which said layer (4b) of barrier material is whole; said packaging material (4) having a surface design (14) defined by graphics periodically recurring with a spacing equal to the spacing of the holes (5) ; characterized in that said design (14) comprises first regions (15a) surrounding said holes (5) and of a color contrasting with the color of said layer (4b) of barrier material.

2) A packaging material as claimed in Claim 1, characterized in that said first regions (15a) are of a homogeneous color contrasting with the color of said holes (5) and with the color of second regions (15b) of said design (14) surrounding said first regions (15a) .

3) A packaging material as claimed in Claims 1 and 2, characterized in that said layer (4a) of paper material is covered on both sides with layers of heat- seal material .

4) A packaging material as claimed in Claims 1 to 3, characterized in that said heat-seal material is polyethylene .

5) A packaging material as claimed in Claims 1 to 4, characterized in that said layer (4b) of barrier material is aluminium. 6) A packaging material as claimed in any one of the foregoing Claims, characterized in that said first regions (15a) are a light color.

7) A packaging material as claimed in any one of Claims 1 to 6, characterized in that said first regions

(15a) are white.

8) A packaging material as claimed in any one of Claims 1 to 7, characterized by comprising crease lines (13) in register with said holes (5) . 9) A continuous web defined by a packaging material (4) as claimed in any one of Claims 1 to 8.

10) A package (70) for pourable food products, comprising a packaging material (4) as claimed in any one of Claims 1 to 8.