HK1074193B - Sheet material for producing packages of food products, and packages made of such material - Google Patents

Description

Sheet material for producing food packages and packages made of such material

Technical Field

The present invention relates to a sheet for packaging food products.

Background

A variety of materials are known for packaging pourable food products such as fruit juice, wine, tomato sauce, pasteurized or long-shelf (UHT) milk, etc.

Such packages are formed from a continuous roll of packaging material. According to one known technique, the roll of material is sealed longitudinally to form a continuous tube.

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

To produce aseptic packages, a web of packaging material is unwound from a reel and conveyed through a sterilizing chamber, in which the web is sterilized, for example by applying a sterilizing agent such as hydrogen peroxide, which is evaporated after sterilization, for example by heating or by applying radiation of a suitable wavelength and intensity to the packaging material.

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

The pillow packs are then separated by cutting the sealed portions between them and are conveyed to a final folding station where they are mechanically folded into the shape of the final package.

The various operations in the packaging material manufacturing process are carried out by using as a reference the register marks printed on the material in the first printing stage.

Registration marks include printed codes that are also commonly used on forming machines to control the feeding of material through various processing stations. More specifically, as is known, the so-called "trim correction" devices act on the packages being formed so as to "drag" the material differently in the direction of feed and ensure that the mechanical forming operation is carried out in match with the decorative portions on the packages.

In known packaging machines, it is also generally necessary to control the transverse position of the web before it is sealed longitudinally to form a tube, in order to perform secondary operations, such as cutting and applying removable tabs or opening mechanisms.

It is also necessary to control the angular position of the tube on the sealing unit, which may vary in use with respect to the desired angular position, due to: the side edges of the roll may not be perfectly straight, the effect of the jaw pairs hitting the tube continuously, and the effect of the roll tension bias.

Since the above-mentioned conditions have a negative effect on the quality of the longitudinal and transverse seals and on the accuracy of the packages formed, the known machines are provided with means for manually adjusting the angular position of the tube. However, such devices are time consuming and involve downtime, thus resulting in lost production. Systems for automatically adjusting the angular position of the tube of packaging material have also been proposed, but they require the use of dedicated sensors to determine the position of the superimposed layers of material at the longitudinal seal.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a sheet packaging material for producing packages of food products, which comprises optically detectable register marks by means of which the position of the material in the machine direction of feed and in the transverse direction can be determined.

According to the present invention there is provided a sheet for producing food packaging comprising a plurality of fold lines and a series of optically detectable register marks; characterized in that each alignment mark comprises at least two parallel portions perpendicular to the feeding direction of the material and an inclined portion between these parallel portions.

According to the invention, the register marks are detectable by one or more optical sensors for controlling the position of the rolls at the various processing stations as the material is conveyed through the machine, and connected to a processing-control unit which can be used to control the means for managing the position of the rolls. The inclined portion, together with the two portions perpendicular to the feed direction, represents the transverse position of the material, which can be used to automatically correct the transverse position of the flat material roll and the angular position of the tube.

Another problem typically associated with known packaging materials is as follows:

the package is formed by folding the packaging material along fold lines "indented" in the material. Although the formation of the packages must be matched to the fold lines, the feeding of the packaging material on the forming machine is generally controlled according to register marks printed on the material.

The reason for this is that conventional direct optical detection of fold lines still presents problems and no satisfactory solution has been proposed so far.

The indentation and printing are performed at different stages in the material production cycle, so that alignment errors between the two are unavoidable. Therefore, using the printed alignment mark as a positional reference for an operation that should be matched with the folding line inevitably leads to an error.

According to a preferred embodiment of the invention, the optically detectable register marks are formed by compression-creased fold lines having a concave profile on a first surface of the material and a non-convex profile on a second surface of the material.

Compression creasing enables a sharper compression line to be obtained than with known creasing methods, which can be optically detected and thus can be used as an alignment mark.

According to a preferred embodiment of the invention, the material may further comprise a decorative portion having a printed area at least partially surrounding the one or more compression-creased fold lines, whereby the fold lines within the printed area form optically detectable "negative print" indicia.

When printing is performed using any known printing technique, the packaging material is compressed between a printing cylinder and an opposing cylinder. If conventional creasing methods are used, the convex profile of the crease on the opposite cylinder side generates a pushing force, resulting in an unexpected and undesired contact between the packaging material and the printing cylinder on the concave side of the crease line, which results in a line with a blurred profile, which to a large extent results in an inability to perform optical detection.

On the other hand, the compression creasing also produces a flat or slightly concave profile on the surface of the packaging material in contact with the counter-roller, eliminating the thrust, and the concave opposite side of the fold line is absolutely free of ink, resulting in a high contrast mark that can be detected ideally by an optical sensor.

Brief description of the drawings

Some non-limiting embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

figure 1 shows schematically a machine for producing aseptic packages from a roll of sheet material according to the present invention;

FIG. 2 shows a portion of a sheet packaging material according to the invention;

FIGS. 3 and 4 schematically illustrate various steps in a method of producing the material of FIG. 2;

fig. 5 shows a portion of a packaging material according to another embodiment of the invention.

Best Mode for Carrying Out The Invention

Number 1 in fig. 2 indicates a portion of sheet packaging material 2 provided in the form of a continuous roll 3.

The roll 3 of material 2 comprises a plurality of folding lines 4 and printed decorative portions 5, which are repeated at intervals R equal to the length of material required to produce a package.

The roll 3 may be used on a machine 6 for producing aseptic packages, as schematically shown in figure 1, the roll 3 being unwound from a reel 7, conveyed through a sterilization chamber (not shown) in which sterilization takes place and an assembly 8, the roll 3 being folded and longitudinally sealed by the assembly 8 to form a continuous vertical tube 9 in a known manner.

The tube 9 of packaging material is filled continuously with pourable food products by a known filling device 10, and the tube 9 is then conveyed to a form-transverse sealing station 14, where the tube 9 is gripped by pairs of jaws (not shown) which seal it transversely to form pillow packs 15.

Pillow packs 15 are then separated by cutting the sealed portions between pillow packs 15 and are conveyed into a final folding station 16, where pillow packs 15 are mechanically folded to form a final package 17.

The package is formed by folding the material along fold line 4 and controlling the feeding of the material by means of an optical sensor 16 which can "read" register marks 18 located on the material at the spacing R.

According to the invention, each alignment mark 18 comprises a broken substantially Z-shaped alignment line 37 formed by a first portion 37a and a second portion 37b parallel to each other and perpendicular to the direction of feed of the rolls 3 on the machine 6, and a portion 37c inclined with respect to the portions 37a, 37 b.

Thus, as the web 3 is conveyed through the machine 6, the register marks 18 are detected by one or more optical sensors 16 for controlling the position of the web 3 at the various processing stations and connected to a processing-control unit 41 for controlling known means (not shown) for managing the position of the web 3.

With the Z-shaped register line 37 it is possible to control the position of the roll 3 in the feed direction and in the transverse direction in order to correct the transverse position of the still flat roll and thus to perform auxiliary operations such as cutting and applying removable tabs or opening mechanisms, or to correct the angular position of the tube 9.

In addition, control of the lateral alignment is performed during the application of adhesive tape on one edge of the web of material to longitudinally seal the web and form the tube, and in the case of splicing webs of material to control the alignment of the edges of the webs of material that are stacked together.

In fact, the optical sensor 16 detects the first portion 37a, the inclined portion 37c and the second portion 37b of the alignment line continuously; the control unit 41 calculates a first time T1 between detection of the first portion 37a and the inclined portion 37c and a second time T2 between detection of the inclined portion 37c and the second portion 37 b; the lateral position error of roll 3 may be calculated and corrected based on the ratio of T1 and T2. More specifically, if sensor 16 is located on the mid-plane of alignment mark 18, i.e. in the correct or reference position of roll 3, then the correct lateral position of the roll of material corresponds to a ratio of T1 to T2 of 1. If the ratio is less than or greater than 1, the roll can be moved laterally in a known manner in the appropriate direction to reduce the positional error.

Similarly, the lateral position error of the roll 3 can be calculated from the ratio of T1 or T2 to the total time T1+ T2. In this case, a value of 0.5 indicates a central position, while a different value indicates the presence of a lateral displacement.

The fold line 4 may be formed by a compression line formed by a compression creasing process (fig. 3).

More specifically, the material 2 is compressed between an creasing roller 20 and a smooth counter roller 22, the profile of creasing roller 20 being partly shown in plan view in fig. 3 and having a plurality of projections 21 corresponding to the compression lines 4, while the counter roller 22 has no pockets corresponding to the projections 21. The roller 20 suitably acts on the surface 23 of the material forming the outer surface of the package, i.e. on the surface on which the decorative portion 5 is printed, while the roller 22 acts on the opposite surface 25.

The height of the protruding portion 21 is between 50% and 90% of the thickness of the material 2, preferably about 80% of the thickness of the material 2. The thickness of the material is reduced by the same percentage during compression, after which the material partially recovers, but retains a permanent compression set. The residual depth of the compression lines is suitably between 30% and 60% of the thickness of the material 2 and is equal to about 50% of the thickness of the material when a deformation of about 80% is produced during indentation.

As clearly shown in fig. 4, compression lines 4 have a concave profile formed by stepped sides 26 on surface 23 of material 2 and a substantially flat or slightly concave profile on opposite surface 25.

Figure 4 also shows schematically, in plan view, the profile of the printing roller 30 and of the counter-roller 31, which are in contact with the surfaces 23 and 25, respectively, of the material 2 at the compression line 4.

As fig. 4 clearly shows, the substantially flat or slightly concave profile of the compression line 4 on the side facing the counter-roller 31 eliminates the thrust on the material 2, which could cause the thinner portion of the material to come into contact with the printing roller 30.

The printing roller 30 is therefore only in contact with the surface of the material 2 outside the compression lines 4, thus presenting a clear "negative print" line on the material.

In a preferred embodiment of the invention, this property of the compression indentation can be exploited to obtain alignment marks 18 that exactly correspond to the compression lines 4. For example, with reference to fig. 2, the register mark 18 may be formed by a rectangular area 36 printed on the portion of the material 2 that ultimately forms the bottom of the finished package 17. The area 36 encloses a portion of the compressed line 4, in particular a zigzag line 37 formed by portions 37a, 37b, 37c of the compressed line 4, thereby forming an alignment mark 18 contrasting with the line 37.

Thus, the zigzag lines 37 are "negatively printed" in the areas 36 forming part of the ornamental portion 5.

Material 2 (fig. 2) is suitably provided with optically detectable indicia 40 readable by optical sensor 16 to prevent indicia 18 (producing three differently spaced readings) from being "confused" with other indicia formed by decorative portion 5, fold line 4, or a combination thereof.

The marks 40 may be printed or indented and may be formed by an alignment code or two or more lines perpendicular to the feed direction and spaced apart by a predetermined distance. The alignment code may be located at any convenient location on the roll of material.

The processing unit 41 may be programmed to open only one reading window, for example after a predetermined time interval and/or distance from having read the known series of marks 40 with a given pitch, the size of which may fully encompass the reading of the alignment mark 18.

In the variant shown in fig. 5, the register marking 18 is formed by compression lines 4, which compression lines 4 are formed only for register purposes, i.e. it does not play a role in the formation of the package, the register marking 18 suitably comprising a square-shaped printed area 36 enclosing four compression lines 37d forming a square and compression lines 37e along the diagonals of the square.

The mark can thus be "read" exactly in the same way as the zigzag alignment line 37, but because of the square shape, the mark can be read in two perpendicular material feed directions X, Y relative to the optical sensor 16.

This is useful in case the marking 18 is used as an alignment mark on a unit for applying opening devices to the finished packages 17, in which the packages are transferred forward in different orientations.

Clearly, changes may be made to material 2 as described herein without, however, departing from the scope as defined in the accompanying claims.

In particular, if the contrast obtained by the compression indentation is sufficient, the printed region 36 can be omitted and the indentation site can be directly read.

Also, instead of compression creasing, the material may be provided with Z-shaped or square-diagonal alignment marks printed positively or negatively in a conventional manner.

Claims (15)

1. A sheet (2) for producing food packages, comprising a plurality of folding lines (4) and at least one optically detectable register mark (18); characterized in that the register mark (18) comprises two parallel portions (37a, 37b) perpendicular to the feeding direction of the sheet (2), and an inclined portion (37c) between the parallel portions.

2. The sheet according to claim 1, wherein the alignment mark (37) comprises four portions (37d) arranged in a square and an inclined portion (37e) formed along a diagonal of the square.

3. A sheet according to claim 1 or 2, wherein the fold lines (4) are compression lines having a concave profile on a first surface of the sheet and a non-convex profile on a second surface of the sheet.

4. A sheet according to claim 3, characterized in that the register marks (18) are formed partly by the compression lines (37).

5. -sheeting according to any one of the preceding claims, characterised in that it comprises a printed decorative portion (5).

6. A sheeting according to claim 5, wherein the decorative portion (5) comprises a printed area (36) which partially surrounds the compression line (37) and contrasts with the compression line (37) to form the register mark (18).

7. The sheeting according to claim 5, wherein the optically detectable register marks (18) form part of the decorative portion (5).

8. The sheeting according to any of the preceding claims, further comprising an optically detectable mark (40) for reading the registration mark (18).

9. A package containing a food product and formed by a sheet (2) through transverse longitudinal sealing and mechanical folding along a folding line (4); the package (17) comprises optically detectable alignment marks (18); characterized in that the alignment mark (18) comprises two parallel portions (37a, 37b), and an inclined portion (37c) between the parallel portions.

10. The package according to claim 9, wherein the alignment mark (37) comprises four portions (37d) arranged in a square and an inclined portion (37e) formed along a diagonal of the square.

11. The package according to claim 9 or 10, wherein the folding line (4) is a compression line having a concave profile on the outer surface of the sheet (2) and a non-convex profile on the inner surface of the sheet (2).

12. The package according to claim 11, wherein the alignment mark (18) is formed by the compression line (37).

13. The packaging according to any one of claims 9 to 11, characterised in that the material comprises a printed decorative portion (5).

14. The packaging according to claim 13, characterised in that the decorative portion (5) comprises a printed area (36) which partially surrounds the compression line (37) and forms the register marking (18) in contrast with the compression line (37).

15. The packaging according to claim 14, characterized in that the optically detectable register marking (18) forms part of the decorative portion (5).