EP4647249A1

EP4647249A1 - Method and unit for applying opening devices on a web of packaging material

Info

Publication number: EP4647249A1
Application number: EP25164904.2A
Authority: EP
Inventors: Fabio GIOVANARDI; Lauro BELLUCCI; Angelo Verardi; Armando STAGLIANO
Original assignee: Tetra Laval Holdings and Finance SA
Current assignee: Tetra Laval Holdings and Finance SA
Priority date: 2024-03-26
Filing date: 2025-03-20
Publication date: 2025-11-12
Also published as: WO2025201999A1

Abstract

There is described a method for applying opening devices (2) at predetermined areas (3) of a web (4) of packaging material including a plurality of web portions (4a), the method comprising the steps of feeding the web (4) through an application station (6) by feeding one web portion (4a) at a time through the application station (6), detecting the position along the advancing path (P) of a first predetermined area (3a) first entering the application station (6) and the position of a second predetermined area (3b) last entering the application station for a respective web portion (4a), calculating a calculated distance (D1) between such detected positions, calculating a distance offset value (E) as a function of the difference between said calculated distance (D1) and a nominal distance (D2), controlling the position of said respective web portion (4a) at the application station (6) as a function of the calculated distance offset value (E) by arranging one first predetermined area (3) at a distance equal to a fraction (E/k) of said distance offset value (E) from a reference position of said one predetermined area (3).

Description

TECHNICAL FIELD

The present invention relates to a method for applying opening devices on a web of packaging material, in particular a web of packaging material for the production of sealed packages containing a pourable product, preferably a pourable food product.
The present invention also relates to a unit for applying opening devices on a web of packaging material, in particular a web of packaging material for the production of sealed packages containing a pourable product, preferably a pourable food product.

BACKGROUND ART

As it is generally known, many pourable food products, such as fruit juice, UHT (ultra-high temperature-treated) milk, wine, tomato sauce, etc., are sold in packages made of sterilized packaging material.
A typical example is the parallelepiped-shaped package for pourable food products known as Tetra Brik Aseptic (registered trademark), which is made by folding and sealing a laminated web of packaging material. The packaging material has a multilayer structure substantially comprising a base layer for stiffness and strength, which may be made of fibrous material, e.g. paper or mineral-filled polypropylene material, and a number of lamination layers made of heat-seal plastic material, e.g. polyethylene films, covering both sides of the base layer. In the case of aseptic packages for long-storage products, such as UHT milk or fruit juice, the packaging material also comprises a layer of gas-barrier material, e.g. an aluminum foil or an ethyl vinyl alcohol (EVOH) film, which is superimposed on a layer of heat-seal plastic material, and is in turn covered with another layer of heat-seal plastic material. This latter layer of heat-seal plastic material forms the inner face of the package eventually contacting the pourable food product.
Packages of this sort are normally produced in fully automatic packaging machines, which form and fill the packages starting from a multilayer web of packaging material. In particular, in such packaging machines a continuous tube is formed from the web which is initially wound in a reel and fed through a plurality of unwinding rollers.
The web is typically fed through a sterilization unit for sterilizing the web by applying a chemical sterilization agent, which is then removed after sterilization is completed, e.g. evaporated by heating.
Subsequently, the web is maintained in a closed, sterile environment and is folded and sealed longitudinally to form the tube.
In order to complete the forming operations, the tube is filled from above, by means of a pipe, with the pourable food product and is formed, sealed and subsequently cut along equally spaced transversal cross sections.
Pillow packs are obtained thereby, which have a longitudinal sealing band, a top transversal sealing band and a bottom transversal sealing band, and which are then folded mechanically to form respective substantially parallelepiped-shaped finished packages.
To open the sealed packages described above, i.e. to allow access to the pourable product therein, various solutions of opening devices have been proposed.
According to a known solution, the web is initially provided with holes, or prelaminated holes (i.e. holes formed through the base layer only and covered by the aforementioned lamination layers and/or barrier layer and defining a pierceable or removable portion of the packaging material), and opening devices which are applied, at an application station, at such holes or prelaminated holes, respectively.
In greater detail, each hole or prelaminated hole defines a predetermined area of the web at which an opening device must be applied.
In particular, each opening device is applied at the respective predetermined area of the web by injecting plastic material directly thereat. In this case, the application station is an injection molding station.
In use, the web is unwound from the aforementioned reel. Subsequently, the web is stepwise fed to the application station before the packaging material is folded to form the tube. In particular, the web is fed towards the application station along an advancing path (or advancing direction).
The application of opening devices on the web requires that the predetermined areas are stopped in respective nominal positions with respect to the application station, for a correct application of each opening device.
EP-A-2357138 , in the name of the same Applicant, discloses a unit for applying opening devices onto respective pre-laminated holes, which define the predetermined areas of the web. The unit comprises a molding station, which is stepwise (i.e. intermittently) fed with the web and is adapted to injection mold a plurality of opening devices on the web and at respective prelaminated holes of the web.
The molding station comprises a plurality of molds, in particular three molds, arranged adjacent to one another along the advancing path and injecting the plastic material forming the opening devices on the web at respective prelaminated holes of the web.
Accordingly, a plurality of portions of the web is fed along the advancing path and through the application station, each portion of the web comprising a number of prelaminated holes corresponding to the number of molds of the molding station, i.e. three in the case of EP-A-2357138 .
Ideally, each prelaminated hole must be centered at the respective mold, i.e. each prelaminated hole must be arranged in the respective nominal position.
According to EP-A-2357138 the intermediate prelaminated hole (i.e. the central prelaminated hole of the three prelaminated holes) is centered under the intermediate mold of the molding station, in particular on the basis of the actual position of the intermediate prelaminated hole detected by a sensor.
In this way, the web is positioned along the advancing path on the basis of the difference between the actual (detected) position and the nominal position of only one prelaminated hole, namely the intermediate one.
However, each of the remaining prelaminated holes, other than the intermediate prelaminated hole, may be arranged at a non-zero distance from its nominal position, measured along the advancing path, due to inherent and inevitable tolerance errors in the distances between homologous points, e.g. central axes, of the prelaminated holes on the web.
The higher the number of the molds in the molding station, the higher the propagation of the tolerance error to the prelaminated holes different from the intermediate prelaminated hole.
EP-A-2848399 , in the name of the same Applicant, shows a unit for applying opening devices onto respective prelaminated holes comprising two molding stations, namely an upstream molding station and a downstream molding station with respect to the advancing direction of the web, each one having three molds.
In order to avoid the propagation of the tolerance error a group of six prelaminated hole (intended to receive opening devices at the same time, i.e. during a single injection molding operation) are divided in two groups of three prelaminated holes. EP-A-2848399 describes an independent centering of the intermediate prelaminated hole of each group with respect to the intermediate mold of the respective molding station.
As far as the downstream molding station is concerned, centering of the respective intermediate prelaminated hole is made on the basis of a signal of a position sensor.
As far as the upstream molding station is concerned, centering of the respective intermediate prelaminated hole is made by means of a roller actuator arranged between the upstream molding station and the downstream molding station and controllable for recovering an intentionally imparted offset between a preliminary position of such intermediate prelaminated hole and the nominal position at which such intermediate prelaminated hole should receive the opening device.
Although the units for applying opening devices on a web of packaging material of the type described above work satisfyingly well, such units are still open to further improvement, in particular as per simplification of architecture, overall cost flexibility and increase of production capacity.

DISCLOSURE OF INVENTION

It is therefore an object of the present invention to provide a method for applying opening devices on a web of packaging material which is designed to meet at least one of the above-mentioned needs in a straightforward and low-cost manner.
This object is achieved by a method as claimed in the appended independent claim 1.
It is a further object of the present invention to provide a unit for applying opening devices on a web of packaging material which is designed to meet at least one of the above-mentioned needs in a straightforward and low-cost manner.
This object is achieved by a unit as claimed in the appended independent claim 8.
Preferred embodiments of the present invention are laid down in the appended dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

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

Figure 1 is a schematic side view, with parts removed for clarity, of a unit for applying opening devices to a web of packaging material according to the present invention;
Figure 2 is a larger-scale side view, with parts removed for clarity, of the unit of Figure 1;
Figures 3a and 4 are schematic views, with parts removed for clarity, of the unit of Figure 2 during two distinct operative conditions; and
Figure 3b is a diagram concerning the operative condition of the unit depicted in Figure 3a.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to Figure 1, number 1 indicates as a whole a non-limiting example of a unit for applying opening devices 2 (only schematically shown) at predetermined areas 3 of a web 4 of packaging material.
In particular, web 4 is designed for the production of sealed packages (not shown) containing a pourable product, preferably a pourable food product, to which the present disclosure will refer without loss of generality.
Preferably, the packaging material has a multilayer structure (not shown) and comprises a layer of fibrous material, e.g. paper, covered on both sides with respective lamination layers of heat-seal plastic material, e.g. polyethylene.
In the case of aseptic packages for long-storage products, such as UHT milk, the packaging material also comprises a layer of gas-and-light barrier material, e.g. aluminum foil or ethylene vinyl alcohol (EVOH) film, which is superimposed on a layer of heat-seal plastic material, and is in turn covered with another layer of heat-seal plastic material, the latter forming the inner face of the package eventually contacting the pourable product.
Such packages are formed by a packaging machine which includes unit 1 and is only partially shown.
In detail, the packaging machine includes a storage unit, at which a reel of web 4 is arranged, unit 1 and downstream of unit 1 a package filling and forming unit for forming the packages containing the pourable product.
In greater detail, the packages are formed starting from a tube (not shown) of packaging material. The tube is formed in a known manner downstream of unit 1 by longitudinally folding and sealing web 4.
The tube of packaging material is then filled with the pourable product, and is sealed and cut along equally spaced cross sections to form a number of pillow packs (not shown), which are then transferred to a folding unit where they are folded mechanically to form respective packages, in a manner known and not described in detail.
According to the preferred and non-limiting embodiment shown, predetermined areas 3 are defined by pierceable portions of web 4.
More precisely, such pierceable portions are defined by so-called prelaminated holes, i.e. holes (or openings) formed through the base layer only and covered by the lamination layers and/or the barrier layer of the packaging material, so that each hole is sealed by a respective sheet cover portion (known per se and neither shown nor described in detail).
According to another non-limiting embodiment, predetermined areas 3 are defined by through holes obtained (e.g. punched) in web 4.
As visible in Figure 1, predetermined areas 3 are distributed along web 4 longitudinally, i.e. in a lengthwise direction of web 4, at a non-zero distance from one another.
In particular, prelaminated areas 3 are arranged along web 4 in respective positions equally spaced from one another, except for some possible tolerance distance errors.
Accordingly, the present disclosure will refer, without loss of generality, to a unit 1 defining a molding unit for molding, in particular for injection molding, a plurality of opening devices 2 onto respective prelaminated holes.
In the following, the expressions "predetermined area" and "prelaminated hole" will be used interchangeably.
Web 4 includes a plurality of web portions 4a.
More precisely, web 4 is defined by a sequence of web portions 4a longitudinally attached to one another.
Unit 1 comprises a conveyor 5 (only schematically shown) configured to convey web 4 along an advancing path P.
Unit 1 comprises an application station 6 including a plurality of applicator devices 7 arranged one after the other along advancing path P and each configured to apply an opening device 2 at a respective predetermined area 3.
In particular, in accordance with the above, each applicator device 7 is preferably a molding device for injection molding an opening device 2 on a respective predetermined area 3.
Unit 1 comprises a feeding device 8, such as a roller actuatable in rotation, configured to feed web 4 through application station 6 and to intermittently feed one web portion 4a at a time through application station 6.
In detail, feeding device 8 stepwise feeds, in use, web portions 4a of web 4 one after the other, each web portion 4a comprising a predetermined number of predetermined areas 3.
In greater detail, feeding device 8 is configured to sequentially feed one web portion 4a at a time through application station 6.
Opportunely, each web portion 4a includes a number of predetermined areas 3 corresponding to the number of applicator devices 7 in the application station 6.
According to the non-limiting embodiment shown, application station 6 includes six applicator devices 7.
Accordingly, each web portion 4a includes six predetermined areas 3, i.e. six prelaminated holes, each configured to receive an opening device 2 molded by a respective applicator device 7.
More specifically, each web portion 4a includes a number of sections of web 4 (six in this preferred embodiment), each section having a prelaminated hole, i.e. a predetermined area 3, and each section being designed to define a respective package, once formed, sealed, cut from web 4 (in particular from the formed and sealed tube) and folded.
Unit 1 further comprises a control unit 10.
Control unit 10 is configured to drive conveyor 5 and feeding device 8 so as to control the stepwise feeding of web portions 4a through application station 6.
Furthermore, control unit 10 is configured to drive applicator devices 7 once each web portion 4a is temporarily stopped at application station 6, thereby determining the application of opening devices 2 onto the respective predetermined areas 3.
Preferably, unit 1 includes two buffer portions 11 arranged respectively upstream of application station 6 and downstream of application station 6 and configured to ensure a smooth and continuous advancement of web 4 along advancing path P, while allowing the temporary stopping of web portions 4a, according to a manner known and not described in detail.
In light of the above, for each web portion 4a a first section of web 4 first entering the application station 6 and a second section of web 4 last entering the application station 6 (due to the stepwise feeding action of feeding device 8) can be identified.
The other sections are comprised between the first section and the second section along advancing path P.
Accordingly, for each web portion 4a a first predetermined area 3a first entering application station 6 and a second predetermined area 3b last entering application station 6 (due to the stepwise feeding action of feeding device 8) can be identified (Figure 3a) .
For example, in the embodiment shown, second predetermined area 3b is the sixth predetermined area entering application station 6, for each web portion 4a.
The remaining predetermined areas 3 of each web portion 4a are comprised between first predetermined area 3a and second predetermined area 3b along advancing path P.
For the sake of brevity, reference will be made in the following to a single web portion 4a to be advanced through application station 6 for receiving corresponding opening devices 2 at its predetermined areas 3. The structural and functional features of unit 1 described hereinafter in connection with such web portion 4a are equally applicable to all web portions 4a of web 4.
As visible in Figure 2, each applicator device 7 has a central axis A arranged in a fixed position along advancing path P.
Conveniently, central axes A are arranged at the same distance from one another along advancing path P.
In light of the above, application station 6 includes at least a first applicator device 7a and a second applicator device 7b, respectively arranged first and last when considering said plurality of applicator devices 7 of application station 6 along advancing path P.
More precisely, first applicator device 7a is configured to apply an opening device 2 on the first predetermined area 3a and second applicator device 7b is configured to apply an opening device 2 on the second predetermined area 3b.
Each predetermined area 3, i.e. each prelaminated hole, has a central axis B.
In nominal operative conditions, feeding device 8 feeds web portion 4a so that each predetermined area 3 is arranged with its central axis B coaxial to a respective central axis A. Such nominal operative condition is shown in Figure 2. However, as said, tolerance errors in the distances between homologous points, i.e. the central axes B, of predetermined areas 3 inevitably occurs during manufacturing of web 4, thereby leading to non-nominal operative conditions.
According to an aspect of the present disclosure, control unit 10 is configured to:

detect the position along advancing path P of first predetermined area 3a (in particular central axis B thereof) and the position of second predetermined area 3b (in particular central axis B thereof);
calculate a calculated distance D1, along advancing path P, between the detected position of first predetermined area 3a (in particular central axis B thereof) and the detected position of second predetermined area 3b (in particular central axis B thereof).

In particular, calculated distance D1 corresponds to the real distance between the position of first predetermined area 3a (in particular central axis B thereof) and the position of second predetermined area 3b (in particular central axis B thereof) and depends on the aforementioned tolerance errors.
According to the present disclosure, control unit 10 is further configured to compare calculated distance D1 with a reference distance D2 correlated to a distance between a pre-set nominal position of first predetermined area 3a (for example, the one shown in Figure 2) and a pre-set nominal position of second predetermined area 3b (for example, the one shown in Figure 2), along advancing path P.
In one embodiment, reference distance D2 is defined by an average distance obtained as an average of a predetermined number of calculated distances D1 respectively calculated (detected) for a corresponding predetermined number of web portions 4a.
More precisely, control unit 10 calculates, in use, a number of calculated distances D1 between the position of first predetermined area 3a (in particular central axis B thereof) and the position of second predetermined area 3b (in particular central axis B thereof) for a predetermined number of web portions 4a. Then, control unit 10 calculates an average distance on the basis of such calculated distances D1. Then, control unit 10 determines the reference distance D2 as the calculated average distance.
Preferably, the aforementioned average distance is calculated on the basis of a predetermined number of calculated distances D1 last calculated (detected) by control unit 10. In other words, reference distance D2 is calculated as a moving average of the last calculated distances D1.
In one embodiment, reference distance D2 is calculated as the moving average of the last 20 calculated distances D1 which are calculated (detected) by control unit 10.
Therefore, according to such embodiment, reference distance D2 is updated at each web portion 4a fed through application station 6.
In one embodiment, reference distance D2 is correlated to, and in particular is defined by, the distance between central axis A of first applicator device 7a and central axis A of second applicator device 7b.
Figure 3a schematically shows calculated distance D1 and reference distance D2.
In Figure 3a calculated distance D1 and reference distance D2 are shown not to scale, in particular the difference between calculated distance D1 and reference distance D2 are amplified for sake of illustration.
According to the present disclosure, control unit 10 is further configured to calculate a distance offset value E (Figure 3b) as a function of the difference between calculated distance D1 and reference distance D2.
In particular, distance offset value E is calculated as the absolute value of the mathematical difference between calculated distance D1 and reference distance D2.
Figure 3b schematically depicts distance offset value E as a difference between calculated distance D1 and reference distance D2.
In other words, distance offset value E defines a distance error between the position of first predetermined area 3a (in particular central axis B thereof) and the position of second predetermined area 3b (in particular central axis B thereof) with respect to reference distance D2, for web portion 4a.
Control unit 10 is further configured to control the position of web portion 4a at application station 6 so that one predetermined area 3 (amongst predetermined areas 3 of web portion 4a) is arranged at a distance equal to a fraction E/k (with k being a predefined constant value) of distance offset value E from a reference position of such one predetermined area 3 along advancing path P.
In particular, the reference position of such one predetermined area 3 is defined by the nominal position of such one predetermined area 3 along advancing path P, i.e. the position that such one predetermined area 3 should have during nominal operative conditions of unit 1. In one embodiment, the nominal position is the position at which axis B of said one predetermined area is aligned, i.e. coincides, with axis A of the applicator device 7 configured to apply an opening device 2 at said one predetermined area 3.
In one embodiment, fraction E/k equals half of distance offset value E and, therefore, corresponds to E/2.
In one embodiment, the reference position is the position of first applicator device 7a, and more in particular the position of central axis A thereof.
In particular, according to the present disclosure, control unit 10 is configured to control the position of web portion 4a at application station 6 so that first predetermined area 3a is arranged at a distance equal to fraction E/k of distance offset value E, and more in particular at a distance equal to half distance offset value, i.e. E/2, from a reference position of first predetermined area 3a. In particular, such reference position is a nominal position of first predetermined area 3a, i.e. a position that first predetermined area 3a should have during nominal operative conditions of unit 1).
In particular, control unit 10 is further configured to control the position of web portion 4a at application station 6 so that second predetermined area 3b is arranged at a distance equal to a further fraction (E - E/k) of distance offset value E, and in particular at a distance equal to half distance offset value E, i.e. E/2, from a reference position of second predetermined area 3b. In particular, such reference position is a nominal position of second predetermined area 3b, i.e. a position that second predetermined area 3b should have during nominal operative conditions of unit 1)
In practice, control unit 10 is advantageously configured to control the position of web portion 4a so that first predetermined area 3a is arranged at a distance equal to fraction E/k of distance offset value E, and in particular at a distance equal to half distance offset value E, i.e. E/2, from central axis A of first applicator device 7a.
Moreover, control unit 10 is advantageously configured to control the position of web portion 4a so that second predetermined area 3b is arranged at a distance equal to further fraction (E - E/k of distance offset value E, and in particular at a distance equal to half distance offset value E from central axis A of second applicator device 7b.
The resulting positioning of web portion 4a at application station 6 is schematically shown in Figure 4, whereby first predetermined area 3a and second predetermined area 3b are each arranged at a distance equal to E/2 from the respective nominal position, i.e. from central axis A of, respectively, first applicator device 7a and second applicator device 7b.
According to the present disclosure, the distance offset value E, i.e. the distance error, is "distributed" amongst all the predetermined areas 3 of web portion 4a.
Therefore, the risk that the difference between the position of a predetermined area 3 and its reference position (i.e. its nominal position) is out of a certain tolerance error range is significantly reduced.
Preferably, unit 1 includes a sensor device 12 arranged upstream of application station 6, in particular arranged upstream of second applicator device 7b, along advancing path P.
Sensor device 12 is configured to detect marks 13 on web 4 and to generate a signal correlated with the detection of marks 13 and to send the generated signal to the control unit 10.
Each mark 13 is associated to one respective predetermined area 3. Each mark 13 is configured to provide information on the position of the respective predetermined area 3.
In one embodiment, each mark 13 includes a magnetic portion, such as a magnetic band, and sensor device 12 is a sensor of magnetic and/or electromagnetic type configured to detect such magnetic portions.
In another embodiment, each mark 13 includes an optically detectable reference band, and sensor device 12 is a sensor of optical type configured to detect such reference band.
Sensor device 12 is advantageously configured to detect a first mark 13a on web portion 4a, such first mark 13a being correlated with the actual position of first predetermined area 3a along advancing path P.
Conveniently, sensor device 12 is further configured to detect a second mark 13b on said respective web portion, such second mark 13b being correlated with the actual position of the second predetermined area 3b along advancing path P.
In this way, control unit 10 is able to effectively detect the positions of at least first predetermined area 3a and second predetermined area 3b.
Preferably, calculation of distance offset value E is performed by control unit 10 while second predetermined area 3b travels from sensor device 12 to second applicator device 7b (in particular central axis A thereof).
This is particularly advantageous, as the detection of the positions, i.e. the reading of marks 13 by sensor device 12, is most effective when the advancing speed of web 4 is low.
More precisely, as advancing of web 4, and particularly of web portions 4a is performed by feeding device 8 in an intermittent, stepwise manner, the advancing speed of web 4, and therefore of each web portion 4a, is low at the start and at the end of each intermittent advancement.
The moment when second predetermined area 3b travels from sensor device 12 to second applicator device 7b (in particular central axis A thereof) corresponds to the end of the intermittent advancement for each web portion 4a.
Therefore, such moment corresponds to a time interval during which web portion 4a slows down, preparing to temporarily stop at application station 6.
As said, during this time interval, reading of marks 13 by sensor device 12 is more effective, as reading errors are less probable when the advancing speed of web is low.
In one advantageous embodiment, control unit 10 is configured to:

compare the calculated distance offset value E with a predetermined distance offset threshold value;
issue a warning and/or control a discard of the respective web portion 4a and/or control a stop of unit 1 if the calculated distance offset value E is equal to, or above of, said distance offset threshold value.

Preferably, control unit 10 is configured to prevent the applicator devices 7 from applying opening devices 2 onto predetermined areas 3 of web portion 4a if the calculated distance offset value E is equal to, or above, said distance offset threshold value.
In this way, application of opening devices 2 on predetermined areas 3 whose actual positions along advancing path P are too deviant from the respective nominal positions can be avoided.
This ultimately results in material savings, and it may also result in production time savings, since opening devices 2 which are applied at positions too deviant from the nominal positions may cause jamming in the packaging machine, downstream of unit 1.
In one embodiment, control unit 10 is configured to detect the positions along advancing path P of all the predetermined areas 3 of the same web portion 4a.
In detail, sensor device 12 is configured to detect the positions of all the marks 13 of web portion 4a, associated to the respective predetermined areas 3.
Accordingly, control unit 10 is configured to:

calculate a distance offset value between the position of each predetermined area 3 and a reference position thereof; and
control corrective operations to be performed if one or more of the calculated distance offset values are equal to, or above, a predetermined distance offset threshold value.

For example, the corrective operations may include issuing a warning and/or controlling a discard of the respective web portion 4a and/or controlling a stop of unit 1.
Thanks to the detection of the position of each predetermined area, the aforementioned "distribution" of the distance offset value E, i.e. of the distance error, can be better controlled for each predetermined area 3 of web portion 4a.
In fact, by knowing the actual position of each predetermined area 3, it can be ensured that each predetermined area 3 is in a position with a distance error within the desired tolerance range.
Hence, the efficacy of the position control of web portions 4a, and therefore the effectiveness and quality of the application of opening devices 2, is further improved.
From the foregoing, it is clear how unit 1 according to the present disclosure enables to implement a method for applying opening devices 2 on a web 4 of packaging material at predetermined areas 3 of said web 4 arranged at a non-zero distance from one another, the method comprising the steps of:

a) conveying the web 4 along an advancing path P, the web 4 including a plurality of web portions 4a;
b) feeding the web 4 through an application station 6 having a plurality of applicator devices 7 arranged one after the other along the advancing path P and each configured to apply an opening device 2 at a respective predetermined area 3, wherein the step b) of feeding includes intermittently feeding one web portion 4a at a time through the application station 6, each web portion 4a having a number of predetermined areas 3 corresponding to the number of applicator devices 7 in the application station 6;
c) detecting the position along the advancing path P of a first predetermined area 3a first entering the application station 6 during the step b) of feeding, for a respective web portion 4a;
d) detecting the position along the advancing path P of a second predetermined area 3b last entering the application station 6 during the step b) of feeding, for the same respective web portion 4a;
e) calculating a calculated distance D1, along the advancing path P, between the detected position of said first predetermined area 3a and the detected position of said second predetermined area 3b;
f) calculating a distance offset value E as a function of the difference between calculated distance D1 and a pre-set reference distance D2 between a pre-set reference position of said first predetermined area 3a and a pre-set reference position of said second predetermined area 3b along the advancing path P;
g) controlling the position of said respective web portion 4a at the application station 6 as a function of the calculated distance offset value E, the step g) of controlling comprising arranging one predetermined area 3 of web portion 4a at a distance equal to a fraction E/k of distance offset value E from a reference (nominal) position of such one predetermined area 3;
h) applying the opening devices 2 on the respective predetermined areas 3 of the respective web portion 4a by means of the applicator devices 7.

In particular, the step g) of controlling comprises arranging the first predetermined area 3a at a distance equal to a fraction E/k of said distance offset value E from said reference position of the first predetermined area 3a.
In a preferred embodiment, the step g) of controlling comprises arranging the first predetermined area 3a at a distance equal to half said distance offset value E, i.e. E/2, from said reference position of the first predetermined area 3a.
Preferably, the step g) of controlling comprises arranging the second predetermined area 3b at a distance equal to a further fraction (E - E/k) of said distance offset value E from said nominal position of the second predetermined area 3b.
In a preferred embodiment, the step g) of controlling comprises arranging the second predetermined area 3b at a distance equal to half said distance offset value E, i.e. E/2, from said reference position of the second predetermined area 3b.
Preferably, the step g) of controlling comprises arranging central axis B of the first predetermined area 3a at a distance equal to half said distance offset value E from central axis A of the first applicator device 7a and/or arranging central axis B of the second predetermined area 3b at a distance equal to half said distance offset value E from central axis A of the second applicator device 7b.
Preferably, the step c) of detecting comprises detecting a first mark 13a on said respective web portion 4a, the first mark 13a being correlated with the first predetermined area 3a along the advancing path P, and/or the step d) of detecting comprises detecting a second mark 13b on said respective web portion 4a, the second mark 13b being correlated with the second predetermined area 3b along the advancing path P.
Preferably, the method further comprises the steps of:

i) comparing the calculated distance offset value E for each web portion 4a with a predetermined distance offset threshold value;
j) issuing a warning and/or discarding the respective web portions 4a and/or stopping the step a) of conveying, the step b) of feeding and the step h) of applying if the calculated distance offset value E is equal to, or above of, said distance offset threshold value.

Preferably, the method further comprises the steps of:

k) detecting respective positions along the advancing path P of all the predetermined areas 3 of the same web portion 4a;
l) calculating a distance offset value between the detected position of each predetermined area 3 and its reference position;
m) performing corrective operations if one or more of the calculated distance offset values are equal to, or above of, a predetermined distance offset threshold value.

The advantages of unit 1 and of the related method according to the present disclosure will be clear from the foregoing description.
In particular, thanks to the above-described control of the positioning of web portions 4a at application station 6, the distance offset value E, i.e. the distance error, is "distributed" amongst all the predetermined areas 3 of web portion 4a.
Therefore, the risk that the position of a predetermined area 3 along advancing path P is out of the desired tolerance error range is significantly reduced.
Moreover, the presence of control unit 10 configured to perform the detections and calculations described above, allows for a simplification of architecture of unit 1.
In fact, it is sufficient to provide a single sensor device 12 arranged upstream of application station 6, without the need for any roller actuator or any tensioning or compensating device arranged in between the applicator devices 7.
This also allows to reduce the overall costs of unit 1.
Moreover, the flexibility of unit 1 is also increased, since the distance between two adjacent applicator devices 7 can be reduced, thanks to the fact that no roller actuator or sensor device 12 needs to be arranged between them.
Clearly, changes may be made to unit 1 or to the related method as described herein without, however, departing from the scope of protection as defined in the accompanying claims.

Claims

Method for applying opening devices (2) on a web (4) of packaging material at predetermined areas (3) of said web (4) arranged at a non-zero distance from one another, the method comprising the steps of:
a) conveying the web (4) along an advancing path (P), the web (4) including a plurality of web portions (4a);

b) feeding the web (4) through an application station (6) having a plurality of applicator devices (7) arranged one after the other along the advancing path (P) and each configured to apply an opening device (2) at a respective predetermined area (2), wherein the step b) of feeding includes intermittently feeding one web portion (4a) at a time through the application station (6), each web portion (4a) having a number of predetermined areas (3) corresponding to the number of applicator devices (7) in the application station (6);

c) detecting the position along the advancing path (P) of a first predetermined area (3a) first entering the application station (6) during the step b) of feeding, for a respective web portion (4a);

d) detecting the position along the advancing path (P) of a second predetermined area (3b) last entering the application station during the step b) of feeding, for the same respective web portion (4a);

e) calculating a calculated distance (D1), along the advancing path (P), between the detected position of said first predetermined area (3a) and the detected position of said second predetermined area (3b);

f) calculating a distance offset value (E) as a function of the difference between the calculated distance (D1) and a pre-set reference distance (D2) between a pre-set reference position of said first predetermined area (3a) and a pre-set reference position of said second predetermined area (3b) along the advancing path (P);

g) controlling the position of said respective web portion (4a) at the application station (6) as a function of the calculated distance offset value (E), the step g) of controlling comprising arranging one predetermined area (3) of said respective web portion (4a) at a distance equal to a fraction (E/k) of said distance offset value (E) from a reference position of said one predetermined area (3);

h) applying the opening devices (2) on the respective predetermined areas (3) of the respective web portion (4a) by means of the applicator devices (7).
Method as claimed in claim 1, wherein the step g) of controlling comprises arranging the first predetermined area (3a) at a distance equal to said fraction (E/k) of said distance offset value (E) from said reference position of the first predetermined area (3a).
Method as claimed in claim 2, wherein the step g) of controlling comprises arranging the second predetermined area (3b) at a distance equal to a further fraction (E - E/k) of said distance offset value (E) from said reference position of the second predetermined area (3b).
Method as claimed in claim 2 or 3, wherein each applicator device (7) includes a central axis (A) arranged in a fixed position along the advancing path (P);
wherein the application station (6) includes at least a first applicator device (7a) and a second applicator device (7b), respectively arranged first and last of said plurality of applicator devices (7) along the advancing path (P), the first applicator device (7a) being configured to apply an opening device (2) on said first predetermined area (3a) and the second applicator device (7b) being configured to apply an opening device (2) on said second predetermined area (3b) , for each web portion (4a) fed through the application station (6); and

wherein the step g) of controlling comprises arranging the first predetermined area (3a) at a distance equal to a fraction (E/k) of said distance offset value (E) from the central axis (A) of the first applicator device (7a) and/or arranging the second predetermined area (3b) at a distance equal to a further fraction (E - E/k) of said distance offset value (E) from the central axis (A) of the second applicator device (7b).
Method as claimed in any one of the foregoing claims, wherein the step c) of detecting comprises detecting a first mark (13a) on said respective web portion (4a), the first mark (13a) being correlated with the first predetermined area (3a) along the advancing path (P); and/or
wherein the step d) of detecting comprises detecting a second mark (13b) on said respective web portion (4a), the second mark (13b) being correlated with the second predetermined area (3b) along the advancing path (P).
Method as claimed in any one of the foregoing claims, and comprising the steps of:
i) comparing the calculated distance offset value (E) for each web portion (4a) with a predetermined distance offset threshold value;

j) issuing a warning and/or discarding the respective web portions and/or stopping the step a) of conveying, the step b) of feeding and the step h) of applying if the calculated distance offset value (E) is equal to, or above of, said distance offset threshold value.
Method as claimed in any one of the foregoing claims, and comprising the steps of:
k) detecting the positions along the advancing path (P) of all the predetermined areas (3) of the same web portion (4a);

l) calculating a distance offset value between the detected position of each predetermined area (3) and its reference position;

m) performing corrective operations if one or more of the calculated distance offset values are equal to, or above of, a predetermined distance offset threshold value.
Unit (1) for applying opening devices (2) on a web (4) of packaging material at predetermined areas (3) of said web (4) arranged at a non-zero distance from one another, the unit (1) comprising:
- a conveyor (5) configured to convey the web (4) along an advancing path (P), the web (4) including a plurality of web portions (4a);

- an application station (6) including a plurality of applicator devices (7) arranged one after the other along the advancing path (P) and each configured to apply an opening device (2) at a respective predetermined area (3);

- a feeding device (8) configured to feed the web (4) through the application station (6) and to feed one web portion (4a) at a time through the application station (6), each web portion (4a) having a number of predetermined areas (3) corresponding to the number of applicator devices (7) in the application station (6);

- a control unit (10);
wherein the control unit (10) is configured to:
- detect the position along the advancing path (P) of a first predetermined area (3a) first entering the application station (6), for a respective web portion (4a);

- detect the position along the advancing path (P) of a second predetermined area (3b) last entering the application station (6), for the same respective web portion (4a);

- calculate a calculated distance (D1), along the advancing path (P), between the detected position of said first predetermined area (3a) and the detected position of said second predetermined area (3b);

- calculate a distance offset value (E) as a function of the difference between the calculated distance (D1) and a pre-set reference distance (D2) between a pre-set reference position of said first predetermined area (3a) and a pre-set reference position of said second predetermined area (3b) along the advancing path (P);

- control the position of said respective web portion (4a) at the application station (6) so that one predetermined area (3) of said respective web portion (4a) is arranged at a distance equal to a fraction (E/k) of said distance offset value (E) from a reference position of said one predetermined area (3).
Unit as claimed in claim 8, wherein the control unit (10) is configured to control the position of said respective web portion (4a) at the application station so that the first predetermined area (3a) is arranged at a distance equal to said fraction (E/k) of said distance offset value (E) from said reference position of the first predetermined area (3a).
Unit as claimed in claim 9, wherein the control unit (10) is configured to control the position of said respective web portion (4a) at the application station (6) so that the second predetermined area (3b) is arranged at a distance equal to a further fraction (E - E/k) of said distance offset value (E) from said reference position of the second predetermined area (3b).
Unit (1) as claimed in claim 9 or 10, wherein each applicator device (7) includes a central axis (A) arranged in a fixed position along the advancing path (P);
wherein the application station (6) includes at least a first applicator device (7a) and a second applicator device (7b), respectively arranged first and last of said plurality of applicator devices (7) along the advancing path (P), the first applicator device (7a) being configured to apply an opening device (2) on said first predetermined area (3a) and the second applicator device (7b) being configured to apply an opening device (2) on said second predetermined area (3b), for each web portion (4a) fed, in use, through the application station (6); and

wherein the control unit (10) is configured to control the position of said respective web portion (4a) so that the first predetermined area (3a) is arranged at a distance equal to a fraction (E/k) of said distance offset value (E) from the central axis (A) of the first applicator device (7a) and/or so that the second predetermined area (3b) is arranged at a distance equal to a further fraction (E- E/k) of said distance offset value (E) from the central axis (A) of the second applicator device (7b).
Unit (1) as claimed in any one of claims 8 to 11, and further comprising a sensor device (12) configured to detect a first mark (13a) on said respective web portion (4a), the first mark (13a) being correlated with the first predetermined area (3a) along the advancing path (P), and/or to detect a second mark (13b) on said respective web portion (4a), the second mark (13b) being correlated with the second predetermined area (3b) along the advancing path (P),
the sensor device (12) being further configured to generate a signal correlated with the detection of said first mark (13a) and said second mark (13b) and to send the generated signal to the control unit (10).
Unit (1) as claimed in any one of claims 8 to 12, wherein the control unit (10) is configured to:
- compare the calculated distance offset value (E) for each web portion (4a) with a predetermined distance offset threshold value; and to

- issue a warning and/or control a discard of the respective web portions (4a) and/or control a stop of the unit (1) if the calculated distance offset value (E) is equal to, or above of, said distance offset threshold value.
Unit (1) as claimed in any one of claims 8 to 13, wherein the control unit (10) is configured to:
- detect respective positions along the advancing path (P) of all the predetermined areas (3) of the same web portion (4a);

- calculate a distance offset value between the position of each predetermined area (3) and its reference position;

- control corrective operations if one or more of the calculated distance offset values are equal to, or above of, a predetermined distance offset threshold value.