HK1058028B - Unit for processing a web of packaging material - Google Patents

Description

Unit for processing a web of packaging material

Technical Field

The present invention relates to a unit for processing a web of packaging material for producing sealed packages of pourable food products.

Background

It is well known that many pourable food products, such as fruit juice, pasteurized or UHT (ultra high temperature treated) milk, wine, tomato sauce, etc., are sold in packages made of sterilized packaging material.

A typical example of such a package is the parallelepiped package for liquid or pourable food products, known as Tetra Brik Aseptic (registered trademark), which is shaped by folding and sealing a web made of laminated packaging material. The packaging material has a multilayer structure comprising a layer of fibrous material, e.g. paper, covered on both sides by layers of heat-sealed 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 oxygen-barrier material, defined for example by an aluminium film, which is superimposed on a layer of heat-seal plastic material, and which is in turn covered with another layer of heat-seal plastic material, eventually defining the inner surface of the package which is in contact with the food product.

As is known, such packages are manufactured on fully automatic packaging machines, on which a continuous tube is made of packaging material supplied in web form.

More specifically, a web of packaging material is sterilized and then fed to a forming unit, where it is folded and sealed longitudinally to form a vertical tube. The tube is filled with the sterilized or sterile-processed food product, is sealed by pairs of jaws and is subsequently cut at equally spaced cross sections to form pillow packs, which are then folded mechanically to form the finished, e.g. substantially parallelepiped-shaped, packages.

Upstream of the forming unit, the web of packaging material may be conveyed through a processing unit for carrying out various auxiliary operations, which may include, for example, making a plurality of through openings or holes at predetermined points on the web, and one or more operations for fixing the opening devices to the holes, when producing packages with opening devices such as tear-off tabs, screw caps or hinged caps.

The most commonly used opening devices comprise a patch defined by a small sheet of heat-seal plastic material, which is heat-sealed to a corresponding hole in the lateral edge of the web to be finally formed inside the package; and a tear-away tab applied to the opposite side edge of the wrapper and heat sealed to the patch. The sheet and patch are bonded to each other so that when the sheet is torn, the portion of the patch heat sealed to the sheet is also removed, thereby opening the hole.

In order to close the package after tearing of the foil, the portion of the packaging material surrounding the foil is fitted with a frame element, usually made of plastic material, which supports a removable, for example screw or hinged, lid for closing the corresponding hole.

Alternatively, it is also known to apply closable opening devices directly to the apertures in the web by injection moulding of plastics material, as described in patent WO 98/18609.

On known machines, the web of packaging material is fed stepwise through the processing unit by a conveyor system comprising conveyor rollers controlled by a servomotor in turn controlled in response to signals emitted by optical sensors for detecting reference elements, typically preprinted indicia such as bar codes, that are repeated at equal intervals along the web.

In the case of a processing unit comprising a punching station and two heat-sealing stations for applying patches and tearing off the sheets, respectively, a high precision is required for the positioning of the web, in particular at the sheet-sealing station.

That is, to ensure a good seal of the holes in the web, the size of the patches and the sheets must be proportional to the maximum deviation between the working position of the heat-sealing station and the holes themselves. The size of the foil is an important parameter which directly determines the size of the frame and the cover applied to the foil, and therefore the foil must be kept as small as possible to avoid significant drawbacks when using relatively large covers.

Similarly, when the processing unit comprises, in addition to the punching station, a station for moulding the closable opening devices directly onto the corresponding holes in the web, the portion of the web surrounding each hole must be correctly positioned in the moulding cavity to ensure that the injected heat-seal plastic material flows correctly into the moulding cavity and thus that the edges of the holes are correctly sealed to both sides of the web.

There is therefore a need in the industry to process webs with greater precision at each station of the unit.

Disclosure of Invention

It is an object of the present invention to provide a unit for processing a web of packaging material for sealed packages of pourable food products, which unit provides a high degree of accuracy during at least two consecutive operations on the same portion of the web.

According to the present invention, there is provided a unit for processing a web of packaging material for the manufacture of sealed packages of pourable food products, comprising at least a first station for forming a plurality of through holes in the web; a second station for sealing the hole by applying respective opening devices for opening the package; a conveyor for stepwise conveying the web along a path through the first and second stations; a position sensor for generating an occurrence signal indicating the passage of a reference element on the web past the sensor; and control means responsive to the presence signal for controlling the conveying means; characterised in that the reference element has a predetermined relationship with the apertures in the web; the unit also comprises actuating means cooperating with the second station to move it in a direction parallel to the path, and actuated by the control means to adjust the position of the second station as a function of the presence signal.

Drawings

Preferred, non-limiting embodiments of the present invention are described below, by way of example, with reference to the accompanying drawings, in which:

fig. 1 is a schematic side view of a unit according to the present invention for processing a web of packaging material for sealed packages of pourable food products;

FIG. 2 is an enlarged side view, partially in section, of the actuating means of the unit shown in FIG. 1;

FIG. 3 is a reduced exploded perspective view of the actuator shown in FIG. 2;

FIG. 4 is a perspective view of a portion of a web during processing;

FIG. 5 is a logical block diagram illustrating a portion of the operation of the control device on the unit of FIG. 1.

Detailed Description

Reference numeral 1 in fig. 1 designates an integral unit according to the invention for processing a web 2 of packaging material for making sealed packages of pourable food products, such as pasteurized or UHT milk, fruit juice, wine, etc.

The unit 1 may be loaded into a packaging machine (not shown) for continuously forming packages from a web 2 of packaging material. More specifically, web 2 is folded and sealed longitudinally in a known manner to form a vertical tube filled with the sterilized or sterile-processed food product, the tube being sealed at equally spaced sections and subjected to successive mechanical folding operations to form the finished package.

The web 2 is fed along a path P through the unit 1 and is provided on one surface with a plurality of optically detectable reference elements, such as preprinted indicia, which typically comprise respective bar codes C (fig. 4) distributed along the path P at equal intervals equal to the length of the web 2 from which a package is made minus the inevitable manufacturing tolerances of the web 2.

The web 2 of packaging material has a multilayer structure substantially comprising a layer of fibrous material, for example paper, covered on both sides with respective layers of heat-seal plastic material, for example polyethylene. The side of web 2 that ultimately forms the inner surface of the package and thus comes into contact with the food product also has a barrier layer, defined for example by an aluminium film, covered on both sides with respective layers of heat-seal plastic material, such as polyethylene.

The unit 1 comprises a known punching station 3 (only schematically illustrated) positioned along a first vertical portion P1 of the path P, where the web 2 is punched to form a plurality of openings or holes 4 (fig. 4) distributed along the path P at equal intervals, in the example shown substantially egg-shaped, equal to the length of the web 2 from which a package is made minus the above-mentioned manufacturing tolerances of the web 2.

The unit 1 also comprises, downstream of the station 3 and arranged in series along a second horizontal portion P2 of the path P, a first and a second station 5, 6 (which are well known and only schematically illustrated) for applying a patch 7 and a tear-off tab 8, respectively, onto each hole 4 and onto the opposite surface of the web 2.

More specifically, patch 7 is defined by a small rectangular sheet made of heat-seal plastic material and is heat-sealed at station 5 to a corresponding hole 4 in the face of web 2 which ultimately forms the inside of the package; the sheet 8, likewise made of heat-seal plastic material and rectangular in shape, is heat-sealed at station 6 to respective patches 7 on the surface of web 2 that ultimately forms the outside of the package. More specifically, at the end of the operations carried out in stations 5 and 6, each tab 8 projects outwardly with respect to a respective hole 4 in web 2 and is engaged with a respective patch 7 on a sealing area extending to the vicinity of the lateral edge of hole 4 and inwardly of the lateral edge of hole 4, the sealing area also defining a tear portion of patch 7 which is removed when tab 8 is torn.

Each sheet 8, like the web 2 of packaging material, has a multilayer structure and is defined by a layer of heat-seal plastic material, for example polyethylene, one face of which is eventually bonded to the respective patch 7, and a layer of barrier material, usually aluminium; which is secured to the layer of heat-seal plastic material on the opposite side to the patch 7.

Unit 1 also comprises a conveyor 10 for stepwise conveying web 2 along path P through stations 3, 5 and 6.

More specifically, conveyor 10 comprises two rollers 11, 12 and web 2, rollers 11, 12 cooperating with opposite surfaces of web 2, defining the downstream end of portion P2 of path P, and controlled by a servomotor 13; web 2 is guided from portion P1 to portion P2 of path P by idle guide roller 14.

More specifically, the roller 11 is controlled by a servomotor 13 via a transmission 15, for example a toothed belt, the roller 11 in turn controlling the roller 12 via a second transmission (not shown), such as a gear.

The transport means 10, and in particular the servomotor 13, are controlled by a control device 20 which responds on the basis of an appearance signal S generated by a position sensor 21, for example a photocell, which position sensor 21 is positioned along the path P and indicates the passage of the barcode C on the web 2 past the sensor 21.

More specifically, the sensor 21 is positioned close to the station 3 along the path P, which in the example shown is located downstream of the station 3, so that the distance between the respective hole 4 formed in the station 3 and the bar code C is not affected by the inevitable pulling of the web 2 when passing through the unit 1, and the detection of the bar code C by the sensor 21 is very precisely equivalent to the detection of the respective hole 4.

When the bar code C on the web 2 runs past the sensor 21, the presence signal S assumes a first logic level, such as a high level; and a second logic level, such as a low level, under any other condition.

An important aspect of the invention is that unit 1 also comprises an actuating device 22, which actuating device 22 cooperates with station 6 to move station 6 in a direction parallel to portion P2 of path P, and that actuating device 22 is activated by control device 20 to adjust the position of station 6 according to presence signal S emitted by sensor 21. More specifically, the above-mentioned adjustment is carried out by sliding the station 6 along the guides 23 schematically shown in fig. 1.

With reference to fig. 2 and 3, the actuating device 22 basically comprises an electric stepping motor 24 carried by a fixed supporting structure 25; and a motion-conversion assembly 26, arranged between the output shaft of motor 24 and plate-like structure portion 28 of station 6, for converting the rotation of shaft 27 into a linear movement of station 6 in a direction parallel to portion P2 of path P.

More specifically, the supporting structure 25 comprises a substantially rectangular base plate 30, the base plate 30 defining a C-shaped peripheral recess 31 facing the structural portion 28 of the station 6; and a substantially prismatic cup-shaped element 32, the cup-shaped element 32 being fixed to the plate 30 so as to engage the recess 31, the cup-shaped element 32 also having a lateral opening 33 facing the station 6 and a top opening 34, the top opening 34 being partially closed by an annular disk element 35 on which the motor 24 is coaxially fixed.

As shown in fig. 2 and 3, shaft 27 engages with a certain amount of radial clearance with disk element 35 and projects inside cup-shaped element 32.

Assembly 26 comprises a cam element 36 fitted to shaft 27 and housed inside cup-shaped element 32; and a thrust roller 37, which thrust roller 37 is fitted in a rotating and axially fixed manner to an appendage 38 of the structural part 28 of the station 6 and cooperates with the cam element 36.

More specifically, the cam element 36 is defined by a substantially cylindrical sleeve 40, from which sleeve 40 a substantially annular shaped flange 41 projects radially. The flange 41 has a cam profile defined by a curve of gradually increasing radius, the ends of which are connected by a substantially radial break-away portion.

The cam element 36, or more specifically the sleeve 40, is fitted coaxially with the interposition of a bearing 42 onto a cylindrical appendage 43 (figure 2) projecting from a bottom wall 44 opposite the top opening 34 of the cup-shaped element 32.

The cam element 36 and the thrust roller 37 are kept in contact by two clamping springs 45 arranged between the plate 30 and the structure 28 of the station 6, which springs have respective axes parallel to the portion P2 of the path P. More specifically, each spring 45 has a first end fixed to a bracket 46 projecting from plate 30; and an opposite second end fixed to a pin 47 projecting from the structural portion 28 of station 6.

Referring to fig. 1, control device 20 receives presence signal S from sensor 21 and issues output signals C1, C2, C3, C4, and C5 that control stations 3, 5, 6, and conveyor 10 and actuator 22, respectively.

More specifically, to adjust the position of station 6 before each sheet 8 is applied to a respective hole 4 in web 2, control device 20 implements the operations described below with reference to the logic block diagram in fig. 5.

As shown in fig. 5, control device 20 obtains an occurrence signal S indicating that bar code C has passed sensor 21 relative to the corresponding aperture 4 in web 2 (block 50).

The control means 20 then processes the presence signal S and calculates the absolute value and sign of the time T between the actual moment when the bar code C runs past the sensor 21 and the expected or planned moment that should have elapsed (block 51).

Based on the time T determined above and on the running speed of web 2, control device 20 calculates the distance and direction of rotation necessary for cam element 36 of actuating device 22 to pass from its current angular position to the work position in station 6 in which sheet 8 is applied correctly centred with respect to hole 4 (block 52). In other words, control device 52 calculates the absolute value and sign of the distance that station 6 must be moved by actuating device 22 in order for sheet 8 to be heat sealed correctly centred on respective hole 4.

Based on the displacement determined above, the control device generates a signal C5 to control the motor 24 of the actuator 22 (block 53).

The advantages of the unit 1 according to the invention are clear from the above description.

In particular, the actual position of each hole 4 in web 2 is detected by sensor 21, and the position of each time of station 6 is adjusted on the basis of the presence signal S emitted by sensor 21 so as to correctly centre sheet 8 on the respective hole 4, thus ensuring optimum sealing of holes 4 and enabling the size of sheet 8 to be reduced.

It is clear that changes may be made to unit 1 as described and illustrated herein without, however, departing from the scope of the accompanying claims.

In particular, unlike the detection of the bar code C, the sensor 21 can detect the passage of the hole 4 itself; in this case, sensor 21 may be positioned at any point between stations 3 and 6, so that the position of station 6 is adjusted after detection and before station 6 is activated to apply sheet 8 onto detected hole 4.

Unit 1 may also comprise another actuating device, identical to actuating device 22, controlled by control device 20, to adjust the position of station 5 in a direction parallel to portion P2 of path P.

Finally, a different operation may be carried out downstream of the punching operation, for example the second operation may comprise moulding the closable opening devices directly onto the corresponding apertures 4 in the web 2.

Claims (15)

1. A unit (1) for processing a web (2) of packaging material for the manufacture of sealed packages of pourable food products, said unit (1) comprising at least a first station (3) for forming a plurality of through holes (4) in said web (2); a second station (6) for sealing the holes by applying respective opening devices (7, 8) for opening the packages; -conveying means (10) for conveying said web (2) step by step along a path (P) through said first and second stations (3, 6); a position sensor (21) generating an appearance signal (S) indicating the passage of the reference element (C; 4) on said web (2) past the sensor (21); and control means (20) responsive to said presence signal (S) for controlling said conveying means (10); characterized in that said reference element (C; 4) has a predetermined relationship with said hole (4) in said web (2); said unit (1) further comprises actuating means (22), said actuating means (22) being associated with said second station (6) to move it in a direction parallel to said path (P) and being actuated by said control means (20) to adjust the position of said second station (6) as a function of said presence signal (S).

2. A unit as claimed in claim 1, characterized in that said control means (20) comprise acquisition means (50) for acquiring said presence signal (S) and generation means (53) for generating an adjustment signal (C5) for said actuating means (22) as a function of the time interval (T) between the actual moment when said reference element (C; 4) passes said sensor (21) and said desired moment of passage.

3. A unit as claimed in claim 2, characterized in that said control means (20) comprise first calculation means (51) for determining the absolute value and the sign of said time interval (T); and second means (52) for determining the absolute value and the sign of the required displacement of said second station (6) as a function of said time interval (T) and the running speed of said web (2) each time, so as to apply each of said opening devices (7, 8) centrally to a respective one of said holes (4) in said web (2).

4. A unit as claimed in any one of the foregoing claims, wherein said sensor (21) is located in the vicinity of said first station (3).

5. A unit as claimed in any one of the foregoing claims from 1 to 3, wherein said sensor (21) is located downstream of said first station (3) along said path (P).

6. A unit as claimed in claim 4, wherein said sensor (21) is located downstream of said first station (3) along said path (P).

7. A unit as claimed in any one of claims 1 to 3, wherein said reference element is a preprinted code (C) repeated along said web (2) of packaging material.

8. A unit as claimed in claim 4, wherein said reference elements are preprinted codes (C) repeated along said web (2) of packaging material.

9. A unit as claimed in claim 5, wherein said reference elements are preprinted codes (C) repeated along said web (2) of packaging material.

10. A unit as claimed in claim 6, wherein said reference elements are preprinted codes (C) repeated along said web (2) of packaging material.

11. The unit according to claim 7, characterized in that said preprinted code is a bar code (C).

12. A unit as claimed in any one of claims 8 to 10, characterized in that said preprinted code is a bar code (C).

13. A unit as claimed in any one of claims 1 to 3, wherein said reference element is defined by said hole (4) formed at said first station (3).

14. A unit as claimed in any one of the preceding claims 1 to 3, characterized in that each of said opening means comprises a tear-off tab (8) and a patch (7) sealed to each other and applied to opposite surfaces of said web (2) at the respective said aperture (4); said second station is a station (6) for applying said tear-off tab (8); said unit (1) further comprises a third station (5) for applying said patch (7) and located between said first and said second stations (3, 6).

15. A unit as claimed in any one of the foregoing claims from 1 to 3, wherein said second station (6) is mounted to slide along a guide (23) in a direction parallel to said path (P); and said actuating means (22) comprising an electric motor (24) and cam and thrust means (36, 37) arranged between an output shaft (27) of said motor (24) and a structural portion (28) of said second station (6).