TEXT OF THE DESCRIPTION

Field of the invention

The present invention falls within the technical sector of automatic machines for forming containers starting from a web of packaging material. More in particular, the present invention relates to a method for forming containers filled with a product and sealed starting from a web of multilayer packaging material. The present invention moreover regards a machine capable of implementing the aforesaid method.

A method for forming containers comprises, for example, the following steps:

- feeding the web of packaging material along a work path parallel to a longitudinal edge of the web; and

- welding a strip of heat-sealable material on the longitudinal edge of the web, according to an arrangement in which the strip of heat-sealable material extends along the longitudinal edge of the web.

Next, the web of packaging material is subjected to a forming operation in which it is folded into a tube, welded along a longitudinal sealing line, and filled with the product, for example a liquid, to be packaged. From the tube thus formed, which contains the liquid to be packaged, there are separated one after another closed semi-finished containers containing the aforesaid liquid.

In the present description, as likewise in the claims associated thereto, some terms and expressions are to be considered, except where otherwise explicitly indicated, as having the meaning given in the ensuing definitions.

By the term “parallel” is meant to refer to a substantial parallelism between two elements, comprising both the ideal case, where these elements are arranged with respect to one another so as to form a zero angle, and more frequent cases, where the two elements are arranged with respect to one another so as to form a nonzero but in any case negligible angle or an angle that is not important for the purposes of operation of the present solution, for example an angle of 10°. By “quality” of a weld, in particular between two elements, for example the longitudinal edge of the web and the strip of heat- sealable material, is understood the ensemble of the intrinsic properties of the weld, which comprise the width and constancy of the weld, the presence of nonwelded parts and/or holes and/or breaks on the weld itself

By the term “indication of quality” is meant a datum or a series of data, in any form, capable of providing information useful for distinguishing between an acceptable weld and an unacceptable weld. A weld is said to be “acceptable” when it has intrinsic properties such as to ensure duration thereof and guarantee the impermeability and integrity of the container. Instead, a weld is said to be “unacceptable” when it has defects, for example a variable width, non-welded parts, and/or holes, and/or breaks, which jeopardize duration thereof and likewise jeopardize impermeability and integrity of the container.

In physics, “colour” is defined as the visual perception of light electromagnetic radiation, or more simply light radiation, having one or more wavelengths. Net of a certain tolerance within the electromagnetic spectrum, it is assumed that an object has a pre-set colour when it reflects light radiation around the wavelength of the given colour perceived visually.

By the term “degree of covering” of an area by a predefined colour is meant the ratio between the extension of one or more portions of the aforesaid area that have the above predefined colour and the total extension of the area.

In a unit for processing, for example forming, a web that advances in a direction of feed, a first station is said to be “upstream” of a second station when the aforesaid first station precedes the second station with reference to the direction of feed of the web; instead, the second station is said to be “downstream” of the first station in so far as it follows the first station once again with reference to the direction of feed of the web.

In the context of the method for formation of containers, the strip of heat-sealable material has the function of making possible to provide a correct longitudinal sealing band for closing the tube in its axial direction. In particular, the aforesaid longitudinal sealing band is provided during the operation of forming the web of packaging material when the latter is folded into a tube and its two opposite longitudinal edges are fixed together via induction-welding means, thus forming the longitudinal sealing band.

The present applicant has noted that, in known methods, some containers may prove defective as regards tightness of their longitudinal sealing band, and has consequently perceived the need to check the weld in order to overcome the aforesaid drawback regarding the possible production of defective containers.

Originally, the present applicant thought of monitoring the position in which the strip of heat-sealable material is fixed to the web of packaging material during the production process. The present applicant, however, found that defective containers having a longitudinal sealing band that is not closed in a fluid-tight way may arise also with a manufacturing process that carries out a constant check on proper positioning of the strip of heat- sealable material on the web of packaging material.

The present applicant then noted that the defects of sealing of the longitudinal sealing band mainly derive from a non-optimal weld performed between the strip of heat-sealable material and the corresponding longitudinal edge of the web of packaging material.

The present applicant then investigated possible solutions to check the quality of the weld between the strip of heat-sealable material and the corresponding longitudinal edge of the web.

A first solution envisaged carrying out a sample check on the finished containers both with non-invasive modalities, for example simply checking whether there were leakages of liquid, and by disassembly of the container to examine directly the weld in question.

However, the present applicant noted that, since such checks are carried out on finished samples, i.e., when the machine has already produced the container filled with liquid, they simply gave rise to rejection of the container that presented the aforesaid defects. Moreover, it was highly likely that also the containers upstream and downstream of the reject presented the same defect, and thus also these constituted a production reject.

The present applicant then realized the need to carry out a check on the longitudinal weld directly on the production line and in particular on the web of packaging material still to be formed so as to identify any possible defects upstream of the forming process and prevent the production of defective containers. Finally, the present applicant understood that use of an optical image-acquisition device that frames the weld performed between the strip of heat-sealable material and the web of packaging material, and processing of the images thus acquired make it possible to obtain an indication of the quality of the weld effectively, it being possible to identify immediately any defects that might, instead, show up on the finished container only after a certain time.

According to a first aspect, the present invention concerns a method for forming containers filled with a product and sealed, starting from a web of packaging material.

The method preferably comprises feeding said web along a work path, preferably parallel to a longitudinal edge of said web.

The method preferably comprises applying, by welding, a strip of heat-sealable material to said longitudinal edge of said web, preferably according to an arrangement in which said strip extends along said longitudinal edge, more preferably according to an arrangement in which said strip has a first portion overlying said longitudinal edge and a second portion projecting from said longitudinal edge in a direction transverse to said longitudinal edge.

Preferably, the method comprises acquiring at least one image of the first portion of said strip applied to said longitudinal edge, preferably via an optical acquisition device.

Preferably, the method comprises processing said at least one image.

Preferably, the method comprises determining an indication of quality of the weld between said strip and said longitudinal edge on the basis of a result of said processing.

Thanks to the above characteristics, it is possible to identify operating conditions of the method that may cause improper welding of the strip on the web of packaging material and it is consequently possible to foresee and prevent production of defective containers.

According to a second aspect, the present invention regards a machine for forming containers filled with a product and sealed starting from a web of packaging material that can move along a work path.

The machine preferably comprises a welding device for welding a strip of heat-sealable material on a longitudinal edge of said web that advances along said work path, preferably according to an arrangement in which said strip extends along said longitudinal edge, more preferably according to an arrangement in which said strip has a first portion overlying said longitudinal edge and a second portion projecting from said longitudinal edge in a direction transverse to said longitudinal edge. Preferably, the welding device is an induction- welding device.

The machine preferably comprises an optical acquisition device, for acquiring preferably at least one image of said strip welded on said longitudinal edge.

The machine preferably comprises a control unit, preferably configured to determine an indication of quality of the weld of said strip on said longitudinal edge, preferably on the basis of said at least one image acquired by said optical acquisition device.

Thanks to the aforesaid characteristics it is possible to identify operating conditions of the machine that can cause improper welding of the strip on the web of packaging material and consequently prevent production of defective containers.

According to one or more of the aforesaid aspects, the present invention may comprise one or more of the characteristics described in what follows.

In one or more embodiments, the method further comprises setting an optical filter between said optical acquisition device and said strip welded on said longitudinal edge.

In one or more embodiments, said optical filter is a polarizing optical filter. Preferably, the method comprises bringing about, via said polarizing optical filter, a chromatic variation towards a predefined colour of a light beam reflected by at least one between said longitudinal edge and ???said [7CONTROLLARE - PROBABILE ERRORE NEL TESTO ITALIANO] welded strip, preferably directed towards said optical acquisition device.

Thanks to the aforesaid characteristics, it is possible to recognize easily, via the optical image-acquisition device the quality of welding of the strip on the web of packaging material.

In particular, the present applicant has noted that the inner coating layer on which the strip is applied is liable to change its own molecular structure when it is heated during application of the strip itself, thus assuming an optical behaviour such that the light reflected thereby is polarized. Moreover, the strip of heat-sealable material is normally translucid or transparent so that also the longitudinal edge of the inner coating layer of the web is visible through the strip welded thereon.

Thanks to the polarizing optical filter that is set between the welded strip and the optical acquisition device, the aforesaid variation of the molecular structure of the coating is converted into a chromatic variation of the light reflected by the coating itself, which can be readily detected via the optical acquisition device. Consequently, the areas of the web in which the expected chromatic variation is detected are adequately heated and hence have a weld of good quality, whereas the areas of the web in which a chromatic variation different from the expected one is detected are heated inadequately and hence have a defective weld.

In one or more embodiments, determining an indication of quality of said weld includes identifying a reference area on said at least one image. In one or more embodiments, determining an indication of quality of said weld includes determining a degree of covering of said reference area by said predefined colour.

In one or more embodiments, determining an indication of quality of said weld includes comparing said determined degree of covering with a reference degree. In one or more embodiments, determining an indication of quality of said weld includes generating an alarm signal if said degree of covering determined is less than said reference degree.

Thanks to the aforesaid characteristics, immediate intervention by an operator is allowed to restore proper operating conditions of the machine.

In one or more embodiments, said reference area includes a representation of said first portion of said strip in said image.

In one or more embodiments, applying, by welding, said strip of heat-sealable material on said longitudinal edge of said web includes heating at least one between said longitudinal edge of said web and said strip of heat- sealable material.

In one or more embodiments, said application by welding includes pressing via a pressure member said strip of heat-sealable material against said longitudinal edge of said web.

In one or more embodiments, said application by welding includes detecting a force exerted by said pressure member on said strip.

In one or more embodiments, said application by welding includes generating an alarm signal if said detected force is less than a reference force.

Thanks to the aforesaid characteristics, it is guaranteed that the strip is pressed against the web of packaging material with the pressure necessary to establish a firm fixing between the two components.

In one or more embodiments, the method comprises, after welding of said strip on said web of heat-sealable material: i) preferably, folding said web about a main axis along which said work path extends, to obtain a tube; ii) preferably, sealing said web folded into a tube along said main axis; iii) preferably, filling said tube with a product; iv) preferably, providing on said tube, in succession, sealing bands transverse to said main axis that define on said tube single semi-finished containers, sealed and filled with the product; and v) preferably, separating, via cutting, said single semi-finished containers from said tube.

In one or more embodiments, the method comprises, when said given indication of quality corresponds to an unacceptable weld, carrying out further welding of the strip of heat-sealable material to the longitudinal edge of the web along said first portion.

In one or more embodiments, the machine comprises an optical filter, preferably configured to filter a light beam reflected by at least one between said longitudinal edge and said first portion of said strip.

In one or more embodiments, said polarizing optical filter is configured to bring about a chromatic variation towards a predefined colour of said light beam reflected by at least one between said longitudinal edge and said first portion of said strip.

Preferably, said light beam reflected is directed towards said optical acquisition device.

Thanks to the aforesaid characteristics, it is possible to recognize easily, via the optical image-acquisition device, the quality of welding of the strip on the web of packaging material.

In one or more embodiments, said control unit is configured to identify on said at least one image a reference area and to determine a degree of covering of said reference area by said predefined colour.

In one or more embodiments, the machine comprises an alarm system, which in particular can be activated if said degree of covering is less than said reference degree.

Thanks to the aforesaid characteristics, immediate intervention by an operator is allowed to restore proper operating conditions.

In one or more embodiments, the machine comprises:

- preferably, a pressure member for pressing said strip against said longitudinal edge;

- preferably, a sensor for detecting a force exerted by said pressure member on said strip; and

- preferably, an alarm system that can be activated if the detected force is less than a reference force.

Thanks to the aforesaid characteristics, it is guaranteed that the strip is pressed against the web of packaging material with the pressure necessary to establish a firm fixing between the two components.

In one or more embodiments, the machine comprises a forming and filling unit set downstream of said welding device along said work path.

In one or more embodiments, the machine comprises a second welding device set downstream of said welding device.

In one or more embodiments, said control unit is configured to activate said second welding device so as to carry out further welding of said strip of heat-sealable material to said longitudinal edge of said web along said first portion. Preferably, said second welding device can be activated if said degree of covering is less than said reference degree.

It is pointed out that some steps of the method described above may be independent of the order of execution presented, except where there is expressly indicated as being necessary a sequentiality or simultaneity between two or more steps. Moreover, some steps may be optional. Furthermore, some steps may be carried out repetitively, or else may be carried out in series or in parallel with other steps of the method.

Further characteristics and advantages of the present invention will emerge clearly from the ensuing description with reference to the annexed drawings, which are provided purely by way of non-limiting example and in which:

- Figure 1 is a schematic illustration of an example of the method described herein;

- Figure 1 A is a schematic illustration of an example of a step of the method described herein;

- Figure 2 is a schematic illustration of an example of image processing envisaged in the method described herein.

In the ensuing description, various specific details are illustrated aimed at enabling an in-depth understanding of the embodiments. The embodiments may be provided without one or more of the specific details, or with other methods, components or materials, etc. In other cases, known structures, materials, or operations are not illustrated or described in detail so that various aspects of the embodiment will not be obscured.

The references provided herein are used merely for convenience and hence do not define the sphere of protection or the scope of the embodiments.

As anticipated above, the method described herein performs the function of forming containers filled with a product and sealed, starting from a web of packaging material.

The web of packaging material - designated by the reference number 100 in Figure 1 - may, for example, be a continuous web run off a reel along a work path K. As is in itself known in the art, the web 100 of packaging material may comprise at least a layer of aluminium, a layer of paper, and an inner coating of heat-sealable material.

With reference to Figure 1, the method described herein comprises the steps of:

- folding the web 100 about a main axis I to obtain a tube 200;

- sealing, along the main axis I, the web 100 folded into a tube, via a longitudinal sealing band 204 that joins two opposite longitudinal edges 100A, 100B of the web 100;

- filling the tube 200 with a product, for example a liquid 202 to be packaged;

- providing, in succession, on the tube 200 sealing bands 208 transverse to the main axis I, which define on the tube 200 single semifinished containers 300, sealed and filled with the liquid 202; and

- separating, via cutting, the single semi-finished containers 300 from the tube 200.

The aforesaid steps are carried out by a forming and filling unit 15, which may be of a known type and consequently will not be described herein in detail so as not to burden the present description.

The semi-finished containers 300 may possibly be subjected to further folding operations to assume a given definitive configuration.

With reference to Figure 1A, before the web is subjected to the operations referred to above, a strip 120 of heat-sealable material, which is for example translucid, is applied on one of the two longitudinal edges 100A, 100B of the web 100 (in the example illustrated, on the longitudinal edge 100A) and is welded thereto, according to an arrangement in which the strip 120 extends along the longitudinal edge itself.

In particular, in one or more preferred embodiments, like the one illustrated, during advance of the web 100 along the work path K the longitudinal edge 100 A is heated via an induction- welding device 50 and, simultaneously, the strip 120 of heat-sealable material is fed along the same work path K until it is brought into contact with the heated longitudinal edge 100A. The welding device 50 may be of a known type.

In one or more preferred embodiments, like the one illustrated, a fixing device 60 is configured for pressing the strip 120 against the longitudinal edge 100 A with a given force. In one or more preferred embodiments, like the one illustrated, the fixing device 60 comprises a pressure member 62 governed by a spring 64 for pressing the strip 120 against the longitudinal edge 100A.

Preferably, the strip 120 is set on the longitudinal edge 100 A in such a way as to overlie it only for a first portion 120 A thereof; the strip 120 moreover has a second portion 120B that projects from the longitudinal edge 100A in a direction transverse to the longitudinal edge 100A; i.e., it projects laterally beyond the longitudinal edge 100A itself.

The induction-welding device 50 is configured to generate a magnetic field such as to induce, in the metal layer that makes up the web 100, currents localized on the longitudinal edge 100 A, which are such as to heat by the thermoelectric effect the metal layer and, indirectly, the inner coating of the web of heat-sealable material.

The strip 120 that moves into contact with the aforesaid coating in the softened state adheres to the above layer, thus bringing about fixing of the two components. The fixing device 60 favours mutual adhesion of the two components.

According to an important characteristic thereof, the method described herein comprises the steps of:

- acquiring at least one image of the strip 120 welded on the longitudinal edge 100A via an optical acquisition device 80;

- processing the image acquired; and

- determining an indication of quality of welding of the strip 120 on the longitudinal edge 100A on the basis of aforesaid processing.

The optical acquisition device 80 may, for example, be a camera. A lighting device 84 may be used in association with the optical acquisition device 80 for lighting up the strip 120 welded on the longitudinal edge 100A of the web 100.

In one or more preferred embodiments, the method moreover envisages setting, between the optical acquisition device 80 and the strip 120 welded on the longitudinal edge 100 A, a polarizing optical filter 82 capable of bringing about a chromatic variation towards a predefined colour of a polarized light beam that is reflected by the longitudinal edge 100A in the direction of the optical acquisition device 80.

Following upon heating performed by the welding device 50, the inner coating layer (for example, a polyethylene layer) is liable to change its own molecular structure so that the light reflected thereby is polarized.

The polarizing optical filter that is set between the welded strip 120 and the optical acquisition device converts the aforesaid variation of the molecular structure of the coating into a chromatic variation of the light reflected by the coating itself, which is detected via the optical acquisition device.

With reference now to Figure 2, this represents an example of image of the strip 120 welded on the web 100, acquired by the optical acquisition device 80.

On the first portion 120A of the strip represented in the above image, which overlies the longitudinal edge 100 A of the web, two distinct areas may be identified, a first area Al and a second area A2, which differ from one another as regards their respective colour. The first area Al has the aforesaid predefined colour brought about by the polarizing optical filter and represents a region of the longitudinal edge 100A where there has been adequate heating of the web 100. Instead, the second area A2 has a colour different from the aforesaid predefined colour and represents a region of the longitudinal edge 100A in which there has been inadequate heating of the web.

It should be noted that the areas Al and A2 are each illustrated as a single continuous region for simplicity of representation. However, it will be understood that the two types of areas may also present each as a plurality of discrete and mutually separate areas.

The method envisages identification on the aforesaid image of a reference area A that encloses the first portion 120A of the strip, and determination of the degree of covering of the reference area A by the first area Al or, in other words, the degree of covering of the reference area A by the aforesaid predefined colour. It should be noted that it is altogether equivalent, for the purposes of the present invention, to calculate the degree of covering of the reference area A by the second area A2, in order to determine, for example by complementarity, the degree of covering of the reference area A by the predefined colour.

Since the degree of covering referred to above represents an indication of quality of welding of the strip 120 on the web 100, the extension of the first area Al (second area A2) is indicative of the effectiveness (ineffectiveness), i.e., of the efficiency, of the heating performed on the web 100, and hence provides an indication of the quality that can be obtained for welding of the strip 120 on the web 100.

In one or more preferred embodiments, the method described herein envisages comparing the determined degree of covering with a reference degree and generating an alarm signal if the degree of covering determined is less (with reference to the degree of covering of the first area Al) or else greater (with reference to the degree of covering of the second area A2) than the aforesaid reference degree.

The reference area A may be identified automatically on the basis of the image acquired by the optical acquisition device 80.

In one or more preferred embodiments, the method envisages identification of the reference area A with the perimeter of the first portion 120A of the strip 120 represented in the image acquired by the device 80.

In alternative embodiments, the reference area is, instead, a predefined digital element, and the method envisages association of the aforesaid area to the image acquired by the device 80 as a function of the position of the first portion 120A in the image.

The reference area A may have dimensions (width and/or length) that are the same as or different from the dimensions of the first portion 120 A represented in the image acquired. For instance, the reference area A may have a shorter length.

The processing described above of the image acquired may be performed via a control unit 90 connected to the optical acquisition device 80 and pre-arranged for executing a digital image-processing program.

The solution of advantageously using a material capable of changing its own optical behaviour when heated may regard, either also or as an alternative, the strip 120 itself, and in this case the degree of covering detected will thus depend also upon the variations undergone by the strip 120 as a result of heating. Evidently, the strip 120 may not be translucid.

In one or more preferred embodiments, the method described herein further comprises:

- detecting, via a sensor 65, a force exerted on the strip 120 by the pressure member 62 of the fixing device 60; and

- generating an alarm signal if the detected force is less than a reference force.

The sensor 65 may, for example, be a load cell.

In one or more preferred embodiments, the alarm signal may cause arrest of production of the containers so as to enable immediate intervention by the operator to restore the reference operating conditions of the fixing device 60.

Thanks to the aforesaid characteristics, it is guaranteed that the strip 120 of heat-sealable material will be pressed against the web 100 with the pressure necessary to establish a firm fixing between the two components.

In one or more embodiments, the solution described herein may envisage welding once again the strip 120 to the longitudinal edge 100 A of the web 100 if the indication of quality determined on the basis of the results of processing of the image acquired by the optical acquisition device 80 corresponds to an unacceptable weld.

In one or more embodiments, a second welding device may, for example, be positioned downstream of the welding device 50 and may be activated by the control unit 90 if the aforesaid indication of quality corresponds to an unacceptable weld.

The second welding device may be identical to the welding device 50. Possibly, a second fixing device similar to the fixing device 60 may be associated to the second welding device for pressing the strip 120 against the longitudinal edge 100 A after the strip 120 has been heated again. Of course, without prejudice to the principle of the invention, the details of construction and the embodiments may vary, even significantly, with respect to what has been illustrated herein purely by way of non-limiting example, without thereby departing from the scope of the invention, as defined by the annexed claims.