Abstract:
A sheet of packaging material to form a package, comprises a receiving region to receive an opening device of the package attached thereon, the sheet of packaging material further comprises two reference marks detectable by a detecting unit of an applying device arranged for applying the opening device on the receiving region. A method for producing a package comprises folding, filling and sealing a sheet of packaging material to obtain the package, the packaging material comprising a receiving region to receive an opening device and two reference marks, the method comprising detecting the reference marks and selecting a subsequent action to be performed on the package and/or the opening device on the basis of the detected position of the reference marks.

Description:
TECHNICAL FIELD 
       [0001]    The present invention refers to a sheet of packaging material for producing a container. The present invention also refers to a method for producing containers, in particular containers provided with an opening device. 
       BACKGROUND OF INVENTION 
       [0002]    As is 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. 
         [0003]    A typical example of this type of package is the parallelepiped-shaped package for liquid or pourable food products known as Tetra Brik Aseptic (registered trademark), which is made by folding and sealing laminated strip packaging material. The packaging material has a multilayer structure comprising a base layer for stiffness and strength, which may comprise a layer of fibrous material, e.g. paper, or of mineral-filled polypropylene material, and which is covered on both sides with layers of thermoplastic material, e.g. polyethylene film. In the case of aseptic packages for long-storage products, such as UHT milk, the packaging material comprises a layer of oxygen-barrier material, e.g. aluminium foil, which is superimposed on a layer of thermoplastic material, and is in turn covered with another layer of thermoplastic material forming the inner face of the package eventually contacting the food product. 
         [0004]    Packages of this sort are produced on fully automatic packaging machines, on which a continuous tube is formed from the web-fed packaging material; the web of packaging material is sterilized on the packaging machine, e.g. by applying a chemical sterilizing agent, such as a hydrogen peroxide solution, which, once sterilization is completed, is removed from the surfaces of the packaging material, e.g. evaporated by heating; and the web of packaging material so sterilized is maintained in a closed, sterile environment, and is folded and sealed longitudinally to form a vertical tube. 
         [0005]    The tube is filled with the sterilized or sterile-processed food product, and is sealed and subsequently cut along equally spaced cross sections to form pillow packs, which are then folded mechanically to form respective finished, e.g. substantially parallelepiped-shaped, packages. 
         [0006]    Alternatively, the packaging material may be cut into blanks, which are formed into packages on forming spindles, and the packages are filled with the food product and sealed. One example of this type of package is the so-called “gable-top” package known by the trade name Tetra Rex (registered trademark). 
         [0007]    Once formed, the above packages may undergo further processing, such as the application of an opening device to enable the product to be poured out. 
         [0008]    At present, the most commonly marketed opening devices comprise a frame portion defining a pour opening and fitted about a removable or pierceable portion of a top wall of the package; and a cap hinged or screwed to the frame portion, and which is removable to open the package. 
         [0009]    In particular, each opening device may be applied to a corresponding so-called “prelaminated” hole of the packaging material, i.e. a hole formed in the base layer only and covered by the other lamination layers, including the layer of gas-barrier material. 
         [0010]    Applying units for applying opening devices to packages are known in which the packages are advanced by a conveying unit, for example a conveyor belt defining a substantially horizontal plane and supporting the packages. The applying units further comprise an applying device having applying elements that receives an opening device from a delivery unit, advance the opening device through a gluing unit, in which a layer of glue is distributed on the frame portion of the opening device, and then apply the opening device to a wall, in particular to a top wall, of the package. 
         [0011]    The applying units further comprise a sensor device, for example a camera, which detects the position of the packages, in particular of the “prelaminated” holes, and generates a signal which controls the applying elements. 
         [0012]    A drawback of the known applying units is that the opening device may be improperly applied to the package. In particular, in case the package is not aligned with the applying element—for instance in case the package is tilted on the conveyor belt—the opening device is not arranged in the right position, for example is not centered on the “prelaminated” hole. In this way, the final package may be defective. 
         [0013]    In case the mutual misalignment of the package and the applying element is even bigger, the applying unit may not be able at all to apply the opening device on the package. 
       DISCLOSURE OF INVENTION 
       [0014]    An object of the present invention is to improve the application of opening devices to packages. 
         [0015]    Another object of the invention is to prevent production of defective packages, having an opening device that is not correctly applied thereon. 
         [0016]    According to a first aspect of the present invention, there is provided a sheet of packaging material as claimed in claim  1 . 
         [0017]    According to a second aspect of the present invention, there is provided a method for producing a package as claimed in claim  11 . 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    A preferred, non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which: 
           [0019]      FIG. 1  is a plan view of a sheet of packaging material according to the invention; 
           [0020]      FIG. 2  is a section II-II of the sheet of packaging material of  FIG. 1 ; 
           [0021]      FIG. 3 , is a perspective view of a package obtained from the sheet of packaging material of  FIG. 1 ; 
           [0022]      FIG. 4  is plan view of a package obtained from the sheet of packaging material of  FIG. 1 , the package being tilted with respect to a reference position; 
           [0023]      FIG. 5  is schematic side view showing an apparatus for producing a package from the sheet of packaging material of  FIG. 1 ; 
           [0024]      FIG. 6  is a schematic top view of the apparatus of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0025]      FIG. 1  shows a sheet of packaging material  1  comprising a creasing pattern  2 , i.e. a number of creasing lines  3  obtained during manufacturing of the sheet of packaging material  1  and defining preferential folding lines along which the sheet of packaging material  1  is folded to form a package  10  (shown in  FIG. 3 ). 
         [0026]    In particular,  FIG. 1  shows a unit of packaging material intended to form a package  10 . This unit can be a portion of a packaging material web, or strip, comprising a plurality of units arranged one after the other, i.e. in a line, along a longitudinal dimension of the web, or strip. The web, or strip, may have the shape of a reel which is unwounded, formed into a tube, filled, sealed and cut into individual packages in a packaging machine. 
         [0027]    As an alternative, the unit may have the shape of a single blank which is folded, filled and sealed to obtain a corresponding package. 
         [0028]    The following description and the claims apply to both the reel-type (i.e. web, or strip) packaging material and the blank-type packaging material. 
         [0029]    As shown in  FIG. 2 , the packaging material  1  comprises a base layer  4  for stiffness and strength, which may be made of fibrous material, e.g. paper, or mineral-filled polypropylene material, and a first covering layer  5   a  and a second covering layer  5   b , made of heat-sealable plastic material, e.g. polyethylene films, and covering both sides of base layer  4 . 
         [0030]    In the case of an aseptic container for long-storage products, such as UHT milk, the sheet of packaging material  1  also comprises a barrier layer  6  made of gas-barrier material, e.g. aluminium foil or ethyl vinyl alcohol (EVOH) film, which is superimposed on the second covering layer  5   b  and is in turn covered with a third covering layer  5   c , made of heat-sealable plastic material, e.g. a polyethylene film, forming the inner face of the package  10  eventually contacting the food product. 
         [0031]    In other words, the first covering layer  5   a , the second covering layer  5   b , the barrier layer  6  and the third covering layer  5   c  define lamination layers applied to the base layer  4  when producing the sheet of packaging material  1 . 
         [0032]    The creasing lines  3  may be obtained by punching, so as to create indentations, or embossments, in the base layer  4 , the indentations, or embossments, being subsequently covered by the above-mentioned lamination layers. 
         [0033]    The sheet of packaging material  1  also comprises a receiving region  7  intended to receive an opening device (shown in  FIG. 3 ), which allows pouring of the product contained in the package  10 . 
         [0034]    As shown in  FIG. 2 , the receiving region  7  comprises a breakable portion  8 , for example a so-called pre-laminated hole, i.e. a hole (or opening)  9  formed through the base layer  4  of the sheet of packaging material  1  and covered by the above-mentioned lamination layers, so that the hole  9  is sealed by a respective sheet cover portion  30 . 
         [0035]    The receiving region  7  further comprises a border portion  11  surrounding the breakable portion  8 . The border portion defines an applying portion for the opening device  12 . The opening device  12  comprises a frame  13  arranged to be fixed, for example glued, or heat sealed, to the border portion  11  and a cutter (not shown) arranged to pierce the cover portion  30 , i.e. the breakable portion  8 , when the package  10  is opened for the first time. Opening devices of this kind are known and therefore not disclosed in detail, not being part of the present invention. 
         [0036]    In an alternative embodiment not shown, the breakable portion may even be defined by only one or some of the above-mentioned lamination layers. For example, the breakable portion may be made solely of gas-barrier material. 
         [0037]    In another alternative embodiment not shown, the breakable portion may be defined by a patch fixed to the rest of the sheet of packaging material to seal a hole formed, in this case, through the full thickness of the sheet of packaging material. 
         [0038]    The sheet of packaging material  1  further comprises two reference marks  14  detectable by a detecting unit  23  ( FIGS. 5 and 6 ) of an applying device  24  ( FIGS. 5 and 6 ) arranged for applying the opening device  12  on the receiving region  7 . In one embodiment, the detecting unit  23  comprises a camera. 
         [0039]    The two reference marks  14  comprise a first reference mark  14   a  and a second reference mark  14   b  which define a direction D. 
         [0040]    As shown in  FIGS. 1 and 2 , direction D is parallel to a first creasing line  15  defining a top front edge  16  and a top rear edge  17  of the package  10 . 
         [0041]    Similarly, direction D is parallel to a second creasing line  18  defining a bottom front edge  19  and a bottom rear edge  20  of the package  10 . 
         [0042]    In general the first reference mark  14   a  and the second reference mark  14   b  are disposed in a pre-determined position with respect to the creasing pattern  2 . In particular, the first reference mark  14   a  and the second reference mark  14   b  are arranged in such a way that direction D is aligned with at least some of the creasing lines  3 . 
         [0043]    As shown in  FIG. 1 , the first reference mark  14   a  and the second reference mark  14   b  are arranged on opposite sides of the receiving region  7 . 
         [0044]    The reference marks  14  may be obtained in different ways on the sheet of packaging material sheet. 
         [0045]    For example, the reference marks  14  may be printed on the base layer  4 , during manufacturing of the sheet of packaging material  1 , and subsequently covered with the first covering layer  5   a . In this case, the first covering layer  5   a  is made of a transparent material. 
         [0046]    As an alternative, the reference marks  14  may be printed on the sheet of packaging material  1  once the sheet of packaging material  1  has been manufactured. In this case, the reference marks are printed on the first covering layer  5   a.    
         [0047]    As a further alternative, the reference marks  14  may be of other types, such as magnetic reference marks detectable by a magnetic sensor. 
         [0048]    The sheet of packaging material  1  usually comprises printings, for instance images or portion of text connected with the product to be packaged into the package  10 . 
         [0049]    The reference marks  14  are, in this case, aligned with the printings. 
         [0050]    As shown in  FIG. 1 , the reference marks  14  are obtained in the receiving region  7 , in particular in the border portion  11 . 
         [0051]    The receiving region  7  has a different appearance with respect to a zone  22  of the sheet of packaging material  1  arranged outside of the receiving region  7 . 
         [0052]    The sheet of packaging material  1 —as disclosed above—may comprise printings in the zone  22  arranged outside of the receiving region  7 . In this case, the border portion  11  is an unprinted area of the sheet of packaging material  1  and the reference marks  14  are placed in the border portion  11 . In particular, the wording “unprinted area” means that the above-mentioned images or portion of text connected with the product to be packaged are not printed in the border portion  10 . 
         [0053]    In particular, the border portion  10  has a different appearance with respect to the breakable zone  8  and the zone  22  of the sheet of packaging material  1  arranged outside of the receiving region  7 . 
         [0054]    With reference to  FIGS. 5 and 6 , there is shown an applying device  24  for applying an opening device  12  to a package  10 . 
         [0055]    The applying device  24  comprises a conveying device  25 , for example a conveyor belt  27 , and an applying unit  26 . The applying unit  26  comprises a plurality of applying elements (not shown), each applying element being arranged to receive an opening device  12  from a delivering unit (not shown), to advance the opening  12  device through a glue distribution unit (not shown), in which a layer of glue is applied to the frame  13  of the opening device  12 , and to apply the opening device  12  to a respective package  10  advanced by the conveying device  25 . 
         [0056]    The applying unit  26  further comprises a detecting unit  23  arranged to detect the reference marks  14  so as to determine the position of the package  10 . 
         [0057]    In particular, the detecting unit  23  detects the first reference mark  14   a  and the second reference mark  14   b  and, therefore, the direction D defined by the first reference mark  14   a  and the second reference mark  14   b . Subsequently, the detecting unit  23  compares the orientation of the detected direction D with the orientation of a reference direction R. 
         [0058]    In case the detected direction D corresponds to the reference direction R, the detecting unit  23  sends a control signal to the applying unit  26  so that the applying element applies the opening device  12  to the package  10 . 
         [0059]    In case the detected direction D does not correspond to the reference direction R—for example if a package  10   a  is tilted with respect to the conveyor belt  27  (as shown in  FIGS. 5 and 6 ) and the detected direction D forms an angle α with the reference direction R (as shown in  FIG. 4 )—a plurality of different actions can be taken. 
         [0060]    According to a first embodiment, the detecting unit  23  sends a control signal to a discarding unit  28  that discards the package  10   a  and conveys the package  10   a  to a waste conveyor  29 . 
         [0061]    According to a second embodiment, the detecting unit  23  sends a control signal to a positioning device—not shown—that moves the package  10   a  with respect to the conveying device  25  until the direction D corresponds to the reference direction R. Subsequently, the applying element applies the opening device  12  to the package  10   a.    
         [0062]    According to a third embodiment, the detecting unit  23  sends a control signal to a moving device—not shown—that moves the applying element with respect to the package  10   a  until the direction D corresponds to the reference direction R. Subsequently, the applying element applies the opening device  12  to the package  10   a.    
         [0063]    According to a fourth embodiment, the detecting unit  23  generates an alarm system for an operator. 
         [0064]    Owing to the sheet of packaging material and to the method according to the invention it is possible to improve the application of opening devices to packages. 
         [0065]    By detecting the reference marks  14 , in fact, it is possible to check if the package is in the correct position before applying the opening device. In this way, it is possible to avoid production of defective packages, in which the opening device is applied in an incorrect position, and production of packages lacking the opening device at all. 
         [0066]    Since the first reference mark  14   a  and the second reference mark  14   b  define direction D—the orientation of which is compared with the orientation of the reference direction R—a very simple and effective detection system is obtained. 
         [0067]    In addition, in case the receiving region has a different appearance with respect to a zone of the packaging material arranged outside of the receiving region and the reference marks are arranged in the receiving region, the reference marks may be detected very easily and precisely. In the image generated by the detecting unit, in fact, the reference marks clearly stand out from the background. This is particularly applicable in case the reference marks are placed in the border portion, the border portion is an unprinted area of the sheet of packaging material and the zone of the packaging material arranged outside of the receiving region, i.e. outside of the border portion, is a printed area. 
         [0068]    Clearly, changes may be made to the sheet of packaging material  1  and the method for producing containers described herein without, however, departing from the scope of protection as defined in the accompanying claims.