Patent Publication Number: US-2022212489-A1

Title: An apparatus for digital printing of carton-based material and a method thereof

Description:
TECHNICAL FIELD 
     The invention generally relates to the field of packaging technology, such as food packaging technology. More particularly, it is presented methods and apparatuses for digital printing of carton-based packaging material for packages holding liquid food products. 
     BACKGROUND ART 
     Today it is commonly known to use roll-fed packaging machines for different types of food products, e.g. milk. The roll-fed packaging machines, also referred to as filling machines, have several advantages. One is that a continuous production of packages makes it possible to achieve higher speeds compared to blanks-fed packaging systems. Another advantage is that by continuously filling a tube of packaging material and forming packages in a lower end of the tube, a risk that unwanted microorganisms enter the packages can be lowered. 
     The packaging material is today most often printed using so-called flexography in packaging material production centers, sometimes also referred to as converting factories, for carton-based packaging material. After being printed and in other ways prepared for holding food products, for example being laminated such that an inner plastic layer is formed between a carton layer of the packaging material and the food product, the packaging material is loaded on to a reel and shipped to a site where a packaging machine is placed. 
     Instead of having the packaging material printed, e.g. by using flexography, and prepared in the packaging material production centers, it has been suggested to use digital printing for printing the packaging material. An advantage of using digital printing instead of flexography is that smaller batches may be printed in a cost efficient manner. 
     Even though it is known to use digital printing for printing the packaging material, there is a number of challenges that needs to be overcome. One of these challenges is to design the apparatus for digital printing such that this may be added to existing lines without requiring costly modifications and rebuilding of the packaging machine and or the building, in which the packaging machine is placed. 
     SUMMARY 
     It is an object to at least partly overcome one or more of the above-identified limitations of the prior art. In particular, it is an object to provide an apparatus for digital printing of packaging material that is designed in a compact manner and that can assure cost efficient packaging processes. 
     According to a first aspect it is provided an apparatus for digital printing of carton-based packaging material for packages holding liquid food products, wherein the packaging material has a first side adapted to form outer surfaces of the packages and a second side adapted to form inner surfaces of the packages, the apparatus comprising an inlet configured to receive a web of the packaging material and an outlet configured to transfer the web of packaging material out of the apparatus, a web feeding assembly, arranged to feed the web in a web feeding direction from the inlet through the apparatus to the outlet, comprising at least one drive unit and at least one web direction device, a number of print bars provided with print heads arranged to provide food graded ink on the first side of the web, wherein the at least one drive unit and at least one web direction device provide a first web turning arrangement for turning the web after being received via the inlet such that the first side of the web is facing towards the print heads, and a second web turning arrangement for turning the web after the food graded ink has been provided by the print heads, wherein the first web turning arrangement provides a first slack upstream the number of print bars and the second web turning arrangement provides a second slack downstream the number of print bars. 
     The apparatus may further comprise a pre-treatment device arranged upstream the printer bars and downstream the first slack. 
     The at least one drive unit may be arranged to feed the web in a reversed web feeding direction (A′) of the web between the first and second slack after an external downstream stop. 
     The at least one drive unit may be arranged, after having fed the web between the first and second slack in the reversed direction, to feed the web in the web feeding direction between the first and second slack for a pre-determined period of time before the web is fed in the web feeding direction between the inlet and the outlet. 
     The at least one drive unit may be arranged to feed the web in the web feeding direction between the second slack and the outlet for a predetermined period of time after an internal stop in the apparatus or after an external upstream stop. 
     The at least one drive unit may be arranged to feed the web in the web feeding direction between the first slack and the outlet after the external upstream stop. 
     The apparatus may further comprise a web tension arrangement arranged to provide for that the web is placed according to a setpoint with respect to the print heads, and placed downstream the first slack and upstream the second slack, wherein a tension or a slackening of the web caused by the web tension arrangement is compensated for by the first and/or second slack. 
     The apparatus may further comprise a number of curing devices provided with curing heads arranged for curing the food graded ink provided on the first side, wherein the curing heads are placed downstream the print heads and upstream the second slack. 
     The first web turning arrangement may be configured to turn the web 180 degrees, and/or the second web turning arrangement may be configured to turn the web 180 degrees. 
     At least part of the number of print bars may be placed above at least part of the number of curing devices. 
     According to a second aspect it is provided a method for digital printing of carton-based packaging material for packages holding liquid food products, wherein the packaging material has a first side adapted to form outer surfaces of the packages and a second side adapted to form inner surfaces of the packages, the method comprising receiving a web of packaging material via an inlet, feeding the web from the inlet to an outlet in web feeding direction by using a web feeding assembly comprising at least one drive unit and at least one web direction device, turning the web by using a first web turning arrangement, wherein the first web turning arrangement forms part of the web feeding assembly, after being received via the inlet such that the first side of the web is facing towards print heads of printer bars, forming a first slack of the web, wherein the first slack is placed upstream the print heads, providing food graded ink on the first side of the web by using the number of print bars provided with the print heads, turning the web by using a second web turning arrangement, wherein the second web turning arrangement forms part of the web feeding assembly, after having provided the food graded ink on the first side, forming a second slack of the web, wherein the second slack is placed downstream the print heads and upstream the outlet, and transferring the web via the outlet. 
     The method may further comprise pre-treating the web by using a pre-treatment device arranged upstream the printer bars and downstream the first slack. 
     The method may further comprise, in case of an external downstream stop, feeding the web in a reversed web feeding direction between the first and second slack, feeding the web in the web feeding direction between the first and second slack for a pre-determined period of time, and feeding the web in the web feeding direction between the inlet and the outlet. 
     The method may further comprise, in case of an internal stop or an external upstream stop, feeding the web in the web feeding direction between the second slack and the outlet for a predetermined period of time. 
     The method may further comprise, in case of the external upstream stop, feeding the web in the web feeding direction between the first slack and the outlet. 
     Still other objectives, features, aspects and advantages will appear from the following detailed description as well as from the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will now be described, by way of example, with reference to the accompanying schematic drawings, in which 
         FIG. 1  is a general illustration of a roll-fed packaging machine. 
         FIGS. 2 a  and 2 b    are side views of two embodiments of an apparatus for digital printing of carton-based packaging material for packages holding liquid food products. 
         FIG. 3  is a flow chart illustrating a method for digital printing of carton-based packaging material. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1 , a packaging machine  100 , sometimes also referred to as a filling machine, is generally illustrated by way of example. The packaging machine  100  is a roll-fed packaging machine used for packaging liquid food products in carton-based packages. Already in the 1940s this type of packaging machines was introduced by Tetra Pak, and it is today a well-known approach for packaging milk and other liquid food products in a safe and cost-efficient manner. The general approach can also be used for non-liquid food products, such as potato crisps. 
     Today, packaging material is often printed and prepared in packaging material production centers, also referred to as converting factories, and is shipped to a site where the packaging machine  100  is placed, e.g. a dairy. Usually the packaging material is loaded onto a reel before being transported. After arriving at the site, the reel is placed in the packaging machine as illustrated in  FIG. 1 . 
     During production a web  102  of packaging material can be fed from the reel through the packaging machine in a web feeding direction A. Even though not illustrated in  FIG. 1 , the packaging material may pass through a sterilization device, e.g. 
     a hydrogen peroxide bath or an LVEB (Low-Voltage Electron Beam) station, for ensuring that the web  102  is free from unwanted microorganisms. Before providing the food product, a tube can be formed from the web  102  by forming a longitudinal sealing. The food product can be fed into the tube via a pipe  104  and a valve  106  may be used for regulating a flow through the pipe  104 . A lower end  108  of the tube can be fed into a folding device  110  in which a transversal sealing is made, the tube is folded according to folding lines, also referred to as weakening lines or creasing lines, and cut off such that packages  112  can be formed. Even though the folding device  110  is illustrated as one single device, the folding device  110  may comprise a number of different devices. 
     Instead of having the web  102  of packaging material printed in packaging material production centers, i.e. off-site printed, the web  102  can be printed on-site using e.g. digital printing in an apparatus  200  as illustrated in  FIGS. 2 a  and 2 b   . The apparatus  200  can be arranged such that the web  102  is fed via the apparatus  200  into the packaging machine  100 . 
     Packaging material may be fed into the apparatus  200  via a reel  202 . The packaging material may be partly printed, i.e. sections of the packaging material is printed in packaging material production centers, or the packaging material may be without printing, such that all printing is made by the apparatus  200 . 
     The packaging material may be loaded on to the reel  202  such that a first side  204 , adapted to form outer surfaces of the packages  112 , is facing outwards, and a second side  206 , adapted to form inner surfaces of the packages  112 , is facing inwards. The web  102  can be fed into the apparatus  200  via an inlet  207  with the first side  204  facing downwards. 
     In the apparatus  200 , the web  102  may be fed forward by a web feeding assembly. The web feeding assembly may comprise a first roller  208   a,  a second roller  208   b,  a third roller  208   c  or any other type of web direction device, and a first drive unit  210 , a second drive unit  211 , a third drive unit  224 , and a fourth drive unit  225  that together are providing for that the web is fed through the apparatus  200  as well as unloaded from the reel  202 . To be able to compensate for that different steps in the apparatus  200  may require different amounts of time at different occasions, the web  102  may form a first slack  212  downstream the first drive unit  210 . The first slack  212  may be formed between the inlet  207  and a pre-treatment device  214 . 
     From the first slack  212 , the web  102  may be fed into the pre-treatment device  214  in which the packaging material is pre-treated such that printing can be made in subsequent stations downstream the pre-treatment device  214 . As illustrated, the printing may be provided by using a number of print bars, herein by example four print bars  216   a,    216   b,    216   c,    216   d,  in combination with a number of pinning devices providing for an initial curing, herein by example four pinning devices  217   a,    217   b,    217   c,    217   d.  The print bars  216   a,    216   b,    216   c,    216   d  can be provided with print heads that are facing downwards such that these can provide for that the first side  204  is printed with food graded ink when passing the print bars. 
     As illustrated in  FIG. 2 a   , after being printed the web can be turned such that the first side is facing downwards. By using a number of curing devices, herein by example three curing devices  218   a,    218   b,    218   c,  the food graded ink provided by the print bars  216   a,    216   b,    216   c,    216   d  can be cured. The curing devices  218   a,    218   b,    218   c  can be provided with curing heads facing upwards such that the curing heads are facing the first side  204  of the packaging material. The curing devices  218   a,    218   b,    218   c  can be an energy curing for example electron beam or UV light. 
     The web  102  may be turned by using a fourth roller  219 , or any other type of web direction device, placed downstream the print bars  216   a,    216   b,    216   c,    216   d  and upstream the curing devices  218   a,    218   b,    218   c.  The fourth roller  219  may form part of a web tension arrangement  220  that can be used to provide for that the web  102  is tensioned when printing, pinning and/or curing, and/or the fourth roller  219  may form part of the web feeding assembly. 
     The web tension arrangement  220  may comprise a shielding arrangement  222  that is hindering emission, for example the UV light, from the curing devices  218   a,    218   b,    218   c  from reaching the print heads of the print bars  216   a,    216   b,    216   c,    216   d.  The shielding arrangement  222  may e.g. be metal plates placed between the curing heads and the print heads. 
     The web tension arrangement  220  may be embodied in various ways. By way of example, as illustrated in  FIGS. 2 a  and 2 b   , the web  102  may be tensioned by moving the fourth roller  219  such that the web is tensioned or loosened, in turn providing for that the web  102  can be placed correctly with respect to the print heads and/or the curing heads. Put differently, the web tension arrangement  220  can provide for that the web  102  is placed according to a set point. 
     After being cured, the web  102  can be fed via the third drive unit  224 , that can form part of the web feeding assembly, to a second slack  226  and thereafter out of the apparatus  200  via an outlet  227 . An advantage with the second slack  226  is that this makes it possible to compensate for minor stops in the packaging machine  100  placed downstream, as well as speed variations within the apparatus  200 . 
     A general advantage with the apparatus  200  is that the print bars  216   a,    216   b,    216   c,    216   d  may be placed above the curing devices  218   a,    218   b,    218   c,  which provides for that a compact design can be achieved. Further, by redirecting the web twice the packaging material can be provided in the same manner as of today, i.e. provided on the reel  202  with the first side  204  facing outwards, and also the packaging machine  100  can be provided in the same manner as of today, i.e. receiving the web with the first side  204  facing downwards. Another advantage with the design is therefore that few or no modifications are required in the packaging machine  100  and in the packaging material production centers. 
     As illustrated in  FIG. 2 a    and as explained above, the web  102  may be turned 180 degrees after passing the print heads and before passing the curing heads such that e.g. the printer bars  216   a,    216   a,    216   c,    216   d  can be placed above the curing devices  218   a,    218   b,    218   c.  Put differently, a normal vector of the first side  204  may be directed in a first direction D 1  when being fed into the apparatus  200  via the inlet  207 . By using the web feeding assembly the web  102  may be redirected such that the normal vector is directed in a second direction D 2  when reaching the print heads of the printer bars  216   a,    216   b,    216   c,    216   d.  After printing, i.e. downstream the print heads, the web  102  may be redirected such that the normal vector of the first side  204  is directed in a third direction D 3 . If having the printer bars placed above the curing devices as illustrated in  FIG. 2 a   , the second direction D 2  and the third direction D 3  may represent two opposite directions, i.e. 180 degrees apart from each other. 
       FIG. 2 b    illustrates another example of how the apparatus may be designed. In the example illustrated in  FIG. 2 b   , the printer bars  216   a,    216   b,    216   c,    216   d  are placed such that the print heads are facing downwards, in line with the print heads of the apparatus  200  illustrated in  FIG. 2 a   , but unlike the apparatus  200  illustrated in  FIG. 2 a   , the curing devices  218   a,    218   b,    218   c  are placed such that the curing heads are facing horizontally such that the web  102  may be cured while this is moving vertically, more particularly, in this example, downwards. Put differently, instead of redirecting the web  102  such that the normal vector of the first side is shifted 180 degrees, as illustrated in  FIG. 2 a   , the normal vector is redirected 90 degrees. 
     Further, even though not illustrated, it is also possible to have both the print bars  216   a,    216   b,    216   c,    216   d  and the curing devices  218   a,    218   b,    218   c  horizontally placed and opposite to each other, and redirecting the web 180 degrees downstream the printer bars  216   a,    216   b,    216   c,    216   d  and upstream the curing devices  218   a,    218   b,    218   c.    
     Even though the examples above are related to redirecting the normal vector downstream the printer heads and upstream the curing heads 90 or 180 degrees, it is to be understood that this only examples and that the web  102  may be directed not only according to these specified examples, e.g. in several minor steps of less than 90 degrees. 
     An advantage with having the first and the second slack  212 ,  226  is that an external upstream stop may be handled efficiently, e.g. the printing and curing may continue even though feeding of the web is interrupted by that the reel  202  is to be changed. By having the first slack  212  it is namely possible to halt the feeding of the web from the inlet  207  to the first slack  212 , but continue to feed the web  102  from the first slack  212  to the print heads and throughout the apparatus  200 . An effect of halting feeding of the web  102  between the inlet  207  and the first slack  212  is that the first slack  212  is reduced, i.e. less packaging material are provided in the first slack  212 . In order to compensate for that the packaging material in the first slack has been reduced it is possible, once feeding between the inlet  207  and the first slack  212  is re-started, to feed the web with higher speed between the inlet and the first slack for a period of time such that the packaging material provided in the first slack is increased to a level held before the feeding between the inlet and first slack was halted. The first slack  212 , as well as the second slack  226 , may comprise packaging material corresponding to at least one package  112  and a maximum amount of packaging material in the first slack  212 , as well as the second slack  226 , may be set such that the packaging material can hang freely, i.e. the maximum amount of packaging material can be set based on what a design of the apparatus  200  allows for. 
     Turning or re-directing the web  102  is therefore not only beneficial from a foot print perspective, i.e. that a compact design can be achieved, and that no or few modifications of the packaging machine  100  are required, but also in that the first and second slack  212 ,  226  can be formed such that interruptions can be handled efficiently and compensated for. 
     In case of an internal stop, e.g. a quality control is made that is requiring that the web  102  is halted between the first and second slack  212 ,  226 , this may be handled by that the web  102  continues to be fed from the inlet  207  to the first slack  212  and, as an effect, that packaging material held in the first slack  212  is increased, and/or that the web  102  continues to be fed from the second slack  226  to the outlet  227  such that the packaging material in the second slack  226  is reduced. 
     In case of an external downstream stop, e.g. the filling machine  100  is halted, the web  102  may be halted as well and thereafter the web  102  may be fed in a reversed direction A′ between the second slack  226  and the first slack  112 . An advantage with this is that a part of the web  102  that has been pre-treated by the pre-treatment device  214 , but not printed and cured may be pre-treated again such that a time between pre-treatment and printing is not extended due to the halting of the filling machine  100 . If extending the time between pre-treatment and printing above a time threshold, the printing will namely be negatively affected. 
     Therefore, in case of the external downstream stop, the web  102  may be fed in the reversed direction A′ between the second and first slack  226 ,  212  and thereafter fed in the direction A between the first and second slack  212 ,  226  such that packaging material levels in the first and second slacks are reverted back to levels held before the external downstream stop. After having adjusted the levels in the first and second slack  212 ,  226  and the external downstream stop is removed, the web  102  may be fed in the direction A between the inlet  207  and the outlet  227 . 
     As illustrated in  FIGS. 2 a  and 2 b   , the web  102  may be turned by using the first and the second drive unit  210 ,  211  such that the first side  204  is facing towards the print heads. These two together with other web direction devices used may together generally be referred to as a first web turning arrangement  228 . The fourth roller  219  may, as illustrated in  FIGS. 2 a  and 2 b   , form part of a second web turning arrangement  230  arranged for turning the web  102  after the food graded ink has been provided by the print heads. The second web turning arrangement  230  may, as illustrated in  FIG. 2 a   , turn the web  102  180 degrees by using a single roller, in this particular example the fourth roller  219 . Another option, as illustrated in  FIG. 2 b   , is to turn the web  102  in several stages. As illustrated in  FIG. 2 b   , the web  102  is turned 90 degrees by using the fourth roller  219  and thereafter 90 degrees using another roller. Further, by way of example, the first slack  212 , which is provided by the first web turning arrangement  228 , may be provided as part of the turning of the web, or as is the case for the second web turning arrangement  230 , which provides the second slack  226 , the second slack  226  may be provided after the web  102  has been turned. 
     In  FIG. 3  it is presented a flowchart illustrating a method for digital printing of carton-based packaging material for packages  112  holding liquid food products by way of example. In a first step  302  the web  102  of packaging material can be received via the inlet  207 . In a second step  304 , the web  102  can be fed from the inlet  207  to the outlet  227  in the web feeding direction A by using the web feeding assembly  208   a,    208   b,    208   c,    210 ,  211 ,  219 ,  224 ,  225 , comprising the at least one drive unit  210 ,  211 ,  224 ,  225  and the at least one web direction device  208   a,    208   b,    208   c,    219 . In a third step  306 , the web can be turned by using the first web turning arrangement  228 , wherein the first web turning arrangement forms part of the web feeding assembly, after being received via the inlet  207  such that the first side  204  of the web  102  is facing towards the print heads of the printer bars  216   a,    216   b,    216   c,    216   d.  In a fourth step  308 , the first slack  212  of the web  102  can be formed, wherein the first slack  212  is placed upstream the print heads. In a fifth step  310 , food graded ink can be provided on the first side  204  of the web  102  by using the number of print bars  216   a,    216   b,    216   c,    216   d  provided with the print heads. In a sixth step  312 , the web can be turned by using the second web turning arrangement  230 , wherein the second web turning arrangement forms part of the web feeding assembly, after having provided the food graded ink on the first side  204 . In a seventh step  314 , the second slack  226  of the web  102  can be formed, wherein the second slack  212  can be placed downstream the print heads and upstream the outlet  227 . In an eighth step  316 , the web can be transferred via the outlet  227 . 
     Optionally, in a ninth step  318 , the web  102  may be pre-treated by using a pre-treatment device  214  arranged upstream the printer bars  216   a,    216   b,    216   c,    216   d  and downstream the first slack  212 . 
     Optionally, in case of the external downstream stop, in a tenth step  320 , the web  102  may be fed in a reversed web feeding direction A′ between the first and second slack  212 ,  226 . Thereafter, in an eleventh step  322 , the web may be fed in the web feeding direction A between the first and second slack  212 ,  226  for a pre-determined period of time, and, in a twelfth step  324 , the web may be fed in the web feeding direction A between the inlet  207  and the outlet  227 . 
     Optionally, in case of an internal stop or an external upstream stop, in a thirteenth step  326 , the web  102  may be fed in the web feeding direction A between the second slack  226  and the outlet  227  for a predetermined period of time. 
     Optionally, in case of the external upstream stop, in a fourteenth step  328 , the web  102  may be fed in the web feeding direction A between the first slack  212  and the outlet  227 . 
     Even if described in a specific order it is to be understood that the steps do not have to be performed in this order. 
     From the description above follows that, although various embodiments of the invention have been described and shown, the invention is not restricted thereto, but may also be embodied in other ways within the scope of the subject-matter defined in the following claims.