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Title:
INDUCTION SEALING SYSTEM, METHOD AND APPARATUS
Document Type and Number:
WIPO Patent Application WO/2015/124830
Kind Code:
A1
Abstract:
The invention relates to an induction sealing apparatus (50) for induction sealing an end of a container. The induction sealing apparatus (50) comprises an induction coil (21) comprising at least one active area (22) and at least one pressing unit (30) comprising jaws (31) arranged inside, or at least coaxial with said active area (22), wherein the induction coil (21) is arranged to induction heat an electrically conductive layer of the container inside the active area (22) for smelting a sealing layer of the container and wherein jaws (31) are arranged to press material layers together inside or at least coaxial with the active area (22) for forming a seam. The invention further relates to an aseptic liquid packaging machine and a method for sealing ends of liquid containers by an induction sealing apparatus.

Inventors:
PELTONEN JUSSI (FI)
PELTOLA MIKA (FI)
Application Number:
PCT/FI2015/050082
Publication Date:
August 27, 2015
Filing Date:
February 10, 2015
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
LAMICAN OY (FI)
International Classes:
H05B6/10; B65B51/22; B21D51/26; B29C65/36; B29C65/46
Domestic Patent References:
WO2010049589A12010-05-06
WO2010020712A12010-02-25
Foreign References:
US20120047847A12012-03-01
US20060124626A12006-06-15
US6167681B12001-01-02
EP0482452A11992-04-29
US4530442A1985-07-23
US20070095698A12007-05-03
US5013878A1991-05-07
US20120047847A12012-03-01
US20060124626A12006-06-15
Other References:
See also references of EP 3213600A4
Attorney, Agent or Firm:
TAMPEREEN PATENTTITOIMISTO OY (Tampere, FI)
Download PDF:
Claims:
Claims:

1. An induction sealing apparatus for induction sealing an end of a container in an aseptic chamber, the induction sealing apparatus (50) comprises an induction coil (21 ) comprising at least one active area (22) and at least one pressing unit (30) comprising jaws (31 ) made of non-electrically conductive material and arranged at least partly inside said active area (22), wherein the induction coil (21 ) is arranged to induction heat an electrically conductive layer of the body of the container and a bottom piece of the container inside the active area (22) for smelting a sealing layer of the body of the container and a bottom piece of the container inside the active area and wherein jaws are arranged to press layers of the container together against an inner wall (33) of the pressing unit (30) inside the active area (22) for forming a seam.

2. An induction sealing apparatus according to claim 1 , wherein jaws (31 ) are arranged to press layers of the container during induction heating of the electrically conductive layer.

3. An induction sealing apparatus according to claim 1 or 2, wherein the jaws (31 ) are arranged to press layers of the container after induction heating of the electrically conductive layer. 4. An induction sealing apparatus according to claim 1 , 2 or 3, wherein the induction sealing apparatus (50) comprises at least one repressing units (63) comprising jaws arranged to repress the formed seam.

5. An induction sealing apparatus according to any of the claims 1 to 4, wherein the induction sealing apparatus (50) is arranged to seal ends of several containers at the time.

6. An aseptic liquid packaging machine comprising at least one induction sealing apparatus (50) according to any of the claims 1 to 5.

7. An aseptic liquid packaging machine according to claim 6, wherein the induction sealing apparatus (50) is arranged inside an aseptic chamber of the aseptic liquid packaging machine. 8. A method for sealing ends of liquid containers in an aseptic chamber by an induction sealing apparatus comprising an inductive coil (21 ) and at least one pressing unit (30) comprising jaws (31 ), the method comprising: arranging a bottom part of a container at least partly within an active area (22) of the inductive coil (21 ), producing an alternating current to flow through the inductive coil for generating a magnetic field inside the active area (22), heating an electrically conductive layer of a body of the container and a bottom piece of the container inside the active area by eddy currents produced by the magnetic field for smelting the sealing layer of the body of the container and the bottom piece of the container inside the active area, and pressing layers of the container together against an inner wall of the pressing unit by jaws (31 ) inside the active area for forming a seam, wherein jaws (31 ) are made of non-electrically conductive material.

9. A method according to claim 8, wherein layers of the container are pressed together inside the active area (22) during induction heating.

10. A method according to claim 8 or 9, wherein layers of the container are pressed together inside the active area (22) after induction heating.

1 1. A method according to claim 8, 9 or 10, wherein the method further comprises: repressing the formed seam by a repressing unit (63).

Description:
Induction sealing system, method and apparatus

Field of the invention The present invention relates to an induction sealing apparatus to be used in liquid packaging machines of liquid containers especially in packaging machines of liquid containers especially in aseptic packaging circumstances of liquid containers. Furthermore, the invention relates to a liquid container packaging machine, especially an aseptic liquid packaging machine, comprising at least one induction sealing apparatus and a method for sealing ends of liquid containers by induction heating and to a method for sealing ends of liquid containers by an induction sealing apparatus.

Background

Bottoms, ends, of liquid containers produced by a packaging machine need to be sealed after filling. Sealing can be done by using a sealing unit comprising heated jaws. The body of the container can consist of, for example, the following material layers, a heating sealed lacquer, varnish, followed by cardboard material, LDPE, alufoil and PE plastic. Heat of the jaws penetrates through material layers of the container so that PE plastic smelts and forms a bottom seam. The level/amount of temperature of jaws has to be high in order to heat and smelt the PE plastic layer through several material layers of the container for forming the bottom seam. The jaws may be heated by separate heating cartridges. Summary

Now there has been invented an improved induction sealing apparatus to be used for sealing bottoms of containers in packaging machines and to present a novel induction sealing apparatus especially for aseptic liquid packaging machines. The induction sealing apparatus according to the invention is characterized in what will be presented in the independent claim 1. Various embodiments of the invention are disclosed in the dependent claims.

According to a first aspect of the invention, there is provided an induction sealing apparatus for induction sealing an end of a container, the induction sealing apparatus comprises an induction coil comprising at least one active area and at least one pressing unit comprising jaws arranged at least partly inside said active area, wherein the induction coil is arranged to induction heat an electrically conductive layer of the body of the container and a bottom piece of the container inside the active area for smelting a sealing layer of the body of the container and a bottom piece of the container inside the active area and wherein jaws are arranged to press layers of the container together against an inner wall of the pressing unit inside the active area for forming a seam.

According to an embodiment, jaws are arranged to press material layers during induction heating of the electrically conductive layer. According to an embodiment, the jaws are arranged to press material layers of the container during induction heating of the electrically conductive layer. According to an embodiment, the jaws are arranged to press material layers of the container after induction heating of the electrically conductive layer. According to an embodiment, the induction sealing apparatus comprises at least one repressing units comprising jaws arranged to repress the formed seam. According to an embodiment, the induction sealing apparatus is arranged to seal ends of several containers at the time. According to an embodiment, the jaws are arranged to press material layers before induction heating of the electrically conductive layer. According to a second aspect of the invention, there is provided an aseptic liquid packaging machine comprising at least one induction sealing apparatus according to a first aspect of the invention or according to any embodiment of the first aspect of the invention. According to an embodiment, the induction sealing apparatus is arranged inside an aseptic chamber of the aseptic liquid packaging machine. According to a third aspect of the invention, there is provided a method for sealing ends of liquid containers by an induction sealing apparatus comprising an inductive coil and at least one pressing unit comprising jaws. The method comprises arranging a bottom part of a container at least partly within an active area of the inductive coil, producing an alternating current to flow through the inductive coil for generating a magnetic field inside the active area, heating an electrically conductive layer of a body of the container and a bottom piece of the container inside the active area by eddy currents produced by the magnetic field for smelting the sealing layer of the body of the container and the bottom piece of the container inside the active area, and pressing layers of the container together against an inner wall of the pressing unit by jaws inside the active area for forming a seam.

According to an embodiment, wherein layers of the container are pressed together inside the active area during induction heating. According to an embodiment, wherein layers of the container are pressed together inside the active area after induction heating. According to an embodiment, the method further comprises: pressing material layers together by jaws before induction heating of the electrically conductive layer. According to an embodiment, the method further comprises repressing the formed seam by a repressing unit. Description of the Drawings

In the following, various embodiments of the invention will be described in more detail with reference to the appended drawings, in which Fig. 1 shows a part of construction of a liquid container according to an embodiment of the invention;

Fig. 2 shows an induction coil structure for an induction sealing unit according to an embodiment of the invention;

Fig. 3 shows a pressing unit for an induction sealing unit according to an embodiment of the invention from below; Fig. 4 shows a cross section view of an induction sealing unit with an induction heating coil and a pressing unit according to an embodiment of the invention;

Fig. 5 shows an induction sealing apparatus according to an embodiment of the invention;

Fig. 6 shows an induction sealing apparatus comprising an induction sealing unit and repressing unit according to an embodiment of the invention; and

Fig. 7 shows a flow chart of a method for sealing ends of liquid containers by an induction sealing apparatus according to an embodiment of the invention.

Description of Example Embodiments Packaging machines produce thousands of sealed liquid containers per hour by forming, filling and sealing those containers. In order to produce a product that guarantees optimal quality level, complies with the latest regulatory requirements and fulfills food legislation, each step of the production process has to be performed with high quality. A well- closed (sealed) container, for example, a hermetic sealed container protects the contents from extraneous solids and from loss of the article under the ordinary or customary conditions of handling, shipment, storage, and distribution. Hermetic seals are airtight seals that prevent the invasion of oxygen, moisture, humidity, and any outside contaminant to enter a sealed environment. In addition, in order to produce a product that also complies with the economical requirements and needs of the packaging machine industry the product needs to be produced with low costs, short lead time and high- throughput.

The last step of the production process of liquid containers is sealing of an end of the container, the bottom of the container, i.e. forming of the bottom seam of the container. Before the sealing process which is so called heat sealing process, a bottom piece is arranged to the bottom part i.e. to end of the tubular body of the container through the opening of the bottom of the container. After this, the sealing process may start. In the sealing process the sealing area of the bottom piece joints to the sealing area of the container, for example, by using heat sealing by which polyethylene (PE) plastic material layers can be weld together without any additional materials like glue by pressing. After the bottom piece is sealed in its place i.e. the end of the container is sealed, the bottom part of the body of the container may be warmed by warm air, the part of the body of the container extending over/beyond the bottom piece may be bent over the edge of the bottom piece and the bent over may be finished by a seam presser of a finishing sealing unit. It is possible to heat sealing area of liquid containers after filling, for example, by an existing traditional heat sealing unit. This heat sealing unit comprises jaws which are arranged to press sealing area of material layers of the container and bottom piece together while heating cartridges of the existing sealing unit produce heat to jaws and further to the sealing area of the material layers of the body part of the container and bottom piece to joint the bottom piece to the body part of the container i.e. hot jaws press layers together by mechanically expanding for forming a bottom seam i.e. a bottom joint. The body of the container may be a cardboard based carton package and consist of several laminated layers, comprising, for example, the following layers: a heat seal lacquer, varnish, followed by cardboard material, LDPE, metal and PE plastic. The bottom piece may comprise similar layers as the body of the container. The existing heat sealing unit uses a large amount of energy for heating a sealing area of a sealing layer, for example, the PE plastic layer or corresponding, because it needs to heat many layers before the heat reaches the sealing layer i.e. heat has to penetrate through many material layers of the container body or the bottom piece before it reaches the sealing layer to be smelted for forming the bottom seam. In addition, temperature accuracy of the existing heat sealing unit may be difficult to adjust, also heating cartridges and sensors used for controlling the heating cartridges may be easily breakable. Further, the existing heat sealing unit may be slowly controllable and it may have low-throughput

Instead of heating a sealing layer of a sealing area of a container through several other layers by using heating cartridges, it is possible to use induction heating for forming a bottom seam. A sealing area of a container may comprise a sealing area of the body of the container and a sealing area of a bottom piece. By induction heating it is possible to heat an electrically conductive material layer of the container, for example, alufoil layer or other suitable metal layer. When the electrically conductive material layer of the container heats, it also heats the sealing layer next to or close to the electrically conductive material layer so that the sealing layer smelts. Induction heating may smelt the sealing layer(s) faster, more uniformly and more energy efficiently than heating cartridges. For forming a bottom joint of good quality, the molten sealing layer is pressed by pressing means, for example, by jaws of the pressing unit through other layers of the container so that a bottom piece joints to the body of the container. It is possible to press sealing area of the container after the induction heating is finished, for example, for few milliseconds. However, it is also possible to press the sealing area already during induction heating in addition to after induction heating. In induction heating, there is no need to transfer heat through several layers when heating the sealing layer, therefore induction heating uses less energy than traditional heating through several layers. In addition induction heating uses less energy, because amount of mass to be heated is usually smaller.

An induction heating unit comprising an induction heating coil and pressing unit takes power from the mains, uses the power to create controllable heat in the electrically conductive material layer for heating at least the sealing area of the sealing layer of the container to be sealed. The sealing area is in the bottom part of the container wherein the bottom seam i.e. a bottom joint is arranged to be formed. The bottom part of the container comprises bottom body of the container and the bottom piece. The bottom part of the container is placed inside an active area of the induction coil for seam forming. After placing the bottom part of the container inside the active area, power may be applied to the bottom part of the container by the induction coil of the induction heating unit. By induction coil the heat can be focused just in the desired location that is the sealing area of the bottom part of the container. An alternating current flowing through the induction coil generates a magnetic field inside the active area(s) of the induction coil. Heat is produced where these eddy currents flow. Output power, the shape of the induction coil and the characteristics of the bottom area of the container determine the heat pattern. The depth of heat penetration into the bottom part of the container depends on the used frequency: the lower the frequency, the deeper the penetration. Suitable frequency for joining a cardboard based carton container comprising several laminated layers, for example, a heat seal lacquer, varnish, followed by cardboard material, LDPE, alufoil and PE plastic and a cardboard based carton bottom piece together by bottom seam may be, for example, 150-250kHz.

Figure 1 shows a part of construction of a container 10 according to an embodiment of the invention. The body of the container 10 may comprise several layers, for example, following layers; the lowest layer i.e. the first layer 1 1 may be, for example, Polyethylene (PE) plastic material layer, the second layer 12 may be an optional layer and it may be made of adhesion plastic, the third layer 13 may be made of aluminium, for example, alufoil, the fourth layer 14 may be again a PE plastic material layer, the fifth layer 15 may be a cardboard layer, the sixth layer 16 may be printing layer and the seventh layer 17, the uppermost layer, may again be made of smeltable PE plastic material or varnish. Polyethylene forms a liquid-tight seal and keeps the product dry. The aluminium layer 13 is used for the purpose of keeping light and oxygen out. A bottom piece 18 is arranged to the bottom area of the container 19 before sealing. The bottom piece 18 may also comprise several layers, for example, following layers: cardboard layer, smeltable PE plastic layer, aluminium layer and again PE plastic layer. It is also possible that it is coated, for example, varnish. The bottom piece 18 can be coated before sealing, if induction heating is used for sealing. If the existing heat sealing with heatable jaws is used, it is possible that the bottom piece 18 cannot be coated before sealing. It is also possible that the body of the container 10 and/or the bottom piece 18 comprises further layers or that one or some of the layers is removed or replaced by some other material layer, for example, instead of Polyethylene (PE) plastic it is possible to use, for example, LD-PE, HDPE, PP or PET plastic. In addition, material layers may be in different order. In any case, the aluminium layer 13 is next to the PE plastic layer 14 or so close to the PE plastic layer 14, that induction heating of the aluminium layer 13 smelts the plastic layer 14. There may be, for example, an adhesion plastic layer between the aluminium layer 13 and the plastic layer 14.

Figure 2 shows an induction heating coil structure 20 for an induction sealing unit according to an embodiment of the invention. The induction heating coil structure 20 comprise an induction coil 21. The induction coil 21 of this embodiment is suitable to be used for six containers. The induction coil 21 is made of electrically conductive material, for example, metal. The induction coil 21 uses induction to heat metal that in packaging process is an aluminium layer of the container(s) so that the sealing layer of the container(s), next to or close to the aluminium layer, smelts and a seam forms.

The induction coil 21 comprises several active areas 22, in this embodiment six active areas 22. Pressing units comprising jaws, which are arranged to be placed coaxially within those active areas 22 so that a bottom part of a container(s) to be sealed can be inductively heated inside those active areas 22 and pressed simultaneously and/or afterward by the pressing units. For sealing, the coil 21 is connected to a transformer 24 which is connected to main induction device (not shown) that receives power from the mains and generates and maintains a constant high frequency AC current. A transformer 24 converts current / voltage ratio into a ratio suitable for induction coil to heat up bottom parts of containers. The coil 21 uses this transferred power to create controllable heat by a magnetic field in the electrically conductive aluminium layer of a container or several containers.

An alternating current flowing through the coil 21 generates the magnetic field to the active areas 22 of the coil 21. When a sealing area of a bottom part of a container is placed within active area 22, the field induces eddy currents in the container. The sealing further needs pressing units comprising jaws for pressing the sealing area inside the active area during and/or at least after induction heating. A pressing unit is shown in figure 3.

The areas of the coil 21 between active areas 22 may be called passive areas 23. The passive areas 23 are not arranged to heat containers inductively. The induction heating coil structure 20 may further comprise cooling means 25 for cooling the coil 21. Cooling means 25 may be, for example, water pipes inside the coil structure. In addition, the induction heating coil structure 20 may comprise cables 26 for powering the induction coil structure 20. Figure 3 shows a pressing unit 30 for an induction sealing unit according to an embodiment of the invention from below. The pressing unit 30 may be actuated by a compressed air cylinder. The pressing unit 30 comprises jaws 31 which are arranged to press material layers of sealing areas of a container and bottom piece together before, while or after induction heating of aluminium layer to join the sealing area of the bottom piece to the sealing area of the body of the container, for example, by using compressed air. The jaws 31 are mechanically pressed together before the bottom part of the container is placed to a sealing and pressing space 32 of the pressing unit 30 as a sealing and pressing position and before the sealing and pressing begin.

After the sealing area of the bottom part of the container is in the sealing and pressing space 32 of the unit 30, the jaws 31 may press layers of sealing areas of the container and bottom piece together by mechanically expanding jaws 31 so that sealing area of material layers of the body of the container and bottom piece presses between expanded jaws 31 and the inner wall 33 of the unit 30 for forming a bottom seam. For the sealing and pressing position, the pressing unit 30 may be laid down so that jaws 31 of the pressing unit 30 settles inside the material layers of bottom part of the body of the container i.e. material layers set between the inner wall 33 of the unit 30 and jaws 31. Jaws 31 and also inner wall 33 of the pressing unit 30 may be made of non-electrically conductive material, for example, high-temperature plastic, ceramic material or other suitable material. One unit 30 may comprise 4 jaws, but it is also possible that there are more or less jaws in one unit 30, for example, 2, 3 or 5 etc. The induction coil for induction heating is not shown in figure 3.

Figure 4 shows a cross section view of a part of an induction sealing unit 40 with an induction coil 41 and jaws 44 according to an embodiment of the invention. In figure 4, a bottom piece 42 is arranged to the bottom of the body of a container 43 through the opening of the bottom of the container 43. The container 43 is arranged in the sealing and pressing position so that the induction coil 41 can induction heat the metallic layer in the sealing area of the body of the container 43 and the bottom piece 42. Jaws 44 press material layers of the sealing areas of the bottom piece 42 and the body of the container 43 towards the inner wall 45 of the pressing unit 40. Also in this figure, there is shown an arrow 46 indicating direction of movement of the jaws 44. In addition, cooling means 47 inside the coil 41 are shown.

Figure 5 shows an induction sealing unit 50 according to an embodiment of the invention. The unit 50 comprises an induction coil 21 with pressing units 30. In sealing position (and in pressing position), at least jaws of the pressing units 30 are arranged to be placed coaxial with active areas of the induction coil 21. The active areas of the induction coil 21 may be, for example, substantially round shaped. The induction sealing unit 50 comprises six active areas of the coil 21 and six pressing units 30 for six containers and the induction sealing unit 50 is arranged to be positioned above a line of containers on a container conveyor of a packaging machine, wherein in the container conveyor, six containers travel as lines. Each operation i.e. sterilizing, filling, defoaming and sealing is done at the same time for each six containers of one line.

It should be noted that the number of containers in one line can vary, for example, from 1 to 10, therefore, the number of pressing units 30 and active areas of the coil 21 may be arranged to correspond to the number of containers in one line.

The induction sealing unit 50 may be fastened to an aseptic packaging machine so that the induction sealing unit 50 is located within the aseptic chamber above the container conveyor. In the aseptic chamber, the induction sealing unit 50 is configured to direct induction heating towards at least one container on the conveyor for induction sealing a bottom piece to a body of the container after the container is filled.

Figure 6 shows an induction sealing apparatus 60 comprising an induction sealing unit and repressing units 63 according to an embodiment of the invention. An induction coil 61 and six pressing units 62 are part of the induction sealing unit. The repressing units 63 are arranged to press a sealed area i.e. the bottom seam after the induction sealing units has jointed sealing area of a bottom piece to a sealing area of a body of the container i.e. formed the bottom seam and sealed the bottom part of the container. The repressing units 63 may correspond pressing units 62, but the repressing units 63 do not comprise an inductive coil. The repressing units 63 also comprise jaws, which are arranged to (re)press sealed material layers of the container and bottom piece together by pressing them towards an inner wall of the repressing unit 63 i.e. correspondingly as jaws of pressing units 62. The repressing units 63 may also be driven with compressed air cylinders. This repressing after sealing may improve the quality of the bottom joint. The number of repressing units 63 depends on number of pressing units 62. Figure 7 shows a flow chart of a method 70 for sealing ends of liquid containers by an induction sealing apparatus according to an embodiment of the invention. In step 71 a bottom part of a container is arranged (placed) into a sealing and pressing position to a pressing unit within an active area of an inductive coil coaxially. In step 72 an alternating current is produced to flow through the inductive coil for generating a magnetic field inside the active area. In step 73 at least one electrically conductive layer of the bottom part of the container is heated by eddy currents produced by the magnetic field so that the sealing layer(s) smelt. The bottom part of the container comprises at least one electrically conductive layer. It might be electrically conductive layer of the body of the container or the bottom piece. It is also possible that both the body of the container and the bottom piece comprises an electrically conductive layer which is heated so that sealing layers next to or near to both of those layers smelts. In step 74 material layers inside the active area are pressed together by jaws of the pressing unit against the inner wall of the pressing unit for forming a seam so that material layers weld together. This pressing step 74 may also be done before the step 72 or 73 or during the step 73. It is also possible that the material layers are pressed together at least at two time points, for example, before and after, during and after or before, during and after the providing of the alternating current. It should be noted that pressing unit is arranged to press the sealing area i.e. area inside or at least coaxial with the active area of the coil at least after the sealing layer in that sealing area is smelt by induction heating. However, it may also be possible that the seam is formed by providing alternating current through the active area(s) without pressing by jaws.

An induction sealing unit for induction sealing an end of a container may also comprise more than one induction coils, for example, 2, 3, 4, etc. The number of induction coils is not restricted to above mentioned numbers, but the number of coils may depend on need and space.

It should also be noted that induction sealing according to this invention can be used even if there is moisture or liquid on the area to be sealed. It should also be noted that if aseptic packaging processes are needed for liquid containers, aseptic liquid packaging machine comprising at least one induction sealing apparatus according to an embodiment of the invention is suitable to be used in aseptic chambers; it does not need complex arrangements, because it does not need a plurality of cables for its operation. In addition, it is advantageous that there is no need to control the temperature of the jaws of induction sealing units according to an embodiment of the invention, because the controlling may be difficult; overheated jaws may break the seam and under heated jaws may not form a proper seam. Temperature of the jaws drops after each use i.e. after each sealing the jaws have to be reheated to certain temperature before next sealing.

It is obvious that the present invention is not limited solely to the above- presented embodiments, but it can be modified within the scope of the appended claims.