Induction Heat Sealing Device and Method for Laterally Sealing Tubes of Packaging Material - Patent application

Abstract

An induction heating sealing device (300) for providing lateral sealing of a tube (104) of packaging material, comprising: a body (302) including first and second sealing surfaces (314a, 314b) arranged to face the packaging material during a sealing state (S); a recess (308) provided in the body (302) for receiving a knife during a cutting state (C), the first and second sealing surfaces (314a, 314b) being located on opposite sides of the recess (308); and a conductor arrangement (306a, 306b, 306c, 306d) provided in the body (302) for inducing eddy currents therein, wherein at least a portion of the first and second sealing surfaces (314a, 314b) are inclined and have first and second upper portions (316a, 316b), respectively, whereby particles within a product held inside the tube (104) are forced away from the sealing zone of the tube when the sealing zone is pressed toward the first and second upper portions (316a, 316b).

Description

[Technical Field]

[0001] The present invention relates generally to induction sealing, and more particularly to a device and method for providing a lateral seal on a tube of packaging material holding a liquid food product. [Background technology]

[0002] Today, it is well known to produce carton packages filled with liquid food products, such as milk-filled Tetra Brik™ packages. The Tetra Brik™ packaging machine is an example of a roll-fed packaging machine, sometimes called a roll-fed filler machine. In a roll-fed packaging machine, a web of packaging material fed to the packaging machine on a reel is formed into a tube and provided with a longitudinal seal. After the tube is formed and provided with a longitudinal seal, the tube is filled with product. Transverse seals are continuously created from the bottom end of the tube. In conjunction with creating the transverse seal, the bottom end of the tube is severed to form a package filled with the liquid product. These packages are then transferred to a folding device, which folds the packages into their final form by using pre-created fold lines (sometimes called weakening lines) provided in the packaging material.

[0003] Another type of packaging machine is the so-called blank-fed packaging machine. Unlike roll-fed packaging machines, packages are created one at a time in a blank-fed packaging machine. Another difference between the two is that the longitudinal seal is pre-formed rather than created in the packaging machine. Therefore, in this context, the blank should be considered a sleeve-shaped piece of packaging material. In a blank-fed packaging machine, the blank is assembled, i.e., unfolded, to form an interior space. After assembly, a closed end is formed by providing a transverse seal at one end of the sleeve. In the next step, the product is filled into the sleeve, and then the other end of the sleeve is closed by providing a transverse seal to form a closed package.

[0004] The side seal should be made in a reliable manner to ensure that the product remains safely within the package. Technology for providing a reliable side seal has been in use for many years, but continuing increases in requirements regarding speed, e.g., the number of packages produced per hour, different types of products filled into the package, e.g., highly viscous products and products containing seeds and other types of particles, maintenance intervals, etc., require improvements in side seal technology. Summary of the Invention [Problem to be solved by the invention]

[0005] It is an object of the present invention to at least partially overcome one or more of the above-defined limitations of the prior art, and in particular to provide an improved induction heating sealing device. [Means for solving the problem]

[0006] According to a first aspect, there is provided an induction heating sealing device for providing lateral sealing of a tube of packaging material, the induction heating sealing device comprising: a body including first and second sealing surfaces arranged to face the packaging material during a sealing state; a recess provided in the body for receiving a knife during a cutting state, the first and second sealing surfaces being located on opposite sides of the recess; and an electrical conductor arrangement provided in the body for inducing eddy currents in the packaging material during the sealing state, at least a portion of the first and second sealing surfaces being inclined and comprising first and second upper portions, respectively, whereby particles within a product held inside the tube are forced away from a sealing zone of the tube when the first and second upper portions are pressed towards the sealing zone.

[0007] The induction heating sealing device may further include a magnetic flux concentrator arrangement that holds the electrical conductor arrangement, the magnetic flux concentrator arrangement comprising one or several inclined magnetic flux concentrator upper surfaces that form part of the first and second sealing surfaces.

[0008] The conductor arrangement may comprise one or several sloped conductor arrangement upper surfaces forming part of the first and second sealing surfaces.

[0009] At least a portion of the first and second sealing surfaces may be angled to control the direction in which molten polymer within the packaging material is displaced when the induction heating sealing device (300) is pressed against the sealing strip.

[0010] The sloped profile of the first and second sealing surfaces of the heat sealing device (300) may be adapted to a particular type of packaging material having a particular type of polymer within the polymer layer.

[0011] Additionally, the sloped profile of the first and second sealing surfaces of the heat sealing device may be adapted to a particular type of product containing a particular type of particle.

[0012] Additionally, the sloped profile of the first and second sealing surfaces of the heat sealing device may be adapted to the dynamics of a particular type of filling machine.

[0013] According to a second aspect, there is provided a lateral sealing system comprising an induction heating sealing device according to the first aspect and a counter pressure arrangement arranged on an opposite side of the induction heating sealing device, the induction heating sealing device and the counter pressure arrangement being arranged such that, during operation, a tube can be fed between the two.

[0014] The counter pressure arrangement may include first and second counter pressure elements with first and second pressure pad surfaces, respectively, the first and second counter pressure pad surfaces being convex in shape.

[0015] A first pressure pad top of the first convex pressure pad may be offset with a first top of the first sealing surface of the induction heating sealing device, and a second pressure pad top of the second convex pressure pad may be offset with a second top of the first sealing surface of the induction heating sealing device.

[0016] According to a third aspect, there is provided a method for transversely sealing a tube of packaging material by using an induction sealing device comprising: a body including first and second sealing surfaces arranged to face the packaging material during a sealing state; a recess provided in the body for receiving a knife during a cutting state, the first and second sealing surfaces being located on opposite sides of the recess; and an electrical conductor arrangement provided in the body for inducing eddy currents in the packaging material during the sealing state, wherein at least a portion of the first and second sealing surfaces are inclined and comprise first and second upper portions, respectively; and a counter pressure arrangement arranged on opposite sides of the induction sealing device, said method comprising: placing the tube so that the sealing zone of the tube faces the induction heating sealing device and counter pressure arrangement; moving the induction heating sealing device and the counter pressure arrangement toward each other so that particles of product held inside the tube are forced apart; Inducing eddy currents in the packaging material of the tube by using an induction heating sealing device; Pressing the first and second sides of the tube toward each other such that molten polymer in the polymer layers on the first and second sides of the tube adhere to each other; Using an inclined sealing surface of the induction heating sealing device to distribute the molten polymer so that the risk of insufficient sealing is reduced. Includes.

[0017] Embodiments of the present invention will now be described, by way of example, with reference to the accompanying schematic drawings, in which: [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a general diagram of a roll-fed packaging machine. [Figure 2] FIG. 10 is a more detailed view of the sealing device used to provide the lateral seal. [Figure 3] 1 shows a cross-sectional view of a thermal induction sealing device. [Figure 4] A lateral sealing system is shown. [Figure 5] 1 shows a flow chart of a method for transversely sealing a tube of packaging material. DETAILED DESCRIPTION OF THE INVENTION

[0019] FIG. 1 generally illustrates a packaging machine 100. In the illustrated example, the packaging machine 100 is a roll-fed carton packaging machine. The general principle of such machines is that a web 102 is formed from a roll of packaging material. Although not shown, to meet food safety regulations as needed, the web 102 may be sterilized using a hydrogen peroxide bath, a low-voltage electron beam (LVEB) device, or any other device capable of reducing many undesirable microorganisms. After sterilization, the web 102 may be formed into a tube 104 using a longitudinal sealing device. Once formed, a product, such as milk, may be conveyed into the tube 104 via a product pipe 106 located at least partially inside the tube 104.

[0020] To form a package 108 from the product-filled tube 104, a lateral seal may be created at the lower end of the tube by using a sealing device 110. Generally, the sealing device 110 has two main functions: providing the lateral seal, i.e., welding two opposing sides of the tube together so that the product in the lower part of the tube placed below the sealing device is separated from the product in the tube placed above the sealing device, and cutting off the lower part of the tube so that the package 108 is formed. Alternatively, instead of providing the lateral seal and cutting off the lower part with the same device as shown, the step of cutting off the lower part may be performed in a subsequent step by a different machine or by the consumer if the package is intended to be sold in a multipack.

[0021] FIG. 2 illustrates the general principle of the sealing apparatus 110 in more detail. The tube 104 can be fed from above, which allows the product to be held inside the tube. In a first stage, the sealing stage S, a first jaw equipped with a sealing device 200 and a second jaw equipped with a counter-pressure device 202 are moved toward each other so that two opposing sides of the tube 104 are pressed toward each other. To provide a lateral seal, heat can be provided by inducing eddy currents in the packaging material while the two opposing sides are pressed together. The heat melts a polymer layer in the packaging material, which then provides a polymer layer that can be used to ensure that the two opposing sides adhere to each other and remain together after the jaws are removed. In a subsequent step (referred to herein as the cutting stage C), the lower portion of the tube 104 can be cut away to form the package 108. To increase the speed at which the package is formed, the jaws can be moved along with the tube 104 in the tube feed direction A during the sealing stage S and the cutting stage C.

[0022] So-called volume forming flaps 204a, 204b can be used to provide a more controlled forming process of the package 108. More specifically, by using these, a tube 104 having a circular cross section may be advanced in a controlled manner into a package 108 having a rectangular cross section.

[0023] The sealing device can include two inductors: a first inductor 206a and a second inductor 206b. In the example shown, the first inductor 206a is disposed above the second inductor 206b. After providing the lateral seal, a knife 208 can be used to cut off the lower portion of the tube, thus forming the package 108. In this example, the knife 208 and the first and second inductors 206a, 206b are provided within the sealing device, but other arrangements are possible. For example, the knife can be provided on opposite sides of the tube within a counter-pressure device, or the cutting step can be performed by a separation device downstream of the sealing device.

[0024] 3, an induction heating sealing device 300 is shown in detail by way of example, which may form part of the sealing apparatus 110. More specifically, the induction heating sealing device 300 may be used as the sealing device 200 shown in FIG.

[0025] The induction heating sealing device 300 may include a body 302. Within the body 302, magnetic flux concentrator arrangements 304a-d may be provided. The purpose of the magnetic flux concentrator arrangements 304a-d is to enable electromagnetic radiation formed by the electronic conductor arrangements 306a-d (which may also be included within the body 302) to be directed towards the tube of packaging material 102 during the sealing stage S. The magnetic flux concentrator arrangements 304a-d may be made from a variety of materials, such as plastoferrite or soft magnetic composite materials.

[0026] The induction heating sealing device 300 may be designed in various ways. In FIG. 3 , a so-called twin-coil inductor is shown as an example. In a twin-coil inductor, the electronic conductor arrangement 306a-d may include a first coil 306a-b and a second coil 306c-d, i.e., one coil is provided on either side of the recess 308 configured to receive the knife during the cutting stage C. Another option is a so-called single-coil inductor, in which one coil is provided and arranged so that one part of the coil is provided on one side of the recess 308 and another part of the coil is provided on the other side of the recess 308. In short, the first inductor 310 and the second inductor 312, which respectively represent the first part of the body 302 on one side of the recess 308 and the second part of the body 302 on the other side of the recess 308, may share a single coil or may each comprise one coil as shown in FIG. 3 .

[0027] Additionally, as shown, the electronic conductor arrangements 306a-d may be held by the magnetic flux concentrator arrangements 304a-d such that the electronic conductor arrangements 306a-d form part of the exterior surface of the body 302. Another option, not shown, is for the electronic conductor arrangements 306a-d to be held entirely within the magnetic flux concentrator arrangements 304a-d such that the electronic conductor arrangements 306a-d do not form part of the exterior surface of the body 302. A further option is to have a surface cover (not shown) such that neither the magnetic flux concentrator arrangements 304a-d nor the electronic conductor arrangements 306a-d form part of the exterior surface.

[0028] The first and second sealing surfaces 314a, 314b of the first and second inductors 310, 312, respectively, may be sloped, as shown in FIG. 3 . Having sloped first and second sealing surfaces 314a, 314b has several advantages. First, during the sealing step S, particles within the food product within the tube 104 may be forced out of the sealing zone of the tube 104, i.e., the section of the tube 104 that forms the transverse seal, in a more controlled manner than with flat-surfaced inductors. More specifically, an advantage of having sloped first and second sealing surfaces 314a, 314b is that a pressure gradient can be successfully established inside the tube 104. Different products differ, for example, in terms of viscosity and whether the product contains particles, and if so, these may have different properties, so different products may require different standards to avoid product retention within the sealing zone. By customizing the slope profile based on the product held inside the tube 104, i.e., how the sealing surfaces 314a, 314b slope, the pressure gradient build-up can be optimized for the product, suggesting even further improved lateral sealing.

[0029] In addition to improving the proper removal of product residue from the sealing strip during the sealing step S, having the inclined sealing surfaces 314a, 314b also has a positive effect on the quality of the seal. A pressure gradient is also formed within the polymer layer that melts during the sealing step S. This allows the way in which the molten polymer moves within the packaging material to be controlled in a more precise manner than when using a flat-surface inductor. This, in turn, reduces the risk of molten polymer agglomeration within the packaging material. In short, the molten polymer can be distributed more efficiently. Another positive effect is that less polymer may be needed to create a reliable lateral seal. Because the way in which the molten polymer is distributed during the sealing step S may be controlled in a more precise manner, this may mean that less polymer is needed, which is advantageous not only from a cost perspective but also from an environmental perspective.

[0030] In the example shown in FIG. 3, the first and second sealing surfaces 314a, 314b include first and second top portions 316a, 316b, respectively. As shown, in this example, the first and second top portions 316a, 316b are positioned adjacent the recess 308, although other arrangements of the first and second top portions 316a, 316b are possible. Furthermore, as shown in FIG. 3, the magnetic flux concentrator top surfaces 318a-d can be angled and form a portion of the first and second sealing surfaces 314a, 314b. As shown, the electron conductor arrangement top surfaces 320a-d can also be angled and form a portion of the sealing surfaces 314a, 314b. Furthermore, the first and second sealing surfaces 314a, 314b can be symmetrical about a recess axis RA that passes through the recess 308.

[0031] FIG. 4 generally illustrates a lateral sealing system 400 including an induction heating sealing device 300 followed by a counter pressure arrangement 402a, 402b including first and second counter pressure elements 402a, 402b.

[0032] The induction heating sealing device 300 shown in Figure 4 differs from the induction heating sealing device shown in Figure 3 in that the first and second top portions 316a, 316b are located at the center of the first and second sealing surfaces 314a, 314b, respectively, rather than next to the recess 308 as in the example shown in Figure 3. Furthermore, the sealing surfaces 314a, 314b in the example shown in Figure 4 are only partially inclined, i.e., the sealing surfaces 314a, 314b include an inclined portion and a flat portion.

[0033] The first and second counter pressure elements 402a, 402b may include first and second counter pressure pads 404a, 404b, respectively, which may be made, for example, from rubber or other resilient material. The first and second counter pressure pads 404a, 404b may include first and second counter pressure pad surfaces 406a, 406b positioned to face the tube 104 during the sealing stage S. The first and second counter pressure pad surfaces 406a, 406b may be convex in shape and include first and second counter pressure pad top portions 408a, 408b, respectively.

[0034] 4, the first and second counter pressure pad tops 408a, 408b are offset relative to the first and second tops 316a, 316b, indicated herein by a first counter pressure pad top FPPTS axis passing through the first counter pressure pad top 408a, a second counter pressure pad top SPPTS axis passing through the second counter pressure pad top 408b, a first top FTS axis passing through the first top 316a, and a second top STS axis passing through the second top 316b. Although not shown, it is also possible to have the first and second counter pressure pad tops 408a, 408b aligned relative to the first and second tops 316a, 316b.

[0035] Further, as indicated above, the sloped profiles of the first and second sealing surfaces 314a, 314b may be adjusted to meet the requirements of a particular product, a particular packaging material, a particular type of sealing device 110, a particular packaging machine 100, or combinations thereof. Additionally, to even further improve sealing characteristics, the sloped profiles of the first and second counter pressure pad surfaces 406a, 406b may also be adjusted to meet the above requirements.

[0036] Additionally, the first and second counter pressure elements 402a, 402b may be differently shaped so that the first and second counter pressure pad surfaces 406a, 406b have different sloped profiles. One reason for these different shapes is that the tube 104, located upstream of the lateral sealing system 400, provides pressure created by a food product held within the tube 104 onto the lateral sealing system 400. By having the first and second counter pressure elements 402a, 402b and optionally also or instead the first and second inductors 310, 312 of different shapes, pressure created by the food product can be compensated for.

[0037] 5 is a flowchart 500 illustrating a method for transversely sealing a tube 104 of packaging material using an induction sealing device 300. The method may include: placing 502 the tube 104 with a sealing band of the tube facing the induction sealing device 300 and counter pressure arrangements 402 a, 402 b; moving 504 the induction sealing device 300 and counter pressure arrangements 402 a, 402 b toward each other so that particles of product held inside the tube are forced apart; inducing 506 eddy currents in the packaging material of the tube using the induction sealing device 300; pressing 508 first and second sides of the tube 104 toward each other so that molten polymer in the polymer layers on the first and second sides of the tube adhere to each other; and distributing 510 the molten polymer using an angled sealing surface of the induction sealing device 300 so that the risk of an insufficient seal is reduced.

[0038] From the foregoing, while various embodiments of the present invention have been described and shown, it will be understood that the present invention is not limited thereto but may be embodied in other ways within the scope of the subject matter defined in the following claims.

Claims

1. A lateral sealing system (400) including an induction heating sealing device (300) and a counter pressure arrangement (402a, 402b), The induction heating sealing device (300) comprises: a body (302) including first and second sealing surfaces (314a, 314b) arranged to face the packaging material in a sealed state (S); a recess (308) provided in said body (302) for receiving a knife during a cutting state (C), said first and second sealing surfaces (314a, 314b) being located on opposite sides of said recess (308); a conductor arrangement (306a, 306b, 306c, 306d) provided in the body (302) for inducing eddy currents in the packaging material during the sealed state (S); Including, at least a portion of the first and second sealing surfaces (314a, 314b) comprise inclined surfaces and comprise first and second upper portions (316a, 316b), respectively, whereby particles within a product held inside the tube (104) are forced away from the sealing zone of the tube when the first and second upper portions (316a, 316b) are pressed against the sealing zone; the counter pressure arrangements (402a, 402b) are located on opposite sides of the induction heating sealing device (300); the induction heating sealing device (300) and the counter pressure arrangement (402a, 402b) are arranged such that, during operation, the tube (104) can be fed between the induction heating sealing device (300) and the counter pressure arrangement (402a, 402b); the counter pressure arrangement (402a, 402b) includes a first counter pressure element (402a) with a first pressure pad surface (406a) and a second counter pressure element (402b) with a second pressure pad surface (406b), the first pressure pad surface (406a) and the second pressure pad surface (406b) being convex; Lateral sealing system (400).

2. 2. The lateral sealing system (400) of claim 1, wherein a first pressure pad top (408a) of a first convex pressure pad (404a) is offset from the first top (316a) of the first sealing surface (314a) of the induction heating sealing device (300), and a second pressure pad top (408b) of a second convex pressure pad (404b) is offset from the second top (316b) of the first sealing surface (314b) of the induction heating sealing device (300).

3. 2. The lateral sealing system (400) of claim 1, further comprising a magnetic flux concentrator arrangement (304a, 304b, 304c, 304d) that holds the conductor arrangement (306a, 306b, 306c, 306d), the magnetic flux concentrator arrangement (304a, 304b, 304c, 304d) comprising one or several inclined magnetic flux concentrator upper surfaces (318a, 318b, 318c, 318d) that form part of the first and second sealing surfaces (314a, 314b).

4. 3. The lateral sealing system (400) of claim 1 or 2, wherein the conductor arrangement (306a, 306b, 306c, 306d) comprises one or several inclined conductor arrangement upper surfaces (320a, 320b, 320c, 320d) forming part of the first and second sealing surfaces (314a, 314b).

5. The lateral sealing system (400) of any one of claims 1 to 3, wherein at least a portion of the first sealing surface (314a) and the second sealing surface (314b) comprises an inclined surface and a flat surface.

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