METHOD AND DEVICE FOR THE MANUFACTURING OF FLEXIBLE TUBES FOR PACKAGING TUBES

Description

[0001] The present invention relates to a device for manufacturing flexible tube bodies for packaging tubes according to the preamble of claim 1.

[0002] Furthermore, the present invention relates to a method for producing flexible tube bodies for packaging tubes with the features of the preamble of claim 6.

[0003] Various devices and methods are already known in the art for producing a tube or continuous tube from an arc-shaped film substrate, which has or consists of at least one weldable plastic layer, by arranging the longitudinal edge surfaces of the plastic laminate butt-jointed or slightly overlapping each other, thus forming the arc-shaped laminate into a tube shape. The longitudinal edge surfaces are then joined together by a joining process, for example a welding process, in particular by welding, and thus an endless tube is initially produced.

[0004] This continuous tube can be further processed, for example to improve its roundness, before being cut to length or slit to produce uniform, preferably cylindrical, tube bodies of a specific length. In the subsequent manufacturing process of packaging tubes, these tube bodies can advantageously be joined to a tube shoulder and / or a tube head, which may in turn carry a cap or to which a cap can be attached. Often, the tube bodies are initially left open at the end not connected to the tube head or shoulder to allow for back-filling of the packaging tube. After filling, the open end can be closed by forming another seam.

[0005] The formation of the longitudinal weld seam along and connecting the longitudinal edges of the film substrate is a critical moment and a demanding process engineering step in the manufacturing process and also for the equipment used to produce the tube bodies. On the one hand, the longitudinal weld seams should be as visually inconspicuous or barely visible as possible. At the same time, the longitudinal weld seams must be sufficiently strong and designed in such a way that the material to be filled or stored and the tubes do not interact adversely.

[0006] In the prior art, regardless of whether the longitudinal edge surfaces are butted or overlapped, it has become widely established to achieve welding of the longitudinal edge surfaces by heating them from both the outside and the inside of the film substrate formed into a tube shape. The use of contact belts, preferably continuously circulating and driven, has proven particularly advantageous. The longitudinal edge surfaces are held between these belts and heated during transport or concurrent transport between the longitudinal edge surfaces, and optionally pressurized, to enable at least partial melting of the longitudinal edge surfaces and the formation of a longitudinal weld seam.

[0007] In the past, inductive heating or corresponding induction heating devices have become established as heating mechanisms for such contact strips, in particular an inner contact strip and an outer contact strip, which preferably use corresponding induction coils of the induction heating devices, which are arranged statically relative to the contact strips, to locally heat the contact strips, preferably at least partially metallic, preferably by effecting the necessary heating of the contact strip via inductive energy transfer.

[0008] Inductive heating of the contact strips has the advantage of achieving high heating rates, which, among other things, allows for a compact design and high throughput of the corresponding devices. Furthermore, induction heating devices for heating the contact strips are advantageous because there is little heated mass, thus enabling both effective, and especially energy-efficient, heating, and because only a small amount of heated mass needs to be cooled when the system is switched off, allowing for rapid cooling.

[0009] However, in induction heating devices, a spatial separation in the transport direction of the contact strips has been provided so far in order to prevent the induction heating devices, in particular the induction coils or heating coils provided therein, from influencing or impairing each other.

[0010] This has the disadvantage that, as a rule, the inner contact belt is heated first along the transport direction using an induction heating device. However, this heating takes place in a state or spatial area where no film substrate, in particular no longitudinal edges of the film substrate, is yet in contact with the inner contact belt. Alternatively, the device must be extended spatially if the film substrate is already in contact with the inner contact belt. In a region further back in the transport direction, the outer belt or outer contact belt is then heated by corresponding induction heating devices. This heating typically occurs in a region of the contact belts and the transport direction where the longitudinal edges of the film substrate are already in contact with the belts.Due to the upstream arrangement of the induction heating device of the inner strip and the low mass and thus limited heat storage capacity, this spatially separated arrangement of the induction heating devices means that the inner contact strip must be heated very strongly or to a relatively high temperature, for example 300°C and more, at the point of the (inner) induction heating device in order to be warm enough or to have enough energy in the area of ​​the contact strips, where the heating of the longitudinal edge sides of the film substrate takes place and the formation of the longitudinal weld seam occurs, to melt the longitudinal edge sides, at least partially, from the inside.

[0011] However, this results in the inner contact strip being heated at a defined point on the endless strip during a complete rotation. As it passes through the induction heating element, it first heats up from room or ambient temperature to a correspondingly high temperature, for example, 300°C, before finally cooling back down to room temperature. These large temperature fluctuations or temperature ramps with upper limits significantly exceeding the temperature required for the formation of the longitudinal weld not only alter the metal structure of the inner contact strip over time but also lead to significant wear and tear, thus constituting a major limiting factor regarding the service life of these inner contact strips. Furthermore, the relatively high heating of the inner contact strip results in increased energy consumption.Extending the induction heating device for the inner contact strip leads to a lengthening of the entire device, especially with regard to the mandrel, which is complex to manufacture.

[0012] From EP 2 829 381 A1 a welding device for producing tube bodies with a first and second contact band is known, wherein a contact band has a polyimide contact surface for contact with the substrate web and the contact bands can be heated by induction.

[0013] Starting from this prior art, the object of the present invention is to overcome the disadvantages in the prior art and in particular to propose a method and a device for manufacturing flexible tube bodies for packaging tubes, in which, despite the provision of induction heating devices, the service life of the contact bands, in particular the inner contact band, is increased and better energy efficiency is achieved, and in addition, the enlargement / lengthening of the device is prevented.

[0014] This problem is solved with regard to a device for manufacturing flexible tube bodies for packaging tubes with the features of claim 1. The problem is further solved by a method for manufacturing flexible tube bodies for the manufacture of packaging tubes with the features of claim 6.

[0015] Advantageous embodiments of the invention are the subject of the following description, the description of the figures, the figures and the dependent claims.

[0016] In principle, all features disclosed and claimed in the device shall also be deemed to be disclosed and claimable in the process accordingly, and vice versa.

[0017] In the device according to the invention for producing flexible tube bodies for packaging tubes from a film substrate, preferably having a print on one outer side, which has or consists of at least one weldable plastic layer and which comprises a first longitudinal edge extending in a longitudinal direction and a second longitudinal edge parallel and spaced apart therefrom, it is provided that the device has forming means for forming the film substrate into a tube shape and furthermore an outer and an inner, preferably rotating, and particularly preferably metallic material, optionallyThe invention comprises a contact band with appropriate coatings, wherein the two longitudinal edge sides are accommodated between the outer and inner contact bands for guidance and / or for forming a longitudinal weld seam and are carried or transported together with the contact bands in a transport direction, wherein respective induction heating devices are provided for the outer and inner contact bands. According to the invention, it is further provided that an induction heating device associated with the inner contact band is arranged in the transport direction at least partially overlapping with an induction heating device associated with the outer contact band.

[0018] The induction heating devices are advantageously assigned to the contact strips through spatial proximity, for example, by arranging the respective induction heating device, preferably correspondingly enclosed inductors, on a side of the respective contact strip facing away from its longitudinal edges, adjacent to the contact strip. The induction heating device preferably includes a power supply unit that provides the inductors with electrical energy. The inductors can include induction coils or heating coils with which an electromagnetic induction field can be generated and maintained.

[0019] The present invention has surprisingly demonstrated that, contrary to previous assumptions, it is indeed possible to arrange the induction heating elements of the inner and outer contact strips in a manner that at least partially overlaps in the transport direction, without the function of one induction heating element being disrupted or otherwise adversely affected by the correspondingly generated induction fields of the other. This, in turn, allows the heating of the contact strips, particularly the inner contact strip, to take place spatially and in the transport direction significantly closer to, or even entirely within, the area where the longitudinal edges of the film substrate are already positioned between the contact strips, or in areas where the longitudinal weld seam is actually to be created or formed.This, in turn, allows the inner contact band to be heated significantly less, resulting in much lower or shallower temperature gradients or ramps and a lower maximum temperature requirement. This minimizes wear on the inner contact band and also leads to an energy-efficient formation of the longitudinal weld seam.

[0020] Furthermore, it was recognized that the arrangement of the induction heating devices according to the invention in spatially at least partial overlap in the transport direction also has advantageous effects on the formed longitudinal weld seam, particularly with regard to the appearance of the longitudinal weld seam in the circumferential direction.

[0021] In a first advantageous embodiment of the device, a portion of the induction heating element associated with the inner contact strip can be arranged upstream of the induction heating element associated with the outer contact strip in the transport direction. This can be particularly advantageously achieved with a further, overlapping portion of the induction heating element associated with the inner contact strip. This is because longitudinal welds with particularly good properties are generally achieved when the inner contact strip transfers more energy to the longitudinal edges of the film substrate.By arranging the induction heating device associated with the inner contact strip partially in front of the induction heating device of the outer contact strip and partially overlapping it, a correspondingly large amount of energy can advantageously be inductively transferred from the induction heating device to the inner contact strip without causing excessive heating of the contact strip. This can also be particularly advantageous when, in addition to the film substrate, a strip is used that is arranged, for example, on the inside of the film substrate formed into a tube shape in the area of ​​the longitudinal edges and / or in the area of ​​the longitudinal weld seam, and provides or covers the weld seam on the inside.

[0022] Even then, it is particularly advantageous if more energy or heat is available on the inside or on the side of the inner contact strip, in order to heat the strip and / or partially melt it if necessary.

[0023] In a further, particularly advantageous embodiment of the device, the induction heating element associated with the inner contact strip can extend over the entire length of the heating element associated with the outer contact strip in the transport direction. This advantageously minimizes the device's dimensions or the required installation space in the transport direction. It is particularly advantageous for both induction heating elements to terminate at approximately the same position in the transport direction. Contrary to the transport direction, as previously explained, the induction heating element associated with the inner contact strip can project beyond or be extended over the induction heating element associated with the outer contact strip.

[0024] According to the invention, the induction heating device associated with the inner contact strip and the outer contact strip each have a heating coil which is supplied by independent AC generators, preferably those encompassed by the device, wherein the respective induction or heating coils form part of a parallel resonant circuit. It has been found that when corresponding generators and induction or heating coils are arranged in a parallel resonant circuit, the susceptibility to or immunity to interference of the respective opposing induction heating device and its induction or heating coil or generator can be significantly improved compared to an arrangement in a series resonant circuit. This makes it even easier to arrange the induction heating devices of the two contact strips partially or completely overlapping in the transport direction.

[0025] Another particularly preferred variant of the device can provide that the generator supplying the induction or heating coil of the induction heating element of the inner contact strip is configured, or operatively connected to a control device (preferably included in the device), such that one and a half to five times more power is coupled into the inner contact strip than into the outer contact strip. As described above, it can be advantageous to heat the inner contact strip more or supply it with more energy than the outer contact strip. By extending the induction heating element associated with the inner contact strip to a sufficiently long length, it can be ensured that the temperature rise and energy transfer remain within moderate limits.Nevertheless, or equally, it is particularly advantageous to design or control the generator accordingly, so that overall and / or regardless of the spatial extent of the induction heating device of the inner contact band in the transport direction, a correspondingly higher, preferably one and a half to five times higher, electrical energy is transferred to the inner contact band than to the adjacent or opposite outer contact band.

[0026] In another, also particularly advantageous embodiment of the device, it can also be provided that a control device is provided which is designed to statically or dynamically control the generators for operating the induction heating devices in order to compensate for interferences between the induction or heating coils of the induction heating devices.

[0027] Depending on how the generators and the heating coils / induction heating devices interact, different methods and measures for static or dynamic control of the generators may be useful in order to minimize or completely eliminate the mutual influence of the heating coils by induction fields of the other heating coil.

[0028] The aforementioned problem is also solved by a method for producing flexible tube bodies for packaging tubes, preferably with a device according to one of the embodiments described above, wherein the packaging tubes are produced from a film substrate, preferably having a print on one outer surface, which has or consists of at least one weldable plastic layer and in which the film substrate has a first longitudinal edge extending in the longitudinal direction and a second longitudinal edge parallel and spaced apart therefrom, wherein the film substrate is formed into a tube shape by means of forming means and the longitudinal edge surfaces are arranged overlapping or butted against each other between an outer and an inner, preferably rotating, and particularly preferably metallic material,The contact band is picked up and, during the transport of the film substrate and / or the longitudinal edge sides between the contact bands in a transport direction, inductive heating of the contact bands, preferably via induction heating devices assigned to the contact bands, results in the formation of a longitudinal weld seam of the longitudinal edge sides, wherein, according to the invention, during the transport of the longitudinal edge sides between the contact bands along the transport direction, at least temporarily and / or sectionally in the transport direction, inductive heating of the inner and outer contact band takes place simultaneously by the induction heating devices assigned to the respective contact bands.

[0029] As described above, a suitable method can be used to take advantage of the benefits of inductive heating of the contact strips and simultaneously utilize or realize the advantages of moderate heating, especially of the inner contact strip, as well as the advantages with regard to the formed longitudinal weld seam.

[0030] According to the invention, the temporary or partial simultaneous inductive heating is to relate to a fixed point along the longitudinal edge sides of the film substrate arranged next to or above one another, so that at least temporarily or partially this point or area of ​​the longitudinal edge sides is heated simultaneously via the induction heating devices, namely from the inside and from the outside with respect to the tube shape, by inductively transferring energy to the contact strips, for example a metallic core of the contact strips.

[0031] According to the invention, the induction or heating coils of the induction heating devices are operated at different frequencies, namely resonant frequencies of a parallel resonant circuit. As already explained above, parallel resonant circuits are particularly advantageous for avoiding or minimizing mutual interference between the generators. Furthermore, by appropriately selecting the capacitances, in particular capacitors, of the parallel resonant circuits, a corresponding resonant frequency can be selected for the respective parallel resonant circuit of the induction heating device of the outer contact strip and the induction heating device of the inner contact strip, thus particularly advantageously preventing mutual interference.For example, the ratio of the resonance frequencies can be in the range between 1.7 and 2.7, wherein the resonance frequencies are selected according to the invention such that they are not in the ratio of fractions whose numerator and denominator have small integers in order to prevent lock-in effects.

[0032] Alternatively, in-phase operation of the induction or heating coils of the inner and outer induction heating device is conceivable, provided that the resonant frequencies of both resonant circuits are very close to each other or, ideally, identical.

[0033] In a further, particularly advantageous variant of the method, it can also be provided that the inner contact strip is heated in such a way that it does not have a temperature at any point that is above 230°C, preferably not above 210°C.

[0034] As described in the introduction, increased and intensified wear occurs when the inner contact band, preferably driven in a rotary motion and especially built on a metallic core, undergoes a steep and significant temperature ramp with each revolution and each passage through the induction heating device, and then cools down again to near room temperature. Accordingly, the advantageous design ensures that sufficient energy is available to form the longitudinal weld seam, while simultaneously preventing the inner contact band from overheating or becoming excessively hot, thus enabling a particularly long service life or operating time.According to the invention, this is supported or enabled by the fact that the heating of the inner contact band takes place as close as possible to or even directly in the area where the actual formation of the longitudinal weld seam takes place, namely at least partially overlapping with the arrangement of the opposite induction heating device associated with the outer contact band.

[0035] In a further, particularly desirable variant of the process, it can be provided that the induction heating device assigned to the inner contact strip couples one and a half to five times higher electrical power into the inner contact strip than the induction heating device assigned to the outer contact strip, which couples energy or power into the outer contact strip. This allows for the particularly advantageous formation of a technically functional and visually high-quality longitudinal weld seam. At the same time, the embedding or tack welding of an inner strip can also be advantageously enabled.

[0036] Of course, in all embodiments of the present invention, an additional strip corresponding to the prior art can be introduced from the outside into the interior of the tube formed into the tube, for example to further reinforce the seam.

[0037] Advantageous embodiments of the present invention are described below by way of example with reference to the schematic drawings. These show: Fig. 1: a section of a generic device for producing flexible tube bodies for packaging tubes; Fig. 2: a section of a device according to the invention in a first embodiment; Fig. 3: a section of a device according to the invention in a second embodiment; Fig. 4: a section of a device according to the invention in a third embodiment.

[0038] The Fig. 1 shows a section of a device 01 according to the prior art.

[0039] The device comprises, in addition to forming means (not shown) for forming a foil substrate 02 into a tube shape, an inner contact band 03 and an outer contact band 04. Only sections of the contact bands 03 and 04 are shown. Preferably, the contact bands 03 and 04 are designed as continuously driven metal endless bands, which preferably have non-stick coatings.

[0040] In the Fig. 1 As already shown, in the transport direction T, the continuously or seamlessly delivered film substrate 02 is formed into a tube shape in an arrangement area 05. However, the film substrate 02, in particular its longitudinal edges, does not yet come into contact with or form a bond with the inner contact band 03 or the outer contact band 04. This is illustrated by the dotted representation of the film substrate 02 in the arrangement area 05.

[0041] In the transition between the arrangement area 05 and an overlap area 06, the longitudinal edge surfaces of the film substrate (not shown in detail) are butted together, overlapping, or with a small gap between them, which is then filled by a material insertion, for example, from a reinforcing strip, and held between the contact strips 03 and 04. During further transport along the transport direction T, the longitudinal weld seam is formed in the area of ​​the longitudinal edge surfaces of the film substrate 02. For this purpose, the inner contact strip 03 is heated by an internal induction heating device 07. The outer contact strip 04 is heated accordingly by an external induction heating device 08.

[0042] In connection with the present disclosure, it may preferably be assumed that an induction heating device 07, 08, which is configured to be associated with a corresponding contact strip 03, 04, has such a spatial arrangement that, on the one hand, inductive energy transfer and heating of the respective contact strip is possible without hindering or disturbing the conveyance or transport of the film substrate 02. In the example of the Fig. 1 This means that the induction heating devices 07, 08 are each arranged on a side of the corresponding contact strip 03, 04 facing away from the longitudinal edge sides of the film substrate.

[0043] In the Fig. 1 With a device 01 according to the prior art, the induction heating device 07 associated with the inner contact band 03 is arranged completely in front of the induction heating device 08 associated with the outer contact band 04 in the transport direction T. This allows mutual interference between the induction heating devices 07 and 08 to be prevented in a simple manner, because the corresponding induction fields are spatially separated to a large extent, namely by the spacing in the transport direction T.However, in order to provide sufficient energy or heat in the overlap area 06 so that the longitudinal weld seam can be formed, the inner contact band 03 must be heated sufficiently by the induction heating device 07 in the arrangement area 05, because the inner contact band 03 leaves the area of ​​the induction heating device 07 and thus the possibility of absorbing further energy or maintaining the achieved temperature before the film substrate 02 enters the overlap area 06.

[0044] In the Fig. 2 Figure 1 shows an embodiment according to the invention in which components with the same function as in the prior art are provided with the same reference numerals. The difference according to the invention is that the induction heating device 07 now forms an overlap area 09 with the induction heating device 08 in the transport direction T, and the induction heating device 07 is thus arranged both in the arrangement area 05 and in the overlap area 06. Even if this is not shown in the not-to-scale sketch of the Fig. 2 Although not immediately apparent, the inventive arrangement of the induction heating device 07 results in the device 01 not being lengthened or enlarged in the transport direction T, even though a correspondingly better / advantageous heating is achieved. Furthermore, the inner contact band 03 can be heated for a longer period with regard to the time or area in which the longitudinal weld is formed. In other words, this means that the inner contact band 03 cools down less or less significantly due to the partially overlapping arrangement of the induction heating devices 07, 08, until the formation of the longitudinal weld in the overlap area 06 is complete.This in turn leads to the advantage that the inner contact band 03 needs to be heated less intensely or to a lower maximum temperature, which can noticeably reduce wear or significantly reduce the consumption of the necessary electrical energy.

[0045] In the Fig. 3 An alternative embodiment is provided in which the induction heating devices 07 and 08 are designed such that the induction heating device 07, which is assigned to the inner contact band 03, extends over the entire length of the induction heating device 08 in the transport direction T.

[0046] This allows the length of the device 01 in the transport direction T to be kept essentially constant, while still further reducing the maximum temperature and / or the energy input into the inner contact band 03.

[0047] Another embodiment is described in the Fig. 4 The induction heating device 07 extends over the entire length of the induction heating device 08 in the transport direction T. However, the induction heating device 07 is, in comparison to the embodiment of the Fig. 3 , significantly more compact in the transport direction T. Depending on the type of tube body to be produced and the film substrate processed, this can be advantageous without resulting in a greater length of the device 01 in the transport direction T. Reference symbol list

[0048] 01 Device 02 Film substrate 03 Inner contact strip 04 Outer contact strip 05 Arrangement area 06 Overlap area 07 Inner induction heating device 08 Outer induction heating device 09 Overlap area T Transport direction

Claims

1. A device for producing flexible tube bodies for packaging tubes from a film substrate (02) which preferably has a print on an outer side, which has at least one weldable plastic layer or consists thereof and which comprises a first longitudinal edge side extending in a longitudinal direction and a second longitudinal edge side parallel thereto and spaced apart therefrom, the device having forming means in order to form the film substrate (02) into a tube shape and the device (01) furthermore comprising an outer (04) and an inner (03), preferably revolving, contact belt (03, 04) between which the two longitudinal edge sides are received for guiding and / or heating in order to form a longitudinal weld seam and are carried along in a transport direction (T), respective induction heating means (07, 08) assigned to the outer (04) and the inner contact belt (03) being provided, an induction heating means (07,08) assigned to the inner contact belt (03) being disposed so as to at least partially overlap with an induction heating means (07, 08) assigned to the outer contact belt (04) in the transport direction, the induction heating means (07, 08) assigned to the inner contact belt (03) and to the outer contact belt (04) each comprising a heating coil, characterized in that the heating coils are fed by independent alternating current generators, the respective induction or heating coils each realizing a part of a parallel resonant circuit and being operated in resonance, the resonance frequencies being selected in such a manner that they are not in the ratio of fractions whose numerator and denominator have small integers.

2. The device according to claim 1, characterized in that a part of the induction heating means (07) assigned to the inner contact belt (03) is disposed in the transport direction (T) upstream of the induction heating means (08) assigned to the outer contact belt (04).

3. The device according to claim 1 or 2, characterized in that the induction heating means (07) assigned to the inner contact belt (03) extends across the entire length of the induction heating means (08) assigned to the outer contact belt (04) in the transport direction (T).

4. The device according to any one of claims 1 to 3, characterized in that the generator feeding the heating coil of the induction heating means (07) of the inner contact belt (03) is configured or operably connected to a control means in such a manner that one and a half to five times higher electrical power is coupled into the inner contact belt (03) than into the outer contact belt (04).

5. The device according to any one of claims 1 to 4, characterized by a control means realized to control the generators statically or dynamically in order to compensate for interferences between the heating coils of the induction heating means (07, 08).

6. A method for producing flexible tube bodies for packaging tubes from a film substrate (02), said method preferably having a device (01) according to any one of claims 1 to 5, said film substrate (02) preferably having a print on an outer side, having at least one weldable plastic layer or consisting thereof and comprising a first longitudinal edge side extending in a longitudinal direction and a second longitudinal edge side parallel thereto and spaced apart therefrom, the film substrate (02) being formed into a tube shape by means of forming means and the longitudinal edge sides being received in an overlapping manner or edge to edge between an outer and an inner, preferably revolving, contact belt (03, 04) and the contact belts (03, 04) being heated inductively preferably via induction heating means (07, 08) assigned to the contact belts (03, 04) during the transport of the film substrate (02) and / or the longitudinal edge sides between the contact belts (03, 04) in a transport direction (T) in order to form a longitudinal weld seam of the longitudinal edge sides, an induction heating of the inner contact belt (03) and the outer contact belt (04) taking place simultaneously at least temporarily and / or sectionally by means of the induction heating means (07, 08) assigned to the respective contact belts (03, 04) when transporting the longitudinal edge sides between the contact belts (03, 04) along the transport direction (T), characterized in that heating coils of the induction heating means (07, 08) each being operated in resonance as part of a parallel resonant circuit, the resonance frequencies being selected in such a manner that they are not in the ratio of fractions whose numerator and denominator have small integers.

7. The method according to claim 6, characterized in that the inner contact belt (03) is heated in such a manner that it has at no point a temperature which is above 230 °C.

8. The method according to claim 6 or 7, characterized in that the induction heating means (07) of the inner contact belt (03) couples two to five times higher electrical power into the inner contact belt (03) than the induction heating means (08) of the outer contact belt (04) couples into the outer contact belt (04).