Hot air shrink tunnel for heat shrinking a shrink label, method for heat shrinking a shrink label, and heat shrinking device for heat shrinking a shrink label

Abstract

The present invention relates to a hot air shrink tunnel (10) of a heat shrink device for heat shrinking shrink labels for packaging products, the hot air shrink tunnel surrounding a conveying path of the products. The hot air shrink tunnel includes a humid air zone (1, 2) and a dry air zone (3, 4) arranged in this order in the conveying direction of the products passing through the hot air shrink tunnel (10), the humid air zone (1, 2) includes a heating means for heating the air flowing in the humid air zone (1, 2) and a water diffusion means for diffusing an amount of water in the air flowing in the humid air zone (1, 2) to generate an air-steam mixture, and the dry air zone (3, 4) includes a heating means for heating the air flowing in the dry air zone (3, 4).

Description

[Technical field]

[0001] The present invention refers to a hot air shrink tunnel of a heat shrinking device for heat shrinking a shrink label for packaging a product, a method for heat shrinking a shrink label packaging a product, and a heat shrinking device for heat shrinking a shrink label packaging a product, the heat shrinking device comprising said hot air shrink tunnel.

[0002] Containers such as PET (polyethylene terephthalate) bottles filled with liquids or pourable materials such as granules or tablets are generally fitted with a label. The label is often formed from a shrink film (hence also called a shrink label) formed into a cylindrical shape to package or encase the container, and the label is printed with a brand name, information about the contents of the container, etc. Such a cylindrical label is generally fitted to the container in a series of steps by a label fitting system including a conveying means for conveying the container along a predetermined conveying path, a label fitting device for fitting an unshrunk cylindrical label to the container while the container is being conveyed by the conveying means, and a heat shrinking device for heat shrinking the cylindrical label fitted to the container. In order for such a shrink label to be shrinkable, the shrink label is usually made of a thermoplastic material such as polypropylene (PP), polyethylene (PE), polystyrene (PS), or polyvinyl chloride (PVC).

[0003] Several "physical" options (heat sources) are known in the art for transferring heat to the shrink label to raise its temperature to a minimum temperature at which shrinking will begin, and several "technical" options for technical implementation and structural design to carry out this process more or less uniformly, i.e. resulting in a more or less wrinkle-free, bubble-free, dry, i.e. ready-to-pack end product. There are challenges in applying any of these techniques, and each of them has its own advantages and disadvantages, resulting in their ideal application areas, which are directly related to their strengths and weaknesses.

[0004] For the physical options, a distinction must be made that determines the physical effects utilized both for the transfer of the thermal energy carrier between the heat source and the product, and for the subsequent heat exchange at the interface or contact area between the thermal energy carrier and the surface of the product, with respect to the heat source. Thus, in general, a distinction is made between (a) heat transfer by infrared radiation, (b) heat transfer by hot air, i.e. by thermal convection and, ultimately, by heat exchange between the hot air and the surface of the product, and (c) heat transfer by steam, i.e. by convection and, ultimately, by condensation of the water contained in the steam on the surface of the product. Correspondingly, devices configured to apply these options are usually so-called infrared tunnels (not considered further here) in the case of (a), "hot air tunnels" in the case of (b) and "steam tunnels" in the case of (c).

[0005] Regarding (b), the biggest advantages of hot air tunnels are, for example, their relative compactness, the wide temperature range over which they can be used, the ability to manipulate the air flow using small nozzles and custom holes / distribution patterns allowing for targeting of critical areas and helping to treat potential problem areas, and their relatively low cost considering the fact that they ultimately result in a dried product.

[0006] The downsides are: (b1) heat transfer from the hot air source to the product is limited to simple geometries due to the dependence of the hot air on the local flow velocity, and (b2) local environmental heating due to the continuous flow of hot air. (b1) is due to the fact that the overall heat transfer coefficient depends on the heat capacity, temperature, and flow rate.

[0007] With regard to (c), as discussed above, the physical effect of heat exchange is condensation, which is a change of state from gas to liquid, and is the reverse of evaporation. As the reverse of evaporation, the enthalpy of evaporation, i.e., the amount of energy that must be added to a liquid substance to effect a phase transition or change to gas, is recovered and used to raise the temperature of the product exterior temperature.

[0008] What is important in this process is the temperature at which this phase transition occurs, i.e. the dew point, the temperature to which a gas must be cooled for it to become saturated with water vapor at a given (constant) air pressure and moisture content. That is, the dew point is an absolute measure of gas humidity at any temperature and is directly related to the amount of water vapor present (water vapor partial pressure). Conversely, by observing the onset of condensation, it becomes possible to estimate the temperature.

[0009] Steam tunnels, which use water vapor as a medium to carry thermal energy via latent energy transfer, allow for a very uniform heat transfer to the product, which is necessary, for example, when high-quality, distortion-free graphics are important.

[0010] The possible disadvantages are: (c1) the product is wet due to condensation when it leaves the tunnel and must be dried before packaging (requiring a dryer), printing or secondary labeling, which may cause corrosion of metallic components, making the application to dry goods such as herbs and grains at least problematic; (c2) the high energy required for steam generation (steam boiler), which is usually fossil energy; (c3) steam tunnels generally have a smaller physical footprint than infrared or hot air tunnels. In fact, the physical footprint is smaller due to the intense energy, which is 10 times higher compared to hot air and 6 times higher compared to infrared. However, it should be noted that infrared is not adapted to shrinkage caused by the printed colors on the sleeve. Infrared can only be used for pre-heating or evaporation of condensation droplets.

[0011] The object of the present invention is to provide a hot air shrink tunnel with steam support at the most critical moment in the shrinking process when low temperatures and low flow rates are required without reducing the total energy, a method for heat shrinking said plastic sleeves for packaging said products using said hot air shrink tunnel, and a heat shrinking device for heat shrinking shrink labels for securely packaging containers, which are products in the terms of the present invention, while ensuring the above-mentioned advantages and avoiding the disadvantages, and a heat shrinking device for heat shrinking shrink labels comprising a hot air shrink tunnel.

[0012] In particular, the above mentioned objectives are intended to be solved taking into account the boundary conditions, namely: reduction of energy consumption, preference of electrical energy over fossil energy, provision of a dry end product from the hot air shrink tunnel, application on irregular surfaces, e.g. having undercuts, simplification of the design of the hot air shrink tunnel to minimize the need for service technicians and to be as self-contained as possible.

[0013] A hot air shrink tunnel, method and heat shrinkage apparatus as set out in the preambles of claims 1, 16 and 17 respectively are described in EP 2 103 527 A1, entitled "Heart shrinkage apparatus for shrink film".

[0014] This object is solved by a hot air shrink tunnel according to claim 1 and by a method according to claim 16. Advantageous modifications are defined in the dependent claims.

[0015] According to a first aspect (claim 1) of the present invention, there is provided a hot air shrink tunnel of a heat shrink apparatus for heat shrinking a shrink label to package a product, the hot air shrink tunnel surrounding a conveying path of the product, characterized by a moist air zone and a dry air zone arranged in this order in the conveying direction of the product through the hot air shrink tunnel, wherein (i) the moist air zone includes a heating means for heating air flowing in the moist air zone and a water diffusion means for diffusing a certain amount of water in the air flowing in the moist air zone to produce an air-steam mixture, and (ii) the dry air zone includes a heating means for heating the air flowing in the dry air zone.

[0016] The expression "hot air shrink tunnel" (hereinafter simply "tunnel") as used herein can also be understood in a certain sense as a continuous oven, and in a more abstract and non-structural sense refers to the connection of several zones, which according to the invention refer to a moist air zone and a dry air zone (naturally understood as "at least one" in each case), each embodied by a separate module. In other words, the word "module" refers to the structural part of the tunnel arranged in the conveying direction, while the term "zone" can be understood in a more functional sense by referring to the atmosphere or environment created in the tunnel and to the part of the shrinking process carried out inside the tunnel. Furthermore, in the following, the three-dimensional space in the module where the product is exposed to said atmosphere or environment is called "chamber".

[0017] The tunnel is adapted to receive products (hereinafter simply "products") as initial products from the infeed side of the tunnel, which, while passing through the tunnel, are tightly wrapped by a shrink label, referred to herein as a "sleeve", which is heat-shrunk or equivalently thermally shrunk to adhere closely to the product and form the final product. Of course, a plurality of products are usually fed one after the other in a conveying direction by some conveying means, such as a production line or a conveyor belt, which represents the embodiment or design of the conveying path.

[0018] Preferably, the shrink label is a thermoplastic material, such as PP, PE, or PS, to be heat shrinkable.

[0019] With regard to the "product", this is preferably, for example, a bottle-like container for liquids, with either a constant or varying cross section perpendicular to the axis of symmetry, said cross section may have any shape, such as, for example, circular, square, and rectangular, it being important that the variation in size, shape, and both of the cross section along the longitudinal axis of the product is taken into account with regard to differences in contact points, as well as differences in adhesive strength and elongation of the shrink label.

[0020] The term "hot air" as used herein refers to air having a temperature higher than ambient temperature, specifically, depending on the type of zone (manufacturing process), a temperature in the range between, for example, 80°C and over 200°C with improved insulation; it should be noted that the temperature of the sleeve is typically below this temperature range, and the temperature outside the product even lower, given that the residence time of the product in each individual zone is relatively short, for example, only a few seconds.

[0021] As a result of the flow of hot air and water diffused within each of the chambers, as defined above, an air-vapor mixture defined and specified by a set of intensive thermodynamic variables such as temperature, pressure, concentration, and absolute humidity is produced within the chamber, and the hot air and water vapor together may be referred to as a gaseous fluid.

[0022] Thus, according to the invention, the sleeve is thermally contracted and the heat for raising the temperature of the sleeve to the appropriate temperature is (i) conveyed to the sleeve by the flow of hot air, i.e. by heat convection, and (ii) supplied by synergistic cooperation by the condensation of water in the form of so-called enthalpy of vaporization, heat of vaporization or latent heat. It should be emphasized that in the humid air zone, two physical effects (convection and condensation) are employed, while in the dry air zone, the curve of the dependence of the contraction (%) on the temperature shows a steep characteristic in the temperature range where the latent heat is responsible for the effect and a flat characteristic in the temperature range where convection is essential, with both effects overlapping to some extent. Due to the combined effect of the hot air and the water vapor, the hot air does not need to be heated as much to achieve the appropriate temperature as in the absence of the thermodynamic support of the water vapor. It should be noted that for condensation to occur, it is necessary to fall below the dew point of water, which is the temperature to which the water-containing air needs to be cooled in order to be saturated with water vapor, assuming constant air pressure and moisture content. Fortunately, the sleeve temperature only needs to be slightly below the dew point to accomplish this.

[0023] According to the invention, air and water vapor or steam are mixed inside the tunnel. Alternatively, it is also envisaged to carry out this process outside the tunnel. Advantageously, the fluid is introduced into the respective module (humid air zone) via a nozzle whose angular position is adjustable, so as to make the fluid controllable not only in terms of temperature and flow rate, but also in terms of the flow direction entering the module and, consequently, in the module. Correspondingly, the modules may be called "nozzle modules".

[0024] Advantageously, once the fluid has been introduced into the chamber, it can be circulated therein by means of a fan, blower, ventilator or the like. According to the invention, each of the humid air zone and the dry air zone "comprises" heating means for heating the air flowing in the respective zone. Taking into account the functional interpretation of the term "zone" explained above, the heating means may be located inside or outside the respective chamber.

[0025] Referring again to the air-steam mixture, it should be emphasized that according to the invention, due to the synergistic interaction of hot air and water vapor, the temperature of each of these fluids can be relatively low, compared to the prior art, which uses, for example, superheated steam, which, as is well known in the art, is steam at a temperature higher than its evaporation point at the absolute pressure at which the temperature is measured (pressure dependence of the evaporation point). This has a positive impact both on the energy consumption and on the service life of the components of the shrink tunnel. That is to say, superheated steam, in contrast to, for example, saturated steam, is adapted to prevent moisture or water droplets from adhering to the surfaces of the shrink labels and products, but at a higher energy consumption and, as a consequence, a shorter service life of the components. In fact, superheated steam means a high temperature. Sleeve fixing at high temperatures is difficult and the time of exposure to the temperature varies depending on the temperature (for example, 0.5 seconds at 90°C and 0.1 seconds at 100°C). Thus, although superheated steam is an option for shrink finishing, it is not a very good option for sleeve fixing and movement. This disadvantage is accompanied by another disadvantage, namely shorter maintenance intervals and therefore increased costs. Therefore, the present invention differs from the prior art in that the known hot air shrink tunnel is improved by injecting a defined amount of water into the hot air.

[0026] Regarding energy consumption, it should be noted that the moisture content of moist air is directly related to the power used to evaporate the water, i.e. the amount of water evaporated changes rapidly as the electrical energy supplied for that purpose changes.

[0027] Furthermore, it is important and crucial for the present invention to note that the variously mentioned pressures are always normal, i.e. all processes according to the invention are carried out only without overpressure. Only without overpressure can hot air recirculation systems be used. Steam tunnels generally exhaust steam.

[0028] In a preferred modification (claim 2), the humid air zone heating means is configured to adjust the temperature of the air flowing through the humid air zone to a given target temperature, and the water diffusion means is configured to adjust a certain amount of water according to the given target temperature to such an extent that a given absolute humidity of the air-steam mixture in the humid air zone is achieved, with the air-steam mixture kept at normal pressure. Here, the absolute humidity is indicated in "kg water / kg dry air". Alternatively, the absolute humidity may be indicated in "kg water / (kg dry air+kg water)". That is, the control according to this embodiment is preferably performed automatically, with the humid area zone heating means and the water diffusion means working synergistically with each other, to achieve the desired environment of each zone (in each chamber) with minimal resources (e.g. electricity), rather than manually. As an example, the combination of hot air and water vapor in zones 1 and 2 (only) does not require any reliance on fossil energy compared to a typical steam tunnel (without water vapor), with better results with an overall energy reduction of 65% and water reduction of 75% with respect to the typical variant.

[0029] In a preferred modification (claim 3), the hot air shrink tunnel further comprises detection means for detecting the absolute humidity of the air-steam mixture in the moist air zone. Absolute humidity is thus the variable to be controlled or measured. Alternatively, other physical values ​​such as partial pressure, oxygen content or nitrogen content can also play that role.

[0030] In a preferred modification (claim 4), the hot air shrink tunnel comprises control means arranged to control the absolute humidity of the air-steam mixture as a controlled variable in the moist air zone in order to adjust the mass concentration of water in the dry air while keeping the temperature at the target temperature. That is to say, according to this embodiment, as already hinted above, the "final goal", i.e. the goal that is ultimately desired and hoped to be achieved using as little energy as possible, is a temperature suitable for the material used in order for the sleeve to shrink tightly without wrinkling on the product when passing through the tunnel. This is achieved in a controlled manner by optimally matching temperature and humidity. It should be noted that the transit time taken to travel through the tunnel is only a few seconds.

[0031] In a preferred modification (claim 5), either the heating means of the humid air zone and / or the dry air zone are adapted to generate hot air controllably in terms of temperature and flow rate. It should be noted here that the heat transfer from the atmosphere of the zone to the sleeve depends in the case of hot air on its flow rate or velocity, temperature and flow direction, whereas in the case of water vapour it depends less on the flow rate and more on the absolute humidity.

[0032] In a preferred modification (claim 6), either the heating means of the humid air zone and / or the dry air zone comprises flow generating means for generating an air flow circulation in a plane perpendicular to said conveying direction. In particular, the direction perpendicular to the conveying direction is essentially also perpendicular to the axis of symmetry or main axis of said product. That is to say, the majority of the hot air and diffused water flows impinge on the sleeve with no or only a small component tangential to the axis of symmetry or main axis. As a result, no or only a small amount of water vapor penetrates into the gap between the sleeve and the product at the beginning of the shrinking process. However, the heating process itself expands the air in the gap, pushing out of the gap any water vapor that nevertheless managed to penetrate therein, resulting in a dry contact area between the sleeve and the product when the sleeve comes into contact with the product at the end of the shrinking process. Preferably, the flow of fluid impinging on the product can be adjusted in terms of angle and / or direction in order to obtain the appropriate heat locally for each spot of the product. Furthermore, two or more nozzles can be used in cooperation with each other to achieve the required temperature at a particular product spot. Specifically, for each individual product spot, the number of nozzles used, and the individual distances and angles of the nozzles relative to each individual product spot can be controlled.

[0033] In a preferred modification (claim 7), the humid air zone comprises at least a first humid air chamber and a second humid air chamber arranged in the conveying direction of the product in the order of the first humid air chamber and the second humid air chamber, the first humid air chamber and the second humid air chamber being defined by a respective humid air atmosphere that is individually controllable at least with respect to temperature, humidity and flow rate. It is noted that the basic design or construction concept is modular. Thus, in order to increase (shorten) the total length of the tunnel, humid air chambers (modules) as well as dry air chambers (modules) can be inserted (or removed from their position) between two existing modules (chambers), thereby adapting the tunnel to the specific conditions, i.e. the material of the sleeves and the products, the conveying speed, the time in the zone. As already mentioned above, the tunnel is composed of several modules (modular concept) forming chambers inside. Within the chambers, zones with specific atmospheres or environments are generated, which are controllable with respect to their thermodynamic state, which is also defined by intensive thermodynamic variables (variously called state variables or state parameters). Intensive thermodynamic variables are those variables that are independent of the size of the physical system (tunnel), such as temperature and pressure. The concept of state naturally assumes a certain constancy and continuity regarding the values ​​of the variables.

[0034] In a preferred modification (claim 8), the first and second humid air chambers are separated from each other by a through-pass for conveying the product from the first humid air chamber to the second humid air chamber, the through-pass being adapted to separate the different adjacent atmospheres so that they can be individually controlled.

[0035] In a preferred modification (claim 9), the dry air zone comprises at least a first dry air chamber and a second dry air chamber arranged in the conveying direction of the product in the order of a first dry air chamber and a second dry air chamber, the first dry air chamber and the second dry air chamber being defined by respective dry air atmospheres which are individually controllable at least with respect to temperature. In particular in the case of the dry zones, the through-passes between them can be omitted (see below), resulting in an extended heated zone with uniform temperature and (remaining) humidity.

[0036] In a preferred modification (claim 10), the humid air zone and the dry air zone are separated from each other by a through-pass for conveying the product from the humid air zone to the dry air zone. As mentioned above, the through-pass serves to enable a clear separation between the different zones (atmospheres) created in the chamber.

[0037] In a preferred modification (claim 11), the hot air shrink tunnel further comprises an infeed zone arranged before the moist air zone in the conveying direction of the products and containing heating means for heating the interior of the infeed zone. Advantageously, the infeed zone is employed as a "preheating zone" which preheats the products only to a temperature moderately higher than the ambient temperature, i.e., for example, to about 80° C. Furthermore, the infeed zone has a length in the conveying direction of, for example, at least 1,000 mm in order to ensure working safety.

[0038] In a preferred modification (claim 12), the infeed zone and the moist air zone are separated from each other by a through-pass for conveying the product from the infeed zone to the moist air zone. Indeed, the through-pass between the moist air zone and the dry air zone is essential in view of the significant difference between the environments created in those zones, which difference is greater than the difference between the main equivalent zones, i.e. between two moist air zones or two dry air zones.

[0039] In a preferred modification (claim 13), the hot air shrink tunnel further comprises an outfeed zone arranged after the dry air zone in the conveying direction of the products and including heating means for heating the interior of the outfeed zone, the heating means being configured to evaporate remaining condensation not removed in the dry air zone.

[0040] In a preferred modification (claim 14), the dry air zone and the delivery zone are separated from each other by a closable / openable passage for conveying the product from the dry air zone to the delivery zone. Optionally, the passage is permanently open with only a small opening surface conforming to the shape or contour of the product, or is only open at the exact moment when the product moves between the chambers and closed otherwise. Naturally, also in the latter case, the passage is as small as possible and shaped accordingly.

[0041] In a preferred modification (claim 15), the passage is adapted to be opened and closed when the product passes from one zone to the next.

[0042] In a preferred modification (claim 16), the hot air shrink tunnel further comprises a recirculation zone arranged between the moist air zone and the dry air zone, the recirculation zone being configured to recirculate the moist air leaving the moist air zone to an infeed zone and / or to a moist air zone arranged before the moist air zone in the conveying direction of the products. For this purpose, a tube or pipe leading from the recirculation zone to the infeed zone and / or a second pipe leading from the recirculation zone to the moist air zone may be provided.

[0043] As outlined above, the infeed zone is employed as a "preheat zone" to preheat the product only moderately above ambient temperature, i.e., for example, to about 80° C. Specifically, the energy stored in the recirculated moist air exiting the moist air zone can raise the sleeve temperature in the preheat zone from room temperature to a shrink initiation temperature of about 70° C. Thus, by recirculating the moist air exiting the moist air zone from the recirculation zone back to the preheat zone, there is an overall savings in the energy required to shrink the sleeve.

[0044] If the energy contained in the wet air leaving the wet air zone and entering the recirculation zone exceeds the amount of energy required in the preheat zone to raise the sleeve temperature from room temperature to the shrink initiation temperature of about 70°C, the energy of the wet air not needed in the preheat zone can be used to heat the air in the wet air zone, thus saving energy overall. Furthermore, since the recirculated wet air already contains water (i.e. evaporated water = steam), the amount of water used by the water diffusion means to generate the air-steam mixture in the wet air zone can also be reduced. Instead of or in addition to using the recirculation energy of the wet air leaving the wet air zone and entering the recirculation zone and / or the wet air zone in the infeed zone to heat the air, the energy of the recirculated wet air may be used to heat the (infeed) water used by the water diffusion means in the wet air zone.

[0045] Another advantage of the recirculation zone is that it creates a structural separation between the wet air zone and the dry air zone, whose conditions, i.e. environment and temperature, are very different from each other. At the end of the wet air zone, the air is wet and has a temperature in the range of 110° C., and at the beginning of the dry air zone, the air is dry and has a temperature in the range of 180° C. By providing a recirculation zone, it is possible to prevent the temperature and condition (wet-dry) differences in the wet air zone and the dry air zone from adversely affecting each other. In particular, the recirculation zone prevents wet air from entering the dry air zone. As a result, the overall shrinkage conditions can be improved and better shrinkage results can be achieved.

[0046] In a preferred modification (claim 17), when the humid air zone comprises a first humid air chamber and a second humid air chamber arranged in the order of the first humid air chamber and the second humid air chamber in the conveying direction of the product, the recirculation zone is configured to recirculate humid air into the first humid air chamber.

[0047] According to a second aspect of the invention (claim 16), a method for heat shrinking a plastic sleeve packaging a product while said product is being conveyed through a hot air shrink tunnel according to any one of the previous claims is characterized in that (i) the air atmosphere in the moist air zone is heated in order to adjust the temperature of said moist air zone to a given target temperature, and (ii) the amount of water diffused in the moist air zone depending on the target temperature, so that the desired sleeve surface temperature is achieved by latent heat release due to condensation of water on the sleeve surface, i.e., as already pointed out above, the processes (i) and (ii) are carried out together in order to achieve the target temperature in cooperation with the lowest possible total energy consumption.

[0048] According to a third aspect of the present invention (claim 17), a heat shrinking device for heat shrinking a shrink label packaging a product comprises the above-mentioned hot air shrink tunnel and a conveying means for conveying the product covered with the shrink label through the hot air shrink tunnel. [Brief description of the drawings]

[0049] [Figure 1] 1 is a photograph showing a perspective view of a hot air shrink tunnel according to the present invention. [Diagram 2] 1 shows a schematic perspective view of a module as part of said hot air shrink tunnel, which serves to generate a moist or dry atmosphere inside. [Diagram 3] FIG. 3 is a longitudinal section of the module shown in FIG. 2 along the conveying or running direction of the products; [Figure 4] FIG. 2 illustrates the relationship between time and temperature along a path through a hot air shrink tunnel in accordance with the present invention. [Diagram 5] FIG. 11 is a diagram showing the relationship between time and temperature along the transport direction. [Figure 6] FIG. 2 is another perspective view of the hot air shrink tunnel according to the present invention. [Figure 7a] FIG. 2 is a front view of a hot air shrink tunnel according to the present invention. [Figure 7b] FIG. 2 is a side view of a hot air shrink tunnel according to the present invention. [Figure 8] FIG. 4 is a perspective view of a hot air shrink tunnel according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] A hot air shrink tunnel (hereinafter simply "tunnel") 10 for a heat shrink apparatus according to an exemplary embodiment of the present invention is shown in Figures 1-7b.

[0051] Figure 1 is a photograph showing a perspective view from the infeed side of a tunnel 10, with an entrance 12 leading into the tunnel 10. Figure 6 shows another perspective view of the tunnel 10 from its infeed side.

[0052] In tunnel 10, a shrinking process is carried out in which a plastic film or shrink label (hereinafter referred to as a "sleeve") made, for example, from polypropylene (PP), polyethylene (PE) or polystyrene (PS) is heat shrunk onto the product in successive stages to form an intimate contact with the product while the product (e.g. a bottle) moves through tunnel 10 in the conveying direction.

[0053] The heat shrinking apparatus housing the tunnel 10 comprises an infeed module 16, a first nozzle module 18, a second nozzle module 20, a third nozzle module 22, a fourth nozzle module 24 and an outfeed module 25 (only a small portion of which is visible at the far left in FIG. 1), which are arranged in this order in the conveying direction along the conveyor means 14 (conveying path), which in this exemplary embodiment is the lower part of the tunnel 10. As shown in FIG. 1, all modules 16-25 straddle the conveyor means 14, thereby "surrounding the product conveying path" as described above.

[0054] Each of the modules, as mentioned above, forms a specific chamber (or in process-oriented language, a zone) within which a well-defined atmosphere can be generated that is controllable with respect to intensive thermodynamic variables such as temperature, humidity and, optionally, pressure, and that is adapted to carry out a specific part of the shrinkage process. That is, the term "module" refers to a structural part of the tunnel 10, while the term "zone" refers to a separate atmosphere generated within the tunnel, which in this interpretation can be understood in a more functional sense referring to a part of the shrinkage process.

[0055] The infeed module 16 and the outfeed module 25 are therefore arranged at the infeed and outfeed sides of the tunnel 10 and form a structural bracket encasing the nozzle modules 18, 20, 22 and 24, which are not nozzle modules, i.e. modules in which no fluid circulates at all. The modules 16 and 25 forming the infeed and outfeed zones respectively are configured (i) as functional modules in terms of the temperature at which condensation occurs with respect to the shrinking process (for example, as shown in FIG. 2, in this embodiment, the temperature of the module 16 acting as a preheating zone is chosen to be 80° C.) and (ii) as safety zones for the personnel in charge of operating the heat shrinking apparatus. For the module 25, point (i) is realised by means of a certain heating device in order to remove residual moisture by evaporation, while point (ii) is realised in particular by the relatively long extension in the conveying direction of the module 25, in this embodiment, of 1000 mm. The same is true for the module 16 in terms of safety, as shown in FIG. 2.

[0056] As shown in Fig. 2, two adjacent zones (modules) are either directly connected (like zones 3 and 4 in this embodiment) or are connected to each other by a partition element 26, which is provided with a passage on the inside, configured to correspond or flexibly adapt in size and shape to the products to be conveyed. That is to say, nozzle modules 3 and 4 are connected to form a composite module with the sum of the lengths of both modules. The passage is arranged to be open while the products are moving from one module to the next, and then closed again, in order to keep the respective atmospheres as constant as possible.

[0057] As shown in Fig. 2, each of the nozzle modules 1 and 2 generates a wet air zone, while each of the nozzle modules 3 and 4 generates a dry air zone, the latter two forming a combined dry air zone of twice the length of what may be called the "standard module distance" within the modular concept of the present invention. Although not shown in Fig. 2, each of the nozzle modules 1 and 2 includes (a) a heating means, (b) a flow generating means, and (c) a water injection means (nozzle), while each of the nozzle modules 3 and 4 includes only (a) and (b). Furthermore, each of the modules 16 and 25 includes only (a), not a nozzle module, as already mentioned above.

[0058] In order to grasp the size and temperature situation of the individual modules, as an example, according to the present embodiment, all modules have a length of 500 mm in the conveying direction, except for the infeed module 16 and the outfeed module 25, each of which has a length of 1000 mm as described above. Furthermore, the preheat temperature in the infeed zone is about 80°C, the preheat temperature in zone 1 (first moist air zone) is about 90°C-130°C, the preheat temperature in zone 2 (second moist air zone) is about 90°C-170°C, and the preheat temperature in zone 3 (first dry air zone) and zone 4 (second dry air zone) is about 220°C. Naturally, the above data should be understood as merely an example. In particular, the "standard module distance" may be different from the above-mentioned 500 mm. Furthermore, the module concept may include modules of various different lengths, which are flexibly added to various overall lengths adapted to the needs and products, for example.

[0059] Figure 3 shows a schematic perspective view of one of the nozzle modules as part of a tunnel 10 within which either a humid or dry atmosphere is generated. Clearly visible is the inlet 28 with its nozzle designed tip (see Figure 4).

[0060] The inlets are oriented perpendicular to the conveying direction to create circulation in a plane perpendicular to the conveying direction, as shown in Figure 4. The atmosphere inside each of the nozzle modules may be circulated using a ventilator 32, the upper portion of which extends outward and can be seen in Figure 3.

[0061] Although not shown in the drawings, according to the invention the air-steam mixture is generated only inside each nozzle module individually, although it will be appreciated that alternatively the air-steam mixture may be generated outside the nozzle modules.

[0062] Figure 5 shows the relationship between time and temperature along the conveying direction. Note that the areas labeled "Preheat", "Fixed Match", "Move Match" and "Finishing and Drying" do not have a one-to-one relationship with Zones 1-4. Instead, the shrinking process begins with a preheating process in the infeed module ("No Shrinkage") and ends in the outfeed module ("Strong Shrinkage and Drying").

[0063] The regions shown in FIG. 5 may be defined according to the following characteristics, by way of example: (i) product, (ii) product contents, (iii) sleeve condition, (iv) sleeve characteristics, (v) process, and (vi) length of time.

[0064] According to this definition, the characteristics of the preheat zone are: (i) dry and at room temperature; (ii) liquid or granular at room temperature or empty of product; (iii) unstable and undefined contact point with the product and standing on a conveyor belt; (iv) shrink time: 4 seconds at 70°C, 1 second at 80°C, 0.5 seconds at 90°C, 0.1 seconds at 100°C, melting point: 120°C; (v) sleeve is heated from room temperature to 70°C where shrinkage begins; and (vi) 1 to 4 seconds.

[0065] Similarly, the characteristics of the fixation zone are: (i) dry and at room temperature; (ii) liquid or granular at room temperature or empty of product; (iii) unstable and undefined contact point with the product, standing on a conveyor belt; (iv) shrink time of 4 seconds at 70°C, 1 second at 80°C, 0.5 seconds at 90°C, 0.1 seconds at 100°C, melting point of 120°C; (v) very low flow rate, sleeve temperature of 70°C-80°C, homogenous conditions, high energy; and (vi) second conditioning time of 1-2 seconds to maintain shrinkage control.

[0066] Additionally, the characteristics of the transfer zone (where "transfer" is to be understood as the shrink label moving towards the product) are: (i) dry and at room temperature; (ii) liquid or granular at room temperature or empty of the product; (iii) stable, consistent, firm contact with the product and continuous movement towards the product; (iv) shrink time of 4 seconds at 70°C, 1 second at 80°C, 0.5 seconds at 90°C, 0.1 seconds at 100°C, melting point of 120°C; (v) gentle flow rate, sleeve temperature of 80°C-90°C, homogenous conditions, high energy, and (vi) conditioning time of 1 second to 4 seconds to maintain shrink control.

[0067] Finally, the finishing zone characteristics are: (i) dry and at room temperature; (ii) liquid at room temperature, granular at room temperature, or empty of product; (iii) stable, no wrinkles in the sleeve and evaporation of microdroplets when in contact with the product; (iv) shrink time of 4 seconds at 70°C, 1 second at 80°C, 0.5 seconds at 90°C, 0.1 seconds at 100°C, melting point of 120°C; (v) high flow rate, sleeve temperature of 90°C-120°C, homogenous conditions, high energy; and (vi) second conditioning time of 2 seconds-3.5 seconds to obtain a product with excellent shrinkage and drying.

[0068] Although not shown or described above, it should be noted that the control and adjustment possibilities for controlling the heat shrinking apparatus and the processes carried out by and within the heat shrinking apparatus may be either manual or automatic, or a combination of both.

[0069] Second embodiment Figure 8 shows a perspective view of a hot air shrink tunnel 100 according to a second embodiment of the invention. The following description focuses on the differences from the exemplary embodiment shown in figures 1 to 7b. Elements of the second embodiment that correspond to elements of the exemplary embodiment have the same reference numbers.

[0070] In contrast to tunnel 10, tunnel 100 comprises a recirculation zone 21 located between the wet air zone and the dry air zone, in particular between nozzle module 20 and nozzle module 22. A pipe 102 leads from the recirculation zone 21 to the infeed zone 16, through which the wet air leaving nozzle module 20 is returned (recirculated) to the infeed zone 16. Furthermore, a second pipe 104 leads from the recirculation zone 21 to nozzle module 18, through which the wet air leaving nozzle module 20 is returned (recirculated) to nozzle module 18.

[0071] The energy stored in the recirculated moist air leaving the nozzle module 20 raises the sleeve temperature in the infeed zone 16 (preheat zone) from room temperature to the shrink initiation temperature of about 70°C. Thus, by recirculating the moist air leaving the nozzle module 20 from the recirculation zone 21 to the infeed zone 16, the energy required to heat the air in the infeed zone 16 can be reduced, and therefore the overall energy required to shrink the sleeve can be saved. Furthermore, by returning (recirculating) the moist air leaving the nozzle module 20 to the nozzle module 18, the energy required to heat the air in the nozzle module 18 can be reduced. Furthermore, since the recirculated moist air already contains water (i.e. evaporated water = steam), the amount of water used by the water diffusion means to generate the air-steam mixture in the nozzle module 18 can also be reduced.

[0072] Furthermore, the recirculation zone 21 provides a structural separation of the wet air zone and the dry air zone, in particular the nozzle module 20 and the nozzle module 22. The conditions, i.e. the environment and temperature, of the nozzle module 20 and the nozzle module 22 are significantly different from each other. In the second embodiment, at the end of the nozzle module 20 in the conveying direction of the product, the air is wet and has a temperature in the range of 110 ° C, and at the beginning of the nozzle module 22, the air is dry and has a temperature in the range of 180 ° C. Furthermore, in order to grasp the condition and temperature situation of the further modules in the second embodiment, it is noted that in the nozzle module 18, the air is wet and has a temperature of about 90 ° C, and in the nozzle module 24, the air is dry and has a temperature of about 200 ° C. By providing the recirculation zone 21, it is possible to prevent the difference in temperature and conditions (wet-dry) of the nozzle module 20 and the nozzle module 22 from adversely affecting each other. In particular, the recirculation zone 21 prevents the wet air leaving the nozzle module 20 from entering the nozzle module 22. As a result, the overall shrink conditions can be improved and better shrink results can be achieved.

Claims

1. A hot air shrink tunnel of a heat shrink device for heat shrinking a shrink label for packaging a product, the hot air shrink tunnel surrounding a conveying path of the product, A moist air zone and a dry air zone arranged in this order in a conveying direction of the product through the hot air shrink tunnel, said humid air zone comprising: a heating means for heating air flowing through said humid air zone; and a water diffusion means for diffusing a quantity of water into said air flowing through said humid air zone to produce an air-steam mixture; the dry air zone including heating means for heating air flowing through the dry air zone; A hot air shrink tunnel characterized by a wet air zone and a dry air zone.

2. the moist air zone heating means is configured to adjust the temperature of the air flowing through the moist air zone to a given target temperature; the water diffusion means is configured to adjust the quantity of water in response to the given target temperature to such an extent that a given absolute humidity of the air-vapor mixture in the humid air zone is achieved while the air-vapor mixture is kept at normal pressure.

2. The hot air shrink tunnel according to claim 1.

3. A hot air shrink tunnel according to claim 1 or 2, further comprising detection means for detecting the absolute humidity of the air-steam mixture in the moist air zone.

4. 4. A hot air shrink tunnel as claimed in claim 2 or 3, comprising a control means configured to control the absolute humidity of the air-steam mixture as a controlled variable in the humid air zone in order to adjust the mass concentration of water in the dry air whilst maintaining the temperature at the target temperature.

5. A hot air shrink tunnel as claimed in any one of claims 1 to 4, wherein either the heating means of the humid air zone and / or the dry air zone is configured to generate hot air in a manner that is controllable in terms of temperature and flow rate.

6. 6. A hot air shrink tunnel as claimed in claim 5, wherein either the heating means of the humid air zone and / or the dry air zone comprises flow generating means for generating air flow circulation in a plane perpendicular to the conveying direction.

7. A hot air shrink tunnel as described in any one of claims 1 to 6, wherein the humid air zone comprises at least a first humid air chamber and a second humid air chamber arranged in the conveying direction of the product in the order of a first humid air chamber and a second humid air chamber, the first humid air chamber and the second humid air chamber being defined by respective humid air atmospheres that are individually controllable at least with respect to temperature, humidity and flow rate.

8. 8. The hot air shrink tunnel of claim 7, wherein the first and second moist air chambers are separated from each other by a through-pass for transporting the product from the first moist air chamber to the second moist air chamber.

9. 9. The hot air shrink tunnel according to claim 1, wherein the dry air zone comprises at least a first dry air chamber and a second dry air chamber arranged in the conveying direction of the product in the order of a first dry air chamber and a second dry air chamber, the first dry air chamber and the second dry air chamber being defined by respective dry air atmospheres which are individually controllable at least with respect to temperature.

10. A hot air shrink tunnel as claimed in any one of claims 1 to 9, characterized in that the moist air zone and the dry air zone are separated from each other by a through-pass for transporting the product from the moist air zone to the dry air zone.

11. 11. The hot air shrink tunnel according to claim 1, further comprising an infeed zone arranged before the moist air zone in the conveying direction of the product, the infeed zone including a heating means for heating the inside of the infeed zone.

12. 12. The hot air shrink tunnel of claim 11, wherein the infeed zone and the moist air zone are separated from each other by a through-pass for transporting the product from the infeed zone to the moist air zone.

13. 13. The hot air shrink tunnel according to claim 1, further comprising an outfeed zone arranged after the dry air zone in the conveying direction of the product, the outfeed zone including a heating means for heating the interior of the outfeed zone.

14. 14. The hot air shrink tunnel according to claim 13, characterized in that the dry air zone and the discharge zone are separated from each other by a closable / openable passage for transporting the product from the dry air zone to the discharge zone.

15. 13. A hot air shrink tunnel as claimed in any one of claims 8, 10 or 12, characterized in that the pass-through is adapted to be opened and closed as the products pass from one zone to the next.

16. 16. The hot air shrink tunnel according to claim 1, further comprising a recirculation zone arranged between the moist air zone and the dry air zone, the recirculation zone being configured to recirculate moist air leaving the moist air zone to an infeed zone and / or to the moist air zone arranged before the moist air zone in the conveying direction of the product.

17. 17. A hot air shrink tunnel according to claim 16 with reference to claim 7, wherein the recirculation zone is configured to recirculate moist air into the first moist air chamber.

18. A method for heat shrinking a shrink label packaging a product while the product is being transported through a hot air shrink tunnel according to any one of claims 1 to 17, comprising the steps of: heating the air atmosphere in the moist air zone to adjust the temperature of said moist air zone to a given target temperature; and adjusting the amount of water diffused into the humid air zone in response to the target temperature such that a desired sleeve surface temperature is achieved by latent heat release due to condensation of water on the sleeve surface; A method comprising:

19. A heat shrinkage apparatus for heat shrinking a shrink label packaging a product, the heat shrinkage apparatus comprising: a hot air shrink tunnel according to any one of claims 1 to 18; and a conveying means for conveying a product covered with the shrink label through the hot air shrink tunnel.

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