HOT AIR SHRINK TUNNEL FOR HEAT SHRINKING A SHRINK LABEL, METHOD FOR HEAT SHRINKING A SHRINK LABEL, AND HEAT SHRINKING APPARATUS FOR HEAT SHRINKING A SHRINK LABEL

Abstract

The invention relates to a hot air shrink tunnel (10) for a heat shrinking apparatus for heat shrinking a shrink label to enclose a product, wherein the hot air shrink tunnel surrounds a conveying path of the product. The hot air shrink tunnel includes a moist air zone (1, 2) and a dry air zone (3, 4) arranged in this order in a conveying direction of the product through the hot air shrink tunnel (10); wherein the moist air zone (1, 2) includes heating means for heating air flowing within the moist air zone (1, 2), and water diffusion means for diffusing an amount of water in the air flowing within the moist air zone (1, 2) to produce an air-steam mixture, and the dry air zone (3, 4) includes heating means for heating air flowing within the dry air zone (3, 4).

Claims

1. A hot air shrink tunnel for a heat shrinking apparatus for heat shrinking a shrink label to enclose a product, wherein the hot air shrink tunnel surrounds a conveying path of the product, wherein the hot air shrink tunnel comprises: 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; wherein the moist air zone includes heating means for heating air flowing within the moist air zone, and water diffusion means for diffusing an amount of water in the air flowing within the moist air zone to produce an air-steam mixture, and the dry air zone includes heating means for heating air flowing within the dry air zone.

2. The hot air shrink tunnel according to claim 1, wherein the moist air zone heating means is configured to adjust a temperature of the air flowing in the moist air zone to a given target temperature, and the water diffusion means is configured to adjust the amount of water depending on the given target temperature to such extent that a given absolute humidity of the air-steam mixture within the moist air zone is achieved with the air-steam mixture being kept at normal pressure.

3. The hot air shrink tunnel according to claim 1, further comprising a detecting means for detecting the absolute humidity of the air-steam mixture within the moist air zone.

4. The hot air shrink tunnel according to claim 2, comprising a control means configured to control the absolute humidity of the air-steam mixture as a controlled variable within the moist air zone to adjust a mass concentration of water in dry air while keeping the temperature at the target temperature.

5. The hot air shrink tunnel according to claim 1, wherein any of the heating means of the moist air zone and/or of the dry air zone is configured to generate hot air controllably in terms of temperature and flow rate.

6. The hot air shrink tunnel according to claim 5, wherein any of the heating means of the moist air zone and/or of the dry air zone includes flow generating means for generating air flow circulation in a plane perpendicular to said conveying direction.

7. The hot air shrink tunnel according to claim 1, wherein the moist air zone includes at least a first moist air chamber and a second moist air chamber arranged in this order in the conveying direction of the product, which are defined by their respective moist air atmospheres individually controllable at least in terms of temperature, humidity and flow.

8. The hot air shrink tunnel according to claim 7, characterized in that a first moist air chamber and a second moist air chamber are separated from each other by a pass through for the product to be conveyed from the first moist air chamber to the second moist air chamber.

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

10. The hot air shrink tunnel according to claim 1, characterized in that the moist air zone and the dry air zone are separated from each other by a pass through for the product to be conveyed from the moist air zone to the dry air zone.

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

12. The hot air shrink tunnel according to claim 11, characterized in that the infeed zone and the moist air zone are separated from each other by a pass through for the product to be conveyed from the infeed zone to the moist air zone.

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

14. The hot air shrink tunnel according to claim 13, characterized in that the dry air zone and the outfeed zone are separated from each other by a closable/openable pass through for the product to be conveyed from the dry air zone to the outfeed zone.

15. The hot air shrink tunnel according to claim 8, characterized in that the pass through is adapted to be closed and opened in the transition of the product from one zone to the next.

16. The hot air shrink tunnel according to claim 1, further comprising a recycling zone arranged between the moist air zone and the dry air zone which is configured to recycle moist air leaving the moist air zone to an infeed zone arranged ahead of the moist air zone in the conveying direction of the product, and/or to the moist air zone.

17. The hot air shrink tunnel according to claim 16, wherein the moist air zone includes at least a first moist air chamber and a second moist air chamber arranged in this order in the conveying direction of the product, which are defined by their respective moist air atmospheres individually controllable at least in terms of temperature, humidity and flow, wherein the recycling zone is configured to recycle moist air to the first moist air chamber.

18. A method for heat shrinking a shrink label enclosing a product while said product is conveyed through a hot air shrink tunnel according to claim 1, the method comprising: heating an air atmosphere within the moist air zone to adjust its temperature to a given target temperature, and depending on the target temperature, adjusting the amount of water diffused in the moist air zone so that by latent heat release due to condensation of water on a sleeve surface a desired sleeve surface temperature is achieved.

19. A heat shrinking apparatus for heat shrinking a shrink label enclosing a product, said heat shrinking apparatus comprising a hot air shrink tunnel in accordance with claim 1, and a conveying means for conveying a shrink label covered product through the hot air shrink tunnel.

20. The hot air shrink tunnel according to claim 10, characterized in that the pass through is adapted to be closed and opened in the transition of the product from one zone to the next.

21. The hot air shrink tunnel according to claim 12, characterized in that the pass through is adapted to be closed and opened in the transition of the product from one zone to the next.

22. A hot air shrink tunnel for a heat shrinking apparatus for heat shrinking a shrink label to enclose a product, wherein the hot air shrink tunnel surrounds a conveying path of the product, wherein the hot air shrink tunnel comprises: a moist air zone arranged in a conveying direction of the product through the hot air shrink tunnel; wherein the moist air zone includes heating means for heating air flowing within the moist air zone, and water diffusion means for diffusing an amount of water in the air flowing within the moist air zone to produce an air-steam mixture, and the moist air zone heating means is configured to adjust a temperature of the air flowing in the moist air zone to a given target temperature, and the water diffusion means is configured to adjust the amount of water depending on the given target temperature to such extent that a given absolute humidity of the air-steam mixture within the moist air zone is achieved with the air-steam mixture being kept at normal pressure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] FIG. 1 is photo showing in a perspective view a hot air shrink tunnel according to the present invention;

[0050] FIG. 2 schematically shows a perspective view of a module as part of said hot air shrink tunnel serving to generate a moist or a dry atmosphere inside;

[0051] FIG. 3 is a longitudinal section along a conveying or running direction of a product of the module shown in FIG. 2;

[0052] FIG. 4 is a diagram showing a time-temperature-relationship along the path through the hot air shrink tunnel according to the present invention;

[0053] FIG. 5 is a diagram showing a time-temperature-relationship along the conveying direction;

[0054] FIG. 6 is another perspective view of the hot air shrink tunnel according to the present invention;

[0055] FIG. 7a is a front view of the hot air shrink tunnel according to the present invention;

[0056] FIG. 7b is a side view of the hot air shrink tunnel according to the present invention; and

[0057] FIG. 8 is a perspective view of a hot air shrink tunnel according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0058] A hot air shrink tunnel (hereafter simply tunnel) 10 for a heat shrinking apparatus according to an exemplary embodiment of the present invention is shown in FIGS. 1 to 7b.

[0059] FIG. 1 is a photo showing, in a perspective view, the tunnel 10 as seen from an infeed side thereof, with an entrance 12 leading into it. FIG. 6 shows another perspective view of the tunnel 10 as seen from an infeed side thereof.

[0060] In the tunnel 10, a shrinkage process, in which a plastic film or shrink label (hereafter referred to as sleeve) made of polypropylene (PP), polyethylene (PE) or polystyrene (PS), for example, is thermally shrunk onto and brought in tight contact with a product (for example a bottle) in successive stages during the movement of the product in a conveying direction through the tunnel 10.

[0061] 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 part thereof is visible leftmost in FIG. 1) that are arranged in this order along a conveyor means 14 (conveying path), which in this exemplary embodiment is lower part of the tunnel 10, in a conveying direction thereof. As shown in FIG. 1, all modules 16 to 25 straddle the conveyer means 14 thereby surrounding a conveying path of the produce as recited above.

[0062] Each of the modules forms a specific chamber (or zone in a process-focusing language), as noted above, in which a well-defined atmosphere, that is controllable in terms of intensive thermodynamic variables like temperature, humidity, andoptionallypressure and that is adapted to carry out a specific part of a shrinkage process, can be created. That is, the term module refers to a structural portion of the tunnel 10, while the term zone refers to a respective atmosphere generated therein and may be understood in a more functional sense referring in this reading to a part of the shrinkage process.

[0063] Therefore, located at the infeed side and at an outfeed side of the tunnel 10 and forming a structural bracket enclosing nozzle modules 18, 20, 22, and 24, are the infeed module 16 and the outfeed module 25 which are not nozzle modules, i. e. modules without any fluid circulating therein. Modules 16 and 25 that form an infeed zone and an outfeed zone, respectively, are configured (i) as functional modules in terms of the shrinkage process in that the temperature is such that condensation takes place (for example, as shown in FIG. 2, in the present embodiment, the temperature in module 16 acting as a pre-heating zone is selected to be 80 C.) and (ii) as safety-zones for the workers in charge with the operation of the heat shrinking apparatus. As for module 25, point (i) is realized by means of some sort of heating device in order to remove residual moisture by vaporization, while point (ii) is realized particularly by its relatively long extension of 1000 mm in the conveying direction in this embodiment. The same in terms of safety holds for module 16, as shown in FIG. 2.

[0064] As shown in FIG. 2, adjacent two zones (modules) are either connected directly (as zones 3 and 4 in the present embodiment) or coupled with each by a partitioning element 26, having provided therein pass-throughs configured to correspond or to be flexibly adaptable to correspond in size and shape to the product conveyed. That is, nozzle modules 3 and 4 are connected in such a way as to form a combined module having the added lengths of both modules. The pass-throughs are arranged to be open during the movement of the product from one module to the next one in order to keep their respective atmospheres as constant as possible, and are closed again afterwards.

[0065] As shown in FIG. 2, in each of nozzle modules 1 and 2 there is created a moist air zone while in each of nozzle modules 3 and 4 there is created a dry air zone, the latter two forming a combined dry air zone of twice the length of a distance that may be called a standard modular distance within the modular concept of the present invention. Although not shown in FIG. 2, each of nozzle modules 1 and 2 comprises (a) a heating means, (b) a flow generating means, and (c) a water ejecting means (nozzles) while each of nozzle modules 3 and 4 comprises only (a) and (b). Furthermore, each of modules 16 and 25, being no nozzle modules as already mentioned above, comprises only (a).

[0066] In order to get an idea of the size and the temperature regime of the individual modules, as an example, according to the present embodiment, all modules except the infeed module 16 and the outfeed module 25 which each have, as stated above, a length of 1000 mm, have a length in the conveying direction of 500 mm. Furthermore, the pre-heat-temperature in the infeed-zone is about 80 C., that of zone 1 (first moist air zone) about 90 C.-130 C., that of zone 2 (second moist air zone) about 90 C.-170 C., and that of zone 3 (first dry air zone) and zone 4 (second dry air zone) about 220 C. As a matter of course, the above data are only to be understood as an example. Specifically, the standard modular distance may differ from the above mentioned 500 mm. Furthermore, the modular concept may include modules of different lengths to be flexibly added to various overall lengths adapted to needs and products, for example.

[0067] FIG. 3 schematically shows a perspective view of one of said nozzle modules as part of the tunnel 10 in which either a moist or a dry atmosphere is created. Clearly visible are inlets 28 with nozzle-designed tip ends (see FIG. 4).

[0068] As shown in FIG. 4, the inlets are directed in a direction perpendicular to the conveying direction in order to generate a circulation in a plane perpendicular to the conveying direction. The atmosphere inside each of the nozzle modules may be circulated by means of a ventilator 32, a top portion thereof extending outside and being visible in FIG. 3.

[0069] Although not illustrated in the drawings, according to the present invention, an air-steam-mixture is generated individually only inside the respective nozzle modules. As a matter of course, alternatively, the air-steam-mixture may be generated outside thereof.

[0070] FIG. 5 is a diagram showing a time-temperature-relationship along the conveying direction. It should be noted that the regions named pre-heat, fixation match, move match, and finish and dry are not to be associated in a one-to-one relationship to zones 1 to 4. Instead, the process of shrinking starts with a pre-heat process (shrink none) in the infeed module and ends in the outfeed module (shrink strong and dry).

[0071] The regions shown in FIG. 5 may be defined, exemplarily, according to the following characteristics: (i) product, (ii) product content, (iii) sleeve state, (iv) sleeve characteristic, (v) process, and (vi) length of time.

[0072] In line with this definition, the characteristics of the pre-heat-region are: (i) dry and at room temperature, (ii) liquid or granulate at room temperature or product empty, (iii) unstable, undefined contact points with the product, standing on transport belt, (iv) shrinkage time 70 C. for 4 s, 80 C. for 1 s, 90 C. for 0.5 s, 100 C. for 0.1 s, melting point 120 C., (v) heating of the sleeve from room temperature to a temperature of 70 C. where shrinkage starts, and (vi) 1 s-4 s.

[0073] Similarly, the characteristics of the fixation-region are (i) dry and at room temperature, (ii) liquid or granulate at room temperature or product empty, (iii) unstable, undefined contact points with the product, standing on transport belt, (iv) shrinkage time 70 C. for 4 s, 80 C. for 1 s, 90 C. for 0.5 s, 100 C. for 0.1 s, melting point 120 C., (v) very low flow, sleeve temperature 70 C.-80 C., homogeneous condition, high energy, and (vi) 1 s-2 s second condition time to keep shrink control.

[0074] Furthermore, the characteristics of the move-region (where move is to be understood as the movement of the shrink label towards the product) are: (i) dry and at room temperature, (ii) liquid or granulate at room temperature or product empty, (iii) stable, defined and firm contact with the product, continuation of movement towards product, (iv) shrinkage time 70 C. for 4 s, 80 C. for 1 s, 90 C. for 0.5 s, 100 C. for 0.1 s, melting point 120 C., (v) mild flow, sleeve temperature 80 C.-90 C., homogeneous condition, high energy, and (vi) 1 s-4 s condition time to keep shrink control.

[0075] Finally, the characteristics of the finish-region are (i) dry and at room temperature, (ii) liquid at room temperature, granulate at room temperature or product empty, (iii) stable, even contact with the product, sleeve smoothes out and evaporation of mini droplets, (iv) shrinkage time 70 C. for 4 s, 80 C. for 1 s, 90 C. for 0.5 s, 100 C. for 0.1 s, melting point 120 C., (v) high flow, sleeve temperature 90 C.-120 C., homogeneous condition, high energy, and (vi) 2 s-3.5 s second condition time to get excellent shrinkage and dry products.

[0076] Although it is not shown and discussed above, it should be noted that the control and adjustment possibilities to control the heat shrinking apparatus and the processes to be carried out by and within it may be either manually or automatically or a combination of both.

Second Embodiment

[0077] FIG. 8 shows a perspective view of a hot air shrink tunnel 100 according to a second embodiment of the present invention. The following description focuses on the differences to the exemplary embodiment as shown in FIGS. 1 to 7b. Elements of the second embodiment corresponding to elements of the exemplary embodiment have same reference signs.

[0078] In contrast to tunnel 10, tunnel 100 comprises a recycling zone 21 arranged between the moist air zone and the dry air zone, in particular between nozzle module 20 and nozzle module 22. A pipe 102 leading from the recycling zone 21 to the infeed zone 16 is provided, through which moist air leaving nozzle module 20 is fed back (recycled) to the infeed zone 16. Further, a second pipe 104 leading from the recycling zone 21 to the nozzle module 18 is provided, through which moist air leaving nozzle module 20 is fed back (recycled) to nozzle module 18.

[0079] Energy stored in the recycled moist air leaving nozzle module 20 lifts the sleeve temperature in the infeed zone 16 (pre-heat zone) from room temperature to a shrink start temperature of about 70 C. Therefore, by recycling moist air leaving the nozzle module 20 from the recycling zone 21 to the infeed zone 16, energy required to heat up air in the infeed zone 16 can be reduced and thus, energy to shrink the sleeve can be saved overall. Further, by feeding back (recycling) moist air leaving nozzle module 20 to nozzle module 18, energy required to heat up air in the nozzle module 18 can be reduced. Further, as the recycled moist air already contains water (i.e. evaporated water=steam), the amount of water used by the water diffusion means to produce an air-steam mixture in the nozzle module 18 can also be reduced.

[0080] Further, the recycling zone 21 creates a structural separation of the moist air zone and the dry air zone, in particular of nozzle module 20 and nozzle module 22. The conditions, i.e. the environments, and temperatures in nozzle module 20 and nozzle module 22 strongly differ from each other. In the second embodiment, at the end of nozzle module 20 in the conveying direction of the product, the air is moist and has a temperature in the range of 110 C., and at the beginning of nozzle module 22, the air is dry and has a temperature in the range of 180 C. Furthermore, in order to get an idea of the condition and temperature regime of the further modules in the second embodiment, it should be noted that in nozzle module 18, the air is moist and has a temperature of about 90 C., and in nozzle module 24, the air is dry and has a temperature of about 200 C. By providing the recycling zone 21, it is possible to prevent the different temperatures and conditions (moistdry) in nozzle module 20 and nozzle module 22 from negatively affecting each other. Specifically, the recycling zone 21 prevents moist air leaving nozzle module 20 from entering nozzle module 22. As a result, the overall shrink conditions can be improved and better shrink results can be achieved.