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 ).

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.