Induction sealing device for heat sealing packaging material for producing sealed packages of pourable food products

Abstract

There is described a heating induction sealing device for forming a seal in a packaging material comprising an electrically conductive element and advancing along a direction; sealing device comprises one first inductive element and one second inductive element; first inductive element comprises a first portion facing second inductive element and defining with second inductive element a passage for packaging material; and a second portion; sealing device is selectively arrangeable in a first configuration, in which alternate currents flow within first and second inductive element; first portion and second inductive element are configured to generate a first magnetic flux transversally to direction, when sealing device is arranged in first configuration; second portion is configured to generate, in use, a second magnetic flux with a main component parallel to direction, when sealing device is arranged in first configuration.

1 . A heating induction sealing device for forming a seal in a packaging material comprising an electrically conductive element and advancing along a direction;
 said sealing device comprising at least one first inductive element comprising:
 at least one second inductive element; 
   said first inductive element comprising:
 a first portion facing said second inductive element and defining with said second inductive element a passage for said packaging material; and 
 a second portion; 
   said sealing device being selectively arrangeable in a first configuration, in which alternate currents flow within said first and second inductive element;   said first portion and second inductive element being configured to generate, in use, a first magnetic flux transversally to said direction, when said sealing device is arranged in said first configuration; the constant-value lines of said first magnetic flux being symmetrical, in use, relative to said packaging material;   said second portion being configured to generate, in use, a second magnetic flux with a main component transversal to said direction, when said sealing device is arranged in said first configuration.   
     
     
         2 . The sealing device of  claim 1 , wherein said first portion of said first inductive element comprises a first and a second leg, and a second inductive element comprises a third and fourth leg;
 said first and third leg being arranged, in use, on opposite sides of said passage;   said second and fourth leg being arranged, in use, on opposite sides of said passage;   said first leg and said third leg being arranged on the same side of said second and fourth leg respectively;   the alternate current flowing, in use, in the same direction in said first and third leg, and in said second and fourth leg at a given time, when said sealing device is arranged in said first configuration.   
     
     
         3 . The induction sealing device of  claim 1 , wherein it may be selectively arranged in a second configuration in which alternate current flows within said second portion of said first inductive element and no alternate current flows within said second inductive element and said first portion of said first inductive element;
 said second portion being configured to generate said second magnetic flux, when said sealing device is arranged in said second configuration.   
     
     
         4 . The induction sealing device of  claim 3 , wherein said second inductive element comprises a first and a second electric contacts; and a first inductive element comprises a third, a fourth and a fifth electric contacts;
 said second and fourth electric contacts being electrically connected to each other;   said fifth electric contact being electrically connected to a first pole of a power/current source;   one between said first or said third electric contact being electrically connected to a second pole of said power/current source, when said sealing device is respectively arranged in said first or second configuration;   said first and fifth electric contacts defining together with said power/current source a first closed electrical circuit within both first and second portions of said first inductive element and said second inductive element, when said sealing device is arranged in said first configuration;   said third and fifth electric contacts defining together with said power/current source a second closed electrical circuit within said second portion of said second inductive element, when said sealing device is arranged in said second configuration.   
     
     
         5 . The sealing device of  claim 1 , comprising:
 a first body housing said first inductive element and a second body housing said second inductive element; and   said first and second body defining therebetween said passage.   
     
     
         6 . The sealing device of  claim 5 , wherein said first and second body extend along respective axes; at least one between said first and second inductive element being shaped at least in part as a serpentine;
 said serpentine being elongated along said respective axis parallel, in use, to said direction and extending at varying distances from said respective axis.   
     
     
         7 . The sealing device of  claim 6 , wherein said serpentine comprises a plurality of repeated modules identical and adjacent to each other. 
     
     
         8 . The sealing device of  claim 7 , wherein each module comprises:
 a first and a second rectilinear stretch which extend at relative different distances from said respective axis; and   at least a curved stretch interposed between said first and second stretch.   
     
     
         9 . The sealing device of  claim 1 , comprising:
 a pair of supports supporting at least one between said first and second inductive element and forming a printed circuit board together with said at least one between said first and second inductive element.   
     
     
         10 . A packaging machine for manufacturing sealed package of a food product pourable into a tube of packaging material, comprising:
 sealing means for applying a strip of a packaging material onto a first edge of said tube and/or for applying a second edge of said tube onto said first edge; and   pressure means for exerting a pressure onto said first and second edges overlapping each other;   wherein said sealing means comprise a sealing device according to  claim 1 .   
     
     
         11 . A method of forming a seal in a packaging material comprising an electrically conductive material and advancing along a direction, comprising:
 interposing said packaging material to be sealed within a passage defined between a first and a second inductive element;   causing alternate current to flow within said first and second inductive element;   generating a first magnetic flux transversally to said first direction by using alternate current flowing within a first portion of said first inductive element and said second inductive element; said first portion facing said second inductive element and defining said passage with said second inductive element; the constant-value lines of said first magnetic flux being symmetrical, in use, relative to said packaging material; and   generating a second magnetic flux having a main component transversal to said direction by using alternate current flowing within a second portion of said first inductive element.   
     
     
         12 . The method of  claim 11 , comprising:
 advancing said packaging material along a path parallel to said direction and relative to said first and second inductive elements;   heating said packaging material by eddy current induced by said first and second inductive elements;   compressing said packaging material so as to complete the formation of said seal, by using pressure means;   arresting said packaging material and interrupting the formation of said seal, thus leaving a heated region of said packaging material not completely sealed;   moving said first and second inductive elements relative to said packaging material in the advancing direction of said packaging material;   advancing again said packaging material; and   heating again and compressing said region;   comprising, during said step of heating again and compressing said region, the steps of:   preventing alternate current from flowing within said second inductive element and within said first portion of said first inductive element, so as to prevent the generation of said first magnetic flux;   causing alternate current to flow within said second portion only of said first inductive element, so as to generate said second magnetic flux only.   
     
     
         13 . The method of  claim 11 , comprising:
 feeding a tube of said packaging material; and   sealing a first and a second edge of said tube along said direction;   said step of sealing comprises:   arranging said first inductive element on the external side of said tube;   arranging said second inductive element inside said tube; and   inserting said first edge within said passage.