Method and Device for Sealing

Abstract

The present invention refers to a method for sealing a first packaging material laminate ( 10 ) to a second packaging laminate ( 12 ), at least the first laminate ( 10 ) comprising at least one layer of magnetizable particles and a sealable layer ( 34 ). The method is characterized in facing the sealable layer ( 34 ) towards the second laminate ( 12 ), providing an alternating magnetic field to the laminates in a sealing zone, thereby generating magnetic hysteresis losses in the laminate ( 10 ) comprising the magnetizable particles, which losses create heat substantially melting the sealable layer ( 34 ) in the sealing zone, and applying a sealing pressure to the first and second laminate ( 10, 12 ), which pressure causes the first and second laminate ( 10, 12 ) to be pressed together in the sealing zone, thereby sealing the laminates ( 10, 12 ) to each other. The invention also relates to a device for carrying out the method.

1 . Method for sealing a first packaging material laminate to a second packaging laminate, at least the first laminate comprising at least one layer of magnetizable particles and a sealable layer, the method comprising:
 providing an alternating magnetic field to the first and second packaging laminates in a sealing zone to generate magnetic hysteresis losses in the laminate comprising the magnetizable particles and create heat substantially melting the sealable layer in the sealing zone, and   applying a sealing pressure to the first and second packaging laminates to press together the first and second packaging laminates in the sealing zone, thereby sealing the first and second packaging laminates to each other.   
     
     
         2 . The method according to  claim 1 , comprising providing the alternating magnetic field in such a way that a main direction of the magnetic field lines is substantially parallel with a plane constituting the first packaging material laminate. 
     
     
         3 . The method according to  claim 1 , comprising generating the alternating magnetic field of a strength substantially large enough to make the magnetizable particles substantially reach the magnetic saturation level. 
     
     
         4 . The method according to  claim 1 , comprising alternating the magnetic field with a frequency in the interval 0.5-5 MHz. 
     
     
         5 . The method according to  claim 1 , wherein the magnetizable particles comprise Fe 3 O 4  particles. 
     
     
         6 . The method according to  claim 1 , comprising providing said alternating magnetic field by at least a sealing jaw, said sealing jaw being an inductor comprising a conductor connected to an alternating current supply. 
     
     
         7 . The method according to  claim 1 , comprising enhancing said magnetic field by using an electrically conducting anvil. 
     
     
         8 . The method according to  claim 7 , comprising providing said anvil opposed to the sealing jaw, the anvil being passive and inducing a current in response to the current in the sealing jaw, thereby generating a magnetic field enhancing the field generated by the sealing jaw. 
     
     
         9 . The method according to  claim 7 , comprising applying said sealing pressure by said sealing jaw and said anvil. 
     
     
         10 . Device for sealing a first packaging material laminate to a second packaging laminate, at least the first laminate comprising at least one layer of magnetizable particles and a sealable layer, the device comprising:
 means for providing an alternating magnetic field to the first and second packaging laminates in a sealing zone to generate magnetic hysteresis losses in the laminate comprising the magnetizable particles and create heat substantially melting the sealable layer in the sealing zone, and   means for applying a sealing pressure to the first and second packaging laminates to press together the first and second packaging laminates in the sealing zone, thereby sealing the first and second packaging laminates to each other.   
     
     
         11 . The device according to  claim 10 , wherein said means for providing the alternating magnetic field is a sealing jaw formed as an inductor comprising a conductor connected to an alternating current supply. 
     
     
         12 . The device according to  claim 11 , comprising an electrically conducting anvil to enhance said magnetic field. 
     
     
         13 . The device according to  claim 12 , wherein said anvil is provided with a conductor adapted to induce a current in response to the current in the sealing jaw, thereby generating a magnetic field enhancing the magnetic field generated by the sealing jaw. 
     
     
         14 . The device according to  claim 12 , wherein said anvil is adapted to be positioned opposed to the sealing jaw, cooperating with the sealing jaw. 
     
     
         15 . The device according to  claim 12 , wherein said means for applying said sealing pressure is said sealing jaw and said anvil. 
     
     
         16 . The device according to  claim 12 , wherein the sealing jaw comprises an action face adapted to bear against one of the first and second packaging material laminates in the sealing zone during sealing, and the anvil comprising a substantially corresponding action face adapted to bear against the other of the first and second packaging material laminates during sealing. 
     
     
         17 . The device according to  claim 16 , wherein the conductor of the sealing jaw is substantially embedded in the action face of the sealing jaw in such a way that the conductor is adapted to be in contact with the one of the first and second packaging laminates. 
     
     
         18 . The device according to  claim 17 , wherein the conductor of the anvil is substantially embedded in the action face of the anvil in such a way that the conductor is adapted to be in contact with the other of the packaging laminates. 
     
     
         19 . The device according to  claim 18 , wherein a protective layer is provided on the action face of the anvil so that said contact between the conductor of the anvil and the one of the first and second packaging laminates is indirect. 
     
     
         20 . The method according to  claim 1 , comprising alternating the magnetic field with a frequency in the interval 1-4 MHz.