Method and device for manufacturing peel-off lids as well as a peel-off lid

Abstract

A peel-off lid with a rolled-in section around the extraction opening is formed in such a way that before forming the rolled-in section a thin plastic strip is applied onto the collar of the lid ring. After forming the rolled-in section, the plastic strip is melted in order to reach a good adhesion of the plastic on the upper side and the underside of the peel-off lid in the rolled-in section. In this way it is possible to reach a practically hermetic sealing of the cutting edge of the peel-off lid in an inexpensive way and with the possibility to manufacture with high cadence.

What is claimed is: 
     
         1 . A method for manufacturing peel-off lids, for which
 a lid ring with a central extraction opening surrounded by a seal flange, is formed from a lid blank by a punching process;   the edge of the extraction opening is formed by drawing towards a collar protruding away from the seal flange;   a strip made of plastic is applied onto the inner side of the collar;   the collar is rolled in at its free end and comes to lie in the strip made of plastic; and   a peel-off foil is sealed onto the sealing flange;   wherein   after rolling in the free end of the collar, the rolled-in section is heated up in such a way that at least a partial melting of the plastic material of the strip occurs.   
     
     
         2 . The method according to  claim 1 , wherein the heating up is carried out before the sealing of the peel-off foil onto the sealing flange. 
     
     
         3 . The method according to  claim 1 , wherein a heating means working inductively is provided for heating up. 
     
     
         4 . The method according to  claim 1 , wherein the heating up of the rolled in section is done during the sealing of the peel-off foil on the sealing flange by a heating means contacting the rolled-in section in the sealing tool. 
     
     
         5 . The method according to  claim 4 , wherein the sealing of the peel-off foil is a two-stage process, comprising firstly a pre-sealing and in a second step the main sealing of the peel-off foil onto the lid ring, and wherein the heating up of the plastic material of the strip is done during the main sealing of the peel-off foil. 
     
     
         6 . The method according to  claim 1 , wherein the plastic material of the strip comprises a polymer or a resin or consists of it, and the heating up is done at least to the flow temperature of the plastic material of the strip, particularly wherein the heating up is done in the range from 100° Celsius to 200° Celsius and in particular in the range from 140° Celsius to 180° Celsius. 
     
     
         7 . The method according to  claim 1 , wherein the upper side of the lid blank forming the sealing surface for the peel-off foil has a heat-sealing-suitable coating consisting of or containing polypropylene, and in that the underside of the lid blank has a coating consisting of interior varnish for cans or containing interior varnish for cans. 
     
     
         8 . The method according to  claim 1 , wherein a foaming agent is added to the plastic material of the strip. 
     
     
         9 . A device for manufacturing peel-off lids, comprising a transport installation for lid blanks, lid rings and peel-off lids, as well as processing stations, which are provided in transport direction (A) in succession for processing the lid blanks, lid rings and peel-off lids, wherein a first processing station is provided as punching station for forming a lid ring from a lid blank, a second processing station is provided for forming a collar of the lid ring, which protrudes away from the underside, and a third processing station, wherein the third processing station is adapted to form a rolled-in section from the collar, and wherein additionally at least a sealing station is provided, which is adapted for sealing a peel-off foil onto a sealing surface of the respective lid ring, wherein an application station is provided in transport direction between the second processing station and the third processing station, which is adapted to apply a circumferential, endless plastic strip onto the inner side of the collar, and the third processing station is adapted such that the rolled-in section comes into contact with the plastic strip, wherein at least a further processing station is provided in transport direction (A) after the third processing station, which is adapted for heating up at least the rolled-in section to at least the melting temperature of the plastic strip. 
     
     
         10 . The device according to  claim 9 , wherein the further processing station has induction heating means. 
     
     
         11 . The device according to  claim 9 , wherein the further processing station is integrated in the at least one sealing station and has a heating means contacting the rolled-in section in the sealing tool. 
     
     
         12 . The device according to  claim 11 , wherein two sealing stations are provided one after the other in transport direction, and wherein the further processing station is integrated in the second sealing station. 
     
     
         13 . The device according to  claim 9 , wherein the further processing station is adapted to heat up the rolled-in section in the temperature range from 100° Celsius to 200° Celsius and particularly in the range from 140° Celsius to 180° Celsius. 
     
     
         14 . The device according to  claim 9 , wherein the application station is adapted to apply a band-shaped plastic layer having a substantially uniform thickness, particularly a thickness in the range from 0.05 mm to 0.2 mm and particularly with a thickness of about 0.1 mm. 
     
     
         15 . A peel-off lid comprising a circumferential attachment section, a sealing flange, with a peel-off foil sealed onto the latter and a rolled-in section extending circumferentially around sealing flange, which limits the extraction opening laterally, wherein the rolled-in edge has a sealing made of a plastic, particularly of a polymer or resin, which is connected in an adhering way to the upper side and the underside of the peel-off lid by melting the plastic in the rolled-in section.