Plastic closure comprising a cutting and perforating device

Abstract

The invention relates to a closing device ( 1 ) consisting of a plastic material for applying to a closed container consisting of a plastic film material. Only two cutting teeth ( 20, 21 ) of the same height are to be applied to the cylindrical perforator ( 5 ) of said device, said teeth being arranged in an angular region of between 70° and 120° of the circumference. In this way, the section of the subsequent tooth extends into the section of the previous tooth, enabling a secure opening, without the risk of cutting an entire rondelle out of the plastic film of the container. The creation of only two partial sections without producing an opening in the container is also prevented.

1 . A closing device ( 1 ) made of a plastic material for applying to a closed container made of a plastic film material, wherein said closing device comprises a lower part ( 2 ) having a cylindrical outlet ( 6 ) and a flange ( 3 ) for attaching to the container and a screw cap ( 4 ) which is screwably fixed to the lower part ( 2 ) as well as a cylindrical perforator ( 5 ) having an external thread, which is open on both sides in an axial direction and travels in an internal thread in the outlet ( 6 ) of said lower part ( 2 ), wherein means ( 44 ) are located in the screw cap ( 4 ) which during initial unscrewing movement of said screw cap ( 4 ) move the perforator ( 5 ) downwards in a helical manner and wherein said cylindrical perforator ( 5 ) has cutting teeth on a cylindrical wall thereof at the end which when mounted is directed towards the container wall, characterized in that said perforator has exactly two cutting teeth of the same height, both of which are arranged in an angular region of between 70° and 120° of a circumference. 
     
     
         2 . The closing device according to  claim 1 , characterized in that a wall thickness of the two cutting teeth is thicker than a wall thickness of a cylindrical jacket wall of the perforator. 
     
     
         3 . The closing device according to  claim 1 , characterized in that a steepness of the external thread ( 12 ) of the perforator ( 5 ) and the internal thread ( 18 ) of the outlet ( 6 ) is selected in such a way that during the unscrewing movement of the screw cap ( 4 ), a tooth moving in a cutting direction travels through a maximum cutting distance of 210° from a point of contact on the plastic film of the container up to a point where the unscrewing movement of said screw cap has completely ended. 
     
     
         4 . The closing device according to  claim 1 , characterized in that the external thread of the outlet is a double-start fine-pitch thread. 
     
     
         5 . The closing device according to  claim 1 , characterized in that the external thread of the perforator and the internal thread of the outlet have a trapezoidal thread profile. 
     
     
         6 . The closing device according to  claim 1 , characterized in that at least one of the two cutting teeth ( 20 ,  21 ) has a number of staggered succeeding teeth ( 24 ), which are arranged at different heights in a descending step-like succession, so that depending upon a penetration depth of the perforator into the film to be cut, one succeeding tooth after the other is operative and wherein a swarf receiving space ( 25 ) is located in each case between the respective foremost cutting tooth ( 20 ,  21 ) and the next operative succeeding tooth as well as between two adjacent succeeding teeth. 
     
     
         7 . The closing device according to  claim 6 , characterized in that the swarf receiving spaces ( 25 ), which are operative at first, are larger than the swarf receiving spaces which are subsequently operative.