Tamper-proof screw cap

Abstract

A screw closure of plastic comprising a head plate (2) and a cylindrical cap skirt (3) which extends downwardly from the head plate and has a female thread (4), and a tamper-evident band (5) connected to the lower edge of the cap skirt (3) and provided with radially inwardly projecting retaining elements (6) which define a smallest inside diameter of the tamper-evident band (5) in such a way that they can engage behind a retaining ring (25) of larger diameter on a container neck (20) in order to remain on the container neck (20) after separation from the cap skirt (2), characterised in that extending between the lower edge of the cap skirt (2) and the tamper-evident band (5) is a peripherally extending tear-off band (7) which is connected by way of a respective tear line (8, 8′) on the one hand to the cap skirt (2) and on the other hand to the tamper-evident band (5).

1 . A screw closure of plastic comprising a head plate ( 2 ) and a cylindrical cap skirt ( 3 ) which extends downwardly from the head plate and has a female thread ( 4 ), and a tamper-evident band ( 5 ) connected to the lower edge of the cap skirt ( 3 ) and provided with radially inwardly projecting retaining elements ( 6 ) which define a smallest inside diameter of the tamper-evident band ( 5 ) in such a way that they can engage behind a retaining ring ( 25 ) of larger diameter on a container neck ( 20 ) in order to remain on the container neck ( 20 ) after separation from the cap skirt ( 2 ), characterised in that extending between the lower edge of the cap skirt ( 2 ) and the tamper-evident band ( 5 ) is a peripherally extending tear-off band ( 7 ) which is connected by way of a respective tear line ( 8 ,  8 ′) on the one hand to the cap skirt ( 2 ) and on the other hand to the tamper-evident band ( 5 ). 
     
     
         2 . A screw closure according to  claim 1  characterised in that the tear-off band ( 7 ) has an internal tooth arrangement ( 9 ) which upon engagement with oppositely directed teeth ( 19 ) on a container neck ( 20 ) prevents a rotary movement of the tear-off band ( 7 ) about the closure axis at least in the opening direction of the closure ( 10 ). 
     
     
         3 . A screw closure according to  claim 1  characterised in that the tamper-evident band ( 6 ) has an internal tooth arrangement ( 11 ) which upon engagement with oppositely directed teeth ( 19 ′) on a container neck ( 20 ) prevents a rotary movement of the tamper-evident band ( 6 ) about the closure axis in an opening direction of the closure ( 10 ). 
     
     
         4 . A screw closure according to  claim 1  characterised in that the tear line ( 8 ,  8 ′) between the tear-off band ( 7 ) and the cap skirt ( 2 ) and/or the tamper-evident band ( 6 ) is produced by an incision in the plastic material which is initially thicker after production by means of injection moulding along the configuration of the tear line. 
     
     
         5 . A screw closure according to  claim 1  characterised in that the tear-off band ( 7 ) is connected to the cap skirt ( 2 ) and/or to the tamper-evident band ( 6 ) exclusively by easily breakable bridges distributed along the peripherally extending tear line ( 8 ,  8 ′). 
     
     
         6 . A screw closure according to  claim 1  characterised in that viewed in the peripheral direction, the tear-off band ( 7 ) comprises alternately relatively more easily ( 7 ″) and less easily stretchable portions ( 7 ′). 
     
     
         7 . A screw closure according to  claim 6  characterised in that the alternately relatively more easily and less easily stretchable portions ( 7 ′,  7 ″) comprise alternately radially thinner and thicker regions of the tear-off band ( 7 ). 
     
     
         8 . A screw closure according to  claim 6  characterised in that the alternately relatively more easily and less easily stretchable portions ( 7 ′,  7 ″) are of a width varying along the periphery as measured in the peripheral direction. 
     
     
         9 . A screw closure according to  claim 6  characterised in that the more easily and less easily stretchable portions ( 7 ′,  7 ″) as viewed in the peripheral direction are distributed differently in axially different regions of the tear-off band ( 7 ). 
     
     
         10 . A screw closure according to  claim 1  characterised in that the cross-section of the tear-off band ( 7 ), as measured perpendicularly to the peripheral direction, varies along the peripheral direction. 
     
     
         11 . A screw closure according to  claim 1  characterised in that the tear-off band ( 7 ) comprises various axial portions of differing outside diameter, which are connected together by a conical transitional portion. 
     
     
         12 . A screw closure according to  claim 1  characterised in that the tear-off band ( 7 ) has two ends, of which at least one end has a gripping tab ( 13 ). 
     
     
         13 . A screw closure according to  claim 1  characterised in that the tear-off band ( 7 ) extends along the entire periphery of the closure with the exception of an interruption limited to less than 5° peripheral angle. 
     
     
         14 . A screw closure according to  claim 1  characterised in that the gripping tab ( 13 ) disposed at a free end of the tear-off band ( 7 ) is arranged radially outside the two mutually oppositely disposed free ends of the tear-off band ( 7 ) and covers said ends outwardly. 
     
     
         15 . A screw closure according to  claim 1  characterised in that the cap skirt ( 3 ) has an outer gripping knurling. 
     
     
         16 . A screw closure according to  claim 1  with external printing, which extends on the outside of the closure cap ( 1 ) over one or both tear lines ( 8 ,  8 ′). 
     
     
         17 . A screw closure according to  claim 19  characterised in that the print image on the cylindrical outside surface of the screw closure ( 1 ) is so designed that it is to be produced only with a complex printing process. 
     
     
         18 . A screw closure according to  claim 16  with external printing which extends on the outside of the closure cap ( 1 ) over one or both tear lines ( 8 ,  8 ′) and over the cap skirt ( 3 ), the tear-off band ( 7 ) and/or the tamper-evident band ( 5 ). 
     
     
         19 . A screw closure according to  claim 16  wherein the external printing is a print image. 
     
     
         20 . A screw closure according to  claim 17  where the complex printing process is laser printing.