Screw cap for pressurised containers

Abstract

The invention relates to a screw cap for containers with a threaded neck, in particular PET bottles designed to hold beverages containing CO 2 . Said cap comprises a top plate ( 1 ), an approximately cylindrical cap jacket ( 2 ), provided with an interior thread ( 3 ), an approximately cylindrical inner sealing collar ( 4 ), emanating from the top plate ( 1 ) and having an annular continuous region that projects radially outwards and an essentially cylindrical outer sealing collar ( 5 ), which concentrically surrounds the inner sealing collar ( 4 ). The maximum outer radius of the inner sealing collar and the minimum inner radius of the outer sealing collar differ only slightly, preferably by less than 2 mm and in particular by less than 1 mm and the inner and outer sealing collars ( 4, 5 ) are designed to receive the upper region of a bottle neck ( 11 ) in the annular gap formed between said collars. The aim of the invention is to provide a screw cap, which in general retains the excellent sealing properties of the known screw cap, even in extreme environmental conditions and is at the same time capable of limiting the pressures that occur in a container with a screw cap, without losing its sealing function. To achieve this, the cap is provided with devices ( 6, 7 ), which limit the axial depth of penetration of the edge of a bottle neck ( 11 ) into the gap between the inner ( 4 ) and the outer sealing collar ( 5 ).

1 - 9 . (canceled)  
   
   
       10 . A Screw cap, for containers with a threaded neck that are designed to hold drinks containing CO 2 , said screw cap having a head plate, a roughly cylindrical cap shell with internal thread, an essentially cylindrical inner sealing web extending from the head plate with a continuous annular region projecting radially outwards and an outer, essentially cylindrical sealing web concentrically surrounding the inner sealing web, the maximum external radius of the inner sealing web and the minimum internal radius of the outer sealing web differing so as to form a concentric intermediate space in the form of an annular intermediate space between the inner and outer sealing webs for receiving an upper region of a bottle neck in the annular intermediate space while permitting contact of both the inner and outer sealing webs with the upper portion of the threaded neck wherein limiting structures are provided for limiting an axial depth by which the neck penetrates the annular intermediate space between the inner and outer sealing web.  
   
   
       11 . The screw cap of  claim 10  where the maximum external radius of the inner sealing web and the minimum internal radius of the outer sealing web differ by less than 2 mm and the inner and outer sealing webs are specifically designed to accommodate the upper region of the bottle neck in the intermediate space formed between them.  
   
   
       12 . The screw cap of  claim 11  where the maximum external radius of the inner sealing web and the minimum internal radius of the outer sealing web differ by less than 1 mm.  
   
   
       13 . The screw cap according to  claim 10 , where the structures for limiting the depth by which the neck penetrates the annular intermediate space comprise limiting webs extending axially into the intermediate space from a base of the intermediate space.  
   
   
       14 . The screw cap according to  claim 13  wherein the limiting webs have an axial height of between 0.3 and 2 mm.  
   
   
       15 . The screw cap according to  claim 13  wherein the limiting webs have a width (measured in peripheral direction) of 0.5 to 3 mm.  
   
   
       16 . The screw cap according to  claim 13  wherein the limiting webs are distributed at roughly equal angular distances along the annular intermediate space.  
   
   
       17 . The screw cap according to  claim 13 , wherein six webs are provided at angular distances of approximately 60° along the annular intermediate space.  
   
   
       18 . The screw cap according to  claim 10  wherein the limiting structures comprise a continuous annular bead provided radially outside the outer sealing web, which annular bead has a stop surface that acts as a stop preventing movement of the outer sealing web so that the outer sealing web acts to limit penetration of the neck into the annular intermediate space, the stop surface of the bead having an axial distance from the base of the intermediate space which is 0.3 to 2 mm bigger than the axial distance of an upper thread edge of a threaded neck of the bottle from the upper rim surface of the threaded neck of a bottle for which the screw cap is provided.  
   
   
       19 . A screw cap according to  claim 10  wherein a wall thickness of the head plate is smaller in a region of the intermediate space than in a region radially inside the inner sealing web.  
   
   
       20 . A screw cap according to  claim 19  wherein a wall thickness of the cap base in a region of the intermediate space is 5 to 15% smaller than a wall thickness of the cap base in the region immediately radially inside the inner sealing web.