Composite stopper made synthetic materials

Abstract

A composite stopper ( 1 ) made of synthetic materials, particularly for bottles and similar containers, comprises a substantially cylindrical central body ( 2 ) made of thermoplastic material and defining a longitudinal axis (L), with a side surface ( 3 ) and two substantially flat end faces ( 4, 4′ ), and at least two elastic rings ( 5, 6 ) located in corresponding annular seats ( 7, 7′ ) on the side surface ( 3 ). The two elastic rings ( 5, 6 ) are made of plastic materials which are different from each other and from the base material of the central body ( 2 ). The base materials of the elastic rings ( 5, 6 ) are non-toxic, in particular at least one of them being made of nitrile rubber having a formulation able to ensure optimum gas impermeability, and at least the other one being made of silicone rubber having a formulation able to ensure complete compatibility for alimentary use and a high resistance to ageing.

1 . Composite stopper ( 1 ) made of synthetic materials, particularly for bottles and similar containers, comprising a substantially cylindrical central body ( 2 ) made of thermoplastic material and defining a longitudinal axis (L), with a side surface ( 3 ) and two substantially flat end faces ( 4 ,  4 ′), and at least two elastic rings ( 5 ,  6 ) located in corresponding annular seats ( 7 ,  7 ′) on said side surface ( 3 ), characterized in that said at least two elastic rings ( 5 ,  6 ) are made of plastic materials which are different from each other and from the base material of said central body ( 2 ).  
   
   
       2 . Stopper according to  claim 1 , characterized in that the base materials of said at least two elastic rings ( 5 ,  6 ) are non-toxic.  
   
   
       3 . Stopper according to  claim 2 , characterized in that at least one of said elastic rings ( 5 ,  6 ) is made of nitrile rubber having a formulation able to ensure optimum gas impermeability.  
   
   
       4 . Stopper according to  claim 3 , characterized in that at least the other of said elastic rings ( 5 ,  6 ) is made of silicone rubber having a formulation able to ensure complete compatibility for alimentary use and a high resistance to ageing.  
   
   
       5 . Stopper according to  claim 1 , characterized in that the minimum diameter (DM) of said annular seats ( 7 ,  7 ′) is slightly greater than the inner diameter (DI) of said elastic rings ( 5 ,  6 ) at rest.  
   
   
       6 . Stopper according to  claim 5 , characterized in that said elastic rings ( 5 ,  6 ) are retained in said annular seats. ( 7 ,  7 ′) without adhesives by their own elastic properties.  
   
   
       7 . Stopper according to  claim 4 , characterized in that said at least two elastic rings ( 5 ,  6 ) comprise at least one first pair ( 8 ) of rings which are longitudinally staggered and located at a predetermined distance, one ring ( 5 ) of said pair ( 8 ) being made of nitrile rubber and the other ( 6 ) being made of silicone rubber.  
   
   
       8 . Stopper according to  claim 7 , characterized in that said first pair ( 8 ) of elastic rings ( 5 ,  6 ) is located close to one of said end faces ( 4 ,  4 ′).  
   
   
       9 . Stopper according to  claim 8 , characterized in that said at least two rings comprise at least one second pair ( 12 ) of rings ( 9 ,  10 ) which are longitudinally staggered and located at a distance similar to that of the first pair ( 8 ), one ring ( 9 ) of said second pair ( 12 ) being made of nitrile rubber and the other ( 10 ) being made of silicone rubber.  
   
   
       10 . Stopper according to  claim 9 , characterized in that said predetermined distance between the rings ( 5 ,  6 ,  9 ,  10 ) of said first and second pair ( 8 ,  12 ) is relatively small with respect to the total length of said central body ( 2 ).  
   
   
       11 . Stopper according to  claim 10 , characterized in that said first and second pair ( 8 ,  12 ) of rings ( 5 ,  6 ,  9 ,  10 ) are arranged in substantially symmetrical positions with respect to a central plane (P) of said central body ( 2 ), said central plane being substantially perpendicular to said longitudinal axis (L).  
   
   
       12 . Stopper according to  claim 11 , characterized in that the elastic rings ( 6 ,  10 ) made of silicone rubber of said first and said second pair ( 8 ,  12 ) are closer to said end faces ( 4 ,  4 ′) than the elastic rings ( 5 ,  9 ) made of nitrile rubber of the same pairs ( 8 , 12 ).  
   
   
       13 . Stopper according to  claim 1 , characterized in that the material of said central body ( 2 ) is polypropylene.