Container preform assembly and method of manufacture

Abstract

A preform assembly for blow molding a container includes a molded plastic preform having an open mouth, a neck surrounding the mouth with an external surface at a first diameter, an external flange at one end of the neck surrounding the mouth, and a preform body integrally molded with the neck at an end of the neck spaced from the flange. The preform body has a second external diameter that is greater than the first diameter of the neck external surface. A circumferentially continuous molded plastic finish ring is externally secured over the external surface of the neck between the flange and the preform body. In the preferred embodiments of the invention, the finish ring is secured to the preform neck by expanding the ring over the flange and then allowing the ring resiliently to shrink onto the external surface of the neck.

1 . A preform assembly for blow molding a container, which includes: 
 a molded plastic preform having an open mouth, a neck surrounding said mouth with an external surface at a first diameter, an external flange at one end of said neck surrounding said mouth, and a preform body integrally molded with said neck at an end of said neck spaced from said flange, said body having a second external diameter greater than said first diameter, and    a circumferentially continuous molded plastic finish ring externally secured to said neck between said flange and said body.    
     
     
         2 . The preform assembly set forth in  claim 1  wherein said finish ring is shrunk fit over said external surface of said neck.  
     
     
         3 . The preform assembly set forth in  claim 2  wherein said finish ring is of material construction selected from the group consisting of PP, PET, PEN and process regrind.  
     
     
         4 . The preform assembly set forth in  claim 1  wherein said finish ring has at least one external thread and an external capping flange at one axial end of said ring.  
     
     
         5 . The preform assembly set forth in  claim 1  wherein said plastic finish ring is of a material construction selected from the group consisting of: PET, PP, PEN and process regrind.  
     
     
         6 . The preform assembly set forth in  claim 1  wherein said plastic finish ring is of a different material construction from said plastic preform.  
     
     
         7 . A method of making a preform assembly that includes the steps of: 
 (a) providing a molded plastic preform that has an open mouth, a neck surrounding said mouth with an external surface at a first diameter, an external flange at one end of said neck surrounding said mouth, and a preform body integrally molded with said neck at an end of said neck spaced from said flange, said body having a second external diameter greater than said first diameter,    (b) providing a circumferentially continuous molded plastic finish ring externally secured to said neck between said flange and said body, and    (c) assembling said finish ring to said preform by locating said finish ring over said external surface of said neck and shrinking said ring onto said neck such that said ring is secured to said neck by interference shrink fit.    
     
     
         8 . The method set forth in  claim 7  wherein said step (c) is carried out by resiliently expanding said ring over said flange and then allowing said ring to shrink onto said external surface of said neck.  
     
     
         9 . The method set forth in  claim 8  wherein said step (c) is carried out by: (c1) positioning an anvil over said mouth, said anvil having an outer surface with a diameter at said flange at least equal to that of said flange, and a diameter spaced from said flange less than the inside diameter of said ring, and (c2) expanding said ring by sliding said ring along said outer surface until said ring snaps over said flange.