Plastic container having crimp-on, pry-off crown finish

Abstract

A plastic bottle mouth has a finish generally symmetric about a vertical axis of the bottle, suitable to receive a metal crown cap. The finish has a top planar surface lying in a plane normal to the vertical axis. A downwardly curved portion extends outward from the planar ring and terminates at an outermost edge located at a radius R 1 bottle axis. An undercutting surface begins adjacent to the outer edge and extends axially inwardly and downwardly as a concave partial toroid. The undercutting surface can be defined in substantial part by a locus of points generated by a radius R having its origin on a circle of radius R 2 lying in a plane normal to the vertical axis, particularly where R<<R 2 <R 1 . The radius R defining the undercutting surface is generally less than about 7% of radius R 1 , and can be only about 4% of radius R 1 . The planar ring on the top surface of the finish can have a width that is greater than about 2% of radius R 1 .

1 . A plastic bottle having a finish at the bottle mouth that is generally symmetric about a vertical axis of the bottle and suitable to receive a metal crown cap, the finish comprising: 
 a top surface including a planar ring lying in a plane normal to the vertical axis and a downwardly curved outer portion terminating at an outermost edge located at a radius R 1  from the vertical axis of the bottle, and    an undercutting surface beginning adjacent to the outer edge and extending axially inwardly and downwardly from the outer edge, the undercutting surface being defined in substantial part by a locus of points generated by a radius R having its origin on a circle of radius R 2  lying in a plane normal to the vertical axis, where R 2 <R 1 .    
   
   
       2 . The plastic bottle of  claim 1  wherein the length of radius R is less than about 10% of radius R 1 .  
   
   
       3 . The plastic bottle of  claim 2  wherein the length of radius r is equal to about 8% of radius R 1 .  
   
   
       4 . The plastic bottle of  claim 1  or  2  or  3  wherein the planar ring of the top surface has a width that is greater than about 2% of radius R 1 .  
   
   
       5 . The plastic bottle of  claim 4  wherein the top surface includes a downwardly curved inner edge defined by a radius having a length that is about equal to the width of the planar ring, the downwardly curved inner edge terminating in a cylindrical inner surface of the bottle mouth defined by a radius R 3 .  
   
   
       6 . The plastic bottle of  claim 5  wherein the distance between the cylindrical inner surface of the bottle mouth and the undercutting surface is less than 25% R 1 .