Tapered thread structure

Abstract

In one embodiment there is provided a novel container neck finish having a substantially cylindrical exterior wall surface surrounding an orifice defined in the container and a thread structure positioned about the exterior wall surface. The thread structure in one aspect has at least a first portion, a second portion positioned substantially axially below the first portion, and a third portion positioned substantially axially below the second portion. The first, second, and third portions, being inclined with respect to the other portions provide a screw on neck finish. The effective maximum diameter of the first portion is less than the effective maximum diameter of the second portion to define a first to second separation distance. And the effective maximum diameter of the second portion is less than the effective maximum diameter of the third portion to define a second to third separation distance.

1 . A method of applying a threaded cap to a threaded neck of a container, the method comprising the steps of:
 providing a threaded neck of a container that includes thread structure having at least one single thread extending entirely around the exterior wall surface, the at least one single thread having at least a first portion, a second portion positioned substantially axially below the first portion, and a third portion positioned substantially axially below the second portion, the first, second, and third portions, being inclined with respect to the other portions to provide a screw on neck finish, the first, second, and third portions further having a corresponding effective maximum diameter, and wherein the effective maximum diameter of said first portion is less than the effective maximum diameter of said second portion and the effective maximum diameter of said second portion is less than the effective maximum diameter of said third portion, whereby the effective maximum diameter of the thread structure changes throughout the section of the exterior wall surface, said threaded neck further having a neck wall having an exterior with a bead-like structure surrounding said neck positioned axially below said thread structure;   placing a threaded cap at an angle offset from a vertical axis defined by said threaded neck;   moving the container and/or moving the cap towards each other such that a neck edge defined by the exterior of said neck wall comes into contact with a cap edge defined by an interior wall of said cap, wherein upon said contact a clearance space is defined between an upper edge of the exterior defined by said neck wall and a free edge of the interior wall of said cap;   leveling said cap onto said threaded neck of said container such that said cap is urged towards a substantially vertical position on said threaded neck.   
     
     
         2 . The method of  claim 1  wherein the step of leveling said cap in a substantially vertical position on said threaded neck further includes contacting said cap with a skid plate or roller to level and align the cap and container to one another. 
     
     
         3 . The method of  claim 1  wherein the step of leveling said cap onto said threaded neck of said container urges a tamper-evidencing band defined on said cap vertically downward past said thread structure. 
     
     
         4 . The method of  claim 1  further including the step of screwing said cap on said container in complimentary threaded engagement. 
     
     
         5 . The method of  claim 1  further including the step of snapping said cap on said container in complimentary threaded engagement by axial force. 
     
     
         6 . The method of  claim 3  further including the step of downwardly urging said cap onto the threaded neck such that said tamper-evidencing band defined on said cap is placed over said bead-like structure surrounding said neck wall. 
     
     
         7 . The method of  claim 6  wherein said placement over said bead-like structure includes said tamper-evidencing band having an upwardly-inwardly extending annular flange whose free edge engages said bead-like structure and, in a stressed state, diametrically expands while traveling over said bead-like structure during said downward urging and ultimately returns to an unstressed state of reduced effective diameter following passage over said bead-like structure.