Stretched container threads and method of manufacture
View Patent ↗A method of making a plastic container having a body and a finish with at least one external thread includes injection or compression molding a plastic preform having a body and a finish with at least one external thread, blow molding the body of the preform to form the body of the container, and either prior to, subsequent to or both prior and subsequent to blow molding the container body, expanding the injection or compression molded preform finish to form a container finish having at least one injection or compression molded external thread. In the preferred embodiments of the invention, the finish is expanded after the container body is blow-molded. The invention can be implemented to expand a narrow-neck preform or container finish to a wide-mouth preform or container finish.
1. A method of making a plastic container having a body and a wide-mouth finish with at least one external thread formed by injection or compression molding, which comprises the steps of:
(a) pressure molding a plastic preform having a body and a narrow-neck finish with at least one external thread,
(b) blow molding the body of said preform to form the body of the container, and
(c) expanding said pressure molded finish radially outwardly to form a wide-mouth finish on the container body and having at least one pressure molded external thread.
2. The method set forth in claim 1 including the additional step of:
(d) crystallizing said wide-mouth finish either simultaneously with or subsequent to said step (c).
3. The method set forth in claim 1 comprising the additional step of: (d) heating said finish prior to or during said step (c).
4. The method set forth in claim 3 wherein said step (c) is carried out by inserting a plug into said finish.
5. The method set forth in claim 4 comprising the additional step of rotating said plug or said finish during insertion of said plug into said finish.
6. The method set forth in claim 5 wherein said finish is expanded at least 32% in said step (c).
7. The method set forth in claim 6 wherein said finish is expanded at least 125% in said step (c).
8. The method set forth in claim 1 wherein said step (c) is carried out prior to said step (b).
9. The method set forth in claim 1 wherein said step (c) is carried out subsequent to said step (b).
10. The method set forth in claim 1 wherein said step (c) is carried out in at least two stages, one stage prior to said step (b) and a second stage subsequent to said step (b).
11. A method of making a plastic container having a body and a finish with at least one external thread, which comprises the steps of:
(a) pressure molding a plastic preform having a body and a finish with at least one external thread,
(b) blow molding the body of said preform to form the body of the container, and
(c) expanding said injection molded preform finish radially outwardly to form a container finish having at least one pressure molded external thread.
12. The method set forth in claim 11 comprising the additional step of: (d) heating said finish prior to or during said step (c).
13. The method set forth in claim 12 wherein said step (c) is carried out by inserting a plug into said finish.
14. The method set forth in claim 13 comprising the additional step of rotating said plug or said finish during insertion of said plug into said finish.
15. The method set forth in claim 11 including the additional step of:
(d) crystallizing said finish either simultaneously with or subsequent to said step (c).
16. A method of making a plastic container having a body and a finish with at least one external thread which comprises the steps of:
(a) pressure molding a plastic preform having a body and a finish with at least one external thread,
(b) blow molding the body of said preform to form the body of the container, and
(c) either priorto or subsequent to said step (b), expanding said pressure molded preform finish radially outwardly at least 32%.
17. The method set forth in claim 16 comprising the additional step of: (d) heating said finis prior to or during said step (c).
18. The method set forth in claim 17 wherein said step (c) is carried out by inserting a plug into said finish.
19. The method set forth in claim 18 comprising the additional step of rotating said plug or said finish during said step (c).
20. The method set forth in claim 16 including the additional step of:
(d) crystallizing said finish either simultaneously with or subsequent to said step (c).