Method of injection molding closure with continuous internal rigid rib, closure made thereby having a lead-in structure and mold for forming same

1. A container closure for a container comprising:

a top positioned generally in a common top plane;

an annular side wall extending from the top, the side wall having an internal thread positioned at a pitch angle relative to the common top plane and adapted to engage with threads of the container around a container opening; and

a tamper-evident portion on a lower portion of the side wall, the tamper-evident portion including a plurality of leaders extending across a score line to a lower band, the lower band including a substantially continuous internal projection below the leaders, wherein the projection includes an angled portion for a portion of a circumference of the tamper-evident portion, the angled portion positioned at a pitch angle relative to the common top plane and forming a one-way lead-in helical thread for the projection, wherein the one-way lead-in thread formed by the angled portion has the pitch extending in a same direction as the internal thread of the annular side wall, whereby the one-way lead-in thread formed by the angled portion allows the projection of the tamper-evident portion to be threaded past a retaining ridge of a container.

2. The closure as claimed in claim 1 wherein the angled portion forming the one way lead-in thread extends for about ninety degrees of the circumference.

3. The closure as claimed in claim 2 further including a plug seal on the top, wherein the angled portion forming the one way lead-in thread includes a rounded end, and wherein the angled portion is angled with the same pitch angle as the threads on the side wall.

4. The closure as claimed in claim 1 wherein the projection is a rib having a length-to-width ratio of at least one and one-half.

5. The closure as claimed in claim 4 wherein the rib is substantially rectangular in cross-section, has a substantially uniform cross section around the circumference, and has a length-to-width ratio of at least two, and is angled away from the top.

6. A tamper-evident portion for a container closure wherein the tamper-evident portion is on a lower portion of the side wall of the container closure, the tamper-evident portion comprising:

a lower band;

a score line between the lower band and the side wall of the container closure, the score line defining a score line plane;

a plurality of leaders extending across the score line between the lower band and the side wall of the container to connect the lower band to the side wall; and

a substantially continuous internal projection on the lower band below the leaders, wherein the projection includes an angled portion for a portion of a circumference of the lower band, the angled portion positioned at a pitch angle relative to the score line plane and farming a one-way lead-in helical thread for the projection, whereby the one-way lead-in thread formed by the angled portion allows the projection of the tamper-evident portion to be threaded past a retaining ridge of a container.

7. The tamper-evident portion as claimed in claim 6 wherein the angled portion forming the one way lead-in thread extends for about ninety degrees of the circumference.

8. The tamper-evident portion as claimed in claim 6 wherein the projection is a rib having a length-to-width ratio of at least one and one-half and wherein the angled portion forming the one way lead-in thread includes a rounded end.

9. The tamper-evident band as claimed in claim 6 wherein the rib is substantially rectangular in cross-section, has a length-to-width ratio of at least two, has a substantially uniform cross section around the circumference, and is angled away from the leaders.

10. A one-piece injection molded container closure for a container comprising:

a top positioned generally in a common top plane;

an annular side wall extending from the top, the side wall having an internal thread having a pitch angled relative to the common top plane and adapted to engage with threads of the container around a container opening, the annular side wall having a distal edge positioned generally in a distal plane; and

a tamper-evident portion on a lower portion of the side wall, the tamper-evident portion including a plurality of leaders extending across a score line to a lower band, the lower band including a substantially continuous internal rib below the leaders, wherein the substantially continuous internal rib extends inwardly and has a length-to-width ratio of at least one and one-half, wherein the rib extends extends inwardly from the lower band away from the top as molded and in use on a container wherein the rib includes an angled portion for a portion of a circumference of the lower band, the angled portion positioned at a pitch angle relative to the common top plane and forming a one-way lead-in helical thread for the rib, whereby the one-one way lead-in thread formed by the angled portion allows the rib of the tamper-evident portion to be thread past a retaining ridge of a container, and wherein substantially the entire length of the rib is positioned between the common top plane and the distal plane.

11. The container closure as claimed in claim 10 wherein the rib is substantially rectangular in cross-section and has a length-to-width ratio of at least two.

12. The container closure of claim 11 , wherein the rib has a substantially constant cross section around a circumference of the lower band.

13. The container closure of claim 12 wherein the rib is designed to flex during exiting of the mold and forms a rigid interference element for the tamper evident portion following molding.

14. The container closure of claim 10 wherein a distal end of the rib is spaced from the side structure is positioned between the common top plane and the distal plane.