Method of inverting container base prior to cooling
A method for hot-filling a polymeric container with heated product. The method includes mechanically inverting a base of the polymeric container prior to the heated product cooling in order to create a positive pressure within the container prior to cooling, and a vacuum in the container after cooling.
1. A method for hot-filling a polymeric container made of a container material with heated product comprising:
hot-filling the container with the heated product, during the hot-filling the heated product heats the container above a glass transition temperature;
capping the container after the container has been hot-filled with the heated product by screwing a cap onto a threaded finish of the container;
after the container has been hot-filled and capped, mechanically inverting with a mechanically adjusted pusher a center inversion area of a base of the polymeric container from a convex configuration to a concave configuration to create a positive pressure within the container prior to the container cooling below the glass transition temperature of the container material to create a positive pressure within the container, the center push-up portion is adjacent to, and surrounded by, a fixed portion of the base that remains stationary during mechanical inversion of the center push-up portion, the fixed portion includes a heel and a standing surface extending inward from the heel to the center inversion area, the center inversion area of the base is inward of the standing surface in both the convex configuration and the concave configuration; and
cooling the container below the glass transition temperature in a cooling tunnel subsequent to mechanically inverting the base;
wherein the positive pressure reinforces the container during conveying and cooling of the container to decrease occurrences of denting as the container cools below the glass transition temperature.
2. The method of claim 1 , wherein the container material is PET and the glass transition temperature is 152° F. to 178° F.
3. The method of claim 1 , wherein the container is hot-filled with product heated to a temperature within the range of 165° F. to 205° F.
4. The method of claim 3 , wherein the product is a beverage or food.
5. The method of claim 1 , wherein the container is hot-filled with product heated to 185° F.
6. The method of claim 1 , wherein the base is mechanically inverted with a force within the range of 40 lbs. to 80 lbs.
7. The method of claim 6 , wherein the base has a thickness within the range of 0.010″ to 0.020″.
8. The method of claim 1 , further comprising, after mechanically inverting the base, cooling the container and the product to create a negative pressure vacuum within the container.
9. The method of claim 8 , further comprising labeling and packing the container subsequent to cooling the container.
10. A method for hot-filling a polymeric container made of a container material with heated product comprising:
hot-filling the polymeric container with the heated product;
heating the container material above a glass transition temperature, during the hot-filling the heated product heats the container above the glass transition temperature;
capping the polymeric container after the container has been hot-filled by screwing a cap onto a threaded finish of the container;
mechanically inverting with a mechanically adjusted pusher a center inversion area of a base of the polymeric container from a convex configuration to a concave configuration prior to the container cooling below the glass transition temperature to create a positive pressure within the container that reinforces the container, the center push-up portion is adjacent to, and surrounded by, a fixed portion of the base that remains stationary during mechanical inversion of the center push-up portion, the fixed portion includes a heel and a standing surface extending inward from the heel to the center push-up portion, the center inversion area of the base is inward of the standing surface in both the convex configuration and the concave configuration; and
subsequent to mechanically inverting the base, cooling the container below the glass transition temperature in a cooling tunnel to create a negative pressure vacuum within the container;
wherein the positive pressure reinforces the container during conveying and cooling of the container to decrease occurrences of denting as the container cools below the glass transition temperature.
11. The method of claim 10 , wherein the container material is PET and the glass transition temperature is 152° F. to 178° F.
12. The method of claim 10 , wherein the container is hot-filled with product heated to 185° F.
13. The method of claim 10 , wherein the base is mechanically inverted with a force of 40 lbs. to 80 lbs.
14. The method of claim 13 , wherein the base has a thickness of from 0.010″ to 0.020″.
15. The method of claim 10 , further comprising labeling and packing the container subsequent to cooling the container.