CONTAINER HAVING A ROLLED RIM, AND METHOD OF FORMING A CONTAINER HAVING A ROLLED RIM
Method of forming a container having a rolled rim, including providing a thermoformable sheet, and thermoforming the sheet to form a hollow body. The hollow body has an open first end and an opposite closed second end with a sidewall extending between the first end and the second end, and a rim structure formed at the first end of the hollow body. The rim structure includes an inner wall portion, a flange, and a skirt. The method further includes coining an upper section of the inner wall portion of the rim to form a controlled inner diameter, and rolling the rim structure to form a rigid rolled rim along an outer diameter of the open first end of the hollow body, the skirt extending toward the sidewall after being rolled.
1 . A method of forming a container having a rolled rim, comprising:
providing a thermoformable sheet comprising a polymeric material;
thermoforming the sheet to form a hollow body having an open first end and an opposite closed second end with a sidewall extending between the first end and the second end, and a rim structure formed at the first end of the hollow body, the rim structure including an inner wall portion extending upwardly from the sidewall, a flange extending outwardly from the inner wall portion, and a skirt extending downwardly from the flange, the flange defining a flange thickness and the skirt defining a skirt thickness, the flange thickness being greater than the skirt thickness;
coining an upper section of the inner wall portion of the rim structure to form a controlled inside diameter to a depth “d” from a top surface of the flange along an inner diameter of the open first end of the hollow body; and
rolling the rim structure to form a rigid rolled rim along an outer diameter of the open first end of the hollow body, wherein the skirt extends toward the sidewall after being rolled, the rolled rim and controlled inside diameter defining a lid-engaging surface.
2 . The method of claim 1 , wherein the depth “d” of the controlled inside diameter is at least about 0.050 inches from the top surface of the flange.
3 . The method of claim 1 , wherein the skirt has an upper portion proximate the flange and a lower portion opposite the upper portion.
4 . The method of claim 3 , wherein the skirt thickness varies between the upper portion and the lower portion prior to being rolled.
5 . The method of claim 3 , wherein the flange has an inner portion proximate the inner wall portion of the rim structure and an outer portion forming a joint with the upper portion of the skirt prior to being rolled.
6 . The method of claim 5 , wherein the flange has a width between the inner portion and the outer portion of the flange of approximately 0.90 to 0.140 inches.
7 . The method of claim 5 , wherein the joint defines a hinge point between the skirt and the flange.
8 . The method of claim 5 , wherein the joint defines a joint thickness, the joint thickness is less than the flange thickness.
9 . The method of claim 1 , wherein the flange extends outward from the inner wall portion at an angle of approximately 90 degrees from the inner wall portion.
10 . The method of claim 1 , wherein the skirt extends downward from the flange at an angle of approximately 90 degrees from the flange prior to being rolled.
11 . The method of claim 1 , wherein the second end includes a bottom wall.
12 . The method of claim 1 , wherein the hollow body is a single piece.
13 . The method of claim 1 , wherein the hollow body has a strengthening rib on the sidewall, the strengthening rib is disposed closer to the first end than the second end.
14 . The method of claim 1 , wherein the polymeric material comprises at least one of polyethylene terephthalate (PET), polypropylene, high-density polyethylene, and blends thereof.
15 . The method of claim 1 , wherein the polymeric material includes at least one filler or additive.
16 . The method of claim 1 , wherein the thermoformable sheet consists essentially of unfoamed polyolefin material.
17 . A container having a rolled rim, comprising:
a hollow body of a thermoformable sheet comprising a polymeric material, having an open first end and an opposite closed second end with a sidewall extending between the first end and the second end, and a rim structure formed at the first end of the hollow body, the rim structure including an inner wall portion extending upwardly from the sidewall, a flange extending outwardly from the inner wall portion, and a skirt extending downwardly from the flange and rolled towards the inner wall portion, the flange defining a flange thickness and the skirt defining a skirt thickness, the flange thickness being greater than the skirt thickness; and
a coined inside diameter on an upper section of the inner wall portion of the rim structure, the coined inside diameter extending to a depth “d” from a top surface of the flange along an inner diameter of the open first end of the hollow body, the rolled rim and coined inside diameter defining a lid-engaging surface.
18 . The container of claim 17 , furthering comprising: a strengthening rib on the sidewall, the strengthening rib disposed closer to the first end than the second end,
wherein the strengthening rib has a first concave portion extending radially outwardly from an interior of the container and a first convex portion extending radially inwardly toward the interior of the container, and wherein the container has an overall height between the first end and the second end, and wherein the strengthening rib is disposed approximately between ½ and ¾ the overall height.
19 . The container of claim 17 , wherein the flange defines a flange thickness and the skirt defines a skirt thickness, the flange thickness being greater than the skirt thickness.