US-12623807-B2 - Method of forming a container having a rolled rim

US12623807B2US 12623807 B2US12623807 B2US 12623807B2US-12623807-B2

Abstract

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.

Inventors

Tom Van Nortwick
Jeff Hautzinger
Frank Petlak

Assignees

Pactiv LLC

Dates

Publication Date: 20260512
Application Date: 20210303

Claims (10)

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 strengthening rib on the sidewall, the strengthening rib disposed closer to the first end than the second end, the hollow body further having 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; 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; 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; 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.
2 . The method of claim 1 , wherein the strengthening rib has a “∠”-shape in side cross-section.
3 . The method of claim 1 , wherein the concave portion of the strengthening rib is closer to the second end of the container than the convex portion of the strengthening rib.
4 . The method of claim 1 , wherein the concave portion of the strengthening rib has a greater depth than the convex portion of the strengthening rib.
5 . The method of claim 1 , wherein the sidewall has a bottom frustoconical portion below the strengthening rib and a top frustoconical portion above the strengthening rib, the bottom frustoconical portion defining a first taper line in side profile and the top portion defining a second taper line in side profile, wherein the first taper line is parallel to the second taper line.
6 . The method of claim 5 , wherein the first taper line is offset from the second taper line by a taper line offset.
7 . The method of claim 6 , wherein the taper line offset is approximately 0.080 to 0.100 inches.
8 . The method of claim 1 , wherein the flange defines a flange thickness and the skirt defines a skirt thickness, the flange thickness being greater than the skirt thickness.
9 . The method of claim 5 , wherein the parallel taper lines allow for printing on an outer surface of the top frustoconical portion and an outer surface of the top frustroconical portion simultaneously and in a single pass.
10 . The method of claim 1 , wherein coining an upper section of the inner wall portion of the rim structure forms a coined ledge at the depth “d” to define a portion of the lid engaging surface.

Description

BACKGROUND OF THE DISCLOSED SUBJECT MATTER Field of the Disclosed Subject Matter The disclosed subject matter relates generally to the field of thermoformed containers, specifically, the construction of a container such as a cup, bowl or the like. More specifically, the disclosed subject matter relates to a container having a rolled rim and a method of forming the same. Description of the Related Art A variety of thermoplastic containers, such as containers for food and beverages, are well known in the art. Such thermoplastic containers are relatively inexpensive and disposable; and therefore are extremely popular. Such containers are often used at parties, picnics, gatherings, and other occasions where minimal clean-up is desired. Containers made of thermoplastic materials are particularly advantageous for both manufacturers and consumers. Such containers are generally more durable than paper containers, yet inexpensive, lightweight, and recyclable. Thermoforming generally begins with a thin sheet or web of material such as polyethylene, polypropylene, polyester, or polystyrene having a thickness within a range of from approximately 8 mils to 100 mils, depending on the size of the container to be manufactured. Cups and similar articles are typically made from plastic sheet or web having a pre-thermoforming thickness from approximately 30 to 60 mils, but the finished articles may be thinner after thermoforming. The sheet or web is heated to a temperature suitable for thermoforming—such as, for example, in a range from approximately 110° C. to about 200° C. for the above-mentioned materials—and is thereafter fed into a conventional forming assembly in which the process proceeds under applied positive and/or negative air pressure conditions. Depending on the thermoforming process, whether melt phase or solid phase, oven temperatures can vary and can reach up to 485° C. in melt phase thermoforming. A mold cavity is used to impart a particular shape to define the thin-walled container as the plastic sheet or web is drawn into the mold using vacuum pressure on one side of the sheet or web and/or a positive pressure on the opposite surface of the sheet or web. A plug assist can be used to aid in the process of imparting a particular shape to define the thin-walled container. The container generally includes a sidewall, and may also be provided with a rim or lip along the mouth of the container. The shape of the container may be decorative, but generally has a particular utility—e.g., ribs for strength, texturing for grasping, and formations for nestability in addition to other utilities. The processing period for a normal thermoforming operation can be between 1 and 20 seconds. One disadvantage of many existing thermoformed cup and container designs is the lack of structural integrity in the sidewall and the rim. Sidewalls and rims of thin-walled thermoformed containers often bend and deflect inward easily. A deflection of this sort can constrict the volume of the container and/or cause spillage and overflows. Additionally, deflection of the sidewall can make the container more difficult to grip, as well as potentially leading to cracking of the container sidewall. An additional disadvantage of many existing cup and container designs is that if provided, the rim may have a squared-off edge. Such a rim is not preferable because the sharp edges of the squared-off edge may be uncomfortable to the touch and germs may collect under the rim when it is not completely rolled, rendering it unsanitary. Alternatively, rolled rim configurations eliminate the disadvantages of squared-off rims or flanges, as well as add rigidity to the overall rim. A rolled rim on a container can additionally improve the fit of a lid onto the container rim. A rolled rim with a controlled inside diameter, such as by coining an inner surface of the cup, can further improve the fit of a lid onto the cup rim. A rolled rim can add significant rigidity to the rim as well as to close the space created at the rim. Such rolled rims have been created in containers formed of alkenyl aromatic polymeric materials such as polystyrene. There are numerous reasons, such as cost and consumer preference, to make consumer containers out of polymeric materials. However, polymeric materials become significantly softer than do alkenyl aromatic polymers during the thermoforming process. Due to the softness of polymeric material during thermoforming, such materials are not conducive to rim rolling processes. Thus, a need further exists for a container having a rolled rim that can be formed of a polymeric material. The disclosed subject matter provides a solution to the recognized problems. The disclosed subject matter is intended to provide a container having a rolled rim made of polymeric material, and a method for forming the same. SUMMARY OF THE DISCLOSED SUBJECT MATTER The purpose and advantages of the disclosed subject matter will be set forth in and apparent fro