US-12617142-B2 - Rolled edge trays having smooth edges and stacking extensions

Abstract

The disclosure relates to forming shaped thermoplastic articles having smooth peripheries. Many thermoplastic articles have sharp edges formed upon molding or cutting the article from a feedstock sheet. Such sharp edges can damage thin plastic films or flesh which they contact, and smoothing the edges is desirable. Described herein are methods of forming a smooth periphery for such sharp-edged articles by rolling over the sharp edge. The smoothing operation is performed by forming a deflectable flange including a bend region separated from the potentially sharp peripheral edge by a spacer, deflecting a portion of the deflectable flange, and softening at least one bent portion of the deflectable flange to yield a smooth periphery upon cooling.

Inventors

• Millard F Wallace

Assignees

• CONVERTER MANUFACTURING, LLC

Dates

Publication Date

20260505

Application Date

20250411

Claims (20)

1. 1 . A tray for containing a food, the tray being formed from a sheet of thermoformable plastic having a peripheral edge and having a shape that includes a concave, rounded rectangular tray-shaped body and a rim connected to the body about its entire periphery, the rim including an extension interposed between the body and a smooth, rolled-over edge wherein the peripheral edge of the sheet is disposed away from the periphery of the tray, the rolled-over edge including a stacking extension at each corner of the rim, wherein a plurality of the tray are stackable in a nested conformation such that when a first tray is nested within a second tray, the rolled-over edge of the first tray contacts the rim of the second tray only at one or more of the stacking extensions.
2. 2 . The tray of claim 1 , wherein the extension includes a substantially planar sealing surface about the entire periphery of the body.
3. 3 . The tray of claim 2 , wherein when the first, upper tray is nested with the second, lower tray, the rolled-over edge of the first tray contacts the substantially planar sealing surface of the second tray only at one or more of the stacking extensions.
4. 4 . The tray of claim 1 , wherein the rolled-over edge comprises a smoothly-curved bend region adjoining the extension and connecting thereto a spacer which carries the peripheral edge of the sheet.
5. 5 . The tray of claim 4 , wherein the peripheral edge of the sheet is contained within the rolled-over edge.
6. 6 . The tray of claim 4 , wherein the rolled-over edge is rolled sufficiently that the peripheral edge of the sheet points toward the body of the tray.
7. 7 . The tray of claim 4 , wherein the rolled-over edge is rolled sufficiently that the peripheral edge of the sheet points toward the underside of the rim.
8. 8 . The tray of claim 4 , wherein the peripheral edge of the sheet is part of a peripheral flange that is connected to the spacer by an elbow.
9. 9 . The tray of claim 8 , wherein the peripheral edge of the sheet is contained within the rolled-over edge.
10. 10 . The tray of claim 8 , wherein the rolled-over edge is rolled sufficiently that the peripheral edge of the sheet points toward the body of the tray.
11. 11 . The tray of claim 8 , wherein the rolled-over edge is rolled sufficiently that the peripheral edge of the sheet points toward the underside of the rim.
12. 12 . The tray of claim 4 , wherein the rolled edge includes a bent portion disposed between the spacer and the peripheral edge of the sheet.
13. 13 . The tray of claim 12 , wherein the peripheral edge of the sheet is contained within the rolled-over edge.
14. 14 . The tray of claim 12 , wherein the rolled-over edge is rolled sufficiently that the peripheral edge of the sheet points toward the body of the tray.
15. 15 . The tray of claim 12 , wherein the rolled-over edge is rolled sufficiently that the peripheral edge of the sheet points toward the underside of the rim.
16. 16 . The tray of claim 4 , wherein the extension includes a substantially planar sealing surface, the spacer is substantially flat, and the bend region connects the sealing surface and the spacer at an angle not less than 75 nor more than 105 degrees.
17. 17 . The tray of claim 16 , wherein the bend region connects the sealing surface and the spacer at an angle not less than 87 nor more than 93 degrees.
18. 18 . The tray of claim 16 , wherein the peripheral edge of the sheet is contained within the rolled-over edge.
19. 19 . The tray of claim 16 , wherein the rolled-over edge is rolled sufficiently that the peripheral edge of the sheet points toward the body of the tray.
20. 20 . The tray of claim 16 , wherein the rolled-over edge is rolled sufficiently that the peripheral edge of the sheet points toward the underside of the rim.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS This application is a continuation of co-pending U.S. application Ser. No. 16/728,618, filed 27 Dec. 2019, which is a continuation of U.S. application Ser. No. 15/445,220 filed 28 Feb. 2017, now U.S. Pat. No. 10,562,222, which is a continuation-in-part of international application PCT/US16/49692 (inactive), filed 31 Aug. 2016, which is entitled to priority to U.S. provisional patent application No. 62/212,367, filed 31 Aug. 2015, each of which applications is incorporated herein by reference in its entirety. BACKGROUND OF THE DISCLOSURE This disclosure relates generally to the field of forming shaped thermoplastic articles. Formation of shaped articles from thermoplastic materials is well known. A wide variety of methods (e.g., thermoforming, casting, molding, and spinning) can be used to confer shape to a molten thermoplastic or to a preformed thermoplastic sheet that has been softened or melted. Trimming of waste material from one or more edges of a shaped article is a common finishing technique, but leaves a sharp edge that can injure flesh or tear or cut materials which come into contact with the edge. One common use for shaped thermoplastics is to form containers that can be sealed with thin plastic films, such as trays, bowls, or bins intended to contain foodstuffs and intended to be sealed with transparent plastic film. Another common use is to contain items and to seal them from moisture or other materials which may come into contact with the container. Sealing of such containers typically involves extending or stretching the film across a compartment formed in the container and sealing the film around the periphery of the compartment, which periphery is often situated adjacent a trimmed edge of the article that includes the compartment. If that edge is sharp, it can cut or break the film, interfering with the sealing process. Three well-known sealing technologies are commonly used in sealing foods and foodstuffs to form containers for commercial shipping, storage, display, and sale. These are referred to herein as OW, VSP, and MAP technologies. All of these technologies involve combining a container and a thin plastic film. Owing to the fragility of such films and the need, in many instances, to minimize or eliminate punctures and tears from film portions which serve to define (together with the container) sealed compartments, it is critical to minimize the opportunities for containers to tear, puncture, or abrade the film of the same or nearby containers. In addition to plastic films used for sealing such containers, plastic films are also employed for shipping the containers, such as the “mother bags” (i.e., typically thin plastic bags) used for containing multiple product-in-container-packages during shipping and the plastic grocery bags used by consumers to transport purchased goods from a retailer. This can be achieved by reducing or eliminating sharp or rough container edges, at least positions on the container at which such edges might reasonably contact the film during packaging, storage, shipment, or display. Overwrap (OW) technology involves enveloping or wrapping a shaped article (e.g., a thermoformed tray, sheet, bowl, or multi-compartment container) with a thin (often transparent) plastic film after a foodstuff or other item has been placed on one or more faces of the article and thereafter sealing the film to itself (e.g., by heating overlapping portions of the film). In such OW technology, sharp or rough edges of the shaped article can cut, abrade, or puncture the film, potentially allowing materials to pass through the film and defeating one or more of its purposes. Heretofore, OW technology has been used primarily together with foamed trays or bins lacking sharp edges. Many municipal recycling schemes exclude or disfavor foamed plastics, and such materials are therefore increasingly disfavored by consumers. It would be desirable if a thermoformable plastic container suitable for use with multiple wrapping technologies, including OW technology, could be made, since thermoformable materials tend to be widely acceptable in recycling programs. Vacuum-sealed package (VSP) technology involves adhering a thin (again, often transparent) plastic film against a face of a shaped article bearing a foodstuff (for example, or a moisture-sensitive object as an alternate example) on a face of the shaped article. When VSP technology is employed, that item(s) to be packaged are placed on a surface or within a cavity of the shaped article, the film is overlain such that the item(s) are interposed between the shaped article and the film, air (or whatever other gases may be present) is withdrawn from the space between the film and the shaped article (optionally in coordination of application of positive pressure to the exterior of one or both of the film and the shaped article) so that the film is closely opposed against the surface of the shaped article and/or