Method and apparatus for forming a notched hinge connection in a thermoformed container

Patent metadata

Field	Value
Publication number	US-10329058-B2
Application number	US-201615156705-A
Country	US
Kind code	B2
Filing date	May 17, 2016
Priority date	Aug 15, 2014
Publication date	Jun 25, 2019
Grant date	Jun 25, 2019

Abstract

Method and apparatus for forming a hinge in a thermoformed container, such as an egg carton, and the resulting container. The hinge is formed in the mold, by severing a thermoformed container along the length of a hinge line, with the exception of plurality of spaced connecting membranes that are not severed. The alternating severed portions and connecting membranes are referred to herein as a notched hinge connection. The width, depth, and location of the connecting membranes can be adjusted so the hinge area is strong enough to withstand multiple openings during use.

First claim

What is claimed is:

1. A method of thermoforming a hinged plastic container comprising:
thermoforming a hinged container from a sheet of thermoformable material in a mold, the mold including a top molding surface having:
a first molding surface for forming a first portion of the container;
a second molding surface for forming a second portion of the container; and
a hinge molding surface between the first and second molding surfaces for forming a flat planar hinge connection area between the first and second portions of the container;

providing a knife positioned above the hinge molding surface, the knife having a cutting blade movable against the hinge molding surface;
clamping the flat planar hinge connection area against the hinge molding surface;
cutting a notched hinge line in the clamped hinge connection area of the thermoformed container in the mold, the notched hinge line including severed portions separated by connecting membranes joining the adjacent portions of the container, and wherein the hinge molding surface has a plurality notches, spaced apart along the hinge line, in which the connecting membrane portions are formed.

2. The method of claim 1 , wherein the notches comprise grooves in the hinge molding surface disposed at an angle to the hinge axis, wherein the knife severs the areas between the grooves and the membranes in the grooves remain at least partially un-severed.

3. The method of claim 2 , wherein the knife partially severs the material in the grooves.

4. The method of claim 1 , wherein the clamping comprises holding the flat planar hinge connection area between a clamping surface of a clamp and the hinge molding surface.

5. The method of claim 4 , wherein the clamping surface engages and holds the hinge connection area on two opposing sides of the hinge axis.

6. The method of claim 1 , wherein the first molding surface is shaped to form a base portion of the container, and the second molding surface is shaped to form a lid portion of the container.

7. The method of claim 6 , wherein the first molding surface comprises a matrix of cells.

8. The method of claim 7 , wherein the mold further includes a third molding surface comprising a plurality of cells complimentary to the cells of the first molding surface for forming a cover cell portion of the carton, wherein the hinge molding surface is provided between the first and third molding surfaces.

9. The method of claim 1 , wherein the container is a tri-fold egg carton, and the molding surfaces include first, second, and third molding surfaces for forming a lid, cell base, and cell cover portions of the carton respectively, with hinge molding surfaces provided between each of the first and second and between the second and third molding surfaces.

10. The method of claim 1 , wherein the container is an egg carton, the first molding surface comprising a plurality of cells for forming a first cell portion of the egg carton, the second molding surface forming a lid portion of the carton.

11. The method of claim 10 , wherein the second molding surface comprises a plurality of cells complimentary to the cells of the first molding surface for forming a second cell portion of the carton, the molding surfaces configured such that when the notched hinge connection is closed the first and second portions of the carton form complimentary cell pockets for holding individual eggs.

12. The method of claim 10 , wherein the thermoforming step comprises thermoforming a unitary molded sheet of clear solid polyester or polystyrene foam.

13. A method of forming a tri-fold plastic thermoformed egg carton comprising:
providing a unitary sheet of plastic material suitable for thermoforming;
thermoforming the sheet to form a cell base, a cell cover and a lid, the thermoformed sheet including a hinge connection between adjoining edges of the cell base and the cell cover for pivoting of the cover and base between open and closed positions, the base and cover each having a complimentary matrix of cells that together form a matrix of cell pockets for holding individual eggs when the cover is in the closed position over the base, the lid and base having a hinge connection between opposing edges for pivoting between open and closed positions, wherein when the cover and base are in the closed position the lid can be closed over the cover to form an assembled carton;
the hinge connection between the cell base and cell cover including a common planar wall portion having an upper planar surface lying in a common plane CP, a plurality of thermoformed connecting membranes recessed from the CP and spaced apart along a hinge axis of the hinge connection;
forming a severed hinge line severing the common planar wall portion without severing the connecting membranes, such that the connecting membranes form a hinged connection between the severed portions of the common planar wall portions, and wherein the hinge connection is formed by thermoforming the sheet against a notched striker bar, the notched striker bar having a planar wall with a plurality of spaced apart grooves, wherein the connecting membranes are formed by deforming the sheet into the grooves of the notched striker bar to form the connecting membranes, and a continuous cutting blade engages the un-notched portions of the sheet formed against the planar wall of the striker bar to form the severed hinge line.

14. The method of claim 13 , wherein the notches comprise grooves in the hinge molding surface disposed at an angle to the hinge axis, and wherein the knife severs the areas between the grooves and the membranes in the grooves remain at least partially un-severed.

15. The method of claim 14 , wherein the knife partially severs the material in the grooves.

16. The method of claim 13 , wherein the unitary sheet of plastic material is clear solid polyester or polystyrene foam.

Assignees

• Tekni Plex Inc

Inventors

• Kuruvilla Babu
• Ramirez Richard L
• Bergeron Mark A

Classifications

• B29C51/265

  Auxiliary operations during the thermoforming operation (B29C51/42, B29C51/46 take precedence) · CPC title

• B29K2105/04

  cellular or porous · CPC title

• B65D85/32

  for eggs · CPC title

• B29K2025/06

  PS, i.e. polystyrene · CPC title

• B65D43/16

  hinged for upward or downward movement · CPC title