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

An apparatus for thermoforming a plastic hinged container from a sheet of thermoformable material in a mold, the apparatus comprising:

• a 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;
• a clamp for holding the flat planar hinge connection area against the hinge molding surface;
• a hinge cutting knife positioned above the hinge molding surface, the knife having a cutting blade movable against the hinge molding surface for 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.

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.