Abstract: Apparatus for cold-forming a thermoplastic sheet to provide a circular container part such as a lid or dish comprising opposing concentric die members for engaging a sheet of thermoplastic material, the sheet being drawn around the circular edge of one of the die members to provide a concentric central portion and a concentric annular depending skirt having a proximal edge adjacent the central portion, an intermediate portion, and a distal free edge, providing an annular void in the die members adjacent the skirt. Apparatus is provided for moving the free edge toward the proximal edge while holding the proximal edge to buckle the intermediate portion into the void. The void has a tapered surface inclining radially outwardly and axially toward the proximal edge to hold the free edge radially inwardly, thereby to permit the intermediate portion to buckle outwardly into the void.

Abstract: Mixer apparatus for use with injection molding, extrusion or mixing and compounding machines wherein a melt chamber is lined with a series of stacked Belleville spring washers to provide a series of axially narrow, annular extrusion passages between the washers. A quantity of thermoplastic material is supplied to the melt chamber at the inner diameter of the washers and is therein subjected to pressure to cause extrusion of the material through the passages. From the washers, the material is directed through axially extending slots about the washers to a mold cavity or forming die.

Abstract: A method of cold-forming a thermoplastic sheet to provide a circular container part such as a lid or dish comprising the steps of engaging a sheet of thermoplastic material between opposing concentric die members, drawing the sheet around the circular edge of one of the die members to provide a concentric central portion and a concentric annular depending skirt having a proximal edge adjacent the central portion, an intermediate portion, and a distal free edge, provide an annular void in the die members adjacent the skirt, then moving the free edge toward the proximal edge while holding the proximal edge to buckle the said intermediate portion into the void. In the apparatus, the void has a tapered surface inclining radially outwardly and axially toward the proximal edge to hold the free edge radially inwardly, thereby to permit the intermediate portion to buckle outwardly into the void.

Abstract: Method and apparatus for scoring one or more lines into the surface of a plastic part such as a container or container lid as the part is being formed. A forming press includes a plurality of die members adapted for movement within, and with respect to, a plurality of draw pads. A blank of sheet stock is placed between die members and draw pads. The die members are then moved relative to the draw pads to draw the radially outer periphery of the blank across the draw pads to form the part. As the part is being formed, scoring knives positioned in at least one of the draw pads and having scoring edges which extend above the draw pad surfaces are held against the surface of the part. As the part is drawn across the surfaces of the draw pads, it is scored in a manner determined by the locations and orientations of the scoring knives in the draw pad and the manner in which the part surface is drawn across the scoring edges.