Self-aligning mold for injection molding of hollow plastic products

Abstract

A self aligning mold for injection molding and controlling the dimensions of a hollow plastic product having a rim, a base and a side wall therebetween. The base-forming portion of a first mold part includes a brink that protrudes in a direction toward a second mold part, and the base-forming portion of the second mold part includes a labrum that protrudes in a direction toward the first mold part to define a throttle situated between the brink and the labrum. The throttle has a variable width, which at any throttle position is defined by the distance between the brink and the labrum. The mold cavity gate is located within an area encompassed by the throttle. The throttle width varies when the first and second mold parts are not axially aligned to thereby, during injection, admit more material into the side wall-forming portion of the mold cavity that is the thinnest as a result of the axial misalignment, for the purpose of forcing the first and second mold parts into alignment. The mold cavity includes flow channels for directing injected plastic material from the base-forming portion of the mold cavity toward the rim-forming portion of the mold cavity, with at least certain particular flow channels having a mold cavity thickness that is significantly thicker than double the prevailing mold cavity thickness between the flow channels when the first and second mold parts are aligned and assembled. The certain particular flow channels prevent such extensive lateral flow of the plastic material as would maintain the axial misalignment of the mold parts. Laminated products are molded by using a third mold part, which in combination with the product formed by the first and second mold parts inherently defines secondary flow channels.