Fluid-assisted core-release method and apparatus

In combination with an ejection-molding machine having a moving platen, a mold core mounted on the moving platen defining in part the space in which an article is molded, and an ejector means movable with respect to the moving platen for mechanically removing a molded article from the mold core, the improvement comprising

• a source of fluid at about atmospheric pressure,
• a conduit leading from a molding space-defining surface of the mold core to the source of fluid, and
• means in said conduit for introducing a measured volume of said fluid to the molding space-defining surface at a rate controlled by the relative motion between the moving platen and the ejector means.

An apparatus for assisting in the removal of an ejection-molded straight wall container from a core of a mold in which the container was formed, the mold core being fixed to a moving platen and having a stripper ring surrounding the core for mechanically removing the container from the core, the apparatus comprising

• a conduit leading to the surface of the mold core defining the bottom of the container, and
• a piston in a cylinder, the interior of the cylinder being connected to the conduit, the cylinder being fixed to said platen, and the piston being fixed to said stripper ring, the volume of the cylinder included by the piston being approximately equal to the container, the cylinder being filled with air at a pressure of approximately 1 atmosphere, the relative movement between the mold core and the stripper ring causing the air within the cylinder to be introduced into the conduit at a rate substantially equal to the rate at which a void develops between the bottom of the container and the mold core as the container is stripped from the mold core.

A method of assisting in the removal of an ejection-molded article from a core of a mold in which the article was formed, the mold core being attached to a platen and having an ejector means movable with respect to the platen for mechanically removing the molded article from the core, the method comprising the steps of

• providing a conduit leading to a surface of the mold core against which the molded article is formed, and
• introducing into the conduit a measured volume of fluid at about atmospheric pressure at a rate controlled by the rate of relative motion between the platen and the ejector means.