| 主权项 |
1. A method of manufacturing a plastic structural article comprising:
blow-molding a plastic preform in a mold cavity in a mold, into a shape of a vertically oriented axially elongated member using compressed gas to at least partially form an elongated tubular plastic shell wall having opposed end sections, and a middle section there between forming a hollow interior cavity; extending a plurality of hollow pins in the mold transversely through the shell wall to project into the hollow interior cavity at axially spaced apart locations, the plurality of hollow pins forming at least a first and a second group of two or more hollow pins; introducing a pressurized gas into the hollow interior cavity through at least one of a first and a second pressurized gas manifold, each respectively connected to a first and a second group of two or more the hollow pins; after the tubular plastic shell is fully conforming the elongated tubular plastic shell wall to the mold cavity, venting the mold to control cavity pressure; forming at least one fill port in an uppermost end section of the shell wall after the cavity pressure reaches a predetermined pressure which is significantly above atmospheric pressure; filling the shell interior cavity with expandable polymer beads maintained in a bead reservoir in a pressurized state by opening a bead fill valve coupling the mold cavity to the bead reservoir while controlling the cavity pressure by regulating the flow of gas exiting the cavity through the hollow pins; injecting a hot, at least partially vaporized heating medium, into the first group of two or more hollow pins while removing the heating medium from the second group of the two or more hollow pins for a period of time, then injecting the hot, at least partially vaporized heating medium, into a second group of the hollow pins while removing the heating medium from a first group of the hollow pins for a period of time to partially melt and expand the expandable polymer beads to form a bead core which substantially filling the interior cavity of the shell with the beads bonding to one another and the shell wall; injecting air into one of the groups of the hollow pins while evacuating the air and condensate formed by the heating medium from the other group of the hollow pins for a period of time, then injecting air into the other group of the hollow pins while evacuating the air and condensate from the one of the groups of the hollow pins for a period of time, and continuing to alternate between injecting air and evacuating air from the first and second groups of hollow pins until the assembly is cooled sufficiently to limit substantial further expansion of the bead; and releasing the plastic structural article from the mold cavity. |
