US 5,759,459 AGranted

Method for producing plastic objects

AssigneeBattenfeld GmbH

InventorsHelmut Eckardt, Jurgen Ehritt, Alfons Seuthe, Michael Gosdin

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Abstract

A method and an apparatus for producing plastic objects with hollow spaces is disclosed. The method comprises the following steps: injecting a sufficient amount of plastic melt into the cavity (2) of the molding tool (1); simultaneously and/or subsequently injecting a pressurized fluid into the melt by means of a fluid injection nozzle (7); allowing the molded part (6) to cool; relieving the cavity (2) of the pressure of the compressed fluid, and demolding the molded part, while plastic melt is driven out into at least one overflow cavity (8), which is connected to the cavity (2). According to the invention, the volume of the overflow cavity (8) is changed, and in particular enlarged. This volume increase advantageously is controlled or regulated. The advantage achieved thereby is that the injection molding cycle, especially the overflow of melt into the overflow cavity (8), remains controllable by simple means.

Claims6

Dependent claims

A method for producing hollow plastic objects, the method comprising:

injecting plastic melt into a main cavity of a molding tool along a melt flow path, which extends from a plasticizing unit through a plastic injection nozzle into the molding tool;
simultaneously and/or subsequently injecting a pressurized fluid into the melt via at least one fluid injection nozzle, so that the melt introduced into the molding tool is distributed in the main cavity while forming a hollow space, and is pressed against walls of the main cavity of the molding tool;
while and/or after the pressurized fluid is injected, driving out a portion of the plastic melt into at least one overflow cavity, which is connected to the main cavity, while enabling enlargement of a volume of the overflow cavity;
reducing the volume of the overflow cavity in order to drive plastic melt back from the overflow cavity into the main cavity:
allowing the molded part to cool down to a temperature below the melting point of the plastic melt;
relieving the cavity of the pressure of the pressurized fluid;
and
demolding the molded part.

5 more elements

Dependencies are inferred from the claim text.