Controlling an extrusion blowing process
AssigneeKrupp Kautex Maschinenbau GmbH
InventorsWerner Daubenbuchel, Dieter Hess
Life of this patent
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Abstract
In extrusion blowing a hollow member, a preform is extruded and then blown in a mold to produce the final member. The weight of the hollow member is determined after its removal from the mold and compared to a reference value, thereby to adjust the size of the extrusion discharge opening to control the amount of material in the preform. The length of the preform is detected to control the movement of the mold thereby to keep a substantially constant length of extruded preform, while the time required to produce a preform is also maintained at a substantially constant value.
Claims14
A process for maintaining substantially constant the final weight of hollow members produced from a plastic material by extrusion blow molding wherein a succession of preforms is continuously extruded from a discharge opening of an extrusion head connected to an extrusion press, the preforms being successively blown in a mold means to form said hollow members, the process comprising:
- detecting the final weight of at least one hollow member after leaving the mold means after blowing thereof;
- comparing said detected final weight to a reference value representing a desired weight;
- adjusting the size of the discharge opening in response to the comparison such that the volume and therefore the weight of a succeeding preform increases when the final weight is less than the reference value and decreases when the final weight is greater than the reference value;
- detecting when the length of a preform has reached a preselected length;
- closing the mold about the preform when the preform attains the preselected length to produce a substantially constant length of preform;
- and
- maintaining substantially constant the time for extruding the preform to the preselected length.
Dependencies are inferred from the claim text.