Method of extrusion blow molding of a hollow body
AssigneeHarald Feuerherm
InventorsHarald Feuerherm, Rolf Kappen-Feuerherm
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Abstract
The extrusion blow molding of hollow bodies is carried out with a wall thickness program which in addition to varying the gap width over the entire perimeter of the gap in accordance with a first program curve and varying the geometry of the gap in response to a second program curve, automatically enhances a profiling of the preform to increase differences between the thick and thin regions with the variation in geometry when the gap width is greater in a reference value and diminishes the profiling of the preform to decrease such differences when the gap width is less than the reference value.
Claims14
A method of extrusion blow molding hollow bodies comprising the steps of:
- (a) extruding a tubular preform through an extrusion-nozzle gap externally delimited by a nozzle ring and internally delimited by a mandrel wherein said ring and said mandrel are relatively axially shiftable to vary a gap width;
- (b) automatically controlling said gap width and a geometry of the extrusion-nozzle gap in response to at least one control variable selected from a wall-thickness program and an extruded length of the preform by at least the steps of:
- (b1) varying the gap width over an entire perimeter of the gap by axially shifting at least one of said ring and said mandrel in accordance with a first program curve (WDS) of said wall-thickness program, and
- (b2) varying said geometry with at least one effector in response to a second program curve (RWDS) of said wall-thickness program;
- (c) forming at least one of said mandrel and said ring with a cross sectional shape selectively generating thick regions and thin regions of a synthetic resin melt as it is extruded through said gap to produce said preform and independently of the variation in said geometry in response to the second program curve (RWDS) of said wall-thickness program;
- (d) enhancing a profiling of said preform to increase differences between said thick and thin regions with said variation in geometry when said gap width is greater than a reference value and diminishing the profiling of said preform to decrease differences between said thick and thin regions with said variation in geometry when said gap width is less than the reference value;
- and
- (e) blowing said preform in a blow sold to produce one of said hollow bodies from each preform extruded from said gap.
Dependencies are inferred from the claim text.