Patent ID: 6284169
Filing Date: 2001-09-04
Classification: B29C

Abstract:
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.