Importance

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Abstract

An extruder has a housing, a core centered on an axis, and a sleeve spacedly coaxially surrounding the core and defining therewith an outlet passage. Thus molten material emerges from the passage as a tube. A plurality of radially extending and angularly spaced adjustment screws are threaded into the housing and radially engage the sleeve so that these screws can be screwed in and out to radially displace the sleeve on the housing and thereby adjust the passage. A detecting unit axially downstream of the extruder includes at least one sensor for measuring the thickness of the tube at a plurality of angularly spaced locations and for producing an output corresponding to the respective measured thickness. An adjustment unit including at least one rotary tool engageable with the screws can selectively rotate same and screw same in the housing. A controller is connected between the detecting unit and adjuster for rotating a screw out when the sensor output for the respective portion of the tube indicates same is too thin and for screwing a screw in when the sensor output for the respective portion of the tube indicates same is too thick.

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First Claim