Method and device for extrusion of a double wall plastics pipe
AssigneeUponor N.V.
InventorsJyri Jarvenkyla, Paul Holso
Life of this patent
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Abstract
Method in extruding a double-walled plastic tube by using plastic materials of different colors for the inner layer and the outer layer, a portion of the material for the inner layer being diverted to form a longitudinal strip of the outer layer on the outside surface of the tube. The invention also relates to an extrusion tool for working the method, wherein an element (21) is provided inside the tool to divert material from a passage (19) for material for the inner layer to a passage (16) for material for the outer layer.
Claims5
Method in extruding a double-walled plastic tube comprising the steps of:
- extruding an inner wall of plastic material having a first color;
- extruding an outer wall of plastic material having a second color concentrically with the inner wall;
- corrugating the outer wall;
- connecting the outer wall at the inside crests thereof to the outside surface of the inner wall;
- diverting from the plastic material for the inner wall a fraction of such material to the outer wall;
- and
- supplying the diverted plastic material to the outer wall as a longitudinal strip of said first color on the outside of the outer wall of plastic material of said second color.
Extrusion tool for extruding a double walled plastic tube comprising:
- a first annular output passage for plastic material for the inner wall of the tube;
- a second annular output passage for plastic material for the outer wall of the tube;
- and
- means inside the tool forming a passage connecting the first passage with the second passage and extending over a fraction of the respective circumferences of said first and second passages for diverting a strip of material from said first passage to said second passage.
Dependencies are inferred from the claim text.