Travelling mold tunnel apparatus for smooth walled pipe
AssigneeCorma Inc.
InventorManfred A. A. Lupke
Life of this patent
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Abstract
An apparatus for making smooth walled tube (20) in a travelling mold tunnel (26) includes corrugations (32) for traction of tube being molded. An extrusion nozzle (16) having an exit angle of 45.degree. or more may provide additional advantage.
Claims28
Apparatus for the extrusion of thermoplastic material tube (20) comprising a forwardly travelling mold tunnel (26) for molding an outer wall of the tube, the mold tunnel comprising a plurality of aligned adjacent mold blocks (14), the mold tunnel (26) having an upstream end and a downstream end and an elongate cylindrical tunnel bore extending between the ends;
- the mold blocks (14) being formed by co-operating mold block parts (13) which, at the upstream end of the mold tunnel, close to provide a closed mold block having a mold block bore, where the plurality of adjacent mold blocks (14) establish an elongate part of the tunnel bore and which, at the downstream end of the mold tunnel, open to release the tube (20) formed within the tunnel;
- an extrusion die (18) for thermoplastic material having an elongate extrusion nozzle (16) for extruding a parison of thermoplastic material into the mold tunnel;
- cylindrical mold block bore walls, and hence a tunnel bore wall (3), being provided with shallow corrugations (32) to aid transport of the tube being molded, the depth of the corrugations corresponding to less than about 2% of the tube diameter and being small with respect to the tube thickness, there being no surface formations of greater than 2% of the tube diameter along the tunnel bore wall for a distance of such length that loss of traction and slippage of the tube would occur during molding if the corrugations were not present.
A method for forming tube (20) comprising the steps of:
- a) extruding a thermoplastic parison from an extrusion nozzle (16) of an extrusion die (18) into a forwardly travelling elongate mold tunnel (26);
- b) molding the parison into a tube within the mold tunnel (26) which comprises a plurality of aligned adjacent mold blocks (14), and which has an upstream end and a downstream end, an elongate cylindrical tunnel bore extending between the ends,
- the mold blocks (14) being formed by co-operating mold block parts (13) which, at the upstream end of the mold tunnel, close to provide a closed mold block (14) having an elongate cylindrical mold block bore forming part of the tunnel bores, and which, at the downstream end of the mold tunnel, open to release the tube formed within the tunnel;
- c) molding an inner wall of the tube (20);
- d) aiding transport of the tube being molded in the mold tunnel by corrugations corresponding to less than about 2% of the tube diameter and the depth of the corrugations being small with respect to the tube thickness while not aiding transport with any surface formations of greater than 2% of the tube diameter along the tunnel bore wall for a distance of such length that loss of traction and slippage of the tube would occur during molding if the corrugations were not present.
Dependencies are inferred from the claim text.