Method and apparatus for continuously extruding single-wall pipe of plastics or other mouldable material
AssigneeUponor N.V.
InventorErik G. W. Nordstrom
Life of this patent
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Abstract
The invention refers to a method and apparatus for manufacturing a single-wall pipe, tube or like conduit (9,44) having smooth inner surfaces and a mechanical-strength enhancing pattern of walls, flanges or ridges on the outer surface thereof, the conduit being made of plastics or like extrudable material.
Claims35
In a method of manufacturing a single-wall ribbed conduit having a smooth inner surface from a thermoplastic extrudable material wherein said material is fed from at least one extruder through an extruder nozzle and into a molding apparatus comprising mould-jaw chains which move adjacent one another along a molding line and include mould-jaw parts whose mutually opposing surfaces in the molding line have a form corresponding to a desired form of an outer surface of the conduit under manufacture, and wherein said material is pressed agains the surfaces of the mould-jaw along at least a part of the molding line and wherein the mould-jaw chain are caused to move away from one another subsequent to passing the moulding line, the mould-jaw parts therewith releasing their engagement with the outer surface of the conduit under manufacture, the improvement comprising:
- producing the conduit under manufacture in at least two stages by supplying said extrudable material to said moulding line to at least two separate locations, a first location and a second location positioned after the first location in the direction of conduit movement;
- supplying said material to said first location from a first channel of circular cross-section and forcing such material against the mould-jaw part by a gaseous medium under pressure and/or suction-drawing such material against said mould-jaw part by a vacuum exerted through passages in said mould-jaw parts, while adjusting the quantity of material supplied and the pressure and/or vacuum at said first location so that grooves in the mould-jaw parts, corresponding to outwardly protruding portions of the conduit under manufacture, are filled with said material at least to the bottom thereof;
- and
- supplying additional extrudable material to said second location from a second channel of circular cross-section formed between an external first mandril and an internal second mandril and discharging such additional material into a cavity located between an input end of a smoothing mandril and ends of said first and second mandrils facing said smoothing mandril, and forcing such additional material against the material delivered to said first location by a pressurized gaseous medium fed to said cavity.
In an apparatus for producing a single-wall ribbed conduit having a smooth inner surface from an extrudable plastics material, said apparatus comprising at least one extruder;
- a plurality of complementary mould-jaws having mutually facing surfaces with recesses therein corresponding to a desired form of outer surface of the conduit being produced, said mould-jaws being arranged for transportation in an endless chain along a select transport distance of said chain to define a moulding line;
- an extrusion nozzle coupled with said extruder for supplying moulten plastics material to said moulding line;
- pressure means for urging the moulten plastics material against said mutually facing surfaces of the mould-jaws along at least a part of the moulding line;
- cooling means for cooling the conduit being produced;
- separating means for moving the mould-jaws apart subsequent to passage past said moulding line, said mould-jaws being arranged to release their engagement with the outer surface of the conduit being produced;
- the improvement comprising:
- at least two stages for supplying material to the moulding line at least at two mutually separated locations, a first location and a second location positioned after the first location in the direction of material movement along said moulding line;
- adjustment means for regulating the amount of material supplied and the pressure and/or vacuum applied at said first location in a manner such that the recesses in the mould-jaws are filled with said material at least to their respective bottom portions;
- supply means for providing a pressurized gaseous medium to said first and second location to press supplied material against the mould-jaws and for providing a vacuum to at least said first location to draw supplied material against the mould-jaws;
- passages in said mould-jaws at the bottom of the grooves of each respective recesses connected to said vacuum supply means at least in the vicinity of said first location;
- a first channel having a circular cross-section positioned to supply material to said first location, said first channel opening into an annular first space formed between an outer first mandril and the mould-jaws and coupled with said supply means for pressurized gaseous medium and vacuum;
- and
- a second channel having a circular cross-section positioned to supply material to said second location, said second channel being formed between said outer said first mandril and an inner second mandril, said second channel opening into an annular second space defined, when seen in the direction of material movement, by respective end of said first and second mandrils facing a smoothing mandril located past said second channel and an input end of said smoothing mandril;
- and means for interconnecting said supply means for pressurized gaseous medium to said second space to provide said pressurized gaseous medium to such second space to press the material supplied at the second location against the material supplied at the first location.
In an apparatus as defined in 16 wherein spacing elements are arranged in said second channel in the region of the ends of said first and second mandrils facing the smoothing mandril for guiding said second inner mandril in relation to said first outer mandril.
Apparatus for producing a single-wall ribbed conduit having a smooth inner surface from an extrudable plastics material, comprising:
- A. a pair of endless chains of complementary mouldjaws formed of a plurality of mould-jaw parts having interior moulding surfaces, said chains being arranged to move through a given distance in close proximity to one another, said distance defining a moulding line;
- B. at least one extrusion nozzle positioned at an input end of said moulding line, sid extrusion nozzle being operationally coupled to at least one extruder providing a stream of extrudable material to said nozzle;
- C. a first, outer mandril positioned within said nozzle so as to define a first channel of circular cross-section for guiding extrudable material to a first location in said moulding line, and a second, inner mandril positioned inwardly of said first mandril so as to define a second channel of circular cross-section for guiding extrudable material to a second location in said moulding line, said second location being spaced from sid first location and positioned after the first location in the direction of material movement;
- said interior moulding surfaces of each mould-jaw part being provided with a plurality of recesses defining a ribbed outer surface of the conduit being produced, each of said recesses having a relatively fine passage at a bottom thereof for passage of a gaseous medium therethrough;
- D. vacuum means operationally coupled at said first location with the interior moulding surfaces of said mouldjaw parts to extract gaseous medium from at least the bottom of said recesses in said mould-jaw parts and draw extrudable material to at least the bottom of each recess;
- E. pressure means operationally coupled at said first location with the interior moulding surface of said mouldjaw parts to provide a pressurized fluid media to a space between said moulding surfaces to force material at said first location at least partially into the recesses in the mould-jaw parts;
- F. a smooothing mandril having a rounded convex surface facing said first and second mandrils and a cylindrical portion joined with said rounded surface, said cylindrical portion being located in close proximity to the moulding surfaces of opposing mould-jaw parts, said smoothing mandril being positioned within said said second location and spaced from said second channel;
- and
- G. fluid-coupling means interconnecting said pressure means with said second locatin at least at the space between said second channel and said smoothing mandril to provide a pressurized fluid medium to said space and force material at said second location against the material supplied at the first location.
Dependencies are inferred from the claim text.