US 4,053,274 A · Tube wall forming apparatus

Abstract

An apparatus and method are provided for forming tubing of plastic which is forced through a die over a mandrel wherein the inside surface of the tubing is relatively smooth in configuration and the exterior surface thereof is formed with one or more helical ribs or teeth protruding outwardly therefrom which serve to enhance the rigidity of the tube wall and, when the plastic itself is relatively rigid, to render the tube wall more flexible so that it may be deformed or bent without collapsing. In one form, the extrusion die through which the extrusion material is forced to form the tube, is configured to provide the helical formations in the outer stratum of the tube wall and is power rotated as the extrudate is forced through the die to form the helical formation therein. In another form, a portion of the extrusion die is power rotated to form the helical formation. In a third form, control of the rotation of the die or a device located at the throat or exit of the die is affected to perform either or both of the functions of variably changing the shape of the helical formation and, providing portions of the tubing which are free of the helical formation to permit fittings to be attached thereto.

Claims7

Dependent claims

An apparatus for continuously extruding tubing having a smooth interior wall surface which has a substantially constant internal diameter and having an exterior wall which varies in configuration along the length thereof wherein said configuration is in the form of corrugations having a depth equal to at least one-half of the wall thickness of the extruded tube to provide a flexible tube having a resistance free flow path comprising:

an extruder including an extrusion die having a die opening,
a mandrel supported within said die and extending beyond said die opening to define with said die opening an annular passageway,
means connected to said die to define a chamber adapted to be filled with an extrudate,
means associated with said chamber for forcing the extrudate about said mandrel and through said annular passageway,
said mandrel having a smooth outer surface to form the tubular extrusion having a smooth regularly shaped internal surface having a substantially constant diameter,
corrugating means operatively associated with said die and having a corrugating formation for engaging the exterior surface of the tubular extrusion formed in said die,
said corrugating formation having a depth equal to at least one-half the thickness of tubular extrusion formed in said die,
drive means connected to said corrugating means for effecting the rotation thereof as said tubular extrusion is being formed in said die to form a series of spiral protrusions in the outer stratum of the tubular extrusion only,
wherein said corrugating means comprises a component part of said die defining said die opening.

6 more elements

an extruder including an extrusion die having a die opening,
a mandrel supported within said die and extending beyond said die opening to define with said die opening an annular passageway,
means connected to said die to define a chamber adapted to be filled with an extrudate,
means associated with said chamber for forcing the extrudate about said mandrel and through said annular passageway,
said mandrel having a smooth outer surface to form the tubular extrusion having a smooth regularly shaped internal surface having a substantially constant diameter,
corrugating means operatively associated with said die and having a corrugating formation for engaging the exterior surface of the tubular extrusion formed in said die,
said corrugating formation having a depth equal to at least one-half the thickness of tubular extrusion formed in said die,
drive means connected to said corrugating means for effecting the rotation thereof as said tubular extrusion is being formed in said die to form a series of spiral protrusions in the outer stratum of the tubular extrusion only,
wherein said corrugating means includes a plurality of forming tools disposed about said die opening and located to engage the outer stratum of the tubular extrusion expressed through said die opening.

6 more elements

Dependencies are inferred from the claim text.

Tube wall forming apparatus

Life of this patent

Tube wall forming apparatus

Life of this patent

Abstract

Claims7