Extrusion method and apparatus

Claim 1

A method of extruding a fused molten mass of a thermoplastic material in a single screw extruder comprising a hollow barrel, a single screw rotatable within said hollow barrel, inlet means for introducing said melt into said barrel and melt discharge means disposed in said barrel downstream of said inlet means, said extruder including a return delivery section upstream of said inlet means, said screw including a return delivery flight in said return delivery section, said barrel means defining a degassing aperture in said return delivery section and vacuum source means communicating with said return delivery section through said degassing aperture, comprising the steps of introducing said melt into said barrel through said inlet means, extruding said melt in said barrel by rotating said screw, actuating said vacuum source means to degas said melt whereby said gas is caused to enter said return delivery section by the reduced pressure produced by said vacuum source, is caused to pass through said aperture and is discharged, said method including the additional step of mechanically separating said gas from any fused mass entrained therewith at at least one location in said return delivery section.

Claim 2

A method of extruding a fused molten mass of a thermoplastic material in a single screw extruder comprising a hollow barrel, a single screw rotatable within said hollow barrel, inlet means for introducing said melt into said barrel and melt discharge means disposed in said barrel downstream of said inlet means, said extruder including a return delivery section upstream of said inlet means, said screw including a return delivery flight in said return delivery section, said barrel means defining a degassing aperture in said return delivery section and vacuum source means communicating with said return delivery section through said degassing aperture, comprising the steps of introducing said melt into said barrel through said inlet means, extruding said melt in said barrel by rotating said screw, actuating said vacuum source means to degas said melt whereby said gas is caused to enter said return delivery section by the reduced pressure produced by said vacuum source, is caused to pass through said aperture and is discharged, said method including the additional step of mechanically separating said gas from any fused mass entrained therewith at at least one location in said return delivery section.

Claim 4

An apparatus for extruding a fused molten mass of thermoplastic material comprising hollow cylindrical barrel means, screw means rotatable in the interior of said barrel means, feed hopper means for introducing said fused mass into said barrel means and discharge means associated with said barrel means and disposed downstream of said feed hopper means for discharging said fused mass conveyed and extruded by said screw means, said screw means and said barrel means jointly forming a delivery section for said melt extending downstream from said feed hopper means to said discharge means and a return delivery section disposed upstream of said feed hopper means, said barrel, in said return delivery section, defining an aperture, and said screw means, in said return delivery section, comprising a core and a return delivery thread helically disposed around said core, vacuum source means communication with the interior of said barrel through said aperture for reducing the pressure in said barrel so as to cause degassing of said melt, means for collecting and discharging said gas removed from said melt by said reduction of pressure, and at least one means for mechanically separating any melt in said return delivery section from said gas, each said separating means including first means disposed within said barrel and extending radially towards said core of said screw in said return delivery section and second means mounted on the exterior of said barrel and acting upon said first means for adjusting the radial penetration of said first means in a direction towards said screw core.

Claim 5

An apparatus for extruding a fused molten mass of thermoplastic material comprising hollow cylindrical barrel means, screw means rotatable in the interior of said barrel means, feed hopper means for introducing said fused mass into said barrel means and discharge means associated with said barrel means and disposed downstream of said feed hopper means for discharging said fused mass conveyed and extruded by said screw means, said screw means and said barrel means jointly forming a delivery section for said melt extending downstream from said feed hopper means to said discharge means and a return delivery section disposed upstream of said feed hopper means, said barrel, in said return delivery section, defining an aperture, and said screw means, in said return delivery section, comprising a core and a return delivery thread helically disposed around said core, vacuum source means communication with the interior of said barrel through said aperture for reducing the pressure in said barrel so as to cause degassing of said melt, means for collecting and discharging said gas removed from said melt by said reduction of pressure, and at least one means for mechanically separating any melt in said return delivery section from said gas, each said separating means including first means disposed within said barrel and extending radially towards said core of said screw in said return delivery section and second means mounted on the exterior of said barrel and acting upon said first means for adjusting the radial penetration of said first means in a direction towards said screw core.