Split extrusion die assembly for thermoplastic materials and methods of using the same

A die spool assembly for extrusion of thermoplastic materials comprising plural die spools coaxially coupled to one another so as to define an extrusion axis, each said die spool including:

• an elongate spool body including means which allow separation of said spool body into first and second spool segments mateable with one another along a longitudinal plane which intercepts said extrusion axis, said first and second spool segments thereby collectively establishing said spool body;
• said first and second spool segments also collectively including means defining an extrusion cavity extending along said extrusion axis between opposing ends of said spool body;
• said spool body including boss means at one of said ends, and means defining a recess at the other of said ends, said boss means and recess defining means for respectively mateably engaging said boss means and said recess defining means of another die spool in said assembly;
• and
• alignment means for ensuring that said defined extrusion cavity of said die spool is exactly aligned with said extrusion cavity of said another die spool in said assembly mateably engaged therewith.

A thermoplastic extrusion apparatus comprising, in combination:

• extruder means for fluxing a thermoplastic material and for discharging molten thermoplastic extrudate through a discharge end thereof;
• and
• a die spool assembly having an inlet end coupled to said discharge end for receiving said thermoplastic extrudate from said extruder means, and an outlet end opposite to said inlet end thereof, said die spool assembly between said inlet and outlet ends establishing an extrusion cavity oriented along an extrusion axis;
• said die spool assembly including a plurality of die spools coupled one to another coaxially relative to said extrusion axis, wherein each said die spool of said die spool assembly comprises an elongate spool body including means which allow separation of said spool body into first and second spool segments which are mateable with one another along a longitudinal plane which intercepts said extrusion axis, said first and second spool segments thereby collectively establishing said spool body;
• and wherein,
• said die spool assembly further comprises temperature control means in heat exchange relationship with at least preselected ones of said die spools for establishing a decreasing temperature gradient between said inlet and discharge ends thereof within said extrusion cavity of said die spool assembly through which said thermoplastic extrudate is conveyed, thereby to at least partially solidify said thermoplastic extrudate upon its being discharged from said outlet end of said die spool assembly.

A method of forming extruded thermoplastic products comprising the steps of:

• (a) extruding a molten thermoplastic material through an extrusion die so as to form a product preform having a preselected cross-sectional geometry;
• (b) supporting a length of said product preform on a portion of an extrusion cavity defined by a lower segment of a die spool by coupling said lower die spool segment to said extrusion die;
• (c) positioning a remaining portion of said extrusion cavity defined by an upper segment of said die spool in mated relationship with said first mentioned portion of said lower die spool segment, by bringing said upper and lower die spool segments into mated relationship with one another while said product preform length is being supported by said lower spool segment;
• and then
• (d) effecting temperature control of said product preform within said extrusion cavity collectively established by said mated upper and lower die spool segments by controlling temperature within said extrusion cavity through which said product preform is conveyed, wherein
• step (a) is practiced continually so as to allow said length of product preform to increase by being conveyed beyond a downstream end of said die spool, and wherein the method further comprises the steps of;
• (e) supporting said increased length of said product preform on a portion of an extrusion cavity defined by a lower segment of a second die spool by coupling said second lower die spool segment to said first mentioned lower die spool segment;
• and then
• (f) positioning a remaining portion of said extrusion cavity defined by an upper segment of said second die spool in mated relationship with said extrusion cavity portion of said second lower die spool segment, by bringing said second upper and lower die spool segments into mated relationship with one another.

A die spool assembly for extrusion of thermoplastic material along a predetermined extrusion axis and adapted to being coupled operatively to a discharge end of an extruder, said die spool assembly comprising a number of die spools coaxially coupled end-to-end along said extrusion axis, wherein each said die spool includes:

• an elongate die spool body including means which allow separation of said spool body into first and second spool segments mateable with one another along said extrusion axis;
• said first and second die segments collectively including means defining an extrusion cavity for shaping said thermoplastic material;
• and
• coupling means associated with said spool body for mateably coupling said die spool end-to-end along said extrusion axis with another said die spool in said assembly.

A die spool assembly as in claim 42, wherein said coupling means includes;

• boss means at one end of said die spool;
• and
• means defining a recess at an opposite end of said die spool;
• said boss means and said recess defining means for respectively mateably engaging said boss means and said recess defining means of said another die spool in said assembly mateably coupled therewith.

A method of forming extruded thermoplastic products comprising the steps of:

• (a) extruding a molten thermoplastic material through an extrusion die so as to form a produce preform having a preselected cross-sectional geometry;
• (b) supporting a length of said product preform on a portion of an extrusion cavity defined by a lower segment of a die spool by coupling said lower die spool segment to said extrusion die;
• (c) positioning a remaining portion of said extrusion cavity defined by an upper segment of said die spool in mated relationship with said first mentioned portion of said lower die spool segment, by bringing said upper and lower die spool segments into mated relationship with one another while said product preform length is being supported by said lower spool segment, wherein
• step (a) is practiced continually so as to allow said length of product preform to increase by being conveyed beyond a downstream end of said die spool, and wherein the method further comprises the steps of;
• (e) supporting said increased length of said product preform on a portion of an extrusion cavity defined by said portion of an extrusion cavity defined by a lower segment of a second die spool by coupling said second lower die spool segment to said first mentioned lower die spool segment;
• and then
• (f) positioning a remaining portion of said extrusion cavity defined by an upper segment of said second die spool in mated relationship with said extrusion cavity portion of said second lower die spool segment, by bringing said second upper and lower die spool segments into mated relationship with one another.