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US 4,501,498 AGranted
Method and apparatus for extruding thermoplastic material
AssigneeLuwa AG
InventorJames M. McKelvey
Life of this patent
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AssigneeLuwa AG
InventorJames M. McKelvey
Estimating the term…
A gear pump assisted screw conveyor extrusion system utilizing a cartridge heating device disposed axially within the screw and having the drives for the gear pump and the screw correlated in speed to create relatively little pressure in the thermoplastic material being extruded such that relatively little mechanical working thereof occurs. The thermoplastic material is melted in the screw conveyor primarily by heat transfer from the cartridge heater and the gear pump is utilized for conveying the melted material under pressure to a subsequent work station. A relatively deep material-conveying spiral channel is provided in the screw for maximized extrusion output per revolution of the screw and minimized mechanical energy generation by the screw. A motionless mixer may be employed intermediate the screw and the work station to homogenize the melted material for reducing temperature gradients therein. The system advantageously is capable of extruding material at a substantially greater rate and a lower material temperature and with substantially increased power economy than conventional systems utilizing a high pressure, externally heated screw conveyor portion.
In a method of extruding thermoplastic material comprising passing said material successively through an extruder having rotating conveying screw means and a rotary gear pump, the improvement comprising operating said extruder and said pump at selected compatible speeds respectively to convey said thermoplastic material through said extruder with relatively little material pressurization in said extruder at said gear pump for relatively little heat generating mechanical working thereof while heating said material by conduction from said screw means to melt said material in said extruder primarily by heat transfer and to convey said melted material by said gear pump under pressure to a subsequent working station, whereby said material is extruded at a substantially greater rate and with substantially increased power economy and energy efficiency than without said selected operating or said heating from said screw means.
In an apparatus for extruding thermoplastic material comprising an extruder having rotating conveying screw means in combination with a rotary gear pump, the improvement comprising heating means disposed interiorly within said screw means for heating said material by conduction therefrom and operating means compatibly arranging said screw means and said gear pump for rotating at selected relative speeds for conveying said material through said extruder with relatively little material pressurization in said extruder at said gear pump for relatively little heat generating mechanical working thereof thereby to melt said material in said extruder primarily by heat transfer from said heating means and for conveying said melted material by said gear pump under pressure to a subsequent work station, whereby said material is extruded at a substantially greater rate and with substantially increased power economy and energy efficiency than without said heating means or said operating means.
Dependencies are inferred from the claim text.