Extruder screw with improved energy efficient melting
First Claim
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1. An extruder screw with a feed end and discharge end for use in a single screw extruder that houses the screw rotatably in a cylindrical barrel for processing solid material to a molten state, the screw comprising:
- a core extending longitudinally between the feed end and the discharge end, said core having an outer surface and including an energy transfer portion;
a helical first thread formed on said core defining with said outer surface a channel for receiving material to be processed;
a helical second thread formed on said core in said channel and extending over said energy transfer portion of said core, said first thread and said second thread cooperating to divide said channel into a front sub-channel and a back sub-channel in said energy transfer portion;
said energy transfer portion having a first barrier section of a first longitudinal length in which said first thread has an outer diameter greater than an outer diameter of said second thread whereby a difference between said first thread outer diameter and said second thread outer diameter is a first barrier clearance;
said energy transfer portion having a second barrier section between said first barrier portion and said discharge end, said second barrier section having a second longitudinal length in which said second thread has an outer diameter greater than an outer diameter of said first Thread whereby a difference between said first thread outer diameter and said second thread outer diameter is a second barrier clearance; and
wherein a ratio of said first barrier clearance to said second barrier clearance is approximately inversely proportional to a ratio of said first longitudinal length to said second longitudinal length.
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Abstract
An extruder screw includes an energy transfer section divided into successive barrier sections in which a channel formed by a first thread is divided into at least two sub-channels by a second thread. A ratio of the difference in outer diameters of the threads is approximately inversely proportional to the ratio of the lengths of adjacent ones of the barrier sections.
37 Citations
20 Claims
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1. An extruder screw with a feed end and discharge end for use in a single screw extruder that houses the screw rotatably in a cylindrical barrel for processing solid material to a molten state, the screw comprising:
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a core extending longitudinally between the feed end and the discharge end, said core having an outer surface and including an energy transfer portion;
a helical first thread formed on said core defining with said outer surface a channel for receiving material to be processed;
a helical second thread formed on said core in said channel and extending over said energy transfer portion of said core, said first thread and said second thread cooperating to divide said channel into a front sub-channel and a back sub-channel in said energy transfer portion;
said energy transfer portion having a first barrier section of a first longitudinal length in which said first thread has an outer diameter greater than an outer diameter of said second thread whereby a difference between said first thread outer diameter and said second thread outer diameter is a first barrier clearance;
said energy transfer portion having a second barrier section between said first barrier portion and said discharge end, said second barrier section having a second longitudinal length in which said second thread has an outer diameter greater than an outer diameter of said first Thread whereby a difference between said first thread outer diameter and said second thread outer diameter is a second barrier clearance; and
wherein a ratio of said first barrier clearance to said second barrier clearance is approximately inversely proportional to a ratio of said first longitudinal length to said second longitudinal length. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An extruder screw with a feed end and discharge end for use in a single screw extruder that houses the screw rotatably in a cylindrical barrel for processing solid material to a molten state, the screw comprising:
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a core extending longitudinally between the feed end and the discharge end, said core having an outer surface and including an energy transfer portion;
a helical first thread formed on said core defining with said outer surface a channel for receiving material to be processed;
a helical second thread formed on said core in said channel and extending over said energy transfer portion of said core, said first thread and said second thread cooperating to divide said channel into a front sub-channel and a back sub-channel in said energy transfer portion;
said energy transfer portion having a plurality of sequential baffler sections, each of said barrier sections having an associated predetermined longitudinal length in which said first thread and said second thread have different outer diameters whereby a difference between said outer diameters is an associated barrier clearance;
wherein a ratio of said associated barrier clearance of one of said barrier sections to said associated barrier clearance of an adjacent one of said barrier sections is approximately inversely proportional to a ratio of said associated longitudinal length of said one barrier section to said associated longitudinal length of said adjacent one barrier section. - View Dependent Claims (11, 12, 13, 14, 15)
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16. An extruder screw with a feed end and discharge end for use in a single screw extruder that houses the screw rotatably in a cylindrical barrel for processing solid material to a molten state, the screw comprising:
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a core extending longitudinally between the feed end and the discharge end, said core having an outer surface and including an energy transfer portion;
a helical first thread formed on said core defining with said outer surface a channel for receiving material to be processed;
a helical second thread formed on said core in said channel and extending over said energy transfer portion of said core, said first thread and said second thread cooperating to divide said channel into a front sub-channel and a back sub-channel in said energy transfer portion, said front sub-channel and said back sub-channel each having a constant depth for less than a length of said energy transfer portion;
said energy transfer portion having a plurality of sequential barrier sections, each of said barrier sections having an associated predetermined longitudinal length in which said first thread and said second thread have different outer diameters whereby a difference between said outer diameters is an associated barrier clearance;
wherein a ratio of said associated barrier clearance of each of said barrier sections to said associated barrier clearance of a one of said barrier sections next in sequence toward the discharge end is approximately inversely proportional to a ratio of said associated longitudinal length of said each barrier section to said associated longitudinal length of said next one barrier section. - View Dependent Claims (17, 18, 19, 20)
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Specification