EP0034505A2
Expired / Lapsed
EP
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Plasticizing screw
Assignee: W H WILLERT Inc
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Filing: 1981-02-19
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Granted: —
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Expires: 2001-02-19
Abstract
Abstract The invention relates to plasticizing screws for use in screw extruders. A problem with known screws and extruders is that the quality and uniformity of the extrudate is poor, with implasticised material being encapsulated in the melt. The screw shown has a first flight (33,37) which extends through a feed section (35) and a plasticizing section (40), and a second flight (36) which extends through the plasticizing section. The flights define a feed channel (34), a solids channel (39) and a melt channel (38). The solids channel (39) has an initial depth greater than the depth of the feed channel (34) and receives any solid material from the feed channel. Thereafter, the depth of the solids channel is reduced, and the diameters of the flights allow plasticized material to pass from the solids channel to the (39) melt channel (38).
Inventors
- 👤 William H. Willert
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 17:31
CPC Classifications
B; B29; B29C; B29C48/00; B29C48/25; B29C48/36; B29C48/50; B29C48/505; B29C48/64; B29C48/65; B29B; B29B7/00; B29B7/30; B29B7/34; B29B7/38; B29B7/40; B29B7/42; B29B7/428; B29B7/429; B29C48/53; B29C48/535; B29C48/03
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
360 words
An extruder screw for use in a plastic extruder including a feed hopper and a heated barrel, said screw comprising a feed section, aplasticizincr section and a metering section and having (a) a primary flight with leading and trailing edges conforming to a substantially uniform pitch over the entire length of said screw, the primary flight forming a feed channel at the inlet end of said screw and having a diameter which is selectively reduced at the beginning of the plasticizing'section to become the barrier flight and restored to its original diameter approximately one turn prior to the reaching the end of the plasticizing section, and (b) a secondary flight formed behind said primary flight at the beginning of the plasticizing section, the secondary flight being generated at a lesser pitch than said primary flight for a predetermined number of turns and until it reaches a predetermined position in the channel of the primary flight and continuing beyond that point at a uniform pitch parallel to the primary flight for the length of the plasticizing section, thereby forming a secondary channel behind said primary flight, the diameter of said secondary flight being equal to that of the primary flight in the feed section and maintained thereat until nearly the last turn in the plasticizing section at which point it is reduced, the primary flight being also restored to its original diameter at that point, the depth of the feed channel in the plasticizing section being progressively reduced until it approaches the last turn thereof, the depth of the secondary channel being progressively increased so that plastic feed will flow as it is plasticized from the feed channel and be collected in said secondary channel, and at approximately the last turn in the plasticzing section the diameter o: the secondary flight is reduced and becomes the barrier flight, the primary flight being restored to its original diameter and the secondary channel being decreased in depth concurrently with the increase in depth of the primary channel, thereby permitting flow of material from the secondary channel back into the primary channel and establishing a metering channel over the final length of the screw.
Claim 2
Dependent Claim
360 words
An extruder screw for use in a plastic extruder including a feed hopper and a heated barrel, said screw comprising a feed section, aplasticizincr section and a metering section and having (a) a primary flight with leading and trailing edges conforming to a substantially uniform pitch over the entire length of said screw, the primary flight forming a feed channel at the inlet end of said screw and having a diameter which is selectively reduced at the beginning of the plasticizing'section to become the barrier flight and restored to its original diameter approximately one turn prior to the reaching the end of the plasticizing section, and (b) a secondary flight formed behind said primary flight at the beginning of the plasticizing section, the secondary flight being generated at a lesser pitch than said primary flight for a predetermined number of turns and until it reaches a predetermined position in the channel of the primary flight and continuing beyond that point at a uniform pitch parallel to the primary flight for the length of the plasticizing section, thereby forming a secondary channel behind said primary flight, the diameter of said secondary flight being equal to that of the primary flight in the feed section and maintained thereat until nearly the last turn in the plasticizing section at which point it is reduced, the primary flight being also restored to its original diameter at that point, the depth of the feed channel in the plasticizing section being progressively reduced until it approaches the last turn thereof, the depth of the secondary channel being progressively increased so that plastic feed will flow as it is plasticized from the feed channel and be collected in said secondary channel, and at approximately the last turn in the plasticzing section the diameter o: the secondary flight is reduced and becomes the barrier flight, the primary flight being restored to its original diameter and the secondary channel being decreased in depth concurrently with the increase in depth of the primary channel, thereby permitting flow of material from the secondary channel back into the primary channel and establishing a metering channel over the final length of the screw.
Claim 3
Dependent Claim
15 words
A plasticizing screw as claimed in Claim 1 for use in a reciprocating screw extruder.
Claim 4
Dependent Claim
204 words
An extruder screw having a feeding section and a plasti zing section, comprising a first flight which extends through the feeding and plasticizing sections,a second flight which extends through the plasticizing section,a feeding channel defined by the leading and trailing edges of the first flight in the feeding section, a solids channel extending through said plasticizing section, defined by the trailing edge of one of said flights which has a predetermined diameter and by the leading edge of the other of said flights which has a diameter which is less than the diameter of said one of said flights, said solids channel having an initial depth which is greater than the depth of the feed channel and said solids channel is in communication with said feed channel to receive solid material therefrom, and a melt channel extending through said plasticizing section, defined by the trailing edge of one of said flights which has a predetermined diameter and by the leading edge of the other of said flights which has a diameter which is greater than the diameter of said one of said flights and said melt channel is adapted to receive plasticized material passing over said one of said flights from the solids channel.
Claim 5
Dependent Claim
204 words
An extruder screw having a feeding section and a plasti zing section, comprising a first flight which extends through the feeding and plasticizing sections,a second flight which extends through the plasticizing section,a feeding channel defined by the leading and trailing edges of the first flight in the feeding section, a solids channel extending through said plasticizing section, defined by the trailing edge of one of said flights which has a predetermined diameter and by the leading edge of the other of said flights which has a diameter which is less than the diameter of said one of said flights, said solids channel having an initial depth which is greater than the depth of the feed channel and said solids channel is in communication with said feed channel to receive solid material therefrom, and a melt channel extending through said plasticizing section, defined by the trailing edge of one of said flights which has a predetermined diameter and by the leading edge of the other of said flights which has a diameter which is greater than the diameter of said one of said flights and said melt channel is adapted to receive plasticized material passing over said one of said flights from the solids channel.
Claim 6
Dependent Claim
29 words
An extruder screw as claiemd in Claim 3 wherein said first flight has a diameter in the plasticizing section which is less than its diameter in said feeding section.
Claim 7
Dependent Claim
19 words
An extruder screw as claimed in Claim-3 or Claim 4 wherein the depth of said solids channel gradually diminishes.
Claim 8
Dependent Claim
23 words
An extruder screw as claimed in Claim 3, or Claim 4 or Claim 5 wherein the depth of said melt channel gradully increases.
Claim 9
Dependent Claim
39 words
An extruder screw as claimed in any one of Claims 3 to 6 wherein the second flight in the plasticizing section has a diameter which is substantially equal to the diameter of the first flight in the feeding section.
Claim 10
Dependent Claim
65 words
An extruder screw as claimed in any one of Claims 3 to 7 wherein the diameter of said one of said flights is reduced for at least one turn of the flight at the end of the plasticizing section and the diameter of said other of said flights is inreased for at least one turn of the flight at the end of the plasticizing section.
References Cited (Backward Citations)
No citation records indexed.
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