US3701512A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Screw extruder for processing thermoplastic materials
Assignee: Oerlikon Barmag AG
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Filing: 1971-04-07
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Granted: 1972-10-31
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Expires: 1991-04-07
Abstract
Abstract A screw extruder for processing thermoplastic materials, e.g. high molecular weight polymers, in which the spiral worm passage formed by a conveying screw is subdivided into two compartments of different and oppositely varying cross-section by an intermediate shearing screw having a radial clearance from the extruder barrel housing of at least twice that of the conveying screw, the thread depth in each subdivision or compartment of the worm passage being continuously varied over the length of the screw between maximum and minimum values, thereby causing a predetermined flow of thermoplastic material across the flight land of the shearing screw.
Inventors
- 👤 Heinz Schippers
- 👤 Friedhelm Hensen
- 👤 Erich Lenk
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 01:53
CPC Classifications
B; B29; B29C; B29C48/00; B29C48/25; B29C48/36; B29C48/50; B29C48/505; B29C48/64; B29C48/65; B29C48/03
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
202 words
In a screw extruder for continuously processing a thermoplastic material wherein screw means are provided to convey said thermoplastic material consecutively through a feed section, a transItion section and a metering section along said screw which is revolved within an elongated extruder barrel housing while melting and mixing the conveyed material, the improvement which comprises: an elongated screw core shaft housed in at least one of said transition and metering sections, said screw core shaft bearing a primary conveying screw in which the thread flight extends radially outwardly to provide a small clearance s between its outer peripheral edge and the interior cylindrical wall of the barrel housing, thereby defining a continuous helical worm passage, said screw core shaft further bearing a secondary shearing screw in which the thread flight extends continuously in a helical path centrally of the worm passage defined by the conveying screw and radially outwardly to a peripheral flight land which is approximately parallel to and spaced inwardly at a distance of at least about 2s from the interior cylindrical wall of the barrel housing, the depth of thread on each side of the shearing screw being continuously and oppositely altered in the direction of worm passage length.
Claim 2
Dependent Claim
202 words
In a screw extruder for continuously processing a thermoplastic material wherein screw means are provided to convey said thermoplastic material consecutively through a feed section, a transItion section and a metering section along said screw which is revolved within an elongated extruder barrel housing while melting and mixing the conveyed material, the improvement which comprises: an elongated screw core shaft housed in at least one of said transition and metering sections, said screw core shaft bearing a primary conveying screw in which the thread flight extends radially outwardly to provide a small clearance s between its outer peripheral edge and the interior cylindrical wall of the barrel housing, thereby defining a continuous helical worm passage, said screw core shaft further bearing a secondary shearing screw in which the thread flight extends continuously in a helical path centrally of the worm passage defined by the conveying screw and radially outwardly to a peripheral flight land which is approximately parallel to and spaced inwardly at a distance of at least about 2s from the interior cylindrical wall of the barrel housing, the depth of thread on each side of the shearing screw being continuously and oppositely altered in the direction of worm passage length.
Claim 3
Dependent Claim
39 words
A screw extruder as claimed in claim 1 wherein the depth of thread varies oppositely on each side of the shearing screw and alternately increases and decreases between a minimum and maximum value over the length of the screw.
Claim 4
Dependent Claim
38 words
A screw extruder as claimed in claim 2 wherein said alternation of thread depth occurs at a screw length of not less than about one-half the diameter of the conveying screw for thermoplastic melts of relatively low viscosity.
Claim 5
Dependent Claim
39 words
A screw extruder as claimed in claim 2 wherein said alternation of thread depth occurs at a screw length of not less than about ten times the diameter of the conveying screw for thermoplastic melts of relatively high viscosity.
Claim 6
Dependent Claim
47 words
A screw extruder as claimed in claim 2 wherein at each alternation of thread depth over the length of the screw, the conveying screw is reduced in diameter to become the shearing screw while the shearing screw is simultaneously increased in diameter to become the conveying screw.
Claim 7
Dependent Claim
92 words
A screw extruder as claimed in claim 1 wherein that portion of the worm passage behind the shearing screw, with reference to the conveying direction, is continuously varied from a maximum to a minimum thread depth while that portion of the worm passage in front of the shearing screw is continuously varied from a minimum to a maximum thread depth, the total cross-sectional area of the worm passage remaining constant such that thermoplastic material is continuously passed over said shearing screw from the back to the front portion of the worm passage.
Claim 8
Dependent Claim
33 words
A screw extruder as claimed in claim 6 wherein the variation between maximum and minimum thread depth in each portion of the worm passage is repeated alternately over the length of the screw.
Claim 9
Dependent Claim
62 words
A screw extruder as claimed as claim 7 wherein at each alternate repetition of thread depth variation, the conveying screw is converted into the shearing screw while the shearing screw is simultaneously converted into the conveying screw such that thermoplastic material flows substantially only from the back to the front portion of the worm passage over the entire length of the screw.
Claim 10
Dependent Claim
29 words
A screw extruder as claimed in claim 1 wherein the width of the flight land of the shearing screw is larger than the flight land of the conveying screw.
Claim 11
Dependent Claim
41 words
A screw extruder as claimed in claim 1 wherein said screw core shaft contains a plurality of radially projecting pins on the helical base of the worm passage between adjacent screws in at least one of said transition and metering sections.
Claim 12
Dependent Claim
44 words
A screw extruder as claimed in claim 1 wherein the flight lands of at least one of said conveying screw and said shearing screw are transversely slotted at predetermined positions to vary the flow of thermoplastic material between adjacent worm passages or subdivisions thereof.
Claim 13
Dependent Claim
40 words
A screw extruder as claimed in claim 1 wherein said worm passage is enlarged at the discharge end of Said screw to provide a substantially longer retention time per unit length of screw as compared to the preceding processing sections.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-10-31 | 1976-05-01 | 1976-10-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-31 | 1980-05-01 | 1980-10-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-31 | 1984-05-01 | 1984-10-31 | $7700.00 | Window Closed / Lapsed |