US3929322A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Multiscrew extruder
Assignee: Mannesmann Demag Krauss Maffei GmbH
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Filing: 1974-03-29
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Granted: 1975-12-30
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Expires: 1994-03-29
Abstract
Abstract An extruder has a housing formed with an axial passage and a relatively large-diameter central screw in the passage. A plurality of small-diameter outer screws angularly spaced within the passage about the central screw mesh therewith. The outer screws form outer flow passages of substantially smaller volume and the screw thread of the central screw forms central flow passages of larger volume than where these screws had geometrically complementary threads. The central screw and the outer screws are rotated in opposite senses at the same peripheral speed. In this manner the synthetic-resin material plasticized in the extruder exits from the extruder at the same temperature both in the region of the outer screws and the central screw. The axial length of the screw threads can be different, the gap between their flanks can be different, or the radial gap between their crowns and roots can be different so as to effect this difference in volume.
Inventors
- 👤 Wilhelm Hanslik
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 05:53
CPC Classifications
B; B29; B29C; B29C48/00; B29C48/25; B29C48/36; B29C48/395; B29C48/40; B29C48/425; B29C48/435; B29C48/44; B29C48/50; B29C48/505; B29C48/59; B29C48/03
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
162 words
In an extruder for thermoplastic synthetic resin having a plurality of parallel auxiliary screws each formed with a respective auxiliary screw thread, and a central screw parallel to said auxiliary screws and formed with a respective central screw thread meshing with said auxiliary threads at meshing zones, said central thread defining a plurality of main flow passages between said zones and said auxiliary threads defining a plurality of auxiliary flow passages outside the respective zones, the improvement comprising: means for rotating all of said screws about their axes with the same peripheral speed, said central and auxiliary screws having respective crown cylinders, the sum of the diameters of said crown cylinders of said auxiliary screws being substantially equal to the diameter of said crown cylinders of said central screw and the ratio of profile areas of the threads of the auxiliary screws to that of the threads of the central screw is in an inverse proportion of the ratio of their lengths.
Claim 2
Dependent Claim
162 words
In an extruder for thermoplastic synthetic resin having a plurality of parallel auxiliary screws each formed with a respective auxiliary screw thread, and a central screw parallel to said auxiliary screws and formed with a respective central screw thread meshing with said auxiliary threads at meshing zones, said central thread defining a plurality of main flow passages between said zones and said auxiliary threads defining a plurality of auxiliary flow passages outside the respective zones, the improvement comprising: means for rotating all of said screws about their axes with the same peripheral speed, said central and auxiliary screws having respective crown cylinders, the sum of the diameters of said crown cylinders of said auxiliary screws being substantially equal to the diameter of said crown cylinders of said central screw and the ratio of profile areas of the threads of the auxiliary screws to that of the threads of the central screw is in an inverse proportion of the ratio of their lengths.
Claim 3
Dependent Claim
74 words
The extruder defined in claim 1 wherein said screw threads of said auxiliary screws are stepped inwardly at least outwardly of pitch cylinders of said auxiliary screws, whereby the axial gap between the flanks of said screw threads of said auxiliary screws and the flanks of the screw thread of said central screw is greater outside the pitch cylinders of said auxiliary screws in the region of mesh of said central and auxiliary screws.
Claim 4
Dependent Claim
62 words
The extruder defined in claim 1 wherein said screw threads of said auxiliary screws of said central screw have respective root cylinders, the root cylinder of said central screw being spaced from the crown cylinders of said auxiliary screws by a distance equal to the spacing of the crown cylinder of said central screw from the root cylinders of said auxiliary screws.
Claim 5
Dependent Claim
32 words
The extruder defined in claim 1 wherein the axial length of said threads of said auxiliary screws is generally 20% shorter than the axial length of said screw of said central screw.
Claim 6
Dependent Claim
63 words
The extruder defined in claim 1 wherein said screw threads of said auxiliary screws and of said central screw have respective root cylinders, the root cylinder of said central screw being spaced from the crown cylinders of said auxiliary screws by a distance greater than the spacing between the crown cylinder of said central screw and the root cylinders of said auxiliary screws.
Claim 7
Dependent Claim
15 words
The extruder defined in claim 3 wherein said screw threads are of substantially rectangular section.
Claim 8
Dependent Claim
49 words
The extruder defined in claim 5 wherein said distance between said root cylinder of said central screw and said crown cylinders of said auxiliary screws is generally 50 percent greater than the spacing between the crown cylindeR of said central screw and the root cylinders of said auxiliary screws.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-12-29 | 1979-06-30 | 1979-12-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-12-29 | 1983-06-30 | 1983-12-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-12-29 | 1987-06-30 | 1987-12-30 | $7700.00 | Window Closed / Lapsed |