Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – With prevention of equipment fouling accumulations or deposits
Reexamination Certificate
1998-04-10
2001-01-09
Davis, Robert (Department: 1722)
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
With prevention of equipment fouling accumulations or deposits
C210S448000, C210S497010, C210S497300, C425S198000, C425S382200, C425S464000
Reexamination Certificate
active
06171536
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to apparatus and method for extrusion of synthetic polymeric material into filaments and, more particularly, to the filtration of polymeric material in molten form during extrusion.
In the conventional manufacturing of synthetic textile yarn, a polymer, such as polyester, is basically prepared in a molten state and extruded under pressure through one or more spinning units, commonly referred to as “spin packs,” each equipped with a spinneret formed with multiple fine openings through which the molten polymer is extruded in elongate continuous filamentary form. Typically, the multiple filaments emitted from the spinneret openings are collected into a bundle, forming a tow, which is subsequently collected in a can or like container.
Regardless of the care taken to ensure the purity and homogeneity of the molten polymeric material delivered to the spinning units, the polymer material nevertheless will often include minute gelled particles of the polymer of unusually high molecular weight as well as other solid contaminants. As such if such contaminants are not removed prior to extrusion through the spinneret, the fine orifices in the spinneret can become clogged, and further, any such contaminants passing through the spinneret can produce weakened locations in the resultant filament. Hence, it is common practice to provide a polymer filter medium within each spinning unit to perform a final filtration step immediately in advance of extrusion through the spinneret.
In conventional spinning units, the extrusion orifices are commonly arranged in a circular or otherwise annular array with the body of the spinning unit being formed with a corresponding annular passageway opening into direct communication with the spinneret orifices. An annular screen is fitted within the downstream end of the passageway to extend upstream into the passageway with the portion of the passage on the upstream side of the screen being filled with sand or a similar filtering material. Thus, the molten polymer entering the annular passageway must follow a torturous path through and about the sand or other filter material to reach the screen at which the polymer flows inwardly through the screen and therefrom to the spinneret. The screen thereby serves not only to assist in filtration of the polymer but also to prevent the filter material from flowing with the polymer into the orifices of the spinneret.
While such polymer filtration arrangements function satisfactorily to substantially remove most contaminants from the molten polymer, the use of sand or a similar filter material as a filtration medium complicates the fabrication of the spin packs as well the periodic cleaning and maintenance thereof. Further, the screens typically used to retain the filter material in place separated from the spinnerets are typically fabricated of two circular pieces of screen affixed along annular abutting edges by an impervious binder clip, which produces the additional disadvantage of creating a stagnant area of polymer in the area surrounding the binder clip. The rate and efficiency of polymer throughput is accordingly affected.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide an improved means and methodology of filtering molten polymer in melt spinning of filaments. A more particular object of the present invention is to provide an improved filtering means and method in which the use of loose filter material as a filtering medium can be eliminated. A further object of the invention is to provide an improved filter screen configuration for use in spin packs for melt spinning, which will provide increased filter area in comparison to conventional filter screens of the type described above.
Briefly summarized, the foregoing objectives are provided in the present invention by a novel apparatus and method for melt spinning of molten polymeric material into filaments utilizing a filter having a substantially continuous screen wall of a generally U-shaped configuration which defines an open end, a merged end and an interior material receiving area. The polymeric material is conveyed by suitable means through the open end and into the interior area of the filter and outwardly therefrom through the screen wall, for delivery of the filtered polymeric material to, and for extrusion through, plural openings in a downstream spinneret communicating with the filter.
In a preferred embodiment, the apparatus and method are embodied in a spin pack assembly having a pack body defining an essentially vertical annular passageway for flow of polymeric material downwardly therethrough. The screen wall of the filter is annular with a generally U-shaped axial cross-section, the filter being disposed in essentially vertical disposition within the annular passageway with the open end facing upwardly and the merged end facing downwardly, for receiving the polymeric material through the open upper end and into the interior material receiving area of the filter. The spinneret is affixed directly to the pack body with its multiple filament extrusion openings in an annular arrangement for communicating directly with the annular passageway to receive the filtered polymeric material.
REFERENCES:
patent: 2288532 (1942-06-01), Knapp
patent: 2747741 (1956-05-01), Jacobson
patent: 2802574 (1957-08-01), Schweppe
patent: 2865511 (1958-12-01), Hopkins, Jr.
patent: 3628930 (1971-12-01), Harris
patent: 3794164 (1974-02-01), Ginaven
patent: 3948767 (1976-04-01), Chapman
patent: 3948768 (1976-04-01), Chapman
patent: 4126560 (1978-11-01), Marcus et al.
patent: 4260350 (1981-04-01), Russell, Jr.
patent: 4341726 (1982-07-01), Wilkes
patent: 4382861 (1983-05-01), Adeboi et al.
patent: 4437986 (1984-03-01), Hutchins et al.
patent: 4512731 (1985-04-01), Cobb
patent: 4655919 (1987-04-01), Schafft
patent: 4804510 (1989-02-01), Luecke et al.
patent: 5092999 (1992-03-01), Valenzuela et al.
patent: 5259955 (1993-11-01), Bolton
patent: 5453193 (1995-09-01), Maher et al.
Goodall J. Richard
Novak William O.
Arteva North America S.a.r.l.
Clements Gregory N.
Davis Robert
Leyson Joseph
LandOfFree
Apparatus and method for melt spinning of molten polymeric... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method for melt spinning of molten polymeric..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method for melt spinning of molten polymeric... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2451717