Plastic and nonmetallic article shaping or treating: processes – With step of cleaning – polishing – or preconditioning...
Reexamination Certificate
2000-03-20
2001-08-07
Heitbrink, Tim (Department: 1722)
Plastic and nonmetallic article shaping or treating: processes
With step of cleaning, polishing, or preconditioning...
C425S197000, C425S198000, C425S199000, C425S559000
Reexamination Certificate
active
06270703
ABSTRACT:
BACKGROUND
Generally, polymer injection molding machines include an elongate barrel with a bore extending therethrough. A powered elongate screw is housed within the bore of the barrel. Rotation of the screw within the bore plasticizes and melts polymer pellets fed into the bore from a hopper. In an injection stroke, forward translation of the screw relative to the bore forces a shot of accumulated molten polymer from the bore for injection into a mold.
In some instances, a filter assembly is positioned at the end of the barrel for filtering contaminants from the molten polymer as the polymer is forced in a shot from the bore by the forward translation of the screw. The filter assembly can include a mechanism which removes contaminated filter elements from the polymer flow path and then repositions clean filter elements back into the flow path. A drawback of such a filter assembly is that filtering the molten polymer during the injection stroke of the screw results in a very high flow rate of polymer through the filter assembly which increases resistance to the injection stroke as well as the time required to perform the injection stroke. In addition, the filter elements usually require handling by the machine operator, which, depending upon the design of the filter assembly, can be unwieldly. Previous attempts to position a purgable filter within the barrel to filter polymer prior to the injection stroke in order to avoid these problems require special channels formed within the barrel for purging contaminants from the filter. Such channels can be difficult to manufacture.
SUMMARY OF THE INVENTION
The present invention includes a filtration apparatus for an injection molding machine where the injection molding machine includes a screw housed within a bore for generating molten polymer. The filtration apparatus filters molten polymer prior to but not during the injection stroke of the screw and does not require any changing of filter elements or special channels in the barrel, thereby avoiding the problems discussed above.
In the present invention filtration apparatus, a tip member extends axially from the screw within the bore. The tip member has radially extending upstream and downstream flanges positioned axially apart from each other. A filter encircles the tip member for filtering contaminants from the molten polymer. An annular ring member encircles the tip member and is slidably positioned within the bore between the upstream and downstream flanges. The ring member is capable of slidably engaging the downstream flange of the tip member for directing the molten polymer through the filter which then accumulates within the bore. The ring member is also capable of slidably engaging the upstream flange for preventing back flow of the molten polymer past the upstream flange when forcing a shot of accumulated molten polymer from the bore with forward translation of the screw. An end stop is positioned within the bore and is capable of engaging and preventing movement of the ring member past the end stop while allowing the downstream flange of the tip member to be translated forwardly therepast to simultaneously space the upstream and downstream flanges apart from the ring member. This allows the molten polymer to bypass the filter for purging contaminants filtered from the molten polymer.
In preferred embodiments, the tip member includes an intermediate shaft portion between the upstream and downstream flanges. A series of first recesses encircle the intermediate shaft portion and extend longitudinally along the intermediate shaft portion between the flanges. A series of second recesses also encircle the intermediate shaft portion starting from a position spaced from the upstream flange and extending longitudinally along the intermediate shaft portion and then through the downstream flange. The first and second recesses are arranged on the intermediate shaft portion in an alternating fashion. Each first recess is laterally separated from a second recess by a ridge. Each ridge includes a series of recesses or slots formed through an outer edge of the ridge in a comb-like fashion which forms a filter element of the filter for filtering molten polymer flowing from the first recesses into the second recesses. The downstream flange is generally conical shaped and becomes narrower moving in the downstream direction. The upstream flange is formed by an annular member mounted at an upstream end of the intermediate shaft portion. The end stop includes an annular ring extending into the bore and the tip member is mounted to the screw.
REFERENCES:
patent: 1163740 (1915-12-01), Cohoe
patent: 1595470 (1926-08-01), Johnson
patent: 2257067 (1941-09-01), Parsons
patent: 2374468 (1945-04-01), Opel
patent: 2636218 (1953-04-01), Orsini
patent: 2653351 (1953-09-01), Henning
patent: 2770836 (1956-11-01), Hankey
patent: 2864126 (1958-12-01), Henning
patent: 2895167 (1959-07-01), Paggi
patent: 3335461 (1967-08-01), Schwartz
patent: 3495299 (1970-02-01), Chazal et al.
patent: 3578741 (1971-05-01), Blumer
patent: 3710988 (1973-01-01), Moslo
patent: 4077756 (1978-03-01), Meadors
patent: 4112516 (1978-09-01), Hotz
patent: 4174198 (1979-11-01), Kinoshita
patent: 4177234 (1979-12-01), Lowry
patent: 4191648 (1980-03-01), Kaplan et al.
patent: 4257901 (1981-03-01), Rapp
patent: 4332541 (1982-06-01), Anders
patent: 4358262 (1982-11-01), Herbert
patent: 4434053 (1984-02-01), Osuna-Diaz
patent: 4477242 (1984-10-01), Eichlseder et al.
patent: 4486304 (1984-12-01), Neuman et al.
patent: 4511472 (1985-04-01), Trott
patent: 4512733 (1985-04-01), Eichlesder et al.
patent: 4627916 (1986-12-01), Dörsam
patent: 4661249 (1987-04-01), Langley
patent: 4714422 (1987-12-01), Meeker et al.
patent: 4849113 (1989-07-01), Hills
patent: 4966539 (1990-10-01), Pena
patent: 5122286 (1992-06-01), Kreyenborg et al.
patent: 5141631 (1992-08-01), Whitman
patent: 5151025 (1992-09-01), Müller
patent: 5246660 (1993-09-01), Tsutsumi
patent: 5417866 (1995-05-01), Trott
patent: 5456828 (1995-10-01), Tersi et al.
patent: 5462653 (1995-10-01), Hills
patent: 5507498 (1996-04-01), Trott
patent: 5510030 (1996-04-01), Bacher et al.
patent: 5587076 (1996-12-01), Herzog
patent: 5618423 (1997-04-01), Lin
patent: 5783223 (1998-07-01), Anderson
patent: 6113380 (2000-09-01), Hara
patent: 2524746 A1 (1976-12-01), None
patent: 2541738 C3 (1977-03-01), None
patent: 4426629A1 (1996-02-01), None
patent: 0172925 (1986-03-01), None
patent: 1272329 (1961-08-01), None
patent: 1553319 (1968-12-01), None
patent: 2324443 (1977-04-01), None
patent: WO 90/03879 (1990-04-01), None
Trott Delano B.
Wildman Paul D.
Dynisco Extrusion, Inc.
Hamilton Brook Smith & Reynolds PC
Heitbrink Tim
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