Plastic article or earthenware shaping or treating: apparatus – Stock pressurizing means operably associated with downstream... – Including restriction upstream of shaping orifice and...
Reexamination Certificate
1998-03-17
2001-03-27
Pyon, Harold (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Stock pressurizing means operably associated with downstream...
Including restriction upstream of shaping orifice and...
C425S19200R, C425S461000
Reexamination Certificate
active
06206680
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to extrusion dies, and more particularly to apparatus for controlling material flow through the die.
BACKGROUND ART
Extrusion processes have long been used to produce sheets or webs of formable material, such as thermoplastic. These processes generally involve forcing a viscous material through a die typically comprising an inlet, a cavity, and an exit. As the material passes through the die, it is often necessary to influence the flow to obtain a product at the die exit having desirable characteristics.
Past methods of influencing material flow have included the use of a flow control device mounted in a channel within a die cavity, such as a restrictor bar, a flexible membrane, or another insert. Since most extrusion processes operate under high pressure, leakage of material into spaces between the insert and the channel is a significant concern. Build-up of material in the channel can prevent proper flow control and result in burning of material therein. Hence, the channel and insert must be designed and machined to tolerances that will ensure a tight sealing fit and thereby prevent leakage.
The assignee of the instant application currently offers for sale a die having a flexible membrane mounted by spaced mounting members in correspondingly-shaped tapered channels in the die cavity. Bolts extend into the mounting members and are tightened to cause the members to seal against walls forming the tapered channel. End surfaces of the membrane are clamped between body members of the die to form a seal between the die and the membrane.
While this arrangement of elements is effective to accomplish flow control, some drawbacks are encountered. Specifically, the installation process is complicated and expensive. Further, machining of the tapered channels is difficult to accomplish with the required degree of precision and is not well suited (due to the channel configuration) to large-scale production techniques. In addition, re-working of such a die would likely result in a substantial amount of refitting of the flow control device in the channels. Manufacture of an aftermarket flow control device without the original tooling would also be problematic. Furthermore, clamping the end surfaces of the membrane can restrict adjustment of the membrane which, in turn, can make it more difficult to achieve a desired flow control.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a flexible membrane for an extrusion die is provided. The membrane includes a horizontal portion, first and second curved portions adjacent the horizontal portion, a first offset portion adjacent the first curved portion, and a second offset portion adjacent the second curved portion. The membrane also includes a first edge adjacent the first offset portion, opposite the first curved portion, and a second edge adjacent the second offset portion, opposite the second curved portion. The membrane is formed of a single piece of material.
According to another aspect of the present invention, a method of producing a flow control device for an extrusion die is provided. The method includes the steps of fabricating a membrane holder from a material, fabricating a flexible membrane from the same material, joining the flexible membrane to the membrane holder, and hardening the membrane holder and membrane.
Other advantages of the invention will be apparent to those skilled in the art from the following detailed description taken in conjunction with the drawings and the appended claims.
REFERENCES:
patent: 2975475 (1961-03-01), Heston
patent: 3377655 (1968-04-01), Kucharski et al.
patent: 3850568 (1974-11-01), Bartha et al.
patent: 3884611 (1975-05-01), Anderson et al.
patent: 4055389 (1977-10-01), Hayward
patent: 4293517 (1981-10-01), Knox
patent: 4372739 (1983-02-01), Vetter et al.
patent: 4411614 (1983-10-01), Feathers
patent: 4521359 (1985-06-01), Tsien
patent: 4533308 (1985-08-01), Cloeren
patent: 4619802 (1986-10-01), Cloeren
patent: 4695236 (1987-09-01), Predöhl et al.
patent: 4778367 (1988-10-01), Hilakos
patent: 4861536 (1989-08-01), Graf et al.
patent: 4892473 (1990-01-01), Elia et al.
patent: 4922192 (1990-05-01), Gross et al.
patent: 4990079 (1991-02-01), Lorenz
patent: 5066435 (1991-11-01), Lorenz et al.
patent: 5067432 (1991-11-01), Lippert
patent: 5094792 (1992-03-01), Baran
patent: 5149481 (1992-09-01), Gross et al.
patent: 5242742 (1993-09-01), Funk et al.
patent: 5256052 (1993-10-01), Cloeren
patent: 5273420 (1993-12-01), Gross et al.
patent: 5275547 (1994-01-01), Brown
patent: 5286436 (1994-02-01), Funk et al.
patent: 5401454 (1995-03-01), Mendel
patent: 5460761 (1995-10-01), Larsson
patent: 5494429 (1996-02-01), Wilson et al.
patent: 5512237 (1996-04-01), Stigenberg
patent: 5516273 (1996-05-01), Delmore et al.
patent: 5516474 (1996-05-01), Cloeren
patent: 5529730 (1996-06-01), Gross
patent: 5542836 (1996-08-01), Gross et al.
patent: 5587184 (1996-12-01), Leonard et al.
patent: 5608637 (1997-03-01), Wang et al.
patent: 5626888 (1997-05-01), Sänze et al.
patent: 5788998 (1998-08-01), Gross
patent: 2032257 (1991-06-01), None
patent: 2054889 (1992-05-01), None
patent: 11 25 146 (1962-03-01), None
patent: 44 00 069 (1995-04-01), None
patent: 295 14 043 U (1995-11-01), None
patent: 195 35 930 (1997-01-01), None
patent: 0 484 721 (1992-05-01), None
patent: 59-114027 (1984-06-01), None
patent: 95/18711 (1995-07-01), None
patent: WO 98/57792 (1998-12-01), None
Patent Abstract of Japan, vol. 008, No. 234 (M-334), Oct. 26, 1984 and JP 59 114027 A (Mitsubishi Jukogyo KK), Jun. 30, 1984.
Extrusion Dies, Inc.
Leyson Joseph
Marshall O'Toole Gerstein Murray & Borun
Pyon Harold
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