Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1994-05-13
2001-04-10
Dixon, Merrick (Department: 1774)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S147000, C156S169000
Reexamination Certificate
active
06214143
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to a method of and an apparatus for forming a uniform blanket of fibers and the blanket formed by the method and apparatus which is initially tubular in configuration and may be slit longitudinally and unfolded to form a blanket having fibers predominately oriented perpendicular to the longitudinal axis of the blanket.
In the manufacture of fibrous blankets using a rotary fiberization process, fibers are produced by the extrusion of a thermoplastic material, including glass and polymeric materials such as polypropylene and polyester through a large number of holes in a peripheral, annular wall of a fiberizing disc or rotor. The disc is rotated at a high rate of speed about a vertical axis causing the thermoplastic material within the disc to be extruded through the holes of the disc to form continuous fibers. The continuous fibers are issued from the holes of the disc in a substantially horizontal direction. These continuous fibers are directed downwardly toward a horizontal collection surface beneath the fiberizing disc by a substantially continuous, downwardly directed air stream which encircles the fiberizing disc. The horizontal collection surface is normally a foraminous conveyor belt passing over a suction chamber which draws air through the conveyor belt to draw the fibers onto the upper surface of the conveyor belt where a blanket of the fibers is formed. One such process of fiberization is described in connection with the manufacture of glass fibers in U.S. Pat. No. 4,058,386, issued Nov. 15, 1977, to D. H. Faulkner et al, and entitled “Method and Apparatus for Eliminating External Hot Gas Attenuation in the Rotary Fiberization of Glass (hereinafter the “386 patent”). The disclosure of this patent is hereby incorporated herein in its entirety by reference.
Several problems have been experience in the formation of fibrous blankets from substantially continuous fibers by the above referenced process. As the continuous fibers are directed downwardly toward the horizontal collection surface, the fibers twist beneath the fiberizing disc into a loosely twisted rope of fibers. In addition, the loosely twisted rope of fibers tends to snake back and forth across the moving collection surface in an irregular fashion and this results in the nonuniform, non-directional collection of the continuous fibers on the collection surface.
Accordingly, the blanket formed by this process is not uniform in thickness or density and has thin spots and/or holes which are undesirable when using the blanket as insulation or air filtration media. The problem of non-uniformity is magnified when thin blankets about one thirty-second of an inch to one inch thick are produced for air filtration or similar uses. Such blankets must have a uniform thickness and density throughout to prevent the passage of dirt or other matter through the filtration media. In addition to the above, the edges of the blanket produced by this process are irregular and this results in edge loss or scrap due to the need to trim the irregular edges from the blanket.
The blankets formed by this process are sometimes further processed by passing the blanket through a chopper to produce short length fibers (e.g. fibers from ¼ to 3 inches in length) for use in processes, such as, paper making, carding, air layering, etc. For these products, it is desired to have the short length fibers produced in the chopping operation uniform in length. With the twist imparted to the continuous fiber tow in the collection process and the irregular collection of the fibers on the collection surface to form the blanket, the orientation of the fibers in the blanket is not unidirectional. Accordingly, when the blanket is chopped to form short length fibers, the fibers vary in length and manufacturing tolerances for fiber length are difficult to maintain. Thus, it would be desirable to manufacture a blanket wherein the fibers are highly directional in their orientation to facilitate the formation of uniform length fibers in the chopping operation.
SUMMARY OF THE INVENTION
The method of the present invention forms a uniform tubular blanket of substantially continuous thermoplastic fibers. The fibers are produced on a rotary fiberizer which issues a tow of continuous thermoplastic fibers, such as polymeric or glass fibers. The tow is collected to form the tubular blanket in a low pitch spiral either directly on a vertically extending, annular collection surface surrounding the rotary fiberizer or on a foraminous backing sheet passing over the annular collection surface. Succeeding portions of the tow at least partially overlap and preferably, substantially completely overlap preceding portions of the tow as the tow is collected. The tubular blanket formed has a uniform thickness and density without thin spots or holes. In addition, the fibers of the tow remain essentially untwisted and parallel so that fibers in the blanket are directionally oriented. The tubular blanket and its foraminous backing sheet, if used, are normally slit and unfolded to form a flat blanket.
The flat blanket thus formed performs well as an air filtration media or as an insulation. The blanket is uniform in thickness having no holes or thin spots. In addition, since the lateral edges of the blanket are formed by the slitting of the tubular blanket, there is no trim loss.
The fibers of the flat blanket are not twisted and are directionally oriented extending substantially perpendicular to the longitudinal axis of the blanket. While a relatively few of the fibers may have some breakage, essentially all of the individual fibers of the blanket are continuous for and extend the width of the blanket. With its unique continuous fiber orientation, the blanket of the present invention can be further processed into short uniform length fibers by passing strips of the blanket through a conventional chopper. The strips are cut to a width that corresponds to the width of the chopper and are fed through the chopper in a direction essentially parallel to the orientation of the continuous fibers in the blanket strips. The short length fibers formed by the chopping operation are quite uniform in length.
REFERENCES:
patent: 4112159 (1978-09-01), Pall
patent: 4116738 (1978-09-01), Pall
patent: 4594202 (1986-06-01), Pall et al.
patent: 4648920 (1987-03-01), Sperber
patent: 4726901 (1988-02-01), Pall et al.
patent: 5169700 (1992-12-01), Meier et al.
patent: 5240527 (1993-08-01), Lostak et al.
patent: 5246514 (1993-09-01), Alderman et al.
patent: 5361466 (1994-11-01), Roberston et al.
Peterson Michael Dean
Robertson John Stuart
Dixon Merrick
Johns Mansville International, Inc.
Lister John D.
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