Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Patent
1993-05-18
1997-03-25
Seidleck, James J.
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
428 3691, 428 3692, 428131, 4283044, 4253823, 425382N, 4253761, 264167, 26417716, 2642092, 26417317, B29D 2300, B29D 2800
Patent
active
056142765
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
This invention is concerned with the extrusion of sheets of plastics or other extrudable materials and in particular the invention relates to the manufacture by extrusion of non-uniform sheet materials, i.e., materials which are not of a constant thickness or are of heterogeneous composition, and which term is used herein to include lattice structures of connected filaments, perforated sheets, and sheets incorporating thickness variations or filaments for reinforcement. Furthermore, "sheet material" should be understood to include non-planar forms, such as cylinders, tubes and other sections besides generally flat layers.
In accordance with the invention there is provided an apparatus for extruding non-uniform sheet material comprising die means including a first part at least partly delimiting extrusion orifice means around an axis, and a second part arranged to cooperate with the first part at the orifice means, and drive means for imparting relative movement between the first and second die parts whereby the second part undergoes a rocking motion progressing along at least part of a generally circular path around the axis relative to the first part and thereby the second part influences the extrusion emanating from each section of the orifice means in a periodic manner.
In order to achieve the relative movement of the first and second parts of the die means, the first part, the second part, or both parts may be driven by the drive means.
The first and second parts may have surfaces which cooperate to define the orifice means. In this case the first and second parts provide inner and outer annular die surfaces, which may be arranged to extrude several continuous filaments spaced apart from each other, and to co-extrude by the relative rocking motion transverse filament sections interconnecting and spaced apart along the continuous filaments. The simultaneously extruded transverse and longitudinal continuous filaments can be substantially perpendicular to each other.
In another construction the first die part defines the extrusion orifice means and the second part controls the flow of material through the orifice means or acts on the material flowing out through the orifice means to vary the extrusion obtained from each element or section of the orifice means about the axis. Thus, the second part may, as a result of the rocking motion, open and close an extrusion slot extending about the axis so that flow through the slot is alternately allowed and interrupted and a transverse or helical filament is produced, or the second part may partially open and close an extrusion slot extending about the axis so that the thickness of the sheet extruded therethrough is varied. Alternatively, the second part may be adapted to produce holes in the extruded sheet by temporarily closing off segments of the extrusion orifice to block flow therethrough, or by stamping holes in the extruded sheet.
Moveable members for controlling or varying flow of molten material through annular extrusion slots have been known for many years, but these members are reciprocated, which is a disadvantage from the point of view of operating smoothness and possibly speed. It is also known to extrude filaments between die members which are rotated relative to each other, but the extrusion openings obtained exhibit lozenge-like shapes which can be undesirable. By employing a rocking motion, i.e., a combined pitching and rolling movement without relative rotation of the first and second parts, in accordance with the present invention, smooth continuous high speed operation is facilitated. The invention also offers greater versatility than the prior art, especially regarding the different forms of extrusion which can be manufactured. One novel form of extrusion which can be produced comprises a sheet of material with continuous longitudinal filaments on one side thereof and transverse filaments on the other side thereof, the filaments on at least one side being of a material, e.g. polypropylene, different to
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Hellenic Plastics and Rubber Industry Memelaos Petsetakis, S.A.
Seidleck James J.
Williamson Michael A.
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