Plastic article or earthenware shaping or treating: apparatus – Means feeding fluent stock from plural sources to common... – Extrusion shaping means
Patent
1991-05-13
1994-08-30
Chiesa, Richard L.
Plastic article or earthenware shaping or treating: apparatus
Means feeding fluent stock from plural sources to common...
Extrusion shaping means
26421123, 425132, 4251331, 425204, 4253761, 425462, 425465, B29C 4704, B29C 4710
Patent
active
RE0347116
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The subject of the present invention is a device for feeding an extrusion head for plastic material.
Devices of this kind, already known, are used especially for fabricating by extrusion elongated products of plastic material presenting a colored surface layer.
It is usual to use two method for that:
1. Master-batches of colors are added to the mass of plastic material,
2. An additional extruder is used, which deposits a colored surface skin around the extruded shape.
The second method has the advantage of saving on the coloring agents since only a thin layer of the extruded product is colored.
The object of the present invention is to improve the feed devices already known, in order to apply the second method described above by achieving an instantaneous change of color without waste of material.
To this end, the device according to the invention is characterized in that is comprises a main extruder connected to a main die and a feed means associated with the main die and capable of being selectively controlled so as to cover the exit flow of the main die with a surface layer formed of successive segments, the appearance of which differs.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the subject of the invention will be described below, by way of example, referring to the appended drawing, in which:
FIG. 1 is a schematic top plan view showing an extrusion installation equipped with the device according to the invention,
FIG. 2 is a sectional view on a horizontal plane showing on a larger scale the extrusion head and its different feed orifices,
FIG. 3 is a sectional view along the line III--III of FIG. 2, and
FIG. 4 is a perspective view, partially cut away, of a length of a section of plastic material fabricated by the device of FIGS. 1 to 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The installation depicted in FIG. 1 is intended for the continuous production of a section of plastic material, for example, a bar, or a tube, the cross-section of which may have any shape. It comprises a main extruder 1 provided with a feed hopper 2 and driven by a motor 3 having a reduction gear 4. Mounted at the end of the cylinder of this extruder 1 is an extrusion head 5, the details of which are visible in FIG. 2. On the other hand, this extrusion head 5 is connected to an auxiliary twinscrew [extruded] extruder 6 provided at its rearward end with two feed hoppers 7 and 8. As is seen in FIG. 2, the auxiliary extruder 6 comprises two parallel cylindrical bores 9 and 10, in each of which a screw 11 or 12 rotates. These screws are driven by a single speed-reduction gear 13 from a single motor 14, ensuring that the two screws constantly rotate at the same speed. As the dimensions of the screws are the same, the flows of plastic material formed in the two cylinders 9 and 10 are of the same rate and reach the exit orifices 15 and 16 of the extruder 6 in the same state of fluidity and compression.
FIG. 2 further shows the structure of the extrusion head 5. Mounted in the cylindrical die body 17 are a main die 18, supported by a die holder 19 and, in front of the die body 17, an auxiliary die 20 supported by a die holder 21 and fixed by a nut 22, the die holder being itself secured to the body 17 by a nut 23. The die 18 is fed at the rear of the extrusion head through the die holder 19 in a conventional manner. Thus, a direct connection of the die holder to the outlet of the cylinder of the extruder 1 is provided for.
The auxiliary extruder 6 is connected to the extrusion head 5 by ducts which form two paths, these pass through a multiple-way valve 24, the body 25 of which is fixed to the end of the body of the extruder 6 in such a way as to be able to feed the head 5 laterally. The multiple-way valve 24 comprises a cylindrical valve needle 26. At one end, this valve needle is provided with a prolongation of square cross-section (FIG. 3) permitting it to be rotated about its axis through an angle of 120.degree. in order to effect the conversion of the colors, as will b
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Chiesa Richard L.
Nokia-Maillefer SA
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