Plastic article or earthenware shaping or treating: apparatus – With apparatus assembly or dismantling means or with idle part – Including support or guide means for disassembled element
Patent
1994-01-13
1996-11-19
Woo, Jay H.
Plastic article or earthenware shaping or treating: apparatus
With apparatus assembly or dismantling means or with idle part
Including support or guide means for disassembled element
26417112, 26417126, 425191, 425192R, 425381, 425464, 425466, B29C 4706, B29C 4726
Patent
active
055760325
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an extrusion die for use in the extrusion of thermoplastics material tube.
BACKGROUND ART
Profiled rigid or semi-rigid thermoplastics material tube is used for a number uses such as for electrical conduit and for drainage tube. It is frequently desirable or necessary to use profiled tube for strength reasons. The tube may be profiled as single walled corrugated tube, double walled corrugated tube, ribbed tube, or sometimes smooth walled tube may be used. Any ribs or corrugations on the tube may be helical or annular. Often, the molding and profiling is done by extruding a parison of extrudate into a travelling mold tunnel into which an elongate extrusion nozzle from an extrusion die extends to direct a parison of thermoplastic material against an inner wall of the mold tunnel.
The extrusion nozzle is usually different for different purposes. For example, an extrusion nozzle which is suitable for use with a travelling mold tunnel structured to mold ribbed tube, may be considerably different than one intended for other purposes. Moreover, it may be preferable for at least some purposes, for example the molding of ribbed tube, that the exit angle of the extrusion nozzle be 450 or more. For the molding of double walled corrugated tube, it may be desirable to provide a splitter to divide the flow of extrudate from the extrusion die into two coaxial streams. Many other variations are sometimes required.
To make the above-mentioned variations in the structure of the extrusion nozzle and, indeed, various other modifications, it has been necessary to dismantle the apparatus and change the extrusion nozzle at the point of its connection to the extrusion die. Shutting down of the production line is required and considerable time may be involved in the changing of the equipment.
SUMMARY OF THE INVENTION
It has now been discovered that it is possible to provide a single extrusion nozzle body which is adaptable to a variety of different extrusions by means of a plurality of end pieces.
According to the invention, there is provided an extrusion die system for use in the extrusion of thermoplastics material profiled tube, comprising: a die body having an elongate extrusion nozzle extending therefrom, the extrusion nozzle having a single annular channel therethrough between an inner and outer sleeve, an inner core extending out of the extrusion die body to beyond a distal end of the outer nozzle sleeve; the core having an upstream portion extending from the die body forming an upstream part of the inner surface and a downstream portion of reduced diameter stepped from the upstream portion through a step housed within the outer nozzle sleeve, a number of interchangeable end fittings for the nozzle, each end fitting comprising an annular sleeve to fit about the downstream portion of the core within the outer nozzle sleeve and abutting the step to extend the inner surface of the nozzle flush with the upstream portion of the core; each end fitting being provided with at least one diverging guide surface to direct extrudate from the extrusion nozzle to diverge from the annular sleeve of the end fitting.
The mandrel sleeve or a hollow core within the mandrel sleeve suitably extends, on the one hand, upstream into and beyond the die body and, on the other hand, downstream and beyond the extrusion nozzle. The hollow core or extended inner sleeve may be utilized to carry services such as gas to blow mold the extrusion when it exits from the extrusion nozzle or cooling fluid or suction for utilization at the surface of a cooling plug or various other services. Frequently, the tube being molded is molded in a travelling mold tunnel or other form of mold into which the exit end of the extrusion nozzle extends. In conventional apparatus, any interchange of parts to re-configure the exit channel of an extrusion nozzle may be extremely complex involving dismantling of the extrusion nozzle within or at the die body and replacement with a completely different extrusion nozzle. The invention
REFERENCES:
patent: 3994646 (1976-11-01), Hauck
patent: 4712993 (1987-12-01), Lupke
patent: 4770618 (1988-09-01), Lupke
patent: 4936768 (1990-06-01), Lupke
patent: 5023029 (1991-06-01), Lupke
patent: 5123827 (1992-06-01), Lupke
patent: 5296188 (1994-03-01), Lupke
Leyson Joseph
Woo Jay H.
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