Extrusion head for producing yarns from a material which has bee

Details Extrusion head for producing yarns from a material which has bee Extrusion head for producing yarns from a material which has bee

1993-03-10

1995-07-11

Heitbrink, Tim

Plastic article or earthenware shaping or treating: apparatus

Stock pressurizing means operably associated with downstream...

Including heating or cooling means

425382R, 4253822, B29C 4712

Patent

active

054315557

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to extrusion heads for producing yarns from a thermoplastic material which is heated to form a paste, of the type comprising at least one body defining a pasty material distribution chamber above a horizontal plate perforated with extrusion apertures, the chamber being supplied with pasty material via at least one upper side feed duct extended about an axis in its terminal section connecting with the chamber.
A particularly important, although not exclusive, application of the invention is in the field of the manufacture of synthetic yarns from molten polymer.
Extrusion heads for producing synthetic yarns are already known. They comprise a body having a distribution zone for the pasty material and an extrusion chamber provided at its base with a spinning plate perforated with holes from which continuous filaments are formed. These filaments are gathered together so as to produce one or a more yarns.
The holes provided in the spinning plate can be distributed over a rectangular, triangular or annular surface.
In general the known extrusion heads further comprise a central molten polymer feed duct disposed along the axis of the extrusion head and of the yarn(s) produced.
In this type of extrusion head it is difficult, or even impossible, to introduce a central filiform component or core into the bundle of extruded synthetic filaments.
An extrusion head is also known (U.S. Pat. No. 3,307,216) which allows a body to be introduced into the bundle of filaments produced. A head of this type comprises a cylindrical body defining an annular chamber for distributing the pasty material above a perforated plate. The chamber is supplied with pasty material via an upper lateral feed duct. The body comprises a central cylindrical recess into which it is possible to introduce a component which is to be incorporated in the bundle of filaments which surround the latter after extrusion.
However, a head of this type is not without disadvantages either.
Irrespective of the path which the product takes between the introduction channel and the plate, this type of head does not allow for the presence of a pasty product of homogeneous viscosity at the plate perforated with holes through which the extruded filaments emerge, so creating differences in quality and durability in the filaments of extruded material produced.


SUMMARY OF THE INVENTION

The present invention aims to provide an extrusion head for producing yarns from a material which is heated to form a paste which meets the practical requirements better than those known hitherto, in particular in that it has a lateral pasty product supply, which in particular enables a central component to be introduced into the bundle of extruded filaments, whilst ensuring large-scale homogeneity in quality and durability in the extruded yarns produced, in a manner which is simple to perform and at low cost.
To this end, the present invention in particular proposes an extrusion head for producing yarns from a material which is heated to form a paste, of the type described above, characterized in that the distribution chamber, in the horizontal plane, has a section through which the pasty material passes downwards and which gradually decreases over at least part of the height of the chamber, in the direction towards the bottom of the feed duct, this decrease being provided so as to create over time substantially identical pressure and shearing stresses on the pasty material, between the lateral feed duct and the bottom of the chamber respectively irrespective of the path the said pasty material takes when it flows out of the lateral feed duct at the bottom of the said chamber.
In addition, in advantageous embodiments, various of the following arrangements are possible, either singly or in combination:
the chamber has a lower area in the form of a slot having a vertical section which decreases gradually in the direction away from the lateral feed duct;
if the gap between the walls in a given horizontal plane is designated by the t

REFERENCES:
patent: 3307216 (1967-03-01), Dunn et al.
patent: 3608137 (1971-09-01), Wilson
patent: 3970417 (1976-07-01), Page
patent: 4376746 (1983-03-01), Ward et al.
patent: 4842504 (1989-06-01), Bentivoglio et al.
patent: 4875846 (1989-10-01), Reinbold

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