Meltblown die tip with capillaries for each counterbore

Details Meltblown die tip with capillaries for each counterbore Meltblown die tip with capillaries for each counterbore

2000-07-25

2003-06-17

Davis, Robert (Department: 1722)

Plastic article or earthenware shaping or treating: apparatus

Means providing a shaping orifice

Plural distinct feed inlets

C425S38200R

Reexamination Certificate

active

06579084

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to die heads for extruded filaments and particularly die heads for extruding meltblown fabrics.
2. Discussion of the Related Art
A general overview of meltblown polymer filament technology may be had by referring to U.S. Pat. No. 3,825,380 (Harding et al.).
Generally a single deep polymer-distribution channel is formed in the die head and multiple capillaries are drilled in the so-called “knife edge”, or extrusion edge of the die tip to contact the distribution channel and provide the extrusion channels and orifices for the fine, or small, diameter, meltblown fibers. The reader is also referred to U.S. Pat. No. 4,486,161 (Middleton) and U.S. Pat. No. 4,013,816 (Sabee et al.).
The words “fibers” and “filaments” will be used interchangeably in this specification.
However, owning to physical constraints of the die head, such as the requirement for a fine edge at the point of extrusion, there have always been tradeoffs between extrusion pressure and meltblown die capillary density in the meltblown die head. Ideally the maker of meltblown fabrics would prefer to have options for utilizing both higher pressures and greater capillary density than were previously available from prior art designs.
SUMMARY OF THE PRESENT INVENTION
In order to accomplish the object of higher die head pressures and greater capillary, or extrusion orifice, density in a meltblown fiber die head, the present invention provides a die head with bores communicating with a central polymer distribution channel and running in the extrusion direction to communicate with multiple capillaries. At least some, or all, of the bores will have multiple capillary extrusion outlets. By distributing multiple capillaries to a bore, more metal may be retained in the die head thereby allowing higher pressures in the extrusion process while permitting higher capillary density.
It is anticipated that the die tip of the present invention will withstand extrusion pressures that would cause other seals in the die head assembly to fail, resulting in no practical pressure limit on the die tip of the present invention.


REFERENCES:
patent: 3825380 (1974-07-01), Harding et al.
patent: 4013816 (1977-03-01), Sabee et al.
patent: 4242075 (1980-12-01), Higuchi et al.
patent: 4486161 (1984-12-01), Middleton
patent: 4887957 (1989-12-01), Ohta et al.
patent: 4934916 (1990-06-01), Lambertus
patent: 6120276 (2000-09-01), Balk
patent: 6164950 (2000-12-01), Barbier et al.

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