Extrusion head

Details Extrusion head Extrusion head

1977-02-07

1978-08-22

Husar, Francis S.

Plastic article or earthenware shaping or treating: apparatus

Means providing a shaping orifice

Adjustable shaping orifice or shape imparting insert member

264209, 425381, 425467, B29D 2304

Patent

active

041085906

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

This invention generally relates to the extrusion of tubular articles. More particularly, this invention relates to an extrusion head for controlling the eccentricity or concentricity of an extruded tubular article. Specifically, this invention relates to such an extrusion head wherein a portion of the head itself is physically deflected to give the desired control of article concentricity.
In the extrusion of tubular articles, such as pipe, from molten material, such as thermoplastic, a continuing problem is control of the concentricity of the finished product. It is undesirable to have a final product which exhibits wall thickness variations when viewed in cross section. To this end, U.S. Pat. No. 3,923,439 purposes the use of movable slides within the extrusion head to compensate for concentricity variations in the output product. This system, while effective, requires a complex and expensive internal mechanism for the extrusion head. I have found that the concentricity of an output tubular article can be adequately controlled by physically deflecting part of the extrusion head with respect to a fixed extrusion mandrel over which the molten material is formed into the final tubular article.


SUMMARY OF THE INVENTION

My invention resides in a new extrusion head being designed to allow control of the concentricity of an extruded tubular article. In the method of operation, a rear flange portion of a generally spool shaped die member, having a bore through a hub portion thereof, is attached to an extrusion material source means. A mandrel is placed in the bore to thereby define an annular space between the inner wall of the bore and the outer surface of the mandrel. Material is flowed through the annular space to form a tubular article. The forward flange portion and the hub portion are deflected relative to the mandrel as is required to maintain a constant wall thickness for the tubular article.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side, elevational view, partially in cross-section, of the extrusion head of the present invention; and
FIG. 2 is a rear, elevational view of the extrusion head of the present invention.


DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an extrusion die 10 which contains the provisions of the present invention for controlling the diameter of the output product. The die 10 illustrated in FIG. 1 is designed to allow production of tubular or pipe like thermoplastic products. The die 10 is actually made in several sections which are fastened together by welding or bolting as is commonly known in the art. However, the die 10 could be made as a unitary article if so desired. The basic configuration of the die 10 includes a forward flange portion 12 and a rear flange portion 14 which are connected together by a connecting hub portion 16. The basic configuration thus obtained of the extrusion die 10 is a somewhat spool shaped member which contains an internal annular bore 18 defined by internal sidewalls 20. Inserted into the bore 18 is an extrusion mandrel or core pin 22. The mandrel 22 may be the type known in the art. The mandrel 22 and die 10 generally define an extrusion head. The result of the insertion of the mandrel 22 into the bore 18 is to define a constricted annular portion or space between the inner sidewalls 20 of the bore 18 and the outer surface 26 of the mandrel 22. This annular space controls the diameter of a tubular product which is extruded through the die 10. By adjustment of the spacing between the sidewalls 20 and the outer surface 26, tubular thermoplastic products of varying internal and external diameter can be produced using the same basic die 10 and mandrel 22. The mandrel 22 is supported near the rear portion of the bore 18 by a spider 28 which connects the mandrel 22 to the internal sidewalls 20. Thermoplastic material will flow around the spider 28 and then reweld itself before issuing from the die 10. The terms "forward" and "rear" which have been used refer to the general path of flow of thermoplastic

REFERENCES:
patent: 2765153 (1956-10-01), Gielow et al.
patent: 2998624 (1961-09-01), Ricketts
patent: 3382539 (1968-05-01), Zehr

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