Metal-extrusion press

Details Metal-extrusion press Metal-extrusion press

2000-06-13

2001-05-22

Tolan, Ed (Department: 3725)

Metal deforming

By extruding through orifice

Utilizing internal forming means

C072S253100, C072S462000

Reexamination Certificate

active

06233997

ABSTRACT:

FIELD OF THE INVENTION
Our present invention relates to a metal-extrusion press, particularly a tube and billet press of the type in which a press ram is hydraulically actuated to drive a billet through the die and a piercing mandrel within the ram is actuatable to form a passage through the extruded material in the production of extruded tubing.
BACKGROUND OF THE INVENTION
In metal-extrusion processes of the type wherein a billet of a material such as aluminum or copper is extruded by a press ram through a die and a piercing mandrel is displaceable within that ram to form a passage in the extruded product in the production of extruded metal tubing, it is common for the hollow press ram to be carried by a traveling beam which serves to receive and guide the piercing mandrel which passes through the press ram. That piercing mandrel is normally carried by a traverse which itself is guided in the traveling beam and which, in turn, is connected to a piercing piston which can be guided or disposed in part in the main press piston coupled with the traveling beam.
In the production of tubing from, for example, extrudable metals like aluminum and copper by extrusion press methods, both direct and indirect extrusion presses are used. The direct press is, however, the predominant apparatus for this purpose. An important characteristic of the direct extrusion press is that the die and the receiver are fixed with respect to one another. By contrast, in an indirect extrusion press, the die penetrates into the receiver. The die then has a hollow ram fitted at its head with a die holder carrying the die. On one side the receiver is sealed by a closure member.
The billet and tube press of this type and the pressing programs for operating same with a variety of materials are described for example in “Sonderdruck aus Zeitschrift für Metallkunde 51 (1960) 2, pages 3 to 10”.
In the operation of such direct or indirect billet and tubing presses it has been found that the traveling beam during production, because of the axial pressing forces, is stressed in compression. This gives rise to a spreading or bulging at approximately the center of the two opposite side walls of the frame-like traveling beam. Since the piercing mandrel traverse is guided between these side walls, it is almost impossible in practice to prevent a shift in the position of the traverse off center. With such shifting of the guide surfaces for the traverse, the passage formed in the product tends to be eccentric and narrow fabrication tolerances of the tubing produced cannot be effectively maintained.
OBJECTS OF THE INVENTION
It is, therefore, the principal object of the present invention to provide a billet and tubing press of the type described which is free from the drawbacks noted.
More specifically it is an object of the invention to provide a billet and tubing extrusion press whose fabrication tolerances can be maintained in spite of compressive stresses on the traveling beam.
It is also an object of the invention to provide a billet and tubing extrusion press which has a reduced tendency toward eccentricity of the piercing mandrel.
SUMMARY OF THE INVENTION
These objects and others which will become apparent hereinafter are attained, in accordance with the invention, by narrowing the cross sections of the side walls or frame members of the traveling beam, especially toward the exterior so that the minimum beam wall cross section is located generally centrally of the lengths of the side walls guiding the traverse carrying the piercing mandrel.
It has been found, quite surprisingly, that such narrowing or reduction in the cross section of the side walls toward the center from the ends of the side wall portions guiding the mandrel-carrying traverse reduces dramatically the spread of the side wall under compression and thereby the eccentricity which can develop for the traverse and the piercing mandrel itself.
More particularly, a metal-extrusion press of the invention can comprise:
an extrusion die;
a hollow press ram movable toward said die;
a traveling beam elongated in a direction of displacement of said hollow press ram, carrying said hollow press ram and movable toward and away from said die;
a piercing mandrel extending through said hollow press ram and carried by a traverse guided in said traveling beam, said traveling beam having side walls framing said traverse on opposite sides thereof over a path of said traverse in said traveling beam; and
a main piston acting upon said traveling beam for displacing same toward said die, said side walls having recessed exteriors and being of a cross section diminishing from each end toward an intermediate region whereby, upon longitudinal stressing of said traveling beam for extrusion of a billet eccentricity of said ram is reduced.
The traveling beam is shaped using the finite-element method “FEM” and tests have shown that by reducing the cross section of the side walls and especially by imparting to the outer contour of the side wall a curvilinearly-concave shape, i.e. a concave outward configuration, the spread or outward bulging of these side walls can be significantly reduced. This is the opposite of what would be expected since it has hitherto been thought that the best way to avoid outward spread or bulging or deformation generally was to make a wall thicker or more massive. The reduced thickness side walls of the invention, under compressive stress, have been found to provide practically straight-line generatrices or guide surfaces for the traverse along the interior of the traveling beam over practically the entire stroke of the traverse and range of compressive forces applied to the traveling beam.
The exterior of the traveling beam has a concave outer contour which continuously receives from either end of the side wall in terms of the length of travel within the beam of the traverse. The curvature of the concavity can follow a circular arc, a catenary or a similar curve. It may, however, also conform to a polygon defined by a multiplicity of straight line segments.


REFERENCES:
patent: 5511450 (1996-04-01), Nagao
patent: 5855135 (1999-01-01), Howe
patent: 5878616 (1999-03-01), Kulakov et al.
patent: 62-57713 (1987-03-01), None
“Hydraulische Horizontale Strang-Und Rohrpressen”; Walter Dohrn et al; DK621.774.385.82; 8 pages.

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