Metal deforming – By extruding through orifice – With product handling
Patent
1989-03-17
1991-02-26
Larson, Lowell A.
Metal deforming
By extruding through orifice
With product handling
B21C 3502
Patent
active
049952536
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATION(S)
This United States application stems from PCT International application Ser. No. PCT/DE88/00439 filed Jul. 18, 1988.
BACKGROUND OF THE INVENTION
The introduction of a mechanized take-up operation for billets produced in an extrusion or tube-making press gave rise to the requirement of limiting the tractive force which is exerted on the billet and keeps the latter straight so as to prevent any effect on the formation of the billet in the die (DE-PS 484 649). If billets are produced which either cannot or are not intended to be wound up, it is usual to provide a table after the press which receives the emerging billets and guides them during extrusion, with support surfaces, which are as flat as possible, being provided to prevent distortion of the billets during cooling. Owing to the risk of thin billets buckling and the reaction of the shear force on the formation of the billet in the die, resulting in compression of the emerging billet, it is usual to use take-up device consisting of carriages which are moved along the table by a traversing drive and provided with grippers which grip the tips of the emerging billets. However it has to be ensured that the tractive force exerted on a billet by a take-up device does not affect the formation of the billet in the die by causing a contraction in area of the emerging billet. In order to meet the demand for increasingly closer tolerances of the cross-sectional dimensions of the billets, the traversing drives, together with the measurement and control of the tractive force to be exerted on the billets, have been improved in numerous proposals with the result that, by means of a more accurate and direct measurement of the tractive force at the grippers and specially developed tranversing drives, the smallest possible tractive force, which is constant within narrow limits, is sufficient to keep the billets straight and prevent compressive forces from arising in the billet.
BRIEF SUMMARY OF THE INVENTION
An object aim of the invention is to improve the cross-sectional tolerances of the extruded billets taken up from an extrusion press by minimizing the tractive force in the billet, which acts in the area of the die and affects the formation of the billet. In this respect the invention is based on the knowledge that, as the distance between the billet and the die increases, the former may be subjected to an increasing tractive force throughout as a result of cooling, without changes in cross section taking place. According to the invention, when the billet is taken up by a controlled tractive force which does not affect the formation of the billet and keeps the billet straight, the procedure is such that a tractive force (pull-away force) which increases in proportion to the extruded billet length and allows for the unit length weight and coefficient of friction between the billet and the delivery table is superimposed upon a tractive force (take-up force) which is adapted to the cross section and the flow behavior in the die. As the tractive force is increased in accordance with the frictional resistance, which increases with the extruded length, the tractive force in the area of the die can be kept at a constant minimum value which is sufficient to keep the billet straight.
A particular difficulty within the scope of the object and solution according to the invention lies in determining with sufficient accuracy the magnitude of the respective tractive force to be superimposed upon the base value. While the respective length of the extruded billet can be continuously measured in a known manner, the coefficient of friction in particular is subject to considerable variations, which are dependent on the operating conditions, so that a particular and essential further object of the invention is to accurately determine the respective specific frictional force. The procedure according to the invention for achieving this object is such that after each billet has been separated and withdrawn from the die, the force required fo
REFERENCES:
patent: 4635459 (1987-01-01), Elhaus
Groos Horst
Schutte Karl-Heinz
Larson Lowell A.
SMS Hasenclever GmbH
SMS Sutton, Inc.
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