Metal deforming – With temperature modification of tool or of specified... – Of tool
Reexamination Certificate
1998-01-02
2001-07-24
Larson, Lowell A. (Department: 3725)
Metal deforming
With temperature modification of tool or of specified...
Of tool
C072S349000
Reexamination Certificate
active
06263718
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The technical field of the invention is a forming method for sheet met al cans made from aluminum or steel sheet or a combination of said both materials, said method being called “ironing”. Said sheets may as well be provided with an additional functional co a ting (e. g. lamination or coat of varnish). In this technical field, ironed can bodies are obtained which in a closing process may be provided with can ends to obtain closed cans.
In said technical field, it is an object of the invention to reduce tool wear and to simultaneously save material.
SUMMARY OF THE INVENTION
According to the invention, this object is achieved by using at least one of a heated or a cooled punch and a heated or a cooled ram and heated or cooled ironing rings and heated or cooled process and supporting agents. Cooling or heating of said punch, ram, ironing rings and process and supporting agents may be controlled externally as well as by providing the ram, punch or ironing rings with an integrated heating or cooling means (claim
1
,
4
). The dimensions of the ironing tool are alterable by its temperature.
With a known tool temperature THETA
st
and a defined (i.e., selected) tool configuration (given clearance between ironing mandrel and ring), the ironed can presents a defined distribution of the wall thickness. A defined (controlled) heating or cooling of the tools results in an expansion or shrinkage, respectively, of the ironing mandrel and ring and a defined change of said clearance, thus achieving a controllable wall thickness or a change in the wall thickness distribution depending on the selected controlled temperature. Thus, according to the invention, the tool geometry is altered by influencing the temperature, which influence is principally avoided by prior art using a substantially constant cooling agent.
The present invention succeeds in compensating temperature influences and tool wear occurring during operation of an ironing press. Without said compensation, raising the cycle numbers of ironing machines would not be possible. Besides, the service life of each ironing tool is markedly prolonged, since tool wear may be compensated without being forced to use new tools. Said compensation permits longer-term usability of the same tool and, despite wearing of the tool material (mostly: hard metal), production of an ironed can with constant wall thicknesses remaining the same for a long term.
According to the invention, both, the forming behavior during forming of a seam and the forming behaviour during reducing the upper can edge diameter (“reduced neck” or “necking”) are improved.
During trimming, material waste may be reduced. Also, the trimming process of the upper can edge may be improved with regard to accuracy.
By an additionally possible diminuation tightening of the window of dimensional tolerance, which can be effected for each reduction of the sheet thickness of a basic metal sheet, the thickness of the remaining wall portion of the can may—if using the invention—be reduced during necking of the upper can portion. According to prior art, diameter variation during reduction of the upper can portion from a main diameter to a reduced upper diameter (“necking”) impedes a further reduction of the wall thickness.
The invention permits such an improvement in favor of material savings.
For compensating tool wear by using temperature influences, the invention uses a physical effect which, according to prior art, was undesired and avoided. In fact, prior art also uses cooling agents and lubricants which, with respect to the environment, present an elevated or reduced temperature; however, said temperature being at a constant level in order to avoid a change of a tool geometry as now intended by the invention. The can wall thickness is measured in contact or contactless and may be controlled by tracking or adjustment or may be “feedbackcontrolled” to remain at constant values, by altering the temperature of the tools (claim
9
).
REFERENCES:
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patent: 5277047 (1994-01-01), Herdzina
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patent: 6055230 (1994-03-01), None
Brandis/Funke, Nutzung des Kaltverfestigungsverhaltens nichtrostender Stahle beim Tiefziehen durch gezielte Temperaturfuhrung, pp. 75-86.
VDI nachrichten, Nr. 21/27. Mai 1977, S. 8-10.
Fertigungsmethoden fur Konservendosen. In: Technische Rundschau, Bern, Nr. 34, Aug. 21, 1979, S. 19, 21.
Hoffmann,: Herstellung von Konserven- und Getrankedosen, Handbuch der fertigungstechbnik, Bd. 2/3, S. 1224, 1225.
Buse Dieter
Grandmann Willi
Duane Morris & Heckscher LLP
Larson Lowell A.
Schmalbac Lubeca AG
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