Metal deforming – By application of fluent medium – or energy field – With actuated tool engaging work
Reexamination Certificate
2002-01-10
2003-09-23
Jones, David B. (Department: 3725)
Metal deforming
By application of fluent medium, or energy field
With actuated tool engaging work
C072S347000, C072S351000
Reexamination Certificate
active
06622539
ABSTRACT:
This is a continuation of International Application No. PCT/EP01/02795, with an International filing date of Mar. 13, 2001, published in German under PCT Article 21(2) which is incorporated herein by reference in its entirety and for all purposes.
BACKGROUND OF THE INVENTION
The present invention relates to a deep-drawing method, with which a drawn part is arranged in a deep-drawing die between a first deep-drawing die part and a second deep-drawing die part and is formed by way of relative movement of the deep-drawing die parts in relation to one another.
Such deep-drawing methods are known from the state of the art.
In particular, deep-drawing methods with rigid deep-drawing die parts are known, with which the drawn part is drawn by a drawing punch into a drawing member (also called a female die), wherein the edge of the drawn part can be held securely by means of a drawing ring.
In order to achieve the desired, final configuration of the drawn part, it is often necessary to form the drawn part in several consecutive drawing processes (also called operations).
In this respect, there is, however, the problem that the structure of the material of the drawn part will be solidified during the first drawing process such that it no longer has sufficient fluidity for an additional drawing process which can lead to the formation of cracks during the additional drawing process.
If the material of the drawn part is steel, martensite is formed, in particular, during the first drawing process and this reduces the formability of the drawn part during an additional deep-drawing process.
In the case of the known, multiple operation deep-drawing methods, the required formability of the drawn part is therefore established again following the first deep-drawing process in that the drawn part is annealed at a temperature of approximately 1050° C., wherein the martensite, in particular, which has been formed during the first deep-drawing process, is converted into austenite which can be formed more easily.
If more than two deep-drawing processes follow one another, the annealing of the drawn part will possibly have to be repeated after each deep-drawing process.
On account of the annealing, cooling and washing processes required prior to each additional drawing process, the known, multiple operation deep-drawing methods require considerable time and energy.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a deep-drawing method of the type described at the outset which—particularly when carrying out several consecutive drawing processes—is more time- and energy-saving than the known deep-drawing methods.
The present invention relates, in addition, to a deep-drawing die, comprising a first deep-drawing die part and a second deep-drawing die part, in which a drawn part can be formed by way of relative movement of the deep-drawing die parts in relation to one another.
A further object underlying the present invention is to provide such a deep-drawing die, with the aid of which drawn parts—in particular within the scope of a multiple operation deep-drawing method—can be formed in a more time- and energy-saving manner than with known deep-drawing dies.
These objects are accomplished in accordance with the invention, in a deep-drawing method using cooperating deep-drawing die parts, in that a pressure variable with time during the drawing process is generated selectively at a limited pressure section of one of the deep-drawing die parts, this pressure pressing a section of the drawn part, which abuts on the pressure section, against the other deep-drawing die part.
The idea underlying the inventive solution is to achieve a flow of the material of the drawn part sufficient for its forming by concertedly acting upon a limited area of the drawn part during the drawing process even when the flowability of the material of the drawn part is reduced as such on account of the previous history of the material, for example on account of a preceding, earlier drawing process.
The desired formability of the drawn part can be ensured, in particular, with the inventive deep-drawing method even when the drawn part contains martensite on account of a preceding drawing process.
An annealing process and the cooling and washing processes associated with the annealing process may be omitted in the case of the inventive deep-drawing method even when the deep-drawing method is carried out in several operations.
The inventive deep-drawing method allows a particularly large drawing ratio to be achieved and leads to a high form stability of the drawn parts.
In a preferred development of the inventive method it is provided for the pressure at the pressure section to be generated hydraulically or pneumatically by means of a pressure fluid.
The hydraulic generation of a pressure at one of the deep-drawing die parts is already known as such from the so-called hydroforming method, with which the drawing member is provided with a membrane which is subjected to water pressure during the forming process. With this method, the drawing punch presses the drawn part against the membrane on the drawing member, wherein the drawn part is formed by the water pressure acting against it. With this method, the entire drawn part is, however, subjected to the same water pressure during the drawing process whereas, in the inventive deep-drawing method, a pressure is generated selectively only at a limited pressure section of one of the deep-drawing die parts and this pressure presses the respective limited section of the drawn part, which abuts on the pressure section, against the respectively other deep-drawing die part.
Moreover, in the case of the hydroforming method the water pressure acting on the drawn part is constant during the drawing process.
One variation of the hydroforming method is the so-called hydro-mec method, with which the drawn part is pressed by a descending drawing punch into water subjected to pressure without a membrane being provided on the drawing member. With this method, as well, no selective action on a limited section of the drawn part with a pressure variable with time during the drawing process is provided.
A uniform distribution of the hydraulic pressure on the surface of the drawn part is the aim not only of the hydroforming method but also of the hydro-mec method and this is completely contrary to the inventive idea of acting upon a limited section of the drawn part selectively with an increased pressure.
In a preferred development of the inventive deep-drawing method it is provided for the pressure at the pressure section to be controlled and/or regulated in accordance with a predetermined temporal pressure course.
This pressure course may provide, for example, for the pressure section to be switched to a no-pressure state during a first forming phase and for an increased pressure constant throughout a second forming phase to be generated at the pressure section during the second forming phase. Such a pressure course can be controlled and/or regulated particularly simply.
However, any optional, other temporal pressure course can also be controlled and/or regulated depending on the type of drawn part and the desired forming of the drawn part.
The formability of the drawn part during the drawing process is particularly increased when the pressure section is aligned essentially parallel to the direction of drawing, along which the deep-drawing die parts are moved relative to one another. In this case, areas of the drawn part which are aligned essentially parallel to the direction of drawing can be pressed concertedly onto areas of the respectively other deep-drawing die part which are aligned essentially parallel to the direction of drawing, and this is not possible in the case of the conventional deep-drawing methods. Side wall areas of the drawn part, which are aligned essentially parallel to the direction of drawing, can, in particular, be formed in a particularly exact manner.
The inventive deep-drawing method has proven to be particularly successful when the side wall of t
Hartzinger Josef
Kaderabek Franz
Krachhudel Torsten
BLANCO GmbH + Co KG
Jones David B.
Townsend and Townsend / and Crew LLP
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