Metal working – Method of mechanical manufacture – Shaping by direct application of fluent pressure
Reexamination Certificate
2001-02-15
2003-06-10
Vidovich, Gregory (Department: 3726)
Metal working
Method of mechanical manufacture
Shaping by direct application of fluent pressure
C029S897200, C029S445000, C029S505000, C029S890148
Reexamination Certificate
active
06574849
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is the US national phase of PCT application PCT/DE99/02431 filed Aug. 4, 1999 with a claim to the priorities of German patent applications 19837130.6 and 19837131.4 both filed Aug. 17, 1998.
FIELD OF THE INVENTION
The invention relates to a method of deforming by high internal pressure at least two hollow bodies each having at least one opening, especially metal tubes or hollow profiles, the hollow body if necessary being produced during an internal high-pressure deformation process.
BACKGROUND OF THE INVENTION
The hollow bodies in question are normally metal tubes, preferably of steel, aluminum, or the like. These metal tubes can be of circular or noncircular as well for example as of rectangular section. Similarly hollow bodies or blanks are used that are put together from several metal parts. In any case it is necessary that the hollow bodies be open at least at one end as is standard with internal high-pressure deformation processes. It is understood that such an internal high-pressure deformation tool can be made of several parts and can be opened so the finished shaped part can be taken out of it.
Internal high-pressure processes are well known (see German patent 4,320,237). Typically they are used when hollow bodies or metal tubes of complicated shape are needed. To this end a tube is deformed which subsequently is shaped by conventional means. This includes inter alia welding-together shaped metal tubes.
In the prior art the standard method is that the individual hollow body is shaped by the internal high-pressure deformation process according to a predetermined design to have a predetermined shape. Such a hollow body is then connected to another hollow body for example by welding. This second hollow body can also be an internal high-pressure deformed hollow body. Classic parts that are made in this manner are complex frame parts as used for example in motor-vehicle frames and/or as chassis parts.
The normally used connection system often creates distortion of the metal tubes being joined or welded together at the connection region. It is also not impossible that the tube walls are weakened in the critical connection region by the welding procedure which is particularly to be avoided in highly loaded tube joints. This applies also to the case when the above-mentioned tubes must be fastened together to be pressure tight as well as in the exemplary complicated torsion-resisting frame parts as for example needed in a motor-vehicle frame or chassis.
In any case the prior art requires a plurality of steps in order to be able to make such complicated tube or frame constructions. In addition the quality could be improved.
OBJECT OF THE INVENTION.
It is therefore the object of the invention to improve on a method of the above-described type such that it allows complicated frame constructions to be made simply and quickly and in addition makes possible a perfect mutual connection of the hollow bodies without distortion.
SUMMARY OF THE INVENTION
This object is attained by the invention according to a first alternative in a method of joining two or more hollow bodies each having at least one opening, in particular metal tubes or profiles, by an internal high-pressure deformation process wherein first
in a joint region between a first hollow body and a second hollow body to be connected thereto at least one intended fracture zone is formed in an outer wall of the first hollow body, and thereafter
the outer wall of the first hollow body is expanded outwardly in a closed cavity of a internal high-pressure shaping tool by means of a hydraulic medium at least in the joint region of the two bodies to form a flange, while
the second body to be joined is held in the cavity of the internal high-pressure shaping tool at a predetermined spacing from the flange, and thereafter
the hydraulic medium flows after exceeding the burst pressure for the intended fracture zone into the second hollow body to optionally shape it by internal high-pressure deformation and to join the first hollow body by its flange with the second hollow body.
A second embodiment of the invention is a method of joining two or more hollow bodies each having at least one opening, in particular metal tubes or profiles, by an internal high-pressure deformation process wherein first
in a joint region between a first hollow body and a second hollow body to be connected thereto at least one intended fracture zone is formed in an outer wall of the first hollow body, thereafter
the first hollow body and the second hollow body are engaged together at the joint region, thereafter
the outer wall of the first hollow body is expanded outwardly in a closed cavity of an internal high-pressure shaping tool by means of a hydraulic medium at least in the joint region of the two bodies, and subsequently
the hydraulic medium flows after exceeding the burst pressure for the intended fracture zone into the second hollow body to shape it by internal high-pressure deformation.
Joining according to the invention means solidly connecting and preferably material joining between the hollow bodies.
With the method of the first embodiment of the invention the hollow bodies can be so joined that the first hollow body simultaneously engages with its flange into the second hollow body and thus forms a joint in the joint region.
The first embodiment also provides that the outer wall of the first hollow body is expanded outward to form a flange so that the second hollow body to be joined thereto is held at a spacing from the flange. The expansion of the first hollow body takes place as is standard in a closed cavity of an internal high-pressure deforming tool by means of the described hydraulic pressure medium. According to a preferred embodiment the to-be-joined second hollow body is held in this cavity at a spacing from the flange region.
Normally the mechanical weakening of the outer wall or the formation of the intended fracture zone is achieved in that the intended fracture zone is defined by a blind bore, stamping, recessing, spark-eroded boring, metal-etch boring, or the like. Normally instead of one intended fracture zone a plurality of intended fracture zones are formed in the outer wall of the first hollow body aligned with the inner profile of the second hollow body. This zone or zones are formed before fitting the hollow body into the internal high-pressure deforming tool by means of an external boring and/or stamping device or inside the internal high-pressure deforming tool, preferably by an integrated drill, stamp, or the like.
Here material is removed at the intended fracture zone according to the stretch-to-break of the material of the first hollow body with reference to a predetermined burst pressure. This is of course determined in particular by the material of the first hollow body which is expanded during internal high-pressure deformation to form the flange. In any case there are generally two possibilities. On the one hand the intended fracture zone produces a weakening of the outer wall of the first hollow body and the pressure in the hydraulic medium increases until the zone breaks and the medium flows into the second hollow body. On the other hand the pressure medium can be used at the predetermined maximum pressure so that in this case the intended fracture zone or zones are such that on reaching this maximum pressure in any case the burst pressure is exceeded or the maximum pressure is equal to this burst pressure.
This can be done by appropriate removal of material and/or a weakening of the material in the intended fracture zone. As a result there is a metallurgical (grain) weakening. The invention is based on the recognition that, after exceeding the so-called flow or stretch limit (measured in N/mm2), the material used normally for the metal tubes has a shape change caused by the actual tension that can break it. In any case it is in particular true with stretching tension—as is particularly obtained with pressure buildup—to create a split at the intended fracture zone
Dubno Herbert
Nguyen T.
Siempelkamp Pressen Systeme GmbH & Co.
Vidovich Gregory
Wilford Andrew
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