Stock material or miscellaneous articles – All metal or with adjacent metals – Porous
Reexamination Certificate
1999-11-24
2002-10-22
Zimmerman, John J. (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Porous
C428S313300, C164S079000, C164S108000, C164S111000
Reexamination Certificate
active
06468671
ABSTRACT:
The invention relates to foamed metal preformed bodies and a method with which a metal foam material of a preformed body is foamed during fabrication of the preformed body.
It is especially in lightweight structural engineering that there has always been a problem in joining individual structures—termed preformed bodies in the following—in keeping with the requirements of the later application, not least due to the demand for low weight while at the same time ensuring high mechanical loading capacity and stability at low cost. This is also basically a problem in other fields, for instance, in shipbuilding where particularly large-area preformed bodies, for example hull segments, need to be joined to each other, although here too, there is always the requirement for the smallest deadweight possible while assuring high mechanical loading capacity of such preformed bodies and the composite bodies composed thereof.
One possibility of saving weight is to make use of preformed bodies of foamed metal foam material or fractions of such materials. The pore structure of the frothed or foamed foam metal results in a frothed or foamed metal preformed body having a lower weight than a solid metal preformed body while still assuring high mechanical loading capacity. Aside from this, metal foam material features a whole series of additional advantageous properties, such as, for example, high shock absorption, noise absorption, as well as a reduced heat conductivity and electrical conductivity as compared to the solid material. To achieve these advantageous properties the foamed material needs to have a foam or porous structure as uniform as possible.
Metal foam materials and the semi-finished products and preformed bodies produced therefrom are known, for example, from DE 41 01 630 C2, DE 43 18 540 A1, DE 44 16 371 A1, DE 44 26 627 A1, DE 196 12 781 C1 and DE 197 17 894 A1. Proposed in DE 43 18 540 A1 is the use of metal foam material in automobile production in which body panels are employed as foamed metal preformed bodies comprising a solid metal skin and a foamed layer of metal foam. For securing fitted items to these body panels mention is made of self-cutting screws and dowel-type fasteners. DE 196 12 781 C 1 likewise relates to preformed bodies for motor vehicles. In the publication “Metallschäume 1997”, MIT Bremen, in the article entitled “Joining of Aluminum Foams” by N. Sedliakova et. al., screw fasteners, soldered, cemented and welded joints as well as the use of foamed fasteners are described as methods for joining foamed metal preformed bodies. These are the accepted methods for joining preformed bodies, the advantages and disadvantages of which are well known in engineering.
An object of the invention is to provide a foamed metal preformed body having a structure of the foamed metal foam material which is favorable for the intended purpose of the preformed body. For the majority of purposes of the preformed body, it is desirable that the porous structure of the foamed metal is as uniform as possible.
This object is achieved by the subject matter as set forth in the independent claims.
The invention relates to a preformed body comprising foamed metal foam material cited in the following as a foamed metal preformed body due to this property.
The foamed material may totally fill a preformed body configured hollow.
The foamed material may be sited also only in one or more zones of the preformed body, where it fills out cavities, or it may also reinforce only one structural part of the preformed body or join structural parts.
In accordance with the invention, the metal foam material is thermally treated internally during foaming. A thermal treatment means is conducted through the metal foam material. The thermal treatment means may be arranged so that is only comes into immediate contact with the material to be foamed when actual foaming has commenced. However, the thermal treatment means can also already come into direct contact with the metal foam material before the material is foamed to, for example, already initiate foaming of the material. Foaming may be supported or even first made possible when, for example, introducing heat to the zone of the thermal treatment means is not possible due to the low thermal conductivity of the foamed metal or possible only to an inadequate degree for foaming. The thermal treatment means may also serve merely as a coolant, or in addition to heating.
The thermal treatment means involved is preferably a flow conduit for communicating, or also merely for introducing, a thermal treatment fluid through or into the zone of the preformed body in which the metal foam material is located. The thermal treatment means may, however, also be formed in principle by some other means such as, for example, an electrically conducting wire of a resistance heating element if only internal heating is to be implemented during foaming. By means of a flow conduit, heating or cooling is optionally possible to advantage within the structure of the metal foam material. With such a thermal treatment means, the metal foam material is heated during its foaming or cooled to discontinue foaming or subsequent to foaming. Also applicable is a combination of two or all three thermal treatment procedures. It is particularly of advantage when the complete foaming procedure is controlled by thermal treatment. The foamed material is heated internally for foaming and, if necessary, maintained at a temperature by means of internal thermal treatment, which, in contrast to external heating, is very accurately adjustable and uniform throughout the foamed metal, and cooled for consolidation.
Internal thermal treatment permits highly accurate thermal treatment of a localized zone in which metal foam material is arranged. Zones are thus attained in which, due to the shape of the preformed body and the amounts of foamed metal located therein, cold or hot spots could materialize should heating or cooling be done merely externally. Directly adjoining zones may even be heated and cooled simultaneously. Zones may be protected from excess heat entry. Heating may be done internally and cooling externally, and vice-versa. Accordingly, the choice of materials possible for the dimensionally stable structural parts during foaming is greater. Different foam materials may even be combined in that a material having a low foaming temperature due to the internal thermal treatment is specifically protected against excessive heating of an adjoining material having a higher foaming temperature.
The result of the above is that foaming any shape of preformed body is made possible. By means of internal thermal treatment, preformed bodies of any internal geometry and also any outer dimensions may be foamed, for which, otherwise, special ovens would need to be built. Such preformed bodies may be foamed fully or partly as a whole in a single heating operation.
A preformed body foamed with foamed metal in accordance with the invention is characterized by a thermal treatment means, preferably at least one flow conduit for a thermal treatment fluid, being guided through the foamed structure. In one preferred embodiment, thermal treatment fluid is passed through in counterflow. For this purpose, two flow conduits, through which the thermal treatment fluid is passed in counterflow, may be oriented closely spaced in parallel or in direct thermal conductive contact with each other. In both flow conduits, thermal treatment fluid is introduced at the desired temperature and passed through in counterflow. Along the pair of flow conduits, the thermal treatment temperature materializes particularly uniform. Instead of a thermal treatment fluid passing through flow conduits separately in flow, it may also be passed through the two flow conduits in sequence. In both flow guidance arrangements, one of the two flow conduits may surround the other.
Cooling the foamed metal internally during its foaming prevents uncontrolled further foaming of the foam material. The foaming procedure is purposefully concluded; the foaming action be
Ratner & Prestia
Zimmerman John J.
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