Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-04-24
2001-01-16
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S272400, C156S273900, C156S275700, C219S633000, C089S036020, C296S182100, C296S190050
Reexamination Certificate
active
06174398
ABSTRACT:
BACKGROUND OF THE INVENTION
A method of fabricating composite metal-and-plastic components is known from European Patent 0 732 234 A2, Layers of plastic are applied (laminated) to the top and bottom of sectional metal cores (bars). Layers of woven plastic fabric are bonded together, and the resulting sandwiches to the metal core with both thermoplastics and duroplastics.
Both vacuum sacking and pressing are employed to fabricate such work (both techniques being described in M. Fleming, G. Ziegmann, and S. Roth, Faserverbundweisen, Berlin, Heidelberg, and New York, Springer, 1996).
Common to both techniques is that, to bond together moldings with many angles, they use molds in the form of upper and lower halves to achieve the desired geometry. Both techniques also depend on indirect supply of the requisite heat. That heat must be diverted entirely out of the finished work by subsequent cooling once the reaction is complete.
In vacuum sacking, the loosely joined separate layers of the eventual composite must be secured in molds entirely enclosed in a sack, which is then totally evacuated to apply pressure by way of woven auxiliary structures. Subsequent to this preparatory phase the total package is heated, either with hotplates or in an enclosed oven. The heating stage, with a maximum temperature of approximately 200° C., is immediately followed, especially in the case of thermoplastics, by a cooling stage at the same pressure to stabilize the molding.
When the components are fabricated by pressing, the requisite pressure is generated (hydraulically, pneumatically, or mechanically) with a press. The individual layers of the eventual work are, when they are not flat, secured in press molds (with an upper and a lower half).
The mold is heated with either an electric hotplate or a hot fluid and cooled with cooling devices.
Due to the physics of heat conduction and transfer, the heating and cooling stages in both procedures are relatively lengthy. This in turn dictates relatively long processing and a relatively low output per unit of time and per tool.
A method of joining the components of motor-vehicle lamps and headlights together is known from German 2 740 071 A1. Plastic reflectors are joined along the edges to housings with a transparent disk over the front. A spiral metal coil is inserted between the edges of the parts and heated. The coil is part of the tool and not of the work. It initially extends into the softened plastic of the edge. Once the heating of the fastener is discontinued and the plastic in the reflector and housing hardens again, the parts are joined to the disk by a layer of adhesive. This known method, however, provides no suggestion as to how to attain the object of the present invention.
SUMMARY OF THE INVENTION
That object is a method of the aforesaid genus that will simplify and improve the economics of lamination in the fabrication of non-flat components with a metal core like those described in European Patent 0 732 234 A2 for example.
Directly heating the metal core exploits the core's inherent heat to fasten it to the upper and lower halves, which are themselves laminates, which it is practical to provide prefabricated and which are usually not electrically conductive.
The metal core's inherent heat softens the thermoplastic or duroplastic masses, usually sheets, between the core and the mold halves and renders them adhesive. The sheets can already be part of the prefabricated upper and lower halves and can be of the same or of a different material. The three layers of the work, i.e. The upper layer, the lower layer, and the core, are then bonded together form-fit and force-fit by the application of external pressure, preferably in a press.
Both the heating phase and the subsequent cooling phase are much shorter in the method in accordance with the present invention than at the state of the art. Whereas the heat must be diverted from the whole molding in the state-of-the-art methods hereintofore described, only the heat of the core, previously heated to processing temperature, must be diverted in accordance with the present invention. Since the heat employed in accordance with the present invention is considerably lower than the heat employed at the state of the art, the overall procedure will take much less time.
Another positive result of the method in accordance with the present invention is the definitely decreased tendency of the upper and lower halves and core of the molding to shift (“float”) relative to one another. This factor increases precision and manufacturing reliability.
To reduce any contamination of the metal core that might be deleterious to adhesion, the core should be heated electrically, either by regulated current flow (resistance heating) or by regulated high-frequency heating (the generation of eddy currents in the core). These two types of electrical heating will allow the application of pressure to the layers being bonded together even during the heating phase. Both procedures can accordingly be carried out simultaneously.
REFERENCES:
patent: 2399184 (1946-04-01), Heckert
patent: 5641933 (1997-06-01), Kim
patent: 5760379 (1998-06-01), Matsen et al.
patent: 5793024 (1998-08-01), Matsen et al.
Dieterich G{umlaut over (u)}nter
Piel Karlheinz
Pleugel Lothar
Ball Michael W.
Fogiel Max
Fried Krupp AG Hoesch-Krupp
Tolin Michael A
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