Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-06-28
2002-09-10
Crispino, Richard (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S295000, C156S304500, C156S310000, C156S314000
Reexamination Certificate
active
06447631
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to a process for joining components and assembly units of rail-borne vehicles.
BACKGROUND OF THE INVENTION
Attempts have been increasingly made in manufacturing rail-borne vehicles to replace complex, stress-transmitting nonpositive and positive welded, riveted or screw connections with equivalent bonded connections. It has been known that bonded assembly units can achieve fatigue strengths specific of rail-borne vehicles with one-component or two-component polyurethane adhesives. One essential drawback of the use of such adhesives is that they require a certain gap width and need defined curing times before they reach a strength that allows handling, transportation and further machining of the assembly units, so that long fixing times with maintenance of a defined joining pressure must be maintained. Adhesives that make possible very short fixing times, such as acrylate adhesives, are, in contrast, frequently not resistant to aging and cannot ensure uniform fatigue strength properties.
To reduce the technological fixing times, it is proposed in DE 35 25 830 A1 that thin-walled body parts be joined by bonding by applying a more slowly curing and permanently load-bearing principal adhesive (e.g., a strip-like strand of a two-component adhesive) to one of the elements, by subsequently bringing together the elements to be joined and joining them under pressure and subsequently applying a quick-curing adhesive (e.g., a quick-curing one-component adhesive based on cyanoacryl) in areas of the bonded joint adjacent to the principal adhesive under joining pressure between the elements, wherein the quick-curing adhesive can assume the function of the prior-art bonding device after a relatively short time. To make it possible to maintain the necessary bonding gap widths, the components to be joined are shaped in a trough-shaped or groove-shaped manner in the area of the bonded joint. In the first exemplary embodiment, the quick-curing adhesive is injected between the components through openings in one of the components. The device intended for the application of the quick-curing adhesive and the application of the necessary joining pressure is complicated; one device is necessary for each site of application or a subsequent positioning of the elements in the case of the application example described. In the second case of application, the quick-curing adhesive is applied, e.g., in troughs of one of the elements by means of glass ampules or film bags, which are destroyed during the joining process. This process cannot be used for cases of application in which components with manufacturing tolerances in relation to one another are to be joined without specially shaped bonded joints with defined layer thicknesses. Such an assembly unit obtains a decorative surface only by a subsequent equalization of the surface and surface coating.
To maintain certain bonded joint gaps, the bonding process described in EP 0 433 513 A1 provides for calibrated limiting and spacing elements in the edge area or within the bonded joint.
In DD 241 768 A1, defined points or areas of the bonded joint are provided with material elevations or applications of the same substance.
If parts with manufacturing tolerances must be joined, the latter two methods fail; moreover, in the case of a given surface, such inclusions interrupting the bonded joint and the means rigidly spacing the components to be joined from one another may reduce the bonding strength that can be theoretically reached with the given adhesive or may make it compulsory to provide much larger joining surfaces than theoretically necessary.
Moreover, the use of adhesives frequently leads to the problem that adhesive residues spreading beyond the surface area intended as a joining surface can be removed with a great mechanical or chemical effort only, which may lead to damage to the component. For example, adhesive tapes are therefore usually used as an edge limitation of the joining surfaces, and these adhesive tapes can then be separated from the surface. Their application and subsequent removal require a great effort; they usually must be disposed of as special waste.
SUMMARY AND OBJECTS OF THE INVENTION
The primary object of the present invention is to provide a novel process for joining assembly units of rail-borne vehicles by means of bonding, in which the application of an adhesive, which ensures fatigue strength and requires a relatively long curing time, is combined with the application of an adhesive that ensures a strength sufficient for handling in a short time, wherein complicated shaping of the bonded joints as well as great efforts in terms of devices are to be avoided, manufacturing tolerances between the components to be joined are to be equalized and defined minimum bonded joint gaps between the components are to be maintained, without strength-reducing disturbances occurring within the bonded joint. Another object of the present invention is to make it possible to limit the wetting of the surfaces of components with adhesive to selected joining surfaces and to avoid the subsequent removal of a covering edge limitation and its disposal as special waste.
According to the invention, a process is provided for joining components of rail-borne vehicles by bonding, in which a preformed first component is joined to a shape-adapted second component by means of the two-dimensionally separate application of adhesives with different reaction characteristics until a strength sufficient for handling is reached. The process includes bringing a first component into the position for joining and fixing in the form of use in the usual manner. A first adhesive layer having the property of being quick-bonding and maintaining a defined joining layer thickness is applied to selected and two-dimensionally limited first joining surfaces of the first component and/or of the second component. A defined amount of a second adhesive layer having the property of curing more slowly and flowing slowly during joining, but being flowable and capable of wetting, is applied to selected second joining surfaces of the first component and/or of the second component. The two components to be joined are positioned in the desired three-dimensional arrangement in relation to one another, are brought close to one another and are joined to one another under the effect of a joining pressure applied in the area of said selected first joining surfaces. The first adhesive layer connects the first component to the second component in the area of the first joining surfaces at a joining space predetermined by the defined joining layer thickness of the first adhesive layer with such a first joining strength that removal and moving of the pre-joined assembly unit is possible after the joining process without any change in the shape and position of the components. The second adhesive layer, whose amount as well as flowability and wetting ability are such that the first adhesive layer applied can contact the other component in the area of the joining surfaces, fills out the joining space left between the first and second components in the area of the second joining surfaces the assembly unit subsequently remains in its joined position or is brought into a resting position or is included in the further technological process, where a second joining strength brought about by the curing of the second adhesive layer is reached.
According to another aspect of the invention, another process for joining components of rail-borne vehicles is provided. The first component is brought into the position for joining and fixed in the form of use in the usual manner. An adhesive layer, having the property of being quick-bonding and maintaining a defined joining layer thickness during joining, is applied to said selected and two-dimensionally limited first joining surfaces of the first component and/or of the second component. The two components to be joined are positioned in the desired three-dimensional arrangement in relation to one another, are brough
Schähl Wolfgang
Weichelt Peter
ABB Daimler-Benz Transportation
Crispino Richard
McGlew and Tuttle , P.C.
Purvis Sue A.
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