Metal fusion bonding – Process – Plural joints
Reexamination Certificate
1996-11-12
2002-04-16
Heinrich, Samuel M. (Department: 1722)
Metal fusion bonding
Process
Plural joints
C228S175000, C228S248100, C228S253000
Reexamination Certificate
active
06371360
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method for applying brazing material to metal structures, in particular honeycomb bodies for exhaust gas catalytic converters, wherein the brazing material is applied in powder form and is firmly held on the metal structure by an adhesive material acting as a bonding agent, binder or adhesion promoter.
Applying brazing material to metal structures, such as metal catalyst carriers for exhaust gas catalytic converters, is a key problem in the effectiveness of the manufacturing process for such catalyst carriers or for the later strength and durability of the carrier itself.
It is known to apply an adhesive or binder to the metal structures to be joined, when brazing material is applied. The brazing material is in powder form and is either already mixed beforehand with the adhesive or binder or applied to them later.
German Published, Non-Prosecuted Patent Application DE 29 24 592 A1, corresponding to U.S. Pat. No. 4,381,590, describes a method for producing a carrier matrix for a catalytic reactor used for cleaning the exhaust gas of internal combustion engines in motor vehicles. In that method, the corrugated and smooth sheet steel layers are brazed together with spot brazing or full surface brazing, which is carried out by applying a brazing material application to the steel plates, particularly in strips, for instance in the direction of the corrugations of the corrugated steel sheets, or at right angles thereto. Brazing of all of the layers to one another takes place through the use of ensuing heating of the matrix. Liquid brazing paste or powdered brazing material is applied with a binder. The application of the brazing medium or binder is carried out by various methods, such as immersion, pressing in, injection into the end surfaces of the honeycomb body, etc. In order to assure uniform brazing at all of the contact points between the sheet steel layers, an excess of brazing material or binder is generally employed.
In European Patent 0 049 489 B1, a method for producing a carrier matrix for an exhaust gas catalytic converter is described. In that method, the smooth and corrugated metal sheets to be provided with a brazing material application, which are wound to make a carrier matrix for an exhaust gas catalytic converter, are first coated with a pressure-sensitive adhesive which evaporates without residue at the brazing temperature and have a surface on which a single-particle layer of dry brazing powder is applied after the drying. With the applied brazing powder, the steel sheets are then wound up and brazed to one another. A disadvantage in that method may be that the grains of brazing material will be located between the sheet-metal layers to be joined, so that when the grains of brazing material melt an undesirable gap can be created, which is detrimental to the outcome of the brazing.
As a remedy therefor, International Patent Application WO 89/11938, corresponding to U.S. application Ser. No. 08/054,161, filed Apr. 26, 1993 and 08/467,591, filed Jun. 6, 1995, describes a method for applying glue and brazing material to a metal catalyst carrier body, and an associated apparatus. In that method, the metal sheets, before being wound up or layered, are coated in the regions to be brazed with an adhesive or binder, in particular with a pressure-sensitive adhesive. Next, the sheets are wound or stacked to make a honeycomb body, and only then is the body acted upon with brazing powder. As the sheets are further transported after being coated with adhesive, and as the catalyst carrier body is being wound up or stacked in layers, or in other words in all of the handling or transport steps to be provided between the various method steps, the adhesive must be kept in a sticky to liquid state, and as a result it is possible for the adhesive to escape or run out of the catalyst carrier body, or at least for the machine parts that come into contact with the adhesive to become contaminated thereby and in the final analysis become vulnerable to malfunction.
A method and an apparatus for applying brazing material to a metal honeycomb body are also described in International Patent Application WO 93/25339, corresponding to U.S. Pat. No. 5,431,330. In that method, if no rolling oil is present on the surfaces from the manufacturing process, a thin layer of rolling oil is then first applied, which is then thermally treated in order to remove highly volatile components. The regions of the sheet-metal layers that are to be provided with brazing material are put into contact with an aqueous solution of a surfactant, and as a result they form a layer that temporarily acts as an adhesion promoter for brazing powder. After that, the sheets are wound up or stacked into honeycomb bodies. That step is followed by putting the honeycomb bodies into contact with brazing powder. The brazing powder sticks to points where residues of rolling oil and surfactant have come together. Although that method achieves economical use of brazing material, nevertheless the adhering brazing material must also be fixed with an adhesive or binder in an additional work step, to prevent it from trickling out later when transported from place to place.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for applying brazing material to metal structures with an adhesive material having different states, which overcomes the hereinafore-mentioned disadvantages of the heretoforeknown methods of this general type, which employs an adhesive material for firmly holding brazing powder to regions that are to be brazed in metal structures to be joined together having an adhesive strength that can be varied during a production process so that a firm holding of brazing powder can be varied, which averts contamination and blocking of machines or machine parts and which cannot unintentionally flow away from a location where it is applied between the various method steps.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for applying brazing material to metal structures, in particular honeycomb bodies for exhaust gas catalytic converters, which comprises applying powdered brazing material on a metal structure in association with a production process of the metal structure; and firmly holding the brazing material on the metal structure with an adhesive material acting as a bonding agent, binder or adhesion promoter, having little or no adhesive action during a portion of the production process of the metal structure and having an ability to be subsequently intermittently adhesively activated.
In accordance with another mode of the invention, an adhesive material that is temporarily not adhesive or only slightly adhesive after application and is activatable later, in particular during the production process of the metal structure, or in other words during the various method steps required for the production process and that can assume at least two states which are different in terms of its adhesive action, is employed to firmly hold the brazing powder. One state is a less adhesive state, the other state is a more strongly adhesive state, the states of the adhesive material can be varied as a function of external conditions, such as the temperature, and in particular can be varied reversibly. An adhesive material of this kind that accomplishes its (reversible) states which can be converted to one another by the influence of light, ultraviolet, or other radiation, chemical action or other external factors, may also be used.
In accordance with a further mode of the invention, in a first exemplary embodiment the adhesive material has two aggregate states, namely a solid and a liquid state, and the solid state of the adhesive material can be converted into the liquid state or vice versa within an allowable temperature range that occurs during the production process.
In accordance with an added mode of the invention, a wax which is solid at a normal temperature of appr
Maus Wolfgang
Wieres Ludwig
Emitec Gesellschaft fuer Emissions-technologie mbH
Greenberg Laurence A.
Heinrich Samuel M.
Lerner Herbert L.
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