Coating processes – Direct application of electrical – magnetic – wave – or... – Pretreatment of substrate or post-treatment of coated substrate
Reexamination Certificate
2001-12-04
2003-09-02
Barr, Michael (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Pretreatment of substrate or post-treatment of coated substrate
C427S580000, C427S376100, C427S379000, C427S380000, C427S402000, C427S404000, C427S405000, C228S209000, C228S211000, C228S223000, C228S262510
Reexamination Certificate
active
06613397
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for manufacturing an Al clad product; and, more particularly, to a method and apparatus for manufacturing an Al clad product for use in a heat exchanger.
BACKGROUND OF THE INVENTION
In general, a heat-exchanger includes a header, a coolant tube and fins. A heat exchange is carried out when a coolant flows through the coolant tube of the heat-exchanger. In a conventional method for manufacturing the heat-exchanger, the coolant tube and the fins are assembled by preparing core material of the fins and clad-rolling clad material at both sides of each fin along with the core material. A bare material, not a clad material, is used as the coolant tube. The assembled coolant tube and fins are bonded by brazing in a brazing furnace.
Since, however, the clad material, which is expensive, is coated on both sides of the fins, required costs are considerable in the conventional method. A vacuum brazing technique is recently losing the popularity despite its merit that it does not require a flux. It is because the vacuum brazing is excessively time-consuming. Instead, the so-called nocolok brazing method is widely used in these days. In the nocolok brazing method, oxidization is prevented by introducing inactive nitrogen gas into a brazing furnace.
However, the nocolok brazing method also has a certain drawback. Namely, since oxygen in the air is introduced into a brazing furnace in a PPM unit, an oxide film is formed on an Al surface during the brazing process. In this case, due to a difference between the thermal expansion coefficient of the oxide film and that of the Al under the oxide film, the oxide film is forced to break.
Accordingly, in order to prevent the Al surface exposed after the oxide film has broken from being oxidized, an extra processing for distributing and coating the flux on the entire surface of the heat-exchanger is required. That is, after the coolant tube and the fins are assembled together to form a heat-exchanger, mixed solution having water and flux should be distributed and coated on the entire surface of the heat exchanger before the brazing process is begun.
However, since the mixed solution of water and flux is coated on the whole surface of the heat exchanger including portions not to be bonded, a great amount of flux is consumed and a final product comes to have an unclean appearance due to the unnecessary flux attached to a Al core.
Further, since the unnecessary flux has a low adhesive property, it is likely that when the heat-exchanger is operated for a long time in, e.g., an air-conditioner disposed in a circumstance where moisture always exists, fallouts of the flux may be absorbed into a user's body, causing a variety of health problems. Still further, if the flux is coated on the fins and the coolant tube not to be bonded, the air-permeability of an air conditioner is greatly reduced, which in turn results in a deterioration in the efficiency of the air conditioner.
Besides, since a great deal of the mixture of the water and flux is blasted to components of the heat-exchanger assembled before the brazing process is initiated, fluoric ingredient of the flux and the water may invade the furnace during the brazing process to thereby entail corrosion diminishing a life time of the components.
Furthermore, if the brazing process is performed after the mixture of water and flux is sprayed and coated on the heat-exchanger assembled by a brazing jig, the flux coated on the portions not to be bonded fuses and permeate into a joint portion between the jig and the heat-exchanger. Accordingly, when the heat-exchanger is taken out of the furnace, the jig should be separated in a state where the flux has been coagulated. Thus, when the jig is separated, traces of the jig is found on the heat-exchanger and, still worse, the jig may not be separated from the heat-exchanger at all, in which case the brazed heat-exchanger should be abandoned.
In another conventional method for manufacturing a clad product for a heat-exchanger, instead of using a rolled clad member for joint portions of the heat-exchanger, a slurry having cladding material, flux powder, binders and a diluent is sprayed and coated on one side of a component to be bonded. The binders are hardened while passing through a binder drying furnace. Thereafter, the assembled heat-exchanger is subjected to the brazing furnace without undergoing through a process for coating the mixture of water and flux.
In the brazing furnace, the binders are gasified or evaporated below a brazing temperature and the cladding material and the flux are brazed so that the components of the heat-exchanger are bonded to each other. This method, however, has many demerits. At the time of preparing the slurry, the gasified diluent generates a stench. Further, material harmful to human body may be produced due to gasification of some binders and complete gasification of the diluent during the hardening process of the binders. Still further, the binders are decomposed during the brazing process so that some of the binders are gasified and some remains on the joint portions as carbons, thereby resulting in a failure to braze those portions. Still further, if the carbons exist in the furnace, the carbons may be fastened to the produced product and reduce a density of the clad material or the flux, thereby deteriorating the adhesive property of the clad material.
In another prior art method developed so as to resolve the above-described problems, there are prepared a slurry Si and flux powder, resin powder mixed with binders and a diluent. The prepared power of Si and flux, the resin powder and the diluent are mixed. Then, the mixed slurry are sprayed by a spraying unit or are coated by employing rolling coating technique or a dipping coating technuque on portions of an Al component at a room temperature. In a subsequent procedure, the diluent is evaporated by elevating the temperature thereof; the binder is decomposed and evaporated during a brazing process and then the flux and the Si are coated thereon.
In this method, however, since the cladding material and the diluent exist between cladding layers, the amount of the cladding material and the Si and the flux as well as the density of the cladding layers are greatly reduced, resulting in decrease of cladding force therefor when the cladding material and the diluent are gasified. Further, since the amount of the diluent is large, malodor is generated when the diluent is gasified and the cleanness of the brazing furnace is deteriorated, which in turn reduces a life time of a furnace muffle.
In still another prior art method, powder of Zn is first coated on an extruding tube of a heat-exchanger so as to obtain a corrosion resistance. Then, powder of Al and Si are melted and blasted to coat cladding material by employing, e.g., a thermal spray technique in which oxygen and polypropylene gases are used as heating gases.
Since, however, in this method, electric power is used as a heating source and oxygen and polypropylene gases are used as heating sources for coating, involved coats are greatly increased. Further, since only the powder of Al and Si or the powder of Al, Si and Zn is coated, the cladding material may be partially oxidized during the brazing process in a nocolok brazing furnace, thereby reducing the adhesive property of the cladding material and resulting in a failure to braze.
SUMMARY OF THE INVENTION
It is, therefore, a primary object of the present invention to provide a method and apparatus having simple structure and high efficiency with reduced procedures for manufacturing an Al clad product.
It is another object of the present invention to provide a brazing method of the Al product to enhance the quality thereof and prolong lifetime of a brazing furnace.
In accordance with a preferred embodiment of the present invention, there is provided a method for manufacturing an Al clad product including the steps of: a) fusing and coating cladding material on base material having Al; b) coating
Bacon & Thomas
Barr Michael
Mando Climate Control Corporation
LandOfFree
Method and apparatus for manufacturing an aluminum clad product does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for manufacturing an aluminum clad product, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for manufacturing an aluminum clad product will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3032328