Electric heating – Metal heating – By arc
Reexamination Certificate
2000-04-10
2002-12-03
Dunn, Tom (Department: 1725)
Electric heating
Metal heating
By arc
Reexamination Certificate
active
06489591
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention pertains to electric arc welding power sources or machines, and more particularly to cooling tungsten inert gas (TIG) welding machine power supplies.
2. Description of the Prior Art
It is well known that the power supplies of electric arc welding machines, including tungsten inert gas (TIG) welding machines, generate considerable amounts of heat. To assure continuous and proper operation, the heat must be removed from the power supplies. For that purpose, various types of air cooling designs have been developed. For example, U.S. Pat. No. 5,831,240 shows a welding machine power supply having end panels with louvers in them. A fan next to one of the louvers blows air through the power supply from one end panel to the other. Some of the cooling air passes through a heat sink to which several major heat generating components are mounted. A deficiency of the design of the Pat. No. 5,831,240 is that much of the cooling air does not flow through the heat sink. Thus, maximum efficiency is not attained for cooling the major heat generating components. In addition, dirty air is blown over delicate electronic components.
U.S. Pat. No. 5,642,260 describes a welding machine having an air tunnel between the two ends of the power supply housing. A fan at one end of the tunnel blows air through the tunnel. Some heat generating components are inside the tunnel. Others are located outside the tunnel but are mounted to two heat sinks that are inside the tunnel. The air flowing through the tunnel directly cools the heat generating components that are inside the tunnel. The cooling air also directly cools the heat sinks inside the tunnel and thus indirectly cools the-heat generating components that are outside the tunnel but that are mounted to the heat sinks. Components of the power supply that are neither in the tunnel nor mounted to the heat sinks are in a dead space, i.e., they are not directly cooled at all.
The Lincoln Electric Company of Cleveland, Ohio, markets an arc converter that includes a fan between two ends of a housing. The fan draws air into the housing from both sides of the housing and pushes the air through a tunnel and out one end of the housing. Both a heat sink and heat generating components are present in the tunnel. The cooling air directly cools the components inside the tunnel and indirectly cools the components mounted to the heat sink outside the tunnel.
Despite the various cooling systems incorporated into prior welding machine power supplies, there nevertheless is room for improvements to them.
SUMMARY OF THE INVENTION
In accordance with the present invention, cooling circuits for electronic equipment is provided that efficiently cools both major and minor heat generating components. This is accomplished by a counterflow circuit that cools the minor heat generating components in addition to a primary circuit that cools major heat generating components.
The primary circuit extends between upstream and downstream ends of a housing. A first chamber at the housing upstream end contains some minor heat generating components. Other minor heat generating components are located within the housing but outside of the primary circuit.
There is a second chamber at the housing downstream end. A fan divides the first and second chambers. The second chamber has a periphery that is aligned with the fan such that all the cooling air blown by the fan flows through the second chamber along the primary circuit. According to one aspect of the invention, the second chamber periphery next to the fan is composed of center and side walls of two symmetrically arranged heat sinks. All the air blown by the fan flows through the two heat sinks. In a preferred embodiment, the first heat sink reaches between the fan and the primary circuit downstream end. First major heat generating components are mounted to the first heat sink outside of the second chamber. Second major heat generating components are mounted to the second heat sink outside of the second chamber. There is a wind tunnel between the second heat sink and the primary circuit downstream end that contains third major heat generating components.
Operation of the fan draws cooling air through the housing upstream end into the first chamber of the primary curcuit. The fan blows the air through the second chamber and out the housing downstream end. The cooling air thus has a negative pressure in the first chamber and a positive pressure in the second chamber.
The cooling air directly cools the minor heat generating components in the first chamber. The cooling air further cools the heat sinks in the second chamber, which in turn cool the major heat generating components mounted to the heat sinks outside the second chamber. Finally, the cooling air in the primary circuit directly cools the major heat generating components in the wind tunnel.
It is a feature of the invention that the minor heat generating components outside the primary circuit are cooled by means of the fan along with the heat generating components associated with the primary circuit. Cooling the minor heat generating components and more delicate electronic components outside the primary circuit is achieved by the counterflow circuit. The counterflow circuit extends between the housing downstream end and the first chamber of the primary circuit. The negative pressure in the first chamber draws cooling air into the first chamber from the counterflow circuit, and into the counterflow circuit through the housing downstream end. The cooling air in the counterflow circuit flows parallel to but in the opposite direction as the air in the primary circuit. The air of the counterflow circuit enters the first chamber from its sides, where it mixes with the air in the primary circuit arriving through the housing upstream end. The fan blows the mixed cooling air in the downstream direction through the primary circuit second chamber. Thus, all the air under positive pressure from the fan flows through the second chamber. The temperature of the air entering the fan is only slightly above ambient, because only the minor heat generating components are cooled by the air in the counterflow circuit and by the air in the primary circuit first chamber. Accordingly, maximum cooling capacity is available to the air in the primary circuit second chamber. The air flowing past the heat sinks and through the wind tunnel provides adequate cooling for the major heat generating components mounted to the first and second heat sinks and for the major heat generating components located in the wind tunnel.
Other advantages, benefits, and features of the present invention will become apparent to those skilled in the art upon reading the detailed description of the invention.
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Maxstar 91 Owners Manual, pp. 24-27, Miller Electric Co.
Croll Mark W.
Dunn Tom
Illinois Tool Works Inc.
Pilarski John H.
Pittman Zidia
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