Heat exchange – With timer – programmer – time delay – or condition responsive... – Temperature responsive or control
Reexamination Certificate
1999-07-23
2001-04-03
Lazarus, Ira S. (Department: 3743)
Heat exchange
With timer, programmer, time delay, or condition responsive...
Temperature responsive or control
C165S274000, C165S104330
Reexamination Certificate
active
06209631
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
This invention relates to sealed enclosures in which electronic components are housed, and more particularly, to apparatus for controlling the temperature within the enclosure to protect the components regardless of the temperature extremes to which the enclosure is subjected.
Certain electronic equipment, for example, traffic monitoring equipment, includes sensors and associated electronic processing circuitry housed in a sealed enclosure. To perform the traffic monitoring function, the enclosure is typically installed outdoors atop a pole or similar support. As a result, the enclosure and the equipment housed in it may be required to operate at temperatures ranging between −40° C. to +50° C. (−40° F. to +122° F.). At very high temperatures, ambient heat must be extracted from the enclosure; while in extremely cold conditions, heat must be supplied to the enclosure.
A traditional approach to thermal management in electrical and electronic equipment is use of heat sinks with components which cannot be allowed to get too hot. Heat sinks are used because their surface area is larger than that of the electronic components mounted on a heat sink and this helps to readily dissipate heat generated by the components. Heat transfer is often enhanced by forcing air flow over the heat sink, typically by use of a fan. The warm air drawn away from the components is then vented outside the enclosure in which the components are housed, typically through openings in the enclosure.
Another approach to thermal management involves use of liquids and thermoelectric cooling for heat extraction. Liquid cooling requires a working fluid, typically chilled water, and a pump to move the fluid from a source through a piping arrangement for heat produced by the components to be drawn to the fluid as it flows past the components. Thermoelectric cooling requires an electrical supply to operate. Again, forced air flow over the components may be used to increase heat extraction, and this requires openings in the enclosure so the heated air can be discharged to the outside environment. With heat sinks, liquid cooling, and thermoelectric cooling, the heat transfer is not 100% efficient, so a certain amount of heat remains inside the enclosure.
When electronic equipment is housed in a sealed enclosure, the above heat extraction approaches are not effective because air within the enclosure is not exchanged with the outside environment. Resulting heat build-up produces a temperature rise within the enclosure which is detrimental to the electronics. A means is therefore required to transfer heat from the equipment to the outside of the enclosure. In certain electronic applications in which components are housed in a sealed enclosure, a printed circuit board is used which has a copper inner-layer. Electronic components requiring heat extraction contact this copper layer. Edges of the board contact sides of the enclosure. While effective, this approach is very expensive. Further, this approach does not have the capability of disabling the heat extraction mechanism when the equipment is operating in a cold environment and heat needs to be retained within the enclosure to maintain the equipment within a desired band of operating temperatures.
BRIEF SUMMARY OF THE INVENTION
Among the several objects of the present invention may be noted the provision of apparatus for extracting heat from a sealed enclosure, the heat being generated by electronic components housed within the enclosure;
the provision of such apparatus in which the enclosure is an outdoors installation and the temperature of the surroundings about the enclosure can vary widely from very hot conditions to extremely cold conditions;
the provision of such apparatus to function effectively to remove heat from within the sealed enclosure to the atmosphere when the outside temperature is warm or hot and the heat generated by the components can cause their operating temperatures to be excessively high and damage the components;
the provision of such apparatus to further have the capability of generating and retaining heat within the enclosure when the outside temperature is cold and the heat generated by the components is needed to maintain their operating temperature within a normal range of operating temperatures;
the provision of such apparatus utilizing heat pipes and heat sinks to accomplish heat transfer out of the sealed enclosure;
the provision of such apparatus to further utilize strip heaters to heat the components within the sealed enclosure when the outside temperature falls below a predetermined temperature;
the provision of such apparatus in which the heat pipes have a heat transfer capacity equal to or greater than the amount of heat produced by the equipment (including electronic components) housed within the enclosure but lower than the total amount of heat produced by both the equipment and the heaters;
the provision of such apparatus in which the heat sinks employed limit the maximum temperature reached within the enclosure at a predetermined maximum temperature outside the enclosure;
the provision of such apparatus to efficiently and effectively maintain the temperature within the sealed enclosure to a range of temperatures which allow all of the equipment to function properly and with no equipment failures occurring because of temperature conditions within the enclosure;
the provision of such apparatus which can be configured for the type of equipment housed within the enclosure, as for example, stacked modular electronic components; and,
the provision of such apparatus which provides a relatively low cost solution for maintaining the temperature within the sealed enclosure to a safe operating temperature.
In accordance with the invention, generally stated, apparatus is provided for controlling the temperature within a sealed enclosure in which are housed electronic components. Operation of these components produces heat, and operation of the components preferably occurs within a desired temperature range. A heat sink extends through a sidewall of the enclosure to conduct heat from within the enclosure to the atmosphere. Additional heat sinks are mounted within the enclosure in a thermal transfer relationship with the components. Heat generated by operation of the components is transferred to these heat sinks thus drawing the heat away from the components. A heat pipe which extends between the respective heat sinks now conducts the heat to the first said heat sink for the heat to be expelled to the atmosphere. A heat generator within the enclosure generates heat to heat the components. A thermostat senses when the temperature within the enclosure falls below a predetermined temperature to energize the heat generator. As a result, the temperature in the enclosure is maintained within the desired range by appropriately removing heat from or generating heat within the enclosure and controlling the heat transfer path. Other objects and features will be in part apparent and in part pointed out hereinafter.
REFERENCES:
patent: 3746081 (1973-07-01), Corman et al.
patent: 3934643 (1976-01-01), Laing
patent: 4370547 (1983-01-01), Ward
patent: 4673030 (1987-06-01), Basiulis
patent: 5647430 (1997-07-01), Tajima
patent: 5771967 (1998-06-01), Hyman
patent: 5950712 (1999-09-01), Gates et al.
patent: 6047766 (2000-04-01), Van Brocklin et al.
Heat Pipe Technology, “The Heat Pipe—How It Works”, Aug., 1997.
Ciric Ljiljana V.
Esco Electronics Corporation
Lazarus Ira S.
Polster Lieder Woodruff & Lucchesi L.C.
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