Electricity: conductors and insulators – With fluids or vacuum – With cooling or fluid feeding – circulating or distributing
Utility Patent
1998-06-11
2001-01-02
Kincaid, Kristine (Department: 2831)
Electricity: conductors and insulators
With fluids or vacuum
With cooling or fluid feeding, circulating or distributing
C174S015200, C361S676000, C361S688000, C361S700000
Utility Patent
active
06169247
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to enclosures for electronic components, and particularly to enclosures for electronic devices intended for use in locations exposed to weather.
BACKGROUND OF THE INVENTION
Electronic components are placed in locations exposed to weather for use in a wide variety of applications, including POTS (plain old telephone service), ISDN (integrated services digital network), data lines, cellular telephone equipment, and cable television equipment. Components placed in outdoor locations include, by way of example, network interface devices, network interface units, and terminal boxes. Conventionally, sealed metal boxes or cabinets are provided for components to protect them from weather and other foreign objects. Enclosures with walls of solid plastic are preferable from the standpoints of cost, ease of manufacture, lack of susceptibility to corrosion, and ability to conform to a desired appearance for aesthetic purposes. Plastics used for walls of solid plastic include, by way of example only, crystalline thermoplastic polyesters, such as that sold by General Electric under the trademark VALOX.
Sealed enclosures for electronics are susceptible to increases in temperature in the air inside the enclosure. Solar loading for enclosures exposed to sunlight, and the heat generated by the electronics, are the principal sources of the heat energy. Solar loading refers to energy received by absorption of solar radiation. Sealed enclosures limit convective cooling. Excessive temperatures of course damage electronic components and reduce component life. Even metal enclosures are provided with heat exchangers and other systems for reducing thermal loading. Heat dissipation in metal enclosures is further improved by the use of designs that increase the ratio of surface area of the metal to the volume of the interior of the enclosure. For example, known designs of metal enclosures include metal boxes with externally extending fins or ridges to increase the surface area of the metal. As electronic devices generate heat, plastic enclosures are often problematic, because they dissipate heat poorly.
A metal enclosure of a given configuration provides superior heat dissipation to a plastic enclosure of the same configuration. However, metal enclosures have greater weight, higher cost of manufacture, and greater susceptibility to corrosion when compared to plastic enclosures. The manufacture of metal enclosures requires additional steps of surface finishing. Modifications to the appearance of metal enclosures are often required for aesthetic purposes.
An advantage of the present invention is that it provides for an enclosure for electronic devices having a wall of a rigid plastic material with improved removal of heat from air within the enclosure.
Additional advantages of the invention, and objects of the invention, will be evident from the detailed description of an embodiment which follows.
SUMMARY OF THE INVENTION
In one aspect of the invention, an enclosure for electronic devices has a wall of a substantially rigid plastic, and a body of a material having thermal conductivity greater than the thermal conductivity of the rigid plastic. The body is in thermal communication with the rigid plastic of the wall at two different locations on the wall, so as to provide substantially improved heat transfer between the rigid plastic at the first location and the rigid plastic at the second location. Greater heat dissipation at the second location and thereby greater overall heat dissipation, is achieved.
In another aspect of the invention, an enclosure for electronic devices has a wall of substantially rigid plastic, and a body of a material having thermal capacity greater than that of the rigid plastic. Thermal capacity of the enclosure as a whole is thereby increased. Temperature fluctuations resulting from diurnal temperature changes are reduced; the material having a greater thermal capacity will tend to dissipate heat into the enclosure during times when the outside temperature is lower than the temperature of the material.
According to another aspect of the invention, an enclosure for electronic devices has a wall of a substantially rigid plastic, and elongated chambers defined in the wall. The elongated chambers contain a phase change material. The phase change material increases the heat capacity of the enclosure and provides transfer of heat energy by spreading the heat throughout the wall, thereby increasing the effective surface area available for heat dissipation. More particularly, the phase change material tends to absorb heat and increase in temperature. As the phase change material reaches a critical temperature, the phase change material changes phase, with no change in temperature until all of the material has changed phase. At higher temperatures, the phase change material conducts heat energy. Examples of phase change materials include paraffins and various salts, such as Glauber's salt.
According to another aspect of the invention, an enclosure for electronic components, has a wall of a rigid plastic material, the wall having a first location tending to be at a relatively high first location temperature, and a second location tending to be at a temperature lower than the first location temperature. A structure is provided for transferring heat from the wall at the first location to the wall at the second location. The structure may be, for example, a heat pipe, or a chamber formed within the wall and filled with a phase change material. The first location may be a top wall of a rectangular enclosure, and the second location may be a bottom or side wall. Heat pipes may be placed on or within the top wall and extend on or through one or more side walls, and extend to a bottom wall. Similarly, chambers defined within the wall and filled with a phase change material may run continuously from the top wall, to one or more side walls, and to a bottom wall.
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Maurice J. Marongiu and Randy Clarksean, Thermal Management of Outdoor Enclosures Using Phase Change Materials, Electronics Cooling, Jan. 1998, vol. 4, No. 1.
Craft, Jr. Thomas F.
D'Alessio Alfonso J.
Kay Jason A.
Pawlenko Ivan
Shevchuk George
Duane Morris & Heckscher LLP
Kincaid Kristine
Lucent Technologies - Inc.
Mayo, III William H
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