Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-01-25
2001-07-03
Thompson, Gregory (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C062S259200, C165S908000, C361S816000, C361S831000
Reexamination Certificate
active
06256198
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method and an apparatus for air-cooling heat generating devices, in particular in a radio transmission system.
DESCRIPTION OF RELATED ART
In radio transmission systems, heat generating devices such as power amplifiers, are usually located at some distance from antennas used for radio signal transmission. Thus, when feeding the antennas with an amplified signal, the signal has to propagate through feeder cables. The propagation in the feeder cables is however not lossless. The losses in the feeder cables are not desired.
One solution to the problem of losses in feeder cables is to locate the power amplifiers close to the antenna, which is to be fed by the amplified signal. However, antennas in radio transmission systems are usually located at locations, which are difficult to reach. For example they can be located at the top of antenna towers and the like.
Furthermore, the power amplifiers should, in the case that they are located in an antenna tower, be small, compact and have a low weight, and therefore need to be cooled in an efficient manner. The cooling must be very efficient and capable of cooling a large amount of heat. The mere use of cooling flanges and the like will in most cases not be sufficient for providing an efficient cooling. This is due to the fact that the amplifiers used usually are very compact and emit a large amount of heat.
In order to solve this problem it is of course possible to locate fans in the vicinity of the power amplifiers. However, this is not desired since the fans are mechanical devices having moving parts, which are in need of frequent service. Thus, the fans will then be located at locations which are hard to reach and therefore difficult to service, repair or exchange. Another problem, which could occur is that the mean time before failure (MTBF) of the whole transmission system is reduced, due to the locations of such fans.
Thus, there is a problem of providing an efficient cooling for heat emitting devices in radio transmission systems, in particular when the heat emitting devices are located at locations which are hard to reach.
Further, U.S. Pat. No. 5,067,047 describes a means for cooling heat generating components mounted on the front surface of printed circuit boards. A pressurised cooling fluid is supplied via holes located where cooling is desired.
Also, U.S. Pat. No. 4,901,029 discloses a power amplifier arrangement, which includes a cooling arrangement.
However, none of the solutions outlined in these documents is suited for cooling components in radio transmission systems, mainly due to that the cooling capacity is too low and due to the cost associated with the cooling systems.
SUMMARY
It is an object of the present invention to solve the problem of providing an efficient cooling for heat emitting devices in radio transmission systems.
This object is obtained by co-locating a Laval nozzle, with the heat emitting device. In a preferred embodiment the nozzle is fed via an air feeding tube, the air pressure preferably being higher than the pressure at the outlet side of the nozzle.
In this manner the air flowing out of the nozzle can have a high velocity. For example the velocity can be the velocity of sound or higher. Thereby the thermal transmission factor is increased significantly.
The use of such an arrangement provides several advantages. Thus, since no moving parts are located at places, which are difficult to access, the MTBF for the transmission system is expected to be reduced and service will be much easier and less costly to perform.
The nozzle can be located close to the device, which it is intended to cool, whereas the unit supplying the nozzle with air, for example a fan or a compressor, can be located at another location. This is very advantageous when the electrical devices to be cooled are located at locations hard to reach or access, such as in the top of antenna towers. The supplying unit can then be located at the foot of the antenna tower where repair and service is easy to carry out.
Furthermore, since the air is compressed, the diameter of the tube used for interconnecting the nozzle with the air supplying unit can be reduced.
REFERENCES:
patent: 3626251 (1971-12-01), Vigue
patent: 4665714 (1987-05-01), Keller
patent: 5052284 (1991-10-01), Schweikert
patent: 5067047 (1991-11-01), Azar
patent: 5601478 (1997-02-01), Mether
patent: 5775122 (1998-07-01), Waase
patent: 6094929 (2000-08-01), Eriksson
patent: 25 37 295 A1 (1976-04-01), None
patent: 2 289 827 (1995-11-01), None
Gudmundsson Bjorn
Larsson Nils-Goran
Nixon & Vanderhye P.C.
Telefonaktiebolaget LM Ericsson
Thompson Gregory
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