Electricity: conductors and insulators – With fluids or vacuum – Boxes and housings
Reexamination Certificate
2000-08-14
2001-11-06
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
With fluids or vacuum
Boxes and housings
C174S016300
Reexamination Certificate
active
06313399
ABSTRACT:
FIELD OF THE INVENTION
In general, the invention relates to the structure of cooling elements in electric devices. In particular, the invention relates to a cooling element in which the cooling of an unevenly distributed heat load can be intensified.
SUMMARY OF THE INVENTION
In electric devices part of the electric energy is converted into heat, as a result of which the electric device warms up at some points. In electric devices, which are encased and contain electronic components, points that warn up particularly strongly are, for example, power transistors and other power semiconductors, which are used as amplifiers or as electronically controlled power switches. In order to make sure that the warming up of the component will not impede the operation of the device, as high a proportion of the heat as possible must be conducted away from the device. Active cooling with fans or Peltier elements is possible in certain cases, but in most cases cooling takes place by means of the convection of the ambient air or some other medium.
FIG. 1
shows an encased electric device
100
, which contains three components
101
,
102
and
103
that produce a lot of heat. In order to achieve convection cooling according to the prior art, these components are fastened in the device so that the heat of the components is conducted to the metallic outer surface
104
of the device, to which surface the cooling element
105
is fastened. Cooling element
105
comprises back plate
107
which supports cooling ribs
106
.
FIG. 2
shows the device with its cooling elements seen from the side of the cooling element. The heat produced in the components
101
,
102
and
103
is conducted via the metallic outer surface of the device to the cooling element
105
, which is thereby heated at certain points. From the ribs
106
of the cooling element at the hot components the heat is conducted to the ambient air, which rises upwards when it warms up. Cooler air flows from below to replace it, and this in turn warms up and starts rising upwards, whereby the cooling convection air flow indicated by arrows in
FIG. 2
is formed.
The solution shown in
FIG. 2
has the problem that the intake of the cooling air takes place at a relatively narrow area
201
. This drawback is emphasized if the device
100
with its cooling elements is installed in a rack, and another device is installed immediately beside it. If there are also other devices in the rack below the device being examined, it is possible that the air that flows from below between the cooling ribs is already warm, whereby the cooling is not very efficient. In order to achieve sufficient cooling, the cooling element
105
must be made relatively large, which reduces the efficiency of space utilization. Another alternative is to accept a substandard quality of cooling and allow a high operation temperature for the components of the electric device, but this reduces the reliablity of the device and shortens its service life.
FIG. 3
shows a known solution, which partly solves the problem of “pre-heated” cooling air. In this solution, the cooling element
301
is placed diagonally, whereby cooling air flows between its ribs at least partly from the front of the device. However, in this application the intake of the cooling air also takes place on a relatively narrow area.
The purpose of this invention is to present a cooling element, which cools an unevenly distributed beat load efficiently.
The purpose of the invention is achieved by arranging the ribs of the cooling element in a layout in which the distance between them is not constant.
The cooling element according to the invention, which comprises ribs at a certain distance from one another is characterized in that the width of at least one space between ribs is different at different points.
The problems of prior art cooling elements are mainly caused by the fact that the cooling element is usually made of an extruded aluminium profile. With the extrusion method it is possible to manufacture only profiles in which the cross-section is the same for the whole length. In the cooling element according to the invention the ribs are not placed parallelly and spaced evenly, but the spaces can become narrower and wider and the ribs can curve. In such an arrangement, the air flowing between the ribs can be guided so that it cools efficiently the parts of the device at which there are many heat-producing components. The curving ribs and the widening and narrowing spaces can also direct the intake of cooling air so that it is as cold as possible and its flow is not blocked. The cooling element according to the invention can be manufactured by casting, for example.
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Mäki Jarmo
Suntio Teuvo
Estrada Angel R.
Greenberg & Traurig, LLP
Muuntolaite Oy
Reichard Dean A.
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