EP1063867A1

EP1063867A1 - Heater for base station

Info

Publication number: EP1063867A1
Application number: EP99304920A
Authority: EP
Inventors: Hamid Reza Falaki; William George Gates; Simon John Kerslake; Anthony John Hutton
Original assignee: Lucent Technologies Inc
Current assignee: Nokia of America Corp
Priority date: 1999-06-23
Filing date: 1999-06-23
Publication date: 2000-12-27

Abstract

There is disclosed a heater comprising: a rod-type heating element; and a means for clamping the heating element against a surface to be heated. The means for clamping the heating element preferably ensures good physical contact between the heating element and the surface to be heated. A minimum gap is preferably maintained between the surface to be heated and the opposing surface of the means for clamping.

Description

Field of the Invention

The present invention relates to heaters, and particularly but not exclusively to heaters suitable for heating a housing enclosure, such as a base station in a mobile communication system.

Background to the Invention

Base stations for mobile communications systems may potentially experience a wide range of ambient temperatures. If the ambient temperature drops below a certain value the electronics in the base station may cease to function. At such low external ambient temperatures, the heating which arises from the electronics itself is insufficient to keep the internal temperature high enough for operation. Even at higher temperatures where the heat dissipation in the electronics is sufficient to keep the electronics operative, there can be a problem if a power cut occurs. If the internal temperature falls below that at which the electronics is operative, it will not restart when the power returns. A heater is therefore desired, and conventionally provided in such environments.
The heater is required to be small, so as not to contribute to an increase in the physical size of the unit.
One currently known heater for this type of environment is described in European Patent Application Publication No. 0912078. In this heater a heating element comprising a foil is compressed between two thin rubber plates onto a surface to be heated. One problem with this arrangement is that the compression must be high in order to lower the temperature of the rubber. There is a limitation on the amount by which the rubber may be compressed, and this limits the temperature at which the foil heating element may be run, and consequently the temperature to which the environment may be heated.
It is an object of the present invention to provide an improved heater suitable for an environment such as a mobile communication system base station.

Summary of the Invention

According to the present invention there is provided a heater comprising: a rod-type heating element; and a means for clamping the heating element against a surface to be heated.
The means for clamping the heating element preferably ensures good physical contact between the heating element and the surface to be heated. A minimum gap is preferably maintained between the surface to be heated and the opposing surface of the means for clamping.
The means for clamping the heating element ensures good contact between the rod-type heating element and the surface to be heated. The rigidity of the means for clamping and the maintenance of a gap between the opposing surfaces of the means for clamping and the surface to be heated together ensure good heat transfer capability between the rod-type heating element and the surface to be heated. The heater can then be run cooler.
The surface to be heated may be the surface of an enclosure to be heated.
The surface to be heated may be a surface of a mobile communications base station.
The invention will now be described by way of example with reference to the accompanying drawings, in which:

Brief Description of the Drawings

Figure 1 illustrates a side-on view of an example heater according to the present invention;
Figure 2 illustrates an above view of the example heater according top the present invention as shown in Figure 1;
Figure 3 illustrates an example implementation of the heater of the present invention in the base station of a mobile communication system;
Figures 4(a) to 4(c) illustrate a selection of example alternative structures of the heating element of the heater according to the present invention; and
Figures 5(a) and 5(b) illustrate two alternative exemplary structures of a rod-type heating element.

Description of the Preferred Embodiment

In the following description the invention will be described particularly with reference to a mobile communication base station. However the invention may be applied more generally to a heater for heating a surface, whether the surface of an enclosure or otherwise.
Referring to Figures 1 and 2, part of a wall 2 of a housing enclosure is shown. The housing may be an enclosure for containing electronic radio equipment for a mobile communications base station. Such an enclosure may be formed from two inter-fitting light metal castings, and the part of the wall 2 preferably forms part of one of these castings.
A heating element generally designated by reference numeral 32 is shown, in the example of Figures 1 and 2, to be generally U-shaped, having a first end designated 14 and a second end designated 16. The heating element is formed in a U-shape by the bend designated generally by reference numeral 22. Although in the described example the heating element is shown as U-shaped, the heating element may in fact be any shape, such as zig-zagged or straight. The only restriction on the shaping of the heating element is that the thermal conductive properties of the element must not be changed.
Referring to Figures 4(a) to 4(c) there are shown, by way of example, three alternate shapes for the heating element 32. In Figure 4(a) the heating element has a general U-shape, as is shown in Figure 1. In Figure 4(b) the heating element 32 has a straight shape. In Figure 4(c) the heating element has a zig-zag shape. The selection of shapes shown in Figure 4 are not exhaustive, and it will be appreciated that a multitude of other shapes may be used.
The one characteristic that the various heating elements of Figure 4 have in common is that the heating element in all cases is rod-shaped, and preferably is a mineral insulated heater rod. The rod-shaped heating element may be either a rigid or a flexible wire.
Figures 5(a) and 5(b) show the cross-section of two examples of this preferable mineral insulated heater rod. Each of the rod-shaped heating elements has an outer sheath 50. The outer sheath may be copper or stainless steel, for example. In Figure 5(a) a single heating element 52 is located at the core of the heating element. In Figure 5(b) two heating elements 52 are located centrally within the heating element. In both examples, the remainder of the heating element within the sheath 50 comprises mineral insulation, generally designated by reference numeral 54.
Turning again to Figures 1 and 2, the heating element 32 of Figure 1 has at the first end 14 an electrical connection 28, and at the second end 16 an electrical connection 30. The electrical connections are connected, in a known manner, to a power source for heating the heating element 32.
In alternative arrangements of the heating element the electrical connections may differ. For example in the arrangements of Figures 4(b) and 4(c) both the electrical connections 28 and 30 are connected to the same end of the heating element. Such heating elements will utilise the twin heating element structure illustrated in Figure 5(c).
Referring to Figures 1 and 2, the heating element 32 is placed on the surface of the part of the wall 2, such that it makes good physical contact with the surface. Good physical contact is guaranteed by a fixing means, or securing block, generally designated by reference numeral 4. The securing block is shown to be fixed to the part of the wall 2 by four screws 6, 8, 24 and 26. The four screws engage with screw threads provided in the surface of the part of the wall 2. In Figure 1, the portions of the screws 6 and 8 extending through the securing block 4 into the part of the wall 2 are designated by reference numerals 10 and 12 respectively.
The securing block 4, which is preferably a metal block, is spaced from the surface of the part of the wall 2 by a distance t. The block is spaced by such a distance to ensure that it guarantees a good contact of the heating element with the surface of the part of the wall 2.
The securing block is provided to prevent movement of the heating element 32 and keep it securely on the surface of the wall. The securing block is provided with a groove matching the profile of the heating element and into which the heating element partially fits. The groove is designated by reference numerals 18 and 20 in Figure 1. The groove must have sufficient tolerance to cope with any thermal expansion of the heating element. The groove is also designed to provide the gap of thickness t between the securing block and the surface of the wall.
In operation, the electrical supply to the electrical terminals 28 and 30 heats the heating element 32, and heat is dispersed through the wall on which the heating element is mounted. The heat is then spread within the housing from the wall, providing a more even distribution of heat than may normally be expected from a locally positioned heating in a housing enclosure.
Figure 3 illustrates an example implementation of the heater of Figures 1 and 2 in the base station of a mobile communications system. The base station comprises two metal castings 40 and 42 connected by a hinge 44. Each have mounted thereon electronic circuits and modules for the operation of the base station. These modules are shown in Figure 3.
Modules 46 and 48 are shown attached to the upper and lower halves respectively of casting 40, and modules 50 and 52 are shown attached to the upper and lower halves respectively of casting 42.
The heater element, generally designated by reference numeral 60, is attached to the wall of the casting 42 adjacent, or proximal to, the module 52.
In operation, the heater heats the portion of the wall of the casting 42 corresponding to the portion 2 shown in Figures 1 and 2. The heat is conducted through the whole of the wall of the casting 42, such that it dissipates into the enclosure all along its length, including the upper portions adjacent the module 50. Thus, a relatively even distribution of heat within the enclosure is maintained. Thus the electronics located at the top of the base station is heated without overheating the electronics at the bottom. A well-controlled all-over temperature can thus be obtained.
Because of the temperature outside the housing tending to be less than that internal to the housing, the heat dissipates into the wall of the enclosure much more easily than into the securing block 4. However, a relatively small portion of the heat will dissipate into the securing block 4 and thus directly into the air in the lower part of the housing.
The presence of the securing block 4 ensures good physical, and hence thermal, contact between the heating element and the wall of the housing.
This allows good conduction flow and avoids radiation heating (where the heating element is not in proper contact with the wall). This good mechanical, and hence thermal, contact between the heating element and the heated surface means that the heating element can be run cooler than may otherwise be expected, because of the good heat transfer. The heating element does not have to be run as hot as the foil that comprises the heating element in European Patent Application Publication No. 0912078.
Thus, the present invention enables the heater temperature to be reduced, relative to other known heaters, whilst being capable of generating the same heating effect. Good heat transfer between the rod-type heating element and the surface to be heated is ensured by the rigidity of the clamping means 4 and the maintenance of the gap 't' between the opposing faces of the clamping means 4 and the surface to be heated 2. Thus a cooler heater can provide more heat transfer to the surface to be heated.

Claims

A heater comprising: a rod-type heating element; and a means for clamping the heating element against a surface to be heated.
The heater of claim 1 in which the means for clamping the heating element ensures good physical contact between the heating element and the surface to be heated.
The heater of claim 1 or claim 2 in which a minimum gap is maintained between the surface to be heated and the opposing surface of the means for clamping.
The heater of any one of claims 1 to 3 in which the surface to be heated is the surface of an enclosure to be heated.
The heater of any one of claims 1 to 4 in which the surface to be heated is a surface of a mobile communications base station.