GB2283089A

GB2283089A - Thermally insulated housing

Info

Publication number: GB2283089A
Application number: GB9420395A
Authority: GB
Inventors: Harald Bohm
Original assignee: AABH Patent Holdings SA
Current assignee: AABH Patent Holdings SA
Priority date: 1993-10-08
Filing date: 1994-10-10
Publication date: 1995-04-26
Also published as: DE4334282A1; GB9420395D0; FR2712120A1; ZA947886B; JPH07226192A

Description

2283089 1 Double-Walled Housin The present invention relates to a

double-walled housing.

According to the invention, there is provided a doublewalled housing comprising an inner wall; an outer wall spaced from the inner wall, such that a cavity is provided between the walls, with the cavity being under vacuum; heat insulation material at least partially filling the cavity; and heat-resistant intermediate material arranged in the f orm of a layer between the inner wall and/or the outer wall and the heat insulation material, with the density of the intermediate material being less than that of the heat insulation material.

The double-walled housing of the invention is particularly suitable for high voltage electrochemical storage batteries.

is High voltage electrochemical storage batteries, such as, for example, Na/NiC'2-based batteries, operate at relatively high temperatures, for example, in the region of 3000C. In order to maintain this operating temperature of the storage is 2 battery, the battery must have a housing which thermally insulates the cells of the battery and, thus, the battery itself, from the environment. Vacuum insulations such as those described in US Patent 5 137 169 have proved to be particularly effective.

According to US Patent 5 137 169 storage battery housings comprise a double-walled casing of thin special steel sheet, which is welded so as to be vacuum-tight and wherein the space between the walls is evacuated. Thermal insulating material, in the form of pre-pressed panels, is located between the two walls. These panels may be of ceramic fibres, glass fibres or powdery commercially available materials.

The space between the two walls, in which the thermal insulating material is located, can be evacuated by means of a short pipe which is attached to the inner or to the outer wall of the casing. The thermal insulation of the storage battery housing is considerably improved by the vacuum drawn between the two walls, thus reducing heat losses during the operation of the battery.

In the manufacture of such storage battery housings it has, however, now been found that the evacuation of the battery housing requires substantial time, since the insulating material between the two walls provides a considerable diffusion resistance for the residual gases. These 3 extended evacuation times which, depending on the dimensions of the battery housing, may endure for up to two days, increase the costs of the manufacturing process in respect of the battery housing. It is thus an object of the present invention to provide an arrangement which permits a reduction in the time required for this evacuation.

is US Patent 5 137 169 also describes panels which have milled grooves which f acilitate the suctioning-of f of the residual gases. These grooves are, however, only effective locally, whereas large regions of the insulating panels are not affected by this measure. In these regions, the panelshaped insulating material abuts fully against the two walls, and continues to provide transmission of heat from the insulating material to the casing material. A further object of the invention is thus, simultaneously, to reduce this transmission of heat from the insulating panel to the casing material.

These objects are met by the double-walled housing according to the invention.

The intermediate layer of relatively low density material has a considerably higher porosity than the insulation material itself, thereby permitting an improved diffusion of the residual gas, which results in a reduction in the evacuation time. The intermediate material may be the same 4 as the insulation material, although it is also possible to use a different material, for example, a mat of glass fibres. This layer of relatively low density also reduces the conduction of heat from the actual insulation material to the outer wall. Since, at this point, the temperatures within the insulation have already been reduced such that they are in the region of the room temperature of the outer wall, there is also virtually no transfer of heat by means of radiation. As a result, heat losses are additionally reduced.

The invention will now be described in more detail hereinafter with reference to the exemplified embodiment which is diagrammatically illustrated in the drawing.

The drawing shows a cross-section of a portion of a doublewalled housing, according to the invention, of a high voltage electrochemical storage battery, in the interior of which an operating temperature of about 3000C prevails. Thus, an inner wall 2 of the housing is also substantially at this operating temperature. An outer wall 1 of the housing is surrounded by the ambient temperature. A heat insulation material 3, preferably in panel form, is provided between the inner wall 2 and the outer wall 1. The walls are composed, for example, of special steel. Said heat insulation material is composed, for example, of ceramic fibres, glass fibres, or a granular type of material, which is, for example, in a pressed form.

is According to the invention, additional intermediate material 4, 5, which is also heat-resistant at the battery operating temperatures and the density of which is less than that of the heat insulation material 3, is provided as a layer between the heat insulation material 3 and the inner wall 2 and/or the outer wall 1. This intermediate material 4, 5 can, f or example, be a mat, and can be corrugated. It can be of the same material as the heat insulation material 3, but its porosity is greater than the porosity of the heat insulation material because of its lower density. It also has good heat insulation properties.

These intermediate layers 4, 5 improve the heat insulation properties of the double-walled evacuated housing, reduce the evacuation time, and permit easy manufacture of the housing. As a result of the fact that the heat insulation material 3 and also the intermediate material 4, 5 are composed of compact materials, an additional effect, whereby the two walls 1, 2 are supported relative to each other, is achieved since, of course, atmospheric pressure acts on the outer sides of the inner wall 2 and the outer wall 1. The double-walled housing can also be regarded as a type of Dewar vessel.

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Claims

1. A double-walled housing comprises an inner wall; an outer wall spaced from the inner wall, such that a cavity is provided between the walls, with the cavity being under vacuum; heat insulation material at least partially filling the cavity; and heat-resistant intermediate material arranged in the form of a layer between the inner wall and/or the outer wall and the heat insulation material, with the density of the intermediate material being less than that of the heat insulation material.

2. A double-walled housing according to Claim 1, wherein the inner wall and/or the outer wall is/are of metal.

3. A double-walled housing according to Claim 2, wherein the intermediate material has a fibrous structure.

is

4. A double-walled housing according to Claim 3, wherein the intermediate material is a fibrous mat.

5. A double-walled housing according to Claim 4, wherein the intermediate material is a mat of glass fibres.

6. A double-walled housing according to any one of Claims 1 to 5, wherein the intermediate material is corrugated.

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7. A novel double-walled housing, substantially as described and illustrated herein.