GB2089950A

GB2089950A - Thermally insulated containers

Info

Publication number: GB2089950A
Application number: GB8119981A
Authority: GB
Original assignee: DUNCAN RONALD FREDERICK HENRY
Current assignee: DUNCAN RONALD FREDERICK HENRY
Priority date: 1980-12-22
Filing date: 1981-06-29
Publication date: 1982-06-30

Abstract

A fluid container, e.g., a domestic hot water tank comprises inner and outer drum-shaped vessels with closed lower ends (5, 6) of plastics material, the vessels being joined at the upper ends by an annular end piece (10) to define a sealed volume between them which is evacuated to provide thermal insulation. Spacers (7, 8, 9) assist in maintaining the vessels apart and inlet and outlet pipes are sealed through the cylindrical walls (3, 4). <IMAGE>

Description

SPECIFICATION Thermally insulated containers DESCRIPTION The invention relates to thermally insulated containers, for example, hot water storage tanks for domestic use, for use on aircraft, or in hospitals.

In storage containers fluids which are to be preserved at a desired temperature above or below that of the surroundings, measures to reduce the flow of heat through the tank walls slow the temperature change towards ambient temperature and thereby minimise the energy needed to maintain the desired temperature. Thus the well known vacuum flask provides an evacuated double wall structure of glass, which is very fragile and which cannot conveniently be provided with more than a single aperture. Also, to retard the loss of heat from domestic hot water storage tanks, usually cylinders of copper which is a good heat conductor, the cylinder exterior is frequently lagged with thermal insulation material.

This operation is performed after installation of the cylinder, and is consequently sometimes difficult to perform and involves extra expense.

It would accordingly be advantageous to provide a container for fluids with a wall structure which offers substantial opposition to the flow of heat across it, whilst being physically robust, and such as to permit apertures therethrough to be formed.

Accordingly, the present invention provides a container for a fluid comprising an inner wall defining a volme for reception of the fluid, and an outer wall around and spaced from the inner wall, the space between the walls being sealed and evacuated, the material of each of the walls being plastics material.

Because of the material of the walls, fluids inlet and outlet pipes can readily be arranged to extend through them, as can heating or cooling coils or heating elements. The evacuated double wall structure can constitute substantially the entire structure of the container or only part of it; for example, the container may have a lid which is conventional or otherwise thermally insulated, or the base on which the container is supported may be solid to provide additional strength. The internal and external wall thicknesses are selected to provide appropriate rigidity and are connected together at apertures extending through the wall structure and if appropriate by internal spacers extending between them, the spacers being designed so as not to impede the evacuation step following assembly together of the walls and the sealing of the space between them.

The invention also provides a domestic hot water container comprising spaced inner and outer vessels of plastics material, each comprising a cylindrical wall portion closed at the lower end by a lower end portion, spacers between the cylindrical and lower end portions to maintain the spacing therebetween, an upper end piece sealingly connecting together the upper edges of the cylindrical wall portions, the space between the vessels being evacuated, a lid closing the upper end of the tank, and inlet and outlet pipes sealed through the cylindrical wall portions.

With such a domestic hot water tank, manufacturing costs can be reduced as compared with conventional metal cylinders, and the tank is lighter in weight. There is no need to add insulation before or after installation, and heat loss from the tank is reduced as compared with conventional tanks, even where these have been insulated with conventional external lagging.

Considerable savings in fuel can be achieved in heating the tank contents and maintaining them at a desired temperature.

Containers embodying the invention are usable not only for the efficient storage of hot liquids but also for storage of liquids and gases which are to be cooled or which have been cooled for example in medical applications, and in the storage of such materials as liquid hydrogen.

The plastics material employed can be of any kind appropriate to the temperatures to which it will be subjected in use, and may be reinforced if desired, as by glass or other mineral fibres.

The invention is further described below by way of example with reference to the accompanying drawing, the single figure of which is a partial sectional side view of a domestic hot water tank embodying the invention.

The illustrated tank comprises an outer vessel 1 and an inner vessel 2 received therein, the vessels being integrally formed with respective circular cylindrical walls 3 and 4 and respective planar closed bottom ends 5 and 6. The vessels 1 and 2 are spaced apart by a plurality of annular spacers 7 which extend between the walls 3 and 4, and in addition, the ends 5 and 6 are similarly spaced apart by radially extending spacers 8 and tangentially extending spacers 9, so that the weight of water on the end 6 is adequately supported from the floor or other support on which the end 5 will rest in use. The vessels and spacers of the tank are moulded in substantially rigid plastics material but need not all be of the same plastics material.Polyethylene can be employed, or other plastics material, with or without glass fibre or other reinforcement, capable of withstanding a temperature of 1 000C.

The upper edges of the cylindrical walls 3 and 4 are substantially coplanar and each is sealed around its entire periphery to an annular end piece 10. The spacers 7, 8 and 9 and the end piece 10 are of plastics material and are secured to the vessels 1 and 2 by welding or adhesive.

The cylindrical double wall of the tank is penetrated by an overflow pipe 11, a water inlet pipe 12, and a water outlet pipe 14 positioned at appropriate relative heights, and also by a means for heating the tank contents, in the form of an electrical heating element 1 6 associated with a thermostat temperature control device.

The flow of water into the tank through the inlet pipe 12 is controlled by a ball cock arrangement 1 5 which is conventional and is therefore not further described. The various pipes and the element 1 6 are sealed by airtight seals bonded with appropriate adhesive through the inner vessel 2 to prevent escape of the tank contents, and also through the outer vessel 1, because of the high temperature of the element 1 6, an appropriate bonding of plastics material and metal can be used if required.

The volume enclosed between the vessels 1 and 2 and the end piece 10 is thus completely sealed and in accordance with the invention, this volume is evacuated in the final stage of manufacture of the tank. Evacuation is effected by pumping out air through an aperture in the wall 4 which is subsequencly closed off by heat sealing of the plastics material of the wall. The resulting protrusion 1 6 is located within the tank so as to be protected from damage during installation. The spacers 7, 8 and 9 are apertured as shown to minimise the possibility of air being trapped within the space to be evacuated.

The tank is completed by a lid 18 closing the upper end, the lid being removable for any necessary servicing of the ball cock arrangement.

The lid 18 8 can be of conventional construction but is preferably, as shown, of construction similar to that of the main body of the tank, with a lower wall 1 9 having a central depression for location within the end piece 10 and an upstanding peripheral portion 20, closed by a flat upper wall 21.

Spacers 22 maintain the' spacing of the walls 19 and 21 when the volume between them is evacuated through an aperture in the lower wall 19 sealed at 24. A valved steam outlet 25 is provided in the lid 18 to prevent rupture of the tank due to steam generated in the event of failure of the thermostat control to limit the heat input into the tank.

It will be evident that the illustrated tank can be modified in various ways, as to its size, shape and construction, and that the invention can be embodied in other forms of container than domestic hot water tanks.

Claims

1. A container for a fluid comprising an inner wall defining a volume for reception of the fluid, and an outer wall around and spaced from the inner wall, the space between the walls being sealed and evacuated, the material of each of the walls being plastics material.

2. A container as claimed in claim 1 having pipe means extending through the inner and outer walls for establishing fluid communication between said volume and the exterior of the container.

3. A container as claimed in claim 1 or 2 having extending into the interior of the container means for heating the contents thereof.

4. A domestic hot water container comprising spaced inner and outer vessels of plastics material, each comprising a cylindrical wall portion closed at the lower end by a lower end portion, spacers between the cylindrical and lower end portions to maintain the spacing therebetween, an upper end piece sealingly connecting together the upper edges of the cylindrical wall portions, the space between the vessels being evacuated, a lid closing the upper end of the tank, and inlet and outlet pipes sealed through the cylindrical wall portions.

5. A container as claimed in claim 4 wherein the lid comprises spaced lower and upper walls of plastics material, the walls being sealed together, and the space between the walls being evacuated.

6. A container as claimed in claim 4 or 5 wherein the spacers are apertured and a single evacuation position is provided in the inner vessel.

7. A container as claimed in claim 4, 5 or 6 having an electrical heating element supported by the cylindrical wall portions and extending into the inner vessel.

8. A container as claimed in any preceding claim wherein the plastics material is a reinforced plastics material.

> . A container as claimed in claim 8 wherein the plastics material is reinforced by glass fibre.

1 0. A container as claimed in any preceding claim, wherein the plastics material is polyethylene.

1 A container as claimed in claim 1, 2 or 3 wherein the inner and outer walls each comprise a base portion and a cylindrical portion extending upwardly from the base portion.

12. A container as claimed in any one of claims 4 to 1 wherein the cylindrical wall portions are circular cylindrical portions.

1 3. A domestic hot water container substantially as herein described with reference to the accompanying drawing.