GB2273469A

GB2273469A - Low pressure vessel

Info

Publication number: GB2273469A
Application number: GB9316574A
Authority: GB
Inventors: Maximilian Michael C Michaelis
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-12-18
Filing date: 1993-08-10
Publication date: 1994-06-22
Also published as: GB9316574D0; WO1994015123A1

Abstract

A vessel for use in circumstances where the pressure within is less than ambient pressure e.g. a vacuum chamber or the hull of an underwater craft, includes an envelope consisting of two relatively thin walls linked by tie members. In use, the space between the walls of the envelope of the pressure vessel is pressurised to a pressure such that the walls of the envelope of the pressure vessel are in a state of tension. The cavity may be filled with a gas eg air, helium, or expanded plastics. <IMAGE>

Description

Low Pressure Vessel The present invention relates to low pressure vessels, that is to say pressure vessels intended for use in circumstances where the pressure inside the vessel is less than ambient pressure.

Low pressure vessels operate in circumstances under which their walls are in a state of compression and their walls have to be made sufficiently massive, shaped and sometimes braced to withstand the considerable imploding forces which in use are imposed upon them. As a result such pressure vessels are heavy, cumbersome to use and, in larger sizes, expensive to construct.

It is an object of the present invention to provide a low pressure vessel in which the above problems are alleviated by constructing the low pressure vessel in such a way that in use, its walls are in a state of tension rather than compression.

According to the present invention there is provided a low pressure vessel including an envelope comprising an inner wall and an outer wall, means linking the inner and outer walls and means for pressurising the space between the inner and outer walls such that in use the walls of the vacuum chamber are in a state of tension.

The means linking the inner and outer walls of the envelope of the low pressure vessel may be wires or membranes attached to the opposed surfaces of the inner and outer walls of the envelope of the low pressure vessel. Alternatively the low pressure vessel may be fabricated out of a plurality of cells appropriate surfaces of which combine to form the inner and outer walls of the envelope of the low pressure vessel and the tension members linking them.

The space between the inner and outer walls of the envelope of the low pressure vessel can be pressurised appropriately by pumping a gas or liquid into it until a pressure is established such that, in use, the inner and outer walls.of the envelope of the low pressure vessel are in a state of tension.

If a gas is used to pressurise the space between the inner and outer walls of the envelope of the low pressure vessel then it can be one which is lighter than air to reduce the weight of the low pressure vessel still further.

Alternatively, the.space between the inner and outer walls of the envelope of the low pressure vessel can be filled with a plastics material which is then caused to foam in situ thus generating tension forces in the inner and outer walls of the envelope of the low pressure vessel.

The inner and outer walls of the envelope of the low pressure vessel can be made of material which is sufficiently flexible as to enable the low pressure vessel to be transported or stored in a collapsed state and inflated when it is desired to use the low pressure vessel.

In one form of the invention the low pressure vessel is a vacuum chamber having a cylindrical section with flat end plates at least one of which has connections by means of which the inside of the vacuum chamber can be evacuated and the space between the inner and outer walls of the envelope of the vacuum chamber can be pressurised.

The inner and outer walls of the envelope of the vacuum chamber are linked by a large number of wires the tensile strength of which is large enough to withstand the tensile stress generated when the envelope of the vacuum vessel is pressurised and the inside is evacuated.

The construction of the low pressure vessel is such that it can be scaled to any desired size readily. Thus it could be used to form tunnels through which bodies can be transported under conditions of reduced pressure.

Other larger structures for which the invention can be used are the pressure hulls and/or buoyancy tanks of underwater craft.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective schematic view of a vacuum chamber embodying the invention, Figure 2 is a cross-section of a portion of the envelope of the vacuum vessel of Figure 1, Figure 3 is a perspective schematic view of another form of vacuum chamber embodying the invention, and Figure 4 is a cross-section of a portion of the envelope of the vacuum chamber of Figure 3.

Referring to the drawings in which like components have the same reference numbers, in Figure 1 there is shown a simple cylindrical vacuum vessel consisting of an envelope 1 enclosing a volume 2. The envelope 1 has relatively thin metal inner and outer walls 3 and 4, respectively. The inner and outer walls 3 and 4 are linked by many tension members in the form of wires 5 the ends of which are attached to the inner and outer walls 3 and 4. The vacuum vessel is enclosed by end pieces 6 and 7, which may be constructed in the same way as the cylindrical part of the envelope 1, if desired. The end piece 6 has a central exhaust port 8 by means of which it can be evacuated in the normal way and a duct 9 by means of which the space 10 between the inner and outer walls 3 and 4 can be pressurised, normally by a gaseous medium although a fluid can be used if desired.Alternatively, the space between the inner and outer walls 3 and 4 can be filled by an expanded plastics material.

In use the space between the inner and outer walls 3 and 4 is pressurised to such an extent that, because the surface of the outer wall has a greater area than that of the inner wall 3 the walls in use are in a state of tension and there is a net outward force sufficient to withstand the inwardly directed forces due to the atmosphere when the interior of the vacuum vessel is at a pressure lower than that of its surroundings.

Figure 2 shows a cross-section of a portion of the envelope 1 in use. It can be seen that, due to the thinness of the walls,3 and 4 bulge somewhat between the wires 5.

Figure 3 shows an alternative structure in which a cellular construction is employed for the cylindrical part of the envelope 1. The inner and outer walls 3 and 4 are formed by the exposed portions of the walls 31 of a plurality of touching and bonded cylindrical cells 32 and the tension members are formed by those portions 33 of the walls 31 of which are in contact and bonded together.

Each cell 32 of the cylindrical part of the envelope 1 can be provided with its own pressurisation connection, or they can communicate with a common pressurisation manifold. The former construction has safety advantages in that a loss of integrity of one cell does not affect the others.

Figure 4 again shows a cross-section of a portion of the envelope 1 of Figure 3 to a greater scale.

If the space between the inner and outer walls 3 and 4 of the envelope 1 is pressurised by a gaseous medium, a gas which is lighter than air, preferably helium because of its inertness, can be used so that the weight of the envelope 1 can be reduced even further.

For simplicity the invention has been described in the form of a simple cylindrical chamber. In practice, because the vacuum vessel does not have to have a shape which provides resistance to inwardly directed forces, the vacuum vessel can be of any desired shape. Also, the walls of the envelope can be thin enough to be flexible, so enabling the vacuum vessel to be transported or stored in a collapsed state and inflated when required.

Furthermore, the vacuum vessel can be of any desired size, thus enabling it to be used for the pressure hulls and/or buoyancy tanks of underwater craft.

Furthermore, as in conventional vacuum apparatus, the envelope 1 can be made in the form of a bell-jar which is used in conjunction with a separate base plate, which may be convenional in form so that structures can be mounted upon it and electrical and other feed-throughs passed through. In this case, the vacuum vessel exhaust port 8 would be situated in the base plate in the usual way.

Claims

1. A low pressure vessel including an envelope comprising an inner wall and an outer wall, means linking the inner and outer walls and means for pressurising the space between the inner and outer walls such that in use the walls of the' vacuum chamber are in a state of tension.

2. A low pressure vessel according to Claim 1 wherein the means for pressurising the space between the inner and outer walls comprises means for filling the space within the inner and outer walls with a fluid under pressure.

3. A low pressure vessel according to Claim 2 wherein the fluid is a gaseous medium.

4. A low pressure vessel according to Claim 3 wherein the gaseous medium is lighter than air.

5. A low pressure vessel according to Claim 1 wherein the space between the inner and outer walls is filled with an expanded plastics material.

6. A low pressure vessel according to any preceding claim wherein the envelope includes elements which in use are in a state of compression.

7. A low pressure vessel according to any preceding claim wherein the walls of the envelope are flexible enough to enable the vacuum vessel to be transported or stored in a collapsed state and inflated when required.

8. A low pressure vessel substantially as hereinbefore described and with reference to the accompanying drawings.