Technical field: The present invention relates to a method of manufacturing shell-shaped constructions, preferably of concrete, such as houses, ships' hulls, etc.

Background art:

It is already known to coat an inflated rubber membrane with concrete either before or after inflation, the membrane being removed after the concrete has set. The known technology can be divided into three groups:

1. A flexible membrane (rubber) is coated with concrete, and suitably reinforcing mesh, after which the membrane is inflated to the desired size and the concrete then allowed to solidify (SE 330435).

2. A non-flexible membrane is inflated and concrete is then applied externally by means of spraying (SE 357230).

3. A flexible or non-flexible membrane is inflated and the "balloon" is then coated internally with an insulating foam which is allowed to solidify, thus improving the rigidity of the balloon, after which concrete is sprayed on internally (EP 0357151).

The drawbacks of the above procedures are:

1. The method functions well for smallish constructions, e.g. a hemisphere with less than 5-6 m diameter. The procedure is difficult to perform satisfactorily with larger constructions due to problems of instability. Very moderate winds during the casting, for instance, may cause deformation of the "balloon" which jeopardizes the entire casting. 2. Here the problems of instability described under 1. are eliminated by the "balloon" being pumped up to a higher pressure, e.g. 0.1 bar, or about 10 times the pressure used under 1.

The drawback with high pressures is the enormous forces required to keep the balloon/ hemisphere on the ground. (One ton per square metre is required for a pressure of 0.1 bar in the hemisphere, a construction with an area of 200 m ² takes 200 ton.)

3. Here the instability problems are solved with the aid of foam and moderate pump pressure can be used. The drawback with this procedure is

the complex internal reinforcing system required and the great waste of concrete which is unavoidable when spraying internally (from below).

It is also known to fill powder into a space between two pipes (membranes) and evacuate the air from this space so the powder is compacted thereby producing a more rigid body (US 3258883). There is no intimation in this publication of using the procedure for building purposes.

Summary of the invention: A method constituting a solution to these problems is claimed in Swedish patent application 9303576-4. This method is characterized in that two flexible sheaths or membranes are arranged, an upper sheath outside a lower sheath, with a space between them into which powder material is filled, both sheaths being attached to a support surface or to the ground, after which pressure medium such as air is blown in between the support surface/ round, or an auxiliary membrane, and a lower sheath/ membrane, so that the sheath/ membrane construction is inflated to the desired shape, after which the space between the sheaths /membranes is evacuated with the aid of a vacuum pump, thereby compacting the powder to rigidity, after which concrete, such as fibre-reinforced concrete, is sprayed onto the exterior of the upper sheath / membrane, and that when the concrete has set/ solidified the pressure medium is released and air is allowed to enter the space. It is thus possible to build normal-sized or large buildings of hemispherical shape, round or flattened, or shapes deviating from these, at relatively low cost.

The present invention relates to a further development of the method for which a patent application has been applied, and entails an equivalent solution to the problems mentioned above. The method according to the present invention is characterized in that two flexible sheaths are arranged, an upper sheath outside a lower sheath, with a space between them into which powder or particle-shaped material and binder are filled. Both sheaths are attached to a support surface or to the ground, after which pres¬ sure medium such as air is blown in between the support surface /ground and the lower sheath/ membrane, so that the sheath/ membrane construc¬ tion is inflated to the desired shape, after which the space between the sheaths / membranes is evacuated with the aid of a vacuum pump, and the

powder/ particles in this layer are allowed to set and a rigid layer is obtained where communication between its particles is retained.

This method is an alternative to the method first mentioned and offers an alternative to build normal-sized or larger buildings of hermispherical or spherical shape and extensions for other house designs.

Brief description of the drawings:

The invention is illustrated in more detail in the accompany drawings in which Figures la-lc show various stages of erection of a mould for the body of a house, a ship's hull, etc. and a template for an insulating layer such as concrete, etc. i.e. a first stage in constructing a house, a ship's hull, etc. Figure Id shows concrete being sprayed on. Figures 2a-2e show the alternative production of ship's hulls or the like, according to the invention.

Preferred embodiment:

Figure la reveals how two membranes, an upper membrane (4) and a lower membrane (1) are placed and anchored in a foundation (2). A powder material such as sand, sawdust, porous clay pellets, etc., and binder such as cement paste, polymers or other binder, are filled into the space (3) between the membranes. However, only in such quantity that the skeleton structure of the layer is obtained, i.e. communication between the particles remains, unlike the previously claimed method. The membranes (1, 4) are attached to the foundation (2) or a support surface.

Figure lb shows how a pressure medium such as air is blown into the space (7) below the lower membrane (1) with the aid of a pump (5), and the membranes (1, 4) with the powder between them are lifted to the desired shape, possibly under partial vacuum. A positive pressure of 0.001-0.01 bar in the space (7) is sufficient, depending on the diameter of the membrane. However, the diameter should be relatively large (for constructing a house, for instance). Leca pellets, i.e. pellets of expanded clay, may be placed in the space, as well as binder. When the desired shape has been obtained, the air is evacuated from the powder space (3), see Figure lc, and after setting a rigid layer is obtained with communication between the various particles. The layer has satisfactory rigidity and strength. This rigidity prevents deformation of the parts of the mould and a firm layer is obtained. An

insulating layer is applied on this mould, intended to provide heat and moisture insulation, either by leaving the upper membrane (4) in place or, after removal thereof, by spraying on an insulating material such as concrete, elastomer (rubber or plastic) (4). Evacuation is obtained with the aid of a vacuum pump (6). The vacuum will cause the membranes (1, 4) to be pressed towards each other, thus compressing the powder. An extremely rigid composite is thus produced, giving good stability to the entire casting mould.

Figure Id shows the next step in which concrete and fibre, fibre-reinforced concrete, is sprayed (at 8) against the mould (9b). When the concrete has set the air is released from the space (7) below the membrane (1) and air is allowed into the space (3) between the membranes (1, 4). Compacting is thus cancelled and the membranes can be removed for re-use while the substructure (9a) remains. The upper member (4) may possibly be retained as an insulating layer.

Lower vacuum may possibly be used during inflation when performing the method according to the invention, in order to prevent the powder from running. Concrete is sprayed on here (Figure Id), such as concrete and fibre, or sand and cement, water and fibre separately.

The procedure also allows a certain modification of the shape after inflation, in that the powder material in the space (3) can be deposited in different thicknesses , or may consist of powder having different density. A more elliptical shape can be achieved, for instance, by using a powder with higher density (sand and sawdust) at the centre, while the remainder may be primarily sawdust. The membrane will be weighted down where the sand is and will not be blown up as high as otherwise. An insulating layer may also be placed below the lower member (1).

Figure 2a-2b shows the production of a ship's hull in accordance with the invention. Figure 2a shows an example of membrane shape. Figure 2b is a section along the line A-A in Figure 2a. (18) is an auxiliary membrane and (1 and 4) are membranes as above. (5) is a pressure pump and (6) a vacuum pump. The procedure is in accordance with the first example. Main lines (19) are secured to the outer membrane, see Figure 2c, in order to achieve the desired hull shape.

Pressure medium (e.g. air) is pumped by a pressure pump (5) into a space between the auxiliary membrane (18) and the inner membrane (1), and the sheath/ membrane body is blown down into a space for the purpose below the construction. The space (3) is then evacuated and the powder therein is compacted to rigidity (Figure 2d). When the hardened mould has been obtained as above, the auxiliary membrane is removed (Figure 2e), and an insulating layer may be sprayed on (at 21) to produce a ship's hull.

The method according to the invention can be varied in many ways within the scope of the following claims.

'.BAD ORIGINAL g