GB2082663A - A method of producing containers - Google Patents

Abstract

"A method of producing open or closed containers and pipes". A closed plastic foil (1) in the form of a bag or a pipe is inflated after which one or more layers of concrete (3) is applied thereto and allowed to set. In the production of an open container, the closed container partly covered with concrete is turned over, after which part of the plastic foil is removed. <IMAGE>

Description

SPECIFICATION A method of producing containers This invention relates to a method of producing containers. Especially the invention relates to a method of producing open and closed containers and pipes of concrete with very varying dimensions and shapes.

Recently, the demand for impermeable, open and closed containers, dams and conduits of large dimensions for storing and conveying liquid and solid materials has strongly increased. This increased demand is based on a number of factors.

One of these factors is the strongly increased demands on the protection of the environment, such as in the disposal of solid and liquid waste. Previously, such waste has simply been deposited on dumps or been buried, which has contaminated the ground water. This is no longer acceptable, and therefore attempts have been made to deposit the waste on an impermeable support, usually of concrete. However, the concrete is sensitive to corrosion attacks from acids and will easily crack when the ground sets, which results in leakage. Another instance where big and impermeable containers are required is in the storage of contaminated process liquids from chemical and other industries. Such liquids have earlier been kept in dams without any great demands on impermeability, the ground water also in this case being polluted, sometimes with very serious consequences.

Another application field that thas become of interest for big containers is in heat technology.

When using alternative energy sources such as solar heat or geothermic heat, a heat transmitting medium such as air or water is heated and in its turn gives off the heat to a heat storing medium, such as water or various kinds of salt mixtures. For storing the heat, large amounts of the heat storage medium is required, and must be stored in suitable containers.

Such containers are usually built of concrete, which will be relatively expensive with the use of conventional technique. The concrete is also relatively sensitive to attacks from various salts, and will also easily crack when the ground sets, which results in leakage.

Common to the dams, containers and conduits used at present is that they are expensive to build, difficult to get tight, and in general they have an inferior chemical resistance. These shortcomings are eliminated by the invention.

According to the present invention, open or closed containers are produced by inflating a closed plastic foil in the form of a bag or a tube to the desired shape, after which one or more layers of concrete is applied to at least a part of the outside of the inflated foil and the concrete is allowed to set. In the production of open containers, the concrete is only applied over a part of the inflated plastic foil and after the setting of the concrete, the container is overturned so that the part not covered by concrete is facing upwards, after which the plastic foil on this part is removed to obtain an open container.

The invention is illustrated more in detail in the enclosing drawing. Figure 1 therein is a longitudinal section of the production of a closed container, whereas Figure 2 shows the corresponding production of an open container. Figures 3,4 and 5 are cross sectional views of various embodiments of the container. Figure 6 shows how the plastic foil can be shaped in the production of a dome-shaped container, and Figure 7 shows an open container according to the invention, inverted and positioned for use. In the Figures, the corresponding details have the same designation numbers.

Figure 1 shows a longitudinal section view of a closed container produced according to the invention. The container consists of a closed plastic foil 1 (shown in the Figures with an exaggerated thickness), which has been inflated to comprise a volume 2. One or more layers of concrete 3 is applied to the plastic foil and has been allowed to set. At 4 a connection with the interior of the container is arranged, which both serves for supplying air for inflating the foil, and provides an opening in the finished container for supply and removal of material to be stored therein. At 5 a liquid in the container is indicated. It may be suitable to introduce a liquid, usually water, in the plastic foil before or during inflation.In this way the shape of the foil is better adapted to the support due to the weight of the liquid, and the shape of the foil can be adjusted by variation of the liquid amount, an increased amount of liquid giving a more flattened container.

In Figure2 an embodiment is shown which is especially suited for production of open containers.

Here the conduit 4 for inflation is introduced from below through the support so that no hole has to be made in the container wall. However, the embodiment shown in Figure 1 can of course be used for production of an open container, where the aperture 4 in the wall of the finished container may be connected to a discharge pipe from the container.

Figures 3-5 are cross sectional views taken along the line A-A in Figure 1 or 2 and show various embodiments of the containers produced according to the invention. Figure 3 shows a containers having a substantially circular cross section, which has been obtained by using a tubular plastic foil, which has been inflated to a relatively high pressure and which does not contain any liquid. By this design it is possible to produce containers in the form of long, seamless pipes for transport of material in a liquid, finely divided or suspended form. The ends of the pipe are then opened after the setting of the concrete.

Figure 4 shows a container of a more flattened form. This has been achieved by using a lower air pressure at the inflating and by filling the plastic foil partly with a liquid 5, preferably water. In this way, the bottom portion of the plastic foil will also be more spread out and will closely follow the support.

The liquid is removed before the container is used.

Figure 5 shows an additional embodiment of a flattened container according to the invention. The flattened shape has here not only been obtained by filling with the liquid 5, but the upper portion of the plastic foil has also been provided with forming welds 6, which are shaped such that the upper portion of the plastic foil does not rise so high in the inflating.

Figure 6 shows schematically the bag-shaped plastic foil as seen from above in the production of a dome-shaped container. The upper portion of the plastic foil is here composed of a number of welded parts 7 each substantially shaped as a sector of a circle. By varying the form of the sector-shaped parts, a more or less pointed dome-shaped form can be obtained as is easily realized by one skilled in the art.

Figure 7 shows a section of a produced open container after turning and positioning it as sunk in the ground. In this way a basin of a definite size has been obtained with its upper edge nearly level with the ground surface 8.

The used bag-shaped plastic foil can consist of a closed bag or a hose of plastic foil with both ends sealed, such as by welding or glueing. A connection pipe for blowing of air and supply of liquid can be arranged in a way known per se. The plastic hose can be manufactured in several manners, e.g. by extrusion (blowing). In this process it is possible to obtain hoses having a diameter up to about 10 m and of a length unlimited in principle. Larger diameters can be obtained by cutting a plurality of hoses in their longitudinal direction and joining them to new hoses after which an arbitrarily large diameter can be obtained. It is also possible to start from extruded planarfoils and weld them to hoses of desired size and embodiment. Thus, it is easy to produce round or elongated containers with a circular, oblong or square bottom contour.

The plastic foils can be simple or composite. A composite foil is preferred for reasons of resistance, and in orderto give the foil suitable chemical or mechanical properties. Thus, it can be suitable that the side of the foil facing the concrete has an increased friction so that the applied concrete layer remains better in place and does not slide off before setting. This can be achieved during or after the production of the foil in a plurality of manners known to one skilled in the art. In the production of the plastic foil, a filler can be admixed giving the finished foil a rough surface.Another preferred way of achieving an increased surface friction is using an extruded blown multi-layerfoilwherethe material supply to the surface at the extrusion of the foil is insufficient to form a coherent layer when the foil is stretched after extrusion. The surface layer will then break up and give a rough surface. This way of achieving an increased surface roughness is described in more detail in Swedish patent No.

7811311-5.

It is also possible to incorporate a heat insulating layer, such as a foamed plastic layer, in a multi-layer foil. This is suitable when it is desired to improve the heat insulating properties of the container. A multilayer foil can then consist of an inner foil with a good chemical resistance to the material to be stored in the container, an intermediate foil with good heat insulating properties, and an outer foil with an increased surface friction.

The materials in a multi-layer foil can be the same or different. As inner layer, polyolefins are to be preferred, and especially high density polyethylene, which has a good strength and a high chemical resistance. Moreover, it is easy to produce hoses of a large diameter from polyolefins, especially polyethylene, by extrusion. However, the invention is not restricted to the use of any special type of plastic material, but any plastic material that can be shaped to a foil with the required properties as to strength and chemical resistance is usable. As examples of suitable plastic material other than polyolefins, can especially and also be mentioned polyethylene and polypropylene with a high or low density, also halogenated polyolefins, polyesters and polyamides.

For supply and discharge of materials, the container is provided with one or more pipe connections, which can be giued or welded. These connections can also be used in the inflation of the plastic foil and the optional supply of liquid. In the production of open containers, special supply conduits are of course not necessary, even if they can be used in certain embodiments, but here the conduits for inflating can be arranged in the parts of the plastic foil which are to be removed after the setting of the concrete. In production of pipes, the conduits for blowing can be arranged in those end pieces of the pipe which are to be removed later.

As is indicated above, the size and shape of the containers can be varied within wide limits and are decided by the foil used. The shape of the inflated foil and consequently the finished container can be varied in various manners. Thus, the shape is influenced by the air pressure to which the foil is inflated such that a higher air pressure provides a more rounded form. Moreover, a suitable amount of liquid, usually water, can be introduced into the bag or pipe of plastic foil. Due to the liquid, the bottom portion of the foil will follow the support better and is spread horizontally and will provide in this way a more spread out and flattened form with a planar bottom if the support is planar. Finally, it is also possible to provide the foil with suitably arranged shaping welds so that it is contracted on suitable places. The shape can be varied to a large extent in this way.The application and design of the shaping welds can easily be determined by one skilled in the art on the basis of simple routine tests. By a suitable design of the inflated foil, it is possible to obtain containers as final products which are practically free of bending moment in a way analogous to known shell constructions of concrete. The suitable conditions for this can be calculated by known methods by one skilled in the art.

In production of the containers and the pipes it is started from the closed bag- or tube-shaped plastic foil. This can be transported to the site of manufaco ture in a folded state and, thus, requires only little space. The plastic foil is then inflated and, if necessary, filled to the desired extent with liquid so that the desired shape is obtained. After this the outer side of the foil is covered with one or more layers of concrete and when the concrete sets, the shape of the container or pipe is fixed. It has then been found to be suitable to apply the concrete in several thin layers, each layer being allowed to dry before the following layer is applied. A specially preferred embodiment is to use light concrete, optionally containing reinforcing fibers, and to spray this mixture onto the outer side of the foil.It is also possible to manufacture subterranean containers in a simple way by excavating a pit in the ground, adapting the plastic foil in the pit and inflating it, after which the concrete is applied over the plastic foil. It can be proceeded in a similar way in the production of subterranean pipes, a ditch being dug, a plastic hose being placed in the ditch and inflated and covered with concrete, after which the ditch is filled.

The choice of the type of concrete is not especially critical but can easily be established by one skilled in the art starting from known properties as to strength, chemical resistance, resistance to frost etc. It is often suitable that the concrete used is reinforced. For this, reinforcing fibers of a type known per se can be added to it, or it can be reinforced by a net such as of metal wire. It can then be proceeded here in such a way that one or more layers of concrete is first applied to the plastic foil, after which the net is applied and then one or more additional layers of concrete. Here it is of course also possible to apply several layers of a reinforcing net with intermediate concrete layers. By the reinforcement, a considerably increased strength of the finished containers is obtained.

Closed containers or pipe conduits according to the invention are usually produced at the place where they are to be used later and only a minimal preparation of the place of manufacture is required.

In principle, only a levelling of the place is needed before manufacture. In the production of open containers, manufacture can be carried out close to the final place of use, where a suitable pit for installation of the container may have been excavated and optionally been provided with the necessary conduits and connections for supply and discharge. When the concrete has set, the container is turned over and the plastic foil over its open part is removed, after which the container can be placed in the excavated pit, and connections, if any, can be prepared in a way known per se. Of course, such connections can also be prepared and arranged in a closed container.

By the invention, containers and pipes for storage and transport of liquid, finely divided or suspended materials can be produced in a very simple and cheap way. On great advantage is that very varying sizes and shapes of the containers can easily be produced and that open as well as closed containers can be made by means of principally the same method.

The containers produced according to the invention can be used in many different fields. As examples can be mentioned storage of water and salts as heat storage medium as well as fresh water and industrial process liquids. Strongly corrosive liquids, which might attack unprotected metal or concrete containers can also be stored in the containers of the invention as the containers are protected by the interior plastic layer. Other application fields are storage of various types of powders or granulates. Open containers can be used as storage dams for municipal and industrial waste water and for insulation of refuse dumps, the ground water being protected against contamination, as leakage is eliminated. The open containers are also useful as sludge and sedimentation basins in wastewater treatment plants, whereby it is readily possible to adapt their size in manufacture to the prevailing need. Moreover, open containers can be produced in an inexpensive way by means of the invention for use as swimming pools. Pipes produced in accordance with the invention have the great advantage that they can be made practically without joints if they are started from a closed hose of plastic foil.

Moreover, such pipes can easily be adapted to the ground due to the flexibility of the plastic foil pipe and to the intended direction, no special pipe bends being necessary to manufacture but being obtained integrally with the rest of pipe line.

Claims (12)

1. A method of producing open or closed containers and pipes, characterized in that a closed plastic foil in the form of a bag or pipe is inflated to a desired shape, after which one or more layers of concrete is applied to at least a part of the outer side of the inflated foil and the concrete is brought to set.

2. The method of claim 1, characterized in that a reinforcing agent, such as reinforcing fibers, is added to the concrete.

3. The method of claim 1 or 2, characterized in that the plastic foil during or after its preparation is subjected to a treatment on at least its outer surface to increase its surface friction.

4. The method of any one of claims 1-3, characterized in that the concrete is applied in two or more layers, each layer being allowed to set before the subsequent layer is applied.

5. The method of any of claims 1-4, characterized in that a liquid is introduced into the closed plastic foil before the concrete is applied, in order to adjust the shape of the inflated plastic foil.

6. The method of any one of claims 1-5, characterized in that the plastic foil is provided with shaping welds before inflation in order to adjust the shape of the inflated foil.

7. The method of any one of claims 1-6, characterized in the plastic foil comprises a layer of insulation foam plastic.

8. The method of any one of claims 1-7, characterized in that the concrete is sprayed against the inflated plastic foil.

9. The method of any of claims 1-8 for the production of open containers, characterized in that concrete is applied over part of the inflated plastic foil and after the setting of the concrete, the closed container partly covered with concrete is turned over, so that the part thereof not covered with concrete will be facing upwards and that this part of the plastic foil material is removed so that an open container is obtained.

10. Open or closed containers or pipes, characterized in that they have been produced by the method of any one of claims 1-9.

11. A method of producing open or closed containers and pipes substantially as hereinbefore particularly described and as illustrated in the accompanying drawings.

12. An open or closed container or pipe produced by the method of claim 11.