Flexible container

Abstract: A flexible container (1) such as a FIBC for transportation and storage of fluid material comprising an outer envelope (2) and one or more inner envelopes (3). The container (1) can also comprise lifting loops (5) and an opening for filling (6). A support (4) is provided between two adjacent envelopes (2,3) which extends the total circumference of the container and has a height corresponding to the fill height of the container.

Description: The present invention relates to a device for a flexible container such as a flexible intermediate bulk container (FIBC) for transportation and storing of fluid material. The term "fluid material" as employed in this application covers liquids, suspensions and materials which at specific conditions behave as liquids, such as fluidized powder material eg Portland cement, ground magnesium powder etc. Today, several types of flexible collapsible containers are in use for bulk transport. Some flexible containers are designed as disposable bags whereas some are made for reuse. Examples of such flexible containers are described in Norwegian Patent Application No. 136744 and No. 138134. These describe containers which comprise an inner waterproof liner of thermoplastic, an outer container of woven fabric etc., lifting loops and an opening for filling. From a technical and economical point of view flexible containers are in many cases the best device for storing and transportation of bulk material. The lack of stiffness of conventional flexible containers is however a disadvantage when it comes to filling, transport and storage of fluid material. These problems can be severe for FIBCS where the volume can be from several hundred litres up to about two thousand litres. As previously mentioned, liquids and fluidized materials, such as Portland cement give specific problems during the filling and handling process. A fluidizable material will during the filling operation start to fluidize and behave as a fluid due to mixing of air. A container filled with a fluid material will be very unstable immediately after it has been filled. Therefore, it can not be disconnected from the filling apparatus and put on a conveyor belt or a pallet. Various methods have been suggested for solving the problem of how to use a flexible container for fluid material. One method in use for fluidizing material is to fill the container while it is hanging on a fork truck and then transport the container directly to the storing room. However, the container has to be on the fork truck until most of the fluidizing air has escaped before it can be stored without support. This method requires the use of several fork trucks and an intermediate storing room for newly filled containers. This method does not allow fast filling and transport of the stable containers. One method and device which gives a faster filling operation and quicker transport of the filled container is described in European Patent Application 0064095. However even though this device allows for a quicker and more economical transport of the filled container, it still has the problem of not being stable immediately after the filling has been performed. It is known to locate the container in a cylindrically shaped form before it is filled with fluidizable material. The filling process is a simple operation, but several problems arise when the cylindrical shaped form is removed. The filling process requires a large area, especially when the container is lifted out from the form. The necessary lifting operation means that special equipment is also required. European Patent application published under No. WO89/09171 (prior art according to Article 54(3) EPC) discloses a flexible container for fluids provided with channels for receiving support pillars which extend upwardly from a wooden pallet. DE-A-2437670, which represents the nearest prior art discloses a flexible, waterproof, depth and shape-variable container having walls formed of cardboard, for example, which are enclosed by a plastic bag which is vacuum-drawn to envelop the walls and to enter both ends of the box to form the bottom of a double-layer of plastic extending between the walls so as to form a box shaped container having an open face, the arrangement being such that the bottom may either be located at either end of the container, that is, extending between either the upper or the lower edges of the container, or it may be located at any intermediate position therebetween. The problems described above have restricted the use of flexible containers and particularly of FIBCs for transportation of bulk material with large particle size, such as granular fertilizer, grain, coal etc. One object of the present invention has been to improve the qualities of the conventional flexible containers in such a way that they can be used for all types of fluid material. Another object is to provide a simple and reliable method of filling which can be carried out without use of extra equipment, the transport and storage of the filled containers being further achieved by a simple and reliable method without using specially designed transport and storage equipment. A further object has been to make the container more impervious to sharp objects thus reducing the danger of puncturing and consequent leakage. It has also been an object of the invention to improve the qualities without changing the basic construction of the container. Further, it has been an object of the present invention to keep the costs of the improvements as low as possible. According to the invention a flexible container for the transportation and storage of fluid material comprises an outer envelope and at least one inner envelope which substantially enclose the contents of the container, the container having a filling opening and a support being provided between two adjacent envelopes, the height of the support corresponding to the fill height of fluid material in the container, the support extending around substantially the total circumference of the container characterised in that the support is adapted to permit circumferential expansion of the container. The invention will now be described in more detail, by way of example, with reference to the accompanying drawings in which: Figure 1 is a schematic prospective view of a flexible container according to the invention with a part cut sectional view to illustrate the construction and Figure 2 (a) to (d) are perspective views illustrating different embodiments for the support of the container of Figure 1. Figure 1 shows an example of a flexible container comprising an inner waterproof envelope 3 and an outer envelope 2. Between the inner and outer envelope is arranged a support 4 which extends around the total circumference of the container and has a height corresponding to the height of the container. Because the container in this example comprises four flat wall panels, the support 4 comprises four rigid plates forming a rectangular shape, the rigid plates being interconnected at their side edges. The rectangular shaped form can be rigid i.e. the plates can be rigidly connected. However, suitably the plates are connected by pin joints or hinge joints and the frame is collapsible. Making the support collapsible gives advantages during transportation of the supports themselves or of empty containers fitted with supports. It should however, be added that as an alternative the supports can be made of separate plates and be interconnected by use of a simple joint or the half finished frames can be mounted and located in the container shortly before the flexible container is filled. Because the supports are used in a flexible container that expands during filling, it is important that the supports can tolerate this expansion (increase of the circumference). One way of allowing for the expansion is by overlapping as discussed in the following example. To achieve maximum stiffness of the container, the plates in the support should be interconnected in such a way that they do not displace with respect to each other in the vertical direction, i.e the supports should be rigid and thus resist the vertical shear forces which occur if the container is vertically unstable. Furthermore , it should be noted that the supports can be made of perforated or corrugated plates, a type of frame construction, wire netting etc. As mentioned above, the support 4 is located between the outer 2 and the inner envelope 3. During filling of the container 1 the supports are held in position due to the static pressure in the container and the friction between the supports and envelopes and thus provide a stiff and stable container. The stiffness of the container is however dependent on what material and thickness the supports are made of and what material the container is made of. All types of construction materials can be selected as material for the supports, such as, for example, paste board or corrugated card board, plastic material, metal or wood. The factors that determine what type of material one should use will be dependent on transport environment, assumed transport load and the size of the container. In the aforementioned example, a container comprising an inner and an outer envelope (double walled container) is illustrated and discussed. It is however possible to arrange supports in a flexible container comprising more than two envelopes (multiple walled container). It should also be added that the word "envelope" does not only mean one layer in a double or multiple walled container, but may be a flexible container as known per se. or a flexible belt employed as a reinforcing belt for the container as described in the applicant's Norwegian Patent No. 142299. The bottom of the container can be common to all envelopes, or each of the envelopes can be arranged with a separate bottom construction. Further, the supports may be arranged in the container during the manufacturing process, but before the bottom is made, or the supports may be located in the container immediately before the container is filled. In the former case advantageously the container is collapsible (see Fig. 2(d)). The supports can be arranged and adjusted in container with different shape and with various volumes. Figures 2 (a)-(d) illustrates in a perspective view different embodiments of suitable supports. Figure 2(a) illustrates a support with nearly cylindrical shape and adjusted to a cylindrical container. Figure 2(b) illustrates a support with a hexagonal shape. Figure 2(c) illustrates a support with narrow ribs 7 connected by pin joints side by side. This type of support is a more flexible solution, easy to adjust for different types of containers. Fig. 2(d) illustrates a support with four sides and collapsible at the folding lines 8. This type is applicable when the supports are arranged in a container during fabrication of the said container, as discussed previously. The supports can be manufactured from one piece of material. In forming a cylinder, Fig. 2(a), the material piece can be bent in such a way that the material ends are overlapping. The overlapping technique can also be applied in the example illustrated in Fig. 2(b),(c) and (d). However, in these examples, the material pieces are supplied with folding lines or "weakning lines" such as grooves, located at a specific distance apart which is equivalent to the width of the sides or the width of the ribs and where the sides or the ribs are made by folding at these lines.

Claims: A flexible container for the transportation and storage of fluid material comprising an outer envelope and at least one inner envelope which substantially enclose the contents of the container, the container having a filling opening and a support being provided between two adjacent envelopes, the height of the support corresponding to the fill height of fluid material in the container, the support extending around substantially the total circumference of the container (1) characterised in that the support (4) is adapted to permit circumferential expansion of the container (1). A fluid container as claimed in Claim 1 wherein the support (4) has three or more sides and is adjusted to fit a container of the same shape. A fluid container as claimed in Claim 1 or 2 wherein the support (4) is formed in one section which is folded to define the sides of the container, the edges of the support overlapping. A fluid container as claimed in Claim 2 wherein each side of the support (4) is formed as a separate section, the sections being interconnected at their inside edges by connecting means which prevent relative movement of the sections in the radial direction, but allow some movement in the circumferential direction to compensate for the circumferential expansion of the container. A fluid container as claimed in Claim 4 wherein the connecting means is a flexible or pin joint whereby the support (4) is collapsible. A flexible container as claimed in any preceding claim wherein the support (4) is made of corrugated or flat plate sections, perforated plate sections or wire netting or comprises a frame. A fluid container as claimed in any preceding claim wherein the support (4) is substantially cylindrical and is adjusted to fit a cylindrical container. A fluid container as claimed in any preceding claim wherein the support (4) comprises a plurality of narrow ribs (7) aligned along the axis of the support (4) the ribs being interconnected at their side edges by a flexible connection or pin joint which allows rotation about the axis of the support (4) and relative circumferential movement, but prevents relative movement in the axial direction. A fluid container as claimed in any preceding claim wherein the support comprises a plurality of narrow ribs (7), adjacent ribs (7) being connected together along their long edges by means of a flexible connection or pin joint which permits adjacent ribs (7) to rotate about, or move parallel to, the connection, but which prevents relative movement between the ribs (7) perpendicularly to the connection therebetween.

Inventors: JUEL ANDERS, STRAND OLAF, JUEL, ANDERS, STRAND, OLAF
Applicants: NORSK HYDRO AS, NORSK HYDRO A.S.
Application year: 1989
Main classification: B65D88
IPC codes: B65D33, B65D88