Improved stackable bulk transport container

Abstract: A stackable bulk transport container (2) for corrosive and/or toxic or oxidising liquids which consists of a cylindrical inner container (4) surrounded by an outer container (3) having a regular stackable shape, both inner and outer containers being made of a corrosion resistant material.

Description: Background of the Invention (a) Field of the Invention The present invention relates to an improved stackable bulk transport container and in particular to an intermediate bulk transport container for Class 5 and Class 8 liquids i.e. corrosive liquids which may also be toxic and/or oxidants. Containers of this type must be corrosion-resistant, and must also be very strong, since typically each container will hold 1000 litres of liquid having a specific gravity of up to 1.8. The containers must be easy to handle and stack. (b) Description of the Prior Art To fulfil the above criteria, containers of this type hitherto have been made of a metal outer structure of rectangular cross-section, for strength and ease of handling and stacking, and an inner liner of plastics material, which actually contains the corrosive liquid. A container of this type is disclosed in US Patent 5156268 ( Nichols ) which describes a rigid rectangular outer container and a thin-walled plastics inner tank, the walls of which are supported by the outer container. However, this construction is not ideal, since it is expensive to manufacture, and the metal outer is susceptible to corrosion damage from spills from the inner liner. US Patent 4815621 (Bartis) discloses an alternative design of double-walled tank, in which an inner liquid-containing tank is surrounded by an outer containment tank. However, the tanks are designed for above-ground long-term storage, and although portable when empty, are not intended or designed for transporting liquid or for stacking. Hence, the inner and outer tanks can be very much thicker than for a transport container, since weight considerations do not really apply. DE-A-2906974 gives an example of a stackable bulk transport container comprising an inner and an outer shell, both corrosion resistant, an upper filling aperture and a lower emptying aperture. However, the inner shell of this container is rectangular in cross-section and thus not efficiently self-supporting. It would be advantageous to construct the whole of the container from a corrosion-resistant material, such as plastics, but proposed designs of this type have encountered two problems:- a rectangular-cross-section plastics container is not strong enough to withstand both the pressure of the contained liquid and stacking pressures, and a cylindrical container, whilst strong enough to withstand the pressure of the contained liquid, is an inconvenient shape to stack. Brief Summary of the Invention The present invention overcomes these problems by providing a stackable bulk transport container comprising: an inner container which is provided with filling means for filling said inner container and emptying means for emptying said inner container; and an outer container which encloses said inner container, the external shape of said outer container being a regular, stackable, shape; and both the inner and outer containers being made of a corrosion-resistant material wherein the filling means is separate from the emptying means, the filling means being located at an upper end of the container and the emptying means being located at the lower end of the container; characterised in that the inner container is a cylindrical container having walls of such thickness that said inner container is capable of fully supporting the pressures of the contained liquid when the inner container is filled. Preferably, said corrosion-resistant material is a plastics material, and may also be transparent or translucent. Preferably, said outer container is, for example, square, hexagonal or octagonal cross-section. Brief Description of the Drawings By way of example only, a preferred embodiment of the present invention is described in detail with reference to the drawings accompanying the specification, in which:- Figure 1 is an isometric side view of a container in accordance with the present invention; Figure 2 is a longitudinal section on line X-X of Figure 1; and Figure 3 is a cross-section on line Y-Y of Figure 1. Detailed Description of the Preferred Embodiments Referring to the drawings, a bulk container 2 comprises an outer container 3 and an inner container 4, both made or a corrosion-resistant translucent plastics material such as polyethylene or polyvinyl chloride. Both inner and outer container preferably are formed by moulding. The inner container 4 comprises a smooth-surfaced cylinder closed at its lower end 5 and formed with an externally screw-threaded filling aperture 6 at the centre of its upper end. The cylinder wall thickness is such that the inner container can fully support the pressures of the contained liquid when the container is full, without requiring support from the outer container. In the centre of the lower end 5, a sump 7 is formed, in which a drain valve 8 (of known type) is fitted. The inner container 4 is filled through the aperture 6 and emptied through the drain valve 8. The outer container 3 is of generally square cross-section externally but each side face is ribbed with two sets of spaced ribs 9; each rib 9 projects inwardly into the container 3. The wall thickness of the outer container is such that it can withstand all handling and stacking pressures when the containers are stacked 2-high. The outer container is dimensioned so that the length L of each side of the outer container is slightly greater than the diameter D of the inner container, and the inner container is a sliding fit within the outer container. As shown in Figure 3 the ribs 9 along each side of the outer container project inwards, and on each side of the outer container, the ribs 9a located nearest the centre of that side project inwards sufficiently to contact the outer surface of the inner container, and act as a locating rib, to hold the inner container 4 in position centrally within the outer container. If extra stabilizing of the inner container is required, the other ribs 9b on each side can be made deeper so that they too contact the inner container. The underside of the outer container is formed with protrusions 10, the bases of which form wide, spaced ledges on which the container rests. The spaces 11 between adjacent protrusions 10 form pockets for fork tine access. The width of the protrusions 10 and the size of the spaces 11 may be varied as required for particular applications. Internally, the base of the inner container 4 is shown as resting on a plate 12 located over the top of the protrusions 10, so that the base of the inner container is evenly supported. However, if the number and/or spacing of the spaces 11 is altered so as to increase the width of the upper surface of each space 11, said surfaces may provide adequate support for the inner container, and the plate 12 can be omitted. The sump 7 fits inside a central protrusion 13 in the outer container, and this helps to locate the inner container within the outer. The top of the outer container 3 is closed by a lid 14 which has a central aperture through which the filling aperture 6 projects; the filling aperture is closed by a removable screw-threaded cap 6a. As shown in Figure 2 the upper end of the inner container is formed with a circular rib 15 surrounding, but spaced a short distance from, the aperture 6; the projecting sides of the aperture 6 and the rib 15 form the sides of a trough 16, which catches any spills when the inner container is filled. A drain hole (not shown) is formed through the side of the trough 16 into the space between the inner and outer containers. The lid 14 is formed with a circular shoulder 17 which locates against the side of the rib 15, leaving the trough 16 open. The outer edge of the lid 14 is formed with a lip 18 which overlaps the upper edge of the outer container. A metal angle 19 is located with one face against the inner surface of the upper edge of the outer container, and the other face against the lower surface of the lid, as reinforcement. The lid is secured in place by screws (not shown) which extend through the overlapping parts of the lid and the outer container and through the metal angle 19. The lid 13 is formed with four spaced lashing hook pockets 20, and may also be formed with protruding locating cleats (not shown) for locating the containers when stacked; corresponding recesses (not shown) are formed in the base of the outer container. The cleats may be formed with indentations so that lashing ropes can be positively located over the top of the container. The container may also be provided with one or more pressure-relief valves or anti-vacuum valves (not shown). If the inner and outer containers are made of a translucent or transparent plastics, preferably one side of the outer container carries a gauge 21, so that a user can see at a glance approximately how much liquid remains in the inner container. The only metal used in the container is in the angle 19 and the screws. The above-described container may be manufactured from moulded components, and is relatively quick and easy to assemble, and to fill and empty. The container is easily handled and stacked. It is envisaged that in a container as described above, both inner and outer containers would be made of medium-density polyethylenes and would be dimensioned and proportioned to hold at least 1030 l of liquid of specific gravity up to 1.8. Such containers could be stacked up to 2 high.

Claims: A stackable bulk transport container (2) comprising: an inner container (4) which is provided with filling means (6) for filling said inner container and emptying means (7,8) for emptying said inner container; and an outer container (3) which encloses said inner container (2), the external shape of said outer container being a regular, stackable, shape; and both the inner (4) and outer (3) containers being made of a corrosion-resistant material wherein the filling means (6) is separate from the emptying means (7,8), the filling means (6) being located at an upper end of the container and the emptying means (7,8) being located at the lower end of the container; characterised in that the inner container is a cylindrical container having walls of such thickness that said inner container (4) is capable of fully supporting the pressures of the contained liquid when the inner container (4) is filled. The container (2) as claimed in claim 1 wherein the outer container (3) is formed with a plurality of equidistantly-spaced inwardly-projecting ribs (9) each of which projects inwards so as to contact or nearly contact the outer wall of the inner container (4). The container (2) as claimed in claim 1 or claim 2 wherein the outer container (3) is of generally square cross-section. The container (2) as claimed in any preceding claim wherein said filling means (6) comprises a closeable aperture (6) formed in the top of the inner container (4); and said emptying means (7,8) comprises a sump (7) fitted with a drain valve (8) which projects through the outer container (3). The container (2) as claimed in any preceding claim wherein the base of said outer container is formed with fork-lift tine pockets (11). The container (2) as claimed in any preceding claim wherein the top of said outer container is closed by a removable lid (14) formed with an aperture through which said filling means (6) projects. The container (2) as claimed in claim 6 wherein said lid (14) overlaps the upper edge of the outer container (3), which is reinforced by an angle-section (19) secured therearound. The container (2) as claimed in claim 6 or claim 7 wherein said lid (14) is formed with outwardly-protruding cleats and the base of the outer container (3) is formed with corresponding recesses to enable the containers (2) to be stacked one on top of the other with the cleats on the lower container (2) nesting in the recesses on the upper container (2). The container (2) as claimed in claim 8 wherein said cleats are formed with recesses for engaging lashing ropes. The container (2) as claimed in claim 4 and any claim dependent thereon wherein the top of the inner container (4) is formed with a trough (16) surrounding said filling means (6) to collect any spills. The container (2) as claimed in claim 10 wherein said trough (6) is formed with a drain hole for draining any spills into the space between the inner (4) and outer (3) containers. The container (2) as claimed in any preceding claim wherein the inner (4) and outer (3) containers are made of a translucent or transparent plastics material and a gauge (21) is mounted on one side of the container (2) so that the level of the contents can be measured. The container (2) as claimed in any preceding claim wherein both inner (4) and outer (3) containers are made of medium-density polyethylene.

Inventors: COOMBES IAN REX, COOMBES, IAN REX
Applicants: IAN COOMBES LIMITED
Application year: 1993
Main classification: B65D77
IPC codes: B65D77, B65D21, B65D85