The invention concerns a base for a transport or liquid container and of the type stated in the introductory por- tion of claim 1.

Liquid containers are well-known and comprise a coated frame having walls to provide a closed container or box- shaped container. The container contains a bag with the fluid to be transported. An example of this is given in the Danish patent application 1787/86. The bag is placed in the container prior to filling. The bag is preferably flexible and possesses a not insignificant tear strength, and it may e.g. be made of a multi-layered plastics mate- rial, such as polyethylene. The bag provides tightness, while the container frame provides the necessary stabi¬ lity. The containers can therefore be constructed rather large and typically have a capacity of more than 1 m ³ . Handling of the containers takes place using fork trucks. It is a very attractive way of handling fluids - not only liquids, but also granulates and other grain material be¬ ing involved - since the transport volume has a very high degree of utilization in contrast to other forms of con¬ tainers, such as barrels and tanks. Further,, the con- tainers are collapsible, which minimizes the space re¬ quirement when empty containers are returned.

Frequently, the fluids to be transported are hazardous liquids, so that liquid containers of this type are to offer good resistance to external impacts. In particular, in spite of some deformation, the container frame must not damage the bag containing the fluid. Thus, the container must be capable of dropping from a height of about i m without the bag contents leaking out, to satisfy the re- quirements made by the authorities for the container to be

used for transport of hazardous goods. Following such im¬ pact the bag must still be tight. It is therefore a re¬ quirement that the container has no sharp corners or edges that might damage the bag following external impacts. It has thus been found that attachment of the base to the frame by welding, as done until now, requires dispropor¬ tionately large thicknesses of material in order to last, while a break zone at the welds often has sharp burrs that may damage the bag.

Although the base vessel is supported by the transverse or longitudinal stiffening elements of the liquid container in the base, external impacts giving rise to even small deformations of the frame structure of the liquid con- tainer might cause formation of burrs capable of destroy¬ ing the bag, which results in leakage. It is in particular the attachment of the base vessel to the rest of the base which is critical, since the entire mass of the fluid in the bag rests on the base vessel during transport, so that an external impact results in an extreme load precisely on the attachment area of the base vessel to the rest of the base.

The object of the invention is therefore to provide a base vessel structure where the base vessel is secured to the rest of the base in a manner such that some base vessel deformation is allowed, without any risk of this causing sharp edges facing the bag.

The base defined in the characterizing portion of claim 1 solves the above-mentioned problems, there being provided along the edge of the metal base vessel a collar with a downwardly extending edge which is caused to engage a com¬ plementary channel on the base frame. The sharp edges on the base frame and the base vessel, respectively, will hereby be received in respective channels, where they con-

tribute to giving the base its mechanical strength. The base vessel is preferably made by compression moulding a metal plate so that the central parts of the vessel are positioned at a lower level than the periphery. Further, the base vessel may advantageously be provided with an opening to receive an outlet of the container bag through which discharge takes place.

When the base frame and the base vessel are formed with two cooperating, bent plate parts which are mutually en¬ gaged, some resilience will be provided in the area of engagement, and this resilience, to some extent, dampens strong impulses caused by external impacts. If the impacts are so great that the base frame and the base vessel are permanently deformed in the area of engagement, precisely the bent plate parts ensure that there will be no sharp edges capable of damaging the bag, as long as the base vessel and the base frame are still engaged. The sharp edges will still be received in the respective annular channels of the base vessel and the base frame. Only when the parts are disengaged, will sharp edges occur, but this requries very strong impacts with a correctly dimensioned structure.

The rim or side walls of the base vessel extend obliquely upwardly, so that the connection between the base vessel and the base frame is subjected to the least possible load when dropped. A considerable portion of the load is con¬ verted into internal tensile forces in the side walls of the base vessel. This effect has been found to be most pronounced when the side walls of the base vessel form an angle with the vertical of the order of 10-30°, an angle of about 15° being preferred owing to said reduction in force and from wishes in terms of production techniques.

The edge of the base vessel is bent by rolling. The channel of the base is provided by bending protruding plate parts from the horizontally arranged beams of the base frame. The base frame is hereby coupled directly to the carrying parts of the frame. The base frame is pre¬ ferably square, and the base vessel may be dimensioned so as to be received in the channel of the frame structure as a form fit. The base vessel will hereby be positioned in connection with the manufacture and cannot subsequently be removed from the base frame.

The invention will be explained more fully below in con¬ nection with a preferred embodiment and with reference to the drawing, in which

fig. 1 is a schematical view of an embodiment of a base according to the invention for a liquid container, the base vessel being lifted out from the rest of the base structure,

fig. 2 is a sectional view of a side of the base structure shown in fig. 1, said side having a channel to receive a downwardly extending edge on the base vessel,

fig. 3 is a sectional view showing how the downwardly ex¬ tending edge of the base vessel engages the annular channel of the base structure, and

fig. 4 is a sectional view of a portion of the base vessel of the invention.

Part of a liquid container structure is shown in fig. 1, here with particular focus on the structure of the base. A base vessel 10, which is rectangular in the shown embodi- ment, has a plane bottom face 11 provided with a rectangu¬ lar hole 12, which is adapted to receive an outlet from a

plastics bag (not shown). This outlet is described in a

Danish patent application 722/92 filed on the same day by the applicant, and it has a rectangular flange which is adapted to be received in a depression 14 in the bottom 11 of the base vessel.

The base vessel has inclined side walls 13 forming an angle of about 15° with the vertical. The sides 13 are bent upwardly so that the actual edge extends slightly downwardly again. This is explained in connection with fig. 3. The base vessel may be manufactured by compression moulding of a metal plate, the side walls being finally rolled so that a downwardly protruding edge extends from these. The hole 12 is punched finally.

Alternatively, the base vessel may be made of a plastics plate by vacuum forming. This means that the plastics plate is arranged above a die having the final shape of the base vessel, following which the plastics plate is heated and shaped in that the air between the die and the plate is withdrawn. Although plastics is a weaker material than metal, the necessary tensile strength may be obtained by suitable shaping of the base vessel.

The actual liquid container has a base structure 20 as well as an upper part, of which only the upright posts 30 and the girders 32 are shown. This is done to illustrate the shape of the liquid container. In the preferred em¬ bodiment the base 20 comprises three legs 22 of sheet metal extending in the length of the base. In practice this is provided by a corrugated plate having regular trapezoidal corrugations. The corrugated plate may be secured to the rest of the base frame by welding or form an integral part of it. In addition, the base has four sides 24, 25 providing a boxshape for the actual base. The base may additionally be stiffened with a plurality of

transverse braces 26, as needed. The sides 24 and 25 are terminated upwardly so as to inwardly form an upwardly open, annular channel, as shown more clearly in fig. 2.

Fig. 2 is a sectional view of part of the side 25, and shows that the corrugated plate continues upwardly. It will be seen how the side 25 forms an angle with the side 22. Upwardly the side 22 terminates in an edge 41. Within this edge there is an upwardly open annular channel 42. The channel 42 and the side 25 define between them a rect¬ angular channel 40 in which stiffening elements may be placed, as needed.

Fig. 3 shows how the base vessel 10 is received in the channel 42, which takes place by bending the rim 16 of the side wall 13 to form a downwardly extending edge 18. The contents of the liquid container presses the base vessel 10 downward, which generates internal stresses in the side wall 13. In the preferred embodiment the side wall 13 forms an angle of 15° with the vertical, which creates some flexibility in the base structure, si'nce the powerful tension can be absorbed to a great extent partly by the side wall and partly by some movability of the channel structure 41, 42 formed on the side wall 25. At the same time the actual base vessel is supported by the transverse braces 26 and the plate parts 21 between the U-shaped legs 22 on the corrugated plate element (fig. 1). It is noted that the transition (fig. 3) between the side walls 13 of the base vessel and the upper termination 41 on the side of the base frame is without sharp edges. This is ex¬ tremely important considering that the liquid container is adapted to contain a bag of thin plastics material with the liquid.

Fig. 4 shows a detail of the base vessel and illustrates that the bottom 11 around the hole 12 is recessed in an

area 14, which has an extent L corresponding to the flange of the outlet. This recess 14 is adapted to receive and guide an outlet through which the contents of the liquid container can be discharged by access in the central U- shaped leg (fig. 1).

Also the upward termination of the side wall 13 is vis¬ ible, it being clear to a skilled person that this shape provides some resilience, making it possible to absorb some of the impacts to which a liquid container is sub¬ jected in daily use.

The base vessel preferably has a size such that when mounted in the annular channel 42 the base vessel 10 urges the rear wall 42a of the channel in a direction toward the outer wall 25. Once mounted, the base vessel will thus be difficult to remove again, which makes further attachment in the form of welding or the like unneccesary.