EP0952094A2

EP0952094A2 - Storage bin

Info

Publication number: EP0952094A2
Application number: EP99303024A
Authority: EP
Inventors: Stephen Frederick Box
Original assignee: Carier Bulk Materials Handling Ltd
Current assignee: Carier Bulk Materials Handling Ltd
Priority date: 1998-04-20
Filing date: 1999-04-20
Publication date: 1999-10-27
Also published as: GB9808317D0; GB2336620A; EP0952094A3

Abstract

A storage bin, for example for flour, wheat and so on, comprises a number of corners as shown in the figure. Typically, there will be four corners. Adjacent wall members (50, 52) are provided with a respective partial fillet (60, 63). In the case of a four-sided storage bin these fillets will preferably have been at an angle of 45° to the adjacent wall but other angles are possible. The partial fillets (60, 63) are joined by a backing plate (71) to which the fillets are riveted (90, 92, 90', 92', 90", 92"). A weld (100) is provided between the partial fillets (60, 63). For larger storage bins, which are assembled on site, the weld (100) will comprise an on-site weld. Such a weld will generally need to be ground subsequently to meet hygiene requirements. In smaller versions of the bin, the weld (100) can be a shop-laid weld which requires no subsequent grinding. The completed bin, therefore, has no crevices or closed voids in which infestation and breeding of unwanted organisms can occur.

Description

The present invention relates to a storage bin having particular, but not exclusive, application to the storage of powdered foodstuffs such as flour.
Traditionally, foodstuffs such as flour, wheat and so on have been stored in cylindrical storage bins made from steel or concrete and assembled on site. Such bins may have capacities of 300-400 tonnes. The combination of load-bearing and hygiene requirements entails girth rings or reinforcing bands around the outside of the bin and particular attention to make the inside surfaces smooth, such that all joints must be welded and then ground. Additionally, the cylindrical nature of such bins gives them a circular "footprint" once erected that leads to an inefficient use of storage area.
To address this latter problem, square and rectangular shaped bins have been provided, but the former problem of hygienic construction methods remain. Figure 1 of the accompanying drawings shows a section through a corner of one such bin. Two adjoining walls 10,12 are connected together via an angled section 14 and secured by a number of bolts 16,18. It is not acceptable from a hygiene point of view for the heads of the bolts 16,18 and the junction of the walls 10,12 with the section 14 to be open to the inside of the bin. These could lead to a build-up of material with a consequent threat of infestation. The Confused Flour Beetle, in particular, is capable of living and breeding in minute crevices such as uneven weld profiles.
Consequently, a clip-in fillet 24 is provided to isolate the bolts and the abrupt surface changes from the stored substance. Apart from requiring many separate parts, this arrangement results in an inaccessible void 26 in which build-up and infestation can occur.
An alternative construction is shown in accompanying Figure 2 in which one wall 30 is flanged to be joined to the adjacent wall 32 by a number of bolts 34. The bolt heads and join between the walls are concealed by a fillet 36 which is welded 38, 40 into position after assembly. For hygiene considerations, these welds must be ground down. For a four-sided bin, therefore, eight welding and grinding operations are required along the full height of the bin.
While requiring fewer parts than the bin-construction shown in Figure 1, the on-site welding required in this case is very time-consuming and the post-weld grinding is difficult because of the angles at which the fillet and walls intersect. In addition, the problem of the inaccessible void (now shown at 42) persists.
These prior art designs also typically require mastic between all of the joints.
It is an object of the present invention to provide a storage bin that ameliorates at least some of the above disadvantages.
According to a first aspect of the present invention, there is provided a storage bin as set out in accompanying Claim 1.
In this storage bin, each wall member is provided with a partial fillet or wing flange section that extends along the height of the wall. In a square or rectangular bin these will typically extend at 45° from the inner face of the wall although other angles are possible. By placing the partial fillets to abut, or substantially abut, a single on-site weld is required at each corner of the bin. In one embodiment, the two partial fillets abut to provide a substantially planar surface. This makes the post-weld grinding operation considerably more straightforward than that required using the technique of Figure 2. Each partial fillet may preferably be 175 mm wide to prevent hang-up in flour and to facilitate the grinding step.
In another refinement, the wall members may be of a twin-skin construction in which the outer face is provided on a separate skin. This eliminates ledges and the like on the outside of the bin (often inaccessible from below) that are commonplace in prior art bins and which often contribute to hygiene problems.
The additional cost of the outer skin can be offset to some degree by arranging a number of storage bins together in which the outer skin of one bin is the inner skin of the adjacent bin. In this way a row (or even a matrix) of bins may be constructed together. The additional load-bearing requirements must clearly be taken into account.
As another possible refinement a backing plate is provided to be mounted between adjoining partial fillets. This can be riveted in place prior to welding. The heads of blind rivets are sufficiently unobtrusive to remain on the inner face of the bin after construction.
The partial fillets may be provided by using a continuous shop-laid weld. Such a weld does not require subsequent grinding because of its consistent nature.
Typically a hopper is provided on such a storage bin. In accordance with an embodiment of the invention such a hopper is arranged to have fillet sections between wall members so that the top of the hopper is contiguous with the bottom of the bin.
Closures for top and bottom of the bin can be of any known suitable type.
The storage bin is preferably constructed to comply with the draft Eurocode DD ENV 1991-4:1996 and entitled "Eurocode 1: Basis of Design and Actions on Structures. The relevant section is part 4, entitled "Actions in Silos and Tanks".
A storage bin constructed in accordance with the present invention can readily be made to comply with the hygiene requirements of the industry.
According to a second aspect of the present invention, there is provided a kit for assembling a storage bin as set out in accompanying Claim 12.
Larger-sized bins in accordance with the invention cannot practically be constructed and then shipped to site. By providing the wall sections separately a kit can be provided in accordance with the invention that minimizes the amount of on-site construction required.
The present invention also comprises a method of assembling such a kit as set out in accompanying Claim 14.
The present invention will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which:
Figure 1 shows a corner section of a prior art storage bin;
Figure 2 shows a corner section of another prior art bin;
Figure 3 shows a plan view of a storage bin according to an embodiment of the present invention having a hopper;
Figure 4 shows a corner section of the bin of Figure 3;
Figure 5 shows a perspective cut-away view of a corner of the bin of Figure 3;
Figure 6 shows an exploded view of Figure 5; and
Figure 7 shows a cut-away view of the join between wall members and a hopper.
Figure 3 shows four double- skinned wall members 50,52,54,56 of a storage bin in accordance with an embodiment of the invention. A hopper section is shown generally at 58 and will be described in greater detail with reference to Figures 5,6 and 7. The walls are joined by fillet sections 60,61,62,63,64,65,66,67 and backing plates 71,73,75,77 as will be described in more detail below. The wall member 56 is shared with an adjacent storage bin of similar construction. This structure could be repeated to provide a row or "terrace" of storage bins.
Figure 4 shows a cross section through one corner of the bin shown in Figure 3. Wall member 50 includes a partial fillet or wing flange 60 which is welded by a shop-laid weld 84 to the inner skin 150. This weld needs no post-weld grinding to comply with hygiene requirements. Wall member 52 similarly includes partial fillet 63 welded at 86. Each wall includes further box sections 80,82 to be discussed further with reference to Figure 5 below. Each partial fillet extends substantially 175mm from the respective inner skin at an angle of substantially 45°. They are joined together by a backing plate 71 to which they are both riveted at 600mm intervals in the vertical direction (perpendicular to page) using dome head blind rivets 90,92. The gap between the partial fillets is then filled with an on-site weld 100. This is then ground down to provide acceptable levels of smoothness for the particular application. Note that no bolting is required and only one on-site weld is required for each corner.
The volume behind the backing plate 71 is also completely accessible. Thus, it can be cleaned and fumigated or filled with an insert, non-toxic material such as concrete.
In addition, the resulting corner fillets of 350mm but at least 100 mm in width eliminate all possibilities of "hang-up" which is otherwise common in silos or storage bins having square corners.
Such a bin may typically be 25m high and 4.5m square in section to store approximately 300 tonnes of flour or 390 tonnes of wheat.
Figure 5 shows part the corner of Figure 4 in perspective view. Further rivets 90',92', 90" and 92" are shown along a portion of the corner. The box sections 80,82 of the wall members 50,52 can also be seen in their entirety, as can the inner skin 152 and the outer skin 252 of the wall member 52. Corresponding features are provided on the other wall members. The inner skin 152 and outer skin 252 are joined by a number of box sections 352 although other techniques could be employed. At the base of the wall member 52 is a plate 452 which can be bolted to a suitable support structure shown generally at S. A hopper 58 includes, inter alia, a fillet section 158 shown in more detail in Figure 7.
While the perspective view shows the top of the skins 152 and 252 as open to show the internal detail, they are covered in practice so as to not provide a volume in which infestation can occur.
Figure 6 is a view of the elements of Figure 5 prior to on-site construction. The relatively small number of parts for on-site assembly can readily be appreciated.
Figure 7 shows a view of the intersection between inner wall faces 150,152; flange sections 60,63; hopper flange section 158; hopper wall sections W1,W2 and lower hopper section 159. The parts 60, 63 and 159 are in the plane of the paper. Parts 150,152 hinge outwards from the plane of the paper at 45° about the weld lines 84,86 respectively.
The hopper 58 is joined to the parts 150,152,60,63 by on-site welds 200,202,204. The hopper parts 158,W1,W2 all hinge out of the plane of the paper at 70° around their respective welds 204,202,200. The valley V between the hopper fillet 158 and each hopper wall section W1,W2 is therefore 68.5°, more than adequate to prevent "build-up" in use. The filleted hopper thus "blends into" the tank section of the bin.
For smaller-sized storage bins the hopper is provided in one piece with factory-laid welds. For larger-sized bins the hopper may be provided in sections, for example with bolted joints on the outside. Secondary cover plates are then placed over the bolted joints and, after riveting, welded in place. The inner joint or joints are welded and ground on-site as described above for the wall members of the tank section.
While substantially square storage bins have been described it will be appreciated that other shapes are possible such as triangles, hexagons, etc., and that different widths of wall sections are possible within a bin.
Claims have been formulated to the present invention but the invention is not limited thereto and includes any novel teaching herein where explicit or implicit.

Claims

A storage bin comprising at least three wall members, each wall member comprising an inner face, an outer face and a partial fillet angled inwardly from the inner face of two opposing sides of the wall member, means for supporting the wall members and means joining each partial fillet to the adjacent partial fillet at each corner of the bin.
A storage bin as claimed in claim 1, wherein the wall members comprise an inner skin including the inner face and an outer skin including the outer face which inner and outer skin are spaced from each other.
A storage bin as claimed in claim 2, wherein the wall members are spaced from each other by at least one box section.
A storage bin as claimed in claim 2 or claim 3, wherein the outer face of at least one of the wall members comprises the inner face of a wall member of an adjacent storage bin.
A storage bin as claimed in any one of the claims 1 to 4, wherein the means joining each partial fillet to the adjacent partial fillet comprises a backing plate.
A storage bin as claimed in claim 5, wherein the means for joining each partial fillet to the adjacent partial fillet further comprise a plurality of rivets and a single weld along the boundary between the fillets.
A storage bin as claimed in any one of the preceding claims, wherein the partial fillet and the inner face of each wall are joined by a shop-laid continuous weld.
A storage bin as claimed in any one of the preceding claims, wherein the bin comprises four wall members.
A storage bin as claimed in any one of the preceding claims, wherein the partial fillets are at least 50 mm wide.
A storage bin as claimed in claim 9, wherein the partial fillets are at least 175 mm wide.
A storage bin as claimed in any one of the preceding claims, further comprising a hopper having a number of hopper faces equal to the number of wall members which hopper faces are contiguous with the inner faces of the wall members, the hopper further comprising a fillet section between each of the hopper faces which fillet section is contiguous the corresponding pair of partial fillets between the inner faces of the bin.
A kit for constructing a storage bin as claimed in any one of the preceding claims, the kit comprising at least three wall members, each wall member comprising an inner face, an outer face and a partial fillet angled inwardly from the inner face of two opposing sides of the wall member, means for supporting the wall members and means for joining each partial fillet to the adjacent partial fillet at each corner of the bin.
A kit as claimed in claim 12, further comprising at least three backing plates for joining each partial fillet to the adjacent partial fillet.
A method of constructing a storage bin as claimed in claim 5 or claim 6, the method comprising erecting the wall members so that the partial fillet on each wall member substantially abuts the partial fillet on the adjacent wall member and, for each corner, aligning a backing plate with rivet holes in the partial fillets, blind riveting the partial fillets to the backing plate, welding the partial fillets together and grinding the welded section to eliminate excessive undulations.