The invention furthermore concerns a shell element for use in a silo according to the invention where the silo has insulating material between inner and outer shell.

Silos and shell elements of the above mentioned kind for storing animal feed exist.

The silo is built up from the bottom so that a ring of inner shell elements are assem- bled and upon which a top is built. Then the ring and the top are lifted by means of lifting devices, whereupon an underlying row of inner shell elements are fitted. In this way is proceeded until the whole inner shell has been built up. Then insulation mate- rial is fitted at the outer side of the inner shell as the inner shell has structures retaining the insulation material. At last, the outer shell is mounted as single elements at the outer side of the inner shell. For securing insulation material and outer shell, the building method necessitate the use of reinforcing elements which form thermal bridges between the inner and outer shells. Thus the full effect of the insulation mate- rial is not achieved.

The present invention is directed, however, toward other applications in which there are special requirements for hygiene, especially toward the foodstuff industry. In the foodstuff industry, it has been common until now to build silos for production plants in full size before they are mounted in the plant. Many silos have to stand in produc- tion halls, and therefore it is often necessary to make openings in roof or walls for placing the silos. The costs by this mounting are very great due to the changes in the building, and it is difficult or impossible to have production running in a hall or a room while the taking down and building up of roof and walls occurs.

For all known silos it is also a problem that the insulation is bad or does not exist at all. For example, this means that hot material poured into a silo on a cold day results

in formation of condensate at the inner side ; the silo is"sweating". Furthermore, in the case of outdoor located silos, temperature changes through the day may result in unfa- vourable temperature variations inside the silo. Finally, the action of the sun may im- ply that one side of the silo is strongly heated while the other side is relatively cold.

Besides the effect on the material inside the silo, this also means material stresses in the silo structure due to the different thermal expansion in the sides of the silo.

Explanation of the Invention The particular features of the invention is that the silo has been built up from shell elements in the form of modules that each comprise an outer and an inner shell mem- ber fastened on each side of a firm insulation material.

The particular features of the shell element according to the invention is that the shell element consists of an outer shell member and an inner shell member which are fas- tened on each side of a firm insulation material.

Shell elements for building up the silo may thus be moved through existing gates and doors in a factory, and the silo may be built up"from the bottom"as there is first mounted a ring of shell elements and a top which are then lifted up for subsequent mounting of an underlying row of shell elements until the silo is completely built. This imply so significant savings in the total cost of mounting that the increased price by making independent modules more than offsets the costs of building changes and other measures to be performed for mounting a fully mounted silo inside a plant or a production hall. In connection with the foodstuff industry it is also of particular sig- nificance that the mounting of the modules may be done much more clean and dustless than by the prior art building methods. Thus the production plant does not have to be shut down or other measures to be made for preventing contamination of the otherwise clean production plant. Finally, the silo according to the invention has the great advan- tage that a very stable insulation ability may be achieved between outer and inner shell. The shell elements may be joined in such a way that thermal stresses due to cli- mate and sun are not transmitted in an unfavourable way.

The silo according to the invention is preferred designed so that the shell elements are mutually connected in horizontal direction by the joining of outer shell members and in vertical direction by through-going fastening means arranged in the insulating ma- terial. By joining the shell elements at the outer shell members, easy and rapid mounting is achieved, and by means of the through-going fastening means, sufficient mechanical strength and stability about horizontal axes against actions from snow and wind are achieved. Furthermore, the indicated passing through of the fastening means is advantageous by mounting of the elements according to the lifting method as de- scribed in method claim 13.

It is preferred to use riveting, preferably with pop rivets, by joining the outer shell members, cf. claim 2. Pop rivets have great strength against tearing forces directed in the plane of the shell members. In order to achieve a very strong structure, the silo is preferred built up as indicated in claim 3 where pipe sections for passing through of the fastening means are embedded in the insulation material.

In claim 4, examples of preferred fastening means are indicated, namely that stay bolts assembled by means of nuts are used. Furthermore, claim 5 specifies a further pre- ferred embodiment of the invention where the nuts are formed with pointed ends which facilitate and guide the insertion of stay bolts with fitted nuts into the pipe sec- tions.

In order to achieve a silo which is air and moisture tight and, besides, pressure tight, it is preferred to design the silo as stated in claim 6 where along the side edges of each shell element there are resilient seals disposed in such a way that seals between mu- tually adjoining shell elements form airtight packing.

By cylindrical silos, the shell elements, when joined along the outer shell members, may be squeezed at the inner shell members due to their thickness. This squeezing may be utilised for providing the sealing force. Thus it is preferred that the seals are disposed in one or more grooves along the side edges of the inner shell member.

A preferred embodiment of the connection between the discharge cone of the silo and the shell elements is indicated in claim 8.

The shell element according to the invention is preferred made as stated in claim 9, where the element is a sandwich construction where outer and inner shell members adhere to each side of a mechanically stable insulating material. This construction is self-supporting, strong and rigid and very suitable as modular element in the silo ac- cording to the invention. The insulating material may, for example, be hard polyure- thane foam which is very well suited, both mechanically and with regard to insulation.

As stated in claim 11 it is preferred that the outer shell member along two mutually adjacent side edges has a part projecting out from the insulating material. The outer shell member may thus overlap along two side edges that are closest to side edges of adjoining side edges.

As indicated in claim 12, each shell member may be provided with a sealing strip of resilient material along its whole rim. Besides ensuring air tightness up to a certain differential pressure, the use of abutting sealing strips may allow a certain mobility between the shell elements, e. g. caused by thermal stresses in the silo.

A method for building a silo according to the invention is indicated in claim 13. The method comprises a number of steps: a) a ring of shell elements is mounted and assembled; b) a top is mounted upon the first ring; c) the first ring including the top is lifted a height at least corresponding to the height of a shell element; d) step a) is repeated, and the rings are assembled with vertical fastening means; e) the assembled rings are lifted a height at least corresponding to the height of a shell element; f) steps d) and e) are repeated until the silo has attained the desired height; g) a support, possibly with built-in weigh cells, and an discharge cone are mounted between the lowermost ring and a base.

Hereby a silo is built up from the bottom as described above.

The Drawing A preferred embodiment of the invention is now described more closely with reference to the drawing, wherein: Figs. 1-3 show a silo according to the invention as seen from the side, from the side partly exposed at the base, and from above, respectively, Figs. 4-5 show a shell element according to the invention as seen from the side and from above, respectively, Figs. 6,7 and 7a show an inner shell member for a shell element according to the in- vention, as seen from the side, from above and of an enlarged part section on the line A-A on Fig. 7, Fig. 8 shows assembly between two stay bolts for use in a silo according to the in- vention, Fig. 9 shows a top for a silo according to the invention in an elevated section and two enlarged details of Fig. 9, and Fig. 10 show the top on Fig. 9 as seen from above.

Description of Example Embodiments A silo according to the invention may be designed as shown on Figs. 1-3. The illus- trated silo is built up on a base frame 1 which is supported on a number of weigh cells 1 and carries the weight of the silo via a support 3. The support 3 supports a discharge cone 4 and thereby the contents of the silo which may be any kind of fluid or loose material. The primary field of application of the silo is materials for the food industry.

In the depicted embodiment, the silo is covered completely down to the ground surface or the base so that the support 3 is not seen from the outside. Therefore, a door 5 is provided in the casing of the silo. In other embodiments, the casing may be finished above the door, and the upper and outer part of the discharge cone meets the casing so that the discharge cone is free.

The silo is built up from modules in the form of shell elements 6 which are joined into rings 7 and then joined under each other.

In the shown embodiment, the silo is made as a cylindric container but other geometric shapes are of course possible, for example with polygonal or box-shaped cross- section. The shell elements are here shown as part cylindric modules but in other em- bodiments of the silo, they may of course be plate shaped and have other shape than rectangular, for example hexagonal.

In the shown embodiment, the silo is finished with a frusto-conical top 8 which is built up from segments 9. The segments 9 are fastened to the uppermost ring 7 along the outer rim. At the centre, the top 8 has an opening 10 which in a way not otherwise shown may be provided with filling unit, inspection hatches etc. in a usual way ; also, it may be provided in the usual way with a not shown platform and a ladder suspended therefrom.

A shell element for use in the described embodiment of the silo is shown more closely on Figs. 4 and 5. The shell element 6 is built up as a sandwich structure with an outer shell member 11 and an inner shell member 12. For application in the foodstuff indus- try, both shell members 11,12 are made of stainless steel sheets. Between the sheets 11,12 is a layer of polyurethane foam 13 as insulating material. The polyurethane foam is hard and sticks to both sheets 11 and 12 so that hereby a mechanically stable and very rigid structure is formed. As the PU-foam 13 is sufficient for keeping the sheets 11,12 in position and has sufficient adhering ability to these, further reinforcing elements, which are liable to form thermal bridges between the ilmer shell member 12 and the outer shell member 11, are not necessary.

On Fig. 4, a part of the inner shell member 12 is removed for showing a pipe section 14 for passing through stay bolts by mounting the shell elements 6. The pipe section 14 is provided with angle bars 15 which anchors the pipe section 14 in the PU-foam 13.

On Fig. 4, the outer shell member 11 projects to the left and downwardly in relation to the insulation 13 and in relation to the inner shell member 12 so that overlap on ad- joining shell members can be formed. The left, overlapping side edge of the outer shell member 11 is provided with a row of holes for pop rivets by riveting to an adjoining shell member. A corresponding row of holes appear at the right side of the outer shell member 11 for use in this joining.

The inner shell member has been shown by itself on Figs. 6 and 7 as Fig. 6 shows the side facing the insulation 13. Along the four side edges of the shell member there is welded a profile as shown in the enlarged detail, the section on Fig. 7a. The profile thereby forms two recesses or grooves of which the one facing the centre of the sheet engages the foam while the other acts as seat for a seal 16. The seal 16 is preferred made of silicon rubber but other types of seals 16 may of course be used, depending on the purpose.

In order to keep together the shell elements 6 in vertical direction, there are nuts 20 which are designed in a special way for connecting the ends of the stay bolts. Thus a lower end 2 la is connected with an upper end 21b with the nut 20. In practice, the nut 20 is first screwed onto the lower end 21 a on an oppositely situated shell element 6, whereafter the shell element below is pushed upwards so that it catches the reduced cone and outer diameter on the lower part of the nut 20. The lower part on the nut 20 is designated 22. The lower part 22 thus engages the upper part of the pipe section 14.

The top 8 of the silo is shown in enlarged detail on Figs. 9 and 10. The top 8 consists of segments 25 which in principle are constructed as the shell elements 6, i. e. with an outer shell member and an inner shell member at each side of a layer of hard polyure- thane foam. The segments 25 are fastened to each other at their side edges with pop rivets as the shell elements 6. Along the outer rim, the outer shell member on each segment 25 is provided with an angular flap 26 as shown in the enlarged detail to the right on Fig. 9. The flap 6 bypasses the upper edge of the uppermost string of shell elements 6 and thus forms protection for the joint against sun and rain. At this joint, along the rim of the segments there are provided tubular lead-ins 27, which the

upper ends of the stay bolts may go through, and whereby the stay bolts may be se- cured by nuts as outlined in the detail on Fig. 9.

The segments 25 around the aperture 10 are kept together with a ring 28 at the centre.

This is screw bolted to the inner edges of the segments 25 as shown in the detail to the left on Fig. 9.