Such a silo as well as the method mentioned above for the stacking into and reclaiming from the silo, are well known from the Dutch patent application NL-A-8202119.

This publication describes the homogenization of the material to be stacked into the silo by depositing said material in horizontally arranged concentric circles and reclaiming it by sinking a screw conveyor to half its dia- meter into the material present in the silo, then by acti- vating said screw conveyor for moving the material in a radial band to the central column of the silo, and from there, under the influence of gravity, to be passed through a discharge opening in order for the material to be deposited onto a conveyor belt that is located in a radially extending tunnel under the floor of the silo. As already mentioned, the known silo is filled as well as emptied by means of the screw conveyor introducing the material into or removing the material from the silo in a radial direction, in the form of the already-mentioned bands. After each addition or removal of such a band the screw conveyor is rotated around the central column of the silo over a small angle in order to continue the operation in the next adjacent band. This sequence of actions con-

tinues until the screw conveyor has made a complete rota- tion around the central column. Then the screw conveyor must be adjusted for height, i.e. raised when adding material and lowered when removing material. Thus the silo is filled or emptied in the configuration of horizontally positioned circular layers. A disadvantage of the prior art is that there is no rearrangement of the material that is introduced into the silo, so that variations in quality of this material existing when stacking the silo, also exist in the material as it is removed from the silo with- out having undergone any form of homogenization, and there is no chance of quality differences in the material being averaged out. There is, however, a great need for homogenization of the material. Especially in the case of such materials as coal, iron-ore, raw materials for cement or agricultural products, which in the course of time and deliveries exhibit differences in quality, a method is needed by which these differences can be averaged out.

The object of this invention is now to provide a silo and a method for stacking and reclaiming by which it is possible to improve homogenization of the material to be stacked in the silo.

According to the invention, a silo is provided for this purpose which is characterized in that a supporting beam is provided, substantially taking up the diameter of the silo, and having near the central column a closable feed-through, and a feed-through near the wall which may be closable, and a second conveyor that is closed on its underside, running between the wall and the central col- umn. The first screw conveyor is mounted on the vertically adjustable first auxiliary beam, which has a feed-through at both ends and is suspended from the supporting beam, while on the supporting beam a second auxiliary beam is suspended to allow movement along the supporting beam and on which the telescopic chute is mounted. When the first auxiliary beam is at least partly lowered, the second aux- iliary beam can be placed above this first auxiliary beam to position the chute.

The silo according to the invention affords several advantages. For example the silo according to the inven- tion advantageously embodies a method by which according to the invention, the material, after being introduced by the chute can, by means of the first screw conveyor, be spread in radial bands whereby the first screw conveyor, after completion of one radial band around the central column of the silo, undergoes an angular displacement in order to continue the spreading of the material in an adjacent band, which band-like spreading and successive angular displacement of the first screw conveyor are con- tinued until an entire surface in the silo is covered by the bulk material, after which the first screw conveyor is repositioned at an angle with respect to the horizontal, and the spreading of the material in radial adjacent bands is repeated.

Furthermore, for the recovery of the material according to the invention it is possible to operate the silo in such a way that after removing a, with respect to the central column radially positioned band of material, the screw conveyor is rotated over an angle to move the screw conveyor to the adjacent band in order to remove that band, this sequence of actions being continued until the screw conveyor has completed a circle around the cen- tral column, after which the screw conveyor is lowered at an angle to the horizontal until it at least partially rests in the material still in the silo, after which the removal of following adjacent radial bands of material is continued.

In a further aspect of the invention, the silo is characterized in that the second auxiliary beam has a channel on the underside and that when the first auxiliary beam is raised, the second auxiliary beam can be posi- tioned such that the channel is at least partly on the underside of the first screw conveyor. This allows posi- tioning of the chute not only at the wall or near the cen- tral column but also at any random intermediate position.

This also allows the silo to be operated such that the chute and the first screw conveyor rotate continuously

in the silo, to ensure symmetrical circular distribution of the material in the silo, the starting position for a first deposit and distribution of the material is then at the chute near the wall or the central column of the silo to form the beginning of a conical layer, and after a com- plete circular stacking movement, the chute is adjusted in a radial direction with respect to the central column to carry out the adjacent circular distribution movement and said circular deposits and successive adjustments of the chute are repeated until the chute reaches an extreme position near the wall or the central column of the silo, after which the chute is readjusted to the starting posi- tion, and the spreading of the material is repeated.

Simple versions of the silo according to the inven- tion are characterized in that the support beam can rotate around the central column, in that the supporting beam is provided with a longitudinally extending first rail on which the movable second auxiliary beam is placed and in that the first auxiliary beam and the second auxiliary beam in their longitudinal direction each are provided with a rail that can be adjusted in each other's extension and on which the movable channel is placed.

The invention will now be explained with reference to the drawing in which Figure 1 shows a cross section of a side and a par- tial top view of the silo according to the invention; Figures 2, 3 and 4 show cross sections along the lines A-A, B-B and C-C respectively of Figure 1; Figures 5 to 10 show various methods of stacking the silo according to the invention; Figures 11 to 13 show various methods of emptying the silo according to the invention; Figure 14 is a table showing typical values for the combination of the methods of stacking and recovery of the silo according to the invention.

The silo according to the invention will now be described with reference to Figs. 1, 2, 3 and 4.

Fig. 1 shows in a side and a partial top view a section of the silo according to the invention, the verti-

cal wall of the silo is indicated by reference number 1, reference number 2 indicates the roof, reference number 4 indicates the central column, and reference number 3 the intermediate bin which is installed between the roof 2 and the central column 4. The intermediate bin 3 is provided with a feeder screw 5. The silo is further provided with a horizontal beam xy, whose length practically corresponds with the diameter of the silo. This beam xy runs just to one side of the central column 4 to which it is rotatably attached by means of running wheels 12. The rotating con- struction is shown in detail in Fig. 4, to be further described below. The beam xy is supported on the outer ends x and y by means of wheels on a horizontal rail 6 extending around the entire circumference of the silo wall 1 and attached thereto. Underneath, the beam xy is on both sides provided with an internal rail 7 extending along the length of beam xy which, as will be described below, serves to support the second auxiliary beam mn (see Figs.

2 and 3). The beam xy supports a screw conveyor st extending from point x near the wall 1 of the silo, to a point close to the central column 4. The distance between this latter point and the central vertical heart-line of the silo or the intermediate bin 3 is bridged by a feeder screw 5 that radially transports the material supplied via the roof into the intermediate bin 3, to the screw con- veyer st. The underside of this conveyor st is closed by a plate provided with a permanent opening at x and which at the end of the feeder screw 5 is provided with a closable opening. From the beam xy a first auxiliary beam uv is suspended, taking up about half the length of the beam xy, and the height of which can be adjusted with the aid of hoisting winches 8. Optionally, the hoisting winches 8 are movable over the first auxiliary beam uv by means of rails installed for this purpose. The beam uv has vertical open- ings on both ends, and underneath, it is provided on both sides with internal rails 9, extending along the length of said beam uv (see Figs. 2 and 4). The function of these rails 9 will be described below. The first auxiliary beam

uv is also provided with a screw conveyor gh, whose screw blade projects partly under the beam uv.

Fig. 4 shows in more detail that the first auxili- ary beam uv is rotatably attached to the central column 4 by means of a connecting piece which comprises a circular guiding ring a, which by means of guiding wheels 11 is enabled to rotate in relation to the central column. Next to this circular guide, a straight, hollow guiding beam b is provided so as to pivot on a hinge sc, which guiding beam b comprises a wheel c that is movably connected to the first auxiliary beam uv by means of a axle ab.

Fig. 3 shows that the rails 7 of the beam xy are actively supporting the second auxiliary beam mn. On the end of said beam near the central column 4 there is a ver- tical opening, and underneath, the beam itself, is provi- ded with an internal rail 10. This rail 10 is positioned such that it can be moved in alignment with rail 9 which is placed in a similar position on the inside of the first auxiliary beam uv (see Fig. 2). These rails 9 and 10 sup- port a movable channel kl. As shown, this channel kl has the shape--of- a half cylinder and is provided at the end k (see Fig. 1) with the telescopic chute ef. When the chan- nel kl is moved along the rails 9 of the first auxiliary beam, it closes off the screw conveyor at its underside.

This makes the use of the device very advantageous.

The operation of the silo according to the inven- tion will now be explained further with the aid of some examples of embodiments, which are not intended to be restrictive. First, with reference to Figs. 5, 6 and 7, a first loading principle based on radial distribution of the bulk material will be described. Then, with reference to Figs. 8 to 10, a second loading principle, based on tangential spreading of the bulk material in the silo will be described.

As explained with reference to Figs. 5 to 7, when radially spreading the bulk material, the channel kl is placed entirely under, and fastened to the beam mn. The first auxiliary beam uv with the screw conveyor gh is lowered with the aid of the winches 8 to above the silo

floor. In relation to the beam xy, the second auxiliary beam mn is positioned with the chute ef above the ends v or u of the first auxiliary beam uv. The underside f of the chute ef is fastened to the first auxiliary beam uv.

The material supplied by means of the feeder screw 5, is transported via the openings in the beam xy and the second auxiliary beam mn at the column side 4 or the silo wall 1 to the screw conveyor gh. By means of the rotation of this conveyor around its own axis and around the central column of the silo the material is spread in the silo. In this way the layers of bulk material are deposited around the central column 4 in a rotation-symmetrical configuration.

Three variations of this configuration, referred to as il, i2 and i3, will be explained.

Method il. horizontal circular layers (Fig. 5-).

In this case, after the first auxiliary beam uv has been lowered, the second auxiliary beam mn is positioned under the beam xy such that the upper side e of the chute ef is under the end of the feeder screw 5. Via the opening in the beam xy near the central column 4, the chute ef and the opening in the first auxiliary beam uv, near the cen- tral column 4, the material delivered by said screw is transported to the screw conveyor gh. From there the screw conveyor gh spreads material horizontally in the direction of the silo wall. Every time a radial band of bulk material has been deposited, the beam xy is displaced over a small angle around the central column 4 and after each complete rotation around said column 4 the screw conveyor gh is raised a small distance at both ends g and h. In this way a configuration of horizontal layers of material is created. In itself, this method of stacking is known from the prior art disclosed in the Dutch patent specifi- cation NL-C-161226.

Method i2. conical layers with the apex upwards (Fig. 6).

In this case, after the first auxiliary beam uv has been lowered, the second auxiliary beam mn is moved under the beam xy such that the telescopic chute ef is positioned under the wall end of the screw conveyor st. If the

opening in the beam xy near the central column 4 is closed, the material introduced by the feeder screw is moved with the aid of the screw conveyor to the silo wall 1. Via openings in the beam xy and the auxiliary beams mn and uv and by means of the chute ef, the material is then guided to the screw conveyor gh that transports the material and spreads it over the material already in the silo.

Beginning with an empty silo, the conveyor gh is raised after every rotation of the beam xy around the cen- tral column 4, but only at the central column. As a result, the material is deposited in the silo in conical layers, with the apex increasingly higher in the central heart line of the silo and with a decreasing apical angle.

When the material in the silo has thus reached the maximum stacking height at the central column 4, the conveyor gh is no longer raised at the central column after each rota- tion, but at the silo wall 1. This results in layers of material forming a cone with the apex at the maximum stac- king height and with an increasing apical angle. This pro- cedure continues until the entire silo has been filled, but can also be stopped sooner.

Method i3 conical layers with the apex downwards (Fig. 7) In this case, after the first auxiliary beam uv has been lowered, the second auxiliary beam mn is moved a short distance under the beam xy, such that the telescopic chute ef is positioned under the end of the screw conveyor st at the central column and the opening in the beam xy is opened at this point. Via the openings in the beam xy, the auxiliary beams mn and uv and the chute ef, the material supplied by the feeder screw 5 is guided to the screw con- veyor gh which transports and spreads the material over the material already in the silo.

Beginning with an empty silo, the conveyor gh is initially raised after each turn of the beam gh around the central column, but only at the silo wall. As a result the material is deposited in the silo in conical layers with the apex at the middle of the silo floor and with a

decreasing apical angle. When the material in the silo has reached the maximum stacking height at the wall 1, the conveyor gh is no longer raised at the wall end after each rotation, but at the central column 4. This results in layers of material being deposited such as to form a cone with the apex increasingly higher at the central heart line of the silo and with an increasing apical angle. This process continues until the entire silo is filled, but may be stopped sooner.

Thanks to the movability of the components of the silo, it is possible at each stage of the stacking accord- ing to methods i2 and i3, to maintain the first auxiliary beam uv with the screw conveyor gh continuously in the desired position just above the material that is already in the silo, by moving the winches 8 on the beam xy. To this end the length of the hoisting cables can also be adjusted if required. In this way maximum spreading of material can be achieved. When stacking methods i2 and i3 are applied, the maximum angle of the screw conveyor gh in relation to the horizontal may have to be limited in order to prevent any uncontrolled movement of the material over the conical configuration, or to prevent the material con- figuration becoming asymmetrical.

With all the three stacking methods il, i2 and i3, rotation of the beam xy around the central column 4 may occur in stages or continuously.

Now the method of tangential spreading of the bulk material in the silo will be described with reference to Fig. 8 to 10.

With this stacking principle the auxiliary beams uv and mn are positioned in each other's extension so that in the longitudinal direction of the beams the channel kl can take up various positions along these beams. The material supplied by the feeder screw 5 is conveyed via the opening in the beam xy near the central column 4 to the screw con- veyor gh which transports it radially in the channel kl to the telescopic chute ef. This chute ensures further guidance of the bulk material to be deposited as desired on top of the material already in the silo.

The beam xy rotates continuously around the central column 4 and with each rotation the channel kl is moved over a short distance in the beams uv and mn. In this way a configuration of rings of stacking material is created.

In view of the changing radius of the rings the rotational speed of the entire device, or the stepped movement of the channel kl along the beams uv and mn, must be adjusted after the deposition of each successive ring to ensure that a layer of deposited rings has the same thickness throughout the silo. To control the flow of the material introduced into the silo it is also possible to make a combined adjustment of both the rotation speed and the stepped movement of the channel kl. In the present stack- ing principle the lower end f of the chute ef is con- tinuously held a short distance above the material just deposited by means of a guide (not drawn). This ensures that the material is accurately positioned.

Three variations of the principle of stacking described above, referred to as i4, i5 and i6, will be further explained.

Method i4. horizontal circular layers (Fig. 8).

In this case the material introduced into the silo is arranged around the central column 4 in horizontal lay- ers of material on top of each other at a specific height, whereby each layer is built up of rings of material accor- ding to the above described stacking principle based on tangential spreading of the bulk material. This stacking method is known from the Dutch patent application NL-A- 8202119.

Method i5, conical layers with the apex upwards (Fiq. 9).

In this case the material introduced into the silo is transformed into rings of material, arranged in the form of conical layers, the axis of which coincides with the axis of the central column 4. The conical con- figuration of the material in the silo is built up from the central column 4 toward the wall 1.

Starting at the foot of an already present cone of bulk material formed against the central column 4, each

successive conical layer is deposited by means of the con- tinuous rotation of the beam xy and with each rotation, the movement of the end k of the channel kl in the direc- tion of the central column 4. At the beginning of the stacking process, first a small cone is deposited in a symmetrical circle around the central column 4 by rotating the beam xy a few times with the chute ef as close as pos- sible to the central column 4.

During the process of depositing the conical lay- ers, the outlet f of the telescopic chute ef is moved horizontally and vertically, so that the, in principle, freely chosen relation between these movements determines the apical angle of the deposited conical layers. After a complete conical layer has been deposited, rings of material are distributed to form the following conical layer starting from the foot of the cone of bulk material already in the silo. In the way described, a configuration of conical layers is created with the apex upwards. When the apex of the cone has reached the maximum stacking height of the silo, stacking may be continued by deposi- ting truncated conical layers in such a way that when the silo has been completely filled, the upper surface of the silo's contents will form a horizontal plane at the maximum stacking height. However, stacking may be inter- rupted sooner.

Method i6 conical lavers with the apex downwards (Fig. 10).

In this case, the material introduced into the silo is transformed into rings of material which are arranged in the form of conical layers and the material configur- ation in the silo is built up from the wall 1 toward the central column 4. The axis of the conical layers coincides with the axis of the central column 4.

Starting at the foot of the material already stacked against the wall of the silo 1, each successive conical layer is deposited while the beam xy rotates con- tinuously and after each rotation the end k of the channel kl is displaced in the direction of the wall.

When starting the stacking process, the material is first deposited along the wall of the silo by rotating the beam xy several times with the chute ef as near to the wall 1 as possible in order to form a slope of material.

During the stacking process the outlet f of the telescopic chute ef is moved horizontally and vertically whereby the, in principle, freely chosen relation between these move- ments determines the apical angle of the conical layers being deposited.

After a complete conical layer of rings of material has been deposited, the rings of material for the next conical layer are deposited starting from the foot of the cone of bulk material then present in the silo. In the way described, a body of conical layers is formed with the apex downwards. Initially the conical layers are truncated until the entire floor of the silo is covered with material. Then the conical layer contains material up to the apex of the cone which then forms a point on the ver- tical heart line of the silo above the floor of the silo.

As soon as the material at the wall has reached the maxi- mum stacking height of the silo, the vertical movement of the end f of the chute ef is restricted to this height, so that when the silo is completely full the upper surface of the contents of the silo forms a horizontal plane at the maximum stacking height.

To prevent uncontrolled, undesired movement of the material in the silo or to prevent the configuration of the contents of the silo becoming asymmetrical, the posi- tions or velocities of the moving installations of the silo during the stacking process are preferably selected such that the angle between the horizontal and the cone inclination, in accordance with the methods il, i2, i5 and i6, is sufficiently small. With stacking methods i5 and i6, the chute kl may be moved continuously as well as in steps. In that case a conical layer is built up in the form of a continuous helical band of material.

The method for the recovery of material from the silo according to the invention will now be elucidated with reference to Figs. 11 to 13. Said method will be

described with reference to a few examples of a completely filled silo, which is, however, not essential for the execution of this method.

At the start of the reclaiming process, the second auxiliary beam mn is moved all the way in the direction y of the beam xy, the chute ef is completely withdrawn and the channel kl is positioned wholly on the second auxili- ary beam mn. Then, by means of the winches 8, both ends of the first auxiliary beam uv are lowered sufficiently far to enable the screw conveyor gh to fully engage the bulk material in the silo. Reclaiming is effectuated by the rotation of the beam xy around the central column 4 and the rotation of the screw conveyor gh around its own axis.

In this way the material is transported toward the central column 4 so that, under the influence of gravity, it moves to the central opening(s) in the floor of the silo. From this point the material is conveyed out of the silo in the usual way via a conveyor belt installed in a tunnel under the floor of the silo. Through the rotation of the beam xy around the central column 4, the material configuration in the silo remains circle-symmetrical in relation to the central column 4 during the reclaiming process. The three variants of the reclaiming process indicated by ul, u2 and u3 will be explained in more detail below.

Method ul, horizontal circular layers (Fig. 11) This reclaiming method is in itself known from the prior art. The method is carried out with the first aux- iliary beam uv whose screw conveyor gh is in the horizon- tal position, whereby after each rotation around the cen- tral column 4 the screw transporter gh is lowered further with the aid of the winches 8. In this way the silo is emptied in horizontal circular layers.

Method u2, conical layers with the apex upwards (Fiq. 12) In this case, the first auxiliary beam uv with the screw conveyor gh, is with each rotation initially only paid out near the silo wall 1. As a result, conical layers are removed, whose apex is the highest point on the verti- cal axis of symmetry of the silo. With this reclaiming

process the apical angle of the conical layers continually decreases until the end g of the screw conveyor gh reaches the floor of the silo. After this, recovery of the material in the form of conical layers is continued by paying out of end v of the beam uv at the middle column 4 after each rotation of the beam xy. This causes the apical angle of the conical layers to increase again until, on reaching the floor of the silo, the screw conveyor gh is again in the horizontal position.

Method u3, conical layers with the apex downwards (Fiq. 13) In this case the first auxiliary beam uv, with the screw conveyor gh, is with each rotation initially only paid out near the central column. As a result, conical layers are removed, whose apex is the lowest point on the axis of symmetry of the silo. The apical angle of the con- ical layers decreases continuously until the end h of the screw conveyor gh reaches the floor of the silo at the central column 4. Then reclaiming is continued by paying out at end u of the beam uv at the silo wall after each rotation of the beam xy. This causes the apical angle of the conical layer to increase again until, when the floor is reached, the screw conveyor gh is again in the horizon- tal position.

Moving the winches 8 on the beam xy and using the means of movement of the first auxiliary beam uv, allows the screw conveyor gh to be kept continuously in the desired position on the surface of the material. If required, the length of the hoisting cables may be adjusted. With the reclaiming methods u2 and u3 it is advisable to limit the maximum angle formed by the screw conveyor gh with the horizontal, in order to prevent uncontrolled displacement of the material over the conical material configuration or to prevent the configuration from becoming asymmetrical.

The combinations of stacking and reclaiming that have been described may be advantageously combined, and the degree of homogenization will be determined by the chosen combination.

As stated above, both the stacking method il and the reclaiming method ul are known from the prior art, see the Dutch Patent specification No. 161226. A variant of this is disclosed in the Dutch patent application NL-A-8202119, from which also the reclaiming method ul is known, although according to this publication the method i4 is used as stacking method.

With regard to the described stacking methods according to the invention, it is not necessary to com- pletely fill the silo before starting the reclaiming.

Usually, the stacking process may be stopped at any moment in order to commence reclaiming, although the position of the respective equipment must be appropriately adjusted with regard to the reclaiming methods described earlier.

The silo according to the invention is suitable for the controlled stacking into and the reclaiming from the silo of both cohesive and free flowing bulk materials.

In the case of free flowing material, a simple movement of the components suffices for some stacking methods.

For example, with the stacking methods i5 and i6, a rotation of the outflow opening f of the discharge chute ef in the horizontal plane is sufficient for each rotation of the beam xy around the central column. In the case of i5, f initially traces small circles around the central column and just above the already deposited material. As soon as the top of the cone has reached the maximum stack- ing height in the silo, f will always trace the circle forming a cross section of the conical surface and the horizontal plane at the maximum stacking height.

In the case of i6, f initially traces circular paths at the wall of the silo just above the material that has already been deposited near the wall. As soon as the material at the wall reaches the maximum stacking height of the silo, f will always trace a circle forming the cross section of the conical surface and the horizontal plane at the maximum stacking height. According to these methods of stacking free flowing material, the inclining

conical surfaces will form an angle with the horizontal plane which is equal to the talus angle.

The advantages according to the invention can be characterized by the concept characteristic mass. By this concept is understood the amount of material of the feed flow from which, as a result of regrouping in the silo, portions of the material are combined to form units of material in the discharge flow. Fig. 14 shows in a table the results that can be achieved with the various combi- nations. For each combination of stacking methods and reclaiming methods, the average and the standard deviation of said characteristic mass are given as percentage of the maximum silo content relating to a particular silo design.

On the left side of the table the various possible stack- ing principles are given, in which stacking principle I stands for the stacking by radial spreading of the bulk material, and stacking principle II stands for stacking by tangential spreading of the bulk material. The reclaiming method selected is always a method in which excavation takes place in the direction of the central column. This table also shows the results of the combinations of embo- diments already known from the prior art using the stack- ing procedure il and reclaiming procedure ul and stacking procedure i4 and reclaiming procedure ul. The average value of the characteristic mass of these respective com- binations amounts to 0% and 5%. This Table clearly shows that maximum results are obtained by the application of radial stacking methods i2 and i3 combined with reclaiming methods u2 and u3 and that when applying tangential stack- ing, the reclaiming processes u2 and u3 are preferably combined with the stacking processes i5 an i6.

Within the context of the invention a number of variants are possible, all of which fall under the scope of protection defined by the appended claims. For instance, the short feeder screw 5 placed in the top of the silo and the screw conveyor st (Fig. 1) placed on the beam xy may be replaced by other equipment, such as con- veyor belts. Also the screw conveyor gh, which is sus- pended from the beam uv, may be replaced by another piece of equipment, for example, a scraper conveyor.