WO2020214032A1

WO2020214032A1 - Hopper for a silo, silo and silo assembly

Info

Publication number: WO2020214032A1
Application number: PCT/NL2020/050254
Authority: WO
Inventors: Harold Hendricus Wilhelmus VERMIJ; Petrus Jacobus Hubertus LEMMEN
Original assignee: Van Aarsen Machinefabriek B.V.
Priority date: 2019-04-18
Filing date: 2020-04-17
Publication date: 2020-10-22
Also published as: NL2022978B1

Abstract

A hopper (200) for a silo comprising at least one cell having a body portion defined by vertical walls, said walls defining a substantially polygonal horizontal cell cross section. The hopper includes an upper hopper section (210) and a lower hopper section (220). The upper hopper section includes a plurality of connecting plates (215) which are slanted and connecting the vertical walls (202) of the cell to an upper edge (212) of the lower hopper section. The lower hopper section has a lower horizontal cross section (222) and an upper horizontal cross section (212) and a lower hopper wall (224) extending between the lower and upper horizontal cross sections. The lower horizontal cross section (222) is substantially circular and the upper horizontal cross section (212) is non-circular, such that an inclination angle between the lower hopper wall (224) and the horizontal plane varies along the circumference of the lower hopper wall.

Description

Title: Hopper for a silo, silo and silo assembly

TECHNICAL FIELD AND BACKGROUND

The present disclosure relates to the field of silos, and more particularly to hoppers for silos.

Silos are well known for containing flowable materials, such as granular materials, powders, etc.. When dispensing the material from the silo, it generally flows out of the silo under the effect of gravity. In a silo a type of flow depends, on the one hand, on the properties of the material, including its cohesiveness and, on the other hand, part of the dimensioning of the emptying hopper (slopes, orifice, etc.).

The ideal flow in a silo, or hopper, is mass flow. In fact, mass flow obeys to the principle of“first-in first-out”. On the contrary, core flow, or funnel flow obeys to the principle of“first-in last-out”.

Depending on the properties of the material, and in particular its cohesiveness, it is not guaranteed that the material will follow a mass flow pattern.

Either excessive roughness of the walls or the change in the properties of the silage product can be at the origin of a core flow.

The geometry of the silo also strongly affects the type of flow.

Figure 1 shows different types of hopper geometries: Figure 1A represents a hopper having a conical shape, Figure IB represents a wedged type hopper, Figure 1C a transition type hopper and Figure ID a pyramidal type.

Other effects may occur in hoppers such as clogging arches, above the outlet opening, and which thereby block the flow of the material. This phenomenon can be due to overlapping particles (for non-cohesive coarse materials) or can be due to cohesion actions between fine particles, in particular for material which has a high cohesiveness. The type of outlet has a strong influence for both cases.

Different methods exist to reduce the arching phenomenon. These include increasing discharge hole dimensions by making it so large that the arch collapses into the opening because the side wall is not present to provide support. Other methods include providing a long rectangular slit as an opening, with a length equivalent to the width of the silo, thereby removing the wall of the hopper on one side. However, feeders which are compatible with such big openings are required. Increasing the walls steepness has also been investigated in combination with a resizing of the outlet.

Other solutions include mechanical means, such as stirrers, or by providing flexing air pads which are mounted inside the hopper, or the use of air blasting devices. The cohesive forces of the product can be reduced by aerating the material. Providing vibrations to the walls of the hopper can also help reduce these undesirable effects.

It is also possible to install a funnel cone pointing upwards inside the hopper so as to modify the flow of the bulk material and prevent the appearance of compressive stresses. In this case, the material can be fed through the gap separating the skirt of the internal cone and the wall of the hopper by vibrating the suspended bottom cone.

All those solutions are more complex to implement and there is thus a need for improvement in the art.

SUMMARY

Aspects of the present disclosure relate to a hopper for a silo. The silo comprises at least one cell having a body portion defined by, e.g. four, vertical walls, said walls defining a cell cross section. The cell can have a horizontal cross section that is substantially polygonal, such as square or rectangular, but other shapes are also possible. The hopper includes an upper hopper section and a lower hopper section. The upper hopper section includes a plurality of connecting plates which are slanted and connecting the vertical walls of the cell to an upper edge of the lower hopper section. The lower hopper section has a lower horizontal cross section and an upper horizontal cross section and a lower hopper wall extending between the lower and upper horizontal cross sections. The lower horizontal cross section is substantially circular. This can allow an outflow funnel to be attached to a lower edge of the lower hopper section in one of a plurality of different rotational positions. The upper horizontal cross section is non-circular, such that an inclination angle between the lower hopper wall and the horizontal plane varies along the circumference of the lower hopper wall.

Providing the inclination angle between the lower hopper wall and the horizontal plane that varies along the circumference of the lower hopper wall provides that during use, the speed of the bulk material while exiting the hopper will have different speeds at different locations within the hopper. These different speeds among the material aid in preventing clogging the hopper as for example a portion of the material will slide beneath another portion of the material.

Optionally, the non-circular upper horizontal cross section is a substantially circular shape having one or more flattened portions, an elliptical or oval shape, a shape corresponding to the polygonal cross section of the cell with smoothed corners, or a combination thereof. Such non circular upper horizontal cross section provides the lower hopper wall having the inclination angle with the horizontal plane that varies along its circumference, in a simple manner.

Optionally, the cell cross section is square or rectangular.

Optionally, the upper horizontal cross section is substantially square (rectangular) with rounded edges. It can also be elliptical, oval or circular with one or more flattened portions.

Optionally, a first inclination angle between a first connecting plate and the horizontal plane, and a second inclination angle between a second connecting plate and the horizontal plane are different. Providing the different first and second inclination angles also provides that during use, the speed of the bulk material while exiting the hopper will have different speeds at different locations within the hopper. These different speeds among the material aid in preventing clogging the hopper as for example a portion of the material will slide beneath another portion of the material

Optionally, the inclination angle between the lower hopper wall and the horizontal plane varies by at most 10 degrees, preferably at most 5 degrees, along the circumference of the lower hopper wall. Alternatively, or additionally, the first and second inclination angles differ by at most 10 degrees, preferably 5. Providing the relatively limited difference of at most about 10 degrees provides the advantage that although a speed difference is obtained aiding in preventing clogging, the speed difference will be limited, avoiding the occurrence of preferential flow paths in the material.

Optionally, the inclination angle between the lower hopper wall and the horizontal plane is in the range of 50 to 100 degrees, preferably 60 to 90 degrees, more preferably 70 to 85 degrees. Alternatively, or additionally, the first and second inclination angles are in the range of 50 to 100 degrees, preferably 60 to 90 degrees, more preferably 70 to 85 degrees. These ranges have proven to provide a good outflow for most products and good prevention of clogging and preferential flow paths.

Optionally, the inclination angle between the lower hopper wall and the horizontal plane is smaller than, or equal to the inclination angle between a connecting plate of the upper hopper section and the horizontal plane at the same radial location relative to the vertical axis of the silo. Hence, when flowing downwardly along the cell wall and then through the hopper, the material at the wall only experiences a reducing angle relative to the horizontal. Thus, stalling of the material in the silo can be avoided.

Optionally, the lower hopper wall comprises a plurality of transition plates whose upper edges extend to the upper edge of the lower hopper section, and whose lower edges extend to the lower hopper section lower horizontal cross section. The hopper can be designed in a plurality of different levels, each level providing a narrower cross section along the hopper, towards the outlet.

Optionally, each transition plate is associated to a connecting plate. Different plates (transition or connecting) can be associated to the same plate (connecting or transition, respectively). Associated means that they are connected at the same location at the upper edge of the lower hopper section.

Optionally, the connecting plates or the transition plates are curved or flat.

Optionally, the connecting plates and/or the transition plates are arranged longitudinally and/or transversely.

Optionally, at least one connecting plate is flat and is arranged transversely such that its length extends horizontally along a portion of the side of the hopper. This allows to reduce the number of plates which are required to assemble the hopper while providing the design solution of having at least two different inclination angles in the connecting plates.

Optionally, the length of the transverse connecting plate extends horizontally at least along a fifth of the side of the hopper, or a quarter, or a third, or a half, or substantially the entire side of the hopper.

Optionally, the inclination angle a relative to the horizontal plane associated to the transverse connecting plate(s) is larger than the inclination angle of the other connecting plates. The sides of the hopper which are flat, or have a flat wall, are steeper than the other sides. This ensures the design solution of providing at least two different inclination angles.

Optionally, the inclination angle of the connecting plates varies by quadrant within the hopper. Also by providing only connecting plates extending longitudinally along the hopper, the different inclination angles can be achieved by varying for example the inclination angle between each quadrant of the hopper, either between two consecutive corners of the hopper or between the consecutive sides. Different arrangements are possible.

Optionally, connecting plates, the lower hopper wall and/or transition plates are provided with reinforcements.

Optionally, a horizontal reinforcement frame plate is provided surrounding the upper and/or lower hopper section.

Optionally, additional vertical reinforcement plates are provided along the horizontal reinforcement plate, these reinforcements further being configured to connect the reinforced plates to the body portion of the cell.

Optionally, additional reinforcements are provided on the transversal plates. Plates which are arranged transversally, by providing the longer edge horizontally may require more reinforcements than plates which are arranged vertically (longitudinal plates, which have their longitudinal direction arranged vertically).

Optionally, the connecting plates, the transition plates and the converging plates can have any of the following shapes: trapezoid, parallelograms, rectangles, squares, quadrilateral or even be triangular, etc.

It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. Other advantages and features of the invention will be apparent from the following

description, drawings and claims.

BRIEF DESCRIPTION OF DRAWINGS

These and other features, aspects, and advantages of the apparatus, systems and methods of the present disclosure will become better understood from the following description, appended claims, and accompanying drawing wherein: Figures 1A to ID are hoppers according to the prior art in which Figure 1A represents a conical shape hopper, Figure IB represents a wedge type hopper, Figure 1C a transition type hopper and Figure ID a pyramidal type hopper;

Figure 2 is a side view of an example of a hopper;

Figure 3 is another side view of the hopper of Figure 1;

Figure 4 is a diagonal view of the hopper shown in Figures 2 and

3;

Figure 5 is a perspective view of the hopper shown in Figures 2 to

4;

Figure 6 is a top plan view of the hopper shown in Figures 2 to 5;

Figure 7 is a perspective view of a hopper having two sides walls which are substantially flat and additional reinforcements on these sides;

Figure 8 is a perspective view of a hopper having one side wall which is substantially flat and additional reinforcements on the flat side;

Figure 9 is a perspective view of a hopper having two sides walls which are substantially flat;

Figure 10 is a perspective view of a hopper having one side wall which is substantially flat;

Figure 11 is a perspective view of a hopper having an angle variation by quadrant from 70 to 75°; and

Figure 12 is a perspective view of a hopper having an angle of 70° on two sides and an angle of 75° on the other two sides.

DESCRIPTION OF EMBODIMENTS

Terminology used for describing particular embodiments is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term "and/or" includes any and all combinations of one or more of the associated listed items. It will be understood that the terms "comprises" and/or "comprising" specify the presence of stated features but do not preclude the presence or addition of one or more other features. It will be further understood that when a particular step of a method is referred to as subsequent to another step, it can directly follow said other step or one or more intermediate steps may be carried out before carrying out the particular step, unless specified

otherwise. Likewise it will be understood that when a connection between structures or components is described, this connection may be established directly or through intermediate structures or components unless specified otherwise.

The present invention will be described with respect to particular examples and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

The terms "about" or "approximate" and the like are synonymous and are used to indicate that the value modified by the term has an understood range associated with it, where the range can be ±20%, ±15%, ±10%, ±5%, or ±1%. The term "substantially" is used to indicate that a result (e.g., measurement value) is close to a targeted value, where close can mean, for example, the result is within 80% of the value, within 90% of the value, within 95% of the value, or within 99% of the value. Definitions:

A hopper is a funnel-shaped container in which materials, such as granular or powder, normally substantially dry, materials, such as grain or coal, are stored in readiness for dispensation. There are different types of hoppers, such conical and wedge-shaped. In more general terms, a hopper is the converging section of a silo.

A silo is a tall, generally elongate, structure, in which silage is produced and stored. The silo can have a cross section in top plan view that is circular, polygonal, such as square, rectangular, etc. Silos can store any granular medium such as sand, gravel, concrete, for the building industry but also grains, flours, cereals, wheat, rice, etc. for the feed/food industry. Silos can comprise a plurality of cells, having a round or polygonal, e.g. a square (rectangular), horizontal cross section, at the bottom of which a hopper is installed.

A hopper is usually installed at the bottom of a silo.

Material cohesiveness is a property of a material which has the ability to remain stable under the action of internal forces.

The flow of a granular medium within a hopper installed in a silo is dictated by factors such as the shape of the silo, the diameter of the outlet of the hopper,

A granular medium can have different shapes, sizes and roughness.

The different types of flows within a silo are the mass flow and the core flow, also known as the funnel flow.

Mass flow or bulk flow is the ideal flow which occurs within a silo as it follows the principle of first-in-first-out for the particles of the medium. Mass flow is a perfect behaviour which occurs when the walls are sufficiently steep and when the granular medium has the property of being capable to flow under stress. In every point of the silo the medium moves uniformly downwards. In the presence of mass flow, the silo is fully emptied and the storage of all the medium is identical.

The speed of all the particles is the same.

Core flow or funnel flow on the contrary obeys to the principle of first-in-last-out. The flow of the medium is not guaranteed to all the particles and only guaranteed to the particles which are in a central chimney. The remaining particles may remain in the hopper. This problem is also known as rat-hole. This type of flow occurs when the walls are not steep enough or when they are not smooth enough. Core flow may also occur under the influence of properties of the silage material.

The invention is described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. In the drawings, the absolute and relative sizes of systems, components, layers, and regions may be exaggerated for clarity.

Embodiments may be described with reference to schematic and/or cross- section illustrations of possibly idealized embodiments and intermediate structures of the invention. In the description and drawings, like numbers refer to like elements throughout. Relative terms as well as derivatives thereof should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the system be constructed or operated in a particular orientation unless stated otherwise.

A silo comprises a cell to store the required material. A silo system can include a plurality of such silos. Each cell advantageously has a polygonal, such as a square (or rectangular), cross section. The following description is for one such cell, all cells of a silo system being identical.

A rectangular cell has four vertical walls. A hopper is installed at the bottom of the cell to provide easy collection of the material by a feeder provided beneath the hopper. The hopper corresponds to the converging section of the cell . Figures 2, 3, 4, 5 and 6 illustrate an example of a hopper installed in or mounted to a cell of a silo. Figure 2 shows a front view, Figure 3 shows a side view, Figure 4 shows a diagonal view at 45°, Figure 5 is a perspective view of the same hopper, and Figure 6 is a top view of the hopper.

The cell of the silo has a body portion defined by four vertical walls 202, said four walls defining a horizontal cell cross section. In this example, the cell has a substantially square horizontal cross section. The vertically extending corners 203 of the cell may be smoothed, such as rounded or chamfered. The hopper 200 comprises a plurality of connecting plates 215 which form an upper hopper section 210. The connecting plates 215 are connecting the vertical walls 202 of the cell to an upper edge 212 of a lower hopper section 220, here at a connecting ridge 213 having a first cross section. The first cross section, i.e the lower hopper section 220 horizontal upper cross section 212, is smaller than the horizontal cell cross section. The upper horizontal cross section 212 is non-circular. In this example, the upper horizontal cross section has a shape corresponding to the square cross section of the cell with smoothed corners. Here the smoothed corners 212a of the upper horizontal cross section are rounded. Generally, the corners of the upper horizontal cross section 212 can be more smoothed than the corners 203 of the cross section of the cell. In this example, the corners 203 of the cross section of the cell are chamfered and the smoothed corners of the upper horizontal cross section 212 are rounded. Here the rounded smoothed corners of the upper horizontal cross section 212 is larger than the chamfered corners 203 of the cross section of the cell. It is also possible that the smoothed corners of the upper horizontal cross section 212 are rounded to a larger radius than the corners of horizontal cross section of the cell.

The lower hopper section 220 has a lower horizontal cross section 222, which is substantially circular, such as circular, and an upper horizontal cross section 212. The lower hopper section 220 includes a lower hopper wall 224 extending between the lower and upper horizontal cross sections. The lower hopper section 220 lower horizontal cross section 222 being substantially circular, and the upper horizontal cross section 212 being non-circular, cause an inclination angle of the lower hopper wall 224 relative to the horizontal plane to vary along the circumference of the lower hopper wall.

The upper edges 201 of the plurality of connecting plates 215 are shaped so as to conform to the interior surface of the cell body portion. The upper edges of the connecting places 215a are configured to be placed in the corners of the cell body portion. The upper edges of the plurality of connecting plates 215b are configured to be placed along the centers of the front and rear walls of the cell. The upper edges of the connecting places 215a are positioned higher than the upper edges of the connecting places 215b. The upper edges of the plurality of connecting plates 215d are configured to be placed along the centers of the left and right side walls of the cell. In this example, the upper edges of the connecting places 215d are positioned higher than the upper edges of the connecting places 215b. These connecting plates 215b, 215d have a horizontal upper edge. The

intermediary connecting plates 215c are configured to be placed between the corners and the centers of the walls of the cell body portion.

Connecting plates 215b, 215d are referred to transverse connecting plate as they are arranged transversely such that their length extends horizontally along a portion of the side of the hopper.

The connecting plates 215 of the upper hopper section 210 are slanted in such a way that they form an inclination angle with the

horizontal plane. In an example, the prolongation of the plates converges in at least one point or in a section.

The first connecting plates 216 in Figure 2 form a first inclination angle a_x with the horizontal plane. The second connecting plates 217 in Figure 3 form a second inclination angle a₂ with the horizontal plane.

Throughout this application, the orientation of a plate is defined by its inclination angle a between the tangent of the plate (which is the intersection between the tangent plane and a vertical plane defined by the normal vector of the plate) and the horizontal plane. The inclination angle a can also be defined as the complementary angle of the angle b defined by the normal vector of the plate and the horizontal plane. The inclination angle a also corresponds to the inclination angle of the plate which is measured at the exterior of the hopper in a vertical plane normal to the plate.

When all the particles of the silage product move along the hopper with an identical speed, effects such as arching are likely to appear. In fact, the particles arrive at the converging section of the hopper with the same speed, and the particles have the tendency of binding together under the effect of compression due to their cohesive property. The resulting arch supports the weight of the material above it and thereby prevents flow.

The inventors have observed that when the inclination angle of the lower hopper wall varies along its circumference, and/or the first inclination angle <¾ is different from the second inclination angle a₂ , the risk of blockage due to arching is reduced. In fact, the slope of the lower hopper wall and/or the connecting plates determines the starting speed of a material particle located at the vertical level of the lower hopper wall and/or connecting plate, respectively. By varying the slope of the lower hopper wall, and or between at least two connecting plates, the starting speed associated to particles at or near the wall or plates will be different and these particles will not be likely to bind together, as they will move along the hopper with a speed having a different vertical component.

Therefore, providing the lower hopper wall having the inclination varying along its circumference, and/or providing a first 216 and a second 217 connecting plate having a first inclination angle a_x and a second inclination angle a₂ respectively, and wherein the inclination angles a_x and a₂ are different, reduces the risk of particles binding together and thereby prevents arching in the hopper.

However, when the difference in inclination angle along the lower hopper wall circumference, and/or between the first and second connecting plates is too large, the inventors have observed that under certain

circumstances some parts of the material may not flow, and a funnel flow may appear, thereby leaving particles stuck within the hopper.

Furthermore, the steepness of the connecting plates is also important. Inclination angles in the range of 50 to 100 degrees, preferably 60 to 90 degrees provide the best results in terms of preventing arching and funnel flow.

Thus, in an example, the silo comprises connecting plates which are slanted at 70° and other connecting plates which are slanted at 75°. The lower hopper wall may have an inclination angle of between 62° and 70°.

In the example of Figures 2, 3, 4, 5 and 6, the silo comprises front and rear connecting plates 215b which are slanted at 70°, left and right connecting plates 215d which are slanted at 75°, and corner connecting plates 215a which are slanted at angles between 70° and 75°. In the example of Figures 2, 3, 4, 5 and 6, the lower hopper wall 224 has an inclination angle of 70° at a position in line with the centers of the cell walls, and an inclination angle of 60-65° at the corners of the cell.

In the example of Figures 2 and 3, the first and second connecting plates correspond to the plates whose upper edge is flat and which is in direct contact with the wall of the cell.

In the example of Figures 2 to 5, the lower hopper wall 224 comprises a plurality of transition plates 225. In this example, the transition plates’ upper edges are connected to the connecting ridge 213 at the upper cross section 212 and the lower edges are connected to a transition ridge 223 at the lower cross section 222. The transition ridge 223 has the lower horizontal cross section 222. The lower horizontal cross section 222 is substantially circular. Here, the lower cross section 222 is smaller than the upper cross section 212, and smaller than the horizontal cell cross section. The transition plates 225 form a transition section 220.

The inclination angle between a transition plate and the horizontal plane is at most the first inclination angle or the second inclination angle.

For example, in Figure 2, the inclination angle associated to a transition plate 226, which is connected to a connecting plate 216 at the ridge 212, is less than <¾, whereas, as shown in Figure 3, the inclination angle associated to a transition plate 227, which is connected to a

connecting plate 217, is identical to a₂. This is also visible in Figure 4 for the plates which are provided at the corners. The transition plates 225

connected to the corner plates 215a also have a smaller inclination angle with respect to the horizontal plane.

In this example, each transition plate 225 is associated to a connecting plate 215. As shown in the Figures, the transition plates connect to the connecting plates at the connecting ridge 212. Two transition plates can be connected to one connecting plate and vice versa, depending on the design.

Figure 5 is a view in perspective of the hopper shown in Figures 2 to 4. In Figure 5, the cell walls have been omitted for clarity.

The connecting plates 215, 215a, 215b, 215c, 215d, 216, 217 and the transition plates 225 can further be curved or flat. The connecting and transition plates further can be horizontal or vertical. The term transverse plate refers to plates whose length, when installed, is along the horizontal axis, whereas the term longitudinal plate refers to plates whose length, when installed, is along the vertical axis.

In the examples shown, the longitudinal plates are (substantially) flat and sufficiently narrow such that after assembly, the general contour formed by the longitudinal plates matches the shape of a curved surface. Such plates are easier to manufacture than curved plates. Preferably, 5 to 10 vertical plates are provided per side wall of the cell, and even more preferably 7 to 8 plates are provided. However, the skilled person will appreciate that the number of vertical plates per side depends on the dimensions of the silo.

The following Figures 7 to 12 show different examples of a hopper.

In the example of Figure 7, two sides of the hopper comprise flat walls. These two flat walls comprise at least one connecting plate 215e which extends horizontally along substantially the entire side of the hopper. These plates are such that the upper horizontal edge of the upper plate for each side is in direct contact with the wall of the cell. The inclination angle a associated to these plates 215e is larger than the inclination angle of the other connecting plates. It is noted that the plate 215f has an inclination angle of 90 degrees.

These flat connecting plates 215e can be provided by a plurality of longitudinal or transverse connecting plates, as shown in the example of Figure 7.

In this example, the lower hopper section 220 lower horizontal cross section 222 is circular. Here, the lower hopper section upper horizontal cross section 212 is circular with two diametrically opposed flattened sides 212a.

Figure 8 is similar to Figure 7, however with only one side which comprises a flat wall. In this example, the lower hopper section 220 lower horizontal cross section 222 is circular. Here, the lower hopper section upper horizontal cross section 212 is circular with one flattened side 212a. The flat wall comprises a plurality of transversal connecting plates 215e which extend horizontally along substantially the entire side of the hopper. It is to be noted that in the examples of Figures 2 to 6, the connecting plates 216 and 217 extend substantially along half of the side of the hopper.

In the examples of Figure 7 to 10, the flat sides 215e are provided by a plurality of flat transverse connecting plates.

These flat sides have the advantage of providing to the hopper an inclination angle which is different from the inclination angle of the other connecting plates such that they provide a different starting speed to the material particles, as described above. In the examples of Figures 7 to 10, the flat sides 215e have an inclination angle of 70-90 degrees while the other longitudinal connecting plates have an inclination angle of 70 degrees.

In the examples shown, the hopper comprises at least one flat connecting plate which is configured to extend along a portion of the wall of the cell, such that the upper horizontal edge of the connecting plate is in direct contact with the wall of the cell. In the Examples of Figures 2 to 6, the flat connecting plates extend along substantially the half of the wall, whereas in the examples of Figures 7 to 10, the flat connecting plates are configured to extend substantially along 80-90% of the wall of the cell.

The connecting plates further can be provided with reinforcements 250 as shown in Figures 2, 5, 6, 7, 8, 9, 10, 11, 12. References are not provided on all Figures for the sake of clarity. Reinforcements can be provided by means of a horizontal reinforcement plate 255 which goes around the hopper, as a frame. Additional vertical reinforcement 256 plates are provided along the horizontal reinforcement plate 255. These reinforcements further are configured to connect the reinforced plates to the body portion of the cell.

On Figures 7 and 8, extra reinforcements are provided on the flat plates 215g. Figures 11 and 12 show a different example of a hopper also achieving different inclination angles, differently from the other examples shown.

In the example of Figure 11, the lower hopper section 220 and the upper hopper section 210 are merged. Each upper hopper section 210 connecting plate 215 is a prolongation of an associated lower hopper section 220 transition plate 225. Thus, the lower hopper section 220 upper horizontal cross section 212 is position along the plate forming the combined connecting/transition plate. Again, the lower hopper lower cross section 222 is substantially circular, and the lower hopper section upper cross section is non-circular. Here, the lower hopper section upper cross section 212 is elliptic or oval.

Below the lower hopper section 220 a third hopper section 257 is positioned. The third hopper section upper cross section is substantially circular, and the third hopper section lower cross section 258 is substantially circular.

In Figure 11, the connecting plates are longitudinal, i.e. arranged such that their length is vertical. The inclination angle a_q of the longitudinal plates varies for each quarter of the hopper. In the first and third quarters the inclination angle is a_ql = a_q3 = 75°, whereas in the second and fourth quarters, the inclination angle is a_q2 = a_q4 = 70°.

In the example of Figure 12, the lower hopper section 220 and the upper hopper section 210 are merged. Each upper hopper section 210 connecting plate 215 is a prolongation of an associated lower hopper section 220 transition plate 225. Thus, the lower hopper section 220 upper horizontal cross section 212 is position along the plate forming the combined connecting/transition plate.

In Figure 12, all connecting plates have the same inclination angle, with the exception of two plates 215g. These two connecting plates have a length (the upper edge) which extends horizontally at least along a quarter of the side of the hopper. In this example, the upper edge of connecting plates 215g extends substantially along a third of the side of the hopper. In the examples these two connecting plates 215g are trapezoidal. In this example, all connecting plates have an inclination angle of 70°, these trapezoidal plates have an inclination angle of 75°. However, the reverse is also possible.

Again, the lower hopper lower cross section 222 is substantially circular, and the lower hopper section upper cross section is non-circular. Here, the lower hopper section upper cross section 212 is substantially circular with two diametrically opposed flattened sides 212a.

In the examples shown, a third converging member 230 comprises a plurality of converging plates 235 which connect the transition ridge 222 (or the third hopper section lower cross section) to a hopper outlet 240 having a cross section smaller than the cross section of the transition ridge 222. In the examples shown, the hopper outlet is wedged however other shapes are also possible, such as a circle or a square.

In general, the connecting plates 215, 215a, 215b, 215c, 215d, 215e, 215f, 215g, 216, 217, the transition plates 225 and the converging plates 235 can have any of the following shapes: trapezoid, parallelograms, rectangles, squares, quadrilateral or even be triangular, etc. The invention is not limited thereto. The shapes of the plates depends on the shape of the hopper and the cell in which it is to be installed. The main requirement to fulfill is that the inclination angle of at least one connecting plate is different from the others. The inclination angle of the transition plates is preferably at most the inclination angle of the connecting plates. As shown in Figures 3 and 5, the inclination angle of the converging plates can decrease, increase or remain the same with respect to the inclination angle of the transition plates.

Herein, the invention is described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications and changes may be made therein, without departing from the essence of the invention. For the purpose of clarity and a concise description features are described herein as part of the same or separate embodiments, however, alternative embodiments having combinations of all or some of the features described in these separate embodiments are also envisaged.

In interpreting the appended claims, it should be understood that the word "comprising" does not exclude the presence of other elements or acts than those listed in a given claim; the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements; any reference signs in the claims do not limit their scope; several "means" may be represented by the same or different item(s) or implemented structure or function; any of the disclosed devices or portions thereof may be combined together or separated into further portions unless specifically stated otherwise. Where one claim refers to another claim, this may indicate synergetic advantage achieved by the combination of their respective features. But the mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot also be used to advantage. The present embodiments may thus include all working combinations of the claims wherein each claim can in principle refer to any preceding claim unless clearly excluded by context.

Claims

1. A hopper for a silo comprising at least one cell having a body portion defined by vertical walls, said walls defining a substantially polygonal horizontal cell cross section,

wherein the hopper includes an upper hopper section and a lower hopper section,

the upper hopper section including a plurality of connecting plates which are slanted and connecting the vertical walls of the cell to an upper edge of the lower hopper section, and

the lower hopper section having a lower horizontal cross section and an upper horizontal cross section and a lower hopper wall extending between the lower and upper horizontal cross sections, wherein the lower horizontal cross section is substantially circular and the upper horizontal cross section is non-circular, such that an inclination angle between the lower hopper wall and the horizontal plane varies along the circumference of the lower hopper wall.

2. The hopper of claim 1, wherein the non-circular upper horizontal cross section is:

a substantially circular shape having one or more flattened portions;

an elliptical or oval shape;

a shape corresponding to the polygonal cross section of the cell with smoothed corners;

or a combination thereof.

3. The hopper of claim 1 or 2, wherein a first inclination angle between a first connecting plate and the horizontal plane, and a second inclination angle between a second connecting plate and the horizontal plane are different.

4. The hopper of any one of claims 1-3, wherein the inclination angle between the lower hopper wall and the horizontal plane is in the range of 50 to 100 degrees, preferably 60 to 90 degrees, more preferably 70 to 85 degrees, and/or wherein the first and second inclination angles are in the range of 50 to 100 degrees, preferably 60 to 90 degrees, more preferably 70 to 85 degrees.

5. The hopper of any one of claims 1-4, wherein the lower hopper wall comprises a plurality of transition plates whose upper edges extend to the upper edge of the lower hopper section, and whose lower edges extend to the lower hopper section lower horizontal cross section.

6. The hopper of claim 5, wherein each transition plate is associated to a connecting plate.

7. The hopper of any of claims 1-6, wherein the connecting plates and/or the transition plates are curved or flat.

8. The hopper of any one of claims 1-7 wherein at least one connecting plate is flat and is arranged transversely such that its length extends horizontally along a portion of the side of the hopper.

9. The hopper of claim 8, wherein the inclination angle a associated to the transverse connecting plates is larger than the inclination angle of other connecting plates.

10. The hopper of any of claims 1-9, wherein connecting plates, the lower hopper wall, and/or transition plates are provided with reinforcements.

11. The hopper of claim 10 wherein a horizontal frame reinforcement plate is provided, surrounding the upper and/or lower hopper section.

12. The hopper of any one of claims 1-11 wherein the cell cross section is substantially square or rectangular.

13. A silo comprising at least one cell having a body portion defined by vertical walls, said walls defining a substantially polygonal horizontal cell cross section, including a hopper according to any one of claims 1-12.

14. A silo assembly, including a silo according to claim 13 and an outflow funnel connected to a lower edge of the lower hopper section.

15. The silo assembly of claim 14, wherein the lower hopper edge is arranged for selectively mounting the outflow funnel thereto in one of a plurality of different rotational positions.