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The invention relates to the field of industrial handling systems and storage systems for bulk materials and concerns a particular management system for stock tanks for granular materials.

The stock tanks used in this field are very capacious structures, which enable a large quantity of product to be stored, making the best use of the available space for logistic purposes, also maintaining, if necessary, the product sheltered from the weather, even for long periods of time.

The materials stocked can be solid bulk materials of any nature, granulometry or size, and in particular they are often materials of vegetable origin, such as combustible biomasses, wood scraps or chips, etc...

There are known management systems for stock tanks comprising stock tanks of cylindrical shape, namely silos, capable of containing enormous quantities of material.

Loading of the material into said silos takes place from above by means of conveyor belts, while extraction takes place from below, by means of milling screws.

Screw extractors are generally installed on the bottom of the silos and emptying therefore takes place through gravity, always starting from the lower part thereof.

To facilitate extraction of the product, the motorized screws, placed on the bottom of the silo, are also provided with a circular movement of rotation about the axis of the silo or of translation in a bottom plane, which causes the granular material to be moved and conveyed toward the outlet. These management systems have limits and disadvantages, mainly due to the type of extraction system.

The main disadvantage consists in the fact that the extraction system is of submerged type, where the screw, placed on the bottom of the tanks, is always under the operating face, and is therefore burdened by the weight of all the material stocked, and subject to very high pressures, which lead easily to wear thereof.

For this reason, extraction means therefore require large operating powers with high energy consumptions.

Moreover, it is impossible to carry out maintenance operations on this type of submersed extractors, without first emptying the silos or stock tanks, with substantial loss of time and consistent economic damages.

A further disadvantage derives from the type of structure of the stock tanks, which necessarily require an overhead automatic loading system. This loading system necessarily causes stratification of the material being fed in. As the material can have considerable differences in terms of product quality, it reaches the extraction system with the same stratification. The extraction system always collects it in successive layers and this can therefore lead to a supply of the plant located downstream of the silo with characteristics of the material that vary greatly over time, to the point that it can constitute a reason for malfunction of this system or for poor quality of the finished product, when this is constituted, for example, by wooden panels for use in the furniture sector.

The object of the present invention is to eliminate the drawbacks mentioned above.

In particular, the main object of the invention is to produce a management system for stock tanks for granular materials that is efficient and functional, has a good yield and is economical, from the point of view of consumptions and from the point of view of production costs.

These objects are achieved with a management system for stock tanks for granular materials, comprising:

- a tank destined to contain granular materials;

- a milling screw driven by motor means for extracting said material from said tank;

- means for removal of the extracted material;

- a control unit,

characterized in that

- said tank comprises at least two vertical straight walls parallel to each other, adapted to delimit said tank longitudinally;

- said system comprises a bridge crane arranged for translating on guide means along said at least two walls;

- said milling screw is associated with a trolley sliding on said bridge crane, so that said milling screw slides both crosswise and longitudinally with respect to said tank, always moving over the operating face.

In particular, said milling screw is rotatingly associated with said trolley so that the axis thereof can vary the angle of inclination with respect to a horizontal plane.

Advantageously, said angle of inclination, varied by said control unit, is comprised between 0° and a suitable angle, below 90°, as a function of the type of material to be extracted, so that said milling screw is more or less submerged in said tank according to the value of said angle.

According to an aspect of the invention, said means for removal of the extracted material comprise a first conveyor belt arranged along said bridge crane, and a second conveyor belt arranged along the direction of said longitudinal walls.

According to a further aspect of the invention, said guide means comprise two rails adapted to be engaged by corresponding wheels belonging to said bridge crane.

In a possible embodiment of the invention, said tank comprises two transversal closing walls, and at least one of said transversal walls is provided with opening means.

According to a further aspect of the invention, said management system comprises automatic loading means for said granular materials.

In particular, said loading means comprise a supply system for said materials arranged in the direction of the longitudinal walls and a distribution system for said materials, the latter translating on said guide means and arranged along the transversal direction of said tank.

In a possible embodiment of the invention, said supply and distribution systems each comprise a first conveyor belt with a fixed point of discharge, beneath which a second conveyor belt, provided with a device for reversing the motion thereof, is slidingly associated.

In a further possible embodiment of the invention, said supply system comprises a conveyor belt with point of discharge for the material movable therealong.

In more complex embodiments of the invention, said management system for stock tanks for granular materials is adapted to operate with at least two stock tanks, arranged one after another or parallel to each other.

The invention has numerous advantages.

Extraction takes place above the mass of the material stocked and is not subject to the weight thereof: advantageously the extraction system is not subjected to loads and pressures and is therefore less subject to wear. Moreover, the extraction system does not require large operating powers and therefore energy consumption is greatly reduced, with consequent economic savings.

The axis of the milling screw can vary the angle of inclination thereof with respect to the horizontal plane so that it is always in contact with the material to be extracted, until reaching the optimal inclination equal to the resting angle typical of the type of accumulated material.

Milling carried out with a certain inclination, and not horizontally as in the prior art described above, enables the material stocked to be mixed during extraction.

Extraction of the product takes place by collecting the materials crosswise with respect to the layers deposited during loading of the tank: this enables, already in the extraction step, homogenization of the characteristics of the product destined for subsequent processing operations.

Even more advantageously, no important masonry works are required for the construction of these stock tanks, two lateral retaining walls being sufficient.

The fact of not having closing walls facilitates access to the stock tank with mechanical means, such as bulldozers and mechanical shovels, in the case of maintenance or cleaning operations of the system, or also facilitates the step of filling the tank with the material to be stocked.

If transversal closing walls are also present, these can advantageously be provided with opening means, always useful to provide rapid access for loading of the material or for emptying with mechanical means in the case of need.

The loading means composed of a plurality of conveyor belts arranged along the two directions of the stock tank, if appropriately combined and synchronized, can constantly vary the point of discharge of the material inside the same tank. By appropriately combining the translation of the conveyor belts and the reversibility of their movement, it is possible to distribute the product homogenously over the whole width of the tank.

More complex versions of the management system provide for the construction of several tanks arranged one after another or parallel to each other, as a function of the space available, each provided with its own extraction and loading systems. This advantageously makes it possible to obtain continuity both of the processes for stocking and for extracting the material: while one tank is being filled, the product destined for subsequent processing operations is extracted from the other, thereby optimizing time and money.

The advantages of the invention will be more apparent below, in the description of preferred embodiments, provided by way of non-limiting example, and with the aid of figures wherein:

Fig. 1 represents, in an axonometric view, a management system for stock tanks for granular materials according to the invention and during a first operating step;

Fig. 2 represents, in a vertical section, the system of Fig. 1 ;

Figs. 3 and 4 represent, respectively in an axonometric view and in a vertical section, a management system for stock tanks for granular materials according to the invention and during a second operating step;

Figs. 5 and 6 represent, respectively in an axonometric view and in a vertical section, a management system according to a possible variant of the invention;

Figs. 7 and 8 represent, respectively in an axonometric view and in a vertical section, ^' a management system according to a further possible variant of the invention;

Fig. 9 represents, in an axonometric view, a detail of the system of Fig.

7.

With reference to the Figures, there is shown a management system 1 for stock tanks for granular materials, and in particular in the embodiment illustrated in Figs. 1-4, the system 1 comprises only one tank 2, with a rectangular plan, destined to contain granular materials.

Said tank 2 comprises two vertical straight walls 2' and 2" parallel to each other, adapted to delimit it longitudinally.

Said tank 2 can also comprise two closing walls 18 provided with opening means 19 useful for the access of mechanical means.

Said management system 1 substantially comprises a milling screw 3 driven by motor means for extracting said material, means for removal of the extracted material, and a control unit (not illustrated).

Said management system 1 also comprises a bridge crane 4 arranged for translating on guide means 5 along said two walls 2' and 2".

Said guide means 5 comprise two rails adapted to be engaged by corresponding wheels belonging to said bridge crane 4.

Said milling screw 3 is associated with a trolley 6 sliding on said bridge crane 4.

In particular, said milling screw 3 is rotatingly associated with said trolley 6 so that it slides both crosswise and longitudinally with respect to said tank 2, always moving over the operating face, as illustrated in Figs. 1 and 2.

The axis x of the screw 3 can vary its angle of inclination a with respect to a horizontal plane between 0° and a suitable value below 90°, controlled by the control unit, so that said milling screw 3 is more or less submerged in said tank 2 and always in contact with the material to be extracted.

The removal means are arranged for transporting the milled material from the tank 2 to areas allocated to subsequent processing operations.

Said means for removal comprise a first conveyor belt 7 arranged along said bridge crane 4 and integral therewith, and adapted to receive the milled material directly from the screw 3, and a second conveyor belt 8 arranged along the direction of said longitudinal walls 2' and 2", onto which the first conveyor belt 7 discharges, and moving toward the subsequent machines.

With particular reference to Figs. 3 and 4, said management system 1 comprises automatic loading means for said granular materials.

In substance, said loading means comprise a supply system 9 for the material, arranged in the direction of the longitudinal walls 2' and 2", and a distribution system 10 for the material, translating on said guide means 5, arranged along the transversal direction of said tank 2.

In particular, said distribution system 10 rests on a further bridge crane 17 provided with wheels adapted to engage the rails forming said guide means 5.

Said supply system 9 conveys the material to be poured into the stock tanks, while said distribution system 10 distributes it homogeneously inside the tank 2 making use of the whole width thereof.

In particular, said supply 9 and distribution 10 systems each comprise a first conveyor belt 9' and 10' with a fixed point of discharge 11 beneath which a second conveyor belt 9" and 10", provided with a device for reversing the motion thereof, is slidingly associated.

Each first conveyor belt 9' and 10' has a length equal to around half of the dimension of the tank to which it is parallel and has a fixed point of discharge 11. Each second conveyor belt 9" and 10" is instead translating and is adapted to receive the material coming from the first conveyor belt 9', 10' respectively. The conveyor belt 10" discharges the product in different points of the tank 2, ensuring homogeneous filling thereof.

With particular reference to Figs. 5 and 6, the management system 1 illustrated comprises two stock tanks 2 and 12 arranged one after another and having a closing wall 18 in common, each provided with its own extraction and distribution system of the material during the loading step, and provided with a single supply system having the same length as both the tanks.

With particular reference to Figs. 7 and 8, the management system illustrated instead comprises two stock tanks 2 and 12 arranged parallel to each other and therefore having a longitudinal wall 2' in common, each provided with its own extraction and distribution system and also having a single supply system of the material.

In fact, along the vertical straight wall 2' which separates the two tanks there is arranged the supply system 9 of the material, which operates simultaneously both on the first 2 and on the second 12 tank.

Said supply system 9 for the material comprises a single conveyor belt 9' having the point of discharge of the material 13 movable therealong.

In particular, with said conveyor belt 9' there is associated a trolley 14 provided with a discharge loop 15 underneath which there is positioned a thrower belt 16, which moves with said trolley 14 along the longitudinal direction of the tanks 2 and 12, as illustrated in the detail of Fig. 9.

Said thrower belt 16 is provided with a device for reversing the motion thereof. In fact, as a function of the tank to be filled, the control unit changes the direction of rotation of the thrower belt 16, which consequently discharges the product onto the transversal distribution system 10 located to the right or left of the dividing wall 2' so as to fill the respective tank 2 or 12.

Operation of the system 1 is described below.

In the simplest embodiment thereof, the system 1 is constituted by only one tank 2, which is completely filled with material and only subsequently emptied.

With reference to Figs. 3-4, the product to be stocked in the tank 2 arrives through the supply system 9, in particular passes from the first fixed conveyor belt 9' to the second translating conveyor belt 9" which can move according to the longitudinal direction of the tank 2 and is provided with a device for reversing the motion thereof.

By appropriately combining translation and direction of movement of the second conveyor belt 9" it is possible to discharge the product arriving onto the distribution system 10, having the same composition as the supply system but with a direction crosswise to the tank 2 and translating therealong.

In this way, the tank 2 is completely filled in a homogeneous way.

With reference to Figs. 1-2, extraction starts with the axis x of the screw 3 in an almost horizontal position and with the bridge crane 4 positioned at one end of the tank 2. The trolley 6 starting from a wall 2' of the tank, translates along the bridge crane 4 and rotation of the screw 3 extracts the product and conveys it on the first conveyor belt 7 for removal integral with the same bridge crane.

Once the trolley 6 has reached the opposite wall 2" of the tank, inclination of the axis of the screw 3 is changed by the control unit so as to submerge its extractor blades in the material. Subsequently, the trolley 6 starts its return passage toward the wall 2' of the tank from which it started. Upon reaching this latter, inclination of the axis of the screw is once again increased to extract the product during the subsequent passage.

The change in inclination a of the axis continues, passage after passage, until reaching an inclination equal to the value of the rest angle typical of the accumulated material. From this point on, the continuity of extraction of the material is obtained by maintaining unchanged the axis of inclination of the screw 3, performing translation of the trolley 6 from one part of the tank 2 to the other and translating the bridge crane 4 by a fixed quantity at the end of each passage before performing reversal of the motion of the trolley.

The cycle thus configured is repeated until the bridge crane 4 reaches the end of the stock tank.

If the tank 2 were provided with closing walls, the back wall would be shaped with an inclination equal to the rest angle of the material, in order to reduce to a minimum accumulations of material in the corners, which would be impossible to extract with the mechanism described above.

The material extracted by the screw 3 and poured onto the first conveyor belt 7 integral with the bridge crane 4 is in turn discharged onto a second conveyor belt 8 arranged laterally to the stock tank, with axis having the same direction as the rails of the bridge crane 4. This second conveyor belt 8 conveys the product to the machines for the subsequent processing steps.

To obtain continuity both of the stocking processes and of material extraction, the system 1 can be composed of two or more tanks 2 and 12 so that, while some of these tanks are being filled, the product destined for subsequent processing operations is being extracted from the others.

Operation of the extraction system is the same as described for the embodiment of the system with a single tank, while the filling method, and consequently operation of the loading system, change.

In particular, for a system 1 composed of two tanks 2 and 12 arranged parallel to each other, the supply system 9, arranged longitudinally between the two tanks 2 and 12 and provided with a discharge loop 15, conveys the material to be stocked.

As a function of the tank to be filled, the thrower belt 16 which slides with the trolley 14 of the discharge loop 15 changes the direction of rotation of its belt and discharges the product to the right or left, in particular onto the distribution system 10 of the tank on the right or left. The distribution system 10, which operates crosswise to the tank, behaves in the same way described for the system with a single tank.

In all the cases described, when a tank is in the filling step, the respective milling screw is located in rest position at the empty end of the loading tank, where it can be easily subjected to any maintenance operations, in the same way as occurs, during the extraction step, for the loading system.