Patent Publication Number: US-11642701-B2

Title: Disc screen for separating solid materials

Description:
FIELD OF APPLICATION 
     The present invention regards a disc screen for separating solid materials. 
     The present disc screen is intended to be used, in a per se conventional manner, for separating solid materials of various type, such as for example: solid urban waste, inert fluvial material, products of the organic fractions of separate waste collection, compost (for the refining thereof), recycled wood, biomass, inert material, demolition material, land drainage material and dump material, glass, plastic, scrap metal and still other materials. 
     The disc screen according to the invention is therefore inserted in the industrial field of treating solid residues and is advantageously intended to be installed downstream of the crushing or grinding plants for the same residues. 
     STATE OF THE ART 
     Hereinbelow, with the term “residues”, any one solid material that requires being separated into its components based on the dimensions or on the mass will be indiscriminately indicated, and for the sake of description brevity. 
     Known on the market are numerous different apparatuses intended to be employed for separating solid residues in multiple application fields, which employ different structural and operational principles. Several examples of such apparatuses comprise: disc screens, mesh screens, screw screens, drum screens, ballistic separators, fluid bed separators, electrostatic separators, magnetic separators and still other apparatuses. 
     In particular, the disc screens comprise a support structure which rotatably carries, mounted thereon, numerous shafts equidistant in succession, parallel to each other and actuatable to rotate in a same rotation sense. Axially fixed on each shaft is a group of discs separated from each other by a distance at least equal to, preferably greater than, the thickness of the single discs in order to allow interposing the mounted discs on the contiguous shafts, such that each disc of any one shaft is interposed between two discs of the adjacent front and rear shafts. One example of such disc screens of known type is described in the patent application WO 2019/197969 A1. 
     In the present field of the art, one measuring item which distinguishes the characteristics of the disc screen is the screening surface. The latter is defined as the area of the openings delimited between the discs and the rotation shafts and is therefore indicative of the sizing of the residues which are separated from the screen, falling via gravity below the screening surface. 
     Known from the patent EP 1106264 is a disc screen provided with idle sleeves mounted around each shaft and interposed between the discs, having the function of preventing or at least limiting the obstruction of the screening surface. 
     More in detail, each sleeve is axially mounted on the shaft between two discs with the clearance adapted to allow it to freely rotate in an idle manner on the shaft or on a tubular body provided outside the shaft. 
     In operation, possible filiform elements, which are externally twisted around the idle sleeves up to affecting the discs mounted on the contiguous shafts, would not compromise the operation of the screen nor could they determine the stoppage thereof since each sleeve, being idle with respect to the shaft on which it is mounted, would not obstruct the rotation of the shaft itself. 
     The disc screens of known type, described above, have in practice demonstrated that they do not lack drawbacks. 
     A first drawback is tied to the poor versatility if it is requested to modify or adjust the screening surface, for example in order to treat different residues containing materials of different piece sizes. Indeed, the aforesaid screens of known type require long and complex operations for dismounting the idle sleeves and the discs fit on the shafts in order to substitute them with others of different dimensions, so as to to modify the screening surface. 
     A further drawback of the screens of known type discussed above is due to the fact that they do not have a high efficiency in separating plastic materials of different sizing, and in particular of the plastic materials for shopper bags, packages, bags, etc. More in detail, several types of plastic material (e.g. the aforesaid materials for shopper bags, packages, bags) but also any flexible sheet-like plastic material, could be fitted between the discs of the screen and generate problems in the operation of the screen and also increase the times and costs of maintenance. The disc screens of known type have a low capacity to direct the aforesaid types of residues towards the advancing direction, which can thus be undesirably screened, or they can be inserted between the discs or even be twisted around the discs and the rotation shafts, causing the stoppage of the screen for a manual removal thereof. 
     The document EP 0169945 A1 describes a disc screen of known type applied to a combine harvester machine in order to advance the cut herbaceous plants and separate the grain. The discs of such screen are provided with projecting tips in order to facilitate the advancing of the herbaceous plants. However, the latter solution of known type is unable to resolve the aforesaid technical problems since, in particular, the flexible plastic materials would tend to cling to the tips of the discs and be driven towards the rotation shafts, leading to the obstruction of the screen. 
     PRESENTATION OF THE INVENTION 
     In this situation, the problem underlying the present invention is therefore that of eliminating the problems of the abovementioned prior art, by providing a disc screen for separating solid materials which allows operating in an efficient manner with many different types of solid residues, in particular allowing the easy modification of the section of the screening surface, simultaneously ensuring a high capacity to separate with respect to the desired sizes. 
     A further object of the present invention is to provide a disc screen for separating solid materials, which is capable of eliminating or significantly reducing the drawbacks due to the twisting of filiform elements around the discs and the rotation shafts, in particular drastically reducing repeated maintenance operations. 
     A further object of the present invention is to provide a disc screen for separating solid materials, which has a high efficiency of separation between plastic materials having different sizing. 
     A further object of the present invention is to provide a disc screen for separating solid materials, which is entirely reliable in operation over time. 
     A further object of the present invention is to provide a disc screen for separating solid materials, which is inexpensive to make. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The technical characteristics of the finding, according to the aforesaid objects, and the advantages thereof, will be more evident in the following detailed description, made with reference to the enclosed drawings, which represent several merely exemplifying and non-limiting embodiments of the invention, in which: 
         FIG.  1    shows a schematic perspective view of the disc screen for separating solid materials, according to the present invention; 
         FIG.  2    shows an enlarged detail of the disc screen of  FIG.  1    in a schematized plan view, relative to several rotation shafts with a plurality of discs mounted thereon; 
         FIG.  3    shows the detail of  FIG.  2    in a side view; 
         FIG.  4    shows a detail of the present disc screen, relative to a shaped ring; 
         FIG.  5    shows an exploded view of a shaped ring of the present disc screen, in accordance with a first embodiment variant; 
         FIG.  6    shows a side view of the shaped ring of  FIG.  5   ; 
         FIG.  7    shows a side view of a sector of the ring of  FIG.  5   ; 
         FIG.  8    shows an exploded view of a shaped ring of the present disc screen, in accordance with a second embodiment variant; 
         FIG.  9    shows a perspective view of a shaped ring of the present disc screen, in accordance with a third embodiment variant; 
         FIG.  10    shows a side view of the shaped ring of  FIG.  9   ; 
         FIG.  11    shows a plan view of a detail of the present disc screen, relative to part of the rotation shafts, in accordance with a first embodiment of the present invention; 
         FIG.  12    shows a plan view of a detail of the present disc screen, relative to part of the rotation shafts, in accordance with a second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     With reference to the enclosed drawings, reference number  1  overall indicates a disc screen for separating solid materials, object of the present invention. 
     The disc screen  1  according to the present invention is adapted to be employed for separating solid materials of various type such as: solid urban waste, inert fluvial material, products of the organic fractions of the separate waste collection, compost (for the refining thereof), recycled wood, biomass, inert material, demolition material, land drainage material and dump material, glass, plastic, scrap metal and still other materials. 
     In particular the present disc screen  1  is particularly suitable for separating plastic waste from the remaining solid material mass. 
     In accordance with the embodiments illustrated in the enclosed figures, the present disc screen  1  comprises a support structure  2 , intended to be abutted against the ground, and extended between an inlet door and an outlet door, according to an advancing direction A along which the solid materials to be screened are susceptible to proceed. 
     The disc screen  1  also comprises a plurality of rotation shafts  3 , which are rotatably mounted on the support structure  2  that are parallel to each other, and are placed in succession along the advancing direction A, spaced one from the next, in particular with constant spacing pitch. 
     Advantageously, each of the rotation shafts  3  is longitudinally extended according to an extension axis X thereof, preferably horizontal and orthogonal to the advancing axis A. In particular, the extension axes X of the rotation shafts  3  identify a screening surface, preferably horizontal in accordance with the embodiments illustrated in the enclosed figures, but which can also take on a tilt, without departing from the protective scope of the present patent. 
     According to the present invention, the disc screen  1  also comprises a plurality of discs  4 , which are axially fixed in succession along the rotation shafts  3  in order to receive a rotational motion from the latter. 
     More in detail, each rotation shaft  3  carries, fixed thereto (and preferably fitted), multiple corresponding discs  4  placed in succession along the extension axis X of the rotation shaft  3  itself. 
     The discs  4  are positioned along the corresponding rotation shaft  3  spaced one from the next, preferably with constant pitch. 
     Each disc  4  is provided with a first rotation axis R 1  thereof parallel to the extension axis X of the corresponding rotation shaft  3  and, preferably, coinciding with such extension axis X. 
     In particular, as is visible for example in the views of  FIGS.  2 ,  9  and  10   , the distance between each disc  4  and the next is greater than the thickness (according to the extension axis X) of each single disc  4 , in order to allow interposing between two adjacent discs  4 , mounted on the same rotation shaft  3 , a disc  4  mounted on the successive rotation shaft  3  according to the advancing direction A, and simultaneously leaving a lateral space SL between each of the two discs  4  of the rotation shaft  3  and the interposed disc  4  of the successive rotation shaft  3 . For such purpose, the discs  4  mounted on each rotation shaft  3  are mounted offset with respect to the discs  4  mounted on the successive rotation shaft  3 , such that they can be interposed therebetween. 
     In particular, the distance between the rotation shafts  3  along the advancing direction A and the distance between the discs  4  along the first rotation axis R 1  (and in particular the aforesaid lateral space SL) define the screening section of the disc screen  1 , which determines the maximum sizing (dimension) of the materials that are sifted (passing below the rotation shafts  3 ), while the larger-size materials are conveyed towards the outlet door of the disc screen  1 . 
     According to the invention, the disc screen  1  comprises a drive system  5  mechanically connected to the rotation shafts  3  in order to actuate each disc  4  to rotate around the first rotation axis R 1  thereof in a specific rotation sense R (represented for example in  FIGS.  1  and  3   ). 
     More in detail, the drive system  5  is arranged in order to rotate each rotation shaft  3  around the extension axis X thereof in the aforesaid rotation sense R, in a manner such that each rotation shaft  3  carries in rotation discs  4 , fixed thereon. For such purpose, in particular, the discs  4  are mechanically rigidly coupled to the corresponding rotation shaft  3  in order to receive the rotation motion thereof. In particular, the rotation of the discs  4  in the aforesaid rotation sense R is such to determine an advancing sense of the residue material along the advancing direction A from the inlet door to the outlet door of the support structure  2  of the disc screen  1 , in a manner per se entirely conventional and for this reason not described in more detail. 
     For example, with reference to the particular embodiment illustrated in  FIGS.  2  and  3   , the drive system  5  comprises an electric motor  7  and a motion transmission  8  mechanically connected to the electric motor  7  and to the rotation shafts  3 . Preferably, such motion transmission  8  in turn comprises a chain  9  wound as a closed loop and being engaged with a pinion  10  fixed to the shaft of the electric motor  7  and to toothed wheels  11  fitted on each rotation shaft  3 . 
     The drive system  5  is adapted to move all the rotation shafts  3  in the same rotation sense R in order to move, as stated above, the solid material to be screened, accompanied by the rotation of the discs  4 , from the inlet door to the outlet door of the disc screen  1 . 
     In particular, the discs  4  are provided with an external section, advantageously convex, e.g. polygonal, which, as better described hereinbelow, is preferably suitably shaped so as to facilitate the advancement of the solid material along the screening plane along the advancing direction A. 
     Advantageously, each disc  4  is extended (according to the first rotation axis R 1 ) between two opposite external lateral faces  4 A and  4 B, which delimit between them the thickness of the disc  4  itself. 
     In particular, the two lateral faces  4 A,  4 B of each disc  4  are substantially orthogonal to the rotation axis Y, preferably parallel to each other, and are directed (towards the exterior of the disc  4 ) in opposite senses with respect to each other. 
     Suitably, each disc  4  is made of rigid material (e.g. metallic) that is sufficiently solid to sustain the stresses during the operation of the disc screen  1  (in a per se known manner). 
     For example, each disc  4  comprises a rigid body extended without interruption around its first rotation axis R 1  and provided with a central hole crossed by the corresponding rotation shaft  3  (coupled to the latter for example via mortise joint). 
     According to the idea underlying the present invention, the disc screen  1  comprises multiple shaped rings  12 , and each of which is removably mounted around the corresponding rotation shaft  3 , is provided with a second rotation axis R 2  parallel to the extension axis X corresponding rotation shaft  3 , and in particular coinciding with the first rotation axis R 1  of the discs mounted on the same corresponding rotation shaft  3 . 
     Each shaped ring  12  is positioned between two successive discs  4  mounted on the same corresponding rotation shaft  3 . Of course, without departing from the protective scope of the present patent, between two successive discs  4  of a same rotation shaft  3 , a shaped ring  12  (such as in the example of  FIG.  2   ) or even multiple shaped rings  12  can be placed, as a function of the specific application requirements. 
     In particular, as is visible from the example of  FIG.  2   , each shaped ring  12  occupies part of the lateral space SL between two discs  4  of successive rotation shafts  3 , therefore participating in defining the screening section of the disc screen  1 . 
     Each shaped ring  12  is actuatable by the corresponding rotation shaft  3  to rotate around the second rotation axis R 2  in the aforesaid rotation sense R. In particular, each shaped ring  12  is connected to the corresponding rotation shaft  3  in a manner such that the latter can transmit to the shaped ring  12  part of its rotation motion, bringing the shaped ring  12  to rotate in the aforesaid rotation sense R. 
     Advantageously, as described in detail hereinbelow, the shaped rings  12  can be mounted on the rotation shafts  3  of screens of different type, for example both directly (of  FIG.  9   ), and indirectly through the interposition of sleeves  40  externally mounted on the rotation shafts  3  between pairs of successive discs  4  (as illustrated in the example of  FIG.  10   ). 
     Operatively, therefore, each shaped ring  12  is susceptible of rotating around the second rotation axis R 2  in the rotation sense R, following the rotation of the corresponding rotation shaft  3 . 
     With reference to the examples of  FIGS.  4  and  5   , each shaped ring  12  comprises at least two sectors  13 , each of which is extended for a given arc of circumference around the second rotation axis R 2  of the shaped ring  12  itself, and removable locking elements  14 , which are mechanically connected to the sectors  13  and removably fix together the latter, in order to close the shaped ring  12  around the corresponding rotation shaft  3 , such that it remains constrained around the latter. 
     Due to the aforesaid arrangement of the shaped rings  12 , it is possible to modify, in an extremely easy manner, the screening surface by simply coming to fix the shaped rings  12  around the rotation shafts  3  between successive pairs of discs  4 . The fixing of such shaped rings  12  is extremely quick and easy due to removable locking elements  14  (regarding which, hereinbelow, several particular embodiments will be described). 
     Then, in order to modify the screening surface, it will no longer be necessary to dismount all of the discs  4  and other components of the disc screen  1  (as in the screens of known type), but it will be sufficient to loosen the removable locking elements  14  which connect the two sectors  13  and move them onto the rotation shaft  3 , varying the distance between the shaped rings  12  and the discs  4  and therefore varying the screening surface, or add the shaped rings  12  (in a suitable number and positioning) which will come to reduce the screening surface, as a function of the specific sizing of the residues to be screened. 
     According to the invention, each shaped ring  12  is extended, transversely to the second rotation axis R 2 , between an internal edge  15 , which defines a through opening  16  crossed by the corresponding rotation shaft  3 , and an external edge  17 , which is extended around the second rotation axis R 2 , enclosing the aforesaid internal edge  15  at its own interior. 
     In accordance with the particular examples of the enclosed figures, internal edge  15  of the shaped ring  12  has circular shape. Of course, such internal edge  15  can also have a different shape (e.g. polygonal) as a function for example of the shape of the external surface of the rotation shaft  3  (or of the sleeve  40 ). 
     The external edge  17  of each shaped ring  12  comprises at least one thrust section  18 , with convex shape and substantially curved. 
     As discussed in detail hereinbelow, such thrust section  18  of the external edge  17  is adapted to intercept a component of the solid material (in particular components of light material, such as filamentous plastic components) and, following the rotation of the corresponding shaped ring  12 , to push such component outside of the lateral spaces SL between the discs  4 , in particular pushing the material in the advancing direction A towards the outlet door of the disc screen  1 , such to prevent possible obstructions or entangling susceptible of blocking the correct operation of the disc screen  1 . 
     In particular, the claimed arrangement of the shaped rings  12  allows opposing the drawbacks shown by the prior art, by preventing residues with sizing different from that to be screened and filamentous residues, which could be potentially twisted around the rotation shafts  3 , from being moved away from the lateral interspaces SL between the discs  4  and made to proceed in the advancing direction A, thus decreasing the maintenance required by the disc screen  1  and increasing the screening efficiency. 
     According to the invention, with reference for example to  FIGS.  6  and  7   , the thrust section  18  of the external edge  17  of each shaped ring  12  is extended (around the second rotation axis R 2 ) approaching the second rotation axis R 2 , according to sense in accordance with the rotation sense R of the shaped ring  12  when the latter is actuated to rotate following the rotation of the rotation shafts  3 . 
     More in detail, the thrust section  18  is extended from a distal segment  19  to a proximal segment  20  closer to the second rotation axis R 2  with respect to the distal segment  19 . 
     In particular, the distal segment  19  of the thrust section  18  is radially extended at a different distance (in particular greater distance) than the proximal segment  20  from the second rotation axis R 2 , such that, following the rotation of the shaped ring  12 , the part of the external edge  17 , which intercepts the screening plane, varies its own height since the screening plane is cyclically affected by the distal portion  19  of the external edge  17  of the shaped ring  12 , which is raised protruding from the screening plane (with respect to the proximal segment) in order to act against the solid material to be screened. 
     Such shape of the external edge  17  of the shaped ring  12  allows the thrust section  18 , following the rotation of the shaped ring  12  itself, to intercept the solid material, conveying it towards the distal segment  19  of the thrust section  18  itself, in this manner pushing the solid material away from the rotation shaft  3  and preventing it from penetrating into the lateral space SL between the discs  4 . Advantageously, each thrust section  18  of the shaped ring  12  is oriented according to the rotation sense R when the shaped ring  12  is actuated to rotate by the corresponding rotation shaft  3 . 
     More in detail, in operation, when the shaped ring  12  is placed in rotation in the rotation sense R, the proximal segment  20  of the thrust section  18  of the external edge  17  precedes the distal segment  19 . In this manner, the solid material is first intercepted by the proximal segment  20  of the thrust section  18  and then by the distal segment  19 , which moves it away from the rotation shaft  3  and, therefore, pushes it outside the lateral space SL between the discs  4  and in the advancing sense due to the particular extension of the thrust section  18 . 
     Advantageously, the distal portion  19  of the thrust section  18  delimits (radially outward) a widened part of the shaped ring  12 , and the proximal portion  20  delimits (radially outward) a narrow part of the shaped ring  12  having width (defined by the radial distance between the internal edge  15  and the external edge  17 ) smaller than the width of the widened part. Such shape ensures that the aforesaid widened part of the shaped ring  12  (following the rotation of the latter) cyclically acts on the screening plane, acting thrustingly against the solid material to be screened, as described above. 
     Preferably, the thrust section  18  of the external edge  17  delimits an eccentric portion of the shaped ring  12  placed in an eccentric manner with respect to the second rotation axis R 2 . In this manner, in particular, such eccentric portion, following the rotation of the shaped ring  12 , intercepts the screening plane, determining the above-described thrust effect of the solid material. 
     Advantageously, the external edge  17  of the shaped ring  12  comprises at least two thrust sections  18 , each placed on the corresponding sector  13  of the shaped ring  12 , preferably distributed in a uniform manner around the second rotation axis R 2 . 
     In particular, the external edge  17  has multiple distal segments  19  that are separated by corresponding proximal segments  20 , such that the distal segments  19  and the proximal segments  20  are placed alternated with respect to each other around the second rotation axis R 2 . 
     With reference to the examples illustrated in the enclosed figures, the external edge  17  of each shaped ring  12  comprises two said thrust sections  18  placed in diametrically opposite position with respect to the second rotation axis R. 
     Suitably, the substantially curved shape of the thrust section  18  is defined by a curvilinear line (e.g. rounded). In accordance with a different non-illustrated embodiment, the substantially curved shape of the thrust section  18  is defined by a dashed linear section. 
     Advantageously, with reference to the examples of  FIGS.  6  and  7   , the thrust section  18  of the external edge  17  has substantially semicircular shape with center spaced from the second rotation axis R 2 , according to a radial direction with respect to the second rotation axis R 2  itself. 
     Preferably, the thrust section  18  in substance defines a semi-circle having the diameter intercepted by the second rotation axis R 2 . In particular, the center of the semicircle is spaced from the second rotation axis R 2 , such that, one end of the diameter is closer to the rotation axis R 2  (at the proximal segment  20  of the thrust section  18 ) and the other end is further away from the second rotation axis R 2  (at the distal segment  19  of the thrust section  18 ). 
     Each sector  13  of the shaped ring  12  is extended, around the second rotation axis R 2  (substantially as an annular sector), between a first end  21 , which is positioned at the distal portion  19  of the thrust section  18  of the external edge  17 , and a second end  22 , which is positioned at the proximal segment  20  of the thrust section  18  of the external edge  17 . 
     In particular, the part of the external edge  17  defined by each sector  13  is extended between a first end  17 ′ intercepted by the first end  21  of the sector  13  (and which delimits, on such first end  21 , the distal segment  19 ) and a second end  17 ″ intercepted by the second end  22  of the sector  13  (and which delimits, on such second end  22 , the proximal segment  20 ). 
     As is visible in the examples illustrated in the enclosed figures, the proximal segment  20  of the thrust section  18  of each sector  13  is placed recessed (i.e. radially closer to the second rotation axis R 2 ) with respect to the first end  21  of the adjacent sector  13 , in particular in this manner defining a discontinuous progression of the external edge  17  of the shaped ring  12  at the proximal segment  20  of each thrust section  18 . 
     Advantageously, such configuration of the external edge  17  of the shaped rings  12  allows the latter, during their rotation, to make the material hop forward in order to facilitate the advancing of the material to convey downstream and prevent the undesired penetration thereof between the discs  4 . 
     Suitably, the proximal segment  20  of the thrust section  18  is placed between the distal segment  19  and the aforesaid connector concavity  25 . 
     In particular, the proximal segment  20  of the thrust section  18  of each sector  13  is placed recessed with respect to the first end  21  of the adjacent sector  13 . 
     Advantageously, the second end  22  of each sector  13  is connected, by means of the aforesaid removable locking elements  14 , to the first end  21  of the adjacent sector  13  according to the extension of the shaped ring  12  around the second rotation axis R 2 . 
     Suitably, the sectors  13  are connected to each other at the respective ends  21 ,  22  in a manner such to circumferentially close the through opening  16  of the shaped ring  12  around the second rotation axis R 2 . 
     Advantageously, according to the examples illustrated in the enclosed figures, each shaped ring  12  comprises two sectors  13 , each of which extended around the second rotation axis R 2  for a circular sector with angle of 180°. 
     In particular, each sector comprises, on the corresponding part of the external edge  17 , a corresponding thrust section  18  placed in diametrically opposite position with respect to the thrust section  18  of the other sector  13 . 
     Preferably, in the event in which the shaped ring  12  comprises two sectors  13 , the first end  21  and the second end  22  are placed in diametrically opposite position with respect to each other, with respect to the second rotation axis R 2 , with the first end  21  of one of the sectors  13  connected to the second end  22  of the other sector  13 . 
     Advantageously, each thrust segment  18  of the external section  17  of each shaped ring  12  is extended around the corresponding second rotation axis R 2  for an extension angle α of at least 120°, in particular in this manner allowing the exercising of its thrust action on the material for a significant arc of rotation of the shaped ring  12 , ensuring an effective action on the material to be advanced. Advantageously, with reference to the embodiments illustrated in  FIGS.  4 - 8   , the sectors  13  of each ring  12  have substantially the same shape and they are placed in rotated position with respect to each other, around an axis passing through the second rotation axis R 2  and orthogonal to the diameter of the shaped ring  12  passing through the ends  21 ,  22  of the sectors  13 . In this manner, in particular, it is possible to use a same mold for making all the sectors  13  of the shaped ring  12 . 
     Advantageously, in accordance with all the embodiments illustrated in the enclosed figures, the external edge  17  of each shaped ring  12  is provided with a concave segment  25  placed between the proximal segment  20  of the thrust section  18  of each sector  13  and the first end  21  of the adjacent sector  13 . More in detail, such concave segment  25  is defined by the recessed position of the proximal segment  20  of each sector  13  with respect to the first end  21  of the adjacent sector  13 . 
     Advantageously, the concave segment  25  of the shaped ring  12  is oriented in opposite manner with respect to the rotation sense R when the shaped ring  12  is actuated to rotate by the corresponding rotation shaft  3 , in particular such to prevent the material to be screened (e.g. that filiform or sheet-like) from clinging to such concave segment  25  and being driven towards the rotation shaft  3 . 
     Preferably, the second end  22  of each sector  13  comprises a projecting portion  23 , which is extended, away from the second rotation axis R 2 , radially protruding with respect to the proximal segment  20  of the thrust section  18  and carries the removable locking elements  14  engaged therewith. 
     Advantageously, the aforesaid projecting portion  23  is extended mainly in radial direction with respect to the second rotation axis R 2 . 
     In particular, the projecting portion  23  is radially extended up to one end thereof, on the external edge  17 , substantially flush with the first end  17 ′ of the part of the external edge  17  of the adjacent sector  13 . 
     Suitably, the projecting portion  23  defines a radial segment  24  of the external edge  17 , which is extended between the thrust section  18  and the second end  17 ″ of the part of the external edge  17  itself of the corresponding sector  13 . 
     Advantageously, the aforesaid radial segment  24  is connected to the proximal segment  20  of the thrust section  18  through the aforesaid concave segment  25  of the external edge  17  of the sector  13 . 
     In accordance with a first embodiment variant of the sector  13 , illustrated in the examples of  FIGS.  5 - 7   , the projecting portion  23  is made in a single body with the remaining part of the sector  13  itself. In accordance with a second embodiment variant, illustrated in the example of  FIG.  8   , the projecting portion  23  is fixed, e.g. via welding, to the remaining part of the sector  13  (and is for example obtained by means of a metal plate). 
     Advantageously, each sector  13  of the shaped ring  12  has substantially plate-like shape and is provided with two faces  13 ′, directed in opposite sense with respect to each other, preferably flat. 
     Suitably, the sector  13  has rigid shape and is for example made of metallic material, plastic material, PVC or another material. 
     Advantageously, in accordance with the embodiments illustrated in the enclosed figures, the removable locking elements  14  comprise screw attachment systems  26 , preferably each placed to connect the first end  21  of each sector  13  with the second end  22  of the adjacent sector  13 . 
     In particular, with reference to  FIGS.  5  and  6   , each screw attachment system  26  comprises a bolt having a screw  27  and a nut  28 . In particular, the screw  27  is provided with a head  27 ′ and with a threaded stem  27 ′ screwed to the nut  28 . Advantageously, with reference to the examples of  FIGS.  6  and  7   , the first end  21  of each sector  13  comprises a first radial wall  29  and the second end  22  of each sector  13  comprises a second radial wall  30  placed in abutment against the first radial wall  29  of the adjacent sector  13 . 
     For example, the first radial wall  29  is placed directly in abutment against the second radial wall  30 , or by means of the interposition of one or more suitable spacers. 
     In particular, the radial walls  29 ,  30  are placed to connect between the internal edge  15  and the external edge  17  of the corresponding sector  13 . 
     According to the examples illustrated in the enclosed figures, the radial walls  29 ,  30  of each sector  13  have rectilinear section with radial section with respect to the second rotation axis R 2 . Of course, such radial walls  29 ,  30  can have different section (e.g. curved) and different tilt (e.g. tangent to the internal edge  15 ), without departing from the protective scope of the present patent. 
     Preferably, the first end  21  of each sector  13  is provided with a first hole  31 , which is obtained starting from the first radial wall  29  and is provided with an enlarged seat  32  placed in the sector  13  internally spaced from the first radial wall  29 . In particular, the enlarged seat  32  (e preferably the internal first hole  31 ) is extended in a through manner between the two opposite faces  13 ′ of the sector  13 . 
     The aforesaid enlarged seat  32  houses the corresponding nut  28  of the screw attachment system  26 . 
     The radial portion  23  of the second end  22  of each sector  13  is provided with a second hole  33 , which is extended in a through manner between the second radial wall  30  and the external edge  17  (in particular the radial segment  24  of the latter) and is aligned with the first hole  31  of the first end  21  of the adjacent sector  13 . 
     The screw  27  of the screw attachment system  26  is inserted in the first hole  31  of the first end  21  of the sector  13  and in the second hole  33  of the second end  22  of the adjacent sector  13 , and is engaged via screwing with the nut  28  placed in the enlarged seat  32  of the first hole  31  so as to retain the aforesaid first end  21  joined with the second end  22 . 
     In particular, the threaded stem  27 ′ of the screw  27  is inserted in the second hole  33  of the second end  22  and in the first hole  31  of the first end  21 , being screwed with the nut  28  placed in the enlarged seat  32  of the first hole  31 , up to bringing the head  27 ′ of the screw  27  in abutment against the projecting portion  23 , so as to tighten the latter against the first radial wall  29  of the first end  21 . 
     In accordance with the embodiments illustrated in  FIGS.  4 - 8   , all the sectors  13  have, at their ends  21 ,  22 , the same type of coupling at the ends  22 ,  21  of the adjacent sector  13 , like that of the above-described example. 
     In accordance with a different embodiment not illustrated in the enclosed figures, the removable locking elements  14  can comprise a hinge, in particular with articulation axis parallel to the second rotation axis R 2  of the shaped ring  12 , placed as a rotatable connection of a pair of the first and second end  21 ,  22  of the sectors  13 , and for example a screw system (like that described above) on order to fix together the other pair of the first and second end  21 ,  22 . In this manner the two sectors  13  of the shaped ring  12  can be opened, by rotating them around the axis of the hinge in order to receive the rotation shaft  3  or to be removed from the latter, maintaining a pair of the first and second end  21 ,  22  (rotatably) connected to each other. 
     In accordance with a third embodiment variant of the sectors  13 , illustrated in the example of  FIGS.  9  and  10   , the first end  21  of one of the sectors  13  is provided with a coupling seat  34 , and the projecting portion  23  of the other (adjacent) sector  13  is provided with an engagement appendage  35  with shape corresponding to the coupling seat  34 . 
     Advantageously, the engagement seat  34  is provided with at least one lateral opening on at least one face  13 ′ of the sector  13  and, preferably, is extended in a through manner between the two opposite faces  13 ′ of the sector  13  itself. Suitably, the engagement seat  34  is provided with a front opening  34 ′ in particular made on the internal edge  15  and/or on the first radial wall  29  of the corresponding sector  13 . 
     The engagement appendage  35  of a sector  13  is coupled in the coupling seat  34  of the other sector  13  via shaping coupling with such coupling seat  34 . 
     Such arrangement allows facilitating the positioning of the sectors  13  in order to couple them to the rotation shaft  3 . 
     Advantageously, in accordance with an optional characteristic, the engagement appendage  35  of a sector  13  is inserted in the coupling seat  34 , with at least rotatable coupling (with axis parallel to the second rotation axis R 2 ) the first end  21  of a sector  13  and the projecting portion  23  of the other sector  13 . 
     Suitably, such at least rotatable coupling (and in particular rotation-translation coupling) is obtained by sliding the engagement appendage  35  within the coupling seat  34 , such that a sector  13  can rotate with respect to the next in one rotation sense or in the opposite sense, by moving the engagement appendage  35 , respectively, insertingly or extractingly with respect to the engagement seat  34 . 
     In particular, the coupling seat  34  and the engagement appendage  35  have at least partially curved shape. 
     The other ends  21 ,  22  of the sectors  13  are fixed to each other by means of the screw attachment system  26 , for example like that described above. 
     In detail, the projecting portion  23  of the sector  13  provided with the engagement seat  34  is fixed to the first end  21  of the other sector  13  (provided with the engagement appendage  35 ) by means of the aforesaid screw attachment system  26 . 
     In operation, in order to couple one sector  13  to the next, the engagement appendage  35  of a sector  13  are inserted in the engagement seat  34  of the other sector  13 , for example by means of the lateral opening or the front opening  34 ′ of the latter, in a manner such to correctly position the sectors  13 . Hence, the screw system  26  is applied at the other ends  21 ,  22  of the sectors  13  in order to fix them integrally with each other. 
     In accordance with a first embodiment of the present invention, illustrated in  FIG.  11   , the shaped rings  12  are directly fixed to the rotation shafts  3 , arranging for example the internal edge  15  of the shaped ring  12  with shape corresponding to that of the external surface of the rotation shaft  3 . 
     In accordance with a second embodiment of the present invention, illustrated in  FIG.  12   , the disc screen  1  comprises a plurality of sleeves  40  interposed between pairs of successive discs  4  (along the extension axis X of the corresponding rotation shaft  3 ) and mounted externally idle on the rotation shaft  3 . 
     In particular, each sleeve  40  comprises a tubular body  41  extended (according to the extension axis X of the corresponding rotation shaft  3 ) between two opposite end edges, placed at the corresponding lateral faces  4 A,  4 B of the two discs  4 , between which the sleeve  40  is interposed. 
     The disc screen  1  comprises preferably a plurality of spacer tubular bodies  42 , each of which externally mounted on the rotation shaft  3  and interposed and in abutment between the lateral faces  4 A,  4 B of two discs  4  in succession. In this manner, in particular, the discs  4  are placed in succession along the rotation shaft  3  alternated with the spacer tubular bodies  42  which, pressed between the contiguous discs  4 , rotate together with the latter. Suitably, the spacer tubular bodies  42  have length slightly greater than that of the sleeves  40  in order to allow the idle rotation of the latter. 
     In accordance with the aforesaid second embodiment, the shaped rings  12  are indirectly connected to the rotation shafts  3  through the interposition of sleeves  40 , mounted externally idle on the rotation shafts  3 . 
     In addition or as an alternative, the shaped rings  12  are mounted directly on the rotation shafts  3 , for example in a manner corresponding to that described above for the first embodiment lacking sleeves. 
     In this second embodiment, in particular the shaped rings  12  mounted on the sleeves  40 , following the rotation of the rotation shafts  3 , are brought to rotate via inertia (together with the sleeves  40 ) in the same rotation sense R as the rotation shafts  3 . The disc screen  1  for separating solid materials thus conceived therefore attains the pre-established objects. 
     The contents of the Italian patent application number 102020000014104, from which this application claims priority, are incorporated herein by reference.