DESCRIPTION

Field of application of the invention

[001] The present invention concerns the technical field of the treatment and purification of liquids, in particular water, and the subject of the invention is a device for filtering a liquid.

State of the art

[002] As is known, devices capable of separating a liquid from the particles and/or solid materials dispersed within it are used in the liquid and water treatment sector.

[003] More specifically, these devices are configured to be installed inside a channel or duct in which the liquid to be filtered circulates and are constituted by a supporting frame suited to support a perforated filtering belt capable of allowing the liquid to flow through and the solid parts present therein to be retained.

[004] The filtering belts used in this type of devices make it possible to separate relatively medium to large-sized solids such as, for example, leaves, branches, particulate matter of various kinds, plastic, waste etc.

[005] During the operation of the device, only part of the filtering belt is immersed in the liquid, and driving means are provided to promote the rotation of the belt along a closed loop.

[006] In this way, it is possible to promote the constant replacement of the portion of the belt that is intended to come into contact with the liquid.

[007] In this way, the accumulation of solids on the outer surface of the belt is avoided; these solids are retained and accumulated as the liquid flows through the holes made in the meshes of the belt.

[008] The movement of the belt along a closed course (quite similar to the course followed by the outer surface of a conveyor belt) makes it possible to constantly renew the outer surface of the belt that comes into contact with the liquid to be filtered, in such a way that the filtering power of the device is maintained high during its operation.

[009] In addition to the above, the movement of the belt drives the solid materials resting on its outer surface (due to the fact that the same portion of the belt previously came into contact with the liquid) towards a remote area where a belt cleaning phase can be carried out before the belt is again immersed into the liquid. [0010] The filtering devices are equipped with scraper means designed to come into contact with the outer surface of the liquid in such a way as to promote the detachment of the solid materials that accumulate on it following a filtration cycle.

[0011] In general, the scraper means comprise a cylindrical brush fitted with semi-rigid bristles; this brush is set rotating around its own axis (by a motor-driven kinematic mechanism) so as to scrape the outer surface of the conveyor belt, promoting the detachment of the solid materials adhering to it.

[0012] The action of the scraper brush (or, more generally, of the scraper means) must, however, be well balanced, as a complete cleaning of the belt can be obtained only if the pressure exerted by the brush on its outer surface is included within a predetermined range of values.

[0013] Too light or, on the contrary, too heavy pressure exerted by the brush on the belt can actually affect the belt cleaning cycle, as it does not allow the removal of all the solid materials adhering to the outer surface of the belt itself.

[0014] In order to achieve the correct setting of the pressure exerted by the brush on the belt, many mechanisms have been developed which are associated with a filtering device and configured to adjust the distance of the belt from the brush, so as to indirectly vary the pressure exerted by the latter on the filtering meshes.

[0015] Document EP2859929 describes a filtering device configured as a belt and suitable for the mechanical purification of a liquid, which is provided with a continuous filtering belt made up of flat filtering elements that can be oriented with respect to each other and connected to each other, and with a flexible control means that is guided on a lower transmission device and on at least one upper transmission device. There is also a frame that carries the transmission devices and the filtering belt, wherein a rotatable scraping device is arranged in proximity to the upper transmission device, said scraping device being positioned on a revolving arm, resting on the frame where the scraping device is supported against its own weight force by means of a supporting device. This supporting device, together with the upper transmission device, is arranged on a common support that can be displaced with respect to the frame.

[0016] The main drawback related to the solution described above lies in that the process for making the filtering device is very complex.

[0017] The mechanism that adjusts the position of the scraper brush with respect to the end of the belt (also referred to as transmission in technical jargon), in fact, is made up of a large number of parts, the manufacture of which requires relatively complex processing cycles both on the individual components and on the supporting frame.

[0018] Moreover, this solution is rather expensive, and its implementation has an all but negligible impact on the total cost of the filtering device.

[0019] A further drawback of this solution lies in that the high complexity of the above mentioned solution, which required a high degree of precision during the assembly of the device, prolonging its production time.

[0020] Another, yet not the least drawback of the previously described filtering device lies in the increased maintenance required for the correct operation of the system that moves the scraper brush.

[0021] In fact, it is well known that the maintenance operations on a filtering device installed outdoors and placed in contact with a predetermined quantity of liquid are not easy to carry out and, in addition to long downtime, also require the presence of particularly experienced operators.

Documents US 3,999,649, US 1 ,875,442 and US 2016/0376108 describe devices for filtering liquids equipped with scraper elements for the filtering belt. The configuration of the scraper elements described in relation to these devices, however, does not allow the upper surface of the filtering belt to be effectively cleaned of the foreign matter adhering to it; moreover, even the solutions proposed in these documents are affected by the above mentioned drawbacks.

Presentation of the invention

[0022] The present invention intends to overcome the above-mentioned technical drawbacks by providing a particularly efficient and high-performance device for filtering liquids.

[0023] More specifically, the main object of the present invention is to provide a device for filtering a liquid that allows the filtering belt to be cleaned of solid particles in a particularly efficient manner.

[0024] A further object of the present invention is to provide a device for filtering a liquid that is relatively simple to manufacture, especially when compared with the devices currently present on the market.

[0025] Another object of the present invention is to provide a device for filtering a liquid that is particularly reliable and requires limited maintenance during its life cycle.

[0026] A further object of the present invention is to provide a device for filtering a liquid that comprises a limited number of components.

[0027] Another object of the present invention is to provide a device for filtering a liquid whose assembly and installation on site are particularly simple and do not require the presence of highly skilled personnel.

[0028] Again, another yet not the least object of the present invention is to provide a device for filtering a liquid that has significantly reduced production costs compared to the similar filtering devices currently present on the market.

[0029] These objects, together with others which are better clarified below, are achieved by a device for filtering a liquid of the type according to claim 1 .

[0030] Other objects that are better described below are achieved by a device for filtering a liquid according to the dependent claims.

Brief description of the drawings

[0031] The advantages and characteristics of the present invention will become clear from the following detailed description of some preferred but not limiting configurations of a device for filtering a liquid, referring in particular to the following drawings:

- Figure 1 shows a perspective view of a device for filtering a liquid according to the invention;

- Figure 2 shows a front view of the device of Figure 1 ;

- Figure 3A and Figure 3B respectively show a right side view and a left side view of the device of Figure 1 ;

- Figure 4 shows a sectional view of the device of Figure 1 ;

- Figure 5 shows an enlargement of a detail of Figure 4.

Detailed description of the invention

[0032] The present invention relates to a device for filtering a liquid. This device, here below indicated by the reference number 1, can be mainly used to separate the solid bodies or particles dispersed in a liquid or sewage.

[0033] More specifically, the device 1 that is the subject of the present invention is configured to be installed in proximity to an open duct or a channel in which the liquid to be filtered circulates.

[0034] As is better clarified later on in the present description, the device 1 must be inserted in the channel or duct through which the liquid to be filtered flows.

[0035] More specifically, the device 1 must be partially immersed in the liquid to be filtered, which must flow in the channel at a predetermined speed and/or flow rate, so as to completely hit the portion of the device 1 with which said liquid comes into contact. [0036] The liquid flows through the immersed part of the device 1 without being held back; while the liquid flows, the solids present therein are held back by the device itself, so that the liquid downstream of the device is filtered and free of dispersed solids.

[0037] The liquid downstream of the device 1 has therefore undergone a filtration process while the liquid upstream of said device 1 hasn’t; this filtration is carried out by the device 1 itself by means of the portion immersed in the liquid to promote its filtration. [0038] Figures 1 to 5 show only a device for filtering liquids, while said Figures show neither the liquid to be filtered nor the channel in which said liquid circulates (as the channel and the liquid to be filtered are known per se and do not need further explanations).

[0039] However, as schematically shown in Figure 3A, Figure 3B and Figure 4, the liquid flows in the channel along the direction indicated by the arrow W.

[0040] As better illustrated in Figures from 1 to 3B, the device 1 comprises a supporting frame 2 that extends along a longitudinal extension direction L.

[0041] More specifically, the supporting frame 2 can define a supporting structure inclined with respect to a vertical reference direction V at a predetermined angle of inclination a.

[0042] Said angle of inclination a can generally be included between 10° and 30° but it can also have different values with respect to the indicated range.

[0043] All the components of the device 1 are supported by the frame 2 and therefore they also follow the inclination of the latter with respect to the vertical reference direction V.

[0044] The inclination of the frame 2 with respect to the vertical V makes it possible to increase the filtering surface provided to the liquid; in other words, during its flow inside the channel, the entire volume of liquid is forced to pass through a filtering portion of the device whose overall extension, precisely because of the inclination, is greater than the extension it would find if the frame 2 were substantially vertical.

[0045] There is also a continuous filtering belt 3 anchored to the supporting frame 2 and having a portion 4 inserted (that is, immersed) in the liquid in such a way as to promote its filtration.

[0046] As is clearly illustrated in the sectional view of Figure 4, the belt 3 is constituted by a plurality of filtering elements 5 having predetermined dimensions and arranged side- by-side with respect to the longitudinal extension direction L.

[0047] These filtering elements 5 are arranged side by side so that they are substantially in contact with one another so as to seamlessly cover the entire extension of the belt 3; this arrangement makes it possible to cover the entire extension of the belt 3 with the filtering elements 5, so that the liquid does not find empty areas while flowing through the device 1 .

[0048] Analogously to the conveyor belts used in other industrial sectors, the filtering elements 5 are connected in such a way as to define a closed-loop course C mainly arranged along a longitudinal direction (substantially parallel to the longitudinal extension direction L of the frame 2) and provided with two respective ends.

[0049] More specifically, the closed course C is defined by a pair of substantially parallel and longitudinal straight sections that are joined at convenient curved ends, in particular said curved ends are constituted by respective semicircles whose centre is a point R'). One of said centres R' is visible in Figure 5.

[0050] These ends are called transmissions because they define the curved areas through which the filtering elements 5 must travel at the end of a straight and longitudinal section.

[0051] In Figure 4, the lower transmission is indicated by the reference number 6, while the upper transmission is indicated by the reference number 7.

[0052] As clearly visible in the Figures, the lower transmission 6 of the belt 3 is intended to be immersed in the liquid and substantially defines the lower end 8 of the frame 2.

[0053] The upper transmission 7 of the belt 3 projects from the liquid and substantially defines the upper end 9 of the frame 2.

[0054] Handling means 10 are also provided, which are suited to promote the controlled movement of the belt 3 along a handling direction that is substantially parallel to the longitudinal extension direction L of the frame 2.

[0055] The handling means 10 can comprise two chains 11 extending along the closed course C of the belt 3 to which the plurality of filtering elements 5 is connected.

[0056] These chains 11 are partially visible in Figure 4 and Figure 5 and are operatively associated with a pair of rollers and/or gear wheels 12 (also belonging to the handling means 10) arranged at the transmissions 6, 7 of the belt 3.

[0057] There is also a gearmotor 13 associated with one of the rollers 12 to promote its controlled rotation around its extension axis R (the extension axis R substantially extends at the centre R' of the semicircles defining the curved sections of the closed course C). [0058] In the configuration of the device illustrated in the Figures, the gearmotor 13 is operatively connected to the roller 12 located at the upper transmission 7 of the belt 3. [0059] The assembly of the gearmotor 13 at the upper transmission 7 makes it possible to maintain the gearmotor itself at a safety distance with respect to the liquid flowing in the channel.

[0060] The operation of the gearmotor 13 promotes the movement of the belt 3 along the closed-loop course C; in this way, it is possible to periodically change the filtering elements 5 that are in contact with the liquid and on which the solids present in the liquid accumulate.

[0061] The rotation of the belt 3 along the closed course C makes it possible to cyclically alternate the filtering elements 5 that are in contact with the liquid.

[0062] The rotation of the belt 3 along a closed loop C makes it possible to define two distinct portions of the belt: an active portion 4 represented by the area of the belt 3 that is first hit by the liquid flowing in the channel, and an inactive portion 14 constituted by the remaining part of the belt.

[0063] The inactive portion 14 does not contribute in any way to the filtration of the liquid and is represented by the area of the belt 3 that is above and below the active portion (that is, the entire extension of the belt except for the active portion 4).

[0064] During the movement of the belt along the closed course C, all the filtering elements, at different moments, contribute to the formation of the active portion 4 and the inactive portion 14.

[0065] Furthermore, during the rotation of the belt 3 along the closed course C, the filtering elements that define the active portion 4 advance towards the inactive portion 14, and vice versa.

[0066] Each filtering element 5 is provided with a plurality of through holes having a predetermined diameter; these holes are not visible in the Figures.

[0067] The liquid can flow through the respective filtering element 5 by passing through said holes; all the solids whose size exceeds that of the holes, instead, are deposited on the outer surface 15 of said elements so that they are held back by the belt 3 and removed from the liquid.

[0068] Also the filtering belt 3 is inclined with respect to the vertical reference direction V at the same inclination angle a as that of the frame 2; thanks to this inclination, it is possible to hold the solids back on the respective filtering element 5, preventing them from falling towards the bottom of the channel.

[0069] More specifically, the solids settle on the outer surface 15 of the filtering elements 5 that make up the belt 3.

[0070] The handling means 10 are suited to promote the rotation of the filtering belt 3 along the closed ring C in a clockwise rotation direction (indicated by the arrow positioned in proximity to the upper transmission 7 in Figure 5).

[0071] In this way, the solid material deposited on the outer surface 15 of the filtering elements 5 that, at that moment, make up the active portion 4 of the belt 3 is progressively moved upwards (that is, raised), until it reaches the upper transmission 7. [0072] The handling means 10 can be configured to make the belt 3 move either continuously or discretely (that is, substantially jerkily).

[0073] The device 1 furthermore comprises scraper means 16 suited to promote the removal of the solid material deposited on the outer surface 15 of the filtering elements 5 of the belt 3 following their interaction with the liquid to be filtered.

[0074] As better illustrated in Figure 4 and Figure 5, the scraper means 16 can be made up of a cylindrical brush arranged in proximity to the upper transmission 7 of the belt 3 and suited to come into contact with the outer surface 15 of the filtering elements 5.

[0075] Throughout the present description, the term brush and the expression scraper means are used as synonyms and indicated by the same reference number in the Figures; however, any other equivalent component suited to promote the removal (or detachment) of the solid material deposited on the outer surface of the filtering elements can be used instead of the brush to define the scraper means.

[0076] More specifically, the width of the brush 16 can be not shorter than the width of the belt 3, so that it interacts with the entire extension of the outer surface 15 of the filtering elements 5.

[0077] This brush 16 can be made using a roller of yielding or semi-rigid material or it can be provided with a plurality of radial bristles whose ends are intended to come into contact with the outer surface 15 of the filtering elements 5.

[0078] Conveniently, the device 1 can comprise at least one connection arm 17 suited to support the scraper means 16.

[0079] Moreover, the connection arm 17 is hinged to the frame 2 in an area above that in which the filtering belt 3 is anchored. [0080] In the configuration of the device that is illustrated in the Figures, there is a pair of connection arms 17, each of which is hinged to the frame 2 above the filtering belt 3. [0081] The connection arms 17 forming this pair have substantially the same shape in plan view, as can be clearly seen in Figure 3A and Figure 3B showing the right side view and the left side view of the device 1 that is the subject of the invention.

[0082] Each connection arm 17 can have a pair of ends: one end 18 can be facing the filtering belt 3 and thus be in a position near to the upper transmission 7, while the other end 19 is opposite the end 18 facing the filtering belt 3, in a position away from the upper transmission 7.

[0083] More specifically, as can be better seen in the Figures, one end 18 of the connection arm 17 is facing towards the upper transmission 7 of the filtering belt while the other end 19 of the arm is facing towards the portion of the belt 3 that defines the upper longitudinal straight section of the closed course C. In this context, the upper longitudinal straight section of the course C is represented by the rectilinear portion that is first hit by the motion of the liquid (the latter, as described above, circulates in the channel along the direction W). The upper longitudinal portion of the course is indicated by the letter J in Figure 4.

[0084] The arm 17 can be hinged to the frame 2 at a hinge point P located between these two ends 18, 19.

[0085] As better illustrated in Figure 4 and in Figure 5, the brush 16 that defines the scraper means can be anchored in proximity to the end 18 of the arm 17 facing towards the upper transmission 7 of the filtering belt 3.

[0086] More specifically, the brush 16 can be connected to both ends 18 of the pair of arms 17 facing towards the filtering belt 3; in this case, this pair of arms can define a fork within which the brush 16 is contained.

[0087] Each arm 17 of the pair can have a widened portion 20 at the end 18 facing towards the filtering belt 3; said widened portion 20 can be provided with a slit 21 suited to allow the insertion of the central shaft 22 on which the brush 16 is mounted.

[0088] Preferably, each connection arm 17 of the pair can be made up of two substantially straight semi-arms 23, 24 joined at a respective end 25, 26.

[0089] Each semi-arm 23, 24 can extend along respective extension directions X, X'; these extension directions are oriented in such a way that together they form a predetermined inclination angle p. [0090] This configuration of the connection arm 17 is clearly visible in Figures from 3A to 5.

[0091] More specifically, the inclination angle p defined by the extension directions X, X' of the semi-arms 23, 24 can be included between 120° and 160°, and preferably close to 130°.

[0092] Conveniently, the inclination angle can be selected in such a way as to maintain the end 18 of each arm 17 in a position close to the belt 3 and to promote substantially uniform contact of the scraper means 16 with the belt 3 itself while at the same time applying a pressure suited to allow the detachment of the solid material deposited on the outer surface 15 of the filtering elements 5.

[0093] Conveniently, in an alternative configuration of the invention not illustrated in the Figures, the connection arms 17 can be constituted by a single element having a curvilinear shape.

[0094] The semi-arms 23, 24 can furthermore comprise free ends suited to respectively define the ends 18, 19 of the connection arm 17.

[0095] The hinge point P can be located in the connection area of the two semi-arms 23, 24, that is, in proximity to their mutually joined ends 25.

[0096] Conveniently, an additional gearmotor 27 anchored to the frame 2 or to one of the connection arms 17 can be provided in proximity to the end 18 intended to support the brush 16.

[0097] This gearmotor 27 can be operatively connected to the central shaft 22 of the brush 16 so as to promote its controlled rotation around its extension axis S.

[0098] More specifically, the rotation direction of the brush 16 can be selected so that it is contrary (that is, opposite) to the rotation direction of the filtering belt 3.

[0099] As already described above, the belt 3 rotates clockwise, and therefore the gearmotor 27 is configured to promote the anticlockwise rotation of the brush 16 (indicated by the arrow located near the brush 16 in Figure 5).

[00100] Opposite rotation directions respectively associated with the belt 3 and the brush 16 make it possible to improve the interaction of the latter with the outer surface 15 of the filtering elements 5.

[00101] More specifically, the impact of the brush 16 (or of the elements that make it up) against the outer surface 15 of the filtering elements 5 occurs at a speed that is proportional to the difference between the rotation speeds associated with these components.

[00102] Thanks to this configuration, it is possible to promote the detachment of all the solids adhering to the outer surface 15 of the filtering elements 5 following their passage through the active portion 4 of the belt 3.

[00103] The device also comprises preloading means 28 associated with at least one connection arm 17.

[00104] The function of the preloading means 28 is to at least partially counteract the weight force exerted on the scraper means 16.

[00105] In this way it is possible to adjust the preload of the latter with respect to the outer surface 15 of the filtering elements 5 that make up the belt 3.

[00106] In the following description, the term preload refers to the force that can be transferred by the scraper means 16 to the outer surface 15 of the filtering elements 5 to promote the detachment of the solid material adhering to said surface.

[00107] In this context, therefore, it is possible to associate the term preload also with the pressure applied by the scraper means to the outer surface 15 of the filtering means 5 to transfer on them the force required to promote the detachment of the solid material adhering to said surface.

[00108] Therefore, by varying the preload it is possible to modify the interaction promoted by the scraper means 16 on the outer surface of the filtering elements 5.

[00109] By acting on the preload, in fact, it is possible to obtain a different action of the scraper means 16 on the belt 3, actually varying the ability of the brush 16 to remove the solids distributed on the outer surface 15 of the filtering elements 5.

[00110] According to a specific characteristic of the invention, the preloading means 28 comprise one or more counterweights 29.

[00111] As can be clearly seen in the device illustrated in Figure 1 and in Figure 2, a single counterweight 29 can be provided, anchored to both connection arms 17 at the end 19, opposite the end 18 to which the brush 16 is anchored.

[00112] The way in which the scraper means 16 and the counterweight (or counterweights) 29 are anchored to the connection arm (or connection arms) 17 is not accidental.

[00113] More specifically, the configuration of the connection arm 17 with two semi-arms 23, 24 extending along directions inclined by a predetermined angle makes it possible to anchor the scraper means 16 and the counterweight 29 as described below: the scraper means 16 are anchored at the end 19 of the connection arm 17 in such a way that they face towards the filtering elements 5 of the belt 3 that define the upper transmission 7; the counterweight 29 is anchored at the end 19 of the arm facing towards the filtering elements 5 of the belt 3 that define the upper longitudinal straight section J of the closed course C.

[00114] The special configuration of the connection arms 17 and the anchorage of the scraper means 16 and the counterweight (or counterweights) 29 at the ends 18, 19 of the latter allow the following characteristics to be defined: the scraper means 16 and the counterweight 29 are arranged on the opposite side with respect to the extension of the filtering belt 3, that is, said elements are arranged on the opposite side with respect to a longitudinal centreline plane TT passing through the centres R' of the curved sections of the closed course C (the plane TT is schematically shown in Figure 5); the height of the counterweight 29 above the ground exceeds the height of the scraper means 29 above the ground, and this is why the counterweight 29 is placed above the scraper means 16 (as better illustrated in Figure 5).

[00115] In this way, the position of the scraper means 16 and of the counterweight 29 described above makes it possible to provide a device 1 that benefits from some important advantages: the scraper means 16 interact with the belt 3 in proximity to the upper transmission 7, that is, at the upper surface 15 of the filtering elements 5 defining one of the curved sections of the course C. When the filtering elements 5 are distributed along a curved section, in fact, the scraper means 16 (or the brush) can easily interact with the entire extension of the outer surface 15 of each filtering element 5, in such a way as to maximize the action intended to detach the solids adhering thereto; the position of the counterweight (or counterweights) 29 above the filtering elements 5 that define the upper straight section J of the course C makes access to this component particularly easy for an operator who intends to carry out maintenance operations on the counterweight 29 (for example, to replace the counterweight or integrate new elements in it); the position of the counterweight (or counterweights) 29 above the scraper means 16 and above the straight section J of the closed course C makes it possible to keep the counterweight 29 clean over time as the latter is not hit by the solids that fall from the belt 3 or that are ejected downwards following their removal from the upper surface 15 of the filtering elements 5 due to the action of the scraper means 16.

[00116] The pair of connection arms 17 forms a unit assembly with the scraper means 16 and the counterweight 29.

[00117] This unit assembly is hinged to the frame 2 at two hinge points P (each associated with the respective arm 17) lying on the same hinge axis.

[00118] The hinge axis is indicated by the reference letter I in the Figures.

[00119] In this way, the unit assembly substantially behaves as a lever hinged at the hinge axis I: the brush 16 is anchored to one end 18 of this lever, while the counterweight 29 is anchored to the other end 19.

[00120] By varying the weight associated with the counterweight 29, it is possible to promote the rotation of the unit assembly (defining the lever) around the hinge axis I, thus obtaining the upward or downward movement of the brush 16, that is, its lifting or lowering movement.

[00121] The lowering of the brush 16 corresponds to its movement towards the belt 3 and the upper transmission 7.

[00122] On the contrary, the lifting of the brush 16 corresponds to its movement away from the belt 3 and the upper transmission 7.

[00123] The presence of a counterweight 29 defines a balanced position for the brush 16.

[00124] As a result of the balancing of the weights applied, respectively, by the counterweight 29 and the brush 16, the connection arm 17 (which in this configuration behaves like a lever) is in a stable balance condition.

[00125] Each value of the counterweight 29 thus corresponds to a specific balance position of the brush 16 and each balance position identifies a given distance (which remains substantially constant during the operation of the device 1 and the rotation of the belt 3) between the brush and the upper transmission 7.

[00126] According to an alternative configuration of the invention, not illustrated in the Figures, the counterweight 29 and the scraper means 16 can be anchored to a single connection arm 17 hinged to the frame 2 at a respective hinge point P. [00127] What has been described with reference to the solution comprising the pair of connection arms 17 also applies to a solution comprising a single arm 17.

[00128] Furthermore, according to the invention, considering both the single-arm and the multiple-arm solution, a plurality of counterweights 29 can be used, anchored not only to the end 19 of said arm/arms but also to the inner area along the extension directions X, X' of the same.

[00129] However, also in this configuration all the counterweights 29 are arranged above the filtering elements 5 that define the upper longitudinal straight section J of the closed course C (and, at the same time, above the scraper means 16).

[00130] Conveniently, each counterweight 29 can be made up of a plurality of mutually superimposed metal plates 30.

[00131] More specifically, each plate 30 can have a reference base weight and the counterweight 29 can be made by superimposing a plurality of plates 30, each of which has a base weight.

[00132] Alternatively, the counterweight 29 can be obtained by superimposing plates 30 having different weights.

[00133] These plates 30 are joined together by suitable connection means suited to define a counterweight 29 made using a plate pack.

[00134] This configuration of the counterweight 29 is visible in Figure 1 and Figure 5.

[00135] In practice, the total weight of the counterweight 29 varies according to the number of metal plates 30 that make up the pack.

[00136] Preferably, the connection means comprise one or more holes made in each metal plate 30 in predetermined positions.

[00137] More specifically, the position of the holes can be the same for all the plates 30, in such a way as to promote the alignment of said holes once the plates 30 have been superimposed on one another.

[00138] The alignment of the holes creates a (through) passage that extends seamlessly between the outer surfaces 31, 32 of the end plates 33, 34 delimiting the pack (that is, the top plate 33 and the bottom plate 34).

[00139] The connection means also comprise a plurality of bolts 35 suited to be inserted in the passages and respective locking nuts 36 suited to be screwed onto said bolts 35 in such a way as to compact the metal plates 30 together to form a corresponding pack having a predetermined weight. [00140] Figure 1 and Figure 5 show the bolts 35 inserted in the respective passages (the latter are not shown in said Figures) and the corresponding nuts 36 suited to lock the plates 30 in such a way as to define a counterweight 29 of the “pack” type.

[00141] As better illustrated in Figure 1 and in Figure 3A, the preloading means 28 can comprise one or more springs 37 whose ends 38, 39 are operatively connected to the frame 2 and to the end 18 of the connection arm 17.

[00142] As already described above, the connection arm 17 can be tilting (or oscillating) with respect to the frame 2 (around the hinge axis I), and the brush 16 can be raised when interacting with large solids adhering to the outer surface 15 of the filtering elements 5.

[00143] The springs 37 have the function to bring the brush 16 back (or return the brush) to its balance position (that is, to the balance position of the connection arm 17, as described above).

[00144] In other words, the springs 37 make it possible to apply a return force directed downwards to the end 18 of the connection arm 17, said force being suited to promote the lowering of the brush 16 (when it is subjected to impulsive upward movements following the interaction of the solids adhering to the filtering elements 5 of the belt 3) and its return to the balance position.

[00145] As better illustrated in Figure 5, the device can comprise a washing bar 40 located within the closed course C that delimits the belt 3.

[00146] The length of this washing bar 40 can be substantially equal to the width of the belt 3, said washing bar 40 being provided with a plurality of nozzles 41 (one of which is visible in Figure 5) suited to direct a jet of liquid A (generally water) towards the inner surface 42 of the filtering elements 5.

[00147] The jet of water A emitted (or sprayed) by the nozzles 37, directed from the inside of the belt 3 towards the outside, promotes the washing of the filtering elements 5 and the removal of any solids that the scraper means 16 were not able to remove from the outer surface 15 of the same during their previous operating cycle.

[00148] For this reason, the washing bar 40 is located downstream of the brush 16 (with respect to the rotation direction of the latter) in the section of the closed course C covered by the filtering elements 5 during their movement from the upper transmission 7 to the lower transmission 6.

[00149] The present invention can be carried out in other variants, all falling within the scope of the inventive features claimed and described herein; said technical features can be replaced by different technically equivalent elements and materials; the shapes and dimensions of the invention can be any as long as they are compatible with its use.

[00150] The reference numbers and signs included in the claims and in the description are only intended to make the text clearer to understand and must not be considered as elements limiting the technical interpretation of the objects or processes identified by them.