Filtration system for molten plastic material with improvement of impurity discharge

Abstract

The present disclosure describes a filtration system for plastic materials having a filtering element configured to be passed through by molten plastic material along a filtering direction, thereby filtering impurities from the molten plastic material, at least one scraper configured to rotate at a surface of the filtering element about a rotation axis and to collect the impurities accumulated on the surface of the filtering element, and a discharge system adapted to allow the outflow of the impurities collected by the scraper. The filtration system further comprises a conveying system configured to push the impurities that are on the scraper towards the discharge system.

Description

[0001] Title: Filtration system for molten plastic material with improvement of impurity discharge

[0002] DESCRIPTION

[0003] Field of application

[0004] The present invention relates to a filtration system for molten plastic material. The following description is written referring to this field of application with the only purpose to simplify its exposition.

[0005] Prior art

[0006] As it is known, it is very important to recycle a plastic material for its subsequent use. To this end, the plastic material to be recycled is subjected to a melting process and to a successive filtration process which has the purpose to remove impurities from it.

[0007] Generally, to carry out said filtration, a hollow cylindrical chamber is provided, in which there are a filtering element, interposed between a feeding inlet for the raw plastic material to be filtered, and an outlet, placed downstream of said filtering element for the outflow of the filtered molten plastic material. The molten material, coming from an extruder and suitably heated until becoming fluid, is then forced to pass through the above-mentioned filtering element (for example in the form of a perforated disc or small plate) which filters the impurities contained in the material, which impurities remain upstream of the perforated disc or small plate, whereas downstream thereof a clean material to be recycled is obtained.

[0008] Moreover, there is a scraper for collecting the impurities accumulated on the filtering element, which is put in rotation on the surface thereof. After some revolutions of rotation of the scraper, the impurities collected and accumulated therein will be expelled outside of the machine; to this end, there is a discharge duct for discharging the impurities which is different from the duct for the outflow of the filtered material.

[0009] Some known solutions provide the opening of a valve, from which the impurities flow out, passing through said discharge duct, which may extend, for example, along the rotation axis of the scraper. According to other solutions, a rotating screw for discharging the impurities is provided, which does not require opening specific valves.

[0010] One of the drawbacks of all these solutions is that the impurities (especially metal impurities) accumulated on the scraper are often not easy to be removed from it, and this may result in clogging when their accumulation becomes excessive, which is obviously to be prevented.

[0011] The technical problem of the present invention is to provide a filtration system having structural and functional features such as to overcome the limits and the drawbacks that currently affect the known solutions, in particular a filtration system that allows to efficiently discharge the impurities.

[0012] Summary

[0013] The solution idea underlying the present invention is to provide a filtration system provided with means able to facilitate conveying the impurities towards the discharge duct, in particular by pushing them towards said discharge duct. It is thus provided to mechanically push the impurities towards the discharge duct when it is opportune, for example after a given number of revolutions of the scraper and / or after a given time.

[0014] Based on said solution idea, the above-mentioned technical problem is solved by a filtration system for plastic materials, comprising a filtering element configured to be passed through by molten plastic material along a filtering direction, thereby filtering impurities from said molten plastic material, at least one scraper (having at least one chamber) configured to rotate at a surface (in particular, the inlet surface) of the filtering element about a rotation axis and to collect the impurities accumulated on said surface of said filtering element, and a discharge system adapted to allow the outflow of the impurities collected by the scraper, characterized in that it comprises a conveying system (or pushing system) configured to push, once activated, the impurities that are on the scraper towards the discharge system.

[0015] According to the present invention, the conveying system is configured to remove (in particular mechanically push) the impurities from the at least one chamber of the scraper starting from an end of said chamber (which in particular is an end of the scraper), said end being opposite to an end of said chamber that, at a certain point of the scraper rotation, is at the discharge system (i.e., the end closest to / facing the discharge system). Therefore, the conveying system is configured to mechanically push the impurities from the end of the scraper chamber that is the farthest end with respect to the discharge system, towards the opposite end (i.e., toward the discharge system).

[0016] More in particular, the invention comprises the following additional and optional features, taken individually or in combination if needed. Said additional and optional features are illustrated, for example, in the dependent claims.

[0017] According to an aspect of the present invention, the conveying system may be configured to perform a movement from a retracted position to an extended position, pushing the impurities that are present on the scraper towards the discharge system through said movement.

[0018] More in general, the conveying system may comprise elements capable of performing the above-mentioned movement, as it is indicated in the following examples.

[0019] According to an aspect of the present invention, the conveying system may comprise a sliding plunger (or rod or piston or mechanical plunger) configured to perform the above-mentioned movement.

[0020] According to an aspect of the present invention, the filtration system may comprise means configured to detect the position of the plunger.

[0021] According to an aspect of the present invention, the conveying system may comprise an actuator configured to move the plunger.

[0022] According to an aspect of the present invention, the actuator may comprise a pneumatic piston or a hydraulic piston (or a so-called pneumatic cylinder or hydraulic cylinder) .

[0023] According to an aspect of the present invention, the conveying system may comprise a worm screw. For example, the worm screw may be used as an actuator in place of the above-mentioned cylinder, or, less preferably, even directly in place of the plunger as a pushing element.

[0024] According to an aspect of the present invention, the filtration system may comprise a hollow body provided with a side wall, at least one inlet for the molten plastic material to be filtered, and at least one outlet for the outflow of the filtered molten plastic material.

[0025] According to an aspect of the present invention, the filtering element may be arranged in the hollow body between the inlet and the outlet and may be surrounded by the side wall.

[0026] According to an aspect of the present invention, the conveying system may operate at an opening formed in the hollow body.

[0027] According to an aspect of the present invention, the plunger may be partially housed in said opening even in the retracted position.

[0028] According to an aspect of the present invention, the filtration system may comprise a control unit configured to control the conveying system based on a position of the scraper (and thus configured to activate said conveying system when the scraper is in a given position, for example with one of its ends at the opening formed in the hollow body) .

[0029] According to an aspect of the present invention, the filtration system may comprise means configured to detect the position of the scraper. According to an aspect of the present invention, the control unit may be configured to control the rotation of the scraper and the activation of the conveying system based on a given rotation time of the scraper and / or based on a given number of revolutions of said scraper.

[0030] According to an aspect of the present invention, the discharge system may comprise an axial discharge duct which is substantially parallel to the rotation axis of the scraper and is in communication with an outlet opening (for example, substantially central) of said scraper.

[0031] According to an aspect of the present invention, the discharge system may comprise a rotating screw arranged in the discharge duct, said rotating screw being configured to discharge the impurities along the discharge duct through its rotary movement.

[0032] According to an aspect of the present invention, the filtration system may comprise first movement means configured to move the scraper and second movement means configured to move the rotating screw (for example, motorized means).

[0033] According to an aspect of the present invention, the first and the second movement means may be controlled independently of each other.

[0034] According to an aspect of the present invention, the speed of rotation of the rotating screw may be synchronized with the conveying system.

[0035] According to another aspect of the present invention, the discharge system may comprise at least one discharge through-opening formed on the side wall of the hollow body.

[0036] According to an aspect of the present invention, the discharge system may comprise at least one valve system arranged at the discharge through-opening and configured to adjust the outflow of the impurities from said discharge through-opening.

[0037] According to an aspect of the present invention, the hollow body may have a cylindrical shape extended along a symmetry axis.

[0038] According to an aspect of the present invention, the discharge through- opening may be arranged in a radial direction with respect to the symmetry axis of said cylindrical- shaped hollow body.

[0039] The features and advantages of the filtration system according to the invention will become apparent from the following description of an embodiment thereof, given by way of non-limiting example with reference to the accompanying drawings.

[0040] Brief description of the drawings

[0041] In the drawings:

[0042] - Figure 1 is a frontal view of a filtration system according to the present invention;

[0043] - Figure 2 is a perspective sectional view of the filtration system according to the present invention;

[0044] - Figures 3A and 3B show details of the filtration system according to the present invention;

[0045] - Figure 4 is a frontal view of the filtration system according to another embodiment of the present invention;

[0046] - Figure 5 is a sectioned detail of the filtration system according to the embodiment of Figure 4; and

[0047] - Figures 6A and 6B show details of the filtration system according to the embodiment of Figure 4.

[0048] Detailed description

[0049] With reference to those figures, a filtration system for plastic materials according to the present invention is globally and schematically indicated with the reference number 100. It should be noted that the figures represent schematic views and are not drawn to scale, but instead they are drawn so as to emphasize the important features of the invention. Furthermore, in the figures, the different elements are schematically depicted, and the shape thereof can change depending on the desired application. Furthermore, it should be noted that, in the figures, identical reference numerals refer to identical elements in terms of shape or function. Finally, arrangements described in relation to an embodiment illustrated in a figure can also be used for the other embodiments illustrated in the other figures.

[0050] Clearly, some technical details of the invention can be replaced with other technically equivalent details without departing from the scope of the claimed invention, as it is known by the person skilled in the art.

[0051] In the following description, relative terms such as “above”, “under”, “upwards”, “downwards”, “upper”, “lower” will be used referring to the illustrations of the solutions shown in the figures only to simplify the exposition thereof.

[0052] Furthermore, indications of particular geometries (circular, rectangular) or of the arrangement of the elements (parallel, orthogonal, contiguous), as well as the term “substantially” are always to be understood in connection with physical and not geometrically abstract elements, and they therefore always have to take into account the tolerances introduced by the passage from a pure mathematical / geometrical world to the real world.

[0053] It is also noted that, unless it is expressly stated to the contrary, process steps can also be inverted if necessary.

[0054] The filtration system 100 is thus adapted to filter molten plastic material for subsequently recycling it, with removal of the impurities from said material.

[0055] It is further noted that, in the context of the present invention, the expression “filtration system” is used to indicate any type of system intended for filtering molten plastic material, without being limited to a specific structure, in addition to what is claimed in the accompanying claims. It is also noted that, in the present description, the term “impurity” is also used as a synonym of “contaminant” and, more in general, of “dirt” contained in the molten plastic material and that is desired to be removed therefrom.

[0056] As illustrated in Figure 1, the filtration system 100 comprises first of all a hollow body (indicated with the reference number 10) containing within it the main filtering components. The hollow body 10 is formed by a bottom wall 11 (or bottom portion) and a side wall 12 (or side portion) extending from said bottom wall 11 , and is preferably extended along a symmetry axis herein indicated with the reference H-H.

[0057] The hollow body 10 may be supported by a suitable support frame F provided with wheels Fr, although the present invention is not limited to a specific configuration and the drawings are provided only by way of example and do not limit the scope of the present invention.

[0058] In one preferred embodiment, the hollow body 10 has a cylindrical shape (and the bottom wall 11 is thus at a base of the cylinder), so that the symmetry axis H-H corresponds to the symmetry axis of said cylinder, although the present invention is not limited to a specific shape and other configurations may be adopted.

[0059] In the hollow body 10 there is at least one inlet lOin for the molten plastic material to be filtered and at least one outlet lOout for the outflow of the filtered molten plastic material. In one embodiment, the inlet lOin and the outlet lOout are formed at the side wall 12 of the hollow body 10 and are offset from each other along the axis along which said side wall 12 extends (for example, along the symmetry axis H-H of the hollow body 10), so as to allow the molten plastic material to flow along the correct path. Obviously, the present invention is not, in any way, limited to a specific position of the inlet lOin of the outlet lOout relative to each other and / or relative to the side wall 12 and / or relative to the bottom wall 11. There is also a filtering element (reference 13, hereinafter simply referred to as “filter”) arranged in the hollow body 10 between the inlet lOin and the outlet lOout and configured to be passed through by the molten plastic material along a filtering direction (indicated in the figures with the arrow Dir), thereby filtering the impurities from said molten plastic material.

[0060] With reference to the configuration shown in the figures, in one embodiment, the symmetry axis H-H of the hollow body 10 is parallel to the filtering direction Dir.

[0061] In one embodiment, the filter 13 is in the form of a disc or small plate comprising a plurality of filtering holes, for example with a diameter from 50 gm to 500 gm, although the present invention is not limited to a specific dimensional value, said holes retaining the dirt of the molten plastic material to be filtered.

[0062] In one embodiment, the filter 13 may be associated with, so as to rest on, a perforated support, which has the mere function of supporting said filter 13.

[0063] The filter 13 is thus surrounded by the side wall 12, which, in one embodiment, extends along a direction coinciding with the filtering direction Dir.

[0064] In one embodiment, the hollow body 10 has an entrance (reference lOo) opposite the bottom wall 11 and associable with a closing cover. The entrance lOo thus allows to insert and remove the filter 13 from the hollow body 10.

[0065] The filtration system 100 also comprises at least one scraper (reference 15), configured to rotate at an inlet surface of the filter 13 about a rotation axis (reference R-R) and to collect, through said rotary movement, the impurities accumulated on said surface of the filter 13. As illustrated in the example of the figures, the rotation axis R-R coincides with the symmetry axis H-H of the hollow body 10. In one embodiment of the present invention, as it is better shown in Figure 2, the scraper 15 comprises a body 15’ having at least one collecting chamber 15r (also referred to as “collecting garage”) configured to store the impurities collected during the rotation and conveyed into it through a respective scraping portion (for example, having the shape of a blade matching the filter surface) of said scraper 15.

[0066] The scraper 15 may comprise only one collecting chamber 15r (singleblade scraper) or two collecting chambers 15r, for example opposite and symmetrical with respect to the rotation axis R-R, without any limitation of the scope of the present invention.

[0067] The collecting chamber 15r is in the form of a cavity formed in the body 15’ of the scraper 15, for example a cylindrical cavity, although the present invention is not limited to a specific configuration and / or shape. In general, the shape of the collecting chamber 15r is optimized to facilitate the accumulation, the flow and the evacuation of the collected material.

[0068] The scraper 15 extends along a longitudinal axis thereof L-L, which is substantially orthogonal to its rotation axis R-R, and the collecting chamber 15r is in the form of a cavity extended along said longitudinal axis L-L.

[0069] The collecting chamber 15r comprises at least one outlet opening (reference 15op) configured to allow the outflow of the impurities collected and accumulated therein, wherein said outlet may be along the rotation axis R-R, as in Figures from 1 to 3A-3B, or along the longitudinal axis L- L in the radial direction, as in Figures from 4 to 6A-6B (as will be detailed below) .

[0070] The scraper 15 also comprises a central region adapted to engage with a rotation shaft 15s to give the desired rotary movement to the scraper 15.

[0071] In order to allow the expulsion of the impurities collected by the scraper 15, the filtration system 100 comprises a discharge system (globally indicated with reference 20) adapted to allow the outflow (discharge) of said impurities, thereby preventing the undesired obstruction of the system.

[0072] In particular, the discharge system 20 is formed by at least one discharge duct (indicated with reference 20c) through which the impurities pass, and also by systems such as valves or a rotating screw, as will be detailed below.

[0073] The rotary movement of the scraper 15 thus allows the impurities to be collected and directed towards the discharge duct 20c. However, some impurities accumulated on the scraper 15 are not easy to be removed and said problem can be solved through the present invention, by mechanically acting on said impurities and pushing them towards the discharge duct 20c.

[0074] In particular, advantageously according to the present invention, there is a conveying system (herein also called “pushing system” and indicated with reference 30) configured to push the impurities that are on the scraper 15 and thereby conveying them towards the discharge system 20.

[0075] In particular, in one preferred embodiment of the present invention, the conveying system 30 is configured to perform a movement from a retracted position to an extended position (when it is activated), and vice versa (at the end of the work), pushing the impurities that are present on the scraper 15 towards the discharge system 20 through said movement from the retracted position to the extended position. More in general, the conveying system 30 comprises mechanical elements (for example, a plunger) capable of performing the above-mentioned movement, as indicated in the examples below, wherein in the extended position said elements are partially inserted in the collecting chamber 15r of the scraper 15.

[0076] In this way, suitably according to the present invention, there is a forced feeding of the impurities towards the discharge system 20, said conveying system 30 thus acting as an aid in discharging the impurities. In other words, the conveying system 30 is configured to push the material accumulated on the scraper 15 from its end (which is the most critical area) in the opposite direction towards the discharge system 20 following its actuation, wherein its actuation may correspond to the above- mentioned movement from the retracted position to the extended position.

[0077] In the example of the figures, the conveying system 30 operates at an opening (indicated with reference 30op) formed in the hollow body 10, in particular a radial opening (namely, an opening extending along the diameter of said hollow body 10). The conveying system 30 is thus at said radial opening 30op and operates in a direction that is parallel to the longitudinal axis L-L of the scraper 15, in particular in the direction indicated by the arrow Dir’ of figures 3A-3B and 6a-6B.

[0078] There is also a control unit (generically indicated with reference C) configured to control the conveying system 30 based on the position of the scraper 15 (in particular, based on its angular position with reference to the surface of the filtering element 13); in particular, the activation of the conveying system 30 is controlled when a longitudinal opening (indicated with reference 15op’) of the scraper 15 is at the above- mentioned opening 30op, for example after a given number of revolutions of said scraper 15. The above-mentioned longitudinal opening 15op’ of the scraper 15 may coincide with its discharge outlet opening 15op (as in Figures 4 to 6A-6B), although this is not necessary (as can be seen in the embodiment of Figures 1 to 3A-3B). In this way, the collecting chamber of the scraper 15r is put in communication with the conveying system 30 through the above-mentioned openings 30op and 15o, and the impurities may be pushed towards the discharge system 20.

[0079] In other words, the control unit C is configured to activate the conveying system 30 when the scraper 15 is in a given position, for example with one of its ends at the opening 30op formed in the hollow body 10 and with which its longitudinal opening 15op’ is in communication. The filtration system 100 thus comprises means (not shown in the figures) configured to detect the position of the scraper 15. For example, said means may comprise a suitable sensor (such as, for example, a position sensor), or may comprise a cam system, without any limitation of the scope of the present invention.

[0080] Furthermore, as mentioned above, the control unit C may be configured to control the rotation of the scraper 15 and the activation of the conveying system 30 based on a given rotation time of the scraper 15 or based on a given number of revolutions of said scraper 15, but this does not limit the scope of the present invention. In general, the conveying system 30 is activated when it is opportune, for example after a given time and / or after a given number of revolutions of the scraper 15, or based on any other opportune circumstance, that is, generally, when a given amount of impurities has accumulated on it.

[0081] It is noted that, in the scope of the present invention, the expression “control unit” is to be understood in a broad sense and may represent any electronic system programmed through suitable programs, without limitation to any specific hardware / software architecture, and any mechanical configuration, whether active or passive, may be provided, without limitation to any specific constructive embodiments.

[0082] In one preferred embodiment of the present invention, the conveying system 30 comprises a plunger (or piston or mechanical plunger, indicated with reference 30p) sliding along an axis that extends in a radial direction with reference to the hollow body 10 (namely, along the axis L- L) and along which it performs the above-mentioned movement from the retracted position to the extended position (through which it pushes the impurities towards the discharge system 20). The plunger 30p is thus the mechanical element of the conveying system 30 that, once pushed, performs the above-mentioned movement.

[0083] In one embodiment, there are means (for example, in communication with the control unit C) configured to detect the position of the plunger 30p.

[0084] As illustrated in the figures, the plunger 30p is moved by an actuator 30a (for example, having a cylindrical shape), said components being supported by an appropriate support structure 30f inside which the plunger 30p performs its sliding movement.

[0085] In other words, the conveying system 30 also comprises the actuator 30a, which is configured to move the plunger 30p. Only by way of example, the actuator 30a may be a pneumatic piston or a hydraulic piston (or, in other words, a pneumatic cylinder or a hydraulic cylinder) .

[0086] In general, the plunger 30p is connected to the actuator 30a (directly or indirectly) at one of its ends (in particular, the end opposite the opening 30op), and the activation of the latter causes, for example through a push, the movement of said plunger 30p from the retracted position to the extended position, as described above.

[0087] However, it is noted that the present invention is not, in any way, limited to the above-mentioned configuration. Indeed, other alternative embodiments are possible, and in general there is no limitation for the type of actuator used (wherein its purpose is to move the plunger 30p) or in general for the configuration causing the push of impurities towards discharge.

[0088] For example, the conveying system 30 may comprise a worm screw moved by a suitable gear system, as well as any suitable system capable of conveying the impurities towards the discharge system 20. For example, the worm screw may be used as an actuator in place of the above- mentioned cylinder, or, less preferably, even directly as a pushing element.

[0089] It is also noted that, in a non-limiting embodiment of the present invention, the end of the plunger 30p that is opposite the actuator 30a may be always housed in the opening 30op, even in the retracted position. Two embodiments of the discharge system 20 will now be described, although this does not exclude the possibility to adopt also other alternative solutions that are not described.

[0090] Embodiment with rotating screw

[0091] Referring to Figures 1 to 3A-3B, the discharge duct 20c of the discharge system 20 is an axial duct which is substantially parallel to the rotation axis R-R of the scraper 15 and is in communication with the outlet opening 15op of said scraper 15; in this case, the outlet opening 15op also extends in axial direction along said rotation axis R-R, in a substantially central position of the scraper 15.

[0092] Suitably, in this embodiment, the discharge system 20 comprises a rotating screw 25 arranged the axial discharge duct 20c, said rotating screw 25 being configured to discharge the impurities along the discharge duct 20c through its rotary movement. The presence of the rotating screw 25 is advantageous since in this way it is possible to maintain a constant pressure inside the filtering chamber.

[0093] The speed of rotation of the rotating screw 25 may be synchronized with the conveying system 30, in particular synchronized with the pushing speed of the actuator 30a (and thus with the speed given to the plunger 30p). In the case of presence of the worm screw, the speed of rotation of the rotating screw 25 may be synchronized with the speed of rotation of said worm screw.

[0094] In one preferred embodiment, the rotating screw 25 and the scraper 15 move independently of each other, and the filtration system 100 thus comprises first movement means configured to move the scraper 15, and second movement means configured to move the rotating screw 25, which are controlled independently of each other. The movement means may for example be motorized means.

[0095] In this embodiment, once the conveying system 30 has been activated, it pushes the impurities towards the rotating screw 25, which will then expel them outside. For example, the plunger 30p penetrates through the opening 30op and the opening 15op’ into the collecting chamber 15r of the scraper 15, thereby pushing the impurities towards the center.

[0096] It is also noted that, in this embodiment, the contamination is pushed to the center, on the rotation axis, to be then collected and transported outside of the rotating screw 25.

[0097] Depending on the constructive embodiment, the discharge may occur in one, two or more steps. For example, in the presence of the rotating screw 25 and with the scraper 15 provided with two collecting chambers 15r, the discharge divides into a first step, in which a first collecting chamber empties, then the scraper rotates 180° and the other collecting chamber empties.

[0098] Embodiment with radial valve

[0099] In one alternative embodiment of the present invention illustrated in Figures 4 to 6A-6B, the discharge system 20 comprises at least one discharge through-opening (indicated with reference 20op) formed on the side wall 12 of the hollow body 10, and thus not along the rotation axis R-R of the scraper 15. In other words, the discharge through-opening 20op is a through-opening formed directly in the hollow body 10 and thus extends in the same direction of longitudinal extension of the scraper 15, in particular along the diameter of the hollow body 10, and not in an axial direction.

[0100] In this way, the discharge through-opening 20op extends at least along the diameter (measured for example along the axis L-L) of said hollow body 10 It is noted that the term “diameter” means herein a direction that is orthogonal to the symmetry axis H-H of the hollow body 10.

[0101] As mentioned above, in one preferred embodiment, the hollow body 10 has a cylindrical shape and the discharge through-opening 20op is thus arranged in a radial direction with respect to the symmetry axis H-H of said cylindrical- shaped hollow body 10, said symmetry axis H-H being parallel to the rotation axis R-R of the scraper 15.

[0102] The discharge system 20 also comprises a valve 20v (or valve system) arranged at the discharge through-opening 20op and configured to adjust the outflow of the impurities from said discharge through-opening 20op. It is noted that the present invention is not, in any way, limited to the configuration of the valve 20v, which may vary depending on the needs and / or circumstances.

[0103] More in particular, the filtration system 100 is configured so that, during the rotation of the scraper 15, its outlet opening 15op can be in fluid communication with the discharge through-opening 20op for a given time period, so as to allow discharge of the impurities collected and contained in the collecting chambers 15r in the most suitable way. In this case, there may be a single collecting chamber (or two communicating collecting chambers) .

[0104] For example, the plunger 30p goes into the collecting chamber 15r of the scraper 15 through the opening 30op and in this case it extends beyond the center of the scraper (unlike what happened before), thereby pushing the impurities towards the radial opening 20op.

[0105] As seen above, the rotation of the scraper 15 can be controlled by the control unit C, which is suitably programmed to adjust and time the operation of said scraper 15 and its coupling with the discharge system 20, and it is also programmed to control the opening / closing of the valve 20v (in this embodiment, the discharge is discrete, whereas in the embodiment with rotating screw the discharge is continuous).

[0106] Moreover, the control unit C may be configured to control the rotation of the scraper 15 and to open the valve 20v according to preset operative settings decided by the user based on the needs and / or circumstances. For example, the control unit C may be programmed to open the valve 20v after a given rotation time of the scraper 15 or after a given number of revolutions (in general, based on a preset timing), or even based on a pressure measured inside the chamber.

[0107] It is also noted that, in this embodiment, the plunger 30p does not stop before reaching the center of the scraper 15, instead, it goes beyond it. Only by way of example, the plunger 30p goes beyond the central point (in which the rotation axis R-R passes through) by about 1 / 3 of the radius, but this does not limit the present invention since an even longer plunger could be used to go all over the entire length of the scraper 15, namely, the entire diameter of the hollow body 10. As seen above, depending on the constructive embodiment, the discharge may occur in one, two or more steps.

[0108] As mentioned, in this embodiment, the conveying system 30 may thus interact in two times so as to maintain the length of the plunger 30p reduced.

[0109] In any case, as mentioned above, other embodiments as an alternative to the two above-described embodiments are not excluded, for example with the discharge system comprising an axial valve.

[0110] In conclusion, summing up, the present invention thus allows to brilliantly overcome the technical problem, providing the above filtration system with forced discharge (for example, forced by means of a plunger) and solving all the drawbacks of the prior art.

[0111] Advantageously according to the present invention, thanks to the new configuration adopted, the operation of discharging the impurities accumulated on the filter surface is considerably facilitated. It is thus made easier for the impurities to travel towards the discharge compared to the known solutions, thereby enabling a much more efficient discharge, especially of the peripheral areas of the filter, namely of the areas with the greatest accumulation of contamination.

[0112] In this way, there is no creation of material accumulation, which would require the user to open the machine to clean the same, because the scraper is mechanically cleaned by the conveying system, without the need to open the machine.

[0113] Obviously, a person skilled in the art, in order to meet particular needs and specifications, may carry out several changes and modifications to the above-described filtration system, all included in the protection scope of the invention as defined by the following claims.

Claims

CLAIMS1. A filtration system (100) for plastic materials, comprising:- a filtering element (13) configured to be passed through by molten plastic material along a filtering direction (Dir), thereby filtering impurities from said molten plastic material;- at least one scraper (15) configured to rotate at a surface of the filtering element (13) about a rotation axis (R-R) and to collect the impurities accumulated on said surface of said filtering element (13); and- a discharge system (20) adapted to allow the outflow of the impurities collected by the scraper (15), characterized in that it comprises a conveying system (30) configured to push the impurities that are on the scraper (15) towards the discharge system (20).

2. The filtration system (100) according to claim 1, wherein the conveying system (30) is configured to perform a movement from a retracted position to an extended position, pushing the impurities that are present on the scraper (15) towards the discharge system (20) through said movement.

3. The filtration system (100) according to claim 1 or 2, wherein the conveying system (30) comprises a sliding plunger (30p).

4. The filtration system (100) according to claim 3, comprising means configured to detect a position of the plunger (30p).

5. The filtration system (100) according to claim 3 or 4, wherein the conveying system (30) comprises an actuator (30a) configured to move the plunger (30p).

6. The filtration system (100) according to claim 5, wherein said actuator (30a) comprises a pneumatic cylinder or a hydraulic cylinder.

7. The filtration system (100) according to claim 1, wherein the conveying system (30) comprises a worm screw.

8. The filtration system (100) according to any one of the preceding claims, comprising a hollow body (10) that includes a side wall (12), at least one inlet (lOin) for the molten plastic material to be filtered and at least one outlet (lOout) for the outflow of the filtered molten plastic material, wherein the filtering element (13) is arranged in the hollow body (10) between the inlet (lOin) and the outlet (lOout) and is surrounded by the side wall ( 12), and wherein the conveying system (30) operates at an opening (30op) formed in said hollow body (10).

9. The filtration system (100) according to any one of the preceding claims, comprising a control unit (C) configured to control the conveying system (30) based on a position of the scraper (15).

10. The filtration system (100) according to claim 9, comprising means configured to detect the position of the scraper (15).

11. The filtration system (100) according to claim 9 or 10, wherein the control unit (C) is configured to control the rotation of the scraper (15) and the activation of the conveying system (30) based on a given rotation time of the scraper (15) and / or based on a given number of revolutions of said scraper (15).

12. The filtration system (100) according to any one of the preceding claims, wherein the discharge system (20) comprises an axial discharge duct (20c) which is substantially parallel to the rotation axis (R-R) of the scraper (15) and is in communication with an outlet opening (15op) of said scraper (15).

13. The filtration system (100) according to claim 12, wherein the discharge system (20) comprises a rotating screw (25) arranged in the discharge duct (20c), said rotating screw (25) being configured to discharge the impurities along the discharge duct (20c) through a rotary movement thereof.

14. The filtration system (100) according to claim 13, comprising first movement means configured to move the scraper (15), and second movement means configured to move the rotating screw (25).

15. The filtration system (100) according to claim 1, comprising a hollow body (10) that includes a side wall (12), at least one inlet (lOin) for the molten plastic material to be filtered and at least one outlet (lOout) for the outflow of the filtered molten plastic material, wherein the discharge system (20) comprises at least one discharge through-opening (20op) formed on the side wall (12) of the hollow body (10), and wherein the discharge system (20) comprises at least one valve system (20v) arranged at the discharge through-opening (20op) and configured to adjust the outflow of the impurities from said discharge through-opening (20op).

16. The filtration system (100) according to claim 15, wherein the hollow body (10) has a cylindrical shape extended along a symmetry axis (H-H) and the discharge through-opening (20op) is arranged in a radial direction with respect to the symmetry axis (H-H) of said cylindricalshaped hollow body (10).

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