Search

EP-4631695-B1 - FILTRATION SYSTEM PROVIDED WITH AN IMPROVED DISCHARGE SYSTEM

EP4631695B1EP 4631695 B1EP4631695 B1EP 4631695B1EP-4631695-B1

Inventors

  • Canaia, Erica

Dates

Publication Date
20260513
Application Date
20240409

Claims (12)

  1. A filtration system (100) for plastic materials, comprising: - a hollow body (10) comprising a side wall (12), at least one inlet (10in) for a molten plastic material to be filtered and at least one outlet (10out) for the outflow of the filtered molten plastic material; - a filtering element (13) arranged in the hollow body (10) between the inlet (10in) and the outlet (10out) and surrounded by the side wall (12), said filtering element (13) being configured to be passed through by the molten plastic material along a filtering direction (Dir), thus 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), wherein the scraper (15) extends along a longitudinal axis (L-L) that is substantially orthogonal to the rotation axis (R-R); and - a discharge system (20) adapted to allow the outflow of the impurities collected by the scraper (15), wherein the discharge system (20) comprises at least one discharge through-opening (20op) formed on the side wall (12) of the hollow body (10), wherein the scraper (15) comprises a body (15') having at least one scraping portion (15p) and at least one collection chamber (15r) in the shape of a cavity in said body (15') and configured to store the impurities collected during the rotation and conveyed thereinto by the scraping portion (15p), and wherein the filtration system (100) is configured so that, during the rotation of the scraper (15), an outlet opening (15op) thereof is in direct fluid communication with the discharge opening (20op) only for a certain period of time to allow discharging the impurities collected and contained in the at least one collection chamber (15r), characterized in that said outlet opening (15op) of the scraper (15) is located at an end portion thereof which is furthest away from the rotation axis (R-R) and is configured to allow the outflow of the impurities along said longitudinal axis (L-L).
  2. The filtration system (100) according to claim 1, wherein the scraper (15) comprises at least one pair of collection chambers (15r) that are separated and arranged orthogonally with respect to the rotation axis (R-R) of said scraper (15).
  3. The filtration system (100) according to any one of the preceding claims, wherein the at least one collection chamber (15r) of the scraper (15) has a diameter, meant as maximum transversal dimension, not greater than 100 mm, preferably comprised between 50 mm and 70 mm, still more preferably 60 mm.
  4. The filtration system (100) according to any one of the preceding claims, wherein the discharge system (20) comprises at least one valve system (20v) arranged at the discharge opening (20op) and configured to adjust the outflow of the impurities from said discharge opening (20op).
  5. The filtration system (100) according to claim 4, wherein the valve system (20v) is configured so as to allow, when impurities are expelled through the discharge opening (20op), a discharge in a direction that is substantially coincident with that of the discharge opening (20op) and/or in a direction that is substantially orthogonal thereto.
  6. The filtration system (100) according to claim 4 or 5, wherein the valve system (20v) comprises a valve body (20v') and a movable element (20vm) inside said valve body (20v') and configured to open and close the discharge opening (20op).
  7. The filtration system (100) according to any one of claims 4 to 6, comprising a control unit (C) configured to control the rotation of the scraper (15) and to open the valve system (20v) based on a certain rotation time of the scraper (15) or a certain number of revolutions of said scraper (15).
  8. The filtration system (100) according to any one of the preceding claims, wherein the filtering element (13) comprises a disc comprising a plurality of filtering holes (13o), for instance with a diameter of 50 µm to 500 µm.
  9. The filtration system (100) according to any one of the preceding claims, wherein the hollow body (10) extends along a symmetry axis (H-H) and wherein said discharge opening (20op) extends at least along a diameter (Y-Y) of said hollow body (10), said diameter being along a direction orthogonal to said symmetry axis (H-H).
  10. The filtration system (100) according to claim 9, wherein the hollow body (10) is cylindrical-shaped and the discharge opening (20op) is arranged in a radial direction with respect to the symmetry axis (H-H) of said cylindrical-shaped hollow body (10).
  11. The filtration system (100) according to any one of the preceding claims, wherein the inlet (10in) and the outlet (10out) of the molten plastic material are formed on the side wall (12) of the hollow body (10).
  12. The filtration system (100) according to any one of the preceding claims, wherein the hollow body (10) comprises: - a bottom wall (11), wherein the side wall (12) extends from said bottom wall (11); and - a mouth (10o) opposite the bottom wall (11) and associable with a closing cover.

Description

Field of application The present invention relates to a filtration system for molten plastic material. The following description relates to this field of application with the only purpose of simplifying the exposition thereof. Prior art As it is known, it is very important to recycle a plastic material for the subsequent reuse thereof. To this end, the plastic material to be recycled is subjected to a melting process and a subsequent filtration step aimed at eliminating impurities therefrom. Generally, to perform said filtration, there is provided a hollow cylindrical chamber provided with a filtering element thereinside, which is interposed between a feeding inlet for the raw plastic material to be filtered and an outlet 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 it becomes fluid, is then forced to pass through the aforementioned filtering element (for instance in the shape of a disk or a perforated plate) that filters the impurities contained in the material, which thus stop upstream of the disc or perforated plate, while downstream thereof the clean material to be recycled is obtained. There is also a scraper for collecting the impurities accumulated on the filter element. Particularly, after a few rotation revolutions of the scraper, the collected impurities must be expelled out of the machine. To this end, it is envisaged to open an outlet duct for discharging the collected impurities which is different from the outlet duct of the filtered material. According to some known solutions, a scraper equipped with two collection chambers is used, both collection chambers being in communication with a central discharge channel arranged between said chambers; for instance, the scraper may be "V"-shaped in which the central discharge channel is at the vertex of the V. Particularly, while the scraper rotates, the impurities accumulate in the two collection chambers, until a valve opens from where they flow out passing through the aforementioned single central channel which extends along the rotation axis of the scraper. This solution is not free from drawbacks since, especially in large filtration systems, there is insufficient and inefficient discharge, in particular as regards the peripheral areas of the disc or plate. WO 2023/012656, CN 107791488, AT 410759, US 7,824,544, US 2014/0224749, CN 116277869, and US 11,103,812 disclose filtration systems comprising a scraper for removing the impurities from the filter and a discharge opening. The technical problem of the present invention is to provide a filtration system having structural and functional features such as to allow overcoming the limitations and drawbacks which still affect the known solutions, in particular a filtration system which allows an effective discharge process of the impurities accumulated on the filter. Summary The solution idea underlying the present invention is to provide a filtration system in which the discharge opening, provided with a suitable valve, is formed on the side surface of the hollow body inside which the filtering filter is arranged. Therefore, a discharge opening is provided, which is directly formed in the hollow body (in particular formed in the side wall thereof) and which is set in direct communication with the outlet opening of the scraper so that, when the latter is brought in communication with the discharge opening of the system during the expulsion of the impurities, said discharge opening develops in the same longitudinal development direction of the scraper. Particularly, in case of a cylindrical-shaped hollow body, the discharge opening is arranged in radial direction with respect to the symmetry axis of the cylinder. Moreover, a suitable scraper is provided which, in a preferred embodiment, is equipped with collection chambers having a substantially constant shape along the longitudinal axis thereof and each having an own discharge outlet along said longitudinal axis (in particular arranged orthogonally to the rotation axis). Based on this solution idea, according to the invention the above technical problem is solved by a filtration system for plastic materials comprising a hollow body comprising a side wall, at least one inlet for a molten plastic material to be filtered and at least one outlet for the outflow of the filtered molten plastic material, a filtering element arranged in the hollow body between the inlet and the outlet and surrounded by the side wall, said filtering element being configured to be passed through by the molten plastic material along a filtering direction, thus filtering impurities from said 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 said surface of said filtering element, and a discharge system adapted to allow the outflow of the impur