Filtration device for plastic materials with a washing system

Abstract

The filtering device (10; 110) for molten plastic material comprises a hollow body (14) with an opening (16) and a cover (20), at least one inlet (22) and at least one outlet (24) for the filtered plastic material, two filters arranged side by side, a rotary cleaning device (40) with a scraping element (48) arranged between the filters and cooperating with the filtering surface (32A), and a discharge device (80; 180) configured to discharge impurities towards a discharge opening (82). The central arrangement of the discharge device (80; 180) ensures that the impurities move through the same path at the same flow rate and are discharged in a balanced manner on the discharge device (80; 180).

Description

Technical Field

[0001] The present patent relates to a system for filtering a molten plastic material, more specifically, a system for filtering a molten plastic material during plastic recycling processing.

[0002] More specifically, the present patent relates to a cleaning system for a filtering device for a molten plastic material, particularly a system for filtering a molten plastic material during plastic recycling processing.

Background Art

[0003] The problem of recycling / reusing plastic materials for the manufacture of new products is widely known and particularly emphasized.

[0004] The plastic material to be recycled is subjected to a melting process and at the same time filtered to remove impurities. Typically, the melted and filtered material is then appropriately processed to be manufactured into granular products. Such granular products are, for example, reintroduced into known plastic manufacturing processes.

[0005] A known type of device for filtering a molten plastic raw material comprises a cylindrical filtering chamber provided with one or more filter media. The filter media is provided between a supply inlet of the raw plastic material to be filtered and a discharge outlet located downstream of the filter media for discharging the filtered molten plastic material. A known type of filtering chamber comprises a first part with a closed bottom, preferably a cylindrical first part with a closed bottom, and a cover corresponding to the opening of the first part. When the cover is corresponding and fixed to the opening of the first part, the filtering chamber is closed and the filtering device is in a usable state. The cover is preferably fixed to the first part by screws and nuts that can be easily loosened during normal maintenance work and / or repairs.

[0006] According to known techniques, molten plastic material is introduced into a filtration chamber and, under pressure, is transported through a filter medium. The filter medium typically consists of a substantially planar (or cylindrical) filter with filtration through-holes configured to the appropriate size to ensure the desired filtration capacity.

[0007] During operation, impurities tend to gradually accumulate on the filter surface while raw materials are continuously supplied. Therefore, a cleaning system located inside the filtration chamber is provided to ensure continuous and reliable cleaning of the filter surface.

[0008] According to known technology, a cleaning system comprises at least one fixed or movable (preferably rotary) scraper. The scraper is provided with a scraping element that slides across the filter surface to remove impurities accumulated thereon. Simultaneously, the removed impurities are carried out of the filtration chamber. The impurities collected by the scraping element are preferably carried along a curved path toward the center of the filter, from there through a channel and out of the filtration chamber by a worm screw / screw feeder or on-off valve extending from the center of the filter.

[0009] According to the first known technique, the scraper and screw feeder are arranged to rotate together around a common axis, conveniently driven by an electric means, usually an electric motor.

[0010] A drawback associated with this type of filtration system is that the rotation speed of the screw feeder and the rotation speed of the scraper cannot be controlled independently, making it impossible to optimize and minimize waste.

[0011] On the other hand, according to the second known technique, the scraper is fixed and the filter media is arranged to rotate. Furthermore, an independent screw feeder is provided for each filter media.

[0012] A drawback associated with this second known technique is that there is only one scraper per filtration surface, and a screw feeder is required for each filtration surface. [Overview of the Initiative]

[0013] To overcome the aforementioned shortcomings, a new type of filtration system was designed and constructed for use with molten plastic materials.

[0014] The objective here is to provide a filtration device for plastic materials that can improve the cleanliness of the filter media compared to known types of devices.

[0015] In particular, a first aspect of the present invention relates to a filtration device for molten plastic materials, wherein the filtration device is A hollow body comprising an opening and a cover configured to correspond to the opening, defining a filtration chamber, At least one inlet for introducing molten plastic material into the filtration chamber, and at least one outlet for discharging molten filtration plastic material from the filtration chamber, A first filter and a second filter are arranged adjacent to each other in a filtration chamber between at least one inlet and at least one outlet, the first filter being configured to define a first surface configured to filter plastic material and recover impurities, and the second filter being configured to define a second surface configured to filter plastic material and recover impurities. A cleaning device positioned between the first filter and the second filter, A discharge device configured to discharge impurities recovered by a washing device toward a discharge port, comprising a discharge device positioned centrally relative to the washing device, Equipped with, The cleaning device comprises a rotating body, and the rotating body is A first side facing the first filter, having a first scraping element that cooperates with the first filtration surface of the first filter, A second side facing the second filter, the second side comprising a second scraping element cooperating with the second filtration surface of the second filter, Equipped with, The main unit is, Multiple first axisymmetric channels communicating with the first side, Multiple second axisymmetric channels communicating with the second side, Equipped with, Multiple first axisymmetric channels and multiple second axisymmetric channels are configured to receive impurities recovered by the first scraping element and the second scraping element, respectively, and to transport the impurities toward a discharge device. Multiple first axisymmetric channels and multiple second axisymmetric channels are arranged alternately on the main body and further arranged symmetrically with respect to the midplane of the main body. This ensures that impurities pass through the multiple first and second channels at the same flow rate and along the same path, and are discharged evenly onto the discharge device via outlets located on the midplane, thus reliably introducing impurities into the discharge device at perfectly equivalent positions. It is characterized by the following:

[0016] Further specific operating characteristics of the apparatus covered by the present invention are illustrated in the corresponding dependent claims. Characteristics of the new apparatus are described in more detail below with reference to the drawings attached herein, as non-limiting examples. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1 shows an axonometric view of a filtration device according to a preferred embodiment of the present invention. [Figure 2] Figure 2 shows a cross-sectional view of the filtration apparatus shown in Figure 1, along the horizontal plane. [Figure 2A] Figure 2A is a magnified view of the details in Figure 2. [Figure 3] Figure 3 shows a cross-sectional view of the filtration apparatus shown in Figure 1, along the vertical cross-section. [Figure 4]FIG. 4 shows a detailed view of the elements of FIG. 2A separated from other elements and enlarged. [Figure 5] FIG. 5 shows an isometric view of the elements shown in FIG. 4 as seen from a first side. [Figure 5A] FIG. 5A shows an exploded view of FIG. 5. [Figure 6] FIG. 6 shows a second isometric view of the elements shown in FIG. 4 as seen from a second side. [Figure 6A] FIG. 6A shows an exploded view of FIG. 6. [Figure 7A] FIG. 7A shows a plan view of the elements of FIG. 5A. [Figure 7B] FIG. 7B shows a plan view of the elements of FIG. 6A. [Figure 8] FIG. 8 shows the filtration device shown in FIG. 1 in a cross-sectional view along a vertical cross-section through an opening for introducing a material. [Figure 9] FIG. 9 shows a cross-sectional view of a filtration device according to a modified embodiment of the present invention.

Mode for Carrying Out the Invention

[0018] The filtration device according to a preferred embodiment of the present invention is indicated by reference numeral 10 in FIGS. 1 to 4.

[0019] The filtration device 10 according to the present invention is suitably used in the plastic recycling process.

[0020] The filtration device has a function of filtering / removing impurities present in the recycled plastic raw material so as to obtain a purity level corresponding to the mesh size of the filter medium used.

[0021] To perform this filtration operation, first, the recycled plastic raw material is heated to a molten state and then conveyed into the filtration device 10, more specifically, into the filtration chamber 12 of the filtration device 10 itself.

[0022] The filtration device 10 preferably comprises a hollow body 14 having an opening 16 to define the filtration chamber 12 and a cover 20 configured to correspond to the opening 16 (Figures 2 and 3).

[0023] In preferred embodiments illustrated herein, the hollow body 14 preferably has a cylindrical shape, and as a result, the cover 20 preferably has a circular cross-section.

[0024] The inlet passage 22 is designed to accommodate the hollow body 14 so that the plastic material to be filtered in a molten state can be introduced into the filtration chamber 12. The outlet passage 24 is also designed to accommodate the hollow body 14 so that the filtered plastic material can be discharged from the filtration chamber 12 in a molten state.

[0025] Preferably, the inlet passage 22 corresponds to a known type of conveyor (not shown), which is configured to transport the molten material to be filtered toward the inlet passage 22 under pressure.

[0026] The filtration means 30 is preferably positioned between the inlet passage 22 and the outlet passage 24 within the filtration chamber 12.

[0027] According to an aspect of the present invention, the filtration means 30 comprises a first filter 32 and a second filter 34 arranged side by side in the filtration chamber 12 between the inlet passage 22 and the outlet passage 24.

[0028] The first filter 32 and the second filter 34 preferably comprise two planar filtration discs arranged parallel to each other. In modified embodiments, they may have different shapes and can conform to the internal shape of the filtration chamber. The first filter 32 defines a first filtration surface 32A configured to recover impurities during the filtration process, and the second filter 34 defines a second filtration surface 34A configured to recover impurities during the filtration process (see Figure 2A). The two respective recovery channels 25, 26 for the filtered material preferably eventually merge at the level of the outflow channel 24 and are defined downstream of the two filters 32, 34.

[0029] Flow channels 25 and 26 are formed as symmetrical paths in order to obtain flows with the same flow rate and pressure.

[0030] The cleaning device 40, which will be described in more detail below, is preferably positioned between the first and second filters 32 and 34, and has the function of cleaning the first filtration surface 32A of the first filter 32 and the second filtration surface 34A of the second filter 34.

[0031] Preferably, a discharge device 80 is also provided, configured to transport impurities recovered by the washing device 40 toward the exhaust port 82 shown in Figure 3. Furthermore, it is preferable that the discharge device 80 is positioned centrally with respect to the washing device 40.

[0032] The discharge device 80 preferably includes an exhaust passage 85 that houses a rotating discharge element 84, preferably a worm screw or screw feeder, and is configured to receive impurities recovered in the filtration chamber 12 and move them along the longitudinal direction toward the discharge port 82.

[0033] In a modified embodiment shown in Figure 9 and described in more detail below, the discharge device 180 preferably comprises an exhaust channel 85 and an on-off valve 190. The on-off valve 190 is configured, when open, to move the impurities collected in the filtration chamber 12 toward the discharge port 82 under the action of pressure.

[0034] A suitable rotating means 28 is preferably an electric motor 28A that operates at a controlled speed, which controls the rotation of the rotating discharge element 84 during the operation of the filtration device 10.

[0035] According to an aspect of the present invention, the cleaning device 40 preferably comprises a circular rotating body 42, the rotating body 42 having a first side portion 44 facing the first filter 32 and a second side portion 46 facing the second filter 34. The first side portion 44 is provided with a first scraping element 48 that cooperates with the first filtration surface 32A of the first filter 32, and the second side portion 46 is provided with a second scraping element 50 that cooperates with the second filtration surface 34A of the second filter 34.

[0036] Therefore, the rotating body 42 can rotate about its own axis of rotation while not constrained in the axial direction.

[0037] The first scraping element 48 and / or the second scraping element 50 preferably comprises scraping blades firmly connected to the respective sides 44, 46 of the body 42. More preferably, they comprise flexible scraping blades configured to be positioned in contact with the first filtration surface 32A of the first filter 32 and the second filtration surface 34A of the second filter 34, respectively. The flexibility of the scraping blades 48, 50 is such that when the device 10 is closed by the cover 20, they are compressed by the two filters 32, 34, providing the scraping blades 48, 50 in contact with the filtration surfaces 32A, 34A with the pressure necessary to scrape and remove impurities from the surfaces 32A, 34A. This is also facilitated by the fact that the body 42 is not axially constrained and is therefore centrally positioned by the pressure from the scraping blades 48, 50. Preferably, the scraping blades 48 and 50 are arranged symmetrically on both sides 44 and 46 of the main body 42 with respect to the central plane M of the main body 42 itself. The advantage is that the scraping blades 48 and 50 deform substantially similarly on both sides 44 and 46 of the main body 42, applying the same pressure to the surfaces 32A and 34A of the filters 32 and 34, thereby improving the filtration quality of the filters 32 and 34 (similar cleanliness of the filters 32 and 34) and ensuring regular and even wear of the filters 32 and 34 and the scraping blades 48 and 50. The scraping blades 48 and 50 are fixed to each side 44 and 46 of the main body 42 by fixing screws.

[0038] In the illustrated preferred embodiment, three scraping blades 48, 50 are provided on each side 44, 46. However, in modified embodiments, the number of blades may differ.

[0039] The suitable rotating means 27 allows for the rotation of the rotating body 42 while the filtration device 10 is in operation.

[0040] The rotating means 27 preferably comprises an electric motor 27A and acts to rotate the drive shaft 27B at a more controlled speed. The end of the drive shaft 27B engages with a corresponding seat 44A formed in the center of the first side portion 44 of the body 42 of the cleaning device 40 (see Figures 5 and 5A for details).

[0041] The ends of the drive shaft 27B and the corresponding seat 44A in the main body 42 are preferably polygonal, and more preferably hexagonal.

[0042] According to another aspect of the present invention, the main body 42 comprises a plurality of first channels 60A, 60B, 60C communicating with a first side portion 44 and a plurality of second channels 70A, 70B, 70C communicating with a second side portion 46.

[0043] Multiple first channels 60A, 60B, and 60C are created within the main body 42 to receive impurities recovered by the first scraping element 48 and transport them towards the center toward the discharge device 80, more preferably toward the outer surface of the rotating discharge element 84, or toward the discharge device 180.

[0044] Similarly, multiple second channels 70A, 70B, and 70C are created within the main body 42 to receive impurities recovered by the second scraping element 50 and transport them towards the discharge device 80, more preferably to the outer surface of the rotating discharge element 84, or towards the discharge device 180.

[0045] Therefore, according to the illustrated preferred embodiment, there are three axisymmetric channels 60A, 60B, and 60C (Figures 5A and 7A) corresponding to the three corresponding scraping blades 48 of the first side portion 44, and three axisymmetric channels 70A, 70B, and 70C (Figures 6A and 7B) corresponding to the three corresponding scraping blades 50 of the second side portion 46. However, in modified embodiments, the number of channels may differ.

[0046] Preferably, the multiple first channels 60A, 60B, 60C and the multiple second channels 70A, 70B, 70C are defined within the main body 42 and arranged alternately so as to be symmetrical with respect to the intermediate plane M. As a result, impurities pass through the multiple first channels 60A, 60B, 60C and the multiple second channels 70A, 70B, 70C in the same path and are discharged in an equally even and balanced manner to the discharge device 80.

[0047] Each channel 60A, 60B, 60C, 70A, 70B, 70C preferably comprises a first portion 62 (see Figures 5A and 6A) defined at the level of and below the respective scraping blades 48, 50, and a second portion 64 that passes through the corresponding discharge port 66 and terminates in an annular discharge chamber into which a rotating discharge element 84 (screw feeder 84) is inserted. The first portion 62 preferably comprises a straight portion, while the second portion 64 is preferably curved to reach the discharge opening 66. Therefore, it is preferable that the channels 60A, 60B, 60C, 70A, 70B, 70C follow a non-radial pattern.

[0048] This pattern takes into account the preferred rotation direction of the cleaning device 40, indicated by R in the figure, thereby allowing impurities to flow easily toward the discharge port 66.

[0049] Furthermore, the discharge ports 66 of all the flow paths 60A, 60B, 60C, 70A, 70B, and 70C are the six openings 66 in the illustrated preferred embodiment, and are arranged at equal intervals around the discharge chamber 68. In addition, since they are all located on the intermediate plane M of the main body 42, it is ensured that material containing impurities is reliably introduced into the discharge device 80 at completely equal positions.

[0050] In this way, the advantages are that the flow rates through channels 60A, 60B, 60C and 70A, 70B, 70C are maintained at an equivalent and balanced level, and corresponding equivalent and balanced pressures can be obtained downstream of the two filters 32 and 34.

[0051] Furthermore, preferably, the cross-sectional area of ​​channels 60A, 60B, 60C and 70A, 70B, 70C increases in the direction toward the discharge device 80, facilitating outflow toward the discharge port 66.

[0052] Therefore, according to embodiments of the present invention, the cleaning device 40 can be configured symmetrically. This makes it possible to maintain a balanced equivalent flow rate of material removed from both filters 32 and 34 using only one discharge device 80 or 180.

[0053] According to the illustrated embodiment, the rotating body 42 comprises three modular parts 42A, 42B, and 42C, shown in Figures 5A and 6A, for facilitating assembly, disassembly, and cleaning, namely two central parts 42A, 42B, and an outer part 42C. The first linear portions 62 of a plurality of first channels 60A, 60B, 60C (Figure 7A) are preferably defined on the first side 44 of the outer part 42C, and the first linear portions 62 of a plurality of second channels 70A, 70B, 70C (Figure 7B) are preferably defined on the second side 46 of the outer part 42C.

[0054] Therefore, this solution allows for improved cleanliness and filtration quality of filters 32 and 34 by using an exhaust system equipped with a screw feeder 84 or an on / off valve 190.

[0055] In the illustrated embodiment, the rotating body 42 and the rotating discharge element 84 are further configured to rotate independently by their respective rotating means 27 and 28. An advantage is that, since their respective rotation directions and rotation speeds are independent of each other, they can be adjusted to ensure that impurities are removed as efficiently and reliably as possible.

[0056] Preferably, during operation, the rotating body 42 and the rotating discharge element 84 rotate in the same direction. Furthermore, it is preferable that the rotational speed of the rotating discharge element 84 is higher than the rotational speed of the discharge device 42 by a value that generates the tangential component of the material outflow velocity from the discharge port 66, and this outflow velocity matches the tangential velocity of the rotating discharge element 84. In this way, the material exiting the flow path 66 comes into contact with the rotating discharge element 84 with good hydrodynamic efficiency.

[0057] Furthermore, in an advantageous configuration, the inlet passage 22 is configured to include an inclined inlet section 22A (Figure 8) tangential to the inner diameter of the filtration chamber 12, such that the fluid rotates in a direction consistent with the rotation direction R of the cleaning device 40.

[0058] Figure 9 shows a modified embodiment of the filtration device 110 according to the present invention. Components corresponding to or equivalent to those of the first embodiment are identified by the same reference numerals.

[0059] In the embodiment, as described above, it is preferable that the discharge device 180 comprises an exhaust channel 85 and an on-off valve 190. Preferably, when the on-off valve 190 is in the open state, it is configured to move the impurities recovered in the filtration chamber 12 toward the discharge port 82 under the action of pressure. Therefore, the discharge device 180 is not equipped with a rotating discharge element (metering screw). Consequently, the corresponding rotating means is also omitted.

[0060] Therefore, according to the embodiment, the impurities recovered by the first and second scraping elements 48 and 50 are transported to the center toward the discharge device 180 through their respective passages 60A, 60B, 60C, 70A, 70B, and 70C. Here, under the action of pressure, the on-off valve 190 opens, and the impurities move along the exhaust passage 85 and reach the discharge port 82.

[0061] Therefore, it is clear from the above description that the set objective can be achieved by the apparatus according to the present invention.

[0062] Therefore, with reference to the above description and attached drawings, the following claims are made.

Claims

1. A filtration apparatus for molten plastic materials (10; 110), A hollow body (14) defining a filtration chamber (12) includes an opening (16) and a cover (20) configured to correspond to the opening (16), The filtration chamber (12) includes at least one inlet passage (22) for introducing the molten plastic material into the filtration chamber (12), and at least one outlet passage (24) for discharging the filtered molten plastic material from the filtration chamber (12), A first filter (32) and a second filter (34) are arranged adjacent to each other in the filtration chamber (12) between the at least one inlet passage (22) and the at least one outlet passage (24), wherein the first filter (32) is configured to define a first filtration surface (32A) configured to filter the plastic material and recover impurities, and the second filter (34) is configured to define a second filtration surface (34A) configured to filter the plastic material and recover impurities, A cleaning device (40) is positioned between the first filter (32) and the second filter (34), A discharge device (80; 180) configured to discharge the impurities recovered by the washing device (40) toward the discharge port (82), wherein the discharge device (80; 180) is positioned centrally with respect to the washing device (40), Equipped with, The cleaning device (40) comprises a rotatable body (42), and the body (42) is A first side portion (44) facing the first filter (32), the first side portion (44) having a first scraping element (48) that cooperates with the first filtration surface (32A) of the first filter (32), A second side portion (46) facing the second filter (34), the second side portion (46) comprising a second scraping element (50) cooperating with the second filtration surface (34A) of the second filter (34), Equipped with, The aforementioned main body (42) is A plurality of first axisymmetric channels (60A, 60B, 60C) communicating with the first side portion (44), A plurality of second axisymmetric channels (70A, 70B, 70C) communicating with the second side portion (46), Equipped with, The plurality of first axisymmetric channels (60A, 60B, 60C) and the plurality of second axisymmetric channels (70A, 70B, 70C) are configured to receive the impurities recovered by the first scraping element (48) and the second scraping element (50), respectively, and to transport the impurities toward the discharge device (80; 180). The plurality of first axisymmetric channels (60A, 60B, 60C) and the plurality of second axisymmetric channels (70A, 70B, 70C) are arranged alternately on the main body (42), and further arranged symmetrically with respect to the intermediate plane (M) of the main body (42). As a result, the impurities pass through the plurality of first axisymmetric channels (60A, 60B, 60C) and the plurality of second axisymmetric channels (70A, 70B, 70C) at the same flow rate and along the same path, and are discharged in a balanced manner onto the discharge device (80;180) via the discharge port (66) located on the intermediate plane (M). Therefore, impurities can be reliably introduced into the discharge device (80;180) at a completely equivalent position. A filtration device (10; 110) characterized by the above.

2. The cleaning device (40) further comprises a first rotating means (27) for rotating the main body (42), The filtration apparatus according to claim 1 (10; 110), characterized in that...

3. The discharge device (80) includes a discharge channel (85) that houses a rotating discharge element (84), and the discharge channel (85) is configured to receive and move the impurities recovered in the filtration chamber (12) along its longitudinal direction toward the discharge port (82). A filtration device (10) according to claim 1 or 2, characterized in that...

4. The system further comprises a second rotating means (28) for rotating the aforementioned rotating discharge element (84), The filtration apparatus (10) according to claim 3, characterized in that

5. The main body (42) and the rotating discharge element (84) of the cleaning device (40) rotate in the same direction. The filtration apparatus (10) according to claim 3, characterized in that

6. Of the plurality of first axisymmetric channels (60A, 60B, 60C) and / or the plurality of second axisymmetric channels (70A, 70B, 70C), one or more channels have a cross-sectional area that increases toward the discharge device (80; 180). A filtration apparatus according to claim 1 or 2, characterized by the above (10; 110).

7. The scraping blade is configured such that the first scraping element (48) and / or the second scraping element (50) are positioned in contact with the first filtration surface (32A) of the first filter (32) and / or the second filtration surface (34A) of the second filter (34). A filtration apparatus according to claim 1 or 2, characterized by the above (10; 110).

8. The scraping blade (48) maintains the main body (42) in an operating position centered between the first filter (32) and the second filter (34), and the main body (42) is not constrained in the axial direction. The filtration apparatus according to claim 7, characterized by (10; 110).

9. The discharge device (180) comprises a discharge channel (85) and an on-off valve (190), and the on-off valve (190) is configured to move the impurities recovered in the filtration chamber (12) toward the discharge port (82) under the action of pressure when it is in the open state. The filtration apparatus according to claim 1 (10; 110), characterized in that...

10. In the hollow body (14) closed by the cover (20), all the scraping elements (48, 50) are subjected to the same degree of compression. A filtration apparatus according to claim 1 or 2, characterized by the above (10; 110).

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