Modified plastic extrusion granulation screen changer

Abstract

The invention relates to the field of high polymer material processing equipment, and particularly discloses a modified plastic extrusion granulation screen exchanger. The screen changer comprises a shell, a screen changing plate and a driving device; a screening element is arranged on the screen changing plate and comprises a filter screen bracket detachably assembled in the mounting through hole and a filter screen fixed on the filter screen bracket; the filter screen is in a spherical crown curved surface shape protruding towards the discharging section, the height of a spherical crown is smaller than the thickness of the screen replacing plate, and the sphere center of the spherical crown is located on the central axis of the feeding channel. The problems of flow field interruption, dead zone deposition and local overheating caused by a multi-layer planar series filter screen are effectively eliminated, continuous, uniform and low-maintenance melt filtration is realized, the purity of plastic particles is improved, the quality of plastic products is enhanced, and the device is particularly suitable for high-requirement scenes such as temperature-sensitive modified plastics, reclaimed materials and chemical fiber spinning.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high polymer material processing equipment, in particular to a modified plastic extrusion granulation screen changer, which is suitable for plastic extrusion, chemical fiber spinning, regenerated material processing and other industrial production scenes that need to continuously filter impurities in molten materials. BACKGROUND

[0002] The screen changer is a filtering device for plastic, chemical fiber, rubber and other high polymer melt production lines, which mainly removes impurities in the melt during the extrusion process to improve product quality and protect downstream equipment. The current mainstream screen changer generally adopts a planar filter screen structure.

[0003] For example, the related art CN211105511U discloses a layered filter screen changer, which has filter screen plates A, B and C installed in the center through hole of the filter screen assembly block in a spaced manner. Although it reduces the single-layer filter screen pressure resistance through multi-layer grading filtration, the series chamber structure inevitably causes the continuity of the flow field to be interrupted, which leads to: (1) the flow velocity gradient between the multiple layers accumulates and expands, which increases the edge dead zone area compared with the single-layer filter screen; (2) the low-speed vortex field in the cavity causes the probability of impurity deposition to multiply; (3) the flow velocity difference induces local overheating, which causes the performance of heat-sensitive materials to deteriorate.

[0004] Therefore, in view of the above technical problems, it is necessary to provide a new solution. SUMMARY

[0005] The present application provides a new screen changer that can eliminate the flow field interruption problem caused by the series structure of the planar filter screen, reduce the melt flow dead zone to improve the filtration uniformity, suppress impurity deposition and local overheating, and maintain the continuous and stable flow field to protect the performance of heat-sensitive materials.

[0006] In order to achieve the above-mentioned purpose, the technical solutions provided by the present application are as follows: A modified plastic extrusion granulation screen changer, comprising a housing, a screen changer plate and a driving device; The housing has at least: a feed section having at least one feed channel, a discharge section having at least one discharge channel; The screen changer plate is at least partially arranged between the feed section and the discharge section, and the screen changer plate has a plurality of mounting through holes; the mounting through holes can be respectively positioned between the feed channel and the discharge channel, and a screening element for the plastic melt to flow through is respectively installed in the mounting through holes; The driving device is used to switch and position different mounting through holes between the feed channel and the discharge channel in a translational or rotational manner; The screening element comprises a filter screen support detachably assembled in the mounting through hole and a filter screen fixed to the filter screen support; the filter screen is in the shape of a spherical cap with a convex discharge section, the height of the spherical cap is less than the thickness of the screen changing plate, and the spherical center of the spherical cap is located on the central axis of the feed channel, so that a smooth converging flow field is formed when the molten material flows through the filter screen, the edge dead zone is reduced, and uniform impurity filtration is promoted.

[0007] The high-temperature melt output by the extruder enters the housing through the feed channel; the driving device drives the screen changing plate to displace, so that the mounting through hole with the filter screen is always coaxially connected with the feed channel-discharge channel. When the differential pressure of a filter screen increases or needs to be cleaned, the driving device switches the standby through hole into position, so that the "on-line screen changing" can be realized without stopping the production line. The filter screen is designed in the shape of a spherical cap with a convex discharge section, the height of the spherical cap is less than the thickness of the screen changing plate, the convex part is prevented from interfering with the housing, the spherical center is located on the central axis of the feed channel, and the flow channel is symmetrical. The melt enters along the tangential direction of the spherical cap surface, the flow lines are forced to converge to the center, and then uniformly diffuse along the back of the spherical cap, so that a smooth, continuous flow field without sudden expansion and sudden contraction is formed. The impurities are intercepted on the inside of the spherical cap; since the flow lines always flow along the wall, the dead zone area is compressed to the minimum, and the impurities will not be deposited in the corners. After stopping, the filter screen can be replaced or cleaned by only drawing out the filter screen support.

[0008] The present application is based on the foregoing scheme: 1. There is no sudden expansion section in the whole filtration area, the melt velocity gradient is continuous, the vortex is eliminated, and the "flow field interruption" caused by the planar series filter screen, i.e. the cavity, vortex and local low-speed dead zone, is effectively reduced. 2. The dead zone area is reduced, the impurity deposition probability is reduced synchronously, and the impurity deposition, decomposition, carbonization and subsequent pollution caused by the dead zone are solved. 3. The temperature rise amplitude is reduced, the performance retention rate of the heat-sensitive material is improved, the local over-temperature caused by the superimposed shear heat of the flow rate difference is solved, and the degradation and yellowing problem of the heat-sensitive modified plastic is solved.

[0009] Further, the filter screen support has an arc-shaped end surface matched with the curvature of the filter screen, and the inner edge of the arc-shaped end surface is provided with a rounded corner. The inner edge between the filter screens and the contact position of the filter screen is a stress concentration point, and the rounded corner is beneficial to dispersing stress, improving the firmness of the filter screen under the impact of high-temperature and high-pressure melt, and reducing the possibility of the filter screen being broken.

[0010] Further, the height of the spherical cap is 1 / 3-2 / 3 of the thickness of the screen changing plate.

[0011] Further, the installation cavity of the feeding section of the shell is provided with a mounting cavity on one side of the screen changing plate; the central axis of the mounting cavity coincides with the central axis of the feeding channel, the diameter of the mounting cavity is larger than the hole diameter of the feeding channel, and the feeding channel is communicated with the mounting cavity; a sealing compression ring is assembled in the mounting cavity; the inner hole wall surface of the sealing compression ring is a tapered surface or a curved surface with gradually decreasing inner diameter from the feeding section to the screen changing plate. The gradually decreasing inner diameter of the sealing compression ring makes the cross-sectional area of the flow channel gradually decrease, and the melt velocity increases, so that the jet flow of the branch flow channel is fully mixed, the filtering uniformity is improved, and the deposition of impurities and local overheating are inhibited. At the same time, under the impact of the molten fluid, the sealing compression ring is driven against the screen changing plate, which is beneficial to improve the sealing performance.

[0012] Further, the inner hole wall surface of the sealing compression ring and the curved surface of the filter screen have matching curvatures, so that a smooth and continuous flow channel surface is formed between the inner hole wall surface and the curved surface of the filter screen. The smooth transition curved surface is beneficial to guide the melt flow, improve the filtering uniformity, and reduce the dead zone.

[0013] Further, the feeding channel comprises a main flow channel and a plurality of branch flow channels, one end of the branch flow channel is communicated with the main flow channel, and the other end is communicated with the mounting cavity; the outlet of the branch flow channel in the mounting cavity is located in the flow channel area defined by the inner hole wall surface of the sealing compression ring.

[0014] Further, the plurality of branch flow channels are distributed equidistantly around the central axis of the main flow channel.

[0015] Further, the mounting cavity is provided with a mounting ring groove, and the end surface of the sealing compression ring is provided with an annular convex rib which is clamped into the mounting ring groove.

[0016] Further, a flow guide cone is fixedly arranged at the center of the filter screen, the apex of the flow guide cone faces the feeding section, and the height of the flow guide cone is less than the height of the spherical cap. Preferably, the height of the flow guide cone is 1 / 5-1 / 2 of the height of the spherical cap. The spherical filter screen has a tendency to converge the melt flow to the center, which may cause the flow velocity to be too fast at the ball top area, the impact of the filler carried by the high-speed fluid may shorten the service life of the filter screen, and may cause impurities to penetrate the filter screen. After the flow guide cone is arranged, the melt flow is guided to spread laterally, which is beneficial to prolong the service life of the filter screen and reduce the possibility of impurity penetration.

[0017] Further, the screen changing plate is rotatably supported in the shell, and the screen changing plate is driven to rotate to switch the filter element by means of a driving device.

[0018] Further, the screen changing plate is translatably assembled in the shell, and the screen changing plate is driven to translate to switch the filter element by means of a driving device.

[0019] The present application has the following beneficial effects: This invention, through a simple yet effective geometric innovation of a "spherical cap curved surface filter screen convex towards the discharge section," eliminates the three major problems of flow field interruption, dead zone deposition, and local overheating caused by traditional multi-layer planar series filters without adding extra components. This achieves continuous, uniform, and low-maintenance melt filtration, which can efficiently filter and improve the purity of plastic particles, thereby enhancing the performance and appearance quality of plastic products and meeting the stringent requirements of the high-end market for high-quality products. It is particularly suitable for demanding scenarios such as temperature-sensitive modified plastics, recycled materials, and chemical fiber spinning. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the modified plastic extrusion granulation screen changer in Embodiment 1 of the present invention; Figure 2 This is a cross-sectional view of the modified plastic extrusion granulator screen changer in Embodiment 1 of the present invention; Figure 3 for Figure 2 Enlarged view of section A; Figure 4 This is a schematic diagram of the modified plastic extrusion granulation screen changer in Embodiment 2 of the present invention; Figure 5 This is a cross-sectional view of the modified plastic extrusion granulator screen changer (shell not shown) in Embodiment 2 of the present invention. Figure 1 ; Figure 6 This is a cross-sectional view of the modified plastic extrusion granulator screen changer in Embodiment 2 of the present invention. Figure 2 ; Figure 7 for Figure 6 Enlarged view of section B; Figure 8 This is a cross-sectional view of the screen changing plate and screening element in Embodiment 2 of the present invention.

[0021] Explanation of reference numerals in the attached figures: 1. Shell; 11. Feeding section; 111. Feeding channel; 1111. Main channel; 1112. Branch channel; 112. Mounting cavity; 1121. Mounting ring groove; 12. Discharge section; 121. Discharge channel; 13. Shell cover; 14. Mounting frame; 2. Screen changing plate; 21. Mounting through hole; 22. Rack; 3. Drive device; 31. Drive motor; 32. Transmission gear; 4. Screening element; 41. Filter screen support; 411. Arc-shaped end face; 42. Filter screen; 421. Guide cone; 5. Sealing pressure ring; 51. Annular convex ridge. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solutions of this invention, the invention will be further described in detail below with reference to the accompanying drawings. Example 1

[0023] A modified plastic extrusion granulator screen changer, as described in the following reference. Figure 1 and Figure 2 The modified plastic extrusion granulator screen changer in this embodiment is a dual-station screen changer, which includes a housing 1 and a screen changing plate 2 that can be translatably assembled on the housing 1 along a direction perpendicular to the flow of molten material. The housing 1 is assembled from a feeding section 11 and a discharging section 12, wherein the feeding section 11 has a feeding channel 111 and the discharging section 12 has a discharging channel 121.

[0024] Reference Figure 1 and Figure 2 A mounting bracket 14 is provided on one side of the housing 1, and a drive device 3 is provided on the mounting bracket 14, the drive end of which is connected to the screen changing plate 2. The drive device 3 is used to provide push and pull power to drive the screen changing plate 2 to move. In this embodiment, the drive device 3 is a hydraulic drive mechanism (cylinder), but in other embodiments, a pneumatic drive mechanism or a linear motor or other drive method can also be used.

[0025] Reference Figure 1 , Figure 2 and Figure 3 In this embodiment, the screen changing plate 2 has two circular mounting holes 21. Each mounting hole 21 is provided with a screening element 4 for filtering impurities and unmelted materials in the molten material. The driving device 3 drives the screen changing plate 2 to move, and can alternately switch the two screening elements 4 between the feed channel 111 and the discharge channel 121 to filter the flowing molten material.

[0026] Reference Figure 1 , Figure 2 and Figure 3 The screening element 4 consists of a circular filter screen support 41 and a filter screen 42 fixed between the filter screens. The filter screen 42 has a pore size of 50-200μm and is made of 316L stainless steel. The mounting through hole 21 is a stepped hole, and the filter screen support 41 is installed at the step of the mounting through hole 21 and fixed by bolts. The filter screen 42 has a spherical crown-shaped curved surface convex towards the discharge section 12, and the height of the crown is less than the thickness of the screen changing plate 2. The center of the crown is located on the central axis of the feed channel 111, so that the molten material forms a smooth and converging flow field when flowing through the filter screen 42, reducing edge dead zones and promoting uniform filtration of impurities. The height of the crown is preferably 1 / 3-2 / 3 of the thickness of the screen changing plate 2, and in this embodiment, it is 1 / 2 of the thickness of the screen changing plate 2.

[0027] Reference Figure 1 , Figure 2 and Figure 3The end face of the filter screen support 41 facing the feed section 11 is an arc-shaped end face 411 that matches the curvature of the filter screen 42, and its inner edge is rounded. On the one hand, this allows the molten material to flow smoothly through the channel, and on the other hand, the rounded inner edge helps to disperse the pressure on the filter screen 42, reducing the possibility of the filter screen 42 being damaged due to excessive stress at the contact point with the inner edge of the filter screen support 41 caused by the impact of the material.

[0028] Reference Figure 1 , Figure 2 and Figure 3 The axes of the feed channel 111 and the discharge channel 121 coincide with the central axis of the filter screen 42 located at the working position. The filter screen 42 protrudes towards the discharge section 12, with its center of gravity biased towards the feed section 11. The discharge section 12 has a gradually narrowing flared opening towards the filter screen 42; the feed channel 111 includes a main channel 1111 and branch channels 1112 communicating with the main channel 1111. The number of branch channels 1112 is 4-8, and the diameter of the branch channels 1112 is 1 / 4-1 / 3 of the main channel 1111; in this embodiment, the number of branch channels 1112 is 6, and the diameter of the branch channels 1112 is 1 / 3 of the main channel 1111. An installation cavity 112 is opened on the end face of the feed section 11 of the housing 1 facing the filter screen. The installation cavity 112 is coaxial with the main channel 1111 and its diameter is larger than that of the main channel 1111. The branch channels 1112 are arranged at equal intervals around the axis of the main channel 1111, and their ends are all connected to the mounting cavity 112.

[0029] Reference Figure 1 . Figure 2 and Figure 3 A sealing ring 5 is coaxially mounted inside the mounting cavity 112. The inner wall of the sealing ring 5 is a conical surface with a gradually decreasing inner diameter from the feed section 11 towards the screen changing plate 2, and the inner diameter of the small diameter end 1 of its inner wall is equal to the outer diameter of the filter screen 42. The outlet of the branch channel 1112 in the mounting cavity 112 is located within the flow channel area defined by the inner wall of the sealing ring 5. In this way, the molten material can be guided by the inner wall of the sealing ring 5 to flow towards the filter screen 42, reducing dead corners at the periphery of the filter screen 42. The outer circumference of the sealing ring 5 is set in a stepped shape, and the side wall of the mounting cavity 112 is adapted to the shape of the sealing ring 5, so that the sealing ring 5 has good installation stability. At the same time, the end face of the sealing ring 5 facing away from the screen changing plate 2 is coaxially provided with an annular protrusion 51, and the mounting cavity 112 has a mounting ring groove 1121 for the annular protrusion 51 to be engaged. The inner diameter of the annular ridge 51 is equal to the inner diameter of the large-diameter section of the inner wall of the sealing ring 5. During the operation of the screen changer, the molten material acts on the inner wall of the sealing ring 5, causing the sealing ring 5 to tend to move towards the screen changing plate 2, which helps to increase the sealing effect between the sealing ring 5 and the screen changing plate 2 and reduce the possibility of leakage.

[0030] The working principle of this embodiment: The molten material enters the shell 1 through the main flow channel 1111, flows into the mounting cavity 112 through the branch channels 1112, and then flows smoothly to the filter screen 42 under the guidance of the inner wall of the sealing ring 5. The filter screen 42 is a spherical crown-shaped surface convex towards the discharge section 12, with the center of the sphere located on the central axis of the feed channel 111. This geometric configuration forms a flow channel profile that is "deep in the center and shallow at the edges". When the melt impacts the center of the filter screen from the feed channel 111, the normal component of the curved surface guides the melt to diffuse radially, and the tangential velocity decays smoothly, avoiding abrupt changes in the 90° direction. Moreover, the positioning of the sphere center ensures the axisymmetric distribution of the flow field, effectively reducing local dead zones caused by flow deviation. At the same time, the impact of the melt causes the sealing ring 5 to tend to move towards the screen changing plate 2, which is beneficial for sealing and reducing leakage. Example 2

[0031] A modified plastic extrusion granulator screen changer, as described in the following reference. Figure 4 and Figure 5 The difference between this embodiment and embodiment 1 is that, compared with the translational replacement of the screening element 4 in embodiment 1, the screen changing plate 2 in this embodiment rotates and switches the screening element 4 to different positions between the feed channel 111 and the discharge channel 121, which can achieve continuous switching; other structures are basically the same as in embodiment 1.

[0032] Specifically, refer to Figure 4 , Figure 5 and Figure 6 The screen changing plate 2 is disc-shaped and rotatably mounted between the feed section 11 and the discharge section 12 of the housing 1 via a rotating shaft. The central axis of the screen changing plate 2 is parallel to the central axis of the discharge channel 121. The screen changing plate 2 has an annular rack 22 around its periphery, and the housing 1 is equipped with a drive device 3. The drive device 3 includes a transmission gear 32 that meshes with the rack 22 and a drive motor 31 for driving the transmission gear 32 to rotate.

[0033] Reference Figure 4 , Figure 5 and Figure 6 The screen changing plate 2 has several mounting through holes 21 evenly spaced around its central axis, and a screening element 4 is installed at each mounting through hole 21. In this embodiment, a total of 5 screening elements 4 are installed on the screen changing plate 2, and the screen changing plate 2 can rotate to switch the screening elements 4.

[0034] Reference Figure 4 , Figure 5 and Figure 6 The top of the housing 1 is provided with a cover 13 to accommodate the portion of the screen changing plate 2 protruding from the top of the housing 1. Cleaning methods known in the art, such as high-pressure backflushing and ultrasonic cleaning, can be installed inside the cover 13 to clean the screening element 4.

[0035] Reference Figure 6 and Figure 7In order to further improve the filtration effect and reduce dead zones, the inner wall of the sealing ring 5 in this embodiment is a curved surface with a gradually decreasing inner diameter. The inner wall of the sealing ring 5 and the curved surface of the filter screen 42 have matching curvatures, so that a smooth and continuous flow channel surface is formed between the inner wall and the curved surface of the filter screen 42.

[0036] Reference Figure 8 A guide cone 421 is fixedly installed at the center of the filter screen 42, with its apex facing the feed section 11. The height of the guide cone 421 is less than the height of the spherical cap. The guide cone 421 is made of tungsten carbide, with a cone angle of 60°-90° and a vertex curvature radius ≤1mm to reduce flow resistance. The height of the guide cone 421 can be set to 1 / 5-1 / 2 of the height of the spherical cap; in this embodiment, it is approximately 1 / 5 of the height of the spherical cap. The spherical filter screen 42 tends to converge the melt flow towards the center, which may cause the flow velocity in the apex region to be too high. The impact of the packing material carried by the high-speed fluid will shorten the service life of the filter screen 42 and may cause impurities to penetrate the filter screen 42. After setting the guide cone 421, the melt flow is guided to diffuse laterally, which is beneficial to extending the service life of the filter screen 42 and reducing the possibility of impurity penetration.

[0037] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of this application.

Claims

1. A modified plastic extrusion granulation screen changer, comprising a housing (1), a screen changing plate (2), and a driving device (3); The housing (1) has at least: The feeding section (11) has at least one feeding channel (111). The discharge section (12) has at least one discharge channel (121); The screen changing plate (2) is at least partially arranged between the feeding section (11) and the discharge section (12), and the screen changing plate (2) has a plurality of mounting through holes (21); the mounting through holes (21) can be positioned between the feeding channel (111) and the discharge channel (121), and a screening element (4) for the plastic melt to flow through is installed in each mounting through hole (21); The driving device (3) is used to switch the different mounting through holes (21) between the feeding channel (111) and the discharging channel (121) by means of translation or rotation of the screen changing plate (2), characterized in that: The screening element (4) includes a filter screen support (41) detachably mounted on the mounting through hole (21) and a filter screen (42) fixed to the filter screen support (41); the filter screen (42) is a spherical crown convex to the discharge section (12), and the height of the spherical crown is less than the thickness of the screen changing plate (2), and the center of the spherical crown is located on the central axis of the feed channel (111).

2. The modified plastic extrusion granulator screen changer according to claim 1, characterized in that: The filter support (41) has an arc-shaped end face (411) that matches the curvature of the filter screen (42), and the inner edge of the arc-shaped end face (411) is rounded.

3. The modified plastic extrusion granulator screen changer according to claim 1 or 2, characterized in that: The feeding section (11) of the housing (1) has an installation cavity (112) on the side facing the screen changing plate (2); the central axis of the installation cavity (112) coincides with the central axis of the feeding channel (111), the diameter of the installation cavity (112) is larger than the aperture of the feeding channel (111), and the feeding channel (111) is connected to the installation cavity (112); a sealing pressure ring (5) is assembled in the installation cavity (112); the inner wall of the sealing pressure ring (5) is a conical or curved surface with the inner diameter gradually decreasing from the feeding section (11) towards the screen changing plate (2).

4. The modified plastic extrusion granulator screen changer according to claim 3, characterized in that: The inner wall of the sealing ring (5) has a matching curvature with the curved surface of the filter screen (42), so that a smooth and continuous flow channel surface is formed between the inner wall and the curved surface of the filter screen (42).

5. The modified plastic extrusion granulator screen changer according to claim 3, characterized in that: The feed channel (111) includes a main channel (1111) and several branch channels (1112). One end of the branch channel (1112) is connected to the main channel (1111) and the other end is connected to the mounting cavity (112). The outlet of the branch channel (1112) is located in the flow channel area defined by the inner wall of the sealing ring (5).

6. The modified plastic extrusion granulator screen changer according to claim 5, characterized in that: Several tributary channels (1112) are distributed circumferentially at equal intervals around the central axis of the main channel (1111).

7. The modified plastic extrusion granulator screen changer according to claim 6, characterized in that: The mounting cavity (112) has a mounting ring groove (1121), and the end face of the sealing pressure ring (5) is provided with an annular protrusion (51) that fits into the mounting ring groove (1121).

8. The modified plastic extrusion granulator screen changer according to claim 1 or 2, characterized in that: A guide cone (421) is fixedly installed at the center of the filter screen (42), the apex of the guide cone (421) faces the feed section (11), and the height of the guide cone (421) is less than the height of the spherical cap.

9. The modified plastic extrusion granulator screen changer according to claim 1 or 2, characterized in that: The screen changing plate (2) is rotatably supported in the housing (1).

10. The modified plastic extrusion granulator screen changer according to claim 1 or 2, characterized in that: The screen replacement plate (2) can be slidably assembled in the housing (1).

Images