Filtering device for plastic extruder of optical cable jacket

Abstract

The application relates to the technical field of optical cable sheathing, and discloses a filtering device of an optical cable sheathing plastic extruder, which comprises a shell body with an upstream feeding port and a downstream discharging port, further comprises two screen cylinder assemblies arranged in the shell body and capable of being switched between an in-place position and a standby position, and the two screen cylinder assemblies are both separated into an unfiltered side and a clean side cavity by an arc-shaped screen mesh; displacement elements are arranged in the two clean side cavities, and the two displacement elements are driven by a control unit to make equal and opposite movements during switching of the two screen cylinder assemblies, so that the total effective volume of the two clean side cavities remains constant during switching. The application realizes the "push-pull" equal and opposite constant volume linkage and compensates the volume flow in the in-place side, instantaneously offsets the natural flow gap caused by the change of the effective opening of the arc-shaped screen mesh in the whole switching process of the screen cylinder assembly, keeps the downstream pressure and flow stable, and eliminates the density fluctuation caused by the sudden change of the instantaneous flow area during screen changing.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of optical cable sheathing, in particular to a filtering device of an optical cable sheathing extruder. BACKGROUND

[0002] In the screen switching process of the filtering device of the optical cable sheathing extruder, the channel opening degree changes with time, which easily causes the effective flow area and the equivalent flow resistance to change suddenly or discontinuously, so that transient fluctuations occur in the downstream flow and pressure, even if the screen changer is arranged before the metering pump to isolate the pre-die fluctuations, a pressure drop jump may still be formed at the pump suction inlet, and then the system compliance is coupled to form a pre-die disturbance. SUMMARY

[0003] The purpose of the application is to provide a filtering device of an optical cable sheathing extruder to solve at least one technical problem existing in the prior art.

[0004] To achieve the above-mentioned purpose, the application provides the following technical scheme: a filtering device of an optical cable sheathing extruder, comprising a shell with an upstream feed inlet and a downstream discharge outlet, and the upstream feed inlet is connected with an extruder, and further comprising:

[0005] Two screen cylinder assemblies arranged in the shell and capable of being switched between an in-place state and a standby state, and each of the two screen cylinder assemblies is divided into an unfiltered side and a clean side cavity by an arc-shaped screen.

[0006] Displacement members are arranged in the two clean side cavities, and the two displacement members are driven by a control unit to move reversely by an equal amount during the switching of the two screen cylinder assemblies, so that the total effective volume of the two clean side cavities remains constant during the switching.

[0007] A switching window is formed in the outer wall of the shell, and when the screen cylinder assembly is switched to the standby state, the arc-shaped screen corresponds to the position of the corresponding switching window.

[0008] Optionally, an adjusting cylinder is slidingly installed on the inner wall of the shell, and the adjusting cylinder is driven by an external hydraulic system, the inside of the adjusting cylinder is hollow, and a partition layer is arranged in the middle to separate the cavity, the displacement member is a piston slidingly installed on the inner wall of the adjusting cylinder, a telescopic cylinder is installed between the piston and the end inner wall of the adjusting cylinder, and the clean side cavity is composed of the two arc-shaped screens, the inner wall of the adjusting cylinder and the piston.

[0009] Optionally, a partition plate is arranged on the inner wall of the downstream discharge outlet, and the partition plate divides the downstream discharge outlet into two independent channels, the ends of the two independent channels are again converged into a clean convergence flow channel, an outlet check valve is arranged in each of the two independent channels, and the outlet check valve only allows the melt to flow from the clean side cavity to the clean convergence flow channel.

[0010] Optionally, two backfill paths are further included, the two backfill paths are respectively led out from the clean converging flow channel and communicated with the respective clean side cavities, backfill check valves are arranged in the two backfill paths, and only the filtered melt is allowed to slowly supplement into the clean side cavity when the corresponding piston is withdrawn.

[0011] Optionally, the backfill path comprises a communication groove opened in the interior of the partition plate and adjusting the axial outer wall of the cylinder and an internal flow channel opened in the interior of the partition layer and communicated with the clean side cavity.

[0012] Optionally, the control unit controls the telescopic cylinder to make the advancing side piston output a compensation volume flow according to a speed trajectory that is increased with the switching progress and has smooth acceleration and deceleration, so as to form a stable downstream flow together with the sum of the natural flows through the arc-shaped screen mesh, and makes the withdrawing side piston perform fluid supplement in the clean side cavity according to a speed trajectory that is decreased in the opposite direction and has smooth acceleration and deceleration.

[0013] Optionally, the contact surface of the piston and the clean side cavity adopts a sealing and guiding structure with high temperature resistance and low friction.

[0014] Optionally, the length of the piston is greater than the width of the arc-shaped screen mesh, and the piston is always located in the range of the clean side cavity where the arc-shaped screen mesh is located.

[0015] Optionally, the shell is composed of two half shells capable of being combined and installed, and is fixed by bolts.

[0016] Optionally, a selection valve is arranged after the downstream discharge port, for selecting whether the filtered melt is sent to the main production line or the waste loop during switching.

[0017] Compared with the prior art, the present application has the following beneficial effects:

[0018] Firstly, the present application offsets the natural flow gap caused by the change of the effective opening of the arc-shaped screen mesh through the equal reverse constant volume linkage of "push-pull" and the compensation volume flow in the in-situ side, so that the downstream pressure and flow are kept stable, the density fluctuation caused by the sudden change of the instantaneous flow area of the double-plate screen changer is eliminated, and the optical cable sheath outer diameter, concentricity and wall thickness can still maintain precision at the screen changing moment, so that zero waste line continuous production is realized.

[0019] Secondly, the present application designs the clean side cavity as a "melt transfer station" that can change the volume in real time, and drives the piston by using the smooth speed curve with acceleration slow start and slow stop and limited jump degree, so that the pressure peak of the viscoelastic melt caused by impact is avoided, and an additional reset cycle is not needed, the system is directly stopped at the new force balance position after completing one switching, and waits for the next role switching.

[0020] Third, this invention constructs a closed-loop flow management system of "one-way output - micro-pressure replenishment" by using a partition + dual independent channels + outlet check valve, two backfilling passages led out from the clean confluence flow channel and backfill check valve, which completely blocks the unfiltered melt from bypassing, backflowing or bubble back-suction, and ensures that all backfilled melt has passed through the arc-shaped screen. Attached Figure Description

[0021] Figure 1 This is a three-dimensional structural diagram of the screen switcher in this invention;

[0022] Figure 2 This is a front view of the network switcher in this invention;

[0023] Figure 3 For the present invention Figure 2 Sectional view along the middle AA;

[0024] Figure 4 This is a three-dimensional structural diagram of the screen switcher in this invention after half of the housing has been removed.

[0025] Figure 5 This is a schematic diagram of the state during the switching process of the network switcher in this invention;

[0026] Figure 6 This is a schematic diagram of the state of the network switcher before or after switching in this invention;

[0027] Figure 7 This is a sectional perspective view of the upstream inlet and downstream outlet of the screen changer in this invention;

[0028] Figure 8 This is a sectional perspective view of the adjusting cylinder of the screen changer in this invention;

[0029] Figure 9 This is a three-dimensional structural diagram of the screen changer regulating cylinder in this invention.

[0030] In the diagram: 1. Shell; 2. Adjusting cylinder; 3. Hydraulic system; 4. Upstream feed inlet; 5. Downstream discharge outlet; 6. Baffle plate; 7. Switching window; 8. Arc-shaped screen; 9. Partition layer; 10. Piston; 11. Internal flow channel; 12. Backfill branch; 13. Connecting groove; 14. Embedded groove; 15. Telescopic cylinder. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Please see Figures 1 to 9The application provides a technical scheme: a filtering device of an optical cable sheath plastic extruder, which comprises a shell 1 provided with an upstream feeding port 4 and a downstream discharging port 5, the upstream feeding port 4 is connected with the extruder, and the filtering device further comprises:

[0033] two screen cylinder assemblies arranged in the shell 1 and capable of switching between an in-place state and a standby state, and each of the two screen cylinder assemblies is divided into an unfiltered side and a clean side cavity by an arc-shaped screen 8;

[0034] displacement members arranged in the two clean side cavities, the two displacement members are driven by a control unit to make equal and opposite movements during switching of the two screen cylinder assemblies, so that the total effective volume of the two clean side cavities remains constant during switching;

[0035] a switching window 7 formed in the outer wall of the shell 1, and when the screen cylinder assembly is switched to the standby state, the arc-shaped screen 8 is positionally corresponding to the corresponding switching window 7.

[0036] In the prior art, the filtering device of the optical cable sheath plastic extruder is usually sequentially composed of a feeding and plasticizing unit, an extruder, a screen changer, an (optional) melt metering pump, a die head / die, a cooling and shaping unit and a traction winding unit, wherein the screen changer is arranged between the discharging end of the extruder and the die head, and mainly functions to intercept and filter impurities of the melt, establish and stabilize necessary back pressure, weaken extrusion pulsation, so as to provide relatively uniform melt flow for the die head;

[0037] However, when the existing double-plate screen changer changes the screen, the material flow channel is closed for half, the downstream material pressure fluctuates greatly, and thus the material density changes. The reason is that the effective flow area of the flow channel changes when the two screens are switched, so that transient fluctuations of the downstream flow and pressure occur. Therefore, a screen changing and melt supplying coordination mechanism suitable for the filtering device of the optical cable sheath plastic extruder is urgently needed, which can keep the downstream flow or pressure basically constant during screen switching, so as to ensure the stability of the subsequent extruded product. The specific mode is as follows:

[0038] Firstly, the material is extruded by the extruder and then enters the shell 1 from the upstream feeding port 4, and then is discharged from the downstream discharging port 5 after being filtered by the in-place screen cylinder assembly, which is the whole filtering process;

[0039] Among them, the screen cylinder assembly is divided into an unfiltered side and a clean side cavity by the arc-shaped screen 8, the unfiltered side is the space between the upstream feeding port 4 and the arc-shaped screen 8, and the clean side cavity is the space region in the screen cylinder assembly after the arc-shaped screen 8. After being filtered by the arc-shaped screen 8, the material enters the clean side cavity and then enters the downstream discharging port 5. The clean side cavity serves as a transition and transfer area. For details, please refer to Figure 6 ;

[0040] And in the two net side cavities are respectively provided displacement members, the two displacement members are driven by a control unit, and the two displacement members make equal and opposite movements during switching of the two screen drum assemblies, so that the total effective volume of the two net side cavities remains constant during switching.

[0041] During switching, the in-position displacement member directs the filtered melt in the net side cavity to push out as a compensation volume flow, and the in-position displacement member is synchronously withdrawn to provide an equal volume for the melt supplemented by the arc-shaped screen 8 upstream, which can be specifically referred to as Figure 5 During the switching window, since the effective opening of the in-position screen drum assembly is decreasing, and the to-be-positioned screen drum assembly has not yet fully taken over, the main flow channel (i.e., the downstream discharge port 5) will have a transient flow gap, at this time, the "filtered melt in the net side cavity" acts as a reserve cavity, and the displacement member extrudes this part of the melt to compensate for the downstream flow / pressure until the to-be-positioned screen drum assembly fully takes over, that is, returns to Figure 6 the state shown again.

[0042] When the to-be-positioned screen drum assembly moves to the in-position and forms a stable flow, the advancing displacement member stops compensating, the withdrawing displacement member stops withdrawing, and the subsequent selection valve switches to the target flow direction according to the strategy (if the aforementioned window is guided to the waste line, then it is cut back to the main line), the system enters a new steady state, and the two displacement members stop at new equilibrium positions, waiting for the next switching role reversal, without the need for a special reset cycle.

[0043] Then, the to-be-positioned arc-shaped screen 8 can be removed for replacement or cleaning by opening the switching window 7.

[0044] And, it is worth noting that since the effective opening of the arc-shaped screen 8 is continuously decreasing, the movement speed of the displacement member should be continuously increasing to maintain the flow extruded into the downstream discharge port 5.

[0045] In this way, through the above-mentioned "push-pull" cooperation, and the constant-volume linkage of "equal and opposite", and the in-position side compensation volume flow, the natural flow fluctuation caused by the change of the effective opening of the arc-shaped screen 8 is offset, so that the downstream pressure and flow remain stable during switching, and the sheath outer diameter and concentricity are easier to control.

[0046] And it is worth mentioning that when the control unit controls the movement of the displacement member, the speed curve of "acceleration slow start and slow stop, and limit of jump degree" is used to complete the flow compensation action at this moment, which is intuitively (slowly accelerate first → to a certain speed → slow down again) in the visual sense, not a sharp trapezoidal shape. Since the melt is "viscoelastic", a sudden speed step will cause a pressure peak. The acceleration of this driving mode can make the mechanical impact smaller and the downstream pressure more stable.

[0047] In one of the more preferred embodiments, the inner wall of the shell 1 is slidingly mounted with the adjusting cylinder 2, and the adjusting cylinder 2 is driven by the external hydraulic system 3, the inside of the adjusting cylinder 2 is provided with a cavity, and the middle is provided with a partition layer 9 for separating the cavity, the displacement member is a piston 10 slidingly mounted in the inner wall of the adjusting cylinder 2, and the piston 10 is mounted with an extension cylinder 15 between the end inner wall of the adjusting cylinder 2, and the net side cavity is composed of two arc-shaped screens 8, the inner wall of the adjusting cylinder 2 and the piston 10.

[0048] Wherein, the control unit controls the extension cylinder 15 to make the advancing side piston 10 output a compensation volume flow according to a speed trajectory that increases with the switching progress and has smooth acceleration and deceleration, so as to form a stable downstream flow together with the sum of the natural flows through the arc-shaped screens 8, and at the same time, the retracting side piston 10 is controlled to decrease in the opposite direction according to a speed trajectory that decreases and has smooth acceleration and deceleration, so as to supplement the fluid in the net side cavity.

[0049] Wherein, the contact surface of the piston 10 and the net side cavity adopts a sealing and guiding structure with high temperature resistance and low friction.

[0050] Specifically, refer to Figures 4-6 In the switching process, the control unit is electrically connected to control the extension and retraction of the two extension cylinders 15 to drive the piston 10 to move in the adjusting cylinder 2, so as to expand or reduce the space volume in the net side cavity, thereby achieving the above-mentioned effect of compensating the flow of the downstream discharge port 5 during switching.

[0051] In one of the more preferred embodiments, the inner wall of the downstream discharge port 5 is provided with a partition plate 6, and the partition plate 6 divides the downstream discharge port 5 into two independent channels, and the ends of the two independent channels are again converged into a clean convergence flow channel, and outlet check valves are installed in the two independent channels, and the outlet check valves only allow the melt to flow from the net side cavity to the clean convergence flow channel.

[0052] The partition plate 6 divides the downstream discharge port 5 into two independent channels, and the outlet check valves are installed respectively, and only allow the melt to flow from each net side cavity to each independent channel to the clean convergence flow channel, and under any working condition, the downstream is prohibited to flow into the net side cavity, thereby ensuring the one-way output of the net side material and the mutual non-interflow.

[0053] Moreover, it is worth mentioning that the partition plate 6 divides the downstream discharge port 5 into two independent channels, and the middle section of the independent channel can gradually change into a channel with a circular cross section, which can also facilitate the installation of the outlet check valve.

[0054] In one of the more preferred embodiments, two backfill paths are further included, the two backfill paths are respectively led out from the clean convergence flow channel and communicated with each net side cavity, and backfill check valves are arranged in the two backfill paths, and only allow the filtered melt to slowly supplement into the net side cavity when the corresponding piston 10 is retracted.

[0055] The backfilling passage comprises a communication groove 13 formed in the inside of the partition plate 6 and adjusting the axial outer wall of the cylinder 2, and an internal flow channel 11 formed in the inside of the partition layer 9 and communicating with the clean side cavity.

[0056] In order to avoid the negative pressure, bubbles and back suction phenomenon caused thereby in the clean side cavity when the displacement member (i.e. the piston 10) is withdrawn, two backfilling passages are arranged, which are respectively led out from the clean converging flow channel and communicate with each clean side cavity, and the specific reference is made to Figures 7-9 The backfilling passage is provided with a backfilling check valve and a flow limiting element, and only the filtered melt is allowed to slowly supplement into the clean side cavity when the corresponding piston 10 is withdrawn, and by fixing the backfilling source in the clean converging flow channel, it is ensured that the backfilled material has passed through the arc-shaped screen 8, so that the unfiltered material can be blocked from bypassing in structure.

[0057] In one of the more preferred embodiments, the length of the piston 10 is greater than the width of the arc-shaped screen 8, and the piston 10 is always located in the range of the clean side cavity where the arc-shaped screen 8 is located, so that it can be ensured that the source of the compensation volume flow is the filtered melt and the end residue is reduced.

[0058] In one of the more preferred embodiments, the shell 1 is composed of two half-shells which can be combined and installed, and is fixed by bolts.

[0059] In a further more preferred embodiment, a selection valve is arranged after the downstream discharge port 5, which is used to select the filtered melt to be sent to the main production line or to the waste loop during switching.

[0060] The standard parts used in the embodiments can be directly purchased from the market, and the non-standard structural parts according to the description and drawings can also be directly processed according to the existing technical knowledge without doubt, and the connection mode of each part adopts the mature conventional means in the existing technology, and the machinery, parts and equipment all adopt the conventional models in the existing technology, so the specific description is not made here.

[0061] Although the embodiments of the present application have been shown and described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A filtering device for optical cable jacketing plastic extruders, comprising a housing (1) having an upstream feed opening (4) and a downstream discharge opening (5), and the upstream feed opening (4) is connected to an extruder, characterized in that, Also comprising: Two screen cylinder assemblies arranged in the shell (1) and switchable between in-place and standby, and each divided by an arc-shaped screen (8) into an unfiltered side and a clean side cavity; A displacement member is arranged in each of the two clean side cavities, and the two displacement members are driven by a control unit to move in opposite directions at equal amounts during switching of the two screen cylinder assemblies, so that the total effective volume of the two clean side cavities remains constant during switching; A switching window (7) is opened on the outer wall of the shell (1), and when the screen cylinder assembly is switched to the standby state, the arc-shaped screen (8) is positioned corresponding to the corresponding switching window (7); The inner wall of the shell (1) is slidably mounted with an adjusting cylinder (2), and the adjusting cylinder (2) is driven by an external hydraulic system (3). The inside of the adjusting cylinder (2) is hollow, and a partition layer (9) is arranged in the middle to separate the hollow. The displacement member is a piston (10) slidably mounted on the inner wall of the adjusting cylinder (2), and a telescopic cylinder (15) is mounted between the piston (10) and the inner wall of the end of the adjusting cylinder (2). The clean side cavity is composed of the two arc-shaped screens (8), the inner wall of the adjusting cylinder (2), and the piston (10); The inner wall of the downstream discharge port (5) is provided with a partition plate (6), and the partition plate (6) divides the downstream discharge port (5) into two independent channels, and the ends of the two independent channels are again converged into a clean convergence flow channel. Each of the two independent channels is provided with an outlet check valve, and the outlet check valve only allows the melt to flow from the clean side cavity to the clean convergence flow channel; It also includes two backfill channels, which are respectively led out from the clean convergence flow channel and communicate with each of the clean side cavities. Each of the two backfill channels is provided with a backfill check valve, and only allows the filtered melt to slowly supplement into the clean side cavity when the corresponding piston (10) is withdrawn.

2. The filtration device for optical cable jacketing plastic extruders according to claim 1, characterized in that: The backfill channel includes a communication groove (13) opened in the inside of the partition plate (6) and the axial outer wall of the adjusting cylinder (2), and an internal flow channel (11) opened in the inside of the partition layer (9) and communicating with the clean side cavity.

3. The filtration device for optical cable jacketing plastic extruders of claim 1, wherein: The control unit controls the telescopic cylinder (15) to make the advancing side piston (10) output a compensation volume flow according to a speed trajectory that increases with the switching progress and has smooth acceleration and deceleration, so as to form a stable downstream flow together with the sum of the natural flows through the arc-shaped screens (8), and at the same time, the retracting side piston (10) moves in the opposite direction according to a speed trajectory that decreases and has smooth acceleration and deceleration to supplement the fluid in the clean side cavity.

4. The filtration device for optical cable jacketing plastic extruders of claim 1, wherein: The contact surface between the piston (10) and the clean side cavity adopts a sealing and guiding structure with high temperature resistance and low friction.

5. The filtration device for optical cable jacketing plastic extruders of claim 1, wherein: The length of the piston (10) is greater than the width of the arc-shaped screen (8), and the piston (10) is always located within the range of the clean side cavity where the arc-shaped screen (8) is located.

6. The filtration device for optical cable jacketing plastic extruders according to any one of claims 1-5, characterized in that: The shell (1) is composed of two half-shells that can be combined and installed with each other, and is fixed by bolts.

7. The filtration device of a cable jacketing plastic extruder according to any one of claims 1-5, wherein: A selection valve is arranged after the downstream discharge port (5) to select whether to send the filtered melt to the main production line or to the waste circuit during switching.

Images