APPARATUS AND METHOD FOR FILTRATION OF POLYMER MELT

Abstract

A device (1) for filtering plastic melt having an inlet valve (14), an outlet valve (15) and a filter canister (2), wherein a cavity (3) closable by means of a cover (4) is formed and into which a melt channel (20) opens. In the filter canister (2) there is arranged a plurality of filter cartridges (5), which are each formed by a filter substrate (6) and a filter lattice (7). The filter substrate (6) comprises a wall having openings, said wall defining an internal space (8), which opens through an outlet (9) into a collection channel (10). The filter lattice (7) covers the openings of the filter substrate (6). The melt channel (20) is adjacent to the inlet valve (14) and may be brought into fluid communication with an outlet channel (16) via the inlet valve (14). The collection channel (10) is adjacent to the outlet valve (15) and may be brought into fluid communication with an outlet channel (18) via the outlet valve (15). The cover (4) fixes the filter lattices (7) onto the filter substrates (6).

Claims

1. A device for filtering plastic melt comprising: an inlet valve, an outlet valve and a filter canister, wherein a cavity closable by means of a removable cover is formed, into which a melt channel opens, wherein in the filter canister there is arranged a plurality of filter cartridges, which are each formed by a filter substrate and a filter lattice, wherein the filter substrate is anchored to the filter canister and comprises a wall having a plurality of openings, said wall defining an internal space, which opens through an outlet into a collection channel, wherein the filter lattice covers the openings of the filter substrate, wherein the melt channel is adjacent to the inlet valve and may be brought into fluid communication with an outlet channel via the inlet valve and wherein the collection channel is adjacent to the outlet valve and may be brought into fluid communication with an outlet channel via the outlet valve, and wherein the cover fixes the filter lattices onto the filter substrates, characterized in that the device has a ventilation channel in communication with the inlet valve and a drainage channel in communication with the outlet valve, wherein the melt channel may be connected to the ventilation channel via the inlet valve and the collection channel may be connected to the drainage channel via the outlet valve.

2. The device according to claim 1, wherein the filter substrates are arranged in the cavity evenly spaced apart from one another and preferably have the same distance starting from the aperture of the melt channel into the cavity.

3. The device according to claim 1, wherein the inlet valve and the outlet valve are formed by rotary and/or slidable valves.

4. The device according to claim 1, wherein the filter canister may be heated in a contact-free way via a heating cup surrounding the filter canister at a distance.

5. The device according to claim 1, wherein the melt channel and the collection channel are formed in at least one wall of the filter canister in the region of a side of the filter canister.

6. The device according to claim 1, wherein the filter cartridges are oriented in a way such that the filter lattices may be removed axially from the cavity after the cover has been removed.

7. The device according to claim 1, wherein the filter cartridges are adapted to filter particles having a size of essentially larger than 36 m, preferably essentially larger than 25 m or even more preferably larger than 15 m out of the plastic melt in the filter operation of the device.

8. The device according to claim 1, wherein the wall of the filter substrate is made from a perforated sheet material.

9. The device according to claim 1, wherein the filter cartridges are made from metal, plastic or ceramic material.

10. The device according to claim 1, wherein the device has gaskets, which may be fixed to the filter cartridges and which are arranged at the cover placed on the filter canister between filter lattices and the cover.

11. A system having at least two devices according to claim 1, wherein the system has a control unit, which controls the inlet valves and the outlet valves of the at least two devices.

12. The system according to claim 11, wherein a total filtration area of the system may be altered by adding individual devices or by switching off individual devices.

13. A method for replacing filter cartridges of a device according to claim 1, characterized by the following steps: a) stopping a supply of plastic melt into the device by switching the inlet valve from a position connecting the inlet channel and the melt channel to a position connecting the ventilation channel and the melt channel; b) switching the outlet valve from a position connecting the outlet channel and the collection channel to a position connecting the drainage channel and the collection channel; c) flushing the device by suppling gas through the ventilation channel; d) opening the cover; e) replacing the filter lattices; f) closing the cover; g) switching the inlet valve to the position, in which the inlet channel and the melt channel are connected to one another; and h) upon exit of the gas still existent in the cavity through the drainage channel, switching the outlet valve to the position, in which the outlet channel and the collection channel are connected to one another.

14. The method according to claim 13, wherein between steps d) and e), the filter canister is manually cleaned from melt residues by means of a cleaning tool.

Description

[0029] Further advantageous embodiment variants of the device according to the invention are explained in greater detail in the following by way of the figures.

[0030] FIG. 1 shows an embodiment variant of the device according to the invention in the filter operation in a schematic sectional view.

[0031] FIG. 2 shows the embodiment variant of the device according to FIG. 1 along a section A-A.

[0032] FIG. 3 shows the embodiment variant of the device according to FIG. 1 along a section B-B.

[0033] The FIGS. 4 to 7 show the embodiment variant of the device according to FIG. 1 in various configurations when replacing the filter lattices in schematic sectional views.

[0034] FIG. 8 shows the embodiment variant of the device according to FIG. 1 with the cover removed from underneath.

[0035] FIG. 9 shows one embodiment variant of a system according to the invention having eight devices according to FIG. 1 in a schematic depiction.

[0036] FIG. 1 shows an embodiment variant of the device 1 according to the invention in the filter operation in a schematic sectional view. The device 1 comprises a cup-like filter canister 2, in which there is formed a cylindrical cavity 3 and which is closed by means of a cover 4. In the cavity 3, there are arranged six filter cartridges 5, which filter cartridges 5 are each formed by a filter substrate 6 and a filter lattice 7. The filter substrates 6 are anchored to the filter canister 2 and have a cylindrical wall, which is formed by a perforated plate material, hence, having a plurality of openings. The openings are not depicted in the figures for reasons of better clarity. The wall of each filter substrate 6 defines a cylindrical internal space 8, which opens into a collection channel 10 formed in one wall 31 of the filter canister 2 via an outlet 9. The filter lattices 7 have the shape of a thick-walled hollow cylinder and are formed of plastic material. In a further embodiment variant the filter lattices 7 are made from metal, in particular a metal fibre fabric, or a ceramic material. The cover 4 may be removed from the filter canister 2, wherein the cover 4 is screwed onto the filter canister 2 by means of several screws not depicted. The cover 4 fixes in the screwed-on condition the filter lattices 7 onto the filter substrates 6, wherein gaskets 11 are formed between each wall of the filter substrates 6 and the cover 4 in order to prevent leakage between the internal spaces 8 and the cavity 3. The gaskets 11 are depicted in FIG. 5. A heating cup 12 is arranged surrounding the filter canister 2 spaced apart therefrom, which is configured to heat the filter canister 2 in a contact-free way. In a wall 31 of the filter canister 2 there is further formed a melt channel 20, which opens centrally into the cylindrical cavity 3. In this way there is obtained the advantage that all six filter cartridges 5 in the cavity 3 are arranged uniformly towards the mouth 24 of the melt channel 20.

[0037] The device 1 further has a melt distributer housing 13, which is adjacent to the wall 31 of the filter canister 2 and which is screwed thereto by way of screws not depicted. In the melt distributor housing 13 there are configured an inlet valve 14 and an outlet valve 15, wherein the inlet valve 14 is a slidable valve and the outlet valve 15 is a slidable valve. The inlet valve 14 is directly connected to the melt channel 20 via a supply channel 32, and the outlet valve 15 is directly connected to the melt channel 10 via a discharge channel 33. Furthermore, there is configured in the melt distributor housing 13 an inlet channel 16, which opens from a first connecting element 17 into the inlet valve 14, and an outlet channel 18, which opens from a second connecting element 19 into the outlet valve 15. Furthermore, in the melt distributor housing 13 there are further formed a ventilation channel 21 and a drainage channel 22, wherein the ventilation channel 21 opens into the inlet valve 14 and wherein the drainage channel 22 opens into the outlet valve 15.

[0038] In FIG. 1 the inlet valve 14 and the outlet valve 15 are in a position corresponding to the filter operation of the device 1. In the filter operation, plastic melt to be filtered is supplied to the device 1 via the inlet channel 16, whereby there is formed a filter flow via the inlet valve 14, the supply channel 32, the melt channel 20, the cavity 3, through the filter lattices 7 and the openings of the walls of the filter substrates 6, farther via the collection channel 10, the discharge channel 33, the outlet valve 15 into the outlet channel 18, wherein the filtration of the plastic melt is carried out when the plastic melt passes through the filter lattices 7. The filter flow through a filter lattice 7 and the openings of a wall of a filter substrate 6 is indicated in FIG. 1 by the arrow 23. As the collection channel 10 as well as the melt channel 20 are formed in the wall 31, the cavity 3 is flown through in the filter operation essentially in the opposite direction to the internal spaces 8 of the filter cartridges 5 by the plastic melt. As a consequence, the device 1 is operated in a counter-flow and thus may be configured in a very compact way. During the filter operation the filter canister 2 is kept at a constant temperature by the heating cup 12 in order to ensure a possibly low viscosity of the plastic melt.

[0039] FIG. 2 shows the embodiment variant of the device 1 according to FIG. 1 along a section A-A.

[0040] FIG. 3 shows the embodiment variant of the device 1 according to FIG. 1 along a section B-B.

[0041] The FIGS. 4 to 7 show the embodiment variant of the device 1 according to FIG. 1 in various configurations when replacing the filter lattices 7 in schematic sectional view. In order to replace the filter lattices 7, there is firstly removed the heating cup 12 from the filter canister 2. Subsequently, the supply of plastic melt to the device 1 and, hence, the filter operation is interrupted by switching the inlet valve 14 from a position connecting the inlet channel 16 and the melt channel 20 to a position connecting the ventilation channel 21 and the melt channel 20. In the next step, the outlet valve 15 is switched from a position connecting the outlet channel 18 and the collection channel 10 to apposition connecting the drainage channel 22 and the collection channel 10. See FIG. 4. Switching of inlet valve 14 and outlet valve 15 may also be carried out simultaneously. By supplying a pressurized gas, for example, air, through the ventilation channel 21, the cavity 3 and the internal spaces 8 of the filter cartridges 5 are flushed, wherein the plastic melt from the drainage channel 22 is pressed into a drainage container not depicted that is connected to the drainage channel 22 either directly or via a line.

[0042] Subsequently, the cover 4 is screwed off and removed from the filter canister 2, whereby the filter lattices 7 are no longer fixed to the filter substrates 6 and may be pulled off the filter substrates 6 by means of a tool 26 axially in the direction of the arrow 25 and removed from the cavity 3. See FIG. 5 and FIG. 6. The gaskets 11 are either removed immediately upon removal of the cover 4 from the filter lattices 7, or they are removed simultaneously with the filter lattices 7 using the tool 26. If required, there may additionally be carried out a cleaning process of the cavity 3 in this condition. Then new or cleaned filter lattices 7 are applied to the filter substrates 6 by means of the tool 26. The filter lattices 7 are advantageously applied onto the filter substrates 6 by means of the tool 26 in a pre-heated condition.

[0043] Upon application of the new or cleaned filter lattices 7, there are arranged new or cleaned gaskets 11 at the filter lattices 7 or in the cover 4 in respective notches that are not depicted, and the gaskets 11 and the filter lattices 7 are again fixed between the cover 4 and the filter substrates 6 by placing the cover 4 thereupon. See FIG. 7. As a consequence, the inlet valve 14 is again switched to the position, in which the inlet channel 16 and the melt channel 20 are connected to one another, and the cavity 3 is again filled with plastic melt. As soon as filtered plastic melt exits the drainage channel 22, the gas used for flushing the cavity 3 and the internal spaces 8 of the filter cartridges 5 has been discharged, and the outlet valve 15 is switched to the position, in which the outlet channel 18 and the collection channel 10 are connected to one another. The device 1 is again in filter operation.

[0044] FIG. 8 shows the embodiment variant of the device 1 according to FIG. 1 having the heating cup 12 removed and the cover 4 taken off, from above, wherein there has already been removed a filter lattice 7 from one filter substrate 6 by means of the tool 26.

[0045] FIG. 9 shows an embodiment variant of a system 27 according to the invention having eight devices 1 according to FIG. 1 in a schematic depiction. The system 27 further comprises a control unit 28 formed by a computer or a micro-controller, which is connected to all eight devices 1 for data exchange. All inlet channels 16 of the device 1 are connected to a supply line 29, and all outlet channels 18 of the device 1 are connected to a discharge line 30. Also the ventilation channels 21 and the drainage channels 22 are each coupled to one another via a line, wherein the lines are not depicted in FIG. 9 for reasons of better clarity. The control unit 28 controls the function of the inlet valves 14 and of the outlet valves 15 of the devices 1, controlling these advantageously in a completely automatic way in the operation of the system 27. Individual devices 1 that are controlled by the control unit 28 may be added or switched off. This is realized either in order to clean individual devices 1 or in order to adjust a total filtration surface of the system 27 to a volume flow and contamination level of the plastic melt. For reasons of clarity, also the heating cups 12 of the individual devices 1 are not depicted in FIG. 9.