Filtering device for filtering a fluid, and relevant operating method

Abstract

The invention relates to a filtering device (2) for filtering a fluid, in particular a plasticized plastic, comprising a housing (4) with a receptacle (6) for receiving a screen support (8), a fluid inlet channel (10) and a fluid outlet channel (12), a screen support (8) which is received movably along a longitudinal axis (26) within the receptacle (6) and has a screen support inlet (16), a screen support outlet (18) and a cavity (20) for receiving a filter element (22), wherein the cavity (20) is connected in a fluid-conducting manner to the screen support inlet (16) and the screen support outlet (18), and wherein the screen support (8) is movable from a screen changing position (S) via a ventilating positional region (E) into a filtering position (F). It is proposed according to the invention that the screen support (8) has a throttle cut-out (24) which is arranged adjacently with respect to the screen support outlet (18) and is connected in a fluid-conducting manner to the cavity (20), and which opens a variable flow cross section (30) between the cavity (20) and the fluid outlet channel (12) in a manner which is dependent on a position of the throttle cut-out (24) relative to the fluid outlet channel (12) in the ventilating positional region (E).

Description

[0001] Filtration device for filtering a fluid and corresponding operating method

[0002] The invention relates to a filtering device for filtering a fluid, in particular a liquefied plastic, comprising a housing with a receptacle for receiving a portafilter, a fluid inlet channel and a fluid outlet channel, a portafilter movably received within the receptacle along a longitudinal axis with a portafilter inlet, a portafilter outlet and a cavity for receiving a filter element, wherein the cavity is fluidly connected to the portafilter inlet and the portafilter outlet, and wherein the portafilter is movable from a portafilter changing position via a venting position area into a filtering position.

[0003] Filtration devices are used, for example, in plastics processing machines when high demands are placed on the purity of the plastic being processed. They are typically arranged between an extrusion device, which melts and conveys the plastic, and an application device. Such filtration devices for filtering a fluid, in particular a liquefied plastic, as well as related methods, are known in the art. For example, DE 10 2007 057 861 A1 describes such a filtration device with a portafilter in which a filter element, also referred to as a screen, is arranged.

[0004] After some time in operation, the filter elements typically need to be replaced or cleaned. To replace the filter element, the portafilter is moved from the filtering position, also known as the production position, to a so-called filter change position, which allows access to the filter element and allows it to be replaced.

[0005] After changing the filter element, it must be reinserted into the production process. This presents the challenge that the interior of the portafilter, known as the cavity, is filled with air after the screen change, and introducing air into the plastic fluid flow must be avoided at all costs. For this reason, after the screen change, the portafilter is first moved to a venting position area, where liquefied plastic flows into the screen cavity and displaces the air contained therein to the outside via venting channels.

[0006] After the cavity has been completely filled or vented, the liquefied plastic must be set in motion again to initiate the filtration process. The plastic melt has a certain inertia, which can lead to undesirable fluctuations in the overall system pressure during the melt acceleration process. It has therefore proven challenging to accelerate the melt after a standstill in such a way that the overall system pressure remains within narrowly defined limits.

[0007] This circumstance also comes into play during the so-called backwashing of filter elements, in which they are backwashed against the filtration direction using a plastic melt for cleaning purposes. In this case, the plastic used for backwashing is taken from the plastic fluid stream to be filtered. Excessively rapid backwashing from the plastic fluid stream can also have a negative impact on the system pressure. Such pressure fluctuations, for example, when using spinnerets, can negatively impact the spinning process, resulting in poor product quality and even leading to the spun threads breaking.

[0008] A method for controlling a plastics processing system is known from the prior art, for example from DE 10 2006 019 445 A1, which proposes compensating for pressure changes by adjusting the flow rate of a conveying device. A disadvantage of this described prior art is the control-related delay time between the system pressure drop caused by filling the cavity and the readjustment of the pumping capacity. As a result, the occurrence of pressure fluctuations cannot be reliably ruled out.

[0009] In addition, such control of the pumping capacity depending on the screen changing process contributes to an increase in the complexity of the system, which increases the manufacturing costs and maintenance effort with regard to such a machine.

[0010] Against this background, the object of the invention was to further develop a device and a method of the type described above in such a way that the disadvantages found in the prior art are eliminated as far as possible. In particular, the object of the invention was to provide a device and a method in which the overall system pressure is kept as constant as possible during a screen change process or backwashing of a filter element, thereby reducing the overall system complexity.

[0011] According to the invention, the object is achieved in a device of the type mentioned at the outset in that the portafilter has a throttle recess which is arranged adjacent to the portafilter outlet and is fluidly connected to the cavity, and which, depending on a position of the throttle recess relative to the fluid outlet channel, releases a variable flow cross-section between the cavity and the fluid outlet channel (claim 1).

[0012] The invention utilizes the finding that by arranging a throttle recess adjacent to the portafilter outlet, a free flow cross-section between the fluid outlet channel and the cavity can be adjusted particularly finely. In this way, particularly after the cavity has been completely vented, a connection between the cavity and the fluid outlet channel can be established via the throttle recess, resulting in a gentle acceleration of the melt, particularly from the cavity, toward the fluid outlet channel. In other words, the melt received in the fluid inlet channel and in the cavity can be controlled and slowly set in motion in such a way that the overall system pressure is virtually unaffected by the acceleration process or is at least kept within tolerable limits.

[0013] According to a preferred embodiment, the portafilter is movable from the venting position region via an acceleration position region into the filtering position, wherein the throttle recess releases a variable flow cross-section between the cavity and the fluid outlet channel depending on a position of the throttle recess relative to the fluid outlet channel in the acceleration position region. The acceleration position region is preferably separated from the venting position region, whereby the melt is thus accelerated in particular only after passing through the venting position region, i.e., after the cavity has been completely vented.

[0014] The acceleration position area according to the invention provides for the first time a flow channel, preferably formed by a recess or groove, which contributes to and serves the purpose of setting the melt in motion again after a functional interruption, in particular a screen change, i.e. accelerating the flow overall, so that this is preferably done carefully in such a way that no major pressure fluctuations occur in the filtering device and preferably the system as a whole and / or major turbulences occur and / or mixing of melt and gas occurs (also occasionally referred to as foam formation).

[0015] The invention is further developed in that the throttle recess extends along the longitudinal axis, starting from the portafilter outlet and, viewed from the portafilter change position, toward the fluid outlet channel. This achieves the effect that the variable flow cross-section between the cavity and the fluid outlet channel is released or adjusted by moving the throttle recess toward the fluid outlet channel by moving the portafilter. In other words, the flow cross-section between the cavity and the fluid outlet channel can be influenced as desired by changing the position of the portafilter along the longitudinal axis.

[0016] According to a preferred embodiment, the throttle recess has a cross-section that changes in the direction of the longitudinal axis. The cross-section of the throttle recess preferably tapers from the portafilter outlet in the direction of the longitudinal axis. In this way, moving the portafilter, and thus moving the throttle recess toward the fluid outlet channel, initially results in only a very small flow cross-section being exposed between the cavity and the fluid outlet channel. Further advancement of the portafilter causes the flow cross-section to increase disproportionately. In this way, the system pressure can be advantageously influenced, as explained, and the melt can be advantageously accelerated.

[0017] Preferably, the cross-section of the throttle recess tapers linearly from the portafilter outlet toward the longitudinal axis. According to a preferred embodiment, the cross-section has a wedge-shaped or notched basic shape. This allows for particularly precise adjustment of the flow cross-section.

[0018] According to a preferred embodiment, the fluid inlet channel and the fluid outlet channel are arranged in the housing in such a way that when the portafilter is moved from the screen change position via the venting position region and the acceleration position region in the direction of the filtering position, the cavity in the venting position region is initially, in particular exclusively, fluidically connected to the fluid inlet channel. When the portafilter is moved further in the direction of the filtering position, the cavity in the acceleration position region is additionally fluidically connected to the fluid outlet channel via the throttle recess. In this way, a particularly gentle filling of the cavity with regard to the overall system pressure is achieved. By connecting the fluid inlet channel to the cavity, the latter is initially vented. A connection to the fluid outlet channel is not yet established in this position.Only by further moving the portafilter toward the filtration position does a very small flow cross-section initially open to the fluid outlet channel via the throttle recess. This, as described, results in a particularly gentle acceleration of the melt in the cavity, which, as explained, is particularly beneficial for maintaining a constant overall system pressure. If a connection to the outlet channel were already established when venting the cavity, air bubbles could be forced into the production process, which is undesirable.

[0019] According to a preferred embodiment, the portafilter has an inlet throttle recess adjacent to the portafilter inlet, which is fluidly connected to the cavity and which, depending on the position of the inlet throttle recess relative to the fluid inlet channel in the venting position range, releases a variable flow cross-section between the cavity and the fluid inlet channel. In this way, even when venting the cavity, melt is supplied to the cavity particularly gently and sensitively via an inlet throttle recess, whereby pressure fluctuations in relation to the overall system pressure are avoided as much as possible.

[0020] The inlet throttle recess preferably extends along the longitudinal axis, starting from the portafilter inlet and, viewed in the portafilter change position, in the direction of the fluid outlet channel. This ensures that the cavity is first connected to the fluid outlet channel via the inlet throttle recess, allowing particularly sensitive flooding of the cavity. The inlet throttle recess preferably has a cross-section that changes in the direction of the longitudinal axis. This design of the inlet throttle recess has proven advantageous in enabling particularly gentle filling of the cavity with regard to the overall system pressure.

[0021] The invention is further developed in that the portafilter has at least one venting recess, which connects the cavity to the environment in a fluid-conducting manner depending on a position of the venting recess relative to the housing. Such a venting recess has proven effective in influencing the venting process not only on the inlet side, i.e., in the region of the fluid inlet channel, but also in the region of an outlet. The venting recess preferably extends along the longitudinal axis. Thus, by positioning the portafilter and thus the venting recess relative to the housing, it is possible to achieve a variable cross-section available for air outlet.According to a preferred embodiment, the venting recess is a first venting recess, and the portafilter has a second venting recess which is fluidly connected to the cavity, the second venting recess having a smaller longitudinal extent along the longitudinal axis than the first venting recess, and is arranged such that when the portafilter is moved from the filter change position towards the filtering position, the cavity is first vented via the first and second venting recesses, and when the portafilter is moved further towards the filtering position, the cavity is only vented via the first venting recess. Preferably, the portafilter has a third venting recess, the third venting recess having a smaller longitudinal extent along the longitudinal axis than the second venting recess.

[0022] According to a preferred embodiment, the first venting recess is fluidly connected to a first partial region of the cavity, and / or the second venting recess is fluidly connected to a second partial region of the cavity, and / or the third venting recess is fluidly connected to a third partial region of the cavity. This allows not only the venting of the cavity as a whole to be influenced, but also individual partial regions of the cavity to be vented in a targeted manner.

[0023] When moving the portafilter from the screen change position toward the filtering position, the portafilter is preferably initially vented through all three venting recesses in the venting position area, although more than three, in particular four, venting recesses may also be provided. Initially, all, in particular all three, venting recesses are preferably connected to the surroundings of the filtering device. Typically, melt then first exits through the shortest venting recess, then, after a delay of a few seconds, also through the medium-length venting recess, then also through the next longer venting recess, and so on.After complete venting via the respective venting recess, the portafilter is successively advanced toward the filtering position, interrupting the connection of the respective venting recess to the environment. First, the connection of the shortest venting recess to the environment, then the medium-length venting recess, and so on, until finally all venting recesses are separated from the environment by retracting into the housing. According to a preferred embodiment, at least one, or in particular all, of the venting recesses is designed as a groove. During venting, the cavity is preferably fluidically connected exclusively to the fluid inlet channel, but not to the fluid outlet channel. This enables gradual venting and re-introduction into the production process.According to an alternative embodiment, at least one, or in particular all, of the venting recesses are designed as venting bores.

[0024] The invention is further developed in that the filtration device has a control device that is configured and designed such that, after venting the cavity, it moves the portafilter further toward the filtration position by means of control signals such that the fluid outlet channel is initially fluidly connected to the cavity exclusively via the throttle recess, and the portafilter is moved toward the filtration position such that a fluid pressure in the fluid inlet channel and / or in the fluid outlet channel remains within a definable pressure range. This achieves particularly advantageous control of the filtration device by utilizing the throttle recess. For example, a specific maximum pressure drop can also be defined, which, to a certain extent, specifies the feed rate of the sieve bolt.For example, if an excessive pressure drop is observed, the portafilter feed speed is reduced. On the other hand, the portafilter feed speed can also be increased if only a very slight pressure drop is observed, which is less than a defined limit.

[0025] For example, the portafilter can be advanced continuously or incrementally, allowing the response to changes, such as system pressure, to be observed and assessed. This type of control logic also has the advantage of being independent of material viscosity and throughput.

[0026] According to a second aspect of the invention, the portafilter is vented in the venting position region by supplying a fluid via the fluid outlet channel, and wherein the portafilter has a throttle recess, in particular an acceleration groove, which is arranged adjacent to the portafilter inlet and is fluidly connected to the cavity, and which, depending on a position of the throttle recess relative to the fluid inlet channel, releases a variable flow cross-section between the cavity and the fluid inlet channel (claim 13). This alternative arrangement of the throttle recess takes into account the fact that in some filtering devices, venting of the portafilter takes place via the fluid outlet channel and not, as shown in the above embodiments, via the fluid inlet channel.Accordingly, in this alternative filter device configuration, the throttle recess is also arranged adjacent to the portafilter inlet. Furthermore, the filter device according to the second aspect utilizes the same advantages and preferred embodiments as the filter device according to the invention of the first aspect, taking into account the alternative functional principle and the location of the throttle recess. In this regard, reference is made to the above explanations, and their content is incorporated herein.

[0027] According to a third aspect of the invention or according to an advantageous development of the invention according to the first and / or second aspect, the invention proposes that the housing has a backwash supply channel, which is designed to supply backwash fluid to the filter element in a backwash position region, starting from a clean side of the filter element to a dirty side, and a backwash channel, which is designed to discharge the backwash fluid after backwashing, wherein the portafilter is movable into a backwash position region by the backwash supply region being at least partially fluidically connected to a clean side of the filter element, and the backwash channel being at least partially fluidically connected to the dirty side of the filter element, wherein the portafilter has a backwash recess, which is arranged between the backwash supply channel and the portafilter outlet and is fluidically connected to the cavity,and which, depending on a position of the backwash recess relative to the backwash supply channel in the backwash position range, releases a variable flow cross-section between the backwash supply channel and the cavity (claim 14).

[0028] This third aspect of the invention, or rather the advantageous development of the invention, takes advantage of the finding that, in the backwash position, a connection to the backwash channel is opened to a large extent, in particular completely. The backwash flow rate is adjusted via the backwash recess between the backwash supply channel and the cavity, and thus in the area of ​​the clean side of the filter element. In this respect, the backwash flow rate can be adjusted as desired to minimize pressure fluctuations in the system.A particular advantage here is that, unlike prior art solutions in which the amount of contaminated melt used for backflushing is adjusted, larger dirt particles have no effect on the backflushing behavior. In prior art devices, it has been observed in particular that dirt particles have to pass through a particular constriction, occasionally clogging it, and thus backflushing becomes ineffective. The fact that the backflushing recess has a variable cross-section along its longitudinal axis enables sensitive adjustment of the backflushing. In other words, the throttling is adjusted on the "clean" side. This prevents blockages. In the prior art, throttling is done on the dirty side, which carries the risk of clogging or leads to a large opening with the inevitable associated pressure fluctuations.

[0029] The invention is further developed in that the backwash recess extends along the longitudinal axis, starting from the portafilter outlet and viewed from the filtering position, in the direction of the backwash feed channel. This configuration ensures that the amount of melt fed in can be finely adjusted by varying the flow cross-section between the backwash feed channel and the cavity. According to the invention, the backwash recess has a cross-section that changes in the direction of the longitudinal axis. Preferably, the cross-section of the backwash recess tapers starting from the portafilter outlet in the direction of the longitudinal axis. According to a preferred embodiment, the cross-section of the backwash recess tapers linearly starting from the portafilter outlet in the direction of the longitudinal axis.In this way, the melt used for backflushing can be metered very precisely, ensuring that the overall system pressure remains within definable limits. According to a preferred embodiment, the cross-section has a wedge-shaped or notched basic shape. This basic shape again contributes to the precise metering of the melt used for backflushing.

[0030] According to a preferred embodiment, the filtering device has a control device which is set up and designed in such a way that it changes the position of the portafilter during backwashing of the portafilter by means of control signals in such a way that the fluid pressure in the fluid inlet channel and / or in the fluid outlet channel remains within a definable pressure range during backwashing, such that when the portafilter is moved in the backwash position range, a variable flow cross-section between the backwash supply channel and the cavity is released by means of the backwash recess.

[0031] The invention has been described above with reference to a filtration device. In a further aspect, the invention relates to a method for operating a filtration device, in particular a filtration device according to one of the preceding embodiments. The invention achieves the object described above with respect to the method with the steps: venting the cavity, moving the portafilter by means of a control signal after venting the cavity further in the direction of the filtration position such that the fluid outlet channel is initially fluidically connected to the cavity exclusively by means of the throttle recess, and moving the portafilter in the direction of the filtration position such that a fluid pressure in the fluid inlet channel and / or in the fluid outlet channel remains within a definable pressure range (claim 21).

[0032] The method utilizes the same advantages and preferred embodiments as the filtration device according to the invention, and vice versa. In this regard, reference is made to the above explanations, and their content is incorporated herein. In summary, the method according to the invention achieves that the melt within the cavity, after venting the cavity, can be accelerated very slowly and sensitively by establishing a connection to the fluid outlet channel via the throttle recess, thus ensuring that the fluid pressure in the fluid inlet channel or fluid outlet channel remains within a defined pressure range.

[0033] The method is further developed, particularly for filtration devices with backwash functionality, by the step of moving the portafilter toward the backwash position range by means of control signals such that the fluid pressure in the fluid inlet channel and / or in the fluid outlet channel remains within a definable pressure range during backwashing. Upon moving the portafilter toward the backwash position range, a variable flow cross-section is released between the backwash supply channel and the cavity by means of the backwash recess. The backwash recess is arranged between the backwash supply channel and the portafilter outlet and is fluidly connected to the cavity. In this way, even during backwashing, pressure fluctuations caused by backwashing are avoided, and larger dirt particles have no effect on the backwash behavior.

[0034] Further features and advantages of the invention emerge from the appended claims and the following description, in which exemplary embodiments are explained in detail with reference to schematic drawings.

[0035] In detail: Fig. 1 shows a first embodiment of an inventive

[0036] Filtration device in a side sectional view in a screen changing position;

[0037] Fig. 2 shows the embodiment of the filtering device according to the invention in a sectional view transverse to a portafilter longitudinal axis;

[0038] Figs. 3 and 4 show the embodiment of the filtering device according to the invention in a first venting position;

[0039] Figs. 5 and 6 show the embodiment of the filtering device according to the invention in a second venting position;

[0040] Figs. 7 and 8 show the embodiment of the filtering device according to the invention in a third venting position;

[0041] Figs. 9 to 10 show the embodiment of the filtering device according to the invention in an acceleration position range;

[0042] Fig. 11 to 12 the embodiment of the portafilter according to the invention in a

[0043] filtering position;

[0044] Figs. 13 to 15 show a second embodiment of a filtering device according to the invention in different representations in a filtering position;

[0045] Figs. 16 and 17 show the second embodiment of the portafilter according to the invention in different operating positions on the way to a backwash position; and

[0046] Figs. 18 and 19 show the second embodiment of the portafilter according to the invention in a backwash position.

[0047] Fig. 1 shows a filtration device 2 for filtering a fluid. The fluid is, in particular, a liquefied plastic. The filtration device 2 comprises a housing 4. The housing 4 has a receptacle 6 for receiving a portafilter 8. The housing 4 also has a fluid inlet channel 10 and a fluid outlet channel 12. A portafilter 8 is received in the receptacle 6. In the following description, reference is only made to the portafilter 8 arranged above. However, the explanations apply analogously to the lower portafilter 8. Each of the portafilters 8 is movably received within the receptacle 6 along a longitudinal axis 26. The portafilter 8 has a portafilter inlet 16, a portafilter outlet 18 and a cavity 20 for receiving a filter element 22. The cavity 20 is fluidly connected to the portafilter inlet 16 and the portafilter outlet 18.

[0048] In Fig. 1, the upper portafilter 8 is shown in a screen change position S. In this screen change position S, the filter element 22 can be replaced. Basically, the portafilter 8 can be moved from the screen change position S shown in Fig. 1 via a venting position range E into a filtering position F. The portafilter 8 has a throttle recess 24. The throttle recess 24 is arranged adjacent to the portafilter outlet 18 and is fluidly connected to the cavity 20. The throttle recess 24 extends along the longitudinal axis 26, starting from the portafilter outlet 18 and, viewed from the screen change position S, in the direction of the fluid outlet channel 12. The throttle recess 24 has a cross-section 28 that changes in the direction of the longitudinal axis 26. The cross section 28 of the throttle recess 24 tapers from the portafilter outlet 18 in the direction of the longitudinal axis 26, in particular linearly.The cross section 28 has a wedge-shaped basic shape 32. The portafilter 8 further has an inlet throttle recess 34 adjacent to the portafilter inlet 16.

[0049] The inlet throttle recess 34 is also fluidically connected to the cavity 20. The inlet throttle recess 34 extends along the longitudinal axis 26, starting from the portafilter inlet 16 and, viewed from the portafilter change position S shown in Fig. 1, in the direction of the fluid inlet channel 10. The inlet throttle recess 34 has a cross-section 36 that changes in the direction of the longitudinal axis 26. The portafilter 8 also has a first venting recess 40, a second venting recess 42, and a third venting recess 44. The venting recesses 40, 42, 44 fluidically connect the cavity 20 to the environment depending on the positions of the venting recesses 40, 42, 44 relative to the housing 4.

[0050] The venting recesses 40, 42, 44 extend along the longitudinal axis 26. When the portafilter 8 is moved from the screen changing position S shown in Fig. 1 in the direction of the filtering position F shown in Fig. 12, the cavity 20 is first vented via all three venting recesses 40, 42, 44, then when the portafilter 8 is moved further in the direction of the filtering position F via the first and second venting recesses 40, 42 and then when the portafilter 8 is moved further exclusively via the first venting recess 40. The second venting recess 42 has a smaller longitudinal extent along the longitudinal axis 26 than the first venting recess 40. The third venting recess 44 has a smaller longitudinal extent along the longitudinal axis 26 than the second venting recess 42. The venting recesses 40, 42, 44 are formed as a groove.

[0051] The filtration device 2 further comprises a control device 52. The control device 52 is configured and designed such that, after venting the cavity 20, it moves the portafilter 8 further in the direction of the filtration position F by means of control signals in an acceleration position range B (cf. Figures 9 and 10) such that the fluid outlet channel 12 is initially fluidly connected to the cavity 20 exclusively via the throttle recess 24, and the portafilter 8 is moved in the direction of the filtration position F such that a fluid pressure in the fluid inlet channel 10 and / or in the fluid outlet channel 12 remains within a definable pressure range.

[0052] Fig. 2 shows a sectional view of the filtering device 2 in the operating state according to Fig. 1. Figures 3 and 4 show the filtering device 2 in a first venting position. In this position, the inlet throttle recess 34 is at least partially overlapped with the fluid inlet channel 10. In other words, a fluid-conducting connection is established between the fluid inlet channel 10 and the cavity 20 via the inlet throttle recess 34 (indicated in Fig. 4 by flow arrows in the region of the fluid inlet channel 10), so that melt can flow from the fluid inlet channel 10 into the cavity 20 in a very finely controlled manner. Depending on the position of the inlet throttle recess 34 relative to the fluid inlet channel 10, a variable flow cross-section 38 is released between the cavity 20 and the fluid inlet channel 10.

[0053] In other words, during venting, the cavity 20 is fluidically connected exclusively to the fluid inlet channel 10. The venting recesses 40, 42, 44 are connected to the surroundings of the filtering device 2, so that air can flow out of the cavity 20 when melt flows into the cavity 20. As can be seen from Fig. 4, which relates to the same operating state, the venting recess 40 is fluidically connected to a first partial region 46 of the cavity 20. The venting recess 40 has a tap hole. The second venting recess 42 is fluidically connected to a second partial region 48 of the cavity 20. The third venting recess 44 is fluidically connected to a third partial region 50 of the cavity 20.

[0054] In the operating state shown in Figures 5 and 6, there is now a direct connection between the fluid inlet channel 10 and the cavity 20 through a corresponding overlap with the portafilter inlet 16. In the position shown in Figures 5 and 6, only the first venting recess 40 and the second venting recess 42 are still connected to the atmosphere. This ensures that melt is forced into the partial areas of the cavity 20 connected to the venting recesses.

[0055] Figures 7 and 8 show a further venting step in which only the first venting recess 40 is still connected to the environment, thereby venting, in particular, that portion 46 of the cavity 20 located adjacent to the filter element 22. In the acceleration position range B shown in Figures 9 and 10, the cavity 20 is completely vented, and there is a fluid-conducting connection to the fluid inlet channel 10 (indicated by flow arrows in Figure 10). The venting recesses 40, 42, 44 are no longer connected to the environment of the filtering device 2. In the state shown in Figures 9 and 10, the throttle recess 24 now comes into contact with the fluid outlet channel 12.Depending on the position of the throttle recess 24 relative to the fluid outlet channel 12, a variable flow cross-section 30 is released between the cavity 20 and the fluid outlet channel 12 in a selective and sensitive manner. By connecting the cavity 20 to the fluid outlet channel 12 via the throttle recess 24, a melt flow is initiated from the cavity 20 in the direction of the fluid outlet channel 12, in such a gentle manner that the effects on the overall system pressure remain strictly limited. After the acceleration process, the portafilter 8 is pushed further to the right in the direction of the filtration position F. In the filtration position F, the cavity 20 is fully connected to both the fluid inlet channel 10 and the fluid outlet channel 12, and the fluid passing through the filtration device 2 is filtered by means of the filter element 22. If the filter element 22 is to be changed, the portafilter 8 is inserted into the position shown in Fig.1 is shifted, and the process begins again. Figures 13 to 19 show an alternative embodiment of a filtration device 102. The filtration device 102 has a housing 104 with a receptacle 106 for receiving a portafilter 108. The housing 104 further has a fluid inlet channel 110 and a fluid outlet channel 112. Within the receptacle 106, a portafilter 108 is movably received along a longitudinal axis 126 and has a portafilter inlet 116 and a portafilter outlet 118 (see Fig. 14). The portafilter 108 further has a cavity 120 for receiving a filter element 122. As can be seen in particular from Fig. 14, the cavity 120 is fluidly connected to the portafilter inlet 116 and the portafilter outlet 118.In the state shown in Figures 13 and 14, the portafilter 108 is in a filtering position F, in which fluid to be filtered flows into the cavity 120 via the fluid inlet channel 110, is filtered therein by the filter element 122 and then leaves the cavity 120 via the fluid outlet channel 112.

[0056] The housing 104 further includes a backwash supply channel 154. The backwash supply channel 154 is configured to supply backwash fluid to the filter element 122 in a backwash position range R, starting from a clean side 156 of the filter element 122 to a dirty side 158. The housing 104 further includes a backwash channel 160. The backwash channel 160 is configured to discharge the backwash fluid after backwashing. The portafilter 108 is movable into a backwash position range in which the backwash supply channel 154 is at least partially fluidically connected to a clean side 156 of the filter element 122. The portafilter 108 further includes a backwash recess 162. The backwash recess 162 is arranged between the backwash supply channel 154 and the portafilter outlet 118 and is fluidly connected to the cavity 120.The backwash recess 162 extends along the longitudinal axis 126, starting from the portafilter outlet 118 and, viewed from the filtration position F, in the direction of the backwash supply channel 154. The backwash recess 162 has a cross-section 166 that changes in the direction of the longitudinal axis 126. The cross-section 166 of the backwash recess 162 tapers, in particular linearly, starting from the portafilter outlet 118 in the direction of the longitudinal axis 126. The cross-section 166 has a wedge-shaped basic shape 132.

[0057] The filtration device 102 further comprises a control device 152. The control device 152 is configured and designed such that it changes the position of the portafilter 108 during backwashing of the portafilter 108 by means of control signals such that the fluid pressure in the fluid inlet channel 110 and / or in the fluid outlet channel 112 remains within a definable pressure range during backwashing, such that when the portafilter 108 is moved in the backwash position range R, a variable flow cross-section 164 between the backwash supply channel 154 and the cavity 120 is released by means of the backwash recess 162.

[0058] In the state shown in Figures 13 to 15, the filtering device 102 is, as explained, in the filtering position F. Fluid or melt is supplied via the fluid inlet channel 110, enters the cavity 120, is filtered there by means of the filter element 122, and finally leaves the housing 104 via the fluid outlet channel 112 and the backwash supply channel / fluid outlet channel 154 (indicated by flow arrows in Figure 14). In the state shown in Figure 16, the portafilter 108 has been moved to the right in the plane of the drawing in such a way that a connection between the cavity 120 and the fluid outlet channel 112 is initially interrupted. If the portafilter 108 is now moved further to the right in the plane of the drawing, as shown in Figure 17, the connection to the fluid inlet channel 110 is also interrupted. At the same time, however, a connection is established between the cavity 120 and the backwash channel 160.

[0059] In the state shown in Fig. 18, the portafilter 108 has now been moved further to the right, such that the backwash recess 162 comes into contact with the backwash feed channel 154. In this way, backwash fluid (in the direction of the flow arrows), in particular already filtered plastic melt, passes from the backwash feed channel 154 via the backwash recess 162 into the cavity 120, in particular to the clean side of the filter element 156. From there, the backwash fluid passes through the filter element 122 against the filtration direction, thereby cleaning it, and finally the contaminated backwash fluid is discharged via the backwash channel 160. By means of the backwash recess 162, a variable flow cross-section 164 between the return feed channel 154 and the cavity 120 can be adjusted very finely, so that during the backwashing the effects on the overall system pressure remain within narrowly definable limits.

[0060] In addition to the above descriptions of a preferred method for operating a filtering device, the mode of operation and preferred method steps are described below with reference to the figures described.

[0061] The method for operating the filtering device 2 comprises the steps:

[0062] - Venting the cavity 20,

[0063] - Moving the portafilter 8 by means of control signals after venting the cavity 20 further in the direction of the filtering position F such that the fluid outlet channel 12 is initially fluidly connected to the cavity 20 exclusively by means of the throttle recess 24, and the portafilter 8 is moved in the direction of the filtering position F such that a fluid pressure in the fluid inlet channel 10 and / or in the fluid outlet channel 12 remains within a definable pressure range.

[0064] The preferred procedure is as follows:

[0065] - Moving the portafilter 108 in the direction of the backwash position range R by means of control signals provided by the control device 52 such that the fluid pressure in the fluid inlet channel 110 and / or in the fluid outlet channel 112 remains within a definable pressure range during backwashing, wherein upon moving the portafilter 108 in the direction of the backwash position range R, a variable flow cross-section 164 between the backwash supply channel 154 and the cavity 120 is released by means of the backwash recess 162, wherein the backwash recess 162 is arranged between the backwash supply channel 154 and the portafilter outlet 118 and is fluidly connected to the cavity 120.

[0066] List of reference symbols

[0067] 2 filter device

[0068] 4 housings

[0069] 6 Recording

[0070] 8 portafilters

[0071] 10 Fluid inlet channel

[0072] 12 Fluid outlet channel

[0073] 16 portafilter inlet

[0074] 18 Portafilter outlet

[0075] 20 cavities

[0076] 22 Filter element

[0077] 24 Throttle recess

[0078] 26 Longitudinal axis

[0079] 28 Cross section of the throttle recess

[0080] 30 variable flow cross-section at the throttle recess

[0081] 32 wedge-shaped basic shape

[0082] 34 Intake throttle recess

[0083] 36 Cross section of the intake throttle recess

[0084] 38 variable flow cross-section at the inlet throttle cutout

[0085] 40 (First) ventilation recess

[0086] 42 Second vent recess

[0087] 44 Third vent recess

[0088] 46 First part of the cavity

[0089] 48 Second part of the cavity

[0090] 50 Third part of the cavity

[0091] 52 Control device

[0092] 102 Filtration device

[0093] 104 housings

[0094] 106 recording

[0095] 108 portafilters

[0096] 110 Fluid inlet channel

[0097] 112 Fluid outlet channel

[0098] 116 portafilter inlet

[0099] 118 portafilter outlet

[0100] 120 Cavity 122 Filter element

[0101] 126 Longitudinal axis

[0102] 152 Control device

[0103] 154 Backwash feed channel / fluid outlet channel 156 Clean side of the filter element

[0104] 158 Dirty side of the filter element

[0105] 160 backwash channel

[0106] 162 Backwash recess

[0107] 164 variable flow cross-section at the backwash recess 166 cross-section of the backwash recess

[0108] 168 wedge-shaped basic form

[0109] B Acceleration position range

[0110] S Screen change position

[0111] E Vent position range

[0112] F Filtration position

[0113] Backwash position range

Claims

Claims 1. Filtration device (2) for filtering a fluid, in particular a liquefied plastic, comprising: - a housing (4) with a receptacle (6) for receiving a portafilter (8), a fluid inlet channel (10) and a fluid outlet channel (12); - a sieve carrier (8) movably mounted within the receptacle (6) along a longitudinal axis (26) having a sieve carrier inlet (16), a sieve carrier outlet (18) and a cavity (20) for receiving a filter element (22), wherein the cavity (20) is fluidly connected to the sieve carrier inlet (16) and the sieve carrier outlet (18), and wherein the sieve carrier (8) is movable from a sieve change position (S) via a venting position area (E) to a filtration position (F), characterized in that the sieve carrier (8) has a throttle recess (24) which is arranged adjacent to the sieve carrier outlet (18) and fluidly connected to the cavity (20), and which, depending on a position of the throttle recess (24) relative to the fluid outlet channel (12), provides a variable flow cross-section (30) between the cavity (20) and the fluid outlet channel (12).

2. Filtration device (2) according to claim 1, wherein the sieve carrier (8) is movable from the venting position area (E) via an acceleration position area (B) into the filtration position (F), and wherein the throttle recess (24) releases a variable flow cross-section (30) between the cavity (20) and the fluid outlet channel (12) depending on a position of the throttle recess (24) relative to the fluid outlet channel (12) in the acceleration position area (B).

3. Filtration device (2) according to one of the preceding claims, wherein the throttle recess (24) extends along the longitudinal axis (26) starting from the sieve carrier outlet (18) and viewed from the sieve change position (S) in the direction of the fluid outlet channel (12).

4. Filtration device (2) according to one of the preceding claims, wherein the throttle recess (24) has a cross-section (28) that changes in the direction of the longitudinal axis (26).

5. Filtration device (2) according to claim 4, characterized in that the cross-section (28) of the throttle recess (24) tapers from the portafilter outlet (18) in the direction of the longitudinal axis (26).

6. Filtration device (2) according to claim 4, characterized in that the cross-section (28) of the throttle recess (24) tapers linearly from the portafilter outlet (18) in the direction of the longitudinal axis (26).

7. Filtration device (2) according to one of claims 4 to 6, characterized in that the cross-section (28) has a wedge-shaped or notch-shaped basic form (32).

8. Filtration device (2) according to one of the preceding claims, wherein the fluid inlet channel (10) and the fluid outlet channel (12) are arranged in the housing (4) such that when the sieve carrier (8) is moved from the sieve change position (S) via the venting position area (E) and the acceleration position area (B) towards the filtration position (F), the cavity (20) in the venting position area (E) is initially, in particular exclusively, fluidly connected to the fluid inlet channel (10), and when the sieve carrier (8) is moved further towards the filtration position (F), the cavity (20) in the acceleration position area (B) is additionally fluidly connected to the fluid outlet channel (12) via the throttle recess (24).

9. Filtration device (2) according to claim 5, wherein the sieve carrier (8) has an inlet throttle recess (34) adjacent to the sieve carrier inlet (16), which is fluidly connected to the cavity (20), and which, depending on the position of the inlet throttle recess (34) relative to the fluid inlet channel (10) in the venting position area (E), releases a variable flow cross-section (38) between the cavity (20) and the fluid inlet channel (10).

10. Filtration device (2) according to claim 9, wherein the inlet throttle recess (34) extends along the longitudinal axis (26) starting from the sieve carrier inlet (16) and viewed in the sieve change position (S) in the direction of the fluid inlet channel (10), and / or wherein the inlet throttle recess (34) has a cross-section (36) that changes in the direction of the longitudinal axis (26).

11. Filtration device (2) according to one of claims 9 or 10, wherein the cavity (20) in the venting position area (E) is exclusively fluid-conductingly connected to the fluid inlet channel (10).

12. Filtration device (2) according to one of the preceding claims, characterized by a control device (52) which is configured and designed such that it moves the sieve carrier (8) by means of control signals after the venting of the cavity (20) further over the acceleration position range (B) in the direction of the filtration position (F) such that the fluid outlet channel (12) is initially connected to the cavity (20) exclusively by means of the throttle recess (24) in a fluid-conducting manner, and the sieve carrier (8) is moved in the direction of the filtration position (F) such that a fluid pressure in the fluid inlet channel (10) and / or in the fluid outlet channel (12) remains within a definable pressure range.

13. Filtration device (102) according to the preamble of claim 1, wherein the sieve carrier is vented in the venting position area (E) by supplying a fluid via the fluid outlet channel (12), and wherein the sieve carrier (8) has a throttle recess which is arranged adjacent to the sieve carrier inlet and is fluidly connected to the cavity (20), and which, depending on a position of the throttle recess relative to the fluid inlet channel, releases a variable flow cross-section between the cavity and the fluid inlet channel.

14. Filtration device (102) according to the preamble of claim 1 or according to any one of claims 1-12, wherein the housing (104) has a backwash supply channel (154) which is configured to supply backwash fluid to the filter element (122) in a backwash position range (R) from a clean side (156) of the filter element (122) to a dirty side (158), and a backwash channel (160) which is configured to discharge the backwash fluid after backwashing, wherein the filter holder (108) is movable into a backwash position range in which the backwash supply channel (154) is at least partially connected to a clean side (156) of the filter element (122). filter element (122) is fluid-conductingly connected, and the backwash channel (160) is at least partially fluid-conductingly connected to the dirty side (158) of the filter element (122), wherein the portafilter (108) has a backwash recess (162) which is arranged between the backwash supply channel (154) and the portafilter outlet (118) and is fluid-conductingly connected to the cavity (120), and which, depending on a position of the backwash recess (162) relative to the backwash supply channel (154) in the backwash position area (R), releases a variable flow cross-section (164) between the backwash supply channel (154) and the cavity (120).

15. Filtration device (102) according to claim 14, wherein the backflush recess (162) extends along the longitudinal axis (126) starting from the portafilter outlet (118) and viewed from the filtration position (F) in the direction of the backflush feed channel (154).

16. Filtration device (102) according to one of claims 14 or 15, wherein the backwash recess (162) has a cross-section (166) that changes in the direction of the longitudinal axis (126).

17. Filtration device (102) according to one of claims 14 to 16, characterized in that the cross-section (166) of the backflush recess (162) tapers from the portafilter outlet (118) in the direction of the longitudinal axis (126).

18. Filtration device (102) according to one of claims 14 to 17, characterized in that the cross-section (166) of the backflush recess (162) tapers linearly from the portafilter outlet (118) in the direction of the longitudinal axis (126).

19. Filtration device (102) according to one of claims 14 to 18, characterized in that the cross-section (166) has a wedge-shaped or notch-shaped basic form (132).

20. Filtration device (102) according to one of claims 14 to 19, characterized by a control device (152) which is configured and designed such that it changes the position of the portafilter (108) during backflushing of the portafilter (108) by means of control signals so that the fluid pressure in the fluid inlet channel (110) and / or in the fluid outlet channel (112) during backflushing within a definable pressure range, such that when the portafilter (108) is moved in the backflush position area (R) a variable flow cross-section (164) is released between the backflush supply channel (154) and the cavity (120) by means of the backflush recess (162).

21. Method for operating a filtration device (2), in particular a filtration device (2) according to one of the preceding claims, comprising the steps: - Venting the cavity (20), - Moving the portafilter (8) by means of control signals after venting the cavity (20) further in the direction of the filtration position (F) such that the fluid outlet channel (12) is initially connected to the cavity (20) exclusively via the throttle recess (24), and the portafilter (8) is moved in the direction of the filtration position (F) in such a way that a fluid pressure in the fluid inlet channel (10) and / or in the fluid outlet channel (12) remains within a definable pressure range.

22. Method for operating a filtration device (102), in particular a filtration device (102) according to one of claims 14-21, comprising the step: - Moving the portafilter (108) towards the backflush position area (R) by means of control signals such that the fluid pressure in the fluid inlet channel (110) and / or in the fluid outlet channel (112) remains within a definable pressure range during backflushing, wherein when moving the portafilter (108) towards the backflush position area (R) a variable flow cross-section (164) between the backflush supply channel (154) and the cavity (120) is released by means of the backflush recess (162), wherein the backflush recess (162) is arranged between the backflush supply channel (154) and the portafilter outlet (118) and is fluid-conductingly connected to the cavity (120).

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