DEVICE FOR FILTING A FLUID, IN PARTICULAR A PLASTIC MELTING CONTAINS, AND A VALVE ARRANGEMENT FOR SUCH A FLUID

Description

[0001] The invention relates to a device for filtering a fluid, in particular a plastic melt containing impurities, comprising a housing which has at least one inlet for introducing the fluid and one outlet for discharging the fluid, as well as a cavity formed in the housing by wall sections of the housing for receiving a filter support, and a filter support movably arranged in the cavity of the housing and having a longitudinal axis for receiving at least one filter element for filtering the fluid.

[0002] Such devices for filtering a fluid are known from the prior art. Filtration devices of this type have at least one filter holder in which one or more filter elements are arranged. The filter holder is partially recessed within a housing cavity and is movably arranged relative to it. The filter holder can be moved into a filtration position, in which fluid supplied via the housing inlet is guided through the filter of the filter holder towards the fluid outlet and filtered, and into a so-called filter change position, in which the filter holder is moved out of the housing cavity so that one or more filter elements become accessible and can be replaced or serviced. After the replacement or service process, the filter holder is returned to the filtration position and the filtration process is then continued.In filtration devices known from the prior art, the filter basket is usually arranged in the housing cavity with virtually no play. This play-free arrangement of the filter basket in the housing cavity seals the filter basket against the housing, thus preventing the escape of molten material even at high operating pressures.

[0003] However, experience with certain molten materials has shown that a high degree of tightness between the portafilter and the housing cavity can have disadvantages. For example, when processing polycarbonate melts, a phenomenon known as "cracking" can occur. Carbon layers form in the contact area between the portafilter and the housing cavity, which can cause the portafilter to become jammed in its holder and require considerable effort and force to remove. Furthermore, when processing cellulose-based lyocell melts, it has been observed that stagnation of the melt in the area between the portafilter and the housing cavity, in conjunction with the portafilter or housing material – typically steel – can form an explosive mixture, which is also undesirable.

[0004] To overcome some of the described disadvantages, EP 0 915 729 B1 proposes arranging plastic spacers on the portafilter, thereby enabling fluid flow between the portafilter and the surrounding housing in certain areas during operation. However, a disadvantage of the proposed solution is that the spacers are arranged unevenly and asymmetrically around the circumference of the portafilter, making precise guidance and, in particular, centering of the portafilter relative to the housing cavity difficult.

[0005] In some applications, the fact that the portafilter base material, usually steel, has a different coefficient of thermal expansion compared to the proposed plastics is also a disadvantage. Furthermore, the use of such spacers increases the manufacturing complexity of these portafilters, as mounting points for the spacers must be provided on the portafilter. Depending on the plastic used, the spacers are also subject to increased wear and tear and therefore need to be replaced regularly.

[0006] From DE 20 2011 106 715 U1, a device for distributing a polymer melt is also known. The device has a housing body which has at least one inlet channel and at least one outlet channel for the polymer melt, wherein at least one receiving opening extends between the at least one inlet channel and the at least one outlet channel for receiving at least one distributor body movable therein. From EP 3 308 939 A1, a flow diverting valve for an extrusion system is known.

[0007] Against this background, the invention was based on the objective of further developing a filtration device of the type described above in such a way as to eliminate the disadvantages found in the prior art as far as possible. In particular, a filtration device is to be provided that enables an exchange of the fluid between the portafilter and the housing cavity, ensures more precise guidance of the portafilter relative to the housing cavity, and is more wear-resistant.

[0008] According to the invention, the problem in the filtration device is solved by the fact that the sieve carrier has several integrally formed projections on the outside, wherein the projections are formed integrally with the sieve carrier and made of the same material and / or have a non-rotationally symmetrical cross-section and / or projections and / or recesses are formed on the wall sections of the housing that bound the cavity, such that several gaps / cavities are formed between the wall section and the sieve carrier, by means of which a small fluid flow is enabled during operation.

[0009] The invention is based on the insight gained from forming raised areas and / or recesses on the filter holder and / or on the cavity-defining wall sections of the housing, wherein the raised areas and / or recesses are integrally formed with the respective body – filter holder and / or housing – and thus integrally made of the same material. The raised areas and / or recesses result in several gaps / cavities being formed between the wall section and the filter holder, allowing fluid to flow into these gaps / cavities during operation, while minimizing fluid leakage from the device. This prevents the formation of carbon layers during the processing of polycarbonate melts or the formation of explosive mixtures during the processing of lyocell melts.

[0010] The integral design of the raised sections and / or recesses results in reduced manufacturing complexity compared to multi-part solutions using multiple materials. Both the portafilter and the housing can be manufactured from a single workpiece and machined cost-effectively using standard machining methods. Furthermore, the one-piece or integral design of the raised sections and / or recesses has the advantage that all parts of the housing and the portafilter are subject to constant thermal expansion, so that the resulting gap dimensions remain largely constant even when the device heats up or cools down. The raised sections are also subject to less wear compared to those made of plastic. This also prevents the occurrence of wear-dependent, variable gap dimensions.

[0011] According to a second aspect of the invention, or according to an advantageous embodiment of the invention according to the first aspect, it is proposed according to the invention that the filter holder has at least three, preferably four, projections on the outside and / or that projections and / or recesses are formed on the wall sections of the housing that define the cavity, which are arranged distributed along the circumference of the filter holder in such a way that the filter holder is arranged substantially centered within the cavity of the housing, such that several gaps / cavities are formed between the wall section and the filter holder, by means of which a small fluid flow is enabled during operation.

[0012] The arrangement of at least three protrusions along the circumference of the portafilter ensures that the filter pin is centered within the cavity of the housing and at the same time allows a small fluid flow between the housing and the portafilter during operation.

[0013] According to a preferred embodiment, the raised sections extend essentially in the direction of a longitudinal axis of the portafilter and in a straight line, preferably over essentially the entire length of the portafilter. Such raised section geometries are not only precise and can be manufactured using standard manufacturing processes, but also enable secure, centered, and tilt-free guidance of the portafilter within the housing cavity.

[0014] Furthermore, it is preferred that the protrusions are arranged uniformly along the circumference of the portafilter. Uniform spacing of the protrusions along the circumference of the portafilter ensures precise centering of the portafilter within the housing cavity, while simultaneously allowing a large circumferential area of ​​the portafilter to be exposed to the desired low fluid flow between the housing and the portafilter during operation.

[0015] According to a preferred embodiment, the raised sections have a height of approximately 0.05–3 mm, preferably approximately 0.1–0.2 mm, relative to the overall diameter of the portafilter. This height range has proven particularly suitable for achieving a sufficient seal between the housing and the portafilter on the one hand, and for allowing the desired low fluid flow between the components on the other.

[0016] Furthermore, according to a preferred embodiment, the raised sections are made of a wear-resistant material, in particular metal or plastic. The use of metal has the advantage of the raised sections having the same or a very similar thermal expansion relative to the housing and the filter holder, so that the resulting gap dimensions remain largely constant. Moreover, the use of plastics has proven preferable for some applications and melt materials due to the high chemical resistance of some plastics and their sliding properties.

[0017] The invention is further developed in that the portafilter has a cross-section of uniform thickness perpendicular to the longitudinal axis of the portafilter and / or the wall section of the housing that defines the cavity, which forms the projections of the portafilter and / or the projections and / or recesses of the wall sections.

[0018] A cross-section of uniform thickness is defined as one in which two opposing parallel support lines, touching the cross-section, are always equidistant from each other. The support lines must be selected such that each has at least one point in common with the boundary of the cross-section but no point in common with any part of the interior of the cross-section. Providing a cross-section of uniform thickness has proven particularly advantageous for achieving precise centering of the screen bolt relative to the housing cavity, as well as for providing a suitably dimensioned gap or cavity to allow for minimal fluid flow between the wall section and the screen carrier.

[0019] Preferably, the wall section of the housing that defines the cavity is cylindrical, with the portafilter having a cross-section of uniform thickness perpendicular to its longitudinal axis. A corresponding portafilter offers the aforementioned advantages and is compatible with existing housing systems.

[0020] According to an alternative embodiment, the portafilter is cylindrical, with the wall section of the housing that defines the cavity having a cross-section of uniform thickness.

[0021] Furthermore, it is preferred that the uniform cross-section be designed as a triangular or quadrilateral cross-section. Depending on the melt material to be processed and the desired fluid flow rate between the wall section and the screen carrier, the uniform cross-section can be suitably selected as a triangular or quadrilateral cross-section.

[0022] The invention is further developed by forming the uniform cross-section as a Reuleaux triangle. Such a triangle is based on an equilateral triangle, in which circular segments replace the legs of the triangle. The radius of these circular segments corresponds to the side length of the underlying equilateral triangle. Forming the uniform cross-section as a Reuleaux triangle offers the advantage of simple manufacturing and allows for precise centering of the portafilter relative to the wall section of the housing. The cross-sectional area is minimal compared to other uniform cross-sectional designs, resulting in an increased volume of the gaps or cavities.

[0023] According to an alternative embodiment, the portafilter has a polygonal cross-section perpendicular to its longitudinal axis and / or the wall section of the housing bounding the cavity, in particular having 3, 4, 5 or more corners, the corners preferably being rounded. According to an alternatively preferred embodiment, the portafilter has an elliptical cross-section perpendicular to its longitudinal axis and / or the wall section bounding the cavity.

[0024] Designing the portafilter cross-section or wall section cross-section as a polygon or ellipse has proven to be an alternative advantageous design to ensure sufficient and easily controllable fluid flow between the wall section and the portafilter, to center the portafilter and housing relative to each other, and to achieve cost-effective manufacturing.

[0025] The invention is further developed by arranging the sieve support so that it is radially and / or axially movable within the cavity. It has been shown that, in addition to purely axial movement of the sieve support, a radial movement component can help to reduce the formation of carbon layers during the processing of polycarbonate melts and the formation of explosive mixtures when using lyocell melts by means of a radial or combined radial-axial movement of the sieve support.

[0026] The invention has been described above with reference to a filtration device.In a further aspect, the invention relates to a valve arrangement, in particular for a polymer melt containing impurities, with a housing which has at least one inlet for introducing the fluid and at least one outlet for discharging the fluid, as well as a cavity formed in the housing by wall sections of the housing for receiving a valve pin, and a valve pin movably arranged in the cavity of the housing for selectively releasing, distributing and / or blocking the fluid flow through the housing, wherein the valve pin has several integrally formed projections and / or a non-rotationally symmetrical cross-section on the outside and / or projections and / or recesses are formed on the wall sections of the housing bounding the cavity, such that several gaps / cavities are formed between the wall section and the valve pin, by means of which a small fluid flow is enabled during operation.

[0027] Even with valve arrangements known from the prior art, the disadvantages described in relation to the filtration device arise, in particular in the processing of polycarbonate melts concerning the deposition of carbon layers between the valve housing and the valve bolt, as well as the risk of the formation of explosive mixtures in the processing of lyocell melts.

[0028] In this respect, the invention solves the problem described above with regard to the valve arrangement in that the valve bolt has a cross-section of uniform thickness perpendicular to the longitudinal axis of the valve bolt and / or the wall section of the housing that defines the cavity, which forms the projections of the valve bolt and / or the projections and / or recesses of the wall sections.

[0029] The valve arrangement utilizes the same advantages as the filtration device according to the invention. In particular, when used with polycarbonate melts, the valve arrangement prevents or reduces the deposition of carbon layers between the valve bolt and the valve housing by allowing a small fluid flow between the wall section and the valve bolt, thereby avoiding stiffness or blockage of the valve bolt and, in the case of lyocell applications, the formation of explosive mixtures.

[0030] The integral design of the raised areas and / or recesses further simplifies manufacturing, leads to predictable gap dimensions that remain largely constant even during thermal expansion, and enables a high degree of centering of the components relative to each other.

[0031] According to a further aspect of the invention or according to an advantageous embodiment of the valve arrangement according to the invention, it is proposed that the valve pin has at least three, preferably four, projections on the outside and / or that projections and / or recesses are formed on the wall sections of the housing that define the cavity, which are arranged distributed along the circumference of the valve pin in such a way that the valve pin is arranged substantially centered within the cavity of the housing, such that several gaps / cavities are formed between the wall section and the valve pin, by means of which a small fluid flow is enabled during operation.

[0032] The invention is further developed in that the projections extend essentially in the direction of the longitudinal axis of the valve pin and in a straight line, preferably essentially over the entire length of the valve pin. According to a preferred embodiment, the projections are arranged uniformly in the direction of the circumference of the valve pin. Furthermore, it is preferred that the projections have a height in the range of approximately 0.05–3 mm, preferably in the range of approximately 0.1–0.2 mm, relative to the overall diameter of the valve pin.

[0033] According to a preferred embodiment, the projections are made of a wear-resistant material, in particular metal or plastic. The invention is further developed in that the valve pin, perpendicular to the longitudinal axis of the valve pin, and / or the wall section of the housing bounding the cavity, has a cross-section of uniform thickness, which forms the projections of the valve pin and / or the projections and / or recesses of the wall sections. Preferably, the cross-section of uniform thickness is designed as a triangular or quadrilateral cross-section of uniform thickness.

[0034] Regarding the advantages of a corresponding design of the valve bolt and / or the wall section of the housing that defines the cavity, reference is made to the above statements concerning the filtration device, which are valid here in an analogous manner.

[0035] According to a preferred embodiment, the cross-section of uniform thickness is designed as a Reuleaux triangle. Such a cross-section can be manufactured with minimal effort, allows fluid flow between the wall section and the valve pin during operation, and simultaneously centers the valve pin relative to the housing.

[0036] According to an alternative embodiment, the valve bolt has a polygonal cross-section perpendicular to the longitudinal axis of the valve bolt and / or the wall section of the housing bounding the cavity, in particular having 3, 4, 5 or more corners. Preferably, the corners are rounded.

[0037] According to another alternative embodiment, the valve bolt has an elliptical cross-section perpendicular to the longitudinal axis of the valve bolt and / or the wall section bounding the cavity.

[0038] Regarding the advantages of the aforementioned embodiments, reference is made to the above statements concerning the filtration device.

[0039] The invention is further developed by designing the valve arrangement as one of the following: a shut-off valve or a distribution valve. The described valve types are frequently used in devices for processing molten plastics.

[0040] The invention is described in more detail below with reference to preferred embodiments and the accompanying figures.

[0041] This shows: Fig. 1 shows a first embodiment of a filtration device according to the invention in a perspective view; Fig. 2 shows an embodiment of the filtration device according to the invention. Fig. 1 in a side view; Fig. 3 the embodiment of the filter device according to the invention. Figure 1 and 2in a sectional view; Figs. 4, 5 further views of the filtration device according to the invention. Figures 1-3 Figs. 6, 7 show a portafilter according to the invention in a perspective view and a side view; Fig. 8a shows a cross-sectional view of the portafilter according to the invention; Fig. 8 shows an alternative embodiment of a portafilter according to the invention in a sectional view; Figs. 9-13 show an embodiment of a shut-off valve according to the invention in various views and operating states; and

[0042] Fig. 1 Figure 1 shows a filtration device 2, which has a housing 4 with a receiving cavity 8 in which a filter holder 10 is received. The filter holder 10 is movably arranged relative to the cavity 8 in the direction of a longitudinal axis 12 of the filter holder. The housing 4 has, in a manner known per se, an inlet for introducing a fluid to be filtered and an outlet for discharging the filtered fluid (not shown).

[0043] The portafilter 10 has several integrally formed portafilter protrusions 16 on its outer surface. The receiving cavity 8 of the housing 4 is cylindrical. This results in gaps or cavities 18 forming between the receiving cavity 8 and the portafilter 10 in the area of ​​housing wall sections 6, through which a small fluid flow is possible during operation. Fig. 2 shows the filter device 2 in a side view.

[0044] Fig. 3 shows the constructive design of the portafilter 10 using a sectional view, cut along the plane AA from Fig. 2The portafilter 10 has filter elements 14 by means of which the fluid is filtered. The portafilter 10 has a total of four portafilter protrusions 16 arranged at equal intervals around its circumference. The arrangement of the portafilter protrusions 16, in addition to centering the portafilter 10 in the receiving cavity 8, creates several gaps or cavities 18 between the wall section 6 and the portafilter 10, allowing fluid flow within these gaps or cavities 18 during operation.

[0045] In Fig. 4 The filter device 2 is shown in a so-called sieve-changing position. The sieve holder 10 is moved out of the housing 4 to such an extent that one of the filter elements 14 is accessible from outside the housing 4 and can be replaced or serviced. Fig. 5The filter device 2 is in an operating position in which fluid can be filtered by means of the filter elements 14. The filter elements 14 are not accessible from outside the filter device 2 in this filtering position.

[0046] The Figure 6 Figures 7 and 7 show a portafilter 10 without filter elements 14 inserted into the filter element receptacles 20. The portafilter protrusions 16 are arranged evenly spaced around the circumference of the portafilter 10 and extend in the direction of the longitudinal axis 12 of the portafilter 10 and in a straight line.

[0047] The cross-section of the portafilter 10 is in Fig. 8aThe evenly spaced arrangement of the portafilter protrusions 16 along the circumference is again illustrated. In this case, the portafilter 10 has four portafilter protrusions, although the invention is not limited to this arrangement. Rather, it is also possible to arrange three portafilter protrusions 16 on the portafilter 10, or even a larger number of portafilter protrusions 16. The protrusions 16 extend in the direction of the longitudinal axis 12 of the portafilter 10 and, in particular, in a straight line. The protrusions 16 have a height h in the range of approximately 0.05–3 mm, preferably in the range of approximately 0.1–0.2 mm, relative to the overall diameter of the portafilter 10. In this case, the protrusions 16 are made of metal, but they can also be made of another material that is resistant to distortion and wear, such as, in particular, plastic.

[0048] Fig. 8bFigure 1 shows an alternative embodiment of a portafilter 10'. The portafilter 10', which is arranged in a cylindrical receiving cavity 8, has a cross-section 22 of uniform thickness. In this case, the cross-section 22 of uniform thickness is designed as a triangular cross-section 22 of uniform thickness. Compared to the one in Figure 1, the cross-section 22 of uniform thickness is... Fig. 8a The exemplary embodiment of a portafilter 10 shown consists of the one described in the Fig. 8b The portafilter 10' shown has larger gaps or cavities 18 between the housing wall section 6 and the portafilter 10'. In principle, the design of the portafilter 10' with the uniform cross-section 22 thus enables a higher fluid flow between the receiving cavity 8 and the portafilter 10', whereby the portafilter 10' is simultaneously centered exactly in the receiving cavity 8.

[0049] The Figures 9 to 13Figure 1 shows an embodiment of a shut-off valve 102 with a housing 104, which has wall sections 106 and forms a receiving cavity 108. The shut-off valve 102 is based on the same inventive idea as the filter device 2. The housing 104 has a first inlet / outlet 120 and a second inlet / outlet 122. A valve pin 110 is arranged in the receiving cavity 108 and is axially movable relative to the housing 104 along a valve pin longitudinal axis 112.

[0050] The valve pin 110 has a continuous flow channel in the form of a preferably cylindrical bore 124, which, when it is in fluid-conducting communication with the first inlet / outlet 120 and the second inlet / outlet 122 due to a relevant positioning of the valve pin 110 relative to the housing 104, opens a channel from the first inlet / outlet 120 to the second inlet / outlet 122 and blocks a fluid flow from the first inlet / outlet 120 to the second inlet / outlet 122 when the flow channel is in non-fluid-conducting communication with the first inlet / outlet 120 and the second inlet / outlet 122.

[0051] In the Figures 9 to 11 In the operating state shown, the shut-off valve 102 is thus in a flow-through position, in which fluid flow from the first inlet / outlet 120 to the second inlet / outlet 122 is permitted. If the valve pin 110 is inserted into the Figure 12and in the position shown in Figure 13, the valve bolt 110 blocks fluid flow from the first inlet / outlet 120 to the second inlet / outlet 122. The shut-off valve 102 is located at the point shown in the Figure 12 as well as the state shown in 13 in a locked position.

[0052] The valve pin 110 has several integrally formed valve pin protrusions 116 on its outer surface. The receiving cavity 108 of the housing 104, or the corresponding housing wall sections 106, form a cylindrical cavity. This results, as is also the case analogously with the filter device 2, in gaps or cavities 118 forming in the areas between the valve pin protrusions 116 and the wall sections 106, whereby a small fluid flow is possible in these gaps or cavities 118 during operation. An arrangement of the valve pin protrusions 116 along the circumference of the valve pin 110 further ensures that it is essentially centered within the cavity 108 of the housing 104.

[0053] According to the invention, the valve pin 110 can alternatively be rotationally symmetrical, and the housing wall sections 106 can have protrusions and / or recesses. Furthermore, according to the invention, both the valve pin 110 can have integrally formed protrusions 116 and / or a non-rotationally symmetrical cross-section, and the housing wall sections 106 can themselves have protrusions and / or recesses. The valve pin 110 can be formed analogously to the illustration in Fig. 8a several elevations evenly spaced along its circumference 116 or, as in Fig. 8b shown, a cross-section of uniform thickness or a polygonal or elliptical cross-section. List of reference symbols used

[0054] 2 Filtration device 4 Housing 6 Housing wall sections 8 Receiving cavity 10, 10' Portafilter 12 Portafilter longitudinal axis 14 Filter element 16 Portafilter protrusions 18 Gap / cavity 20 Filter element receptacle 22 Uniform cross-section (triangular) h Height of protrusions 102 Shut-off valve 104 Housing 106 Housing wall sections 108 Receiving cavity 110 Valve bolt 112 Valve bolt longitudinal axis 116 Valve bolt protrusions 118 Gap / cavity 120 First inlet / outlet 122 Second inlet / outlet 124 Flow channel 202 Distributor valve 204 Housing 206 Housing wall sections 208 Intake cavity 210 Valve pin 212 Valve pin longitudinal axis 216 Valve pin protrusions 218 Gap / cavity 220 First inlet / outlet 222 Second inlet / outlet 224 Third inlet / outlet 226 Fourth inlet / outlet 228 Upper inlet / outlet

Claims

1. Filtering apparatus (2) for filtering a fluid, in particular a plastic melt having impurities, comprising a housing (4), which has at least one inlet for introducing the fluid and an outlet for delivery of the fluid and a cavity (8) formed in the housing (4) by wall portions (6) of the housing (4) for receiving a sieve support (10, 10'), a sieve support (10, 10') which is arranged movably in the cavity (6) of the housing (4) and has a longitudinal axis (12) for receiving at least one filter element (14) for filtering the fluid, characterized in that the sieve support (10, 10') externally has a plurality of integrally formed raised portions (16), wherein the raised portions (16) are formed integrally with the sieve support (10, 10') and from the same material, and / or has a non-rotationally symmetrical cross-section (22), and / or raised portions and / or recesses are formed on the wall portions (6) of the housing (4), that delimit the cavity (6), in such a way that provided between the wall portion (6) and the sieve support (10, 10') are a plurality of gaps / cavities (18), by means of which a slight fluid flow is enabled in operation.

2. Filtering apparatus (2) according to claim 1, characterized in that the sieve support (10, 10') externally has at least three, preferably four raised portions (16) and / or provided at wall portions (6) of the housing (4), that delimit the cavity (8) are raised portions and / or recesses which are arranged distributed along the periphery of the sieve support (10, 10') in such a way that the sieve support (10, 10') is arranged substantially centered within the cavity (8) of the housing (4), in such a way that provided between the wall portion (6) and the sieve support (10, 10') are a plurality of gaps / cavities (18), by means of which a slight fluid flow is enabled in operation.

3. Filtering apparatus (2) according to at least one of the preceding claims, characterized in that the raised portions (16) extend substantially in the direction of the longitudinal axis (12) of the sieve support (10, 10') and rectilinearly.

4. Filtering apparatus (2) according to at least one of the preceding claims, characterized in that the raised portions (16) are arranged uniformly spaced in the direction of the periphery of the sieve support (10, 10').

5. Filtering apparatus (2) according to at least one of the preceding claims, characterized in that the raised portions (16) are of a height (h) in the region of about 0.05 to 3 mm, preferably in the region of about 0.1 to 0.2 mm, in relation to the otherwise diameter of the sieve support (10).

6. Filtering device (2) according to at least one of the preceding claims, characterized in that the raised portions (16) are formed from a low-wear material, in particular metal or plastic.

7. Filtering device (2) according to at least one of the preceding claims, characterized in that the sieve support (10') perpendicular to the sieve support longitudinal axis (12) and / or the wall portion (6) of the housing (4), that delimits the cavity (8), is of a cross-section (22) of equal thickness, said cross-section providing the raised portions (16) of the sieve support (10) and / or the raised portions and / or recesses of the wall portions (6).

8. Filtering apparatus (2) according to claim 7, characterized in that the equal-thickness cross-section (22) is in the form of a triangular or quadrangular equal thickness cross-section (22).

9. Filtering apparatus (2) according to at least one of claims 7 or 8, characterized in that the equal-thickness cross-section (22) is in the form of a Reuleaux triangle.

10. Filtering apparatus (2) according to at least one of the preceding claims, characterized in that the sieve support (10, 10') perpendicular to the sieve support longitudinal axis (12) and / or the wall portion (6) of the housing (4), that delimits the cavity (8), is of a polygonal cross-section, the cross-section in particular having three, four, five or more corners, wherein the corners are preferably rounded.

11. Filtering apparatus (2) according to at least one of the preceding claims, characterized in that the sieve support (10, 10') perpendicular to the sieve support longitudinal axis (12) and / or the wall portion (6) of the housing (4), that delimits the cavity (8), is of an elliptical cross-section.

12. Filtering device (2) according to at least one of the preceding claims, characterized in that the sieve support (10, 10') is arranged radially and / or axially movable in the cavity (8).

13. Valve arrangement (102, 202), in particular for a plastic melt having impurities, comprising a housing (104, 204), which has at least one inlet for introduction of the fluid and at least one outlet for delivery of the fluid and a cavity (108, 208) formed in the housing (104, 204) by wall portions (106, 206) of the housing (104, 204) for receiving a valve bolt (110, 210), a valve bolt (110, 210) which is arranged movably in the cavity (108, 208) of the housing (104, 204) for selectively enabling, distributing, and / or blocking the fluid flow through the housing (104, 204), wherein the valve bolt (110, 210) externally has a plurality of integrally formed raised portions (116, 216) and / or a non-rotationally symmetrical cross-section and / or raised portions and / or recesses are formed at wall portions (106, 206) of the housing (104, 204), that delimit the cavity (108, 208), in such a way that provided between the wall portion (106, 206) and the valve bolt (110, 210) are a plurality of gaps / cavities (118, 218), by means of which a slight fluid flow is enabled in operation, characterized in that the valve bolt perpendicular to the valve bolt longitudinal axis and / or the wall portion of the housing, that delimits the cavity, is of a cross-section of equal thickness, said cross-section providing the raised portions of the valve bolt and / or the raised portions and / or the recesses of the wall portions.