Filtering device

Abstract

The invention relates to a filter device (10) for a fluid to be filtered, comprising a filter housing (12). The dimensions of the first opening (36a) of the through channel (36) of the filter support wall (30, 32) and the cleaning piston (66) are adapted to each other in such a way that the total area of the first opening (36a) and the region of the first opening (36a) protruding into the receiving recess (68, 70) obtains a value F1, wherein the value F1 is always the same in the action path of the cleaning piston (66) in the region of the first opening (36a) of the through channel (36) of the filter support wall (30, 32).

Description

Technical Field

[0001] The invention relates to a filter device of the type specified in the preamble of claim 1 and to a method for filtering a fluid by means of a filter device. Background Art

[0002] Such filter devices are used in plastics processing. In plastics processing plants, plastic granules, materials to be ground or powdered components are usually heated to form liquid plastics in order to subsequently process them. Plastic granules are usually made from recycled materials, which often also contain impurities due to foreign matter. Extruders are used, for example, as plastics processing plants. Extruders are conveying devices that use the operating principle of screw conveyors to uniformly press solid or even viscous substances out of a shaped opening at high pressure and temperature, for example to produce products such as flat films or blown films by extrusion. Other systems also use gear pumps for this purpose, for example.

[0003] Even when pure raw materials are used, heated viscous plastics often contain dirt particles. These dirt particles must be kept out of the plastic processing plant and the end product. For this purpose, suitable filters are used, which filter these dirt particles out of the liquid plastic. Before the raw material is further processed in the plastic processing plant, the liquid plastic is guided under pressure through a filter device.

[0004] In order to maintain a uniform process, a process pressure that is as constant as possible is required. Therefore, in the case of filter devices, the filter screen must be replaced or cleaned regularly in order to ensure uniform discharge and thus a constant process pressure.

[0005] For this purpose, different devices for changing the screens forming the filters are used. The screen changing systems currently used include piston screen changers, screen wheel filters, belt screen changers, rotary screen changers and smoothing valves. Screen changing systems usually work automatically and are driven mechanically or hydraulically. However, manual screen changing systems are also used.

[0006] DE 20 2017 007 054 U1 discloses a filter device of the same type for a fluid to be filtered. The filter device is provided with a filter housing, which comprises an inlet for entering a channel and an outlet for discharging a channel. A fluid flow, together with a filter screen and a stop wall for the filter screen, separates a first chamber and a second chamber in the filter housing from each other. The fluid flow may be a part of a piston for extending from the filter housing to replace a filter in the filter device. The fluid flow has a filter support wall including a first side and a second side away from the first side, and the filter support wall at least partially abuts against the filter screen with its second side and holds the filter screen on the stop wall. The first chamber is connected to the inlet channel, and the second chamber is connected to the outlet channel. A through-channel having corresponding openings on each side of the filter support wall is provided in the filter support wall, which is used to guide the fluid from the first chamber to the second opening through the through-channel via the first opening to filter from the first chamber to the filter screen. A through-channel having openings on each side of the stop wall is also provided in the stop wall for conducting the filtered fluid from the filter screen into the second chamber.

[0007] Furthermore, a movable cleaning piston is provided, which rests on the first side of the filter support wall by means of a guide area. The cleaning piston has at least one receiving recess arranged in the guide area, into which a part of the first opening of the filter support wall extends. Furthermore, the cleaning piston is provided with a discharge channel for discharging the backflushing fluid, so that by moving the cleaning piston along the filter support wall, a part of the filtered fluid is backflushed from the second chamber through the stop wall, the filter screen, the filter support wall via the second opening, the through-channel of the filter support wall, the first opening and the receiving recess of the cleaning piston into the discharge channel of the cleaning piston, respectively, to remove the sediment on the filter screen and the filter support wall.

[0008] In order to clean the filter screen and thus backflush the filter screen, the cleaning piston is moved continuously from a rest position outside the region of the through-channel of the filter support wall with the opening into the region of the through-channel of the filter support wall. The cleaning piston is moved over the entire region of the opening of the through-channel of the filter support wall to the relative rest position or then back to the initial rest position of the cleaning piston again.

[0009] However, a problem with this known design is that during the backflushing process, pressure fluctuations occur in the entire system, since the backflushing or subsequent backflushing of the individual backflushing zones changes the volume of filtered fluid discharged from the filter device. These pressure fluctuations can have a negative impact, for example, in the production of films or in the granulation process, in particular in the area of ​​tools such as nozzles. In the production of films, the material can tear if the pressure is too low. As in all other extrusion processes, however, quality defects can also occur in the form of different layer and wall thicknesses or granule sizes, but this should be avoided. Summary of the invention

[0010] The object of the present invention is therefore to improve a filter device of the type given in the preamble to claim 1 in such a way that, while avoiding the above-mentioned disadvantages, constant pressure conditions are achieved upstream and downstream of the filter and effective backflushing is simultaneously carried out, thereby increasing the quality of the process and the service life of the filter device.

[0011] According to a first aspect, the solution of the invention for achieving the above-mentioned objects consists in the characterizing features of claim 1 and its preamble.

[0012] The dependent claims relate to advantageous developments of the invention.

[0013] The invention is based on the recognition that the pressure during backflushing can be kept constant independently of the displacement position of the cleaning piston by matching the receiving recess of the cleaning piston to the first opening of the filter support wall so that the sum of the cross-sectional areas of the first opening extending into the receiving recess of the cleaning piston is the same over the entire movement path of the cleaning piston along the filter support wall. As a result, at least the quality of the product can be kept constant. In addition, the service life of the filter device is increased.

[0014] Furthermore, pressure fluctuations can be avoided by permanent backflushing, since pressure fluctuations in the outlet channel caused by moving the cleaning piston into the region of the opening of the filter support wall are avoided. This further improves the quality of the product achieved with this filter device.

[0015] According to the invention, the dimensions of the first opening of the filter support wall and the cleaning piston are therefore matched to one another in such a way that the total area of ​​the opening projecting into the receiving recess and the area of ​​the opening results in a value F1, wherein the value F1 is always the same within the movement path of the cleaning piston in the area of ​​the first opening of the through-channel of the filter support wall. The sum of the cross-sectional areas of the openings of the filter support wall projecting into the receiving recess of the cleaning piston is therefore always the same, regardless of the displacement position of the cleaning piston, so that pressure fluctuations which occur during displacement of the cleaning piston (for example from one row of first openings of the filter support wall to the next row of first openings) and in particular when moving from the rest position into the area of ​​the first opening of the filter support wall can be easily avoided. In this case, a permanent backflushing occurs, which increases the service life until the filter is replaced.

[0016] According to an advantageous improvement of the invention, the cleaning piston has a first and a second end position. The movement path of the cleaning piston extends between the first and the second end position. Whether in the two end positions or in the entire movement path, the value F1 always remains unchanged.

[0017] In principle, a rotating cleaning piston can be used. However, the action path of the cleaning piston relative to the filter support wall is preferably linear, in particular completely linear.

[0018] Starting from the end position of the cleaning piston in the direction of the action path, in particular, multiple rows of first openings of the through-channel of the filter support wall can be provided. In this case, the center point of a row of first openings is in a plane perpendicular to the action path of the cleaning piston. The value of the cross-sectional area of ​​a row is F2. Here, F1=K×F2, where K>0.

[0019] In this context, it has proven advantageous if adjacent rows of first openings are arranged offset to one another, in particular perpendicular to the axis of the cleaning piston, for example axially offset to the longitudinal axis and / or offset at an angle relative to the longitudinal axis.

[0020] In order to keep the design and production as simple as possible, the value F2 of the sum of the cross-sectional areas of a row of first openings corresponds to the value F1.

[0021] At least the cross section of each first opening and the cross section of the through-channel connected to the first opening can be constructed in the same way, in particular, their peripheral shapes can be constructed in the same way. Each first opening and the through-channel connected thereto can, for example, have a circular cross section with a diameter of D and a radius of R. As an alternative, each first opening and the through-channel connected thereto can also have other cross sections, such as a hexagonal or elliptical cross section.

[0022] According to one embodiment of the present invention, the distance of the accommodating recess of the cleaning piston in the moving direction of the cleaning piston is equal to or greater than the diameter D of the first opening. In this way, the cleaning piston can be kept compact in size in a simple manner.

[0023] In this case, several rows of first openings can be arranged in a certain way so that in the moving position of the cleaning piston, when K=1 and F1=F2, the first edge of the accommodating recess of this cleaning piston is aligned with the edge of a row of first openings, and these openings are completely located in the accommodating recess, and the second edge of this accommodating recess is aligned with the edge of an adjacent row of first openings and these openings are just not located in this accommodating recess.

[0024] The filter device is therefore suitable in particular for applications with higher quality requirements and is preferably suitable for integration into a plant for membrane production.

[0025] In principle, the cleaning piston can be adapted to the shape of the filter support wall. The area of ​​the flow passage corresponding to the cleaning piston and the cleaning piston are designed in a rotationally symmetrical manner. In this case, the filter support wall is adapted to the cleaning piston and the filter screen, and the stop wall is adapted to the shape of the filter support wall. This allows simple production of the cleaning piston and the flow passage.

[0026] According to one embodiment of the present invention, the filter support wall, the filter screen and the stop wall extend only within a partial circumference of the cleaning piston in the circumferential direction.

[0027] In this case, the receiving recess of the cleaning piston may include at least this partial circumference, and in particular, the receiving recess of the cleaning piston extends at least within this partial circumference in the circumferential direction.

[0028] The receiving recess of the cleaning piston is preferably designed as a groove with a channel leading to the discharge channel or extends radially inwardly to the discharge channel in the form of a cylinder segment, depending on which design is more favorable for discharging the backflushing fluid in terms of the default dimensions.

[0029] The filter screen and the stop wall can be designed in two parts, in particular, can be constructed as two identical components.

[0030] In this case, the filter support wall also has at least two regions corresponding to the filter mesh and the filter support wall, in which through-channels with openings are provided.

[0031] Finally, at least two receiving recesses may also be provided in the cleaning piston, which correspond to the regions of the filter support wall having the first opening and the through-channel.

[0032] According to one embodiment of the invention, each component of the stop wall is constructed as a cylindrical segment. This cylindrical segment extends only within a partial angle in the circumferential direction. In addition, this cylindrical segment has an outer wall that extends radially outward away from the filter screen and laterally surrounds the area with the opening. In this case, the area of ​​the stop wall with the radially outer opening is radially offset inward relative to the free end area of ​​the outer wall (i.e., the radially outward end face).

[0033] In order to ensure a secure arrangement of the stop wall and the filter screen in the flow-through body, the flow-through body at least partially surrounds the outer walls, in particular completely, as far as the end face.

[0034] The flow body with the filter screen and the stop wall and the cleaning piston arranged in the flow body can be part of a piston that can be extended from the filter housing to replace the filter screen. In this case, the individual components of the support wall and the individual components of the filter screen are arranged in the flow body in a manner that can be removable in any case.

[0035] The through-channels of the filter support wall preferably extend radially relative to the coaxial axis of the cleaning piston, and in particular these through-channels of the filter support wall are aligned with the through-channels corresponding to each other of the stop wall. In this case, these through-channels can also extend radially outwards.

[0036] According to a further aspect, the invention is based on the recognition that the quality of the end product and the service life of the filter device can be increased by permanent backflushing, in particular by means of a permanently constant amount of backflushing fluid.

[0037] According to this aspect of the invention, a method for filtering a fluid by means of a filter device, in particular a filter device as described above, is therefore provided, wherein a permanent backflushing of the filtered fluid takes place in the filter device.

[0038] In this case, the amount of backflushing fluid in the filter device remains constant.

[0039] With regard to the operation of the filter device, in particular low-viscosity fluids, preferably fluids with a viscosity between 50 Pas and 5000 Pas, are filtered.

[0040] With regard to the service life of the filter device, it is advantageous if the cleaning piston is permanently moved back and forth between the first end position and the second end position.

[0041] In this case, the movement speed of the cleaning piston may be in the range of 10% to 200%, in particular in the range of 45% to 150%, of the discharge speed of the filtered fluid / input speed of the fluid to be filtered.

[0042] The backflushing fluid amount is preferably in the range of 0.1% to 2.0%, in particular in the range of 0.5% to 1.0%, of the fluid introduced into the filter device.

[0043] The filter support wall is preferably equipped with an inner sleeve and a basic filter support wall. In this case, the inner sleeve comprises a first and a second opening as well as a through-channel. This makes it possible to implement different requirements on the material or structure of the inner sleeve and the basic filter support wall. Thus, these components can be optimized with respect to their use and the resulting material-related loads. In this case, the manufacturing process is also simplified.

[0044] According to another advantageous embodiment of the invention, the inner sleeve is detachably connected to the basic filter support wall. This allows the openings and through-channels to be optimized and adapted rheologically and fluidically to the viscosity of the medium to be processed. Furthermore, in the event of wear, for example due to abrasion caused by the permanent movement of the recoil piston, the inner sleeve can be replaced in order to ensure reliable filtration over a longer filtration time.

[0045] The cross section of the opening and the through-channel preferably has a certain height and a certain width, wherein the height is several times greater than the width, thereby ensuring that the cleaning piston has a reduced dimension in the longitudinal direction.

[0046] The cross-sectional area of ​​the opening is preferably equivalent to 65% of the cross-sectional area of ​​the receiving recess, thereby reducing the pressure at the inlet side of the filter support wall and increasing the effective filtering area.

[0047] According to another advantageous design form of the present invention, the shape of each opening corresponds to the shape of the corresponding receiving recess. This can reduce the pressure at the inlet side of the filter support wall. In addition, the flow conditions for the fluid to be filtered are also optimized.

[0048] For other advantages, features and uses of the present invention, please refer to the following description in conjunction with the embodiments shown in the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The following table of reference numerals and the corresponding reference numerals are used in the specification, claims and drawings.

[0050] Figure 1 An oblique top perspective view of a filter device according to the invention in the form of a piston screen changer with an extended piston according to a first embodiment, seen from a first side;

[0051] Figure 2 for Figure 1 an oblique top perspective view of the filter device as viewed from the second side;

[0052] Figure 3 For a retracted piston Figure 1an oblique top perspective view of the filter device as viewed from a first side;

[0053] Figure 4 for Figure 3 a first longitudinal cross-sectional view of the filter device;

[0054] Figure 5 for Figure 3 A second longitudinal cross-sectional view of the filter device, which is offset by 90° about the longitudinal axis compared to the first longitudinal cross-sectional view;

[0055] Figure 6a for Figure 3 A cross-sectional view of the filter device shown, which filter device has a first type of cleaning piston as far as the cleaning piston is concerned;

[0056] Figure 6b for Figure 3 A cross-sectional view of the filter device shown, which filter device has a cleaning piston of the second type as far as the cleaning piston is concerned;

[0057] Figure 7 for Figure 1 's perspective view, but with a stop wall that is explosively away from the arrangement;

[0058] Figure 8 is a perspective view of a piston of a filter device without a stop wall and a filter screen, whereby the filter support wall is visible;

[0059] Fig. 9 for Figure 1 A perspective view of the filter device shown with the piston partially retracted, as viewed from a first side, after a filter screen has been replaced;

[0060] Fig.10 For a filter having a two-part filter support wall Figure 4 A longitudinal cross-sectional view of the filter device shown;

[0061] Fig.11 A perspective view of a piston of a filter device with a disassembled stop wall and a slot-shaped through hole, and

[0062] Fig.12 A perspective view of an inner sleeve of a filter device with an end stop. DETAILED DESCRIPTION

[0063] Figures 1 to 10 A filter device 10 according to the invention is shown having a piston screen changer. Fig.10 A variation is shown, Fig.11 and 12Another variant of the filter device 10 according to the invention is shown. The filter device 10 comprises a housing 12 in which a piston 14 can be moved between a screen changing position and a filtering position as required. In the screen changing position, the filter screen can be replaced. In the filtering position, a fluid can flow through the filter device 10 and be filtered. Figure 1 , Figure 2 and Figure 7 In the embodiment, the piston 14 is in a screen changing position extending relative to the housing 12. Figure 3 , Figure 4 , Figure 5 , Figure 6a and Figure 6b In the embodiment shown in FIG. 1 , the piston 14 is in a filtering position retracted relative to the housing 12 .

[0064] An inlet 16 is provided laterally on the first side of the housing 12, through which a low-viscosity fluid, preferably a fluid with a viscosity between 50 Pas and 5000 Pas (e.g. a plastic fluid), is fed to the filter device 10, which flows through the filter device and is filtered, as will be described in detail below. The fluid is fed to the housing 12 via a feed line (not shown here) via the inlet 16. This feed line can be screwed to the housing 12 via a flange connection. For this purpose, the housing 12 has corresponding threaded holes 18, see for example Figure 1 and Figure 3 The screws engage in threaded holes 18 and corresponding bores in the flange of the feed line, which screws secure this flange with the feed line to the housing 12 .

[0065] Accordingly, an outlet 20 is provided on a second side of the housing 12 remote from the first side, through which the filtered fluid is conveyed away from the filter device 10 via a discharge line (not shown here) for further processing. This discharge line can also be screwed to the housing 12 via a flange connection. For this purpose, the housing 12 has corresponding threaded holes 22, for example, Figure 2 The screws engage in threaded holes 22 and corresponding bores in the flange of the discharge line, which screws secure this flange with the discharge line to the housing 12 .

[0066] The filter device 10 can be an integral component of a device for film manufacturing or granulation, for example. In this case, the filtered plastic fluid is fed to the nozzle through a discharge line for outputting the filtered plastic fluid and transferring it to the film to be output from the nozzle.

[0067] The drive of the piston 14 in the housing 12 for moving it between the screen changing position and the filtering position is known in principle and will therefore not be described in further detail.

[0068] Especially from Figure 4 and Figure 5 It can be seen that the inlet opening 16 is connected to a cylindrical inner chamber 26 in the piston 14 via an inlet line 24 extending in the housing 12 and the piston 14. The inner chamber 26 is bounded radially outwardly in the circumferential direction by an inner wall 28 of the piston 14 and two filter support walls 30 and 32 in the form of cylindrical segments. The filter support walls 30, 32 each enclose an angle of approximately 120°. The closed inner wall 28 of the piston 14 also extends between the filter support walls 30, 32 at an angle of 120°.

[0069] In each filter support wall 30, 32, a through hole 36 is introduced which is arranged radially relative to the longitudinal axis 34 of the piston 14. In this case, the through hole 36 has an identical bore cross section with an internal input port 36a and an external output port 36b, which has a consistent diameter D and thus a consistent radius R. Therefore, the input port 36a, the output port 36b and the through hole 36 all have the same radius. The center points of the input ports 36a of the through hole 36 are located in a plane, thereby forming a row of input ports 36a arranged side by side in the circumferential direction. Another row of input ports 36a is provided in a longitudinal and circumferentially staggered manner, and its center points are also located in a plane. In this case, the planes of the center points of each row are parallel to each other. Then, several other rows of inlet ports 36a of the through hole 36 are provided, which are arranged staggered with the previous row, so that the inner surface of the filter support wall 30 is almost completely composed of several rows of inlet ports 36a of the through hole 36.

[0070] In an alternative embodiment not shown, the through hole 36, the input port 36a and the output port 36b are groove-shaped in the radial direction relative to the longitudinal axis 34. In this case, the height is several times greater than the width. In this case, the cross-sectional area of ​​the through hole 36 corresponds to 75% of the cross-sectional area of ​​the receiving recesses 68, 70 of the cleaning piston 66. The shape of the through hole 36 corresponds to the shape of the receiving recesses 68, 70 of the cleaning piston 66.

[0071] Each filter support wall 30, 32 is constructed in a manner that is integrally formed with the piston 14 and of the same material and that a filter screen 38, 40 (see FIG. 1 ) that can be removed from the piston 14 is formed. Figure 6a , Figure 6b , Figure 7 ) is held to stop walls 42, 44 which can also be removed from the piston. The stop walls 42, 44 also have through holes 46 oriented radially relative to the longitudinal axis 34 of the piston 14, which are oriented relative to the through holes 36 of the filter support wall 30, in particular aligned therewith.

[0072] The stop walls 42, 44 are recessed relative to the outer circumference of the piston 14 and form a respective discharge chamber 48, 50 for the filtered fluid. The stop wall 42 has side walls 42a that laterally delimit the discharge chamber 48, which laterally completely surround the surface of the stop wall 42 with the through hole 46. Correspondingly, the stop wall 44 has side walls 44a that laterally delimit the discharge chamber 50, which laterally completely surround the surface of the stop wall 44 with the through hole 46. In the correctly installed state, the side walls 42a, 44a are flush with the outer circumference of the piston 14 on the outside. The piston 14 completely surrounds the side walls 42a, 44a on the side. The stop walls 42, 44 are held in the piston 14 by a clamping connection. The discharge chambers 48, 50 are connected to the discharge line 52. For this purpose, the side walls 42 a , 44 a have on the outside semicircular recesses 42 b , 44 b which are oriented relative to the discharge line 52 , which is designed as a semicircular recess, on the outside of the piston.

[0073] The discharge line 52 extends from the discharge chamber 48, 50 firstly transversely to the longitudinal axis 34 of the piston 14 on this piston, then along the longitudinal axis 34 of the piston 14, and finally again transversely to the longitudinal axis 34 of the piston 14, finally transitioning to the tubular region of the housing 12 and subsequently to the discharge opening 20 of the filter device 10. In the piston, the discharge line 52 has a U-shaped / semicircular cross section, which extends on the outside of the piston 14 and is limited on the side opposite to the discharge line 52 by the cylindrical inner side of the housing 12.

[0074] Two opposite sides of the receiving area 14a, 14b for the stop wall 42, 44 of the piston 14 are each provided with a plate 54, which is screwed to the piston 14 by means of screws 54a. The plate 54 has two grooves 54b in each case, so that the stop wall 42, 44 and then the filter 38, 40 can be easily removed from the piston 14. In this case, the groove 54b extends radially relative to the longitudinal axis 34 of the piston 14 or an axis parallel to the longitudinal axis 34.

[0075] A seal 56 is provided at the free end of the piston 14. Figure 8 Furthermore, a further seal 58 is provided in the piston 14 in the longitudinal direction downstream of the feed line 24 and the discharge line 52. A flow passage 14c of the piston 14 is provided between the seals 56, 58. During operation, the flow passage of the fluid through the piston 14 (i.e. through the flow passage 14c) and thus through the flow passage area of ​​the filter device 10 is sealed in the housing 12 by the seals 56, 58 in the filter position.

[0076] At the free end of the piston 14 which protrudes from the housing 12 in the filtering position, an end stop 60 is screwed onto the end face of the piston 14. For this purpose, a corresponding threaded hole 62 is provided in the piston 14. In addition, a piston rod 64 for a cleaning piston 66 which can be moved in the inner chamber 26 is guided by the end stop 60. The cleaning piston 66 is located in the inner chamber 26 and rests on the filter support walls 30, 32 and the inner wall 28 of the piston 14. The cleaning piston 66 is cylindrical and is adapted to the inner contour formed by the filter support walls 30, 32 and the inner wall 28 of the piston 14. The piston rod 64 is firmly connected to the cleaning piston 66 and extends on the side away from the end stop 60 to a drive for the cleaning piston 66 which is not shown in detail here. During the operation of the filter device, the cleaning piston 66 is continuously moved back and forth between the first end position and the second end position by the drive. In addition, the end stop 60 limits the inner chamber 26 in the longitudinal direction.

[0077] The cleaning piston 66 is provided with two identically constructed receiving recesses 68, 70 corresponding to the filter support walls 30, 32 and arranged on the circumference. The receiving recess 68 corresponds to the filter support wall 30 and the receiving recess 70 corresponds to the filter support wall 32, and the two receiving recesses extend along the circumference of the inner chamber 26 in a manner corresponding to the rows of inlet openings 36a of the filter support wall 30. The receiving recesses 68, 70 are connected to a discharge channel 72 arranged concentrically in the cleaning piston 66 for discharging backflushing fluid. During operation of the filter device 10, the cleaning piston 66 is linearly moved from a starting position at the edge of the filter support walls 30, 32 to an end position at the distal edge of the filter support walls 30, 32 and then continuously linearly moved back by means of a drive not shown here. The action path is parallel to the longitudinal axis 34 of the piston 14.

[0078] By continuously moving the cleaning piston 66 along the filter support walls 30, 32, the backflushing fluid and the sediment from the stop walls 42, 44, the filter screens 38, 40 and the filter support walls 30, 32 enter the discharge channel 72 of the cleaning piston 66. In this case, the filtered fluid flows from the discharge chambers 48, 50 through the stop walls 42, 44, the filter screens 38, 40 and the filter support walls 30, 32 again into the receiving recesses 68, 70 and the discharge channel 72 of the cleaning piston 66. The fluid contaminated with impurities / sediments is discharged in a known manner through the discharge channel 72.

[0079] The receiving recesses 68, 70 of the cleaning piston 66 extend in a portion of the inlet opening 36a of the filter support wall 30, 32. The total area of ​​the sum of the areas of the inlet opening 36a or the sub-areas of the inlet opening 36a covered by the receiving recesses 68, 70 produces a predetermined total area having a value F1. Although the number of rows of the inlet openings 36a and the sub-areas of the inlet openings 36a change continuously with the movement of the cleaning piston 66, the value F1 always remains the same within the action path of the cleaning piston 66 in the starting position and the end position.

[0080] In this case, the receiving recesses 68, 70 are at least as large as the diameter D of the through holes 36 of the filter support walls 30, 32 in the moving direction. In this case, a row of input ports 36a can be arranged in such a way that in the moving position of the cleaning piston 66, the first edges of the receiving recesses 68, 70 of the cleaning piston 66 are aligned with the edges of a row of input ports 36a and these openings are completely in the receiving recesses 68, 70. The second edges of the receiving recesses 68, 70 can be aligned with the edges of the input ports 36a of the adjacent row. The input ports 36a are just not in the recesses 68, 70.

[0081] The receiving recesses 68 , 70 are both constructed in the same way. They can be constructed as grooves with a channel leading to the discharge channel 72 or in the form of cylindrical segments extending radially inwardly to the discharge channel 72 .

[0082] Furthermore, a mounting ring 74 is movably arranged on the piston 14. The mounting ring 74 is provided with four handles 74a, 74b, 74c, 74d for moving the mounting ring 74 on the piston 14. In this case, the piston 14 has a length such that the piston 14 protrudes from the housing 12 in the filtering position by a greater amount than the ratio of the width of the mounting ring 74 to the width of the end stop 60. In the filtering position, the mounting ring 74 is arranged between the seal 56 and the end stop 60.

[0083] Each filter support wall 30, 32, filter screen 38, 40, and stop wall 42, 44 is constructed in the same manner.

[0084] The mounting ring 74 is oriented in such a way that its first stop surface 74e facing the housing 12 and its second stop surface 74f facing the end stop 60 are oriented in parallel planes. The surface of the housing 12 to which the mounting ring 74 corresponds and the surface of the end stop 60 to which the mounting ring 74 corresponds are correspondingly constructed in parallel.

[0085] If the filter screens 38, 40 are to be replaced, the piston 14 is moved from the filtering position to the filter changing position. The stop walls 42, 44 are then removed by engaging them in the recess 54b with a corresponding tool, lifting the stop walls 42, 44 and removing them from the piston 14. The filter screens 38, 40 are then engaged in the recess 54b with a corresponding tool, lifting the filter screens 38, 40 and removing them from the piston 14. The filter screens 38, 40 are replaced by inserting new filter screens 38, 40 into the piston 14 again. The stop walls 42, 44 are then inserted into the piston 14 again until the side walls 42a, 44a are aligned with the outer circumference of the piston 14. To facilitate inspection and to ensure that the stop walls 42, 44 do not come loose and protrude beyond the outer circumference of the piston 14, the mounting ring 74 is engaged on at least one of the handles 74a, 74b, 74c, 74d and pushed over the stop walls 42, 44. The mounting ring 74 remains in this position 2. Subsequently, the piston 14 moves from the screen changing position to the filtering position. In this case, the mounting ring 74 moves with its first stop surface 74e toward the corresponding surface of the housing 12. Depending on the situation, the piston 14 is moved to a certain extent so that the end stop 60 abuts against the second stop surface 74f with its surface corresponding to the removal ring 74. This ensures that during the entire movement of the piston 14, the stop walls 42 and 44 do not protrude from the outer peripheral surface of the piston under any circumstances. The filtering device 10 can then filter other fluids again.

[0086] The present invention is characterized in that the filtered fluid is permanently backflushed in the filter device 10, thereby avoiding pressure fluctuations caused by backflushing. The amount of backflushing fluid in the filter device 10 always remains constant. In this case, the cleaning piston 66 is permanently moved back and forth from the starting position to the second end position. The movement speed of the cleaning piston 66 is in the range of 10% to 200% of the discharge speed of the filtered fluid / the input speed of the fluid to be filtered, in particular in the range of 45% to 150%. The amount of backflushing fluid is in the range of 0.1% to 2% of the fluid introduced into the filter device 10, in particular in the range of 0.5% to 1%.

[0087] Fig.10 Show Figures 1 to 9 A variant of an embodiment of the invention described in the figure is a longitudinal cross-sectional view of a filter device 10. In this case, the filter device 10 has a filter support wall 76 with a two-part structure. The filter support wall 76 includes an inner sleeve 78 and a basic filter support wall 80 that accommodates and retains this inner sleeve. In this case, the inner sleeve 78 is connected to the basic filter support wall 80 in a detachable manner. During introduction, the inner sleeve 78 is centered at the front and rear ends of the inner cavity 26 along the longitudinal axis 34. In addition, Fig.10 The structure of the filter device 10 shown is identical to that explained with reference to the previous figures. Therefore, identical components are provided with the same reference numerals.

[0088] Fig.11 and 12 Another variant of an embodiment according to the present invention is shown. In these figures, the through hole 36, the input port 36a and the output port 36b are groove-shaped in the radial direction relative to the longitudinal axis 34. In this case, the height is several times greater than the width. In this case, the cross-sectional area of ​​the through hole 36 is equivalent to 75% of the cross-sectional area of ​​the receiving recesses 68, 70 of the cleaning piston 66. The shape of the through hole 36 is equivalent to the shape of the receiving recesses 68, 70 of the cleaning piston 66. In this case, the through hole 36 is introduced into the inner sleeve 78 constructed in a detachable manner. The actual filtering area is increased in a simple manner by the groove-shaped design of the through hole 36.

[0089] The present embodiment shows an extendable piston 14 having a flow passage 14c, filter support walls 30, 32, 76, filter screens 38, 40 and stop walls 42, 44. However, a plurality of extendable pistons 14 of this type may also be used.

[0090] Reference numerals list

[0091] 10Filter device with piston screen changer

[0092] 12 Shell

[0093] 14 Piston

[0094] 14a Accommodation area - left side

[0095] 14b Accommodation area - right side

[0096] 14c Fluid

[0097] 16Entrance

[0098] 18 threaded holes

[0099] 20 Exhaust port

[0100] 22 threaded holes

[0101] 24 Feeding lines

[0102] 26 Inner cavity

[0103] 28 inner wall of piston 14

[0104] 30 Filter support wall - left side

[0105] 32 Filter support wall - right side

[0106] 34 longitudinal axis of piston 14

[0107] 36 Through holes of filter support walls 30, 32

[0108] 36a Input port

[0109] 36b output port

[0110] 38 filter - left side

[0111] 40 filter-right side

[0112] 42 Stop wall - left side

[0113] 42a Side wall of stopper wall 42 - left side

[0114] 42b U-shaped recess of side wall 42a - left side

[0115] 44 Stop wall - right side

[0116] 44a Side wall of stop wall 44 - right side

[0117] 44b U-shaped recess of side wall 44a - right side

[0118] 46 The through holes of the stop walls 42 and 44

[0119] 48 Exhaust Chamber - Left Side

[0120] 50 Exhaust chamber - right side

[0121] 52 discharge pipeline

[0122] 54 Plate member for one side of the receiving area 14a, 14b of the piston 14

[0123] 54a Screws for fixing the plate 54

[0124] 54b Recesses in plate 54 for easier removal of stop walls 42, 44

[0125] 56 Seals

[0126] 58Other seals

[0127] 60 end stop

[0128] 62 threaded hole at the end surface of piston 14

[0129] 64 Piston rod for cleaning piston 66

[0130] 66 Clean the piston

[0131] 68 Recess - Left Side

[0132] 70 Accommodation notch - right side

[0133] 72 discharge channel

[0134] 74 Mounting ring

[0135] 74a Handle - Left

[0136] 74b Handle - Bottom

[0137] 74c handle-right side

[0138] 74d Handlebar-Top

[0139] 74e first contact surface - corresponding to the housing 12

[0140] 74f Second contact surface - corresponds to end stop 60

[0141] 76 filter support wall

[0142] 78 inner sleeve

[0143] 80 Basic filter support wall

Claims

1. A filter device (10) for a fluid to be filtered, comprising a filter housing (12), wherein a. a fluid passage (14c), a filter screen (38, 40) and a stop wall (42, 44) for the filter screen (38, 40) are provided in the filter housing (12), wherein the fluid passage, the filter screen and the stop wall separate the first chamber (26) and the second chamber (48, 50) from each other, b. the flow passage (14c) comprises a filter support wall (30, 32) comprising a first side and a second side remote from the first side, the filter support wall at least partially resting with its second side on the filter screen (38, 40) and holding the filter screen (38, 40) on the stop wall (42, 44), c. The first chamber (26) is connected to the inlet channel (24), and the second chamber (48, 50) is connected to the outlet channel (52), d. a through-channel (36) having corresponding openings (36a, 36b) on each side of the filter support wall (30, 32) is provided in the filter support wall (30, 32) for guiding the fluid from the first chamber (26) through the through-channel (36) via the first opening (36a) to the second opening (36b) to be filtered from the first chamber (26) to the filter screen (38, 40), e. a through-channel (46) having openings on each side of the stop wall (42, 44) is provided in the stop wall (42, 44) for guiding the filtered fluid from the filter screen (38, 40) into the second chamber (48, 50), f. A movable cleaning piston (66) is provided, wherein the cleaning piston i. abutting against the first side of the filter support wall (30, 32) by means of the guide area, ii. having at least one receiving recess (68, 70), a portion of the first opening (36a) of the filter support wall (30, 32) extends into the accommodating recess, iii. a discharge passage connected to the receiving recess (68, 70) for discharging backflushing fluid is provided so as to remove the sediment on the stop wall (42, 44), the filter screen (38, 40) and the filter support wall (30, 32) by moving the cleaning piston (66) along the filter support wall (30, 32) and by backflushing a portion of the filtered fluid from the second chamber (48, 50) through the stop wall (42, 44), the filter screen (38, 40), the filter support wall (30, 32) and the receiving recess (68, 70) of the cleaning piston (66) into the discharge passage (72) of the cleaning piston (66), It is characterized in that The dimensions of the first opening (36a) of the through-channel (36) of the filter support wall (30, 32) and the cleaning piston (66) are matched to each other in such a way that the total area of ​​the first opening (36a) and the area of ​​the first opening (36a) extending into the receiving recess (68, 70) yields a value F1, wherein the value F1 is always the same within the movement path of the cleaning piston (66) in the area of ​​the first opening (36a) of the through-channel (36) of the filter support wall (30, 32).

2. The filtering device according to claim 1, characterized in that: The cleaning piston (66) has a first and a second end position, and a movement path of the cleaning piston (66) extends between the first end position and the second end position. Whether in the two end positions or in the entire movement path, the value F1 always remains unchanged.

3. The filtering device according to claim 1 or 2, characterized in that: The movement path of the cleaning piston (66) is linear.

4. The filtering device according to claim 3, characterized in that: Starting from the end position of the cleaning piston (66) in the direction of the action path, a plurality of rows of first openings (36a) of the filter support wall (30, 32) are provided, wherein the center point of one row of the first openings (36a) is located in a plane perpendicular to the action path, and the value of the cross-sectional area of ​​one row is F2, wherein F1=K×F2 applies, wherein K>0.

5. The filtering device according to claim 4, characterized in that: A plurality of adjacent rows of first openings (36a) are arranged in a staggered manner, in particular, perpendicular to the axis of the cleaning piston (66).

6. The filtering device according to any one of claims 4 or 5, characterized in that: The value F2 of the sum of the cross-sectional areas of a row of first openings corresponds to the value F1.

7. The filter device according to any one of the preceding claims, characterized in that At least the cross-section of each first opening (36a) and the cross-section of the through-channel (36) connected to the first opening can be constructed in the same manner, in particular, their peripheral shapes can be constructed in the same manner, each first opening (36a) and the through-channel (36) connected thereto preferably have a circular cross-section with a diameter D and a radius R, and each first opening (36a) and the through-channel (36) connected thereto particularly preferably have a hexagonal cross-section.

8. The filtering device according to claim 6 or 7, characterized in that: The distance of the accommodating recesses (68, 70) of the cleaning piston (66) in the moving direction of the cleaning piston (66) is equal to or greater than the diameter D of the first opening.

9. The filtering device according to claim 8, characterized in that: The plurality of rows of first openings (36a) are arranged in a certain manner so that in the moving position of the cleaning piston (66), when K=1 and F1=F2, the first edge of the accommodating recess (68, 70) of the cleaning piston (66) is aligned with the edge of a row of first openings (36a), and the opening is completely located in the accommodating recess, and the second edge of the accommodating recess (68, 70) is aligned with the edge of an adjacent row of first openings (36a) and its opening is just not located in the accommodating recess (68, 70).

10. The filter device according to any one of the preceding claims, characterized in that For integration into systems for the production of profiles, films, sheets or pelletizing.

11. The filter device according to any one of the preceding claims, characterized in that The cleaning piston (66) is cylindrical, the filter support wall (30, 32) is adapted to the cleaning piston (66) and the filter screen (38, 40), and the stop wall (42, 44) is adapted to the shape of the filter support wall (30, 32).

12. The filtering device according to claim 11, characterized in that: The filter support wall (30, 32), the filter screen (38, 40) and the stop wall (42, 44) extend circumferentially within a partial circumference of the cleaning piston (66).

13. The filtering device according to claim 12, characterized in that: The accommodating recess (68, 70) of the cleaning piston (66) includes at least part of the circumference, and in particular, the accommodating recess (68, 70) of the cleaning piston (66) extends at least within the part of the circumference in the circumferential direction.

14. The filtering device according to claim 13, characterized in that: The receiving recess (68, 70) of the cleaning piston (66) is designed as a groove with a channel leading to the discharge channel (72) or extends radially inwardly to the discharge channel (72) in the form of a cylindrical segment.

15. The filtering device according to any one of claims 11 to 14, characterized in that The filter screens (38, 40) and the stop walls (42, 44) are designed in two parts, in particular, are constructed as two identical components.

16. The filtering device according to claim 15, characterized in that The filter support wall (30, 32) has at least two areas corresponding to the filter screen and the filter support wall, in which a through channel (36) having the openings (36a, 36b) is provided.

17. The filtering device according to claim 16, characterized in that At least two accommodation recesses (68, 70) are provided in the cleaning piston (66), the accommodation recesses corresponding to the areas of the filter support wall (30, 32) having the first opening (36a) and the through-channel (36).

18. The filtering device according to any one of claims 15 to 17, characterized in that Each part of the stop wall (42, 44) is designed as a cylindrical segment, which extends in the circumferential direction only over a partial angle and has an outer wall (42a, 44a) extending radially outwardly away from the filter screen (38, 40) and laterally surrounding a region having the opening (36b).

19. The filtering device according to claim 18, characterized in that The flow body (14c) at least partially surrounds, in particular completely surrounds, the outer wall (42a, 44a) as far as the outward end face.

20. The filter device according to any one of the preceding claims, characterized in that The fluid-passing body (14c) having the filter screens (38, 40) and the stop walls (42, 44) and the cleaning piston (66) arranged in the fluid-passing body (14c) is a part of a piston (14) that can be extended from the filter housing (12) to replace the filter screens (38, 40), wherein the individual components of the stop walls (42, 44) and the individual components of the filter screens (38, 40) are arranged in the fluid-passing body (14c) in a detachable manner.

21. The filtering device according to claim 20, characterized in that At least two extendable pistons (14) are installed, which have filters (38, 40) and stop walls (42, 44) and a cleaning piston (66) arranged in the flow-through fluid (14c).

22. The filter device according to any one of the preceding claims, characterized in that The through-channel (36) of the filter support wall (30, 32) extends radially relative to the coaxial axis of the cleaning piston (66), and in particular, the through-channel (36) of the filter support wall (30, 32) is aligned with the corresponding through-channels (46) of the stop wall (42, 44).

23. A method for filtering a fluid by means of a filter device, in particular according to any of the preceding claims, characterized in that In the filter device (10), the filtered fluid is permanently backflushed.

24. The method according to claim 23, characterized in that The amount of backflushing fluid in the filtering device (10) remains constant.

25. The method according to claim 23 or 24, characterized in that Fluids with low viscosity, preferably fluids with a viscosity between 50 Pas and 5000 Pas, are filtered.

26. The method according to any one of claims 23 to 25, characterized in that The cleaning piston (66) is permanently moved back and forth between the first end position and the second end position.

27. The method according to any one of claims 23 to 26, characterized in that The moving speed of the cleaning piston (66) is in the range of 10% to 200% of the discharge speed of the filtered fluid / the input speed of the fluid to be filtered, in particular in the range of 45% to 150%.

28. The method according to any one of claims 23 to 27, characterized in that The backflushing fluid amount is in the range of 0.1% to 2.0%, in particular in the range of 0.5% to 1.0%, of the fluid introduced into the filtering device (10).

29. The method according to any one of the preceding claims, characterized in that The filter support wall (76) is provided with an inner sleeve (78) and a base filter support wall (80), wherein the inner sleeve (78) comprises the first and second openings (36a, 36b) and the through-channel (36).

30. The method according to claim 29, characterized in that The inner sleeve (78) is detachably connected to the base filter support wall (80).

31. The method according to any one of the preceding claims, characterized in that The cross-sections of the openings (36a, 36b) and the through-channel (36) have a certain height and a certain width, wherein the height is several times greater than the width.

32. The method according to any one of the preceding claims, characterized in that The cross-sectional area of ​​the opening (36a, 36b) corresponds to 75% of the cross-sectional area of ​​the receiving recess (68, 70).

33. The method according to claim 32, characterized in that The cross-sectional shape of each opening (36a, 36b) corresponds to the cross-sectional shape of the corresponding receiving recess (68, 70).

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