Device and suction nozzle as well as method for cleaning a filter element

Abstract

Suction nozzle (24) for cleaning a filter element (15), in particular a hollow cylindrical filter element (15), with a nozzle shaft (25) and a nozzle body (26), wherein the nozzle body (26) is assigned to an inner side (28) of the filter element (15), the nozzle body (26) cleans the inner side (28) of the filter element (15) by means of negative pressure in the suction nozzle (24), and the suction nozzle (24) is connected to a nozzle distributor (18) which can move and rotate along and about a longitudinal axis (17) of the filter element (15), characterized in that the nozzle body (26) is movable relative to the nozzle shaft (25) along a common longitudinal axis (33) and thus the length of the suction nozzle (24) can be changed transversely to the longitudinal axis (17) of the filter element (15) during cleaning in order to approach the inner side (28) of the filter element (15), wherein a nozzle hood (34) is assigned to the nozzle shaft (25) and the nozzle body (26),in which an axial diaphragm ring (38) is arranged, which enables a resilient movement between the nozzle shaft (25) and the nozzle body (27), and wherein the diaphragm ring (38) in the nozzle hood (34) and / or in the nozzle body (26) is assigned at least one channel (43, 44) through which pressure can be exerted on the diaphragm ring (38) so that the diaphragm ring (38) changes its shape.

Description

The invention relates to an apparatus and a suction nozzle for cleaning a filter element according to the preamble of claims 1 and 6.Liquids, such as water, often contain impurities or suspended matter which can be of different origin and thus of different types. Thus, the suspended materials can be leaves, cereals, small stones, but also small livestock, such as mussels, algae or the like, but also lint, for example. This is particularly the case when the water is taken from a natural reservoir, such as a lake, a river or the sea.In particular when using a liquid such as water as cooling liquid for installations, such as engines on board ships, power plants, plants and for comparable purposes of use, the accumulation of suspended materials and, in particular in the case of small-scale dwellings, their multiplication leads to the installations becoming sludge and a surface crew with small-scale dwelling forming therefrom within the installations. In order to free the installations from these effects or to avoid such contamination, the liquid is conducted through filter elements. Depending on the type of use, these filter elements must be cleaned regularly so that the liquid throughput is not reduced too much.Filter systems are known, in particular back-flushing filters, in which liquid or water is conducted into a first chamber and then through a filter element into a second chamber and is subsequently supplied to the actual determination. These filter elements are cleaned from the first chamber by cleaning the inside of the filter element with a suction nozzle. In the known filter systems, this cleaning is effected by generating a negative pressure in the suction nozzles with respect to their surroundings or in the first chamber. As a result of this vacuum, the contaminants on the inside of the filter element are drawn into the suction nozzles and discharged. In order that in this way each point of the inner side of the filter element can be reached and cleaned by suction nozzles, a plurality of suction nozzles, which are associated with a nozzle distributor, are moved along a longitudinal axis of the filter element and rotated about this axis. Systems of this type are described, for example, in US 2008 / 0 047 885 A1, US 2006 / 0 043 014 A1, DE 10 2014 012 032 A1 and WO 2006 / 080 653 A1.In the known cleaning method, the suction nozzles move on constant circular paths. Due to the manufacturing process, the inside of the filter element has non-roundness or can also be deformed by intensive use of the filter element. This leads to the suction nozzles hitting the inside of the filter element and thus being damaged, or the suction nozzles are located too far away from the inside of the filter walls, so that the cleaning is possible only very inefficiently.The object of the invention is to provide a device, as well as a suction nozzle for cleaning a filter element, as well as a corresponding method for cleaning a filter element.A suction nozzle for achieving this object is characterized by the features of claim 1. Accordingly, a suction nozzle has a nozzle shaft and a nozzle body, wherein the nozzle body is movable relative to the nozzle shaft along a common longitudinal axis and thus the length of the suction nozzle transversely to the longitudinal axis of the filter element can be changed during the cleaning in order to adapt to the inner side of the filter element.The invention also provides that a nozzle hood is assigned to the nozzle shaft and the nozzle body, in which hood a spring element, namely an axial diaphragm ring, is arranged, which spring element enables a resilient movement between the nozzle shaft and the nozzle body. This resilient movement can take place in both directions along the longitudinal axis of the suction nozzle. The stroke of this resilient movement can be from a few millimeters to a few centimeters and is design-dependent. The membrane ring is preferably made of a plastic.It is also provided that the diaphragm ring in the nozzle hood and / or in the nozzle body is assigned at least one channel through which pressure can be exerted on the diaphragm ring, so that the diaphragm ring changes its shape. Such a channel has a diameter of a few millimeters up to a few centimeters and can be arranged along an outer side or inner side of the diaphragm ring. It is conceivable that a plurality of channels are assigned to the membrane ring. Due to the fact that a lower pressure prevails in the suction nozzle than in its environment, in particular in the first chamber, water passes from outside the suction nozzle through the channels and presses on the membrane ring or water is sucked from the interior of the suction nozzle out of the channels.By this pressure caused by the pressure difference inside and outside of the suction nozzle, the diaphragm ring is deformed to be increased in width. When the pressure difference decreases, the diaphragm ring deforms back into its original shape. Because the diaphragm ring is arranged between the nozzle body and the nozzle shaft, these move apart or together relative to one another and namely along the common longitudinal axis when the diaphragm ring is deformed.For the cleaning process, an electronic monitoring unit opens a valve which is connected to the nozzle distributor and thus to the suction nozzles. As a result of the water flowing out of the valve, a negative pressure relative to the surroundings thereof arises in the nozzle body or in the suction nozzle. This reduced pressure not only draws water to be purified or the substances collected on the filter element into the suction nozzle, but also deforms the membrane ring in such a way that the nozzle body moves toward the inside of the filter element. When the valve is closed, a pressure equilibrium again occurs between the nozzle distributor or suction nozzle and the surroundings thereof, with the result that the diaphragm ring and thus the nozzle body move back into their starting position again.In particular, it is provided that the nozzle body has a nozzle head with a flexible sealant, preferably fibers, brushes or a rubber or silicone body. This rubber body is preferably designed as a ring or conical hollow cylinder, the outer diameter of which is greater than that of the nozzle head. Towards a front end, the walls of the rubber body taper continuously and terminate in a narrow ridge. This burr can be smooth, but also profiled, in particular corrugated. With this burr, the rubber body comes into contact with the wall or inner side of the filter element. An inner edge region is assigned to the rubber body a ring made of metal, plastic, composite material or the like. The rubber body is bonded, shrunk on, vulcanized or, for example, screwed on via a thread to this ring. The sealing means is fastened to the nozzle body in particular by a fixing means. The ring on the inner edge region of the rubber body has a thread on an inner diameter, with which it can be screwed together with the rubber body onto the nozzle body or nozzle head. However, it is also conceivable for the ring to be glued or the like to the nozzle head. The nozzle head with the fibers, brushes or the rubber body is moved so close to the inside of the filter element as to use the cleaning pressure or to allow cleaning flows between the nozzle head and the filter element. In addition, too much water is thus prevented from being drawn from the first chamber into the suction nozzle.Preferably, the invention further provides that the flexible sealing means on the nozzle head has a diameter which tapers in a cone-like manner towards the nozzle body. This cone-like shape further improves the suction force of the suction nozzle.A further advantageous embodiment of the invention provides that the inner diameter of the nozzle body and / or of the nozzle shaft increases cone-like towards the longitudinal axis of the filter element. This cone-like increase in the inner diameters increases the flow rate in the nozzle head and thus the cleaning effect of the suction nozzle.In addition, the invention provides that the nozzle hood is sealed with respect to the nozzle shaft and the nozzle body by a liquid sealing agent and / or O-ring in a threaded region. This ensures that pressure compensation can take place only by the nozzle head or the channels.A further solution to the object mentioned at the beginning has the features of claim 6. Accordingly, it is provided that a backwash filter for filtering a liquid or water has a plurality of suction nozzles which are connected to one another by a nozzle distributor and clean the inside of a filter element. The cleaning is effected by an axial and rotational movement of the nozzle distributor, so that each point of the inner side of the filter element is scanned.A method for achieving the object mentioned at the beginning has the features of claim 7. Accordingly, it is provided that a length of at least one suction nozzle is adapted to a distance between the longitudinal axis of the filter element and the inner side of the filter element during the cleaning of a filter element. This adaptation is effected by a pressure difference between the interior of the suction nozzle and its surroundings, which leads to a nozzle body moving in the direction of the inner side of the filter element. There, the nozzle body comes into contact with the inside of the filter element and follows its circumstances or non-roundness. When the inner diameter of the filter element is reduced, the nozzle body is pressed back again, for example counter to the pressure. When the radius of the filter element is increased, the nozzle body automatically follows this increase according to the invention.Furthermore, the invention provides that during the cleaning of the filter element a nozzle body is moved relative to a nozzle shaft, the at least one suction nozzle, along a common longitudinal axis, so that the distance between the nozzle body and the inner side of the filter element remains small, in particular that the nozzle body contacts the inner side of the filter element, preferably that the distance between the nozzle body and the inner side of the filter element remains constant.In particular, it is provided that the nozzle body is moved relative to the nozzle shaft in the direction of the inner side of the filter element by a pressure acting from the outside on the at least one suction nozzle, preferably on a membrane ring, in particular by the liquid pressure prevailing in the first chamber.The invention preferably further provides that the at least one suction nozzle has a nozzle head with a flexible sealant, preferably fibers, brushes or a rubber body, with which the inner side of the filter element is cleaned. The rubber body is formed as a conically tapering hollow cylinder made of rubber, silicone or a similar material, which has a narrow ridge at a front end. This narrow ridge is moved over the inside of the filter element. Due to the increased elasticity of the ridge or of the rubber body, the latter is placed particularly closely against the filter element, which leads to a better cleaning process of the filter element. The rubber body also has an internal thread, with which the rubber body can be detachably connected to the suction nozzle and in particular can be exchanged. However, it is also conceivable for the rubber body to be firmly connected, preferably glued, to the suction nozzle.A further advantageous embodiment of the present invention provides that, for cleaning the inner side of the filter element, a nozzle distributor, the longitudinal axis of which is equal to the longitudinal axis of the filter element, has a plurality of suction nozzles and is moved along and about its longitudinal axis relative to the filter element.A preferred exemplary embodiment of the invention is explained in more detail with reference to the drawings. In these show: FIG. 1 shows a perspective view of a device for cleaning a filter element, FIG. 2 is a sectional view of the device according to the invention, FIG. 3 shows a perspective view of a suction nozzle according to the invention for cleaning a filter element, and FIG. 4 shows a section through the suction nozzle according to the invention, FIG. 5 is a perspective view of a rubber body; and FIG. 6 shows a section through the rubber body according to FIG. 5.FIG. 1 shows a device 10 in which liquids, in particular water, can be purified or filtered. For this purpose, the device 10 has an inlet opening 11 and an outlet opening 12. For cleaning or filtering the water, it passes through the inlet opening 11 into the device 10, is filtered there and passes cleaned or filtered again from the outlet opening 12 out of the device 10. Depending on the field of application and requirements for the water throughput, the device 10 can be dimensioned accordingly.Inside the device 10, it has a first chamber 13 and a second chamber 14. The two chambers 13 and 14 are separated from one another by a filter element 15. The water to be purified first passes through the inlet opening 11 into the first chamber 13 and then passes through the filter element 15 into the second chamber 14, which leaves the water purified through the outlet opening 12.The filter element 15 consists of a cylindrical wall which has screen-like openings. Depending on the field of application and requirements, these openings of the filter element 15 can be made larger or smaller. Contaminants that are introduced into the first chamber 13 with the water are filtered off by the filter element 15.In the exemplary embodiment of the present invention illustrated in FIG. 2, the first chamber 13, the second chamber 14 and the filter element 15 have a common longitudinal axis 17. This nozzle distributor 18 can be moved back and forth along the longitudinal axis 17 and rotated about the longitudinal axis 17. During this movement of the nozzle distributor 18 in the filter element 15 or in the first chamber 13, the nozzle distributor 18 is guided in end faces 19 and 20 of the filter element 15, namely in such a way that no liquid can emerge between the first chamber 13 and the second chamber 14.The nozzle manifold 18 is connected via a spindle-like coupling 21 to a motor 22 outside the device 10. Via the motor 22, the nozzle distributor can perform the translatory and rotating movement relative to the longitudinal axis 17.The nozzle distributor 18 is pipe-like and connected to a flushing outlet 29. Suction nozzles 24 are assigned to the nozzle distributor 18 on its wall 23 perpendicular to the longitudinal axis 17. These suction nozzles 24 are distributed over the entire length of the nozzle distributor 18 and enclose angles with one another. These suction nozzles 24 are likewise of tubular design and are connected to the nozzle distributor 18.The suction nozzles 24 have a nozzle shaft 25, a nozzle body 26, and a nozzle head 27. The nozzle distributor 18 can be moved via the motor 22 in such a way that the suction nozzles 24 with their nozzle heads 27 can reach any location of an inner side 28 of the filter element 15. By means of an electronic control, in particular by means of a computer-assisted, preprogrammed movement sequence, the entire inner side 28 of the filter element 15 can thus be automatically scanned.The second chamber 14 of the device 10 has a flushing outlet 29. This flushing outlet 29 is separated from a flushing line 31 by a valve 30. Because the nozzle heads 27 have an opening through which water can enter the suction nozzle 24 and thus the nozzle distributor 18, a constant pressure prevails within the device 10 when the valve 30 is closed, rather no pressure drop exists. When the valve 30 is opened, the water flows out of the apparatus 10 from the suction nozzles 24 and the nozzle distributor 18 through the flushing line 31. This opening of the valve 30 produces a pressure drop at the nozzle head 27 of the suction nozzle 24, and water from the first chamber 13 is drawn into the suction nozzle 24. Thus, at least at the nozzle heads 27 of the suction nozzles 24, a forced reversal of the liquid flow occurs.The nozzle distributor 18 is now moved by the motor 22 in such a way that each region of the inner side 28 of the filter element 15 is reached by the nozzle head 27. Due to the local vacuum between the suction nozzle 24 and its surroundings, the contaminants 16 on the inner side 28 of the filter element 15 are sucked into the suction nozzle 24 and conveyed out of the first chamber 13 through the nozzle distributor 18, the flushing outlet 29 and the flushing line 31. After the end of the cleaning or scanning of the inner side 28 of the filter element 15 by the suction nozzles 24, the valve 30 is automatically closed again and a pressure equilibrium is established again.The suction nozzle 24 according to the invention can be firmly connected to the nozzle distributor 18 via a thread 32 (FIG. 3 ). This connection by means of thread 32 is particularly advantageous for cleaning and maintenance purposes of the suction nozzle 24. A defective suction nozzle 24 can be easily replaced by a new one.The nozzle shaft 25 and the nozzle body 26 of the suction nozzle 24 have the same longitudinal axis 33. Both the inner diameter of the nozzle body 26 and of the nozzle shaft 25 are conical and increase in the direction of the nozzle distributor 18. The nozzle body 26 and the nozzle shaft 25 are connected to one another via a nozzle hood 34. This nozzle shroud 34 extends over one end of the nozzle shaft 25 to a central portion of the body 26, and the nozzle shroud 34 is fixedly connected to the nozzle shaft 25 via a seal 35. This seal can be a sealing ring or otherwise. The nozzle body 26 may move relative to the nozzle hood 34. So that no water enters between nozzle hood 24 and nozzle body 26, its contact surface is sealed by a further seal 36.The nozzle hood 34 has an annular chamber 37 which radially surrounds the part of the nozzle body facing the nozzle shaft 25. This chamber is assigned a spring element or a diaphragm ring 38 in the manner of a ring. This diaphragm ring 38 is preferably formed from a plastic or rubber and has a U-shaped cross section. The diaphragm ring 38 is associated with the chamber 37 in such a way that the apex 39 of the U-shaped cross section faces the nozzle hood 34. The flanks 40 of the U-shaped cross section of the diaphragm ring 38 are each assigned to contact surfaces 41 of the nozzle shank 25 and contact surfaces 42 of the nozzle body 26. Thus, the diaphragm ring 38 forms a resilient element which permits relative resilient movement between the nozzle shaft 25 and the nozzle body 26 along the longitudinal axis 33.The nozzle shroud 34 has channels 43 positioned directly above the apex 39 of the diaphragm ring 38. According to the invention, provision is made for channels 43 to be assigned to the diaphragm ring 38 along the entire circumference of the nozzle cap 34. The nozzle body 26 also has channels 44 at a location associated with the diaphragm ring 38. Through these channels 44, water can flow from the interior of the nozzle body 26 into the chamber 37.In the above-described cleaning process, in which the valve 30 is open, the pressure in the interior of the suction nozzle 24 is lower than outside the suction nozzle 24. in this configuration, the water outside the suction nozzle 24 pushes through the channels 43 into the chamber 37 and thus onto the vertices 39 of the membrane ring 38. As a result, the nozzle body 26 is moved relative to the nozzle shaft 25 along the longitudinal axis 33, namely toward the inner side 28 of the filter element 15. In addition, the vertex 39 of the membrane ring 38 is pulled apart by a suction effect of the channels 44 by the pressure difference, so that the relative movement of the nozzle shaft 25 and of the nozzle body 26 is further enhanced. If the channels 44 and 43 are not aligned due to relative movement between the nozzle shaft 25 and the nozzle body 26, the pressure differential decreases slightly and the relative movement reverses.Due to the pressure effect on the membrane ring 38 in the case of a prevailing pressure gradient, the nozzle head 27 is pressed against the inner side 28 of the filter element 15. In the exemplary embodiment shown in FIG. 4, the nozzle head 27 has brush-like sealing means 45. These sealing means 45 are firmly connected to the nozzle head 27. According to the invention, the sealing means 45 are guided past or contact the inner side 28 of the filter element 15 as close as possible in order to optimally use the pressure difference for cleaning the inner side 28. If the distance between the sealing means 45 and the inner side 28 is too large, water is also sucked out of the first chamber 13 directly by the suction nozzle 24. The cleaning process of the filter element 15 is thereby disturbed.As an alternative to the brush-like sealing means 45, the invention further provides a rubber body 47 as sealing means 45. This rubber body 47 is fixedly, in particular releasably, associated with the nozzle head 27 (FIG. 5 ). The rubber body 47 is designed as a hollow cylinder tapering conically towards a front end 48 (FIG. 6 ). As a result of the continuously conical course of the inner wall 49 of the hollow cylinder, an annular ridge 50 is formed at the front end 48 of the rubber body 47. This ridge 50 is formed as a pointed rubber lip. However, it is also provided according to the invention that this ridge 50 is profiled, preferably corrugated, along its circular shape. An outer wall 51 runs parallel to a longitudinal axis 52 of the rubber body 47, but it is also conceivable for the outer wall 51 to run conically or not parallel to the longitudinal axis 52. The conically shaped hollow cylinder is made of rubber, silicone or a similar material. A ring 54 is fixedly assigned to a lower inner region 53 of the hollow cylinder (FIG. 6 ). This ring 54 made of metal, plastic or the like is firmly bonded, screwed or galvanically connected to the rubber body 47. The inner diameter of the ring 54 is dimensioned such that the inner wall 49 of the hollow cylinder adjoins the latter. Furthermore, in the embodiment of the invention shown in FIG. 6, the ring 54 has an internal thread 55. The rubber body 47 or the ring 54 is screwed onto the nozzle head 27 by means of this internal thread 55. This has the advantage that in the case of a defective rubber body 47, the latter can be replaced in a simple manner. The nozzle head is schematically indicated in FIGS. 5 and 6. However, it is also conceivable for the rubber body 47 to be bonded to the nozzle head 27 or the like.To produce the rubber body 47, the latter is machined from the smaller internal diameter toward the front end 48, preferably by mechanical machining or by machining in a mold. By this manner of manufacture following the taper toward the front end burr 50, the elasticity of the rubber body 47, particularly the burr 50, is improved. The improvement in the elasticity serves primarily for better contact of the rubber body 47 on the wall 23 of the filter element 15 for suction and cleaning. In addition, the increased elasticity reduces the wear of the rubber body 47 or the burr 50 due to mechanical friction on the wall 23, thus increasing the service life.An outer diameter of the rubber body 47 is several centimeters. The inner diameter of the rubber body 47 is determined by the diameter of the nozzle head 27 and is also a few centimeters. The thickness of the wall of the hollow cylindrical rubber body 47 is a few millimeters to centimeters at a lower base 56 and tapers conically to the ridge 50. The angle between the inner wall 49 and the outer wall 51 is acute. The inner wall 49 can, however, also be asymptotically led towards the outer wall 51 and converge with the latter to form the burr 50.It should be expressly pointed out that the exemplary embodiments shown in FIGS. 5 and 6 are only schematic in nature and therefore do not correspond to reality in terms of their dimensioning and relative size ratios.Due to the production, the inner side 28 of the filter element 15 is not circular in its course, but rather wavy. Furthermore, local accumulation of contaminants 16 occurs due to the contamination of the inner side 28, and in order to ensure adequate contact between the brush-like sealing means 25 or respectively with the rubber body 47 with the inner side 28 even in the case of these irregularities in the inner side 28 of the filter element 15, the nozzle body 26 is pressed against the inner side of the filter element by the membrane ring 38 in such a way that irregularities caused by the production or contamination are compensated. If the nozzle body 26 is moved, for example, over an elevation on the inner side 28 of the filter element 15, the nozzle body 26 is pressed against the clamping force of the diaphragm ring 38 in the direction of the nozzle shaft 25. In this way, the inner side 28 of the filter element can be effectively cleaned.List of reference numbers:10 Device 11 Inlet opening 12 Outlet opening 13 First chamber 14 Second chamber 15 Filter element 16 Contaminants 17 Longitudinal axis 18 Nozzle distributor 19 End side 20 End side 21 Coupling 22 Motor 23 Wall 24 Suction nozzle 25 Nozzle shaft 26 Nozzle body 27 Nozzle head 28 Inner side 29 Flushing outlet 30 Valve 31 Flushing line 32 Thread 33 Longitudinal axis 34 Nozzle hood 35 Seal 36 Seal 37 Chamber 38 Diaphragm ring 39 Apex 40 Flank 41 Contact surface 42 Contact surface 43 Channel 44 Channel 45 Sealing means 46 Diameter 47 Rubber body 48 Front end 49 Inner wall 50 Burr 51 Outer wall 52 Longitudinal axis 53 Inner region 54 Ring 55 Inner thread 56 Base

Claims

Suction nozzle (24) for cleaning a filter element (15), in particular a hollow cylindrical filter element (15), having a nozzle shaft (25) and a nozzle body (26), wherein the nozzle body (26) is assigned to an inner side (28) of the filter element (15), the nozzle body (26) cleans the inner side (28) of the filter element (15) by means of negative pressure in the suction nozzle (24), and the suction nozzle (24) is connected to a nozzle distributor (18), which can move and rotate along and about a longitudinal axis (17) of the filter element (15), characterized in that the nozzle body (26) can be moved relative to the nozzle shaft (25) along a common longitudinal axis (33) and thus the length of the suction nozzle (24) can be changed transversely to the longitudinal axis (17) of the filter element (15) during the cleaning in order to adapt to the inner side (28) of the filter element (15), wherein the nozzle shaft (25) and the nozzle body (26) are assigned a nozzle hood (34), in which an axial membrane ring (38) is arranged, which permits a resilient movement between the nozzle shaft (25) and the nozzle body (27), and wherein the membrane ring (38) in the nozzle hood (34) and / or in the nozzle body (26) is assigned at least one channel (43, 44), through which pressure can be exerted on the membrane ring (38), so that the membrane ring (38) changes its shape.Suction nozzle (24) according to claim 1, characterised in that the nozzle body (26) has a nozzle head (27) with a flexible sealing means (45), preferably fibres or brushes, which is fastened to the nozzle body (26) in particular by a fixing means.Suction nozzle (24) according to one of the preceding claims, characterized in that the flexible sealing means (45) on the nozzle head (27) has a diameter which is tapered in a cone-like manner towards the nozzle body (26).Suction nozzle (24) according to one of the preceding claims, characterized in that the inner diameter (46) of the nozzle body (26) and / or of the nozzle shaft (25) increases in a cone-like manner towards the longitudinal axis (17) of the filter element (15).Suction nozzle (24) according to one of the preceding claims, characterized in that the nozzle hood (34) is sealed off with respect to the nozzle shaft (25) and the nozzle body (26) by a liquid sealing means (35, 36) and / or an O-ring.Device (10), in particular a back-flushing filter, for filtering a liquid, having at least two chambers (13, 14), wherein a first chamber (13) has at least one inlet opening (11) and a second chamber (14) has at least one outlet opening (12), the at least two chambers (13, 14) being separated from one another by a filter element (15), the liquid flowing from the inlet opening (11) of the first chamber (13) to the outlet opening (12) of the second chamber (14) flows through the filter element (15) and the filter element (15) can be cleaned off by means of at least one suction nozzle (24) in the first chamber (13), wherein the suction nozzle (24) can be moved along and about a longitudinal axis (17) of the first chamber (13) in order to clean off the filter element (15), characterized byat least one suction nozzle (24) according to one or more of Claims 1 to 5.Method for cleaning a filter element (15), in particular a hollow cylindrical filter element (15), which is arranged between two chambers (13, 14), namely a first chamber (13) with at least one inlet opening (11) and a second chamber (14) with at least one outlet opening (12), a liquid flowing from the inlet opening (11) of the first chamber (13) to the outlet opening (12) of the second chamber (14) flows through the filter element (15) and an inner side (28) of the filter element (15) is cleaned with at least one suction nozzle (24) according to one of Claims 1 to 5 in the first chamber (13) on the basis of a negative pressure in the suction nozzle (24), wherein the at least one suction nozzle (24) is movable along and about a longitudinal axis (17) of the filter element (15), characterized in that, a length of the at least one suction nozzle (24) is adapted to a distance between the longitudinal axis (17) of the filter element (15) and the inner side (28) of the filter element (15) during the cleaning of the filter element (15).Method according to claim 7, characterised in that during the cleaning of the filter element (15), a nozzle body (26) is moved relative to a nozzle shaft (25) of the at least one suction nozzle (24) along a common longitudinal axis (33), so that the distance between the nozzle body (26) and the inner side (28) of the filter element (15) remains small, in particular that the nozzle body (26) contacts the inner side (28) of the filter element (15), preferably that the distance between the nozzle body (26) and the inner side (28) of the filter element (15) remains constant.Method according to claim 7 or 8, characterised in that the nozzle body (26) is moved relative to the nozzle shaft (25) in the direction of the inner side (28) of the filter element (15) by a pressure acting from the outside on the at least one suction nozzle (24), preferably on a membrane ring (38), in particular by the liquid pressure prevailing in the first chamber (13).Method according to one of Claims 7 to 9, characterized in that the at least one suction nozzle (24) has a nozzle head (27) with a flexible sealant (45), preferably fibres or brushes, with which the inner side (28) of the filter element (15) is cleaned off.Method according to one of Claims 7 to 10, characterized in that, in order to clean the inner side (28) of the filter element (15), a nozzle distributor (18), the longitudinal axis (17) of which is equal to the longitudinal axis (17) of the filter element, has a plurality of suction nozzles (24) and is moved along and about its longitudinal axis (17) relative to the filter element (15).

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