DE4340275A1 - Continuous backwash filter - Google Patents

Abstract

Backwash filter with axial flow cartridge elements open at both ends during the filtration cycle and assembled concentrically. During the backwash cycle a powered mechanism presents one end of the cartridges singly, or in groups, to a dirt drain. Also claimed are cartridges with axial supports having a star-shaped cross-section with at least three edges over which a filter sleeve is fitted. Further claimed is the drive for the central shaft through a turbine driven reduction gear.

Description

The invention relates to a backwash filter with the dirty liquid to be filtered is backwashed with arranged in a circular manner in the filter housing, in The dirty liquid flowed through in the longitudinal direction Filter elements connected to the filter inlet or are connectable and for backwashing individually or in groups point at one end to a sludge drain related, powered by a rotary actuator ben flushing member can be connected.

In this known backwash filter (DE-OS 40 30 084) filter elements are used, which at one end are open to the dirty liquid side and on their connected at the other end via an annular channel are. The filter elements become this in the filtering mode known filter from its open end to the ring channel flows through. In backwash mode, at least one Filter element connected to the flushing element, so that the Dirty liquid entering the ring channel from the remaining filter elements at high speed in Counterflow to the direction of filtration through the or backwashing filter element (s) to the sludge drain flows and the filtered dirt from the fil takes the inside.  

This known filter has the disadvantage that the pressure losses especially when using smaller fil ter elements are relatively large. There is also the risk that the filter elements in the area of Clog the channel with dirt, as this is where the flow speed of the dirty liquid is only low. For backwashing the individual filter elements Dirty liquid used that is particularly strong is contaminated as it is already contaminated by others Filter elements was passed through and there the dirt concentration compared to the entrance load has increased. This is for successful backwashing a relatively large amount of dirty liquid required.

The object of the invention is to provide a backwash filter to create the kind mentioned above, in addition to a high Filtration performance with small filter dimensions a be particularly effective backwashing of the individual filter elements enables and at which the risk of clogging the Safe filter elements due to dirt can be avoided.

This object is achieved with the invention in that the filter elements in the filtering operation with their two Connect the ends to the filter inlet.

This configuration has the advantage that the filter elements Apply dirty liquid from both ends be struck and so the inflow cross section for the dirty liquid doubled in each filter element. This will make the pressure drops on the dirty liquid speed side of the filter elements significantly reduced. There the filter elements on both sides to the dirty liquid are open and flow through both ends, is the danger of clogging by dirt particles  very low. When connecting the flushing member to one end a filter element is particularly effective with backwashed unfiltered dirty liquid, the in turbulent flow in cross flow, d. H. across the fil direction through which the filter element flows. Because of against the backwash inside the filter element lower pressure levels prevailing on the outside is the cleaning of the filter element by the in Cross-flow of dirty liquid still flowing through it Filtrate flowing back inside the filter improved. Thereby becomes a very effective backwash of the filter elements also possible with small amounts of backwash liquid.

It is particularly advantageous if the filter elements are on their inlet end opposite the flushing member one or more throttle element (s) covered or can be covered. As a result, the pressure level in the backwashing filter element exactly adjustable and it it is ensured that the pressure inside the Dirty liquid flowing through the filter element on the total filter element length is lower than the pressure in the filtrate chamber surrounding the filter element. This ensures that during the backwash process nowhere in the filter element dirty liquid Filtering direction is pressed through the filter medium, but rather over the entire length of filtrate in that Can flow back inside the filter element.

The throttle element is expediently a throttle disc, which is at a distance from the inlet end and with this forms an annular gap. This configuration is particularly easy to set up and low maintenance. Since that throttle element designed as a throttle disk. in the Distance from the inlet end of the filter element can at this point on elaborate sealing surfaces or the like can be dispensed with.  

It when the throttle plate in is particularly advantageous their distance from the inlet end is adjustable. Thereby the inlet cross section of the filter to be backwashed element and thus the pressure level is precisely set become. The throttle element and the flushing member are for the purpose moderately on a common, inside the filter housing arranged rotary shaft attached. Flushing element and throttle element can then be twisted together and onto the or the filter element (s) to be backwashed become.

If the filter elements on at least two to each other concentric circles of holes can be arranged large number of them in a comparatively small space be arranged, of which then the largest number works in the filtering operation and only ever one or a few few filter elements are backwashed. This will major pressure drops due to backwashing avoided the amount of necessary for backwashing Liquid in relation to the total throughput of the filter kept low.

A particularly favorable arrangement results if that Filter housing a first inlet chamber and one with the ser second connected via a connecting line has running chamber. The connecting line is for the purpose moderately in the center of the filters arranged in circular rings elements, which is a particularly compact filter construction allowed. The filter elements can then preferably ge filter candles that run in a straight line and are open on both sides be between a first perforated ring plate and a second perforated ring plate are arranged for each fil candle a hole for the dirty liquid to pass through exhibit. In this embodiment, the filter elements elements after removing the filter housing cover can be replaced individually by lengthways  through the respective hole in one perforated plate to be pulled. It is also possible to use the entire sentence Filter candles together with a perforated plate from the filter and remove it against a new filter insert To deceive. One of the perforated ring plates suitably forms one Control mirror surface for the rinsing element, which with at least one sliding on the control mirror surface Connector is provided and the holes in his Rotating movement in an alternating sequence with the sludge drain connects. This configuration represents the dense Connection between the respective backwashing Filter elements and the rinsing element on particularly simple Way safe and is particularly wear and tear low maintenance.

If the flushing element has at least two radial flushing arms has, the one flushing arm on the filter elements outer ring and the other rinse arm the Filterele controls on the inner annulus for backwashing, can the individual filter elements on the inside and outside Ren ring with only one backwash device be rinsed. In this case a Fil same element on the inner ring and one on the outer ring cleaned in time.

The rotary shaft for the flushing member is preferably as Hollow shaft formed and forms a sludge discharge line device for the rinsing liquid. This arrangement is special it saves space and avoids expensive sealing connections se between the rotatable flushing member and a non-rotatable Sludge discharge line. The sludge discharge line can be in a sludge collection chamber with a post-filter and / or sieve in which coarse impurities such as for example, coarse fibers or the like, which after the Backwash are in the backwash sludge from the strainer too be held back before this one downstream  Sludge treatment is fed. The Nachschaltfil ter or the sieve can be a cylindrical filter surface have, which is flowed from the inside to the outside and the expediently a cleaning on the inside Direction is assigned, the rotationally fixed with the rotary shaft the flushing member is connected. When turning the rinse the cleaning device moves on the Along the inside of the filter surface and thereby removed the coarse impurities retained by this, which is then removed from the Sludge collection chamber can be removed. It is particularly advantageous if the cleaning device is equipped with mud spray nozzles, which with the Sludge discharge line are connected and from this with Are exposed to mud. The mud spray nozzles are preferably approximately tangential to the cylindrical filter surface aligned and spray over the flushing member withdrawn backwash liquid tangential to the strainer on, which is thereby both mechanically by the Cleaning device as well as hydraulically adhering impurities is cleaned.

As filter elements for the invention Backwash filters can be known filter cartridges to serve. However, filter candles are particularly suitable a support body extending in the longitudinal direction at least three mutually parallel support edges and a surrounding the support body and only on the Filter media applied to the support edges. Such Filter candle, which is also preferred with other filters can be used and has independent protection the advantage that the filter medium also inside the Candle forms a largely flat surface, which in Flow direction of the dirty liquid none of the Support body formed obstacles on which dirt particles and the filter medium  can clog. It is special with this type of candle well possible, backwashing with turbulent flow perform, with the flow rate up directly to the filter medium is very high and no eddies or the like caused by obstacles occur that favor the accumulation of dirt. Due to the smooth over the entire length of the candle, not this filter cartridge does not have an interrupted filter surface only a slight tendency to constipation, but can be also particularly light and with little liquid backwash.

The support body can have an approximately star-shaped cross section profile, the star tips of which form the supporting edges. The support body, which are made of plastic or metal then divides the filter candle into several individual, approximately triangular in cross section Filter chambers that have no connection with each other and one side of which is formed by the filter medium, that supports itself over the supporting edges around the Support body is placed. Depending on the size of the one you want The passage cross section of a filter chamber has Support body about four to six support edges, with smaller candles prefer only four supporting edges are provided so that the cross-sectional area of the individual filter chambers is still sufficiently large to the lowest possible pressure loss dirty liquid to ensure flow. For larger size candles six or more supporting edges are preferably provided, to thereby narrow the span between the supporting edges to keep.

The filter medium suitably consists of a fabric hose that is like a stocking open on both sides over the Support body can be pulled. It can be  also a particularly fine-mesh fabric with a size width of 50 µm, in special cases even le act only 25 µm. With such a fine fabric can also have very small particles in the liquid flow be held back.

The support body for the filter medium can also consist of several ren, preferably six support rods, which the Form support edges and which are at least one zen support central stiffening element, the stiffener tion element expediently from a cross section there is an annular spiral body. This shape tion is particularly advantageous if it is undesirable, the filter candle inside again to divide several individual chambers, for example then when with individual larger dirt particles in the Liquid flow is to be expected, which is due to the narrow flow cross section of the individual filter chambers stuck in this and difficult to read again sen. In this embodiment too, the filter lies with tel only a few, in the longitudinal direction of the filter candle extending support edges and otherwise forms on the Filter inside smooth surfaces on which the Dirty liquid when backwashing with great turbulence Flow along and the filtered Can take particles. The spiral body can be preferred from a steel wire in the form of a helical compression spring exist on which the support rods from the outside in eveni polygonal arrangement soldered, welded or are otherwise attached.

Further advantageous design features of the filter candle for the backwash filter according to the invention are in claims 25 to 27 indicated.

The drive for the backwashing device of the Invention  appropriate backwash filter z. B. an electric turn be drive, which is arranged on the outside of the filter and via a gearbox with the zen inside the filter tral arranged rotary shaft of the flushing member is connected.

Especially with backwash filters with continuous Backwashing, however, is beneficial if the drive a hydraulic drive with one in the liquid circuit arranged turbine wheel and a reduction gear is coupled to the rotary shaft of the flushing member. Such a hydraulic drive that also with others Filter types are used and their own worthy of protection has the advantage that electrically operated components on the filter are practical can be completely dispensed with, since it drives the Backwashing device of the liquid Fluid pressure is used.

The turbine wheel of the hydraulic drive, which is practical is an axial turbine can in the turbid inlet of the backwash filters can be arranged. In this case the sub is speed reducer, which is the high speed of the turbine in the low one required to rotate the flushing member Speed reduced, expedient in the first Inlet chamber of the filter housing in the immediate vicinity arranged to the flushing member. Especially if the in the contain dirty liquid to be filtered Dirt particles are too abrasive and the turbine or could damage the transmission, it is possible, the turbine in the filtrate drain of the filter to arrange.

In some cases it is also conceivable if the turbines wheel is arranged in the sludge drain and from the backwash liquid is driven.  

The reduction gear expediently has a Schnec kenradg gear stage so that the required sub setting the high turbine wheel speeds to the low ones Speeds of the flushing element shaft in just a few steps can follow and the gearbox is built accordingly compact is.

Further features and advantages of the invention result from the following description and the drawings, based on which the invention in preferred embodiments play is explained in more detail. It shows:

Figure 1 shows a backwash filter according to the invention in a longitudinal section.

Figure 2 shows the subject of Figure 1 in a cross section along the line II-II.

Fig. 3 is a cross section along the line III-III of FIG. 1;

Fig. 4 is a cross section along the line IV-IV of FIG. 1;

Figure 5 shows a filter element for use in the invention back-flushing filter in a longitudinal view and partly in section.

Figure 6 shows the subject of Figure 5 in a section along the line VI-VI.

Fig. 7 shows another embodiment of the Fil terkerze in a Fig. 6 corresponding cross-sectional view;

Fig. 8 shows a further embodiment of the Fil terkerze in a representation corresponding to Fig. 5; and

Fig. 9 shows the subject of Fig. 8 in a section along the line VIII-VIII.

In the drawing, 10 denotes a backflushing filter with an approximately cylindrical filter housing 11 and a housing cover 12 which closes this at the top and which is detachably connected to the filter housing with screws 13 . The filter housing 11 has in its unte ren area a filter inlet 14 arranged transversely to its longitudinal axis, which mün det into a lower inlet chamber 15 . In the central area, the filter housing 11 has a filter outlet 16 above the filter inlet 14 , through which the filtrate is discharged. The filter outlet 16 is connected to a filtrate chamber 17 , which is located above half of the lower inlet chamber and opposite the water is separated by a lower perforated ring plate 18 . Above the filtrate chamber 17 there is an upper inlet chamber 19 in the filter housing 11 , which is sealed off from the filtrate chamber 17 by a second, upper perforated ring plate 20 and which is connected to the lower filtrate chamber 15 via a central connecting line 21 .

The perforated ring plates 18 , 20 are provided with a plurality of mutually aligned bores 22 which are arranged on two circles 23 , 24 which are concentric with one another around the center of the plate. Elongated filter elements 25 or filter cartridges are arranged in the filtrate chamber between the mutually aligned bores 22 of the upper and lower perforated ring plates 20 and 18 in such a way that their upper and lower ends 26 and 27 are fastened in a sealing manner in the respective bore 22 with a connecting sleeve 28 .

Below the lower inlet chamber 15 , a sludge collecting housing 29 is flanged to the filter housing 11 , which forms a chamber and which has a sludge discharge nozzle 30 , at the outer end of which a sludge drain valve, not shown, can be flanged for the sludge discharge. The sludge collecting chamber 29 is sealed off from the lower inlet chamber 15 and connected via a hollow shaft 32 rotatably mounted in a slide bearing 31 to a flushing element 33 which is located in the lower inlet chamber 15 and has two transverse arms 34 , 35 which are designed as hollow arms . At their free ends, the arms 34 , 35 have a connector 36 in the form of a spring-loaded hollow piston 37 , which presses from below against the control surface 38 forming a lower perforated ring plate 18 . The arrangement is such that the connector 36 of one arm 34 covers the holes 22 on the outer bolt circle 23 and the connector of the second arm 35 covers the holes on the inner bolt circle upon rotation of the hollow shaft 32 , so that a fluid connection between the individual filter elements 25 and the rinsing member 33 is reached. The hollow pistons 37 each have an annular sliding coating, preferably made of wear-resistant plastic, with which they bear against the control surface 38 with a seal.

The hollow shaft 32 is rotatably connected at its upper end 39 to a connecting shaft 40 which is guided centrally in the filter housing 11 through the connecting line 21 and the upper inlet chamber 19 and is rotatably supported in the housing cover 12 in a head bearing 41 . Little un below the head bearing 41 , a throttle device 42 is attached to the connecting shaft 40 by means of a clamp 43 , which consists of a two-armed extension rod 44 and throttle disks 45 , 46 attached thereto. The arrangement is such that the one throttle plate 45 is aligned with the connector 36 of the first flushing member arm 34 and the other throttle plate 46 is aligned with the connector of the second flushing member arm 35 , so that the throttle discs when the shaft 32 , 40 rotates the bolt circles 23rd , 24 paint over the upper perforated ring plate 20 . The throttle disks 45 , 46 are fastened to the extension rod 44 by means of adjusting screws 47 and can thus be adjusted in position and distance a to the upper perforated ring plate 20 .

To drive the Rückspüleinrich device described above, a hydraulic drive 48 is provided in the lower inlet chamber 15 of the filter 10 , which consists of a turbine shaft 49 with an axial turbine wheel 50 arranged in the filter inlet 14 and a reduction worm gear 51 , the output shaft 52 of which is connected to the hollow shaft 32 is coupled via a step-down gear drive 53 .

The hollow shaft 32 opens out with its lower end 55 , which projects into the sludge collecting chamber 29, into a sludge distributor 56 and is connected to it in a rotationally fixed manner. The sludge distributor 56 is rotatably mounted centrally on the bottom 57 of the sludge collecting housing 29 and has an axial bore 58 and a radial bore 59 connected to it, which opens into a carrier tube 60 with a cleaning device 61 attached to it for a switching sieve 62 , one of which forms cylindrical filter or screen surface 63 in the sludge collecting housing 29 . From the cleaning device 61 consists essentially of a tube piece 64 closed at the top and bottom with a quadratic cross-section in which a plurality of mud spray nozzles 65 are fastened in such a way that their spray direction is approximately tangent to the secondary sieve 62 .

The filter described works as follows:

The dirty liquid loaded with dirt particles enters the filter housing 11 through the filter inlet 14 and fills the lower inlet chamber 15 and, via the central connecting line 21, the upper inlet chamber 19 . The incoming dirty liquid drives the axial turbine wheel 50 and thus rotates the rotary shaft for the flushing element 33 , throttle device 42 and cleaning device 61 via the reduction gear 51 , 52 .

The dirty and non-backwashed filter elements are equally flowed through from the lower and upper ends, the filtrate collecting in the filtrate chamber 17 and leaving the filter via the filter outlet 16 . The filter elements in each case be backwashed - in Fig. 1 the outer filter element on the left filter side and the inner filter elements on the right filter side - are connected at their lower end 27 with the flushing member 33 and at their upper end 26 of the Throttle disks 45 , 46 covered with the formation of an annular gap 66 . In this position of the flushing member and throttle device, dirty liquid flows out of the upper inlet chamber 19 into the filter candles 25 to be cleaned, whereby when it flows through the annular gap 66 it loses so much of its pressure that the liquid pressure inside the filter candles to be cleaned is less than the pressure in the the filtrate chamber 17 surrounding the candles 25 . Due to this pressure drop, the candles are not only flowed through from top to bottom with dirty fluid of high turbulence and speed, but additionally, filtrate flows back over the entire length of the filter candle from the filtrate collecting chamber 17 into the interior of the filter candle, as indicated by the arrows 67 in FIG. 1 is. This results in a particularly effective cleaning of the filter web on the inside of the filter elements.

The filter sludge is then passed through the flushing member 33 and the hollow shaft 32 into the sludge distributor 56 and from there to the cleaning device 61 and sprayed approximately tangentially from the inside onto the cylindrical secondary filter 62 via the sludge spray nozzles 65 . The secondary sieve is relatively coarse-meshed and serves to retain particularly coarse impurities which are scraped off by the cleaning device 61 rotating along the sieve and collect on the bottom 57 of the sludge collecting chamber 29 , where they can be removed from the filter via a drain device (not shown). The sludge thus freed from coarse impurities leaves the filter via the sludge discharge nozzle 30 .

The purge element is used together with the throttle device continuously rotated and thus cleans at one complete rotation of all filter elements one after the other from.

5 to 9 show filter candles 25 as Trains t before can be used in the backwash filter according to the invention, the Fig.. The Filterker shown in FIGS. 5 and 6 ze consists of a star-shaped in cross-section support body 70 with six star points 71 that form at their free ends supporting edges 72 for the existing of a fabric tube 73 filter means 74, such as a stocking over the Support body is pulled. At the front and rear end 26 and 27 , the filter candle 25 is provided with a connecting sleeve 28 each with an approximately circular cross section 75 , which are plugged onto the star tips 71 . The fabric hose 73 covers the connecting sleeves 28 on their outer circumference and is clamped there by means of clamps 76 . As can be seen in particular from FIG. 6, the filter candle in this embodiment 6 has approximately triangular Fil terkkammer 77 in cross section, which are limited on the one hand by the star tips 71 and on the other hand by fabric hose 73 . It can be seen that the filter fabric in this case forms a smooth surface 78 which has no obstacles in the direction of flow of the dirty liquid, at which eddy particles can form and accumulate. Rather, it is in this arrangement that the flow of the dirt or Rückspülflüs liquid along the filter medium 73 can be close to this in the turbulent range, so that a particularly good cleaning of the candle during backwashing follows.

The embodiment of the filter candle shown in FIG. 7 is particularly suitable for small nominal candle diameters. Here, the support body 70 has only four Sternspit zen 71 , over which the fabric tube 73 is pulled and on the support edges 72 is supported. The connection sleeves 28 are arranged in this case over the fabric hose and clamp this between itself and the support body.

FIGS. 8 and 9 show a particularly advantageous Substituted staltung of the filter candle. In this case, the support body 70 consists of six support rods 79 with a circular cross-section, which are connected on their inner side 80 with a reinforcement element 81 designed in the manner of a helical compression spring. Both the stiffening element 81 and the support rods 79 are made of steel wire and can be welded or soldered to one another in a simple manner. On its outside 82 bil the support rods 79, the supporting edges for the Filterge webe, which can consist of a wire mesh hose and pulled over the support body and attached to the end sleeves 28 attached in a suitable manner. In this embodiment too, the filter medium forms smooth surfaces 78 on the inside of the candle, on which the backwashing liquid can flow unhindered.

The invention is not based on the embodiment described example limited, but there are a variety of Changes possible without ver ver the scope of the invention to let. So it is possible, for example, the hydraulics drive for the flushing element at the filter outlet or even at Arrange sludge drain. It is also possible instead a hydraulic motor an electric motor drive to provide what can be particularly useful if the backwash of the filter elements is discontinuous to be carried out. The sludge to be discharged can also directly, d. H. not over the sludge discharge chamber the filter. Instead of the throttle other throttle elements, e.g. B. Dros selblende or the like. If used in detail case is advantageous. For large filter capacities can Concentrate the filter elements in three or more rings be arranged around each other.

Claims (33)

1. Backwash filter, which can be backwashed with the dirt to be filtered, with filter elements arranged in a circle with respect to one another in the filter housing, flowed through in the longitudinal direction, which are connected or connectable to the fil ter inlet and for backwashing individually or in groups with one end to one a sludge drain connected, driven by a rotary drive flushing member, characterized in that the filter elements ( 25 ) are in filtering operation with their two ends ( 26 , 27 ) with the filter inlet ( 14 ) in connection. 2. Backwash filter according to claim 1, characterized in that the filter elements ( 25 ) on their flushing member ( 33 ) opposite inlet end ( 26 ) with one or more throttle element (s) ( 45 , 46 ) are covered or can be covered. 3. Backwash filter according to claim 1 or 2, characterized in that the throttle element ( 45 or 46 ) is a throttle disc which is at a distance (a) from the inlet end ( 26 ) and forms an annular gap ( 66 ) with this. 4. Backwash filter according to one of claims 1 to 3, characterized in that the throttle disc ( 45 or 46 ) in its distance (a) to the inlet end ( 20 ) is adjustable. 5. Backwash filter according to one of claims 1 to 4, characterized in that the or the throttle element (s) ( 45, 46 ) and the flushing member ( 33 ) on a common, arranged in the interior of the filter housing rotating shaft ( 32 , 40 ) attached are. 6. Backwash filter according to one of claims 1 to 5, characterized in that the filter elements ( 25 ) are arranged on at least two concentric circles ( 23 , 24 ). 7. Backwash filter according to one of claims 1 to 6, characterized in that the filter housing ( 11 ) has a first inlet chamber ( 15 ) and with this via a connecting line ( 21 ) connected second inlet chamber ( 19 ). 8. Backwash filter according to one of claims 1 to 7, characterized in that the connecting line ( 21 ) in the center of the annular elements ( 23 , 24 ) arranged filter elements ( 25 ). 9. backwash filter according to one of claims 1 to 8, characterized in that the filter elements ( 25 ) are rectilinear open-ended filter cartridges on both sides, which are arranged between a first perforated ring plate ( 18 ) and a second perforated ring plate ( 20 ) for each filter candle ( 25 ) have a hole ( 22 ) for the dirt liquid passage. 10. Backwash filter according to one of claims 1 to 9, characterized in that one of the perforated ring plates ( 18 ) forms a control mirror surface ( 38 ) for the flushing member ( 33 ) which with at least one on the control mirror surface ( 38 ) sliding connector ( 36 ) is provided and connects the holes ( 22 ) during its rotary movement in an alternating sequence with the sludge drain ( 32 ). 11. Backwash filter according to one of claims 1 to 10, characterized in that the flushing member ( 33 ) has at least two radial flushing arms ( 34 , 35 ), the one flushing arm ( 34 ) the filter elements ( 25 ) on the outer ring ( 23 ) and the other rinsing arm ( 35 ) controls the filter elements ( 25 ) on the inner annulus ( 24 ) for backwashing. 12. Backwash filter according to one of claims 1 to 11, characterized in that the rotary shaft ( 32 ) for the flushing member ( 33 ) is designed as a hollow shaft and forms a sludge discharge line. 13. Backwash filter according to one of claims 1 to 12, characterized in that the sludge discharge line ( 32 ) in a Schlammsam melkammer ( 29 ) with a secondary filter and / or sieve ( 62 ) opens. 14. Backwash filter according to one of claims 1 to 13, characterized in that the secondary filter ( 62 ) has a cylindrical Fil terfläche ( 63 ) which is flowed through from the inside to the outside. 15. Backwash filter according to one of claims 1 to 14, characterized in that the filter surface ( 63 ) on its inside is assigned a cleaning device ( 61 ) which is rotatably connected to the rotary shaft ( 32 ) of the flushing member ( 33 ). 16. Backwash filter according to one of claims 1 to 15, characterized in that the cleaning device ( 61 ) is provided with sludge spray nozzles ( 65 ) which are connected to the sludge discharge line ( 32 ) and are acted upon by this with sludge. 17. Backwash filter according to one of claims 1 to 16, characterized in that the mud spray nozzles ( 65 ) are aligned approximately tangentially to the cylindrical filter surface ( 63 ). 18, filter candle, in particular for backwash filter according to one of claims 1 to 17, characterized marked by a in the longitudinal direction Ker extending support body ( 70 ) with at least three mutually parallel support edges ( 72 ) and one surrounding the support body ( 70 ) and only on the support edges ( 72 ) filter means ( 74 ). 19. Filter candle according to claim 18, characterized in that the support body ( 70 ) has an approximately star-shaped cross-sectional profile, the star tips ( 71 ) form the support edges ( 72 ). 20. Filter candle according to claim 18 or 19, characterized in that the support body ( 70 ) has about four to six support edges ( 72 ). 21. Filter candle according to one of claims 18 to 20, characterized in that the filter means ( 74 ) consists of a fabric hose. 22. Filter candle according to one of claims 18 to 21, characterized in that the support body ( 70 ) consists of several, preferably six support rods ( 79 ) which form the Stützkan th ( 72 ) and on at least one central stiffening element ( 81 ) support. 23. Filter candle according to one of claims 18 to 22, characterized in that the stiffening element ( 81 ) consists of a cross-section approximately circular spiral body. 24. Filter candle according to one of claims 18 to 23, characterized in that the spiral body ( 81 ) consists of steel wire. 25. Filter candle according to one of claims 18 to 24, characterized in that the support body ( 70 ) at its ends with connection sleeves ( 28 ) for connection to the perforated ring plates ( 18 , 20 ) is provided. 26. Filter candle according to one of claims 18 to 25, characterized in that the filter means ( 73 ) at least partially overlaps the connecting sleeves ( 28 ) on their outer circumference and is fastened to them by means of a clamp ( 76 ). 27. Filter candle according to one of claims 18 to 25, characterized in that the connecting sleeves ( 28 ) clamp the filter means ( 73 ) between themselves and the support body ( 70 ). 28. Drive for a rotatable flushing member of a back flush filter, in particular according to one of claims 1 to 17, characterized in that the drive is a hydraulic drive ( 48 ) with a turbine wheel arranged in the liquid circuit ( 50 ) and a reduction gear ( 51 , 53 ) , which is coupled to the rotary shaft ( 32 ) of the flushing member ( 33 ). 29. Drive according to claim 28, characterized in that the turbine wheel ( 50 ) is an axial turbine. 30. Drive according to claim 28 or 29, characterized in that the turbine wheel ( 50 ) in the slurry inlet ( 14 ) of the backwash filter ( 10 ) is arranged. 31. Drive according to claim 28 or 29, characterized in that the turbine wheel ( 50 ) in the filtrate outlet ( 16 ) of the backwash filter ( 10 ) is arranged. 32. Drive according to claim 28 or 29, characterized in that the turbine wheel ( 50 ) in the sludge outlet ( 30 ) of the backwash filter ( 10 ) is arranged. 33. Drive according to one of claims 28 to 32, characterized in that the reduction gear ( 51 , 53 ) has a worm gear stage ( 51 ).