WO2013114329A1

WO2013114329A1 - Backflush type filter

Info

Publication number: WO2013114329A1
Application number: PCT/IB2013/050864
Authority: WO
Inventors: Wilhelm Vieten
Original assignee: Boll & Kirch Filterbau Gmbh
Priority date: 2012-02-03
Filing date: 2013-02-01
Publication date: 2013-08-08
Also published as: DE202012100368U1

Abstract

The invention relates to a backflush filter for filtering liquids, with the filter having a filter housing (1) with inlet (5) and an outlet (6) an filter elements (7), which are arranged offset with respect to each other on at least one circle, which are open at both ends (8, 9) and which have an outer surface of filter material (14) which is passed through for the filtering. The filter housing (1) has an inlet chamber (4) and an outlet chamber (11) and a cleaning device (30) which is rotatable about the centre axis (M) for backflushing individual filter elements (7), The cleaning device has a first body (32) associated with the first ends (8) and a second body (34) associated with the second ends (9) of the filter elements and movable together with the first body (32). According to the invention, the inlet chamber (4) is associated with the first ends (8) of the filter elements (7) for unidirectional supply of the filter elements (7) with liquid to be filtered in the filtering operation, while the second body (34) of the cleaning device forms a closure member (33) for the second ends (9) of all the filter elements (7) undergoing the filtering operation. Furthermore, the second body comprises for each circle (18) a backflush opening for backflushing individual filter elements (7) in the backflush operation, and the first body (32) forms a partial closure member for the associated first end (8) of the filter element (7) undergoing the back- flushing operation.

Description

BACKFLUSH TYPE FILTER

The invention relates to a backflush type filter for filtering liquids, said filter having a filter housing, which has an inlet for liquid to be filtered and an outlet for filtered liquid, having filter elements which are arranged in the filter housing offset in an angular manner with respect to each other about a centre axis on at least one pitch circle, which are open at both ends and which have an outer surface which can be traversed for the filtering, having in the filter housing an inlet chamber connected fluidically to the inlet, having an outlet chamber connected fluidically to the outlet for filtered liquid and having a cleaning device which is rotatable about the centre axis for back flushing individual filter elements, wherein the cleaning device has a first body which is associated with the first ends of the filter elements and a second body which is associated with the second ends and is movable together with the first body.

To filter out contamination or solid constituents from liquids such as, for example, water, lubricating oil, cutting oil and the like, it is known to use automatic filters which are designated as backflush filters, where a backflush device is provided in order to clean the filter surface of the filter elements from time to time without having to interrupt the filtering operation. The backflushing ensures such a filtering device with backflushing has as long an operation as possible without it being necessary to have to replace the individual filter elements, such as, for example, filter cartridges, which form the filter material on the outer surface by way of a filter sieve or filter cloth.

In the case of liquids, the liquid to be filtered is referred to mostly as sludge or contaminated liquid and filtered liquid as filtrate or filtered liquid. In the case of filter elements that are open at both the ends thereof and are flowed through with a contaminated liquid from both ends, in order to achieve intensive cleaning even in the case of long filter elements, it is known from WO01/89658 A1 to carry out the backflushing alternately from one end and from the other end in the reverse flow to the direction of filtering. For each pitch circle on which several filter elements are arranged offset in an angular manner with respect to each other, the one filter element end has associated therewith a hollow backflushing arm and the other filter element end has associated therewith a closure or throttle member, which are rotated simultaneously, as a result of which the backflushing operation is introduced alternately from the first end and from the second end. In the filtering operation, via perforated plates, which, inside a filter housing, separate an outlet chamber for filtrate or filtered liquid from the inlet chambers arranged at both ends of the filter elements, the contaminated liquid enters into the interior of the cartridge-like filter elements via both ends and exits through the filter wall as filtrate. In the backflushing operation, the direction of flow is reversed and by connecting the respective flow arm to a contamination attraction line, where applicable by connecting an openable and closable flushing valve, negative pressure is generated in the interior of the filter element in relation to the filtrate side, as a result of which, filtrate is drawn back in the reverse flow to the filtering direction through the filtering material and, in so doing, detaches solid particles and contamination deposited on the inner surface of the filter material. From WO01/89658 A1 it is also known to support the backflushing in the reverse flow by a brief back flushing in the cross flow, i.e. to support a flow parallel to the outer surface of the filter element by the backflushing valve being opened at a moment when the backflushing member connects the one end of the filter element completely to the valve outlet, whilst at the same time the closure member still leaves a gap open at the opposite other end.

By alternately back flushing individual filter elements in opposite directions from both ends, the backflushing concept with flow reversal certainly brings about a comparably intensive cleaning of the filter surface of the filter. However, disadvantages are the relatively large time delays when transferring from the filtration phase into the backflushing phase and relatively large pulsation effects in the liquid flow.

It is the object of the invention to create a backflush filter where the aforementioned disadvantages do not arise.

To this end, it is proposed according to the invention that the inlet chamber is associated with the first ends of the filter elements in order to supply the filter elements with liquid to be filtered unidirectional in the filtering operation, that the second body of the cleaning device forms a closure member for the second ends of all the filter elements currently undergoing the filtering operation, with the second body comprising for each pitch or graduated circle at least one or preferably precisely one backflush opening for back flushing individual filter elements undergoing the backflushing operation, and that the first body forms a closure member for the associated first end of the filter element undergoing the backflushing operation.

In the case of the backflush filter according to the invention, the majority of the several filter elements are undergoing the filtering operation in a manner known per se and only a few, preferably only one single filter element(s) per circle on which the filter elements are arranged, are/is in the backflushing operation. Although all the filter elements are open at both ends, the flow coming into the interior of the individual filter elements is effected only at one end via the inlet chamber, which is associated with the first ends of the filter elements. The second body of the cleaning device creates a closure member, by way of which the second ends of all the filter elements undergoing the filtering operation are closed, the second body having for each circle at least one, preferably precisely one, backflush opening, via which individual filter elements on the associated circle are back flushed in the backflushing operation. The current position of the backflush opening or of the backflush openings therefore determines which filter element is or which filter elements are undergoing the backflushing operation. The or those filter elements which are being cleaned momentarily in the backflushing operation are closed by means of the first body, which, in turn, with reference to all the first ends certainly only forms a partial closure member for individual filter elements, at their first ends in such a manner that the filter elements can be backflushed in the reverse flow in the backflushing operation via the second end which is opposite the inflow end of each filter element and therefore forms exclusively an outlet end for the back flushing. During the entire time the backflush filter is operating, consequently both in the filtering phase and in the backflushing phase, the flow through the individual filter elements remains aligned in the axial direction of the individual filter elements. A flow reversal is avoided, as a result of which, at the same time, there are no time delays during the transition between the filtration operation and the backflushing operation.

According to a particularly advantageous development, the second body as a disc-shaped diaphragm is provided with one single backflush opening per circle. During a 360° rotation of the cleaning device, each filter element per circle is then back flushed once. The backflush opening can be realized as a circular hole and then, where applicable, can have the identical or approximately the identical inside width to the inside width in the cavity of the individual filter elements. Depending on the liquid to be filtered and on the anticipated degree of contamination of the liquid to be filtered, by choosing another cross-sectional form for the backflush opening, such as, for example, a slot-shaped design for the backflush opening, the strength of the back flush and in particular the amount of back flush which is drawn through in the reverse flow to the filtering direction is able to be influenced. If, per circle, several backflush openings are realized in the second body, it could also be possible to achieve a back flush with different back flush strengths even per revolution through different cross sections of the several backflush openings. In the case of slot-like backflush openings, for example, the slot length could be adapted to the inside diameter or the inside width of the filter elements and the slot width could be developed in a correspondingly narrower manner.

It is particularly advantageous when the first body is realized as a covering arm which, when viewed in the circumferential direction, is wider in the region of each circle than the inside diameter of the ends of the filter elements and the width of opening of the backflush opening in the second body. In the backflushing operation, when the first body as a closure member for the first end cooperates with the backflush opening in the second body, which opens the second ends exclusively for the backflushing operation, the corresponding development provides that over the entire period or at least the largest period of the backflushing phase, the cleaning of the filter material is effected exclusively in the reverse flow to the filtering direction, i.e. in the case of filter cartridges which are traversed from in to out in the filtering operation, the back flushing is effected from out to in, so that the particles filtered out in the filtering operation are detached from the filter material.

In the case of the particularly preferred development, the backflush opening in the second body and the cover surface of the first body forming a closure member for the first ends are arranged offset in such a manner that the filter element to be back flushed momentarily is open briefly at the first and second end during the backflushing operation, before or after the closure member formed by way of the first body completely covers the first end of the associated filter element. In the case of said development, in addition an aligned flow of the filter cartridge is ensured in the axial direction and a back flush is achieved in the reverse flow during a large part of the duration of the backflushing phase, however additionally utilized for the back flush is a cross flow which is generated as a result of an axial flow through the filter element to be back flushed from the inlet chamber to the second end. Said cross flow breaks off all of a sudden when the first end of the filter element to be back flushed is completely covered and the backflushing phase then transfers from the cross flow or combined cross / and reverse flow into a backflushing phase with a flow through the filter material in an exclusive reverse flow. The sudden break-off of the flow and the eddy this induces bring about a particularly effective removal of the particles of dirt on the contaminated side of the filter material.

To simplify the construction and the assembly of corresponding backflush filters, it is particularly advantageous when the filter elements are arranged in a filter insert with a first perforated plate for the first ends and a second perforated plate for the second ends, wherein the first perforated plate forms the separating wall between the inlet chamber and the outlet chamber. In an expedient manner, the perforated plates are connected by means of rods and/or the filter elements are clamped between the perforated plates. If the filtering output of a backflush filter comprising a corresponding filter insert decreases in an over-proportional manner in spite of regular back flushing , the entire filter insert can then be replaced by a new filter insert at little cost.

In order to minimize expenditure on hardware for the backflush device, according to a particularly advantageous development a collecting chamber for backflushing liquid can be formed in the filter housing . In a manner known per se, the collecting chamber can have associated therewith a flushing valve in order to provide for the, where applicable, necessary pressure difference between the collecting chamber and the outlet chamber and the inlet chamber. It is particularly advantageous when the second perforated plate forms the separating wall between the outlet chamber and the collecting chamber .

In order to create a large filter surface in the case of a backflush filter with several filter elements, the filter elements can be arranged on two, where applicable also three or more, concentric circles, wherein the first body has a first part arm for the inner circle and a second part arm for the other circle. In the case of the preferred development, two circles are provided and the covering arms are arranged offset with respect to each other by 180° . In the case of particularly large-scale backflush filters, three covering arms, preferably then each arranged offset with respect to each other by 120° or four covering arms, preferably then arranged offset with respect to each other by 90°, could be provided. In the case of several circles, openings can be realized in the second covering arm for the outer circle or circles in the region of the first or inner circle , so that the incoming flow to the filter cartridges on the inner circle is not interrupted by the covering arm in the filtering operation. As an alternative to this, the respective covering arm could also have a crank or taper in order to maintain a flow coming into a filter element situated under the covering arm. As an alternative to this, in the case of a backflush filter with filter elements arranged on two circles, one single covering arm could be provided, on which the backflush opening for the first circle is adjacent the backflush openings for the second circle .

In the case of all of the developments, it is particularly advantageous when the first body and the second body are connected by means of a rotary shaft and are mounted on the filter insert so as to be rotatable. In order to provide for a rotary drive, a gear wheel which is non-rotatably connected to the rotary shaft and has an outer toothing can be arranged in the inlet chamber. In the case of said development, the covering arms can be connected to the gear wheel and/or are realized integrally on the gear wheel . It is additionally advantageous when a turbine is arranged in the inlet region, preferably downstream of the inlet, as a rotary drive for the cleaning device, said turbine preferably being coupled to the gear wheel by means of an interposed transmission .

In numerous cases of application a complete breaking off of the liquid flow behind the backflush filter could result in serious damage to a machine provided with the filtering apparatus. It is possible to provide, in particular for said purposes, an overflow valve which is preferably arranged in the filter insert. The overflow valve can consist, in particular, of a first sleeve which is arranged concentrically with respect to the centre axis and a second sleeve which is arranged concentrically with respect to the centre axis and is pre-tensioned by means of a compression spring against the first perforated plate, wherein the end face of the second sleeve is acted upon with the pressure of the liquid in the inlet chamber . If then as a result of the filter material of all of the filter elements being too greatly contaminated or on account of other circumstances, a preset pressure level in the inlet chamber is exceeded, the overflow valve can open automatically as a result of the pressure difference between the outlet chamber and the inlet chamber. The pressure difference at which the overflow valve opens can be preset by means of the tension of the spring. According to the particularly preferred development, the gear wheel has openings in the centre for liquid to act on the second sleeve through the gear wheel. The invention also relates to the filter insert.

Further advantages and developments of a backflush filter or filter insert according to the invention are produced from the following description of exemplary embodiments which are shown in the drawing, in which:

Fig. 1 shows a schematic representation of a longitudinal section through a backflush filter according to the invention according to a first exemplary embodiment;

Fig. 2 shows a highly simplified schematic view in perspective of the top surface of a filter insert for a backflush filter according to Fig. 1;

Fig. 3 shows a schematic view of the under surface of the filter insert from Fig. 2;

Fig. 4A-C show three individual schematic representations of a filter element in the filtration phase and in different flow states during the backflushing phase;

Fig. 5A-C show schematic top views onto the ends of adjacent filter elements, the adjusting positions of the first body and of the backflush opening in the second body of the cleaning device;

Fig. 6 shows alternative variants of the form and size of the backflush opening in the second body;

Fig. 7 shows a schematic top view of a filter insert according to a second exemplary embodiment; and

Fig. 8 shows a perspective view of the filter insert according to the second exemplary embodiment.

In Fig. 1, a backflush filter according to the invention according to a first exemplary embodiment is designated overall by the reference 10. The backflush filter 10 is suitable in particular for the filtering of liquids such as water or lubricating oil and has a multiple-part filter housing 1 with a housing bottom part 2 and a housing top part 3 which is releasably screw connected to said housing top part. The interior of the housing top part 3 essentially forms an inlet chamber 4, into which a liquid can flow via the inlet 5 for liquids to be filtered, hereafter referred to as contaminated liquid. An outlet 6 for liquid filtered by means of numerous candle-shaped filter elements 7, hereafter referred to as filtrate, is realized on the housing bottom part 2, in this case at the side. In the case of the backflush filter 10, all the filter cartridges or filter elements 7 are arranged offset to each other in an angular manner on a circle about a centre axis M, the centre axis M at the same time forming a rotational axis for a cleaning device 30, the design of which will be explained again below and by way of which individual filter elements 7 are able to be back flushed in the backflushing operation. All the filter elements 7, together with the essential elements of the backflush device 30 in the exemplary embodiment shown, are components of a filter insert 20, which is accommodated in the housing bottom part 2 of the filter housing 1 so as to be replaceable as a unit and of which a highly schematic simplified view is also shown in Fig. 2 and 3, to which reference is now made.

It can easily be seen from Fig. 2 and 3 that the filter insert 20 is provided with a plurality of filter cartridges as filter elements 7, in the exemplary embodiment shown 20, arranged on a circle offset in an angular manner around the centre axis M, all the filter elements 7 in the filter insert 20 being clamped between a top perforated plate 21 and a bottom perforated plate 22. Both perforated plates 21, 22 are preferably braced against each other by means of rods and fastening screws (not shown), which are screwed into the internal thread of the rods (not shown), in such a manner that the respective top ends 8 of all the filter elements 7 sit sealingly in holes 23 in the top perforated plate 21 and the bottom ends 9 of the filter elements 7 sit sealingly in corresponding holes 24 in the bottom perforated plate 22. In the assembled state of the filter insert 20, the top perforated plate 21 forms a separating wall between the inlet chamber 4 and an outlet chamber 11, which is generated in the housing bottom part 2 between the two perforated plates 21, 22 and which is connected fluidically to the outlet 6; the bottom perforated plate 22 forms a separating wall between the outlet chamber 11 and a collecting chamber 13 for backflushing liquid on the bottom of the housing bottom part 2, it being possible for the collecting chamber to be connected via a bottom outlet 15 e.g. to an openable and closable flow valve (not shown) or to a permanently open subsequent treatment device for flush liquid, such as, for example, a centrifuge, in order to provide negative pressure in the collecting chamber in relation to the pressure level in the inlet chamber 4 and the outlet chamber 11. The chambers are sealed by means of seals 12 which are arranged on the circumferential side of the perforated plates 21, 22 such that in normal operation the contaminated liquid to be filtered can flow exclusively from the inlet chamber 4 into the cavity of the filter elements 7 and from there can pass through filter material, such as, for example, screen mesh which forms the outer surface of each filter element 7, as filtrate filtered of contaminants into the outlet chamber 11. In operating of the backflushing filter 10, the majority of the filter elements 7 are in the filtering operation, consequently are in a phase where the filter material is traversed or passed through from in to out for filtering the contaminated liquid, and liquid passes as filtrate into the outlet chamber 11, as is shown on the right-hand filter element 7. The contaminated liquid flows into the individual filter elements 7 exclusively via the inlet chamber 4 and the top ends 8 of the filter elements 7, as the bottom ends 9 of the filter elements 7, although they are open and sit in the through holes 24 of the perforated plate 22, are closed by means of a disc-shaped closure diaphragm 31 of the cleaning device 30. In each case only one individual filter element 7, or, however, a few filter elements 7, are undergoing at a certain moment in time the backflushing operation, each filter element 7 being backflushed depending on the actual rotation position of the cleaning device 30. In Fig. 1, the left-hand filter element 7 is undergoing the backflushing operation. For the backflushing operation, the backflush device 30, which is rotatable about a centre axis M, has a first body 32 which is arranged in the inlet chamber 4 and is associated with the top perforated plate 21 or the top ends 8 (inlet ends) of the filter elements 7, the first body 32 being realized as a covering arm 33, by way of which in each rotational position a maximum of the top ends 8 of two filter elements lying adjacent on the same circle are partially covered and at the same time a maximum of one is completely covered. The cleaning device 30 additionally has a closure diaphragm 31 as second body 34, which, in principle, forms a rotatable closure member for the second ends 9 of the filter elements, however provided with at least one or preferably precisely one backflush opening 35 for the single circle in this case of filter elements 7. The covering arm 33 and the backflush opening 35 in the diaphragm 31 are positioned in such a manner that they act, in each case, on essentially only one individual filter element 7 at the same time, so that only said filter element 7 is then undergoing the backflushing operation, whilst the other filter elements 7 continue to be undergoing the filtering operation and provide a liquid flow with filtrate at the outlet 6.

The closure diaphragm 31 and the covering arm 33 are rotated simultaneously and with fixed association with each other about the centre axis M and in the exemplary embodiment shown a turbine 40 as the rotary drive is arranged behind the inlet 5 inside the inlet chamber 4, said turbine meshing via a driven gear wheel 41 on the turbine side with a drive gear wheel 36 for the cleaning device 30. The gear wheel 36 is connected non-rotatably to a rotary shaft 37, on which, the closure diaphragm 31 is fastened, once again non-rotatably. The rotary shaft 37 penetrates the filter insert 20 centrally inside a normally closed pipe, via which no liquid can flow out of the inlet chamber 4 into the collecting chamber 13 and across said collecting chamber to the bottom ends 9, as the flow is introduced exclusively to the top filter element ends 8 via the inlet chamber 4. The rotatability of the two bodies 32, 34 connected together via the rotary shaft 37 in relation to the stationary filter insert 20 is achieved via the bearings indicated in Fig. 1, which can consist in particular of ball bearings, by way of which the rotatable interconnection of rotary shaft 37, bodies 32, 34 etc. is supported in a rotatably mounted manner on the two perforated plates 21, 22.

In the exemplary embodiment shown, the central pipes additionally form an overflow valve 60, which is arranged in the centre of the filter insert 20 between the perforated plates 21, 22. The overflow valve 60 is formed by means of an inner first sleeve 61 formed centrally with respect to the centre axis M and a second sleeve 62 which is supported with pre-tensioning by means of a compression spring 63 in relation to the bottom perforated plate 22 and is pressed by way of the pre-tensioning of the spring 63 against a contact face on the under surface of the top perforated plate 21. The end face 64 of the outer sleeve 62, which is guided on the inner sleeve 61 so as to be displaceable and is sealed by means of seals, protrudes inward over an annular space at the bottom end of a centre bore 29 in the top perforated plate 21. The exposed surface of the end face 64 is acted upon in part with the pressure of the contaminated liquid in the inlet chamber 4. If the pressure in the inlet chamber 4 exceeds the counter pressure applied by means of the spring 63, the overflow valve 60 can open and consequently liquid, even if not-filtered, can flow directly from the inlet chamber 4 into the outlet chamber 11 and an interruption in the liquid flow can be prevented. A filter mounted behind the outlet 6 can prevent contaminants from non-filtered liquid resulting in damage to a machine downstream and it can be displayed by means of a display device that the overflow valve 60 had opened or the pressure difference between the inlet chamber and the outlet chamber has reached values which require the filter insert 20 to be replaced or at least serviced.

Fig. 4A-C show the different operating phases in the filtering operation and the backflushing operation by way of a filter element 7. The operating phases are set by means of the closure diaphragm 31 and the covering arm 33 of the cleaning machine. Fig. 4A shows the filtering phase, during which the contaminated liquid flows into the top open end 8 via the hole 23 in the perforated plate and into the interior of the filter element 7 and exits at the outer surface of the filter element as filtrate through the filter material 14, which is formed for example by screen mesh. This causes contaminants inside the contaminated liquid to be deposited on the inner wall of the filter material 14. The bottom end 9 of the filter elements 7 is closed by way of the closure diaphragm 31 which abuts in a sealing manner against the bottom surface of the perforated plate 22.

Fig. 4B shows a filter element 7 in a first backflushing phase in the backflushing operation. The covering arm 33 covers the top end 8 in a partial manner, a remaining cross section of the top end 8 of the filter element 7 or of the hole 23 in the perforated plate 21 is still open, which is why contaminated liquid continues to be able to flow via the top end 8 into the interior of the filter element 7. At the same time, however, the backflush opening 35 is also situated inside the perforated diaphragm 31 below the bottom end 9 of the filter element 7. The interior of the filter element 7 is consequently traversed in the same direction as the normal inflow direction from the top end 8 to the bottom end 9, at which there is a lower pressure than at the top end 8. Said through-flow, which is indicated by the arrows Q, forms a cross flow, by means of which the particles adhering to the inner surface of the filter material of the filter elements 7 can be detached and flushed away at a relatively high speed. Through the pressure gradient as a result of the lower pressure underneath the diaphragm 31, in addition to the cross flow Q also a reverse flow G from out to in is set up by the filter material 14 forming the outer surface of the filter elements 7, as shown by the arrows G. In the first backflushing phase of the backflushing operation, the cleaning of the filter material is effected with a combined cross flow and reverse flow, the entire flow path remaining in the same direction and leading from the inlet at the top end 8 to the outlet at the bottom end 9.

In Fig. 4C the filter element 7 is undergoing that time phase of the backflushing operation in which the hole 23 in the perforated plate 21, and consequently also the top end 8 of the filter element 7, is completely blocked by the covering arm 33 and the bottom end 9 over the backflush opening 35 in the diaphragm 31 is still completely open or at least still partially open. A relatively strong reverse flow G is generated as a result of the pressure difference above the low pressure present at the bottom end 9 of the filter element 7 and filtrate is drawn back into the interior of the filter element 7 and from there is drawn off into the collecting chamber via the bottom end 9. Since, as Fig. 4A-C clarify in particular, the direction of flow through the respective filter element 7 remains the same in each case and is always directed from the top perforated plate 21 to the bottom perforated plate 22, hardly any pulsation effects are created at the transition between filtering operations and backflushing operations and vice versa.

Fig. 5A to 5C, by way of three adjacent filter elements 7 on one circle 18 about the centre axis M, clarify the respective relative position of the covering arm 33 and of the backflush opening 35 indicated by the dotted line in relation to the ends 8, 9 of the individual filter elements, which are designated in Fig. 5A-5C for differentiation with the indexing (1)-(3). In Fig. 1 the filter element 7⁽¹⁾ is situated at the end of the backflushing operation in the backflushing phase with pure reverse flow corresponding to Fig. 4C. The covering arm 33 covers the top end 8 completely; the backflush opening 35 is aligned still in part with the bottom end 9 of the filter element 7⁽¹⁾. The filter elements 7⁽²⁾ and 7⁽³⁾ are undergoing the filtering phase (cf. Fig. 4A).

In the representation according to Fig. 5B, through its rotation about the centre axis M in the direction of the arrow R, the covering arm 33 has reached a position in which it covers just the top end of the filter element 7⁽²⁾. The backflush opening 35 is situated exactly beneath the bottom end 9 of the filter element 7⁽²⁾. In said position, the cross flow just breaks off and the pure backflushing phase in the reverse flow begins for the filter element 7⁽²⁾, whilst the filter elements 7⁽¹⁾ and 7⁽³⁾ are undergoing the filtering phase. In the rotational position according to Fig. 5C, the covering arm 33 still just covers the top end 8 of the filter element 7⁽²⁾. The backflush opening 35, contrary to this, is situated in a position in which it does open the bottom end 9 of the filter element 7⁽³⁾ in part, the bottom end 9 of the filter element 7⁽²⁾ on the other hand is completely closed. The filter element 7⁽²⁾ is consequently situated precisely at the transition between the end of the backflushing operation and the beginning of the filtering operation. The filter element 7⁽³⁾ is already undergoing the backflushing operation, in the phase of the combined cross and reverse flow (cf. Fig. 4B).

Fig. 5A to 5C also show that the covering arm 33 has a central portion, in which the covering arm 33 has, for example, the same width as the inside opening of the ends 8, 9 of the filter elements 7, and in the region of the circle on which the individual filter elements 7⁽¹⁾ are arranged, has an end portion which is approximately twice as wide as the inside width of the individual filter elements 7. The backflush opening 35 in the closure diaphragm is positioned in such a manner in relation to the covering arm 33 that the leading edge 33A of the covering arm 33 still just covers the leading edge 35A of the backflush opening 35. When viewed in the direction of rotation, the leading edge of the backflush opening 35 and the leading edge of the covering arm consequently reach the ends of the filter elements at the same time, which is why both ends of the filter elements are only partially open in the backflushing phase with cross flow.

Fig. 6 shows different possible developments for the cross section of the backflush opening 35 in the closure diaphragm 31, which forms the second, in this case bottom body of the cleaning device. The left-hand representation in Fig. 6 shows a circular cross section for the backflush opening 35, it being possible to adapt the inside width of the circular backflush opening 35 to an inside width of the ends of the filter elements and it being possible, in particular, to realize said inside width of the circular backflush opening in an identical manner to same. The central representation shows a slot-like backflush opening 35' on a closure diaphragm 31', where the longer slot length of the slot lies in the direction of rotation and, where applicable, is of a length which corresponds to the inside width of the ends of the filter elements, whilst in the radial direction the slot 35' is clearly smaller than the opening width of the ends of the filter elements. The right-hand representation in Fig. 6 shows a slot-like backflush opening 35'' for a closure diaphragm 31'', where the slot in the radial direction has the same inside width as the inside width of the ends of the filter elements, whilst the width of the slot in the direction of rotation is considerably less and is, for example, between 1/3 and 1/6. However, multiple other slot geometries are also possible, by way of which, on the one hand, it is possible to set the amount which is sucked out of the interior of the filter element in the backflushing operation in the phase with combined cross and reverse flow and in the phase with pure reverse flow and occurs in this respect as filtration loss in the current filtering operation.

Fig. 7 and 8 show a second exemplary embodiment of a filter insert 120, which could be installed into the same filter housing 1, for example in place of the filter insert 20 shown in Fig. 1. The filter insert 120 differs from the filter insert 20 by the number of graduated circles about the centre axis M, as in the case of the filter insert 120 the filter elements 107A are arranged on an inner circle 118A and the filter elements 107B are arranged on an outer circle 118B. The covering arm 133, in this case, has in a corresponding manner a first covering arm 133A for the filter elements 107A on the inner circle 118A and a second covering arm 133B for the filter elements 107B on the outer circle 118B. The closure diaphragm 131 as the second body 132 of the cleaning device 130 also has in a corresponding manner a first backflush opening 135A, which is associated with the covering arm 133A or the inner circle 118A, and a second backflush opening 135B, which is associated with the second covering arm 133B. In the exemplary embodiment shown, the two covering arms 133A, 133B are offset with respect to each other by 180°. The covering arm 133B for the outer circle 118B is provided with openings 137 in the region of the inner circle 118A, so that in the current operation, independently of the position of the covering arm 133B, the upper ends of the filter elements 107A on the inner circle 118A can be flowed against with contaminated liquid and the filtering operation of the filter cartridge situated on the inner circle 118A adjacent a filter cartridge situated on the other circle 118B in the backflushing operation is not interrupted.

Fig. 8 shows a perspective view of the filter insert 120 according to the exemplary embodiment in Fig. 7 with filter elements 107A on the inner circle and filter elements 107B on the outer circle. The perforated plates 121 and 122, which are detachably connected by means of rods 190, are also in a corresponding manner provided with holes on two circles. The closure diaphragm 131 forms the bottom portion of the filter insert 120 and, with the exception of those regions in which the backflush openings 135B (or 135A, Fig. 7) are situated, covers all the bottom ends 109 of the filter elements 107A, 107B. Both the covering arm 133A and the covering arm 133B for the filter elements on the outer circle are, in this case, integral components of a gear wheel 136, which is provided with openings 139 in the centre. The openings 139 through the gear wheel 136 open out into the inner region of an overflow valve 160, which consists of an inner first sleeve 161, which is formed centrally with respect to the centre axis M, and a second sleeve 162 which is supported with pretensioning by means of a compression spring 163 in relation to the bottom perforated plate 122 and by way of the pretensioning of the spring 163 is pressed against a contact face on the under surface of the top perforated plate 121. The end face of the outer sleeve 162, guided so as to be displaceable on the inner sleeve 161, protrudes inward over a central bore 129 in the top perforated plate 121 or via an annular space 165 is partially acted upon with the pressure of the contaminated liquid in the inlet chamber (4, Fig. 1). If the pressure in the inlet chamber exceeds the counter pressure applied by means of the spring 163, the otherwise passive and closed overflow valve 160 opens.

The above description provides the expert with numerous modifications, which are to fall in the area of protection of the accompanying claims. The covering arms could also be provided without extra width or with extra widths formed in another manner. The sealing between the closure diaphragm and the bottom perforated plate and the covering arm and the top perforated plate can be achieved by means of sealing rings and the like. The number of filter elements on one circle and the number of circles can vary in an almost arbitrary manner. The duration for the backflushing phase can be selected and optimized by means of the geometry of the backflush opening and the rotational speed of the cleaning device depending on the application. The covering arm and the backflush opening could also be positioned in such a manner that the backflushing phase occurs with combined cross and reverse flow at the end of the backflushing operation.

Claims

1. Backflush filter for filtering liquids, said filter having a filter housing (1) with an inlet (5) for liquid to be filtered and an outlet (6) for filtered liquid, having filter elements (7), which are arranged in the filter housing (1) offset with respect to each other about a centre axis (M) on at least one circle (18), which are open at both ends (8, 9) and which have an outer surface of filter material (14) which is passed through for the filtering, having in the filter housing (1) an inlet chamber (4) connected fluidically to the inlet (5), having an outlet chamber (11) connected fluidically to the outlet (6) for filtered liquid and having a cleaning device (30) which is rotatable about the centre axis (M) for backflushing individual filter elements (7) and which has a first body (32) which is associated with the first ends (8) of the filter elements (7) and a second body (34) which is associated with the second ends (9) and is movable together with the first body (32), characterized in that the inlet chamber (4) is associated with the first ends (8) of the filter elements (7) for unidirectional supply of the filter elements (7) with liquid to be filtered in the filtering operation, in that the second body (34) of the cleaning device forms a closure member (33) for the second ends (9) of all the filter elements (7) undergoing the filtering operation and comprises for each circle (18) a backflush opening (35) for backflushing individual filter elements (7) in the backflush operation, and in that the first body (32) forms a partial closure member for the associated first end (8) of the filter element (7) undergoing the backflushing operation.

2. Backflush filter according to Claim 1, characterized in that the second body (34) forms a disc-shaped closure diaphragm (33; 133) and is provided with one single backflush opening (35; 135A, 135B) per circle (18; 118A, 118B).

3. Backflush filter according to Claim 1 or 2, characterized in that the backflush opening (35) is formed as a circular hole.

4. Backflush filter according to Claim 1 or 2, characterized in that the backflush opening (35', 35'') is formed as a slot, wherein the slot length is preferably adapted to the inside diameter of the filter elements.

5. Backflush filter according to one of Claims 1 to 4, characterized in that the first body (32) is formed as a covering arm (33) which, when viewed in the circumferential direction, is wider in the region of each circle (18) than the first end (8) of the filter elements (7) and/or an opening width of the backflush opening (35) in the second body (34).

6. Backflush filter according to one of Claims 1 to 5, characterized in that the backflush opening (35) is arranged in the direction of rotation of the cleaning device (30) in such a manner offset with respect to the closure member formed by means of the first body (32) that the filter element to be backflushed is partially open at the second end (9) thereof prior to or after the closure member (32) covers the first end (8) completely.

7. Backflush filter according to one of Claims 1 to 6, characterized in that the filter elements (7; 107) are arranged in a filter insert (20; 120) with a first perforated plate (21; 121) for the first ends (8; 108) and a second perforated plate (22; 122) for the second ends (9; 109, wherein the first perforated plate (21; 121) forms the separating wall between the inlet chamber (4) and the outlet chamber (11).

8. Backflush filter according to Claim 7, characterized in that the perforated plates (121, 122) are connected by means of rods (190) and the filter elements (107) are clamped between the perforated plates (121, 122).

9. Backflush filter according to one of Claims 1 to 8, characterized in that a collecting chamber (13) for backflush liquid is formed in the filter housing (1).

10. Backflush filter according to Claim 9, characterized in that the second perforated plate (22) forms the separating wall between the outlet chamber (11) and the collecting chamber (13).

11. Backflush filter according to one of Claims 1 to 10, characterized in that the filter elements (107A, 107B) are arranged on two concentric circles (118A, 118B), wherein the first body has a fist covering arm (133A) for the inner circle (118A) and a second covering arm (133B) for the outer circle (118B), which are preferably arranged offset with respect to each other by 180°.

12. Backflush filter according to Claim 11, characterized in that the second covering arm (133B) has openings (137) for the outer circle (118A) in the region of the first circle (118A).

13. Backflush filter according to one of Claims 1 to 10, characterized in that the filter elements are arranged on two circles, wherein one single covering arm is provided and the backflush opening for the first circle is adjacent the backflush opening for the second circle.

14. Backflush filter according to one of Claims 1 to 13, characterized in that the first body (32) and the second body (34) are connected by means of a rotary shaft (37) and are mounted on the filter insert (20) so as to be rotatable, preferably by means of bearings.

15. Backflush filter according to one of Claims 1 to 14, characterized in that a gear wheel (36; 136) which is non-rotatably connected to the rotary shaft and has an outer toothing is arranged in the inlet chamber (4).

16. Backflush filter according to Claim 15, characterized in that the covering arm (33) or the covering arms (133A, 133B) is/are connected to the gear wheel (36; 136) and/or is/are realized integrally on the gear wheel.

17. Backflush filter according to one of Claims 1 to 16, characterized in that a turbine (40) is arranged in the inlet region as a rotary drive for the cleaning device (30).

18. Backflush filter according to one of Claims 1 to 17, characterized in that an overflow valve (60; 160) is arranged in the filter insert.

19. Backflush filter according to Claim 18, characterized in that the overflow valve (60; 160) consists of a first sleeve (61; 161) which is arranged concentrically with respect to the centre axis (M) and a second sleeve (62; 162) which is arranged concentrically with respect to the centre axis (M) and is pre-tensioned by means of a compression spring (63; 163) against the first perforated plate (21; 121), wherein the end face (64) of the second sleeve (62) can be acted upon or is acted upon with the pressure of the liquid in the inlet chamber (4).

20. Backflush filter according to Claims 16 and 19, characterized in that the gear wheel (136) has openings (139) in the centre, through which the end face (64) of the second sleeve (62) can be acted upon with the pressure from the inlet chamber (4).

21. Filter insert for a backflush filter according to one of Claims 1 to 20 for filtering liquids, having filter elements (7) which are arranged offset with respect to each other about a centre axis (M) on at least one circle (18), which are open at both ends (8, 9) and which have an outer surface of filter material (14) which is passable through for the filtering, having a first perforated plate (21; 121) for the first ends (8; 108) and a second perforated plate (22; 122) for the second ends (9; 109), between which the filter elements (7; 107A, 107B) are arranged, and having a cleaning device (30) which is rotatable about the centre axis (M) for backflushing individual filter elements (7), which has a first body (32) which is associated with the first ends (8) of the filter elements (7) and a second body (34) which is associated with the second ends (9) and is movable together with the first body (32), characterized in that the second body (34) of the cleaning device forms a closure member (33) for the second ends (9) of all of the filter elements (7) undergoing the filtering operation and for each circle (18) has a backflush opening (35) for backflushing individual filter elements (7) in the backflush operation, and in that the first body (32) forms a partial closure member for the associated first end (8) of a filter element (7) undergoing the backflush operation.