BACK FLUSHABLE FILTERS

Abstract: A back flushable filter which has number of separable sections (2) which can be separately accessed and there can be provided a flow pattern so that one of the sections is being back flushed while the other sections are providing normal filtering. Valve means (11) providing for such access can be inched around to select each section in turn. The filtering means can comprise sand or it can comprise a stack of separable segments which provide for inclined gaps between adjacent parts of each adjoining stack element with the convergence and gap size selected to encourage compaction of particles within the converging part of each gap but further selected such that on back flushing such compacted particles can be readily easily disgorged for total cleansing.

Description: BLACK FLUSHABLE FILTERS This invention relat.es to back flushable filters. It is presently known to use filters comprising siliceous particles such as sand in which water is filtered by being caused to pass through the compacted sand particles and from time to time, a cleansing of the 5. sand is effected by causing water to flow in a contra direction hence causing the sand to rise against an otherwise compacted condition but being held against excessive removal by gravitational forces, but such that detritus, which will normally catch within water flow more effectively than sand particles, will be carried away by the so called 10. back flushing water flow. A number of problems do exist with such an arrangement in the connventional systems. A first of these is that in order to effect an adequate back flushing, a sufficient water flow capacity must be provided to ensure is . that there is provided adequate flow to separate the detritus from the sand particles. There is a further problem namely that in order to maintain sand within a filtering chamber a lowermost outlet is provided by a screen beneath which water will necessarily have to be provided for the back 20. flushing step. In order to provide sufficient quantity of water for adequate velocity, it is conventional that such water should be provided from a main volume of water provided by perhaps a storage tank or swimming pool or like and on most occaisions, there is no assurance that such 25. water is of itself clean. The result in practice is that such water will have a primary filtering as it passes through the lowermost mesh so that this detritus will, when the water flow is reversed, be returned to the water storage. This could perhaps be avoided by providing that a first shot of water subsequent to a back flushing step, should be directed to waste but this requires significant extra costs which can rarely be justified. The further problem with present back flushing techniques is that 5 . because the velocities of water are inherently necessarily different, the capacity of pumps, pipes, and control valves must all be selected to allow for the back flushing capacity so that the cost is governed by a capacity which is necessarily far in excess of that which would normally be necessary for merely the filtering function. 0 • I have discovered that the problems discussed can be at least significantly reduced by providing that the back f lushable filter has parts which are separately accessible, so that a part only can be selected for a back flushing action while other parts of the filter are accessible for a conventional filtering process. is. The invention can be said then to reside in a back f lushable filter comprising a body liquid filter means within the body adapted to provide for a filtering effect when liquid is directed in a first direction through the liquid filter means, and adapted to provide for a flushing effect when liquid is directed in an oppositive direction through the liquid filter 20. means, the liquid filter means being divided into at least two parts in such a way that back flushing can be effected in at least one of the parts while filtering is being effected in the other of the parts and the valve means arranged to direct liquid flow through the liquid filter means, such that back flushing will be effected in at least one of the parts 25 • while filtering is being effected in the other of the parts. In preference, there are provided drive means adapted to drive said valve means, such that the valve means will be stepped through after a selected time from a first position to a- second positon whereby a back flushing effect is then effected in a further of the parts. 30 • By having such separately accessible parts of a filter, there is a further significant advantage in that if a sufficiently large part of the f ilter is provided for conventional filtering, a significant quantity of water is then available and a selected proportion of this can then be used as completely filtered water to provide for sufficient capacity to effect a back flushing of another part of the filter. Because the water is being directly filtered and then provided from a lower end, there will be at most negligible detritus with the 5. result that a significantly better filtering action can be expected. Furthermore, however, the total capacity of water being necessarily pumped at one stage is governed then more by the capacity of the parts providing for conventional filtering and hence it can be expected that in commercial circumstances, a filter along the lines o . described can be made significantly more economically. In preference, the back flushable filter is characterised in that the body is of substantially cylindrical shape, with the parts of the filter being divided into chambers by divisions radially extending from its axial centre, each chamber including an upper access aperture and a is . lower access aperture, the valve means being adapted to direct through put of a selected chamber either in the case of back flushing, from the lower access aperture to the upper access aperture, or, in the case of effecting filtering from an upper access aperture through the chamber to a lower access aperture. 20. It is inherent that a lower access aperture can be consituted by a plurality of apertures providing thereby a screen so that in the case that the filtering medium is sand or some fine particulate material, such will be retained from egress through any such aperture. Now that it becomes possible to provide for significant back 25. flushing pressures and volumes at an economic price, it further becomes viable then to consider a filter medium of different type in which some of the particles which are indeed the detritus can in fact be retained within a converging aperture, so as to provide of themselves the filtering effect but such that these can be adequately dislodged with a 30. back flushing even though such back flushing flow must be provided through the narrowest gap and be expected to dislodge significantly wedged particles. Accordingly as a further preferred form of this invention there Is proposed that the above be now used in combination with a filter which Is comprised of a plurality of members located in an adjoining relationship to form a stack, and a plurality of filtering gaps being 5. defined between adjacent edges of the adjoining members. In preference, in respect of the stack there are communicating passage ways passing transversely through the stack so as to provide for an access conduit on one side of each gap and a disposal conduit on the other side of the gap. 10. These and other features will be discernable by reference to the accompanying claims, and also by further reference to the description relating the preferred embodiment which shall now be described. Referring to the several embodiments and the illustrations of these we note that:- 15. FI6. 1 is a cross-sectional view with part cut away parts illustrating a filter constructed according to a first embodiment, FIG. 2 is a perspective view of the filter of Fig. 1 , with however, part cut away showing three separate chambers two of which are in a conventional filtering mode and a third of which is a back flushing mode, 20. FIG. 3 is a cross-sectional view of a second embodiment incorporating a stack of filter elements, FIG. 4 is a view from above of the same emodiment as in Fig. 3 with a top cover part removed, FIG. 5 is in an enlargement of a part of the stack of filter elements 25. illustrating the arrangement for providing the filtering effect, and FIG. 6 is a plan view of one of the elements constituted in the stack of filter parts In the second embodiment. Referring in detail to the drawings and particularly to the first embodiment as shown In Figs 1 and 2, there is a pressure sand filter which has a plurality of chambers 2 which are divided by dividers 3 which are fitted between an outer cylindrical container 4 and an inner 5. upright conduit 5. Each of the chambers 2 is characterised by having a lower access aperture 6 and an upper access aperture 7. The lower access aperture is connected to be accessible to a lower part of the central conduit 5 at 8 through a tube 9 which includes a 10. number of straining slots 10. The straining slots 10 are selected to provide resistance to passage of siliceous particles e.g. sand during the filtering mode. The upper access aperture 7 is adapted to be variously connected by means of rotary valve 1 1 so that one of the upper access apertures 7 is . Is connected to conduit 12 which is directed to a disposal outlet while the remainder of the apertures 7 are connected through the upper part of the vertical conduit 5 at 13 whereby they are connected to inlet conduit 1 through which water can be directed which requires filtering. The lower part of the vertical conduit 5 at 8 is connected to the 20. outlet conduit 15 which is directed to provide passage for water that has been filtered. The position of rotary valve 1 1 is adapted to be controlled by motor 16 operating which operates through shaft 17 whereby to effect rotation of gear 18 which operates against corresponding gear teeth on 25. the outer side of the cover 1 1 at 19. The controls operating gear 16 are such that there is a timer and a stepping function such that the rotary valve 1 1 is stepped through from a position corresponding as shown in Fig. 1 with a first upper access aperture 7 to a next positon which is the next upper access aperture 7 in 30. the adjacent vicinity so providing back flushing for a next adjacent chamber 2. In practice with this arrangement, each of the chambers 2 is loaded with sand so that the height of sand In a compacted state that is for conventional filtering will be approximately half the height of the respective chamber, and that the size of the sand particles is generally 5. greater to the extent of the slots 10. As can now be seen by setting the timing function, controlling the motor 16, the rotary valve 1 1 can be variously positioned so as to provide for a back flushing effect for each of the chambers. Of significance, however, is that the extent of back flushing can be ιo - controlled in that all of the water being filtered is available for back flushing if necessary by control using valves variously in the conduit 12 and the conduit 15 in that if the conduit 12 is completely closed, all of the water being filtered will issue through conduit 15 while if the conduit 15 is closed all of the water will issue through conduit 12. is. Of further signficance, however, is that the water being directed through the slots 10 when entering the back flushing mode chamber 2 is filtered so that detritus will simply not be available to be collected on the inside of the slots and hence available for return into the main body of water through conduit 15. 20. The extent of water available and the extent of pumping capacity necessary can be calculated for various sized filters but it will now be found that adequate back flushing flow is available from very much smaller pumps than has hitherto been the case, providing significant total economic advantage. 25 • Now referring to the second embodiment as described in Figs. 3,4,5 and 6, there is provided a substantially cylindrical container 20 which has within it a stack of filtering elements 21 which are each of annular shape as shown in Fig. 6 and each located one upon the other and held in this position by retaining ring 22 at the bottom and a top plate 23. 30 - At the bottom there is likewise a cover plate 24 of similar annular shape which has a plurality of aperture segments 25 passing At the bottom there is likewise a cover plate 24 of similar annular shape which has a plurality of aperture segments 25 passing therethrough which are aligned with egress columns 26 within the stack 21. 5. The top cover plate 23 has a plurality of apertures 27 which are In turn aligned with the entry columns 28 within the stack 21. The drawing in Fig. 3 because of its small size only schematically shows these whereas the detail is shown in the enlarged cross-sectional view in Fig. 5. 10. To this extent therefore it is the detail of Fig. 5 that illustrates the cross-sectional parts of the stack of filter elements. Each of the filter elements is comprised of wedge shape sections in cross-section as is shown at 29, each of the elements 21 having a substantially identical cross-sectional shape so that each of the is . elements provides an inclined surface as at 30 and at 31 each of which has the same angle of inclination providing a planar surface aligned to a meeting edge at 32 such that there is provided then a symetrically aligned passage way of decreasing width from an entry end at passage way 28 to an exit end at passage way 26. 20. The narrowest gap at 33, the degree of inclination provided by the respective adjoining parts and the full length of the entry into the aperture is chosen so as to ensure in respect of the particles which will be required to be filtered, that there will be a trapping and compacting of such particles so that the particles themselves provide substantially 25. the effective filtering. Of importance, however, is that these factors are also chosen so that with the available water pressure in reverse, this will be sufficient to at least substantially remove such trapped particles such as Is shown at 34 so that trapped detritus which would be blocking the filter could 30. then be assuredly removed. Such factors as the smoothness of the surface defining the gap, the material comprising a polypropelene plastic or otherwise which is used, and the comparitive gradient all contribute to the effectiveness of the technique described but it is Important to realise that such criteria s • must be chosen with the particular particles and detritus that are to be involved, accordingly some experimentation is Inevitably necessary but the Illustration given especially in Fig. 5 presuming the sides are smooth the defining sides 30 and 31 in each case are of the proportionate length as shown and are planar along their length accordingly. In this preferred ιo • instance, the absolute value of the gap 33 is 0.1 mm, and the walls or surfaces 30 and 31 defining the gap have a large distance apart of 0.8mm. The remaining measurements can be proportioned from the specific measurements. Now reverting the broader description of the filter as a whole, the 15. container 20 further includes a rotary valve 35 the lower end of which at 36 is shaped so as to coincide with a segment shaped upper part of the stack and so as to engage with this to the extent that a reasonable water seal is effected especially with the entry passage ways 27. The position of the rotary valve 35 is governed by motor 37 which 20. in turn drives through shaft 2>Q onto cog 39 which engages gears 40. The motor 37 1s once again governed so that it has two controlling functions a first a timing period function and a second a stepping function so that it is adapted to be driven for a period of time on a cyclic basis with a further given period between such actions such that the 25 .. rotary valve 35 will accurately coincide with an appropriate segment at 36. Each of the elements in the stack 21 Includes radial dividing elements 41 together with the cover plate 23 such that each passage way 27 and 26 are separated segment to segment so that coincidence of 30. the rotary valve 35 with one of the said segments will allow separately Isolated flow of water through the respective segment. In this way, by appropriately coupling an inlet water supply into conduit. 42, water can be then initially directed in direction of arrow 43 whereupon the water will pass through the stack of filter elements 21 providing a filtering effect thereby. A majority of the water can then be flushed out of outlet aperture in the direction of AA while a proportion of the water can be directed by 5. reason of controlling the respective openness or closedness of the respective conduits through the segment being connected through the rotary valve 35. Such a portion is then directed in the direction 46 so as to pass to a sump through outlet 47. This then describes the second embodiment 10. from which it will be seen that there can be provided a filter which in this case is not dependent upon being in any relative position to the ground to provide a filtering effect but which can be providing continuing back flushing with a sufficient head to provide back flushing effect which to a signf icant extent can be effected with cleansed water. is . A disadvantage of the second embodiment is the fact that it relies upon some gathering of particulate materials upon a filtering function being returned but in practice as this is a very small proportion of the total amount of water which will actually be passing through the filter and further that it can be expected such detritus and particles will very 20. quickly gather within the constraining gaps, this can provide filtered water with sufficient speed so as the small amount of detritus that might pass can be in most cases ignored. Once again, however, the size of conduits, the capacity for pumping, and the total size of the filtering element all can be based on 25. significantly smaller pressures and flow rates because of the concept of the invention. It is self-evident that form time to time, the second embodiment article can be disassembled and completely cleansed if this is necessary by disassembling each of the filter elements from the stack, but it is ■ 30. expected that with careful selection of the gap inclinations and with the ability to provide high pressure back flushing with even the smallest of pumping capacity will make such action now very rare.

Claims: THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A back f lushable filter comprising a body, liquid filter means within the body adapted to provide for a filtering effect when liquid is directed in a first direction through the liquid filter means, and adapted to provide for a flushing effect when liquid is directed in an opposite 5. direction through the liquid filter means, the liquid filter means being divided into at least two parts in such a way that back flushing can be effected in at least one of the parts while filtering is being effected in other of the parts, and valve means arranged to direct liquid flow through the liquid filter means such that.back flushing will be effected o . in at least one of the parts while filtering is being effected 1n other of the parts. 2. A back flushable filter as in claim 1 further characterised in that there are drive means adapted to drive said valve means such that the valve means will be stepped through after a selected time from a first position to a second position whereby a back flushing effect is then 5. being effected in a further of the parts. 3. A back flushable filter as in either of the claims 1 or 2 further characterised in that the valve means are further arranged such that liquid being directed to effect the back flushing is part of liquid having been first filtered in other parts of the filter. 4. A back flushable filter as in any one of the preceding claims further characterised in that each of the parts of the filter is divided for the back flushing function by there being provided separate chambers. 5. A back flushable filter as in any one of the preceding claims further characterised in that the filtering medium is sand. 6. A back flushable filter as in any one of the preceding claims further characterised in that the body is of substantially cylindrical shape with the parts of the filter being divided Into chambers by divisions radially extending from its axial centre, each chamber 5. including an upper access aperture and a lower access aperture, the valve means being adapted to direct throughput of a selected chamber either, in the case of back flushing, from the lower access aperture to the upper access aperture or, in the case of effecting filtering from an upper access aperture through the chamber to a lower access aperture. 1. A back flushable filter as in any one of the preceding claims further characterised in that the liquid filter means are comprised of a plurality of members located in an adjoining relationship to form a stack, and there are provided a plurality of filtering gaps being defined 5. between adjacent edges of the adjoining members providing the said stack. 8. A back flushable filter as in claim 7 further characterised in that there are communicating passage ways passing jointly through the said members of the stack providing for passage of liquid to be filtered in the one case, and filtered liquid in the other. 9. A back flushable filter as in either of the last 2 preceding claims further characterised in that at least a plurality of the filtering gaps have walls which are inclined one with respect to the other whereby to provide for a collection of compacted particles therein to provide a 5. filtering effect. 10. A back flushable filter wherein there is filtering means comprising a stack of members each of circular shape and confined within a container, each of the members including a shape such as to match with an adjoining member to define thereby a separating aperture 5. for filtering purposes for water, each of the members having walls matching between adjacent members so as to isolate one segment and apertures within a segment form adjacent segments, a cover plate over the stack having apertures passing therethrough coinciding with entrance apertures within the stack, a base plate on an opposite side of the stack o . from the cover plate having apertures passing therethrough coinciding with exit path ways in the stack, and means adjustably positioned so as to be moveable from location to location in rotating fashion from segment to segment of the stack whereby to provide for a back flushing effect isolated to a selected segment or segments. 1 1. A back flushing filter substantially described in the specification with reference to and as illustrated by Figs 1 and 2 of the accompanying drawings. 12. A back flushing filter as substantially described in the specification with reference to and as illustrated by Figs 3,4,5 and 6 of the accompanying drawings. 13. A filter wherein a portion of the liquid filtering means is adapted to be cleansed by back flushing while a remaining portion of the filter means is providing for a filtering effect of water passing therethrough. 14. A filter as in the last preceding claim wherein the arrangement is further characterised in that some of the water subsequent to being filtered is directed through the portion of the filter being back washed.

Inventors: SNELLING PETER JOHN, SNELLING, PETER, JOHN
Applicants: SNELLING PETER JOHN, SNELLING, PETER, JOHN
Application year: 1986
Main classification: B01D29
IPC codes: B01D24, B01D35