AU612516B2 - Back flushable filters - Google Patents

Description

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1111L 25 le 1 I: i i I COMMONWEALTH OF AUSTRALIA Form Patents Act 1952-1969 COMPLETE SPECIFICATION (ORIGINAL) 6125 1 6 FOR OFFICE USE: Class Int. Class Application No Lodged

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Complete Application No Specification Lodged Published Priority: Related art: TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: Actual Inventor: Address for Service: PETER JOHN SNELLING Qr C C

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C' C' Unit 1, 14 Cocos Grove, West Lakes, State of South Australia, Commonwealth of Australia PETER JOHN SNELLING Care of COLLISON CO., 117 King William Street, Adelaide, South Australia, 5000 Complete Specification for the invention entitled: BACK FLUSHABLE FILTERS The following statements is a full description of this invention, including the best method of performing it known to me: AE II7 IIILI UII u i u aria irue copy) S2 This invention relates to back flushable filters.

It is known to use filter members held together as a stack which define between the adjoining members filter apertures which act to define a narrow gap and thereby restrict detritus from passing therethrough.

All of the formerly known devices have required eventual cleansing by separating the filter members and then separately hosing the filter members which are usually in the form of plates. Needless to say such an operation is considered to be less than ideal and it is very time consuming.

The present invention has for its purpose to propose an arrangement by which 1 5 the efficiencies of preformed filter members can be achieved and that there can be provided means whereby a more sensible and economic technique can be used for cleansing the filter from time to time.

Accordingly there is proposed a filter which is comprised of a plurality of °2 members located in an adjoining relationship to form a stack, and a plurality of 0 0 filtering gaps being defined between adjacent edges of the adjoining members, and in respect of the stack there are communicating passageways 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.

ArA problem with present back flushing techniques is that because the velocities %o of water are inherently necessarily different, the capacity of pumps, pipes and S control valves must all be selected to allow for the back flushing capacity so that S 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.

The problems discussed can be at least significantly reduced by the invention o o 0 by providing that the back flushable 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.

I U: I he Commissioner of Patents I3 Because the water is being directly filtered and then provided from a lower end for back flushing, there will be at most negligible detritus with the 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 accordingly to this invention can be made significantly more economically.

The invention could thus be said to reside in a back flushable filter comprising a plurality of filter members, each filter member being located in an adjoining relationship with other of the filter members to form a stack, each of the filter members including a plurality of filter parts and a plurality of divisions, said divisions dividing filter parts into sectors, each filter part in each sector being located and being shaped so as to provide in cooperation with and between 0 n, filter parts of adjoining filter members a plurality of filter apertures concentrically 4.2* spaced apart in each sector, each of said filter apertures having a shape 0a.J defining converging sides to a narrowest gap, the filter members in the stack defining for each thus formed converging filter aperture and within each sector a supply conduit connecting to a widest end of each filter aperture, and the filter members defining an exit conduit within each sector connecting to a narrowest end of each filter aperture and means to connect a back flush flow to the exit conduit for each selected sector whereby to effect a back flush through filter anon o oo apertures within the selected sector or sectors.

SIn preference, the back flushable filter is characterised in that the body is of substantially cylindrical shape, with the parts of the filter being divided by divisions radially extending from its axial centre, each chamber including a j oo plurality of upper access apertures and a plurality of lower access apertures, the Svalve 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 f-om an upper access aperture through the chamber to a lower access aperture.

4 It is inherent that a lower access aperture can be constituted by a plurality of apertures providing thereby a screen.

Now that it becomes possible to provide for significant back flushing pressures and volumes at an economic price, it further becomes viable then to consider a filter medium 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 back flushing even though such back flushing flow must be provided through the narrowest gap and be expected to dislodge significantly wedged particles.

These and other features will be discernible by reference to the accompanying 1 5 claims, and also by further reference to the description relating to the preferred o•embodiment which shall now be described.

o eq Referring to the embodiment and the illustrations of this we note that:- 6*00 00 0 FIG. 1 is a cross-sectional view of the embodiment incorporating a 9 stack of filter elements; FIG. 2 is a view from above of the same embodiment as in Fig. 1 with a top cover part removed; o FIG. 3 is an enlargement of a part of the stack of filter elements illustrating the arrangement for providing the filtering effect, and FIG. 4 is a plan view of one of the elements constituted in the stack ,3,Q of filter parts in the embodiment.

0 0t Now referring to the embodiment as described in Figs. 1, 2, 3 and 4, 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. 4 and each located one upon the other and held in this position by retaining ring 22 at the bottom and a top plate 23.

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4a 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.- 0a-« 0 0/ 0 0 90 o 00 04 t O 0, 0 0/ 00 0 -e- 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. 1, because of its small size, only schematically shows these whereas the detail is shown in the enlarged cross-sectional view in Fig. 3.

To this extent therefore it is the detail of Fig. 3 that illustrates the cross-sectional parts of the stack of filter elements.

Each of the filter elements is comprised of wedge shape sections in crosssection as is shown at 29, each of the elements 21 having a substantially identical cross-sectional shape so that each of the elements provides an inclined surface as at 30 and 31 each of which providing a planar surface 1 5 aligned to a meeting edge at 32 such that there is provided then a symmetrically aligned passageway of decreasing width from an entry end at passageway 28 to an exit end at passageway 26.

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 the effective filtering.

2 b" 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 then be assuredly removed.

3 0 Such factors as the smoothness of the surface defining the gap, the material comprising a polypropylene plastic or otherwise which is used, and the comparative gradient all contribute to the effectiveness of the technique described but it is important to realise that such criteria must be chosen with the particular particles and detritus that are to be involved, accordingly some 3 5 experimentation is inevitably necessary but the illustration given especially in Fig. 3, presuming the sides are smooth the defining sides 30 and 31 in each *1 ;f 1 ~I.;~OPF"U~""DI"-"ICWll~ 1101~131C -111_13--.i 1 1111 case are of the proportionate length as shown. In this preferred 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 0.8 mm. The remaining measurements can be proportioned from the specific measurements.

i; i -r ,i Now reverting to the broader description of the filter as a whole, the container 20 further includes a rotary valve 35 the lower end of which at 36 is shaped so as to coincide with a shaped upper part of a respective sector above the stack and so as to engage with this to the extent that a reasonable water seal is 1 0 effected especially with the entry passageways 27.

The position of the rotary valve 35 is governed by motor 37 which in turn drives through shaft 38 onto cog 39 which engages gears 0 The motor 37 is 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 rotary valve 35 will accurately coincide with an appropriate segment at 36.

Although the motor and thus the rotation of the valve may be stepped this is not necessary and a continuous rotation of the rotary valve is sufficient to effect a backflush of each segment.

o oJ A lower elongate slit 48 is provided at the lower surface of the rotary valve .oo as shown by broken lines in Fig. 2, so that even with a continuous rotation of the ,,rotary valve a backflush is effected in substantially only one sector at a time. As shown in the embodiment the elongate slit is only marginally wider than the radially dividing elements 41. The elongate slit 48 thus only accounts for a small proportion of the width of the rotary valve Each of the elements in the stack 21 includes radial dividing elements 41 together with the cover plate 23 such that each passageway 27 and 26 are separated segment to segment so that coincidence of the rotary valve 35 with one of the said sectors will allow separately isolated flow of water through the respective sectors.

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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 44 while a proportion of the water can be directed by reason of controlling the respective openness or closedness of the respective conduits through the 1 0 segment being connected through the rotary valve -1 5 o 0 ooC o o0 o 0 0 0 a Such a portion is then directed in the direction 46 so as to pass to a sump through outlet 47. This then describes the embodiment 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 is effected with cleansed water.

A small disadvantage of this embodiment in some applications 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 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.

q 2 Once again, however, the size of conduits, the capacity for pumping, and the total size of the filtering element all can be based on significantly smaller pressures and flow rates because of the concept of the invention.

It is self-evident that from time to time, the 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 expected that with careful selection of the gap inclinations and with the ability to provide high pressure 3 5 back flushing with even the smallest of pumping capacity will make such action now very rare.

Claims (4)

1. A back flushable filter comprising a plurality of filter members, each filter member being located in an adjoining relationship with other of the filter members to form a stack, each of the filter members including a plurality of filter parts and a plurality of divisions, said divisions dividing filter parts into sectors, each filter part in each sector being located and being shaped so as to 1 0 provide in cooperation with and between filter parts of adjoining filter members a plurality of filter apertures concentrically spaced apart in each sector, each of said filter apertures having a shape defining converging sides to a narrowest gap, the filter members in the stack defining for each thus formed converging filter aperture and within each sector a supply conduit connecting to a widest 1 5 end of each filter aperture, and the filter members defining an exit conduit within each sector connecting to a narrowest end of each filter aperture and means to o, connect a back flush flow to the exit conduit for each selected sector whereby to effect a back flush through filter apertures within the selected sector or sectors. ,0

2. A back flushable filter as in the last preceding claim in which each of the filter members is of a substantially annular shape in plan and each of the divisions extends in a direction radially aligned where the radial direction is aligned with a centre of the annular shape. Q A back flushable filter as in either of the last two preceding claims in which each filter part extends in a substantially circumferential direction with respect to a centre of the annular shape.

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4. A back flushable filter as in either claims 1 or 2 in which each 3,JQ sector is defined by divisions comprised of walls extending when viewed in plan S in a radially aligned direction from the centre of the annular shape and providing a fluid seal from adjacent sectors by reason of abutting edges of the respective walls. A back flushable filter wherein there are filter means comprising a stack of filter members each of circular shape and plan, the stack being confined within a container, each of the filter members including a shape which co-operates with a shape of adjoining members to define therebetween a 0 y o tuon O3 r O 0 00 00 0 ooo CO v 0 D0 T. C i 9 separating and converging aperture for filtering purposes for water, each of the filter members having a dividing wall purposes for water, each of the filter members having a dividing wall arranged to isolate a sector and filter apertures within the sector from adjacent sectors, a cover plate located at one end of the stack having apertures passing therethrough coinciding with entrance apertures within the stack which in turn coincide with a supply conduit defined between i the segments interconnecting filter apertures within respective segments, a base plate at an opposite end of the stack from the cover plate, and having y apertures passing therethrough coinciding with existing apertures in the stack 1 0 which in turn coincide with existing conduits interconnecting the exit ends of filter apertures within respective sectors, and means adjustably positionable so as to be movable from location to location of the stack whereby to connect for a back flushing directed through a selected sector or sectors. 015oo 6. A back flushable filter substantially described in the specification with reference to and or illustrated by the accompanying drawings. Dated this 3rd day of October 1989. PETER JOHN SNELLING By his Patent Attorneys, i COLLISON CO. i *I\ 11 a^ -i" 1 j