GB2492640A - A tubular filter unit especially for use in extracting water using a hose from a natural source - Google Patents

Abstract

A filter unit 10 comprises a tubular perforated member 14 mounted between two end caps (16, 18) (the end caps and the tubular member define an interior space within the unit) and at least one end cap has an opening therein in communication with the interior space and is adapted to receive a coupling for a hose, pipe or other fixture. The filter unit may comprise two tubular perforated members 12, 14 mounted concentrically one within another between the two end caps to define an annular space therebetween, the end caps and the innermost tubular member defining the interior space within the unit. The tubular member(s) and end caps may be may be made of plastics. The holes 24 in one tubular member may not be in direct registry with the holes in an adjacent tubular member. The filter unit may be especially useful for extracting water using a hose from a natural source.

Description

I

FILTER UNIT

Field of the Invention

lire invention relates to Filter utiits and, in particular. to filter units for filtering or screening coarse debris from fluid sources. More especially, the iiventlon relates to filter units for filtering or screening coarse dehris from water sources such as rivers, ponds and lakes.

Background of the Invention

\Vhen extracting raw water from sources such as rivers, potids and lakes or reservoirs for use in for example fire fighting, irrigation etc, problems arise from coarse dehris being sacked tip with die water When pump vacuum is applled to the hose, pipe or other fixture used for extracting the water from the source. Providing a filter or screening unit on die etid of the hose hefore it is throwti into the water source reduces the problems associated with such coarse debris.

One prior proposal for a filter or strainer unit used a perforated metal sheet located within a wicker basket. However, it was found that, in use, the metal sheet was relatively easily danraged owing the rough treatment the filter unit received. Additionally, with such filters odour was a significant problem arising from decaying organic eletricus trapped at the intersections of the weven strands forming the wicker basket, the removal of such detritus during cleaning of the wicker basket being very difficult to achieve.

Repeated wetting of both the wicker basket and the metal filter causes these two components to rot.

Where the wicket basket is not cleaned effectively, it may he the source of disease.

An alternative prior proposal as exemplified iti US 6978900 B2 consists of providitig an annular cage framework that supports hraided filter strands. As will be apparent from the construction shown in LS 6978900 B2, the assembly/disassembly of such a filcer unit is relatively complex and the odour problem arising from trapped decaying organic detritus would appear nit te have been eliminated owing to the voveti tiature of the braided filter strands. To clean such a filter unit effectively, it would appear to he necessary to disassemble it and particularly clean the contact areas of the individual braids.

It is desirable, therefore, to provide a filter unit that is of simple construction, is easy to assemble/disassemble, reduces the trapping of organic detritus and is easy to clean.

Summary of the Invention

According to the present invention, a filter unit comprises at least one tubtilar perforated member mounted between two end caps to define a space therebetween, the end caps and the tubular iiieiiiher defining an interior space within the unit, at least one end cap having an opening therein in communication with the interior space and being ad-(iltet] to receive a coupllng for a hose, pipe or Other fixture.

Preferably, the filter utiit comprises at least two tubular perforated members mounted concetitrically one vithiti atiother between two end caps to define an annular space therehetweeti, tile end caps and the innermost tubular member defining an interior space within the unit, at least one end cap having an opening therein iii communication with the interior space arid being adapted to receive a coupling for a hose, pipe or other fixture..

The at least one tubular member and end caps of the filter unit may be made of suitable metal, plastics or plastics-coated metal. If desired, mixtures of materials may be used; for example, the tubular members may he made of plastics and die end caps may he made of metal.

In a preferred embodiment of the invention, the at least one tubular member and end caps of the filter unit arc made of plastics. Preferably, the plastics are low wetting plastics. The plastics may have a surface energy of not more than 40 dynes/cni, more preferably not more than 38 dynes/cm.

Suitable plastics from which the tubular members and end caps of the filter unit according to the invention are made include polyhydrocarbons such as polypropylene and polyethylene and copolymers thereof, polyfluorocarbons such as polytetrafluoroethylene, fluorinated ethylene and propylene copolymers and poly vinyl fluoride, polyamides, polyinrides, polyacetals and polyphenylene sulphide.

Preferred polymers for use in the invention are polyhydrocarbons and copolymers thereof. In particular, polypropylene and polyethylene, and copolymers thereof, are preferred polymers for use in the invention; polypropylene and copolymers thereof are particularly preferred.

The tubular members may be perforated by holes selected from a variety of shapes and sizes. For example, the shapes of the holes may include circular, non-circular, elongate, ie slots, holes or mixtures thereof Preferably, the sizes of the holes may he the same, at least within each tubular member, ie they may differ between tubular members; or they may differ, at least within one tubular member.

Preferably, within the filter unit, the holes in one tubular member are riot in direct registrY with the holes in an adjacent tubular member.

Preferably, the perfirations in each tubular member occupy at least 20%, more especially at least 30% of die surface area 0f the member. Preferably, die perforations in each tubular member occupy not more than 60%, more especially at least 50% of the surface area of the member. It is preferred the perforations in each tubular member occupy between 20% and 601, more especially occupy between 30% and 504, of the surface area of die member.

In a preferred embodiment of the invention, the tubular members are perforated by circular holes.

Preferably, the holes each have die same diameter, at least within each tubular member, i.e. the diameters of the holes in one tubular member may lie different to the diameters of the holes in another mhular member. In yet another preferred embodiment of the inventitrn, the tubular members are each perforated by circular holes each having the same diameter. It is prefcrred the diameters of the holes are not less than 2 mm, more especially are not less than 2.5 mm. It is also preferred the diameters of the holes arc not more than 6 mm, more especially not are more than 4 mm. It is preferred the holes have a diameter in the range 2 nun to 6 nim, more especially a diameter in the range 2.5 mm to 4 mm.

in yet another preferred emboeliment of the invention, the tubular members are perforated by circular holes each having the same diameter, said diameter being as defined in the preceding paragraph and wherein the holes are arranged iii rows. Preferably, within a row, the centre-to-centre spacing of adjacent holes is equal to at least twice the diameter of the holes. Preferably, within a row, the centre-to-centre spacing of adjacent holes is equal to not more than six times the diameter of the holes, more especially is equal to not more than four times thc diameter of the holes. Typically, within a row, the centre-to-centre spacing of adjacent holes is in the range between twice and four times the diameters of adjacent holes.

Preferably, the spacing between alternate rows of holes, which may be offset in relation to one another, is equal to at least 1.4 dines, niore especially at least twice, the diameter of the holes. When adjacent rows of hoies are offset from one another, preferably the centres of holes in one rov are equidistant from the centres of holes in an adjacent row of holes.

When the tubular members have alternate rows of holes that are offset in relation to adjacent rows of holes as described in the preceding paragraph, in a preferred embodiment of the invention the rows in one tubular member run perpendicularly to the rows in an adjacent tubular member. It is particularly preferred that the rows in one tubular member lie in radial planes and the rows in an adjacent tubular member lie in axial planes.

As will he appreciated, the size of the holes, the centre-to-centre spacing and the spacing between adjacent rows of holes will be selected to suit the application for which the filter unit is intended, for example based on the potential amount of debris to he filtered and the How rate of tluid required.

Conveniently, the tubular inenibers of the filter uiut of the invention are made from perforated, platiar sheet material formed into a tubular shape around a suitably shaped and sized device. One suitable device comprisesaframe that is square in cross-section and has elongate members extending from each corner of the franie. The sheet material is cut to size then rolled up in the franie to engage oppositely located sides of the sheet with one another, the engaging sidcs then being attached together for cxample by welding to form a cylinder. Alternatively, thc device may be a mandrel, cg a cylindrical mandrel, to etigage oppositely located sides of the sheet with one another and securing the sides together. The sheet material may be provided as a large sheet from which sections of suitable sire are cut for use in making the tubular members. Typically, the sheet is at least 2 miii thick and, more preferably, is 3 nun thick.

However, iii some applications, heavier gauge sheet may be used, if desirable.

if necessary, heat may he applied to the sheet to aid in the shaping of the sheet into a substantially cylindrical shape whilst it is in the device or immediately prior to its introduction into the device, or whilst the sheet is located around the mandrel. The engaging sides of the sheet may he secured by being welded together. When the tubular members are made of plastics material, eg polypropylene, typically the hcat applied to the sheet and the welding together of the engaged sides of the sheet may be accomplished usi fig a suitable hot air gun.

Although the filter unit may have more than two tubular members, in a preferred embodiment of the invention the filter unit has only two tubular members. Whilst the tubular members may he ot]1e1 than cylindrical, in a preferred embodiment of the invention the tubular members are cylindrical.

Preferably, an inner tubular member, in relation to an outer adjacent tubular member, has annular end flanges extending radially outwardly therefrom. The flanges may function as strengtlleners for the tubular member from which they depend. if required, for example in a filter unit which has a length that is greater than that normally used for filter units for filtering or screening coarse debris, an additional flange or additional flanges may be provided intermediate the end flanges on the inner tubular member.

in one embodiment of the invention, said flanges may have a radial extent sufficient to contact and support the outer adjacent tubular member.

Preferably, each end flange is provided with at least one through, threaded aperture; more especially a plurality of through, threadeti apertures, for example typically four to eight but six being preferreti. Tile aperture or apertures may accept a cylindrical metal sleeve threaded on its internal surface. The end caps are provided with at least one corresponding plain through aperture, preferably countersunk at its external end whereby when the end caps and tubular members are assembled together a bolt or bolts passing through the plain apertures in the end caps and eugaiig with the tilreaded apertures in the flanged tubular memhcr lock the components together.

The end caps eacil have a first anuuiar shoulder for receiving arld locating an end of an inner tubular member and a second annular shoulder, located radially outwardly of the first shoulder, for receiving and locating an end of an outer tubular member. When the inner tubular member has end flanges as previously described, the first annular shoulder of each end cap abuts a flange thereby to locate the ill ncr tubular member through the flanges.

in a preferred embodiment of tile invention, the opening of said at least one end cap having an opening therein in communication with the interior space and being adapted to receive a coupling for a hose, pipe or other fixture is provided over at least part of its axial length with a screw thread for receiving said coupllng during use of the filter unit. Preferably, the screw thread extends only partially along the opening in the end cap and terminates at an inwardly-extending annular collar that forius an end stop to prevent a coupling engaging with the screw thread in use of the filter unit from penetrating into the Interior space.

it will he appreciated, however, that, in other enlhodiments, other means for attaching the coupllng for a hose, pipe or other fixture nay be used as are well known in the art, the end cap or caps being adapted to accommodate the particular fitting selected.

in an alternative embodiment, both end caps are provided with an opening therein in communication with the interior space uld being adapted to receive a cOuplitlg for a hose, pipe or other fixture. Tn this Instance, couplings may be engaged with a respective end cap whereby fluid is extracted from the filter unit at both ends thereof.

As will be appreciated, couplings suitable for connection may be available in different sizes. For example, screw-threaded couplings are typically available in 4" (101.6 mm) and 5.5" (139.7 mm) sizes. One option to accommodate such variation in size, is to provide two separate filter units, which units eacli being capable of connecting with one of the coupling utiits.

Alternatively, in accordance with the invention, the filter unit may accommodate couplings of different sizes in a variety 0f ways.

in accordance with otle elilbodillient, a jilter unit according to tile invention niay he supplied with alternative end caps each having an opening to tccc)nmc)d-ate a specific coupling size. For example, referring to die screw-threaded couplings described above, the filter unit would he supplied with two interchangeable end caps, one liavlilg an opening capable of receiving the 4" (101.6 mm) coupling and the other having an opening capable of receiving die 5.5" (139.7 mm) coupling.

in accordance with another embodiment, in a jilter unit according to the invention, both end caps may have an opening to accommodate a specific coupli[ig size. Such a filter unit would he provided with closure plugs, for example threaded plugs, for plugging the end cap not connected to the coupling being used. Alternatively, in use of the filter unit, couplings of different sizes could be simultaneously connected to the unit.

in accordance with yet anotlier embodiment, in a filter unit according to the invention, one end cap may have an opening to accommodate a specific coupliug size, preferably the larger or largest coupling size, and would he provided with at least one adapter having a corresponding opening and being capable of being connected with the opening and with a coupling of a different size to the coupling connectable with the end cap.

Such embodiments may be used in combination with one another.

in another embodiment of the invention, the filter unit comprises an end flange, the end flange ilavillg a periphertd wall and walls located inwardly of the peripheral wall, the inner tubular member engaging with said inner walls. Preferably, the filter unit comprises two such end flanges, one engaging each end of the inner tubular member.

Preferably, the inner walls form a shoulder, which may be a right angle.

Advantageously, the filter unit further includes an end cap, the end cap including a base and walls extending from the base, the walls configured to engage with the outer tubular member.

Preferably, the end cap is configured to engage the cad flange. The wall extending from the base engages \vith the peripheral wall of the flange.

Advantageously, the wall extending from the base includes a rebate, and the outer tubular member sits in the rebate. Preferably, the peripheral wall of the flange extends beyond the lower edge of t]ie rebate arid forms a recess having a substantially U shaped cross section with the walls of the recess, the outer tubular member sitting in the recess.

The filter unit preferably includes a fitting including two bores, each of a different diameter and configured to receive and engage with a corresponding coupling, such as a hose fitting. Preferably, each bore is internally threaded Advantageously, the fitting includes an inwardly-extending annular wall elements that each form all end stop for the respective bores.

The end cap may mount lugs and may include bores configured to receive such lug.

The end cap may include a lanyard attachment means, which may comprise a bore extending through a part of the end cap.

It will he apparent from the foregoing description that the filter unit of the invention is easy to make and is simple to assemble and disassemble thus making it easy to clean debris and organic detritus from the components thereof. That the preferred materials from which the filter unit components are made are non-wetting plastics contributes to the ease with which the filter unit components may he cleaned.

Additionally, as the tubular members do not have interstices such as those formed owing to the weave construction of some prior constructions of filters, detritus is not as readily apped by the filter unit components in a mariner such that it cannot be readily cleaned from the components.

Brief Description of the Drawings

The present invention will now lie illustrated by way of example only with reference to the accompanying drawings in x;hieli: Figure 1 is an elevation in the eirection of A_rrow C in Figure 2 of an end cap for a filter unit according to the invention; Figure 2 is a section on Arrow A-A in Figure 1; Figure 3 is a sectmon on Arrow B-B in Figure 1; Figure 4 is an elevation the same as that shown in Figure 1 but of an end cap at the opposite end of the filter; Figure 5 is a photograph of an unassembled filter of the present invention without its end cap as shown in Figure 1 hut with the outer tubular member located on the end cap as shown in Figure 4; Figure 6 illustrates an intermediate flange; Figtire 7a is a schematic representation of an alternative embodiment of a filter unit of the invention; Figure 7h is a side view of the lilter unit illustrated in Figures 7a; Figure 7c is a cross-sectional elevation on the axis A-A shown in Figure 7h; Figure 7d is a plan view of the filter unit illustrated in Figures 7a to 7c; and Figure 8 is a cross-sectional elevation of an alternative embodiment of an end cap for a filter unit according to the invenflon.

Detailed Description of the Preferred Embodiments

Referring now the drawings, a filter unit 10 according to the invention has two tubular, cylindrical perforate members 12, 14 mounted between concentrically one within the another between two end caps 6, 18 to define an annular space therehetween, the end caps 16, 18 and the inner tubular member 14 defining an interior space within the unit 10.

If) The tubular members 12, 14 (see Figure S) are made of polypropylene copolymer (SG 0.91).

The tubular members 12, 14 were made from 3 mm gauge plastic sheet perforated with circular holes 24.

The holes are arranged in rows 26 and are typically 3 mm diameter and have a centre-to-centre spacing of 8 mm, which results in approximately 37-40% of the surface area of the sheet being occupied by holes.

In an alternative embodiment the holes are typically 3.5 mm diameter and have a centre-to-centre spacing of 9.5mm The spacing between alternate rows 26 of holes 24 is 6 mm, the holes 24 in one row 26 being offset from die holes 24 in an adjacent row 26 and the centres of holes 24 in one row 26 being equidistant from the centres of holes 24 in an adjacent row 26. The rows 26 in the outer tubular member 12 run perpendicularly to the rows 26 in the inner tubular member 14, the rows 26 in the tubular member 12 being located in radial planes and the rows 26 in the tubular member 14 being located in axial planes. The holes 24 in the outer tubular member 12 are not in direct registry with the holes 24 in the inner tubular niember 14.

ille tubular members 12, 14 of the filter unit 10 were made by cutting appropriately sized sections from the sheet material, which sections then being formed into a tubular shape around a suitably shaped and siaed mandrel, eg a cylindrical mandrel, to engage oppositely located sides of the sheet with one another and securing the sides together. The sections of the sheet material were heated using a hot air gun to assist in the forming process, the hot air gull then being used to weld the engaging sides of the sections together, the weld lines being visible at 28 and 30, respectively, for the tubular members 12, 14.

The tubular member 14 has annular end flanges 32 extending radially outwardly therefrom. The flanges 32 are made from the same plastics niaterial as the tubular members 12, 14 and, conveniently, are welded to the ends of the tubular melnber 14 using the hot air gun. The flanges 32 are each lrovidetl with six, equally spaced, through, threaded apertures 34 in the form of cylindrical metal sleeves threaded on their internal surfaces, the sleeves being tnoulded into the plastics of the flanges 32.

The end caps 16, 18 are niade from propylene homopolymer (SG 0.91).

The end cap 16 has an opening 36 therein in communication with the interior space and its inner peripheral wall 38, which defines the opening 36, is formed with a screw threaded section 40 for receiving a threaded coupling (not shown) for a hose, pipe or other fixture (not shown). The inner peripheral wall 38 has at its axially inner end an inwardly-extending annular collar 42 that terminates and forms an end S stop for the screw threaded section 40 to prevent a coupling (not shown) engaging with the screw threaded section 40 in use of the filter unit 10 from penetlating through the opening 36 into the interior space.

The side of the end cap 16 contacting the tubular tnenihers 12, 14 has a first annular shoulder 44 for receiving and locating an end of the inner tubular member 14, the periphery of the flange 32 thereof engaging with the shoulder 44, and a second annular shoulder 46, located radially outwardly of the first shoulder 44, for receiving and locating an end of the outer tubular member 12. The cat1 cap 16 also has six equally spaced, plain through apertures 48, countersunk at their external ends, for receiving bolts that engage the threaded apertures 34 in the llange..32 on the inner tubular member 14.

The end cap 16 further includes bores 43 configured to receive a lug element that protrudes beyond the outer surface of the end cap. Also, the end cap 16 further inclndes a bore 41 to receive a rope so that the filter may be retrieved in the event that it becomes detached from the hose to \vhicli it is connected.

The end cap 18, located at the opposite end of the filter unit 10 from the end cap 16, closes that end of die filter unit 10. The side of the end cap 1$ contacting the tubular members 12, 14 has a first annular shoulder 50 for receiving and locating an end of the inner tubular member 14, the periphery of the flange 32 thereof engaging with the shoulder SC, and a second annular shoulder 52, located radially outwardly of die first shoulder 50, for receiving and locating an end of the outer tubular member 12. Similarly to the end cap 16, the end cap 18 has six equally spaced plain through apertures 54, countersunk at their external ends, for receiving bolts that engage the threaded apertures 34 in the flange 32 on the inner tubular member 14.

Typically, the filter unit 10 may be assembled as follows: * The inner tubular member 14 is engaged with the end cap 1$, the flange 32 on the member 14 engaging with the first annular shoulder SC on the end cap 18, the apertures 54 in the end cap 1$ being located in registry with the threaded apertures 34 in the flange 32. Bolts (not shown) arc passed through the apertures 54 to engage die threaded apertures 34 and flghtenecl to retain the.

inner tubular member 14 relative to the end cap 18.

* The outer tubular member 12 is then passed over the inner tubular member 14 to engage with the end cap 1$ and abut die second annular shciulder 52.

* liie end cap 16 is then located on to the other ends of the tubular members 12, 14, the flange 32 on the inner member 14 engaging with the first annular shoulder 44 thereon and the end of the outer member 12 engaging with the second annular shoulder 46 thereon, the apertures 48 in the end cap 16 being located in registry with the threaded apertures 34 in the flange 32. Bolts (not shown) are passed through the apertures 48 to engage the threaded apertures 34 and tightened to retain the in tier tubular member 14 relative to the end cap 16.

lhe outer tubular member 12 is retained relative to the end caps 16, 18 by virtue of its engagement at each end of the filter unit 10 with the respective an nular shoulders 46, 52 on thc end caps 16, 18.

Figure 6 illustrates an intermediate flange 60. The filter unit 10 may lie sengthcned by the inclusion of one or more of such flanges mounted within the unit. The flange 60 includes an opening 61 through which the inner tubular member 14 passes, the opening 61 having a diameter that substantially corresponds to the external diameter of die inner tubular member 14. The external diameter of the flange 60 corresponds substantially to the internal diameter of the outer tubular member 12. The flange 60 may be attached to the filter tmit 10 simply by being a push fit on to the inner tubular member 14, and/or a push fit in to the outer tubular meuiher 12. Alternatively, the flange 61 may be fixed to one or both of the inner and outer tubular members 12, 14, for example by welding or adhesive.

it will he apparent that disassembly of the filter unit 10 for cleaning etc is as easy as the assembly of the components and may he done repeateelly.

Referring now to Figures 7a to 7d, there is shown an alternative embodiment of the filter unit 10, which includes strengthening rods 70. The rods 70 are threaded and engage with threaded apertures 34 in the flanges 32'. The filter unit 10 includes an intermediate flange 60, which includes apertures 61 through which the rods 70 pass. The apertures may be threaded to engage with the threads of the rods 70. ilie rods 70 also pass through apertures in the end cap 18' which are aligned with the apertures 34. Whilst an end cap is shown only attached to the base of the filter unit i, iii this embodiment, an end cap 18' is also attached to the top of the filter unit.

The flanges 32' and end cap 18' differ in some respects to corresponding components iii the embodiment of the filter unit IA) illustrated in Figures 1 to 5. The flanges 32' include a shoulder 32' formed by an annular rebate in the flange 32'. Each end of the inner tubular member 14 sits against the shoulder of a respective flange, with its end face abutting the surface of the rebate 32" that extends radially. The inner tubular member 14 is therefore constrained against imvvement with respect to the flanges 32'.

in the illustrated example, each flange 32' inclndes an opening 32a. \X7hilst the flange 32' at the lower end of the filter unit could be closed, it is preferred to use the same component at each end of the filter unit for ease of manufacture.

An end cap 18' is attached to each flange 32', the end caps being configured to engage with outer tubular member 12. The end cap 18' includes a base I 8a' and a wall portion I 8la' extending perpenthciiltu to the base ISa'. The free end of the wall portion ISh' includes a rebate l$c' fomilng a shoulder. The inner surface of the wall portion below the rebate engages with the peripheral surface of the flange 32'. As can he seen from Figure 7c in particular, the peripheral surface of the flange 32' and the rebate The' together form a recess which receives the end of the outer tubular member 12.

As is best appreciated from Figures 7b and 7c, the lower end of each rod 70 is secured in position by a nut 71. The upper end of each rod 70 may also be secured by a nut 71 (not shown) to thereby exert a compressive force on the elements of the filter unit 10.

The upper end of the filter unit 10 receives art end cap, for example of the type illustrated in Figure 8.

A fitting 80 has an opening therein for communication with the interior space of the filter unit 10. Ihe fitting 80 includes two screw threaded sections 82, 83, each defining a different diameter arid each configured to receive one of a standard size of hose coupling. The fitting 80 includes bores 81 which receive rods 70. The fitting 80 provides an inwardly-extending annular wall 82', 83' that each form an end stop for the respective screw threaded section 82, 83 to prevent a coupling (not shown) engaging with the screw threaded section 40 in use of the filter unit 10 from penetrating through the opening therein into the interior space.

The fitting 80 further includes lug elements 84 and may include a bore for receiving a rope so that the filter n-my be retrieved in the event that it becomes detached from the hose to which it is connected.

\Vhen the end cap is mounted on the rods 70 and nuts 71 are attached to the rods 70, the components of the whole filter unit 10 are compressed so as to form a strong assembly.

1he filter unit 10 can he configured to operate with two different sizes of hose. All that is required is for the fltting 80 to be removed, inverted and re-attached.

\Xhilst the fitting 80 illustrated provides threaded sections 82, 83 to receive two different sizes of coupllng, the fitting may only include one threaded section in the manner illustrated in Figures 1 to 5, with alternate sizes of coupllng being acconiniodateci by dllfferent fittings each with a single opening for receiving a coupllng, such as a hose coupling.

The fitting 80 is described as having threaded sections for receiving hose couplings. Of course the fitting may be provided with alternate means of attaching a hose coupling thereto and is not restricted to screw threads for this Purpose.

Where the filter unit 10 is to be used in bodies of water that are shallower than the height of the filter unit it is necessary to blank off the holes in the outer tubular member. The invention therefore provides a sleeve made of a flexible material, such as rubber, which may he used to cover sonic of the holes. The sleeve may he located at the tipper end of the filter unit and rolled down as far as is required to cover the.

holes to below the level of the body of water in which the filter unit is situated. Such a sleeve 90 is shown in Figure 7b, indicated in its rolled up state in broken Ii nes, and iii its fully extended state in solid Ii nes.

The sleeve when fully extended does riot fully cover the outer tubular member, since to do so would seal the filter unit completely.

The sleeve may be attached to the tipper end of the outermost tubular member, or to the end cap situated at the upper end of the filter wilt, for exampie by means of adhesive.

it will he apparent from the foregoing descripthni that the filter unit of the invennon is easy to make and is simple to assemble and disassemble thus makkig it easy to clean debris and organic detritus from the components thereof. That the preferred materials from winch the filter unit components are made are non-wetting plastics contributes to the ease with which the filter unit components may he cleaned.

Additionally, as the tubular members do not have interstices such as those formed owing to the weave construction of sonic prior constructions of filters, detritus is not as readily trapped by the filter unit components in a manner such that it cannot he readily cleaned from the components.

Although a preferred embodiment has been described with reference to the drawings, as previously described the filter unit of the invention nmy he realised in a number of embodiments and it will be understtx)d the description of the preferred embodiment is not intended to linilt the invention to that embodiment but that the scope of the invention is as expressed in the claims hereto.

Claims (1)

1. <claim-text>Claims 1. A filter unit comprising at least one tubular perforated member mounted between two end caps to define a space therebetween, the end caps and the tubular member defining an interior space within the unit, at least one end cap having an opening therein in conimunication with the interior space and being adapted to receive a coupling for a hose, pipe or other fixture.</claim-text> <claim-text>2. A filter unit according to Claim 1, comprising at least two tubular perforated members mounted coticentrically otie withiti another between the two end caps to define ati antiular space therebetween, the end caps and the intiermost tubular member definitig the interior space within the unit.</claim-text> <claim-text>3. A filter unit according to Claim I or 2, wherein the or each tubular member anti end caps of the filter unit are made of plastics.</claim-text> <claim-text>4. A filter unit according to Claim 3, wherein the plastics have a surface energy of not more than 40 dynes/cm, more preferably not more than 38 dynes/em.</claim-text> <claim-text>5. A filter unit according to atly preceditig claim wherein the plastics are selected from the group comprising polvhydrocarhons and copolyniers thereof, polyfluorocarbotis, fluorinated ethylene and propylene copolymers and poly vinyl fluoride, polyamides, polyimides, polyacetals and polyphenylene sulphide.</claim-text> <claim-text>6. A filter unit according to any of Claims 3 to 5, wherein the plastics polyhvdrocarbons and copolymers thereof.</claim-text> <claim-text>7. A filter unit according to any preceditig claim, wherein the or each tubular member is perforated by circular holes each having the same diameter, at least within each tubular member.</claim-text> <claim-text>8. A filter unit according to any of Claims 1-7, wherein the tubular members are perforated by circular holes each having tile same diameter, at least within each tubular member, the holes in one tubular member not being in direct registry with the holes in an adjacent tubular member.</claim-text> <claim-text>9. A filter unit accorditig to any preceding claim, whereiti the perforations in the or each tubular member occupy between 20% atid 60% of tile surface area of the member.</claim-text> <claim-text>10. A filter unit according to any preceding claim, wherein the or each tubular member is perforated by circular holes each having the same diameter, at least within each tubular member, the holes having a diameter in the range 2 mm to 6 mm.</claim-text> <claim-text>II. A filter unit accorthing to any preceding claim, whcrein the or each tubular member is perforateti by circular holes each having the same thiameter, at least within each tubular member, and wherein the holes are arranged in rows.</claim-text> <claim-text>12. A filter unit acccrding to any of Claims 2-1 1, wherein an inner tubular member, in relation to an outer adjacent tubular member, has annular end flanges extending radially outwardly therefrom.</claim-text> <claim-text>13. A filter unit according to Claim 12, wherein each end flange is provided with at least one through, threaded aperture, the end caps each being provided with at least one corresponding plain through aperture through which is located a bolt screwed into respective said threaded aperture in the flange to lock the tubular members and the end caps together.</claim-text> <claim-text>14. A filter unit according to any of Claims 2-13, wherein die end caps each have a first annular shoulder for receiving and locating an end of an inner tubular member and a second annular shoulder, located radially outwardly of the first shoulder, for receiving and locating an end of an outer tubular member.</claim-text> <claim-text>15. A filter unit according to any preceding Claim, further including at least one flange niounted within the outer tubular member and between the end caps.</claim-text> <claim-text>16. A filter unit according to Claim 15 when dependent on Claim 2, wherein the at least one flange is mounted between the tiller and outer tubular members.</claim-text> <claim-text>17. A filter unit according to any preceding claim, wherein, to accommodate coupling units of different sizes, said unit further comprises: alternative end caps each having an opening to accommodate a specific coupling sLze; and/or both end caps having an opening to accommodate a specific coupling siae and, optionally, closure plugs for plugging said openings; and/or an adapter for a coupling winch engages with the opening in said end.</claim-text> <claim-text>18. A filter uilit according to any of Claims 2 to 11, comprising an end flange, the end flange having a peripheral wall and walls located inwardly of the peripheral wall, the in ncr tubular member engaging with said inner walls.</claim-text> <claim-text>19. A filter unit according to Claim 18, wherein the filter unit comprises two such end flanges, one engaging each end of the inner tubular member.</claim-text> <claim-text>20. A filter unit according to Claim 18 or 19, wherein the inner \valls form a shoulder.</claim-text> <claim-text>21. A filter unit according to Claim 20, wherein the shoulder is a right angle.</claim-text> <claim-text>22. A filter unit according to Claim 18 to 21, wherein at least one of the flanges includes an opening therein.</claim-text> <claim-text>23. A filter unit according to any of Claims 18 to 22, wherein the filter unit further includes an end cap, the end cap including a base and walls extending from the base, the walls configured to engage with the outer tubular uiel nher.</claim-text> <claim-text>24. A filter unit according to any of Claims 18 to 23, wherein the end cap is configured to engage the end flange.</claim-text> <claim-text>25. A filter unit according to Claim 23 or 24, wherein the wall extending from the base engages with the peripheral wall of ti-ic flange.</claim-text> <claim-text>26. A filter unit according to any of Claims 23 to 25, wherein the wall extending from the base inclneles a rebate, and the outer tubular member sits in the rebate.</claim-text> <claim-text>27. A filter unit according to Claim 26, wherein the peripheral wall of the flange extends beyond the lower edge of the rebate and forms a recess having a substanually L shaped cross section with the walls of the recess, the outer tubular member sitting iii the recess.</claim-text> <claim-text>28. A filter unit according to any preceding claims, further comprising a fitting including at least one bore configured to engage with a corresponding coupling and attachment means for attaching said fitting to another component of the filter unit.</claim-text> <claim-text>29. A filter nnit according to any preceding claim, further comprising a fitting including two bores, each of a different diameter and configured to receive and engage with a corresponding coupling.</claim-text> <claim-text>30. A filter unit according to Claim 28 or 29, wherein the or each bore is internally threaded.</claim-text> <claim-text>31. A filter unit according to Claim 30, wherein the fitting includes at least one inwardly-extending annular wall element forming an end stop for a respectivc bore.</claim-text> <claim-text>32. A filter unit according to any preceding claim, further including at least one rod, the or each rod configured to pass through bores in end caps and/or flanges and/or fitting.</claim-text> <claim-text>33. A filter unit according to Claim 30, wherein at least one rod includes a threaded portion.</claim-text> <claim-text>34. A filter unit according to Claim 31, further including at least one nut, the nut engaging tile threaded portion of the rod.</claim-text> <claim-text>35. A filter unit according to any of Claims 31 to 34, wherein at least one of the bores is threaded.</claim-text> <claim-text>36. A filter unit according to any preceding claim, furthcr including a sleeve of flexible inatcrial configured to cover a part of the outermost perforated tubular member.</claim-text> <claim-text>37. A filter unit according to Claim 36, wherein the sleeve is moveable between extended and retracted configurarnns to cover more or fewer of the perforations of the outermost perforated tubular member.</claim-text> <claim-text>38. A filter unit substantially as shown in, and as described with reference to, the drawings.</claim-text>