NZ545812A - Filtration system - Google Patents

Abstract

The fluid filter system has a filter element (10) with a cylindrical body (11) composed of filter medium through which the liquid is drawn by suction into the central pump intake volume (15). The top end member (16) comprises a solid disc (17) which is fixed to the end of the cylindrical body by being fused thereto and thus closes the upper end of the volume (15). At the lower end of the cylindrical body there is an annular open end member (18) also fused to the cylindrical body (11). The end members (16) and (18) support the opposite ends of the cylindrical body (11) so that the body retains the required cylindrical shape. These elements 11, 16 and 18 constitute the removable and replaceable operative filtering component of the filtration system. A filter mount (20) includes a central support (21), such as a cylindrical perforated stainless steel drum or wire cage. The support (21) receives the cylindrical filter body (11) around the outside and prevents the filter body inwardly collapsing or distorting excessively in use. The filter mount (20) also includes mounting (25) for releasably locating and retaining the filter element (10) and an end closure (30) which cooperates with the open end member (18) to close the end of the volume (15) opposite to the top end closed by the disc (17) other than the water outlet (31).

Description

545812 No.: Date: NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION FILTRATION SYSTEM TYLAC TRADING PTY LTD, an Australian company, of PO Box 216, Lilydale, Victoria 3140, Australia hereby declares the invention, for which it prays that a patent may be granted to it, and the method by which it is to be performed, to be particularly described in and by the following statement: 1 INTELLECTUAL PROPERTY OFFICE OF N.Z. - 8 MAY 2006 RECEIVED FILTRATION SYSTEM Related Application This application claims priority from Australian Patent Application No. 2005901136, filed 9 March 2005. The entire contents of the specification including drawings of this prior Australian patent application are incorporated herein in full by this cross reference.

Field of the invention This invention relates to filtration of liquids to separate particulates, particularly, but not exclusively, to filtering particulates from water.

Although being described in detail herein in relation to filtering liquids, particularly water, the invention is useful for filtering particulates from gases, e.g. pre-filtering particulates in air being drawn into an air conditioning system.

Background There are many types of filter systems using various constructions, designs and materials for separating particulates from liquids being pumped. Filters are in most systems located on the pressure side, i.e. downstream, of the pump so that the liquid is forced under pressure through the filter medium. Downstream filtering is usual since it is 20 known that any restriction on the suction side of the pumping equipment creates a loss of positive head (pressure) at the discharge side. However, because the liquid which includes the particulates to be separated first passes through the pump, the presence of the particulates within the pump must be allowed for in the design and construction of the pump and, in many situations, the effects of the particulates can increase the 25 complication, the construction costs, and the maintenance costs of the pumping system, e.g. by causing wear within the pump equipment.

It is known to first separate larger or oversized particulates from a liquid being pumped, before the liquid is then passed through a filtration system on the pressure side of the pump. For example, in agricultural uses where water is drawn from a supply such as a water course, canal, reservoir, etc. and, for example, sprayed for irrigation of crops, the water can first be passed through screening material before entering the intake side of the pump. However, such screening apparatus is operative primarily to separate larger particles or contaminants entrained in the water to stop them entering and damaging the pumping apparatus.

Objects of the invention It is an object of the present invention to provide a fluid filtration system which can be effectively used to separate particulates from fluid being moved and which can provide advantages over, or at least provide a useful alternative to, other or known fluid filtration systems.

It is a further object of the present invention to provide a method of effectively filtering a fluid to separate particulates from the fluid being moved and which can provide advantages over, or at least provide a useful alternative to, other or known fluid filtration methods.

A further object is to provide a fluid filter useable with the system and method of the invention.

Summary of the invention According to a first aspect of the present invention there is provided a fluid filtration system for use with a fluid moving means which has a fluid intake and a fluid outlet through which pressurised fluid is discharged, the filtration system including: a filter element which has a cylindrical body composed of a filter medium and through which fluid is drawn when in use by suction to separate particulates from the fluid, a central region of the cylindrical body constituting an intake volume from which fluid is drawn to enter the fluid intake of the moving means; end members located at both ends of the cylindrical body and which in use locate and support opposite ends of the cylindrical body in the required shape thereof, one of 5 the end members being an open end member which provides an opening therein for the moving means to draw fluid from the intake volume into the fluid intake of the moving means; a filter mount which includes a central support around which the cylindrical body of the filter element is located in use and which provides structural support to prevent the 10 cylindrical body substantially deforming or collapsing inwardly in use; the filter mount further including a mounting means for releasably locating and retaining the filter element in position so that the open end member having the opening therein is in communication with an outlet leading from the intake volume to the fluid intake of the moving means in use.

With this construction and arrangement of the filtration system, there is no need to provide a support as part of the filter element to support the cylindrical body in use. In turn, this enables a large filter area to be provided for flow of fluid through the filter medium and consequently there can be a low pressure drop across the cylindrical filter body and hence the efficiency and effectiveness of the moving means (pump or fan) with 20 the filtration system located upstream of the intake of the moving means may not be significantly compromised or reduced. By providing such a filtration system upstream of the moving means, the filtrated fluid is therefore being moved with significant potential savings and efficiencies in the design and construction, in the power consumption, and in the maintenance and repair of the pump or other fluid moving means.

According to a second aspect of the present invention there is provided a method of filtering a liquid to be pumped by a liquid pump which has a liquid intake and a liquid outlet through which liquid pressurised by the pump is discharged, the method including the steps of: providing a liquid filtration system which includes: a filter element which has a cylindrical body composed of a filter medium and through which liquid is drawn by suction to separate particulates from the liquid, a central region of the cylindrical body constituting an intake volume from which liquid is drawn to enter the liquid intake of the pump; end members located at both ends of the cylindrical body and which locate and support opposite ends of the cylindrical body in the required shape thereof, one of the end members being an open end member which provides an opening therein for the pump to draw liquid from the intake volume into the l iquid intake of the pump; a filter mount which includes a central support around which the cylindrical body of the filter element is located and which provides structural support to prevent the cylindrical body substantially deforming or collapsing inwardly; the filter mount further including a mounting means releasably locating and retaining the filter element in position so that the open end member having the opening therein is in communication with an outlet leading from the intake volume to the liquid intake of the pump; installing the liquid filtration system so that the liquid intake of the pump is connected to the system and operating the system and pump so as to draw the liquid to be filtered by suction from the intake volume and through the open end member of the filter element and through the outlet leading to the fluid intake of the pump.

The present invention also provides a filter element itself having the construction and configuration to be useable in the filtration system and method of the first and second aspect of the invention. In particular the invention in a third aspect provides a filter element for use in a fluid filtration system having a fluid moving means having a fluid intake and a fluid outlet through which pressurised fluid is discharged, the filter element including: a cylindrical body composed of a filter medium and through which fluid is drawn when in use by suction to separate particulates from the fluid, a central region of the cylindrical body constituting an intake volume from which fluid is drawn to enter the fluid intake of the moving means; end members located at both ends of the cylindrical body and which in use locate and support opposite ends of the cylindrical body in the required shape thereof, one of the end members being an open end member which provides an opening therein for the moving means to draw fluid from the intake volume into the fluid intake of the moving means, the end member of the filter element remote from the open end member being a closed end member, both the open end member and the closed end member being moulded to opposite ends of the cylindrical body composed of the filter medium so as to seal the medium against passage of fluid around the ends of the cylindrical body and so as to define end members having functional formations for mounting of the filter element; the filter element being arranged to be installed and used with a filter mount which includes a central support around which the cylindrical body of the filter element is located in use and which provides structural support to prevent the cylindrical body substantially deforming or collapsing inwardly in use; the filter mount further including a mounting means for releasably locating and retaining the filter element in position so that the open end member having the opening therein is in communication with an outlet leading from the intake volume to the fluid intake of the moving means in use, the mounting means of the filter mount comprising an end mount having: a central outlet through which in use fluid passes from the intake volume to the fluid intake of the moving means; an annular body to which the central support is fixed so as to extend away from the annular body and support the cylindrical body of the filter element, and a sealing formation located radially outwardly beyond the central support and with which a complementary formation of the open end member of the filter element forms a sealing relationship, the sealing formation of the end mount comprising a bevelled surface facing partially in the general direction of the central support; wherein the complementary formation of the open end member of the filter element comprises a bevelled surface facing partially in the general direction of the mounting means and which engages with the bevelled surface of the end mount.

The apparatus of the filtration system will be further described herein in more detail and it can be understood from this description of the apparatus and its operation how the apparatus is used in the filtration method according to the second aspect of the invention. Consequently there is no need to repeat in detail the steps of the preferred filtration method.

In the preferred embodiment, the cylindrical body composed of a filter medium may be composed of a pleated filter medium which can be of generally conventional construction and operation. For example the pleated filter medium may be a polyester fabric having a porosity selected for the particular field of application. Pore sizes of the filter medium down to as low as 15 microns may be possible with the present invention. The pleated construction provides a large surface area through which fluid being filtered can pass. The diameter and axial length of the cylindrical body can be selected to minimise pressure drop across the filter medium in use.

In the preferred embodiment, the end member of the filter element remote from the open end member is a closed end member, and both the open end member and the closed end member are moulded to opposite ends of the cylindrical body composed of the filter medium so as to seal the medium against passage of fluid around the ends of the cylindrical body and so as to define end members having functional formations for mounting of the filter element. The closed end member for example may comprise a 5 solid or imperforate disc. The open end member may comprise an annular member around the cylindrical body. The opposite ends of the cylindrical body are preferably attached securely to the end members so as to be located and supported thereby, e.g. by moulding the end members so that the respective end members are fused to the cylindrical body and, in particular, by embedding the end edges of the filter medium in 10 the moulded end member as part of the moulding process.

The central support is preferably a cylindrical support of pervious construction, i.e. providing less flow restriction to the filtrate than the filter element. The support may comprise for example a perforated cylinder made of any suitable material such as stainless steel, polycarbonate, etc. or may comprise a generally cylindrical cage or mesh 15 such as one made of a number of upright support rods and a helical wire around and welded to the rods. The support cylinder in use is located within and preferably closely adjacent to the inside of the cylindrical body so that during the filtration operation in which filtrate is being drawn by suction by the pump from the internal pump intake volume, the cylindrical support will provide structural support to the surrounding 20 cylindrical filter body particularly against any tendency of the filter body to deform or collapse inwardly. The cylindrical support however does not offer any significant restriction to the flow of filtrate therethrough which has already passed through the filter medium.

The mounting of the filter mount in the preferred embodiment includes an end 25 closure which co-operates with the open end member associated with the filter element 8 and which closes the intake volume against fluid passage except through an outlet in the end closure which communicates in use with the fluid intake of the moving means. Preferably the mounting means of the filter mount comprises an end mount having: a central outlet through which in use fluid passes from the intake volume to the fluid intake 5 of the moving means; an annular body to which the central support is fixed so as to extend away from the annular body and support the cylindrical body of the filter element, and a sealing formation located radially outwardly beyond the central support and with which a complementary formation of the open end member of the filter element forms a sealing relationship.

The sealing formation of the end mount may comprise a bevel led surface facing partially in the general direction of the central support, and the complementary formation of the open end member of the filter element may comprise a bevelled surface facing partially in the general direction of the mounting means and which engages with the bevelled surface of the end mount. In this embodiment, the bevelled sealing surface 15 of the end mount preferably comprises a male surface extending around the outside of the annular body and the complementary bevelled sealing formation of the open end member of the filter element comprises a female bevelled surface formed in a step or shoulder surrounding the opening in the end member and spaced radially outwardly therefrom. The use of this type of radial sealing engagement obviates the need to strongly press the 20 filter element into sealing engagement with the mounting as would be otherwise necessary or desirable if a face to face sealing contact was used.

The annular body of the end mount preferably comprises a moulded annular body having the central support fixed to the body by being embedded in the moulding.

The annular body may have a bevelled surface surrounding and defining the 25 central outlet with that bevelled surface forming a sealing surface facing partially away from the intake volume to form a seal with a complementary male member of a downstream fluid path. for one type of installation, the mounting means may further include an internally threaded connector with a central hole for fluid passage therethrough, the connector facing away from the opposi te side of the annular body of the filter mount to the side where the central support is located and being arranged to be coupled to a complementary threaded male connector of a downstream fluid path.

The filter element is urged into a sealing relationship of its open end member with the filter mount by releasable means acting in the direction from the end of the cylindrical body remote from the open end and towards the open end.

The fluid filtration system can be suitable for installations where the fluid is water and the fluid moving means is a water pump, the installation includes a housing connected to a water source, the filter element and filter mount being located within the housing, so that the water being filtered is drawn out of the housing by suction of the water pump.

In another different type of installation where the fluid filtration system can be suitable, the fluid is water and the moving means comprises a water pump, and the filter element and filter mount assembly is immersed in a body of water from which water is drawn and filtered before entering the intake of the water pump.

In one possible embodiment, the filtration system may also include a filter washer for periodically washing particulates from the filter element to enable prolonged usage of that filter element. The filter washer may be mounted by or in association with the filter mount so that it is located in proximity or in association with the filter element during filtration operations and so that it can be intermittently operated to wash particulates from the filter element. The filter washer can include for example washing elements rotatably mounted for directing washing liquid from within the pump intake volume outwardly through the cylindrical body of the filter element to backwash particulates from the outside surfaces of the cylindrical body. This washing operation can be performed by interrupting the filtering operation for a short period for backwashing, the resulting liquid 5 slurry or suspension or the like with the particulates entrained being separated from the system prior to recommencing of filtering operation.

When the fluid is a gas such as air, the filter element may be periodically cleaned to prolong its use by blowing air back through the filter medium, i.e. from the intake volume outwards through the walls of the cylindrical body, such as by an intermittent or 10 pulsed reverse direction air blower.

The filter element in the preferred embodiment can be readily replaceable by sliding the cylindrical body off the central support, together with the end members, and a replacement filter element can be readily reinstalled. The filter element to be disposed of after use can be of modest cost, consisting only of the cylindrical body composed of the 15 filter medium and, in the preferred embodiment, a closed solid disc forming one end member fused to the cylindrical body and, at the other end, an annular open end member likewise fused to the opposite end of the cylindrical body.

Summary of the drawings Possible and preferred features of the present invention will now be described 20 with particular reference to the accompanying drawings. However it is to be understood that the features illustrated in and described with reference to the drawings are not to be construed as limiting on the scope of the invention. In the drawings: Fig. 1 is a vertical cross-section through a filtration system according to an embodiment of the present invention, Fig. 2 is a wire cage sectional perspective view of the filtration system of Fig. 1, Fig. 3 is a partial sectional and exploded view through the lower end of the filter element and associated filter mount useful with a closed chamber filter system, Fig. 4 is a partial sectional and exploded view of the filter element and filter mount useful for drawing fluid from ambient surroundings without enclosing the assembly, Fig. 5 is a plan view of the end mount of the filter mounting of Fig. 4, and Fig. 6 is a plan view of a filtration system using multiple non-enclosed filter elements installed in parallel.

Description of particular embodiments Referring to the Figs. 1 and 2 of the drawings, the filter element 10 has a cylindrical body 11 composed of filter medium through which the liquid is drawn by suction into the central pump intake volume 15. The top end member 16 comprises a solid disc 17 which is fixed to the end of the cylindrical body 11, e.g. by being fused thereto, and thus closes the upper end of the volume 15. At the lower end of the cylindrical body 11, there is an annular open end member 18 which also may be fused to the cylindrical body 11. The end members 16 and 18 support the opposite ends of the cylindrical body 11 so that the body retains the required cylindrical shape. These elements 11, 16, 18 constitute the removable and replaceable operative filtering component of the filtration system.

A filter mount 20 includes a central support 21, such as a cylindrical perforated stainless steel drum. The support 21 receives the cylindrical filter body 11 around the outside and prevents the filter body inwardly collapsing or distorting excessively in use.

The filter mount 20 also includes mounting 25 for releasably locating and retaining the filter element 10 and an end closure 30 which co-operates with the open end 12 member 18 to close the end of the volume 15 opposite to the top end closed by the disc 17 other than the water outlet 31.

More particularly describing the illustrated embodiment, a manifold 40, e.g. of moulded plastic pipe or of any other suitable material, is closed at one end by an end cap 5 41 which has centrally therein a suction type connector 42 which in use leads to the suction side liquid intake 61 of the pump 60. At the other end of the manifold 40 is an end cap 44 through which a backwash pipe 45 passes into the manifold 40. The backwash pipe 45 leads to a vertical riser 46 which passes backwash water to a T-connection 47, leading to the horizontal pipes 48, 49. The T-connection 47 enables 10 swivelling or rotating movement of the horizontal pipes 48, 49 as is known for back flushing of pressure filter elements. The horizontal pipes 48, 49 carry backwash water to the risers 50, 51 which are provided with outlet holes or jets 52, 53. A cross-bar 54 connects the closed top ends of the risers 50, 51.

A central rod 55 extends vertically through the assembly, i.e. through the 15 manifold 40, the T-connection 47, through the centre of the cross-bar 54, and through the top end member 16, so that the risers 50, 51 of the backwash system can rotate about the central axis of the centre rod 55. The backwashing operation involves pumping water under pressure through the backwash pipe 45 and, because the outlet holes or jets 52, 53 are directed with a tangential component, the assembly of the riser pipes 50, 51 rotates 20 within the chamber 15 to force flushing water outwardly through the cylindrical filter body 11 to thereby dislodged particulates that have been collected thereby during the filtration operation.

Attached at the top of the T-shaped manifold 40 is the end closure 30 in the form of a disc 32 which has at its outer periphery a step 33 which provides a seat for receiving 13 the end member 18 of the filter element 10. Also supported on the disc 32 is the central support core 21, e.g. a cylinder of stainless steel mesh.

The cylindrical filter body 11 can be a pleated polyester cartridge style filter element with a full solid disc 17 closing the top end, e.g. made of polyurethane moulded to the filter body so as to be fused thereto. The annular end member 18 can be moulded so as to be fused to the open lower end of the cylindrical filter body 11. However there is no central core support forming part of the filter element 10. The filter mount 25 includes a wing nut 35 which can be attached to the threaded top end of the centre rod 55 after passing through the top end member 16 thus fixing the filter element 10 in position. Tightening the wing nut 37 clamps the filter body 11 to the lower end member 30.

In operation, the filtration apparatus is installed as schematically illustrated with the suction liquid intake 61 of the pump 60 in communication with the volume 15, through suction pipe connector 42, manifold 40, and outlet 31. In the illustrated embodiment which is designed and constructed to be installed submerged in a water source, such as a water course, irrigation supply channel, reservoir, etc. there is no need for any housing surrounding the filter element 10 - the water is drawn directly through the filter element 10 and thence into the pump 60. The cylindrical filter body 11 does not require a structural support core or the like as part of the replaceable filter element or cartridge because support during suction of water through the body 11 is provided by the central support 21. It can be readily seen therefore that this construction provides for an economical filter replacement because only the filter medium 11, the top end member 16 and the open bottom end member 18 together form the replaceable element or cartridge.

The water is filtered as it is drawn through the cylindrical body 11 and passes via the pump intake volume 15 into the pump inlet 61, whence it is discharged under pressure through outlet 62, e.g. for distribution through sprinklers or sprayers to crops.

As the filter element 10 becomes progressively more obstructed with particulates, the filter washer can be operated to backwash and dislodge the particulates from the cylindrical filter body 11 enabling subsequent continued use thereof. For example, a vacuum gauge (not shown) can be operatively associated with the pump 60 to activate the backwash cycle in accordance with the pump manufacturer's specifications. In particular, when the vacuum gauge is used to initiate the backwash operation, the pump 60 can be stopped and valves (not shown) can be operated to direct a water flow through the backwash pipe 45, riser 46, pipes 48, 49, and risers 50, 51. As the water under pressure exits from the holes 52, 53, the risers 50, 51 rotate about the axis of the centre rod 55 so that the water jets backwash through the filter medium constituting the cylindrical body 11. In the case of a filtration system as illustrated when installed in a body from which irrigation water is being drawn, the particulates dislodged from the cylindrical filter body 11 do not constitute a pollutant of the water source since they have in fact been separated from water being drawn from that source.

In some applications of the filtration system, such as in continuous industrial applications, it may not be feasible or at least desirable to interrupt the filtering operation, even for relatively short times to allow backwashing of the filter element, or indeed to allow replacement of a filter element to be discarded. In such situations, two similar filtration systems can be installed in parallel so that water can be directed through one filtration system while the other is temporarily being backwashed or while the filter element is being replaced and vice versa.

In the embodiment of Fig. 3, a housing 70 can be provided totally surrounding the filter element 10 and into which the liquid to be filtered is introduced. The housing may be for example a conventional polypropylene swimming pool filter housing. Only a portion 71 of the bottom wall of the housing 70 is illustrated. That part of the bottom wall 71 has the water outlet 31 defined by the spigot 72. In this embodiment, the filtration system is suitable to be installed externally of a source of liquid from which the liquid to be filtered is to be drawn (e.g. in the case of an agricultural irrigation water source where the filtration system is not submerged in the body of water). The housing 70 can sealingly engage with the filter mount 20, and can surround totally the cylindrical body 11, and have a top closure either above or formed by a large diameter top end member 17. A liquid inlet (not shown) would be provided into the housing 70 so that water to be filtered is drawn from within the housing through the filter element 10 as described above. Such a system can be used for agricultural purposes, in industrial applications such as in food processing operations e.g. where fruit or vegetables are washed and the wash water is to be filtered and recycled, in swimming pool water recycling and treatment systems, in reverse osmosis and desalination plants, and in many other applications.

To describe the filter mount 20 of Fig. 3 in more detail, there is provided by the filter mount 20 a central outlet hole 75 through which liquid passes from the intake volume 15 through the outlet 31 into the intake 61 of the pump 60. An annular body 77 has the central support 21 fixed thereto so as to extend away from the annular body 77 and to support the cylindrical body 11 of the filter element 10. The rods 21a of the support 21 are shown embedded in the annular body 77 for this purpose.

A sealing formation 80 is located radially outwardly beyond the central support 21 and this cooperates with a complementary formation 85 at the open end member of the filter element 10 to form a sealing relationship. In particular, the sealing formation 80 of the end mount comprises a bevelled surface 81 facing partially in the general direction of the central support 21. The complementary formation 85 of the filter element 10 comprises a bevelled surface 86 facing partially in the general direction of the 16 mounting means 20 and which engages with the bevelled surface 81. The bevelled sealing surface 81 of the end mount comprises a male surface extending around the outside perimeter of the annular body 77 and a complementary bevelled sealing formation 86 of the open end member 18 comprises a female bevelled surface formed in a step or shoulder surrounding the opening in the end member 18 and spaced outwardly therefrom.

The annular body 77 comprises a moulded annular body having the central support 21 affixed to the body by being embedded in the moulding as part of the moulding process. To achieve this, any suitable plastics, synthetic rubber, or similar materials can be used, such as polyurethane. The annular body 77 and the annular preformed mouldings shown in Fig. 3, one of which is surrounding the outlet hole 75 and the other of which is surrounding the outer periphery and defining the sealing formation 80, can be moulded with the central support 21 being held in a suitable jig for its accurate location and alignment so that the filter element 10 is accurately located and held in position. As shown in Fig. 5, there may be three upright support rods 21a but other numbers can obviously be used.

The annular body 77 has a bevelled surface 76 surrounding and defining the central outlet hole 75. That bevelled surface 76 forms a sealing surface facing partially away from the intake volume 15 and forms a seal with the complementary male member of the downstream fluid path, namely the outer surface 73 of the spigot 72 in the base wall 71 of the housing 70.

The embodiment of Fig. 4 is in most respects the same as Fig. 3 and the same reference numerals are used for corresponding parts. In this embodiment however the mounting means 25 includes an internally threaded connector 90 having a central hole 91 for fluid passage therethrough. The connector 90 faces away from the annular body 77 so as to be fitted to a complementary threaded male connector 95 of the downstream fluid path which can, as illustrated, consist of a conventional plumbing fitting such as T-junction having a lateral inspection port or water inlet 96. The connector 90 can be mounted to the annular body 77 by means of bolts 92 which can be embedded in the body 77 during the moulding process. The upper surface 93 of the connector 90 can form a seal with the lower surface of the annular body 77 in any convenient way, e.g. by providing a sealing gasket, a sealing ring, or a bead of silicone or the like applied at the time of assembly.

In the embodiments of Figs. 3 and 4 there may be provided other releasable means, although different to the retention of the filter element by means of the wing nut 35 applied to central rod 55 and holding the top cap 17 clamped down onto the filter element. In particular, the filter element in Figs. 3 and 4 is preferably urged into sealing relationship of its open end member 18 with the filter mount 20 by releasable means (not shown in Fig.3, or shown schematically by numeral 98 in Fig. 4) acting in the direction from the end of the cylindrical body 10 remote from the open end 18. In the case of the embodiment of Fig. 3, the releasable means acting in that direction may comprise for example a removable lid or cap of the housing 70 having for example a compression spring on its under surface so that when the lid is fitted to the housing, the filter element 10 is urged by the spring downwardly and the complementary sealing surfaces 86 and 81 are urged into and maintained in sealing relationship. In the embodiment of Fig. 4, a generally U-shape strap or band may be passed over the top of the filter element 10, and tension applied to that strap, e.g. by clips or clamps securing the strap at its ends to the connector fitting 95, 96. This is schematically illustrated only in Fig. 4 by the broken line 98.

In the embodiment of Fig. 4, the mounting means 25 can be readily mounted to the plumbing fitting 95 by screwing the assembly consisting of the support 21, body 77 and connector 90 onto the fitting 95. The filter element 10 can then be readily slid over the support 21 so that the open end element 18 seals to the outer edge of the filter mount 20. The filter element 10 can then be clipped or clamped releasably in its operative position. The assembly can be immersed in a body of water from which water is to be drawn so that the water being drawn through the filter 10 is filtered before passing out of the intake volume 15 through the outlet holes 75 and 91 to the intake of the water pump. As shown in Fig. 6, multiple such assemblies can be installed in parallel so that the required volume and flow rate of water can be achieved for higher water supply capacity requirements.

It will be understood from the preceding description that various modifications can be made to the system as described and illustrated without departing from the scope of the invention. For example only, the filter element 10 may have end members at both ends thereof which are open, similar to the illustrated open end member 18. In this case, the closed top disc 17 may be part of a removable filter mount which is secured in position atop the filter element each time the filter element 10 is installed. In this embodiment, the only element which is replaced comprises the cylindrical filter body 11 with an annular end member extending around each of the two opposite ends of the pleated filter body.

For some possible applications of the invention, the central support particularly those forms having an open internal space as in the illustrated embodiments, can be arranged to locate and hold therein a body of filter medium through which the filtrate is passed after having passed first through the cylindrical filter body. For example, a porous sleeve or bag (which can be selectively removed for replacement) containing a second filtering medium (e.g. activated charcoal, diatomaceous earth, zeolite, other reactive media, etc.) can be placed inside the support 21. This can be particularly useful for water treatment involving some chemical conditioning as well as the removal of particulates.

Although initially developed for, and particularly described in relation to, suction side installations, the system and filter body of the invention can be used with pressure side installations of the filter, i.e. downstream of the pump.

It is to be understood that various alterations, modifications and/or additions may be made to the features of the possible and prefeired embodiment(s) of the invention as ]() herein described without departing from the scope of the invention as defined in the claims.

Claims (17)

What we claim is:

1. A fluid filtration system for use with a fluid moving means which has a fluid intake and a fluid outlet through which pressurised fluid is discharged, the filtration system including: 5 a filter element which has a cylindrical body composed of a filter medium and through which fluid is drawn when in use by suction to s^narate particulates from the fluid, a central region of the cylindrical body constituting an intake volume from which fluid is drawn to enter the fluid intake of the moving means; end members located at both ends of the cylindrical body and which in use locate 10 and support opposite ends of the cylindrical body in the required shape thereof, one of the end members being an open end member which provides an opening therein for the moving means to draw fluid from the intake volume into the fluid intake of the moving means; a filter mount which includes a central support around which the cylindrical body 15 of the filter element is located in use and which provides structural support to prevent the cylindrical body substantially deforming or collapsing inwardly in use; the filter mount further including a mounting means for releasably locating and retaining the filter element in position so that the open end member having the opening therein is in communication with an outlet leading from the intake volume to the fluid 20 intake of the moving means in use.

2. A system as claimed in claim 1 wherein the end member of the filter element remote from the open end member is a closed end member, and wherein both the open end member and the closed end member are moulded to opposite ends of the cylindrical body composed of the filter medium so as to seal the medium against passage of fluid 21 around the ends of the cylindrical body and so as to define end members having functional formations for mounting of the filter element.

3. A system as claimed in claim 1 or 2 wherein the mounting means of the filter mount comprises an end mount having: 5 a central outlet through which in use fluid passes from the intake volume to the fluid intake of the moving means; an annular body to which the central support is fixed so as to extend away from the annular body and support the cylindrical body of the filter element, and a sealing formation located radially outwardly beyond the central support and 10 with which a complementary formation of the open end member of the filter element forms a sealing relationship.

4. A system as claimed in claim 3 wherein the sealing formation of the end mount comprises a bevelled surface facing partially in the general direction of the central support, and wherein the complementary formation of the open end member of the filter 15 element comprises a bevelled surface facing partially in the general direction of the mounting means and which engages with the bevelled surface of the end mount.

5. A system as claimed in claim 4 wherein the bevelled sealing surface of the end mount comprises a male surface extending around the outside of the annular body and wherein the complementary bevelled sealing formation of the open end member of the 20 filter element comprises a female bevelled surface formed in a step or shoulder surrounding the opening in the end member and spaced radially outwardly therefrom.

6. A system as claimed in any one of claims 3 to 5 wherein the annular body of the end mount comprises a moulded annular body having the central support fixed to the body by being embedded in the moulding. 00

7. A system as claimed in any one of claims 3 to 6 wherein the annular body has a bevelled surface surrounding and defining the central outlet with that bevelled surface forming a sealing surface facing partially away from the intake volume to form a seal with a complementary male member o-' ■ downstream fluiJ j.ath. 5

8. A system as claimed in any one ;.s 3 to 7 wherein the mounting means further includes an internally threaded connector with a central hole for fluid passage therethrough, the connector facing away from the opposite side of the annular body of the filter mount to the side where the central support is located and being arranged to be coupled to a complementary threaded male connector of a downstream fluid path. 10

9. A system as claimed in any one of the preceding claims wherein the filter element is urged into a seal ing relationship of its open end member with the filter mount by releasable means acting in the direction from the end of the cylindrical body remote from the open end and towards the open end.

10. A fluid filtration system as claimed in any one of the preceding claims and 15 installed in use for fluid filtering, wherein the fiuid is water ar;d wherein the fluid moving means is a water pump, the system further including a housing connected to a water source, the filter element and filter mount being located within the housing, and wherein the water being filtered is drawn out of the housing by suction of the water pump.

11. A fluid filtration system as claimed in any one of claims 1 to 9 and installed in 20 use for fluid filtering, wherein the fluid is water and the moving means comprises a water pump, wherein the filter element and filter mount assembly is immersed in a body of water from which water is drawn and filtered before entering the intake of the water pump.

12. A method of filtering a liquid to be pumped by a liquid pump which has a liquid intake and a liquid outlet through which liquid pressurised by the pump is discharged, the method including the steps of: providing a liquid filtration system which includes: a filter element which has a cylindrical body composed of a filter medium and through which liquid is drawn by suction to separate particulates from the liquid, a central region of the cylindrical body constituting an intake volume from which liquid is drawn to enter the liquid intake of the pump; end members located at both ends of the cylindrical body and which locate and support opposite ends of the cylindrical body in the required shape thereof, one of the end members being an open end member which provides an opening therein for the pump to draw liquid from the intake volume into the liquid intake of the pump; a filter mount which includes a central support around which the cylindrical body of the filter element is located and which provides structural support to prevent the cylindrical body substantially deforming or collapsing inwardly; the filter mount further including a mounting means releasably locating and retaining the filter element in position so that the open end member having the opening therein is in communication with an outlet leading from the intake volume to the liquid intake of the pump; installing the liquid filtration system so that the liquid intake of the pump is connected to the system and operating the system and pump so as to draw the liquid to be filtered by suction from the intake volume and through the open end member of the filter element and through the outlet leading to the fluid intake of the pump.

13. A filter element for use in a fluid filtration system having a fluid moving means having a fluid intake and a fluid outlet through which pressurised fluid is discharged, the filter element including: a cylindrical body composed of a filter medium and through which fluid is drawn when in use by suction to separate particulates from the fluid, a central region of the cylindrical body constituting an intake volume from which fluid is drawn to enter the fluid intake of the moving means; 5 end members located at both ends of the cylindrical body and which in use locate and support opposite ends of the cylindrical body in the required shape thereof, one of the end members being an open end member which provides an opening therein for the moving means to draw fluid from the intake volume into the fluid intake of the moving means, the end member of the filter element remote from the open end member being a 10 closed end member, both the open end member and the closed end member being moulded to opposite ends of the cylindrical body composed of the filter medium so as to seal the medium against passage of fluid around the ends of the cylindrical body and so as to define end members having functional fc"''-.v.r!;ions for rr.minting of the filter clement; 15 the filter element being arranged to be installed and used with a filter mount which includes a central support around which the cylindrical body of the filter element is located in use and which provides structural support to prevent the cylindrical body substantially deforming or collapsing inwardly in use; the filter mount further including a mounting means for releasably locating and retaining the filter element in position so that 20 the open end member having the opening therein is in communication with an outlet leading from the intake volume to the fluid intake of the moving means in use, the mounting means of the filter mount comprising an end mount having: a central outlet through which in use fluid passes from the intake volume to the fluid intake of the moving means; an annular body to which the central support is fixed so as to extend 25 away from the annular body and support the cylindrical body of the filter element, and a sealing fonnation located radially outwardly beyond the central support and with which a coraplementaiy fonnation of the open end member of the filter element fonns a sealing relationship, the sealing fonnation of the end mount comprising a bevelled surface facing partially in the general direction of the central support; 5 wherein the coraplementaiy fonnation of the open end member of the filter element comprises a bevelled surface facing partially in the general direction of the mounting means and which engages with the bevelled surface of the end mount.

14. A filter element as claimed in claim 13 wherein the coraplementaiy bevelled sealing fonnation of the open end member of the filter element comprises a female 10 bevelled surface formed in a step or shoulder surrounding the opening in the end member and spaced radially outwardly therefrom, the sealing fonnation of the open end member being operable to form a sealing relationship to the bevelled sealing surface of the end mount which comprises a male surfacc expending around the outside of the annular body.

15. A fluid filtration system as claimed in claim 1 and substantially as herein before 15 described with particular reference to the accompanying drawings.

16. A method of filtering a liquid as claimed in claim 12 and substantially as herein before described with particular reference to the accompanying drawings.

17. A filter element as claimed in claim 13 and substantially as herein before described with particular reference to the accompanying drawings. INTELLECTUAL PROPERTY OFFICE OF N.Z. - 8 MAY 2006 RECEIVED The fluid filter system has a filter element 10 with a cylindrical body 11 composed of filter medium through which the liquid is drawn by suction into the central pump intake volume 15. The top end member 16 comprises a solid disc 17 which is fixed to the end of the cylindrical body 11, e.g. by being fused thereto, and thus closes the upper end of the volume 15. At the lower end of the cylindrical body 11, there is an annular open end member 18 also fused to the cylindrical body 11. The end members 16 and 18 support the opposite ends of the cylindrical body 11 so that the body retains the required cylindrical shape. These elements 11, 16, 18 constitute the removable and replaceable operative filtering component of the filtration s;, stem. A filter mount 20 includes a central support 21, such as a cylindrical perforated stainless steel drum or wire cage. The support 21 receives the cylindrical filter body 11 around the outside and prevents the filter body inwardly collapsing or distorting excessively in use. The filter mount 20 also includes mounting 25 for releasably locating and retaining the filter element 10 and an end closure 30 which cooperates with the open end member 18 to close the end of the volume 15 opposite to the top end closed by the disc 17 other than the water outlet 31. 27