GB2427155A

GB2427155A - A backflushed filter assembly

Info

Publication number: GB2427155A
Application number: GB0617523A
Authority: GB
Inventors: James Peter Hosford
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-03-17
Filing date: 2004-03-17
Publication date: 2006-12-20
Anticipated expiration: 2024-03-17
Also published as: GB2427155B; GB2413098A; WO2004082803A3; GB0306022D0; WO2004082803A2; GB0517408D0; GB2413098B; GB0617523D0

Abstract

A backflushed filter assembly, and method of backflushing such a filter. The assembly comprises a filter 1, a backflushing arrangement 2 which generates and directs a backflushing flow to backflush the filter, and a drive arrangement 12 which provides motive power to operate the backflushing arrangement 2. The drive arrangement 12 comprises a turbine 14 located in the outlet 6 of the filter and driven in use by a flow of filtered fluid through the outlet of the filter assembly. A further invention is also disclosed for a method of backflushing a backflushed filter assembly by providing a storage and release arrangement; supplying motive power to the backflushed filter via the drive arrangement; storing and accumulating the motive power supplied to the backflushed filter over a first period; and releasing the stored motive power over a second period to intermittently operate the backflushing arrangement to generate and direct the backflushing flow to backflush the filter. Advantageously the assembly is used for filtering water from garden ponds, fish ponds, tanks, aquariums; for prefiltration of biological media in aquaculture; and for treatment of wastewater from industrial processes, sewage and agriculture.

Description

A FILTER ASSEMBLY AND METHOD OF FILTRATION

This invention relates to filters, and to a method of filtration, and in particular to filters and filtration incorporating backflushing.

The invention is applicable to any situation where liquids and gases require filtration to remove suspended particles. A few examples of applications are the filtering of water from garden ponds, fish ponds, tanks, aquariums, both domestic and commercial, pre-filtration before biological media in aquaculture and the treatment of waste water from industrial processes, sewage and agriculture.

Pre-filtration, and pre filters, are also used before and in conjunction other filter membranes and reverse osmosis membranes. Filters are also used for the removal of particulate matters from final effluent in sewage works and package sewage stations, and fish farms. The invention may also be applicable to filtration of air in ventilation systems, cooling systems, final filtration of air and gases after treatment by cyclones.

Filters used to carry out such filtration are well known. Such filters typically require frequent cleaning as they become blocked by particles that will not pass through the filter media.

Backflushirig, or backwashing, a filter screen,or other filter media, to clear the particles blocking the filter is a known technique. In such backflushing arrangements a flow of backflushing fluid is directed against the filter screen or media, and in particular back through the filter media in the opposite direction to the main flow in order to dislodge and clear particles which may be blocking the filter media.

It has been found in our experiments with backflushing filters that the higher the velocity and quantity of the backf lush stream the better the filter media is cleaned. It is a combination of velocity and volume of the backflushing stream that is important.

More specifically in use the filter screen or media also causes a resistance to backflushing. Since the backflushing fluid (liquid or gas) must be forced through the filter media, this usually requires a considerable force to accomplish this. The particles that will not pass through the filter media are also trapped in or on the filter media. A considerable force by way of a backflushing stream of liquid or gas is then required to remove the particles from the filter media. Also as the filter media becomes blocked a greater force is required in general to force backflushing fluid through the blocked filter. The power (dependent upon the velocity) of the backflushing flow required is dependent on the resistance of the filter media to backflushing and the pressure differential across the filter media.

The generation of such a powerful backflushing flow, in a simple practical manner however presents a particular challenge. As a result number of conventional backflushing arrangements are complicated and expensive.

In addition since the backflushing flow opposes the main flow through the filter, and requires an additional pressurised fluid flow, backflushing arrangements, especially those which generate the required significant flows to effectively clear the filter, require additional energy and power which reduces overall efficiency and increase operating costs.

It is therefore desirable to provide an improved filter arrangement, and method of filtration, incorporating a backflushing which address the above described problems, is relatively simple and/or which offers improvements generally.

In particular it is desirable to provide a filter arrangement, and method of filtration incorporating backflushing in which a required backflushing flow is generated to clear the filter in a simple, effective and efficient manner.

More specifically it is has been found that continuous backflushing of the filter is not needed in order to ensure adequate operation of the filter and that it is kept sufficiently clear. For example, when the filter media has relatively small apertures and the liquid or gas to be filtered contains relatively small quantities of particles, the filter may take some time to block. On the other hand such a filter then requires considerable backflushing force to remove the particles from the filter media. In this situation an intermittent but powerful backflush can advantageously be used to provide adequate clearing and operation of the filter and filter media. More generally it has been found that the required frequency of backflushing is determined by the flow rate per unit area through the filter media, the size of the apertures in the filter media and the number and size per unit volume of particles in the liquid or gas to be filtered. The power of the backflushing stream required is however dependent on different factors and the resistance of the filter media to backflushing and the pressure differential across the filter media.

It is therefore, in accordance with these findings and understanding, desirable to provide a simple method and means of producing a powerful backflushing force at intermittent intervals.

Accordingly the present invention provides a backflushed filter assembly, and a method of backflushing a backflushed filter, as described in the accompanying claims.

In first aspect of an embodiment of the invention there is provided a backflushed filter assembly comprising a filter, a backflushing arrangement which generates and directs a backflushing flow to backflush the filter, and a drive arrangement to provide motive power to operate the backflushing arrangement. The drive arrangement comprises a turbine driven in use by a flow of filtered fluid through the filter and which drives the backflushing arrangement.

The filter assembly further comprises an outlet duct through which filtered fluid flow from the filter flows and the turbine is located within the outlet duct.

With this arrangement motive power to drive the backflushing arrangement and generate the backflushing of the filter is generated internally within the filter assembly without requiring a specific external power supply. This results in a particularly simple and advantageous filter arrangement driven simply by the flow of fluid through the filter.

Preferably the filter assembly is cylindrical and the backflushing arrangement comprises a least one angled vane rotatably and coaxially mounted within the filter assembly to rotate about the axis of the assembly. The drive arrangement in use rotates the vane to urge fluid against the filter and generate a backflushing flow.

In a second aspect of an embodiment of the invention there is provided a backflushed filter assembly comprising a filter, a backflushing arrangement which in use generates and directs a backflushing flow to backflush the filter, and a drive arrangement which in use provides motive power to operate the backflushing arrangement. The assembly further comprises a storage and release arrangement which in use accumulates and stores motive power supplied from the drive arrangement over a first period of time and then releases the stored motive power over a second period to intermittently operate the backflushing arrangement to generate and direct the backflushing flow to backflush the filter.

By this arrangement a more powerful intermittent backflushing flow is generated and provided, in which the backflushing flow is greater than that which would be produced directly from the motive power supplied. The storage and release arrangement concentrates the motive power supplied to generate a more powerful backflushing flow to achieve improved backflushing, whilst by operating the backflushing intermittently the required power supplied is minimised and reduced. The storage and release arrangement also achieves such an intermittent and more powerful backflushing flow from a continuous lower level continuous supply of motive power which is relatively straightforward to supply to the filter assembly. Such an arrangement is also able to operate substantially automatically and in a simple manner without requiring manual activation.

The second period is preferably shorter than the first period.

Preferably the storage and release arrangement comprises a resilient member which is in use deformed by the drive arrangement to store the motive power. In particular the resilient member may comprise a spring.

The backflushing arrangement preferably comprises a moveable member which in use is moved relative to the filter to direct a backflushing flow against at least a portion of the filter to backflush the filter. The moveable member may in particular comprise an angled vane which in use is moved adjacent to the filter to urge fluid against the filter and generate a backflushing flow. Furthermore the moveable member of the backflushing arrangement is mounted upon the distal end of an arm. The arm may comprise a resilient arm fixed at one end.

Alternatively the moveable member of the backflushing arrangement may comprise a plate which is moveable toward and away from filter to direct a backflushing flow against at least a portion of the filter to backflush the filter.

S The storage and release arrangement may then comprise spring assembly between the plate and filter. The spring assembly is extended as the plate is moved away from the filter, and urges the plate toward the filter once the plate is in use moved from the filter and released.

Preferably the drive arrangement moves the moveable member of the backflushing arrangement in a first direction from a first position over the first period of time to a second position from which the movable member is released and moves in a second opposite direction back to the first position over the second period of time to generate and direct the backflushing flow.

The drive arrangement may in use drive and move a catcher arm which engages the moveable member to move the movable member to a first position from which it is subsequently released.

In a preferred arrangement the filter assembly is cylindrical and the arms are coaxially mounted within the cylindrical filter assembly to rotate about the axis of the cylindrical filter assembly. The storage and release arrangement may further comprises a torsion spring which is in use wound up by the drive arrangement and released to rotate arm.

The drive arrangement preferably comprises a rotary drive arrangement. In particular the drive arrangement may comprise an electric motor. Alternatively, arid preferably the drive arrangement comprises a turbine driven in use by a flow of filtered fluid through the filter and which drives the backflushing arrangement.

In a third aspect of an embodiment of the invention there is provided a method of backflushing a backflushed filter assembly comprising a filter, a backflushing arrangement, and a drive arrangement. The method comprises providing a storage and release arrangement; supplying motive power to the backflushed filter via the drive arrangement; storing and accumulating the motive power supplied to the backflushed filter over a first period; and releasing the stored motive power over a second period to intermittently operate the backflushing arrangement to generate and direct the backflushing flow to backf lush the filter.

Preferably the storage and release arrangement comprises a resilient member, and the storing an accumulating power comprises deforming the resilient member.

The backflushing arrangement may in particular comprise a moveable member. Preferably the method then comprises operating the backflushing arrangement to generate and direct the backflushing flow to backflush the filter by moving the moveable member relative to the filter to direct a backflushing flow against at least a portion of the filter to backflush the filter.

Furthermore the method may comprise moving the moveable member of the backflushing arrangement in a first direction from a first position over the first period of time to a second position against a resilient biassing force, and then releasing the movable member from the second position such that the biassing force moves the moveable member in a second opposite direction back to the first position over the second period of time to generate and direct the backflushing flow.

The present invention will now be described by way of example only with reference to the following figures in which: Figure 1 is a schematic cross section of the filter assembly in accordance with a first embodiment of the invention and including a backflushing assembly driven by a geared electric motor; Figure 2 is a schematic section along section X-X of the filter assembly of figure 1; Figure 3 is a schematic cross section of a filter assembly in accordance with a second embodiment of the invention and including a backflushing assembly driven by a geared turbine; Figure 4 is a schematic section along section X-X of the filter assembly in figure 3; Figure 5 is a schematic cross section of the filter assembly in accordance with a third embodiment of the invention and including a backflushing assembly with radially moving backwash plates; Figure 6 is a schematic section along section X-X of the filter assembly in figure 6; Figure 7 is schematic cross section of a filter assembly in accordance with a fourth embodiment of the invention incorporating a backflushing assembly which includes a torsion spring drive arrangement; Figure 8 is a schematic section along section X-X of the filter assembly in figure 7; Figure 9 is a schematic sectional illustration of the filter assembly shown in figure 7 installed within a filter container; Figure 10 is a schematic section of a filtration system incorporating the filter assembly as shown in figure 9; Figure 11 is a schematic cross section of a filter assembly in accordance with a fifth embodiment of the invention including a turbine which directly drives a backflushing vane; Figure 12 is a schematic section along section X-X of the filter assembly in Figure 11; and Figure 13 is a more detailed perspective illustration of a backflushing vane for use with filter assemblies as shown in figures 1-4 and 7-12.

In general a backflushed filter comprises a filter screen and a backflushing arrangement which in use directs a flow of backflushing fluid against the filter screen or media, and in particular back through the filter media in the opposite direction to the main flow through the filter in order to dislodge and clear particles which may be blocking the filter media.

In accordance with an aspect of embodiments of the invention, the backflushing arrangement is configured to automatically generate and produce a powerful backflushing flow at intermittent intervals that is able to pass through the filter media and dislodge any particles that are blocking the media. This is advantageously achieved, in the embodiments which will be described further below, from a continuous source of power, at a relatively low level, which is stored and accumulated over time and then released rapidly at intervals to drive the backflushing arrangement and generate a powerful backflushing flow from the accumulated power.

This storage and release of the power can, as will be explained and illustrated further below in relation to the specific embodiments, be achieved in many ways, for example by a spring, which can be made of any elastic material so that when it is deformed it reverts to its original shape.

Other methods may include the elastic properties of gases, or the temporary storage of energy in a flywheel or in a battery. Indeed any method of storing energy over a period, which can then be released over a shorter period in a more concentrated form, can be used.

The low level continuous power source for example could be a geared electric motor, that slowly deforms an elastic material and then the material is released at a pre-determined position or when a predetermined force has been applied to it, to drive a backflushing arrangement and provide a powerful backf lush. Alternatively another source of power could be the flow of the liquid or gas into or out of the filter. For example by turning a turbine or propeller that drives a gear box that deforms the elastic material which is then released to provide the backflushing. Indeed any source of power can be used including muscle power. For certain power sources some gearing may be required, and provided, this however is not essential and depends on the properties of the power source and the properties of the power storage mechanism.

Specific particular detailed embodiments of the invention are shown in the figures, and will now be described further.

Referring to figure 1, the filter media 1, comprising a filter screen, is formed in to a cylinder with end plates 10 and 11 at each end of the cylinder. Inside the cylinder are mounted a number of spring steel rods 3 which extend radially from a fixed central mounting 4 within the centre of the cylindrical filter. Upon the distal ends of each rod 3 is mounted a backflushing vane 2 angled at approximately 45 degrees to the rods 3. The vane 2 extends longitudinally adjacent the inside of the filter media 1. As shown more clearly in figure 2 in this embodiment there are six rods 3 equally spaced at 60 degree intervals about the central mounting 4. At the bottom of the filter is an outlet 6 for the filtered fluid or gas. At the top of the filter an electric motor 8 and gearbox 7 are mounted on the top plate 10. The output shaft 12 of the gearbox 7 is connected to a radially extended arm 5 to which a further catcher rod 9 extends downwards.

In operation the liquid or gas to be filtered flows through the filter media 1 from outside the cylinder into the body of the cylinder and exits the via the outlet duct 6. The motor S is energised and rotates the extended arm 5 (in this example in an anti clockwise direction) which rotates within the filter cylinder. As the arm 5 rotates the catcher rod 9 engages with one of the backflushing vanes 2 attached to a first of the spring steel rods 3 (indicated as rod A in figure 2) . As a result the vane 2 and distal end of rod 2 is slowly swept around by the rotating arm 5 bending the spring steel rod 3. In so doing the radius of the rod 3 decreases and the vane 2 is pulled radially inward away for the filter screen and slowly out of engagement with the catcher rod 9 which rotates at a fixed radius. Consequently at a certain point in the rotation of the arm 5 the bending of the rod 3 is such that the catcher rod 9 becomes disengaged from the vane 2 and is released from the catcher rod 9. In figure 2 dotted line 13 represents the bent position of the spring steel rod 3 in its maximum bent back position just before release from the catcher rod 9. As the spring rod 3 springs back it sweeps the backflushing vane 2 over the arcuate sector of the filter screen 1 over which the spring rod 3 was bent and, due to the angling of the vane 2 and speed of movement forces the liquid or gas through the filter media 1 generating a backflushing flow through the filter media 1 in a radially outwards direction removing any particles that may have stuck to the outside of the filter cylinder.

The rate at which the rod 3 springs back is much faster than the rate that it is initially bent. For example if it takes 6 seconds for the rod 3 to be bent by action of the geared motor and it may spring back in 0.1 seconds. As a result the power that was applied to the rod over 6 seconds to bend the rod 3 to its maximum bent position, and stored in the resilience of the spring rod 3, is released as a burst of power, moving the vane 2 rapidly over an arcuate sector of the inner circumference of the filter cylinder and creating a high pressure wave, and powerful backflushing flow to push the filtered liquid or gas through the filter mesh to dislodge any particles on or in the filter media. The bending of the spring rod 3 in effect stores and accumulates the rotary power delivered at a low level by the slower continuous rotation of the arm 5. This stored energy in the bent rod 3, is then released in an intermittent burst to generate a backflushing flow, much greater than would be produced by simply moving the vane 2 at the rate of rotation of the arm 5, with under the return of the bent spring rod 3 the vane moving a significantly faster rate. It should be noted however that the overall power supplied is sirnpiy that required to rotate the arm 5 at its slow low power rate, and that this is magnified and concentrated by the backflushing arrangement to generate a much more powerful backflushing flow.

As the arm S continues to rotate the catcher rod 9 engages with one of the backflushing vanes 2 attached to the next spring steel rod 3 (indicated as rod B in figure 2), and the process is repeated with this next rod B and vane 2 over the next arcuate sector of the filter screen.

Accordingly, and by spacing the rods 3 about the filter such that they are bent back to a position close to the next rod 3, backflushing of the entire circumference of the filter can be achieved, a sector at a time, as the arm 5 rotates around the circumference.

-13- - The backflushing force of the backflushing flow generated and applied to the filter media 1 can be considerable and fine woven mesh screens may be damaged.

Therefore for fine screens sintered stainless steel mesh screens are more suitable as the very fine mesh is bonded to a more robust backing, or sandwiched between layers of stronger coarser filter material. This allows a very fine but robust filter material, which will stand the strong intermittent forces generated.

Figure 3 shows a cross section of the filter assembly in accordance with a second embodiment. This is generally the same as the filter assembly shown in figure 1, and like reference numerals have been used for like features. The principal difference in this second embodiment is that the extended arm 5 is driven by a gearbox 7 that is connected to a turbine/propeller 14 which is mounted in the exit/outlet duct 6 of the filter.

The operation of the back flushing mechanism is the same as the configuration shown in Figures 1 and 2. In this embodiment however the source of power is the flow of fluid or gas through the filter itself, in particular through the outlet duct 6 which rotates the turbine 14 and drives the backflushing mechanism. The flow of the fluid or gas through the filter can be by gravity or by a pump which either sucks or pumps the fluid or gas, or any other means of providing a flow of fluid or gas, through the filter media 1 and out via the duct 6. In the duct 6 it passes the turbine or propeller or other mechanical means of converting flow through the duct 6 into motion.

This arrangement has the advantage that no further external power source is required to be supplied to the backflushing filter which may have advantages in certain applications. It should however be noted that the power generated by a turbine whilst generated without any external power supply, is typically relatively low and is dependent upon the flow of fluid through the filter.

However by using the energy storage arrangement of the invention, this low power is stored and released intermittently to generate a required more powerful backflushing flow.

In an alternative method and arrangement a torsion or motor spring could be used which is wound up by the power source and is then released at a certain tension, for example by a spring loaded catch that will release the vane at a pre-determined force. The vane will then rotate, as the spring unwinds releasing its stored power, in the cylinder backflushing the filter media with force. Such an embodiment is shown by way of example in Figures 7 and 8 where a torsion spring 19 is used an energy storage device in place of the bending of the spring rods 3 as in the previous embodiment shown in figures 1 to 4.

In the embodiment shown in figures 7 and 8 the filter media 1 is formed into a cylinder with end plates 10 and 11 at each end of the cylinder. Inside the cylinder is a spring holder 22, this holds the torsion spring 19 in position. The spring holder 22 is attached to the gearbox output shaft 12. One end of the torsion spring 20 is positioned in a slot in the spring holder 22, so that it rotates with the spring holder 22. The other end 21, of the torsion spring is attached to a backflushing vane 2. There are a number of vane stops 23 around the inner periphery of the filter cylinder.

In operation when fluid starts to flow through the filter media and out through exit 6 passing the turbine/propeller 14, the turbine/propeller starts to turn and the output shaft 12 of the gearbox 7 also turns. The spring holder 22 and backflushing vane 2 also turn until the backflushing vane2 comes to a vane stop 23. Then the backflushing vane 2 stops turning and the torsion spring is wound up. The vane stops 23 project sufficiently into the cylinder so that when in this case the spring holder 22 has rotated a further 60 degrees, (there are 6 equally spaced vane stops 23 in this example, although 2 or 3 may be sufficient depending on the strength of the torsion spring 19) . The force of the spring 19 pushes the vane 2 past the vane stop 23 and the backflushing vane 2 rotates at high velocity, backflushing the filter mesh 1. It then comes to rest at the next vane stop 23 and the process is repeated.

In the embodiment shown in figures 7 and 8 a turbine/propeller is used and shown to provide the motive force, and as the power source.

A yet further variation and alternative embodiment is shown in figures 5 and 6. As in the previous embodiments the filter media 1 is formed into a cylinder with end plates 10 and 11 at each end of the cylinder. Inside the filter cylinder are panels 15, which are movable in a radial direction. The panels 15 are supported on guide rails or similar, (not shown) . In this example each panel has an extension spring 17. One end of the spring 17 is attached to the panel 15 and one end to the inside of the cylinder. Each panel 15 has a curved plate 18 attached to it. A catcher pin 9 is attached to the output shaft 12 of the gearbox 7 via a radially extended arm 5. In this example the motive force is provided by a turbine/propeller but it could equally be provided by an electric motor 8 as shown in figure 1.

In operation as fluid starts to flow through the filter mesh 1 and out via exit 6, the turbine/propeller turns the gearbox 7 and in turn the gearbox output shaft, radially extended arm 5 and catcher 9. As the catcher 9 is rotated, it engages the curved plate 18 attached to the panel 15. As it engages, by virtue of the shape of the curved plate 18, the panel is pulled radially inwards towards the centre of the cylinder. This extends the extension spring 17 (as shown as spring 16) . As the catcher 9 continues to turn it comes to the end of the curved plate 18 and releases the panel 15. The panel 15 is then pulled by the extension spring towards the filter mesh 1 at speed.

As it moves it creates a pulse of fluid that backflushes the filter mesh 1. As the catcher 9 continues to turn and rotate it engages with the next curved plate 18 and the process is repeated continuously with each panel 15.

The radially moving panels 15 are provided adjacent to the inside of the filter screen 1 and are radially and consecutively pulled radially inwards away from the filter mesh against the extension springs 17. As the panels 15 are each released they return and move radially outwards under the force of the extension spring 17 to thereby generate a radially outwards backflushing flow through the filter over consecutive sectors of the filter thereby backflushing the entire filter media 1 and screen.

In a yet further alternative embodiment (not shown) a flywheel is connected to a central shaft in the axial direction with respect to the filter cylinder. An arm or arms extend radially outwards from the axial shaft are connected to a backflushing vane or vanes. The angle of the vane or vanes are movable so that they initially run parallel to the inside of the filter media cylinder and therefore produce little drag. However when they reach a certain speed the angle automatically changes either by theaction of centrifugal force or the force of the liquid or gas on the vane so that they then present a greater angle to the inside of the filter media cylinder. As a result they directed and urge a backflushing flow of fluid radially outwards through the filter. In addition and as a result the drag generated by the vane increases. The power stored in the momentum of the flywheel however causes the vane to carry on for a period at speed causing a powerful backwash. As the increased drag slows the rotation of the vanes down angle of the vanes reverts to its parallel position with respect to the filter media cylinder. The power source then with reduced drag on the vane will accelerate the flywheel again to a higher angular velocity when the process will be repeated.

Although the preferred embodiments of the invention described above relate to a filter in the form of a filter cylinder it is easy to envisage other embodiments where for example a flat filter media is backflushed by a vane moving at speed near to its surface, for example by the vane sliding on a rail positioned over the media with an extension spring or similar being extended and released by a power source causing the angled vane to traverse the filter media backflushing the filter media.

The use of a turbine to drive a backflushing system and generate a backflushing flow from the flow of fluid through the filter, as in embodiments shown in figures 3 to 8 is a significant aspect of the invention. In particular such arrangements advantageously generates a backflushing flow without requiring any external power source. Whilst this arrangement is preferably used in conjunction with the intermittent generation of a backflushing flow, it can, in particular if the flow through the filter is sufficiently high, be used to directly generate a continuous backflushing flow. In particular when the velocity of the fluid flow through the exit/outlet duct 6 is relatively high considerable power can be generated by a turbine/propeller enabling a backflushing vane 2 directly attached thereto to rotate at high speed generating a powerful backwash. A gearbox may or may not be necessary in this situation. Such an alternative arrangement is shown in figures 11 and 12 where the turbine/propeller directly drives backflush vane 2. In this arrangement there is no energy storage device. In this example there is no gear box but in some situations a gearbox may be necessary depending on the characteristics of the turbine/propeller 14 and the backf lush vane 2.

As shown in the arrangement of figures 11 and 12 there is a central shaft 35 supported by a top bearing and bottom bearing 37. The backflush vane 2 is attached to the shaft 35. The turbine/propeller 14 is attached to the top of the central shaft 35. The above arrangement is situated within the filter cylinder.

In operation fluid flows through the filter media 1 and out via exit/outlet 6 passing the turbine impeller 14.

The flow of fluid makes the turbine/propeller 14 turn, turning and rotating the central shaft 35 and backflush vane 2. The rotation of the backflush vane 2 causes fluid within the filter cylinder to be pushed outwards, generating a backflushing flow through the filter media 1 removing any particles that may have settled on it.

Similarly a further variation on the arrangement shown in figure 3 is that the extended arm 5 could be attached directly to a backflushing vane 2, without the requirement for intermittent backflushing. The extension arm 5 would then continuously rotate the vane 2 forcing liquid or gas through the filter media thereby cleaning it. In this situation a gearbox may not be necessary.

These direct drive arrangements are particularly applicable for use with a coarse filter media in which a lower backflushing force from the backflushing flow to backflush the filter is required.

Figure 13 shows the preferred design for a backflush vane 2,41 which can be used in the above described embodiments. Although this in no way means that this is the only design of vane 2,41 that would be suitable for filters of this type. This design allows fluid to flow uninterrupted over both sides of the vane 2,41. The arrows 38 shows the movement of fluid over the forward face of the vane 41, the arrows 39 show the movement of fluid over the trailing face of the vane 41. Arrow 40 shows the direction of travel of the vane. Plates 42 provide attachment to the arm 43 that propels the vane, allowing a gap between the vane 41 and the arm 43. This allows fluid to flow over both surfaces of the vane 2,41. If the arm 43 were attached directly to the vane 41, the arm 43 would create turbulence around it as it moves through the fluid. This turbulence would greatly reduce the effectiveness of the trailing face of the vane 41 to produce a backwash.

Whilst the filter assemblies described above and illustrated in figures 1 to 8 and 11 and 12 can be directly immersed within the fluid (or gas) to be filtered the filter is enclosed within a container in so that detritus backflushed from the filter media is collected in the container for disposal. The container has an inlet, which delivers the fluid or gas to the out side of the filter cylinder and an exit duct from the container, which is connected to the exit duct 6 of the filter. A further outlet from the container is provided for removal of the detritus that has been filtered from the fluid or gas. The container could thus be connected in a pipeline or in the main body of the fluid or gas.

Ey way of example figure 9 shows a filter assembly 29 as shown in figures 7 and 8 in a container 24. Filters as shown in figures 1 to B and 1]. and 12 could also be fitted in a container 24 in the similar way.

The container 24 has an inlet 25 for contaminated fluid and an exit 26 for fluid that has been through the filter unit 29. The container 24 also has an outlet 27 for removing the detritus 30 via a valve 31. The container 24 has baffles 28 these encourage the backflushed particles to move downwards across the filter media and settle at the bottom of the container. The baffles 28 cause a slightly reduced pressure, between the inner circumference of the baffle 28 and the outer circumference of the filter media 1. As the liquid or gas moves from the area of filter media above the baffle 28 to the area of filter media below the baffle 28, the reduced pressure encourages the particles to move across the filter media 1 and it the acts as a cross flow filter as well as a baclcflushing filter.

In operation the container is connected as part of a pipeline, with the upstream pipeline attached to inlet 25 and the down stream pipe attached to exit 26. As the fluid flows into the container it flows through the filter 29 and out via exit 26 the detritus 30 settles on the filter media 1. The backflushing pulse 33 pushes the detritus away from the filter media 1. It is then moved in a downwards direction over the filter media by the flow 32. This is repeated until the particles move off the bottom of the filter media and collect in the bottom of container 24.

Figure 10 shows a configuration where the filter unit 29 is positioned in an enlarged container 24 which is open to the atmosphere.

The fluid flows into the container 24 either by gravity or by a pump. Fluid flows through the filter 29 as in previous examples and is drawn upwards through siphonic outlet duct 27 and into a second chamber 34, divided from the first chamber 24. The fluid level in the second chamber 34 is maintained at a lower level than the fluid level in the container 24,with the outlet fo the siphonic duct 27 kept below the surface level of the second chamber 34. The difference in fluid levels between the two chambers provides the fluid head to drive the fluid flow through the filter assembly 29.

The second container 34 is not always necessary.

However for example in fish keeping filtration systems it is common to have a second container that contains media that acts as a biological filter. It will also be appreciated that other arrangements to generate a flow through the filter can be used.

Claims

-22- - CLAI MS

1. A backflushed filter assembly comprising a filter, a backtlushing arrangement which generates and directs a backflushing flow to backflush the filter, and a drive arrangement to provide motive power to operate the backflushing arrangement; wherein the drive arrangement comprises a turbine located in an outlet duct through which fluid flow from the filter flows, and in which the turbine which drives the backflushing arrangement is driven, in use, by the flow of fluid through outlet of the filter.

2. A backflushed filter assembly as claimed in claim 1 in which the backflushing arrangement comprises a rrioveable member which in use is moved relative to the filter to direct a backflushirig flow against at least a portion of the filter to backflush the filter.

3. A backflushed filter assembly as claimed in claim 2 in which the moveable member of the backflushing arrangement comprises a plate which is moveable toward and away from filter to direct a backflushing flow against at least a portion of the filter to backflush the filter.

4. A backflushed filter assembly as claimed in claim 3 further comprising a spring assembly between the plate and filter; the spring assembly being extended as the plate is moved away from the filter, and urging the plate toward the filter once the plate is in use moved from the filter and released.

5. A backflushed filter assembly as claimed in any one of claims 2 to 4 in which the drive arrangement moves the moveable member of the backflushing arrangement in a first direction from a first position over the first period of time to a second position from which the movable member is released and moves in a second opposite direction back to the first position over the second period of time to generate and direct the backflushing flow.

6. A backflushed filter assembly as claimed in any one of claims 2 to 5 in which the drive arrangement in use drives and moves a catcher arm which engages the moveable member to move the movable member to a first position from which it is subsequently released.

7. A backflushed filter assembly as claimed in any one of claims 2 to 6 in which the moveable member of the backflushing arrangement is mounted upon the distal end of an arm.

8. A backflushed filter assembly as claimed in claim 7 in which the arm comprises a resilient arm fixed at one end.

9. A backflushed filter assembly as claimed in claim 7 or 8 in which the filter assembly is cylindrical and the arm is coaxially mounted within the cylindrical filter assembly to rotate about the axis of the cylindrical filter assembly.

10. A backflushed filter assembly as claimed in any one of claims 2 to 9 in which the moveable member comprises an angled vane which in use is moved adjacent to the filter to urge fluid against the filter and generate the backflushing flow.

11. A backflushed filter assembly as claimed in any one of claims 1 to 9 further comprising a storage and release arrangement which in use accumulates and stores motive power supplied from the drive arrangement over a first period of time and then releases the stored motive power over a second period to intermittently operate the backflushing arrangement to generate and direct the backflushing flow to backflush the filter.

12. A backflushed filter assembly as claimed in claim 11 in which the second period is shorter than the first period.

13. A backflushed filter assembly as claimed in claim 11 or 12 in which the storage and release arrangement comprises a resilient member which is in use deformed by the drive arrangement to store the motive power.

14. A backflushed filter assembly as claimed in claim 13 in which the resilient member comprises a spring.

15. A backflushed filter assembly as claimed in claim 14 in which the storage and release arrangement comprises a torsion spring which is in use wound up by the drive arrangement and released to rotate the backflushing arrangement.

16. A backflushed filter assembly as claimed in any preceding claim in which the filter assembly is cylindrical and the filter comprises at least part of the cylindrical JO wall of the cylindrical filter assembly.

17. A backflushed filter assembly as claimed in any preceding claim in which the drive arrangement comprises a gearbox.

18. A backflushed filter assembly as claimed in any preceding claim in which the filter comprises perforated filter screen.

19. A backflushed filter assembly as claimed in any preceding claim in which the filter assembly is contained within an outer container.

20. A backflushed filter assembly as claimed in claim 1 in which the filter assembly is cylindrical and the backflushing arrangement comprises a least one angled vane rotatably and coaxially mounted within the filter assembly to rotate about the axis of the assembly; the drive arrangement in use rotating the vane to urge fluid against the filter and generate a backflushing flow.

21. A method of backflushing a backflushed filter assembly comprising a filter, and outlet, and a backflushing arrangement; the method comprising generating a flow of fluid through the assembly and outlet; and using a turbine located in the outlet of the filter and which is driven by a flow of fluid through the outlet to drive the backflushing arrangement to generate and direct a backflushing flow against at least a portion of the filter.

22. A method of backflushing as claimed in claim 21 in which the backflushing arrangement comprises a moveable member, and in which driving the backflushing arrangement to generate and direct the backflushirtg flow to backflush the filter comprises moving the moveable member relative to the filter to direct a backflushing flow against at least a portion of the filter to backflush the filter.

23. A method of backflushing as claimed in claim 22 in which the moveable member is rotated by the turbine.

24. A method of backflushing as claimed in claim 22 or 23 in which the filter assembly is cylindrical and the filter comprises at least part of the cylindrical wall of the cylindrical filter assembly.

25. A method of backflushing as claimed in claim 24 in which the moveable memeber is mounted upon the distal end of an arm coaxially mounted within the cylindrical filter, driving the backflsuign arrangemetn comprises rotating the arm about the axis of the cylindrical filter assembly.

26. A method of backflushing as claimed in any one of claims 22 to 25 comprising moving the moveable member of the backflushing arrangement in a first direction from a first position over the first period of time to a second position against a resilient biassing force, and then releasing the movable member from the second position such that the biassing force moves the moveable member in a second opposite direction back to the first position over the second period of time to generate and direct the backflushing flow.

27. A method of backflushing as claimed in any one of claims 21 to 26 in which the moveable member comprises an angled vane, and in which driving the backflushing arrangement to generate and direct the backflushing flow to backflush the filter comprises moving the angled vane adjacent to the filter to urge fluid against the filter and generate the backflushing flow.

28. A method of backflushing as claimed in any one of claims 21 to 26 in which the backflushing arrangement furterh comprises a drive storage and release arrangement, and in which driving the backflushing arrangement comprises storing and accumulating the motive power supplied to the backflushed filter over a first period, and releasing the stored motive power over a second period to intermittently operate the backflushing arrangement to generate and direct the backflushing flow to backflush the filter.

29. A method of backflushing as claimed in claim 28 in which the storage and release arrangement comprises a resilient member, and the storing an accumulating power comprises deforming the resilient member.

30. A filter assembly substantially as hereinbefore described with reference to, and/or as shown in figures 10 and 11.

31. A method of backflushing a filter substantially hereinbefore described with reference to, and/or as shown in figures 10 and 11.

32. A backflushed filter assembly comprising a filter, a backflushing arrangement which generates and directs a backflushing flow to backflush the filter, and a drive arrangement to provide motive power to operate the backflushing arrangement; wherein the drive arrangement comprises a turbine driven in use by a flow of fluid through the filter and which drives the backflushing arrangement.

33. A backflushed filter assembly comprising a filter, a backflushing arrangement which in use generates and directs a backflushing flow to backflush the filter, and a drive arrangement which in use provides motive power to operate the backflushing arrangement; wherein the assembly further comprises a storage and release arrangement which in use accumulates and stores motive power supplied from the drive arrangement over a first period of time and then releases the stored motive power over a second period to intermittently operate the backflushing arrangement to generate and direct the backflushing flow to backf lush the filter.

34. A method of backflushing a backflushed filter assembly comprising a filter, a backflushirig arrangement, and a drive arrangement; the method comprising: providing a storage and release arrangement; supplying motive power to the backflushed filter via the drive arrangement; storing and accumulating the motive power supplied to the backflushed filter over a first period; releasing the stored motive power over a second period to intermittently operate the backflushing arrangement to generate and direct the backflushing flow to backflush the filter.

Amendments to the claims have been filed as follows: 29(

1. A backflushed filter assembly comprising a filter, a backflushing arrangement which generates and directs a backflushing flow to backflush the filter, and a drive arrangement to provide motive power to operate the backflushing arrangement; wherein the drive arrangement comprises a turbine located in an outlet duct through which fluid flow from the filter flows, and in which the turbine which drives the backflushing arrangement is driven, in use, by the flow of fluid through outlet of the filter.

2. A backflushed filter assembly as claimed in claim 1 in which the backflushing arrangement comprises a moveable member which in use is moved relative to the filter to direct a backflushing flow against at least a portion of the filter to backflush the filter.

6. A backflushed filter assembly as claimed in any one of claims 2 to 5 in which the drive arrangement in use drives and moves a catcher arm which engages the rnoveable member to move the movable member to a first position from which it is subsequently released.

11. A backflushed filter assembly as claimed in any one of claims 1 to 9 further comprising a storage and release arrangement which in use accumulates and stores motive power supplied from the drive arrangement over a first period of time and then releases the stored motive power S over a second period to intermittently operate the backflushing arrangement to generate and direct the backflushing flow to backflush the filter.

16. A backflushed filter assembly as claimed in any preceding claim in which the filter assembly is cylindrical and the filter comprises at least part of the cylindrical wall of the cylindrical filter assembly.

22. A method of backflushing as claimed in claim 21 in which the backflushing arrangement comprises a moveable member, and in which driving the backflushing arrangement to generate and direct the backflushing flow to backflush the filter comprises moving the moveable member relative to the filter to direct a backflushing flow against at least a portion of the filter to backflush the filter.

23. A method of backflushing as claimed in claim 22 in which the moveab]. e member is rotated by the turbine.

27. A method of backflushing as claimed in any one of claims 21 to 26 in which the moveable member comprises an angled vane, and in which driving the backflushing arrangement to generate and direct the backflushing flow to backflush the filter comprises moving the angled vane adlacent to the filter to urge fluid against the filter arid generate the backflushing flow.

28. A method of backflushing as claimed in any one of claims 21 to 26 in which the backflushing arrangement further comprises a drive storage and release arrangement, and in which driving the backflushing arrangement comprises storing and accumulating the motive power supplied to the backflushed filter over a first period, and releasing the stored motive power over a second period to intermittently operate the backflushing arrangement to generate and direct the backflushing flow to backflush the filter.