EP1812135A2

EP1812135A2 - A fluid filtration system and method of filtering fluid

Info

Publication number: EP1812135A2
Application number: EP05803555A
Authority: EP
Inventors: Nicholas Evolution Aqua Limited JACKSON; Andrew Clark; Colin Evolution Aqua Limited FRENCH
Original assignee: Evolution Aqua Ltd
Current assignee: Evolution Aqua Ltd
Priority date: 2004-11-15
Filing date: 2005-11-15
Publication date: 2007-08-01
Also published as: WO2006051336A3; GB0425199D0; WO2006051336A2

Abstract

The present application relates to a filtration system (1) for filtering particulate material from a fluid. The filtration system (1) has a system inlet (7), a bypass valve (85), a first filter (21), and a system outlet (9). The bypass valve (85) is operable to place the system inlet (7) in fluid communication with the system outlet (9) and to allow at least a portion of the fluid passing through the filtration system to bypass the first filter (21). The application also relates to methods of filtering fluid and installing a filtration system.

Description

A FLUID FILTRATION SYSTEM AND METHOD OF FILTERING FLUID

The present application relates to a fluid filtration system and a method of filtering fluid. The present application also relates to a method of installing a filtration system.

It is known from the Applicant's earlier International patent application PCT/GB01/05533 to provide a pressurised filtration system having a sealed housing inside of which is located a filter. A circulatory pump supplies water to the system from a pond and the water is filtered before being returned to the pond. A debris discharge outlet is provided to expel accumulated debris from the system.

However, there remain a number of areas where filtration systems may be improved. The inventors in the present case have recognised, for example, that problems may arise if the filter becomes clogged and the introduction of fluid into the filtering system is continued. The increase in pressure may cause damage to the filter. Similarly, if an unsuitable pump is used, the pressure in the filtration system may exceed safe levels.

Viewed from a first aspect, the present application relates to a filtration system for filtering particulate material from a fluid, the filtration system comprising a system inlet, a bypass valve, a first filter, and a system outlet; the bypass valve being operable to place the system inlet in fluid communication with the system outlet and to allow at least a portion of the fluid passing through the filtration system to bypass the first filter.

If the first filter becomes clogged with filtered material, the bypass valve is operable to allow some or all of the fluid introduced into the filtration system through the system inlet to exit through the system outlet and to bypass the first filter. The possibility of damage occurring to the first filter is thereby reduced.

Advantageously, the filtration system may be used as a pre-filter for a further filter. The filtration system may thereby perform a first filtration step before the fluid is passed to the further filter to undergo a second filtration step. The further filter may mechanically filter the fluid but preferably it comprises media for biologically filtering the fluid. The filtration system may be retro-fitted to supply filtered fluid to an existing filter. Thus, at least in preferred embodiments, the filtration system is suitable for use in a wide range of applications. The filtration system preferably comprises cleaning apparatus for cleaning the first filter. The cleaning apparatus preferably projects a fluid onto the first filter to dislodge material trapped therein. The cleaning apparatus, in use, preferably cleans the first filter whilst the bypass fluid operates to cause fluid introduced into the system inlet to bypass the first filter and exit through the system outlet. The cleaning apparatus may operate continuously or may only operate when the bypass valve operates to bypass the first filter. The cleaning apparatus preferably comprises a rotatable member for projecting a flow of fluid onto the first filter.

The bypass valve could place the system inlet in communication with a debris discharge outlet, but since the debris discharge outlet is typically not returned to the fluid source (e.g. a pond), the fluid source may be drained by the filtration system if the bypass valve does not revert to supplying fluid to the first filter.

The bypass valve may be operable in response to a signal from a timer or a pressure sensor. The bypass valve may alternatively be operable manually. The bypass valve is preferably operable to bypass the first filter when the pressure differential between the system inlet and the system outlet is greater than a predetermined value. This is preferably achieved by placing the bypass valve in fluid communication with the system inlet and the system outlet.

The bypass valve is preferably biased towards a closed position in which the system inlet is in fluid communication only with the first filter. Spring means are preferably provided to bias the bypass valve towards its closed position. The strength of the spring means typically determines the pressure differential at which the bypass valve operates to bypass the first filter.

The filtration system preferably comprises a filtrate chamber for receiving fluid filtered by the first filter. The first filter is preferably cylindrical and at least a portion of the filtrate chamber is preferably defined by the filter.

The filtrate chamber is preferably maintained in fluid communication with the system outlet. Most preferably, a second filter is provided between the filtrate chamber and the system outlet. The second filter helps to prevent particulate material or other debris entering the filtrate chamber when the bypass valve operates to allow unfiltered fluid to bypass the first filter. Fluid exiting the filtrate chamber passes through the second filter and may dislodge debris collected therein. The debris collected in the second filter may thereby be expelled through the system outlet.

The first and second filters may filter particulate material of substantially the same size. Preferably, however, the first filter is finer than the second filter. The second filter preferably filters particulate material which may otherwise block the cleaning apparatus. The first filter preferably has a mesh size of between 0.05mm and 0.3mm. Preferably the first filter has a mesh size of 0.08mm.

The second filter preferably has a mesh size of between 0.5mm and 2mm. Preferably the second filter has a mesh size of 0.5mm.

The filtration system may be gravity fed, but preferably a pump is provided to supply the fluid to be filtered. The pump may be located in the pond or other fluid source and supply fluid to the filtration system under pressure. If the filtration system is to be used as a pre-filter for a further filter, the filtration system may not require a pump. For example, the filter may have a pump and this may draw the fluid through the filtration system.

The filtration system is preferably sealed. The filtration system may thereby be installed more readily, for example as a pre-filter for a further filter or retrofitted to an existing filter.

If the filtration system is to be used as a pre-filter for a further filter, the bypass valve may be operable to bypass the filter provided in the filtration system and also the further filter. The bypass valve may thereby be operable to place the system inlet in fluid communication with an outlet of the further filter. Thus, the bypass valve may protect the filtration system and the further filter in the event that the filter in the filtration system becomes clogged. The bypass valve is preferably operable when the pressure differential between the inlet of the pre- filter and the outlet of the further filter exceeds a predetermined level.

Similarly, the filtration system may be provided with a pressure relief valve for allowing unfiltered fluid to exit the filtration system if the pressure exceeds a predetermined level. The pressure relief valve may return the unfiltered fluid to the fluid source and may thereby protect the filtration system and also any further apparatus, such as additional mechanical and/or biological filters.

Viewed from a further aspect, the present application relates to apparatus for bypassing a filter in a filtration system, the apparatus being connectable to an inlet and an outlet of the filtration system, the apparatus comprising a bypass valve operable to place the system inlet in fluid communication with the system outlet and to allow at least a portion of the fluid supplied to the system inlet to bypass the filter. This apparatus may be retrofitted to existing filtration systems to provide filter bypass functionality.

The present application also relates to a method of retrofitting the apparatus described herein to a filtration system, the method including placing the bypass valve in fluid communication with the system inlet and the system outlet. The filtration system preferably comprises cleaning apparatus for cleaning a filter provided therein.

The bypass valve is preferably operable to bypass the first filter when the difference between the fluid pressure in the system inlet and the fluid pressure in the system outlet exceeds a predetermined value.

The present application also relates to a kit of parts for producing apparatus for bypassing a filter in a filtration system, as described herein.

The present application also relates to a filtration system for filtering particulate material from a fluid, the filtration system comprising a system inlet for introducing unfiltered fluid into the filtration system, a bypass valve, a first filter, and a system outlet; the bypass valve being operable to allow unfiltered fluid to bypass the first filter and exit through the system outlet.

Viewed from a still further aspect, the present application relates to a filtration system operable in a bypass mode and a filtration mode for filtering particulate material from a fluid, the filtration system comprising a system inlet, a bypass valve, a first filter, a second filter, a filtrate chamber for receiving filtrate, and a system outlet; wherein, in use, fluid entering the filtrate chamber when the filtration system is operating in said filtration mode is filtered by the first filter, and fluid entering the filtrate chamber when the filtration system is operating in said bypass mode is filtered by said second filter.

The bypass valve is preferably operable to direct at least a portion of the fluid introduced through the system inlet to the system outlet bypassing the first filter when the filtration system is operating in its bypass mode.

Again, the filtration system preferably comprises cleaning apparatus for cleaning the first filter. The cleaning apparatus preferably projects a fluid onto the first filter to dislodge material trapped therein. The cleaning apparatus preferably comprises a rotatable member for projecting a flow of fluid onto the first filter. The bypass valve may be operable manually or automatically, for example in response to a signal from a timer or a pressure sensor. Preferably, however, the bypass valve is operable when the difference between the fluid pressure in the system inlet and the fluid pressure in the system outlet exceeds a predetermined value. The bypass valve is preferably provided in fluid communication with the system inlet and the system outlet.

The second filter is preferably provided between the filtrate chamber and the system outlet. The second filter may be made of a wire gauze or mesh, or moulded from plastics material. Preferably, however, the second filter is made of foam. The first and second filters may filter particulate material of substantially the same size. Preferably, however, the first filter is finer than the second filter.

Debris filtered by the second filter may be expelled through the system outlet when the filtration system is operating in its filtration mode.

Viewed from a further aspect, the present application relates to a filtration system operable in a bypass mode and a filtration mode for filtering particulate material from a fluid, the filtration system comprising a first filter, a second filter and a filtrate chamber for receiving filtrate; wherein, when the filtration system is operating in said bypass mode, fluid bypasses the first filter and fluid entering the filtrate chamber is filtered by the second filter.

The first and second filters may be suitable for filtering particulate material of substantially the same size. Preferably, however, the first filter is finer than the second filter. The present application also relates to a method of operating a filtration system in a filtration mode and a bypass mode, the filtration system comprising a system inlet, a first filter, and a system outlet; wherein, in the filtration mode, fluid introduced through the system inlet is passed through the first filter and expelled through the system outlet; and, in the bypass mode, at least a portion of the fluid introduced through the system inlet is allowed to bypass the first filter and exit through the system outlet.

A bypass valve is preferably provided to change between said filtration and bypass modes of operation. The bypass valve may be operated manually or automatically, for example in response to a signal from a timer or a pressure sensor. Preferably, however, the bypass valve operates when the difference between the fluid pressure in the system inlet and the fluid pressure in the system outlet exceeds a predetermined value. Cleaning apparatus may be provided to clean the first filter and the method preferably includes the step of operating the cleaning apparatus whilst the filtration system is operating in its bypass mode.

Viewed from a yet still further aspect, the present application relates to a filtration system for filtering particulate material from a fluid, the filtration system comprising a filter, a system inlet and a pressure relief valve; the pressure relief valve being operable to allow fluid to exit the filtration system when the fluid pressure exceeds a predetermined level.

The filtration system preferably comprises cleaning apparatus for cleaning the filter. The cleaning apparatus preferably projects a fluid onto the filter to dislodge material trapped therein. The cleaning apparatus preferably comprises a rotatable member for projecting a flow of fluid onto the filter.

The pressure relief valve is preferably operable when the fluid pressure in the system inlet exceeds a predetermined level. The pressure relief valve is preferably provided in the system inlet.

The pressure relief valve preferably allows unfiltered fluid to exit the filtration system.

The filtration system may include a pump for pumping the fluid to be filtered from a fluid source to the system inlet. The pressure relief valve preferably allows the fluid exiting the filtration system to be returned to the fluid source. The fluid to be filtered is preferably water.

Viewed from a further aspect, the present application relates to pressure relief apparatus for a filtration system, the apparatus comprising a pressure relief valve locatable in fluid communication with an inlet of a filtration system, the pressure relief valve being operable to allow fluid to exit through an outlet when the fluid pressure exceeds a predetermined level. The pressure relief apparatus may be retrofitted to existing filtration systems.

The present application also relates to a kit of parts for producing pressure relief apparatus as described herein.

Viewed from a yet further aspect, the present application relates to a filtration system for filtering particulate material from a fluid, the filtration system comprising a system inlet for allowing unfiltered fluid to enter the filtration system, a pressure relief valve, a filter, and a system outlet for allowing filtered fluid to exit the filtration system; the pressure relief valve being operable to allow unfiltered fluid to exit through a release outlet.

The present application further relates to an inlet assembly for a filtration system, the inlet assembly comprising apparatus for bypassing a filter as described herein in combination with pressure relief apparatus as described herein. The present application also relates to a kit of parts for an inlet assembly as described herein.

Viewed from a further aspect, the present application relates to a valve mechanism for a filtration system, the valve mechanism comprising a movable valve closure member for selectively closing a system outlet and a debris discharge outlet of the filtration system, wherein the valve closure member is movable along a linear axis.

The system outlet and the debris discharge outlet preferably have first and second axes respectively and said first and second axes are substantially parallel. The linear axis along which the valve closure member is movable preferably transects and is substantially perpendicular to said first and second axes.

The valve mechanism preferably also comprises a spring means to bias the valve closure member to a position where the debris discharge outlet is closed. This helps to ensure that the filtration system is not left running in a purging mode in which fluid is expelled continuously from the debris discharge outlet, which may result in the fluid source being drained.

The valve mechanism may be operated automatically, for example in response to a timer signal. Preferably, however, the valve mechanism is operated manually. A handle is preferably provided to facilitate manual operation of the valve mechanism.

The present application relates to a valve mechanism as described herein in combination with a filtration system.

Viewed from a further aspect, the present application relates to a filtration system operable in a filtration mode and a purging mode, the filtration system comprising a system inlet for allowing unfiltered fluid to enter the filtration system, a system outlet for allowing filtered fluid to exit the filtration system, and a debris discharge outlet for allowing collected debris to be expelled, a valve mechanism being provided for selectively opening and closing the system outlet and the debris discharge outlet. Unfiltered fluid is preferably introduced into a first chamber when the filtration system is operating in both said filtration mode and said purging mode.

The system inlet is preferably in fluid communication with the first chamber. A portion of the first chamber preferably forms a debris collection chamber for collecting filtered particulate material and other debris. The debris collection chamber preferably has a volume greater than or equal to 5, 10 or 15 litres. The debris collected in the debris collection chamber is preferably expelled through the debris discharge outlet during the purging mode by the introduction of unfiltered fluid into the first chamber. The filter preferably defines a second chamber for receiving filtered fluid.

The valve mechanism preferably comprises a movable valve closure member for selectively opening and closing the system outlet and the debris discharge outlet. The valve closure member is preferably movable along a linear axis. The valve closure member is preferably biased towards a system outlet open position. The valve mechanism is preferably manually operable.

The filtration systems described herein are typically sealed and the unfiltered fluid introduced through the system inlets is generally at a pressure greater than atmospheric pressure.

Viewed from a yet still further aspect, the present application relates to a filtration system for filtering particulate material from a fluid, the filtration system comprising a filter for filtering the fluid, and a collection chamber for collecting particulate material filtered from the fluid. The debris collection chamber may have a volume greater than or equal to 1 , 3, 5, 10, 15, 25 or 50 litres. The debris collection chamber is preferably provided below the filter.

The frequency with which the system must be purged is dependent on the rate at which the debris is collected and the volume of the debris collection chamber. The volume of the debris collection chamber is preferably sufficient to allow the system to require purging only once every 3 to 4 days, once a week or longer.

Viewed from a still further aspect the present application relates to a filtration system comprising at least one flexible filter for filtering a fluid and cleaning apparatus for projecting a flow of fluid onto the at least one flexible filter; wherein, in use, the fluid to be filtered passes through the at least one flexible filter and causes the at least one flexible filter to be deflected in a first direction, and the flow of fluid projected onto the at least one flexible filter from the cleaning apparatus causes the at least one flexible filter to be deflected in a second direction. The first and second directions may be substantially opposite to each other.

The deflection of the at least one flexible filter in opposite directions when the system is operating helps to dislodge particulate material and may thereby assist in the cleaning thereof. The deflection of the at least one flexible filter may also help to prevent bacteria growing on the mesh.

The cleaning apparatus for projecting a flow of fluid onto the at least one flexible filter may be fixed in position and the at least one flexible filter moveable. Preferably, however, the at least one flexible filter is fixed in position and the cleaning apparatus is moveable.

The at least one flexible filter typically flexes, bows or curves when it is deflected in said first or second direction.

The at least one flexible filter may be generally planar, for example suitable for extending across a pipe or other conduit. Preferably, however, the at least one flexible filter defines a chamber. Most preferably, the system comprises a plurality of flexible filters that collectively form a cylinder. The cleaning apparatus may be provided inside the chamber for projecting fluid onto an interior surface thereof; or the cleaning apparatus may be provided outside of the chamber for projecting fluid onto an exterior surface thereof.

In arrangements where the at least one flexible filter defines a chamber and the fluid passes through the at least one flexible filter to the interior of the chamber to be filtered, the at least one flexible filter is deflected inwardly, into said chamber, when the fluid passes through the flexible filter to be filtered. The at least one flexible filter is deflected outwardly, out of said chamber, by the fluid expelled from the cleaning apparatus. Conversely, in arrangements where the at least one flexible filter defines a chamber and the fluid passes from the interior of the chamber to the exterior thereof to be filtered, the at least one flexible filter is deflected outwardly, out of said chamber, when the fluid passes through the filter to be filtered. The at least one flexible filter is deflected inwardly, into said chamber, by the fluid expelled from the cleaning apparatus. The cleaning apparatus preferably comprises a member through which the fluid is projected. The member is preferably moveable. The member may be moveable along a linear path but it is preferably rotatable.

The flexible filter(s) is/are typically supported by one or more frame members. The filter may thereby be sufficiently flexible to undergo deflection in use, whilst allowing it readily to be mounted in place. Arrangements where the flexible filter(s) is/are directly attached to a housing member, for example by adhesive or mechanical fastening means, are also envisaged.

The at least one flexible filter may be wire gauze or other lightweight metal material. Preferably, however, the at least one flexible filter is made of a plastics material, such as polyester or nylon. The at least one flexible filter may alternatively be made of foam.

The at least one flexible filter may be provided with an anti-bacterial coating further to assist in maintaining the flexible filter free from bacteria. Alternatively, an anti-bacterial additive, such as Microban (RTM) may be added to the plastics material from which the flexible filter is formed.

Viewed from a further aspect, the present invention relates to a filtration system for filtering particulate material from a fluid, the filtration system comprising at least one flexible filter capable of being deflected by the flow of fluid through it. The at least one flexible filter mesh is deflected, in use, in the same direction as the flow of fluid through the mesh. The flow of fluid typically causes the at least one flexible filter to flex.

Viewed form a still further aspect, the present application relates to a filter for filtering particulates from a flow of fluid, the filter comprising at least one flexible filter mesh capable of being deflected by the flow of fluid through it. The filter mesh is deflected, in use, in the same direction as the flow of fluid through the mesh.

Viewed form a yet further aspect, the present application relates to a filter for filtering particulates from a flow of fluid, the filter being flexible and capable of being deflected by the flow of fluid through it.

The arrangements outlined herein in respect of the filter and filter mesh employed in the filtration system are equally applicable to the filter described herein.

The filter is preferably a cylindrical filter. Viewed a still further aspect, the present application relates to a filtration system for filtering particulate material from a fluid, the filtration system comprising at least one flexible filter for filtering the fluid, said at least one filter being capable of being deflected in the same direction as the fluid flow.

The filter and filter mesh described herein may be moveable, for example rotatable, relative to cleaning apparatus for projecting a fluid onto the filter or filter mesh. Preferably, however, the filter or filter mesh is fixed and the cleaning apparatus is moveable.

Viewed from a further aspect, the present application relates to a filtration system operable in a filtration mode and a purging mode, the system comprising at least one flexible filter; wherein, in use, said at least one flexible filter is deflected in a first direction when the system is operating in said filtration mode, and is deflected in a second direction when the system is operating in said purging mode. The first and second directions may be substantially opposite to each other.

The filtration system preferably comprises cleaning apparatus for projecting a flow of fluid onto the at least one flexible filter to dislodge material trapped in the at least one flexible filter. The at least one flexible filter is preferably deflected in said second direction by the flow of the fluid from the cleaning apparatus even if the filtration system is operating in its filtration mode.

The various aspects described herein are applicable to unpressurised filtration systems and filtration systems operable at less than atmospheric pressure. Preferably, however, the different aspects described herein are employed in a pressurised filtration system.

Viewed from a further aspect, the present application relates to a system for filtering a fluid, the apparatus comprising a first filtration system as described herein and further comprising a second filtration system arranged in fluid communication with the first filtration system, wherein the first and second filtration systems are separate from each other.

The first filtration system is preferably provided in a first housing and the second filtration system provided in a second housing. The first and second housings are separate from each other. The first filtration system preferably comprises a filter for mechanically filtering the fluid. The second filtration system may comprise a further filter for performing further mechanical filtration. Preferably, however, the second filtration system comprises media for biologically filtering the fluid.

Viewed from a further aspect the present application relates to a system for filtering a fluid, the system comprising a pre-filter for performing a first filtration step and a filter for performing a second filtration step, the pre-filter being in fluid communication with the filter, wherein the pre-filter and the filter are separate from each other. The system preferably filters water from a pond.

The pre-filter is preferably sealed. This allows the pre-filter more readily to be installed in existing systems. The fluid is preferably supplied to the pre-filter under pressure. The pre-filter is preferably provided in a first housing and the filter provided in a second housing. The first housing and the second housing are separate from each other. The pre-filter and the filter may be located remotely from each other and a conduit provided for supplying fluid from the pre-filter to the filter.

The pre-filter preferably comprises a filter for mechanically filtering the fluid. The filter may be suitable for performing further mechanical filtration. Preferably, however, the filter comprises media for biologically filtering the fluid. Most preferably, the filter comprises a mechanical filter, such as a filter mesh, and media for biologically filtering the fluid. The filter may further comprise an ultra-violet filter.

The pre-filter may further comprise a bypass valve for bypassing a filter provided in the pre-filter. The bypass valve may also be arranged to bypass the filter which is separate from the pre-filter. The bypass valve may thereby be operable to place an inlet of the pre-filter in fluid communication with an outlet of the filter. Thus, the bypass valve may protect the pre-filter and the filter in the event that the pre-filter becomes clogged.

Similarly, the pre-filter may be provided with a pressure relief valve for allowing unfiltered fluid to exit the pre-filter if the pressure exceeds a predetermined level. The pressure relief valve may return the unfiltered fluid to the fluid source and may thereby protect the pre-filter and also any further apparatus in the system, such as the further filter. The pre-filter is preferably the filtration system described herein. Viewed from a still further aspect the present application relates to a system for filtering a fluid, the system comprising a pre-filter for performing a first filtration step and a filter for performing a second filtration step, the pre-filter being in fluid communication with the filter, wherein the system further comprises a bypass valve operable to place an inlet of the pre-filter in fluid communication with an outlet of the filter. The bypass valve is preferably operable when the pressure differential between the inlet of the pre-filter and the outlet of the filter exceeds a predetermined level.

Viewed from a further aspect, the present application relates to a method of filtering fluid, the method comprising supplying fluid to be filtered to a pre-filter to undergo a first filtration step, and supplying the fluid filtered by the pre-filter to a separate filter to undergo a second filtration step. The method is preferably employed to filter water from a pond. The pre-filter is preferably a filtration system of the type described herein. The filter may perform a mechanical and/or a biological filtration step. The filter may perform a UV filtration step.

Viewed from a yet still further aspect, the present application relates to a method of installing a pre-filter, wherein the pre-filter has a first inlet and a first outlet, the method comprising placing the first inlet in fluid communication with a body of fluid to be filtered and placing the outlet in fluid communication with a filter.

The pre-filter and the filter are preferably separate form each other. Indeed, the pre-filter and the filter may be located remotely from each other.

The pre-filter may be installed along with the filter or the pre-filter may be installed subsequently. In other words, the pre-filter may be retrofitted to an existing system.

Viewed from a further aspect the present application relates to a filter cleaning apparatus comprising a rotatably mounted member having at least one outlet for projecting cleaning liquid onto a surface of a filter, the rotatable member having a channel connecting at least one inlet aperture to said at least one outlet, the rotatable member being mounted on a tubular member having at least one side-opening therein, the at least one side-opening being in liquid communication with said at least one inlet provided in the rotatable member. Providing at least one side-opening in the tubular member advantageously results in the liquid supplied to the rotatable member travelling in a radial direction. The resulting axial forces on the rotatable member, and consequently the loads between the rotatable member and the tubular member, may be significantly reduced. Frictional forces acting on the rotational member may also be reduced. The balancing of the rotatable member is particularly advantageous and filter cleaning apparatus of this type may be employed in a range of applications, including: liquid and gas filtration systems; pressurised, un-pressurised and suction filtration systems.

The rotatable member is preferably symmetrical about a plane perpendicular to the axis about which it rotates. The rotatable member then has substantially equal upper and lower internal surface areas and the force exerted by the cleaning liquid along the axis about which the rotatable member rotates is minimised.

Preferably, fluid is allowed also to escape at the junction between the rotatable member and the tubular member on which it is mounted. This additional flow of fluid advantageously maintains the bearing surfaces substantially free of particulates. Indeed, the flow of liquid around the base of the rotatable member may support the rotatable member and further reduce frictional forces and also reduce wear on the components as they rotate. A gap of, for example, 1mm or less may be provided between the rotatable member and the tubular member.

The rotatable member preferably has a central collar portion extending around the tubular member. The at least one inlet aperture is preferably provided on the inside of said collar. The at least one inlet aperture preferably extends substantially around the circumference of the tubular member. More preferably the collar is at least partially open to the interior thereof to define said at least one inlet aperture. This arrangement advantageously ensures that liquid communication between said at least one outlet and said at least one inlet aperture is maintained irrespective of the angular orientation of the rotatable member.

First and second annular projections are preferably provided on the outer surface of the tubular member to locate axially the rotatable member. A closure member is preferably provided to direct liquid introduced into the tubular member radially outwardly into the at least one inlet aperture in the rotatable member. The closure member is preferably frusto-conical in shape.

A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows a perspective view of a filtration system in accordance with the present invention;

Figure 2 shows a cross-section through the filtration system shown in Figure 1 ;

Figure 3 shows a cross-section through the filter and filter cleaning mechanism according to the present invention;

Figure 4 shows a perspective view of the filter and filter cleaning mechanism shown in Figure 3;

Figure 5 shows a cross-section through the pressure relief valve and bypass valve of the present invention;

Figure 6 shows a cross-section through the change-over mechanism of the present invention; and

Figure 7 shows an enlarged view of the handle of the change-over mechanism shown in Figure 6.

A pressurised filtration system 1 for filtering water from a pond in accordance with the present invention is shown in Figure 1. The filtration system 1 comprises a container 3 and a lid 5. The lid 5 is secured to the container 3 by a series of bolts around the circumference thereof. A seal is created between the container 3 and the lid 5 to allow the filtration system 1 to operate at pressures greater than atmospheric pressure.

The filtration system 1 is provided with a system inlet 7; a pressure release outlet 9; a system outlet 11 ; and a debris discharge outlet 13. The filtration system 1 is operable in a filtration mode and a purging mode. The water to be filtered is supplied to the system inlet 7 by a pump (not shown) provided in the pond. The filtered water exits through the system outlet 11 and is returned to the pond. The debris collected in the filtration system 1 is periodically expelled through the debris discharge outlet 13 when the filtration system operates in its purging mode. A pressure relief assembly 15 is provided to allow water to return to the pond via the pressure release outlet 9 if the pressure in the system inlet 7 exceeds a safe level.

The filtration system 1 is also provided with a bypass assembly 17 to open a fluid pathway between the system inlet 7 and the system outlet 11 if the pressure differential between the system inlet and the system outlet exceeds a predetermined level.

A change-over mechanism 19 is provided to switch the filtration system 1 between its filtration mode and its purging mode.

A cross-section of the filtration system 1 is shown in Figure 2. A filter 21 and a filter cleaning mechanism 23 are housed in the container 3. The filter 21 is cylindrical and defines a lower portion of a filtrate chamber 24 in which filtered fluid is received. The filter 21 is made up of a plurality of filter meshes 25 supported by a rigid frame 26. The meshes 25 are flexible and, in use, bow under the action of the water passing through them. This flexibility helps to prevent the build-up of debris or bacteria on the filter meshes 25. The filter meshes 25 have a mesh size of 0.08mm.

The filter cleaning mechanism 23 comprises a member 27 rotatable about a vertical axis. The rotatable member 27 comprises first and second radial arms 29, 31. The rotatable member 27 is rotatably mounted on a tubular support member 33 supported at its upper end by a series of radial struts 35. The rotatable member 27 is provided with a central collar 36 which extends around the circumference of the support member 33.

As shown in Figure 3, an upper guide member 37 fixedly mounted on the support member 33 limits upwards displacement of the rotatable member 27. Similarly, a lower guide member 39 fixedly mounted on the support member 33 limits downwards displacement of the rotatable member 27.

The first and second radial arms 29, 31 have first and second nozzles 41 , 43 respectively provided at the radially outermost ends thereof for directing a flow of water against the interior surface of the filter 21 to dislodge material trapped on the outer surface thereof. The first and second nozzles 41 , 43 extend vertically and are substantially parallel with the filter 21. The first and second nozzles 41 , 43 traverse substantially the whole of the interior of the filter meshes 25 in the filter 21 each time the rotatable member 27 rotates through one complete revolution. The first and second nozzles 41 , 43 are formed by slots having a width of approximately 0.5mm wide.

The first and second nozzles 41 , 43 are arranged to direct the fluid against the filter 21 at an angle of 15° relative to a radial line extending through the vertical axis about which the rotatable member 27 rotates. This angular offset causes the rotatable member 27 to rotate when water is expelled from the first and second nozzles 41 , 43.

The water to be expelled through the first and second nozzles 41 , 43 is drawn from the filtrate chamber 24 through a conduit 45 into a dedicated pump 47. The pump 47 is housed in a cylindrical housing 48 and pumps the water into a channel 49 provided in the support member 33. A series of apertures 51 are formed around the circumference of the support member 33 and the water enters the interior of the rotatable member 27 through these apertures. A deflecting member 53 is provided in the support member 33 to deflect the water radially outwardly through the apertures 51.

Annular gaps are provided between the rotatable member 27 and the first and second guide members 37, 39. Water expelled from the support member 33 exits through these annular gaps and thereby keeps the bearing surfaces free from contaminants. The annular gaps are typically 1mm across.

A first baffle plate 55 is provided around the base of the filter 21. A second baffle plate 57 is provided below the first baffle plate 55 and is attached to the cylindrical housing 48 by a plurality of radial members 58. The first and second baffle plates 55, 57 are hollow frusto-conical in shape. A top surface of the first baffle plate 55 slopes downwardly in a radially outwards direction; and a top surface of the second baffle plate 57 slopes downwardly in a radially inwards direction.

A lower edge of the second baffle plate 57 engages the inside wall of the container 3 and supports the filter 21 and the filter cleaning mechanism 23 above the base of the container. The portion of the container 3 beneath the filter 21 and the filter cleaning mechanism 23 forms a debris collection chamber 59 in which filtered particulate material and other debris is collected. The debris collection chamber 59 has a volume of 15 litres. An opening 61 at the base of the container 3 is connected to the debris discharge outlet 13 by a discharge conduit 63. The discharge conduit 63 can be formed by a plate provided inside the container 3 or it may be a separate pipe (not shown) extending upwardly from the opening 61 at the base of the container 3 to the discharge outlet 13.

An annular channel 65 is formed around the top of the container 3 and is in fluid communication with the system outlet 11. An annular opening 67 is formed between the lid 5 and the top of the filter 21. The filtrate chamber 24 is in fluid communication with the annular channel 65 via the annular opening 67. Thus, the filtrate chamber 24 is in fluid communication with the system outlet 11. A second filter 69 is provided in the annular opening 67. The second filter 69 is made of foam and is retained in position by a plurality of upwardly projecting locating members 71 provided on the top of the filter 21.

The second filter 69 filters particulate material of a size greater than or equal to the width of the first and second nozzles 41 , 43. Thus, if particulate material passes through the second filter 69 it will be small enough to travel through the first and second nozzles 41, 43 without blocking them.

As shown in Figure 4, the water enters the container 3 through an inlet port 73. The water is then guided downwardly around the outside of the filter 21 by a helical guide member 75.

The pressure relief assembly 15 and the bypass assembly 17 will now be described with reference to Figure 5.

The pressure relief assembly 15 comprises a pressure relief valve 77 for controlling the flow of fluid between the system inlet 7 and the pressure release outlet 9. The pressure relief valve 77 is biased by a first coil spring 81 to a closed position in which the pressure relief valve 77 is seated in a relief valve seat 79.

The pressure relief valve 77 is displaced out of the relief valve seat 79 to an open position when the pressure in the system inlet 7 is sufficient to overcome the force exerted by the first coil spring 81. Thus, the pressure at which the pressure relief valve 77 is opened is determined by the strength of the first coil spring 81. When the pressure relief valve 77 is open, a fluid pathway is provided between the system inlet 7 and the pressure release outlet 9 thereby allowing water to exit through the pressure release outlet. The pressure relief valve 77 helps to prevent the pressure in the filtration system 1 exceeding a safe level.

The pressure relief valve assembly 15 is provided with a first screw cap 83 which may be removed to allow the pressure relief valve 77 to be serviced. The bypass valve assembly 17 comprises a bypass valve 85 for controlling the flow of fluid from the system inlet 7 to the annular channel 65.

The bypass valve 85 is biased by a second coil spring 87 towards a closed position whereby the bypass valve is seated in a bypass valve seat 89. With the bypass valve 85 seated in the bypass valve seat 89, the water introduced through the system inlet 7 is directed to the inlet port 73 and the fluid pathway to the annular channel 65 is closed.

When the filter 21 becomes clogged, the system inlet pressure increases relative to the system outlet pressure. Once the pressure differential between the system inlet 7 and the system outlet 11 (which is in fluid communication with the annular channel 65) is sufficiently large to overcome the bias of the second coil spring 87, the bypass valve 85 is displaced to an open position. A fluid pathway between the system inlet 7 and the annular channel 65 is thereby created which allows the unfiltered water introduced into the system 7 to bypass the filter 21 and exit through the system outlet 11. The second filter 69 prevents particulate material or debris suspended in the unfiltered water introduced into the annular channel 65 entering the filtrate chamber 24.

When the bypass valve 85 is open, water continues to be expelled from the rotating member 27 and dislodges particulate material from the filter meshes 25 to unclog the filter 21. Water is then able to be filtered by the filter 21 before exiting through the system outlet 11. The pressure differential between the system inlet 7 and the system outlet 11 may thereby be reduced and once it is insufficient to overcome the bias of the second coil spring 87 the bypass valve 85 closes.

The bypass valve assembly 17 is provided with a second screw cap 90 to allow the bypass valve 85 to be serviced.

The change-over mechanism 19 will now be described with reference to Figures 6 and 7. The change-over mechanism 19 comprises a closure member 91 provided inside a housing 93. The system outlet 11 and the debris discharge outlet 13 pass through the housing 93 along parallel axes.

The closure member 91 is movable along an axis which transects and is perpendicular to the axes of the system outlet 11 and the debris discharge outlet 13. The closure member 91 is movable between a first position in which the system outlet 11 is sealed and the debris discharge outlet 13 is open (the filtration system 1 operates in its purge mode); and a second position in which the debris discharge outlet 13 is sealed and the system outlet 11 is open (the filtration system 1 operates in its filtration mode). The closure member 91 is shown in its second position in Figure 6. A third coil spring 95 is provided to bias the closure member 91 to the second position to help ensure that the pond is not inadvertently drained, which may occur if the closure member 91 was left in the first position for an extended period of time with the fluid supply pump running.

The closure member 91 is provided with an actuating arm 93 which extends out of the housing 91 to facilitate manual operation of the change-over mechanism 19. As shown in Figure 7, a third screw cap 97 is provided on the housing 91 around the actuating arm 93 to provide access to the third coil spring 95. An O-ring 99 is provided around the actuating arm 93 to form a seal with the third screw cap 97. A handle 101 is provided on an end of the actuating arm 93.

The operation of the filtration system 1 will now be described. The pump (not shown) pumps water from the pond into the system inlet 7 at a pressure greater than atmospheric pressure.

When the filtration system 1 is operating in a filtration mode, the water from the pump passes through the system inlet 7 and enters the container 3 through the inlet port 73. If, however, the pressure of the water introduced into the system inlet 7 is too high, for example because the pump is too powerful, the pressure relief valve 77 is displaced, against the bias of the first coil spring 81 , to an open position and a portion of the water introduced into the system inlet 7 is returned to the pond through the pressure release outlet 9. The remainder of the water enters the container 3 through the inlet port 73.

The water entering the container 3 through the inlet port 73 is guided by the helical guide member 75 and follows a helical path down the outside of the filter 21. Water passes through the filter meshes 25 and the filtered water enters the filtrate chamber 24. Particulate material and other debris is retained in the filter meshes 25.

The first and second baffle plates 55, 57 slow the water in the container 3 outside of the filter 21 and thereby reduce its ability to maintain particles and debris in suspension. The material suspended in the water is thereby more rapidly deposited in the debris collection chamber 59 at the base of the container 3. The dedicated pump 47 draws filtered water from the interior of the filtrate chamber 24 and pumps it into the channel 49 formed in the tubular support member 33. A portion of the water introduced into the channel 49 exits through the gaps provided between the rotatable member 27 and the first and second guide members 37, 39 and thereby keeps the bearing surfaces free from contaminants. The remainder of the water exits the support member 33 through the apertures 51 and enters the first and second arms 29, 31 of the rotatable member 27. The water is then expelled through the nozzles 41 , 43 against the interior surface of the filter meshes 25 to dislodge particulate material trapped therein. The dislodged particulate material settles in the debris collection chamber 59 at the base of the container 3.

The passage of water through the filter meshes 25 during filtration, and also as it is expelled from the rotatable member 27, causes the filter meshes 25 to deflect (for example by bowing radially inwardly when water enters the filtrate chamber 24 and radially outwardly under the action of the water expelled from the rotatable member 27). This deflection of the filter meshes 25 further assists in dislodging particulate material.

The water is expelled from the rotatable member 27 at an angle of 15° to a radial direction and this causes rotation of the rotatable member. The rotation ensures that substantially all of the filter meshes 25 are acted on by the water expelled from the rotatable member 27.

The filtered water exits the filtrate chamber 24 through the annular opening 67 provided between the top of the container 3 and the lid 5. The filtered water passes through the second filter 69 and enters the annular channel 65 before leaving the system through the system outlet 11.

Despite the cleaning action of the rotatable member 27, the filter 21 may become clogged over a period of time, or when the filtration system 1 is used for the first time to filter a heavily contaminated pond. The amount of water able to pass through the filter meshes 25 is thereby reduced and the pressure in the system inlet 7 increases. Conversely, there is a reduced pressure in the system outlet 11 since less water is able to travel through the filter 21.

When the pressure differential between the system inlet 7 and the system outlet 11 is sufficiently large to cause the bypass valve 85 to be displaced to an open position, at least a portion of the water pumped into the system inlet 7 may travel around the annular channel 65 and exit through the system outlet 11 without passing through the filter 21 (i.e. the filter is bypassed).

The annular channel 65 is open to the interior of the filtrate chamber 24 via the annular opening 67 and the second filter 69 prevents particulate material from the bypassed fluid entering the filtrate chamber 24. The second filter 69 is subsequently cleaned by filtrate exiting the filtrate chamber 24 and entering the annular channel 65 when the bypass valve 87 is closed.

The filter cleaning mechanism 23 continues to operate to clear the filter 21 even when the bypass valve 85 is open. Once the filter 21 has been cleared sufficiently the pressure differential between the system inlet 7 and the system outlet 11 is reduced and the bypass valve 85 closes.

Particulate material and debris collected in the debris collection chamber 59 must periodically be expelled from the filtration system 1. The filtration system 1 is switched to its purge mode by displacing the closure member 91 to its first position (with the debris discharge outlet 13 open and the system outlet 11 sealed). The pump continues to introduce water through the system inlet 7 and, since the system outlet 11 is closed, the water enters the debris collection chamber 59 under pressure and expels the debris collected therein through the opening 61 at the base of the container 3. The debris exits the filtration system 1 through the debris discharge outlet 13 and is disposed of remotely from the pond. The filtration system 1 is typically run in the purge mode for 10-15 seconds before the closure member 91 is returned to its second position (with the debris discharge outlet 13 sealed and the system outlet 11 open). The filtration system 1 then reverts to operating in the filtration mode.

Although the embodiment described herein has been outlined with reference to filtering water from a pond, it will be appreciated that the present application relates also to filtration system for liquids other than water. The filtration system may also be used in gas filtration systems.

Claims

CLAIMS:

1. A filtration system for filtering particulate material from a fluid, the filtration system comprising a system inlet, a bypass valve, a first filter, and a system outlet; the bypass valve being operable to place the system inlet in fluid communication with the system outlet and to allow at least a portion of the fluid passing through the filtration system to bypass the first filter.

2. A filtration system as claimed in claim 1 , wherein the bypass valve is operable to bypass the first filter when the difference between the fluid pressure in the system inlet and the fluid pressure in the system outlet exceeds a predetermined value.

3. A filtration system as claimed in claim 2, wherein the bypass valve comprises a spring means and the pressure differential at which the bypass valve is operable to bypass the first filter is determined by the strength of said spring means.

4. A filtration system as claimed in any one of claims 1 , 2 or 3, wherein the bypass valve is biased towards a position where the system inlet is in fluid communication with the system outlet only via the first filter.

5. A filtration system as claimed in any one of the preceding claims further comprising a filtrate chamber for receiving fluid filtered by the first filter.

6. A filtration system as claimed in claim 5, wherein said filtrate chamber is in fluid communication with the system outlet.

7. A filtration system as claimed in claim 6 further comprising a second filter provided between the filtrate chamber and the system outlet.

8. A filtration system as claimed in claim 7, wherein, in use, fluid exiting the filtrate chamber passes through the second filter and dislodges debris collected therein.

9. A filtration system for filtering particulate material from a fluid, the filtration system comprising a system inlet for introducing unfiltered fluid into the filtration system, a bypass valve, a first filter, and a system outlet; the bypass valve being operable to allow unfiltered fluid to bypass the first filter and exit through the system outlet.

10. A filtration system operable in a bypass mode and a filtration mode for filtering particulate material from a fluid, the filtration system comprising a system inlet, a bypass valve, a first filter, a second filter, a filtrate chamber for receiving filtrate, and a system outlet; wherein, in use, fluid entering the filtrate chamber when the filtration system is operating in said filtration mode is filtered by the first filter, and fluid entering the filtrate chamber when the filtration system is operating in said bypass mode is filtered by said second filter.

11. A filtration system as claimed in claim 10, wherein the bypass valve is operable to direct at least a portion of the fluid introduced through the system inlet to the system outlet bypassing the first filter.

12. A filtration system as claimed in claim 11 , wherein the bypass valve is operable to bypass the first filter when the difference between the fluid pressure in the system inlet and the fluid pressure in the system outlet exceeds a predetermined value.

13. A filtration system as claimed in any one of claims 10, 11 or 12, wherein the second filter is provided between the filtrate chamber and the system outlet.

14. A filtration system as claimed in any one of claims 10 to 13, wherein the second filter is made of foam.

15. A filtration system as claimed in any one of claims 10 to 14, wherein, in use, debris collected in the second filter is expelled through the system outlet when the filtration system is operating in said filtration mode.

16. A filtration system operable in a bypass mode and a filtration mode for filtering particulate material from a fluid, the filtration system comprising a first filter, a second filter and a filtrate chamber for receiving filtrate; wherein when the filtration system is operating in said bypass mode fluid bypasses the first filter and fluid entering the filtrate chamber is filtered by the second filter.

17. A filtration system as claimed in any one of claims 7, 8 and 10 to 16, wherein the first filter is finer than the second filter.

18. A filtration system as claimed in any one of the preceding claims further comprising cleaning apparatus for cleaning the first filter.

19. A filtration system as claimed in claim 18, wherein the cleaning apparatus is suitable for projecting a flow of fluid onto the first filter.

20. A filtration system as claimed in claim 18 or 19, wherein the cleaning apparatus comprises a rotatable member.

21. A method of operating a filtration system in a filtration mode and a bypass mode, the filtration system comprising a system inlet, a first filter, and a system outlet; wherein, in the filtration mode, fluid introduced through the system inlet is passed through the first filter and expelled through the system outlet; and, in the bypass mode, at least a portion of the fluid introduced through the system inlet is allowed to bypass the first filter and exit through the system outlet.

22. Apparatus for bypassing a filter in a filtration system, the apparatus being connectable to an inlet and an outlet of the filtration system, the apparatus comprising a bypass valve operable to place the system inlet in fluid communication with the system outlet and to allow at least a portion of the fluid supplied to the system inlet to bypass the filter.

23. Apparatus as claimed in claim 12, wherein the bypass valve is operable to bypass the first filter when the difference between the fluid pressure in the system inlet and the fluid pressure in the system outlet exceeds a predetermined value.

24. A kit of parts for producing apparatus as claimed in claim 22 or 23.

25. A filtration system for filtering particulate material from a fluid, the filtration system comprising a filter, a system inlet and a pressure relief valve; the pressure relief valve being operable to allow fluid to exit the filtration system when the fluid pressure exceeds a predetermined level.

26. A filtration system as claimed in claim 25, wherein the pressure relief valve is operable when the fluid pressure in the system inlet exceeds a predetermined level.

27. A filtration system as claimed in claim 25 or 26, wherein the pressure relief valve is provided in the system inlet.

28. A filtration system as claimed in claim 25, 26 or 27, wherein, in use, the pressure relief valve allows unfiltered fluid to exit the filtration system.

29. A filtration system as claimed in any one of claims 25 to 28 further comprising a pump for pumping fluid to be filtered from a fluid source to the system inlet.

30. A filtration system as claimed in claim 29, wherein the pressure relief valve allows the fluid exiting the filtration system to be returned to said fluid source.

31. A filtration system as claimed in any one of claims 25 to 30, wherein the fluid to be filtered is water.

32. Pressure relief apparatus for a filtration system, the apparatus comprising a pressure relief valve locatable in fluid communication with an inlet of a filtration system, the pressure relief valve being operable to allow fluid to exit through an outlet when the fluid pressure exceeds a predetermined level.

33. A kit of parts for producing a pressure relief valve as claimed in claim 32.

34. A filtration system for filtering particulate material from a fluid, the filtration system comprising a system inlet for allowing unfiltered fluid to enter the filtration system, a pressure relief valve, a filter, and a system outlet for allowing filtered fluid to exit the filtration system; the pressure relief valve being operable to allow unfiltered fluid to exit through a release outlet.

35. An inlet assembly for a filtration system, the inlet assembly comprising apparatus for bypassing a filter as claimed in claim 22 or claim 23 and pressure relief apparatus as claimed in claim 32.

36. A valve mechanism for a filtration system, the valve mechanism comprising a movable valve closure member for selectively closing a system outlet and a debris discharge outlet of the filtration system.

37. A valve mechanism as claimed in claim 36, wherein the valve closure member is movable along a linear axis.

38. A valve mechanism as claimed in claim 36 or 37, wherein the system outlet and the debris discharge outlet have first and second axes respectively and said first and second axes are substantially parallel.

39. A valve mechanism as claimed in claim 36, 37 or 38, wherein the linear axis along which the valve closure member is movable transects and is substantially perpendicular to said first and second axes.

40. A valve mechanism as claimed in any one of claims 36 to 39 further comprising spring means to bias the valve closure member to a position where the debris discharge outlet is closed.

41. A valve mechanism as claimed in any one of claims 36 to 40 further comprising a handle to facilitate manual operation of the valve mechanism.

42. A filtration system for filtering particulate material from a fluid, the filtration system comprising a filter for filtering the fluid, and a collection chamber for collecting particulate material filtered from the fluid; wherein the debris collection chamber has a volume greater than or equal to 5 litres.

43. A system for filtering a fluid, the apparatus comprising a first filtration system as claimed in any one of claims 1 to 20, 25 to 31 , 34 or 42 and further comprising a second filtration system arranged in fluid communication with the first filtration system, wherein the first and second filtration systems are separate from each other.

44. A system as claimed in claim 43, wherein the second filtration system is a biological filter.

45. A system for filtering a fluid, the system comprising a pre-filter for performing a first filtration step and a filter for performing a second filtration step, the pre-filter being in fluid communication with the filter, wherein the pre-filter and the filter are separate from each other.

46. A system as claimed in claim 45, wherein the pre-filter comprises a filter for mechanically filtering the fluid.

47. A system as claimed in claim 45 or 46, wherein the filter comprises biological media for biologically filtering the fluid.

48. A system as claimed in any one of claims 45, 46 or 47, wherein the pre- filter is the filtration system as claimed in any one of claims 1 to 20, 25 to 31 , 34 or 42.

49. A method of filtering fluid comprising supplying fluid to be filtered to a pre- filter to undergo a first filtration step, and supplying the fluid filtered by the pre- filter to a separate filter to undergo a second filtration step.

50. A method of installing a pre-filter, wherein the pre-filter has a first inlet and a first outlet, the method comprising placing the first inlet in fluid communication with a body of fluid to be filtered and placing the outlet in fluid communication with a filter.

51. A method as claimed in claim 50, wherein the pre-filter is retrofitted to the filter.

52. A filtration system substantially as herein described with reference to the accompanying figures.

53. An inlet assembly for a filtration system substantially as herein described with reference to Figures 1 , 2 and 5.