WO2019034879A1

WO2019034879A1 - Water filter

Info

Publication number: WO2019034879A1
Application number: PCT/GB2018/052324
Authority: WO
Inventors: John Griffith
Original assignee: John Griffith
Priority date: 2017-08-16
Filing date: 2018-08-16
Publication date: 2019-02-21
Also published as: CN111194297A; GB201713111D0; EP3668818A1

Abstract

A fluid filter includes a filtration element; a supply conduit that is positioned to supply fluid to be filtered into the filtration element; a delivery conduit that is positioned to received filtered fluid from the filtration element; a pressure chamber which is fluidly continuous with the delivery conduit; and a filtered fluid outlet in fluid communication with the pressure chamber, the filtered fluid outlet including a flow limiter that restricts the flow of filtered fluid. When the flow limiter is operated, filtered fluid is caused to flow back from the pressure chamber to back flush the filtration element. The flow limiter can be actuatable manually or automatically.

Description

WATER FILTER

The invention relates to a fluid filter including a flow limiter, which can be operated manually or automatically, configured to cause back flushing of the fluid filter. The invention also relates to a method of operating such a fluid filter.

INTRODUCTION The invention generally relates to a fluid filter for making water biologically safe to drink at the point of use. Discussion of the invention below is in particular in the context of this example use, but the invention may be applicable to any fluid filter where the advantages of the back-flushing capability might apply. The invention uses a known method of purification, for example using a filter module, which may include a hollow fibre membrane module, which contains hollow fibres. The hollow fibres of the filter module allow the passage of water through microscopic pores in their walls, but hold back pathogens and other particles. For example, PCT publication WO 2008/1 10172 describes such a filtration system using hollow fibre membranes.

It is also known that when purifying turbid water, the microscopic pores can become clogged with particles, which can slow down, and eventually stop the flow of water therethrough. To rectify this, the hollow fibres may be cleaned by cross flow cleaning, where excess water flows through the microscopic pores of the fibres, and/or by back flushing, when clean water is forced back through the microscopic pores. In large installations purifying water with membrane modules, these operations may be carried out automatically by means of pumps, valves and timers. However, such means is not without its drawbacks. Typical water filters making use of pumps, valves and timers and complex in construction, which results in a more expensive water filter to manufacture. Thus, such water filters are typically too expensive for use in low income areas. Moreover, owing to the complex nature of the water filter's construction, the operation of such water filters is rarely straightforward, particularly concerning cross-flow cleaning and back flushing of the system. The present invention aims to obviate and/or mitigate such problems associated with water filters. For example, one object of the invention is to provide a simpler system of back flushing. This feature is particularly important when used in emergency situations and by low income communities. Another object of the invention is to provide a simple automatic means of back flushing suitable for a hand operated filter. Yet another object of the invention is to combine automatic back flushing with automatic cross flow. A further object of the invention is to provide a water filter suitable for use in emergencies, and by low income families and communities.

SUMMARY OF INVENTION

In accordance with one embodiment of the invention, there is provided a fluid filter including: a filtration element; a supply conduit positioned to supply fluid to be filtered to the filtration element; a delivery conduit positioned to receive filtered fluid from the filtration element; a pressure chamber fluidly continuous with the delivery conduit; a filtered fluid outlet in fluid communication with the pressure chamber, wherein the filtered fluid outlet includes a flow limiter that is operable to restrict and is preferably operable to substantially or entirely prevent flow of filtered fluid from the filtered fluid outlet; wherein, when the flow limiter is so operated, filtered fluid is caused to flow back from the pressure chamber to back flush the filtration element.

In normal operational mode as a filter, unfiltered fluid, such as water to be filtered, is caused to flow into the filtration element, via the supply conduit, through the filtration element and into the pressure chamber, via the delivery conduit, and out of the filtered fluid outlet.

In back-flush operational mode, the filtered fluid outlet is restricted and, for example, substantially or entirely closed by the flow limiter. The filtered fluid which accumulates in the pressure chamber reaches a point where a back-pressure is created that causes filtered fluid to flow back through the filtration element passing in the opposition direction to the normal operational mode, or to "back flush", and thus to clean the filtration element. Thus, the arrangement provides a means of cleaning the filtration element by forcing clean fluid, under back-pressure, through the filtration element. This provides the advantage that the fluid filter is a less complex design and is less expensive to manufacture. Additionally, the fluid filter is easy to operate by a user, particularly in an emergency situation. Optionally, the fluid filter may further include a filtration module, wherein the filtration module comprises: a housing defining a filtration volume therein containing the filtration element; an inlet for the ingress of fluid to be filtered, the inlet being in fluid communication with the supply conduit; a primary outlet for the egress of filtered fluid, the primary outlet being in fluid communication with the delivery conduit.

Optionally, the inlet to the filtration volume may be provided with a one-way flow regulator. For example, the one-way flow regulator may be so structured as to allow flow of unfiltered fluid in a direction into the filtration volume, but to limit, and preferably at normal operating fluid pressures substantially or entirely prevent, flow of unfiltered fluid in the other direction out of the filtration volume.

That is to say, there may be provided a one-way flow regulator which allows passage of fluid in a first direction into the filtration volume, but limits, either substantially or entirely, the passage of fluid in a second direction out of the filtration volume.

Thus, if the outlet flow is limited by operation of the flow limiter in a back-flush operational mode, pressure will build up within the fluid volume defined by the filtration volume and the pressure chamber volume, and thereby filtered fluid may be caused to flow back from the pressure chamber to back flush, and thus clean, the filtration element with filtered fluid.

Most preferably, the one-way flow regulator is a one-way valve.

This provides the advantage that the fluid filter is more efficient, since filtered fluid is retained within the fluid filter until outputted at the filtered fluid outlet, thus less or no filtered fluid is returned back to the fluid to be filtered.

Preferably, the filtration module may include a secondary outlet, the secondary outlet being in fluid communication with the filtration volume for the egress of fluid therefrom. Thus, during back-flush operational mode, as filtered fluid is caused to flow under back pressure in a reverse direction through the filtration module by the build-up of pressure in the pressure vessel on operation of the flow limiter, an alternative route is provided for the egress of fluid from the filtration volume.

This provides the advantage that a flow is maintained in the reverse direction through the filtration module and the further advantage that back-flushed fluid, which typically will be contaminated as a result of cleaning the filtration element, is output separately to the filtered fluid. This provides a safer and more reliable fluid filter.

The secondary outlet should be on the opposite side of the filtration module to the primary outlet in a flow direction, which is to say that the primary outlet should be downstream of the filtration module during normal operational mode and the secondary outlet should be downstream of the filtration module during back-flush operational mode.

The secondary outlet may be provided with a closure, wherein the closure is selectively operable to close the secondary outlet at fluid pressures below a predetermined pressure, and wherein the closure is selectively operable to open the secondary outlet at fluid pressure above the predetermined pressure.

The predetermined pressure is selected such that the selectively operable closure is closed in normal operational mode, but opens at a higher pressure such as those arising in the back-flush operational mode. These higher pressures arise when fluid to be filtered continues to flow into the filtration volume, but filtered fluid outflow, via the filtered fluid outlet and flow limiter, is restricted. Thus, pressure builds up within the pressure chamber volume. The closure may be, for example, disposed to be opened in back-flush operational mode by pressure of the fluid to be filtered. Preferably, the closure may comprise a valve. Said valve may, for example, be biased and for example spring-biased to a closed position. Said valve may, for example, include a diaphragm that is spring-biased in a closed position during the normal operational mode. When the back-flush operation mode is engaged, the spring-biased diaphragm opens, against the spring force, thus being selectively operable to open at a higher pressure. That is to say, the valve may include a diaphragm, which may include a generally flat resilient piece of material that is biased by a spring in use. The resilient material may be an elastic material. The diaphragm may close, or otherwise shut off, an opening in use, as the spring biases the diaphragm to make a hermetic seal with the opening. Once the spring force is overcome in the back-flush operation mode, the diaphragm is forced to deflect, thereby breaking the hermetic seal, and allowing fluid to flow through the opening and out of the fluid filter.

Thus, the closure, whether it be a valve, diaphragm or the like, is opened at a relatively high pressure and remains open at a lower pressure.

This provides the advantage that the flow limiter can respond to changes in fluid pressure within the fluid filter.

Optionally, the secondary outlet may be provided with a bleed pipe, wherein the bleed pipe substantially prevents the flow of fluid.

That is to say, there may be provided a pipe including a lumen sized such that the flow of fluid is restricted therethrough. In a similar way to the selectively operable closure above, this allows pressure builds up within the fluid filter to cause back flushing of filtered fluid through the filtration element.

This provides the advantage that contaminated fluid, as a result of the back-flush operational mode, can be returned to a container which includes the fluid to be filter. In other words, contaminated fluid is recycled such that it can be filtered again.

Preferably, the pressure chamber may include: a pressure chamber inlet in fluid communication with the primary outlet of the filtration volume; and a pressure chamber outlet in fluid communication with the delivery conduit. That is to say, the pressure chamber can include an inlet for the ingress of filtered fluid received from the primary outlet of the filtration volume via the delivery conduit. The pressure chamber can also include an outlet for the egress of said filtered fluid, the outlet being in fluid communication, or otherwise fluidly connected, with the delivery conduit. Preferably, the pressure chamber may include an elongate conduit extending from the pressure chamber outlet, wherein the elongate conduit is in fluid communication with the delivery conduit. That is to say, a generally elongate conduit or pipe, having a length, extends within the pressure chamber from the pressure chamber outlet and substantially towards the pressure chamber inlet.

In this way, the pressure chamber conveniently defines a pressure chamber volume, and the inlet of the pressure chamber volume communicates directly with the outlet of the filtration volume, and an elongate supply conduit extends from a delivery conduit inlet within the pressure chamber volume through the pressure chamber outlet to the closable delivery conduit outlet positioned beyond the pressure chamber outlet. In one example, the supply conduit may be configured to input fluid to the filter under pressure, and thereby constitute a means of passing fluid through the filtration element under pressure.

Preferably, the fluid filter may further include a pumping module configured to input fluid through the supply conduit, and into the filtration element, under pressure.

In use, it is preferable that, during the back-flush operational mode, the user slows down or stops the supply of input fluid from the pumping module, through the supply conduit and into the filtration element. Optionally, the user completely stops supplying filtered to be fluid during the back-flush operational mode. This allows for the pressure that has built up within the fluid filter, due to supplying fluid to be filtered under pressure, to force filtered fluid back through, and thus back-flushing, the filtration element. For example, the pumping module may include a manually operated pump.

More preferably, the manually operated pump may include: a piston enclosed by a barrel, wherein the piston is coupled to a handle; a fluid cavity in fluid communication with the piston, the fluid cavity comprising an inlet for the ingress of fluid to be filtered, wherein the fluid cavity is in fluid communication with the supply conduit. As discussed above, it is preferable that, during the back-flush operational mode, the user slows down or stops operating the manually operated pump. Optionally, the user completely stops operating the manually operated pump during the back-flush operational mode. This allows for the pressure that has built up within the fluid filter, due to the operation of the manually operated pump, to force filtered fluid back through, and thus back-flushing, the filtration element.

This provides the advantage that the user can easily and simply input fluid to be filtered under pressure. The pumping module also provides for a less complex construction, and thus reduces manufacturing costs.

Even more preferably, the inlet of the manually operated pump may include a one-way flow regulator, for example a one-way valve. That is to say, the one-way flow regulator may allow flow of unfiltered fluid in a direction into the fluid cavity, but which limits, and preferably at normal operating fluid pressures substantially or entirely, flow of unfiltered fluid in the other direction out of the fluid cavity.

That is to say, there may be provided a one-way flow regulator which allows passage of fluid in a first direction into the fluid cavity, but limits, either substantially or entirely, the passage of fluid in a second direction out of the fluid cavity.

Optionally, the fluid filter may include a bleed hole that may be configured to allow for fluid communication between the fluid cavity of the manually operated pump and the filtration element. That is to say, a bleed hole may be provided within a plate that separates the fluid cavity of the manually operated pump and the filtration element, to allow fluid communication therebetween. Thus, when the user operates the manually operated pump to draw fluid to be filtered into the fluid cavity, the bleed hole also allows for unfiltered fluid to flow back into the fluid cavity from the filtration element.

This provides the advantage that cross flow cleaning within the filtration element is increased.

Preferably, the filtration element of the fluid filter may include hollow filter fibres. That is to say, the filtration element may include filter media such as hollow filter fibres, which are generally elongate fibres having a lumen. The generally elongate fibres, being hollow, may also include microscopic pores which allow only clean fluid to pass therethrough. Thus, contaminants are trapped within these microscopic pores, and filtered fluid results as fluid leaks out of these microscopic pores.

The fluid filter may also include a pre-filter.

The pre-filter may allow for filtering of coarse or larger particles before the fluid is filtered. The pre-filter may be in fluid communication with the supply conduit, or may be in fluid communication with the fluid cavity of the pumping module.

This provides the advantage that, as larger contaminants and debris are removed, the filtration element does not clog as quickly. Thus, the back-flush operational mode can be utilised less, and so the normal operation mode, which provides filtered fluid, can be utilised more.

Preferably, the filtered fluid outlet may include a filtered fluid outlet tube including a non-return device.

That is to say, the filtered fluid outlet tube includes a device which allows for passageway of the filtered fluid out of the outlet only, and does not allow for return towards the flow limiter or pressure chamber. This provides the advantage that contamination of the pressure chamber, in which filtered fluid is retained, is minimised.

More preferably, the filtered fluid outlet tube can be an elastic tube, and the non-return device is a flattened portion of the elastic tube.

Even more preferably, the flattened portion of the elastic tube can be held in place by a rigid outer portion. That is to say, an elastic tube is substantially surrounded by, and contained within, a rigid outer portion, wherein the rigid out portion engages the elastic tube to provide the flattened portion. This provides a suitable seal to provide contamination of the pressure chamber, in which the filtered fluid is retained.

The supply conduit may be configured to input fluid to the filter under pressure and thereby constitute a means of passing fluid through the filtration element under pressure.

The fluid filter preferably further comprises a fluid supply module, for example adapted to supply fluid to the supply conduit, for example comprising a pumping module disposed to supply to supply fluid to be filtered via the supply conduit to and through the filtration element.

The pumping module may include a manually operated pump

In a first principal alternative arrangement, the flow limiter is actuatable manually.

That is to say, the flow limiter may be adapted to be actuated manually, by a user or by other intervention. Further, the flow limiter may be actuatable directly, or otherwise independently of the fluid flow in the delivery conduit. Such a flow limiter generally requires a user's intervention to substantially or entirely prevent the flow of filtered fluid from the filtered fluid outlet.

For example, it may be preferable that the flow limiter is a manually-operated tap that is manually closed by the user. This provides the advantage that the user can control when the back-flush operational mode is engaged, thus providing more user control over the fluid filter.

Thus, the invention in the first alternative arrangement comprises a filter, the filter comprising a filtration element, a means of passing a fluid through it under pressure, and a means of cleaning the element by forcing clean fluid under pressure back through the filtration element, characterised by the method of initiating the back flow of clean fluid by a valve which is opened by the pressure of the untreated fluid.

In a possible mode of operation, the valve is opened by a relatively high pressure and remains open at a lower pressure. It follows that preferably the valve is structured to be opened by a relatively higher opening pressure but to remain open until a relatively lower closure pressure is reached.

Optionally, the valve consists of a diaphragm.

In a possible arrangement, the valve is opened by opening a small stopper under pressure, and is held open at a lower pressure by a piston with a larger cross section than the stopper. In one aspect, the clean fluid for back flushing is stored in a reservoir. In such an aspect the fluid filter further includes a reservoir. The reservoir may be fluidly continuous with and for example provided by the pressure vessel.

The reservoir may be closed at the top, so that fluid is put under pressure by air trapped in the top as it is filled.

Optionally, the reservoir is filled by closing an outlet tap and applying input fluid under pressure. In this way, the reservoir functions as a pressure vessel as above described. In one example, the input fluid is supplied by a pump. Preferably, the pump is manually operated.

Optionally, the filter can include a pre-filter to remove coarse particles from the fluid. In yet another example of this arrangement, the filter is also cleaned by cross flow produced by an intermittent pump pushing the fluid into its lower end, and a dosed air reservoir at its upper end.

Therefore, it can be seen that there is provided a filter with a hollow fibre membrane module, a clean water reservoir, a pump, an outlet for the treated water with a tap, and an outlet for untreated water with a valve which opens under pressure. Back flushing can then be carried out by closing the outlet tap and pumping.

In a second principal alternative arrangement, the flow limiter may be actuatable automatically in response to fluid flow in the delivery conduit.

That is to say, the flow limiter is actuated automatically as a result of the fluid flow in the delivery conduit. For example, the flow limiter may be configured to be actuated automatically at a predetermined flow rate.

Thus, such a flow limiter may be directly dependent upon the fluid flow in the delivery conduit. Such a flow limiter may require no user intervention, thus automatically controlling the back-flush operational mode. Moreover, the fluid filter may be provided with automatic back-flush capability, characterised by one or more valves, closures or the like, including at least the flow limiter, being directly operated by fluid in the system.

Most preferably, the automatically-actuatable flow limiter may be in fluid communication with the delivery conduit.

This provides the advantage that, should the filtration element become clogged as a result of contaminants, the user simply has to keep pumping fluid to be filtered into the fluid filter. The construction of this arrangement provides an automatic back-flushing system, thus making the fluid filter easier to operate. Such an automatic back-flushing system requires minimal instruction to use, and can be used for a longer period of time.

In another aspect of this arrangement, the automatically-actuatable flow limiter may open in response to the secondary outlet of the filtration module closing.

That is to say, the automatically-actuatable flow limiter may be in communication, for example fluid communication, with the secondary outlet of the filtration module. Thus, when the secondary outlet of the filtration module closes, pressure builds within the system as described, which causes the automatically-actuatable flow limiter to open. Most preferably, the automatically-actuatable flow limiter is a valve. For example, the valve may be a diaphragm that is spring-biased closed in use. The diaphragm may be of resilient material, for example an elastic material, such that it can be deflected upon against the spring force when pressure builds.

Thus, the invention in the second principal alternative arrangement comprises a fluid filter with automatic back flush, which includes an input of fluid under pressure, and an output fluid store, characterised in that the back-flushing is implemented by one or more valves operated directly by fluid pressure.

In one aspect, the input fluid pressure closes the outlet flow at a set pressure by means of a valve, and the input fluid opens a second valve at a higher pressure, enabling the stored output water to flow backwards through the filter.

In another aspect, the filter comprises hollow membrane fibres.

Preferably, in an aspect of this arrangement, automatic cross flow cleaning is provided by means of a piston pump, a water reservoir, and an air cushion.

In a possible mode of operation, the valve controlling the output fluid opens at a set pressure of the input fluid, and closes at a lower pressure. Accordingly, the valve controlling the output fluid may be configured to open at a set opening pressure of the input fluid and to close at a set closing pressure of the input fluid, wherein the said opening pressure is higher than the said closing pressure.

In a possible mode of operation, the valve controlling the input fluid is opened at a set pressure of the same fluid, and closes at a lower pressure. Accordingly, the valve controlling the input fluid may be configured to open at a set opening pressure of the input fluid and to close at a set closing pressure of the input fluid, wherein the said opening pressure is higher than the said closing pressure

Optionally, the set pressure of the valve controlling the input fluid is set at a higher input fluid pressure than the input fluid pressure closing the output fluid. Optionally, the valves are opened or closed directly by air or fluid pressure, and not by any other means. Preferably, both valves controlling back flushing are returned by springs. Optionally, there is a continuous bleed of input fluid out of the filter, and a valve by which the input fluid doses the output flow at a set pressure.

Therefore, it can be seen that there is provided a filter with a membrane module and an automatic system to back flush the membrane fibres by the pressure of the untreated water, which is achieved by spring loaded valves. Optionally, this system of back flushing is combined with automatic cross flow cleaning.

Further in accordance with the invention, a method of filtering a fluid comprises: a) Supplying fluid to be filtered into a filtration element from a supply conduit; b) Supplying filtered fluid from the filtration element, through a delivery conduit and into a pressure chamber, wherein the pressure chamber is fluidly continuous with the delivery conduit;

c) Operating a flow limiter to substantially or entirely limit the flow of filtered fluid from the pressure chamber to a filtered fluid outlet; and

d) Thereby causing filtered fluid from the pressure chamber to flow back through the delivery conduit and into the filtration element, thereby back flushing the filter element.

The method is preferably a method of use of the filter of the first aspect of the invention, and most particularly is a method of cleaning a filter of the first aspect of the invention by back flushing with filtered water.

Other preferred features of the method will therefore be understood by analogy from the discussion of the use of the filter of the first aspect of the invention herein. That is to say, any one of the above recited optional features of the fluid filter apply equally to a method of using said fluid filter.

Optionally, the method may include a flow limiter that is actuatable manually. That is to say, the flow limiter may be adapted to be actuated manually, by a user or by other intervention. Further, the flow limiter may be actuatable directly, or otherwise independently of the fluid flow in the delivery conduit. Such a flow limiter generally requires a user's intervention to substantially or entirely prevent the flow of filtered fluid from the filtered fluid outlet.

For example, it may be preferable that the flow limiter is a manually-operated tap that is manually closed by the user. Thus, the method may include the step of manually closing the manually actuatable flow limiter. For example, the method may include the step of manually closing a manually-operated tap to cause back flushing of the filtration element.

This provides the advantage that the user can control when the back-flush operational mode is engaged, thus providing more user control over the fluid filter.

Optionally, the method may include a flow limiter that is automatically actuatable. The flow limiter that is automatically actuatable may be actuatable automatically in response to fluid flow in the delivery conduit. That is to say, the flow limiter is actuated automatically as a result of the fluid flow in the delivery conduit. For example, the flow limiter may be configured to be actuated automatically at a predetermined flow rate.

Thus, such a flow limiter may be directly dependent upon the fluid flow in the delivery conduit. Such a flow limiter may require no user intervention, thus automatically controlling the back-flush operational mode.

Moreover, the fluid filter may be provided with automatic back-flush capability, characterised by one or more valves, closures or the like, including at least the flow limiter, being directly operated by fluid in the system.

The method may include an automatically-actuatable flow limiter that is in fluid communication with the delivery conduit. This provides the advantage that, should the filtration element become clogged as a result of contaminants, the user simply has to keep pumping fluid to be filtered into the fluid filter. The construction of this arrangement provides an automatic back-flushing system, thus making the fluid filter easier to operate. Such an automatic back-flushing system requires minimal instruction to use, and can be used for a longer period of time.

Optionally, the filtration element includes a primary outlet - the primary outlet being for the egress of filtered fluid - which is in fluid communication with the delivery conduit; and a secondary outlet - for the egress of fluid from the back-flush of the filtration element - which is in fluid communication with the filtration element. The method may include the step of, in response to the secondary outlet closing, automatically opening the automatically-actuatable flow limiter. That is to say, the automatically-actuatable flow limiter may be in communication, for example fluid communication, with the secondary outlet of the filtration module. Thus, when the secondary outlet of the filtration module closes, pressure builds within the system as described, which causes the automatically-actuatable flow limiter to open. Most preferably, the automatically-actuatable flow limiter is a valve. For example, the valve may be a diaphragm that is spring-biased closed in use. The diaphragm may be of resilient material, for example an elastic material, such that it can be deflected upon against the spring force when pressure builds. DESCRIPTION OF DRAWINGS

The accompanying drawings illustrate presently exemplary embodiments of the disclosure, and together with the general description above and the detailed description of the embodiments below, serve to explain, by way of example only, the principles of the disclosure. In the accompanying drawings:

Figure 1 is a cross-sectional view of a water filter according to a first arrangement of the invention; Figure 2 is a cross-sectional view of an alternative valve for use in the water filter of Figure 1 ;

Figure 3 is a cross-sectional view of another alternative valve for use in the water filter of Figure 1 ;

Figure 4 is a cross-sectional view of a water filter according to a second arrangement of the invention; Figure 5 is a cross-sectional view of an alternative valve for use in the water filter of Figure 4;

Figure 6 is a cross-sectional view of an outlet tube of the water filter of Figure 4; and Figure 7 is a cross-sectional view of a water filter according to another aspect of the invention.

In the detailed description and the drawings, like elements are denoted by the same reference numeral. Like elements in different embodiments are given the same reference numeral offset by 100.

DETAILED DESCRIPTION

Referring to Figure 1 , in a first arrangement of the invention, a water filter 10 includes a water filter module 20, a pressure chamber 30 and a pumping module 40. The water filter module 20 includes a housing 22 and hollow membrane fibres 24. The hollow fibres 24 are sealed within the housing 22 by known means. In the embodiment shown, the water filter 10 is placed in water to be filtered 1. The untreated water 1 is passed through a pre-filter, such as a gauze strainer 12, and then pumped into the water filter module 20, specifically the cores of the hollow fibres 24, by means of the pumping module 40. The pumping module 40 in the depicted embodiment is a user-operated pump which includes a cylindrical housing 42, a piston and seal 44, a piston rod 46 and a handle 48. Flow is facilitated by pushing the handle 48 up and down, so that the water to be filtered 1 passes into a fluid cavity 18 via a first valve 14, such as a suction valve, and then through an inlet 16 of the water filter module 20, which is a second valve in the described embodiment. The first and second valves 14, 16 incorporate resilient elements which allow water to pass one-way only by known means. That is to say, the valves 14, 16 in the described embodiment are one-way valves. The water to be filtered 1 is then forced through the walls of the hollow fibres 24, with the contaminants held back, and out through an outlet 26 to the pressure chamber 30. In other words, untreated water is forced through the walls of the hollow fibres 24, the contaminants are held back in the microscopic pores thereof, and treated water is pushed out of the hollow fibres 24 and through the outlet 26.

The pressure chamber 30 includes an inlet 32, which is in fluid communication with the outlet 26 of the water filter module 20, a reservoir 34, an elongate pipe 36 and a tap or stopper 38. In this way, treated water flows from the pores of the hollow fibres 24, through the outlet 26 and into the pressure chamber 30 via the inlet 32. The treated water then flows up the elongate pipe 36 and through the tap or stopper 38, when open, and out of the treated water outlet 39.

With further reference to Figure 1 , continuous cross flow is optionally achieved by a dosed air chamber 50 when the tap or stopper 38 is open. On the down stroke of the pump 40, water is pushed up the bores of the hollow fibres 24 and compresses the air in the air chamber 50, so that on the up stroke of the pump 40, the air within the air chamber 50 expands and pushes water back down. By this means, the inner walls of the hollow fibres 24 are continually washed by cross flow. On both strokes some of the water passes though the walls of the hollow fibres 24, causing a continuous flow at the outlet 26.

When it is required to back flush, the tap or stopper 38 is closed, and the pump 40 is operated so that clean water now partially fills the reservoir 34, and compresses the air trapped in its top. In other words, the air trapped between the closed tap 38 and the reservoir 34, through the elongate pipe 36, is compressed as clean water fills the reservoir 34. This increases the pressure of the water input into the filter module 20 until a diaphragm 54, covering the outlet of a pipe 52 which is in fluid communication with the filter module 20 via the air chamber 50, is forced to deflect open by water in the pipe 52. The diaphragm 54 is normally biased closed in use by a spring 56, and when the pressure builds by the fluid, the spring force is overcome to deflect open the diaphragm 54.

In the depicted embodiment, the diaphragm 54 is of a resilient material. Once opened, the diaphragm 54 stays open under water pressure, and because the force of the water is now over a greater area of the diaphragm 54, it only closes again due to the force of the spring 56 at a lower pressure.

In the depicted embodiment, continuous pumping causes clean water from the reservoir 34 of the pressure chamber 30 to first go back through the walls of the hollow fibres 24, and then be flushed out of the filter module 20 through via the air chamber 50 and through the pipe 52. Thus, when the diaphragm 54 is open, the clean water flows through the pipe 52 and out of a back-flushed water outlet pipe 58. Both back flushing and purging the contaminants are achieved by the above described means. In this embodiment, there is preferably a means to restrict the flow of water in outlet pipe 58 to retain enough pressure to keep the diaphragm 54 open while the contaminants are flushed out. This is can be achieved, for example, by restricting the bore of the back-flushed water outlet pipe 58.

After back-flushing the operator simply stops pumping, opens the tap 38, and then resumes pumping clean water, as described above, out of the clean water outlet 39.

Referring to Figure 2, there is provided an alternative pressure operated valve 60. Like the diaphragm 54 of Figure 1 , the valve 60 closes the pipe 52. In Figure 2, the outlet of the pipe 52 is closed with a stopper 62. The stopper 62 incorporates a disk 64 which is a close fit in the housing 66, so once the stopper 62 is opened, water pressure keeps it open, and allows the water to escape through the back-flushed water outlet pipe 58. Referring to Figure 3, there is provided another alternative pressure operated valve 70. The pressure operated valve 70 closes the pipe 52 with a stopper 72, which is held down by a spring 74 within housing 76. In this embodiment, the back flush still works, but the purging is less effective. When the stopper 72 is open to allow the passage of water therethough, water flows out of the back-flushed water outlet 78. Referring to Figure 4, in a second arrangement of the invention, there is provided a water filter 100 including a water filter module 120, a pressure chamber 130 and a pumping module 140. The water filter module 120 contains hollow fibres 124 sealed in a housing 122 with cement 122a, 122b. In use, the filter is placed in water to be treated 101. As described in relation to the first embodiment (Figure 1), untreated water 101 typically passes into fluid cavity 1 18 via pre-filter 1 12, which may be a gauze strainer as shown, and a valve 1 14. The untreated water 101 is then pumped through a valve 1 16, which is the inlet to the water filter module. As described in the water filter of Figure 1 , valves 1 14, 1 16 may be one-way valves. The untreated water 101 is thus pumped through the bores of the hollow fibres 124, and clean water leaks through microscopic pores in their walls.

The clean water then flows out of the module 120 via an outlet 126 and into the pressure chamber 130 via the inlet 132. The inlet 132 is in fluid communication with the outlet 126. The clean water is pumped up through a pipe 136, along a tube 136a, through a valve 138, which in the depicted embodiment is a diaphragm biased open in use, and out through the treated water outlet 170. In order to prevent contamination of the filter 100 during storage, there is optionally provided a non-return opening in the form of a flattened elastic tube, or other non-return device, or a tap.

In the event that the pores of the hollow fibres 124 become partially clogged, continued pumping will increase the pressure of the untreated water within the filter 100. This will increase the air pressure in the air chamber 150, which will be transmitted via a passage 150a and through a hole 150b, to the upper side of the valve 138. The valve 138, shown as a diaphragm, is made of an elastic material, and is normally biased open by spring 138a to allow passage of clean water therethrough. However, above a set air pressure from the untreated water, caused by the increase in pressure due to the clogging of hollow fibres 124, the valve 138 is made to close, which shuts off the supply of clean water. Continued pumping then forces clean water into the reservoir 134 to a level 134a. Since the valve 138 is closed, air is trapped within the pipes 136, 136a as water fills the reservoir 134. Thus, the air trapped within the pipes 136, 136a then pushes clean water back through the filter module 120, thereby increasing the air pressure in the air chamber 150. This increased air pressure opens another valve 154, in this embodiment it is another diaphragm, which is normally biased closed by a spring 156. Untreated water can flow through the air chamber 150, through a passage 152 and out of the filter through the back-flushed water outlet 158. The passage from outlet 158 to the outside of the filter 100 is not shown, but the water can exit either into a separate container, or back into the untreated water where the water to be treated 101 is contained. This passage to the outside of the filter has some form of restriction so that the diaphragm stays open while pumping continues. Clean water is then pushed by air pressure in the reservoir 134 back through the hollow fibres 124 and outside of the filter. By these means, on occasions when the hollow fibres 124 begin to clog, the operator simply needs to keep on pumping, and flow will stop and back-flushing take place. In other words, the back-flushing of the filter 100 is automatic.

The valve 154, depicted as a diaphragm is this embodiment, also acts as a pressure relief valve, which limits the pressure of fluid in the filter in the event of excessive pumping force.

It can be seen from Figure 4 that the valves 138, 154 require a high pressure in passage 150b and hole 152, and on account of a greater surface once open, stay in that condition until the pressures become much lower. This means that when the pressures drop after back-flushing, the valves 138, 154 return to their operating positions for continued supply of clean water.

With reference to Figure 5, an alternative non-return valve 160 is shown, which can replace either, or both, valves 138, 154. As shown in Figure 5, the non-return valve 160 includes a seal 162 closing an input hole 164, and a rod with a disc 166. The rod and disk 166 are biased downwards, in other words the rod and disk 166 are biased closed, by a spring 166a. Thus, the rod and the disk 166 are held down with the spring 166a. When input pressure opens the seal, as described above, the pressure behind the disc 166 and lifts it, or opens the valve, to uncover exit 168. That is to say, the air pressure builds up on the disk 166 and acts upon it, such that it is forced against the spring force urged upon it by spring 166a, thereby opening the valve 160. The disk 166 and seal 162 stay above the outlet 168 until a lower pressure is achieved at which point they can return to the closed state.

Referring to Figure 6, the treated water outlet 170 of Figure 1 is shown in more detail. In the depicted embodiment, the treated water outlet 170 includes an outer piece 172 and an inner piece 139. The inner piece 139 forms the actual outlet for outputting treated water. As can be seen in Figure 6, the outer piece 172 engages the inner piece 139 to hold the mouth of the inner piece 139 closed. In turn, this makes the treated water outlet 170 leak resistant by encasing the inner piece 139 within an outer piece 172 to provide a larger flattened shape.

Figure 7 shows a third arrangement of the invention. The water filter 200 is similar to the construction of the water filter 100 shown in Figure 5, with the exception that the diaphragm valve 158 is replaced by a bleed pipe 258. All other elements of the water filter 200 are substantially the same as water filter 100, shown in Figure 4, and operate in the same manner.

The bleed pipe 258 enables a proportion of the pumped input water to continually return to an input container (not shown), which contains the water to be treated. When a valve 238, shown again as a diaphragm in this embodiment, closes the treated water output 270, continued rapid pumping will fill the reservoir of the pressure chamber (not shown, but equivalent to 134 shown in Figure 4), and when pumping stops, the water in the reservoir pushes water back through the microscopic pores of the hollow fibres and out through the bleed pipe 258.

The construction and operation of valve 238 is the same as that described in relation to valve 138 of Figure 4. In particular, the valve 238 is biased open in use by a spring 238a. There is also a passage 250a and a hole 250b which allows fluid communication between an air chamber 250 and the valve 238. In this way, when air pressure increases in the air chamber 250, the valve 238 is forced to close against the force of the spring 238a. Thus, a treated water outlet 270, including an outer piece 272 and inner piece 239, is closed off due to the closing of valve 238. This allows back-flushing of the hollow fibres of filter module 220, and thus the flow of water out of the bleed pipe 258.

With reference to Figures 4 and 7, water filters 100, 200 may include automatic cross flow by making use of a second air chamber 180, 280. On the down stroke of the pumping module 140, water goes up through the bores of the hollow fibres 124 and compresses air in the second air chamber 180, 280, and on the return stroke the air can expand and push the water back down the hollow fibres 124. At the same time some of the water leaks through the walls of the hollow fibres 124, and through the outlet 126. By this means the inner walls of the hollow fibres 124 are washed in both directions. If the cross flow needs to be increased, a small bleed hole 182 (see Figure 4) can be included which is in fluid communication with the cavity 1 18. This makes some of the untreated water flow back into the pump barrel 142, which is returned on the down stroke of the pumping module 140.

With further reference to Figures 4 and 7, the valves 138, 154, 238, passageways 150a, 150b, 250a, 250b are housing by housing components 184, 186, 188; 284, 286, 288. Said housing components 184, 186, 188; 284, 286, 288 illustrate a possible construction of this part of the filter, although other constructions can be recognised by the person skilled in the art. The housing components 184, 186, 188; 284, 286, 288 are conveniently screwed together and sealed with gaskets and rubber rings. The pump and reservoir do not show constructional detail, but together with this disclosure and the common general knowledge, the person skilled in the art could envisage such detail.

It will be appreciated for persons skilled in the art that the above embodiments have been described by way of example only and not in any limiting sense, and that various alterations and modifications are possible without departing from the scope of the invention as defined by the appended claims.

Claims

What is claimed is: 1 . A fluid filter comprising:

A filtration element;

A supply conduit positioned to supply fluid to be filtered to the filtration element;

A delivery conduit positioned to receive filtered fluid from the filtration element;

A pressure chamber fluidly continuous with the delivery conduit;

A filtered fluid outlet in fluid communication with the pressure chamber, including a flow limiter that is operable to restrict flow of filtered fluid from the filtered fluid outlet;

Wherein, when the flow limiter is operated, filtered fluid is caused to flow back from the pressure chamber to back flush the filtration element.

2. The fluid filter of claim 1 , further comprising a filtration module, wherein the filtration module comprises:

A housing defining a filtration volume therein containing the filtration element;

An inlet for the ingress of fluid to be filtered, the inlet being in fluid communication with the supply conduit;

A primary outlet for the egress of filtered fluid, the primary outlet being in fluid communication with the delivery conduit.

3. The fluid filter of claim 2, wherein the inlet includes a one-way valve.

4. The fluid filter of claim 2 or 3, wherein the filtration module comprises a secondary outlet, the second outlet being in fluid communication with the filtration volume, for the egress of fluid from the back-flush of the filtration element.

5. The fluid filter of claim 4, wherein the secondary outlet is provided with a closure, wherein the closure is selectively operable to close the secondary outlet at fluid pressures below a predetermined pressure, and wherein the closure is selectively operable to open the secondary outlet at fluid pressure above the predetermined pressure.

6. The fluid filter of claim 5, wherein the closure comprises a valve.

7. The fluid filter of claim 6, wherein the valve is a diaphragm that is spring- biased.

8. The fluid filter of claim 4, wherein the secondary outlet is provided with a bleed pipe, wherein the bleed pipe substantially prevents the flow of fluid.

9. The fluid filter of any preceding claim, wherein the pressure chamber comprises:

A pressure chamber inlet in fluid communication with the primary outlet of the filtration volume; and

A pressure chamber outlet in fluid communication with the delivery conduit.

10. The fluid filter of claim any preceding claim, further comprising a pumping module configured to input fluid through the supply conduit, and into the filtration element, under pressure.

1 1 . The fluid filter of any preceding claim, further comprising a pre-filter.

12. The fluid filter of any preceding claim, wherein the filtered fluid outlet comprises a filtered fluid outlet tube including a non-return device.

13. The fluid filter of any preceding claim, wherein the flow limiter is actuatable manually.

14. The fluid filter of claim 13, wherein the flow limiter is a manually-operated tap that is manually opened and closed by the user.

15. The fluid filter of any one of claims 1 - 12, wherein the flow limiter is actuatable automatically in response to fluid flow in the delivery conduit.

16. The fluid filter of claim 15, wherein the automatically-actuatable flow limiter is in fluid communication with the delivery conduit.

17. The fluid filter of claim 16, wherein, in response to the secondary outlet of the filtration module closing, the automatically-actuatable flow limiter opens.

18. The fluid filter of claim 17, wherein the automatically-actuatable flow limiter is a diaphragm that is spring-biased closed in use.

19. A method of filtering a fluid, comprising:

a) Supplying fluid to be filtered into a filtration element from a supply conduit; b) Supplying filtered fluid from the filtration element, through a delivery conduit and into a pressure chamber, wherein the pressure chamber is fluidly continuous with the delivery conduit;

d) Thereby causing filtered fluid from the pressure chamber to flow back through the delivery conduit and into the filtration element, thereby back flushing the filtration element.

20. The method of claim 19, wherein the flow limiter is actuatable manually.

21 . The method of claim 20, further comprising the step of manually closing a manually-operated tap to cause back flushing of the filtration element.

22. The method of claim 19, wherein the flow limiter is actuatable

automatically in response to fluid flow in the delivery conduit.

23. The method of claim 22, wherein the automatically-actuatable flow limiter is in fluid communication with the delivery conduit.

24. The method of claim 23, wherein the filtration element includes a primary outlet, for the egress of filtered fluid which is in fluid communication with the delivery conduit, and a secondary outlet, for the egress of fluid from the back- flush of the filtration element, wherein, in response to the secondary outlet closing, the automatically-actuatable flow limiter opens.

25. The method of claim 24, wherein the automatically-actuatable flow limiter is a diaphragm that is spring-biased closed in use.