TECHNICAL FIELD OF THE INVENTION

This invention relates to a micro-fibre filter which is suitable for removing micro-fibres from the waste water from a washing machine. The filter may be installed in a washing machine during manufacture of the machine or retro-fitted in the waste water outlet from a washing machine.

BACKGROUND

The kinetic action of washing machines abrades fibrous material from clothes, which is flushed out with the waste water. Once redistributed within a large water mass as in a public sewer, these micro-fibres are difficult to remove at water treatment facilities. Hence, plastic micro-fibres from the washing of synthetic clothes often pass into natural water-courses (rivers, and ultimately seas) where they have a prolonged detrimental impact.

A general objective of this invention is to provide a washing machine outlet filter which removes such entrained micro-fibres. A further objective is to provide such a filter which is suitable to be installed in a waste water outlet from a washing machine. Another objective is to provide a filter which can be incorporated into the machine by washing machine manufacturers.

While many kinds of washing machine lint filter are currently available, the volume of lint which is generated and the user convenience requirements of a micro-fibre filter present many challenges.

United Kingdom patent No. GB 884 524 published on 13 December 1961 discloses a liquid filter in which a sheet of filter paper rolled on a spool is carried through a tank of liquid and out of the tank without positive attachment of the filter medium to its drive means. The filter medium is moved by an electric motor which is controlled by a pressure switch in response to a decrease in pressure at the liquid outlet caused by clogging of the filter paper.

The present invention seeks to provide a new and inventive form of micro-fibre filter which is easy and convenient to use, whether incorporated into a washing machine or installed externally.

SUMMARY OF THE INVENTION

When viewed from one aspect the present invention proposes a micro-fibre filter:

- a housing (1) containing a filter chamber (2) with an inlet (3) for unfiltered liquid and an outlet (4) for filtered liquid;

- a filter cartridge (7) removably receivable within the filter chamber and including :

a delivery spool (21) and an uptake spool (22),

a perforated partition wall (23) extending between said spools (21, 23),

a filter medium (24) in the form of an elongate liquid permeable sheet wound about the delivery spool (21) and the uptake spool (22) and extending along the perforated partition wall (23), wherein the portion of the filter medium which extends along the perforated partition wall is positioned within the path of liquid flowing through the filter chamber (2) to filter the liquid;

wherein the filter chamber (2) contains a device (20) which is rotatably driven by flow of liquid through the filter chamber.

The device (20) may have multiple uses. For example, the device may operate a flow sensor to permit monitoring and recording water flow through the filter. Such flow data can be used to monitor users washing habits and advise accordingly.

In a preferred embodiment the micro-fibre filter includes an energy storage unit (31) to receive and store energy from the rotatable device (20).

In a preferred embodiment the micro-fibre filter includes a drive coupling (32-34) powered by the energy storage unit (31) to advance the filter medium from the delivery spool to the uptake spool.

In a preferred embodiment the drive coupling (32-34) is triggered by a pressure sensor (35) located in the filter chamber to advance the filter medium from the delivery spool to the uptake spool.

In one preferred embodiment the energy storage unit (31) includes a mechanical storage device such as a spring.

In another preferred embodiment the energy storage unit (31) includes an electrical storage device such as an electrical cell or cells.

When viewed from one aspect the present invention proposes a micro-fibre filter:

- a housing (1) containing a filter chamber (2) with an inlet (3) for unfiltered liquid and an outlet (4) for filtered liquid;

- a filter cartridge (7) removably receivable within the filter chamber and including :

a delivery spool (21) and an uptake spool (22),

a perforated partition wall (23) extending between said spools (21, 23),

a filter medium (24) in the form of an elongate liquid permeable sheet wound about the delivery spool (21) and the uptake spool (22) and extending along the perforated partition wall (23), wherein the portion of the filter medium which extends along the perforated partition wall is positioned within the path of liquid flowing through the filter chamber (2) to filter the liquid;

wherein the filter chamber (2) communicates with a drainage chamber (43) bounded by a movable wall (45).

In a preferred embodiment the movable wall (45) is connected to an operating member (8).

In a preferred embodiment the filter chamber (2) is provided with inlet and outlet valves (41, 42) which are closed by the operating member (8).

In a preferred embodiment the operating member (8) is arranged to eject the filter cartridge (7) from the filter chamber.

In a preferred embodiment the filter medium (24) has an aperture size of 5 pm to 20 pm.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description and the accompanying drawings referred to therein are included by way of non-limiting example in order to illustrate how the invention may be put into practice. In the drawings:

Figure 1 is a general view of a micro-fibre filter which is suitable to be installed in the waste water outlet of a washing machine; Figure 2 is another general view of the micro-fibre filter showing filter cartridge removal;

Figure 3 is a diagrammatic internal plan view of the micro-fibre filter with the filter cartridge installed, and including an indexing mechanism;

Figure 4 is a further diagrammatic internal plan view of the micro-fibre filter with the filter cartridge installed, and including a drainage mechanism;

Figure 5 is a diagrammatic internal side view of the micro-fibre filter showing a drainage chamber.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring firstly to Fig.1, the micro-fibre filter which is shown in the drawing is particularly suitable to be connected in the water drain outlet hose of a washing machine, e.g. installed in a cupboard under a sink. The filter comprises a generally rectangular housing 1 which contains a filter chamber 2 provided with an inlet 3 for unfiltered liquid and an outlet 4 for filtered liquid. A top wall 5 of the housing is provided with an aperture 6 which is shaped to receive a filter cartridge 7. The cartridge may be configured to sealably engage the periphery of the aperture 6 when installed in the housing 1 as shown. Alternatively, a separate lid may be provided to seal the aperture 6. Extending along a front edge of the top wall there is an operating member in the form of an ejection lever 8 which is pivotally connected to the housing 1 at one end and provided with a lifting flange 9 at the opposite end. When the filter cartridge is installed as shown, the ejection lever is snugly received within a shaped recess 10 in the top wall 5. An adjacent wall 11 of the housing is provided with a finger notch 12 which enables the lifting flange 9 to be used to lift the lever and pivot it to a raised position, as shown in Fig. 2. As the lever 8 is raised it operates a simple mechanical ejection mechanism to automatically eject the filter cartridge 7 from the filter chamber 2, as in Fig. 2.

Turning to Fig. 3, the filter cartridge 7 has an outer casing 20 which contains a delivery spool 21 and an uptake spool 22 rotatably mounted at opposite ends of the casing. Part of the casing 20 extends between the two spools forming a double-skin perforated twin partition wall 23, also seen in Fig. 2. A filter medium 24 in the form of an elongate liquid permeable sheet of paper, cotton or other natural fibres, extends between the spools 21 and 22 between the two skins of the perforated partition wall 23 between internal end seals 25 and 26. A filter medium with an aperture (pore) size of 5 pm to 20 pm is preferred, although smaller or larger sizes can be used depending on the size of the micro-fibres being targeted. Wet strengthened Whatman filter paper with a pore size of 10 pm has been used with good results. In a new cartridge most of the filter medium is wound on the delivery spool 21 as shown, but the filter medium medium is progressively wound onto the uptake spool by mans of a mechanical indexing mechanism as described below.

When the cartridge 7 is installed in the filter as in Fig. 3 the filter cartridge divides the interior filter chamber 2 into an inlet chamber 2A and an outlet chamber 2B located on opposite sides of the perforated partition wall 23. The two chambers 2A and 2B respectively connect with the water inlet 3 and the water outlet 4. The walls of the filter chamber are provided with leak-proof seals 27 and 28 which respectively make sealing contact with opposite sides of the filter cartridge 7 to prevent water from leaking between the inlet and outlet chambers.

The outlet chamber 2B contains an impeller or paddle wheel 30 (perhaps more accurately described as a turbine) which drives a mechanical energy storage unit 31, for example to wind up a coil spring against a ratchet mechanism, or similar energy storage device. The energy storage unit 31 has a rotary output 32, which is connected by a belt 33 to a rotary drive element 34 which is, in turn, drivably and releasably engaged with the uptake spool 22, e.g. via a splined or friction drive arrangement. The inlet chamber 2A contains a pressure sensor 35 (for example a pressure-responsive diaphragm) which is linked to the energy storage unit 31, e.g. by a pneumatic or mechanical operating linkage 36. During normal flow from inlet 3 to outlet 4 the impeller 30 winds up the spring in energy storage unit 31. When the filter paper becomes clogged the resulting rise in pressure within the inlet chamber 2A triggers the ratchet to release the spring causing the output 32 to drive the uptake spool via the drive belt 33. The clogged portion of the filter medium is therefore wound into the uptake spool, drawing a clean section of the filter medium across the partition wall 23. The inlet pressure will then drop as the water flow re-commences, disengaging the drive and allowing the energy storage unit to re-charge by rotation of the impeller 30.

When all of the filter medium on the delivery spool has been used a flag is set to indicate that the cartridge requires changing. In a simple form, this could be a transparent window in the cartridge casing, positioned above the delivery spool to reveal when no filter medium remains. The micro-fibre filter incorporates an arrangement to ensure that changing of the cartridge can take place with minimum spillage. Referring to Fig. 4, the water inlet and outlet chambers 2A and 2B contain simple shut-off valves, 41 and 42 respectively, which are closed by the ejection lever 8 at the start of its travel when the lever is raised. As shown in Fig. 5, the filter also includes a drainage chamber 43, located below the filter chamber 2 and connected to the filter chamber by a port 44. The drainage chamber is bounded by a movable wall such as a diaphragm or a piston 45. This piston is connected by a piston rod 46 to the ejection lever 8 so that as the lever is raised, after the shut-off valves 41 and 42 are closed, the piston is withdrawn to expand the volume of the drainage chamber. As the spent filter cartridge is ejected any remaining water within the filter chamber 2 is drawn out of the chamber into the drainage chamber 43, which allows the spent cartridge to be removed with minimum spillage. When a new filter cartridge is installed, lowering the lever allows the cartridge to enter the chamber 2, simultaneously emptying the drainage chamber 43 back into the filter chamber 2. At the end of its travel the lever 8 re-opens the shut-off valves 41 and 42.

Although the above example describes a mechanical energy storage unit 31 the impeller 30 could drive a low power electro-mechanical current generator which charges an electrical cell or cells. The stored electrical charge can be used to operate a solenoid or electric motor which indexes the uptake spool 22 when a rise in back-pressure is detected by pressure sensor 35.

The important features of the micro-fibre washing machine filter may be summarised as follows:

• The filter is suitable for installation under a kitchen sink, accepting the washing machine outlet flow and passing to the washing machine drain.

• A replaceable filter cartridge is used.

• The filter can be easily installed by a plumber or other competent person, not requiring any special tools, training or experience.

• The filter unit is a relatively low cost - a potential "give-away" by water companies, and/or sale through DIY shops.

• The cartridge system is easy and convenient to change by any user, without requiring any special tools.

• The filter cartridge typically has an in-situ service life of around 6 months, so as not to require frequent recharging or other maintenance.

• A 5 pm to 20 pm filter mesh size is suitable to remove at least 90% of all synthetic micro-fibres.

• A back pressure sensor is included to renew the used filter medium.

• A flag or window provides a visual cue to the user at, or approaching, the need for cartridge change.

• The filter cartridge is a mailable item to enable central processing and exchange of filters.

• Filter medium movement is self-powered e.g. by water flow.

• The filter system can be retro-fitted to existing washing machines.

• All components of the filter can have high environmental credentials through use of recycled plastics etc.

Although an external micro-fibre filter has been described herein for purposes of example the filter could equally be incorporated into washing machines at manufacture. When the filter is intended to be installed in a washing machine the drainage chamber may not be necessary since an electrical signal from the door interlock of the washing machine can be used to operate a solenoid which prevents the filter from being opened while the machine is in use. Furthermore, the cartridge ejection mechanism itself could be operated by a solenoid or electric servo-motor instead of a manual lever, which is again linked to the door interlock to prevent the cartridge from being ejected while the machine is operating. It will also be appreciated that since an electrical supply is readily available inside a washing machine the filter medium in the filter cartridge can be indexed by an electric motor or solenoid controlled by water back-pressure. The development of the micro-fibre filter has been driven by a desire to make the unit easy and convenient to use, reducing the barriers to actual deployment, and by the filter's environmental benefit. Central filter processing would prevent users cleaning the filters themselves and the plastic micro-fibres ending up in landfill where they are not suitably contained within a closed loop recycling system and still have a high likelihood of being carried into a water course.

Whilst the above description places emphasis on the areas which are believed to be new and addresses specific problems which have been identified, it is intended that the features disclosed herein may be used in any combination which is capable of providing a new and useful advance in the art.