Field of the invention

[001 J This invention relates to self-cleaning lint filters for cleaning apparatus, and to methods of operating such apparatus.

[002] The invention is particularly suited for use in domestic appliances such as recirculating spin bowl (RSB) washing machines.

Background of the invention

[003] Non-RSB washing machines flush the wash water from the washing machine during the wash and drain cycles, so much of the lint and washing powder solids tend to move to the outer wall of the bowl to be flushed to the drain. However, such machines use large amounts of water.

[004] RSB washing machines are designed to reduce water consumption by recirculating the washing water through the wash bowl. This results in the lint and powder solids being retained in the washing water and recirculated back onto the clothes during the wash cycle. Accordingly, lint filters have been inserted in the water recirculation path.

However, the filters can become clogged fairly quickly. The lint in recirculating washing machines causes unique problems for the filters due to the elongated nature of the lint which can accumulate on the filter mesh more readily than particles and rapidly clog the filter.

[005] US3727435 discloses a self cleaning diaphragm filter which uses vibration and pumped tangential flushing of the upstream side of the filter membrane (i.e., on the wash bowl side) to dislodge the accumulated lint during the drain cycle of the wash.

[006] US3282427 describes a self cleaning lint filter arrangement (Figure 9) having a reversible pump, a filter, a recirculation path sharing a common pipe with the discharge path, and a one way valve. The one way valve is arranged to block discharge water from returning to the bowl during a discharge operation with the pump operating in the forward direction, and to allow the recirculation flow through the pump during reverse operation of the pump. In US3282427 the recirculation return is at the base of the bowl via the bowl drain.

[007] US3282427 also discloses a filter having a two-piece filter element, one being a flexible disc, and the other being a rigid disc. The facing sides of the disc are patterned to form a filter maze when the flexible disc is forced into contact with the rigid disc, during the recirculation operation. In the flush operation, the flexible disc is forced away from the rigid disc so the water can dislodge the lint from the filter maze. {008] In the arrangement shown in Figure 9 of US3282427 the water in the discharge pipe is permitted to flow back through the pump during reverse operation of the pump during recirculation. As this water can contain lint from a previous filter flush operation, this retained lint will be returned to the filter. ,

[009] In the system described in US3282427, as well as in other recirculating spin bowl washing machines, the need for repeated flushing of the filter can consume a significant amount of water. Other problems which can occur during the recirculation and flushing cycles include cavitation noise during draining, and the need for manual cleaning of the filter after each use of the washing machine.

[010] It is desirable to reduce or eliminate the build-up of lint and detergent residue on the clothes to improve the results of the washing process and provide a cleaner washing action.

[011] In this specification, reference to a document, disclosure, or other publication or use is not an admission that the document, disclosure, publication or use forms part of the common general knowledge of the skilled worker in the field of this invention at the priority date of this specification, unless otherwise stated.

Summary of the invention

[012] This invention proposes a self-cleaning lint filter, filter arrangement, and operating method which mitigate these and other problems or otherwise improve the performance of domestic appliances such as washing machines by, for example increasing the load capacity of the machine.

[013] It is thus an object of the invention to provide an improved filter arrangement for domestic appliances such as washing machines and the like.

[014] It is also an object of the invention to provide a method of operating a washing machine to reduce lint retention in the wash bowl.

[015] It is also an object of the invention to provide an improved self-cleaning filter system.

[016] It is also an object of the invention to provide a washing machine with an improved filter system.

[017] It is an advantage of the present invention to provide an improved filter element.

[018] It is a further advantage of the present invention to provide an improved valve. [019] The applicant has thus provided a system which uses a reverse flush to dislodge lint from the filter back to the inside of the filter.

[020] A subsequent drain pump operation can then remove the lint from the filter and discharges the lint to the drain.

[021] The amount of water used for the reverse flush can be limited.

[022] A one-way valve can be used to prevent reverse flow from the drain pump after the pump is switched off carrying lint back into the filter;

[023] Accordingly, an embodiment of the invention provides a filter arrangement

(6.0 0) for a domestic appliance, including a filter element (6.038) and a filter housing (6.030); wherein the housing has a first port (6.032) , a second port (6.034), and a third port (6.036), wherein the first port and the second port are located on a first side of the filter element, and the third port is located on the second side of the filter element.

[024] The filter element can divide the interior of the housing providing an unfiltered liquid path between the first port and the second port, and a filtered liquid path between the first port and the third port.

[025] The filter element can include a tubular filter.

[026] The tubular filter can be adapted to withstand inward fluid pressure.

[027] The tubular filter can be self-supporting.

[028] The tubular filter can be a mesh filter.

[029] The filter element can include a first peripheral seal (13.104) at a first end of the tubular filter and a second peripheral seal (13.106) at a second end of the tubular filter, the first seal being located proximate the first port, and the second seal being located proximate the second port.

[030] The filter arrangement can include a one-way valve (6.040) downstream of the second port.

[031] The valve can be adapted to inhibit liquid to flow in the upstream direction.

[032] The one-way valve includes a valve housing (9.068) having a stepped through-bore (10.074) defining a first bore (10.075) and a second bore (10.072), the first bore being larger than the second bore and being on the downstream side thereof to provide a valve seat, the valve element (10.070) being affixed to the valve seat at a distance from the rim of the smaller bore (9.072). [033] The filter arrangement can include a second valve housing member (11.080) having a third through bore (11.082) larger than the first bore and adapted to fit within the second bore, the valve element being affixed by the interface between first valve housing member and the second valve housing member.

[034] According to another embodiment of the invention, there is provided a self- cleaning filter system including a filter arrangement, which includes a recirculation pump (4.014) connected to the third port and a recirculation pipe (2.018) having an outlet above the water level of a wash bowl.

[035] The recirculation pump is adapted to draw water from the housing via the filter element.

[036] The self-cleaning filter system can include a drain pump connected to the second port and adapted to draw water from the filter housing.

[037] The drain pump can be connected to a drain pipe having an outlet at or above the height of the recirculation pipe outlet.

[038] The drain pump can be downstream of the one-way valve.

[039] The self-cleaning filter system can include programmable control means

(3.022) to control the operation of the recirculation pump and the drain pump.

[040] The invention also includes a washing machine including a wash bowl (1.004,

1.006), a recirculation path including a drain connection (2.012) from the base of the wash bowl to the first port (3.032) of the filter housing (3.010), the filter element (3.038), recirculation pump (3.014), and a recirculation pipe (2.018) connected to the outlet of the recirculation pump and extending above the maximum water level of the wash bowl, characterized in that it includes a self-cleaning filter system as described above.

[041] The washing machine can include programmable control means (3.022) programmed to turn the recirculation pump off for a first period of time during the wash cycle, whereby water in the recirculation pipe is enabled to flow in a reverse direction through the third port of the filter housing to dislodge at least some of the matter entrapped in the filter.

[042] A further embodiment of the invention provides a method of operating a self cleaning filter system in a washing machine,

characterized in that the method includes the steps of:

operating the recirculation pump for a first time period, and turning the recirculation pump off to permit at least part of the liquid in the recirculation pipe to flow into the filter element to dislodge matter caught by the filter.

[043] The method can include the step of turning the recirculation pump on after a first time period after the recirculation pump was turned off.

[044] The method can include repeating the step of turning the recirculation pump on and off for a time interval two Or more times.

[045] The method can include the step of turning the drain pump on to draw water out via the second port and beyond the one way valve after the recirculation pump has been turned on and off one or more times.

[046] The recirculation pump can be turned on before the drain pump is turned off.

This provides an overlap of the operating times of the drain pump and the recirculation pump.

[047] According to a further aspect of the invention the above and other objects are fulfilled by a method of operating a self cleaning filter system in a washing machine having a wash tub, a filter having an intake port, a drain port and a recirculation port, a recirculation path including a recirculation pump connected to the recirculation port and a recirculation pipe delivering recirculated water to the top of the tub, characterized in that the method includes the steps of: operating the recirculation pump for a first time period, and turning the recirculation pump off to permit at least part of the liquid in the recirculation path to flow transversely into the filter element to dislodge matter caught by the filter.

[048] The recirculation pump is turned off only for a short time before being turned on again. This has the effect of returning the dislodged matter to the outer bowl by the bowl outlet, but little, if any, is returned to the inner wash bowl. This operation can be repeated several times during a wash cycle without any water exiting the machine via the drain pipe. Thus this method improves the wash operation, and also conserves water.

[049] According to a further embodiment of the invention, there is provided a filter element having a tubular body (14.120) having a first end and a second end, characterized in that it includes a first peripheral seal (14.104) around the first end and a second peripheral seal (14.106) around the second end.

[050] The tubular body is self-supporting and adapted to withstand fluid pressure.

[051] According to a further embodiment of the invention, there is provided a oneway valve including a first valve housing and a valve element, characterized in that the valve housing (9.068) includes a stepped through-bore (10.074) defining a first bore (10.075) and a second bore (10.072), the first bore being larger than the second bore and being on the downstream side thereof to provide a valve seat, the valve element (10.070) being affixed to the valve seat at a distance from the rim of the smaller bore (9.072).

[052] The one-way valve can include a second valve housing member (11.080) having a third through bore (11.082) larger than the first bore and adapted to fit within the second bore, the valve element being affixed by the interface between first valve housing member and the second valve housing member.

[053] The system and method according to the invention substantially mitigate the problem of lint contamination in washing machines, and is particularly advantageous when used in RSB washing machines.

Brief description of the drawings

[054] An embodiment or embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[055] Figure 1 is an illustrative schematic drawing of the bowl arrangement of a top loading washing machine.

[056] Figure 2 is a schematic illustration of the underside of a washing machine including a self cleaning filter arrangement according to an embodiment of the invention.

[057] Figure 3 is a schematic illustration of a filter arrangement according to an embodiment of the invention.

[058] Figure 4 is an alternative illustration of a filter arrangement according to an embodiment of the invention.

[059] Figure 5 illustrates flow through the filter during a recirculation cycle.

[060] Figure 6 illustrates flow through the filter during a flush operation.

[061] Figure 7 illustrates flow through the filter during a filter cleaning cycle.

[062] Figure 8 illustrates an exemplary timing chart showing the recirculation, flush, and clean operations.

[063] Figure 9 illustrates a valve according to an embodiment of the invention.

[064] Figure 10 is a side view of the valve of Figure 9.

[065] Figure 11 is a side view of an outlet section adapted for use with the valve of Figure 9.

[066] Figure 12 illustrates an alternative valve according to an embodiment of the invention. [067] Figure 13 illustrates a known filter.

[068] Figure 14 illustrates a filter according to an embodiment of the invention.

[069] Figure 15 illustrates an alternative filter according to an embodiment the invention.

[070] Figure 16 is a flow chart illustrating a method of implementing the reverse flush and drain process according to an embodiment of the invention.

[071] Figure 17 illustrates a filter arrangement according to a further embodiment of the invention.

[072] Figure 18 illustrates an alternative flow diagram of the reverse flush and drain process according to an embodiment of the invention.

[073] Figure 19 illustrates a modified system similar to that of Figure 4.

[074] Figure 20 illustrates an alternative three-port filter arrangement.

[075] The numbering convention used in the drawings is that the digits in front of the full stop indicate the drawing number, and the digits after the full stop are the element reference numbers. Where possible, the same element reference number is used in different drawings to indicate corresponding elements.

[076] It is understood that, unless indicated otherwise, the drawings are intended to be illustrative rather than exact representations, and are not necessarily drawn to scale. The orientation of the drawings is chosen to illustrate the features of the objects shown, and does not necessarily represent the orientation of the objects in use.

Detailed description of the embodiment or embodiments

[077] Figure 1 shows the bowl arrangement 1.002 of a top loading washing machine with an external stationary bowl 1.004 and an internal revolving bowl 1.006. The internal bowl has perforations in its walls to permit the washing water to enter and exit. The external bowl 1.006 is watertight, and is provided with a drain hole at the lowest point or sump in its base as shown at 2.012 in Figure 2.

[078] Figure 2 is an underside view of a bowl arrangement including a filter arrangement. The filter arrangement includes the filter 2.010, a drain pump 2.016, and a recirculation pump 2.014.

[079] The external bowl 2.004 has a recirculation pipe 2.018 running from the filter

2.010 via recirculation pump 2.014 to return water to the bowl. In the embodiment shown in Figure 2, a reservoir chamber 2.019 can be provided proximate the top of the recirculation pipe and this is used to store water for use in the gravitational back flush process according to an embodiment of the invention. The larger volume of the chamber helps maintain the back flush flow at a higher rate. The reservoir chamber has an outlet into the wash bowl.

[080] The drain pump 2.016 is connected to a drain pipe 2.020 and discharge pipe

2.021 which can extend to near the top of the machine.

[081] The discharge pipe 2.021 can deliver the water to an outlet such as a municipal drain or grey water collection system.

[082] In alternative embodiments, the filter arrangement can be mounted wholly on the washing machine casing, or partly on the base of the outer bowl and partly on the washing machine casing.

[083] The filter arrangement is shown in more detail in Figure 3. The filter 3.010 has a housing 3.030 with first, second, and third ports 3,032, 3.034, 3.036. The first port 3.032, the filter intake port, is adapted to be connected to the bowl drain 2.012 (Figure 2). The second port 3.034, the filter outlet port, is adapted to be connected to the drain pump 3.018. The third port 3.036, the recirculation port, is adapted to be connected to a recirculation pump 3.014. A filter element 3.038 can be of cylindrical construction with seals at either end, the central bore being unobstructed to permit uninterrupted flow between the filter intake port 3.032 and the filter outlet port 3.034. The filter element 3.038 is permeable and adapted to permit the recirculating wash water to pass through its wall in the recirculation mode and during filter flush process. A programmable controller or processor 3.022 is provided to control the operation of the pumps and the wash bowl motor during each selected wash cycle. In the recirculation mode with the recirculation pump 3.014 operating in a forward direction, the water exits the filter via recirculation port 3.036.

[084] The three-port configuration of the filter housing is such as to enable both axial flow and transverse or radial flow.

[085] Embodiments of the invention can provide two processes for flushing the filter.

The first process is a gravity reverse flush, and the second process is a pulsed flush. These processes are combined in a preferred embodiment of the invention.

[086] During the gravity filter flush mode using a reverse flush, the water from the recirculation pipe is injected into the filter via the recirculation port to dislodge the lint and solids from the filter element pores. The recirculation pipe extends to the top of the tub, while the water level in the bowl is always below this. This creates a hydrostatic pressure differential between the water in the recirculation pipe and the water in the bowl. This pressure differential can be of the order of 500 mm of water. Thus, when the recirculation pump is turned off, the water in the recirculation pipe will flow back into the filter housing and will exit the housing via the intake port and or the outlet port of the filter. The flow rate of this reverse flow will depend on the pressure differential, and on the flow characteristics of the recirculation path, such as minimum diameters of the pipes. Preferably, the reverse flow rate is greater than the forward recirculation flow rate. The pressure differential will decrease as the level of water in the recirculation pipe drops, and this will decrease the reverse flow rate during the gravitational flush.

[087] In one embodiment, the cross-section of at least part of the recirculation pipe can be increased to provide a reverse flow of greater duration. Preferably, the increased cross-section is at the upper part of the recirculation pipe. The reason for providing the increased duration flow is to ensure that the reverse flow is of a sufficient flow rate for a sufficient time to remove at least a substantial part of the lint and solids collected by the filter.

[088] This gravity feed reverse flush will result in the dislodgement of much of the trapped lint and solids into the interior of the filter. Some of the dislodged lint and solids may also return to the base of the bowl via the bowl drain. However, we have found that this process can be repeated two or more times without substantially degrading the washing performance of the machine. The short period of the reverse flush and the limited volume of water used in the reverse flush help reduce the amount of lint and solids returned to the base of the bowl. The gravity reverse flush has the advantage that it maintains the filter in operating condition without blocking for a greater period of time between pulsed flushes.

[089] A pulsed flush is implemented by operating the drain pump to draw the water through the filter and discharge some of the water to the system outlet. The pulsed flush can occur one or more times during a washing cycle. To conserve water, it is desirable to minimize the amount of water discharged from the system during the pulsed flush. However, because of the presence of the one way valve, it is not necessary to completely drain the recirculation pipe, because the one way valve prevents the lint drawn off from re-entering the filter. The combination of one or more gravity reverse flushes with each one of one or more pulsed flushes during the wash cycle reduce the amount of water discharged, while maintaining the filter in an unclogged state.

[090] Figure 4 is a representation of a filter arrangement showing a one way valve

4.040 at the discharge end of the filter housing. The one-way valve prevents water in the drain pipe (2.021) from re-entering the filter. Thus, the drain pipe will normally be full of water. The water in the drain pipe can create pressure which prevents the gravitational back flush water from exiting via the drain port of the filter housing during the gravitational back flush. However, when the drain pump is turned on, as described below, the one way valve will open due to the pressure drop caused by the drain pipe. The drain pump flow then draws the lint laden water from the filter to the drain.

[091] Mounting blocks 4.042, 4.044 are provided for mounting the filter

arrangement, for example, to the base of the outer bowl. The one way valve 4.040 is normally biased closed. The valve permits free flow of water out of the filter via outlet port 4.034 when the drain pump 4.016 is operating so the pressure in the filter housing is greater than the pressure on the drain pump side of the valve element. However, the one way valve is designed so that, in the recirculation mode when the recirculation pump is operating, the pressure in the filter housing is lower than the external pressure impinging on the valve element on the drain side of the valve element, so the valve is closed.

[092] Preferably, the one way valve is located close to the drain pump inlet. This helps to reduce circulation of air and water through the pump when close to empty.

[093] Figure 19 illustrates a modification of the system of Figure 4, in which the oneway valve 19.040 is located at the outlet of the drain pump 19.016. The flush can be of sufficient volume to ensure that minimal lint is left on the washing machine side of the oneway vale or in the pump. Placing the one-way valve on the outlet side of the drain pump helps to prevent lint removed from the tank from returning to block the drain pump.

[094] Figures 5, 6, and 7 illustrate the water flow through the filter during

recirculation, flush, and drain operations respectively. Flow from port 7.032 to port 7.034 is described herein as "downstream'' flow. Figure 8 is a chart illustrating the operation of a washing machine according to an embodiment of the invention.

[095] Washing machines include programmable controllers or processors to implement a number different wash cycles. The controller or processor can be programmed to implement a method of flushing a filter according to an embodiment of the invention. In the chart of Figure 8, the solid line intervals such as 8.058 indicate the operation of the recirculation pump, the dashed line pulse 8.060 indicates the drain pump flush pulse, and the intervals such as 8.059 between the recirculation pump operations indicate gravitational flush periods. As shown in Figure 8, a number of gravitational reverse flushes 8.059 precede a single pulsed flush 8.60. One or more of such combinations of gravitational reverse flushes with a single pulsed flush can be incorporated into a wash cycle. The back flush pulses can be of varying duration as shown in Figure 8, where the duration decreases progressively from 7.3 seconds to 4 seconds. The drain pump operation can overlap with the reverse flush pulse by a time period T ₀ , as shown at 8.061. [096] In one mode of operating the system, illustrated in Figure 8, the drain pump operating pulse can overlap with the recirculation pump operation.

[097] As shown in Figure 5, during recirculation, the recirculation pump operates to draw water from the bowl drain (arrow 5.050) through filter inlet port 5.032 and out of the recirculation port 5.036 (arrow 5.056), the water passing through the filter mesh as indicated by the arrows in the filter housing. The operation of the recirculating pump results in a reduction in hydrostatic pressure inside the filter housing, and thus serves to hold the one way valve 5.040 at drain port 5.034 closed.

[098] Figure 6 illustrates the filter gravitational flush mode. Immediately before the gravitational flush, the recirculation pump is operating, so the recirculation pipe is full of water. As soon as the recirculation pump is turned off, the water in the recirculation pipe begins to flow back through the recirculation port 6.036, as indicated by arrow 6.057. This causes water to be forced into the filter through the filter element mesh as indicated by the arrows inside the filter housing. This causes water to flow out of the filter inlet port 6.032 (arrow 6.051) because the hydrostatic pressure in the filter housing is determined by the height of the water in the recirculation pipe. Where the drain pipe extends to near the top of the washing machine, the water will not flow out of the filter drain port 6.034 because the drain pipe is at about the same height as the top of the recirculation pipe and will thus provide about the same hydrostatic pressure. In addition, the pressure from the drain pipe will prevent the one way valve from opening. Flow 6.051 stops when the level of the water in the recirculation pipe matches the height of the water in the tub, unless previously terminated by resumption of the recirculation process.

[099] As shown in Figure 8, the reverse gravitational flow is maintained for a time period (e.g., about 1 second) to dislodge the lint and solids collected on the inside of the filter element. The reverse flow can be varied according to the washing machine model and the size of the chamber. Preferably, the reverse gravitational flow is at an increased flow rate in the reverse mode to provide a strong pulse of water flow of short duration in the reverse direction to assist in dislodging the lint and solids in the filter element. We have found that a reverse flow of about 40 l/min for a duration of about 0.6 seconds provides adequate results.

[0100] Preferably, the drain pump pulse is turned on short time before the

recirculation period is turned off. For example, in one embodiment, the drain pump can be turned on approximately 0.1 to 0.2 seconds before the recirculation pump is turned off. This ensures that the lint is retained in the filter for discharge via the drain pump.

[0101] For a height differential between the top of the recirculation pipe and the water in the bowl of 500 mm, and a minimum diameter of 24 mm in the recirculation path, a peak reverse flow of 60 l/m is possible. This flow rate drops off as the height of the water in the recirculation pipe falls.

[0102] We have found that providing the recirculation pipe with additional storage at its upper end improves the operation of the back flush process.

[0103] In one embodiment, a reservoir or chamber 2.0 9 can replace the enlarged diameter tube to provide a larger volume of water for back flushing. The chamber can be located near the upper rim of the wash bowl so the additional water provides sufficient pressure to maintain the back flush flow rate above a required minimum, for example, 40 l/min.

[0104] As a result of the reverse flow pulse during the gravitational flush operation, the lint and solids collected by the filter mesh are displaced into the pipe connecting the bowl drain to the filter at port 6.032.

[0105] One or more gravitational reverse flush operations can be carried out before a drain pulse 8.060 is initiated. This can result in some of the lint and solids dislodged from the filter being returned to the bottom of the bowl.

[0106] When the drain pulse flush is initiated by running the drain pump for a short interval, the water in the drain pipe from the bowl is drawn into the filter via port 7.032 and out through outlet port 7.034, taking the lint and solids with it. Because the one way valve 7.040 is located proximate or adjacent the end of the filter element, little or no lint and solids discharged via the filter outlet port 6.034 can re-enter the filter.

[0107] We have found that, the orientation of the one way valve can also influence performance. For example, orienting the one way valve with the attachment at the top of the valve provides satisfactory operation.

[0108] In addition, we have found that the orientation and location of the filter arrangement can influence performance of the system, and different configurations may be suited to different conditions. For example, where the filter housing is oriented with its axis between the intake port and the outlet port is vertical, hard granular material such as sand will pass easily through the filter. On the other hand, we have found that where the filter is oriented with its axis horizontal, satisfactory performance in most circumstances is achieved. With the drain pump exit facing upwards and the one way valve of Figure 9 between the filter and the drain pump, with the valve flap hinge at the top, excellent performance was achieved without cavitation noise.

[0109] ^' Figures 9, 10, & 11 show a one way valve having a valve seat body 9.068 which is of cylindrical construction with a through bore 9.072 resiliency closed by one way valve element 9.070. The valve element has a truncated triangular shape with a rounded free end 9.071 and a rounded attached end 9.069. The valve element is made of a suitable resilient material, such as neoprene rubber or any other suitable polymeric or other material. The valve seat includes threaded holes such as 9.076 for attachment to a second valve housing member 11.080 which includes an attachment flange 11.086 fitted with through holes for the attachment screws to be inserted into the threaded screw holes 9.076. As seen in Figure 10, the valve seat body includes a stepped rim 10.074 in which the valve element 10.070 is located. The second valve housing member 11.080 has a complementary stepped projection 11.084 adapted to fit into the stepped recess 10.074. A seal can be seated in the stepped projection. The second valve housing member 11.080 has an internal bore 11.082 which is larger than the bore 10.072 so that the valve element 10.070 is captured in the interface between the two housing members. The valve element can pivot from its fixed end into the larger bore 11.082 when the pressure on the upstream side (the side facing bore 10.072) is greater than the pressure on the downstream side (the side facing bore 11.082). The valve element 10.070 can be resiliently biased to the closed position shown in Figure 10. Thus, when the pressure in bore 10.072 is sufficiently greater than the pressure in the bore 11.082, the valve element 10.070 will open.

[0 0] A significant feature of the design of the valve is that the "hinge" at 9.069 is spaced from the rim of the through-hole 9.072 as shown at "D". This contrasts with conventional one way flap type valves where the flap is a disc hinged at the rim of the bore. Such conventional valves are quickly disabled by the accumulation of lint around the hinge. The spacing of the hinge portion from the rim of the hole prevents the build up of lint around the hinge. In addition, the flap of the present embodiment is clamped at its widest dimension, so there is nowhere for the lint to collect.

[0111] An alternative one way valve design is shown in Figure 12. The valve 12.088 is made of a suitable pliable, resilient material, such as neoprene rubber or other suitable polymeric material or combination of materials. It has a substantially cylindrical body 12.090 with a tapered front end 12.092 with an aperture 12.094, biased to the closed position as shown. When the upstream pressure (the cylindrical body side of the aperture) is sufficiently greater than the downstream pressure, the aperture opens.

[0112] Figure 13 illustrates a known irrigation filter 13.102 having seals 13.104,

13.106 and a filter element 13.112 illustrated as a mesh. The filter has a through bore 13.114.

[0113] The filter element is constrained by ribs 13.108 and uprights 13.1-10. The ribs and uprights may have a flat, rectangular section. Typically the ribs and uprights have rough edges which act as initiators for lint accretion. Such a filter may work satisfactorily for light loads, eg, 3 kg, but are inadequate for heavy loads due to the rapid accumulation of lint. We have found that the ribs and uprights can act to accelerate the accretion of lint in the filter and to inhibit cleaning of the filter by reverse flushing.

[0 14] Accordingly, there is provided a filter as shown in Figure 14 having a self supporting mesh 14.120 without constraining ribs and uprights. The filter has end seals 14.104, 14.106 and a through bore 14.114. The mesh can be, for example stainless steel. The mesh can be between 80 micron and 600 micron.

[0115] We have found that mesh between 100 micron and 500 micron provides satisfactory performance.

[0116] In an alternative arrangement shown in Figure 15, the filter can have streamlined ribs and uprights, for example the ribs and uprights can have a rounded cross- section. Additionally, with a sufficiently strong mesh, fewer ribs and uprights can be used. As shown in Figure 15, there are only two ribs 15.122, and each rib has its own truncated upright such as 15.124.

[0117] Figure 16 is a flow diagram illustrating the reverse flush and drain process according to an embodiment of the invention.

[0118] At step 16.202, the user selects the wash cycle, and then the machine weighs the dry load at 16.204 and determines the amount of water to be used at 16.206. Then the wash cycle commences at 16.208. The recirculation pump is run to bring the level of Water in the outer bowl to the empty level and agitation then starts at 16.210. The recirculation pump has a greater flow rate than the flow rate between the spin bowl and the outer bowl. The presence of clothes in the spin bowl inhibits the flow rate from the spin bowl to the outer bowl. During agitation, the recirculation pump is run for a number of pulses (N) with intermediate periods when the recirculation pump is switched off at step 16.212. The number of pulses N of the recirculation pump can be adjusted according to the washing machine model and the chamber size. The number of pulses can be varied according to the particular mode of operating, eg, short wash cycle or long wash cycle, etc. The duration of the pulses can vary depending on factors such as the weight of the load or the selected cycle. The period for which the recirculation pump is switched off can be, for example, 1 second. The number of pulses of the recirculation pump operation is counted at 16.214 and when the programmed number N is reached, the drain pump is initiated with overlap T ₀ at the end of the N* pulse (step 16.216). In this embodiment, the start of each recirculation pulse is counted so the drain pump operation can be initiated within the N ^m pulse. In this

embodiment, to simplify the timing of the drain pump operation, the N" ¹ pulse is set at a predetermined pulse period independent of the preceding (N-1) pulses. For example the N** ¹ pulse can be equal to the minimum pulse period, for example, 4 seconds. The drain pump is initiated a period T ₀ before the end of the N* recirculation pump pulse. The duration of T ₀ can be, for example 0.1 seconds. The drain pulse period T _D can be, for example, 0.8 seconds. At step 16.218 the controller checks whether the number (M) of recirculation/drain cycles (P _R ) has been completed, and then moves to the post-wash operations at 16.220.

[0119] The time for each pulse can be calculated from the following:

Rmin + (R<**(N-1)), R _mjn + (Rc _h *(N-2)), R _min + (Rc _h *(N-3)), ... R _min + (Γ¾,*(Ν-Ν)).

[0120] The flow diagram of Figure 16 illustrates the following steps:

Step 1 - select the wash cycle 16.202;

Step 2 - weigh load 16.204;

Step 3 - supply water 16.206;

Step 4 - start wash cycle 16.208;

Step 5 - run recirculation pump to bring water level in outer bowl to empty & start agitation 16.210;

Step 6 - during agitation run recirculation pump for N pulses with back flushes 16.212;

Step 7 - have N cycles of recirculation/gravity back flush occurred? (if NO, return to 16.212), (if YES, continue to 16.216) 16.214;

Step 8 - In run drain pump for T _D with overlap T ₀ 16.216;

Step 9 - has the wash cycle completed? (If NO, return to 16.212. If Yes continue to 16.220; Step 10 - continue post-wash actions.

_,

16

Table 1 shows examples of suitable parameters for various loads.

Where:

Rmin (s) = RSB on time minimum;

N = RSB on-off pulses before drain;

Rch (s) = time differences between consecutive RSB pulses; Rmin+Rch (N-1), Rmin + Rch(N-2) Rmin + Rch (N-N);

Roff = RSB off time;

C (s) = drain on time;

overlap = Overlap time between RSB on and Drain on.

[0121] The table illustrates, by way of example, a mode of operation according to an embodiment of the invention in which Rch varies inversely with the load. That is, for heavier loads, Rch is less than for light loads. While the other parameters are shown as fixed in this example, they can be varied in different selectable wash cycles. When agitation is finished, the machine pauses until the water in the outer bowl rises to settle level, and then the drain pump starts. This process is added because, depending on the design, the spin bowl holes can be obstructed. This delays the flow of water from spin bowl to the outer bowl. Without this delay, there will be too much water left in spin bowl which may result in suds lock when the motor spins at high speed.

[0122] Because the inlet of drain pump is horizontal, an air lock may form in the pump which will effect to efficiency of draining. Shortening the "on" time will help to get rid of air lock in the drain pump while water in the outer bowl increases rapidly at high speed spin. This process assists in avoiding suds lock.

[0123] Figure 17 illustrates an exploded view of an embodiment of the filter system according to an embodiment of the invention adapted for mounting on the case of the washing machine. The wall mount 17.180 is adapted to be attached to the wall of the machine case at an aperture around the edge of which the attachment flange 17.184 is used to attach the wall mount. The wall mount has a rear aperture 17.186 to which the filter system can be sealingly attached. Details of the sealing arrangement are well known to the person skilled in the technology and are not illustrated. The arrangement is adapted to enable the filter to be removed for periodic cleaning. A watertight closure 17.176 is provided to close the end of the filter arrangement in a known manner. The filter is modified by the addition of an extension 17.174 so the filter can be set back in the filter housing while providing an inlet opening 17.172 for the bowl drain inlet 17.032. The filter and extension can pass through the aperture 17.186 in the wall mount so the filter can be located in the filter housing 17.010 with the inlet port 17.032 aligned with aperture 17.172. The closure seals the end of the assembled filter and filter housing.

[0124] The self cleaning filter system of Figure 17 has the filter oriented in a substantially horizontal orientation. The recirculation pump 17.056 supplies the recirculation pipe connection 17.104, which has its exit point at the highest level in order to avoid air entrapment. Air can freely exit the system during operation. The recirculation pipe connection can be inclined to facilitate the layout of the recirculation pipe.

[0125] The drain pump 17.016 feeds the drain outlet 17.034. The one way valve

17.040 is mounted adjacent the drain pump.

[0126] Figure 18 is a flow diagram illustrating a method of operating a self-cleaning filter system according to an embodiment of the invention. The process follows the normal process of loading clothes in the machine, 18.130, weighing the load 18.132, adding the appropriate amount of water 18.134, and commencing the selected wash cycle 18.136. The recirculation pump is run intermittently, as exemplified in Figure 8, a detailed by way of example in steps 18.140 to 18.162.

[0127] The flow chart of Figure 18 illustrates the following steps: Step 1 , 18.130 - load articles into bowl & select wash cycle;

Step 2, 18.132 - weigh load;

Step 3, 18.134 - supply water;

Step 5, 18.136 - start wash cycle;

Step 6, 18.138 - run recirculation pump with reverse flush;

Step 7, 18.140 - check if the drain pump operation is due (recirculation pulses P _R = N). [(If NO check if recirculation pulse period has expired.

If NO return to 18.138.

If YES, continue to 18.146);

(lf YES (pR = N ), go to 18.150;

If NO, go to 18.142)];

Step 8, 18.146 - check if reverse flush time T _f = F. If NO, return to 18.138. If Yes, go to 18.148.

Step 9, 18.148 - check if the total number of recirculation pump pulses equals the total number of those pulses for the selected wash cycle P _R = W. If NO, return to 18.138. If YES, go to 18.152;

Step 10, 18.150 - Check if the recirculation pump/drain pump overlap commencement is due T _R = (R- T ₀ );

Step 11, 18.152 - run drain pump;

Step 12, 18.154 - check recirculation pump duration T _R = R. If NO, return to 18.152. If YES, go to 18.156;

Step 13, 18.156 - turn recirculation pump off;

Step 14, 18.158 - check drain pump duration T _D = Y. If NO, return to 18.152. If YES, go to 18.160;

Step 15, 18.160 - turn drain pump off;

Step 16, 18.162 - check if f total recirculation pulses complete P _R = W. If NO, return to 18.138. If YES, go to 18.164.

Step 17, 18.164 - post-wash operations.

[0128] The following parameters are used in the flow chart of Figure 18: T _R = recirculation pulse lapsed time

T _F = back flush lapsed time

T _D = Drain pump lapsed time

P _R = recirculation pump count

N = no. of gravity back flushes between drain pump operations

M = no. of drain cycles selected

W = total no. of back flushes selected

Y = drain pump burst period

F = back flush period

R = recirculation burst period

T ₀ = pump overlap

[0129] The specific wash cycle can determine one or more of the wash cycle parameters. For example, the number of gravity back flushes N between drain pump pulses, the number of drain cycles M for the selected wash cycle, the total number of gravity back flushes W for the wash cycle. Other parameters may be standard for each wash cycle, for example, the duration of the back flush F, the duration of the drain pump pulse Y, the recirculation period R between gravity back flushes, the time relationship between the drain pump and the recirculation pump operation, eg, overlap period X. The control means includes counters and timers to monitor the various operational parameters of each selectable wash cycle. The counters are re-settable after each process or sub-process as required during a wash cycle.

[0130] At step 18.140, the processor checks the number of recirculation pump operations P _R against the number N required between drain pump operations for the selected wash cycle. If P _R < N, the processor continues running the recirculation pump with gravity back flushes, checking the recirculation pump operating time Tr at 18.142, and turning the recirculation pump off when the recirculation period R has been achieved. The recirculation pump is then turned off at 18.146 for the gravity back flush period F. When the back flush period expires, the processor checks that the total number of back flushes W for the selected cycle have been implemented at 18.148. If not, the process s returned to step 18.138.

[0131] If the number of back flushes for the selected wash cycle has been completed, the process diverts to the drain pump path. [0132] At step 18.1 0, if the number of recirculation pump operations equal N, the drain pump pulse is initiated.

[0133] At step 18.150, the processor checks that the overlap time X (the time the drain pump is turned on before the recirculation pump is turned off) has occurredj and turns the drain pump on at 16152. The processor checks for the recirculation pump period R at 8.154. When the period R has expired, the recirculation pump is turned off at 18.156.

[0134] At 18.158, the processor checks the operating period Y of the drain pump, and turns the drain pump off at 18.160. At 161.12, the processor then checks if any more drain pump operations are required, and, if so the control of the operation passes to the recirculation cycle at 18.148. If the number of drain pump operations has been completed, the processor will then proceed with the remainder of the wash cycle, eg, rinse, and spin at 18.164.

[0135] Figure 20 illustrates an alternative filter arrangement, in which a three port filter housing 20.030 has a first port 20.032 and a second port 20.034 on a first side of a filter element 20.038, and a third port 20.036 on the opposite side of the filter element. The element in this case is shown as a flat filter with a mesh arranged in a frame 20.039. The filter mesh can be made to have a degree of "play" (i.e., the area of the mesh can be slightly larger than the filter frame 20.039) so that, when the flow through the filter element is in the forward or recirculation direction (port 20.032 to port 20.036), the filter mesh will deflect in the direction of the recirculation flow, while in the reverse flush direction (from port 20.036 through the filter element 20.038, the filter mesh can deflect in reverse flush flow direction.

[0136] The self cleaning filter can also be used where a drain pump is not used and the drain action is performed by gravity. In this case, the drain pipe does not extend to the top of the bowl, but may be entirely below the base of the bowl. An electro-mechanical valve closing the drain outlet in place of the one way valve can be provided to control the drain pulse operation. The electro-mechanical valve can be opened to perform the back flush operation. As there is no drain pump, the overlap between the drain pump operation and the recirculation pump is not performed in this embodiment. However, the recirculation pump can be turned on before the top of the back flush water falls to the level of the water in the tank, and the electro-magnetic valve can be turner off after the recirculation pump is turned on to provide an overlap between the back flush operation and the start of the recirculation pump.

[0137] In the above description the mesh material is described as being made from metal such as stainless steel. However, it will be understood that the mesh can be made from any appropriate material including metals: such as brass, stainless steel, copper or appropriate alloys; plastics or polymers: such as polyester, polypropylene; nylon or other appropriate polymer; Organics: such as wool; Inorganics such as synthetics or other fibres. The method of manufacture can include weaving, injection moulding, casting or other forming and or fabricating techniques, as appropriate.

[0138] In a further embodiment, the recirculation pump can be a reversible pump, and can be run in reverse during at least one back flush operation until the water in the recirculation pipe is emptied. In particular, the recirculation pump can be run in reverse during the drain phase of the washing operation.

[0139] The invention also permits loads size to be increased by washing heavy lint producing articles such as towels, flannel sheets, flannelette sheets etc, with other items, instead of the current recommendation which is to wash these separately. This may also reduce the number of loads per week.-

[0140] In this specification, terms indicating orientation or direction, such as "up",

"down", "vertical", "horizontal", "left", "right" "upright", "transverse" etc. are not intended to be absolute terms unless the context requires or indicates otherwise. These terms will normally refer to orientations shown in the drawings.

[0141] Where ever it is used, the word "comprising" is to be understood in its "open" sense, that is, in the sense of "including", and thus not limited to its "closed" sense, that is the sense of "consisting only of. A corresponding meaning is to be attributed to the

corresponding words "comprise", "comprised" and "comprises" where they appear.

[0142] It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text. All of these different combinations constitute various alternative aspects of the invention.

[0143] While particular embodiments of this invention have been described, it will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. The present embodiments and examples are therefore to be considered in all respects as illustrative and not restrictive, and all modifications which would be obvious to those skilled in the art are therefore intended to be embraced therein.

[0144] Numerals included within parentheses in the accompanying claims are intended to assist understanding of the claims and should not be construed in any way to limit subject matter claimed by these claims.