WO2002048445A1

WO2002048445A1 - Washing machine having re-circulation path for washing fluid including sub-micron filter

Info

Publication number: WO2002048445A1
Application number: PCT/GB2001/005561
Authority: WO
Inventors: Michael Graham Reid
Original assignee: Monotub Industries, Plc
Priority date: 2000-12-14
Filing date: 2001-12-14
Publication date: 2002-06-20
Also published as: GB0030521D0; AU2002219321A1

Abstract

Washing machine including a re-circulation path along which washing fluid passes from the washing chamber (9) to be returned to the washing chamber (9). The path includes a filter (3) having pores with an average size of less than 1 νm for removal of small particles including bacteria and zeolites. Preferably, a bypass path is provided for bypassing the sub-micron filter (3), the bypass path preferably including a filter having a coarse pore size.

Description

WASHING MACHINE HAVING RE-CIRCULATION PATH FOR WASHING FLUID INCLUDING SUB-MICRON FILTER

Most washing machines comprise a water tank within which is mounted a clothes-containing drum. In use, the required amount of water is provided to the water tank, and the washing cycle commenced. When the washing phase is completed, the water is drained from the water tank. Fresh water is typically then introduced to the water tank to rinse the items in the clothes- containing drum.

In some washing machines, it is known to provide a re-circulation path for the washing water. In this case, the water may be drained from the water tank during the washing phase, and may then re-enter the washing tank during the washing phase. The water re-entering the water tank may be sprayed into the water tank, thereby assisting with the washing. In some such re-circulation systems, a coarse filter is provided to remove particles of dirt or fluff from the items being washed. In re-circulation systems, a water heater may be provided in the sump below the water tank, or elsewhere in the re-circulation path to heat the water before this is reintroduced.

It is increasingly common for clothes and other items to be washed at low temperatures, such as at 40°C. This is possible due to improved detergents. However, at these temperatures, many bacteria are not killed. It is therefore possible that bacteria from one wash load may contaminate items in subsequent wash loads. It is therefore recommended that high temperature washes be carried out regularly to kill any bacteria in the washing machine. However, this recommended practice is not always followed.

A further problem with conventional washing machines, especially when using modern detergents, is that some elements of the detergent may remain in the washed items despite rinsing, and these elements may cause an allergic reaction when the items come into contact with skin. These particles include zeolites that are provided to soften the washing fluid.

According to the present invention, a washing machine includes a washing chamber for containing items to be washed, a re-circulation path along which, in use, washing fluid may pass from the washing chamber and be returned to the washing chamber, the re-circulation path including a filter having pores with an average size of less than 1 μm.

The inclusion of a filter with sub-micron pores allows for the filtering out of microscopic particles, including bacteria and small particles from the washing detergent that may cause an allergic reaction. For all re-circulating fluid to pass through the sub-micron filter, a large capacity high-pressure pump would be required for all fluid to pass through the sub-micron filter at a sufficiently high rate. Further, the filter would need to have a large area to avoid the filter becoming quickly blinded by the particles in the fluid. It is therefore preferred that the re-circulation path includes a bypass path for bypassing the filter. This allows some or all of the re-circulated fluid to bypass the sub-micron filter.

It is preferred that the bypass path includes a second filter, having an average pore size greater than 1 μm, and preferably having an average pore size greater than 0.5 mm. In this way, large particles are removed from the fluid passing along the bypass path, in the manner that particles are removed from the fluid in a conventional washing machine. The particles removed by the second filter do not pass to the sub-micron filter.

It is preferable to include such an additional filter, as this will remove larger particles that may otherwise block the sub-micron filter. Whilst a second filter with relatively large particles will not remove bacteria and other microscopic particles from the fluid, where a portion of the washing fluid passes through the sub-micron filter, the small particles will be removed from this portion, thereby reducing the overall concentration of such particles in the re-circulated fluid. Repeated recycling of the fluid, with at least part of the fluid passing through the sub-micron filter, will continually decrease the overall concentration of microscopic particles from the fluid.

Preferably less than 20% of the re-circulated fluid, and more preferably about 10% of the re-circulated fluid, passes through the sub-micron filter on each pass along the re-circulation path.

Advantageously, the proportion of re-circulated fluid that passes through the sub-micron filter and that which bypasses the sub-micron filter is regulated. The regulation may be pre-set so that the same proportion of fluid is passed through the sub-micron filter on each pass. In this case, the control or regulation may be achieved merely by selecting the appropriate diameter of the pipes for passing the fluid through the sub-micron filter and through the bypass path. Alternatively, the proportion of fluid passing though the sub- micron filter and through the bypass path may vary using a regulator. In this case, the regulator may comprise a valve and/or a pump. The regulator is preferably controlled by a controller, which may be in the form of control electronics, for example a microprocessor. Where the bypass path includes a large pore filter, it may be advantageous initially to pass all or a high proportion of the fluid through the large pore filter to remove larger particles from the fluid which would easily clog the sub-micron filter, and then, on subsequent passes of the fluid, passing this through the sub-micron filter to remove the sub-micron particles. Alternatively, the proportion of the fluid passing through the sub-micron filter may be progressively increased on each pass, thereby removing a greater proportion of the remaining particles entrained in the fluid on each pass.

Beneficially, the washing machine includes a system for cleaning the sub-micron filter. The system preferably comprises a system for back flushing, thereby removing the particles collected in or on the sub-micron filter, and for dispelling the flushing fluid and the particles removed from the filter. This system may comprise a reversible pump that, in normal operation, draws fluid from the washing chamber through the filter and back to the chamber, but which is reversed to back flush and clean the filter. Alternatively, water from the water inlet may be used to flush the filters. This is advantageous as mains water is usually provided at high pressure, and therefore it may not be necessary to provide an additional pump to force the fluid through the filter to backwash this. Preferably, where a second filter is provided in the re-circulation path, this filter is also cleaned.

According to a second aspect of the present invention, a method of operating a washing machine according to the first aspect of the present invention includes the step of initially passing all or a high proportion of the fluid through the large pore filter to remove larger particles from the fluid which would easily clog the sub-micron filter, and then, on subsequent passes of the fluid, passing this through the sub-micron filter to remove the sub-micron particles. Alternatively, the proportion of the fluid passing through the sub-micron filter may be progressively increased on each pass, thereby removing a greater proportion of the remaining particles entrained in the fluid on each pass.

Examples in accordance with the present invention will be described with respect to the accompanying drawings, in which:

Figure 1 shows a schematic view of a first example of a washing machine;

Figure 2 shows a schematic view of a second example of a washing machine; and

Figure 3 shows a schematic view of a third example of a washing machine.

In the example shown in Figure 1 , the washing machine includes a fixed water tank 1 within which is provided a perforated, rotatable, clothes-containing drum 9. Washing fluid, typically water, is introduced into the tank 1 through an inlet 5, and passes through the perforations in the sidewall of the drum 9 to wet clothes contained in the drum 9. The drum 9 rotates to agitate the clothes in the water contained therein. Other arrangements for washing machines are known, for example as disclosed and claimed in our earlier International Patent Application W098/21393. This discloses a washing machine having a single, inclined, rotatable clothes-containing drum into which water is introduced directly, for example through channels extending along the inside of the drum. The water is collected and expelled from the rear of the drum, without requiring a separate, fixed, water tank. Other types of washing machine fall within the scope of the present invention.

A sump 4 is provided below the tank 1. A drain 7 is connected to the sump 4 for draining water from the tank 1 at the end of the washing cycle. A valve can be provided in the drain outlet 7 to control the draining of water. A re-circulation path is provided, along which the washing fluid can pass from the sump 4 before being returned to the tank 1. As shown in the example in Figure 1 , from the sump, the re-circulation path passes through a heater 6 and a re-circulation pump 8, and then splits into two. One path passes from an upstream to a downstream side of a filter 2 having pores of about 0.5 to 4 mm average diameter. The other path passes from an upstream to a downstream side of a sub-micron filter 3, namely a filter in which the pores have a minimum dimension of less than 1 μm. Downstream of the filters 2,3 the two paths converge, and pass back to the water tank 1.

In operation, water is introduced into the water tank 1 through the inlet 5. The washing cycle may then commence. Thereafter, the re-circulation pump 8 is activated to draw washing fluid from the water tank 1 , through the heater 6 in which the water is heated, and through the filters 2,3 before returning this to the water tank 1. Due to the larger size of the pipe leading to the filter 2 compared to the pipe leading to the sub-micron filter 3, a greater proportion of the re-circulated fluid passes through the filter 2 than through the sub-micron filter 3. Typically, approximately 10% of the re-circulated fluid will pass through the sub-micron filter 3, with the remainder passing through the large pore filter 2.

Large particles suspending in the fluid will be removed from the fluid passing through the filter 2. These particles will include fluff and dirt from the items being washed. However, particles smaller than the pores in the filter 2 will not be removed from the fluid, and these will continue to be reintroduced to the washing chamber.

The sub-micron filter 3 will remove all particles from the fluid that are larger than the small pore size of the filter 3. This will include bacteria and small components of the detergent, as well as larger particles such as dirt and fluff. The components of the detergent removed will include zeolites designed to soften the water. Therefore, from the fluid passing through the sub-micron filter 3, most particles, including small particles, will be removed.

By passing 10% of the fluid though the sub-micron filter 3 to remove bacteria and other small particles, on each cycle of the washing fluid through the recirculation path, approximately 10% of the remaining small particles will be removed. It will therefore be appreciated that the overall concentration of particles in the washing fluid will be reduced as the fluid is repeatedly recycled. However, as a large proportion of the fluid passes through the large pore filter 2, most of the larger particles in the fluid will be removed by the large pore filter 2, and therefore will not block the sub-micron filter 3. This is important as the smaller pore size of the sub-micron filter 3 means this is more susceptible to blockages.

As noted above, the particles removed by the sub-micron filter 3 will include zeolites provided to soften the water used to wash the clothes. Whilst this may be considered undesirable, since the zeolites are removed from the washing chamber, this is in fact advantageous. The zeolites may cause an allergic reaction if these remain on the washed clothes, and therefore it is advantageous that they be removed. However, the zeolites will already have acted to soften the water before they are removed.

In the example shown in Figure 1 , the relative proportion of re-circulated fluid passing through each of the filters 2, 3 remains constant. However, in an alternative example, a proportioning control valve (not shown) may be provided to control the relative amount of fluid passing through each of the filters 2, 3. Alternatively, or additionally, a pump (not shown) may be provided in one or both of the paths to the filters 2, 3 to control the amount of fluid passing through each filter 2, 3. In either case, the relative amounts of fluid flowing through each filter 2, 3 may be controlled. For example, the amount of fluid flowing through each filter 2, 3 may be pre-set to any desired level. Alternatively, or additionally, the relative fluid flows may be varied during the cycle. In one example, the fluid initially flows primarily or exclusively through the large pore filter 2 to remove many of the large particles from the fluid. Then, a greater amount of fluid can be passed through the sub-micron filter 3. Since many of the large particles have been removed, there are fewer large particles to block the sub-micron filter 3. The amount of fluid passing through the sub-micron filter 3 may progressively be increased in subsequent cycles of the fluid. The control of the proportioning control valve or pumps may be achieved through suitable control electronics, for example by a microprocessor.

A further example of the present invention is shown in Figure 2. In this example, the normal re-circulation path from the sump 4 passes through the heater 6, the re-circulation pump 8, along pipe 20 to a proportioning valve 11 where the fluid flow branches into two paths 22, 23 through the filters 2, 3. The re-circulation path passes back to the water tank 1 along pipe 21 , via a control valve 12. The water inlet 5 passes through an inlet valve 10 into the re-circulation path.

In use, the inlet valve 10 and control valve 12 are opened, and water is fed in through the inlet 5. The water passes through the re-circulation pipe 21 and fills the water tank 1. To assist this, the proportioning valve 11 may be controlled to prevent fluid flow through the filters 2,3. When the required amount of water has been added to the water tank 1 , the inlet valve 10 is closed, and the washing Gycle commences. As described with respect to the first example, water from the water tank 1 is re-circulated through the filters 2, 3 to be returned to the water tank 1. During this re-circulation, the relative flow of fluid through the filters 2, 3 is controlled by control of the proportioning valve 11. As described with respect to the previous example, this control can be achieved through suitable control electronics. As an alternative, or in addition to, the proportioning valve 11 , pumps (not shown) may be provided to control the flow of fluid through the valves 2, 3. The pumps may include a high-pressure pump for pumping fluid through the sub-micron filter 3, and a low-pressure pump for pumping fluid through the other filter 2. The filtered fluid is returned to the water tank 1 through the line 21 and valve 12.

When the washing cycle is complete, the drain valve 14 is opened, and the re- circulation pump 8 acts to pump the water from the sump 4 to the drain 7.

In the washing machine shown in Figure 2, it is possible to clean the filters 2, 3 by a backwash operation. In this case, the control valve 12 is closed, and the inlet valve 10 and drain valve 14 opened. Water is then fed from the inlet 5 and passes through the filters 2, 3 in a reverse direction. In this way, particles that have been constrained on or in the filters 2, 3 during the washing cycle are entrained by the water flowing through the filters 2, 3. The water with entrained particles is then drained though drain valve 1 and drain 7. Water cannot pass to the sump 4 or into the water tank 1 due to the pump 8. In this way, it is possible to clean the filters 2, 3 and therefore help these from becoming blocked or blinded.

In an alternative example, by the provision of suitable control valves, water from the sump 4 may be pumped by the pump 8 to the "downstream" side of the filters 2, 3, to flow in a reverse direction through the filters 2, 3 to backwash these. The fluid with entrained particles from the filters 2, 3 can then be drained through a suitable outlet. This avoids the need for using fresh water to clean the filters 2, 3, but will require additional control valves.

A further example of a washing machine is shown in Figure 3. This arrangement is similar to that of Figure 2, but with the proportioning valve 11 being replaced by a pump 31 in the path to the sub-micron filter 3. Control of the pump 31 will control the amount of fluid passing through the sub-micron filter 3. The pump 31 , which may be provided upstream or downstream of the filter 3 is of particular advantage during backwashing of the filter as this enables the fluid to be pumped through the filter at a high velocity to clean this. A further pump may be included in the bypass path containing another filter 2.

In the examples shown in the accompanying drawings, a large pore filter 2 is provided in a bypass path, bypassing the sub-micron filter 3. However, the large pore filter 2 may be omitted, allowing some of the re-circulated fluid to bypass the sub-micron filter 3. Bypassing of the sub-micron filter 3 is necessary since the maximum flow rate through the sub-micron filter 3 is too low for re-circulation of all fluid.

It is possible to omit the bypass path, provided other measures are taken to ensure the sub-micron filter does not become blocked too quickly. Such measures may include providing a large area sub-micron filter or a pre-filter of coarse pore size.

Claims

1. A washing machine including a washing chamber for containing items to be washed, a re-circulation path along which, in use, washing fluid may pass from the washing chamber and be returned to the washing chamber, the re-circulation path including a filter having pores with an average size of less than 1 μm.

2. A washing machine according to Claim 1 , further including a bypass path for bypassing the filter.

3. A washing machine according to Claim 2, in which the bypass path includes a second filter, having an average pore size greater than 1 μm.

4. A washing machine according to Claim 3, in which the second filter has an average pore size greater than 0.5 mm.

5. A washing machine according to Claim 1 , in which the re-circulation path is split into two paths connected in parallel, the first path including the first filter having pores with an average size less than 1 μm, the second path including a second filter having pores with an average size greater than 1 μm, the second filter arranged to remove particles from the fluid to prevent these passing to the first filter.

6. A washing machine according to any one of Claims 2 to 5, arranged such that, in use, less than 20% of the re-circulated fluid passes through the sub-micron filter on each pass along the re-circulation path.

7. A washing machine according to Claim 6, arranged such that, in use, about 10% of the re-circulated fluid passes through the sub-micron filter on each pass along the re-circulation path.

8. A washing machine according to any one of Claims 2 to 7, arranged such that, in use, a predetermined proportion of the re-circulated fluid is passed through the sub-micron filter on each pass.

9. A washing machine according to any one of Claims 2 to 8, including a regulator for regulating the proportion of re-circulated fluid that passes through the sub-micron filter and that which bypasses the sub-micron filter.

10. A washing machine according to Claim 9, in which the regulator comprises openings of predetermined relative size for the fluid in the path to the sub-micron filter and the bypass path.

11. A washing machine according to Claim 9, further comprising a controller arranged to control the regulator to change the proportion of fluid passing through the sub-micron filter and the bypass path.

12. A washing machine according to Claim 11 , in which the regulator includes a valve.

13. A washing machine according to Claim 11 or Claim 12, in which the regulator includes at least one pump.

14. A washing machine according to any one of Claims 11 to 13, in which the controller comprises control electronics, preferably a microprocessor.

15. A washing machine according to any one of Claims 11 to 14, in which the controller is arranged such that, in use, the proportion of re-circulated fluid passing through the sub-micron filter compared to that bypassing the sub- micron filter is initially low, and is subsequently increased.

16. A washing machine according to Claim 15, in which the proportion of re-circulated fluid passing through the sub-micron filter is arranged to be increased for subsequent cycles.

17. A washing machine according to any one of the preceding claims, further comprising a system for cleaning the sub-micron filter.

18. A washing machine according to Claim 16, in which the system for cleaning the sub-micron filter comprises a system for passing fluid in a reverse flow direction through the sub-micron filter, and for dispelling the flushing fluid and the particles removed from the filter.

19. A washing machine according to Claim 17, in which a pump is provided for re-circulating the washing fluid, the pump being reversible such that, in use, the flushing fluid comprises the washing fluid.

20. A washing machine according to Claim 17, in which the flushing fluid is provided to the washing machine through an inlet.

21. A washing machine according to any one of Claims 17 to 20, when dependent on Claim 4 or 5 or any claim dependent thereon, in which a system is provided for cleaning the second filter.

22. A washing machine substantially as shown in or as described with respect to any of the accompanying drawings.

23. A method of using a washing machine according to Claim 11 or any claim dependent thereon, including the step of initially passing all or a high proportion of the fluid through the large pore filter to remove larger particles from the fluid which would easily clog the sub-micron filter, and then, on subsequent passes of the fluid, passing this through the sub-micron filter to remove the sub-micron particles.

24. A method according to Claim 23, in which the proportion of the fluid passing through the sub-micron filter is progressively increased on each pass.

25. A method of using a washing machine substantially as described with respect to any of the accompanying drawings.