U.S. patent application number 12/672334 was filed with the patent office on 2011-08-18 for dishwasher,.
Invention is credited to Stefan Fueglein, Rolf Stahlmann.
Application Number | 20110197934 12/672334 |
Document ID | / |
Family ID | 38871562 |
Filed Date | 2011-08-18 |
United States Patent
Application |
20110197934 |
Kind Code |
A1 |
Fueglein; Stefan ; et
al. |
August 18, 2011 |
DISHWASHER,
Abstract
Dishwasher, comprising a first wash circulation system (7) with
a wash circulation pump (6) to circulate washing liquid from a sump
(5) to at least one spray device (3, 4) arranged in a wash tank
(2), wherein a second circulation system (10) comprising a further
pump and a filtration device (11) is provided to filter washing
liquid independently from actuation of the circulation pump (6) of
the first circulation system (7).
Inventors: |
Fueglein; Stefan; (Nuemberg,
DE) ; Stahlmann; Rolf; (Wolframs-Eschenbach,
DE) |
Family ID: |
38871562 |
Appl. No.: |
12/672334 |
Filed: |
July 16, 2008 |
PCT Filed: |
July 16, 2008 |
PCT NO: |
PCT/EP08/05802 |
371 Date: |
May 3, 2011 |
Current U.S.
Class: |
134/111 |
Current CPC
Class: |
A47L 15/4246 20130101;
A47L 15/4208 20130101; A47L 15/4221 20130101 |
Class at
Publication: |
134/111 |
International
Class: |
A47L 15/42 20060101
A47L015/42 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 8, 2007 |
EP |
07015582.5 |
Claims
1. Dishwasher, comprising a first wash circulation system with a
wash circulation pump to circulate washing liquid from a sump to at
least one spray device arranged in a wash tank, characterised in
that a second circulation system comprising a further pump and a
filtration device is provided to filter washing liquid
independently from actuation of the circulation pump of the first
circulation system.
2. Dishwasher according to claim 1, wherein the filtration device
comprises at least one of a micro fine filter and a fine
filter.
3. Dishwasher according to claim 2, wherein at least one filter of
the filtration device forms part of the wall of the wash tank.
4. Dishwasher according to claim 3, wherein a device for
backwashing the filter is provided in the wash tank.
5. Dishwasher according to claim 4, wherein the device for
backwashing the filter comprises nozzles located at the outwardly
facing ends of at least one spray arm.
6. Dishwasher according to claim 1, wherein the first circulation
system also comprises a filtration device.
7. Dishwasher according to claim 1, wherein one of an additional
filtration device and part of the filtration device is located in
the sump.
8. Dishwasher according to claim 1, wherein the further pump is the
drain pump.
9. Dishwasher according to claim 8, wherein a backflow valve is
provided upstream of the drain pump.
10. Dishwasher according to claim 8, wherein the second circulation
system comprises a sedimentation chamber located downstream of the
drain pump and having a micro fine filter in its upper part.
11. Dishwasher according to claim 10, wherein the dishwasher
comprises a junction having at least one inlet connected to the
outlet side of the drain pump and at least two outlets, wherein a
first outlet is connected to the sedimentation chamber and a second
outlet is connected to a drain tube for final drainage of washing
liquid.
12. Dishwasher according to claim 11, wherein a u-like bend of the
drain tube for finally draining washing liquid is located higher
than the sedimentation chamber of the second circulation
system.
13. Dishwasher according to claim 11, wherein a switch is provided
at the junction, wherein the switch is adapted selectively connect
at least the inlet and the first outlet and the inlet and the
second outlet.
14. Dishwasher according to claim 13, wherein an outlet in the
upper part of the sedimentation chamber is connected to the drain
tube such that an overflow for a completely filled sedimentation
chamber is formed.
15. Dishwasher according to claim 14, wherein the drain pump is
controllable to effect a tangential cleaning of the filter.
16. Dishwasher according to claim 14, wherein a backflow valve is
provided downstream of the outlet of the sedimentation chamber.
17. Dishwasher according to claim 13, wherein the junction
comprises a second inlet connected to an outlet in the upper part
of the sedimentation chamber such that an overflow for a completely
filled sedimentation chamber is formed and the switch can be
actuated so that the first inlet is connected to the first outlet
and at the same time the second inlet is connected to the first
outlet, and so that the first inlet is connected to the second
outlet.
18. Dishwasher according to claim 17, wherein the switch can
additionally be actuated so that the first inlet is connected to
the first outlet and at the same time the second inlet and the
second outlet are closed.
19. Dishwasher according to claim 1, wherein the further pump is an
additional pump.
20. Dishwasher according to claim 19, wherein the additional pump
draws washing liquid to be filtered from the sump.
21. Dishwasher according to claim 19, wherein the additional pump
draws washing liquid from an area of the sump separated by a fine
filter from which area also the circulation pump draws washing
liquid.
22. Dishwasher according to claim 20, wherein the outlet of the
additional pump is connected to an inlet located in the upper part
of a sedimentation chamber, wherein a part of the sedimentation
chamber's wall is formed as a micro fine filter, and the lower part
of the sedimentation chamber has an outlet connected to a feeding
tube leading from the sump to a drain pump, the backflow of washing
liquid from the sedimentation chamber to the sump being prevented
by a backflow valve.
23. Dishwasher according to claim 22, wherein a u-like bend of the
drain tube for finally draining washing liquid is located higher
than the sedimentation chamber of the second circulation
system.
24. Dishwasher according to claim 22, wherein a sensor device
adapted to sense a clogging of the filter is provided.
25. Dishwasher according to claim 24, wherein the sensor device is
a hydrostatic sensor.
26. Dishwasher according to claim 25, wherein the second
circulation system comprises a sedimentation chamber, wherein the
sensor is connected to the upper end of the sedimentation chamber.
Description
[0001] The invention concerns a dishwasher, comprising a first wash
circulation system with a wash circulation pump to circulate
washing liquid from a sump to at least one spray device arranged in
a wash tank.
[0002] In known dishwashers, washing liquid is normally drawn from
a sump at the bottom of a wash tank, pumped by a circulation pump
into spray arms distributing the wash liquid within the wash tank
to remove soils from dishes located in dish baskets in the
tank.
[0003] To prevent the redistribution of soil onto the dishes,
various filter devices are known. These filters separate soil out
of the circulating wash liquid. Two basic solutions are known in
the art.
[0004] In one solution, a filter screen or filter mesh is deposited
on the outlet side of the circulation pump. A fine filter or even a
micro fine filter can be used. However, the risk of clogging of the
filter exists. Typically, backwash jets are directed against the
filter in an attempt to clear the filter and prevent clogging.
However, to drive these backwash jets, the circulation pump itself
needs to be actuated so that the backwash jets work against a high
pressure so that cleaning may be incomplete. Additionally, behind a
clogged filter increasing pressure builds up so that soil is
pressed into the filter and embedding itself fixedly, so that it
cannot be easily removed.
[0005] Another known solution is to arrange a filter in the sump,
normally comprising a fine filter surrounding the final drain inlet
where only a coarse filter is provided. Backwashing or cleaning
filter is very complex and sophisticated in such a case, so that
usually no micro-fine filters are used. Water or washing liquid
passing the circumferential fine filter is recirculated again by
the circulation pump.
[0006] In general, filter clogging can adversely effect the
dishwashers cleaning ability, causing poor washability and
indirectly increased water and energy consumption.
[0007] An additional drawback of these filtering solutions is that
filtering and, if applicable, filter cleaning, all depend on the
actuation of the circulation pump. The design of the washing cycles
is therefore limited as the filtration process is not independently
controllable. Moreover, soil particles are recirculated through the
circulation system causing clogging not only of the filter
device.
[0008] It is therefore the object of the present invention to
provide a dishwasher with an improved filtration system essentially
obviating the aforementioned drawbacks of the state of the art.
According the present invention, such an aim is reached in a
dishwasher of the above mentioned type, wherein a second
circulation system comprising a further pump and a filtration
device is provided to filter washing liquid independently from
actuation of the circulation pump of the first circulation
system.
[0009] In the dishwasher according to the invention, a second
circulation system is provided, which is dedicated to the process
of filtering the washing liquid. The circulation pump of the first
circulation system and the further pump driving the second
circulation system can be controlled independently. Filtration and
filter cleaning no longer effect the washing cycle itself, so that
the freedom for cycle design is increased. Phases with 100%
filtration and/or 100% filter cleaning are now possible.
[0010] Additionally, less soil particles are depositioned in the
first circulation system, causing clogging or the like. The
separation of the circulation of the washing liquid and the
filtering also allows an improved dirt handling. Soil can be pumped
out of the dishwasher without actuating the circulation pump of the
first circulation system.
[0011] Another advantage of the current invention is that a flat
sump design can be achieved, since the filtration device no longer
needs to be positioned in the sump itself, as well as backwashing
devices. A reduction of the total water volume in the sump is
possible.
[0012] The filtration device can comprise a micro fine filter
and/or a fine filter. 100% micro fine filtering is now possible
without the risk of adversely effecting the dishwashers cleaning
ability.
[0013] Preferably, at least one filter of the filtration device
forms part of the wall of the wash tank. This filter can for
example be a filter screen or a filter mesh and is preferably a
micro fine filter. In this manner, a visible clue to the improved
filtering is given to the customer. Additionally, easy replacement
of the filter is possible and space is effectively used.
[0014] In such a configuration, a device for backwashing the filter
can advantageously be provided in the wash tank. In one variation,
the device for backwashing the filter comprises nozzles located at
the outwardly facing ends of at least one spray arm. The device for
backwashing the filter is preferably driven by the circulation pump
of the first circulation system, while the further pump is not
active. Cleaning of the filter forming part of the wall of the wash
tank can this manner be effected at the same time the dishes are
washed.
[0015] It is to be noted that in the dishwasher according to the
invention no high pressure needs to be built up against the filter
of the filtration device. If, for example, a micro fine filter
forms part of the wall of a wash tank, washing liquid containing
soil particles only needs to be pumped up at a pressure which
allows the washing liquid to run through the filter being part of
the wall of the wash tank. Consequently, minimal pressure is
exerted on the micro fine filter itself. Soil particles therefore
do not tend to be embedded into the filter and can for example
easily be backwashed by a device for backwashing the filter. This
contrasts be aforementioned state of the art, wherein the
filtration device is part of the first circulation system and is
subject to high pressure.
[0016] It is, however, possible that the first circulation system
also comprises a filtration device. Typically, this additional
filtration device will only comprise coarse filters and/or fine
filters, so that micro fine filtering remains the domain of the
second circulation system.
[0017] Such an additional filtration device or part of the
filtration device of the second circulation system may be located
in the sump. For example, the already known fine filter placed in
the sump can be used for the first as well as for the second
circulation system. In other embodiments, the additional filtration
device or the part of the filtration device located in the sump
only apply to the first or the second circulation system. Such an
additional filtration device, or part of the filtration device,
can, if assigned to the second circulation system, act as a
prefiltering stage for a micro fine filter, for example forming
part of the wall of the wash tank.
[0018] In a first embodiment of the invention, the further pump is
the drain pump. This means, the drain pump not only drives the
draining of water out of the dishwasher, but also the second
circulation system. Advantageously, no additional pump is needed in
this configuration. A control unit of the dishwasher may then
independently control operation of the drain pump so that either
draining or filtration/cleaning of the filter or the filters is
effected. To prevent the backflow of water containing soil
particles into the sump from the filtration device, a backflow
valve can be provided upstream of the drain pump.
[0019] Preferably, the second circulation system comprises a
sedimentation chamber located downstream of the drain pump and
having a filter, in particular a micro fine filter, in its upper
part. In this configuration, water is pumped into the sedimentation
chamber by the drain pump, at a pressure such that the water level
just reaches the filter arranged in the upper part of the
sedimentation chamber wall. The filter can, like already mentioned,
form a part of the wall of the wash tank. The soil particles, which
cannot pass the filter, remain in the sedimentation chamber. Once
actuation of the drain pump is stopped, due to the backflow valve,
washing liquid may remain in the sedimentation chamber and the soil
particles slowly begin to sediment, i.e. sink down to the bottom of
the sedimentation chamber, where they can be simply drained
away.
[0020] Washing liquid should not be drained through the
sedimentation chamber, because in this case it would simply flow
back into the wash tank through the filter. Therefore, the
dishwasher may comprise a junction having at least one inlet
connected to the outlet side of the drain pump and at least two
outlets, wherein a first outlet is connected to the sedimentation
chamber and a second outlet is connected to a drain tube for final
drainage of washing liquid. To prevent the draining of washing
liquid during filtration, a u-like bend of the drain tube for
finally draining washing liquid can be located higher than the
highest point of the second circulation system, in particular the
sedimentation chamber. In such a configuration, if washing liquid
is pumped by the drain pump at a low pressure, the water level can
only be raised to reach the filter located in the sedimentation
chamber, but no water is drained. If driven at a higher speed,
water can be drained. Still, the possibility exists that washing
liquid may flow back into the wash tank during draining.
[0021] Thus, preferably a switch is provided at the junction,
wherein the switch is adapted to selectively connect at least the
inlet and the first outlet and the inlet and the second outlet. The
at least two positions of the switch correspond to "filtration",
i.e. use of the second circulation system, and "draining". If the
switch is in a first position, connecting the inlet with the first
outlet, washing liquid is circulated through the second circulation
system, passing the sedimentation chamber and the filter. Please
note that when the pump is turned off, soil particles begin to sink
down to the bottom of the sedimentation chamber, which can
preferably be adjacent to the junction and the switch. To drain
water from the dishwasher, the switch is in the second position,
connecting the inlet with the second outlet. On actuation of the
pump, water is drained from the dishwasher. At this time, water can
be reloaded from the sedimentation chamber by turning the pump off
and switching the switch back to the first position, so that water
and soil particles residing at least in the lower part of the
sedimentation chamber flow into the tub section between the
backflow valve or the drain pump and the junction. Then again, the
switch is actuated into the second position and the soil-laden
washing liquid can easily be drained. Depending on how much washing
liquid can flow back from the sedimentation chamber, this process
can be repeated one or more times. In this manner, at least in
multiple steps, the sedimentation chamber can be fully drained.
Even heavy dirt can be handled. If the filter of the sedimentation
chamber is formed as part of the wall of the wash tank and a device
for backwashing the filter is used to clean the filter, the water
accumulating in the sedimentation chamber can also be drained in
this manner.
[0022] In another variant, an outlet in the upper part of the
sedimentation chamber can be connected to the drain tube such that
an overflow for a completely filled sedimentation chamber is
formed. In this manner, if the filter is clogged or the drain pump
is driven at a too high speed, washing liquid can be drained.
However, such an overflow can also be used to effect a tangential
cleaning of the filter. Thus, preferably, if such an overflow is
provided, the drain pump is controllable to effect a tangential
cleaning of the filter. This means, the drain pump is driven at a
high speed so that the water passes tangentially along the filter
in the sedimentation chamber, taking along the soil particles which
are drained through the overflow and subsequently through the drain
tube.
[0023] Additionally, if such an overflow is provided and,
especially when the u-like bend of the drain tube is located higher
than the highest point of the overflow, a backflow valve can be
provided downstream of the outlet of the sedimentation chamber.
[0024] In a third variant of the first embodiment of the invention,
the junction can comprise a second inlet connected to an outlet in
the upper part of the sedimentation chamber such that an overflow
for a completely filled sedimentation chamber is formed and the
switch can be actuated so that the first inlet is connected to the
first outlet and at the same time the second inlet is connected to
the first outlet, and so that the first inlet is connected to the
second outlet. The first position of the switch, connecting the
first inlet to the first outlet and the second inlet to the second
outlet allows for filtration of the washing liquid at a low speed
of the drain pump. Even if the filter is clogged in such a
situation, overflowing washing liquid can simply be drained through
the final drain tube. If the pump is driven at a higher speed,
tangential cleaning of the filter can be effected and the washing
liquid is directly drained to the drain tube. If the switch is in
the second position, connecting the first inlet to the second
outlet, washing liquid can be directly be drained.
[0025] In a further development of this third variant of the first
embodiment, the switch can additionally be actuated so that the
first inlet is connected to the first outlet and at the same time
the second inlet and the second outlet are closed. This third
position is especially preferable if a sensor device adapted to
sense a clogging of the filter is used, for example a hydrostatic
sensor connected to the upper end of the sedimentation chamber. If
during filtration of the washing liquid the filter is clogged,
washing liquid filling the overflow is not drained through the
drain tube, but confined to the overflow so that a strong increase
in pressure can be measured. Adequate measures can be taken in such
a case, like notifying the user that the filter is to be cleaned.
Cleaning or draining of the filter is again effected in the first
position of the switch, when the second inlet is connected to the
second outlet.
[0026] In a second embodiment of the invention, the further pump
can be an additional pump. This means, the dishwasher comprises the
circulation pump of the first circulation system, the drain pump
and an additional pump dedicated to drive the second circulation
system. The advantage of this configuration is that the filtration
process is now even decoupled from the draining process. A switch
that might be clogged is also not needed.
[0027] The additional pump may also draw washing liquid to be
filtered from the sump. Preferably, the additional pump draws
washing liquid from an area of the sump separated by a filter, in
particular a fine filter, from which area also the circulation pump
draws washing liquid. In this case, both circulation systems share
the fine filter, while the second circulation system's filtration
device preferably comprises a micro fine filter.
[0028] Drawing washing liquid from the sump, the outlet of the
additional pump can be connected to an inlet located in the upper
part of a sedimentation chamber, wherein a part of the
sedimentation chamber's wall is formed as a filter, in particular a
micro fine filter, and the lower part of the sedimentation chamber
has an outlet connected to a feeding tube leading from the sump to
a drain pump, the backflow of water from the sedimentation chamber
to the sump being prevented by a backflow valve. In this preferred
configuration, washing liquid can be fed into the sedimentation
chamber from its upper part. Through the filter, which may be
formed as a part of the wall of the wash tank, filtered washing
liquid can re-enter the wash tank. The lower part of the
sedimentation chamber remains filled with washing liquid, so that
soil particles sediment, i.e. sink downwards. The soil filtered out
during the filtration of the washing liquid can now easily be
drained by actuation of the drain pump through the feeding tube, so
that only a small amount of water needs to be drained.
Additionally, if a device for backwashing the filter is provided in
the wash tank, washing liquid or water from the backwash jets
cleaning the filter can also be easily drained, removing all the
soil from the sedimentation chamber and the filter.
[0029] To prevent the drainage of washing liquid during the
filtration process, an u-like bend of the drain tube for finally
draining washing liquid can be located higher than the highest
point of the second circulation system, in particular the
sedimentation chamber. The additional pump, in the following also
named filter pump, is driven at a speed such that washing liquid
enters the sedimentation chamber and passes through the filter, but
is not drained through the drain tube.
[0030] In both embodiments, a flat sump can be realised, possibly
comprising a flat fine filter acting as a pre-filtering stage for
the filtration system.
[0031] It should be noted that in the second embodiment, if washing
liquid is drawn directly from the sump without passing a fine
filter, a two layer filter can be used in the wall of the
sedimentation chamber. In this case, the water would first pass a
fine filter and afterwards a micro fine filter to prevent clogging
of the micro fine filter by bigger soil particles.
[0032] In any of the two embodiments, a sensor device adapted to
sense a clogging of the filter can be provided. This sensor device
can be hydrostatic sensor, which, in case a sedimentation chamber
is provided, can be connected to the upper end of the sedimentation
chamber. Advantageously, clogging of the filter can be detected in
such a configuration and countermeasures can be taken and/or a
warning can be output to a user to exchange or manually clean the
filter.
[0033] Please note that the first wash circulation system,
filtration devices as such, especially filters located in the sump,
are considered well-known by the person skilled in the art and will
not discussed in detail in this description.
[0034] Further advantages and details of the current invention can
be learned from the following description of preferred embodiments
in connection with the drawings, wherein:
[0035] FIG. 1 is a schematic diagram of a dishwasher according to
the first variant of the first embodiment of the invention,
[0036] FIG. 2 is a schematic diagram showing a dishwasher according
to the second variant of the first embodiment of the invention,
[0037] FIG. 3 is a schematic diagram of a dishwasher according to a
third variant of the first embodiment of the invention,
[0038] FIG. 4 is a view showing a switch used in the dishwasher of
FIG. 3,
[0039] FIG. 5 shows different positions of the switch of FIG. 4
[0040] FIG. 6 is a schematic view of a dishwasher according to the
second embodiment of the invention, and
[0041] FIG. 7 is a schematic diagram of a variation of the
dishwasher of the second embodiment.
[0042] FIG. 1 shows a dishwasher 1 according to the first variant
of the first embodiment of the invention. It comprises a wash tank
wherein soiled dishes can be loaded in dish baskets (not shown) to
be washed. Two spray arms 3, 4 are provided in the wash tank 2.
During operation of the dishwasher 1, washing liquid is drawn from
a sump 5 by a circulation pump 6 and recirculated into the wash
tank 2 via the spray arms 3, 4. While circulating in this first
circulation system 7, the washing liquid passes a flat fine filter
8 located in the sump 5. In this variant, the fine filter 8 is part
of a filtration device 9 of the first circulation system 7.
However, filtration in the first circulation system 7 depends on
the actuation of the circulation pump 6, and no micro fine
filtering is available. A coarse filter 25 can be provided in the
sump 5 where washing liquid is drained.
[0043] According to the invention, the dishwasher 1 comprises a
second circulation system 10 comprising a filtration device 11 with
a micro fine filter 12 to filter washing liquid independently from
actuation of the circulation pump 6 of the first circulation system
7. The second circulation system 10 is driven by the drain pump 13,
by which usually water is drained from the sump 5 to a drain tube
14. To effect draining of washing liquid as well as filtering of
washing liquid by the same drain pump 13, the dishwasher 1
comprises a junction 15 with a switch 16. The junction 15 has one
inlet connected to the outlet side of the drain pump 13 and two
outlets, namely a first outlet connected to a sedimentation chamber
17 and a second outlet connected to the drain tube 14. The switch
16 can be actuated between two positions. In a first position, the
inlet is connected to a first outlet, in a second position the
inlet is connected to the second outlet. Also provided are backflow
valves 18 preventing the flowback of water into the sump 5 or the
sedimentation chamber 17. Please note that the narrow, lower
portion 24 is also a part of the sedimentation chamber 17.
[0044] The micro fine filter 12 is arranged so that it forms part
of the wall 19 of the wash tank 2. Washing liquid passing through
the micro fine filter 12 from the sedimentation chamber 17 is
directly recirculated into the wash tank 2.
[0045] Additionally, the micro fine filter 12 can easily be cleaned
by backwashing using a device 20 for backwashing the filter 12
located in the wash tank 2. The device 20 comprises nozzles 21
arranged circumferentially around the upper spray arm 3 facing
outwardly, so that backwash jets ejected from the nozzles 21 hit
the micro fine filter 12, thereby cleaning it.
[0046] Of course, additional nozzles aimed at the filter 12 can be
provided at the lower spray arm 4 or other spray devices.
[0047] In this configuration, a filtration process or phase is
independent from actuation of the circulation pump 6. The
filtration process will now be described in more detail.
[0048] If the washing liquid is to be filtered, the switch 16 is
actuated into the first position, connecting the inlet to the first
outlet and therewith the sedimentation chamber 17. The drain pump
13 is now actuated at a speed which raises the washing liquid level
in the sedimentation chamber to a height in which washing liquid
can just pass the filter 12. In this manner, the pressure exerted
on the filter 12 is as low as possible, preventing soil particles
from being pressed into the filter mesh or screen. This means, soil
particles at or in the filter 12 can usually still be removed by
actuation of the device 20 for backwashing the filter 12. At the
end of the filtration phase the drain pump 13 is stopped and the
switch 16 is actuated to the second position, now connecting the
inlet to the second outlet and therewith the drain tube 14.
Meanwhile, the soil particles in the remaining column of washing
liquid filling the sedimentation chamber 17 begin to sink down to
the bottom of the sedimentation chamber 17, i.e. the lower portion
24. There, the sedimented particles remain close to the switch
16.
[0049] With the switch 16 in the second position, washing liquid
can be drained from the sump 5 to the drain tube 14. Now, the
portion 22 between the sump-side backflow valve 18 and the switch
16 can at least partly be emptied. In this condition, the switch 16
is again actuated into the first position so that at least part of
the washing liquid column in the sedimentation chamber 17, in
particular the lower part containing the soil particles, flows into
the portion 22. The switch 16 is then again actuated into the
second position, so that the washing liquid reloaded from the
sedimentation chamber 17 containing the soil particles can be
drained through the drain tube 14. This process of draining the
sedimentation chamber 17 can, if required, be repeated one or
several times, for example, if it cannot be completely drained in
one step. In this case, after the portion 22 has been at least
partly emptied, the switch is again actuated into the first
position, washing liquid from the sedimentation, chamber 17
containing soil particles is drained into the portion 22, the
switch is again actuated into the second position, and the washing
liquid is drained.
[0050] After or during the actuation of the device 20 for
backwashing the filter 12, this process of draining the
sedimentation chamber 17 is also effected.
[0051] In this manner, the soil filtered out from the washing
liquid can easily be drained without consuming too much washing
liquid. Additionally, a smaller sump can be realised as the
filtration of the washing liquid takes place in the filtration
device 11.
[0052] The micro fine filter 12 as part of the wall 19 of the wash
tank 2 can be seen by the user looking into the dishwasher,
assuring him of a good cleaning performance wherein soil particles
are less often recirculated through the first circulation system 7.
Additionally, the micro fine filter 12 can easily be disassembled
and cleaned by hand.
[0053] The dishwasher also comprises a hydrostatic sensor 23,
located at the upper end of the sedimentation chamber 17. In the
rare case of a clogged filter 12, the hydrostatic sensor 23
measures a high pressure and therefore countermeasures and/or
warnings to the user can be effected.
[0054] FIG. 2 shows a dishwasher 1' according to the second variant
of the first embodiment, wherein like parts are designated by like
numerals.
[0055] In particular, the first circulation system 7 and the part
of a filter device 9 located in the sump 5 are similar in all
embodiments, thus, the description is omitted in the following.
[0056] In the variant of FIG. 2, the drain pump 13 also acts as a
further pump, having a switch 16 at a junction 15 downstream.
However, differing from the variant in FIG. 1, an outlet 26 is
provided in the'upper part of the sedimentation chamber 17. This
outlet 26 is connected to the final drain tube 14 so that an
overflow 27 of a completely filled sedimentation chamber 17 is
formed. To prevent washing liquid from flowing back from the drain
tube 14 through the overflow. 27 into the sedimentation chamber 17,
a backflow valve 28 is provided along the overflow 27.
[0057] Apart from acting as an overflow 27 for the sedimentation
chamber 17, thus preventing an excess pressure on the filter 12,
the overflow 27 may be used in a tangential cleaning step for the
filter 12. During tangential cleaning, the switch 16 is in a first
position, so that the inlet on the drain pump 13 side and the first
outlet leading to the sedimentation chamber are connected. The
drain pump 13 is then driven at a high speed, so that washing
liquid passes tangentially upwards along the filter 12, which again
can be a micro fine filter, taking with it soil particles sticking
to the filter or sedimented in the sedimentation chamber 17. The
soil-laden washing liquid then passes through the overflow 27 and
is discharged through the drain tube 14.
[0058] If tangential cleaning is effected, a device 20 for
backwashing the filter 12 is in principle not needed, but may
additionally be provided. Please note that soil accumulated in the
lower portion 24 of the sedimentation chamber 17 can also be
drained using the same process as described with reference to FIG.
1, i.e. at least partly emptying the section 22, moving the switch
16 to the first position, moving the switch 16 to the second
position and again driving the pump.
[0059] Thus, in this second variant of the first embodiment,
cleaning of the filter 12 is improved as tangential cleaning
becomes possible.
[0060] A third variant of the first embodiment of a dishwasher 1''
according to the invention is shown in FIG. 3. The difference to
the variant in FIG. 2 is that in this case a second inlet connected
to the overflow 27 is provided at the junction 15 and a different
switch 16' is used which can be actuated into three positions.
[0061] An embodiment of the switch 16' is shown in FIG. 4. The
switch 16' comprises a rotatable actuator 29 having an expanded
section 30 at one side. This configuration allows to dispense with
the backflow valve 28.
[0062] The switch 16' can be actuated into three positions, shown
in FIG. 5, each corresponding to a mode of function of the
dishwasher 1''. In a first position I, the first inlet
corresponding to the section 22 is connected to the first outlet
corresponding to the sedimentation chamber 17, while the second
inlet corresponding to the overflow 27 and the second outlet
corresponding to the drain tube 14 are blocked. In this first
position, the filter 12 of the filtration device 11 and the
sedimentation chamber 17 are used for filtration of the washing
liquid in the second circulation system 10. Washing liquid is
pumped into the sedimentation chamber 17 by the drain pump 13 at a
low speed such that, at nearly zero pressure washing liquid may
pass through the filter 12 into the wash tank 2, thereby being
filtered. Please note that, as the connection between the overflow
27 and the drain tube 14 is blocked, a hydrostatic sensor 23 can
again be used in this variant to detect clogging of the filter
12.
[0063] In the second position II a first inlet corresponding to the
section 22 is connected to the second outlet corresponding to the
drain tube 14. In this position, washing liquid can be directly
drained from the dishwasher 1''.
[0064] The third position III connects a first inlet corresponding
to the section 22 to the first outlet corresponding to the
sedimentation chamber 17 and at the same time the second inlet
corresponding to the overflow 27 to the second outlet corresponding
to the drain tube 14. In this position, a tangential cleaning of
the filter 12 as described above with reference to FIG. 2 can be
effected while the drain pump 13 runs at a high speed. Washing
liquid is pumped from the sump 5 through the section 22, then
through switch 16' into the sedimentation chamber 17, passing the
filter 12. Afterwards, the washing liquid passes the overflow 27,
again flows through switch 16' to be drained through a drain tube
14.
[0065] Finally, FIG. 6 shows a dishwasher 1''' according to the
second embodiment of the invention. Again, the dishwasher 1'41
comprises a first circulation system 7 as described with respect to
FIG. 1 as well as a drain pump 13 drawing washing liquid from a
sump 5 to discharge it through a drain tube 14. In the sump, a fine
filter 8 and a coarse filter 25 are provided. However, in this
embodiment, the second circulation system 10 for filtration is not
driven by the drain pump 13, but by an additional pump or filter
pump 30. The filter pump 30 draws water filtered by the flat fine
filter 8 from the sump 5 through a tube 31 to the upper end of a
sedimentation chamber 17. A micro fine filter 12 forms a boundary
of the sedimentation chamber 17 in its upper part. The micro fine
filter 12, which is a part of a filtration device 11, again is
formed as a part of the wall 19 of the wash tank 2. The
sedimentation chamber 17 is connected to a feeding tube 32 for the
drain pump 13.
[0066] To prevent the draining of washing liquid during operation
of the filter pump 30, the u-like bend 33 of the drain tube 14 is
located higher than the upper end of the sedimentation chamber 17.
During filtration, the filter pump 30 is driven at a low speed so
that washing liquid may enter the sedimentation chamber from above,
but no washing liquid is drained from the dishwasher 1''' through
the drain tube 14. Advantageously, during filtering, soil particles
sedimented at the bottom of the sedimentation chamber 17 are not
swirled up again in the direction of the filter 12. Draining of the
sedimentation chamber 17 is easily effected by actuation of the
drain pump 13. Backflow valves 33, 18 prevent washing liquid from
flowing back to the sedimentation chamber 17 or the sump 5.
[0067] Tangential cleaning of the filter 12 can also be effected by
running the filter pump 30 at a higher speed so that washing liquid
not only enters the sedimentation chamber 17, but is also drained
through the drain tube 14. Additionally or alternatively, cleaning
of the filter 12 can also be effected using a device 20 for
backwashing the filter 12 as described with respect to FIG. 1.
[0068] As can be seen, no switch that is subject to clogging is
needed in this second embodiment of the invention.
[0069] In the example shown in FIG. 6, both the circulation pump 6
and the additional pump 30 draw washing liquid from behind the flat
fine filter 8 in the sump 5. However, as shown in the modified
second embodiment in FIG. 7, the filter pump 30 may also draw
washing liquid from the feeding tube 32 upstream the backflow valve
33. In this embodiment, however, washing liquid is not yet fine
filtered before entering the sedimentation chamber 17. Hence, a
two-layer filter 12' is used instead of the micro fine filter 12. A
first layer of the filter 12' acts as a fine filter, a second layer
acts as a micro fine filter. Optionally, it is also possible to
provide any additional filters in all described embodiments and
variants.
[0070] In summary, in the second embodiment shown in FIGS. 6 and 7,
virtually no filter cleaning is needed since minimal pressure is
exerted on the filter 12 or 12' and soil particles simply sink down
in the sedimentation chamber 17. No switch is needed in the
drainage network, and a low noise filter pump 30 can be used.
* * * * *