U.S. patent application number 14/916715 was filed with the patent office on 2016-07-28 for foam-reducing procedure in a washing machine during a spinning cycle.
This patent application is currently assigned to Electrolux Appliances Aktiebolag. The applicant listed for this patent is ELECTROLUX APPLIANCES AKTIEBOLAG. Invention is credited to Mirko Gasparini.
Application Number | 20160215435 14/916715 |
Document ID | / |
Family ID | 49123773 |
Filed Date | 2016-07-28 |
United States Patent
Application |
20160215435 |
Kind Code |
A1 |
Gasparini; Mirko |
July 28, 2016 |
Foam-Reducing Procedure in a Washing Machine During a Spinning
Cycle
Abstract
The present invention relates to a method for operating a
washing machine (10) adapted to perform a washing cycle and
comprising a washing tub (24) in which a laundry drum (26) is
contained, said method comprises the steps of: .cndot.--rotating
said laundry drum (26) at a sticking speed (vst) at which laundry
(28) clings at an inner periphery of said laundry drum (26),
.cndot.--detecting a liquid level (44) in a washing tub (24) and/or
in a draining region thereof while said laundry drum (26) is
rotating at said sticking speed (vst), and .cndot.--starting a
foam-reducing procedure if the detected liquid level (44)
corresponds to a prefixed value or is within a prefixed range of
values, or if the time dependent behaviour of said the detected
liquid level (44) corresponds to a prefixed time dependent
behaviour. Further, the present invention relates to a
corresponding washing machine (10). Moreover, the present invention
relates to a computer program product for performing the method for
controlling a washing cycle in a washing machine (10).
Inventors: |
Gasparini; Mirko;
(Spilimbergo (PN), IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ELECTROLUX APPLIANCES AKTIEBOLAG |
Stockholm |
|
SE |
|
|
Assignee: |
Electrolux Appliances
Aktiebolag
Stockholm
SE
|
Family ID: |
49123773 |
Appl. No.: |
14/916715 |
Filed: |
September 5, 2014 |
PCT Filed: |
September 5, 2014 |
PCT NO: |
PCT/EP2014/068994 |
371 Date: |
March 4, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D06F 2204/065 20130101;
D06F 39/087 20130101; D06F 33/00 20130101; D06F 2204/084 20130101;
G05B 2219/2633 20130101; D06F 39/06 20130101; G05B 19/042 20130101;
D06F 2212/02 20130101; D06F 2202/085 20130101; D06F 35/006
20130101 |
International
Class: |
D06F 39/06 20060101
D06F039/06; D06F 39/08 20060101 D06F039/08; D06F 35/00 20060101
D06F035/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 11, 2013 |
EP |
13183951.6 |
Claims
1. A method for operating a washing machine (10) adapted to perform
a washing cycle and comprising a washing tub (24) in which a
laundry drum (26) is contained, said method comprises the steps of:
rotating said laundry drum (26) at a sticking speed (vst), at which
laundry (28) clings at an inner periphery of said laundry drum
(26), detecting a liquid level (44) in a washing tub (24) and/or in
a draining region to thereof while said laundry drum (26) is
rotating at said sticking speed (vst), and starting a foam-reducing
procedure if the detected liquid level (44) corresponds to a
prefixed value or is within prefixed range of values, or if the
time dependent behaviour of the detected liquid level (44)
correspond to a prefixed time dependent behaviour.
2. The method according to claim 1, wherein: the method is
performed during a spinning phase of the washing cycle and after a
unbalancing detecting/reducing phase has been performed, said step
of rotating said laundry drum (26) at a sticking speed (vst) at
which laundry (28) clings at an inner periphery of said laundry
drum (26), is performed during or after said unbalancing
detecting/reducing phase.
3. The method according to claim 2, wherein: if, after said step of
detecting a liquid level (44) in a washing tub (24) and/or in a
draining region thereof while said laundry drum (26) is rotating at
said sticking speed (vst), said foam-reducing procedure is not
started, said laundry drum (26) is accelerated from said sticking
speed (vst) to a final speed of said spinning phase without
performing a further unbalancing detecting/reducing phase.
4. The method according to claim 1 or 2 or 3, wherein the sticking
speed (vst) of the laundry drum (26) is equal or marginally bigger
than a minimum threshold value allowing that the laundry (28)
clings at the inner periphery of said laundry drum (26).
5. The method according to claim 4, wherein said minimum threshold
value for the rotational speed (v) of the laundry drum (26) is
between 80 rpm and 100 rpm.
6. The method according to claim 1, wherein the method is performed
during and/or before a dewatering phase and/or a spinning phase of
the washing cycle.
7. The method according to any one of the preceding claims,
comprising the following steps: starting a predetermined monitoring
period (54), detecting the liquid level (44) in the washing tub
(24) and/or in the draining region thereof during said
predetermined monitoring period (54), comparing the detected liquid
level (44) with a lower threshold value (46) during the
predetermined monitoring period (54), and if the detected liquid
level (44) does not decrease or drop below the lower threshold
value (46) within the predetermined monitoring period (54), then
starting said foam-reducing procedure.
8. The method according to claim 7, wherein said predetermined
monitoring period (54) is between five seconds and twenty seconds,
preferably ten seconds.
9. The method according to any one of the claims 1 to 6, comprising
the following steps: detecting and storing the liquid level (44) in
the washing tub (24) and/or in the draining region thereof during a
drain pump (32) of said washing machine (10) is activated and the
laundry drum (26) is rotating at said sticking speed (vst),
smoothing a signal of the stored liquid level (44), determining
gradient of the smoothed liquid level (44), starting said
foam-reducing procedure if the determined gradient corresponds to a
prefixed range of values or is within a prefixed range of
values.
10. The method according to claim 7 or 8, wherein the drain pump
(32) is switched on within the predetermined monitoring period (54)
and, if said foam-reducing procedure is started, then the drain
pump (32) remains activated, and, if said foam-reducing procedure
is not started, then the drain pump (32) is switched off for a
predetermined period and then switched on again.
11. The method according to claim 10 wherein said predetermined
period for switching off the drain pump (32) is between 20 seconds
and 40 seconds, preferably 30 seconds.
12. The method according to any one of the preceding claims,
wherein said foam-reducing procedure comprises reducing the
rotational speed (v) of the laundry drum (26) or stopping the
latter and switching off a drain pump (32) of said washing machine
(10) for a predetermined period and then switching it on again.
13. The method according to claim 12, wherein said predetermined
period in which said drain pump (32) is switched off between a half
minute and two minutes, preferably one minute.
14. The method according to claim 12 or 13, wherein said
foam-reducing procedure comprises, after reducing the rotational
speed (v) of the laundry drum (26) or stopping the latter and
switching off the drain pump (32) for a predetermined period and
then switching it on again, the steps of: detecting again the
liquid level (44) in the washing tub (24) and/or in the draining
region thereof, and, if the detected liquid level (44) does still
not decrease or drop below the lower threshold value (46) within
the predetermined period, adding water into in the washing tub
(24), and draining the washing tub (24) and starting a balancing
phase.
15. A washing machine, wherein the washing machine is provided for
the method according to any one of the claims 1 to 14.
Description
[0001] The present invention relates to a method for operating a
washing machine. Further, the present invention relates to a
corresponding washing machine.
[0002] Known washing machines comprise a casing containing a
washing tub in which there is a rotatable laundry drum in which the
laundry to be washed can be loaded. A hydraulic circuit is provided
for taking washing liquid, i.e. water and water mixed with a
cleaning product, inside the washing tub and the laundry drum, so
as to wash or rinse the laundry, and for draining, e.g. by using a
drain pump, this liquid outside the machine. In other known washing
machines drain pump is not provided and the washing liquid is
drained from the tub by gravity.
[0003] During a washing cycle in a washing machine one or more
dewatering phases, balancing phases, spinning phases and rinsing
phases are performed. When the washing liquid is moved, for example
by rotating the laundry drum, in particular when such liquid
contains a detergent, a certain amount of foam is typically
generated. If too much foam is generated in the washing tub or in
the draining region thereof, then some phases of the washing cycle
cannot be faultlessly performed.
[0004] In particular an high amount of foam can be very negative
during the spinning and draining phase of the washing cycle (in
which the laundry drum is rotated at high speed and the liquid
present in the washing tub is drained from the machine), since the
foam compromises a correct functioning of the drain pump (if
provided) and it obstructs the draining of the liquid from the
machine.
[0005] Some known methods for operating a washing machine are
known, in which the amount of foam in the washing tub is monitored,
in particular during the spinning phase, in order to start a foam
reducing procedure if this amount is too high; these known methods
detects the amount of the foam after stopping the rotation of the
drum. Stopping the rotation of the drum causes the laundry
contained therein to fall in the bottom of the drum and to
rearrange itself in a stochastic way.
[0006] These known washing methods comprise, at the beginning of
any spinning phase, an unbalancing detecting/reducing phase, in
which, before reaching the final spinning speed, the degree of
unbalance of the laundry inside the drum is detected, and possibly
reduced by performing one or more stops and/or slow movements of
the drum, which causes the laundry to rearrange its position. The
problem of these known methods for detecting the amount of foam is
that, since the drum is stopped before detecting the amount of foam
(and the amount is detected with the drum stationary), any time the
foam amount is detected during a spinning phase, a new unbalance
phase has to be performed (since even if the laundry was previously
in a balanced condition, by stopping the drum for detecting the
amount of foam, the laundry rearranges itself in the drum, and
therefore its position changes), which increases the duration and
the energy consumption of the cycle.
[0007] It is an object of the present invention to provide an
improved method for operating a washing machine which allows
controlling the amount of foam in a washing cycle, in particular
during a spinning phase, and which keeps the duration and the
energy consumption of the cycle low.
[0008] The object of the present invention is achieved by the
method according to claim 1.
[0009] According to the present invention a method for operating a
washing machine adapted to perform a washing cycle and comprising a
washing tub in which a laundry drum is contained, said method
comprises the steps of: [0010] rotating said laundry drum at a
sticking speed at which laundry clings at an inner periphery of
said laundry drum, [0011] detecting a liquid level in a washing tub
and/or in a draining region thereof while said laundry drum is
rotating at said sticking speed, and [0012] starting a
foam-reducing procedure if the detected liquid level corresponds to
a prefixed value or is within prefixed range of values, or if the
time dependent behaviour of the detected liquid level correspond to
a prefixed time dependent behaviour.
[0013] The main idea of the present invention is the monitoring of
the foam while keeping the laundry drum in rotation at the sticking
speed at which the laundry clings at an inner periphery of the
laundry drum. In this way, in particular during a spinning phase,
if the laundry is already in a balanced condition inside the drum
immediately before the monitoring of the foam is started, the
laundry keeps this balanced condition also during the monitoring of
the foam.
[0014] If the monitoring of the foam confirms that the foam
reducing procedure is not necessary, since the foam amount is low
enough, the drum can be accelerated up to the final spinning speed
without having to perform again the unbalancing detecting/reducing
phase, since it is already in a balanced state. This reduces the
overall time and energy consumption of the washing cycle.
Preferably the method is performed during a spinning phase of the
washing cycle and after an unbalancing detecting/reducing phase has
been performed; in this case the step of rotating the laundry drum
at a sticking speed at which laundry clings at an inner periphery
of the laundry drum, is performed during or after the unbalancing
detecting/reducing phase.
[0015] More preferably, if, after the step of detecting a liquid
level in a washing tub and/or in a draining region thereof while
the laundry drum is rotating at the sticking speed, the
foam-reducing procedure is not started, the laundry drum is
accelerated from the sticking speed to a final speed of the
spinning phase without performing a further unbalancing
detecting/reducing phase.
[0016] Preferably, the sticking speed of the laundry drum is equal
or marginally bigger than a minimum threshold value allowing that
the laundry clings at the inner periphery of said laundry drum.
[0017] Advantageously, said minimum threshold value for the
rotational speed of the laundry drum is between 80 rpm and 100
rpm.
[0018] Preferably the method is performed during and/or before a
dewatering phase and/or a spinning phase of the washing cycle.
[0019] According to one advantageous embodiment of the present
invention, the method comprises the following steps: [0020]
starting a predetermined monitoring period, [0021] detecting the
liquid level in the washing tub and/or in the draining region
thereof during said predetermined monitoring period, [0022]
comparing the detected liquid level with a lower threshold value
during the predetermined monitoring period, and [0023] if the
detected liquid level does not decrease or drop below the lower
threshold value within the predetermined monitoring period, then
starting said foam-reducing procedure.
[0024] Advantageously, the predetermined monitoring period is
between five seconds and twenty seconds, preferably ten
seconds.
[0025] According to an alternative embodiment of the present
invention, the method advantageously comprises the following steps:
[0026] detecting and storing the liquid level in the washing tub
and/or in the draining region thereof during a drain pump or the
washing machine is activated and the laundry drum is rotating at
said sticking speed, [0027] smoothing a signal of the stored liquid
level, [0028] determining gradient of the smoothed liquid level,
[0029] starting said foam-reducing procedure if the determined
gradient corresponds to a pre-fixed range of values or is within a
prefixed range of values.
[0030] Advantageously, a drain pump of the washing machine may be
advantageously switched on within the predetermined monitoring
period and, if said foam-reducing procedure is started, then the
drain pump remains activated, and, if said foam-reducing procedure
is not started, then the drain pump is switched off for a
predetermined period and then switched on again.
[0031] Moreover, said predetermined period for switching off the
drain pump may be advantageously between 20 seconds and 40 seconds,
preferably 30 seconds.
[0032] Furthermore, said foam-reducing procedure advantageously
comprises reducing the rotational speed of the laundry drum or
stopping the latter and switching off the drain pump for a
predetermined period and then switching it on again.
[0033] Advantageously, the predetermined period for switching off
the drain pump is between a half minute and two minutes, preferably
one minute.
[0034] For example, said foam-reducing procedure advantageously
comprises, after reducing the rotational speed of the laundry drum
or stopping the latter and switching off the drain pump of the
washing machine for a predetermined period and then switching it on
again, the steps of: [0035] detecting again the liquid level in the
washing tub and/or in the draining region thereof, and, [0036] if
the detected liquid level does still not decrease or drop below the
lower threshold value within the predetermined period, adding water
into in the washing tub, and draining the washing tub and starting
a balancing phase.
[0037] Moreover, the present invention relates to a washing
machine, wherein the washing machine is provided for the method
mentioned above.
[0038] At last, the present invention relates to a computer program
product stored on a computer usable medium, comprising computer
readable program means for causing a computer to perform the method
mentioned above.
[0039] Novel and inventive features believed to be the
characteristic of the present invention are set forth in the
appended claims.
[0040] The invention will be described in further detail with
reference to the drawings, in which
[0041] FIG. 1 illustrates a schematic perspective view of a washing
machine according to a preferred embodiment of the present
invention,
[0042] FIG. 2 illustrates a schematic sectional front view of the
washing machine according to the preferred embodiment of the
present invention,
[0043] FIG. 3 illustrates a schematic set of diagrams as functions
of the time during a time slot of a washing cycle in a first
situation according to the preferred embodiment of the present
invention,
[0044] FIG. 4 illustrates a schematic set of diagrams as functions
of the time during the time slot of the washing cycle in a second
situation according to the preferred embodiment of the present
invention,
[0045] FIG. 5 illustrates a schematic set of diagrams as functions
of the time during the time slot of the washing cycle in a third
situation according to the preferred embodiment of the present
invention, and
[0046] FIG. 6 illustrates a schematic flow chart diagram of a
method for controlling a washing cycle in a washing machine
according to a fourth embodiment of the present invention.
[0047] FIG. 1 illustrates a schematic perspective view of a washing
machine 10 according to a preferred embodiment of the present
invention.
[0048] The washing machine 10 comprises a casing 12. A front panel
14 is preferably attached at the to front side of the casing 12. A
front door 16 is advantageously arranged in the centre of the front
panel 14. A detergent drawer 18 and a control panel 20 are
advantageously arranged at the front side of the casing 12 and
above the front panel 14. A top cover 22 is advantageously arranged
on the top side of the casing 12.
[0049] Even if the present invention has been illustrated with
reference to a front loading washing machine, it is clear that the
present invention is not limited to a front loading washing
machine, but it also relates to a top loading washing machine.
[0050] FIG. 2 illustrates a schematic sectional front view of the
washing machine 10 according to the preferred embodiment of the
present invention. FIG. 2 shows components of the washing machine
10 inside the casing 12.
[0051] The washing machine 10 advantageously comprises the casing
12 and preferably the top cover 22 arranged upon said casing 12. A
washing tub 24 is arranged advantageously in a central portion
inside the casing 12. A rotatable laundry drum 26 is arranged
inside the washing tub 24. The laundry drum 26 and the washing tub
24 are advantageously arranged behind the front door 16. A control
unit 30 is advantageously provided, preferably arranged in an upper
portion of the casing 12 of the washing machine 10. The detergent
drawer 18 is advantageously arranged above the washing tub 24. A
drain pump 32 and preferably also a three-way valve 34 are
preferably provided, preferably arranged in a lower portion of the
casing 12 of the washing machine 10. A drain duct 36 is arranged
partially inside and outside the casing 12 of the washing machine
10. Further, the washing machine 10 advantageously comprises an air
trap 38, a pressure sensor 40 and, preferably, a circulation duct
42.
[0052] The control unit 30 is advantageously an electronic circuit.
The control unit 30 is preferably electrically connected to the
detergent drawer 18, and/or to the drain pump 32, and/or to the
three-way valve 34 and/or to the pressure sensor 40. The detergent
drawer 18 is advantageously mechanically connected to the washing
tub 24 via a pipe. A bottom of the washing tub 24 is advantageously
connected to an inlet of the drain pump 32. An outlet of the drain
pump 32 is advantageously connected to the three-way valve 34.
Further, the three-way valve 34 is advantageously directly
connected to the drain duct 36 and to the circulation duct 42. The
circulation duct 42 advantageously interconnects the three-way
valve 34 and a top side of the washing tub 24. The fluid delivered
by the drain pump 32 is preferably casted away via the drain duct
36 and/or recirculated into the washing tub 24 via the circulation
duct 42, if said duct is really provided. A lower end of the air
trap 38 is advantageously connected to the bottom side of the
washing tub 24. A higher end of the air trap 38 is advantageously
connected to the pressure sensor 40.
[0053] The three-way valve 34 and the circulation duct 42 are
optional, so that the recirculation is also optional. Instead of
the one drain pump 32 the washing machine 10 may comprise two drain
pumps, wherein the one drain pump is provided for casting away the
fluid from the washing tub 24, while the other drain pump is
provided for the recirculation. Further, a filter element may be
advantageously arranged downstream of the drain pump 32.
[0054] The pressure sensor 40 is provided for detecting the liquid
level in the washing tub 24 or in a draining region thereof.
Instead of the pressure sensor 40, other suitable sensors may be
provided for detecting the liquid level in the washing tub 24 or in
the draining region thereof. There are several applications of the
pressure sensor 40 as explained below.
[0055] An important application of the pressure sensor 40 is the
determination of the presence and/or amount of foam in the washing
tub 24 and/or the draining region thereof. During the drain pump 32
is running and the laundry drum 26 is rotating, it is detected by
the pressure sensor 40, if the liquid level 44 in the washing tub
24 or in a draining region thereof is dropped below a predetermined
threshold value within a certain time period. Preferably, this is
performed during the spinning phase of the washing cycle.
Preferably, it is determined the presence and/or a high amount of
foam in the washing tub 24 tub and/or in the draining region
thereof if a signal from the pressure sensor 40 has decreased or
dropped below a threshold value during a predetermined monitoring
period 54. For example, said monitoring period 54 may be about ten
seconds. If the liquid level 44 has decreased or dropped below a
lower threshold value 46 within the monitoring period 54, then
presence of only water or a low amount of foam is detected. If the
liquid level 44 has not decreased or dropped below the lower
threshold value 46, then presence of foam or a high amount of foam
is detected.
[0056] According to an alternative method the detection of the
presence and/or of the amount of foam inside the washing tub and/or
in the draining region thereof may be performed as follows. The
liquid level in the washing tub 24 and/or in the draining region
thereof is detected during the drain pump is activated and the
laundry drum is rotating. The detected liquid level is preferably
stored. Then the signal of the stored liquid level is preferably
smoothed. After that, a gradient, preferably subsequent gradients,
of the smoothed liquid level are determined. Said gradient(s)
allows the detection of the presence and/or of the amount of foam
inside the washing tub and/or in the draining region thereof. By
this alternative method the foam is detected, if the gradient of
the smoothed liquid level corresponds to a prefixed value or is
within a prefixed range of values, or, as an alternative, if a
detected gradient is smaller than a previously detected gradient of
the smoothed liquid level.
[0057] Another application of the pressure sensor 40 may be
advantageously performed during the rotation of the laundry drum
26, preferably during a dewatering or spinning phase.
[0058] If, when the drum is rotating at a certain first speed,
named for example first speed v1, the liquid level in the washing
tub 24 or in the draining region thereof would reach a
corresponding upper threshold value 48, then a closed liquid
ringliquid ringliquid ring would be formed along the
circumferential wall of the laundry drum 26, which impedes the
draining of the liquid.
[0059] When the drum is rotating at a certain first speed v1, if
the control unit 30 detects that the liquid level in the washing
tub 24 or in the draining region thereof has reached a
corresponding upper threshold value 48, it advantageously reduces
the rotational speed of the laundry drum 26, so that the closed
liquid ringliquid ringliquid ring is not formed and the draining of
the liquid is not impeded.
[0060] Then control unit 30 advantageously detects, as mentioned
above, the presence and/or the amount of foam in the washing tub 24
or the draining region thereof, and, if an high amount of foam is
detected, it advantageously starts a foam-reducing procedure.
[0061] Further, the drain pump 32 may be advantageously switched
off for a short time, e.g. about two seconds, after reaching the
upper threshold value during a monitoring time period. This allows
avoiding the formation of the closed liquid ringliquid ringliquid
ring, and that air may exit the drain pump 32.
[0062] According to the present invention, a further advantageous
application of the pressure sensor 40 is the detection of the foam
as mentioned above, when the laundry drum 26 is rotating at a
rotational speed at which the laundry 28 sticks, clings or remains
attached to the circumferential wall of the laundry drum 26. This
avoids a complete repetition of the balancing phase before the
spinning phase. During the balancing phase the laundry 28 is
distributed at the circumferential wall of the laundry drum 26. For
attaching the laundry 28 to the circumferential wall of the laundry
drum 26 with a standard diameter, a rotational speed of at least 80
rpm to 100 rpm is advantageously required. The rotational speed of
the laundry drum 26 is controlled in such a way that the laundry 28
is kept attached to the circumferential wall of the laundry drum
26.
[0063] An additional application of the pressure sensor 40 may be
performed after the detection of the foam as mentioned above. The
drain pump 32 may be advantageously switched on again during a
monitoring period. If a high amount of foam is detected, i.e. the
liquid level in the washing tub 24 or in the draining region
thereof exceeds the upper threshold value, the drain pump 32 is
advantageously switched off again for a period, for example about
30 s, in order to settle the foam for draining. Then, then the
drain pump 32 is switched on again. If the liquid level in the
washing tub 24 or in the draining region thereof is below the upper
threshold value, then absence of foam or a low amount of foam is
detected.
[0064] If an high amount of foam is detected at the end of the
monitoring period by a liquid level which is higher than the upper
threshold value 48, then the rotational speed of the laundry drum
26 is preferably reduced to a low value or the laundry drum 26 is
stopped and the drain pump 32 is switched off for a certain period,
e.g. for one minute, in order to allow the foam to settle. Then the
drain pump 32 is preferably switched on again and the liquid level
is detected again. If the liquid level still does not drop below
the second threshold value after the monitoring period, then
preferably water is added and the washing tub 24 is drained and a
balancing phase before the spinning phase is started. However, if
the liquid level is lower than the threshold value, then the
spinning phase is preferably commenced again, more preferably after
another balancing phase.
[0065] FIG. 3 illustrates a schematic set of diagrams as functions
of the time during a time slot of the washing cycle in a first
situation according to the preferred embodiment of the present
invention.
[0066] The time slot between t=12940 s and t=13090 s of the washing
cycle is shown in FIG. 3. Within said time slot the balancing phase
and the spinning phase are performed. A washing phase has been
performed before said time slot. During the balancing phase the
rotational speed v of the laundry drum 26 increases. In the
beginning of the balancing phase the laundry 28 is not attached at
the circumferential wall of the laundry drum 26. However, in the
end of the balancing phase the laundry 28 is attached at the
circumferential wall of the laundry drum 26. In FIG. 3 the spinning
phase is started at about t=12985 s.
[0067] A liquid level 44 in the washing tub 24 varies between 0 mm
and about 22 mm within the time slot. A lower threshold value 46 of
the liquid level is defined at 10 mm. An upper threshold value 48
of the liquid level is defined at 25 mm. The liquid level 44 in the
washing tub 24 is always below the upper threshold value 48. A
state 50 of the drain pump 32 is always activated during the time
slot. During the spinning phase a rotational speed 52 of the
laundry drum 26 reaches about 800 rpm and then about 1200 rpm. In
FIG. 3 the sticking speed vst is 80 rpm. In general, the sticking
speed vst may be between 80 rpm and 100 rpm.
[0068] FIG. 4 illustrates a schematic set of diagrams as functions
of the time during the time slot of the washing cycle in a second
situation according to the preferred embodiment of the present
invention. Also FIG. 4 shows the time slot between t=12940 s and
t=13090 s of the washing cycle, in which time slot the balancing
phase and the spinning phase occurs. In FIG. 4 the spinning phase
is started also at t=12985 s.
[0069] The liquid level 44 in the washing tub 24 varies between 0
mm and about 40 mm within the time slot. The lower threshold value
46 of the liquid level is defined at 10 mm, while the upper
threshold value 48 of the liquid level is defined at 25 mm. Between
about t=13048 s and t=13055 s the liquid level 44 in the washing
tub 24 exceeds the upper threshold value 48. This is the only
excess of the liquid level 44 within the time slot. During the
remaining times of the time slot the liquid level 44 in the washing
tub 24 is below the upper threshold value 48. The state 50 of the
drain pump 32 is deactivated between about t=13048 s to t=13052 s,
after the liquid level 44 in the washing tub 24 has exceeded the
upper threshold value 48. During the remaining times of the time
slot the state 50 of the drain pump 32 is activated. The spinning
phase is stopped at t=13048 s, since the liquid level 44 in the
washing tub 24 has exceeded the upper threshold value 48. The
spinning phase remains interrupted during a timeout 54 of about ten
seconds. During this timeout 54 the rotational speed 52 of the
laundry drum 26 is reduced to v=100 rpm. The liquid level 44 in the
washing tub 24 goes below the lower threshold value 46 during the
timeout 54. The spinning phase is restarted at t=13060 s, after the
liquid level 44 in the washing tub 24 has been detected. In FIG. 4
the sticking speed vst is also 80 rpm.
[0070] FIG. 5 illustrates a schematic set of diagrams as functions
of the time during the time slot of the washing cycle in a third
situation according to the preferred embodiment of the present
invention. FIG. 5 shows also the time slot between t=12940 s and
t=13090 s of the washing cycle, in which time slot the balancing
phase and the spinning phase occurs. In FIG. 5 the spinning phase
is started at about t=12985 s.
[0071] The liquid level 44 in the washing tub 24 varies between 0
mm and about 53 mm within the time slot. The lower threshold value
46 of the liquid level is defined at 10 mm, while the upper
threshold value 48 of the liquid level is defined at 25 mm. Between
about t=13048 s and t=13080 s the liquid level 44 in the washing
tub 24 exceeds the upper threshold value 48 within the time slot.
During the remaining times of the time slot the liquid level 44 in
the washing tub 24 is below said upper threshold value 48.
[0072] The state 50 of the drain pump 32 is deactivated between
about t=13048 s to t=13050 s, after the liquid level 44 in the
washing tub 24 has exceeded the upper threshold value 48. The
spinning phase is stopped at t=13048 s, since the liquid level 44
in the washing tub 24 has exceeded the upper threshold value 48.
After the timeout 54 the rotation of the laundry drum 26 is
completely stopped and the state 50 of the drain pump 32 is
deactivated again between about t=13058 s to t=13060 s, since the
liquid level 44 in the washing tub 24 has not been decreased below
the upper threshold value 48 and foam has been detected. The
complete stop of the rotation of the laundry drum 26 at about
t=13058 s and the deactivation of the drain pump 32 between about
t=13058 s to t=13060 s causes a decreasing of the foam. After the
liquid level 44 in the washing tub 24 goes below the lower
threshold value 46 at about t=13095 s, the rotation of the laundry
drum 26 is activated again. A further spinning phase is started at
about t=13125 s. In FIG. 5 the sticking speed vst is also 80
rpm.
[0073] FIG. 6 illustrates a schematic flow chart diagram of a
method for controlling a washing cycle in a washing machine
according to a fourth embodiment of the present invention.
[0074] In a step 60 the method for controlling the washing cycle is
started. As a next step 62 a balancing phase is started, wherein
the rotational speed of the laundry drum 26 is increased from a low
speed to a high speed. During the rotation at said low speed the
laundry 28 is not attached at the circumferential wall of the
laundry drum 26, while the rotation at said high speed the laundry
28 is attached at the circumferential wall of the laundry drum
26.
[0075] In a further step 64 it is checked if the unbalance
satisfies safety conditions. If the safety conditions are not
satisfied, then the step 62 is repeated. If the safety conditions
are satisfied, then the rotational speed of the laundry drum is
increased in a further step 66. In a subsequent step 68 the liquid
level in the washing tub 24 and/or in the draining region thereof
is detected and compared with a threshold value in order to
determine if a high amount of foam occurs in the washing tub 24
and/or in the draining region thereof.
[0076] If a high amount of foam is detected, then the method is set
forth in a step 76. If low amount of foam or no foam at all is
detected, then in a next step 70 the speed profile of the laundry
drum 26 is checked. If the speed profile of the laundry drum 26 is
finished, then the finalisation of the spinning phase is checked in
a step 72. If the speed profile of the laundry drum 26 is not yet
finished, then the step 64 and the subsequent steps are repeated
again. If in the step 72 the finalisation of the spinning phase is
detected, then the washing cycle is continued in a step 74.
[0077] If in the step 68 the high amount of foam has been detected,
then the rotational speed of the laundry drum 26 is decreased to a
predetermined minimum value in the step 76. Then the drain pump 32
is running with a constant speed in a step 78.
[0078] In a next step 80 the liquid level 44 in the washing tub 24
is detected and compared with an upper threshold value 48. If the
liquid level 44 is below the upper threshold value 48, then the
step 64 and its subsequent steps are repeated again. If the liquid
level 44 exceeds the upper threshold value 48, then the expiring of
the timeout 54 is checked in a step 82. If the timeout 54 is not
yet expired, then the steps 78 and 80 are repeated again. If the
timeout 54 is expired, then the laundry drum 26 and the drain pump
32 are stopped in a step 84 for a predetermined time. In this
example, said predetermined time is about 30 seconds. In a next
step 86 the drain pump 32 is stopped.
[0079] As a next step 88 the liquid level 44 in the washing tub 24
is detected and compared with the upper threshold value 48 again.
If the liquid level 44 is below the upper threshold value 48, then
the step 62 and 64 are repeated again. If the liquid level 44
exceeds the upper threshold value 48, then the expiring of the
timeout 54 is checked again in a step 90. If the timeout 54 is not
yet expired, then the steps 86 and 88 are repeated again. If the
timeout 54 is expired, then the laundry drum 26 and the drain pump
32 are stopped in a step 92.
[0080] In a next step 96 the liquid level 44 in the washing tub 24
is detected and compared with the upper threshold value 48 again.
If the liquid level 44 is below the upper threshold value 48, then
the step 62 and 64 are repeated again. If the liquid level 44
exceeds the upper threshold value 48, then the expiring of the
timeout 54 is checked again in a step 98. If the timeout 54 is not
yet expired in the step 98, then the steps 94 and 96 are repeated
again. If the timeout 54 is expired in the step 98, then the drain
pump 32 is stopped in a step 100 and then the washing cycle is
continued in the step 74.
[0081] The present invention is in practice the monitoring of the
foam when the laundry drum is rotating at the sticking speed at
which the laundry remains attached at the circumferential walls of
the laundry drum. This avoids the repetition of the balancing phase
from the beginning. The balancing phase is provided before the
spinning phase.
[0082] Although illustrative embodiments of the present invention
have been described herein with reference to the accompanying
drawings, it is to be understood that the present invention is not
limited to those precise embodiments, and that various other
changes and modifications may be affected therein by one skilled in
the art without departing from the scope or spirit of the
invention. All such changes and modifications are intended to be
included within the scope of the invention as defined by the
appended claims.
* * * * *