U.S. patent application number 14/127182 was filed with the patent office on 2014-05-01 for method of controlling a rotatable-drum laundry dryer and a rotatable-drum laundry dryer implementing the method.
This patent application is currently assigned to ELECTROLUX HOME PRODUCTS CORPORATION N.V.. The applicant listed for this patent is Fabio Altinier, Michele Bisaro, Fabio Pasut, Roberto Ragogna. Invention is credited to Fabio Altinier, Michele Bisaro, Fabio Pasut, Roberto Ragogna.
Application Number | 20140115916 14/127182 |
Document ID | / |
Family ID | 46354329 |
Filed Date | 2014-05-01 |
United States Patent
Application |
20140115916 |
Kind Code |
A1 |
Altinier; Fabio ; et
al. |
May 1, 2014 |
Method of Controlling a Rotatable-Drum Laundry Dryer and a
Rotatable-Drum Laundry Dryer Implementing the Method
Abstract
A method is provided for controlling a drying operation of a
rotatable-drum laundry dryer (1) having a rotatable drum (3) for
loading laundry (5) and at least an electrode sensor (22) for
sensing dryness of the laundry (5). The method includes the step of
detecting the presence/absence of moist laundry (5) inside the
rotatable drum (3) by the electrode sensor (22). If a presence of
moist laundry inside the rotatable drum (3) is detected, a drying
cycle is started. The dryness of the laundry (5) is sensed during
the drying cycle and a cycle time (TD) at which the sensed dryness
reaches a preset dryness threshold is measured. If the cycle time
(TD) is lower than a preset dryness threshold time (Sm), the drying
cycle is continued for a first additional time (D1), and the drying
cycle is stopped at the end of the first additional time (D1).
Inventors: |
Altinier; Fabio; (Codogne
(TV), IT) ; Pasut; Fabio; (Pordenone, IT) ;
Bisaro; Michele; (Spilimbergo )PN), IT) ; Ragogna;
Roberto; (Montereale Valcellina (PN), IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Altinier; Fabio
Pasut; Fabio
Bisaro; Michele
Ragogna; Roberto |
Codogne (TV)
Pordenone
Spilimbergo )PN)
Montereale Valcellina (PN) |
|
IT
IT
IT
IT |
|
|
Assignee: |
; ELECTROLUX HOME PRODUCTS
CORPORATION N.V.
Brussels
BE
|
Family ID: |
46354329 |
Appl. No.: |
14/127182 |
Filed: |
June 21, 2012 |
PCT Filed: |
June 21, 2012 |
PCT NO: |
PCT/EP2012/062033 |
371 Date: |
December 18, 2013 |
Current U.S.
Class: |
34/282 ;
34/572 |
Current CPC
Class: |
D06F 58/38 20200201;
D06F 58/04 20130101; D06F 58/30 20200201; D06F 58/203 20130101 |
Class at
Publication: |
34/282 ;
34/572 |
International
Class: |
D06F 58/04 20060101
D06F058/04; D06F 58/28 20060101 D06F058/28 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 22, 2011 |
EP |
11171072.9 |
Claims
1. A method of controlling a drying operation of a rotatable-drum
laundry dryer comprising a rotatable drum for loading laundry and
at least one electrode sensor for sensing dryness of the laundry;
the method comprising: detecting the presence/absence of moist
laundry inside the rotatable drum by said at least one electrode
sensor; upon a presence of moist laundry inside the rotatable drum
being detected, starting a drying cycle; sensing dryness of the
laundry during said drying cycle; measuring a cycle time at which
the sensed dryness reaches a preset dryness threshold; upon the
measured cycle time being lower than a preset dryness threshold
time, continuing the drying cycle for a first additional time, and
stopping the drying cycle at the end of said first additional
time.
2. The method according to claim 1, wherein said first additional
time is such that the time elapsed from the beginning of said
drying cycle to the stopping of the drying cycle is a preset
minimum dryness time.
3. The method according to claim 1, wherein said first additional
time is set as the difference between said preset minimum dryness
time and said cycle time.
4. The method according to claim 1, further comprising: upon said
cycle time being not lower than said preset dryness threshold time,
continuing the drying cycle for a preset second additional time;
and stopping the drying cycle at the end of said second additional
time.
5. The method according to claim 4, wherein said second additional
time is between zero and ten seconds.
6. The method according to claim 1, wherein determining the
presence/absence of moist laundry inside the rotatable-drum
comprises: performing a starting detection phase for a starting
detection time; upon no moist laundry being detected during said
starting detection time, performing one or more additional
detection phases, each of which lasts an additional detection time;
and upon no moist laundry being detected during said additional
detection phase/s, ending operation of the rotatable-drum laundry
dryer.
7. The method according to claim 6, wherein said additional
detection time is less than said starting detection time.
8. A rotatable-drum laundry drier comprising: a rotatable drum for
loading laundry, at least one electrode sensor for sensing dryness
of the laundry; drying air feeding means for feeding drying air
into the drum, and rotation driving means for rotating the drum
about an axis of rotation; and electronic control means configured
to: detect presence/absence of moist laundry inside the rotatable
drum by said at least one electrode sensor; if upon a presence of
moist laundry inside rotatable drum being detected, start a drying
cycle; sensing dryness of the laundry during said drying cycle;
measure a cycle time at which the sensed dryness reaches a preset
dryness threshold; and upon the measured cycle time being lower
than a preset dryness threshold time, continue to perform the
drying cycle for a first additional time, and stop the drying cycle
at the end of said first additional time.
9. The dryer according to claim 8, wherein said first additional
time is such that the time elapsed from the beginning of said
drying cycle to the stopping of the drying cycle is a preset
minimum dryness time.
10. The dryer according to claim 8, wherein said first additional
time is set as the difference between said preset minimum dryness
time and said cycle time.
11. The dryer according to claim 8, wherein said electronic control
means are further configured to: continue to perform said drying
cycle for a preset second additional dryness time if upon said
cycle time being not lower than said preset dryness threshold time;
and stop the drying cycle at the end of said preset second
increased cycle time.
12. The dryer according to claim 11, wherein said second additional
time is between zero and ten seconds.
13. The dryer according to claim 9, wherein said electronic control
means are further configured to: perform a starting detection phase
for a starting detection time; upon no moist laundry being detected
within said starting detection time, perform one or more additional
detection phases; and upon no moist laundry being detected during
said additional detection phase/s, end operation of rotatable-drum
laundry drier.
14. The dryer according to claim 13, wherein, each of said one or
more additional detection phases lasts an additional detection time
less than said starting detection time.
15. The method according to claim 2, wherein said first additional
time is set as the difference between said preset minimum dryness
time and said cycle time.
16. The method according to claim 2, further comprising: upon said
cycle time being not lower than said preset dryness threshold time,
continuing the drying cycle for a preset second additional time;
and stopping the drying cycle at the end of said second additional
time.
17. The method according to claim 2, wherein determining the
presence/absence of moist laundry inside the rotatable-drum
comprises: performing a starting detection phase for a starting
detection time; upon no moist laundry being detected during said
starting detection time, performing one or more additional
detection phases, each of which lasts an additional detection time;
and upon no moist laundry being detected during said additional
detection phase/s, ending operation of the rotatable-drum laundry
dryer.
18. The dryer according to claim 9, wherein said first additional
time is set as the difference between said preset minimum dryness
time and said cycle time.
19. The dryer according to claim 9, wherein said electronic control
means are further configured to: continue to perform said drying
cycle for a preset second additional dryness time upon said cycle
time being not lower than said preset dryness threshold time; and
stop the drying cycle at the end of said preset second increased
cycle time.
20. The dryer according to claim 9, wherein said electronic control
means are further configured to: perform a starting detection phase
for a starting detection time; upon no moist laundry being detected
within said starting detection time, perform one or more additional
detection phases; and upon no moist laundry being detected during
said additional detection phase/s, end operation of rotatable-drum
laundry drier.
Description
[0001] The present invention relates to a method of controlling a
rotatable-drum laundry dryer and a rotatable-drum laundry dryer
implementing the method.
[0002] Methods of controlling rotatable-drum laundry dryers are
known, in which: hot air is fed into the rotatable drum so as to
flow over the laundry inside the drum; an electric parameter
associated with the laundry moisture is measured by means of an
electrode sensor arranged in order to contact with the laundry when
drum rotates; the dryness of the laundry is determined according to
the measured electric parameter; and the drying cycle is stopped
when the measured electric parameter reaches a preset value
associated with a prefixed final dryness.
[0003] More specifically, laundry dryers are known comprising an
electronic control unit which receives a plurality of voltage
signals having an amplitude and/or a frequency associated with the
electric parameter of the laundry, i.e. impedance or resistance, or
conductance, and measured a prefixed number of times; the
electronic control unit determines the dryness of the laundry
according to the measured voltage signals, and controls the drying
cycle according to determined laundry dryness. For example the
electrode sensor may be configured to output a voltage signal which
is proportional to the dryness of the laundry. Thus, more dried is
the laundry, higher is its electric parameter and consequently
bigger is the voltage signal outputted from the electrode
sensor.
[0004] The technical problem of the above-described prior-art
laundry dryer is that when contacts between laundry and electrode
sensor, during the drying cycle, are very few, an incomplete
dryness condition of the laundry may be performed, since the
electronic control unit may erroneously conclude (or determine,
resolve) that the few number of contacts between the laundry and
the electrode corresponds to a dry condition of the laundry.
[0005] As a matter of the fact, research by the Applicant shows
that when the above control method is performed in a rotary-drum
home laundry dryer in which the electrode sensor is arranged
outside the drum, i.e. in a position facing the opening in the
drum, the frequency with which the laundry contacts the electrode
sensor is reduced, or tends towards zero, when, for example, the
laundry corresponds to a small load quantity, i.e. a single
T-shirt, or when, for example, a "special" kind of laundry (e.g. a
pillow), is loaded in the laundry dryer in such a way that it gets
stuck inside the drum in such a position that it doesn't contact or
only rarely contacts the electrode sensor.
[0006] In such cases, because the number of contacts
laundry-electrode is very few and/or the electric signals outputted
from electrode sensor are affected by high electric noise, the
electronic control unit determines a high average value and, as a
consequence, calculates a high electric parameter (impedance or
resistance or conductance), and erroneously associate the latter
with a dryness condition. Thus, electronic control unit may
incorrectly conclude (or determine, resolve) that an expected
drying condition of the laundry has been reached, and it may and
stop the drying cycle too early, even if the laundry is still
wet.
[0007] JP2000229200 discloses a clothes drying machine in which
drying operation are controlled in the case of a small amount of
laundry into the rotating drum. In particular, the drying machine
is configured to start a drying course by measuring the number of
contacts between electrode and laundry; to determine whether the
laundry is a high load or small load based on the measured number
of contacts; and if the determined laundry is a small load, to set
the drying cycle period for twenty-five minutes, independently of
the moisture of the laundry.
[0008] JP6312095 discloses a clothes drying machine which dries
laundry independently of the its quantity, by executing the drying
operation by a drying time setting timer when a small quantity
signal is outputted from a clothes quantity judging device, while
executing the drying operation, monitoring the dried state if the
small quantity signal is not outputted. In detail, the clothes are
agitated, and each time when the clothes come to an electrode which
operates as clothes detector, is detected repeatedly. When the
clothes detection signal which is detected up to the time-up of a
clothes quantity judging timer is less than a standard value, a
microcomputer incorporated in a control circuit outputs a small
quantity signal from a clothes quantity judging device and forcibly
executes the drying operation without monitoring the dried state of
the clothes up to the time-up of a drying time setting timer. Under
the condition that it is considered that the contact frequency of
the clothes with the electrode is high and the reliability of the
signal of the electrode is high, the drying operation is executed,
judging the degree of dryness by the electrode.
[0009] Clothes drying machines disclosed in JP2000229200 and in
JP6312095 have the problem that systems starts the drying cycle
selected by the user and maintains operating the same in any case
for a preset time, even if the drum is empty or the laundry is
already dry, causing a useless wastage of electric energy.
[0010] It is therefore an object of the present invention to
provide a solution designed to obviate one or more problems due to
limitations and disadvantages of the related art, and in particular
a solution which guarantees the user to control the rotatable-drum
laundry dryer in order to assure a uniform laundry dryness, even if
the laundry inside of the drum is few and/or is arranged inside the
rotatable-drum so that number of contacts with the electrode sensor
is very low, and at the same time strongly reducing the wastage of
electric energy, in particular in case no laundry or already dry
laundry is loaded in the rotatable drum.
[0011] According to the present invention, there is provided a
method of controlling a drying operation of a rotatable-drum
laundry dryer comprising a rotatable drum for loading laundry and
at least an electrode sensor for sensing dryness of the laundry.
The method comprises: detecting the presence/absence of moist
laundry inside the rotatable drum by the electrode sensor; if
presence of moist laundry inside the rotatable drum is detected,
starting a drying cycle; sensing dryness of the laundry during the
drying cycle; measuring a cycle time at which the sensed dryness
reaches a preset dryness threshold; if the cycle time is lower than
a preset dryness threshold time, continuing the drying cycle for a
first additional time, and stopping the drying cycle at the end of
the first additional time.
[0012] Preferably the first additional time is such that the time
elapsed from the beginning of the drying cycle and the stopping of
the drying cycle is a preset minimum dryness time.
[0013] More preferably the first additional time is set as the
difference from the preset minimum dryness time and the cycle
time.
[0014] Advantageously the method comprises: if the cycle time is
not lower than the preset dryness threshold time, continuing the
drying cycle for a preset second additional time; and stopping the
drying cycle at the end of the second additional time.
[0015] Preferably the second additional time is between zero and
ten seconds.
[0016] Preferably determining the presence/absence of moist laundry
inside the rotatable-drum comprises: performing a starting
detection phase for a starting detection time; if no moist laundry
has been detected during the starting detection time, performing
one or more additional detection phases, each of which lasts an
additional detection time; if no moist laundry has been detected
during the additional detection phase/s, ending operation of
rotatable-drum laundry dryer.
[0017] Advantageously the additional detection time is lower than
the starting detection time.
[0018] The invention regards also a rotatable-drum laundry drier
comprising: a rotatable drum for loading laundry, a least an
electrode sensor for sensing dryness of the laundry; feeding drying
air means for feeding drying air into the drum, and rotating means
for rotating the drum about an axis of rotation. The rotatable-drum
dryer comprises electronic control means configured to: detect
presence/absence of moist laundry inside the rotatable drum by the
electrode sensor; if presence of moist laundry inside rotatable
drum is detected, start a drying cycle; sense dryness of the
laundry during the drying cycle; measure a cycle time at which the
sensed dryness reaches a preset dryness threshold; if the cycle
time is lower than a preset dryness threshold time, continue to
perform the drying cycle for a first additional time, and stop the
drying cycle at the end of the first additional time.
[0019] Advantageously the first additional time is such that the
time elapsed from the beginning of the drying cycle and the
stopping of the drying cycle is a preset minimum dryness time.
[0020] Preferably the first additional time is set as the
difference from the preset minimum dryness time and the cycle
time.
[0021] Opportunely the electronic control means are further
configured to: continue to perform the drying cycle for a preset
second additional dryness time if the cycle time is not lower than
the preset dryness threshold time; and stop the drying cycle at the
end of the preset second increased cycle time.
[0022] Advantageously the second additional time is between zero
and ten seconds.
[0023] Preferably the electronic control means are further
configured to: perform a starting detection phase for a starting
detection time; if no moist laundry has been detected during the
starting detection time, perform one or more additional detection
phases; and if moist laundry have been detected during the
additional detection phase/s, end operation of rotatable-drum
laundry drier.
[0024] Advantageously each of the one or more additional detection
phases lasts an additional detection time lower than the starting
detection time.
[0025] A non-limiting embodiment of the present invention will be
described by way of example with reference to the accompanying
drawings, in which:
[0026] FIG. 1 shows a schematic lateral cross section of a
rotatable-drum laundry drier implementing the laundry drying
control method according to the present invention;
[0027] FIG. 2 shows an inner lateral wall of the FIG. 1
rotatable-drum laundry drier; while
[0028] FIG. 3 shows an operation flow chart of the control method
implemented according to the present invention.
[0029] Number 1 in FIG. 1 indicates as a whole a rotatable-drum
laundry dryer comprising an outer casing 2, which preferably rests
on the floor on a number of feet.
[0030] Casing 2 supports a rotatable laundry drum 3, which defines
a drying chamber 4 for laundry 5 and rotates about a preferably,
though not necessarily, horizontal axis of rotation 6. In an
alternative embodiment not shown, axis of rotation 6 may be
vertical or inclined.
[0031] Drying chamber 4 has a preferably frontal access opening 7
closable by a door 8 preferably hinged to casing 2.
[0032] Drum 3 may be rotated about axis of rotation 6 by an
electric motor, schematically represented in FIG. 1 and indicated
with reference number 9, is fed with hot air heated by a heating
device, schematically represented in FIG. 1 and indicated with
reference number 10, and is fed into drum 3 preferably by a fan
schematically represented in FIG. 1 and indicated with reference
number 11. Fan 11 may preferably, though not necessarily, be driven
by electric motor 9 or, in an alternative embodiment (not shown),
by an auxiliary electric motor (not shown) independent of electric
motor 9.
[0033] In the FIG. 1 example, one opened side of the drum 3 of the
laundry drier 1 is advantageously associated, in a rotatable and
substantially air-tight way, to a perforated inner wall 12 fixed to
a lateral wall of casing 2 and through which hot air flows into
drum 3; the other opened side of the drum 3 is advantageously
associated, in a rotatable and substantially air-tight way, to a
flange 13 associated to casing 2 and interposed between door 8 and
front access opening 7 of drum 3.
[0034] In the FIGS. 1 and 2 example, flange 13 is fixed firmly to
casing 2, and is positioned at front access opening 7 so as to
project at least partly inside drum 3, so that its inner surface
faces the laundry 5 when the latter is loaded into the drum 3.
[0035] Heating device 10 may advantageously comprise one or more
electric heating components, such as electric resistors (not shown)
or, in an alternative embodiment, a heat pump.
[0036] In actual use, fan 11 blows a stream of drying air
(represented by the white arrows in FIG. 1), produced by heating
device 10, preferably through perforated inner wall 12 into drum 3.
After contacting laundry 5 inside drum 3, the moisture-laden drying
air flows out of drum 3 and it is preferably directed to a
condensing device 15, which cools the drying air to condense the
moisture inside it. For this purpose, condensing device 15 may be
supplied with cold air from outside the drier, and feeds the
moisture-free air to fan 11. It should be pointed out that
condensing device 15 as described above applies, purely by way of
example, to one possible embodiment of the present invention, and
may be omitted in the case of an exhaust-type rotatable-drum
laundry drier 1 (i.e. in which the hot and moisture-laden drying
air from the rotatable laundry drum 3 is expelled directly out of
rotatable-drum laundry drier 1).
[0037] The rotatable-drum laundry drier 1 also comprises an
electronic control system 16, which is configured to control the
rotatable-drum laundry drier 1, advantageously on the basis of a
drying cycle selected by a user via a user control interface
18.
[0038] The electronic control system 16 advantageously comprises an
electrode sensor 22 for detecting dryness of the laundry.
[0039] According to a preferred embodiment, the electrode sensor 22
is a contact electrode sensor type and comprises two metal plates
23 arranged on the flange 13 in a position facing the inside of the
drum 3, for sensing the dryness of laundry by using impedances
generated at opposite ends of the metal plates 23 according to
moisture content of the laundry 5 when the later is brought into
contact with the opposite metal plates 23, and forwards the dryness
as a electrical signal, i.e. a voltage signal. Nevertheless, it is
obvious that electrical signal outputted by the electrode sensor 22
could be associated, for example, with the resistance and/or
conductance of the laundry 5 sensed between the metal plates
23.
[0040] Preferably the electrode sensor is configured to generate an
oscillating electrical signal and vary the frequency of oscillation
of the electrical signal according to the laundry
moisture/dryness.
[0041] The electronic control system 16 further comprises an
electronic control unit 14, which is configured to control the
electric motor 9, heating device 10 and/or fan 11 in order to
regulate the rotation speed of the drum 3, the temperature and/or
the flow rate of hot air entering the drum 3 according to preset
temperatures and flow rates specified for the laundry drying cycle
selected by the user.
[0042] Preferably, selectable laundry cycles may comprise for
example, a "cotton laundry drying cycle", a "synthetic fabric
laundry drying cycle", a "wool laundry drying cycle", and a
"delicate laundry drying cycle".
[0043] The electronic control unit 14 is further configured to:
[0044] detect the presence/absence of moist laundry 5 inside the
rotatable drum 3 by the electrode sensor 22; [0045] if presence of
moist laundry 5 inside the rotatable drum 3 is detected, start a
drying cycle that user selected.
[0046] Advantageously, if presence of moist laundry 5 inside the
rotatable drum 3 is not detected, the electronic control unit 14
stops operation of the rotatable-drum laundry dryer 1.
[0047] It should be pointed out that "detecting the
presence/absence of moist laundry 5 inside the rotatable drum 3"
comprises both simply detecting the presence/absence of laundry
inside the drum 3 (i.e. independently on the moisture of the
laundry), and detecting the presence/absence of laundry having a
prefixed degree of moisture (or in other words having a prefixed
degree of dryness).
[0048] In other words the electronic control unit 14 is configured
to sense (by using the electric signals coming from the electrode
sensor 22) both if there is laundry or not inside the drum, and if
the laundry is moist or not, i.e. if the dryness of the laundry
sensed by the electrode sensor 22 is below or above a threshold
value (DRL) which may preferably depend on the drying cycle
selected by the user.
[0049] If laundry is not sensed at all, or if laundry is sensed,
but its dryness is above a prefixed threshold (DRL), i.e. if moist
laundry has not been detected inside the drum 3, the drying cycle
is not started, while if laundry is sensed, and its dryness is
below a prefixed threshold (DRL), i.e. if moist laundry has been
detected inside the drum 3, electronic control unit 14 starts the
drying cycle that user selected.
[0050] The electronic control unit 14 is further configured to:
[0051] sense dryness of the laundry 5 during the drying cycle;
[0052] measure (or calculate, determine, estimate, detect) the
cycle time TD at which the sensed dryness reaches a preset dryness
threshold (which preferably depends on the specific laundry cycle
selected by the user); [0053] if the cycle time TD is lower than a
preset dryness threshold time (Sm), continue the drying cycle for a
first additional time D1, [0054] stop the drying cycle at the end
of this first additional time D1.
[0055] Preferably the first additional time D1 is such that the
time elapsed from the beginning of the drying cycle and the
stopping of the drying cycle is a preset minimum dryness time Tmin
(e.g. 30 minutes).
[0056] More preferably the first additional time D1 is set as the
difference from the preset minimum dryness time Tmin and the cycle
time TD at which the sensed dryness reaches a preset dryness
threshold (e.g. if TD is 10 minutes, and Tmin is 30 minutes, then
D1 is 20 minutes).
[0057] It should be pointed out that in the present application
"drying cycle" indicates the part of the cycle starting when the
heating device 10, i.e. electric resistor or heat pump, is
switched-on for the first time, and ending when the heating device
10 is permanently switched-off.
[0058] During the "drying cycle" the heating device 10 may be
continuously switched on, or it may be repeatedly switched on and
off according to a time pattern depending on the laundry cycle
selected by the user.
[0059] Advantageously the above mentioned preset dryness threshold
depends on the laundry cycle selected by the user.
[0060] In other words, the electronic control unit 14 is configured
to: [0061] determine the presence/absence of moist laundry 5 inside
the rotatable drum 3 by using electric signal coming from electrode
sensor 22; [0062] start a selected drying cycle if the rotatable
drum 3 is not empty and if the dryness of the loaded laundry is
below a certain prefixed threshold value (DRL) (or in other words
if the laundry moisture is above a certain prefixed threshold);
[0063] sense, preferably continuously, the dryness of the laundry,
i.e. based on the frequency of the electric signal outputted from
the electrode sensor 22; [0064] compare sensed dryness with a
preset dryness threshold, and measure (or calculate, estimate,
detect, determine) the cycle time TD when sensed dryness reaches
the preset dryness threshold.
[0065] The electronic control unit 14 compares the cycle time TD
when sensed dryness reaches the preset dryness threshold with a
preset dryness threshold time Sm, and if the measured cycle time TD
is lower than a the dryness threshold time Sm, electronic control
unit 14 continues to perform the drying cycle for a certain time
(first additional time D1), preferably for a period of time such
that the time elapsed (e.g. measured) from the beginning of the
drying cycle, reaches a preset minimum dryness time Tmin.
[0066] It is underlined that the phase of "detecting the
presence/absence of moist laundry 5 inside the rotatable drum 3 and
starting a drying cycle if presence of moist laundry 5 inside the
rotatable drum 3 is detected" (while don't starting the drying
cycle if presence of moist laundry 5 inside the rotatable drum 3 is
not detected) has a sort of synergic effect with the phases of
"measuring (or calculating, determining, estimating, detecting) the
cycle time TD at which the sensed dryness reaches a preset dryness
threshold and, if the cycle time TD is lower than a preset dryness
threshold time (Sm), continuing the drying cycle for a first
additional time D1"; in fact if the phase of "detecting the
presence/absence of moist laundry 5 inside the rotatable drum 3 and
starting a drying cycle only if presence of moist laundry 5 inside
the rotatable drum 3 is detected" weren't comprised in the method,
and if the user erroneously started a drying cycle without loading
any piece of laundry in the drum or loading already dry laundry,
the drying cycle would start and (for the reasons explained above
with reference to the problems of the prior art solutions) the
sensed dryness would reach a preset dryness threshold very quickly,
and therefore the drying cycle would continue for a first
additional time D1, with a further useless energy consumption.
[0067] Therefore the combination of the phases of "detecting the
presence/absence of moist laundry 5 inside the rotatable drum 3 and
starting a drying cycle only if presence of moist laundry 5 inside
the rotatable drum 3" and of "measuring (or calculating,
determining, estimating, detecting) the cycle time TD at which the
sensed dryness reaches a preset dryness threshold and, if the cycle
time TD is lower than a preset dryness threshold time (Sm),
continuing the drying cycle for a first additional time D1" is very
effective in solving the above mentioned problems of the prior art
(i.e. obtaining a uniform laundry dryness even if the laundry
inside of the drum is few and/or is arranged inside the
rotatable-drum so that number of contacts with the electrode sensor
is very low, and at the same time strongly reducing the wastage of
electric energy).
[0068] With reference to FIG. 3, an example of the operations
implemented by the control method performed by the electronic
control system 16 made according to the principles of the present
invention shall now be described.
[0069] In the initial phase (block 100), heating device 10 is
turned-off, the electronic control unit 14 recognises the selected
drying cycle/program and preferably performs a detach phase,
wherein it turns-on and controls the electric motor 9 to rotate the
rotatable laundry drum 3 for a preset detaching time so as to
detach the laundry 5 from the inner surface of the rotatable
laundry drum 3 for increasing the probability that laundry 5 is
brought into contact with the electrode sensor 22. According to the
preferred embodiment, the preset detaching time could be set
between ten and twenty seconds, preferably about fifteen
seconds.
[0070] The electronic control unit 14 performs a starting detection
phase (block 110) for a starting detection time, during which it
controls the electric motor 9 to rotate the rotatable laundry drum
3 with preset rotation speed/s, and determines the presence/absence
of the moist laundry 5 inside the drum 3 based on the electric
signal outputted from the electric sensor 22.
[0071] Preferably, electronic control unit 14 determinates (i.e.
concludes or resolves) presence of moist laundry based on the
impedance of the laundry 5 sensed between the metal plates 23
and/or according to the frequency of the electric signal outputted
from the electrode sensor 22.
[0072] The electronic control unit 14 advantageously checks whether
moist laundry is present or absent inside of the drum 3 (block 120)
based on presence or absence condition is detected and in positive
case (YES output from block 120) controls the rotatable-drum
laundry dryer 1 in order to perform the user selected drying cycle
(block 130). In that case, electronic control unit 14 controls the
electric motor 9, the heating device 10 and the fan 11 according to
preset control-parameters/control program associated with the
drying cycle that user selected.
[0073] In negative case (NO output from block 120), the electronic
control unit 14 preferably sets a counter N=1 (block 140), performs
an additional detection phase for an additional detection time ADT,
e.g. thirty seconds, during which it determinates, preferably by
impedance sensed by the electrode sensor 22 and/or according to the
frequency of the electric signal outputted from the electrode
sensor 22 (block 150) if moist laundry is present or absent inside
of the drum 3 (block 160).
[0074] Advantageously the additional detection time (ADT) is lower
than the starting detection time of the starting detection phase
(block 110).
[0075] In negative case (NO output from block 160), the electronic
control unit 14 advantageously increases the counter N=N+1 (block
170), and checks if increased counter N=N+1 is equal or greater
than a preset maximum threshold N.sub.MAX, i.e. N>N.sub.MAX
(block 180).
[0076] In negative case (NO output from block 180), the electronic
control unit 14 performs again the additional detection phase for
the additional detection time ADT (block 150), whereas in positive
case (YES output from block 180), the electronic control unit 14
confirms absence of moist laundry inside of the rotatable laundry
drum 3 (i.e. according to the electronic control unit 14 there is
no moist laundry in the drum) and advantageously stops operation of
the rotatable-drum laundry dryer 1.
[0077] If the electronic control unit 14 detects a moist laundry
presence condition during the starting detection phase (YES output
from block 120) or one of the additional detection phases (YES
output from block 160), it controls the rotatable-drum laundry
dryer 1 to perform the selected drying cycle (block 130).
[0078] In that case, electronic control unit 14 starts drying cycle
by switching-on/controlling the electric motor 9, the heating
device 10 and the fan 11.
[0079] During the drying cycle, the electrode sensor 22 provides
voltage signals associated with the moisture contents of the
laundry 5 so as to sense the dryness of the laundry 5, the
electronic control unit 14 receives the electric signals from the
electrode sensor 22 and measures the cycle time TD at which the
sensed dryness reaches a preset dryness threshold (block 190).
[0080] Advantageously, after starting the drying cycle, electronic
control unit 14 repeatedly senses the dryness of the laundry and
compares, preferably continuously, sensed laundry dryness with the
preset dryness threshold; the electronic control unit 14 measures
(calculates, detects, obtains) the cycle time TD corresponding to
the time at which sensed dryness reaches the preset dryness
threshold.
[0081] The electronic control unit 14 checks if the cycle time TD
is lower than a preset minimum dryness threshold time Sm (i.e. if
TD<Sm) (block 200).
[0082] In positive case (YES output from block 200), i.e. the cycle
time TD is lower than the preset minimum dryness threshold time Sm,
the electronic control unit 14 concludes (or determines, resolves)
an insufficient dryness condition, and continues to perform the
drying cycle for a first additional time D1 (block 210), after
which the drying cycle is stopped (block 220).
[0083] Preferably electronic control unit 14 sets the first
additional time D1 in such a way that the drying cycle ends when
the time elapsed from the beginning of the drying cycle reaches a
preset minimum dryness time Tmin.
[0084] Advantageously the electronic control unit 14 sets the first
additional time D1 as the difference between the preset minimum
dryness time Tmin and the cycle time TD at which sensed dryness
reaches the preset dryness threshold.
[0085] Regarding what has been described above, it should be
pointed out that during the first additional time D1, the
electronic control unit 14 continues to keep switched on the
electric motor 9, the fan 11 and the heating device 10 according to
the selected drying cycle.
[0086] According to a preferred embodiment, the preset minimum
dryness time Tmin may vary according to the selected drying cycle
or may be a preset value, preferably comprised between twenty and
thirty-five minutes, preferably about thirty minutes.
[0087] In negative case (No output from block 200), i.e. whether
cycle time TD at which sensed dryness reaches the preset dryness
threshold is equal or greater than preset minimum dryness threshold
time Sm, the electronic control unit 14 concludes (or determines,
resolves) an admissible dryness condition, and continues to perform
the drying cycle for a preset second additional time D2 (block
230). In other words, if admissible dryness condition is detected,
the electronic control unit 14 continues to perform the drying
cycle, after the cycle time TD, for the preset additional time D2,
after which the drying cycle is stopped (block 230).
[0088] Preferably the preset additional time D2 depends on the
selected drying cycle.
[0089] Preferably, the preset additional time D2 is between 0 and
ten seconds; if D2 is 0 seconds, the drying cycle is stopped
immediately or substantially immediately after the electronic
control unit 14 concludes (or determines, resolves) that it has
been reached the admissible dryness condition.
[0090] According to the preferred embodiment, after stopping of the
drying cycle, electronic control unit 14 may preferably perform a
final cooling phase (block 240), wherein drum 3 may be kept
turning, and non-heated air (since the heating device 10 has been
permanently switched-off) may be fed into drum by the fan 11 so as
to lower the high temperature to a predetermined low temperature
(e.g. 30.degree. C.) at which laundry 5 can be handled by the
user.
[0091] Regarding what has been described above, it should be
pointed out that the above-described control method may
advantageously be encoded in software that can be loaded in the
electronic control unit 14 of the rotatable-drum laundry drier 1
and designed to ensure that, when executed, the electronic control
unit 14 becomes configured for controlling the rotatable-drum
laundry drier 1 according to the provisions of the method.
[0092] The laundry dryer of the present invention has the following
advantages.
[0093] The additional detecting phases permit the laundry dryer to
improve detecting the condition of empty-drum or of already-dry
laundry loaded, and in this case to immediately stop operating the
laundry dryer, so as to decrease wastage of electric energy.
[0094] Moreover, increasing of cycle time in case of detection of
an insufficient dryness condition assures uniform laundry dryness,
even in case of small load/quantity of laundry, and/or when the
latter is arranged inside the rotatable-drum so that number of
contacts with the electrode sensor is very low.
[0095] Clearly, changes may be made to the method and the
rotatable-drum laundry dryer as described and illustrated herein
without, however, departing from the scope of the present
invention.
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