U.S. patent application number 09/761245 was filed with the patent office on 2001-10-25 for steam iron.
Invention is credited to Arun, Sundaram S., Har, Tang Pong.
Application Number | 20010032403 09/761245 |
Document ID | / |
Family ID | 20430517 |
Filed Date | 2001-10-25 |
United States Patent
Application |
20010032403 |
Kind Code |
A1 |
Har, Tang Pong ; et
al. |
October 25, 2001 |
Steam iron
Abstract
Electric steam iron comprising an electrically heated soleplate
(2), said soleplate (2) having at least one steam vent (20); a
controllable steam generator (6) for supplying steam to the at
least one steam vent (20), and control means (16) for controlling
the steam generator (6); wherein the steam iron further comprises a
temperature sensor means (24) for sensing the temperature of the
soleplate (2), said temperature sensor means (24) in use supplying
a temperature dependent signal to the control means (16) and the
control means (16) being adapted to activate the steam generator
(6) in accordance with a predetermined steam pattern comprising at
least a first phase of a first predetermined duration, in which
steam is supplied at a substantially constant peak steam rate, and
at least a second phase, in which steam is supplied at a
substantially constant lower steam rate, wherein at least said peak
steam rate depends upon the temperature of the soleplate (2).
Inventors: |
Har, Tang Pong; (Singapore,
SG) ; Arun, Sundaram S.; (Singapore, SG) |
Correspondence
Address: |
Jack E. Haken
Corporate Patent Counsel
U.S. Philips Corporation
580 White Plains Road
Tarrytown
NY
10591
US
|
Family ID: |
20430517 |
Appl. No.: |
09/761245 |
Filed: |
January 16, 2001 |
Current U.S.
Class: |
38/77.7 |
Current CPC
Class: |
D06F 75/26 20130101;
D06F 75/18 20130101 |
Class at
Publication: |
38/77.7 |
International
Class: |
D06F 075/26 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 25, 2000 |
SG |
200000430-9 |
Claims
1. An electric steam iron comprising an electrically heated
soleplate (2), said soleplate (2) having at least one steam vent
(20); a controllable steam generator (6) for supplying steam to the
at least one steam vent (20), and control means (16) for
controlling the steam generator (6), wherein the steam iron further
comprises a temperature sensor means (24) for sensing the
temperature of the soleplate (2), said temperature sensor means
(24) in operation supplying a temperature dependent signal to the
control means (16), and wherein the control means (16) is adapted
to activate the steam generator (6) in accordance with a
predetermined steam pattern comprising at least a first phase of a
first predetermined duration, in which steam is supplied at a
substantially constant peak steam rate, and at least a second
phase, in which steam is supplied at a substantially constant lower
steam rate, wherein at least said peak steam rate depends upon the
temperature of the soleplate (2).
2. An electric steam iron as claimed in claim 1, wherein the lower
steam rate depends upon the temperature of the soleplate (2).
3. An electric steam iron as claimed in claim 2, wherein the lower
steam rate is substantially equal to the steam rate that can be
sustained by the electric power available for heating the soleplate
(2).
4. An electric steam iron as claimed in claim 1, 2 or 3, wherein
the control means (16) include a programmable microcomputer using a
look-up table in order to select a steam pattern depending upon the
temperature dependent signal from the temperature sensor (24).
5. An electric steam iron as claimed in claim 1, 2, 3, or 4,
comprising a steam on/off-switch (26) which in operation supplies
an input signal to the control means.
6. An electric steam iron as claimed in claim 1, 2, 3, 4, or 5,
comprising a hand-presence sensor (28) for supplying an input
signal to the control means (16).
7. An electric steam iron as claimed in claim 1, 2, 3, or 4,
comprising a setting means (26) for selecting a fabric type and for
supplying an input signal to the control means (16).
8. An electric steam iron as claimed in claim 4, 5, 6, or 7,
wherein a plurality of look-up tables or look up table sections
selectable by the user have been provided.
Description
[0001] The invention relates to an electric steam iron comprising
an electrically heated soleplate, said soleplate having at least
one steam vent, a controllable steam generator for supplying steam
to the at least one steam vent, and control means for controlling
the steam generator.
[0002] An electric steam iron of the above type has been disclosed
in European patent application No. 0 390 264.
[0003] In ironing of clothing three different processes can be
distinguished: conditioning of the fibers, relaxation of the fibers
and fixation of the fibers. During the conditioning the fibers are
prepared for the relaxation. The conditioning is done by increasing
the temperature of the fibers in order to make the fibers weak,
which during the relaxation, enhance the recovery of the fibers
from the plastic deformation caused by wearing of the clothing. The
use of steam is an effective way to increase the temperature.
Moreover, the weakness of some fibers also increases with the water
content, especially for cotton, linen, viscose and wool. After the
conditioning the relaxation or real ironing takes place. During the
relaxation the weak fibers are being pressed between the soleplate
and the ironing board. This should last sufficiently long to allow
the fibers to recover from the plastic deformation. The moisture
content of the fabric should not decrease too fast during
relaxation in the case of cotton, linen and wool, as this would
adversely affect the relaxation process. After relaxation the
opposite from the conditioning takes place. This means that the
weakness of the fibers is reduced to prevent the return of
wrinkles. The fixation comprises the drying of the fibers, followed
by cooling down.
[0004] During the conditioning the temperature of the fabric
increases to about 100.degree. C., partly by condensation of steam
and partly due to heating by the soleplate. During the relaxation
the temperature should be kept at about 100.degree. C. to maintain
both a high temperature and a high moisture content of the fabric,
which provides for a fast recovery of the fibers. After the
relaxation the fabric is being dried, indicated by a temperature
increase in the fabric above 100.degree. C., and followed by
cooling down to assure a proper fixation. This cooling down takes
place partly on the ironing board and partly after removal of the
cloth from the board to clear the board for the next cloth.
[0005] In conventional steam irons the steam rate is set and the
iron is moved forwards and backwards over the fabric. In the
forward stroke the amount of steam is insufficient in most cases to
heat the fabric up to 100.degree. C., whereas after passing of the
steam vents the fabric is heated further by the soleplate to a
higher temperature closer to 100.degree. C. In the backward stroke
the production of steam still continues, but the fabric will
already reach 100.degree. C. and will not adsorb much water.
Although it does not affect the fabric, steam is wasted that could
have been used to warm up and more intensively moisten the fabric
in order to obtain a weaker fabric at a higher temperature during
the forward stroke. Unused steam is blown through the fabric into
the ironing board and to the surrounding air without the desired
condensation onto and in the fabric. Thus, a lot of heat and water
is wasted.
[0006] In the steam iron disclosed in the above mentioned European
patent application No. 0 390 264 waste of steam is reduced by
controlling the amount of steam produced by the steam generator as
a function of time. The steam generator includes a steam chamber
which is designed as a pressure tank and in which a buffer stock of
steam is formed, which is released at the beginning of an ironing
cycle. The amount of steam produced starts with a high value and
decreases more or less from that value linearly to a lower value.
The steam production is controlled by regulating the output power
of an additional heating element specifically provided for the
steam buffer chamber. It is further known to adapt the steam
production in said known steam iron to the amount of heat required
to heat the fabric, by measuring the power need of the heating
element of the soleplate. Such measuring, however, is inaccurate
and slow.
[0007] An electric steam iron having an improved steam generation
as compared to the iron disclosed in EP-A-0 390 264 is disclosed in
U.S. Pat. No. 5,642,579. In accordance with U.S. Pat. No. 5,642,579
a steam iron comprises a fabric temperature sensor for detecting
the temperature of the fabric to be ironed and control means
responsive to a signal from the fabric temperature sensor for
controlling the amount of steam produced. Thus steam generation is
controlled by the fabric temperature and this is done in such a
manner that steaming is stopped when a predetermined fabric
temperature of about 100.degree. C. or a slightly lower temperature
is reached. A cool fabric automatically triggers the steam
production and the steam production is automatically shut off when
the fabric has reached the predetermined fabric temperature.
[0008] In accordance with the present invention the steam
production does not depend upon a buffer stock in a heated pressure
tank. Moreover, the steam production is not based on the
temperature of the fabric being ironed but on the soleplate
temperature. More in particular, in accordance with the present
invention each soleplate temperature value or range of values
corresponds to a specific steam generation pattern comprising a
substantially constant peak steam rate during a first time interval
and a substantially constant lower peak steam rate during a second
time interval.
[0009] The invention provides an improved electric steam iron
comprising an electrically heated soleplate, said soleplate having
at least one steam vent; a controllable steam generator for
supplying steam to the at least one steam vent and control means
for controlling the steam generator, wherein the steam iron further
comprises temperature sensor means for sensing the temperature of
the soleplate, said temperature sensor means in use supplying a
temperature dependent signal to the control means, and wherein the
control means is arranged to activate the steam generator in
accordance with a predetermined steam pattern comprising at least a
first phase of a first predetermined duration, in which steam is
supplied at a substantially constant peak steam rate, and at least
a second phase, in which steam is supplied at a substantially
constant lower steam rate, wherein at least said peak steam rate
depends upon the soleplate temperature.
[0010] The invention will now be explained in greater detail with
reference to the drawing.
[0011] FIG. 1 schematically shows an example of an electric steam
iron in accordance with the invention;
[0012] FIG. 2 graphically shows by way of example two steam/time
patterns for use in an electric steam iron in accordance with the
present invention; and
[0013] FIG. 3 shows a flow chart of an example of a control program
for an electric steam iron according to the invention.
[0014] FIG. 1 shows an example of of a steam iron embodying the
invention, having soleplate temperature dependent steam generation.
The steam iron has a conventional soleplate 2, which is heated by
an electric heating element 4. The temperature of the soleplate 2
is kept at a desired temperature by means of a conventional
thermostat (not shown) and a temperature dial 5 as known from the
art of conventional steam irons. However, alternatively other known
means to control the temperature of the soleplate 2 can be
employed, such as fully electronic control with a triac, a
temperature sensor for measuring the temperature of the soleplate
and an adjustable reference for changing the desired temperature of
the soleplate. Steam is generated by a steam generator 6, which
comprises a water tank 8, a water dosing means, in this example a
pump 10, and a steam chamber 12. The water pump 10 pumps water from
the water tank 8 to the steam chamber 12 via a hose 14 under
command of a pump signal PS from an electric control device 16. The
steam chamber 12 is heated by the soleplate, but an auxiliary
heating element may be provided. FIG. 1 by way of example shows an
auxiliary heating element 18, which may be controlled by a
conventional thermostat (not shown), or an electronic or a similar
control device. The steam from the steam chamber 12 reaches steam
vents 20 connected to the steam chamber or to a steam duct 22. A
soleplate temperature sensor 24 is embedded in the soleplate 2 at a
suitable location and in this embodiment it is surrounded by the
steam vents 20. The temperature sensor 24 may be the same sensor as
used in some irons for monitoring the soleplate temperature in
order to control the soleplate temperature, or it may be a separate
temperature sensor. The temperature sensor 24 senses the soleplate
temperature during ironing and sends a soleplate temperature signal
SPTS to the control device 16, which signal is indicative of the
actual temperature of the soleplate. The temperature sensor 24 may
be a resistor with a positive temperature coefficient (PTC) or a
negative temperature coefficient (NTC) of suitable dimensions. A
thermocouple or a contactless infra-red sensor may be used as
well.
[0015] All electrical parts, such as the heating element 4, the
heating element 18 (if present), the water pump 10 and the control
device 16 receive suitable AC or DC supply voltages in a
conventional manner, not shown.
[0016] The steam iron shown in FIG. 1 further has a selector switch
or button 26 by means of which the user may select dry ironing or
activate steam ironing. The present embodiment has also a
handsensor 28 in or on the handle 30 of the iron. The hand sensor
may be for example a switch device, or a photocell, a touch control
device or a leakage current switch. A suitable hand sensor would be
a capacitive sensor. However, a movement detector located anywhere
in the iron may also be used as a hand sensor.
[0017] The selector switch 26 and the hand sensor 28 both supply
signals to the control device 16. Said signals may be received, for
example, by an AND-device (not shown), whose output signal is an
enabling signal for the control device, without which signal no
pump signal activating PS will be supplied. In a preferred
embodiment the predetermined steam pattern will selectively either
be started automatically at the beginning of a new ironing cycle
after a preceding ironing cycle has been terminated by placing the
iron on its heel, or it will be started after the user has operated
a control button or the like. For the selection of automatic (smart
steam) operation or user initiated operation a suitable selector
means may be provided. Said selector means could be combined with
the selector switch mentioned above or it could be a separate
means.
[0018] The control device may comprise a microcomputer suitably
programmed with control software, or it may be a dedicated
electronic circuit.
[0019] A flow chart representing an example of a program for a
programmable control device is shown in FIG. 3. The elements of the
flow chart have the following inscriptions:
[0020] 40 START
[0021] 41 T>Tmin?
[0022] 42 DEACTIVATE PUMP
[0023] 43 RECORD SOLEPLATE TEMPERATURE
[0024] 44 USER'S HAND PRESENT?
[0025] 45 RETRIEVE SUITABLE STEAM PATTERN FROM LUT
[0026] 46 ACTIVATE PUMP
[0027] N means NO (false) and Y means YES (true)
[0028] The control device starts at step 40 in FIG. 3 after having
received the necessary enabling signal(s) as indicated above.
[0029] In use the control device receives a soleplate temperature
signal SPTS and first compares this signal with a predetermined
value corresponding to a predetermined minimum temperature Tmin of,
for example, 110.degree. C. This is represented by step 41 in FIG.
3.
[0030] If the soleplate temperature is lower than the predetermined
temperature a deactivation signal is sent to the pump, as shown in
step 42. If the soleplate temperature is higher than the
predetermined temperature the actual temperature value is
determined and stored in step 43. In step 44 it is checked whether
the user's hand is present. If not, the program returns to step 41.
If the hand sensor is activated by the user's hand a suitable steam
pattern is retrieved in step 45 from a look up table (LUT) stored
in a memory of the microcomputer. As an alternative, the LUT may be
incorporated in a chip. In a dedicated hardware circuit such a look
up table may be represented, for example, by a number of
comparators or a number of binary values which are compared with a
binary value representing the actual soleplate temperature or a
certain range including the actual soleplate temperature.
[0031] After having found a suitable steam pattern a corresponding
pump signal is generated and the pump is activated correspondingly
in step 46.
[0032] In accordance with the present invention a suitable steam
pattern comprises a first phase of a predetermined duration during
which steam is generated at a substantially constant peak steam
rate. The first phase is immediately followed by a second phase
during which steam is generated at a substantially constant but
lower steam rate.
[0033] An example of a look-up table is shown below.
1 Soleplate Temp (.degree. C.) Peak Steam (g/min) Average Steam
(g/min) 190-230 60 35 160-190 45 25 130-160 30 15 110-130 15
5-10
[0034] FIG. 2 schematically shows two examples of steam patterns in
accordance with the present invention. In the left-hand part of the
graph of FIG. 2 the soleplate temperature is 220.degree. C.
[0035] This results in a steam pattern comprising a peak steam
production of 60 g/min for T1 seconds. T1 may be, for example, 6
seconds. Thereafter the steam production is reduced to a much lower
value of 35 g/min during a second time interval which may or may
not have a predetermined duration.
[0036] The right-hand part of FIG. 2 relates to a soleplate
temperature of 160.degree. C., which results in a peak steam
production of 40 g/min during T1' seconds and then a reduced steam
production of 20 g/min.
[0037] The initial peak steam production phase during every new
ironing cycle serves to wet the fabric with a large amount of
moisture (condensed steam) before the fabric heats up to
>100.degree. C. and the moisture absorption decreases.
[0038] The initial peak steam production is much higher than the
average steam production as can be sustained by the heating of the
soleplate through the electric power absorbed by the iron. Such an
initial high peak steam production is possible even though the
soleplate temperature will decrease to a certain extent during
steaming because of the thermal capacity of the soleplate, which
thermal capacity allows the storage of heat in the soleplate
between ironing cycles. Thus the maximum value of the peak steam
production as well as the maximum value of T1 depend upon the
thermal capacity of the soleplate. Thus, if the thermal capacity of
the soleplate would allow a maximum steam peak rate of 60 g/min for
6 seconds it would also be possible to select a steam peak rate of,
for example, 80 g/min for 41/2 seconds or 120 g/min for 3 seconds.
In general, the maximum steam peak rate SPRmax multiplied by T1max
will provide a maximum value, which cannot be exceeded. Of course,
lower values would be possible. Instead of 60 g/min for 6 seconds,
one could choose to steam 40 g/min for 6 seconds or 120 g/min for 2
seconds etc. Thus, a plurality of LUT's, or a LUT having a
plurality of sections to be chosen by the user, might be used.
[0039] The steam peak is follwed bythe second phase in which a
lower steam rate prevails. The lower steam rate may be the average
steam rate corresponding to the electrical energy used for heating
the soleplate and the withdrawal of heat from the soleplate by the
fabric and by the steam generation. Said average value could be
maintained as long as desired, but a lower steam rate would also be
possible. In order to obtain the desired amounts of steam the pump
can be controlled by a suitable electric pump signal, for example a
pulse signal, in order to pump the required amount of water from
the water tank 8 to the steam chamber 12.
[0040] In a preferred embodiment the initial peak steam rate is the
maximum peak steam rate allowed by the soleplate temperature, the
thermal capacity of the soleplate and the peak steam time T1,
whereas the lower steam rate in the second phase is also as high as
possible and will be maintained as long as the ironing cycle
lasts.
[0041] In the example of a look up table given above, the peak
steam rate decreases as the soleplate temperature decreases, while
the time interval during which the peak steam rate is generated is
kept constant. As may have become clear from the above explanation,
it would be possible to select a higher peak steam rate for a given
soleplate temperature range if a shorter time interval is used.
Thus, it would be possible to generate 60 g/min of steam at a
soleplate temperature in the range 160 - 190.degree. C. if T1 is
not 6 seconds but 4.5 seconds.
[0042] The steam rate during the second phase should be equal to or
lower than the maximum possible average steam rate. It would be
possible to use less steps than the four steps indicated in the
look-up table provided as an example. It would even be possible to
use only a single average steam rate, which then should be such
that it can be sustained even at the lowest soleplate temperature
range.
[0043] However, as stated before, the maximum amount of steam will
be desired in general.
[0044] It is to be noted that after the above explanation of the
invention various modifications will be obvious to a person skilled
in the art. For example, a look-up table having more than one
section may be used, wherein the section to be used depends upon
the type of fabric to be ironed, for example thick, medium or thin
fabrics. Settings operable by the user to this effect may be
available on the iron. As an alternative, the duration of the first
and possibly second phase might be varied depending upon the type
of fabric.
[0045] Further, instead of an electronic control means an at least
partly mechanical control means including at least one bimetal
element could be used.
* * * * *