Ironing system with water delivery mechanism FIELD

The present invention relates to an ironing system with water delivery mechanism, in particular to an ironing system comprising a steam iron and a base unit.

The invention has some applications in the field to garment care. BACKGROUND

A cordless steam iron with energy and water charging offers convenience to users by freeing them from a cord, as compared to more traditional solutions in which energy and steam/water are provided by a cord. A cordless steam iron thus does not restrict freedom of movement of the user.

However, the ability of generating steam in known cordless systems is not optimal, since it has to be compromised due to the limited thermal energy stored in the steam iron, and to the limited amount of water stored in the steam iron. This may result in situations where the thermal energy stored in the steam iron is not sufficient to generate steam, resulting in water spitting on the garments being ironed.

This may also result in situations where the thermal energy stored in the steam iron is sufficient to generate steam, but the water stored in the steam iron is not sufficient and/or has been fully used-up.

There is thus a need to find solutions for cordless steam irons to ensure a more optimal compromise between stored thermal energy for generating steam and water amount stored in the steam iron. Prior art US6176026B1 discloses a cordless steam iron provided with an external reservoir assembly for automatically re-filling an internal reservoir when the iron rests on an iron stand. The reservoir assembly includes a removable bottle that can be readily filled with water and then placed upside down in a water container. A valve automatically maintains the water level in the container (and the internal reservoir) to a desired maximum level see chain-dotted line A. Water valves cooperate with one another and open automatically when the iron is placed on the stand, to allow water to flow from the container to the reservoir.

SUMMARY

It is an object of the invention to provide an improved ironing system that substantially alleviates or overcomes one or more of the problems mentioned above.

The invention is defined by the independent claims. The dependent claims define advantageous embodiments.

According to an aspect of the present invention, there is provided an ironing system comprising a steam iron and a base unit adapted to cooperate with each other such that the steam iron can take a first position in which the steam iron is docked on the base unit, and a second position in which the steam iron is undocked from the base unit, the steam iron being cordlessly detached from the base unit in the second position.

The steam iron comprises:

a water reservoir arranged to store water,

a soleplate for generating steam from water in the water reservoir when the steam iron is in the second position,

The base unit comprises:

a water delivery mechanism for supplying water to the water reservoir when the steam iron is in the first position,

a power supply unit for supplying energy to the soleplate when the steam iron is in the first position, for heating the soleplate.

The ironing system is characterized in that it comprises:

a temperature sensor for sensing temperature of the soleplate,

a controller for determining, based on a variation of temperature of the soleplate, an amount of water to be supplied to the water reservoir by the water delivery mechanism. A main contributor to the temperature drop of the soleplate is linked to the amount of water consumed during steam ironing of garments. Therefore, the variation of the sensed soleplate temperature can be used to determine the amount of water to be provided by the water delivery mechanism to the water reservoir when the steam iron is in the first position. Hence, an ironing system according to the above aspect can determine the amount of water to be provided by the water delivery mechanism to the water reservoir when the steam iron is in the first position without using a water sensor in the steam iron. Moreover, this reduces the manufacturing costs when compared to systems including a water sensor. In some conventional systems, a pump is used at full power to fill a water reservoir of a cordless steam iron when it is docked until, for example, the water reservoir is determined to be full by means of sensed back pressure. However, such conventional systems put stress on the seals and the piping system within the steam iron and/or base unit. In contrast, using an ironing system according to the invention, the controller can achieve that a proper amount of water is supplied to the water reservoir to reduce the side effects of water being over- supplied and under- supplied, without using sensed back pressure. This can enable that the water reservoir is filled- in to the proper or near correct amount, with reduced stress on the components of the steam iron and/or base unit (e.g. seals). In a preferred embodiment, the variation of temperature corresponds to the difference between the temperature of the soleplate when the steam iron is in a current first position, and the temperature of the soleplate when the steam iron was in a previous first position.

Measuring the drop of temperature between two successive docking in the first position, when the iron is just undock and when the iron is just docked back, allows an estimation of the amount of water used during ironing, and thus fill-in the water reservoir with about the same amount of water when the steam iron is retuned in the first position.

In a preferred embodiment, the controller is further adapted to determine the amount of water, based on a time duration between two successive docking of the steam iron on the base unit. On top of temperature sensing, adding the time duration between two successive docking of the steam iron on the base unit allows a more accurate determination of the amount of water to be filled-in the water reservoir. Indeed, the longer this time duration, the higher the probability that non-steaming period of time have occurred as well, also contributing to causing a drop of temperature of the soleplate (although for a combination of dry ironing and steam ironing the error margin is not high because the heat energy used to convert water into steam is much higher than heat loss during dry ironing). Using the time duration between two successive docking of the steam iron, together with the sensed drop of temperature, allows a more accurate determination of the water consumption.

In a preferred embodiment, the controller is further adapted to determine, based on the sensed soleplate temperature, a thermal energy amount to be stored in the soleplate by the power supply unit, and to determine, based on the thermal energy amount, the amount of water to be supplied to the water reservoir, such that the amount of water can be fully transformed into steam by the thermal energy amount.

This allows a proper fill-in of water in the water reservoir, because the amount of water which is filled-in can be fully evaporated based with the thermal energy stored in the soleplate. This also allows that the steam iron can be undocked anytime from the base unit, while safeguarding that the amount of water filled-in the water reservoir could be fully evaporated. As a result, water spitting risk during ironing of garments that would be caused by a lack of thermal energy in the soleplate will be reduced.

In a preferred embodiment, the temperature sensor is arranged in a location taken from the set of locations defined by the base unit and the steam iron.

Arranging the temperature sensor in the iron, and sensing soleplate temperature directly, allows an accurate sensing of core temperature. When the steam iron embeds a source of energy to supply the temperature sensor (e.g. battery), arranging the temperature sensor in the steam iron allows conducting temperature sensing even when the steam iron is undocked from the base unit.

Arranging the temperature sensor in the base unit allows an easy implementation considering the relatively large space in the base unit and ease of wiring. In a preferred embodiment, the controller is arranged in a location taken from the set of locations defined by the base unit and the steam iron.

Arranging the controller in the base unit allows an easy implementation considering the relatively large space in the base unit and accessibility to continuous power supply.

Arranging the controller in the steam iron allows conducting calculations even when the steam iron is undocked from the base unit, provided that the steam iron embeds a source of energy to supply the controller (e.g. battery).

In a preferred embodiment, the steam iron comprises a heating element for receiving energy supplied by the power supply unit.

Using a heating element in the steam iron defines a cost-effective solution for heating the soleplate.

In a preferred embodiment, the heating element and the power supply unit are adapted to be electrically connected when the steam iron is in the first position.

Using this electrical connection between the heating element and the power supply unit defines a cost-effective solution for supplying electrical energy to the heating element for thermal energy generation.

In a preferred embodiment, the base unit comprises an induction system powered by the power supply unit for generating electromagnetic energy towards the steam iron when the steam iron is in the first position.

Using an induction system to provide energy to the steam iron avoids any electrical connector between the base unit and the steam iron.

In a preferred embodiment, the controller is further adapted to generate a first alert signal when the steam iron is in the second position, if the time duration elapsed since the steam iron was undocked from the first position exceeds a given time duration threshold. The generation of this alert signal reminds the user to return the steam iron on the base unit if the undocked period is too long, which would anyway reflects the need to supplying energy to the soleplate and/or fill-in water in the water reservoir. As a result, the user can re-dock the steam iron before the performance of steam generation is reduced due to a lack of thermal energy and/or water. This can enhance ironing performance.

In a preferred embodiment, the controller is further adapted to generate a second alert signal when the steam iron is in the first position, after the thermal energy amount is stored in the soleplate and the amount of water supplied to the water reservoir.

This alert mechanism allows informing the user that the steam iron is ready for ironing. Hence, premature (i.e. too early) undocking from the base unit may be avoided.

The present invention also relates to a method of determining, in an ironing system as described above, an amount of water and energy to be supplied from the base unit to the steam iron.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 shows a schematic graph of temperature variation against water consumed during ironing;

FIGs. 2a and 2b show an ironing system according to the invention in first and second positions, respectively;

FIG. 3 shows a schematic graph of temperature against time during ironing; FIG. 4 is a flow chart of operation of an ironing system according to the invention; FIG. 5 shows a flow chart of a method according to the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS FIGs. 2a and 2b show an ironing system 20 according to the invention. The ironing system 20 comprises a steam iron 200 and a base unit 250.

FIG.2a represents the steam iron 200 in a first position PI being undocked from the base unit 250, while FIG.2b represents the steam iron 200 in a second position P2 being docked on the base unit 250.

The steam iron 200 and the base unit 250 are adapted to cooperate with each other such that the steam iron 200 can take a first position PI in which the steam iron 200 is docked on the base unit 250, and a second position P2 in which the steam iron 200 is undocked from the base unit 250.

The steam iron 200 is cordlessly detached from the base unit 250 in the second position. In other words, no cords to carry electricity, water, signals, etc ...are linking the steam iron 200 and the base unit 250. The steam iron 200 includes a water reservoir 201 arranged to store water. The steam iron 200 also comprises a soleplate 202 for generating steam from the water in the water reservoir 201 when the steam iron 200 is in the second position P2.

The base unit 250 comprises a water delivery mechanism 251 for supplying water to the water reservoir 201 when the steam iron 200 is in the first position PI . The base unit 250 also comprises a power supply unit 252 for supplying energy to the soleplate 202 when the steam iron 200 is in the first position PI, for heating the soleplate 202.

The ironing system 20 further comprises a temperature sensor 203 for sensing temperature of the soleplate 202. The ironing system 20 also comprises a controller 253 for determining, based on a variation of temperature of the soleplate, an amount of water to be supplied to the water reservoir 201 by the water delivery mechanism 251.

The controller 253 may correspond to a microcontroller unit (MCU), or more generally a processing unit or a calculator executing instructions of a computer program stored in a local memory (not shown).

It will be appreciated that FIGs. 2a and 2b show the system schematically, and that various electrical and water flow interconnections (e.g. between the water reservoir 201 and the soleplate 202) are not shown for convenience.

The determination of the water amount by the controller 253 will now be explained in more details along with FIG. 1 and the following Table 1.

Table 1 is an example of the relation between the amount of water evaporated by the soleplate, and the corresponding temperature of the soleplate. This example is given for a soleplate having a thermal mass of 500g. The corresponding curve CI is illustrated in FIG. 1.

For example, if the variation of temperature of the soleplate is between an initial temperature TO = 190 degC and a final temperature Tl = 171 degC, it can be determined that the corresponding amount of water evaporated that caused this drop of temperature is ml - mO = 4.5 - 1.5 = 3 grams. This amount of water evaporated corresponds to the amount of water determined by controller 253 to be filled- in the water reservoir.

The above Table 1 can be stored in a memory in the steam iron or in the base unit, as a thermal characteristic of the soleplate implemented in the steam iron. Alternatively, in case the temperature of the soleplate decreases quasi- linearly with the amount of water evaporated by the soleplate, as illustrated in the example of FIG. 1, the curve CI can be approximated by a linear relation:

T = - 6.33 * m + 200 The amount of water evaporated by the soleplate (and corresponding to the amount to be filled- in) is expressed as follows:

(m2 - ml) = (Tl - T2) / 6.33

So only the slope coefficient of the curve CI (having absolute value 6.33 in the present example) needs to be stored in memory. The controller 253 then determines the amount of water to be supplied to the water reservoir 201 by the water delivery mechanism by dividing the variation of temperature by this slope coefficient. The slope coefficient depends on the design parameters of the iron such as thermal mass, material used, etc... For any given design, with required design parameters, there is a corresponding curve that is stored and used by controller 253. Preferably, the variation of temperature corresponds to the difference between the temperature of the soleplate 202 when the steam iron 200 is in a current first position PI, and the temperature of the soleplate 202 when the steam iron 200 was in a previous first position PI .

The steam iron 200 comprises a heating element 204, a water interface 205, and an electrical interface 206. In this embodiment, the soleplate 202 comprises an ironing plate 202a and a steam generator 202b. The base unit 250 includes a power supply 252, a water interface 255, an electrical interface 256, an external water inlet 257, an external power inlet 258, and a user interfacing means 259.

In this embodiment, the water delivery mechanism 251 comprises a water tank 25 la and a pump 25 lb. The water tank 251 a of the water delivery mechanism 251 may also be provided separately to the apparatus comprising the pump, for example by being arranged fluidly connected to the base unit.

When the steam iron 200 is in the first position PI, the base unit 250 provides water to fill the water reservoir 201. Water is pumped from the water tank 251 a to the steam iron 200 by the pump 25 lb via a connection between the water interfaces 205 and 255 when the steam iron is in the first position PI . This connection can take many forms, and embodiments of the invention are not limited by any particular water interface type. The pump 25 lb and the water tank 25 la provide the water delivery mechanism 251 in this embodiment. However, other embodiments can have other water delivery mechanisms.

When the steam iron 200 is in the first position PI, the base unit 250 provides power to heat the soleplate 202. In this embodiment, the base unit 250 provides electrical power to the heating element 204 which heats the soleplate 202. The electrical power is provided from the base unit 250 to the steam iron 200 via an electrical connection between the electrical interfaces 206 and 256 when in the first position PI . This connection can take many forms, and embodiments of the invention are not limited by any particular electrical interface type. During ironing, the steam iron is in the second position P2 and the ironing plate 202a contacts the garment. The steam generator 202b, in this embodiment, is a separate component to the ironing plate 202a. Water from the water reservoir 201 is provided to the steam generator 202b, where it is heated using stored thermal energy of the steam generator 202b. The steam can then pass through holes in the ironing plate 202a in order to provide steam to the garment. In this embodiment, the heating element 204 heats the ironing plate 202a and the steam generator 202b when in the first position. While embodiments are not limited to a particular arrangement of the ironing plate 202a and steam generator 202b, it will be appreciated that the ironing system may be arranged so that the heating element 204 heats the steam generator 202b to a higher temperature than the ironing plate 202a. This can maximise stored thermal energy.

In other embodiments, the soleplate 202 may be provided by a combined ironing plate and steam generator, e.g. a single plate for contacting garments and generating steam.

The water tank 25 la is connected to the external water inlet 257 (e.g. mains water or a suitable inlet to enable the user to refill the water tank 25 la), and the power supply 252 is connected to the external power inlet 258 (e.g. mains electrical supply).

Preferably, the controller 253 is further adapted to determine the amount of water, based on a time duration between two successive docking of the steam iron 200 on the base unit 250. More explanation on this will be given with reference to FIG. 3. FIG. 3 shows a graph of temperature along axis 1 (e.g. in °C) against time along axis 3 (e.g. in s). Dotted curve 5 a corresponds to temperature loss when dry ironing and plain curve 5b corresponds to temperature loss when steam ironing.

When the user undocks the steam iron 200, the controller 253 measures the temperature of the soleplate to be TO, at time tO. Hence, TO is the temperature of the soleplate 202 measured just prior to undocking at time tO. Once the steam iron 200 is re-docked, a measured temperature of Tl at time tl would indicate 100% steam ironing, and from that a certain amount of water consumption during ironing can be determined (e.g. from a look-up table) . A measured temperature of T3 at time tl would indicate 0% steam ironing (i.e. 100% dry ironing), which would imply no water consumption during ironing.

If the measured temperature is T2 at time tl, then it can be assumed that the ironing performed by the user was a combination of dry ironing and steam ironing. The controller 253 can use the two reference curves 5 a and 5b to calculate the amount of water used to generate steam. In particular, as an example, the controller 253 can calculate two extreme cases where the user could have gone to T2 by using least and most amount of steaming (see curves 6a and 6b). These two numbers can be used by the controller 253 in order to decide how much water will be put in the water reservoir 201. Preferably, the controller 253 is further adapted to determine, based on the sensed soleplate temperature, a thermal energy amount to be stored in the soleplate 202 by the power supply unit 252, and to determine, based on the thermal energy amount, the amount of water to be supplied to the water reservoir 201, such that the amount of water can be fully transformed into steam by the thermal energy amount.

Preferably, the temperature sensor 203 is arranged in a location taken from the set of locations defined by the base unit 250 and the steam iron 200. The temperature sensor may correspond to a passive component (for example a so-called "NTC"). If the temperature sensor 203 is arranged in the steam iron, as illustrated in FIGs. 2a and 2b, the temperature sensor 203 is electrically connected to the base unit 250 when the steam iron in the first position PI . If the temperature sensor 203 is arranged in the base unit 250, the steam iron must be adapted such that the soleplate gets into contact with or proximate to the temperature sensor 203 when the steam iron in the first position PI Preferably, the controller 253 is arranged in a location taken from the set of locations defined by the base unit 250 and the steam iron 200. If the controller 253 is arranged in the base unit 250, as illustrated in FIGs. 2a and 2b, the controller 253 is electrically connected to the base unit 250.

Possibly, the controller 253 is arranged in the steam iron 200, and the controller 253 is electrically connected to a battery (not shown) arranged in the steam iron, which is for example charged when the steam iron is in the first position PI ..

Preferably, the steam iron 200 comprises a heating element 204 for receiving energy supplied by the power supply unit 252. The heating element 204 and the power supply unit 252 are adapted to be electrically connected when the steam iron 200 is in the first position PI .

Possibly, the base unit 250 comprises an induction system powered by the power supply unit 252 for generating electromagnetic energy towards the steam iron 200 when it is in the first position PI, which is converted into thermal energy in the steam iron 200 by metal or coil (not shown).

Preferably, the controller 253 is further adapted to generate a first alert signal when the steam iron 200 is in the second position P2, if the time duration elapsed since the steam iron 200 was undocked from the first position PI exceeds a given time duration threshold.

This signal is used to indicate the user to return the steam iron 200 to the first position PI, for example after about 20 seconds when the steam iron is in the second position P2.

Preferably, the controller 253 is further adapted to generate a second alert signal when the steam iron 200 is in the first position PI, after the sufficient thermal energy amount is stored in the soleplate 202 and the matched amount of water supplied to the water reservoir 201.

For example, the first alert signal and the second alert signal may correspond to an alert via visual, audible, mechanical or other means. The alerts are generated to user via the user interfacing means 259 that may correspond to a display, a speaker, or a vibrating system. The power supply 252 supplies power to the controller 253, the pump 25 lb, and the user interfacing means 259, as well as to other components of the base unit 250 controlled by the controller 253. Hence, the power supply 252 powers various elements of the base unit 250. Also, as discussed below, when in the first position PI, the power supply 252 supplies power to the heating element 204 and temperature sensor 203 in the steam iron 200.

The operation of the ironing system 20 will be explained in more details in relation to FIG.4. At step SI 1 of FIG. 4, a user is performing cordless ironing using the steam iron 200 in the second position P2. In this embodiment, no power is provided to the heating element 204 when the in the second position P2.

During cordless ironing, water from the water reservoir 201 is converted to steam using heat from the soleplate 202. This depletes the amount of water in the water reservoir 201 and lowers the temperature of the soleplate 202. In this embodiment, when the steam iron 200 is in the second position P2, water may be provided from the water reservoir 201 to the soleplate 202 for steam ironing. Hence, steam may be generated by the steam iron 200 in the second position P2. This can continue until the water reservoir 201 is emptied. In this example, ironing can be 100% steam ironing, dry ironing or a combination, though as discussed below, embodiments of the invention are not limited in this way.

In this embodiment, the steam iron 200 includes a mechanism (not shown) for ensuring that steam is generated only in the second position P2. In this embodiment, this mechanism (not shown) ensures that steam is not generated when the steam iron 200 is in the first position PI . It will be appreciated that there are a variety of forms such a mechanism could take (e.g. a gravity controlled switch or mechanical valve), and embodiments of the invention are not limited in this way. In this embodiment, the user may continue cordless ironing until an indication on the user interfacing means 259 informs the user to dock the iron 200 on the base unit, otherwise directly dock the iron 200 on the base unit before an indication on the user interfacing means 259 is generated.

At step S12, the user docks the steam iron 200 with the base unit 250. In other words, the user puts the steam iron 200 into the first position PI . For example, the user may have ironed a portion of a garment and may need to rearrange the garment. At this point, the user may dock the steam iron with the base unit.

Then at step S13, the controller 253 determines the temperature variation of the soleplate 202 by reading status of the temperature sensor 203. In this embodiment, in the first position PI, the controller 253 can get temperature reading from the temperature sensor 203 via the electrical connection between the electrical interfaces 206 and 256 when in the first position PI . In this embodiment, the temperature sensor 203 comprises a thermistor in contact with the soleplate 202. However, embodiments of the invention can use other forms of temperature sensor.

In step S14, based on the sensed variation of temperature, the controller 253 calculates the amount of water consumed during ironing and how much water is left in the water reservoir 201.

Then, at step S15, the controller 253 controls the power supply 252 to supply power to heat the soleplate 202 to a desired ironing temperature. In this embodiment, when in the first position PI, the power supply 252 can supply electrical power to the heating element 204 via the electrical connection between the electrical interfaces 206 and 256.

Thus, at step S15, the controller 253 controls the power supply 252 to supply energy to heat the soleplate 202 to a desired temperature set point. The soleplate 202 is heated to a desired ironing temperature (e.g. 200°C), based on information from the temperature sensor 203. In this embodiment, the temperature set point is a temperature (e.g. 200 °C) of the steam generator 202b. In this embodiment, the power of heating element 204 is fixed, and the ON-OFF time of the heating element 204 is controlled by the controller 253. In other words, the controller 253 varies the heating of the heating element 204 by controlling the supply of electrical power from the power supply 252. In other embodiments, the heating element 204 may be controlled by the controller 253 to have varying heating power.

It can be assumed that whilst the steam iron 200 is in the second position P2, the main cause of temperature drop of the soleplate 202 is the conversion of water to steam. As discussed, when in the second position P2, as an approximation, the drop in temperature of the soleplate 202 can be related to the drop in water in the water reservoir 201. As a result, the controller 253 can use the drop in temperature of the soleplate 202 to determine the amount of water left in the water reservoir 201, without the need for a dedicated water sensor to detect the level of water in the reservoir 201. At step SI 6, the controller 253 calculates an amount of water to supply to the water reservoir 201 via the connection between the water interfaces 205 and 255, as well as a flow rate of the pump 25 lb based on the calculated amount of water left in the water reservoir 201 from step S14. The capacity of the water reservoir 201 is fixed (i.e. it is a design feature) and the controller 253 may know that the water reservoir 201 was filled the last time the steam iron 200 was docked to a certain level (e.g. full). Using this information, the controller 253 can determine the amount of water left in the water reservoir 201 together with the soleplate temperature information.

For example, by knowing the volume of water previously in the water reservoir 201, the controller 253 can determine that a certain drop in temperature of the soleplate 202 equates to a temperature drop associated with converting half the water in the water reservoir 201 to steam, and thus the controller 253 can control the water reservoir 251 to supply an amount of water equal to half the volume of the water reservoir 201 to the water reservoir 201. As a result, the amount of water supplied to the water reservoir 201 can be supplied without needing a water sensor in the steam iron 200.

At step SI 7, the controller 253 controls the pump 251b to supply water to the water reservoir 201 via the connection between the water interfaces 205 and 225.

Preferably, steps S16 and S17 occur in parallel.

As a result, a suitable amount of water can supplied to the water reservoir 201 by the pump 25 lb. This contrasts to using a conventional system in which a pump in a dock is activated whenever the steam iron is docked.

In a preferred embodiment, the pumping rate and time pattern of the pump 25 lb are variable. Using the above embodiment, achieving smooth and soft charging patterns that minimize shocks and stress applied onto water delivery system can be achieved.

The pumping rate transition may also be gradual. For example, by knowing the amount of water needed to supply to the water reservoir 201, a gradual pumping rate transition can be achieved, further minimising stress on the system 20. For example, by gradual it is meant that the flow rate of water pumped to the water reservoir 201 in the steam iron decreases over time according to a given value known by the controller.

It may happen that a user only uses certain amount of the water in the water reservoir 201. The controller 253 can determine that not all the water is used, and rather than simply pumping the water to partially full water reservoir 201 with high pumping rate and/or pressure with full pumping time, the controller 253 can moderate pumping rate or shorten pumping time according to calculated water condition in reservoir. This minimize over pumping to reduce stress on the system 20. It is preferred that heating of the heating element 204 and the supply of the water to the water reservoir 201 are done simultaneously. Furthermore, the controller 253 can control the heating and water pumping in a balanced way. Hence, the appropriate balance between thermal energy and water supply can be achieved. This balance can be obtained by not pumping more water to the water reservoir 201 than thermal energy enough to convert the stored water in the water reservoir 201 into steam. In other words, the amount of water and amount of thermal energy can be matched.

The controller 253 can be arranged to control a water delivery rate of the pump 25 lb so that a time taken to provide the required amount of water to the water reservoir 201 is the same as a time taken to supply the required thermal energy amount to the soleplate 202. At step SI 8, once the controller 253 has supplied sufficient water and power to the steam iron 200 is in the first position PI, the steam iron 200 is charged in water and thermal energy and is thus ready for more ironing. At this point, the readiness of the steam iron 200 is displayed, for example on the user interfacing means 259. Hence, the user interfacing means 259 can alert the user when the steam iron 200 is ready for ironing. For example, the alert mechanism may alert the user that the soleplate 202 is at the desired temperature and that the water reservoir 201 is full. Hence, premature undocking may be avoided. The user can then undock the steam iron 200 and can begin cordless ironing again (step SI 1), until the user interfacing means 259 indicates that is time to re-dock the steam iron 200, if the un-docking duration exceeds a given duration threshold. The user has the freedom to choose when to dock and undock, and that is not fixed by the appliance. The system can record energy and water charged and lost condition by knowing charged and used temperature as well as a time span to decide what to do for next cycles.

In this embodiment, the water reservoir 201 has for example a volume of 10 cm ³ . As an example, the steam iron 200 may generate a continuous amount of steam rate of 30g/min in average for around 20 seconds when in the second position P2 (for 100% steam ironing). It might typically take four minutes to iron one whole garment. With this volume for the water reservoir, user should dock the steam iron 200 multiple times (e.g. around four to five times) to top up the water in the water reservoir 201 and to re-heat the soleplate 202 during the ironing process. In this embodiment, in each cycle, water and energy are charged in a balanced way, done by power and flow regulation.

According to the invention, a heating element 204 of 3200 Watts power may be used, with a water reservoir 201 able to store 10 cm ³ of water after previous charge-user cycle, with the soleplate 202 generating steam at an average 30 g/minute steam rate for 20 seconds, and a 500g active mass of the soleplate 202. The pump 251b may be capable to supply 120 g/minute, but it is preferably regulated to reduce pumping rate to about 50 g/minute, to match with energy flow. As a result, it might typically take about 11 seconds for the base unit 250 to provide a balanced amount of heat and water to the steam iron 200. If energy is fully consumed by last ironing cycles, known from temperature sensing, it may take around 15 seconds (i.e. of heating element 204 ON time) to recharge the energy (considering losses) of the soleplate 202. As a result, the pumping rate of the pump 25 lb may be adjusted to equivalent 40g/minute to make total energy balance. Whilst energy and water are being provided to the steam iron 20, the controller 253 performs temperature reading, energy balance calculations, heating element 204 ON/OFF power control and pump 251b ON/OFF rate control.

The ironing system may use a "safety factor" for the amount of water determined by controller 253 and supplied to the water reservoir. For example the controller 253 may assume a certain error margin for determining the water amount (based on temperature and time, and in some embodiments usage patterns of the device) that has been consumed in ironing. The controller may then control the supply of water to the steam iron so that an amount of water is provided that is less than the calculated water amount, while taking into account this error margin.

For an ironing session in which each ironing time after undocked is about 30 second, the accuracy of such a system may be very high, as the majority of the energy is taken by steam generation. By reading temperature change, as well as and time span preferably, the controller 253 can correlation the energy loss to water consumption - the amount of water used to generate steam, i.e. to cause temperature drop. In some embodiments, there is a water release path from the water reservoir 201, which allow excess water to pass in case there is over-charge of water. However, fully relying on such a water release path would increase stress in water delivery system during releasing. As a result, a system with only a water release path (and no fully accurate determination of water amount) would have increased stress compared to embodiments of the invention.

In some embodiments, the controller 253 is further arranged to predict the usage pattern of the steam iron 200 by using multiple temperature changes and time span information, for example, based on repeated measurements, the controller 253 may estimate that the next movement of the user (e.g. with a certain mix of steam and dry ironing). The controller 253 may store information on such a usage pattern and use it to estimate when call back is required.

As an example, if the controller 253 determines, based on repeated measurements, that the user typically irons with 50% steam ironing and 50% dry ironing, then the controller 253 can use stored data on temperature/time to determine the time when the water reservoir 201 is going to be emptied and activate a call-back alert before then.

By activating a call back function, the user's ironing experience can be improved. For example, the predetermined threshold can be set to be one or two seconds before it is estimated by the controller 253 (e.g. based on a starting water amount, e.g. 10 g for a full water reservoir 201) that the water reservoir 201 is going to be emptied. As a result, the user can re-dock the steam iron 201 before steam producing performance is reduced due to a lack of water and/or energy. This can help ensure optimum ironing performance.

As shown in the flow chart of FIG. 5, the invention also relates to a method of determining, in an ironing system 20 as described previously and comprising a steam iron 200 and a base unit 250, an amount of water to be supplied from the base unit 250 to the steam iron 200, the base unit 250 and the steam iron 200 being adapted to cooperate with each other such that the steam iron 200 can take a first position PI in which the steam iron 200 is docked on the base unit 250, and a second position P2 in which the steam iron 200 is undocked from the base unit 250, the steam iron 200 being cordlessly detached from the base unit 250 in the second position P2, the steam iron 200 comprising a water reservoir 201 arranged to store water and a soleplate 202 for generating steam from water in the water reservoir 201 when the steam iron 200 is in the second position P2, the base unit 250 comprising water delivery mechanism 251 for supplying water to the water reservoir 201 when the steam iron 200 is in the first position PI and a power supply unit 252 for supplying energy to the soleplate 202 when the steam iron 200 is in the first position PI, for heating the soleplate 202.

The method comprises the steps of:

sensing SSI the temperature of the soleplate 202,

determining SS2, based on a variation of temperature of the soleplate, an amount of water to be supplied to the water reservoir 201 by the water delivery mechanism 251.

Preferably, the step of determining SS2 comprises a step SS3 of calculating the variation of temperature between the temperature of the soleplate 202 when the steam iron 200 is in a current first position PI, and the temperature of the soleplate 202 when the steam iron 200 was in a previous first position PI .

The above embodiments as described are only illustrative, and not intended to limit the technique approaches of the present invention. Although the present invention is described in details referring to the preferable embodiments, those skilled in the art will understand that the technique approaches of the present invention can be modified or equally displaced without departing from the scope of the technique approaches of the present invention, which will also fall into the protective scope of the claims of the present invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. Any reference signs in the claims should not be construed as limiting the scope.