Patent Publication Number: US-10767305-B2

Title: Steam iron with thermal bridge arrangement

Description:
This application is the U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2017/060395, filed on May 2, 2017, which claims the benefit of International Application No. 16167968.3 filed on May 2, 2016. These applications are hereby incorporated by reference herein. 
     FIELD OF THE INVENTION 
     The present invention relates to a steam iron and to a steam iron system comprising such a steam iron. 
     The invention has some applications in the field of garment care. 
     BACKGROUND OF THE INVENTION 
     Steam irons are known that include a steam generator and an ironing plate coupled to the steam generator and which contacts the garments to be ironed. Steam generated in the steam generator is expelled onto the garments through holes in the ironing plate. Such irons contain a controller, for example, control electronics, to control the operation of the steam generator within an ironing temperature range for generating steam. The ironing plate is passively heated by conduction of heat from the steam generator at the areas of contact between the steam generator and the ironing plate. The control electronics maintain the operation of the steam generator and the thermally coupled ironing plate within an ironing temperature range. 
     Steam generators in such known steam irons include a heating element. In certain circumstances, the thermal energy in the steam generator can cause the ironing plate to heat up to a temperature exceeding the upper limit of the ironing temperature range, at which point garments in contact with the ironing plate may be damaged. Such overheating can also create hot spots in the ironing plate proximate the areas where the steam generator is coupled to the ironing plate. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a steam iron which 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 the present invention, there is provided a steam iron for ironing garments. The steam iron comprises a steam generator comprising a main body and a heating element to heat the main body. The steam iron also comprises an ironing plate. The steam iron also comprises a thermal bridge arrangement extending between the main body and a thermal coupling area of the ironing plate to heat the ironing plate by conduction of heat from the main body. The thermal bridge arrangement comprises a first portion extending in a first direction away from the thermal coupling area and a second portion extending in a second direction towards the thermal coupling area. 
     The thermal bridge arrangement increases the cumulated length of the thermal path between the main body and the thermal coupling area with the ironing plate because the heat must first flow in the first direction along the first portion of the thermal bridge arrangement and subsequently flow in the second direction along the second portion of the thermal bridge arrangement. The increased cumulated length of the path of heat transfer between the main body and the ironing plate restricts the rate of heat transfer from the steam generator to the ironing plate and thus reduces the temperature of the ironing plate for a given temperature of steam generator. This is advantageous because it allows for a relatively high temperature of steam generator, to promote steam generation efficiency, while keeping a lower temperature of ironing plate, to prevent damage to a garment in contact with the ironing plate. In addition, an increased temperature of the steam generator results in an increased capability to handle higher rate of steam generation when water is initially over supplied to the steam generator for steam boost. 
     In addition, the restricted rate of heat transfer of the thermal bridge arrangement prevents any large fluctuations in the temperature of the main body of the steam generator from causing large fluctuations in the ironing plate temperature, for example, due to water being poured onto the steam generator to generate steam. Therefore, the thermal bridge arrangement acts as a thermal “damper” to allow the ironing plate temperature to remain more constant. 
     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  is a schematic side view of a steam iron according to an embodiment of the invention; 
         FIG. 2  is a schematic cross-sectional view of part of the steam iron of  FIG. 1 ; 
         FIG. 3  is a block diagram schematically representing a controller of the steam iron of  FIG. 1 ; 
         FIG. 4  is a graph of temperature against time schematically illustrating a control operation performed by the controller of  FIG. 3 ; 
         FIG. 5  is a schematic cross-sectional view of a steam iron according to another embodiment of the invention; and, 
         FIG. 6  is a schematic cross-sectional view of a steam iron according to another embodiment of the invention, 
         FIG. 7  is a schematic cross-sectional view of a steam iron according to another embodiment of the invention, 
         FIGS. 8A-8B  are schematic side views of a first steam iron system according to an embodiment of the invention, 
         FIG. 9  is schematic view of a second steam iron system according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  is a schematic side view of a steam iron  10  for ironing garments according to an embodiment of the invention. The steam iron  10  comprises an ironing plate  13 . For sake of clarity, further details of the invention will be illustrated by  FIGS. 2-5-6-7  showing a cross-sectional partial view of the steam iron  10  along the plan X-X. 
       FIG. 2  is a schematic cross-sectional view of part of the steam iron of  FIG. 1 . The steam iron  10  comprises a steam generator  11  which comprises a main body  11 A and a heating element  12  to heat the main body  11 A. The steam iron  10  comprises a thermal bridge arrangement  14  extending between the main body  11 A and a thermal coupling area  15  of the ironing plate  13  to heat the ironing plate  13  by conduction of heat from the main body  11 A. The thermal bridge arrangement  14  comprises a first portion  16  extending in a first direction (shown by arrow A) away from the thermal coupling area  15  and a second portion  17  extending in a second direction (shown by arrow B) towards the thermal coupling area  15 . 
     As it will be described in the following, it is noted that apart from comprising the first portion  16  and the second portion  17 , the thermal bridge arrangement  14  may also comprise additional portions extending either away and/or towards the thermal coupling area A. 
     The heating element  12  is operable to heat the main body  11 A of the steam generator  11  to generate steam. Moreover, heat is transferred from the heated main body  11 A to the ironing plate  13  via the thermal bridge arrangement  14  such that the ironing plate  13  is passively heated (i.e. the ironing plate  13  does not embed a separate heating element). For example, the heating element  12  is a resistance intended to be connected to an electrical power supply. For example, the main body  11 A of the steam generator  11  is a plate. 
     The thermal bridge arrangement  14  forms an indirect thermal path between the main body  11 A and the ironing plate  13  to passively heat the ironing plate  13  by conduction of heat from the main body  11 A. 
     The thermal bridge arrangement  14  increases the cumulated length (shown by the solid line L 1  in  FIG. 2 ) of the thermal path between the main body  11 A and the thermal coupling area  15  with the ironing plate  13  since the heat flows in the first direction A along the first portion  16  of the thermal bridge arrangement  14 , and flows in the second direction B along the second portion  17  of the thermal bridge arrangement  14 . The increased cumulated length L 1  of the path of heat transfer between the main body  11 A and the ironing plate  13  restricts the rate of heat transfer to the ironing plate  13  and thus limits the temperature of the ironing plate  13  compared to the temperature of main body  11 A. This is advantageous because having a relatively high temperature of steam generator  11  allows promoting the steam generation capability of the steam generator  11 , and a having a lower temperature for the ironing plate  13  which prevents damaging garments in contact with the ironing plate  13  during ironing. 
     Reducing the thermal coupling area of the thermal bridge arrangement  14  increases the thermal resistance of the thermal bridge arrangement  14  and thus reduces the rate of heat transfer from the main body  11 A to the ironing plate  13 . 
     The steam iron  10  of the present invention allows reducing the rate of heat transfer from the main body  11 A to the ironing plate  13  by increasing the cumulated length L 1  of the thermal path between the main body  11 A and the ironing plate  13 . 
     The main body  11 A and the thermal bridge arrangement  14  may be integrally formed and, for example, may be cast together. The main body  11 A and the thermal bridge arrangement  14  may be manufactured from a metal, for example, aluminium or iron. 
     Preferably, as illustrated in  FIG. 2 , the first direction (A) of the first portion  16  extends away from the ironing plate ( 13 ). 
     The first direction A and/or second direction B may be perpendicular to the ironing surface of the ironing plate  13 . Thus, the first portion  16  and/or second portion  17  of the thermal bridge arrangement  14  may extend substantially perpendicularly to the ironing surface of the ironing plate  13 , as illustrated in  FIG. 2 . 
     In one embodiment, the thermal bridge arrangement  14  extends in the second direction B for a distance longer than in the first direction A, as illustrated in  FIG. 2 . For example, this can be achieved by having the second portion  17  being twice long as the first portion  16 . 
     Preferably, the first portion  16  and the second portion  17  define a thermal path having a cumulated length L 1  at least 1.5 time the distance D 1  between the main body  11 A and the thermal coupling area  15 . 
     Preferably, the first portion  16  and the second portion  17  define a thermal path having an average cumulated length L 1  that is at least 10 mm. By the term “average”, it is meant that the mean value of the cumulated length is considered, which is measured over a middle point along the length of the thermal path, across the whole thermal coupling area. 
     Preferably, the heating element  12  is configured to heat the main body  11 A to a temperature between 160° C. and 300° C. Under such conditions, the thermal bridge arrangement  14  preferably has a thermal transmittance and an average area (A) at the thermal coupling area  15  such that the ironing plate  13  has a temperature between 70° C. and 210° C. In case the thermal bridge arrangement  14  extends over a peripheral portion of the steam iron, the thermal coupling area  15  may also extends over this peripheral portion, and the average area (A) at the thermal coupling area  15  corresponds to the cumulated area over this peripheral portion. 
     The thermal transmittance and thermal coupling area of the thermal bridge arrangement  14  therefore allows for the main body  11 A of the steam generator  11  to be heated to a relatively high temperature, for example 300° C., without the ironing plate  13  exceeding a temperature, for example 210° C., that would otherwise damage the garment in contact with the ironing plate  13 . This is advantageous because the relatively high temperature of main body  11 A means that the steam generator surface can contribute to a high amount of energy transfer to promote the efficiency of steam generation. In addition, the lower temperature of ironing plate  13  prevents damaging the garments in contact with the ironing plate  13 . In addition, the relatively high temperature of the steam generator  11  results in an increased capability to handle higher rate of steam generation when water is initially over supplied to the steam generator  11 . 
     Preferably, the thermal coupling area  15  has a thickness d between 1 to 3 mm. Preferably, the thermal coupling area  15  is a flat portion. The thermal bridge arrangement  14  may extend from the perimeter of the main body  11 A of the steam generator  11 . The thermal bridge arrangement  14  may extend from at least 75% of the perimeter of the main body  11 A such that the thermal bridge arrangement  14  extends about at least 75% of the circumference of the main body  11 A. In one such embodiment, the thermal bridge arrangement  14  is made of aluminium. In another embodiment, the thermal bridge arrangement  14  extends from all peripheral edges of the main body  11 A. 
     The thermal transmittance of the thermal bridge arrangement  14  is dependent on the length L 1  of the thermal bridge arrangement  14  and the thermal conductivity of the material (e.g. Aluminium) of the thermal bridge arrangement  14 . Therefore, to achieve the necessary thermal management, these properties may be selected such that, if the main body  11 A of the steam generator  11  is heated to between 160° C. and 300° C., the temperature of the ironing plate  13  has a temperature between 70° C. and 210° C. 
     For example, the necessary thermal transmittance and thermal coupling area A of the thermal bridge arrangement  14  may be selected after successive tests or simulations conducted by the skilled person, for instance, by varying the length L 1  and the thermal coupling area A (result of contact wall thickness and contact perimeter), of the thermal bridge arrangement  14  until the heat transfer is achieved such that the energy flowing from the main body  11 A, temperature of which is between 160° C. and 300° C., to the ironing plate  13  to maintain its temperature between 70° C. and 210° C. Those tests or simulations may be performed by successive experiments, for example, by heating the main body  11 A to 300° C. and measuring the temperature of the ironing plate  13 . Alternatively, the thermal transmittance and thermal coupling area may be calculated according to the following Equation 1:
 
 Q=AU ( T   1   −T   2 )  [Equation 1]
 
     Wherein 
     Q (in W) is the heat transfer rate from the steam generator  11  to the ironing plate  13 ; 
     A (in m 2 ) is the cumulated thermal transfer area of the thermal bridge arrangement  14  (dependent on the perimeter and width of the thermal bridge arrangement  14 ); 
     U (in W/m 2 K) is the thermal transmittance of the thermal bridge arrangement  14 , which is the result of k (in W/mK), the thermal conductivity of the material used for making the steam generator, a material property, over L 1 , the length (in m) of the thermal bridge arrangement  14 ; 
     T 1  is the operation temperature (K/° C.) of the main body  11 A; 
     T 2 is the operation temperature (K/° C.) of the ironing plate  13 . 
     Equation 1 shows that the temperature T 2  of the ironing plate  13  for a given temperature T 1  of the main body  11 A is dependent on the thermal transmittance U of the thermal bridge arrangement  14  and the thermal coupling area A (in a direction perpendicular to the heat flow) of the thermal bridge arrangement  14 . 
     For example, if aluminium material is selected for the steam generator and the thermal bridge arrangement (the value of k for aluminium is 205 W/mK), the energy supply required to maintain the ironing plate temperature, for a domestic steam iron, for example ˜300 Watts; for a steam generator operating at 235° C., to achieve its ironing plate to be able to operate at 145° C., the length L 1  of the thermal bridge arrangement  14  need to be ˜36 mm with a thermal coupling area A of about 600 mm 2  that is achieved by arranging a ˜1.2 mm thickness d contact at the coupling area along the circumference of the main body  11 A By choosing parameters L 1  and A, the desired heat transfer rate can be determined. 
     In another example, by choosing a different material for the steam generator and the thermal bridge arrangement, this material having a value of k as 96 W/mK, the length L 1  of the thermal bridge arrangement can be chosen with a value around 17 mm for the same heat transfer condition as in the previous example, the other parameters being kept as same as in the previous example. 
     The first portion  16  may be connected to the second portion  17  by an intermediate portion  18  that allows changing the direction of those two portions. 
     The thermal bridge arrangement  14  according to the invention is generally U-shaped when viewed in cross-section. Alternatively, the thermal bridge arrangement can be generally V-shaped when viewed in cross-section. 
     The thermal coupling area  15  may comprise a protrusion  13 A of the ironing plate  13  that extends towards an end of the second section  17  of the thermal bridge arrangement  14 . 
     Preferably, the main body  11 A and the ironing plate  13  face each other, and wherein an air gap  19  is provided between the main body  11 A and the ironing plate  13 . The air gap  19  thermally insulates the facing portions of the main body  11 A and the ironing plate  13  and thus reduces the temperature of the ironing plate  13 . The facing portions of the main body and ironing plate may comprise major surfaces of the main body and ironing plate. The ironing plate  13  is thus primarily heated by the main body  11 A via the thermal bridge arrangement. 
     In one embodiment, the steam iron  10  further comprises a controller  20  (not shown) to control operations of the steam iron  10 . In one such embodiment, the controller  20  is configured to perform a primary heating operation upon initial heating of the steam iron  10 , and perform a secondary heating operation during subsequent operation of the steam iron  10 . The primary heating operation comprises heating the steam generator  11  to a higher temperature range than for the secondary heating operation. 
     Optionally, the primary heating operation comprises heating the main body  11 A to a much higher temperature, for example 240° C., than the ironing plate required temperature, for example 150° C. Optionally, the secondary heating operation comprises heating the main body  11 A to a less higher temperature, for example 170° C., than the ironing plate required temperature. 
     The primary heating operation may be performed upon initial powering of the heating element  12 . Heating of the main body  11 A to the elevated temperature for the primary heating operation during start up ensures quicker heat transfer to the ironing plate  13  and so a quicker iron ready time. The thermal bridge arrangement  14  ensures that the ironing plate  13  does not overheat when the primary heating operation is performed. After the temperature of steam generator  11  drops close to, but higher than, the required operating temperature of ironing plate  13 , while ironing plate temperature is rising from initial low level, the controller  20  performs the second heating operation so that the steam generator  11  is then operates at a lower operating temperature. For example, the required operating temperature of the ironing plate  13  may be about 150° C., initial temperature of which is 105° C., and the operating temperature of the steam generator  11  for the first heating operation may be around 240° C. and the second heating operation may be around 170° C. 
     The main body  11 A and the thermal bridge arrangement  14  can be integrally formed and the thermal bridge arrangement  14  abuts the thermal coupling area  15  of the ironing plate  13 . In an alternative embodiment, the thermal bridge arrangement  14  is integrally formed with the thermal coupling area  15  of the ironing plate  13  and abuts the main body  11 A without being integrally formed with the main body  11 A. In yet another embodiment, the thermal bridge arrangement  14  is integrally formed with both the main body  11 A and the thermal coupling area  15  of the ironing plate  13 . 
     In the above described embodiments, the thermal bridge arrangement  14  is configured such that the first portion  16  and second portion  17  each extend substantially parallel or perpendicular to the ironing surface of the ironing plate  13 . However, it should be recognised that other configurations of thermal bridge arrangement  14  are also intended to fall within the scope of the invention and, for example, the first portion  16  and second portion  16  may each extend at an angle to the ironing surface which is neither parallel nor perpendicular. 
       FIG. 3  is a block diagram schematically representing an exemplary configuration of the controller  20 . 
     Optionally, the controller  20  comprises a processor  21  and a memory  22 . The memory  22  may store a number of control parameters for controlling the operation of the steam iron  10 , such as various threshold temperatures for the steam generator  11  and optimum operating temperatures for the ironing plate  13  and/or the steam generator  11 . 
     Optionally, the steam iron  10  comprises a temperature sensor  23 , for example, a thermocouple or thermistor, which measures the temperature of the steam generator  11 . The controller  20  may be connected to the temperature sensor  23  so as to receive signals relating to the temperature of the steam generator  11 . The controller  20  may be connected to the heating element  12  of the steam generator  11  in order to control operation of the heating element  12  in accordance with the control scheme described above. 
     Optionally, the steam iron  10  further comprises a temperature sensor (not shown), for example, a thermistor or thermocouple, configured to measure the temperature of the ironing plate  13 , and the controller  20  is connected to said temperature sensor to receive signals relating to the temperature of the ironing plate  13 . 
       FIG. 4  is a graph of temperature against time showing a schematic representation of an exemplary control operation of the controller  20 . 
     Line (i) represents the temperature of the steam generator  11 . 
     Line (ii) represents the temperature of the ironing plate  13 . 
     Peak (a) of line (i) represents the steam generator  11  being heated during the primary heating operation, for example to 240° C. 
     Trough (b) of line (i) represents the steam generator  11  cooling, to a temperature of for example 155° C. 
     Peak (c) of line (i) represents the steam generator  11  being heated during the secondary heating operation to 170° C. 
     Referring now to  FIG. 5 , a steam iron  10  according to another embodiment of the invention is shown. 
     The steam iron  10  of  FIG. 5  is similar to the steam iron  10  described above in relation to  FIGS. 2 . A difference is that the thermal bridge arrangement  14  of  FIG. 5  has a different structure. 
     The thermal bridge arrangement  14  comprises a first portion  16  extending in a first direction (shown by arrow ‘A’) away from the thermal coupling area  15 , and a second portion  17  extending in a second direction (shown by arrow ‘B’) towards the thermal coupling area  15 . 
     The first portion  16  extends from the main body  11 A in the first direction A substantially parallel to the ironing surface of the ironing plate  13 . The second portion  17  extends in the second direction B substantially parallel to the ironing surface of the ironing plate  13 , but in the opposite direction to the first direction A. For example, as illustrated, the thermal bridge arrangement  14  extends in the first direction A for a distance longer than in the second direction B, as illustrated in  FIG. 5 . 
     Referring now to  FIG. 6 , a steam iron  10  according to another embodiment of the invention is shown. 
     The steam iron  10  is similar to the steam iron  10  described above in relation to  FIGS. 5 . A difference is that the thermal bridge arrangement  14  of  FIG. 6  has a different structure. 
     The thermal bridge arrangement  14  comprises a first portion  16  extending in a first direction (shown by arrow ‘A’) away from the thermal coupling area  15 , and a second portion  17  extending in a second direction (shown by arrow ‘B’) towards the thermal coupling area  15 . Additionally, the thermal bridge arrangement  14  comprises a third portion  16 A extending in a third direction (shown by arrow ‘C’) away from thermal coupling area  15 . The third portion  16 A extends upwards from the main body  11 A, and has, for example, a thickness relatively larger (e.g. 2 to 5 times) than the thickness of the first and second portions. 
     Referring now to  FIG. 7 , a steam iron  10  according to another embodiment of the invention is shown. 
     The steam iron  10  is similar to the steam iron  10  previously described. A difference is that the thermal bridge arrangement  14  of  FIG. 7  has a different structure. 
     The thermal bridge arrangement  14  comprises a first portion  16  extending in a first direction (shown by arrow ‘A’) away from the thermal coupling area  15 , and a second portion  17  extending in a second direction (shown by arrow ‘B’) towards the thermal coupling area  15 . Additionally, the thermal bridge arrangement  14  comprises a third portion  16 B extending in a fourth direction (shown by arrow ‘D’) towards from the thermal coupling area  15 . The third portion  16 B extends downwards from the main body  11 A. 
     Optionally, the mass of the steam generator  11  is greater than about 300 g and, preferably, greater than about 450 g. Preferably, the mass of the steam generator  11  is at least 500 g. In some embodiments, the steam generator  11  is manufactured from aluminium and may be cast. 
     Optionally, the mass of the ironing plate  13  is less than about 250 g. Preferably, the mass of the ironing plate  13  is less than 150 g. In some embodiments, the ironing plate  13  is manufactured from aluminium and may be cast. 
     Preferably, the steam generator  11  and the ironing plate  13  each have a heat capacity, and the ratio of the heat capacity of the steam generator  11  to the heat capacity of the ironing plate  13  is between 3:1 and 4:1. 
     The larger heat capacity of the steam generator means that the steam generator is able to store more thermal energy and therefore more thermal energy is available to evaporate water into steam than if the water was only heated directly by the heating element or if the heat capacity of the steam generator was smaller. Thus, the larger heat capacity of the steam generator allows for an increased steam generation rate because an increased rate of water can be supplied to the steam generator and evaporated into steam. In addition, the larger heat capacity of the steam generator means that the steam generator remains above the temperature required to generate steam for a relatively long period of time because more thermal energy is stored in the steam generator. Thus, the steam iron can be used without powering the heating element for a relatively long period of time, which is particularly advantageous if the steam iron is cordless. The smaller heat capacity of the ironing plate means that the ironing plate is heated to within the desired temperature range relatively quickly and, furthermore, means that if the temperature of the ironing plate reduces, for example, due to contact with a cooler garment, the ironing plate may be reheated to within the desired temperature range relatively quickly by heat transfer from the steam generator via the thermal bridge arrangement. 
     The relatively high heat capacity of the steam generator  11  means that the steam generator  11  is able to stay above the temperature required to effectively generate steam, for example, 100° C. or 105° C., for a relatively long period of time. Thus, the steam iron  10  may be used without powering the heating element  12  for a relatively long period of time. For example, if the steam iron  10  is a cordless steam iron  10  (i.e. without embedded electrical supply to power the heating element), then it may be used for a longer period of time without being reconnected to a power source. The relatively small heat capacity of the ironing plate  13  means that the ironing plate  13  is heated to within the desired temperature range relatively quickly and, furthermore, means that if the temperature of the ironing plate  13  reduces, for example, due to contact with a cooler garment, the ironing plate  13  may be reheated to within the desired temperature range relatively quickly by heat transfer from the steam generator  11 . 
     The stored thermal energy level in the steam generator  11  over the working temperature range of the steam generator  11  (i.e. whilst the steam generator  11  remains above the minimum temperature necessary to effectively generate steam, for example, 105° C.) may be characterised by following Equation 2:
 
 E=mC   p (T initial   −T   min )   [Equation 2]
 
     Wherein E is the stored thermal energy (J) in the steam generator  11 , m is the mass (kg) of the steam generator  11 , C p  is the specific heat capacity (J/kgK) of the material of the steam generator  11 , T initial  is the temperature (° C.) of the steam generator  11  after heating, and T min  is the minimum temperature (° C.) of the steam generator  11  required to effectively generate steam. 
     Thus, Equation 2 shows that increasing the heat capacity of the steam generator  11 , for example, by increasing the mass m thereof, increases the stored thermal energy level E in the steam generator  11  over the working temperature range of the steam generator  11 . In addition, the restricted rate of heat transfer provided by the thermal bridge arrangement  14  allows the steam generator  11  to be heated to a higher temperature T initial  without the ironing plate  13  exceeding a temperature that would damage garments, which also increases the stored thermal energy level E in the steam generator  11 . 
     Preferably, the heat capacity of the steam generator  11  is at least 450 J/K, where J is the energy in Joules and K the temperature in degrees Kelvin. 
     The heat capacity of the steam generator  11  may comprise the heat capacity of the main body  11 A. 
     Preferably, the heat capacity of the ironing plate ( 13 ) is less than 150 J/K. 
     The steam iron  10  according to the invention may correspond to any of the following products:
         a corded steam iron (i.e. comprising a cord to be connected to external power supply to provide electrical energy to the heating element  12 ). Preferably, the corded steam iron comprises a water reservoir and optionally a water pump to carry water from the water reservoir to the steam generator  11 . Alternatively, the corded steam iron is adapted to cooperate with a base station comprising a water reservoir and a water pump to carry water from the water reservoir to the steam generator  11  via the cord.   a cordless steam iron (i.e. without any cord to provide electrical energy to the heating element  12 ). Preferably, the cordless steam iron is adapted to cooperate with a docking station as it will be further illustrated in  FIG. 8A-8B .       

       FIGS. 8A-8B  show a first steam iron system  40  according to an embodiment of the invention. 
     The steam iron system  40  comprises a steam iron system  10  of the type described above in relation to  FIGS. 2-5-6-7 . The steam iron system  40  further comprises a docking station  41  for detachably resting the steam iron  10 . In one embodiment, the user may rest the heel of the steam iron  10  on the docking station  41  when the steam iron  10  is not being used to iron a garment. The rest position is illustrated in  FIG. 8A , and the detached position is illustrated in  FIG. 8B . 
     Optionally, the heating element  12  (not shown) is powered when the steam iron  10  is rested on the docking station  41 . In one embodiment, the docking station  41  and steam iron  10  each comprise a connector (not shown). The connectors may be configured to engage with each other when the steam iron  10  is resting on the docking station  41  to provide power to the heating element  12  and/or the controller  20 . Thus, when the user rests the steam iron  10  on the docking station  41 , power is provided to the heating element  12  such that the heating element  12  heats the main body  11 A of the steam generator  11  and also passively heats the ironing plate  13  via the thermal bridge arrangement  14 . Optionally, the connectors may comprise a male and female connector, for example, a plug and socket configuration. 
     In one embodiment, the controller  20  (not shown) is provided in the docking station  41 . 
     In another embodiment, the controller  20  (not shown) is provided in the steam iron  10 , but is only powered when the steam iron  10  is rested on the docking station  41 . Alternatively, the controller  20  is powered by an energy storage device, for example a battery or a capacitor arranged in the steam iron  10 , when the steam iron  10  is detached from docking station  41 . 
     In one embodiment, there is no active temperature control of the heating element  12  when the steam iron  10  is detached from the docking station  41 . 
       FIG. 9  shows a second steam iron system  50  according to an embodiment of the invention. 
     The steam iron system  50  comprises a steam iron system  10  of the type described above in relation to  FIGS. 2-5-6-7 . The steam iron system  50  further comprises a base station  51  cooperating with the steam iron  10  via a cord  52 . 
     The base station  51  comprises a water reservoir  53  and a water pump  54  to carry water from the water reservoir  53  to the steam generator  11  (not shown) via the cord  52 . The heating element  12  (not shown) is power supplied from the base station  51  via the cord  52 . 
     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 spirit and 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.