WO2011110979A2

WO2011110979A2 - Steam generation device and method for reducing scale in such steam generation device

Info

Publication number: WO2011110979A2
Application number: PCT/IB2011/050887
Authority: WO
Inventors: Lanying Ji; Maarten Van Den Boogaard
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2010-03-09
Filing date: 2011-03-02
Publication date: 2011-09-15
Also published as: WO2011110979A3

Abstract

The invention provides a steam generation device (50) comprising a water infrastructure (100) comprising a water supply system (110) and a heating unit (120) for heating water to steam; and a container (200) containing an anti-scaling agent (201) connected to the water infrastructure (100), wherein the anti-scaling agent (201) comprises a sodium-calcium double salt of hydroxyethylidene-(1,2-disphonic acid) with chemical formula Na_x-Ca_y-HEDP, x+2y being equal to 4. The benefit that consumers may be able to experience when applying the anti-scaling agent of the invention is the more effective calc- clean function and longer life time of device.

Description

Steam generation device and method for reducing scale in such steam generation device

FIELD OF THE INVENTION

The present invention relates to a steam generation device for use as or with a steaming device, such as a steam iron or a system iron, as well as to a method for reducing scale in such steam generation device.

BACKGROUND OF THE INVENTION

Such a steam generation device is known in practice and is designed to be used in combination with a steam iron or is embedded in a steam iron.

An important function of the steam generation device is generating steam and, for instance in the case of a system iron, supplying the steam to the steam iron (wherein the steam iron comprises steam outlets arranged in a soleplate for letting out steam to objects to be ironed). During operation of the steam generation device the steam is generated in the boiler, and a supply of steam to the steam iron is controlled by means of a steam valve connected to a steam outlet of the boiler. In many steam generation devices, for the purpose of supplying water to the boiler and pressurizing the water inside the boiler, a pump is arranged.

During operation of the steam generation device, water is supplied to a part of the water infrastructure where it is heated, such as in the (external) boiler of a system iron, as a consequence of which scale may be formed. This scale formation causes problems, as it may occur that scale particles are displaced and may land on an object to be ironed, causing stains on this object. Furthermore, over time, the water in at least part of the water infrastructure gradually gets contaminated with ions. This phenomenon is caused by the fact that during operation of the arrangement, only water is evaporated, while most of the other components which are present in the water stay behind. In a water infrastructure containing contaminated water, a foaming effect may occur during heating of the water, which may disturbs a continuous supply of steam, and which may cause the boiler to supply hot water along with the steam. If the scale is not periodically removed clogging up may occur, as a result of which the performance of the steam generation device may decrease and, eventually, the steam generation device may not be fit to be used anymore.

WO-2007/007241 for instance describes a steam ironing system comprises a steam iron and a boiler system having a boiler for generating steam, wherein the steam iron and the boiler are connected to each other through a steam hose. During operation of the boiler system, scale is formed in the boiler. For the purpose of removing the scale from the boiler, a rinsing process is performed on the boiler system at regular intervals. During the rinsing process, a rinse valve connected to a water outlet positioned at a bottom of the boiler is opened, and water is discharged from the boiler to a rinse container. In the process, scale particles are carried along with the flow of water. Preferably, pressure is built up inside the boiler prior to opening the rinse valve, so that the water is forcibly ejected from the boiler, whereby the effectiveness of the rinsing process is enhanced. During the rinsing process or at the end of the rinsing process, scale solvent may be introduced into the boiler.

EP-0610997 describes a steam iron comprising a water reservoir, a steam chamber and a water-supply system for conveying water from the reservoir to the steam chamber. EP-0610997 suggests using phosphonate compounds as a scale-growth inhibiting agent, in particular, by which obstruction of the water-supply system may be overcome.

Further, US-5507108 describes a steam iron comprises a water reservoir, a steam chamber, a water-supply system for conveying water from the reservoir to the steam chamber and a metering system for injecting a phosphonate compound which acts to inhibit scale growth into the reservoir.

SUMMARY OF THE INVENTION

As mentioned above, anti-scaling agents may be used to inhibit or remove scaling. The sodium salt of 1 -hydroxy ethylidene (1,1-diphosphonic acid) (HEDP; the CAS number of the hydrogen version of HEDP, CH₂H₈O₇P₂ is 2809-21-4) may for instance be applied (see also EP-0610997), such as in the form of aqueous solution or powder. Due to its high solubility in water (>1000 mg/L) and fast dissolution rate, Na_x-HEDP (x = 1, 2, 3,4) it requires a complicated release system to control the release rate so that it can last for life time use in a steam generation device, such as of a domestic steam generating appliance.

Hence, it is an aspect of the invention to provide an alternative anti-scaling agent, which preferably further at least partly obviates one or more of above-described drawbacks. The invention proposes a dual or double salt form, sodium and calcium, of phosphonate (Na-Ca-HEDP) which surprisingly appears to be able to release sufficient amount of phosphonate in water and thus to enhance the performance of calcium cleaning (calc-clean) in steam generating appliances. It may be obtained by partially converting the sodium form (Na₄-HEDP) into calcium form using reagent calcium chloride (CaCl₂), preferably in DI (de-ionized) water. The relative amount of Na and Ca in the final salt form Na-Ca-HEDP may be controlled by the equivalent ratio of Na₄-HEDP and CaCl₂. Lower ratio (<1) results in higher ratio of Na in the dual salt of phosphonate, and thus higher solubility. The equivalent ratio of 1 and above may lead to the complete conversion of sodium form to calcium form, that is, Ca₂-HEDP, which is undesired.

The benefit that consumers may be able to experience when applying the anti- scaling agent of the invention is the more effective calc-clean function and longer life time of steaming product (i.e. the device). The amount of scale, both hard and soft scale removed by calc-clean, may be increased. Further, the amount of steam generated from the steam iron may be maintained relatively constant throughout the life time of the product.

Another benefit that the dual salt form of Na_x-Ca_y-HEDP may bring about is the improved cleanness of metallic mesh from forming scale crust over it. For instance system irons, a metallic mesh may be attached to a steam generating device, e.g. a (mini) boiler, to filter out the scale particles so that they will not go into the steam hose with steam. Scale by nature has a high tendency to stick to metal surface and form a hard scale layer. As a result the mesh size is reduced over time and eventually water or steam cannot flow through it, leading to the total failure of steam generating appliances. Using Na_x-Ca_y-HEDP may effectively increase the release amount of phosphonate in water, modify the chemical nature of the scale fully, and may make it less sticky to metallic surface, and thus prolong the life time of the steam generator.

Therefore, in a first aspect, the invention provides a steam generation device comprising a water infrastructure comprising a water supply system and a heating unit for heating water to steam, and a container containing an anti-scaling agent connected to the water infrastructure, wherein the anti-scaling agent comprises a sodium-calcium double salt of hydroxy ethylidene-(l,2-disphonic acid) with chemical formula Na_x-Ca_y-HEDP, x+2y being equal to 4.

The term "water infrastructure" refers to the all tubes and parts wherein water may be stored, heated, transported, within the steam generation device. The term "connected" refers to a connection through which water may flow. The term "connected" may thus refer to a fluid connection between parts (of the water infrastructure). The term "connected" does not exclude the presence of valves, which may temporarily keep a connection closed and which may be opened at dedicated times, such as for instance based on user instructions or on predefined instructions in a controller. Herein, the term "iron" is for brevity also used for "steam iron".

In specific embodiments, the invention provides such steam generation device, wherein the water infrastructure comprises a boiler for containing water and heating water to steam, comprising at least one inlet for letting in water, at least one outlet for letting out steam, and optionally at least one outlet for letting out water, a steam hose connected to a steam outlet of the boiler, which is suitable to be applied for connecting the boiler to a steaming device and for conducting steam from the boiler to the steaming device during operation of the steam generation device, a steam valve connected to the steam outlet of the boiler, and optionally a rinse valve connected to the optional water outlet of the boiler.

Such irons are also called system irons and comprise an external boiler.

Hence, the invention also provides such steam generation device further comprising a steam iron in connection with the steam outlet (i.e. the combination of external steam generation device and iron connected to such steam generation device). Such combination is indicated in WO-2007/007241 (incorporated herein by reference) as "steam iron system". As will be clear to the person skilled in the art, also the non-connected combination of steam generation device and steam iron is part of the invention.

The boiler of the boiler system may not only comprise an outlet for releasing steam, but also comprises an outlet for draining water. A rinse valve, which is opened for the purpose of a rinsing process of the boiler, is connected to this outlet. During normal operation of the boiler system, the rinse valve is kept closed. Preferably, the water outlet is positioned at a bottom of the boiler, so that it is possible to drain practically all of the water from the boiler. The rinse valve may be positioned at the bottom of the boiler as well. In a preferred way of rinsing the boiler system, the rinse valve is opened while the boiler is in a cold state, while the steam valve and the water inlet of the boiler are kept closed. In the process, the water is allowed to flow from the boiler, through the rinse valve, mainly under the influence of gravity. After a specified period of time, or when the water stops flowing, one of the steam valve and the water inlet of the boiler is opened, so that air is let into the boiler, and the outgoing flow of water continues until the boiler is completely empty. In this way, effective removal of scale particles and possibly other contaminants from the boiler is realized. It is noted that the above-described way of rinsing the boiler system may particularly be suitable in case the boiler system does not comprise a pump for pressurizing the water inside the boiler. In case the boiler system comprises such a pump, it is an advantageous option to operate this pump during a rinsing process.

According to another way of rinsing the boiler system, which is suitable to be applied when the boiler system comprises a pump, water is pumped into the boiler for a specified period of time, or until a predetermined pressure is reached inside the boiler.

Subsequently, the rinse valve is opened. As a consequence, a jet of water may be discharged through the rinse valve, which carries along with it scale particles and possibly other contaminants from the boiler. Due to the pressure in the boiler, any scale that blocks the water outlet of the boiler is broken up. After the boiler has been emptied, the rinse valve is closed again. A first round of rinsing may be followed by a second round of rinsing (and optional further rounds of rinsing) in order to obtain cleaner water in the boiler. In this case, in principle, the rinse valve can have any position, while it is preferred to have the water outlet to which the rinse valve is connected positioned at a low point in the boiler in order to ensure that practically all of the water in the boiler is flushed out.

According to another way of rinsing the boiler, the rinsing process involves a supply of power for the purpose of heating up the boiler. The heating helps in stirring up the scale particles in the water. When a predetermined pressure is reached, the rinse valve is opened. The effect is comparable to the effect as described in respect of the second preferred way of rinsing the boiler. After the boiler has been emptied, the rinse valve is closed again. Also, when the boiler is rinsed in this third preferred way, a first round of rinsing may be followed by a second round of rinsing in order to obtain cleaner water in the boiler.

Furthermore, in a boiler system which is adapted to letting a rinsing process of the boiler take place according to this third preferred way, the rinse valve can have any position, while it is preferred to have the water outlet to which the rinse valve is connected positioned at a low point in the boiler in order to ensure that practically all of the water in the boiler is flushed out. Preferably, during the rinsing process or at the end of the rinsing process, scale solvent is introduced into the boiler. Under the influence of the scale solvent, the scale is kept in solution, and scale flakes are reduced. As an advantageous result, the efficiency of the rinsing process is improved. In the rinsing process, it may happen that one or more small scale particles end up on a seat of the rinse valve. Advantageously, towards the end of the water discharge which takes place during the rinsing process, the rinse valve is rapidly opened and closed for a number of times in order to dislodge such scale particles. In this way, leakage of the rinse valve during operation of the boiler, which may occur in case complete closure of the rinse valve is hindered by scale particles, is prevented.

In an embodiment, the boiler system according to the present invention comprises a rinse container for receiving water from the boiler and containing the water, which rinse container is removably arranged at an outlet side of the rinse valve. When a boiler system having a rinse container is subjected to a rinsing process, the water that is used in the process is received in the rinse container and remains inside the container until a user removes the container from the boiler system and pours away this water. An advantage of the application of the rinse container is that there is no need for positioning the outlet side of the rinse valve or a discharge member connected to the outlet side of the rinse valve above a separate container or a sink or the like when the rinsing process is carried out.

Advantageously, the boiler system comprises a flow smoothener, which is arranged at an outlet side of the rinse valve. An important function of the flow smoothener is prevention of splashing of the water. Consequently, when a flow smoothener is applied, the safety is enhanced, especially in case the boiler system does not comprise a rinse container.

Alternatively, a device, which may be in the form of a tube of predetermined cross-sectional area and length, may be used to smoothen the flow (close to laminar flow) and to prevent splashing at the outlet side of the rinse valve. Furthermore, it is advantageous to have a filter arranged at an inlet side of the rinse valve, so that clogging up of the inlet side of the rinse valve by scale particles does not occur.

During rinsing, anti-scaling agent may be applied to at least part of the water infrastructure.

For the purpose of controlling the various steps to be taken during a rinsing process, the boiler system may be provided with a suitable controller, for example a microcontroller or a memory IC. It is possible that a rinsing process is initiated on the basis of input of a user, wherein the boiler system may comprise a push button or the like for receiving input from the user and communicating this input to the controller. However, it is also possible that the rinsing process is automatically initiated after a specific duration of operation of the boiler system. For example, the rinsing process is initiated at every interval often hours of steaming, i.e. ten hours of the steam valve being opened. In such a case, the boiler system comprises measuring means for measuring a length of time of an opened condition of the steam valve, and the controller is adapted to keeping record of a total length of time of the opened condition of the steam valve, to comparing the total length of time of the opened condition of the steam valve to the maximum length of time often hours, and to operating the rinsing process in case the total length of time of the opened condition of the steam valve has reached the maximum length of time often hours. This is an accurate manner of determining the time when a rinsing process should be performed.

It is possible that the boiler comprises more than one steam outlet. In such a case, it is advantageous if the sum of cumulative times of opening of all of the steam valves is taken into account in the process of determining an appropriate moment for a rinsing process to take place. Another method for determining an appropriate moment for triggering a rinsing process, which is applicable in boiler systems comprising a pump for supplying water to the boiler, comprises the steps of determining the total time of operation of the pump, and comparing the total time to a maximum time.

It is also possible to apply an indirect method of determining the moment at which a rinsing process may be initiated. For example, the number of times the boiler system is operated is counted, and the rinsing process is initiated when the total number of times of operation has reached a predetermined maximum number. In particular, the boiler system may comprise detecting means for detecting operation of the boiler, wherein the controller is adapted to keeping record of a total number of times of operation, to comparing the total number of times of operation to a maximum number of times, and to operating the rinsing process in case the total number of times of operation has reached the maximum number of times.

In order to achieve a greater accuracy when the above-described indirect method is applied, the temperature of the boiler or the steaming device is measured at various positions. As scale builds up inside the boiler, it acts like a thermal barrier, as a result of which the temperature distribution is disturbed. Thus, by measuring the temperature at various positions, it is possible to find out if the temperature distribution is still within normal limits, or not. In the latter case, an indication that the rinsing process should be performed is obtained. In view of the foregoing, in a preferred embodiment in which the boiler system according to the present invention is adapted to determining a suitable moment for initiating a rinsing process, measuring means for measuring a temperature at various positions in the boiler or the steaming device are provided, and the controller is adapted to calculating differences between the measured temperatures and a predetermined temperature, to comparing the calculated temperature differences to a maximum difference, and to operating the rinsing process in case the calculated temperature differences have reached the maximum difference. In an embodiment, the boiler system according to the present invention comprises indicator means for providing feedback to a user in respect of a rinsing process of the boiler. In particular, the indicator means may be controlled by the controller such as to indicate that a rinsing process is in progress, or that a rinsing process has been completed. The indicator means may be of any nature, and may for example be mechanical, electrical, electronic or electromechanical. Furthermore, the indicator means may be adapted to providing feedback to the user in any suitable way, for example by providing an audible signal or a visible signal.

The present invention also relates to a steam ironing system, comprising a boiler system according to the present invention and a steam iron or a garment steamer, wherein the boiler system and the steam iron or the garment steamer are connected to each other through the steam hose of the boiler system. Furthermore, the present invention relates to an active ironing board comprising a steam supplying arrangement and a boiler system according to the present invention, wherein the steam supplying arrangement and the boiler system are connected to each other through the steam hose of the boiler system.

In further aspects, the invention also provides a steam generation device wherein the water infrastructure comprises a water reservoir, a steam chamber, the steam generation device further comprising a sole plate with steam ports as part of a boundary defining the steam chamber, wherein the water supply system is arranged to convey water from the reservoir to the steam chamber and wherein the heating unit is arranged to heat the sole plate. Here, the steam is generated within the iron itself. Embodiments of such steam irons are described in EP-0610997, which is herein incorporated by reference.

In a specific embodiment, the anti-scaling agent is in the form of a compressed pellet. This may allow dedicated application to the container of the steam generation device. Good results may especially be when x is in the range of 1.5 to 2.5, especially when x is 2.

In a further aspect, the invention provides a method for reducing scale in a water infrastructure of a steam generation device comprising introducing in at least part of the water infrastructure an anti-scaling agent comprising a sodium-calcium double salt of hydroxy ethylidene-(l,2-disphonic acid) (Na_x-Ca_y-HEDP, with x+2y being equal to 4). As mentioned above, especially x is in the range of 1.5 to 2.5, such as x is 2. The method may especially involve introducing the anti-scaling agent during a rinsing of at least part of the water infrastructure, such as the space where the water is heated to steam (such as the boiler unit or the steam hose, respectively). Hence, in an embodiment, the method includes introducing the anti-scaling agent in a boiler for containing water and heating water to steam, and in another embodiment, the method involves introducing the anti-scaling agent in a steam chamber of a steam iron.

The invention further provides to an anti-scaling agent for use in a water infrastructure of a steam generation device comprising a sodium- calcium double salt of hydroxy ethylidene-(l,2-disphonic acid) (Na_x-Ca_y-HEDP, with x+2y being equal to 4). By introduction or arrangement in at least part of the water infrastructure, due to contact with water, scale may be removed in at least part of the water infrastructure. The invention especially provides an anti-scaling agent tablet.

The invention provides in a further aspect the use of a sodium-calcium double salt of hydroxy ethylidene-(l,2-disphonic acid) (Na_x-Ca_y-HEDP, with x+2y being equal to 4) as anti-scaling agent, especially as anti-scaling agent in a steam generation device. As mentioned above, the double salt may be used in a water infrastructure of a steam generation device. Further, as indicated herein, especially x is in the range of 1.5 to 2.5, such as wherein x is 2. The double salt may be provided as powder, or as suspension, and may especially be provided as tablet.

The phrase "sodium-calcium double salt of hydroxy ethylidene-(l,2-disphonic acid) (Na_x-Ca_y-HEDP, with x+2y being equal to 4)" especially implies that both x and y are larger than zero (x>0, y>0), i.e. both sodium and calcium are present in the salt.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Figs, la-lc schematically depict a non- limiting number of embodiments of the steam generation device.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Fig. la schematically depicts an embodiment of the steam generation device 50 according to the invention. The steam generation device 50 comprises a water

infrastructure 100 (which is here part of a boiler system 320) comprising a water supply system 110 and a heating unit 120 for heating water to steam. The steam generation device 50 further comprises a container 200 (containing an anti-scaling agent 201) connected to the water infrastructure 100, wherein the anti-scaling agent 201 comprises a sodium-calcium double salt of hydroxy ethylidene-(l,2-disphonic acid) (Na_x-Ca_y-HEDP, with x+2y being equal to 4). Fig. la schematically depicts a specific embodiment, wherein the steam generation device 50 comprises a steam system comprising a steam iron 10 and a boiler system 320. Herein, the steam generation device 50 may relate to the boiler system 320 per se, as well as to the combination of boiler system 320 and steam iron 10.

Fig. la diagrammatically shows an embodiment of the steam generation device 50, here a steam ironing system, comprising steam iron 10 and boiler system 320. The boiler system 320 comprises a boiler 330 for containing water and heating water to steam. In Fig. la, a quantity of water such as may be present inside the boiler 330 is diagrammatically depicted as a collection of water droplets. For the purpose of receiving water, the boiler 330 comprises a water inlet 331. At the position of this water inlet 331 , a water filling cap 332 may be arranged. At a bottom of the boiler 330, a heating element 333 is arranged. During operation of the boiler system 320, the heating element 333 is activated, as a result of which the water inside the boiler 330 is heated and steam is generated.

On demand of a user, the steam that is generated in the boiler 330 is supplied to the steam iron 10, so that the steam may be applied during a steam ironing process which is performed with the help of the steam iron 10. The boiler 330 comprises a steam outlet 334 for letting out steam, and the steam iron 10 is connected to the boiler 330 through a steam hose 335 and a steam valve 336 which is arranged at the steam outlet 334. When the user desires to have steam supplied from the boiler 330 to the steam iron 10, the steam valve 336 is put to an opened condition, in which the steam valve 336 is capable of letting pass a flow of steam. When there is no need for a supply of steam from the boiler 330 to the steam iron 10, the steam valve 336 is put to a closed condition, in which the steam valve 336 blocks the steam outlet 334 of the boiler 330. The steam generation device 50 (here more precisely the boiler system 320) comprises an outlet 51 (in this embodiment in the steam hose 335) to allow steam escape from the steam generation device 50 (more precisely here, the boiler system 320).

The boiler system 320 comprises a controller 40 such as a microcontroller or a memory IC for controlling the condition of the steam valve 336. Preferably, the steam iron 10 comprises means which are operable by a user for the purpose of communicating to the controller 40 a desire to have a supply of steam. However, that does not alter the fact that in principle, such means may also be arranged at another position.

During operation of the boiler 330, scale may be formed inside the boiler 330, mainly as a deposit on inner sides of walls of the boiler 330. The formation of the scale deposit has many disadvantageous consequences. For example, scale particles may break lose during operation of the boiler 330 and be carried along with the steam to the steam iron 10. Such scale particles are spit out by the steam iron 10 and land on the object which is subjected to a steam ironing process, as a result of which this object gets stained. Also, the presence of scale inside the boiler 330 reduces the effectiveness of the heating process of the water inside the boiler 330, so that the process of putting water to steam takes more time and energy. Furthermore, over time, the water inside the boiler 330 gets contaminated, as a result of which a foaming effect occurs during heating of the water, which disturbs a continuous supply of steam by the boiler 330, and which may cause the boiler 330 to let out hot water along with the steam through the steam outlet 334. In view of the above-sketched problems, it is desirable to have means which are applicable for the purpose of removing water and scale from the boiler 330. In the boiler system 320 as shown in Fig. la, such means comprise a water outlet 337 of the boiler 330, which is arranged near a bottom of the boiler 330, and a rinse valve 338 which is arranged at the water outlet 337. Furthermore, the boiler system 320 comprises a flow smoothener 350 and a rinse container 355.

Due to the presence of the water outlet 337 and the rinse valve 338, it is possible to have a rinsing process performed in the boiler system 320. In particular, in the boiler system 320, the rinsing process is carried out prior to the start of a steam ironing session. During the rinsing process, the rinse valve 338 is opened, so that water is drained from the boiler 330, through the water outlet 337 and the rinse valve 338, mainly under the influence of gravity. After a specified period of time, or when the water stops flowing, the steam valve 336 or the water filling cap 332 is opened, so that air is let into the boiler 330, and the outgoing flow of water continues until the boiler 330 is completely empty. In this way, effective removal of scale particles and possibly other contaminants from the boiler 330 is realized. Preferably, in order to avoid clogging up of the water outlet 337 by scale particles, a filter (not shown) is arranged at the water outlet 337.

The water that is drained from the boiler 330 flows through the flow smoothener 350, and is eventually received in the rinse container 355. As a result of the presence of the flow smoothener 350, turbulence of the outgoing flow of water is reduced, and splashing of the water is prevented. The rinse container 355 is removably arranged, so that it is convenient for a user of the steam ironing system 50 to empty the rinse container 355, as the user may simply take the rinse container 355, carry it to a sink or the like, empty it, and put the empty rinse container 355 back in place again. Preferably, suitable indicating means are provided for indicating to the user that the rinse container 355 is full and needs emptying. At the end of the rinsing process, the rinse valve 338 is closed again, and the steam ironing system50 is fit to be used in a steam ironing session.

The boiler system 320 may comprise means which may be operated by a user for the purpose of communicating to the controller 340 a need for starting a rinsing process. However, it is preferred if the rinsing process is started automatically, after a predetermined duration of usage of the steam ironing system 50, wherein the controller 340 is programmed such as to automatically start a rinsing process when a detected duration of usage appears to have reached the predetermined duration of usage.

For example, the controller 340 is adapted to keeping record of the number of times a power supply to the boiler system 320 has taken place, and comparing a total number of times to a predetermined number of times. In case the total number of times appears to have reached the predetermined number of times, it is time for the rinsing process to be carried out, and the rinsing process is started by the controller 340, prior to the start of a steam ironing session. For greater accuracy, it is advantageous if not only the number of times of operation is taken into account. Preferably, temperature measurements are performed as well, at various positions in the boiler 330 or the steam iron 10. As scale builds up inside the boiler 330, it acts as a thermal barrier. When a deviant temperature is found during the temperature measurements, an indication that the rinsing process needs to be carried out is obtained.

It is also possible that the controller 340 is adapted to keeping record of a total time of an opened condition of the steam valve 336. In such a case, the need for starting a rinsing process is determined in a highly accurate manner, as the total time of the opened condition of the steam valve 336 is directly related to the total amount of generated steam and the total amount of scale. Also, in this case, the total time of the opened condition is compared to a predetermined total time by the controller 340, and the rinsing process is started in case the total time as measured appears to have reached the predetermined total time.

Advantageously, in case the controller 340 of the boiler system 320 is not adapted to automatically starting the rinsing process, the boiler system 320 comprises indicating means for indicating to a user a need of having a rinsing process carried out.

The boiler system 320 may also be used in combination with another steaming device than a steam iron 10. For example, the boiler system 320 may be mounted in an active ironing board having a steam supplying arrangement. Usually, such an ironing board comprises an ironing surface for supporting objects to be ironed, and is adapted to performing at least one of the functions of blowing air or drawing in air through the ironing surface, and may also comprise at least one heating element for heating the ironing surface. Other embodiments described in WO2007007241 are herein incorporated by reference.

The steam generation device 50 comprises the container 200 containing the anti-scaling agent 201. In the schematic drawing, the container 200 is connected with the water infrastructure with a connection to the boiler 330 and downstream of the rinse valve 338. As will be clear to the person skilled in the art, either or both of those connection options may be arranged, but also other options may be possible. Between the container 200 and the rest of the water infrastructure 100, valve(s) may be present (not drawn). The valve(s) may be controlled by the controller 340.

Figs, lb-lc schematically depict embodiments of the steam generation device 50, wherein the steam iron 10 itself is the steam generation device, and steam generation is performed with the steam iron 10.

Fig. lb is a diagrammatic sectional view of an embodiment of the steam iron 10 in accordance with the invention. Here, the steam iron 10 is not a system iron, and the steam iron 10 is in fact the steam generation device 50. This steam iron 10 comprises a water reservoir 401 and a steam chamber 402, which are separated by a partition 403. The water reservoir can be fried with hard tap water via the inlet opening 404 which can be closed. By means of the water-supply system 110, here especially indicated with reference 405, this water can be pumped from the water reservoir to the steam chamber. This water then contacts the sole plate 406 of the steam chamber which is heated by means of heating elements (not shown). The water thus introduced is vaporized on the hot sole plate, after which the steam leaves the steam iron via the steam ports 407. In this embodiment, opening(s) 51 refers to the steam port(s) 407. The sole plate 406 may be an embodiment of the heating unit 120.

The iron may also comprise a metering system 408 for introducing the phosphonate compound into the water reservoir. A metering system for the phosphonate compound is diagrammatically shown in more detail in Figs. 2a and 2b of EP0610997, which is herein incorporated by reference. Reference 470 indicates the boundary ("wall") defining the steam chamber 402. Part of this boundary 470 is formed by the sole plate 406 (with ports 407).

Fig. lc is a diagrammatic sectional view of another advantageous embodiment of the steam iron in accordance with the invention. Corresponding parts in this Fig. and Fig. lb bear the same reference numerals. In this embodiment a phosphonate compound which is poorly soluble in water is used. This compound is present in a housing 431 which is arranged at the bottom of the water reservoir. The housing comprises walls 432 of synthetic resin material (for example PMNA) and a water-permeable wall 433 in the form of a gauze of synthetic resin (for example polyester). In the present case the mesh size of the gauze was approximately 150 microns. This housing accommodates a compressed pellet or tablet of the anti-scaling agent 201. The pellet or tablet was manufactured by axially isostatically compressing approximately 2 grams of powder of this compound into a molded article. After filling the iron in accordance with this embodiment with water, a portion of the anti-scaling agent can dissolve via the permeable gauze.

The steam generation device(s) 50 described herein may further comprise a controller 340, arranged to control one or more selected from the group consisting of the heating of the water, the production of steam, a rinsing process, and the introduction of anti- scaling agent 201 into (part of) the water infrastructure 100, etc.. The controller may control in response to user commands and/or in response to predefined settings (for instance after a certain period of using time) and/or in response to sensor signals (such in response to a sensor signal indicating scaling or indicating passing a certain scale threshold).

Examples

Example 1 (including comparison)

Na_x-Ca_y-HEDP was prepared from Na₄-HEDP and CaCl₂ in an equivalent ratio of 1/2. The analyzing results from Ion Chromatography (IC) are listed below and compared with Ca₂-HEDP.

It is noticed that the concentration of Na ion in both cases is unexpectedly high. This is probably due to the incomplete washing of powder after the chemical conversion. Because Na₄-HEDP is in excess and CaCl₂ is in short, Ca²⁺ ion might be a better indicator of the amount of HEDP phosphonate dissolved in water. From the table the solubility of Na_x-Ca_y-HEDP is about 10 times of that of Ca₂-HEDP.

A satisfactory result is observed in scaling life test of a steam iron, where the dual salt is compounded and compressed into pellets, and the pellets are enveloped with a mesh and placed in water tank. Calc-clean is performed once every 30 liters of water consumption.

Table 1. Amount of scale removed by calc-clean and the maximum amount of water converted to steam before the irons failed to steaming, both non-treated and treated water with various HEDP phosphonate agents.

Compared to no-treatment and treatment with Ca₂-HEDP, the dual salt form of Na_x-Ca_y-HEDP has a superior effect on scale removal and scaling life time. The amount of scale removed by calc-clean is increased, and the amount of water converted into steam before the iron is fully clogged and failed to steam is higher. Reaching the scaling life time of 250 L of standard hard water (Hardness: 17 °dH) well indicates that the iron can last for at least 6 years of life time.

Visual inspection of the part of the water infrastructure of a steam generation device which is untreated, treated with the calcium salt of HEDP and treated with the anti- scaling agent of the invention showed the superiority of the treatment according to the invention.

Example 2

An anti-scaling agent was prepared based on Na₂-Ca-HEDP (ratio of Na- Dequest to CaCl₂: 1/2):

Na₄-Dequest: 5.0 gm, dissolved in 50 ml of DI water;

CaCl₂.H₂0: 2.4 gm, dissolved in 50 ml of DI water;

Additional DI water: 25 ml

Duration: 1.5 hrs

The solution was allowed to precipitate for at least 1 hr till the water on the top is clear. Water is allowed to leach away and then the precipitate was washed with 100 ml of DI water. Then, the solution was again allowed to precipitate for at least 1 hr till the water on the top is clear, and water is again allowed to leach away. This precipitate is washed with 100 ml of DI water. The precipitate was heated in an oven at 120 °C to dry, until the weight is constant. Example 2 (including comparison)

One way to improve the release amount of phosphonate might be to combine calcium form of HEDP with a more soluble form of HEDP, e.g. sodium salt of HEDP, in a compressed pellet.

It proves that it can improve the release amount of phosphonate by dissolving more Na_x-HEDP. However this happens only in the initial stage. After Na_x-HEDP is depleted in very short period of time, the release amount of phosphonate goes back to normal again.

The sodium-calcium double salt does not suffer from this problem.

The term "substantially" herein, such as in "substantially all emission" or in "substantially consists", will be understood by the person skilled in the art. The term

"substantially" may also include embodiments with "entirely", "completely", "all", etc.

Hence, in embodiments the adjective substantially may also be removed. Where applicable, the term "substantially" may also relate to 90% or higher, such as 95% or higher, especially 99%) or higher, even more especially 99.5% or higher, including 100%). The term "comprise" includes also embodiments wherein the term "comprises" means "consists of.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

The devices herein are amongst others described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation or devices in operation.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

CLAIMS:

1. A steam generation device (50) comprising:

a water infrastructure (100) comprising a water supply system (110) and a heating unit (120) for heating water to steam; and

a container (200) containing an anti-scaling agent (201) connected to the water infrastructure (100),

wherein the anti-scaling agent (201) comprises a sodium-calcium double salt of hydroxy ethylidene-(l,2-disphonic acid) with chemical formula Na_x-Ca_y-HEDP, x+2y being equal to 4.

2. The steam generation device (50) according to claim 1, wherein the water infrastructure (100) comprises a boiler (330) for containing water and heating water to steam, comprising at least one inlet (331) for letting in water, at least one outlet (334) for letting out steam, and optionally at least one outlet (337) for letting out water, a steam hose (335) connected to a steam outlet (334) of the boiler (330), which is suitable to be applied for connecting the boiler (330) to a steaming device (310) and for conducting steam from the boiler (330) to the steaming device (310) during operation of the steam generation device (50), a steam valve (336) connected to the steam outlet (334) of the boiler (330), and optionally a rinse valve (338) connected to the optional water outlet (337) of the boiler (330).

3. The steam generation device (50) according to claim 2, further comprising a steam iron (10) in connection with the steam outlet (334).

4. The steam generation device (50) according to claim 1, wherein the water infrastructure (100) comprises a water reservoir (401), a steam chamber (402), the steam generation device (50) further comprising a sole plate (406) with steam ports (407) as part of a boundary (470) defining the steam chamber (402), wherein the water supply system (110) is arranged to convey water from the reservoir (401) to the steam chamber (402) and wherein the heating unit (120) is arranged to heat the sole plate (406).

5. The steam generation device (50) according to any one of the preceding claims, wherein the anti-scaling agent (201) is in the form of a compressed pellet.

6. The steam generation device (50) according to any one of the preceding claims, wherein x is in the range of 1.5 to 2.5.

7. The steam generation device (50) according to any one of the preceding claims, wherein x is 2.

8. A method for reducing scale in a water infrastructure (100) of a steam generation device (50) comprising introducing in at least part of the water infrastructure (100) an anti-scaling agent (201) comprising a sodium-calcium double salt of

hydroxy ethylidene-(l,2-disphonic acid) with chemical formula Na_x-Ca_y-HEDP, x+2y being equal to 4.

9. The method according to claim 8, wherein x is in the range of 1.5 to 2.5, especially wherein x is 2.

10. The method according to any one of claim 8-9, comprising introducing the anti-scaling agent (201) during a rinsing of at least part of the water infrastructure (100).

11. The method according to any one of claim 8-10, comprising introducing the anti-scaling agent (201) in a boiler (330) for containing water and heating water to steam.

12. The method according to any one of claim 8-11 , comprising introducing the anti-scaling agent (201) in a steam chamber (402) of a steam iron (10).

13. An anti-scaling agent tablet for use in a water infrastructure (100) of a steam generation device (50) comprising a sodium-calcium double salt of hydroxyethylidene-(l,2- disphonic acid) with chemical formula Na_x-Ca_y-HEDP, x+2y being equal to 4.

14. The anti-scaling agent tablet according to claim 13, wherein x is in the range of 1.5 to 2.5, especially wherein x is 2.

15. Use of a sodium-calcium double salt of hydroxy ethylidene-(l,2-disphonic acid) with chemical formula Na_x-Ca_y-HEDP, x+2y being equal to 4, as anti-scaling agent, especially as anti-scaling agent in a steam generation device.