DESCRIPTION

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The present invention relates to a steam generator, in particular, the present invention relates to a steam generator of the type known as instantaneous or direct evaporation generator, i.e. a steam generator apt to evaporate almost instantaneously or anyhow in a very short time the whole liquid which is progressively supplied therein and to immediately let out the steam thus obtained. This steam generator is exploited in several steam user devices, such as e.g. ironing systems, steam cleaners, steam cooking devices, etc. This type of steam generators differs from and contrast steam boilers since, unlike the latter, it does not contain inside a reservoir for a liquid to be evaporated, which is progressively evaporated and kept pressurized inside the reservoir itself, for being let out only after opening a steam outlet duct. An example of an instantaneous steam generator is disclosed by patent EP0023855 whose generator has an in- , ner compartment defined by two substantially flat containment portions, a first portion in which is defined an access duct for a liquid to be evaporated, which is reached by the liquid coming from a reservoir by means of a pump, and a second closing portion. Between the first and the second portion a disk is housed, which is kept in contact with the first portion by means of elastic elements, thus closing the access duct in rest conditions of the steam generator. When the liquid is pushed into the generator by the pump between the first portion and the disk, the disk is slightly lifted up and the liquid is evaporated almost instantaneously and the steam thus produced is let out by the generator by means of a suitable outlet duct.

The steam generator described above has some relevant drawbacks.

First of all, if the liquid to be evaporated contains solid residues, such as e.g. common water containing limestone, these solid residues are rapidly deposited inside the compartment of the steam generator, thus forming in particular a layer which gets progressively thicker between the first portion and the disk. This limestone layer rapidly deteriorates the performance of the steam generator since it reduces heat exchange between the liquid and the electrical resistors usually housed at least in the first portion. As a result, the known generator must be used with demineralized water only or must be provided upstream from the water inlet with a decalcification device, since otherwise its performance would rapidly sink and it would no longer be able to produce the necessary amount of steam.

Further drawbacks of known instantaneous steam generators are related to the so-called "steam tail", i.e. the amount of residual steam forming inside the generator when the user decides to interrupt the steam flow. As a matter of fact, when the steam flow is interrupted, known devices block the pump pushing the fluid into the generator, but the fluid which is already inside the generator is however evaporated and sent to the steam user device. This residual flow or "steam tail" cannot be blocked inside the generator since this would involve a relevant and sudden pressure rise inside the system with possible damages or dangers to various parts of the device. Therefore, this residual flow can last even for sev- 5 eral seconds and is both uncomfortable and dangerous for the user, which would rather have an interruption of the steam flow when s/he gives the corresponding command.

Under these circumstances, the technical task underlying the present invention is to propose an instantaneous steam generator without the drawbacks mentioned above. In particular, an aim of the present invention is to propose a steam generator which enables an efficient removal of deposits, e.g. scale de- O posits, forming in the steam generator when it is used with non-demineralized liquids. Moreover, an aim of the present invention is to propose a steam generator which has high operating performance levels and which basically keeps them unchanged over time. Another aim of the present invention is to carry out a steam generator which enables a very rapid interruption of the steam flow getting out after interrupting the liquid flow getting in, thus eliminating or considerably reducing the so-called "steam tail". A 5 further aim of the present invention is to provide a steam generator which is simple and cheap to manufacture.

According to the present invention, the technical tasks and the aims described above are achieved by a steam generator comprising the technical characteristics disclosed in one or more of the appended claims, each of them being considered alone, without its dependent claims, or in combination with any O one or more of the remaining claims and/or of the aspects described below. In a further aspect, the invention relates to a steam generator according to any one of the claims, wherein a rubbing movement between at least one portion of a working surface and at least one portion of an evaporation surface takes place in a second direction transversal to a first direction, and/or wherein the second direction lies in a plane perpendicular to the first direction. In another aspect, the invention relates to a steam genera- 5 tor according to any one of the claims, wherein movement means are apt to rotate a contrast element in a containment body for obtaining a rubbing movement of rotational type. In a further aspect, the invention relates to a steam generator according to any one of the claims, wherein the containment body comprises at least a first containment portion and at least a second containment portion mounted onto the first portion for defining the containment body, the contrast element being housed between the first O and second containment portion. In another aspect, the invention relates to a steam generator according to any one of the claims, wherein rubbing takes place between the whole working surface and the whole corresponding evaporation surface. In another aspect, the invention relates to a steam generator according to any one of the claims, wherein the first containment portion and/or the second containment portion and/or the contrast element have a substantially disk-like shape. In another aspect, the invention relates to a steam generator according to any one of the claims, wherein an evaporation surface and a fluid inlet opening are made in the first containment portion, and wherein the contrast element has the working surface substantially counter shaped to the evaporation surface. In a further aspect, the inven- 5 tion relates to a steam generator according to any one of the claims, further comprising a fluid supply reservoir operatively connected to the inlet opening, and a pump operatively interposed between the reservoir and the inlet opening. In a further aspect, the invention relates to a steam generator according to any one of the claims, wherein at least the evaporation surface and the working surface are made of the same material, preferably aluminum. In a further aspect, the invention relates to a method for producing 0 steam according to any one of the appended claims, characterized in that it comprises the steps of letting a fluid into a containment body, evaporating the fluid in the containment body and letting the evaporated fluid out of an outlet opening, and further the step of rubbing at least one portion of a working surface against at least one portion of an evaporation surface. In another aspect, the invention relates to a method wherein the rubbing step is carried out by rotating the contrast element with respect to the con- 5 tainment body. In another aspect, the invention relates to a method wherein the rubbing step is carried out simultaneously to the steps of evaporating the fluid in the containment body and letting the evaporated fluid out of the outlet opening.

Further characteristics and advantages of the present invention will be more apparent from the indicative, and therefore non-limiting, description of some embodiments among which a preferred, though not O exclusive, embodiment of a steam generator, as shown in the accompanying drawings, in which:

- Figure 1 shows a schematic side view of a steam generator according to the invention connected to a steam user device;

- Figure 2 shows a top view of the generator and of the device of Figure 1 ;

- Figure 3 shows a partially sectioned view of Figure 1 according to lines Ill-Ill of Figure 2; 5 - Figure 4 shows a detail of Figure 2 concerning the steam generator according to the present invention in a first operating position;

- Figure 5 is a view analogous to Figure 4 in a second operating position;

- Figure 6 shows an exploded view of some components of the generator of Figure 4.

With reference to the accompanying figures, the numeral 1 globally refers to a steam apparatus com- O prising an instantaneous steam generator 2 according to the present invention.

The generator 2 is connected, as shown in Figures 1-3, to a steam user device 3, in the example a smoothing iron, which is part of the steam apparatus 1 and is connected by means of a steam supply duct 4. The invention can advantageously apply to several other types of steam user devices, such as steam cleaning devices, steam cooking devices, etc.

The instantaneous steam generator 2 comprises a containment body 5 having inside a compartment 6 and at least one evaporation surface 7. The containment body 5 comprises at least a first containment portion 8 and at least a second containment portion 9 mounted onto the first portion 8 for defining the containment body 5. The generator 2 further comprises at least one heating element 10 associated with the containment body 5 for heating at least the evaporation surface 7, which heating element 10 can be made up e.g. of a conventional electrical resistor preferably fitted into the first containment portion 8. The generator 2 is provided with at least one opening 11 for letting into the compartment 6 a fluid to be evaporated, obtained in the containment body 5 and preferably in the first containment portion 8. In the example shown, the inlet opening 11 is carried out in the middle of the first containment portion 8. The generator 2 further comprises a contrast element 12 having a working surface 13 and housed in the containment body 5 so as to move in a first direction (preferably perpendicular to the plane in which lie the evaporation surface 7 and the working surface 13) between a first operating position in which the working surface 13 is in contact with the evaporation surface 7 and closes the inlet opening 11, and at least a second operating position in which the working surface 13 is at a distance from the evaporation surface 7 and enables the fluid to get into the compartment 6 through the inlet opening 11. Preferably, the contrast element 12 is housed between the first and the second containment portions 8 and 9. Advantageously the evaporation surface 7 and the inlet opening 11 to let the fluid in are made in the first containment portion 8 and the contrast element 12 has its working surface basically counter shaped with the evaporation surface 7. Preferably, said surfaces 7, 13 are flat. The generator 2 further comprises at least one elastic element 14 operatively active upon the contrast element 12 for pushing the working surface 13 against the inlet opening 11 and in contact with the evaporation surface 7, the elastic element 14 being apt to allow the working surface 13 to get at a distance from the inlet opening 11 and from the evaporation surface 7 as a result of a thrust of a fluid having a predefined pressure from the inlet opening 11. The thrust exerted by the elastic element 14, e.g. a helical spring, can be e.g. in the order of 5-20 kg, or another value suitably calibrated taking other factors into consideration. Preferably, as shown in the accompanying figures, the first containment portion 8, the second containment portion 9 and the contrast element 12 are basically disk-shaped. The generator 2 is further provided with at least one opening 15 for letting evaporated fluid out of the compartment 6, obtained in the containment body 5. The steam generator 2 can further comprise a fluid supply reservoir 23 operatively connected to the inlet opening 11 , and a pump 24 operatively interposed between the reservoir 23 and the inlet opening 11. Advantageously, the generator 2 further comprises movement means 16 apt to carry out a relative rubbing movement in a second direction between at least one portion of the working surface 13 and at least one portion of the evaporation surface 7. Preferably, rubbing takes place at least in the first operating position. It should be pointed out that in the present text the definition of rubbing between the two surfaces 7, 13 mentioned also encompasses the case in which a layer of solid deposit (e.g. limestone) lies between these surfaces 7, 13, and in which therefore rubbing necessarily takes place between one of the surfaces 7, 13 and the limestone layer deposited on the other surface. Preferably, rubbing takes place between the whole working surface 13 and the corresponding whole evaporation surface 7. It is however possible, due to the inhomogeneity of the surfaces 7, 13 or to limestone deposits in some areas, that rubbing takes place only in some portions of the two surfaces 7, 13. Ad- vantageously, the contrast element 12 and the containment body 5 are mutually mounted in a movable manner for enabling the relative rubbing movement between the working surface 13 and the evaporation surface 7. Advantageously, the movement means 16 are operatively active for moving the contrast element 12 in the second direction with respect to the containment body 5, thus obtaining the rubbing movement. Preferably, the rubbing movement takes place in a second direction transversal to said first direction and/or the second direction lies in a plane perpendicular to the first direction. Advantageously, as shown in the figures, the contrast element 12 and the containment body 5 are turnably mounted one with respect to the other, and the second direction is a rotational direction. In this case, advantageously, the movement means 16 are apt to rotate the contrast element 12 in the containment body 5 for obtaining said rubbing movement of rotational type. In an alternative embodiment, not shown, it is possible that both the first containment portion 8 and/or the evaporation surface 7 moves with respect to the contrast element 12 for obtaining said rubbing movement. In other embodiments, the second direction could be a direction, e.g. either linear or curved, lying in a plane perpendicular to the first direction, or any direction ensuring rubbing between the two surfaces 7, 13 referred to. In a further embodiment, not shown, the second direction could coincide with the first direction, so that rubbing is obtained by re- peated collisions between the two surfaces 7, 13 in an alternated to-and-fro movement. Preferably, the movement means 16 comprise a motor 17, e.g. an electric motor, mounted onto the containment body 5 and operatively active upon a drive portion 18 of the contrast element 12. The motor 17 is preferably equipped with a gear motor 19 for obtaining the suitable number of revolutions for the contrast element and for applying the suitable force to enable the desired rubbing. The number of revolutions made by the contrast element 12 can be varied as a function of the effectiveness to be obtained for the removal of limestone residues, of the type of materials and thus of friction between the evaporation and working surfaces, of the shape and size of the surfaces, etc. Acceptable values for rotational speed are e.g. 1 to 150 rpm, preferably 5 to 60 rpm and still more pref- erably 10 to 30 rpm, and e.g. 15 rpm.

Preferably, the outlet opening 15 for evaporated fluid is made in the containment body 5 and configured to as to be arranged at a lower height above the ground than the inlet opening 11 for the fluid, for making the release of fluid and of solid residues from the containment body 5 easier. As can be seen in Fig- ures 1-5, preferably the evaporation surface 7 and the working surface 13 are arranged inclined with respect to the horizontal line downwards in the direction of the outlet opening 15 for evaporated fluid, so that the outlet opening 15 for evaporated fluid lies in an area at a lower height with respect to the compartment 6 and to the containment body 5. Thus it is easier for the evaporated fluid and for the fluid not yet evaporated to get out of the compartment 6 (beyond the solid residues), and as a result the so- called "steam tail" generating when the user commands the interruption of the fluid flow getting into the steam generator 2 is significantly reduced. Advantageously, the generator further comprises a filter 20 apt to retain solid residues, mounted onto an outlet duct 21 for the evaporated fluid downstream from the outlet opening 15 for evaporated fluid. The filter 20 is apt to retain solid residues so that these do not reach the supply duct 4 and therefore the steam user device 3. The generator further comprises an in- stantaneous shut-off valve 22 for the flow of evaporated fluid, mounted into the outlet duct 21 for the evaporated fluid downstream from the outlet opening 15 for evaporated fluid (in the figures the valve is mounted into the final portion of the steam supply duct 4, which is part of the outlet duct 21 for the evaporated fluid). This valve 22, e.g. an electromechanical or a diaphragm valve, interrupts instantaneously the steam flow getting out of the steam user device 3 simultaneously to the stop of the pump 24 for supplying the fluid to the generator 2. Thanks to the particular configuration above described of the generator 2, no significant pressure rise is thus created in the generator 2, unlike known devices, but the usual operating pressure is maintained. Preferably, at least the evaporation surface 7 and the working surface 13 are made of the same material, preferably aluminum. Preferably, the first containment portion 8 and the contrast element 12 are made of the same material, e.g. aluminum, for obtaining a higher friction during rubbing. As an alternative, these elements 8, 12 could be made of different materials.

Advantageously, the evaporation surface 7 and the working surface 13 are basically flat, but in an alternative embodiment at least one of these surfaces could be provided with one or more shaped reliefs. These shaped reliefs, e.g. helix- or cusp-shaped, are in this case preferably made for obtaining an effect of centrifugal thrust towards the periphery of these surfaces, thus conveying solid residues towards the outlet opening. In a further aspect, the invention relates to a method for producing steam in a steam generator 2, comprising at least the steps of letting a fluid, e.g. water, into the containment body 5, evaporating the fluid in the containment body 5 and letting the evaporated fluid out of the outlet opening 15, and further the step of rubbing at least one portion of the working surface 13 against at least one portion of the evaporation surface 7. In another aspect, the invention relates to a method wherein the rubbing step is carried out by rotating the contrast element 12 with respect to the containment body 5. In another aspect, the invention relates to a method wherein the rubbing step is carried out simultaneously to the steps of evaporating the fluid in the containment body 5 and letting the evaporated fluid out of the outlet 5 opening 15.

The rubbing step can also be carried out at a different moment with respect to the evaporation step, but it is preferably carried out simultaneously so as to remove solid residues together with the evaporated fluid (which is filtered by the filter 20). It is also possible to carry out rubbing at certain moments only during the operation of the generator 2, e.g. in some operating intervals of the generator 2. l O The invention attains the appointed aims and achieves important advantages. As a matter of fact, a steam generator according to the invention enables an efficient removal of deposits, e.g. limestone deposits, which form in the steam generator when the latter is used with non-demineralized liquids. Moreover, the steam generator offers high operating performance levels and keeps them basically unchanged over time. Furthermore, the steam generator according to the invention basically eliminates the

15 so-called "steam tail", offers a high operating safety for users and is also easy and cheap to manufacture. Eventually, it should be pointed out that the invention provides an instantaneous steam generator which is a valid alternative to steam boilers and is basically maintenance-free (except for the periodical cleaning of the filter).