Instant steam generators normally used in stream household appliances currently available on the market, essentially consist of a die-cast metal core, wherein an electrical resistance is incorporated. In the metal core, a vaporisation chamber provided with a steam inlet section, a vaporisation path and a water outlet section is defined.

In particular, the vaporisation chamber consists of a longitudinal recess obtained, by pressing, on a surface of the metal core, and intended to be sealingly closed through a subsequent superimposition of a suitable closing means.

As known, in steam household appliances there is the need of guaranteeing an almost instantaneous steam generation.

For this purpose, it is necessary to increase the efficiency of the thermal exchange between the heating walls of the steam generator and the water fed into the same ; this normally occurs by increasing the thermal exchange surface between the metal core of the generator and the feeding water.

A larger thermal exchange surface is obtained, for example, in steam generators of the known type, by obtaining in the metal core two superimposed longitudinal recesses, in reciprocal fluid communication; in this case, the electrical resistance is embedded into a wall of the metal core interposed between the two recesses.

It has been proved in the practice that the steam generators of the type described above exhibit some drawbacks when used in steam appliances intended to be used in various working positions, in particular in inclined positions with respect to a horizontal plane. This occurs, for example, in steam cleaning and/or disinfecting appliances, which are generally handled so as to take different steam delivery positions depending on the position of the surface to be cleaned or of the areas to which the steam jet is to be directed. Typically, in fact, during use, said appliances are inclined with respect to a horizontal plane so as to direct the steam jet downwards or upwards.

A drawback associated to the use of steam generators of the known type in steam cleaning appliances is correlated to the variability of the performances of the same when the working position taken by the cleaning appliance varies (more or less inclined, downwards or upwards). In fact, in these cases, instead of circulating with continuity in the vaporisation chamber from the water inlet section to the steam outlet section, the feeding water tends to accumulate in the proximity of the water inlet section, when the appliance is inclined upwards, or of the steam outlet section, when the appliance is inclined downwards; this causes a variation of the steam amount delivered in the unit of time, in function of the inclination angle of the appliance.

Moreover, when the appliance is inclined downwards, the accumulation of water in the proximity of the steam outlet section implies the risk of having an undesired leakage of hot water from the steam emission nozzle; when the appliance is inclined upwards, the accumulation of water in the proximity of the water inlet section implies the risk of causing the obstruction of the water inlet to the vaporisation chamber (due to the formation of large quantities of calcareous deposits at this area).

The technical problem at the basis of the present invention is that of providing a small-sized instant steam generator with high thermal exchange efficiency, capable of guaranteeing constant performances irrespective of the working position of the same.

Thus, the invention relates to an instant steam generator comprising: -a metal core including an electrical resistance, -a water vaporisation. chamber defined into the metal core and comprising a water inlet section and a steam outlet section; -a vaporisation path in the vaporisation chamber between the water inlet section and the steam outlet section; characterised in that the vaporisation path comprises a plurality of substantially parallel and rectilinear sections in reciprocal fluid communication through respective elbow sections.

The generator of the invention has a compact shape, and at the same time it exhibits a large thermal exchange surface (and thus, a high thermal exchange efficiency). This is due to the presence of a winding or tortuous vaporisation path comprising a plurality of sections, respectively rectilinear and elbow-wise.

Advantageously, the generator of the invention is particularly suitable to be used in household appliances (such as, for example, steam cleaning and/or disinfecting appliances) intended to take up, during use, inclined positions with respect to a horizontal plane. In fact, the elbow sections define, in the vaporisation path, opposed loops, separate from the water inlet and steam outlet sections ; some of said loops are intended for the water accumulation when the appliance is inclined downwards, and the others are intended for the water accumulation when the appliance is inclined upwards.

Thus, when the cleaning appliance is inclined, the water

circulating along the vaporisation path finds in any case and independently of the direction of inclination, some accumulation and vaporisation areas arranged in the vaporisation path in remote position with respect to the steam outlet section ; in this way, the amount of generated steam per unit of time remains almost constant as the inclination angle of the appliance changes.

Moreover, the presence of separate water accumulation areas arranged in remote position with respect to the water inlet and steam outlet sections allows to prevent the risk of having hot water leakages from the steam emission nozzle, when the appliance is inclined downwards, or obstruction of the water inlet to the vaporisation chamber (due to the formation of calcareous deposits in the proximity of said inlet), when the appliance is inclined upwards.

Preferably, the metal core has an elongated shape, and the rectilinear sections extend into the metal core in a substantially longitudinal direction. As a consequence, the water collecting loops are arranged substantially perpendicularly to the inclination axis so that, when the appliance is inclined, the water tends to reach said loops, where it is accumulated and vaporised.

Advantageously, the vaporisation path comprises a plurality of barriers, which are preferably integral with the metal core. The barriers are arranged in the vaporisation path in a substantially transversal direction with respect to the water and/or steam flow and define a plurality of consecutive vaporisation chambers in reciprocal fluid communication. Said barriers, thus, obstruct the water flow, but not that of steam; a portion of the water flow is thus retained upstream of each barrier, where it vaporises.

This allows to increase the quantity of steam produced in the unit of time.

Advantageously, the generator of the invention comprises a metal member for closing the vaporisation chamber, provided

with water inlet and steam outlet ducts in fluid communication with the water inlet and steam outlet sections of the vaporisation chamber. Said member sealingly closes the vaporisation chamber.

In an alternative embodiment of the steam generator of the present invention, the barriers are integral with the closing metal member. In any case, the barriers extend for a height lower than the distance between the bottom of the vaporisation path provided in the metal core and the closing member, thus allowing the water and/or steam to flow from the water inlet section to the steam outlet section.

In a preferred embodiment'of the generator of the present invention, the substantially rectilinear sections of the vaporisation path are all in a series fluid communication with one another.

In an alternative embodiment, the substantially rectilinear sections of the vaporisation path comprise a first pair of opposed rectilinear sections that are in fluid communication with the water inlet section and in parallel with one another, a second pair of opposed rectilinear sections, each one being in a series fluid communication associated with a respective section of the first pair of sections, and a plurality of substantially rectilinear successive sections that are in a series fluid communication with one another and with the sections of the second pair of opposed rectilinear sections.

Further features and advantages of the present invention will appear more clearly from the following detailed description of some preferred embodiments, made with reference to the attached drawings. In such drawings, -figure 1 is a perspective view of a first embodiment of a generator according to the present invention ; -figure 2 is a front view of the generator of figure 1 ; -figure 3 is a perspective view of a second embodiment

of a generator according to the present invention ; -figure 4 is a front view of the generator of figure 3.

In such figures, reference numeral 1 refers to an instant steam generator according to the present invention.

Generator 1 is particularly suitable to be used in household appliances such as steam cleaners and/or disinfecting appliances, which-as known-are intended to take up inclined positions with respect to a horizontal plane, during use.

Generator 1 comprises a metal core 2 having an elongated shape, generally obtained through die-casting. The metal core 2 comprises a base body 2a, wherein there is incorporated an electrical resistance (not shown), and an upper surface 3, wherein a vaporisation chamber 4 is defined. A closing member (not shown) is intended to be arranged on the surface 3 of core 2 so as to sealingly close the vaporisation chamber 4.

The vaporisation chamber 4 consists, in particular, of a groove obtained during pressing on the surface 3 of core 2, and defining a vaporisation path 4a of the feeding water of generator 1. Upstream of the vaporisation path 4a there is provided a water inlet section 5; downstream of the vaporisation path 4a there is provided a steam outlet section 6.

The respectively water inlet and steam outlet sections 5 and 6 are intended to be in fluid communication with respective water inlet and steam outlet ducts provided into the closing member of the vaporisation chamber 4.

Between the water inlet section 5 and the steam outlet section 6, the vaporisation path 4a comprises a plurality of substantially rectilinear and parallel sections 10 in reciprocal fluid communication through respective elbow sections lla, llb.

The rectilinear sections 10 extend into the metal core 2 in

a substantially longitudinal direction, whereas the elbow sections lla, llb are arranged substantially perpendicularly to the longitudinal axis of generator 1.

In the vaporisation chamber 4, the elbow sections lla, llb define respective loops having concavities facing to opposed sides with respect to a plane perpendicular to the longitudinal axis of generator 1. Sections lla are intended for water accumulation when the appliance is inclined downwards, whereas sections lib are intended for water accumulation when the appliance is inclined upwards.

In a preferred embodiment of generator 1 of the present invention, shown in figures 1 and 2, the water inlet section 5 and the steam outlet section 6 are both arranged in the proximity of a same end la of generator 1, and the rectilinear sections 10 of the vaporisation path 4a are all in a series fluid communication with one another. In particular, the rectilinear sections 10 of the vaporisation path comprise a first section 10a whose length is substantially equal to the length of the generator 1, a pair of successive sections 10b whose length is substantially equal to half the length of generator 1, and a second section 10c whose length is substantially equal to the length of generator 1. Sections 10a, lOb and 10c are in reciprocal fluid communication through the elbow sections lla, llb.

In said embodiment, the water inlet section 5 consists of a longitudinal recess, whose length is substantially equal to half the length of generator 1, in fluid communication- through a sill 12-to the first rectilinear section 10a.

The steam outlet section 6 is in fluid communication with the second rectilinear section lOc.

In an alternative embodiment of generator 1 of the present invention, shown in figures 3 and 4, the water inlet section 5 is provided in a substantially central position on the upper surface 3 of core 2, whereas the outlet

section 6 is arranged in the proximity of an end 3a of generator 1. In this embodiment, the rectilinear sections 10 of the vaporisation path 4a comprise, in particular, a first pair of opposed sections 10d in fluid communication with the water inlet section 5 and in parallel with one another, a second pair of opposed sections 10e, each one being in a series fluid communication with a respective section of the first pair of sections 10d, and a plurality of successive sections, all referred to with reference numeral 10f, which are in a reciprocal series fluid communication with one another and with the second pair of sections 10e. Sections 10d, 10e and 10f are in reciprocal 'fluid communication through the elbow sections lla, llb.

In both embodiments illustrated above, the vaporisation path 4a comprises a plurality of barriers, all referred to with reference numeral 13, preferably integral with the metal core 2, arranged into the rectilinear 10 and elbow lla, llb sections in a substantially transversal direction with respect to the water and/or steam flow. Barriers 13 define a plurality of consecutive vaporisation chambers in reciprocal fluid communication.

In an alternative embodiment (not shown) of the steam generator of the present invention, barriers 13 are integral with the metal closing member of the vaporisation chamber 5.

In any case, barriers 13 extend for a height lower than the distance between the bottom of the vaporisation path 4a provided into the metal core 2 and the closing member of the vaporisation chamber 4.

During operation, the feeding water enters into generator 1 through the inlet duct provided into the covering member of the vaporisation chamber 4; the electrical resistance is actuated so as to heat the metal core 2 and the metal closing member. In said conditions, the water vaporises as it passes through the vaporisation path 4a from the water

inlet section 5 to the steam outlet section 6, from which it exits exclusively as steam. During the circulation into the vaporisation path 4a, a portion of the feeding water is retained upstream of the various transversal barriers 13, whereas the remaining portion and the steam gradually generated pass downstream of the same, towards the steam outlet sections 6. If during use, the cleaning appliance wherein generator 1 of the invention is installed is inclined downwards or upwards, the water present into the vaporisation path 4a will tend to accumulate into the elbow sections lla or llb respectively, where it shall vaporise.

The steam gradually generated flows towards the steam outlet section 6.