EP2341176A1

EP2341176A1 - Laundry washing machine with steam-based clothes refreshing cycle

Info

Publication number: EP2341176A1
Application number: EP09180842A
Authority: EP
Inventors: Gisella Ruffati; Martino Bondi
Original assignee: Electrolux Home Products Corp NV
Current assignee: Electrolux Home Products Corp NV
Priority date: 2009-12-29
Filing date: 2009-12-29
Publication date: 2011-07-06

Abstract

A laundry washing machine (1) comprising an outer casing (2) and, inside the casing, a washing tub (3) and a revolving drum (4) for housing the laundry to be washed, and which is fixed in axially rotating manner inside the washing tub (3); the laundry washing machine being also provided with drum moving means (6) structured for rotating, on command, the revolving drum (4) about its longitudinal axis (L) inside the washing tub (3), with a detergent dispenser (9) structured for temporarily storing a given quantity of detergent product/s to be poured into the washing tub (3), with a fresh water supply circuit (10) which is structured for supplying, on command, tap water into the detergent dispenser (9) so to drag away into the washing tub (3) the detergent product/s stored into detergent dispenser (9), and with an electronic central control unit (14) which controls at least said moving means (6) and said fresh water supply circuit (10); the electronic central control unit (14) being designed to control said drum moving means (6) and said fresh water supply circuit (10), so to maintain the revolving drum (4) into rotation when the fresh water supply circuit (10) supplies tap water into the washing tub (3).

Description

The present invention relates to a laundry washing machine.
More specifically, the present invention relates to a top-loading home laundry washing machine, to which the following description refers purely by way of example.
As is known, top-loading laundry washing machines generally comprise a substantially parallelepiped-shaped outer box casing structured for resting on the floor; a substantially cylindrical washing tub which is suspended in floating manner inside the casing by means of a number of coil springs and shock-absorbers, with the longitudinal reference axis of the washing tub oriented substantially horizontally; a door hinged to the top of the casing so as to rotate to and from a closing position in which the door rests on the top of the casing for closing a laundry loading and unloading opening realized in the top wall of said casing; a substantially cylindrical revolving drum for housing the laundry to be washed, and which is housed substantially horizontally inside the washing tub with the possibility to rotate about its longitudinal reference axis; and an electric motor assembly for rotating the revolving drum about its longitudinal axis inside the washing tub.
More specifically, the upper section of the lateral wall of the washing tub is provided with a broad substantially rectangular-shaped through opening, which is aligned to the laundry loading and unloading opening on the top wall of the casing, and the laundry washing machine is provided with an elastic-deformable connecting bellows which connects in watertight manner the through opening on the lateral wall of the washing tub to the laundry loading and unloading opening realized on the top of the casing.
Laundry washing machines of the above type are also provided with a detergent dispenser which is usually integrated within the door so as to be located, when the door is in the closing position, immediately above the through opening of the washing tub; with a fresh water supply circuit which is structured for supplying, on command, tap water into the detergent dispenser so to drag away into the washing tub the detergent product/s stored into the detergent dispenser; with a washing-water recirculating and draining circuit which is structured for, on command, sucking the washing water from the bottom of the washing tub and feeding said water back inside the revolving drum, or alternatively draining the washing water accumulated on the bottom of the washing tub directly outside of the washing machine casing, into a generic external waste-water exhaust duct; and with an electric heating device, namely a resistor, which is located on the bottom of the washing tub and is structured for rapidly heating the washing water accumulated on the bottom of washing tub.
More specifically, the electric heating device is housed into an outwards-projecting sink or bowl which is realized on the lower section of the lateral wall of the washing tub, and the washing-water recirculating and draining circuit communicates directly with the bottom of said outwards-projecting sink so that the sink operates also as draining sump for the washing-water recirculating and draining circuit.
In the more sophisticated laundry washing machines disclosed in W02006/129912 and CH-695383 , the electric heating device located on the bottom of the washing tub, into the outwards-projecting sink, is also structured for boiling the tap water so as to produce steam which is used for performing a special refreshing cycle which is totally independent from the traditional washing cycle, and which serves for de-wrinkling, refreshing and/or removing rank smell from the laundry stored inside the revolving drum.
Since wetting of the laundry stored inside the revolving drum must be totally avoided during the steam-based refreshing cycles, the laundry washing machines disclosed in W02006/129912 and CH-695383 are provided with a much more sophisticated fresh-water supply circuit which has an auxiliary water supply line structured for supplying, on command, the tap water directly into the outwards-projecting sink located on the bottom of the washing tub, without wetting the laundry stored inside the revolving drum. In fact, steam generation requires to fill up with tap water only the outwards-projecting sink which houses the electric heating device normally used for heating up the washing water.
Unfortunately this more sophisticated fresh-water supply circuit is rather costly and quite complicated to install within the washing machine casing, causing a considerable increase in the appliance production costs.
Aim of the present invention is therefore to provide a laundry washing machine structured for performing a steam-based clothing refreshing cycle, which is less expensive to produce.
In compliance with the above aim, according to the present invention there is provided a laundry washing machine as defined in Claim 1 and preferably, though not necessarily, in any one of the dependent claims.
Additionally, according to the present invention there is provided an operating method of a laundry washing machine as defined in Claim 10 and preferably, though not necessarily, in any one of the dependent claims.
A non-limiting embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a schematic front view, with parts in section and parts removed for clarity, of a top-loading laundry washing machine realized in accordance with the teachings of the present invention;
Figure 2 shows an enlarged view of the top portion of the Figure 1 laundry washing machine in an opened configuration, with parts in section and parts removed for clarity;
Figure 3 shows an enlarged view of the top portion of an alternative embodiment of the Figure 1 laundry washing machine, with parts in section and parts removed for clarity.

With reference to Figures 1 and 2, number 1 indicates as a whole a home laundry washing machine structured for performing both a washing cycle and a steam-based clothing refreshing cycle.
Washing machine 1 comprises: a preferably, though not necessarily, parallelepiped-shaped outer box-like casing 2 structured for resting on the floor; a substantially cylindrical washing tub 3 suspended in floating manner inside casing 2 via a suspension system (not shown) preferably, though not necessarily, comprising a number of coil springs combined with one or more vibration dampers; a substantially cylindrical revolving drum 4 for housing the laundry to be washed, and which is fixed in axially rotating manner inside washing tub 3 for rotating about its longitudinal axis L; a door 5 movably fixed onto casing 2 so as to move to and from a closing position in which door 5 closes a laundry loading and unloading opening 2a realized on casing 2 for providing access to the inside of the washing tub 3; and an electric motor assembly 6 which is able to rotate, on command, revolving drum 4 about its longitudinal axis L inside washing tub 3.
In the example shown, in particular, washing tub 3 is suspended in floating manner inside casing 2 so that its longitudinal reverence axis is oriented substantially horizontally, and revolving drum 4 is housed inside washing tub 3 so that its longitudinal axis L is oriented substantially horizontally and approximately coincides with the longitudinal axis of washing tub 3. Washing tub 3 and revolving drum 4 form the washing group of the washing machine.
More specifically, in the example shown the washing machine 1 is a top-loading washing machine, therefore the laundry loading and unloading opening 2a is realized on the top of casing 2, and the upper section of the cylindrical lateral wall of washing tub 3 is provided with a preferably, though non necessarily, substantially rectangular-shaped large through opening 3a which is aligned to the laundry loading and unloading opening 2a realized on the top wall of casing 2.
Moreover, washing machine 1 is also provided with a substantially cylindrical elastic-deformable bellows 7, which is structured for connecting in watertight manner the upper opening 3a realized on the lateral wall of washing tub 3 to the laundry loading and unloading opening 2a realized on the top wall of casing 2; and door 5 is hinged to the top of casing 2 so as to rotate about a preferably, though non necessarily, horizontal reference axis A to and from a closing position (see figure 1) in which door 5 lays on the top of casing 2 so to close opening 2a and watertight seal washing tub 3.
In the example shown, in particular, opening 3a is preferably, though non necessarily, bordered by a upwards projecting sleeve or perimetrical flange which is realized in one piece with the cylindrical lateral wall of washing tub 3, and elastic-deformable bellows 7 is fitted onto said upwards projecting sleeve or perimetrical flange.
Revolving drum 4, in turn, has a perforated lateral wall and is provided with a preferably, though not necessarily, double-leaf and manually-openable trapdoor 8 which is located on the cylindrical lateral wall of the drum, and is dimensioned for providing, when opened, temporary access to the inside of the revolving drum 4, previous alignment of trapdoor 8 to the upper opening 3a on the lateral wall of washing tub 3.
With reference to Figures 1 and 2, laundry washing machine 1 is also provided with a detergent dispenser 9 which is located on the top of washing tub 3, immediately above upper opening 3a, and is structured for temporarily storing a given quantity of detergent product/s to be poured into washing tub 3; with a fresh water supply circuit 10 which is structured for supplying, on command, a given amount of tap water into detergent dispenser 9 so to drag away into washing tub 3 the detergent product/s stored into detergent dispenser 9; and with a washing-water recirculating and/or draining circuit 11 which is structured for, on command, sucking the washing water from the bottom of washing tub 3 and feeding said water back inside revolving drum 4 during the washing and rinsing phases of the washing cycle, or alternatively draining the washing water accumulated on the bottom of washing tub 3 outside of the washing machine casing, into a generic waste-water exhaust duct (non shown).
Furthermore, laundry washing machine 1 comprises an electric heating device 12, namely a resistor, which is located on the bottom of washing tub 3 and is structured for rapidly heating up, on command, the washing water accumulated on the bottom of washing tub 3.
More specifically, with reference to Figure 1, electric heating device 12 is housed into a sump or outwards-projecting sink or bowl 13 which is realized on the lower section of the lateral wall of washing tub 3, i.e. more or less on the opposite side of opening 3a, and the washing-water recirculating and draining circuit 11 communicates directly with the bottom of sink 13 so that sink 13 operates also as draining sump 13 for the washing-water recirculating and/or draining circuit 11.
In addition to the above, electric heating device 12 is also structured for boiling, on command, the tap water accumulated within sink 13, so as to produce a great amount of steam which spreads inside washing tub 3 and revolving drum 4, and which is used for performing, onto the laundry stored within revolving drum 4, a special refreshing cycle which serves for de-wrinkling, refreshing and/or removing rank smell from the laundry.
Laundry washing machine 1 is finally provided with an electronic central control unit 14 which controls the electric motor of electric motor assembly 6, the fresh water supply circuit 10, the washing-water recirculating and/or draining circuit 11 and the electric heating device 12, so as to perform, according to the user requests, either a washing cycle or a steam-based refreshing cycle.
In the example shown, in particular, the user selects the desired washing cycle, hybrid steam and water washing cycle, or steam-based refreshing cycle via an external control panel (not shown) which is properly connected to the electronic central control unit 14 and is preferably, though not necessarily, located on the front wall of casing 2.
Differently from known laundry washing machine, central control unit 14 is however designed/programmed to control the electric motor of electric motor assembly 6 and the fresh water supply circuit 10, so as to maintain, when the fresh water supply circuit 10 supplies tap water into washing tub 3, revolving drum 4 into rotation at a predetermined angular speed ω ₀ preferably, thought not necessarily, constant in time, to prevent the tap water from wetting the laundry located inside revolving drum 4.
Optionally, electronic central control unit 14 may also be designed/programmed to control the electric motor of electric motor assembly 6, the fresh water supply circuit 10, the washing-water recirculating and/or draining circuit 11 and the electric heating device 12, so as to perform a steam-based pre-washing cycle at beginning of a traditional washing cycle.
With reference to Figures 1 and 2, in the example shown the detergent dispenser 9 is preferably, though not necessarily, located on the back of door 5 so as to be faced to upper opening 3a when door 5 is placed in the closing position, and comprises a substantially basin-shaped vessel 15 which is laterally hinged to the back of door 5 so as to rotate about a horizontal reference axis B, which is locally substantially tangent to the rear face of door 5 and is preferably, though not necessarily, parallel to door rotation axis A, to and from a working position (shown in dotted line in Figure 2) in which the perimetrical rim of the basin-shaped vessel 15 completely abuts on the back of door 5; a preferably, though not necessarily, manually-operated locking device 16 which is structured for rigidly locking the basin-shaped vessel 15 to the body of door 5 when the former is located in the working position; and at least one separate detergent container 17 which is capable to store a given amount of liquid or powdered detergent product, is properly dimensioned for being fitted in easy-removable manner into a corresponding seat or compartment realized inside the basin-shaped vessel 15, and is structured for discharging the detergent product into the basin-shaped vessel 15 when flooded by the tap water supplied by the fresh water supply circuit 10.
More specifically, detergent container 17 consists in a stand-alone basin 17 which is dimensioned for being inserted in easy-removable manner into a corresponding seat or compartment realized inside the basin-shaped vessel 15, and has a calibrated thought opening 17a on one of its lateral walls. The detergent product comes out of basin 17 by opening 17a.
In turn, the basin-shaped vessel 15 lacks a lateral wall so as to discharge both the detergent product and the tap water directly into the beneath washing tub 3, and the bottom wall of the basin-shaped vessel 15 is designed to favor the flowing of both the detergent product and the tap water towards the missing lateral wall. More specifically, in the example shown the bottom wall of the basin-shaped vessel 15 is barrel-like bended so as to extend locally substantially tangent to the cylindrical lateral wall of the revolving drum 4, and both tap water and detergent products fall within washing tub 3 through a lateral chink between the bottom wall of the basin-shaped vessel 15 and the lateral wall of washing tub 3.
With reference to Figure 1, in the example shown the washing-water recirculating and draining circuit 11 instead comprises:

an electric water-circulating pump 18 located inside casing 2, preferably, though not necessarily, immediately beneath the outwards-projecting sink or bowl 13 of washing tub 3;
a water exhaust manifold 19 connecting the bottom of sink 13 with the suction of pump 18;
an electrically controlled tree-way valve 20 or similar valve assembly having the inlet in direct communication with the delivery of pump 18;
a water recirculating pipe 21 which connects a first outlet of the tree-way valve 20 in known manner to the upper portion of washing tub 3 or directly to the inside of revolving drum 4; and
a water draining pipe 22 which connects a second outlet of the tree-way valve 20 to a generic waste-water exhaust duct located outside of casing 2.

Likewise to known laundry washing machines, the electrically controlled tree-way valve 20 is structured for channeling, on command of the central control unit 14, the washing water arriving from electric pump 18 alternatively to the water recirculating pipe 21 or to the water draining pipe 22.
Obviously, water-circulating pump 18 and tree-way valve 20 may be replaced by two independent electric water-circulating pumps having the suction/inlet directly connected to water exhaust manifold 19, and the delivery/outlet directly connected, respectively, to water recirculating pipe 21 and to water draining pipe 22.
With particular reference to Figure 2, in turn the fresh water supply circuit 10 comprises a water supply pipe 23 which ends immediately above the detergent container 17 of detergent dispenser 9, in a sprinkler manifold 23a designed for feeding a dense shower of water droplets by gravity into the detergent container 17 underneath; and an electrically controlled on-off valve 24 which is interposed between the water supply pipe 23 and the water mains (not shown) of the building in which the laundry washing machine is installed, and is structured for regulating, on command of the central control unit 14, the outflow of pressurized tap water along the water supply pipe 23, towards the sprinkler manifold 23a, so as to selectively sprinkle the detergent container 17 of detergent dispenser 9. The tap water flooding into detergent dispenser 9 drags away to washing tub 3 the detergent product/s stored into the detergent container 17 of detergent dispenser 9.
In the example shown, electrically controlled on-off valve 24 is a conventional controlled-open-close solenoid valve 24, whereas water supply pipe 23 is preferably, though not necessarily, divide into two consecutive sections extending one inside casing 2, and the other inside door 5 up to detergent dispenser 9. When door 5 is placed in the closing position, the two sections of water supply pipe 23 connects one another in watertight manner so as to channel the tap water from the solenoid valve 24 to the sprinkler manifold 23a located immediately above detergent container 17.
General operation of the laundry washing machine 1 during washing cycles is almost identical to that of known top-loading laundry washing machines, with no further explanations required.
On the contrary, operation of the laundry washing machine 1 when a steam-based refreshing cycle is selected is completely different from known top-loading laundry washing machines.
More specifically, at beginning of the steam-based refreshing cycle, central control unit 14 firstly switches on and controls the electric motor of electric motor assembly 6 so to drive revolving drum 4 into rotation at a predetermined angular speed ω ₀ greater than 50 rpm (range per minute) and preferably, thought not necessarily, also greater than 100 rpm (range per minute); and subsequently opens the on-off valve 24 of the fresh water supply circuit 10 for supplying tap water into the detergent dispenser 9.
Assuming that detergent container 17 is empty of detergent product/s, tab water flows directly into washing tub 3, passing through the lateral chink between the bottom wall of the basin-shaped vessel 15 and the lateral wall of washing tub 3.
Due to high speed rotation of the revolving drum 4, when reaching the perforated lateral wall of revolving drum 4, the tap water falling down from the chink is immediately thrown towards the cylindrical lateral wall of washing tub 3, upon which it flows towards the bottom of washing tub 3 without entering into revolving drum 4 and wetting the laundry located inside revolving drum 4.
In other words, high speed movement of the lateral wall of revolving drum 4 operates like a watertight shield for the tap water entering into the washing tub 3 through the upper opening 3a.
When sink 13 is filled with enough tap water to cover up heating device 12 and/or to perform the whole steam-based refreshing cycle, central control unit 14 closes on-off valve 24; controls the electric motor of electric motor assembly 6 so to slowly stop rotation of revolving drum 4; and finally switches on heating device 12 to boil the tap water within sink 13 and produce a great amount of steam which spreads inside revolving drum 4 for de-wrinkling, refreshing and/or removing rank smell from the laundry stored within revolving drum 4.
During spreading of the steam inside revolving drum 4, central control unit 14 preferably, though not necessarily, controls the electric motor of electric motor assembly 6 so to rotate revolving drum 4 alternatively and repeatedly in clockwise and anticlockwise direction with an angular speed lower that 10 rpm (range per minute) and preferably, thought not necessarily, also lower that 5 rpm (range per minute).
High speed rotation of revolving drum 4 during the pouring of tap water into the outwards-projecting sink 13 located on the bottom of washing tub 3 has considerable advantages. First of all, the laundry washing machine no more requires a sophisticated fresh-water supply circuit which has an auxiliary water supply line structured for supplying, on command, the tap water directly into the outwards-projecting sink which is located on the bottom of the washing tub and contains the washing-water heating means, without wetting the laundry stored inside the revolving drum. Thus allowing a remarkable reduction of the appliance production costs.
Clearly, changes may be made to the laundry washing machine 1 as described herein without, however, departing from the scope of the present invention.
For example, with reference to Figure 3, in an alternative embodiment the detergent dispenser 9 of washing machine 1 is fixed on the lateral wall of the hopper 25 realized on the top of casing 2 for connecting the laundry loading and unloading opening 2a to the upper rim of the elastic-deformable bellows 7. In this case, the water supply pipe 23 of the fresh water supply circuit 10 extends through the lateral wall of hopper 25 for feeding the tap water into the detergent container (not shown) located into the detergent dispenser 9, so as to drag away into washing tub 3 the detergent product/s stored into the detergent dispenser 9.
Furthermore, in both embodiments referred above, the central control unit 14 may be configure for controlling the electric motor of electric motor assembly 6 so to rotate revolving drum 4 also when, at beginning of the washing cycle, the fresh water supply circuit 10 feeds tap water into detergent dispenser 9 for dragging into washing tub 3 the detergent product/s stored therein. Also in this case, the angular speed of revolving drum 4 may be greater that 50 rpm (range per minute) and preferably, thought not necessarily, also greater that 100 rpm (range per minute).
Likewise to what happens during the steam-based refreshing cycles, when moving at high speed, the lateral wall of revolving drum 4 operates like a watertight shield for the mixture of tap water and detergent product/s entering into the washing tub 3 through the upper opening 3a. This trick avoids, at beginning of the washing cycle, any undesired deposit of detergent product/s on the laundry stored inside revolving drum 4, thus avoiding the staining of delicates fabrics.
Moreover rotation of revolving drum 4 at beginning of the washing cycle, when the fresh water supply circuit 10 feeds tap water into detergent dispenser 9 for dragging into washing tub 3 the detergent product/s stored therein, maximizes the detergent-product/s content within the washing water on the bottom of washing tub 3, thus improving cleaning performances of the washing cycle.
Optionally, rotation of revolving drum 4 may also continue even after all the detergent product/s stored into the detergent dispenser 9 reaches the bottom of washing tub 3, or even after sink 13 is completely filled up with tap water.
Likewise known laundry washing machines, after the predetermined quantity of tap water has reached the bottom of washing tub 3, central control unit 14 closes on-off valve 24 of the fresh water supply circuit 10 and switches on heating device 12 for heating up the washing water and start the prewashing or washing phase of the washing cycle.

Claims

Laundry washing machine (1) comprising an outer casing (2) and, inside the casing, a washing tub (3) and a revolving drum (4) for housing the laundry to be washed, and which is fixed in axially rotating manner inside the washing tub (3); the laundry washing machine being also provided
- with drum moving means (6) structured for rotating, on command, the revolving drum (4) about its longitudinal axis (L) inside the washing tub (3);

- with a detergent dispenser (9) structured for temporarily storing a given quantity of detergent product/s to be poured into the washing tub (3);

- with a fresh water supply circuit (10) which is structured for supplying, on command, tap water into the detergent dispenser (9) so to drag away into the washing tub (3) the detergent product/s stored into detergent dispenser (9); and

- with an electronic central control unit (14) which controls at least said moving means (6) and said fresh water supply circuit (10);
the laundry washing machine (1) being characterized in that the electronic central control unit (14) is designed to control said drum moving means (6) and said fresh water supply circuit (10), so to maintain the revolving drum (4) into rotation when the fresh water supply circuit (10) supplies tap water into the washing tub (3), for preventing the tap water from wetting the laundry located inside the revolving drum (4).
A laundry washing machine as claimed in Claim 1, characterized in that the electronic central control unit (14) controls said drum moving means (6) so to rotate the revolving drum (4) at a predetermined angular speed greater than 50 range per minute.
A laundry washing machine as claimed in Claim 2, characterized in that the electronic central control unit (14) controls said drum moving means (6) so to rotate the revolving drum (4) at a predetermined angular speed ( greater than 100 range per minute.
A laundry washing machine as claimed in anyone of the foregoing claims, characterized by also comprising heating means (12) which are located on the bottom of the washing tub (3), and are structured for heating up, on command, the washing water accumulated on the bottom of the washing tub (3); the electronic central control unit (14) controlling also said heating means (12).
A laundry washing machine as claimed in Claim 4, characterized in that said heating means (12) are also structured for boiling, on command, the water accumulated on the bottom of the washing tub (3), so as to produce a great amount of steam which spreads inside the washing tub (3) and the revolving drum (4).
A laundry washing machine as claimed in Claim 4 or 4, characterized in that said heating means (12) are housed into a sink (13) which is realized on the bottom of the washing tub (3).
A laundry washing machine as claimed in anyone of the foregoing claims, characterized by also comprising a washing-water recirculating and/or draining circuit (11) which is structured for, on command, sucking the washing water from the bottom of the washing tub (3) and feeding said water back inside the revolving drum (4), or alternatively draining the washing water accumulated on the bottom of the washing tub (3) outside of the washing machine casing (2).
A laundry washing machine as claimed in Claim 6 and 7, characterized in that the washing-water recirculating and/or draining circuit (11) communicates directly with the bottom of the sink (13).
A laundry washing machine as claimed in anyone of the foregoing claims, characterized in that said drum moving means (6) comprise an electric motor, and in that said heating means (12) comprise an electric heating device (12).
Operating method of a laundry washing machine (1) comprising an outer casing (2) and, inside the casing, a washing tub (3) and a revolving drum (4) for housing the laundry to be washed, and which is fixed in axially rotating manner inside the washing tub (3); the laundry washing machine being also provided with a detergent dispenser (9) structured for temporarily storing a given quantity of detergent product/s to be poured into the washing tub (3), and with a fresh water supply circuit (10) which is structured for supplying, on command, tap water into the detergent dispenser (9) so to drag away into the washing tub (3) the detergent product/s stored into detergent dispenser (9); the operating method being characterized in that the revolving drum (4) is maintained into rotation inside the washing tub (3) when the fresh water supply circuit (10) supplies tap water into the washing tub (3),), for preventing the tap water from wetting the laundry located inside the revolving drum (4).
Operating method as claimed in Claim 10, wherein the revolving drum (4) is maintained into rotation at a predetermined angular speed (ω ₀) greater than 50 range per minute.
Operating method as claimed in Claim 11, wherein the revolving drum (4) is maintained into rotation at a predetermined angular speed (ω ₀) greater than 100 range per minute.
Operating method as claimed in Claim 10, 11 or 12, characterized by also comprising the step of heating up the water accumulated on the bottom of the washing tub (3), so as to produce a great amount of steam which spreads inside the washing tub (3) and the revolving drum (4).