Patent Description:
Nowadays washing machines, for example laundry washing machines and dishwashers, comprise a washing tub wherein items to be washed can be loaded via an access opening closable by a door or porthole.

In particular, in known laundry washing machines the items to be washed (i.e. the laundry) are loaded within a rotating drum contained within the washing tub, and in known dishwasher items to be washed (i.e. crockery or tableware) are typically loaded within racks removably mounted within the washing tub. Known washing machines typically comprise a plurality of electric loads (user interface(s), pump(s), valve(s), electric motor(s), etc.), and an electronic control unit configured for controlling such electric loads, in particular during the washing cycles.

In known washing machines, water is admitted in the tub by a water supply circuit connected to water delivery mains present outside the machine; before or after entering the tub, water can be mixed with a washing and/or rinsing additive and/or it can be heated to a desired temperature.

Typically, the water supply circuit comprises one or more electro-valves controlled by the control unit for selectively regulating the admission of water from the water delivery means.

After a washing cycle, the washing liquid, i.e. water, or water mixed with washing/rinsing additive(s), is discharged from the tub by a discharge circuit, typically comprising a drain pump, controlled by the control unit.

Nowadays, in order to reduce electric power consumption, most of known washing machines are configured in such a way that, after a washing cycle, and/or when they are not operated for a certain time, they are automatically taken in a "stand-by" condition, i.e. a condition in which all, or most of, their electric loads are not supplied with electric power.

In fact, it is known that many electric loads, when electrically powered (i.e. when electrically connected to an electric power supply), absorb electric power even when they are not operating, and therefore the only way to completely nullify their electric energy absorption is temporarily cutting off their power supply (i.e. disconnecting them from the electric power supply).

In known washing machines, sometimes the electro-valve(s) of the water supply circuit can start to leak, and therefore water coming from the water delivery mains present outside the machine can enter the washing tub and accumulate in the bottom of the latter. If the washing machine is used frequently, it is possible that the user does not notice the leak, since nowadays many washing cycles start with the drain of possible residual liquid from the bottom of the washing tub.

In addition, in most of known washing machines, during the washing cycle the liquid level within the tub is monitored by a level detection device, and the control unit is typically configured for generating an alert message (e.g. a specific sound), and/or to interrupt the washing cycle in case the water level within the tub is higher than expected, as it can happen in case of leakage of the electro-valve(s).

Anyway, this control of the liquid level is active at most during the washing cycles, and not, for example, when the washing machine is in above mentioned stand-by condition.

In known washing machine there is therefore the problem that, while the washing machine is in the stand-by condition, it is very difficult that the user can notice the leak, and therefore the water level within the tub can raise until overflowing outside the washing machine, for example via the opening for loading the items to be washed in the washing tub (if the door or porthole of the machine is opened), and/or via other openings connecting the internal of the washing tub to the external environment (e.g. the air-gap provided in the washing machines for preventing that a liquid can flow back from the washing tub to the water delivery mains to which the washing machine is fluidly connected).

The aim of the present invention is therefore to provide a solution for avoiding that liquid could overflow from the tub of a washing machine, for example a laundry washing machine, a washer drier, a dishwasher, while the washing machine is in a stand-by condition in which at least some of its electrical loads are not supplied with electric power.

Applicant has found that by activating a liquid level detector of a washing machine while the latter is in a stand-by condition, it is possible detecting an anomalous increase of the liquid level within the washing tub also during such a stand-by condition and, consequently, activating a drain pump and/or generating an alert, so as to reduce the risk that the liquid could overflow from the washing machine.

In particular, above aim is solved by a method for operating a washing machine comprising a washing tub, one or more electro valves through which a liquid is admitted into the washing tub, a liquid level detector configured for detecting a quantity indicative of the liquid level within the washing tub, a drain pump configured for draining liquid from the washing tub, a plurality of further electric loads, a control unit configured for controlling the one or more electro valves, the liquid level detector, the drain pump, and the plurality of further electric loads, wherein the method comprises taking the washing machine in a stand-by condition in which the one or more electro valves and one or more of the plurality of further electric loads are disconnected from electric power supply, wherein the method comprises the following steps:.

In a preferred embodiment, the first prefixed condition for the first value comprises reaching or exceeding a prefixed first threshold value.

In a preferred embodiment, the first switch-on time interval is comprised between <NUM> and <NUM> seconds.

More preferably the first switch-on time interval is <NUM> seconds.

In an advantageous embodiment, the method comprises, while the washing machine is in the stand-by condition, and after the phase of supplying electric power to the liquid level detector for at least a first switch-on time interval, the following phase:.

Preferably, the first switch-off time interval is comprised between <NUM> and <NUM> seconds.

More preferably, the first switch-off time interval is <NUM> seconds.

In an advantageous embodiment, the method comprises:.

In a further advantageous embodiment, the method comprises, while the washing machine is in the stand-by condition, and after the phase of supplying electric power to the liquid level detector for at least a first switch-on time interval, the following phases:.

Preferably, the method comprises, while the washing machine is in the stand-by condition, and after the phase of supplying electric power to the liquid level detector for a second switch-on time interval, the following phase:.

In a preferred embodiment, the second switch-off time interval is comprised between <NUM> and <NUM> seconds.

More preferably, the second switch-off time interval is <NUM> seconds.

According to the invention, the phase of supplying electric power to the liquid level detector for at least a first switch-on time interval while the washing machine is in the stand-by condition, is performed after a prefixed first delay time since the washing machine has been taken in the stand-by condition, during which the liquid level detector is disconnected from electric power supply.

Preferably, the first delay time is comprised between <NUM> and <NUM> seconds.

More preferably, the first delay time is <NUM> seconds.

In a further advantageous embodiment, the phase of supplying electric power to the liquid level detector for at least a first switch-on time interval, is started simultaneously with taking the washing machine in the stand-by condition.

In a preferred embodiment, the phase of supplying electric power to the liquid level detector for at least a second switch-on time interval while the washing machine is in the stand-by condition, is performed after a prefixed second delay time has lapsed since when the washing machine has been taken in the stand-by condition.

According to the invention, the plurality of further electric loads comprises a user interface, wherein when the washing machine is in the stand-by condition, the user interface is disconnected from electric power supply.

In an advantageous embodiment, while the washing machine is in the stand-by condition, once the drain pump has been activated for draining liquid from the washing tub, the drain pump is kept active until the value of a quantity indicative of the liquid level within the washing tub detected by the liquid level detector meets a second prefixed condition and/or for a prefixed activation time.

In a further advantageous embodiment, while the washing machine is in the stand-by condition, the drain pump is electrically powered for all the duration of the stand-by condition.

In a further advantageous embodiment, while the washing machine is in the stand-by condition, the drain pump is electrically powered only if the first value meets the first prefixed condition.

In a preferred embodiment, while the washing machine is in the stand-by condition, the following three phases are repeated a plurality of times in this order;.

Preferably, while the washing machine is in the stand-by condition, the three phases are repeated a plurality of times at prefixed time intervals.

Preferably, while the washing machine is in the stand-by condition, during the repetition of the three phases, the drain pump is activated if the first level meets the first prefixed condition.

In an advantageous embodiment, while the washing machine is in the stand-by condition, if the first value detected by the liquid level detector meets the first prefixed condition, the liquid level detector is kept electrically powered for all the rest of the stand-by condition.

In a further advantageous embodiment, the method comprises supplying electric power to the liquid level detector for the whole duration of the stand-by condition.

In a further advantageous embodiment, the washing machine comprises a door or porthole configured for selectively closing the washing tub, and a closure detection device, operatively connected to the control unit, configured for detecting if the door or porthole is opened or closed, wherein the method comprises, while the washing machine is in the stand-by condition, and before the step of activating the drain pump for draining liquid from the washing tub and/or generating an alert, if the first value meets a first prefixed condition, the following step:.

It is highlighted that the first prefixed condition to be used depending on the closure state of the door, can be advantageously selected, for example by the electronic control unit, between a plurality of first prefixed conditions stored in a memory device of the washing machine, preferably comprised and/or functionally associated to the control unit. In a further advantageous embodiment, the first prefixed condition to be used depending on the closure state of the door, can be advantageously set and/or calculated and/or processed, for example by the electronic control unit, depending on data indicative of the closure state of the door, and, optionally, also to other data related to the washing machine.

Advantageously, if the door or porthole is closed, the value of the prefixed first threshold is higher than the value of the first threshold if the door or porthole is opened.

In a further advantageous embodiment, if the door or porthole is closed, the value of the prefixed second threshold is higher than the value of the second threshold if the door or porthole is opened.

In a still further advantageous embodiment, if the door or porthole is closed, the prefixed value of the third threshold is higher than the value of the third threshold if the door or porthole is opened.

Above aim is solved also by a washing machine comprising:.

Other advantages and features of a washing machine according to the present invention will be clear from the following detailed description, provided only as a not limitative example, in which:.

In the figures, same parts are indicated with the same reference numbers.

Advantageously, the washing machine <NUM> illustrated in the attached figures is a laundry washing machine, and in particular a laundry washing machine of the front-loading type; it is however clear that the invention can be applied, without any substantial modification, also to top-loading washing machines, both of the "horizontal axis" and of the "vertical axis" type.

In addition, the invention can be applied, without any substantial modification, also to washer-driers (i.e. laundry washing machines that, in addition to be able to wash the laundry, are also provided with a drying system for drying the laundry).

It is also clear that the invention can be applied, without any substantial modification, also to dishwashers, not illustrated.

The washing machine <NUM> advantageously comprises a cabinet <NUM>, or housing, preferably substantially parallelepiped, advantageously provided with feet <NUM> configured to be positioned on a horizontal surface <NUM>, for example the floor of a building.

The cabinet <NUM> houses a washing tub <NUM> wherein items to be washed (i.e. laundry in the case of a laundry washing machine or washer-drier, or crockery or tableware in the case of a dishwasher) can be loaded via an access opening, not illustrated, closable by a door or porthole <NUM>, preferably hinged to cabinet <NUM>.

In the advantageous embodiment in which the washing machine <NUM> is a laundry washing machine or washer-drier, like in the example illustrated in <FIG>, the washing tub <NUM> can be preferably suspended to the cabinet <NUM> through springs and dampers, not illustrated.

In the advantageous embodiment in which the washing machine <NUM> is a laundry washing machine or washer-drier, like in the example illustrated in <FIG>, the washing tub <NUM> advantageously contains a drum <NUM> rotatable with respect to a rotation axis, not illustrated, in which the laundry can be loaded.

In the so called "horizontal-axis" laundry washing machines, the rotation axis of the drum <NUM> is advantageously horizontal, or slightly inclined, while in the so called "vertical-axis" laundry washing machines the axis is vertical.

In the advantageous embodiment in which the washing machine <NUM> is a laundry washing machine or washer-drier, like in the example illustrated in <FIG>, it comprises at least one (preferably two or more) lifter <NUM> (called also elevator, or rib, or diverter), adapted to improve the stirring of the laundry during the rotation of the drum <NUM>.

In a further advantageous embodiment, not illustrated, in which the washing machine is a dishwasher, the washing tub <NUM> advantageously contains one or more racks, not illustrated, wherein the items to be washed can be loaded.

The washing machine <NUM> advantageously comprises a water inlet circuit <NUM>, adapted to feed water, or water mixed with washing/rinsing additives, into the tub <NUM>; the water inlet circuit <NUM> advantageously comprises a first pipe <NUM>, a first end of which is preferably connected or connectable to water delivery mains, not illustrated, external to the washing machine <NUM>, for example the water delivery mains of a building (not illustrated). A second end of the first pipe <NUM> is fluidly connected to one or more electro-valves <NUM>, configured for allowing/preventing the passage of water from the first pipe <NUM> to a second pipe <NUM> fluidly connected to the internal of the washing tub <NUM>.

In the advantageous embodiment in which the washing machine <NUM> is a laundry washing machine or washer-drier, like in the example illustrated in <FIG>, preferably, between the one or more electro-valves <NUM> and the second pipe <NUM>, there is an additive drawer <NUM>, arranged in such a way that water coming from the first pipe <NUM> and passing through the one or more electro-valves <NUM> can mix with an additive (e.g. a detergent and/or a softener) contained in the additive drawer <NUM>, before being admitted into the washing tub <NUM> via the second duct <NUM>.

In a further advantageous embodiment, not illustrated, in which the washing machine <NUM> is a dishwasher, such an additive drawer <NUM> is preferably not provided, and water coming from the water delivery mains external to the washing machine <NUM> is admitted into the washing tub <NUM>, without being mixed with an additive, passing through the first pipe <NUM>, the one or more electro valves <NUM> and the second pipe <NUM>; in this case, preferably, the washing machine <NUM> comprises an additive dispenser positioned, preferably, on the inner side of the door or porthole facing the internal of the washing tub <NUM>, and configured for delivering an additive within the washing tub <NUM> during a washing cycle, so that such an additive mixes with the water present in the washing tub <NUM>.

Advantageously, the washing tub <NUM> is fluidly connected to a drain circuit <NUM> configured for draining liquid from the bottom of the washing tub <NUM>.

Advantageously, the drain circuit <NUM> comprises one or more draining ducts <NUM> and a drain pump <NUM>, configured for withdrawing liquid from the bottom of the washing tub <NUM> and draining such a liquid outside the washing machine <NUM>. Preferably, the drain circuit <NUM> comprises a filter <NUM> fluidly connected upstream the drain pump <NUM> for preventing foreign bodies to reach and obstruct/damage the latter.

In an advantageous embodiment, like for example the embodiment illustrated in <FIG>, the washing machine <NUM> can comprise a check valve <NUM> that is arranged, preferably, at the outlet of the washing tub <NUM> or at the inlet of the drain circuit <NUM>, for keeping the washing liquid within the washing tub <NUM> during part of the washing cycles.

For example, in an advantageous embodiment, like the one illustrated in <FIG>, the check valve <NUM> comprises a float <NUM> (e.g. a hollow plastic ball) which is freely moveable or floatable within the drain circuit <NUM> in such a way to engage with a valve seat <NUM> and fluidly separating the washing tub <NUM> from the drain circuit <NUM> when the liquid level in the drain circuit <NUM> raises over a certain value.

The washing machine <NUM> can advantageously comprise a recirculation circuit, not illustrated, configured for withdrawing liquid from the washing tub <NUM> and re-admitting such a liquid into a different region of the washing tub <NUM>, so as to reach more effectively all the items to be washed loaded into the latter.

The washing machine <NUM> comprises also a liquid level detector <NUM> configured for detecting a quantity indicative of the level of liquid within the washing tub <NUM>.

It is underlined that in the present application the expression "a quantity indicative of the level of liquid within the washing tub" means a quantity that has a specific and biunivocal relation with the level of the liquid within the washing tub <NUM>; for example, the quantity indicative of the level of liquid within the washing tub could be the liquid level itself (for example if the liquid level detector is an optical sensor configured for sensing directly the level of the liquid), or a quantity, for example the pressure of the liquid within the washing tub <NUM>, which value has a biunivocal relation with (for example it is directly proportional to) the level of the liquid within the washing tub <NUM>.

It is underlined that the level of the liquid in the washing tub <NUM> is advantageously defined with respect to a reference level Lref about which the level detector <NUM> is set, and that can be a pre-set reference level, or, in a further advantageous embodiment, a level that can be set by the user, for example by operating on a user interface <NUM>, that will be better described in the following.

For example, in an advantageous embodiment, like the one illustrated in <FIG>, the reference level Lref against which the level of the liquid within the washing tub <NUM> is measured can be the level of the valve seat <NUM> of the check valve <NUM>.

In a further advantageous embodiment, not illustrated, the reference level Lref can be, for example, the level of the lowest point of the washing tub <NUM>, or the level of the bottom of the casing <NUM>, or the level of a surface <NUM> on which the washing machine <NUM> is configured to be positioned; anyway, other reference levels Lref can be used.

In a preferred embodiment, the liquid level detector <NUM> comprises an air chamber <NUM> having a liquid inlet provided at the washing tub <NUM> and in fluid communication with the internal of the latter; the air chamber <NUM> is preferably fluidly connected, more preferably by a third pipe <NUM>, to a sensing element <NUM> of the liquid level detector <NUM>.

Advantageously, the sensing element <NUM> can be a pressure sensor; advantageously, the sensing element <NUM> can comprise an electronic unit, not illustrated, configured for calculating/determining the liquid level within the washing tub <NUM> from the detected pressure; alternatively, or in addition, the electronic unit of the sensing element <NUM> can be connected to a control unit <NUM> of the washing machine <NUM>, that will be better described in the following.

In an advantageous embodiment, during a washing cycle, when a washing/rinsing liquid contained in the washing tub <NUM> reaches a certain level at which it enters the air chamber <NUM>, such a washing/rinsing liquid compresses the air contained in the air chamber <NUM>, which pressure is transmitted by the third pipe <NUM> to the sensing element <NUM>, for example a pressor sensor, configured for detecting the pressure in the air chamber <NUM>. The pressure detected by the sensing element <NUM> is then used, directly by the sensing element <NUM> (e.g. if provided with an integrated electronic unit), or by an external electronic unit, e.g. the control unit <NUM> of the washing machine <NUM>, that will be better described in the following, to which the sensing element <NUM> is connected, for calculating the level of the liquid within the washing tub <NUM>.

Advantageously, as mentioned above, the washing machine <NUM> comprises a user interface <NUM>, comprising advantageously one or more electric or electronic input/output devices, like, for example, a display <NUM> (e.g. a so called "touch-screen" display), one or more knobs <NUM>, one or more switch <NUM>, one or more speaker, not illustrated, etc..

As mentioned above, the washing machine <NUM> advantageously comprises a control unit <NUM>, for example an electronic board provided with a microcontroller, schematically illustrated in <FIG> as a rectangle, configured for controlling the one or more electro-valves <NUM>, the liquid level detector <NUM>, the drain pump <NUM>, and a plurality of further electric loads of the washing machine <NUM>.

Such a plurality of further electric loads comprises the user interface <NUM>, and/or an electric heater for heating the washing liquid, not illustrated, and/or an electric motor, not illustrated, and/or a speaker, not illustrated, and/or one or more further sensors, for example a turbidity sensor, a temperature sensor, etc., not illustrated. In a preferred embodiment, the control unit <NUM> can be advantageously configured/programmed in such a way to control the one or more electro-valves <NUM> depending on the washing cycle and/or on the value of a quantity indicative of the liquid level within the washing tub <NUM> detected by the liquid level detector <NUM>.

The method according to the invention comprises taking the washing machine <NUM> in a stand-by condition in which the one or more electro-valves <NUM> and one or more of the plurality of further electric loads are disconnected from the electric power supply.

It is highlighted that, in the present application, in case the electric power is supplied by an alternated current, the moments in which the alternated electric power is periodically inverted (i.e. when its value is zero) are not considered as an interruption of the power supply; in the case of an alternated current, the power supply is considered disconnected if it is not supplied for at least a full period of the periodic electric power.

For example, in the stand-by condition, one of the electric loads that is disconnected from the electric power supply is the user interface <NUM>. Further electric loads that can be disconnected from the electric power supply are an electric heater (if provided), and/or a temperature sensor (if provided), and/or an electric motor (if provided), etc..

By disconnecting the electric power supply, it is guaranteed that such electric loads do not absorb electric power when they are not operating, and therefore the overall energy consumption of the washing machine <NUM> is reduced. Advantageously, the control unit <NUM> can be configured for taking the washing machine <NUM> in the stand-by condition automatically at the end of a washing cycle, and/or after receiving a specific command by the user, for example by the user interface <NUM>.

The method according to the invention comprises, while the washing machine <NUM> is in above mentioned stand-by condition, supplying electric power to the liquid level detector <NUM> for at least a first switch-on time interval tON1.

The first switch-on time interval tON1 is preferably comprised between <NUM> and <NUM> seconds, more preferably <NUM> seconds. According to the inventive method, during such a first switch-on time interval tON1, a first value L1 of a quantity indicative of the liquid level within the washing tub <NUM> is detected by the liquid level detector <NUM>.

Then, according to the invention, if the first value L1 meets a first prefixed condition, the drain pump <NUM> is activated for draining liquid from the washing tub <NUM> and/or an alert (e.g. a sound) is generated.

In a first advantageous embodiment, the drain pump <NUM> is electrically powered (and therefore it can be activated in order to drain the liquid from the washing tub <NUM>) for all the duration of the stand-by condition.

In a different advantageous embodiment, in the stand-by condition the drain pump <NUM> is electrically powered (and therefore it can be activated in order to drain the liquid from the washing tub <NUM>) only if the first value L1 meets a first prefixed condition.

In a further advantageous embodiment, while the washing machine <NUM> is in the stand-by condition, once the drain pump <NUM> has been activated for draining liquid from the washing tub <NUM>, it is kept active until a quantity indicative of the level of liquid within the washing tub <NUM> detected by the liquid level detector <NUM> meets a second prefixed condition (for example if the value of a quantity indicative of the level of liquid within the washing tub <NUM> detected by the liquid level detector <NUM> is below a prefixed value LOFF) and/or for a prefixed activation time tact (for example in the range between <NUM>-<NUM> minutes).

In a first advantageous embodiment, the first prefixed condition for the first value L1 is or comprises reaching or exceeding a prefixed first threshold value Lthr1; in this first advantageous embodiment, therefore, if the liquid level within the washing tub <NUM> during the stand-by condition, i.e. when the one or more electro-valves <NUM> are not operating, is increasing over a prefixed threshold value (which increase corresponds to an increased value of the detected value L1), this could mean that the one or more electro-valves <NUM> are leaking, and therefore the drain pump <NUM> is activated for draining the liquid from the washing tub <NUM>, so as to avoid further raise of the liquid level, and/or an alert is generated, for example a sound is emitted by a speaker, not illustrated, provided in the washing machine <NUM>, for informing the user about the leakage.

It is highlighted that the prefixed first threshold value Lthr1 can be selected, for example during the design of the washing machine <NUM>, depending on the specific dimensions and/or shape or the washing tub <NUM> and/or drain circuit <NUM>, in such a way that, while the first value L1 is below such first threshold value Lthr1, liquid can't overflow from the washing tub <NUM>. Preferably, if the quantity indicative of the level of liquid within the washing tub is the liquid level itself, the first threshold value Lthr1 could be comprised between <NUM>-<NUM>.

In this first advantageous embodiment (in which the first prefixed condition for the first value L1 is or comprises reaching or exceeding a prefixed first threshold value Lthr1), if the drain pump <NUM>, once activated, it is kept active until a quantity indicative of the level of liquid within the washing tub <NUM> detected by the liquid level detector <NUM> is below a prefixed value LOFF, this prefixed value LOFF can be the same as the prefixed first threshold value Lthr1 or, preferably, it can be a different value, more preferably a value lower than the prefixed first threshold value Lthr1 so as to introduce an hysteresis in the activation/deactivation of the drain pump <NUM>.

Other possible advantageous first prefixed conditions according to the invention for the first value L1 will be described in the following.

In an advantageous embodiment, while the washing machine <NUM> is in the stand-by condition, and after the phase of supplying electric power to the liquid level detector <NUM> for at least a first switch-on time interval tON1, the method comprises disconnecting the liquid level detector from electric power supply for a first switch-off time interval tOFF1; in this way, the overall energy consumption during the stand-by condition is reduced.

In a preferred embodiment, the first switch-off time interval tOFF1 is comprised between <NUM> and <NUM> seconds, more preferably <NUM> seconds.

In a further advantageous embodiment, while the washing machine <NUM> is in the stand-by condition, if the first value L1 detected by the liquid level detector <NUM> meets a first prefixed condition, the liquid level detector <NUM> is kept electrically powered for all the rest of the stand-by condition.

In an advantageous embodiment, the method comprises detecting or estimating a starting value L0 of a quantity indicative of the liquid level within the washing tub <NUM> at the beginning of the stand-by condition; this starting value L0 can be, for example, the last value of the quantity indicative of liquid level detected before taking the washing machine <NUM> in the stand-by condition. In another advantageous embodiment, the starting value L0 could be for example estimated as the value of the quantity indicative of the level of the liquid that could remain within the washing tub <NUM> after the last drain phase of a washing cycle, for example due to the specific layout of the drain circuit <NUM>. In this advantageous embodiment, the first value L1 is compared to the starting value L0, and the drain pump <NUM> is activated if the difference between the first value L1 and the starting value L0 reaches or exceeds a prefixed second threshold value Lthr2; in this case, therefore, the first prefixed condition that has to be met by the first value L1 is related to its difference from the starting value L0; it is clear that this difference grows together with the amount of the leak in the one or more electro-valves <NUM>.

It is highlighted that the prefixed second threshold value Lthr2 can be selected, for example during the design of the washing machine <NUM>, depending on the specific dimensions and/or shape or the washing tub <NUM> and/or drain circuit <NUM>, in such a way that, while the difference between the first value L1 and the starting value L0 is below such second threshold value Lthr2, liquid can't overflow from the washing tub <NUM>.

For example, if the quantity indicative of the level of liquid within the washing tub is the liquid level itself, the second threshold value Lthr2 could be advantageously comprised between <NUM>-<NUM>.

In a further advantageous embodiment of the invention, the method comprises, while the washing machine <NUM> is in the stand-by condition, and after the phase of supplying electric power to the liquid level detector <NUM> for at least a first switch-on time interval tON1, the phase of supplying electric power to the liquid level detector <NUM> for a second switch-on time interval tON2, during which a second value L2 of a quantity indicative of the liquid level within the washing tub <NUM> is detected by the liquid level detector <NUM>. In this advantageous embodiment, the second value L2 is compared with the first value L1, and, if the difference between the second value L2 and the first value L1 reaches or exceeds a prefixed third threshold value Lthr3 the drain pump <NUM> is activated for draining the liquid from the washing tub <NUM>, and/or an alert is generated, for example by a speaker, not illustrated. In this case, therefore, the first prefixed condition that has to be met by the first value L1 is related to the difference of the second value L2 from the first value L1; it is clear that this difference grows together with the amount of the leak in the one or more electro-valves <NUM>.

It is highlighted that the prefixed third threshold value Lthr3 can be selected, for example during the design of the washing machine <NUM>, depending on the specific dimensions and/or shape or the washing tub <NUM> and/or drain circuit <NUM>, in such a way that, while the difference between the second value L2 and the first value L1 is below such third threshold value Lthr3, liquid can't overflow from the washing tub <NUM>.

For example, if the quantity indicative of the level of liquid within the washing tub is the liquid level itself, the third threshold value Lthr3 could be advantageously comprised between <NUM>-<NUM>.

In this advantageous embodiment, the phase of disconnecting the liquid level detector from electric power supply for a first switch-off time interval tOFF1 is preferably performed between the phase of supplying electric power to the liquid level detector <NUM> for a first switch-on time interval tON1 and the phase of supplying electric power to the liquid level detector <NUM> for a second switch-on time interval tON2. Alternatively, in a further advantageous embodiment, the phase of supplying electric power to the liquid level detector <NUM> for a first switch-on time interval tON1 and the phase of supplying electric power to the liquid level detector <NUM> for a second switch-on time interval tON2 are performed without disconnecting the liquid level detector <NUM> from electric power supply between these phases (i.e. the liquid level detector <NUM> is continuously supplied with electric power at least from the beginning of the first switch-on time interval tON1 to the end of the second switch-on time interval tON2). Preferably, while the washing machine <NUM> is in the stand-by condition, and after the phase of supplying electric power to the liquid level detector <NUM> for a second switch-on time interval tON2, the method comprises the phase of disconnecting the liquid level detector <NUM> from electric power supply for a second switch-off time interval tOFF2, so as to reduce electric consumption. Preferably, the second switch-off time interval tOFF2 is comprised between <NUM> and <NUM> seconds, more preferably <NUM> seconds.

According to the invention, the phase of supplying electric power to the liquid level detector <NUM> for at least a first switch-on time interval TON1 while the washing machine <NUM> is in the stand-by condition is performed after a prefixed first delay time td1 since when the washing machine <NUM> has been taken in the stand-by condition, during which the liquid level detector <NUM> is disconnected from electric power supply; in other words, in this advantageous embodiment when the washing machine <NUM> is taken in the stand-by condition, the liquid level detector <NUM> is disconnected from the electric power supply, and it is then connected to the electric power supply, so as to be supplied with electric power, only after the first delay time td1.

Preferably, the first delay time td1 is comprised between <NUM> and <NUM> seconds, more preferably between <NUM> and <NUM> seconds, even more preferably <NUM> seconds.

In an advantageous embodiment, the phase of supplying electric power to the liquid level detector <NUM> for at least a second switch-on time interval tON2, is performed after a prefixed second delay time td2 has lapsed since when the washing machine <NUM> has been taken in the stand-by condition. Preferably, the second switch-on time interval tON2 is comprised between <NUM> second and <NUM> seconds more preferably between <NUM> seconds and <NUM> second, even more preferably <NUM> seconds.

In a different advantageous embodiment, the phase of supplying electric power to the liquid level detector for at least a first switch-on time interval tON1 is started simultaneously with taking the washing machine <NUM> in the stand-by condition. In a different advantageous embodiment, electric power is supplied to the liquid level detector <NUM> for the whole duration of the stand-by condition.

During the stand-by condition, the user interface <NUM> is disconnected from electric power supply.

Preferably, while the washing machine <NUM> is in the stand-by condition, the following three phases are repeated a plurality of times in this order:.

Preferably, in this advantageous embodiment the drain pump <NUM> is activated if, during the repetition of the three phases, the first value L1 meets the first prefixed condition, for example it reaches or exceeds the prefixed first threshold value Lthr1.

In a further advantageous embodiment, the washing machine <NUM> comprises a closure detection device, schematically illustrated in <FIG> as a rectangle <NUM>, like for example a sensor (e.g. a magnetic sensor), operatively connected to the control unit <NUM> and configured for detecting if the door or porthole <NUM> is opened or closed. In this advantageous embodiment, the method according to the invention can advantageously comprise, while the washing machine <NUM> is in the stand-by condition, and before the step of activating the drain pump <NUM> for draining liquid from the washing tub <NUM> and/or generating an alert, if the first value L1 meets a first prefixed condition, the further step of detecting by the closure detection device <NUM> if the door or porthole <NUM> is closed or opened, and making use of a first prefixed condition if the door or porthole <NUM> is closed, and of a different first prefixed condition if the door or porthole <NUM> is opened.

For example, if the first prefixed conditions comprises reaching or exceeding a prefixed first threshold value Lthr1, such a prefixed first threshold value Lthr1 can advantageously have a value, for example <NUM> (in case the quantity indicative of the level of liquid within the washing tub is the liquid level itself), if the door or pothole <NUM> is closed, and a different value, for example <NUM> if the door or porthole <NUM> is opened; in fact, if the door or pothole <NUM> is closed the liquid can't overflow via the opening closed by the door or pothole <NUM>, and therefore an higher value of the prefixed first threshold value Lthr1 can be used.

In a further advantageous embodiment, in which the first prefixed condition is related to the difference between the first value L1 and the starting value L0, and in particular requires that the difference between the first value L1 and the starting value L0 reaches or exceeds a prefixed second threshold value Lthr2, such a prefixed second threshold value Lthr2 can advantageously have a value, for example <NUM> (in case the quantity indicative of the level of liquid within the washing tub is the liquid level itself), if the door or pothole <NUM> is closed, and a different value, for example <NUM> if the door or porthole <NUM> is opened; in fact, if the door or pothole <NUM> is closed the liquid can't overflow via the opening closed by the door or pothole <NUM>, and therefore the prefixed second threshold value Lthr2 can have an higher value.

In a further advantageous embodiment, in which the first prefixed condition is related to the difference between the second value L2 and the first value L1, and in particular requires that the difference between the second value L2 and the first value L1 reaches or exceeds a prefixed third threshold value Lthr3, such a prefixed third threshold value Lthr3 can advantageously have a value, for example <NUM> (in case the quantity indicative of the level of liquid within the washing tub is the liquid level itself), if the door or pothole <NUM> is closed, and a different value, for example <NUM> if the door or porthole <NUM> is opened; in fact, if the door or pothole <NUM> is closed the liquid can't overflow via the opening closed by the door or pothole <NUM>, and therefore the prefixed third threshold value Lthr3 can have an higher level.

An advantageous example of a first flow chart <NUM> illustrating an advantageous embodiment of the logical steps performed by the control unit <NUM> for implementing a possible embodiment of the method according to the invention is illustrated in <FIG>.

The first flow chart <NUM> starts with a first step <NUM> in which it is checked (advantageously by the control unit <NUM>) if the washing machine <NUM> is in the stand by condition; if NOT (indicated by letter "N" in the drawings), first step <NUM> is repeated, if YES (indicated by letter "Y" in the drawings), a second step <NUM> is performed, in which the liquid level detector <NUM> is supplied with electric power, and the water level (or better a first value L1 of a quantity indicative of the liquid level) in the washing tub <NUM> is detected by the liquid level detector <NUM>, and then the liquid level detector <NUM> (called pressure switch in <FIG>) is switched off (third step <NUM>).

Then, a fourth step <NUM> is performed, in which it is checked if the first switch-off time interval tOFF1 for the liquid level detector <NUM> (called "off time" in <FIG>) has been reached; if NOT, fourth step <NUM> is repeated, if YES, the liquid level detector <NUM> is electrically powered (fifth step <NUM>) again for a second switch-on time interval tON2 (sixth step <NUM>, "on time"), and then water level (or better a second value L2 of a quantity indicative of the liquid level) within the washing tub <NUM> is checked again (seventh step <NUM>).

If (eight step <NUM>, option NOT) the level is not increasing over a certain threshold (or, in other words, if the difference between L2 and L1 is below a third threshold), the flow chart comes back to the third step <NUM>, while if (eight step <NUM>, option YES) the level is increasing over a certain threshold (or, in other words, if the difference between L2 and L1 reaches or exceeds a third threshold value Lthr3), an alert (called alarm in <FIG>) is generated and the drain pump <NUM> is operated for draining the water from the washing tub <NUM> (ninth step <NUM>), after which (tenth step <NUM>) the alert is transmitted to the user interface <NUM>, or to an APP of an external device, not illustrated, to which the washing machine <NUM> is connected, and the drain continues until completely emptying the washing tub <NUM>.

A further advantageous example of the logical steps performed by the control unit <NUM> for implementing a possible embodiment of a method according to the invention is illustrated in the second a second flow chart <NUM> of <FIG>.

The second flow chart <NUM> starts with a first step <NUM> in which it is checked if the washing machine <NUM> is in the stand by condition; if NOT, first step <NUM> is repeated, if YES, a second step <NUM> is performed, in which the liquid level detector <NUM> is supplied with electric power, and the water level (or better a first value L1 of a quantity indicative of the liquid level) in the washing tub <NUM> is detected.

Then, a third step <NUM> is performed, in which it is checked if a certain time has lapsed; if NOT, third step <NUM> is repeated, if YES, the water level (or better a second value L2 of a quantity indicative of the liquid level) within the washing tub <NUM> is checked again (fourth step <NUM>).

If (fifth step <NUM>, option NOT) the level is not increasing over a certain threshold (or, in other words, if the difference between L2 and L1 is below a third threshold), the second flow chart <NUM> comes back to the third step <NUM>, while if (fifth step <NUM>, option YES) the level is increasing over a certain threshold (or, in other words, if the difference between L2 and L1 reaches or exceeds a third threshold Lthr3), an alert (called alarm in <FIG>) is generated and the drain pump <NUM> is operated for draining the water from the washing tub <NUM> (sixth step <NUM>), after which (seventh step <NUM>) the alert is transmitted to the user interface <NUM>, or to an APP of an external device, not illustrated, to which the washing machine <NUM> is connected, and the drain continues until completely emptying the washing tub <NUM>.

<FIG> shows an advantageous example an alternative logical step <NUM> that can be performed, in the first flow chart <NUM> or in the second flow chart <NUM>, as an alternative, respectively, to step <NUM> and to step <NUM>, in an advantageous embodiment in which the washing machine <NUM> comprises a closure detection device <NUM>, operatively connected to the control unit <NUM> and configured for detecting if the door or porthole <NUM> is opened or closed.

This alternative logical step <NUM> advantageously comprises, a first step <NUM> in which it is checked if the washing machine <NUM> is in the stand by condition; if NOT, first step <NUM> is repeated, if YES, a second step <NUM> is performed, in which it is checked by the closure detection device <NUM> if the door or porthole <NUM> is closed.

If NOT, (i.e. the door or porthole <NUM> is opened), a low threshold level (e.g. Lthr1, Lthr2 or Lth3) is selected and used (step <NUM>), while if YES (i.e. the door or porthole <NUM> is closed) a high threshold level (e.g. the Lthr1, Lthr2 or Lth3) is selected and used (step <NUM>), since in this case the liquid can't overflow via the opening closed by the door or porthole <NUM>, and therefore the level causing the overflow is higher. Then, the flow chart can continue respectively with step <NUM> or <NUM>, depending if it is the first flow chart <NUM> or the second flow chart <NUM>.

It is seen therefore how the invention achieves the proposed aim and objects, there being provided a method for operating a washing machine, for example a laundry washing machine or a dishwasher, that, by activating the liquid level detector when the washing machine is in the stand-by condition, and by activating the drain pump and/or generating an alert if the liquid level grows abnormally, allows preventing the risk of liquid overflow even in the stand-by condition.

Claim 1:
A method for operating a washing machine (<NUM>) comprising a washing tub (<NUM>), one or more electro valves (<NUM>) through which a liquid is admitted into said washing tub (<NUM>), a liquid level detector (<NUM>) configured for detecting a quantity indicative of the liquid level within said washing tub (<NUM>), a drain pump (<NUM>) configured for draining liquid from said washing tub (<NUM>), a plurality of further electric loads (<NUM>, <NUM>, <NUM>, <NUM>), a control unit (<NUM>) configured for controlling said one or more electro valves (<NUM>), said liquid level detector (<NUM>), said drain pump (<NUM>), and said plurality of further electric loads (<NUM>, <NUM>, <NUM>, <NUM>), wherein said method comprises taking said washing machine (<NUM>) in a stand-by condition in which said one or more electro valves (<NUM>) and one or more of said plurality of further electric loads (<NUM>, <NUM>, <NUM>, <NUM>) are disconnected from electric power supply, wherein said plurality of further electric loads (<NUM>, <NUM>, <NUM>, <NUM>) comprises a user interface (<NUM>), wherein when said washing machine (<NUM>) is in said stand-by condition, said user interface (<NUM>) is disconnected from electric power supply, wherein said method comprises the following steps:
- while said washing machine (<NUM>) is in said stand-by condition, supplying electric power to said liquid level detector (<NUM>) for at least a first switch-on time interval (tON<NUM>);
- during said first switch-on time interval (tON1), detecting by said liquid level detector (<NUM>) a first value (L1) of a quantity indicative of the liquid level within said washing tub (<NUM>);
- activating said drain pump (<NUM>) for draining liquid from said washing tub (<NUM>) and/or generating an alert, if said first value (L1) meets a first prefixed condition,
characterized in that
said phase of supplying electric power to said liquid level detector (<NUM>) for at least said first switch-on time interval (tON1) while said washing machine (<NUM>) is in said stand-by condition, is performed after a prefixed first delay time (td1) since when said washing machine (<NUM>) has been taken in said stand-by condition, during which said liquid level detector (<NUM>) is disconnected from electric power supply.