EP2886702A1

EP2886702A1 - Overflow control system

Info

Publication number: EP2886702A1
Application number: EP13198415.5A
Authority: EP
Inventors: Paolo Driussi; Alessandro Cecco
Original assignee: Electrolux Appliances AB
Current assignee: Electrolux Appliances AB
Priority date: 2013-12-19
Filing date: 2013-12-19
Publication date: 2015-06-24
Anticipated expiration: 2033-12-19
Also published as: EP2886702B1; PL2886702T3

Abstract

A laundry washing machine (100) is provided. The laundry washing comprises:
- a washing tub (107) configured to be supplied with washing liquid for treating laundry;
- a rotatable drum (110), in which laundry (112) to be washed can be loaded, mounted in the washing tub (107);
- a drain pump (170) operable to selectively cause washing liquid located in the washing tub (107) to be discharged;
- an overflow control system (193, 194; 193, 194') for detecting an occurrence of an overflow condition of the laundry washing machine (100) in which a level of washing liquid collected at the bottom of the laundry washing machine (100) is equal to or higher than a predetermined threshold, and for driving the drain pump (170) to discharge washing liquid from the washing tub (107) in case an overflow condition has been detected, the overflow control system (193, 194; 193, 194') comprising a switching unit (193) and a detection unit (194; 194'), wherein:
- the switching unit (193) comprises a switch (420) having a first terminal connected to a terminal (TL) of an AC electric power supply and a second terminal connected to the detection unit (194; 194'), the switch (420) being configured to electrically connect the first terminal with the second terminal in a closed configuration and to electrically insulate the first terminal from the second terminal in an open configuration, the switching unit (193) being configured to switch the switch (420) to the closed configuration when the level of washing liquid collected at the bottom of the laundry washing machine (100) is equal to or higher than said predetermined threshold, and
- the detection unit (194; 194') is configured to detect an overflow condition occurrence and to drive the drain pump (170) to discharge washing liquid from the washing tub (107) when the switch (420) is in the closed configuration.

Description

The present invention generally relates to the field of the laundry washing machines.
A laundry washing machine - both of the type which can only wash and rinse laundry and of the type which can also dry laundry - comprises an external, substantially parallelepiped-shaped, casing in which a washing tub is provided. The washing tub contains a perforated washing drum where the laundry to be washed can be loaded. The washing drum is operated by an electric motor for being rotated, usually about a horizontal axis. A washing liquid supply system is provided for supplying washing liquid (i.e., clean water or water mixed with cleaning products) into the washing tub through an inlet line in fluid communication with the washing tub. For this purpose, the washing liquid supply system is selectively operable to be in fluid communication with an external water supply line, preferably by means of a controlled input supply valve. A discharge system is provided to selectively remove washing liquid from the washing tub. For example, the discharge system may comprise a discharge duct fluidly connected to the washing tub for receiving the washing liquid to be discharged. A drain pump is provided, which is operable to selectively cause liquid located into the discharge duct to be discharged through a drain duct adapted to be connected to a water drain network system. In parallel with the drain pump, a recirculation pump may be also provided, which is operable to selectively cause washing liquid located into the discharge duct to be conveyed back into the washing tub through a recirculation conduit, preferably for being sprayed inside the drum. The drain pump - and the recirculation pump, if present - are selectively operable by means of proper driving devices, such as TRIACs (Triode for Alternating Current).
A laundry washing machine may overflow because of a leakage in the washing tub, in the washing liquid supply system, in the discharge system, or in the recirculation conduit, because of a failure in the input supply valve, or because of excessive water intake in the machine. In this condition, washing liquid collects at the bottom of the laundry washing machine. When the level of uncontained washing liquid collected at the bottom of the laundry washing machine reaches or exceeds a threshold for which said washing liquid may cause external damage to the floor or other surroundings where the laundry washing machine is located, and for which said washing liquid may damage internal, particularly electrical, components of the laundry washing machine, the laundry washing machine is said to be in an "overflow condition".
For these reasons, laundry washing machines should be advantageously provided with an overflow control system adapted to detect any overflow condition occurrence, and, in case an overflow condition has been assessed, to drain the washing liquid already contained in the washing tub.
An overflow control system is typically provided with a float located in the portion of the laundry washing machine wherein washing liquid collects in the overflow condition (such as at the bottom of the casing) and provided with a switch adapted to be switched in accordance with the height of the float, and a detection unit electrically coupled with said switch. As washing liquid collects at the bottom of the laundry washing machine, the float rises. When the washing liquid exceeds a predetermined level, the float switches the switch, and the detection unit accordingly generate an overflow detection signal indicative of the overflow condition. The detection unit may be advantageously configured to generate an, e.g., visual and/or audible, warning according to the detection signal, so as to inform the user of the overflow condition occurrence.
US 7,032,434 discloses a water leakage detecting device for a dishwasher. The water leakage detecting device comprises a stick turning a switch on or off depending upon the height of a floating unit, and a signal output unit configured to generate signals based on the detection of leaked water. The circuit configuration disclosed in US 7,032,434 is not efficient, since dissipates electric power during the stand-by of the dishwasher, when the dishwasher is not in the overflow condition. Indeed, in absence of leaked water inside the dishwasher, the switch is in the closed configuration, establishing a closed electric conductive path between a power supply terminal of the dishwasher and a ground terminal thereof.
In view of the state The Applicant has found that the abovementioned solution is not satisfactory, since dissipates electric power when the appliance is in the stand-by state.
The aim of the present invention is to provide a laundry washing machine provided with an efficient overflow control system adapted to dissipate low amounts of electric power when the laundry washing machine is in the stand-by state.
One aspect of the present invention proposes a laundry washing machine. The laundry washing machine comprises a washing tub configured to be supplied with washing liquid for treating laundry; a rotatable drum, in which laundry to be washed can be loaded, mounted in the washing tub, and a drain pump operable to selectively cause washing liquid located in the washing tub to be discharged. The laundry washing machine further comprises an overflow control system for detecting an occurrence of an overflow condition of the laundry washing machine in which a level of washing liquid collected at the bottom of the laundry washing machine is equal to or higher than a predetermined threshold, and for driving the drain pump to discharge washing liquid from the washing tub in case an overflow condition has been detected. The overflow control system comprises a switching unit and a detection unit. The switching unit comprises a switch having a first terminal connected to a terminal of an AC electric power supply and a second terminal connected to the detection unit. The switch is configured to electrically connect the first terminal with the second terminal in a closed configuration and to electrically insulate the first terminal from the second terminal in an open configuration. The switching unit is configured to switch the switch to the closed configuration when the level of washing liquid collected at the bottom of the laundry washing machine is equal to or higher than said predetermined threshold. The detection unit is configured to detect an overflow condition occurrence and to drive the drain pump to discharge washing liquid from the washing tub when the switch is in the closed configuration.
According to an embodiment of the present invention, the detection unit comprises a microcontroller and a detection circuit coupled between the second terminal of the switch and an input terminal of the microcontroller for generating a detection signal indicative of the configuration of the switch. The microcontroller is configured to drive the drain pump to discharge washing liquid from the washing tub according to said detection signal.
According to an embodiment of the present invention, said detection circuit is configured to generate said detection signal in such a way that:

if the switch is in the open configuration, the detection signal is a constant trend signal, and
if the switch is in the closed configuration, the detection signal is an oscillating trend signal.

According to an embodiment of the present invention, the laundry washing machine further comprises an AC-DC conversion unit for receiving said AC electric power supply and providing a corresponding DC supply voltage and a corresponding ground voltage. The microcontroller is supplied between the DC supply voltage and the ground voltage. Said constant trend signal is a constant trend signal at the ground voltage. Said oscillating trend signal is a signal oscillating between the ground voltage and the DC supply voltage.
According to an embodiment of the present invention, said detection circuit comprises a voltage divider arrangement having an input terminal connected to the second terminal of the switch and an output terminal coupled with the input terminal of the microcontroller for providing the detection signal.
According to an embodiment of the present invention, said voltage divider arrangement comprises a first resistor having a first terminal connected to the second terminal of the switch and a second terminal connected to a first terminal of a second resistor. The second resistor has a second terminal connected to a terminal providing the ground voltage. The second terminal of the first resistor is coupled with the input terminal of the microcontroller for providing the detection signal.
According to an embodiment of the present invention, the microcontroller is further configured to assess a resistance value mismatch in the first resistor and/or in the second resistor if the detection signal oscillates between the ground voltage and a voltage different than the DC supply voltage.
According to an embodiment of the present invention, the laundry washing machine further comprises a filter unit connected to the input terminal of the microcontroller for filtering possible noises affecting the detection signal generated by the detection circuit.
According to an embodiment of the present invention the filter unit is a low-pass filter.
According to an embodiment of the present invention, the microcontroller is further configured to assess that the filter unit and/or the detection circuit are disconnected from the input terminal of the microcontroller if the microcontroller detects that its input terminal is floating.
According to an embodiment of the present invention, the laundry washing machine further comprises a driving apparatus for driving the drain pump. The driving apparatus comprises a TRIAC comprising a first anode terminal coupled with a first terminal of an AC electric power supply and a second anode terminal coupled with a first terminal of the drain pump. The drain pump comprises a second terminal coupled with a second terminal of the AC electric power supply. The driving apparatus further comprises a triggering circuit configured to receive a driving signal and to activate the TRIAC by providing triggering pulse signals to a gate terminal of the TRIAC based on the received driving signal. The detection unit is coupled between the second terminal of the switch and the triggering circuit to provide the driving signal to the triggering circuit. The detection unit is configured to set the driving signal according to the configuration of the switch.
According to an embodiment of the present invention, the detection unit comprises a microcontroller and a detection circuit coupled between the second terminal of the switch and an input terminal of the microcontroller for generating a detection signal indicative of the configuration of the switch. The microcontroller is configured to set the driving signal according to the detection signal and to provide the driving signal to the triggering circuit.
According to an embodiment of the present invention, the detection unit comprises a detection circuit coupled with the second terminal of the switch and configured to generate a detection signal indicative of the configuration of the switch in such a way that:

a) if the switch is in the open configuration, the detection signal is a constant trend signal, and
b) if the switch is in the closed configuration, the detection signal is an oscillating trend signal.

The detection unit comprises a peak detector unit coupled between the detection circuit and the triggering circuit and configured to set the driving signal to the peak value of the detection signal and to provide the driving signal to the triggering circuit.
According to an embodiment of the present invention, the detection unit further comprises a microcontroller for managing the operation of the laundry washing machine. The detection unit is configured to activate the drain pump during an overflow condition occurrence when the microcontroller is turned off or is in a sleep mode, in such a way to discharge washing liquid from the washing tub when the laundry washing machine is in a stand-by state.
According to an embodiment of the present invention, the detection unit is located on a programmable electronic board of the laundry washing machine.
According to an embodiment of the present invention, the switching unit further comprises a floating member capable of floating in the washing liquid. The floating member is slidingly coupled with a support member connected to a bottom floor of an external casing of the laundry washing machine so as to be free to move with respect to the support member according to the level of washing liquid collected at the bottom of the laundry washing machine.
According to an embodiment of the present invention, the switch is arranged on the support member in such a way that:

when the level of washing liquid collected at the bottom of the laundry washing machine is lower than the predetermined threshold, the floating member is spaced from the switch, and the switch is in the open configuration;
when the level of washing liquid collected at the bottom of the laundry washing machine is equal to or higher than the predetermined threshold, the floating member pushes against the switch, causing the switch to switch to the closed configuration.

According to an embodiment of the present invention, the laundry washing machine comprises a drying unit configured to dry the laundry.
These, and others, features and advantages of the solution according to the present invention will be better understood by reading the following detailed description of some embodiments thereof, provided merely by way of exemplary and non-limitative examples, to be read in conjunction with the attached drawings, wherein:

Figure 1 is a schematic view of a laundry washing machine in which embodiments of the present invention may be implemented, and
Figure 2 schematically illustrates a driving apparatus of the appliance of Figure 1 and a switch and a detection unit of an overflow control system according to an embodiment of the present invention;
Figure 3 is a perspective view with partially removed parts of the laundry washing machine of Figure 1 ;
Figure 4A and 4B illustrates a switching unit of the overflow control system according to an embodiment of the present invention in two different positions, and
Figure 5 schematically illustrates a driving apparatus of the appliance of Figure 1 and a switch and a detection unit of an overflow control system according to another embodiment of the present invention.

With reference to the drawings, Figure 1 illustrates a laundry washing machine 100 in which embodiments of the present invention may be implemented. The laundry washing machine 100 illustrated in Figure 1 is a washing machine which can only wash and rinse laundry. Anyway, it should be apparent form the following description that the invention can be applied, without any substantial modification, to a washing and drying machine comprising a drying unit configured to dry laundry.
In the example at issue, the laundry washing machine 100 advantageously comprises an external casing 105, preferably substantially parallelepiped-shaped, that encloses a washing tub 107 wherein laundry is treated, along with any other components of the washing machine 100 necessary for the operation (e.g., hydraulic, electronic and electromechanical apparatuses). The washing tub 107 has preferably a substantially cylindrical shape and it is made of waterproof material which is also able to withstand operating temperatures and chemicals reactions promoted by washing liquids during the washing machine operation, such as a plastic polymer.
A rotatable drum 110, preferably perforated, preferably substantially cylindricalshaped, in which laundry 112 to be washed can be loaded, is mounted in the washing tub 107 (in either a horizontal or vertical configuration). The rotatable drum 110 is adapted to be selectively rotated, preferably at variable rotation speeds, by an electric motor, only conceptually depicted in figure and denoted, as a whole, by the reference 115.
In order to allow a user to access the washing tub and the inside of the drum 110 (for loading/unloading the laundry), a loading/unloading opening, closable by a door, not illustrated, is advantageously provided, preferably on a front side of the laundry washing machine 100. It has to be appreciated that the concepts of the present invention may be applied also to a laundry washing machine of the top-loading type, i.e., in which the loading/unloading opening is provided on a top side thereof.
A water supply system 120 and a detergent supply system 122 are arranged preferably in the upper part of the laundry washing machine 100 for supplying washing liquid into the washing tub 107. The detergent supply system 122 advantageously comprises a removable drawer 123 provided with compartments suited to be filled with washing and/or rinsing products.
Water flowing through the water supply system 120 is advantageously supplied into the washing tub 107 by making it flow through the drawer 123 and through an inlet line 125 in fluid communication with the washing tub 107. Advantageously, the water supply system 120 further comprises a main pipe 130 fluidly connecting the drawer 123 to an external water supply line 135, preferably by means of a controlled input supply valve 140.
Washing liquid which reaches the washing tub 107 may selectively contain one of the products (e.g., detergent, softener, bleach) contained in the compartments of the drawer 123, or may be clean water (i.e., which does not contain any product), depending on the washing program which is actually performed. Alternative arrangements may be provided, for example with a separate water inlet line adapted to supply exclusively clean water into the washing tub 107.
A heating element 144, such as an electric resistor, is located on the bottom portion of the washing tub 107, for heating the washing/rinsing liquid inside the washing tub 107 when activated.
The laundry washing machine 100 is provided with a discharge system 145 adapted to selectively remove (or drain) washing/rinsing liquid from the washing tub 107.
The discharge system 145 comprises a discharge duct 150 fluidly connected to the washing tub 107 for receiving the washing/rinsing liquid to be discharged. The discharge duct 150 may be made of a rigid material, such as plastic. Anyway, the discharge duct 150 may be a flexible hose, for example made of a flexible material, such as rubber. The discharge duct 150 is arranged to be, preferably selectively, in fluid communication with the washing tub 107 through a discharge hole 155 provided at the bottom of the washing tub 107. Preferably, a valve 160 is provided for selectively opening/closing the discharge hole 155, in order to selectively allow/block liquid to flow between the washing tub and 107 the discharge duct 150. Downstream the valve 160, an anti-fluff / anti-clog filter 165 is preferably provided.
Downstream the anti-fluff / anti-clog filter 165, a drain pump 170 is provided, which is operable to selectively cause liquid located in the discharge duct 150 (and therefore, in the washing tub 107) to be discharged through a drain duct 175 adapted to be connected to a water drain network system (not illustrated).
A recirculation pump 177 may be also provided - preferably in parallel with the drain pump 170 -, which is operable to selectively cause liquid located into the discharge duct 150 to be conveyed back into the washing tub 107 through a recirculation conduit 180, preferably for being sprayed inside the drum 110, e.g., by means of nozzle(s) 185 located on the drum 110 in proximity of the rotation axis thereof.
The electric motor 115, the heating element 144, the drain pump 170, and - if present - the recirculation pump 177, are each one driven by a respective driving apparatus comprising a respective TRIAC - or a similar switching device, such as a relay - arranged to selectively couple said electric motor 115, heating element 144, drain pump 170, or recirculation pump 177 to line and neutral terminals of an AC electric power supply. Said driving apparatuses (not illustrated in Figure 1 ) are preferably located on the electronic control unit 190 (e.g., a programmable electronic board) of the laundry washing machine 100.
Figure 2 schematically illustrates in terms of circuit elements the driving apparatus, identified with the reference 200, designed to drive the drain pump 170.
The driving apparatus 200 comprises a TRIAC 205 having a first anode terminal M1 connected to the neutral terminal (identified in Figure 2 with reference TN) of the AC electric power supply providing a reference signal Vn, a second anode terminal M2 connected to a first terminal of the drain pump 170, and a gate terminal G connected to a triggering circuit 208 adapted to generate triggering pulse signals for activating the TRIAC 205. The drain pump 170 comprises a second terminal connected to the line terminal (identified in Figure 2 with reference TL) of the AC electric power supply providing an AC supply signal Vl with respect to the reference signal Vn. In the example at issue, the AC supply signal Vl is a 230V or 125V alternating voltage at a 50Hz or 60Hz frequency, having a full-wave periodic, e.g., sinusoidal, waveform. Although in the embodiment illustrated in figure the first anode terminal M1 of the TRIAC 205 is directly connected to the neutral terminal TN of the AC electric power supply, and the second terminal of the drain pump 170 is directly connected to the line terminal TL of the AC electric power supply, similar considerations apply if the first anode terminal M1 of the TRIAC 205 and/or the second terminal of the drain pump 170 are/is coupled with said terminals of the AC electric power supply through electric components (not illustrated), such as for example switches or relays.
An AC-DC conversion circuit (only conceptually illustrated in the figure and denoted, as a whole, by the reference 210) is provided, comprising transforming, rectifying and regulation components for receiving the (AC) electric power supply (from line TL and neutral TN terminals) and providing one or more DC voltages, such as a ground voltage GND and a DC supply voltage Vcc (e.g., a 3V, 5V or 12V DC voltage with respect to the ground voltage GND). The DC voltages generated by the AC-DC conversion unit 210 are used for supplying the electric and electronic components included in the electronic control unit 190, such as a microcontroller 215 directed to manage the operation of the laundry washing machine 100. For this purpose, the microcontroller 215 is connected between a DC supply terminal Th for receiving the DC supply voltage Vcc and a ground terminal GND for receiving the ground voltage GND for being supplied with the DC supply voltage Vcc and with the ground voltage GND. As visible in Figure 2 , the neutral terminal TN is preferably coupled with the terminal of the AC-DC conversion unit 210 providing the DC supply voltage Vcc, and therefore to the DC supply terminal Th of the microcontroller 215, so that the reference signal Vn is set to the DC supply voltage Vcc for allowing proper driving of power components, such as the TRIAC 205.
According to an embodiment, the triggering circuit 208 comprises a bipolar transistor 220 having a base terminal adapted to receive a driving signal Vd capable of selectively taking a high value corresponding to the DC supply voltage Vcc and a low value corresponding to the ground voltage GND, an emitter terminal connected to the ground terminal GND for receiving the ground voltage GND, and a collector terminal connected to a first terminal of a resistor R. The resistor R has a second terminal connected to the gate terminal G of the TRIAC 205.
According to an embodiment of the present invention, the triggering circuit 208 for activating the TRIAC 205 is driven by the microcontroller 215. In this case, the driving signal Vd is set by the microcontroller 215 and the base terminal of the transistor 220 is coupled with an output terminal O of the microcontroller 215 for receiving the driving signal Vd. When the microcontroller 215 sets the driving signal Vd to the low value, the transistor 220 is off, and the gate terminal G of the TRIAC 205 is floating. In this condition, the TRIAC 205, and therefore the drain pump 170, are off.
In order to trigger the activation of the TRIAC 205 for turning on the drain pump 170, the microcontroller 215 sets the driving signal Vd to the high value, turning on the transistor 220. In this condition, a current pulse flows from the gate terminal G toward the ground terminal GND flowing across the resistor R and the transistor 220, triggering the activation of the TRIAC 205, and then turning on the drain pump 170. As it is well known to the person skilled in the art, the delay at which the current pulse is generated with respect to the start of the half-cycles of the AC supply signal Vl at the line terminal TL sets the actual voltage difference waveform applied between the drain pump 170 terminals, thus determining its RMS effective value (which sets in turn the actual flow rate of the drain pump 170).
Returning to Figure 1 , washing liquid may collect at the bottom of the laundry washing machine 100, such as on the bottom floor 192 of the casing 105, because of a leakage in the washing tub 107, in the water supply system 120, in the inlet line 125, in the discharge system 145, and/or in the recirculation conduit 180, because of a failure in the input supply valve 140, and/or because of excessive washing liquid intake in the washing tub 107. When the level of washing liquid collected at the bottom of the laundry washing machine 100 is equal to or higher than an overflow threshold for which such washing liquid may cause external damage to the floor or other surroundings where the laundry washing machine 100 is located, and may damage internal, particularly electrical, components of the laundry washing machine 100, such as for example the electric motor 115 and/or the drain pump 170, the laundry washing machine 100 is in an "overflow condition".
For these reason, the laundry washing machine 100 comprises an overflow control system adapted to detect overflow condition occurrences, and to cause washing liquid already contained in the washing tub 107 to be drained as soon as an overflow condition occurrence is assessed.
Said overflow control system comprises a switching unit located on the bottom floor 192 of the casing 105 and a detection unit, preferably located on the electronic control unit 190. The switching unit and the detection unit are only conceptually depicted in Figure 1 , and denoted by the references 193, 194, respectively.
Figure 3 is a perspective view with partially removed parts of the laundry washing machine 100 depicting the switching unit 193 of the overflow control system. In the considered example, the switching unit 193 is located on the bottom floor 192 of the casing 105 close to the drain pump 107. Similar considerations apply if the switching unit 193 is located on other portions of the bottom floor 192 of the casing 105.
The switching unit 193 comprises a floating member 195 made of a material capable of floating in the washing liquid, such as polystyrene, slidingly coupled with a support member 196 connected to the bottom floor 192 of the casing 105, in such a way that the floating member 195 is free to move - along a direction substantially perpendicular to the bottom floor 192 - with respect to the support member 196 according to the level of washing liquid collected at the bottom of the laundry washing machine 100.
Figures 4A and 4B illustrates in greater detail the switching unit 193 with the floating member 195 in two different positions with respect to the support member 196.
The support member 196 comprises connection members 197 (two, in the figures) for connecting the switching unit 193 to the bottom floor 192 of the casing 105. For example, the connection members 197 may be snap-fit engaging members adapted to engage corresponding seats provided on base members 198 protruding from the bottom floor 192 of the casing 105. Similar considerations apply if the support member 196 is connected to the bottom floor 192 of the casing 105 in a different manner, such as for example by means of pins or screws.
The floating member 195 is provided with a hole 400 extending along a direction substantially perpendicular to the bottom floor 192 of the casing 105, and the support member 196 further comprises a guide member 410, for example a rail, extending along the same direction. The floating member 195 is slidingly coupled with the support member 196 with the guide member 410 of the latter that is fitted in the hole 400 of the former. In this way, the floating member 195 is free to slide along the guide member 410 according to the level of washing liquid collected at the bottom of the laundry washing machine 100.
Figure 4A illustrates the switching unit 193 with the floating member 195 in a lowered position, corresponding to a level of washing liquid at the bottom of the laundry washing machine 100 lower than the overflow threshold, such as for example with the bottom floor 192 lacking of washing liquid; Figure 4B illustrates the switching unit 193 with the floating member 195 in a raised position, corresponding to an overflow condition in which the level of washing liquid collected at the bottom of the laundry washing machine 100 is equal to or higher than the overflow threshold.
The support member 196 of the switching unit 193 further comprises a switch 420 adapted to be selectively switched by the floating member 195 in accordance with the level of washing liquid collected at the bottom of the laundry washing machine 100. According to an embodiment of the present invention, the switching unit 193 is designed in such a way that when the level of washing liquid is lower than the overflow threshold, the floating member 195 is spaced from the switch 420, and the latter is in an open configuration; in an overflow condition, when the level of washing liquid is equal to or higher than the overflow threshold, the floating member 195 pushes against the switch 420, causing the latter to switch to a closed configuration.
In order to allow the switch 420 to be efficiently switched into the closed configuration by the floating member 195 in the overflow condition, the floating member 195 may be advantageously provided with a protruding element facing toward the switch, and/or the switch may be advantageously provided with a protruding element facing toward the floating member 195.
According to an embodiment of the present invention, the switch 420 is configured to electrically connect the line terminal TL of the AC electrical power supply to the detection unit 194 of the overflow control system when in the closed configuration, and to electrically disconnect them one form the another when in the open configuration.
Making reference back to Figure 2 , the detection unit 194 and the switch 420 of the overflow control system according to an embodiment of the present invention are depicted in terms of circuit elements.
The switch 420 comprises a first conduction terminal connected to the line terminal TL, and a second conduction terminal connected to the detection unit 194. The detection unit 194 comprises a detection circuit 460 coupled between the switch 420 and an (analog) input terminal I of the microcontroller 215 for generating a detection signal D indicative of the configuration of the switch 420 and providing said detection signal D to the input terminal I of the microcontroller 215. According to an embodiment of the present invention, said detection circuit 460 comprises a first resistor R1 having a first terminal connected to the second conduction terminal of the switch 420 and a second terminal connected to a first terminal of a second resistor R2, defining a circuit node N. The second resistor R2 has a second terminal connected to the ground terminal GND. The circuit node N is connected to the (analog) input terminal I of the microcontroller 215 for providing the detection signal D to the microcontroller 215. Preferably, although not necessarily, a filter unit 235 may be provided at the input terminal I of the microcontroller 215 connected to the circuit node N to filter possible noises affecting the detection signal D. For example, the filter unit 235 may be a low-pass filter comprising suitably connected resistors and capacitors (not illustrated in figure but well known to those skilled in the art). The first resistor R1 and the second resistor R2 of the detection circuit 460 form a voltage divider arrangement having an input terminal corresponding to the first terminal of the first resistor R1 and an output terminal corresponding to the circuit node N.
With the detection unit 194 according to the invention:

a) If the switch 420 is in the open configuration - corresponding to the condition in which the level of washing liquid collected at the bottom of the laundry washing machine 100 is lower than the overflow threshold, so that the floating member 195 is in a lowered position, spaced from the switch 420 -, the detection signal D is a constant trend signal at the ground voltage GND.
b) If the switch 420 is in the closed configuration - corresponding to the overflow condition, in which the level of washing liquid collected at the bottom of the laundry washing machine 100 is equal to or higher than the overflow threshold, so that the floating member 195 is in the raised position, pushing against the switch 420 -, the detection signal D is an oscillating trend signal corresponding to a scaled version of the AC supply signal Vl provided by the line terminal TL, i.e., with substantially the same frequency and the same phase of the AC supply signal Vl, but with an amplitude that is a fraction thereof.

The ratio between the (higher) amplitude of AC supply signal Vl and the (lower) detection signal D when the switch 420 is in the closed configuration is determined by the resistance values of the first resistor R1 and the second resistor R2, according to relationships well known to those skilled in the art.
According to an embodiment of the present invention, the resistance values of the first resistor R1 and of the second resistor R2 are advantageously chosen in such a way that when the switch 420 is in the closed configuration, the detection signal D oscillates between a value corresponding to the ground voltage GND and a value corresponding to the DC supply voltage Vcc provided by the supply terminal Th, i.e., it advantageously oscillates in a range of values complying with the supply voltages of the microcontroller 215.
Similar considerations apply if the detection circuit 460 comprises a voltage divider structured in a different way, such as if comprises more resistors, and/or if comprises capacitive and/or inductive elements. In case the voltage divider comprises capacitive and/or inductive elements, the phase of the detection signal D may in general differ from the one of the AC supply signal Vl. Moreover, similar considerations apply in case the detection circuit 460 comprises a circuit arrangement that, although different from a voltage divider, it is anyway configured to generate the detection signal D in the same way as previously described.
According to an embodiment of the present invention, the microcontroller 215 is configured to assess whether the laundry washing machine 100 is in an overflow condition or not based on the detection signal D received from the detection circuit 460.
If the detection signal D is a constant trend signal at the ground voltage GND, the microcontroller 215 assesses that the laundry washing machine 100 is not in an overflow condition, i.e., it assesses that the amount of washing liquid collected at the bottom of the laundry washing machine 100 is not sufficient to impair the correct operation of the laundry washing machine 100.
If the detection signal D is instead an oscillating signal that oscillates between the ground voltage GND and the DC supply voltage Vcc, the microcontroller 215 assesses that the laundry washing machine 100 is in an overflow condition, i.e., it assesses that the washing liquid collected at the bottom of the laundry washing machine 100 has reached a level so high to require the activation of the drain pump 170 for draining the washing liquid included therein. For this purpose, according to an embodiment of the present invention, once the microcontroller 215 detects that the detection signal D oscillates, it sets the driving signal Vd to the high value, for triggering the activation of the TRIAC 205 in order to turn on the drain pump 170.
The proposed solution is effective, simple and cheap, requiring very few additional components. Indeed, it is sufficient to provide components for forming a voltage divider arrangement, such as two resistors.
Moreover, since the overflow condition is assessed when the switch 420 is in the closed configuration, unlike the known solutions, the monitoring circuit according to the present invention consumes additional electric power only when said overflow condition occurs, and not during the stand-by state of the laundry washing machine 100.
Furthermore, the proposed solution does not require any expensive and time-consuming calibration.
According to an embodiment of the present invention, the microcontroller 215 is further configured provide an overflow condition warning to the user, for example by driving proper visual and/or audio signaling apparatuses (not illustrated in the figure), once the overflow condition has been assessed.
According to an embodiment of the present invention, the microcontroller 215 is further configured to assess a resistance value mismatch in the resistor R1 and/or in the resistor R2 if the detection signal D received by the microcontroller 215 oscillates between the ground voltage GND and a voltage different (e.g., lower) than the DC supply voltage Vcc.
According to an embodiment of the present invention, the microcontroller 215 is further configured to assess that the filter unit 235 and/or the detection circuit 460 are disconnected from the microcontroller 215 if it detects that its input terminal adapted to receive the detection signal D is floating.
Figure 5 illustrates a modified detection unit, identified with the reference 194', according to another embodiment of the present invention. While in the previously described embodiments the drain pump 170 is adapted to be activated by providing to the base terminal of the transistor 220 a driving signal Vd which is generated by the microcontroller 215 both during the normal operation and during an overflow condition, the detection unit 194' is configured in such a way that, when an overflow condition is assessed, the driving signal Vd to be provided to the base terminal of the transistor 220 is generated by a circuit unit different from the microcontroller 215.
The detection unit 194' comprises a peak detection unit 505, for example comprising a diode and a capacitor (not illustrated in figure) or other known circuit arrangements carrying out a peak detection function, connected to the circuit node N to receive the detection signal D and to generate an output signal OS corresponding to the peak value of the detection signal D. The detection unit 505 has an output terminal connected to the (analog) input terminal I of the microcontroller 215 and to an anode terminal of a first diode D1, defining a circuit node P. The first diode D1 has a cathode terminal connected to the base terminal of the transistor 220, defining a circuit node M. The output terminal O of the microcontroller 215 is connected to an anode terminal of a second diode D2. The second diode D2 has a cathode terminal connected to the circuit node M.
When the switch 420 is in the open configuration, the detection signal D is a constant trend signal at the ground voltage GND, and the peak detection unit 505 sets the output signal OS to a constant trend signal at the ground voltage GND, too. In this situation, the circuit node P is electrically decoupled from the circuit node M by means of the diode D1, and the management of the drain pump 170 is carried out by the microcontroller 215, which generates the driving signal Vd and provides it to the base terminal of the transistor 220 as described in the previous embodiments.
When the switch 420 is in the closed configuration (overflow condition), the detection signal D is an oscillating trend signal corresponding to a scaled version of the AC supply signal Vl provided by the line terminal TL, i.e., with substantially the same frequency and the same phase of the AC supply signal Vl, but with an amplitude that is a fraction thereof, and the peak detection unit 505 accordingly sets the output signal OS to a constant trend signal corresponding to the peak value of the oscillating detection signal D. According to an embodiment of the present invention, the voltage divider arrangement of the detection circuit 460 is such that said peak value of the oscillating detection signal D is a value sufficiently high to allow the activation of the transistor 220 when provided to the base terminal thereof. In this situation, the output terminal O of the microcontroller 215 is electrically decoupled from the circuit node M by means of the diode D2, and the driving signal Vd is set to the output signal OS - which in this case corresponds to the peak value of the oscillating detection signal D- through the diode D1, and is provided to the base terminal of the transistor 220 for activating the drain pump 170 without involving the microcontroller 215.
The detection unit 194' according to this embodiment of the invention is advantageously adapted to turn on the drain pump 170 in the overflow condition without involving the microcontroller 215. Therefore, this embodiment is particularly suited to be employed in laundry washing machines 100 in which the power supply of the electronic control unit 190 is interrupted during the stand-by of the laundry washing machine 100 (e.g., by means of a switch provided in the AC-DC conversion circuit 210) and the microcontroller 215 is therefore turned off, and/or in which the microcontroller 215 is configured to enter in a sleep mode during the stand-by of the laundry washing machine 100. Indeed, even if the electronic control unit 190 is not supplied and/or the microcontroller 215 is in the sleep mode, when the switch 420 switches to the closed configuration in the overflow condition, the detection unit 194' is still capable of turning on the drain pump 170.
Naturally, in order to satisfy local and specific requirements, a person skilled in the art may apply to the solution described above many logical and/or physical modifications and alterations.

Claims

A laundry washing machine (100), comprising:
- a washing tub (107) configured to be supplied with washing liquid for treating laundry;

- a rotatable drum (110), in which laundry (112) to be washed can be loaded, mounted in the washing tub (107);

- a drain pump (170) operable to selectively cause washing liquid located in the washing tub (107) to be discharged;

- an overflow control system (193, 194; 193, 194') for detecting an occurrence of an overflow condition of the laundry washing machine (100) in which a level of washing liquid collected at the bottom of the laundry washing machine (100) is equal to or higher than a predetermined threshold, and for driving the drain pump (170) to discharge washing liquid from the washing tub (107) in case an overflow condition has been detected, the overflow control system (193, 194; 193, 194') comprising a switching unit (193) and a detection unit (194; 194'), wherein:

- the switching unit (193) comprises a switch (420) having a first terminal connected to a terminal (TL) of an AC electric power supply and a second terminal connected to the detection unit (194; 194'), the switch (420) being configured to electrically connect the first terminal with the second terminal in a closed configuration and to electrically insulate the first terminal from the second terminal in an open configuration, the switching unit (193) being configured to switch the switch (420) to the closed configuration when the level of washing liquid collected at the bottom of the laundry washing machine (100) is equal to or higher than said predetermined threshold, and

- the detection unit (194; 194') is configured to detect an overflow condition occurrence and to drive the drain pump (170) to discharge washing liquid from the washing tub (107) when the switch (420) is in the closed configuration.
The laundry washing machine (100) of claim 1, wherein the detection unit (194) comprises:
- a microcontroller (215);

- a detection circuit (460) coupled between the second terminal of the switch (420) and an input terminal of the microcontroller (215) for generating a detection signal indicative of the configuration of the switch (420), wherein the microcontroller (215) is configured to drive the drain pump (170) to discharge washing liquid from the washing tub (107) according to said detection signal.
The laundry washing machine (100) of claim 2, wherein said detection circuit (460) is configured to generate said detection signal in such a way that:
- if the switch (420) is in the open configuration, the detection signal is a constant trend signal, and

- if the switch (420) is in the closed configuration, the detection signal is an oscillating trend signal.
The laundry washing machine (100) of claim 3, further comprising an AC-DC conversion unit (210) for receiving said AC electric power supply and providing a corresponding DC supply voltage and a corresponding ground voltage, wherein:
- the microcontroller (215) is supplied between the DC supply voltage and the ground voltage;

- said constant trend signal is a constant trend signal at the ground voltage, and

- said oscillating trend signal is a signal oscillating between the ground voltage and the DC supply voltage.
The laundry washing machine (100) of claim 4, wherein said detection circuit (460) comprises a voltage divider arrangement (R1; R2) having an input terminal connected to the second terminal of the switch (420) and an output terminal coupled with the input terminal of the microcontroller (215) for providing the detection signal.
The laundry washing machine (100) of claim 5, wherein said voltage divider arrangement (R1; R2) comprises a first resistor (R1) having a first terminal connected to the second terminal of the switch (420) and a second terminal connected to a first terminal of a second resistor (R2), the second resistor (R2) having a second terminal connected to a terminal providing the ground voltage, the second terminal of the first resistor (R1) being coupled with the input terminal of the microcontroller (215) for providing the detection signal.
The laundry washing machine (100) of claim 6, wherein the microcontroller (215) is further configured to assess a resistance value mismatch in the first resistor (R1) and/or in the second resistor (R2) if the detection signal oscillates between the ground voltage and a voltage different than the DC supply voltage.
The laundry washing machine (100) of any one among claims 2 to 7, further comprising a filter unit (235) connected to the input terminal of the microcontroller (215) for filtering possible noises affecting the detection signal generated by the detection circuit (460).
The laundry washing machine (100) of claim 8, wherein the filter unit (235) is a low-pass filter.
The laundry washing machine (100) of claim 8 or 9, wherein the microcontroller (215) is further configured to assess that the filter unit (235) and/or the detection circuit (460) are disconnected from the input terminal of the microcontroller (215) if the microcontroller (215) detects that its input terminal is floating.
The laundry washing machine (100) of claim 1, further comprising a driving apparatus (200) for driving the drain pump (170), the driving apparatus (200) comprising:
- a TRIAC (205) comprising a first anode terminal (M1) coupled with a first terminal (TN) of an AC electric power supply and a second anode terminal (M2) coupled with a first terminal of the drain pump (170), the drain pump (170) comprising a second terminal coupled with a second terminal (TL) of the AC electric power supply;

- a triggering circuit (208) configured to receive a driving signal and to activate the TRIAC (205) by providing triggering pulse signals to a gate terminal (G) of the TRIAC (205) based on the received driving signal, wherein:
the detection unit (194; 194') is coupled between the second terminal of the switch (420) and the triggering circuit (208) to provide the driving signal to the triggering circuit (208), the detection unit (194; 194') being configured to set the driving signal according to the configuration of the switch (420).
The laundry washing machine (100) of claim 11, wherein the detection unit (194) comprises:
- a microcontroller (215);

- a detection circuit (460) coupled between the second terminal of the switch (420) and an input terminal of the microcontroller (215) for generating a detection signal indicative of the configuration of the switch (420), wherein the microcontroller (215) is configured to set the driving signal according to the detection signal and to provide the driving signal to the triggering circuit (208).
The laundry washing machine (100) of claim 11, wherein the detection unit (194') comprises:
- a detection circuit (460) coupled with the second terminal of the switch (420) and configured to generate a detection signal indicative of the configuration of the switch (420) in such a way that:
a) if the switch (420) is in the open configuration, the detection signal is a constant trend signal, and

b) if the switch (420) is in the closed configuration, the detection signal is an oscillating trend signal,

- a peak detector unit (505) coupled between the detection circuit (460) and the triggering circuit (208) and configured to set the driving signal to the peak value of the detection signal and to provide the driving signal to the triggering circuit (208).
The laundry washing machine (100) of claim 13, wherein the detection unit (194') further comprises a microcontroller (215) for managing the operation of the laundry washing machine (100), the detection unit (194') being configured to activate the drain pump (170) during an overflow condition occurrence when the microcontroller (215) is turned off or is in a sleep mode, in such a way to discharge washing liquid from the washing tub (107) when the laundry washing machine (100) is in a stand-by state.
The laundry washing machine (100) of any one among the preceding claims, wherein the detection unit (194) is located on a programmable electronic board (190) of the laundry washing machine (100).
The laundry washing machine (100) of any one among the preceding claims, wherein the switching unit (193) further comprises a floating member (195) capable of floating in the washing liquid, the floating member (195) being slidingly coupled with a support member (196) connected to a bottom floor (192) of an external casing (105) of the laundry washing machine (100) so as to be free to move with respect to the support member (196) according to the level of washing liquid collected at the bottom of the laundry washing machine (100).
The laundry washing machine (100) of claim 16, wherein the switch (420) is arranged on the support member (196) in such a way that:
- when the level of washing liquid collected at the bottom of the laundry washing machine (100) is lower than the predetermined threshold, the floating member (196) is spaced from the switch (420), and the switch (420) is in the open configuration;

- when the level of washing liquid collected at the bottom of the laundry washing machine (100) is equal to or higher than the predetermined threshold, the floating member (196) pushes against the switch (420), causing the switch (420) to switch to the closed configuration.
The laundry washing machine (100) of any one among the preceding claims, wherein the laundry washing machine (100) comprises a drying unit configured to dry the laundry (112).