EP3788196A1

EP3788196A1 - Laundry washing machine and method for operating the laundry washing machine

Info

Publication number: EP3788196A1
Application number: EP18722973.7A
Authority: EP
Inventors: Andrea Contarini; Mariano Tartuferi; Stefano De Paoli; Mauro Cinello; Maurizio Del Pos
Original assignee: Electrolux Appliances AB
Current assignee: Electrolux Appliances AB
Priority date: 2018-05-04
Filing date: 2018-05-04
Publication date: 2021-03-10
Also published as: CN112041498A; AU2018421968A1; US20210047768A1; WO2019210973A1

Abstract

The invention relates to a laundry washing machine (1) comprising a washing tub (3) external to a washing drum (4) suited to receive the laundry to be washed, a recirculation system (20; 120; 220) comprising a first duct (33) to circulate liquid into a first region of the washing tub (3) and a second duct (43) to circulate liquid into a second region of the washing tub (3). The recirculation system (20; 120; 220) comprises a recirculation pump (22; 122; 222) operable in a first direction of rotation (R1) and in a second direction of rotation (R2) opposite to the first direction (Rl). The recirculation pump (22; 122; 222) is operated in the first direction (R1) to circulate liquid in the first duct (33) and is operated in the second direction (R2) to circulate liquid in the second duct (43).

Description

LAUNDRY WASHING MACHINE AND METHOD FOR OPERATING THE LAUNDRY WASHING MACHINE

The present invention concerns the field of laundry washing techniques.

Specifically, the invention relates to a laundry washing machine with recirculation circuits.

The invention relates also a method for controlling said recirculation circuits.

BACKGROUND ART

Nowadays the use of laundry washing machines, both“simple” laundry washing machines (i.e. laundry washing machines which can only wash and rinse laundry) and laundry washing-drying machines (i.e. laundry washing machines which can also dry laundry), is widespread.

In the present description, therefore, the term“laundry washing machine” will refer to both a simple laundry washing machine and a laundry washing-drying machine.

Laundry washing machines generally comprise an external casing, or cabinet, provided with a washing tub which contains a rotatable perforated washing drum where the laundry is placed. A loading/unloading door ensures access to the washing drum.

Laundry washing machines typically comprise a water supply unit and a treating agents dispenser, preferably equipped with a drawer, for the introduction of water and washing/rinsing products (i.e. detergent, softener, rinse conditioner, etc.) into the washing tub.

Known laundry washing machines are typically provided with a water outlet circuit suitable for withdrawing liquid, for example dirty water, from the bottom of the washing tub to the outside. The water outlet circuit is typically provided with a controllable draining pump.

Known laundry washing machines are also typically provided with recirculation circuits.

A first known recirculation circuit which equips laundry washing machines is adapted to drain liquid from the bottom region of the washing tub and to re-admit such a liquid into an upper region of the washing tub. The first recirculation circuit is preferably provided with a terminal nozzle opportunely arranged so that the recirculated liquid is conveyed over the laundry and distribution of the same liquid over the laundry is enhanced. The first recirculation circuit is typically provided with a first controllable recirculation pump.

A second known recirculation circuit which equips laundry washing machines, or mixing circuit, is adapted to drain liquid from a bottom region of the washing tub and to re- admit such a liquid (recirculated mixing liquid) into a region of the washing tub which corresponds substantially to the same bottom region of the washing tub.

The mixing circuit is preferably realized for transferring a portion of a liquid from a bottom region of the washing tub to the same bottom region for the mixing and/or the dissolution of the products, in particular for liquid and/or powder detergent. The second recirculation circuit is typically provided with a second controllable recirculation pump.

During the washing cycle, the controlled pumps are opportunely activated at proper times to drain and/or recirculate liquid from the bottom of the washing tub.

In particular, the first and second recirculation pumps of the first and second recirculation circuits are selectively activated to recirculate liquid when necessary.

In known laundry washing machines of different type, the first and the second recirculation circuits are realized so that they comprise a first common part, namely a draining tube connected to the bottom of the washing tub, a unique controlled recirculation pump and two recirculation tubes that respectively connect the pump outlet to the upper region of the washing tub and the bottom region of the washing tub.

Between the pump outlet and the recirculation tubes a controllable valve is arranged, preferably a two-way valve, that allows the liquid to flow selectively into the first or the second recirculation tube when the recirculation pump is activated.

However, laundry washing machines of the known art pose some drawbacks.

A drawback of the laundry washing machines of the known art is the complex structural construction. According to known art, in fact, two pumps and/or one or more valves are required.

This increases the manufacturing and/or maintenance time and costs of the laundry washing machine. A further drawback posed by this known technique is constituted by the high failure rate due to the complex structural construction.

The object of the present invention is therefore to overcome the drawbacks posed by the known technique.

It is an object of the invention to implement a laundry washing machine which has a simplified structural construction with respect to the known laundry washing machines.

It is a further object of the invention to implement a laundry washing machine that makes it possible to reduce manufacturing and/or maintenance time and costs.

It is a further object of the invention to implement a laundry washing machine that makes it possible to increase reliability thereof.

DISCLOSURE OF INVENTION

Applicant has found that by providing a laundry washing machine comprising a washing tub external to a washing drum and a recirculation system comprising a first duct terminating at a first region of the washing tub and a second duct terminating at a second region of the washing tub and by providing a recirculation pump operable in a first direction of rotation and in a second direction of rotation for conveying liquid to a said first duct or said second duct, it is possible to reach the mentioned objects.

In a first aspect thereof the present invention relates, therefore, to a laundry washing machine comprising:

- a washing tub external to a washing drum suited to receive the laundry to be washed;

- a water supply system suitable to convey water to said washing tub;

- a recirculation system for draining liquid from the bottom of said washing tub and to re-admit such liquid into a first region and a second region of said washing tub, said recirculation system comprising:

- a first duct terminating at said first region wherein said liquid may circulate to reach said washing tub;

- a second duct terminating at said second region wherein said liquid may circulate to reach said washing tub;

wherein said recirculation system comprises a recirculation pump operable in a first direction of rotation and in a second direction of rotation opposite to said first direction, said recirculation pump comprising a pump chamber having an inlet connected to said bottom of said washing tub and an outlet arrangement for the connection to said first duct and said second duct, wherein said ducts are configured so that a liquid in said first duct requires a pressure to reach said washing tub which is lower than the pressure required for a liquid in said second duct to reach said washing tub, and wherein said recirculation pump is operated in said first direction to circulate liquid in said first duct to reach said washing tub and is operated in said second direction to circulate liquid in said second duct to reach said washing tub.

Preferably, the pump chamber receives an impeller apt to be rotated and to force liquid from the pump chamber towards the outlet arrangement.

It has to be noted that when the recirculation pump is operated in the first direction to circulate liquid in the first duct it is preferably meant that the impeller is rotated in the first direction to circulate in the first duct. Analogously, when the recirculation pump is operated in the second direction to circulate liquid in the second duct it is preferably meant that the impeller is rotated in the second direction to circulate in the second duct.

Preferably, the outlet arrangement comprises a first outlet from said pump chamber for said first duct and a second outlet from said pump chamber for said second duct.

In a preferred embodiment of the invention, the first and second outlets are realized at a body portion of the recirculation pump.

According to a preferred embodiment of the invention, the first outlet is tangentially arranged with respect to the pump chamber and/or the second outlet is tangentially arranged with respect to the pump chamber.

Preferably, the first outlet is parallel to the second outlet.

According to a further preferred embodiment of the invention, the outlet arrangement comprises a common outlet portion from said pump chamber and a bifurcation for the first duct and the second duct.

In a preferred embodiment of the invention, the common outlet portion and the bifurcation are realized at a body portion of the recirculation pump.

According to a preferred embodiment of the invention, the recirculation pump is a fixed speed pump.

Preferably, in the first direction the recirculation pump is operated at a first fixed speed and/or in the second direction the recirculation pump is operated at a second fixed speed.

Preferably, the first fixed speed is higher than the second fixed speed (S2).

According to a further preferred embodiment of the invention, the recirculation pump is a variable speed pump.

Preferably, in the first direction the recirculation pump is operated at a first fixed speed or at a first speed varying over the time and/or in the second direction the recirculation pump is operated at a second fixed speed or at a second speed varying over the time.

In a preferred embodiment of the invention, the recirculation pump is operated with a continuous driving signal.

In a further preferred embodiment of the invention, the recirculation pump is operated with a pulsed driving signal.

According to a preferred embodiment of the invention, the machine further comprises a treatment agents dispenser to supply one or more treating agents into the washing tub.

Preferably, the first region is a bottom part of the washing tub.

Preferably, the second region is an upper part of the washing tub.

In a preferred embodiment of the invention, the first duct defines a first volume and the second duct defines a second volume, wherein the first volume is lower than the second volume.

In a further aspect, the present invention relates to a method for operating a laundry washing machine comprising:

- a water supply system suitable to convey water to said washing tub;

- a recirculation pump operable in a first direction of rotation and in a second direction of rotation opposite to said first direction, said recirculation pump comprising a pump chamber having an inlet connected to said bottom of said washing tub and an outlet arrangement for the connection to said first duct and said second duct, wherein said ducts are configured so that a liquid in said first duct requires a pressure to reach said washing tub which is lower than the pressure required for a liquid in said second duct to reach said washing tub;

wherein said recirculation pump is operated in said first direction to circulate liquid in said first duct to reach said washing tub and is operated in said second direction to circulate liquid in said second duct to reach said washing tub.

In a preferred embodiment of the invention, the recirculation pump is operated in the first direction to circulate liquid only in the first duct.

In a preferred embodiment of the invention, the recirculation pump is operated in the second direction to circulate liquid mainly in the second duct. Preferably, the recirculation pump is operated in the second direction to circulate liquid also in the first duct.

According to a preferred embodiment of the invention, the recirculation pump is a fixed speed pump, wherein in the first direction the recirculation pump is operated at a first fixed speed and/or in the second direction the recirculation pump is operated at a second fixed speed.

Preferably, the first fixed speed is higher than the second fixed speed (S2).

According to a further preferred embodiment of the invention, the recirculation pump is a variable speed pump, wherein in the first direction the recirculation pump is operated at a first fixed speed or at a first speed varying over the time and/or in the second direction the recirculation pump is operated at a second fixed speed or at a second speed varying over the time.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention will be highlighted in greater detail in the following detailed description of some of its preferred embodiments, provided with reference to the enclosed drawings. In the drawings, corresponding characteristics and/or components are identified by the same reference numbers. In particular:

- Figure 1 shows a perspective view of a laundry washing machine according to a first embodiment of the invention;

- Figure 2 shows the laundry washing machine of Figure 1 with some external casing sides removed therefrom;

- Figure 3 shows a schematic view of the laundry washing machine of Figure 2;

- Figure 4 shows some elements of Figure 2 isolated from the rest;

- Figure 5 shows an element of Figure 4 isolated from the rest;

- Figure 6 is a plan view from above of the element of Figure 5;

- Figure 7 is a plan sectional view taken along line VII°-VII° of Figure 6;

- Figure 8 shows a side schematic view of the laundry washing machine of Figure 1;

- Figure 9A shows circulation pump speeds as a function of the time according to a first preferred embodiment of the method of the invention;

- Figures 10A and 10B show the circulation pump speed as a function of the time according to another preferred embodiment of the method of the invention;

- Figures 11 A and 11B show the circulation pump speed as a function of the time according to a further preferred embodiment of the method of the invention;

- Figure 12 shows a detail of a further embodiment of Figure 2;

- Figure 13 shows some elements of Figure 12 isolated from the rest;

- Figure 14 shows an element of Figure 13 isolated from the rest;

- Figure 15 is a plan view from above of the element of Figure 14;

- Figure 16 is a plan sectional view taken along line XVI°-XVI° of Figure 15;

- Figure 17 shows a detail of a further embodiment of Figure 2;

- Figure 18 shows some elements of Figure 17 isolated from the rest;

- Figure 19 shows an element of Figure 18 isolated from the rest;

- Figure 20 is a plan view from above of the element of Figure 19;

- Figure 21 is a plan sectional view taken along line XXI°-XXI° of Figure 20.

DETAILED DESCRIPTION OF PREFERRED EMBODIMETS OF THE

INVENTION

The present invention has proved to be particularly advantageous when applied to laundry washing machines, as described below. It should in any case be underlined that the present invention is not limited to laundry washing machines. On the contrary, the present invention can be conveniently applied to laundry washing-drying machines (i.e. laundry washing machines which can also dry laundry).

With reference to Figures 1 to 3, a preferred embodiment of a laundry washing machine 1 according to the invention is described, in which also a method according to a preferred embodiment of the invention is implemented.

The laundry washing machine 1 preferably comprises an external casing or cabinet 2, a washing tub 3, a container 4, preferably a perforated washing drum 4, where the laundry to be treated can be loaded.

The washing tub 3 and the washing drum 4 both preferably have a substantially cylindrical shape.

The washing tub 3 is preferably connected to the cabinet 2 by means of an elastic bellows 7, or gasket. The bellows 7 is preferably S-shaped.

The cabinet 2 is provided with a loading/unloading door 8 which allows access to the washing drum 4.

The washing drum 4 is advantageously rotated by an electric motor, not illustrated, which preferably transmits the rotating motion to the shaft 4a of the washing drum 4, advantageously by means of a belt/pulley system. In a different embodiment of the invention, the motor can be directly associated with the shaft of the washing drum 4.

The washing drum 4 is advantageously provided with holes which allow the liquid flowing therethrough. Said holes are typically and preferably homogeneously distributed on the cylindrical side wall of the washing drum 4. The bottom region 3a of the washing tub 3 preferably comprises a seat 15, or sump, suitable for receiving a heating device 10. The heating device 10, when activated, heats the liquid inside the sump 15.

In different embodiments, nevertheless, the bottom region of the washing tub may be configured differently. For example, the bottom region of the washing tub may not comprise a seat for the heating device. The heating device may be advantageously placed in the annular gap between the washing tub and the washing drum.

Preferably, the laundry washing machine 1 comprises a device 19 suited to sense (or detect) the liquid level inside the washing tub 3.

The sensor device 19 preferably comprises a pressure sensor which senses the pressure in the washing tub 3. From the values sensed by the sensor device 19 it is possible to determine the liquid level of the liquid inside the washing tub 3. In another embodiment, not illustrated, laundry washing machine may preferably comprise (in addition to or as a replacement of the pressure sensor) a level sensor (for example mechanical, electro-mechanical, optical, etc.) adapted to sense (or detect) the liquid level inside the washing tub 3.

A water supply circuit 5 is preferably arranged in the upper part of the laundry washing machine 1 and is suited to supply water into the washing tub 3 from an external water supply line E. The water supply circuit 5 preferably comprises a controlled supply valve 5a which is properly controlled, opened and closed, during the washing cycle. The water supply circuit of a laundry washing machine is well known in the art, and therefore it will not be described in detail.

The laundry washing machine 1 advantageously comprises a treating agents dispenser 14 to supply one or more treating agents into the washing tub 3 during a washing cycle. Treating agents may comprise, for example, detergents, rinse additives, fabric softeners or fabric conditioners, waterproofing agents, fabric enhancers, rinse sanitization additives, chlorine-based additives, etc.

Preferably, the treating agents dispenser 14 comprises a removable drawer 6 provided with various compartments suited to be filled with treating agents.

In a preferred embodiment, not illustrated, the treating agents dispenser may comprise a pump suitable to convey one or more of said agents from the dispenser to the washing tub.

In the preferred embodiment here illustrated, the water is supplied into the washing tub 3 from the water supply circuit 5 by making it flow through the treating agents dispenser 14 and then through a supply pipe 18.

In an alternative embodiment of the invention, a further separate water supply pipe can be provided, which supplies exclusively clean water into the washing tub from the external water supply line.

In further preferred embodiments, not illustrated herein, a water softening device may preferably be arranged/interposed between the external water supply line and the treating agents dispenser so as to be crossed by the fresh water flowing from the external water supply line. The water softening device, as known, is structured for reducing the hardness degree of the fresh water drawn from the external water supply line E and conveyed to the treating agents dispenser.

In a different embodiment, the water softening device may be arranged/interposed between the external water supply line and the washing tub, so as to be crossed by the fresh water flowing from the external water supply line and conveying it directly to the washing tub.

Laundry washing machine 1 preferably comprises a water outlet circuit 25 suitable for withdrawing liquid from the bottom region 3 a of the washing tub 3. The water outlet circuit 25 preferably comprises a main pipe 17, a draining pump 27 and an outlet pipe 28 ending outside the cabinet 2.

The water outlet circuit 25 preferably further comprises a filtering device 12 arranged between the main pipe 17 and the draining pump 27. The filtering device 12 is adapted to retain all the undesirable bodies (for example buttons that have come off the laundry, coins erroneously introduced into the laundry washing machine, etc.). The filtering device 12 can preferably be removed, and then cleaned, through a gate 13 placed advantageously on the front wall of the cabinet 2 of the laundry washing machine 1, as illustrated in Figure 1.

The main pipe 17 connects the bottom region 3 a of the washing tub 3 to the filtering device 12.

In a further embodiment, not illustrated, the filtering device 12 may be provided directly in the washing tub 3, preferably obtained in a single piece construction with the latter. In this case, the filtering device 12 is fluidly connected to the outlet of the washing tub 3, in such a way that water and washing liquid drained from the washing tub 3 enters the filtering device 12.

Activation of the draining pump 27 drains the liquid, i.e. dirty water or water mixed with washing and/or rinsing products, from the washing tub 3 to the outside.

According to the invention, the laundry washing machine 1 then preferably comprises a recirculation system 20, as better illustrated in Figure 4, which is adapted to drain liquid from the bottom region 3 a of the washing tub 3 and to re admit such a liquid into a first region 3 a and a second region 3b of the washing tub 3, as better described below.

Preferably, the first region 3a of the washing tub 3 substantially corresponds to the same bottom region 3 a of the washing tub 3. The liquid is preferably re admitted to the bottom region 3a of the washing tub 3 for the mixing and/or the dissolution of the products, in particular of the detergent. Mixing and/or dissolution of a product is preferably carried out during a washing cycle when one of the products is supplied into the washing tub 3 from the treating agents dispenser 14. Preferably, the second region 3b of the washing tub 3 substantially corresponds to an upper region 3b of the washing tub 3. The liquid is preferably re-admitted to the upper region 3b of the washing tub 3 in order to improve wetting of the laundry inside the washing drum 4. This action is preferably carried out at the beginning of a washing cycle when the laundry needs to be completely soaked. Furthermore, this action is preferably carried out during rinsing phases at the beginning of the washing cycle or during rinsing phases in successive steps of the washing cycle.

The recirculation system 20 preferably comprises a first recirculation line 30 for conveying liquid to the first region 3 a of the washing tub 3 and a second recirculation line 40 for conveying liquid to the second region 3b of the washing tub 3.

The first recirculation line 30 preferably comprises a first duct 33 terminating at said first region 3a, preferably ending inside the sump 15. The fist duct 33 is preferably provided with a terminal nozzle 33 a.

The second recirculation line 40 preferably comprises a second duct 43 terminating at said second region 3b, preferably ending at the bellows 7, as better illustrated in Figure 2. The second duct 43 is preferably provided with a terminal nozzle 43 a.

The recirculation system 20 then preferably comprises a common recirculation pump 22 for conveying liquid to the first and second recirculation lines 30, 40, more preferably to the first and second ducts 33, 43.

The recirculation pump 22 preferably comprises a pump chamber 23 having an inlet 24 connected to the bottom 3a of the washing tub 3. Inlet 24 of the recirculation pump 22 is preferably connected to the bottom 3 a of the washing tub 3 through a suction pipe 32 preferably connected to the filtering device 12. The recirculation pump 22 then preferably has an outlet arrangement 26 for conveying liquid from the pump chamber 23 to the first and second recirculation lines 30, 40.

The pump chamber 23 preferably receives an impeller 23 a apt to be rotated and to force liquid from the pump chamber 23 towards the outlet arrangement 26.

The pump chamber 23 preferably has a substantially cylindrical shape.

In a preferred embodiment of the invention and according to Figures 5 to 7, the outlet arrangement 26 preferably comprises a first outlet 58a connected to the first duct 33 and a second outlet 58b connected to the second duct 43. The first outlet 58a preferably comprises a portion of duct which extends tangentially from the pump chamber 23.

The second outlet 58b preferably comprises a portion of duct which extends tangentially from the pump chamber 23.

First and the second outlets (ducts) 58a, 58b are preferably parallel one to the other.

Preferably, first and second outlets 58a, 58b are preferably realized at a body portion 50 of the recirculation pump 22.

Preferably, the recirculation lines 30, 40 are configured so that the liquid in the first recirculation line 30 requires a pressure Pl to reach the first region 3a of washing tub 3 which is lower than the pressure P2 required for the liquid in the second recirculation line 40 to reach the second region 3b of the washing tub 3. More preferably, the ducts 33, 43 are configured so that the liquid in the first duct 33 requires a pressure Pl to reach the first region 3a of the washing tub 3 which is lower than the pressure P2 required for a liquid in the second duct 43 to reach the second region 3b of the washing tub 3.

It should be noted that the pressure required for the liquid in the first duct 33 to reach the first region 3 a of the washing tub 3 may vary according to the operational condition of the same first recirculation line 30.

Namely, the pressure required for the liquid in the first duct 33 to reach the first region 3 a of the washing tub 3 while the liquid level inside the washing tub 3 is lower than the position of the terminal nozzle 33a, has a first value Pl which is lower than the value RG of the pressure required for the liquid in the first duct 33 to reach the first region 3 a of the washing tub 3 while the liquid level inside the washing tub 3 is equal or higher than the position of the terminal nozzle 33a.

At the same time, the value P2 of the pressure required for the liquid in the second duct 43 to reach the second region 3b of the washing tub 3 does not vary according to the operational conditions of the first recirculation line 30.

Said pressure value P2 has the same value irrespective of the liquid level inside the washing tub 3.

In any case, and according to the invention, said pressure values Pl, RG for the liquid in the first duct 33 are lower than the pressure value P2 for the liquid in the second duct 43.

According to the preferred embodiment illustrated herein, the first duct 33 preferably defines a first volume V 1. The first volume VI is closely related to the size of the first duct 33 and preferably depends on diameter and length of the same. Analogously, the second duct 43 preferably defines a second volume V2. The second volume V2 is closely related to the size of the second duct 43 and preferably depends on diameter and length of the same.

According to the spatial arrangement of the components of the recirculation system 20, in particular the position of the recirculation pump 22 and the layout of the ducts 33, 43, the first volume VI defined by the first duct 33 is lower than the second volume V2 defined by the second duct 43.

The first duct 33 preferably comprises a first pipe connecting the first outlet 58a to the lower region 3a of the washing tub 3. The second duct 43 preferably comprises a second pipe, substantially having the same diameter of the first pipe but much longer than the first pipe, connecting the second outlet 58b to the upper region 3b of the washing tub 3.

Preferably, in such a case, the recirculation lines 30, 40 are configured so that the liquid in the first recirculation line 30 requires a pressure Pl to fill the first volume VI and then to reach the first region 3 a of washing tub 3 which is lower than the pressure P2 required for the liquid to fill the second volume V2 in the second recirculation line 40 and to reach the second region 3b of the washing tub 3.

More preferably, in such a case, the ducts 33, 43 are configured so that the liquid in the first duct 33 requires a pressure Pl to fill the first volume VI and then to reach the first region 3a of washing tub 3 which is lower than the pressure P2 required for the liquid to fill the second volume V2 in the second duct 43 and to reach the second region 3b of the washing tub 3.

In different embodiments, ducts of the recirculation system may be differently configured to achieve the same effect.

For example, the first and the second duct may have the same volume but extending at different heights.

According to an advantageous aspect of the invention, the recirculation pump 22 comprises a bi-directional pump operable in a first direction of rotation Rl and in a second direction of rotation R2 opposite to the first direction Rl.

It has to be noted that saying that the recirculation pump 22 is operable in a first direction of rotation Rl means that the impeller 23a is rotatable in the first direction of rotation Rl and saying that the recirculation pump 22 is operable in a second direction of rotation R2 opposite to the first direction Rl means that the impeller 23a is rotatable in the second direction of rotation R2 opposite to the first direction Rl.

According to an advantageous aspect of the invention, therefore, the impeller 23 a may be rotated in the first direction of rotation Rl and in the second direction of rotation R2 opposite to the first direction Rl.

The two directions Rl and R2 are depicted in particular in Figures 4 and 7.

According to an advantageous aspect of the invention, the recirculation pump 22 is operated in the first direction Rl to circulate liquid in the first duct 33 through the first outlet 58a to reach the washing tub 3 and is operated in the second direction R2 to circulate liquid in the second duct 43 through the second outlet 58b to reach the washing tub 3.

In other words, preferably, the impeller 23a is rotated in the first direction Rl to circulate liquid in the first duct 33 through the first outlet 58a to reach the washing tub 3 and is rotated in the second direction R2 to circulate liquid in the second duct 43 through the second outlet 58b to reach the washing tub 3.

As illustrated in Figure 7, the pump chamber 23, the impeller 23 a, first and second outlets 58a, 58b are shaped so that when the impeller 23a rotates in the first direction Rl the liquid forced by the impeller 23a itself principally meets the first outlet 58a and, vice versa, when the impeller 23a rotates in the second direction R2 the liquid forced by the impeller 23 a itself principally meets the second outlet 58b.

Preferably, the recirculation pump 22 is operated in the first direction Rl to circulate liquid only in the first duct 33 through the first outlet 58a to reach the washing tub 3.

When the recirculation pump 22 is operated in the first direction Rl, the liquid circulates in the first duct 33 and is sprayed inside the washing tub 3 through the terminal nozzle 33a, more preferably sprayed inside the sump 15.

Advantageously, during the washing cycle when the liquid needs to be re admitted to the bottom region 3 a of the washing tub 3, for example for the mixing and/or the dissolution of the products, the recirculation pump 22 is operated in the first direction Rl .

In a preferred embodiment of the invention, the bi-directional recirculation pump 22 comprises a fixed speed pump and is therefore preferably operated in the first direction Rl at a predetermined first fixed speed SI.

In a further preferred embodiment of the invention, the bi-directional recirculation pump 22 comprises a variable speed pump and may be operated in the first direction Rl either at a predetermined first fixed speed Sl or at a speed sl varying over time. In the latest, the liquid is preferably re-admitted to the bottom region 3a of the washing tub 3 at a variable speed. Said variation of speed causes a respective variation of the flow rate of the liquid circulating in the first duct 33. In turn, the liquid is sprayed inside the sump 15 through the terminal nozzle 33a at variable intensity. This advantageously enhances mixing and/or dissolution of the products.

In a preferred embodiment, the first speed sl of the recirculation pump 22 in the first direction Rl varies according to a step function.

In a further preferred embodiment, the first speed sl of the recirculation pump 22 in the first direction Rl varies according to a continuous function.

When the recirculation pump 22 is operated in the second direction R2, the liquid circulates in the second duct 43 and sprayed inside the washing tub 3 through the terminal nozzle 43 a, more preferably sprayed over the laundry inside the washing drum 4. Advantageously, when the liquid needs to be re-admitted to the upper region 3b of the washing tub 3, preferably to soak the laundry, the recirculation pump 22 is operated in the second direction R2.

In a preferred embodiment of the invention, the bi-directional recirculation pump 22 comprises a fixed speed pump and is therefore preferably operated in the second direction R2 at a predetermined second fixed speed S2.

Preferably, the first fixed speed Sl of the recirculation pump 22 in the first direction Rl is higher than the second fixed speed S2 of the recirculation pump 22 in the second direction R2.

In a further preferred embodiment of the invention, the bi-directional recirculation pump 22 comprises a variable speed pump and may be operated in the second direction R2 either at a predetermined second fixed speed S 2 or at a second speed s2 varying over time.

In a preferred embodiment, the second speed s2 of the recirculation pump 22 in the second direction R2 varies according to a step function.

In a further preferred embodiment, the second speed s2 of the recirculation pump 22 in the second direction R2 varies according to a continuous function.

The second speed s2 is advantageously varied to control the flow direction of the liquid leaving the terminal nozzle 43 a and sprayed over the laundry and therefore to control the liquid distribution over the laundry. Functioning of the laundry washing machine 1 by varying the second speed s2 of the recirculation pump 22 in the second direction R2 is exemplary described with reference to Figure 8.

If the recirculation pump 22 is operated in the second direction R2 at a low speed s2i_ow, the liquid in the second recirculation line 40 is pumped at a corresponding low flow rate. The liquid L leaves the terminal nozzle 43a of the second duct 43 and shows a first course so that it is sprayed onto the laundry at the near side in front of the washing drum 4 (as indicated with line Lf in Figure 8).

If the recirculation pump 22 is operated in the second direction R2 at a medium speed s2_med, the liquid in the second recirculation line 40 is pumped at a corresponding medium flow rate. The liquid L leaves the terminal nozzle 43a of the second duct 43 and shows a second course so that it is sprayed onto the laundry at the centre of the washing drum 4 (as indicated with line Mf in Figure 8).

If the recirculation pump 22 is operated in the second direction R2 at a high speed s2_high, the liquid in the second recirculation line 40 is pumped at a corresponding high flow rate. The liquid L leaves the terminal nozzle 43a of the second duct 43 and shows a third course so that it is sprayed onto the laundry at the far side of the washing drum 4 (as indicated with line Hf in Figure 8).

From the above, it follows that the proposed solution advantageously enables the control of the flow direction of the liquid over the laundry as a function of the speed pump s2 in the second direction R2 assuring the optimal liquid distribution over the laundry.

In a preferred embodiment of the invention, the second speed s2 varies according to a step function which assumes said three discrete values s2i_ow, s2_medmm and s2high.

In a further preferred embodiment of the invention, the second speed s2 may be varied continuously between a minimum value, for example equal to s2i_ow, and a high value, for example s2_high, and the liquid L leaving the terminal nozzle 43 a shows corresponding courses from the near side in front of the washing drum 4 (line Lf in Figure 8) to the far side of the washing drum 4 (line Hf in Figure 8). According to a preferred embodiment of the invention, the recirculation pump 22 is operated at the desired speed continuously over time, either in the first direction Rl or in the second direction R2, as illustrated in Figure 9A where first fixed speed Sl and second fixed speed S2 are depicted. According to a further preferred embodiment of the invention, the recirculation pump 22 is operated so that its speed has a pulsed waveform Spl having a proper duty cycle Dl, as illustrated in figure 10A. The pulsed waveform Spl is preferably an on-and-off signal, wherein the recirculation pump 22 is opportunely switched on and off. The pulsed waveform Spl therefore preferably comprises a train of pulses.

The speed of the recirculation pump 22, either in the first direction Rl or in the second direction R2, is preferably varied by correspondingly varying the duty cycle. For example, the speed Sp2 of the recirculation pump 22 may be increased by increasing the respective duty cycle, as illustrated in Figure 10B.

As known, the duty cycle is the fraction of one period in which a system is active. In the present invention, the duty cycle is the fraction of one period in which the recirculation pump is switched on.

According to a further preferred embodiment of the invention, the speed of the recirculation pump 22, either in the first direction Rl or in the second direction R2, has a pulsed waveform. In this case, the recirculation pump 22 is operated so that its speed has a pulsed waveform Spl’ comprising a train of pulses different one to the other, as illustrated in Figure 11 A.

The speed of the recirculation pump 22, either in the first direction Rl or in the second direction R2, is preferably varied by correspondingly varying the shape of the pulses. For example, the speed Sp2’ of the recirculation pump 22 may be increased by increasing the duration of each pulse, as illustrated in Figure 1 IB.

It can be appreciated that the two recirculation lines of the recirculation system according to the invention can be easily controlled by means of a single recirculation pump opportunely operated as described above. Advantageously, the liquid is selectively circulated through the first duct 33 or the second duct 43, while the recirculation system 20 does not require any valve as in the known system.

The laundry washing machine according to the invention has therefore a simplified structural constmction with respect to the known laundry washing machines. Reliability is therefore increased and manufacturing and/or maintenance time and costs are reduced.

According to an advantageous aspect of the invention, due to the fact that the ducts 33, 43 are configured so that the liquid in the first duct 33 requires a pressure Pl to reach the first region 3a of the washing tub 3 which is lower than the pressure P2 required for a liquid in the second duct 43 to reach the second region 3b of the washing tub 3 it is possible to bring the first speed Sl, sl of the recirculation pump 22 in the first direction Rl at high values to improve mixing and/or dissolution. For the same reason, while the recirculation pump 22 is rotated in the first direction Rl, the liquid does not flow through the second duct 43 and preferably only the mixing and/or dissolution effect is guarantee, even at high speed of rotation.

Instead, when the recirculation pump 22 is operated in the second direction R2, liquid circulates mainly in the second duct 43. Therefore, when the recirculation pump 22 is rotated in the second direction R2, the liquid is re-admitted to the upper region 3b of the washing tub 3, preferably to soak the laundry, while a small amount of liquid is (may) also re-admitted to the bottom region 3a of the washing tub 3 through the first recirculation line 30. Nevertheless, re-admission of liquid to the bottom region 3 a of the washing tub 3 is accepted since it does not negatively affect the soaking process.

Figures 12 to 16 show a further preferred embodiment of the invention which differs from the preferred embodiment previously described in the shape of the recirculation pump 122. In the drawings, corresponding characteristics and/or components of the first embodiment previously described are identified by the same reference numbers.

The recirculation system 120 preferably comprises a common recirculation pump 122 for conveying liquid to the first and second recirculation lines 30, 40, more preferably to the first and second ducts 33, 43.

The recirculation pump 122 preferably comprises a pump chamber 123 having an inlet 124 connected to the bottom 3a of the washing tub 3. Inlet 124 of the recirculation pump 122 is preferably connected to the bottom 3a of the washing tub 3 through a suction pipe 32 preferably connected to the filtering device 12. The recirculation pump 122 then preferably has an outlet arrangement 126 for conveying liquid from the pump chamber 123 to the first and second recirculation lines 30, 40.

The pump chamber 123 preferably receives an impeller 123 a apt to be rotated and to force liquid from the pump chamber 123 towards the outlet arrangement 126.

The pump chamber 123 preferably has a substantially cylindrical shape.

The outlet arrangement 126 preferably comprises a first outlet 158a connected to the first duct 33 and a second outlet 158b connected to the second duct 43.

The first outlet l58a preferably comprises a portion of duct which extends obliquely from the pump chamber 123.

The second outlet l58b preferably comprises a portion of duct which extends obliquely from the pump chamber 123.

First and the second outlets (ducts) l58a, 158b are preferably parallel one to the other.

Preferably, first and second outlets l58a, l58b are preferably realized at a body portion 150 of the recirculation pump 122.

According to the advantageous aspect of the invention, the recirculation pump 122 is operated in the first direction Rl to circulate liquid in the first duct 33 through the first outlet l58a to reach the washing tub 3 and is operated in the second direction R2 to circulate liquid in the second duct 43 through the second outlet 158b to reach the washing tub 3.

In other words, preferably, the impeller l23a is rotated in the first direction Rl to circulate liquid in the first duct 33 through the first outlet l58a to reach the washing tub 3 and is rotated in the second direction R2 to circulate liquid in the second duct 43 through the second outlet 158b to reach the washing tub 3.

As illustrated in Figure 16, the pump chamber 123, the impeller 123a, first and second outlets 158a, 158b are shaped so that when the impeller 123a rotates in the first direction Rl the liquid forced by the impeller 123a itself principally meets the first outlet 158a and, vice versa, when the impeller 123a rotates in the second direction R2 the liquid forced by the impeller 123 a itself principally meets the second outlet 158b.

Preferably, the speed of the recirculation pump 122 in the first direction Rl is lower than the speed of the recirculation pump 122 in the second direction R2. Advantageously, all the effects and/or advantages above-mentioned with reference to the first embodiment are achieved.

Figures 17 to 21 show a further preferred embodiment of the invention which differs from the preferred embodiments previously described in the shape of the recirculation pump 222. In the drawings, corresponding characteristics and/or components of the first embodiment previously described are identified by the same reference numbers.

The recirculation system 220 preferably comprises a common recirculation pump 222 for conveying liquid to the first and second recirculation lines 30, 40, more preferably to the first and second ducts 33, 43.

The recirculation pump 222 preferably comprises a pump chamber 223 having an inlet 224 connected to the bottom 3a of the washing tub 3. Inlet 224 of the recirculation pump 222 is preferably connected to the bottom 3 a of the washing tub 3 through a suction pipe 32 preferably connected to the filtering device 12. The recirculation pump 222 then preferably has an outlet arrangement 226 for conveying liquid from the pump chamber 223 to the first and second recirculation lines 30, 40.

The pump chamber 223 preferably receives an impeller 223a apt to be rotated and to force liquid from the pump chamber 223 towards the outlet arrangement 226.

The pump chamber 223 preferably has a substantially cylindrical shape.

The outlet arrangement 226 preferably comprises a common outlet portion 258 from the pump chamber 223 and a bifurcation 260 for the first duct 33 and the second duct 43.

Preferably, common outlet portion 258 and bifurcation 260 are realized at a body portion 250 of the pump recirculation 222. The bifurcation 260 is preferably substantially Y shaped and configured so that the two ducts 33, 43 preferably extend upwardly from the bifurcation 260.

According to the advantageous aspect of the invention, the recirculation pump 222 is operated in the first direction Rl to circulate liquid in the first duct 33 to reach the washing tub 3 and is operated in the second direction R2 to circulate liquid in the second duct 43 to reach the washing tub 3.

In other words, preferably, the impeller 223a is rotated in the first direction Rl to circulate liquid in the first duct 33 to reach the washing tub 3 and is rotated in the second direction R2 to circulate liquid in the second duct 43 to reach the washing tub 3.

Preferably, the speed of the recirculation pump 222 in the first direction Rl is lower than the speed of the recirculation pump 222 in the second direction R2. Advantageously, all the effects and/or advantages above-mentioned with reference to the first embodiment are achieved.

It has thus been shown that the present invention allows all the set objects to be achieved. In particular, it makes it possible to provide a laundry washing machine having a simplified structural construction with respect to the known laundry washing machines. While the present invention has been described with reference to the particular embodiments shown in the figures, it should be noted that the present invention is not limited to the specific embodiments illustrated and described herein; on the contrary, further variants of the embodiments described herein fall within the scope of the present invention, which is defined in the claims.

Claims

1. A laundry washing machine (1) comprising:

- a washing tub (3) external to a washing drum (4) suited to receive the laundry to be washed;

- a water supply system (5) suitable to convey water to said washing tub (3);

- a recirculation system (20; 120; 220) for draining liquid from the bottom (3a) of said washing tub (3) and to re-admit such liquid into a first region (3a) and a second region (3b) of said washing tub (3), said recirculation system (20; 120; 220) comprising:

- a first duct (33) terminating at said first region (3 a) wherein said liquid may circulate to reach said washing tub (3);

- a second duct (43) terminating at said second region (3b) wherein said liquid may circulate to reach said washing tub (3);

characterized in that said recirculation system (20; 120; 220) comprises a recirculation pump (22; 122; 222) operable in a first direction of rotation (Rl) and in a second direction of rotation (R2) opposite to said first direction (Rl), said recirculation pump (22; 122; 222) comprising a pump chamber (23; 123; 223) having an inlet (24; 124; 224) connected to said bottom (3 a) of said washing tub (3) and an outlet arrangement (26; 126; 226) for the connection to said first duct (33) and said second duct (43), wherein said ducts (33, 43) are configured so that a liquid in said first duct (33) requires a pressure (Pl ; R ) to reach said washing tub (3) which is lower than the pressure (P2) required for a liquid in said second duct (43) to reach said washing tub (3), and in that said recirculation pump (22; 122; 222) is operated in said first direction (Rl) to circulate liquid in said first duct (33) to reach said washing tub (3) and is operated in said second direction (R2) to circulate liquid in said second duct (43) to reach said washing tub (3).

2. Washing machine (1) according to claim 1, characterized in that said outlet arrangement (26; 126; 226) comprises a first outlet (58a; l58a) from said pump chamber (23; 123; 223) for said first duct (33) and a second outlet (58b; l58b) from said pump chamber (23; 123; 223) for said second duct (43).

3. Washing machine (1) according to claim 2, characterized in that said first and second outlets (58a, 58b; l58a, l58b) are realized at a body portion (50; 150) of said recirculation pump (22; 122).

4. Washing machine (1) according to claim 2 or 3, characterized in that said first outlet (58a) is tangentially arranged with respect to said pump chamber (23) and/or said second outlet (58b) is tangentially arranged with respect to said pump chamber (23).

5. Washing machine (1) according to any of the claims 2 to 4, characterized in that said first outlet (58a; l58a) is parallel to said second outlet (58b; l58b).

6. Washing machine (1) according to claim 1, characterized in that said outlet arrangement (226) comprises a common outlet portion (258) from said pump chamber (223) and a bifurcation (260) for said first duct (33) and said second duct (43).

7. Washing machine (1) according to claim 6, characterized in that said common outlet portion (258) and said bifurcation (260) are realized at a body portion (250) of said recirculation pump (222).

8. Washing machine (1) according to any of the preceding claims, characterized in that said recirculation pump (22; 122; 222) is a fixed speed pump.

9. Washing machine (1) according to any of the claims 1 to 7, characterized in that said recirculation pump (22; 122; 222) is a variable speed pump.

10. Washing machine (1) according to any of the preceding claims, characterized in that said first region (3 a) is a bottom part (3 a) of said washing tub (3).

11. Washing machine (1) according to any of the preceding claims, characterized in that said second region (3b) is an upper part (3b) of said washing tub (3).

12. Washing machine (1) according to any of the preceding claims, characterized in that said first duct (33) defines a first volume (VI) and said second duct (43) defines a second volume (V2), wherein said first volume (VI) is lower than said second volume (V2).

13. A method for operating a laundry washing machine (1) comprising:

- a water supply system (5) suitable to convey water to said washing tub (3);

- a recirculation system (20; 120; 220) for draining liquid from the bottom (3a) of said washing tub (3) and to re-admit such liquid into a first region (3a) and a second region (3b) of said washing tub (3), said recirculation system (20; 120; 220) comprising: - a first duct (33) terminating at said first region (3 a) wherein said liquid may circulate to reach said washing tub (3);

- a recirculation pump (22; 122; 222) operable in a first direction of rotation (Rl) and in a second direction of rotation (R2) opposite to said first direction (Rl), said recirculation pump (22; 122; 222) comprising a pump chamber (23; 123; 223) having an inlet (24) connected to said bottom (3 a) of said washing tub (3) and an outlet arrangement (26; 126; 226) for the connection to said first duct (33) and said second duct (43), wherein said ducts (33, 43) are configured so that a liquid in said first duct (33) requires a pressure (Pl ; R ) to reach said washing tub (3) which is lower than the pressure (P2) required for a liquid in said second duct (43) to reach said washing tub (3);

wherein said recirculation pump (22; 122; 222) is operated in said first direction (Rl) to circulate liquid in said first duct (33) to reach said washing tub (3) and is operated in said second direction (R2) to circulate liquid in said second duct (43) to reach said washing tub (3).

14. A method according to claim 13, characterized in that said recirculation pump (22; 122; 222) is operated in said first direction (Rl) to circulate liquid only in said first duct (33).

15. A method according to claim 13 or 14, characterized in that said recirculation pump (22; 122; 222) is operated in said second direction (R2) to circulate liquid mainly in said second duct (43).