FR3143380A1 - Filtration unit for filtering microplastics - Google Patents

Abstract

Filtration unit for filtering microplastics One aspect of the invention relates to a filtration unit for filtering microplastics present in wash water comprising a screen, a brush connected to a motor, in which, when the motor is in operation, the brush is rotated by the motor so as to be in contact with a surface of the sieve to brush it. Figure to be published with the abstract: Figure 1

Description

Filtration unit for filtering microplastics TECHNICAL FIELD OF THE INVENTION

The technical field of the invention is that of filters for washing machines, in particular filters for microplastics.

In particular, the invention relates to a self-cleaning microplastic filter for a washing machine.

TECHNOLOGICAL BACKGROUND OF THE INVENTION

The term “microplastics” (or “plastic microfibres”) refers to small solid particles of plastic, generally between 1 micrometre and 5 millimetres in size, which are insoluble in water and are not biodegradable on a human scale. Microplastics have become a concern because they are found in soil, drinking water systems, bodies of water (oceans, seas, lakes, etc.), as well as in certain foods. A European would ingest the equivalent in weight of a credit card of plastic every week.

In particular, the amount of microplastics in the oceans is currently estimated at 14.4 million tonnes, of which 35% comes from synthetic textiles, which release large quantities of plastic fibres into laundry water, for example polyester, acrylic, nylon or elastane fibres.

To combat this phenomenon, some countries are starting to take measures. In France in particular, an "anti-waste law for a circular economy" was passed in 2020 and includes an obligation for manufacturers of washing machines (or "washing machines", subsequently simply called "washing machines") to install a microplastic filter, internal or external to the machine, to prevent their dispersion, for any new machine placed on the market from ^January 1, 2025.

Some washing machine manufacturers have already started to design washing machines with integrated filters for microplastics. For example, there are washing machines with a filter located in the detergent drawer, which captures microfibres during the washing cycles of synthetic clothes. The filter needs to be changed regularly, which is costly and inconvenient for the user, and generates waste.

There are also "external" filters, mainly in the form of cylindrical sieves through which the water passes at the washing outlet, before reaching the water evacuation circuit through which it is directed to the wastewater network. An "external" filter is understood to mean a filter placed outside the drum of the washing machine, for example at the water outlet, upstream of the evacuation pipe to the wastewater circuit. These filters need to be cleaned regularly by hand, by removing the fibres accumulated on the wall of the sieve, to prevent it from becoming completely clogged. This cleaning should of course not be done by simply "washing" the filter, as the fibres would end up dispersed in the wastewater circuit. For such filters, cleaning the filter therefore remains restrictive for the user, and requires that the user remains vigilant about its state of fouling so as not to compromise the evacuation of water and the effectiveness of the filter in capturing microplastics.

Other solutions exist, for example devices to be placed in the drum of the machine before starting a washing cycle, which mechanically retain the fibres that come off the textiles. However, their effectiveness is generally less than external filters, and these devices also need to be cleaned by hand, manually removing the fibres accumulated inside. These devices therefore suffer from the same drawbacks as those mentioned above.

There is therefore a need for microplastic filters for washing machines that are both effective and easy for the user to clean.

The invention improves the situation.

The invention offers a solution to the problems mentioned above, by proposing a microplastic filtration unit for washing water integrating a simple and effective self-cleaning system.

• un boîtier définissant un volume ;
• un tamis séparant le volume en une chambre de réception d’eau non filtrée et une chambre de réception d’eau filtrée, le tamis comprenant une surface interne dirigée vers la chambre de réception d’eau non filtrée et une surface externe dirigée vers la chambre de réception d’eau filtrée ;
• une brosse située dans la chambre de réception d’eau non filtrée ;
• un moteur placé dans un compartiment situé dans la chambre de réception d’eau non filtrée et relié à la brosse pour l’entraîner en rotation ;
• un orifice d’entrée traversant le boîtier en débouchant dans la chambre de réception d’eau non filtrée ;
• un orifice de sortie traversant le boîtier depuis la chambre de réception d’eau filtrée ; et
• un orifice d’évacuation de microplastiques traversant le boîtier depuis la chambre de réception d’eau non filtrée ;

A first aspect of the invention thus relates to a filtration unit for filtering microplastics present in washing water leaving a washing machine, which may comprise:

• a box defining a volume;
• a screen separating the volume into an unfiltered water receiving chamber and a filtered water receiving chamber, the screen comprising an inner surface facing the unfiltered water receiving chamber and an outer surface facing the filtered water receiving chamber;
• a brush located in the unfiltered water receiving chamber;
• a motor placed in a compartment located in the unfiltered water receiving chamber and connected to the brush to drive it in rotation;
• an inlet opening passing through the housing and opening into the unfiltered water receiving chamber;
• an outlet port passing through the housing from the filtered water receiving chamber; and
• a microplastic discharge port passing through the housing from the unfiltered water receiving chamber;

wherein, when the motor is operating, the brush is rotated by the motor so as to be in contact with the internal surface of the screen to brush it.

It is noted that in the following, the inlet port is also called “unfiltered wash water inlet port” and the outlet port is also called “filtered wash water outlet port”.

By "sieve" is meant any filter element capable of retaining elements of the flow passing through it. Thus, a filtration membrane can also be used as a sieve according to the present invention.

When wash water flows through the filtration unit from the inlet to the outlet, the wash water is filtered through the sieve. By “filtered” it is understood that the sieve retains microplastics present in the wash water entering the filtration unit. Of course, it is possible that other microparticles are also retained by the sieve, and it is possible that microplastics (e.g. having a dimension smaller than holes or pores in the sieve) are not retained by the sieve. Thus, in the following “filtered water” simply means water that has passed through the sieve of the filtration unit, in which microplastics may possibly remain. Similarly “unfiltered water” means water that has not yet passed through the sieve of the filtration unit.

By "unfiltered water receiving chamber" is meant the part of the volume located upstream of the sieve, in which unfiltered water is caused to circulate. Similarly, by "filtered water receiving chamber" is meant the part of the volume located downstream of the sieve, in which filtered water is caused to circulate.

As unfiltered wash water passes through the sieve, microplastic particles accumulate on the surface of the sieve, more precisely on the surface facing the unfiltered water receiving chamber. Thanks to the filter unit according to the invention, it is possible to clean this surface of the sieve in a simple manner, thanks to the brush connected to the motor. When the motor is actuated, the brush starts rotating and cleans the dirty surface of the sieve by brushing it. The microplastics are then dislodged from the surface of the sieve.

In one or more embodiments, the motor may drive the brush to rotate about an axis of rotation orthogonal to the internal surface of the screen.

In one or more embodiments, the axis of rotation passes through a center of the inner surface of the sieve.

In one or more embodiments, an assembly formed of the compartment and the motor disposed within the compartment may be at least partially covered with a sealing layer.

In fact, the motor is located inside the housing, and can therefore be at least partially submerged under the washing water. Thanks to the sealing layer, the motor is protected from contact with water.

Alternatively or in addition, a motor specifically designed to be submerged can be used.

In one or more embodiments, the housing includes an inner surface, and the screen has dimensions similar to dimensions of a section of the inner surface of the housing. The screen may be press-fit against said section of the inner surface of the housing.

Alternatively, an internal face of the housing may comprise at least one rim and at least one tab, the screen being held in contact with the at least one rim by the at least one retaining tab.

In particular, the housing may comprise a tank and a lid closing the tank, an inner face of the lid may comprise at least one retaining tab, and an inner face of the tank may comprise at least one rim. When the lid is positioned so as to close the tank, the screen may be held in abutment on the at least one rim by the at least one retaining tab.

Thus, the sieve is easily accessible by removing the tank cover, and can be easily removed for cleaning, repair or replacement. This makes maintenance of the filtration unit easier.

Advantageously, the inlet port is adapted to be connected via an inlet tube to a washing machine drain pipe, wherein the outlet port is adapted to be connected via an outlet tube to a waste water drain.

The term "drain hose" means a hose for draining wash water from the drum of the washing machine. In conventional washing machines, this drain hose is directly connected to the waste water outlet. According to the invention, it is connected to the filter unit via the inlet.

“Wastewater disposal” means any system for recovering wastewater, for example, disposal to a separate sewer or to a combined sewer.

In one or more embodiments, the microplastic discharge port is located opposite the brush in the unfiltered water receiving chamber.

This means that microplastics, once dislodged from the filter unit screen during cleaning, can be drawn by gravity towards the microplastic discharge port. This avoids the need for an additional mechanism to recover microplastics dislodged from the screen.

In one or more embodiments, the housing includes an inner surface extending between the screen and the microplastic discharge port. The inner surface portion may have a flared shape having a characteristic dimension of a section decreasing from the screen toward the microplastic discharge port.

Again, this helps direct microplastics dislodged from the sieve towards the microplastic discharge port, making them easier to recover later.

In particular, the internal surface may be a surface of revolution of circular section, in which the characteristic dimension is equal to the diameter or the radius of said circular section.

It is understood that the internal surface may have asperities and discontinuities relative to a surface of revolution (in particular at the level of the orifices or the compartment receiving the engine), but the “overall” shape (not taking into account these asperities) of the internal surface is a surface of revolution.

Among these embodiments, the screen may be circular in shape, the brush may comprise a portion extending longitudinally from a first free end to a second free end, the second end of the motor being symmetrical to the first end relative to an axis of rotation of the motor, the axis of rotation of the motor being transverse to the portion of the brush, the portion of the brush having a length less than or equal to a diameter of said portion of the screen.

Alternatively, the screen may be circular in shape, the brush may comprise a portion extending longitudinally from a free end to an axis of rotation of the motor, the axis of rotation of the motor being transverse to the portion of the brush, the portion of the brush having a length less than or equal to a radius of said portion of the screen.

• un tambour ;
• un circuit d’eau comprenant un tuyau d’arrivée d’eau pour faire entrer de l’eau dans le tambour et un tuyau de sortie d’eau pour faire sortir de l’eau du tambour ;
• une unité de filtration définie précédemment ;

Another aspect of the invention relates to a washing machine incorporating a filtration unit defined above. Such a washing machine may comprise:

• a drum;
• a water circuit comprising a water inlet pipe for supplying water to the drum and a water outlet pipe for supplying water to the drum;
• a previously defined filtration unit;

wherein the inlet of the filtration unit is connected to the water outlet pipe of the washing machine;

the washing machine further comprising a drain hose for discharging water to a waste water circuit, the outlet port of the filtration unit being connected to the drain hose.

In this aspect, the filtration unit is “internal” to the washing machine, that is, it is integrated into a casing (or housing) of the washing machine.

The washing machine may further comprise a microplastic recovery compartment connected to the microplastic discharge port of the filtration unit.

This means that microplastics from the wash water are easily recovered.

• une machine à laver comprenant :
  • un tambour ;
  • un circuit d’eau comprenant un tuyau d’arrivée d’eau pour faire entrer de l’eau dans le tambour et un tuyau de vidange pour faire sortir de l’eau du tambour et l’évacuer vers un circuit d’eaux usées ;
• une unité de filtration comme définie précédemment externe à la machine à laver ;

Another aspect of the invention relates to a system which may comprise:

• a washing machine comprising:
  • a drum;
  • a water circuit comprising a water inlet pipe for supplying water to the drum and a drain pipe for supplying water to the drum and a waste water circuit;
• a filtration unit as previously defined external to the washing machine;

wherein the inlet of the filtration unit is connected, directly or via an additional device, to the drain pipe of the washing machine and the outlet of the filtration unit is connected to a water discharge pipe to a waste water circuit.

By “external” it is meant that the filtration unit is outside the washing machine casing. Thus, the filtration unit can be connected to any existing washing machine.

By “directly” it is understood that the drain pipe is connected to the inlet of the filtration unit without any intermediate device or circuit.

By “via an additional device” it is understood that there may be, between the drain hose and the inlet of the filtration unit, a device which may have its own water circuit, for example a pre-filter positioned between the drain hose of the washing machine and the inlet of the filtration unit, so as to capture larger particles present in the washing water which could damage the microplastic filtration unit.

The system may further include a microplastics recovery compartment connected to the microplastics discharge port of the filtration unit.

This means that microplastics from the wash water are easily recovered.

One aspect of the invention thus relates to a method for filtering microplastics present in washing water leaving a washing machine using a filtration unit as defined above, said filtration unit being external to the washing machine; in which the washing machine comprises a drum and a water circuit comprising a water inlet pipe for bringing water into the drum and a drain pipe for bringing water out of the drum and discharging it to a waste water circuit; in which the inlet port of the filtration unit is connected to the drain pipe of the washing machine and the outlet port of the filtration unit is connected to a water discharge pipe to a waste water circuit; in which during a laundry washing cycle, the discharge port is closed and the motor is stopped, and washing water enters the filtration unit via the inlet port and exits the filtration unit via the outlet port.

Another aspect of the invention relates to a method of cleaning a microplastic filtration unit as defined above, in which the inlet port is closed and the outlet port is open, a cleaning portion of the brush is in contact with a surface of the screen located towards the unfiltered water receiving chamber, and the motor is operated to drive the brush in rotation so as to be in contact with a surface of the screen to brush it.

The invention and its various applications will be better understood by reading the description which follows and by examining the figures which accompany it.

BRIEF DESCRIPTION OF THE FIGURES

Other features and advantages of the invention will become apparent upon reading the description, which can be read in conjunction with the figures. These figures are provided for information purposes only and are in no way limiting of the invention.

There represents a filtration unit according to one embodiment of the invention;

, Figures 2a and 2b show examples of brushes according to different embodiments of the invention;

There represents a system comprising a washing machine and a filtration unit 100 according to one embodiment of the invention;

, Figures 4a and 4b show the filtration unit according to the embodiment of the , in two different operating modes;

There represents a valve system for the filtration unit according to one embodiment of the invention;

There represents a flowchart of a method of controlling the valves and the motor according to an embodiment of the invention;

There represents a method of using a filtration unit 100 according to an embodiment of the invention;

, , Figures 8a, 8b and 8c show different views of a housing of the filtration unit according to one embodiment of the invention;

There represents a motor receiving chamber, the motor and a sealing layer according to one embodiment of the invention.

DETAILED DESCRIPTION

There represents a filtration unit according to one embodiment of the invention.

The filtration unit 100 is intended to be connected to a wash water outlet (water leaving the drum of the washing machine during and after a wash cycle) to filter microplastics present in this water, called “wash water”. Thus, “unfiltered” wash water enters the filtration unit 100, is filtered by the filtration unit 100, and exits the filtration unit 100 in the form of “filtered” wash water. By “filtered”, it is simply understood that the wash water has passed through the filtration unit 100.

As shown in the , the filtration unit 100 comprises a housing 1 defining a volume inside the housing. The housing 1 may consist of a single element (one-piece housing), or may consist of several elements. In particular, the housing 1 may comprise a tank 1a and a cover 1b for closing the tank. For example, the cover 1b may be screwed onto the tank 1a or may be tightly mounted onto the tank 1a. When the housing 1 consists of several elements, the parts inside the housing (in particular the screen 2) are more easily accessible and can be repaired, cleaned or changed, which increases the service life of the filtration unit 100 and limits the amount of waste generated.

The filtration unit 100 also comprises a sieve 2. This sieve 2 advantageously separates the volume inside the housing 1 into two spaces: a chamber 3 for receiving unfiltered water (i.e. a portion of the volume intended to receive unfiltered washing water) and a chamber 4 for receiving filtered water (i.e. a portion of the volume intended to receive washing water filtered by the sieve). Preferably, the sieve 2 extends over a complete section of the housing 1, so that all the washing water that enters the filtration unit 100 (into the chamber 3 for receiving unfiltered water) passes through the sieve 2 to be filtered (and therefore reach the chamber 4 for receiving filtered water). For example, as shown in the on which the space is represented by an orthogonal reference (X,Y,Z), if the filtration unit 100 extends along a longitudinal axis Y, the sieve can extend over an entire section of the housing 1 along a plane parallel to the plane (X,Z).

It is recalled that a sieve has a network structure, like a grid, which mechanically blocks elements larger than the size of the holes in this grid. The use of a sieve to filter microplastics is particularly suitable, because microplastics are solid fibers that are not likely to deform to pass through the holes.

As an alternative to a sieve 2, a membrane can be used. It is recalled that a membrane corresponds to a layer of porous material allowing water to pass through as well as elements small enough to pass through the pores. A defect associated with the use of a membrane is that it will allow part of the liquid to pass through (called "permeate") which will be largely filtered, but another part of the liquid (called "concentrate") will never be able to pass through and will concentrate all the microparticles. Thus, microplastics risk concentrating in the concentrate, which is never filtered.

Various materials may be used for the sieve 2, for example nylon or polycarbonate. The size of the holes in the sieve 2 must be adapted to the filtration of microplastics, and may be for example between 20 µm and 200 µm, preferably between 50 µm and 120 µm. The threads of the sieve 2 may be monofilament or multifilament, but multifilament threads are preferred because monofilament threads are more vulnerable to chemical compositions and break more easily than multifilament threads.

Furthermore, instead of a single sieve 2, several superimposed sieves can be used (principle of the multi-layer filter, which are therefore composed of several filtration layers, traditionally having different porosities – for example sieves having smaller holes as one approaches the chamber 4 receiving filtered water). For example, it is possible to use a filter having a triple-layer weave.

In some embodiments, the sieve 2 may have dimensions equal to the dimensions of a section of the volume inside the housing, and may be, for example, force-fitted inside the housing 1 to thereby delimit the chamber 3 for receiving unfiltered water and the chamber 4 for receiving filtered water. For example, the housing may have a general shape of a surface of revolution, i.e. a surface that is invariant about a fixed axis. In the example of the , the housing 1 has a general shape (without taking into account orifices or possible connectors) of a surface of revolution with an axis of rotation Y, having successive sections along planes parallel to the plane (X,Z) of circular shape. More precisely, the housing 1 has an internal surface defined by the internal walls of the housing, this internal surface having successive sections along planes parallel to the plane (X,Z) of circular shape. In this example, the sieve may be a disk having a diameter equal to the diameter of a section of the internal surface along a plane parallel to the plane (X,Z). Advantageously, in certain embodiments, the housing has a flared shape (as in the example of the ) and the diameter of the successive sections of the internal surface of the housing along planes parallel to the plane (X,Z) decreases from the section which receives the sieve 2 in a direction opposite to that of the chamber 3 for receiving filtered water (in other words, the diameter of these sections decreases from the sieve 2 in a direction opposite to the Y axis shown in the figure). ). Thus, when the sieve is force-inserted, the flared shape of the housing 1 prevents the sieve from sliding towards the bottom of the housing and holds it in position.

Of course, the above embodiments are not limited to a housing having the overall shape of a surface of revolution, nor to sections and a sieve 2 of circular shape. The shape of the sections can be any, and the sieve 2 can also have any shape corresponding to the shape of a section of the internal surface of the housing 1.

In other embodiments, the housing 1 (or more precisely the internal surface of the housing 1) comprises an internal rim 5 and the screen 2 can be placed on this internal rim 5 and supported by it. The internal rim can be a rim extending all around a section of the internal surface of the housing 1. For example, if the internal surface has a circular shape, the internal rim 5 can have the shape of a ring having a certain thickness - which must have dimensions sufficiently small compared to the section of the internal surface, so as not to excessively reduce the surface through which the water circulates from the chamber 3 for receiving unfiltered water to the chamber 4 for receiving filtered water. Alternatively, there can be a plurality of rims in the form of tabs extending from the surface of the housing 2 towards the interior of the housing 1, all located at the same height, so as to be able to place the screen 2 thereon.

In these embodiments, in order to prevent the sieve 2 from being moved, for example, by the circulation of water during filtration of the washing water by the filtration unit 100 or by the pressure exerted by the brush 7 during cleaning of the sieve 2, one or more retaining tabs 6 may be provided. For example, these retaining tabs 6 may extend from the inner surface of the upper part of the housing (i.e. the part of the housing located “above” the sieve, i.e. on the side of the filtered water receiving chamber 4) towards the sieve 2, in order to block the sieve 2 between the internal rim 5 and the retaining tab(s) 6. Such retaining tabs may of course also be used in the embodiments where the sieve 2 is force-fitted inside the housing 1.

In advantageous embodiments, the housing 1 comprises a tank 1a and a cover 1b closing the tank, the tank 1b comprises an internal rim 5, the cover comprises at least one retaining tab 6 and the sieve is placed on the internal rim 5 and held in position by the retaining tab(s) 6. Thus, when the cover 1b is removed, the retaining tabs 6 cease to bear on the sieve 2, which can be easily removed to, for example, be cleaned by hand, repaired or replaced with a new sieve. Maintenance of the filtration unit 100 is thus simplified.

The filtration unit 100 also comprises a brush 7 connected to a motor 8. The brush 7 and the motor 8 are arranged in the unfiltered water receiving chamber 3, since the brush 7 is intended to be used to brush the surface of the sieve 2 on which the microplastics (and possibly other bodies, for example microfibers of a material other than plastic) are deposited when the washing water is filtered, i.e. circulates from the unfiltered water receiving chamber 3 to the filtered water receiving chamber 4 through the sieve 2. The brush 7 is therefore arranged so as to be able to brush the surface of the sieve 2 located towards the unfiltered water receiving chamber 3, called the internal surface of the sieve 2.

The brush 7 may have any shape and typically comprises bristles (i.e. filaments or tufts of filaments) made of any material, in particular vegetable, animal, metallic or synthetic, these bristles being fixed on a brush support. The brush 7 may be connected to the motor 8 at one or more locations on the brush support, for example at its center or at one of its ends, via a transmission shaft 9. When the motor 8 is in operation, the transmission shaft 9 drives the brush 7 in rotation about an axis perpendicular to the internal surface of the sieve 2 (i.e. on the , around the Y axis). The brush 7 can be in contact with the internal surface of the sieve permanently (i.e. while the filtration unit 100 is used to filter the wash water and during cleaning of the sieve 2), or only during cleaning of the sieve 2. In the latter case, the brush 2 is located in the chamber 3 for receiving unfiltered water but without being in contact with the internal surface of the sieve 2 (on the , this means that the brush can extend on a plane parallel to the plane (X,Y) located "below" - i.e. in the direction opposite to Y - of the plane of the sieve 2) when the filtration unit is used to filter wash water. A mechanism (for example, a telescopic transmission shaft 9) can allow, when cleaning of the sieve 2 is to be carried out, to translate the brush 7 in the Y direction to make it come into contact with the internal surface of the sieve 2. Once the brush 7 is in contact with the internal surface of the sieve 2, the motor 8 can be put into operation to rotate the brush 7.

To accommodate the motor 8, the housing may comprise a compartment 10 in which the motor 8 is positioned. This compartment 10, located upstream of the sieve 2 (i.e. in the part of the volume of the housing 1 corresponding to the chamber 3 for receiving unfiltered water) may also comprise a cable passage hole for passing the power cables of the motor 8, as shown in Figures 8a, 8b and 8c.

, , Figures 8a, 8b and 8c show different views of a housing of the filtration unit according to one embodiment of the invention.

In the example of Figures 8a, 8b and 8c, the housing comprises a tank 1a and a cover 1b for closing the tank, and Figures 8a, 8b and 8c show the tank 1a of the housing. Of course, the example can be extended to the case where the housing is formed from a single block.

As shown in these Figures 8a, 8b and 8c, the housing 1 comprises a compartment 10 for receiving the motor 8, and a cable passage hole 14 passing through the housing 1 from the compartment 10 for passing cables, in particular the power supply cable(s) of the motor 8.

Preferably, the compartment 10 for receiving the motor 8 has dimensions corresponding to the dimensions of the motor 8, that is to say that the compartment 10 is designed so that, when the motor 8 is positioned in the compartment 10, the residual space between the internal walls of the compartment 10 and the motor 8 is reduced to a minimum. This makes it possible to prevent too much water from infiltrating between the internal walls of the compartment 10 and the motor 8, and from risking damaging the latter. Furthermore, as shown in the , to further minimize the risk of water infiltrating the compartment 10 and “flooding” the motor, a sealing layer 15 may be provided to fill the remaining volume between the motor 8 and the internal volume of the compartment 10 for receiving the motor 8. In these embodiments, the height of the compartment 10 receiving the motor 8 is greater than or equal to the height of the motor 8 (preferably slightly greater). This optional sealing layer 15 may be made of any waterproof material, for example wax or an elastomeric material, such as silicone or rubber.

Furthermore, it is possible, in order to avoid any problem due to possible contact between the motor 8 and water circulating in the filtration unit, it is possible to use a motor 8 designed to withstand immersion, such as is found for example in boats or other devices intended for aquatic environments.

, Figures 2a and 2b show examples of brushes according to different embodiments of the invention.

On the example of the , the brush 7 comprises bristles 7a mounted on a brush body 7b. The brush body 7b is connected at its center to the transmission shaft 9. The brush body 7b has, in this example, a rectangular parallelepiped shape. The length L of the brush body 7b is such that the brush can rotate inside the housing when cleaning the screen 2 is carried out. For example, if the section of the internal surface of the housing is circular with a diameter D, the length L is chosen to be less than or equal to D. Optionally, the brush body 7b can be rounded on its ends with a curvature identical to or greater than that of the section of the internal surface of the housing 1, to take into account the width of the brush body 7b. If the section of the internal surface of the housing is square with a length D, the length L is chosen to be less than D (the maximum length also depending on the width of the brush body 7b).

On the example of the , the brush 7 also comprises bristles 7a mounted on a brush body 7b, but the brush body 7b is connected to the transmission shaft 9 at one of its ends, the other end being free. The same remarks as for the apply to the dimensions of the brush, which can have for example a length l corresponding to half of L (L/2).

Preferably, the dimensions of the brush 7 are chosen so that the brush can brush the entire surface of the sieve 2 through which the washing water can circulate, herein called the useful surface. This useful surface of the sieve 2 corresponds for example to the complete surface of the sieve 2 when the latter is inserted by force, or to the “remaining” surface if the sieve 2 is placed on an internal rim 5. For example, if the internal rim 5 forms a ring of thickness d1 and the sieve is circular of radius d2, the sieve 2 being placed on the internal rim 5, the useful surface of the sieve is a disk of radius d2 minus d1. In this case, the length of the brush 7 can be chosen equal to or close to (d2 – d1), to brush the entire useful surface. Of course, the length of the brush 7 can be less than (d2 – d1), but the shorter the length of the brush, the smaller the surface of the sieve 2 that the brush can clean.

It appears that a useful surface of the sieve 2 having the shape of a disk is particularly advantageous, since it can be brushed in its entirety or over a very large part of its surface by a brush rotating around an axis passing perpendicularly through the useful surface of the sieve 2 at its center. This is particularly the case in the example of the , in which the successive sections of the housing and its internal surface are circular. Of course, other shapes of useful surfaces of the sieve 2 are conceivable. For example, if the useful surface of the sieve 2 is square in shape, it is possible to clean a large part of it using the brush 7 when the latter is rotating, even if parts "in the corners" of the useful surface of the sieve 2 are never reached.

Referring again to the , the filtration unit 100 also comprises an unfiltered wash water inlet 11, a filtered wash water outlet 12 and a microplastic discharge port 13. These ports 11, 12, 13 can be connected to connectors for connecting pipes to the unfiltered wash water inlet 11 and the filtered wash water outlet 12, and/or a microplastic recovery compartment for the microplastic discharge port 13.

The unfiltered washing water inlet 11, the filtered washing water outlet 12, and the microplastic discharge port 13 are ports passing through the housing 1. The unfiltered washing water inlet 11 and the microplastic discharge port 13 are located on the side of the unfiltered water receiving chamber 3, and the filtered washing water outlet 12 is located on the side of the filtered water receiving chamber 4.

In the example shown in the , wherein the housing 1 comprises a tank 1a and a cover 1b closing the tank 1a, the unfiltered wash water inlet 11 and the microplastics discharge 13 pass through the tank 1a, and the filtered wash water outlet 12 passes through the cover 1b.

The unfiltered wash water outlet 11 may typically be connected to a wash water outlet pipe of a washing machine, and the filtered wash water outlet 12 may be connected to a drain pipe for discharging the wash water to a waste water circuit after it has passed through the filtration unit. Exemplary embodiments are presented below with reference to the .

It is noted that advantageously, the housing 1 and the microplastic discharge orifice 13 can be designed so that microplastics dislodged from the internal surface of the sieve 2 by brushing by the brush 7 are drawn towards the microplastic discharge orifice 13 by the effect of gravity. This is particularly the case in the example of the , in which the housing has a generally flared shape with a narrowing in a direction opposite to the Y axis, from the sieve 2 towards the microplastic discharge orifice 13. Thus, when the microplastics detach from the internal surface of the sieve 2 after a passage of the brush 7, they fall directly towards the microplastic discharge orifice 13 or they fall onto the internal surface of the housing 1 and then slide towards the microplastic discharge orifice 13. The recovery of the microplastics initially present in the washing water and filtered by the sieve 2 is thus simplified, since it suffices to connect the microplastic discharge orifice 13 to a recovery compartment located below the microplastic discharge orifice 13 (or even simply to place a microplastic recovery compartment below the microplastic discharge orifice 13) to recover the microplastics and dispose of them or put them for recycling.

Of course, other configurations than that of the are possible and allow simplified evacuation and recovery of microplastics. For example, the housing 1 may be cylindrical in shape open at its base (i.e. the part of the cylinder furthest from the sieve 2 in the direction opposite to Y), the microplastic evacuation orifice 13 of which therefore corresponds to the open base of the cylinder, and connected to a microplastic recovery compartment.

There represents a system comprising a washing machine and a filtration unit 100 according to one embodiment of the invention.

The system of the comprises a washing machine 31. The washing machine 31 conventionally comprises a power supply circuit (not shown in the ) to connect the washing machine 31 to an electrical circuit and supply the washing machine 31 with electricity. The washing machine also conventionally comprises a connection circuit to be connected on the one hand to a water inlet tap 32 via a first connection pipe 33 in order to bring water into the drum 34 of the washing machine during a washing cycle, and on the other hand to be connected to a waste water circuit 35 via a drain pipe 36.

On the example of the , the filtration unit 100 is external to the washing machine, in the sense that it is located outside the housing (or “body”) of the washing machine 31. In this example, the filtration unit 100 is located inside a housing 37, which is not mandatory. When the filtration unit 100 is external to the washing machine 31, it is conventionally arranged at the outlet of the washing machine 31, in order to circulate washing water from a washing cycle by the washing machine 31 through the filtration unit 100, and upstream of the waste water circuit 35. For example, the drain pipe 36 of the washing machine 31 can be connected to the unfiltered washing water inlet 11, and a second connecting pipe 38 can be connected at one of its ends to the filtered washing water outlet 12 of the filtration unit 100, and at the other of its ends to the waste water circuit 35.

Thus, washing water can flow from the drum 34 of the washing machine 31 to the filtration unit 100, where it can be filtered, and the washing water thus filtered can be discharged into the waste water circuit 35.

As previously mentioned, the microplastic discharge port 13 may be connected to a microplastic recovery compartment 39, for recovering microplastics that are dislodged from the internal surface of the filter unit screen during filter cleaning.

In one or more embodiments, it is possible to add, between the washing machine 31 and the filtration unit 100, one or more additional devices, in particular a filter, here called a “pre-filter”, having a sieve whose holes have dimensions greater than the sieve 2 of the filtration unit 100, in order to filter the largest particles found in the washing water leaving the washing machine 31, so that they are filtered before entering the filtration unit 100. Indeed, these large particles could damage the filtration unit and thus reduce its service life. For example, this pre-filter can be connected on the one hand to the drain pipe 36 of the washing machine 31, and on the other hand to the unfiltered washing water inlet 11 of the filtration unit, via an additional pipe. Thus, the unfiltered washing water exits the washing machine 31 via the drain pipe 36, passes through the prefilter and exits therefrom to then enter the filtration unit 100 via the unfiltered washing water inlet 11, where the plastic microparticles can be filtered there.

On the example of the , the filtration unit 100 is external to the washing machine 31. However, in some embodiments, the filtration unit 100 may be located inside the housing of the washing machine 31. In these embodiments, a connecting pipe may be used to drain water from the drum to the filtration unit 100 (with the water from the drum entering the filtration unit 100 via the unfiltered wash water inlet 11 of the filtration unit 100), and the drain pipe of the washing machine may connect the filtered wash water outlet 12 of the filtration unit 100 to the waste water circuit 35.

When the filtration unit 100 is internal to the washing machine 31, it is preferable to provide, in the housing of the washing machine 31, a hatch (or any other mechanism) to have access to the filtration unit 100, in particular to the microplastic recovery compartment 39, to be able to empty it when it is full, and/or to the sieve of the filtration unit 100, to be able to change it, and/or to any part of the filtration unit which would be defective and which would need to be repaired or exchanged.

For washing machines for private use (i.e. washing machines used by the general public), the filtration unit can be internal or external. A 100% external filtration unit has the advantage of being able to be connected to any type of washing machine, and allows easier access to the various elements when the user needs to work on them (for example to repair a part or to change the sieve). Conversely, an internal filtration unit has the advantage of taking up less space and avoiding a multiplicity of household appliances.

For professional washing machines (e.g. used in dry cleaners), using an external filtration unit 100 has the advantage of having a filtration unit and a recovery compartment large enough to effectively filter the wash water and not having to empty the recovery compartment 39 too often.

, Figures 4a and 4b show the filtration unit 100 according to the embodiment of the , in two different operating modes.

There shows the filtration unit 100 filtering washing water leaving a washing machine. In this configuration, washing water (from the drum of the washing machine) enters the filtration unit 100 through the unfiltered washing water inlet 11, passes through the screen 2 through which it is filtered, and exits the filtration unit through the filtered washing water outlet 12. The circulation of the water is shown in FIG. by the arrow entering the filtration unit 100 via the unfiltered wash water inlet port 11 and the arrow exiting the filtration unit 100 via the filtered wash water outlet port 12. The motor 8 is stopped, and the brush 7 is in a fixed position.

The microplastic discharge port 13 is then closed to prevent water from escaping through it (and spreading, for example, into the recovery compartment).

There represents the filtration unit 100 during cleaning of the sieve 2. The cleaning of the sieve is implemented once there is no more water inside the filtration unit 100, therefore after emptying it via the filtered washing water outlet 12.

The cleaning of the sieve 2 of the filtration unit 100 can be implemented after each washing cycle, or after a predefined number of washing cycles (e.g. 5, 10, 15 cycles, etc.). Alternatively or in addition, the level of fouling of the sieve 2 can be evaluated using a pressure sensor as a function of the pressure difference upstream and downstream of the sieve 2. The cleaning of the sieve 2 can also be implemented when the user himself detects that the sieve 2 is fouled.

The microplastic discharge port 13 is then open, the motor 8 is in operation, rotating the brush 7 in contact with the internal surface of the sieve 2 (it is recalled that the term “internal surface of the sieve” designates the surface of the sieve located on the side of the chamber 3 for receiving unfiltered water). The contact of the rotating brush 7 on the internal surface of the sieve 2 makes it possible to dislodge the microplastics encrusted or trapped in the sieve 2, which “fall back” into the bottom of the housing towards the microplastic discharge port 13. The microplastic discharge port 13 can open into a microplastic recovery compartment. This microplastic recovery compartment can be emptied after each cleaning of the filter, or after a certain number of cleanings of the filter. The filling level of the microplastic recovery compartment can be checked “manually”, by the user, by taking out the compartment and seeing if the filling level requires emptying the compartment, or automatically, for example using an existing filling level (or “rate”) sensor.

Of course, it is noted that microparticles other than microplastics may be retained by the sieve and discharged through the microplastic discharge port 13. Also, the terminology “microplastic discharge port” or “microplastic recovery compartment” does not exclude another type of microparticles.

When cleaning the sieve 2, it is preferable that water cannot enter the filtration unit 100. Thus, the unfiltered wash water inlet 11 can advantageously be closed during cleaning of the sieve 2.

To close or open the unfiltered wash water inlet 11 and the microplastics outlet 13, a valve system can advantageously be used, as described with reference to the .

There represents a valve system for the filtration unit according to one embodiment of the invention.

As shown in the , a valve 51 may be placed upstream of the unfiltered wash water inlet orifice 11, and a valve 25 may be placed at the outlet of the microplastic discharge orifice 13, for example between the microplastic discharge orifice 13 and the microplastic recovery compartment.

Preferably, the valves 51, 52 are solenoid valves controlled by a microcontroller 53. For example, the microcontroller can be configured to detect the end of a washing cycle, or to detect that no washing cycle is in progress, and to control the closing of the unfiltered washing water inlet orifice 11 and the opening of the microplastics discharge orifice 13.

The detection of an end of a washing cycle can be done, for example, by sending a signal from a processor of the washing machine to the microcontroller 53. Alternatively or in addition, the detection of an end of a washing cycle and/or the detection that no washing cycle is in progress can be done using a liquid flow sensor placed in the water circuit, downstream of the water discharge pipe from the drum of the washing machine and upstream of the unfiltered washing water inlet 11. In the example of the , the liquid flow sensor can be arranged on the drain pipe 36. By means of this flow sensor, it is possible to check that no water enters or circulates in the filtration unit 100, and that the cleaning of the screen 2 can be implemented.

The microcontroller 53 can control the starting or stopping of the motor 8, depending on whether the filtration unit 100 is in “cleaning” operation ( ) or “filtration” ( ). The cable(s) connecting the microcontroller 53 to the motor 8 may pass through the grommet hole 14 of Figures 8a, 8b and 8c.

In addition, the microcontroller may implement a counter that counts the number of washing cycles performed since the last cleaning of the sieve 2, and trigger a cleaning of the sieve 2 when this counter reaches a predefined value (for example 5, 10, 15, etc.). Alternatively or in addition, the microcontroller may be connected to a pressure sensor, receive from the latter pressure data relating to the internal and external surfaces of the sieve 2, and control the actuation of the valves 51, 52 and the motor 8 as a function of a pressure difference between the internal and external surfaces of the sieve 2 (for example, when this pressure difference exceeds a predetermined threshold).

There represents a flowchart of a method for controlling the valves and the motor according to an embodiment of the invention. The method can be implemented by the microcontroller 53.

It is assumed that when implementing step 610, the unfiltered wash water inlet 11 is open, the microplastics discharge 13 is closed and the motor 8 is stopped.

At step 610, the microcontroller obtains a command to clean the screen. For example, this command may be sent directly from the washing machine. Alternatively, this command may be determined by the microcontroller. For example, as mentioned previously, it may be determined that cleaning the screen is necessary when the number of wash cycles since the last cleaning of the screen reaches a predefined threshold, or when it is determined that the clogging rate of the filter exceeds a predefined threshold.

In a step 620, the microcontroller can receive flow rate data relating to a flow rate of liquid in a pipe located downstream of the outlet of the drum of the washing machine and upstream of the unfiltered washing water inlet 11 of the filtration unit.

It is noted that step 620 can advantageously be performed continuously (i.e. at a predetermined frequency, which does not depend on the occurrence of an event). Thus, steps 610 and 620 can also be implemented in the reverse order (620 then 610).

From the flow rate data received in step 630, it is determined (step 630) whether water is flowing in the pipe located downstream of the outlet of the washing machine drum and upstream of the unfiltered wash water inlet 11, which means that a wash cycle is in progress or that the draining of the drum and the filter unit has not yet been completed. If it is determined that water is flowing (arrow “O” at the outlet of step 630), the process stops (step 640), and the cleaning of the screen is not performed. The unfiltered wash water inlet 11 remains open, the microplastic discharge port 13 remains closed, and the motor 8 remains stopped.

In one or more embodiments, in step 640, the method is not completely stopped, but paused. In these embodiments, after a predefined time, it is determined again whether water is flowing in the pipe located downstream of the outlet of the washing machine drum and upstream of the unfiltered wash water inlet 11 (step 630), from the flow rate data relating to a liquid flow rate in a pipe located downstream of the outlet of the washing machine drum and upstream of the unfiltered wash water inlet 11 of the filtration unit received in a new step 620. In these embodiments, the method therefore resumes in step 620 after a stop in step 640.

Otherwise, (arrow “N” at the output of step 630), the microcontroller can command (step 650) the closing of the unfiltered washing water inlet orifice 11, the opening of the microplastics discharge orifice 13, and the starting of the motor 8. The cleaning of the sieve 2 then begins.

During cleaning of the sieve 2, the microcontroller continues to receive (step 660) flow rate data to detect a flow rate of liquid in the pipe located downstream of the outlet of the washing machine drum and upstream of the unfiltered wash water inlet 11 of the filter unit. This allows the microcontroller to monitor (step 670) whether water is arriving again to the filter unit (this can happen, for example, if a new wash cycle is implemented during a filter cleaning).

If it is not detected that water is arriving towards the filtration unit (arrow “N” at the output of step 670), it is determined whether or not the cleaning must be stopped (step 680). For example, this determination can be made from a timer implemented by the microcontroller: this timer can count the time elapsed since the start of the cleaning, and the cleaning can be stopped when this time reaches a predetermined duration. Alternatively, this determination can be made from pressure data relating to the sieve 2, and from a level of residual fouling of the sieve determined from this pressure data; if the level of residual fouling exceeds a predefined threshold, the cleaning continues, otherwise it is stopped. If it is determined that cleaning must be stopped (arrow “O” at the output of step 680), the filtration unit is switched back to “filtration” mode: the microcontroller commands (step 690) the stopping of the motor 8, the opening of the unfiltered wash water inlet orifice 11 and the closing of the microplastic discharge orifice 13. The filtration unit remains in this configuration until a new cleaning command is obtained (new step 610). If it is determined that cleaning must be continued (arrow “N” at the output of step 680), the unfiltered wash water inlet orifice 11 remains closed, the microplastic discharge orifice 13 remains open and the motor 8 continues to operate. Steps 660, 670 and 680 are implemented again.

If it is detected that water is arriving at the filtration unit (arrow “O” at the output of step 670), the cleaning mode is stopped and the filtration unit switches to “filtration” operation. To do this, the microcontroller commands (step 690) the stopping of the motor 8, the opening of the unfiltered wash water inlet orifice 11 and the closing of the microplastic discharge orifice 13. The filtration unit remains in this configuration until a new cleaning command is obtained (new step 610).

There represents a method of using a filtration unit 100 according to one embodiment of the invention.

In step 710, the filtration unit is connected to the water circuit of the washing machine as previously described with reference to the .

In step 720, a laundry washing cycle is performed by the washing machine. During this step, washing water exits the drum, enters the filtration unit to be filtered therein, and exits the filtration unit to be discharged, for example into a wastewater circuit.

In step 730, it is determined whether a cleaning of the screen must be implemented. As previously described, this determination can be made by the user, from a counter counting the number of washing cycles carried out since the last cleaning of the screen, from the determination of a clogging rate of the filter, etc.

If it is not determined that a sieve cleaning should be implemented (arrow “N” at the output of step 730), a new washing cycle can be performed (step 720). If it is determined that a sieve cleaning should be implemented (arrow “O” at the output of step 730), the sieve cleaning is implemented (step 740) as previously described.

Of course, the present invention is not limited to the embodiments described above as examples; it extends to other variants.

Claims (12)

Filtration unit for filtering microplastics present in washing water leaving a washing machine, comprising:

• a box defining a volume;
• a screen separating the volume into an unfiltered water receiving chamber and a filtered water receiving chamber, the screen comprising an inner surface facing the unfiltered water receiving chamber and an outer surface facing the filtered water receiving chamber;
• a brush located in the unfiltered water receiving chamber;
• a motor placed in a compartment located in the unfiltered water receiving chamber and connected to the brush to drive it in rotation;
• an inlet opening passing through the housing and opening into the unfiltered water receiving chamber;
• an outlet port passing through the housing from the filtered water receiving chamber; and
• a microplastic discharge port passing through the housing from the unfiltered water receiving chamber;

wherein, when the motor is operating, the brush is rotated by the motor so as to be in contact with the internal surface of the screen to brush it. A filtration unit according to claim 1, wherein the motor drives the brush in rotation about an axis of rotation orthogonal to the internal surface of the screen. A filtration unit according to claim 2, wherein the axis of rotation passes through a centre of the internal surface of the screen. Filtration unit according to one of claims 1 to 3, in which the housing comprises a tank and a cover closing the tank, in which an internal face of the cover comprises at least one retaining tab, in which an internal face of the tank comprises at least one rim, and in which, when the cover is positioned so as to close the tank, the screen is held in contact with the at least one rim by the at least one retaining tab. A filtration unit according to any preceding claim, wherein the inlet port is adapted to be connected via an inlet tube to a washing machine drain pipe, wherein the outlet port is adapted to be connected via an outlet tube to a waste water drain. Filtration unit according to one of the preceding claims, in which the microplastic discharge orifice is located opposite the brush in the unfiltered water receiving chamber. A filtration unit according to any preceding claim, wherein the housing comprises an internal surface extending between the screen and the microplastic discharge port, said internal surface portion having a flared shape of which a characteristic dimension of a section decreases from the screen towards the microplastic discharge port. Filtration unit according to claim 7, in which the internal surface is a surface of revolution of circular section, and in which the characteristic dimension is equal to the diameter or the radius of said circular section. System comprising:

• a washing machine comprising:
  • a drum;
  • a water circuit comprising a water inlet pipe for supplying water to the drum and a drain pipe for supplying water to the drum and a waste water circuit;
• a filtration unit according to one of claims 1 to 8 external to the washing machine;

wherein the inlet of the filtration unit is connected, directly or via an additional device, to the drain pipe of the washing machine and the outlet of the filtration unit is connected to a water discharge pipe to a waste water circuit. The system of claim 9, further comprising a microplastics recovery compartment connected to the microplastics discharge port of the filtration unit. Method for filtering microplastics present in washing water leaving a washing machine using a filtration unit according to one of claims 1 to 8, said filtration unit being external to the washing machine; wherein the washing machine comprises a drum and a water circuit comprising a water inlet pipe for bringing water into the drum and a drain pipe for bringing water out of the drum and discharging it to a waste water circuit; wherein the inlet port of the filtration unit is connected, directly or via an additional device, to the drain pipe of the washing machine and the outlet port of the filtration unit is connected to a water discharge pipe to a waste water circuit; wherein during a laundry wash cycle, the drain port is closed and the motor is stopped, and wash water enters the filtration unit through the inlet port and exits the filtration unit through the outlet port. A method of cleaning a microplastic filtration unit according to one of claims 1 to 8, wherein the inlet port is closed and the outlet port is open, a cleaning portion of the brush is in contact with a surface of the screen located towards the unfiltered water receiving chamber, and the motor is operated to drive the brush in rotation so as to be in contact with a surface of the screen to brush it.