Immersed Surface Cleaning Device Provided with a Nonreturn Inlet Conduit

Abstract

The invention relates to am immersed surface cleaning device comprising a filtering chamber (6) provided, through a lower rigid wall (8), with at least one liquid inlet (9a, 9b) which has a non-return unit at least one filter (7) remote from each liquid inlet (9a, 9b) in such a way that a solid impurities retaining area (12) is defined and with a hydraulic circuit for forming a liquid flow by pumping means (4). At least one non-return unit comprises an anti-return conduit (20) which extends through the retaining area (12) away from the liquid inlet and whose free end (21) enters said retaining area (12), wherein the conduit is used for preventing at least the passage of impurities in an opposite direction from the retaining area through the liquid inlet at least when said pumping means is unused.

Description

The invention relates to a device for cleaning a surface immersed in a liquid, such as the walls of a swimming pool basin containing water.

Already known are surface cleaning devices having a filtration chamber with a stiff lower wall extending facing the surface to be cleaned and between two axles bearing rolling components intended for rolling on the surface to be cleaned, at least one liquid inlet in the filtration chamber, at least one liquid inlet in the filtration chamber [sic; line repeated] and at least one filter extending a distance from each liquid inlet so that a holding zone for solid impurities is defined between the liquid inlet(s) and the filter(s). A hydraulic circuit is formed in the device so that circulation of liquid can be established in the filtration chamber from and through the liquid inlet(s) and through the filter(s) under the effect of pumping means.

In the case of an electrical device as described in FR-2 818 680, the pumping means are integrated in the device, particularly in the filtration chamber.

In order to avoid backflow of impurities out of the holding zone when the pumping means are inactive and when the device is removed from the liquid by the user, for example, in order to empty the filtration chamber, the liquid inlets of the lower wall are generally given non-return valves (US-2002/0104790). Such a valve is most often formed by a membrane with bending elasticity attached inside the holding zone on one side of the inlet, or is formed by a stiff articulated flap.

These non-return valves nevertheless prove to pose efficiency and/or design problems. In effect, an elastic membrane must be provided to be sufficiently stiff to be returned and applied with force against the inlet. But in this case, in operation, it generates an extensive load loss encumbering the hydraulic efficiency of the pumping means. If the membrane is too flexible, it risks undergoing permanent deformation with use, allowing passage of opposite flow and impurities.

In the case of a flexible membrane as well as the case of a stiff flap, it frequently happens that impurities with large dimensions and/or with specific shapes (leaves, pine needles . . . ) become wedged in the liquid inlet, particularly between the valve and wall portion forming the seat for this valve. In this case, the valve remains open, and impurities can come out again in the opposite direction through the liquid inlet.

Additionally, the operation of extracting a device out of the liquid is often done by successive irregular pulls exerted on a hose or cable connected to the device. These irregular pulls can lead to alternating variations of pressure at the site of the valves that can be made to open, allowing inadvertent backflow of impurities in the opposite direction.

This problem is a serious detriment to the efficiency of the device inasmuch as when the user extracts the device from the liquid after a cleaning cycle, the immersed surface is considered to be particularly clean. Inadvertent discard of impurities into the pool at that time resulting simply from extraction of the device out of the pool puts back in question, in the mind of the user, the efficiency of the device and a great part of the value of the cleaning operation done before.

The reliability of non-return devices at the site of liquid inlets therefore constitutes a problem of great practical importance in the mind of the user of these cleaning devices with a filtration chamber incorporated in the device.

However, the solutions that should be used for solving this problem must remain extremely economical and simple in order to be compatible with the relatively low prices of these devices and the need to make their maintenance and use within reach of each user.

The invention therefore aims to alleviate these problems.

U.S. Pat. No. 4,856,913 and U.S. Pat. No. 6,706,175 proposed equipping certain filter bags for devices of the so-called pressure type, with flexible non-return conduits. However, these solutions cannot be transposed to devices with a stiff lower wall with liquid inlets. These documents do not refer to the problems posed by the non-return valves for such liquid inlets, and do not provide any solution to these problems.

The invention therefore relates to an immersed surface cleaning device comprising:

a filtration chamber with:

a stiff lower wall extending facing the surface to be cleaned, and between two axles bearing rolling components intended for rolling on the surface to be cleaned,

at least one liquid inlet into the filtration chamber, each liquid inlet provided through this lower wall and given a non-return device,

and at least one filter extending a distance from each liquid inlet so that a holding zone for solid impurities is defined between the liquid inlet(s) and the filter(s),

a hydraulic circuit suitable for forming a circulation of liquid through the liquid inlet(s) and into the filtration chamber under the effect of pumping means,

characterized by the fact that at least one non-return device of a liquid inlet consists of a conduit, a so-called non-return conduit, suitable for extending into the holding zone from the liquid inlet and said lower wall, having a free end opening into the holding zone, and for preventing passage at least of the impurities in the opposite direction from the holding zone through the liquid inlet at least when the pumping means are inactive.

The inventors in effect have observed that such a non-return conduit makes it possible, for a minimal cost, to prevent any inadvertent backflow of impurities when the pumping means are stopped and/or during extraction of the device out of the liquid, even if the latter is done by successive pulls. It moreover induces a very small load loss, almost zero, and in any case much less than that due to a valve.

The invention can be the object of different embodiments, particularly depending on the general architecture of the device.

Advantageously and according to the invention, with said liquid inlet equipped with a non-return conduit situated in the lower part of the filtration chamber, and with the filter(s) extending above this liquid inlet, the non-return conduit extends upward into the holding zone at least when the pumping means are active and when the device is facing a horizontal surface portion. In this way, the conduit has the effect of raising the entrance of the liquid into the holding zone to a height greater than the base of the holding zone, which limits the possibilities of backflow of the impurities by gravity.

Advantageously and according to the invention, the non-return conduit has one end opening at the upper part of the holding zone under the filter(s) and a distance from the filter(s). Preferably, the height of the non-return conduit in the holding zone is greater than half that of the holding zone.

In a possible variant of the invention, the non-return conduit is stiff. In the case in which it extends upward, it then forms a shaft for feeding liquid into the holding zone.

In another preferred and advantageous variant of the invention, the non-return conduit has at least one distal part (that is to say farthest from the corresponding liquid inlet) formed by a flexible sleeve capable of flattening on itself and spontaneously closing when the pumping means are inactive. When the pumping means are active, the liquid and the impurities circulate in the flexible sleeve which is inflated by the flow of liquid. When the pumping means stop, this inflating effect disappears, and any exterior pressure exerted on the flexible sleeve leads to flattening and closing of it. In particular, any exterior pressure on the sleeve that would tend to deliver liquid and/or impurities back in the opposite direction in the sleeve would have the effect of closing the sleeve spontaneously and in effect preventing this backflow. Such is the case in particular when the device is extracted out of the liquid, even by irregular successive pulls. This phenomenon of flattening of the sleeve, depending on the flexibility of the sleeve, can be obtained when the pumping means stop, taking into account the pressure that can then predominate in the holding zone, and the possible deformation of the flexible filter(s) which flatten(s) completely or partly against the flexible sleeve.

It should be noted that when the flexible sleeve is flattened, it prevents any backflow of impurities to the outside of the holding zone, even if it possibly happens that an impurity such as a leaf or pine needle remains blocked in the flexible sleeve. In effect, this flattening has the effect not only of then blocking this impurity but also above all of effectively closing off the flexible sleeve in spite of the presence of the impurity. In effect, the flexible sleeve is capable of flattening around the impurity.

Advantageously and according to the invention, the flexible sleeve is suited so that it cannot turn inside-out spontaneously in the opposite direction. The material of which it is constituted, the shape of its cross section (rather elongated) and the length of the flexible sleeve are chosen so as to prevent any inadvertent turning inside-out with use, particularly during extraction of the device out of the liquid when the pumping means are inactive. In particular, the material of which it is constituted must not be too flexible. But the material constituting the flexible sleeve can be chosen to be as flexible as possible as long as this condition remains satisfied (absence of risk of inadvertently turning inside-out).

The flexible sleeve is preferably non-elastic or has a slight bending elasticity. There is nothing stopping one from providing a flexible sleeve with a certain shape elasticity, preferably tending to return it to the state in which it is flattened on itself and closed, at least in its distal end portion (farthest from the liquid inlet).

Advantageously and according to the invention, the flexible sleeve is formed by a material based on synthetic fibers—particularly resistant to the liquid in consideration, for example, polyester fibers. This material is advantageously formed by a fabric, a non-woven material, a mesh (knit), a complex or layered material or any other composite assembly of such fibers.

It should be noted that the non-return conduit must be at least impervious to the solid impurities contained in the holding zone. It can also preferably be roughly impervious to the liquid, but there is nothing preventing it in contrast from having a certain permeability to the liquid.

Furthermore, advantageously and according to the invention, the non-return conduit has a stiff base extending into the holding zone from the liquid inlet and suitable for receiving the flexible sleeve. Advantageously and according to the invention, the flexible sleeve is suited so that it can be mounted on the base in a removable manner in order to allow changing of this flexible sleeve.

This assembly can be produced by elastic tightening of the mounting end of the flexible sleeve, which has fast removable fastening means, for example, a collar or a ring with traction elasticity, and/or loop and hook fittings (VELCRO®), and/or an annular rib of the sleeve with stiffness in traction, which is elastically engaged in a groove of the base, or any other equivalent means forming a fast removable assembly.

Furthermore, advantageously and according to an embodiment of the invention, the free end of the non-return conduit opens horizontally or downward. This arrangement is particularly advantageous in the case of a stiff non-return conduit extending upward. In this case, it prevents falling of impurities back from the holding zone into the non-return conduit by gravity. It is also possible to envisage a non-return conduit having a distal flexible sleeve extending roughly horizontally from its base.

In a preferred variant of the invention, the free end of the non-return conduit—that is to say, that of the flexible sleeve—opens upward, regardless of whether the flexible sleeve extends upward or on the contrary more or less horizontally. In effect, in all cases, impurities will not be able to flow back in the flexible sleeve that will flatten as indicated above.

Furthermore, advantageously and according to the invention, the non-return conduit is suited for forming at least one baffle starting from the liquid inlet. It is possible, for example, to provide a single baffle or two successive baffles in two orthogonal directions. Such a baffle can be formed by the stiff base for mounting of the flexible sleeve. It has the effect of making it so that a wall portion forms a screen between the holding zone and the exterior of the liquid inlet, according to any direction normal to the wall in which this liquid inlet is arranged.

Furthermore, with the non-return device according to the invention consisting of said non-return conduit, this non-return device is free of any other means preventing impurities from flowing back towards the exterior, and in particular is free of any valves.

Preferably, in a device according to the invention, each non-return device equipping each liquid inlet of the stiff lower wall consists of a non-return conduit. And preferably, each of the liquid inlets has such a non-return device appropriate for this liquid inlet. Preferably, all the non-return devices of the same device according to the invention are identical.

Furthermore, advantageously and according to the invention, with the holding zone having at least one concave holding volume generally elongated horizontally between two end portions, at least one liquid inlet is arranged in the lower part and is offset on the side of an end portion of the concave holding volume. Such a concave holding volume is, for example, formed by a pouch of a filter bag. Advantageously and according to the invention, the device has a single liquid inlet for each concave holding volume. In an advantageous embodiment and according to the invention, the device has two concave holding volumes on both sides of a transverse motor casing, each having a liquid inlet in the lower part, the two liquid inlets being on opposite sides from one another. In other words, one of the liquid inlets is offset on one side of the device, whereas the other liquid inlet is offset on the other side of the device.

The device according to the invention is also advantageously characterized by the fact that it has at least two liquid inlets arranged on both sides of a median transverse zone of the lower wall. Advantageously and according to the invention, each liquid inlet is flared towards the axle to which it is closest. This flared form makes it possible, on one hand, to produce a baffle as mentioned above, but it also makes possible the suction of impurities even when the liquid inlet, not centered on the transverse median zone of the device, is partially outside the liquid, for example, when the device arrives at the water line of the basin.

Furthermore, advantageously, a device according to the invention has at least one pumping component situated in the upper part of the device, and at least one electric motor device for driving this pumping component. Advantageously, the electric motor device and each pumping component are incorporated in the filtration chamber and/or borne by a stiff casing wall delimiting this filtration chamber.

Advantageously, a device according to the invention is also characterized by the fact that said stiff lower wall is mounted in a removable manner with respect to a stiff casing wall that defines a lower opening closed by the lower wall, and by the fact that it has a filter mounted on the stiff lower wall in such a way as to cover each liquid inlet. Advantageously and according to the invention, the filter is mounted on said lower wall so as to extend at least roughly on the periphery of the lower opening when said lower wall is in place. Advantageously and according to the invention, the filter is mounted on the periphery of said lower wall that is contiguous with the periphery of the lower opening of the stiff casing wall.

The invention moreover relates to an immersed surface cleaning device characterized by combination of all or some of the characteristics mentioned above or hereafter.

Other aims, characteristics and advantages of the invention will appear upon reading of the following description that refers to the appended figures representing different embodiments given only as non-limiting examples and in which:

FIG. 1 is a diagrammatic view in vertical section of an example of an electrical cleaning device according to a first embodiment in accordance with the preferred variant of the invention, represented with the pumping means active,

FIG. 2 is a view similar to FIG. 1 representing the device when the pumping means are inactive, particularly during extraction of the device out of the water,

FIG. 3 is a diagrammatic view in cross section of the device of FIG. 1,

FIG. 4 is a diagrammatic view in cross section representing an example of a device similar to that of FIGS. 1 to 3 but according to a second embodiment in accordance with another variant of the invention,

FIG. 5 is a diagrammatic view in cross section representing a device similar to that of FIGS. 1 to 3 but according to a third embodiment in accordance with the preferred variant of the invention, represented with the pumping means active,

FIG. 6 is a view similar to FIG. 5 representing the device when the pumping means are inactive, particularly during extraction of the device out of the water,

FIG. 7 is a diagrammatic bottom view of the device according to the invention, as represented in FIGS. 1 to 6.

It should be noted that in the sectional figures, the planes of section are not straight and have breaks and/or torn away parts for purposes of illustration.

The immersed surface cleaning devices represented in the figures are of the type described in patent FR-2 818 680, for example. They are self-propelled rolling cleaning devices having at least one electric motor for driving and/or pumping enclosed in a stiff transverse motor casing, the whole forming motor unit 1 which is not represented in detail in the figures. This motor unit 1 can be supplied with electrical energy by a supply cable (not represented) connected to an electrical energy source outside the basin in which the device is immersed, for example, the electrical supply network. Motor unit 1 drives, on one hand, rolling components such as transverse rollers 2 and/or lateral belts 3, and on the other hand, at least one pumping component 4 such as a propeller situated in the upper part of the device. The device furthermore has external stiff casing wall 5 defining, around motor unit 1 and inside the enclosure defined by this stiff wall 5, filtration chamber 6, which in the example represented contains filter bag 7. This casing wall 5 can be in the form of a number of pieces assembled together.

Lower bottom 8 of stiff wall 5 is removable and has water inlets 9a, 9b as represented in FIG. 7. This bottom 8 has stiff rods 10a, 10b that support two pouches 11a, 11b of filter bag 7, each forming holding volume 11a, 11b for solid impurities, each of these pouches extending respectively on one side of motor unit 1, transversely along this motor unit 1. Filter bag 7 thus defines holding zone 12 for impurities, including these two pouches and a middle part connecting them under motor unit 1. Filter bag 7 is borne by removable bottom 8 so that it can be removed with bottom 8 for the purpose of cleaning holding zone 12 in order to rid it of the impurities extending between filter bag 7 and water inlets 9a, 9b.

Stiff casing wall 5 defines a lower opening closed by bottom 8, this lower opening being clear when bottom 8 is removed from casing wall 5.

Filter bag 7 is mounted on bottom 8 so as to extend at least roughly on the periphery of the lower opening when bottom 8 is in place on casing wall 5. When bottom 8 is removed, filter bag 7 is extracted through the lower opening.

Bottom 8 is mounted on casing wall 5 with its peripheral edges that are contiguous with the peripheral edges of the lower opening, possibly with partial overlapping and/or nesting together of these peripheral edges. Bottom 8 is held in place by screws and/or tabs and/or elastic locking hooks or other fast removable fastening means.

Filter bag 7 has a lower main opening delimited by its peripheral edges that are connected in the vicinity of the peripheral edges of bottom 8, for example, in a groove made by parallel ribs along these edges towards the interior of the filtration chamber.

As seen in the figures, a hydraulic circuit is formed from each of water inlets 9a, 9b provided on lower bottom 8, to upper water outlet 13 immediately above pumping component 4, through filter bag 7 and in filtration chamber 6. When pumping component 4 is put into rotation and is active, a circulation of liquid is established from bottom to top through the device as represented by the arrows of FIG. 1.

In the example represented in the figures, bottom 8 has two water inlets 9a, 9b, namely a water inlet for each of pouches 11a, 11b formed by filter bag 7, that is to say on both sides of motor unit 1. However, as represented in FIGS. 1 and 6, each water inlet 9a, 9b forms at least one baffle according to the longitudinal direction of movement of the device so that wall portion 14 forms a screen according to any direction normal to bottom 8, between holding zone 12 and the exterior of bottom 8. Each water inlet 9a, 9b is furthermore in the form of a flared channel from at least one transverse median zone of bottom 8 to a zone facing the corresponding pouch 11a, 11b of filter bag 7 (FIG. 7).

In the embodiment represented in FIGS. 1 to 3, each water inlet 9a, 9b is extended inside holding zone 12 by stiff base 15 (forming the baffle and wall portion 14 described above) whose inner end part 16 is in the form of a cylinder (in the mathematical sense of the term), whose cross section is not necessarily symmetrical in rotation, and which can be polygonal, for example, rectangular, with its axis oriented perpendicularly to bottom 8 and on the opposite side from immersed surface 17, that is to say vertically towards the top when this immersed surface 17 is horizontal.

Except when indicated otherwise, in all of the text, it is assumed that the device rests on a horizontal immersed surface 17, and this is the case simply to facilitate its description.

End part 16 of base 15 forms peripheral bearing surface 18 that is cylindrical (in the mathematical sense of the term) with a curved or polygonal base, not necessarily symmetrical in rotation, for example, rectangular as represented. This bearing surface 18 is suitable for receiving lower end 19 of flexible sleeve 20 extending upward into holding zone 12. Lower end 19 of flexible sleeve 20 is, for example, formed by a collar or elastic ring elastically tightened on cylindrical bearing surface 18 of base 15. In this way, flexible sleeve 20 is maintained on base 15 but can be separated easily from this base 15 for the purpose of changing flexible sleeve 20 if necessary. Other means for fastening flexible sleeve 20 on base 15 can be foreseen (loops and hooks, stiff rib in a groove, etc.). Preferably, these fastening means are of the type allowing fast removable fastening of flexible sleeve 20.

The device represented in FIG. 1 has two flexible sleeves 20a, 20b, one for each water inlet 9a, 9b respectively. Each flexible sleeve 20a, 20b extends upward into pouch 11a, 11b formed by filter bag 7, and forms, in this pouch 11a, 11b, a non-return conduit having upper free end 21a, 21b opening in holding zone 12 immediately under filter bag 7 held in high position by rods 10a, 10b. Flexible sleeve 20 extends over the greater part of the height of holding zone 12. However, upper end 21 of the flexible sleeve extends a sufficient distance from the uppermost part of filter bag 7 to allow the exit of impurities from flexible sleeve 20 to the interior of holding zone 12 formed between filter bag 7 and the exterior wall of flexible sleeve 20.

Flexible sleeve 20 is made of a flexible material, preferably non-elastic or with little bending elasticity, and is suited so that it can flatten upon itself and close spontaneously when pumping component 4 is stopped and inactive, as represented in FIG. 2. Flexible sleeve 20 is, for example, made of a synthetic fabric, for example, a polyester fabric.

The thickness and dimensions given to flexible sleeve 20 are nevertheless suited so that the latter cannot turn inside-out spontaneously in the opposite direction, particularly when the device is extracted from the liquid. In the example represented in FIGS. 1 to 3, flexible sleeve 20 has a height such that it cannot turn inside-out. Furthermore, its cross section is elongated, for example, rectangular, as represented, or oblong, and this asymmetry of shape also prevents any turning of the flexible sleeve inside-out. Additionally, the nature of the material used and the thickness of the wall of the flexible sleeve give it sufficient bending stiffness to prevent this turning inside-out. In other words, the flexible sleeve is sufficiently flexible to flatten on itself when the pumping means are inactive, but sufficiently stiff not to turn inside-out spontaneously under the effect of the pressure of suction towards the exterior of water inlets 9a, 9b when the device is extracted from the liquid.

In the embodiment represented in FIGS. 1 to 3, upper end 21 of the flexible sleeve that opens in holding zone 12 is generally oriented upward. This orientation is of no importance inasmuch as when pumping component 4 is stopped, this upper end 21 flattens inside-out and is blocked, so that an impurity cannot fall back inside flexible sleeve 20 by gravity.

There is nothing preventing the use of a flexible sleeve 20 with a certain elasticity of shape and a shape at rest with its upper end 21 flattened and closed, when the pumping means are inactive. When pumping component 4 is being driven, this upper end 21 is then opened by the flow sucked in by pumping component 4.

Such a flexible sleeve 20 actually performs a dual function. In a first function, it forms a device for unidirectional circulation of impurities from the corresponding water inlet 9a, 9b towards holding zone 12, preventing any backflow of these impurities in the opposite direction. Because it extends upward, it moreover imposes a high point of entrance of the impurities and possibly of the liquid into holding zone 12 in the manner of a sink drain, so that when pumping component 4 stops, the impurities fall back on both sides of flexible sleeve 20 by gravity.

It should be noted that during functioning, such a flexible sleeve only imposes a very small load loss inside the hydraulic circuit formed in the device, contrary to a valve.

In the variant represented in FIG. 4, the flexible sleeve is replaced by a stiff conduit extending upward in a continuous manner from base 15, so as to form stiff non-return conduit 22. This non-return conduit has upper free end 23 that opens horizontally and transversely in the upper part of holding zone 12, immediately under filter bag 7. This execution variant produces a high point in the circuit for entrance of the impurities and water into holding zone 12, so that when pumping component 4 stops and during extraction of the device from the water, the impurities fall back into the lower part of the holding zone against bottom 8 and are not driven in the opposite direction in non-return conduit 22. However, since opening end 23 of non-return conduit 22 remains open, the risk that one or more impurities will run in the opposite direction is not completely excluded. The risk is nevertheless slight, and in any case, the quantity of impurities driven back is still much less than that capable of being driven back in earlier devices, for example, when an impurity keeps a valve open.

FIGS. 5 and 6 represent a third embodiment that differs from the first embodiment of FIGS. 1 to 3 by the fact that flexible sleeve 24 is provided extending generally horizontally and transversely in the holding zone and not upward as in the preceding. As seen in FIG. 5, when pumping component 4 is active, the water and debris penetrate freely into holding zone 12, only creating a small load loss in the hydraulic circuits. When pumping [component] 4 stops, flexible sleeve 24 falls back against bottom 8, flattens and closes on itself, preventing any inadvertent return of impurities in the opposite direction. In this case again, even if impurities remain wedged inside flexible sleeve 24, the latter having adopted the shapes of these impurities, and because of its flexibility, blocks the impurities that it contains and prevents passage of other impurities. This third embodiment can nevertheless present the problem of faster and more extensive fouling of the flexible sleeve because it is in the lower part of the holding zone where the impurities accumulate progressively with use of the device.

As seen in FIG. 7, the two water inlets 9a, 9b are on opposite sides from one another, that is to say on one side and the other of the device. Each of them feeds a holding volume elongated in a transverse direction formed by each pocket 11a, 11b of filter bag 7. The fact that the two inlets 9a, 9b are arranged on both sides enables one to improve the symmetry of the circulation of water inside the device itself.

The invention can be the object of numerous execution variants other than those represented only as non-limiting examples in the figures, particularly with regard to the constitution of non-return conduit 15, 20, 22, 24, mounting of it with respect to bottom 8 and with respect to each water inlet 9a, 9b arranged in or through this bottom 8.

Furthermore, the invention applies not only to a cleaning device with an electric motor or motors as represented in the figures, but also to any other category of device for cleaning a surface immersed in a liquid, if this device has a filtration chamber with at least one liquid inlet arranged through a stiff lower wall and with at least one filter. It is particularly advantageous for equipping at least one liquid inlet arranged under a filter when the device moves along a horizontal immersed surface.

In certain execution variants and depending on the applications, it is possible to equip only certain of the liquid inlets with such a non-return conduit, others being equipped with valves, or even without any no non-return device if this is not necessary, for example, as a function of the shape of the hydraulic circuit provided in the filtration chamber.

Claims

1. An immersed surface-cleaning device comprising:

a filtration chamber with:

a stiff lower wall extending facing the surface to be cleaned and between two axles bearing rolling components intended for rolling on the surface to be cleaned,

at least one liquid inlet into filtration chamber, each liquid inlet provided through said lower wall and given a non-return device, and

at least one filter extending a distance from each liquid inlet so that holding zone for solid impurities is defined between liquid inlet(s) and filter(s),

a hydraulic circuit suitable for forming a circulation of liquid through liquid inlet(s) and into filtration chamber under the effect of pumping means,

wherein at least one non-return device of liquid inlet consists of a conduit, a so-called non-return conduit, suitable for extending into holding zone from liquid inlet and said lower wall, having free end opening into holding zone, and for preventing passage at least of impurities in the opposite direction from holding zone through liquid inlet at least when pumping means are inactive.

2. A device according to claim 1, wherein liquid inlet situated in the lower part of filtration chamber, and filter(s) extending above this liquid inlet non-return conduit extends upward into holding zone at least when pumping means are active and when the device is facing a horizontal surface portion.

3. A device according to claim 1, wherein non-return conduit has end opening at the upper part of holding zone under the filter(s) and a distance from the filter(s).

4. A device according to claim 1, wherein-non-return conduit is stiff.

5. A device according to claim 1, wherein-non-return conduit has at least one distal part formed by flexible sleeve capable of flattening on itself and closing spontaneously when pumping means are inactive.

6. A device according to claim 5, wherein flexible sleeve is suited so that it is not capable of spontaneously turning inside-out in the opposite direction.

7. A device according to claim 5, wherein flexible sleeve is made of a material based on synthetic fibers.

8. A device according to claim 5, wherein non-return conduit has stiff base extending into holding zone from liquid inlet and suitable for receiving flexible sleeve.

9. A device according to claim 8, wherein flexible sleeve is suited so that it can be mounted on base in a removable manner in order to allow changing of this flexible sleeve.

10. A device according to claim 1, wherein free end of non-return conduit opens horizontally or downward.

11. A device according to claim 5, wherein free end of non-return conduit opens upward.

12. A device according to claim 1, wherein non-return conduit is suitable for forming at least one baffle starting from liquid inlet.

13. A device according to claim 1, wherein each non-return device consists of non-return conduit.

14. A device according to claim 1, wherein with holding zone having at least one concave holding volume, generally elongated horizontally between two end portions, at least one liquid inlet is arranged at the lower part and offset on the side of an end portion of concave holding volume.

15. A device according to claim 14, wherein for each concave holding volume, it has a single liquid inlet.

16. A device according to claim 14, wherein it has two concave holding volumes on both sides of transverse motor casing, the two liquid inlets being on opposite sides from one another.

17. A device according to claim 1, wherein it has at least two liquid inlets arranged on both sides of a median transverse zone of lower wall.

18. A device according to claim 17, wherein each liquid inlet is flared towards the axle to which it is closest.

19. A device according to claim 1, wherein it has at least one pumping component situated in the upper part of the device, and at least one electric motor device for driving this pumping component.

20. A device according to claim 1, wherein said stiff lower wall is mounted so as to be removable with respect to stiff casing wall that defines a lower opening closed by lower wall, and by the fact that it has filter mounted on stiff lower wall so as to cover each liquid inlet.

21. A device according to claim 20, wherein filter is mounted on said lower wall in such a way as to extend at least roughly on the periphery of the lower opening when said lower wall is in place.

22. A device according to claim 21, wherein filter is mounted on the periphery of said lower wall, which is contiguous with the periphery of the lower opening of stiff casing wall.