Cleaning device, cleaning device assembly and wet cleaning apparatus

Abstract

Provided is a cleaning device (110) that includes a cleaning liquid tank (152) for containing cleaning liquid (154), and a cleaning liquid outlet structure (156) for delivering the cleaning liquid towards a surface to be cleaned (158). The cleaning device further includes a conduit assembly (164, 166) and a valve assembly (168). The valve assembly has a valve member (170) displaceable between a first position, in which first position the valve member restricts transport of the cleaning liquid from the cleaning liquid tank, and being positioned to allow transport of the cleaning liquid from the cleaning liquid tank, past the valve member, towards the cleaning liquid outlet structure. The valve assembly also has a valve actuator (172) arranged to displace the valve member, in response to an underpressure being provided in the conduit assembly, to being positioned to allow the transport of the cleaning liquid past the valve member in a direction away from the valve actuator. Additionally provided is a cleaning device assembly including the cleaning device and a cleaning liquid applicator material for applying the cleaning liquid to the surface to be cleaned. Further provided is a wet cleaning apparatus (100) including an underpressure generator, and the cleaning device or the cleaning device assembly.

Description

FIELD OF THE INVENTION

[0001] The invention relates to a cleaning device comprising a cleaning liquid tank for containing cleaning liquid, and a cleaning liquid outlet structure for delivering the cleaning liquid towards a surface to be cleaned. The invention also relates to a cleaning device assembly including the cleaning device and a cleaning material for applying the cleaning liquid to the surface to be cleaned. The invention further relates to a wet cleaning apparatus including an underpressure generator, and the cleaning device or the cleaning device assembly.

[0002] The cleaning device, surface cleaning assembly and wet cleaning apparatus can be used, for example, for cleaning a floor, an indoor surface, or a window.BACKGROUND OF THE INVENTION

[0003] Wet cleaning apparatuses, for example wet mopping devices, are known which remove water from a surface to be cleaned. Wet cleaning apparatuses can alternatively or additionally apply cleaning liquid, e.g. water, to the surface to be cleaned, and then remove the liquid, e.g. with a suitable cloth.

[0004] Some wet cleaning apparatuses have powered pick-up functionality for removing the water from the surface to be cleaned. Wet vacuum cleaners, for instance, may pick up liquid by generating sufficient air speed (e.g. at least 10 m / s) and / or brush power to exert enough shear force on liquid droplets to cause them to enter the device. Typical power consumption values for such vacuum cleaners are relatively high, for example in the order of several hundred watts.

[0005] A further challenge can arise when the wet cleaning apparatus is arranged to deliver cleaning liquid as well as pick up the liquid using suction. Providing both functionalities can, in at least some designs, risk that the wet cleaning apparatus is prohibitively expensive to produce, for example due to having a pump for providing the liquid pick-up functionality and an additional pump for controlling delivery of cleaning liquid towards the surface to be cleaned.SUMMARY OF THE INVENTION

[0006] The invention is defined by the claims.

[0007] According to examples in accordance with an aspect of the invention, there is provided a cleaning device comprising: a cleaning liquid tank for containing cleaning liquid; a cleaning liquid outlet structure for delivering the cleaning liquid towards a surface to be cleaned; a conduit assembly; and a valve assembly comprising: a valve member displaceable between a first position, in which first position the valve member restricts transport of the cleaning liquid from the cleaning liquid tank, and being positioned to allow transport of the cleaning liquid from the cleaning liquid tank, past the valve member, towards the cleaning liquid outlet structure; and a valve actuator arranged to displace the valve member, in response to an underpressure being provided in the conduit assembly, to being positioned to allow the transport of the cleaning liquid past the valve member in a direction away from the valve actuator.

[0008] Since the valve actuator displaces the valve member in response to the underpressure provided in the conduit assembly, the delivery of the cleaning liquid towards the surface to be cleaned can be controlled, for example, using an underpressure generator already included in a vacuum cleaner to which the cleaning device is attached / attachable.

[0009] It is noted in this connection that the present disclosure being directed, in part, to the cleaning device by itself reflects the fact that a user can be supplied with the cleaning device and can connect the conduit assembly thereof to an underpressure generator, e.g. an underpressure generator included in a vacuum cleaner, already in the user's possession or sourced separately from the cleaning device.

[0010] Alternatively or additionally, the delivery of the cleaning liquid towards the surface to be cleaned can be controlled using an underpressure generator provided also for removal of liquid from the surface to be cleaned. In this case, both dirty liquid pick-up and cleaning liquid delivery control functionalities can be realized using the same underpressure generator, thereby reducing costs compared to, for example, a scenario in which a dedicated cleaning liquid pump is included in addition to the underpressure generator.

[0011] In such embodiments, a dirt inlet structure of the cleaning device can be fluidly connected to the conduit assembly, as well as the valve actuator being arranged to displace the valve member in response to the underpressure provided in the conduit assembly.

[0012] For example, the conduit assembly can comprise a first conduit and a second conduit, with the valve actuator being arranged to displace the valve member in response to the underpressure being provided in the first conduit, and with the dirt inlet structure being fluidly connected to the second conduit. In such embodiments, the first conduit and the second conduit may be fluidly connected / connectable to the underpressure generator.

[0013] By the valve actuator being arranged so that the cleaning liquid is transported past the valve member in a direction away from the valve actuator, the risk of the cleaning liquid being transported interfering with functioning of the valve actuator can be lessened or removed.

[0014] In some embodiments, the cleaning liquid tank and the cleaning liquid outlet structure are arranged so that, when the cleaning device is orientated for use on a floor, the cleaning liquid is transportable at least partly by gravity past the valve member. Using gravity in this manner can assist in simplifying the design of the cleaning liquid delivery functionality.

[0015] In such embodiments, the valve actuator may be arranged above the valve member when the cleaning device is orientated for use on the floor.

[0016] It is generally noted that the valve actuator may be arranged, e.g. biased, to cause the valve member to be in the first position when no underpressure is provided in the conduit assembly (or at least when there is insufficient underpressure to cause the valve actuator to move the valve member from the first position).

[0017] Thus, no cleaning liquid may leak from the cleaning device when the underpressure is not being provided in the conduit assembly, e.g. due to the underpressure generator being switched off, because of the valve member being in the first position closing the cleaning liquid tank.

[0018] In some embodiments, the cleaning device comprises a dirty liquid collection tank arranged to receive the dirty liquid from the dirt inlet structure. The dirty liquid collection tank can thus store the dirty liquid picked up from the surface to be cleaned during use of the cleaning device. The dirty liquid received in the dirty liquid collection tank can be subsequently emptied therefrom after use.

[0019] The dirt inlet structure may be covered by a porous layer. When the porous layer is dry, the porous layer may be regarded as being in an "air transport state" in which air is transported through each of the dry pores of the porous layer. A "liquid transport state" corresponds to liquid, e.g. water, being transported through the (wetted) pores of the porous layer. When there is no longer a feed of liquid to the pores, a "fluid block state" may be adopted. The "fluid block state" corresponds to the state at which the surface tension of the (residual) liquid retained in the wetted pores of the porous layer prevents fluid transport through the pores. In the latter state, a surface or barrier is created at the boundary between air and liquid, e.g. water. This barrier can assist to maintain the underpressure in the dirt inlet structure between the porous layer and the underpressure generator.

[0020] A liquid pick-up region of the porous layer may be delimited by sealing attachment of the porous layer around the dirt inlet structure.

[0021] The sealing attachment of the cleaning material layer around the dirt inlet structure may assist to maintain an underpressure in the dirt inlet structure with or without a flow being applied by the underpressure generator fluidly connected to the conduit assembly.

[0022] The valve actuator can be arranged in any suitable manner in order to be responsive to the underpressure in the conduit assembly, e.g. the first conduit thereof, to move the valve member to being positioned to allow the transport of the cleaning liquid past the valve member. In some embodiments, the valve actuator comprises a membrane coupled to the valve member, with the membrane being deformable by the underpressure provided in the conduit assembly to move the valve member to being positioned to allow the transport of the cleaning liquid past the valve member. Such a membrane can provide a relatively straightforwardly manufacturable way of implementing the valve actuator.

[0023] The cleaning device can include an air valve arranged to control air ingress into the cleaning liquid tank when the cleaning liquid is being transported past the valve member. In such embodiments, the air valve, for example air restriction valve, can restrict ingress of air into the cleaning liquid tank, and hence restrict outflow of the cleaning liquid from the cleaning liquid tank when the valve member is positioned to allow the transport of the cleaning liquid past the valve member.

[0024] Thus, the air valve can operate as a flow regulator for regulating flow of the cleaning liquid towards the cleaning liquid outlet structure.

[0025] In some embodiments, the cleaning device comprises a support substrate. The support substrate may, for example, be regarded as a main body of the cleaning device.

[0026] The support substrate may, for instance, be a pliable support substrate. Such a pliable support substrate can assist the cleaning device to follow contours on the surface to be cleaned. Alternatively or additionally, the pliability of the pliable support substrate may assist cleaning of the cleaning device after use, for example involving wringing liquid from the cleaning device and / or washing at least part of the cleaning device in the user's washing machine.

[0027] In embodiments in which the support substrate is a pliable support substrate, the support substrate may be formed from any suitable pliable material. In some embodiments, the pliable material forming the pliable support substrate comprises a polymeric material and / or elastomeric material.

[0028] In embodiments in which the cleaning device comprises the support substrate, e.g. the pliable support substrate, the cleaning liquid outlet structure and / or the dirt inlet structure may be provided at, e.g. recessed into and / or embossed on, a bottom surface of the support substrate, which bottom surface faces, in use, the surface to be cleaned.

[0029] In some embodiments, the cleaning liquid outlet structure comprises at least one cleaning liquid distribution strip, with each of the at least one cleaning liquid distribution strip comprising a channel arranged to receive the cleaning liquid from the cleaning liquid tank when the valve member is positioned to allow the transport of the cleaning liquid past the valve member. Each of the at least one cleaning liquid distribution strip may comprise apertures arranged along its length.

[0030] The channel can, for example, be defined in the bottom surface of the support substrate, e.g. in the bottom surface of the pliable support substrate.

[0031] In some embodiments, the cleaning liquid outlet structure comprises a first cleaning liquid outlet portion and a second cleaning liquid outlet portion, with the dirt inlet structure being arranged in-between the first cleaning liquid outlet portion and the second cleaning liquid outlet portion.

[0032] For example, the at least one cleaning liquid distribution strip can include a first cleaning liquid distribution strip and a second cleaning liquid distribution strip, with the dirt inlet structure being arranged in-between the first cleaning liquid distribution strip and the second cleaning liquid distribution strip.

[0033] In other embodiments, the dirt inlet structure comprises a first dirt inlet portion and a second dirt inlet portion, with the cleaning liquid outlet structure being arranged in-between the first dirt inlet portion and the second dirt inlet portion.

[0034] According to another aspect there is provided a cleaning device assembly comprising: the cleaning device according to any of the embodiments described herein; and a cleaning liquid applicator material for applying the cleaning liquid to the surface to be cleaned.

[0035] In some embodiments, the cleaning liquid applicator material is detachable from the cleaning device. Thus, the cleaning liquid applicator material can be detached for cleaning and / or replacement after use.

[0036] The cleaning liquid applicator material can be detachably coupled to the cleaning device in any suitable manner. In some embodiments, the cleaning liquid applicator material is detachable from the cleaning device via a hooks-loops fastening assembly, e.g. Velcro ®< .

[0037] In some embodiments, the cleaning liquid applicator material comprises a backing member that includes a back side and a projections-comprising side, with the projections-comprising side comprising projections, e.g. tufts and / or ridges, that project from the backing member so that at least some of the projections are contactable with the surface to be cleaned. Implicit in the projections each projecting from the backing member is that points at which the projections join to the backing member are spatially separated from each other.

[0038] Thus, coarse dirt, e.g. sand, may be accommodated in spaces between the projections, thereby alleviating the risk of scratching of the surface to be cleaned. It is also noted that the projections can accommodate unevenness of the surface to be cleaned, noting that individual projections can enter recesses, dislocations etc. in the surface to be cleaned.

[0039] According to a further aspect there is provided a wet cleaning apparatus comprising: an underpressure generator; and the cleaning device according to any of the embodiments described herein or the cleaning device assembly according to any of the embodiments described herein, wherein the underpressure generator is configured to provide the underpressure in the conduit assembly.

[0040] Thus, the user can be conveniently supplied with the cleaning device / cleaning device assembly together with the underpressure generator.

[0041] In some embodiments, the wet cleaning apparatus comprises a nozzle to which the cleaning device is detachably couplable. In such embodiments, the nozzle and the cleaning device can be arranged so that when the cleaning device is coupled to the nozzle, the conduit assembly is fluidly connected to the underpressure generator to enable the underpressure to be provided in the conduit assembly.

[0042] In such embodiments, the nozzle can be, for example, the nozzle of a vacuum cleaner. Thus, cleaning liquid delivery, as well as, in some embodiments, dirty liquid pick-up functionality, can be added to the vacuum cleaner by coupling its nozzle to the cleaning device.

[0043] The nozzle and the cleaning device can be detachably coupled in any suitable manner. In some embodiments, the nozzle and the cleaning device are detachably couplable to each other via a magnetic coupling assembly. This can make attaching / detaching the cleaning device to / from the nozzle relatively simple and convenient for the user to implement.

[0044] The underpressure generator can be of any suitable type, provided that the underpressure generator is capable of generating a sufficient underpressure for actuating the valve actuator to move the valve member to being positioned to allow the transport of the cleaning liquid past the valve member. In some embodiments, the underpressure generator comprises a motor and a fan rotatable by the motor to provide the underpressure in the conduit assembly. Such a motor and fan-comprising underpressure generator can be included, for example, in a vacuum cleaner, e.g. a vacuum cleaner whose nozzle is detachably couplable to the cleaning device.

[0045] In more general terms, the wet cleaning apparatus can comprise a vacuum cleaner; for example a stick-type vacuum cleaner, an upright vacuum cleaner, a canister-type vacuum cleaner or a robotic vacuum cleaner.

[0046] In embodiments in which the cleaning device comprises the porous layer covering the dirt inlet structure, the underpressure generator may be configured to provide a pressure difference between an inside of the wet cleaning apparatus and atmospheric pressure for drawing fluid through the porous layer, with the pressure difference being in a range of 3000 Pa to 13500 Pa, preferably 5000 Pa to 9000 Pa, most preferably 7000 Pa to 9000 Pa.

[0047] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.BRIEF DESCRIPTION OF THE DRAWINGS

[0048] For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which: FIG. 1 schematically depicts a liquid transport state, intermediate regime and end regime sequence of a porous layer when liquid and suction are applied thereto; FIG. 2 schematically depicts a test arrangement for testing the behavior of the porous layer when liquid and suction are applied thereto; FIG. 3 provides a graph of underpressure vs time from data acquired using the test arrangement shown in FIG. 2; FIG. 4 schematically depicts a wet cleaning apparatus according to a comparative example in which a dedicated cleaning liquid pump transports cleaning liquid towards a surface to be cleaned; FIGs. 5A and 5B schematically depict a wet cleaning apparatus according to an example; FIG. 6 schematically depicts a wet cleaning apparatus according to another example; and FIG. 7 schematically depicts a wet cleaning apparatus according to a further example. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0049] The invention will be described with reference to the Figures.

[0050] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

[0051] Provided is a cleaning device that includes a cleaning liquid tank for containing cleaning liquid, and a cleaning liquid outlet structure for delivering the cleaning liquid towards a surface to be cleaned. The cleaning device further includes a conduit assembly and a valve assembly. The valve assembly has a valve member displaceable between a first position, in which first position the valve member restricts transport of the cleaning liquid from the cleaning liquid tank, and being positioned to allow transport of the cleaning liquid from the cleaning liquid tank, past the valve member, towards the cleaning liquid outlet structure. The valve assembly also has a valve actuator arranged to displace the valve member, in response to an underpressure being provided in the conduit assembly, to being positioned to allow the transport of the cleaning liquid past the valve member in a direction away from the valve actuator.

[0052] Additionally provided is a cleaning device assembly including the cleaning device and a cleaning material for applying the cleaning liquid to the surface to be cleaned.

[0053] Further provided is a wet cleaning apparatus including an underpressure generator, and the cleaning device or the cleaning device assembly.

[0054] FIG. 1 schematically depicts a working principle of a wet cleaning apparatus 100 comprising an underpressure generator 102 and a porous layer 104. The underpressure generator 102 is arranged to apply suction to a back side 106 of the porous layer 104. The front side 108 of the porous layer 104 can, in use, face the surface to be cleaned (not visible in FIG. 1).

[0055] The wet cleaning apparatus 100 can comprise a cleaning device 110 in which a dirt inlet structure 112 is defined, with the dirt inlet structure 112 being arranged to apply the suction generated by the underpressure generator 102 to the back side 106 of the porous layer 104.

[0056] A liquid pick-up region of the porous layer 104 may be delimited by sealing attachment of the porous layer 104 around the dirt inlet structure 112.

[0057] The sealing attachment of the porous layer 104 around the dirt inlet structure 112, may assist to maintain an underpressure in the dirt inlet structure 112 with or without the flow being applied by the underpressure generator 102 included in the wet cleaning apparatus 100.

[0058] The sealing attachment can be implemented in any suitable manner, such as by gluing or welding the porous layer 104 around the dirt inlet structure 112, for example gluing and / or welding the porous layer 104 around one or more tubes or channels that define the dirt inlet structure 112.

[0059] Still referring to FIG. 1, the cleaning device 110 can comprise a support substrate 114. The support substrate 114 may, for example, be regarded as a main body of the cleaning device 110.

[0060] The support substrate 114 may, for instance, be a pliable support substrate 114. Such a pliable support substrate 114 can assist the cleaning device 110 to follow contours on the surface to be cleaned. Alternatively or additionally, the pliability of the pliable support substrate 114 may assist cleaning of the cleaning device 110 after use, for example involving wringing liquid from the cleaning device 110 and / or washing at least part of the cleaning device 110 in the user's washing machine.

[0061] Such a pliable support substrate 114 may be formed from any suitable pliable material. For example, the pliable material forming the pliable support substrate 114 can comprise a polymeric material and / or elastomeric material.

[0062] Particular mention is made of silicone rubber and ethylene-vinyl acetate, in other words a copolymer of ethylene and vinyl acetate, for the pliable material.

[0063] Other polymeric and / or elastomeric materials, such as a polydiene, e.g. polybutadiene, a thermoplastic elastomer, and so on, can also be contemplated for the pliable material.

[0064] Alternatively or additionally, the pliable material can be less than 50 Shore A, preferably less than 20 Shore A, most preferably less than 10 Shore A.

[0065] In a non-limiting example, the pliable material is 4 Shore A silicone rubber.

[0066] The pliable support substrate 114 can, for instance, be formed from a closed cell foam material, for example an ethylene-vinyl acetate closed cell foam material.

[0067] Such a closed cell foam material may facilitate an efficient (and inexpensive) production / assembly process for fabricating the cleaning device 110. Moreover, the closed cellular structure of the closed cell foam material can assist to retain liquid in the dirt inlet structure 112.

[0068] When the cleaning device 110 comprises the support substrate 114, e.g. the pliable support substrate 114, the dirt inlet structure 112 may be recessed into and / or embossed on a bottom surface of the support substrate 114, which bottom surface faces, in use, the surface to be cleaned.

[0069] In the scenario that the dirt inlet structure 112 is recessed into the bottom surface of the support substrate 114, the dirt inlet structure 112 may comprise, e.g. be defined by, a groove defined in and extending across at least part of the bottom surface.

[0070] When the dirt inlet structure 112 is embossed on the bottom surface of the support substrate 114, the dirt inlet structure 112 may comprise, e.g. be defined by, an arrangement of protruding elements protruding from the bottom surface and extending across at least part of the bottom surface, with path(s) for the dirty liquid being defined between protruding elements of the arrangement of protruding elements.

[0071] As shown in FIG. 1, a dirt conduit 116 can fluidly connect the dirt inlet structure 112 to the underpressure generator 102. At least part of the dirt conduit 116 can be defined, for example, in a connector for connecting the cleaning device 110 to the underpressure generator 102.

[0072] FIG. 1 schematically depicts pores 118 of the porous layer 104. When the porous layer 104 is dry, the porous layer 104 may be regarded as being in an "air transport state" in which air is transported through each of the dry pores 118 of the porous layer 104. A "liquid transport state", as shown in a) of FIG. 1, corresponds to liquid, e.g. water, being transported through all of the (wetted) pores 118 of the porous layer 104 (but note that the (ample) liquid below the pores is not visible in a)). The end of the "liquid transport state" is shown in b) of FIG. 1, an intermediate regime is shown in c) of FIG. 1, and an end regime is shown in d) of FIG. 1.

[0073] The pores 118, e.g. micropores, may each have a different "breaking pressure." This is represented in FIG. 1 by the number provided underneath each pore 118. For the sake of simplicity, each number is rounded to a single digit.

[0074] Taking as an illustrative example a porous layer 104 in the form of a cloth made from fibers and yarns, which are woven together into a sheet of fabric, the pore sizes present in such a porous layer 104 may be defined between all fibers and yarns, so the pore sizes present in the cloth are not fixed to exactly one size, but rather vary statistically. This variation is represented in FIG. 1 via the different numbers under each pore 118.

[0075] At start-up of the underpressure generator 102, e.g. pump, all liquid, e.g. water, is drawn from the surface to be cleaned, and the required pressure is the liquid transport pressure, in this example set at "1". The underpressure in the dirt inlet structure 112 behind the porous layer 104 is correspondingly "1".

[0076] In b), the underpressure starts to rise. When all the liquid, e.g. water, has been removed from the surface to be cleaned, all pores 118 may be blocked via the surface tension of the residual liquid therein. In the depicted illustrative example, the underpressure generator 102 is a fixed flow pump, and hence continued operation of the pump may increase the underpressure. At a certain point, the underpressure in the dirt inlet structure 112 may rise to the level, such as "4", of the breaking pressure of the "weakest" pores 118, and exceeding of the breaking pressure of these pores 118 means that air starts to be transported therethrough. Since the pressure in the dirt inlet structure 112 behind the porous layer 104 may already be significant when these first pores 118 "break", the air transported by these pores 118 at this point may be significant. Step c) in FIG. 1 can thus be regarded as schematically representing an intermediate regime.

[0077] In the intermediate regime, pores 118 may be getting blocked while other pores 118 are still transporting liquid from further regions (further away from the dirt inlet structure 112), hence creating more underpressure close to the dirt inlet structure 112. This can make the underpressure rise relatively slowly until all free liquid is gone. This may all be influenced by the pump rate and, in at least some examples, the properties of the dirt inlet structure 112, together with the flexibility of all elements, deforming when underpressure is applied.

[0078] This process may continue until the air transported is equal to the pump rate in this illustrative example, and the underpressure in the dirt inlet structure 112 behind the porous layer 104 is lower than the breaking pressure of the remaining "unbroken" pores 118 having the lowest breaking pressure. Step d) in FIG. 1 can thus be regarded as schematically representing an end regime.

[0079] FIG. 2 schematically depicts an exemplary test arrangement 120 for testing the breaking pressure characteristics of the porous layer 104. The porous layer 104 is clamped between a clamping member 122 and a base plate 124. The clamping member 122 delimits holes for bolts 126, which bolts 126 are received in threaded holes in the base plate 124. Turning of the bolts 126 in the appropriate direction enables clamping / releasing of the porous layer 104.

[0080] In this specific example, the clamping member 122 is an aluminium ring having a thickness of 10 mm, and the base plate 124 is made of poly (methyl methacrylate) having a thickness of 10 mm. The sample of the porous layer 104 is a circular disk having a diameter of 140 mm. The sample is secured using eight bolts 126.

[0081] The dirt inlet structure 112 in this test arrangement 120 is provided in the form of a coarse mesh with a diameter of 80 mm. The dirt conduit 116 is partly defined by an opening of a transport duct 128 provided in the base plate 124.

[0082] The test arrangement 120 comprises an underpressure generator 102 for generating an underpressure in the dirt inlet structure 112, and a pressure sensor 130, e.g. a pressure gauge, arranged to measure the pressure in the dirt inlet structure 112.

[0083] The pressure sensor 130 in this specific example comprises a pressure gauge in combination with a data acquisition unit (LabQuest ®< 2) to enable monitoring of the pressure as a function of time.

[0084] The underpressure generator 102 in this specific example is in the form of a peristaltic pump or a syringe pump, e.g. a 250 mL syringe pump. The peristaltic pump can provide a pulsed water flow. The syringe pump was found to permit more precise measurements than the peristaltic pump.

[0085] The test arrangement 120 also comprises a pressure line filter 132 in the form of a chamber arranged to prevent liquid from entering the pressure sensor line 134 connecting the pressure line filter 132 with the pressure sensor 130. Downstream of the pressure line filter 132 and the underpressure generator 102 is a collection reservoir 136 for collecting the liquid pumped through the porous layer 104.

[0086] The testing procedure comprises clamping the sample of the porous layer 104 between the clamping member 122 and the base plate 124, and then setting the underpressure generator 102 to deliver a flow rate of 100 cm 3< / minute. The pressure line filter 132 is checked to ensure that it is empty, the pressure gauge of the pressure sensor 130 is zeroed and reconnected before each measurement. 25 cm 3< of water is then poured onto the sample of the porous layer 104, leaving a layer of water on the porous layer 104 having a depth of approximately 4 mm. A flushing run is then implemented by starting the underpressure generator 102 such that the water is pulled through the sample of the porous layer 104. Following the flushing run, the underpressure generator 102 is stopped and 25 cm 3< of water is poured onto the sample of the porous layer 104, and a measurement run is implemented by triggering the data acquisition unit to start the data acquisition and starting the underpressure generator 102.

[0087] A typical graph of underpressure vs time from the data acquisition is provided in FIG. 3, together with schematic diagrams of the porous layer 104. Initially, the above-described "liquid transport state" 138 is adopted in which the liquid 140, in this example water, is transported through the (pre-wetted) pore 118. The recorded "transport pressure" in this case corresponds to the pressure difference required to transport the liquid 140 through the porous layer 104 and the dirt inlet structure 112.

[0088] The governing equation describing the "liquid transport state" 138 may be the following Poiseuille equation: Δ P = 8 ηLϕ πr 4 where ΔP is the pressure difference across the pore 118; η is the dynamic viscosity of the liquid; L is the length of the pore 118; ϕ is the volumetric flow rate; and r is the radius of the pore 118.

[0089] Assuming, for instance, a pore diameter of 20 µm, with the pore 118 extending across a porous layer 104 having a thickness of 0.8 mm, with an estimated volumetric flow rate of about 4.96*10 -14< m 3< / s per pore 118 (from a typical fluid flow of 100 cm 3< / minute), and with η water being 1*10 -3< Pa s, ΔP = 10.1 Pa.

[0090] Subsequently to the "liquid transport state" 138, the intermediate regime 142 is adopted in which almost all of the liquid 140 has been removed from the surface of the sample of the porous layer 104, such that most of the pores 118 are in the above-described "fluid block state" in which the surface tension of the (residual) liquid 140 retained in the wetted pore(s) 118 of the porous layer 104 prevents air 144 from being transported through the pore 118. An ever decreasing number of pores 118 may be in the "liquid transport state" in the intermediate regime 142. The "fluid block state" allows a significantly higher underpressure, so during the intermediate regime 142 the underpressure increases relatively rapidly, as shown.

[0091] The governing equation describing the "fluid block state" may be the following Droplet dP equation: P i − P O = 2 T R where P i and Po are the inside and outside pressures, and R is the fluid drop radius, as schematically depicted in FIG. 3. T is the surface tension.

[0092] Assuming, for instance, that R is 10 µm for a typical 20 µm diameter pore 118, and T water is 0.073 N / m, P i - P O = ΔP = 14600 Pa.

[0093] The ΔP of 14600 Pa from the above Droplet dP equation may be increased to 18000 Pa when detergent is added to the water. Whilst water surface tension decreases when detergent is added (T soapy water is 0.045 N / m.), two surfaces in the bubble over the pore 118 are created: the inside and the outside of the bubble. Thus, the breaking pressure in the case of detergent being added to the water may be approximately double that of a single-layer surface: P i − P O = 4 T R

[0094] Following the intermediate regime 142, the end regime 146 is adopted in which all free water has been removed from the surface of the porous layer 104, and all the pores 118 are initially in the "fluid block state". Since the underpressure generator 102 continues drawing water through the porous layer 104, hence increasing the underpressure, this may cause some of the fluid blocks to break such that air 144 is transported through the respective pores 118 in an "air transport state". The associated ingress of air may come to an equilibrium in the end regime 146 in which the applied flow results in an underpressure which causes no more fluid blocks to break. The latter corresponds to the "breaking pressure" of the porous layer 104 being investigated.

[0095] The governing equation describing the "air transport state" may be the Poiseuille equation provided above for the "liquid transport state". Assuming, for instance, a pore diameter of 20 µm, with the pore 118 extending across a porous layer 104 having a thickness of 0.8 mm, with an estimated volumetric flow rate of about 4.96*10 -14< m 3< / s per pore 118 (from a typical fluid flow of 100 cm 3< / minute), and with η air being 18.1*10 -6< Pa·s, ΔP = 0.18 Pa.

[0096] Overall, the air transport pressure (e.g. 0.18 Pa) and the water transport pressure (e.g. 10.1 Pa) may both be significantly smaller, e.g. negligible, in comparison to the surface tension-derived pressure difference (e.g. 14600 Pa).

[0097] The porous layer 104 may accordingly be selected to provide a relatively large difference between breaking pressure and water transport pressure. The significant advantage of this is that the porous layer 104 can be "pre-tensioned" by the underpressure generator 102. A wetted porous layer 104, e.g. pick-up pad, can be set to a pressure of, for example, 14600 Pa. When this state is reached, no more power may be needed. Whenever a droplet of liquid, e.g. water, is added to the porous layer 104, the air-liquid surface disappears and suddenly the function of transporting the liquid can be fulfilled at a pressure difference of, for example, 10 Pa.

[0098] Thus, the wet cleaning apparatus 100 can be highly energy-efficient and effective. Liquid, e.g. water, may only be transported at the position where it is fed to the porous layer 104. Once no liquid is provided for transportation, the wet cleaning apparatus 100 can return to its "pre-tensioned" state.

[0099] The pore size, in other words pore diameter, of the pores 118 of the porous layer 104 may be selected in order to balance a relatively high underpressure with a relatively low resistance to transport of liquid through the porous layer 104.

[0100] Whilst the foregoing has focussed on pick-up of liquid from the surface to be cleaned, a key consideration is delivery of cleaning liquid towards the surface to be cleaned. FIG. 4 schematically depicts a wet cleaning apparatus 100 comprising the underpressure generator 102, the porous layer 104, the dirt inlet structure 112, and the dirt conduit 116, as well as a dirty liquid collection tank 148 arranged to receive the dirty liquid 150 from the dirt inlet structure 112. Moreover, the wet cleaning apparatus 100 shown in FIG. 4 comprises a cleaning liquid tank 152 for containing cleaning liquid 154, and a cleaning liquid outlet structure 156 for delivering the cleaning liquid 154 towards the surface to be cleaned 158, for example by delivering the cleaning liquid 154 to a cleaning liquid applicator material 160 that applies the cleaning liquid 154 to the surface to be cleaned 158.

[0101] As shown in FIG. 4, a cleaning liquid pump 162 can transport the cleaning liquid 154 towards the surface to be cleaned 158. Thus, the cleaning liquid pump 162 can pump the cleaning liquid 154 towards the surface to be cleaned 158, while the underpressure generator 102, e.g. peristaltic pump, removes liquid from the porous layer 104, to fill the dirty liquid collection tank 148.

[0102] Inclusion of both the underpressure generator 102 and the additional cleaning liquid pump 162, as well as components, e.g. a battery pack, for powering each of the underpressure generator 102 and the cleaning liquid pump 162, can significantly increase the cost of the wet cleaning apparatus 100.

[0103] Referring to FIGs. 5A and 5B, the cleaning device 110 according to the present disclosure includes a conduit assembly 164, 166 and a valve assembly 168. The valve assembly 168 comprises a valve member 170 displaceable between a first position that restricts transport of the cleaning liquid 154 from the cleaning liquid tank 152 (see FIG. 5A) to a second position that allows transport of the cleaning liquid 154 from the cleaning liquid tank 152, past the valve member 170 in the second position, towards the cleaning liquid outlet structure 156 (see FIG. 5B).

[0104] It is noted that despite the term "a second position" using the indefinite article, "a", this should not be regarded as limiting the number of positions of the valve member 170 that allow the transport of the cleaning liquid 154 past the valve member 170 towards the cleaning liquid outlet structure 156 to only a single second position. Rather, the label "second position" is used herein to denote any displaced position of the valve member 170 (relative to the first position) that allows the transport of the cleaning liquid 154 past the valve member 170 towards the cleaning liquid outlet structure 156.

[0105] With continued reference to FIGs. 5A and 5B, the cleaning device 110 comprises a valve actuator 172 arranged to displace the valve member 170, in response to an underpressure being provided in the conduit assembly 164, 166, to the second position to allow the transport of the cleaning liquid 154 past the valve member 170 in a direction away from the valve actuator 172.

[0106] Since the valve actuator 172 displaces the valve member 170 in response to the underpressure provided in the conduit assembly 164, 166, the delivery of the cleaning liquid 154 towards the surface to be cleaned 158 can be controlled, for example, using an underpressure generator 102 already included in a vacuum cleaner to which the cleaning device 110 is attached / attachable. It is noted in this connection that the present disclosure being directed, in part, to the valve assembly-comprising cleaning device 110 by itself reflects the fact that a user can be supplied with the cleaning device 110 and can connect the conduit assembly 164, 166 thereof to an underpressure generator 102, e.g. an underpressure generator 102 included in a vacuum cleaner, already in the user's possession or sourced separately from the cleaning device 110.

[0107] The transporting of the cleaning liquid 154 can thus be actively switched on and off when the underpressure generator 102, e.g. the vacuum cleaner comprising the underpressure generator 102, is powered on and off.

[0108] It is generally noted that no cleaning liquid 154 may leak from the cleaning device 110 when the underpressure is not being provided in the conduit assembly 164, 166, e.g. due to the underpressure generator 102 being switched off, because of the valve member 170 being in the first position closing the cleaning liquid tank 152.

[0109] To this end, the valve actuator 172 may be arranged, e.g. biased, to cause the valve member 170 to be in the first position when no underpressure is provided in the conduit assembly 164, 166 (or at least when there is insufficient underpressure to cause the valve actuator 172 to move the valve member 170 from the first position).

[0110] The cleaning device 110 may be relatively inexpensive, due to the cleaning device 110 not itself requiring pumps and batteries, and can also benefit from being relatively simple due to the cleaning device 110 not itself requiring electrical components.

[0111] Moreover, and as shown in FIGs. 5A and 5B, the delivery of the cleaning liquid 154 towards the surface to be cleaned 158 can be controlled using an underpressure generator 102 provided also for removal of liquid from the surface to be cleaned 158, e.g. via the porous layer 104. In this case, both dirty liquid pick-up and cleaning liquid delivery control functionalities can be realized using the same underpressure generator 102, thereby reducing costs compared to, for example, a scenario in which a dedicated cleaning liquid pump 162 is included in addition to the underpressure generator 102 (as shown in FIG. 4).

[0112] In such embodiments, the dirt inlet structure 112 can be fluidly connected to the conduit assembly 164, 166, as well as the valve actuator 172 being arranged to displace the valve member 170 in response to the underpressure provided in the conduit assembly 164, 166.

[0113] For example, and with continued reference to FIGs. 5A and 5B, the conduit assembly 164, 166 can comprise a first conduit 164 and a second conduit 166, with the valve actuator 172 being arranged to displace the valve member 170 in response to the underpressure being provided in the first conduit 164, and with the dirt inlet structure 112 being fluidly connected to the second conduit 166, e.g. via the dirt conduit 116.

[0114] In such embodiments, the dirt conduit 116 can fluidly connect the dirt inlet structure 112 to the dirty liquid collection tank 148, with the dirty liquid collection tank 148 being fluidly connected / connectable to the underpressure generator 102 via the second conduit 166.

[0115] The dirty liquid collection tank 148 may be directly connected to, for example, the vacuum of a vacuum cleaner. In this way, the dirty liquid collection tank 148 can be provided with an underpressure as soon as the vacuum cleaner powers up. The liquid present in the porous layer 104 may therefore be sucked into the dirty liquid collection tank 148 directly.

[0116] By the valve actuator 172 being arranged so that the cleaning liquid 154 is transported past the valve member 170 in a direction away from the valve actuator 172, the risk of the cleaning liquid 154 being transported interfering with functioning of the valve actuator 172 can be lessened or removed.

[0117] In some embodiments, such as shown in FIGs. 5A and 5B, the cleaning liquid tank 152 and the cleaning liquid outlet structure 156 are arranged so that, when the cleaning device 110 is orientated for use on a floor, the cleaning liquid 154 is transportable at least partly by gravity past the valve member 170 in the second position. Using gravity in this manner can assist to simplify design of the cleaning liquid delivery functionality.

[0118] In such embodiments, the valve actuator 172 may be arranged above the valve member 170 when the cleaning device 110 is orientated for use on the floor, as shown in FIGs. 5A and 5B.

[0119] It is noted at this point that the cleaning liquid outlet structure 156 can be implemented in any suitable manner. In embodiments in which the cleaning device 110 comprises the support substrate 114, e.g. the pliable support substrate 114, the cleaning liquid outlet structure 156 may be recessed into and / or embossed on the bottom surface of the support substrate 114, e.g. together with the dirt inlet structure 112.

[0120] In the scenario that the cleaning liquid outlet structure 156 is recessed into the bottom surface of the support substrate 114, the cleaning liquid outlet structure 156 may comprise a groove defined in and extending across at least part of the bottom surface.

[0121] When the cleaning liquid outlet structure 156 is embossed on the bottom surface of the support substrate 114, the cleaning liquid outlet structure 156 may comprise, e.g. be defined by, an arrangement of protruding portions protruding from the bottom surface and extending across at least part of the bottom surface, with path(s) for the cleaning liquid 154 being defined between protruding portions of the arrangement of protruding portions.

[0122] In some embodiments, the cleaning liquid outlet structure 156 comprises at least one cleaning liquid distribution strip, with each of the at least one cleaning liquid distribution strip comprising a channel arranged to receive the cleaning liquid 154 from the cleaning liquid tank 152 when the valve member 170 is in the second position. Each of the at least one cleaning liquid distribution strip may comprise apertures arranged along its length.

[0123] The channel can, for example, be defined in the bottom surface of the support substrate, e.g. in the bottom surface of the pliable support substrate.

[0124] The apertures may, for example, be dimensioned such that passage of the cleaning liquid 154, e.g. aqueous cleaning liquid, through the apertures is restricted, due to the surface tension of the cleaning liquid 154, while the channel is being filled with the cleaning liquid 154, but with passage of the cleaning liquid 154 through all of the apertures of the cleaning liquid distribution strip at the same time being permitted once the channel has been filled. This may enable relatively uniform wetting of the surface to be cleaned 158 across the length of the cleaning liquid distribution strip.

[0125] To this end, each aperture may have, for example, a diameter less than 1 mm, for example a diameter in the range of 0.1 to 1 mm, preferably 0.1 to 0.8 mm, most preferably 0.1 to 0.5 mm, such as about 0.3 mm.

[0126] The cleaning liquid distribution strip can be formed of any suitable material, such as a metal, a metal alloy, e.g. stainless steel, and / or a polymer. Forming the cleaning liquid distribution strip from a polymer can make the cleaning liquid distribution strip more lightweight and / or cheaper to manufacture.

[0127] In some embodiments, such as shown in FIGs. 5A and 5B, the cleaning liquid outlet structure 156 comprises a first cleaning liquid outlet portion and a second cleaning liquid outlet portion, with the dirt inlet structure 112 being arranged in-between the first cleaning liquid outlet portion and the second cleaning liquid outlet portion.

[0128] For example, the at least one cleaning liquid distribution strip can include a first cleaning liquid distribution strip and a second cleaning liquid distribution strip, with the dirt inlet structure 112 being arranged in-between the first cleaning liquid distribution strip and the second cleaning liquid distribution strip.

[0129] In other embodiments (not shown), the dirt inlet structure 112 comprises a first dirt inlet portion and a second dirt inlet portion, with the cleaning liquid outlet structure 156 being arranged in-between the first dirt inlet portion and the second dirt inlet portion.

[0130] As shown in FIGs. 5A and 5B, a cleaning liquid conduit 174 can fluidly connect the cleaning liquid tank 152 to the cleaning liquid outlet structure 156.

[0131] The valve actuator 172 can be arranged in any suitable manner in order to be responsive to the underpressure in the conduit assembly 164, 166, e.g. the first conduit 164 thereof, to move the valve member 170 to the second position. In some embodiments, such as shown in FIGs. 5A and 5B, the valve actuator 172 comprises a membrane coupled to the valve member 170, with the membrane being deformable by the underpressure provided in the conduit assembly 164, 166 to move the valve member 170 to the second position. Such a membrane can provide a relatively straightforwardly manufacturable way of implementing the valve actuator 172.

[0132] The valve actuator 172, e.g. the membrane, can, for example, be coupled to the valve member 170 by a connecting member 176 extending from the valve actuator 172 to the valve member 170.

[0133] The connecting member 176 can, for example, traverse part of an interior of the cleaning liquid tank 152 in order to couple the valve actuator 172, e.g. the membrane, to the valve member 170.

[0134] The valve actuator 172, e.g. membrane, can be arranged in a housing 178, in which housing 178 an air vent 180 is defined. The air vent 180 can allow outside air to be drawn into the housing 178 to avoid a lower pressure being otherwise generated at a side of the valve actuator 172 due to a volume increase when the valve actuator 172 is moved by the underpressure in the conduit assembly 164, 166. Thus, the air vent 180 can facilitate movement of the valve actuator 172, by avoiding such a lower pressure pulling the valve actuator 172 in an opposite direction to the direction in which the valve actuator 172 is being drawn by the underpressure in the conduit assembly 164, 166.

[0135] Prior to the underpressure being provided in the conduit assembly 164, 166, e.g. prior to the underpressure generator 102 being activated, the valve member 170 in the first position can close the downstream path, via the cleaning liquid conduit 174, for the cleaning liquid 154 to flow towards the cleaning liquid outlet structure 156 (as shown in FIG. 5A). However, when the underpressure is provided in the conduit assembly 164, 166, for instance when the underpressure generator 102 is activated, the valve actuator 172 can be drawn towards or into the conduit assembly 164, 166, causing the valve member 170 to move in the same direction as the valve actuator 172 to adopt the second position (as shown in FIG. 5B).

[0136] It is noted that the level of the cleaning liquid 154 in the cleaning liquid tank 152 is lower in FIG. 5B as compared with FIG. 5A to reflect the fact that some of the cleaning liquid 154 has been transported from the cleaning liquid tank 152 past the valve member 170 in the second position towards the cleaning liquid outlet structure 156, as a consequence of the underpressure being provided in the conduit assembly 164, 166, e.g. in the first conduit 164 thereof.

[0137] The level of the dirty liquid 150 in the dirty liquid collection tank 148 is higher in FIG. 5B as compared with FIG. 5A to reflect the fact that dirty liquid 150 has been transported via the porous layer 104 and the dirt inlet structure 112 to the dirty liquid collection tank 148, as a consequence of the underpressure being provided in the conduit assembly 164, 166, e.g. in the second conduit 166 thereof.

[0138] With continued reference to FIGs. 5A and 5B, the cleaning device 110 can include an air valve 182 arranged to control air ingress into the cleaning liquid tank 152 when the cleaning liquid 154 is being transported past the valve member 170 in the second position. In such embodiments, the air valve 182, for example air restriction valve 182, can restrict ingress of air into the cleaning liquid tank 152, and hence restrict outflow of the cleaning liquid 154 from the cleaning liquid tank 152 when the valve member 170 is in the second position.

[0139] Thus, the air valve 182 can operate as a flow regulator for regulating flow of the cleaning liquid 154 towards the cleaning liquid outlet structure 156.

[0140] In some embodiments, the cleaning device 110 is included together with the cleaning liquid applicator material 160 in a cleaning device assembly. In such embodiments, the cleaning liquid applicator material 160 may be detachable from the cleaning device 110. Thus, the cleaning liquid applicator material 160 can be detached for cleaning and / or replacement after use.

[0141] The cleaning liquid applicator material 160 can be detachably coupled to the cleaning device 110 in any suitable manner. In some embodiments, the cleaning liquid applicator material 160 is detachable from the cleaning device 110 via a hooks-loops fastening assembly, e.g. Velcro ®< .

[0142] In such embodiments, part of the hooks-loops fastening assembly can be arranged at an upwardly facing portion of the support substrate 114, such that the cleaning liquid applicator material 160 is required to wrap at least partially around the support substrate 114 in order to fasten to the cleaning device 110.

[0143] In some embodiments, the cleaning liquid applicator material 160 comprises a backing member that includes a back side and a projections-comprising side, with the projections-comprising side comprising projections, e.g. tufts and / or ridges, that project from the backing member so that at least some of the projections are contactable with the surface to be cleaned 158.

[0144] Implicit in the projections each projecting from the backing member is that points at which the projections join to the backing member are spatially separated from each other.

[0145] Thus, coarse dirt, e.g. sand, may be accommodated in spaces between the projections, thereby alleviating the risk of scratching of the surface to be cleaned 158. It is also noted that the projections can accommodate unevenness of the surface to be cleaned 158, noting that individual projections can enter recesses, dislocations etc. in the surface to be cleaned 158.

[0146] The present disclosure further relates to the wet cleaning apparatus 100 comprising the underpressure generator 102, and the cleaning device 110 or the cleaning device assembly, with the underpressure generator 102 being configured to provide the underpressure in the conduit assembly 164, 166. In such embodiments, the user can be conveniently supplied with the cleaning device 110 / cleaning device assembly together with the underpressure generator 102.

[0147] In some embodiments, the wet cleaning apparatus 100 comprises a nozzle to which the cleaning device 110 is detachably couplable. In such embodiments, the nozzle and the cleaning device 110 can be arranged so that when the cleaning device 110 is coupled to the nozzle, the conduit assembly 164, 166 is fluidly connected to the underpressure generator 102 to enable the underpressure to be provided in the conduit assembly 164, 166.

[0148] In such embodiments, the nozzle can be, for example, the nozzle of a vacuum cleaner. Thus, cleaning liquid delivery, as well as, in some embodiments, dirty liquid pick-up functionality, can be added to the vacuum cleaner by coupling its nozzle to the cleaning device 110.

[0149] The nozzle and the cleaning device 110 can be detachably coupled in any suitable manner. In some embodiments, the nozzle and the cleaning device 110 are detachably couplable to each other via a magnetic coupling assembly. This can make attaching / detaching the cleaning device 110 to / from the nozzle relatively simple and convenient for the user to implement.

[0150] The underpressure generator 102 can be of any suitable type, provided that the underpressure generator 102 is capable of generating a sufficient underpressure for actuating the valve actuator 172 to move the valve member 170 to the second position. In some embodiments, the underpressure generator 102 comprises a motor and a fan rotatable by the motor to provide the underpressure in the conduit assembly 164, 166. Such a motor and fan-comprising underpressure generator 102 can be included, for example, in a vacuum cleaner, e.g. a vacuum cleaner whose nozzle is detachably couplable to the cleaning device 110.

[0151] In embodiments in which the cleaning device 110 comprises the porous layer 104 covering the dirt inlet structure 112, the underpressure generator 102 may be configured to provide a pressure difference between an inside of the wet cleaning apparatus 100 and atmospheric pressure for drawing fluid through the porous layer 104, with the pressure difference being in a range of 3000 Pa to 13500 Pa, preferably 5000 Pa to 9000 Pa, most preferably 7000 Pa to 9000 Pa.

[0152] The pressure difference can be directly and positively verified in a given wet cleaning apparatus 100 by, for example, drilling a hole in a tube of the wet cleaning apparatus 100 which is fluidly connected with the dirt inlet structure 112 and using the hole to couple to a pneumatic pressure sensor itself having a tube with a membrane covering an end thereof; the sensor being thus connected using an airtight connection. The sensor may be arranged to avoid disturbing the flow, hence the skilled person will arrange the sensor to avoid, for instance, creating a bypass flow. No flow may be towards or from the sensor: only pressure is transmitted. In this way, the flow of the appliance may never be compromised (hence may remain at the set level in spite of the sensor installation).

[0153] The pressure sensor is connected between the porous layer 104 and the underpressure generator 102 and as close to the porous layer 104 as possible, to minimise the influence of other factors, such as flow resistance etc., on the sensed pressure difference.

[0154] The sensing element / membrane of the pressure sensor / gauge is ideally arranged / positioned in the pressure sensor so that the sensing element can be placed directly (without the requirement for connecting tubes) in the tube, or in a cavity behind the porous layer 104.

[0155] By positioning the membrane of the pressure sensor, in other words membrane pressure gauge, with the membrane positioned at, in other words in line with, the wall of the tube (or exposed to the cavity), measurement errors may be minimized, as will be appreciated by a person skilled in the art.

[0156] It is noted that air bubbles inside narrow tubes may generate resistance (capillary / surface tension effects), and hence may influence the measurement. Hence the skilled person will further appreciate that care is also to be taken that air bubbles (water-air surfaces) do not unduly influence the pressure difference measurement.

[0157] It is further noted that a column of water present between the pressure sensor and the porous layer 104 should be deducted from the measurement result (if such a column of water is present during the measurement), to compensate for the static pressure generated by the column of water.

[0158] Once the pressure sensor is arranged as described above, it may be ascertained that maintenance of the underpressure is due to the porous layer 104 and not some other element, such as a valve. Any such element that influences the underpressure that is presented to the porous layer 104 should be rendered inoperable for the purpose of performing the measurement.

[0159] Component(s) that dispense the cleaning liquid 154 is / are disengaged when performing the pressure difference measurement. Accordingly, the position of the valve member 170 is fixed (and any further adjustments made) to block transport of the cleaning liquid 154 from the cleaning liquid tank 152 while the measurement is being performed.

[0160] The wet cleaning apparatus 100 is turned on (in the desired setting), so that the pick-up system comprising the underpressure generator 102 is activated. Recording of data from the pressure sensor is started.

[0161] The pick-up area of the cleaning device 110 is suspended in a layer of water, at max. 5 mm depth.

[0162] The pick-up area is then lifted from the water without tilting it in any way (so that the cleaning device 110 remains in a cleaning position, as if it were positioned to clean the floor), so that the water is no longer touching the porous layer 104. At this point, "free water" will be removed from the porous layer 104, all pores 118 will go into their "blocked state", and the breaking pressure is determinable. The measurement result will resemble the graph shown in FIG. 3, once again noting that an equilibrium is established in the end regime 146 in which the applied flow results in an underpressure which causes no more fluid blocks to break.

[0163] The breaking pressure obtained from this measurement result, referring to the end regime 146, is the "pressure difference between the inside of the wet cleaning apparatus 100 and atmospheric pressure for drawing fluid through the porous layer 104." It is verified from the measurement result whether or not the 3000 Pa to 13500 Pa range (or the 5000 Pa to 9000 Pa range or the 7000 Pa to 9000 Pa range, if applicable) is satisfied.

[0164] It is noted that the porous layer 104 may be arranged to contact liquid on the surface to be cleaned 158. Thus, the porous layer 104 may be defined from the front side 108 of the porous layer 104 exposable to liquid on the surface to be cleaned 158 to the back side 106 exposed to the dirt inlet structure 112.

[0165] In some embodiments, the wet cleaning apparatus 100 comprises a vacuum cleaner; for example a stick-type vacuum cleaner, an upright vacuum cleaner, a canister-type vacuum cleaner (see FIG. 6) or a robotic vacuum cleaner (see FIG. 7).

[0166] It is noted that a vacuum cleaner can generate about 20000 Pa of underpressure, and a flow of about 30 L / s (resulting in about 200 W of mechanical power). The above-described liquid pick-up functionality, involving the porous layer 104, may only require an underpressure of >5000 Pa and a flow of about 250 cm 3< / minute (resulting in roughly 0.02 W of power). This means that the liquid pick-up functionality can easily be implemented using the vacuum cleaner.

[0167] The cleaning device 110 included in the vacuum cleaner-comprising wet cleaning apparatus 100 shown in FIG. 6 can be moved over the surface to be cleaned 158 during vacuuming as well as when applying the cleaning liquid 154 to the surface to be cleaned 158. Such movement can be assisted, for example, by wheels 184 included in the vacuum cleaner.

[0168] The wet cleaning apparatus 100 may in some examples be or comprise a robotic vacuum cleaner or a robotic wet mopping device configured to autonomously move the cleaning device 110 on the surface to be cleaned 158, such as the surface of a floor.

[0169] FIG. 7 schematically depicts an exemplary wet cleaning apparatus 100 comprising a robotic vacuum cleaner. The robotic vacuum cleaner may move autonomously on the surface to be cleaned 158, e.g. via automated control over the wheels 184.

[0170] The cleaning liquid stored in the cleaning liquid tank 152 can be delivered to the surface to be cleaned 158, and liquid can be picked up via the porous layer 104 and collected in the dirty liquid collection tank 148, during autonomous movement of the robotic vacuum cleaner. The underpressure generator 102, and thus delivery of the cleaning liquid 154 past the valve member 170 in the second position, may also be under automated control.

[0171] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0172] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0173] If the term "adapted to" is used in the claims or description, it is noted the term "adapted to" is intended to be equivalent to the term "configured to".

[0174] Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A cleaning device (110) comprising: a cleaning liquid tank (152) for containing cleaning liquid (154); a cleaning liquid outlet structure (156) for delivering the cleaning liquid towards a surface to be cleaned (158); a conduit assembly (164, 166); and a valve assembly (168) comprising: a valve member (170) displaceable between a first position, in which first position the valve member restricts transport of the cleaning liquid from the cleaning liquid tank, and being positioned to allow transport of the cleaning liquid from the cleaning liquid tank, past the valve member, towards the cleaning liquid outlet structure; and a valve actuator (172) arranged to displace the valve member, in response to an underpressure being provided in the conduit assembly, to being positioned to allow the transport of the cleaning liquid past the valve member in a direction away from the valve actuator.

2. The cleaning device (110) according to claim 1, comprising a dirt inlet structure (112) for receiving dirty liquid (150) from the surface to be cleaned (158), the dirt inlet structure being fluidly connected to the conduit assembly (164, 166).

3. The cleaning device (110) according to claim 2, comprising a dirty liquid collection tank (148) arranged to receive the dirty liquid (150) from the dirt inlet structure (112).

4. The cleaning device (110) according to claim 2 or claim 3, comprising a porous layer (104) for covering the dirt inlet structure (112).

5. The cleaning device (110) according to any one of claims 1 to 4, wherein the valve actuator (172) comprises a membrane coupled to the valve member (170), the membrane being deformable by the underpressure provided in the conduit assembly (164, 166) to move the valve member to being positioned to allow the transport of the cleaning liquid (154) past the valve member in the direction away from the valve actuator.

6. The cleaning device (110) according to any one of claims 1 to 5, comprising an air valve (182) arranged to control air ingress into the cleaning liquid tank (152) when the cleaning liquid (154) is being transported past the valve member (170).

7. The cleaning device (110) according to any one of claims 1 to 6, comprising a support substrate that includes a bottom surface for facing the surface to be cleaned (158), wherein the cleaning liquid outlet structure (156) is at least partly provided at the bottom surface.

8. The cleaning device (110) according to any one of claims 1 to 7, wherein the cleaning liquid tank (152) and the cleaning liquid outlet structure (156) are arranged so that, when the cleaning device is orientated for use on a floor, the cleaning liquid (154) is transportable at least partly by gravity past the valve member (170).

9. A cleaning device assembly comprising: the cleaning device (110) according to any one of claims 1 to 8; and a cleaning liquid applicator material (160) for applying the cleaning liquid (154) to the surface to be cleaned (158).

10. The cleaning device assembly according to claim 9, wherein the cleaning liquid applicator material (160) is detachable from the cleaning device (110); optionally wherein the cleaning liquid applicator material is detachable from the cleaning device via a hooks-loops fastening assembly.

11. The cleaning device assembly according to claim 9 or claim 10, wherein the cleaning liquid applicator material (160) comprises a backing member that includes a back side and a projections-comprising side, the projections-comprising side comprising projections that project from the backing member so that at least some of the projections are contactable with the surface to be cleaned (158).

12. A wet cleaning apparatus (100) comprising: an underpressure generator (102); and the cleaning device (110) according to any one of claims 1 to 8 or the cleaning device assembly according to any one of claims 9 to 11, wherein the underpressure generator is configured to provide the underpressure in the conduit assembly (164, 166).

13. The wet cleaning apparatus (100) according to claim 12, comprising a nozzle to which the cleaning device (110) is detachably couplable, wherein the nozzle and the cleaning device are arranged so that when the cleaning device is coupled to the nozzle, the conduit assembly (164, 166) is fluidly connected to the underpressure generator (102) to enable the underpressure to be provided in the conduit assembly; optionally wherein the nozzle and the cleaning device are detachably couplable to each other via a magnetic coupling assembly.

14. The wet cleaning apparatus (100) according to claim 12 or claim 13, wherein the underpressure generator (102) comprises a motor and a fan rotatable by the motor to provide the underpressure in the conduit assembly (164, 166); and / or wherein the wet cleaning apparatus comprises a vacuum cleaner.

15. The wet cleaning apparatus (100) according to any one of claims 12 to 14, wherein the wet cleaning apparatus (100) comprises the cleaning device (110) according to claim 4, and wherein the underpressure generator (102) is configured to provide a pressure difference between an inside of the wet cleaning apparatus and atmospheric pressure for drawing fluid through the porous layer (104), with the pressure difference being in a range of 3000 Pa to 13500 Pa.

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