Patent Description:
Wet cleaning apparatuses, for example wet mopping devices, are known which remove water from a surface to be cleaned. Such wet cleaning apparatuses can also apply cleaning liquid, e.g. water, to the surface to be cleaned, and then remove the liquid, e.g. with a suitable cloth.

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 airspeed (e.g. at least <NUM>/s) and/or brushpower 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.

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 cleaning liquid is used inefficiently.

When, for example, a replaceable/detachable cleaning material, e.g. a cleaning fabric, is included in the wet cleaning apparatus, it may be challenging for the user to (re-)attach the cleaning material to the wet cleaning apparatus, e.g. to a cleaner head included in the wet cleaning apparatus, in a reliable manner.

<CIT> discloses an apparatus for use with a vacuum cleaner nozzle having an intake opening with a flow area that receives a flow of working air. The apparatus comprises a cleaning pad with a structure that permits the working air to pass through the pad. The cleaning pad is configured to be installed over the intake opening in a position extending across the flow area.

<CIT> discloses a vacuum cleaner with a wet duster.

<CIT> discloses a mop adapted for attachment to a vacuum cleaner comprising a frame member and a mop element detachably secured to said frame member by a plurality of snap fasteners. The mop element has an opening therein adapted to receive a vacuum cleaner's nozzle, suction head, or other attachment. The mop element may be further secured to said frame member by a pair of hook and loop material fastening straps. In the preferred embodiment said straps are sewn onto the mop element and provide for convenient attachment and removal of the mop element from the frame member.

<CIT> discloses methods and an apparatus for cleaning a surface with a cleaning device having a body with a handle, a connector, and one or more cleaning heads that are removably attached to the cleaning device. Each cleaning head includes a lower surface arranged to contact a surface to be cleaned, a dirt collection chamber, and a pocket arranged to receive an insert of the connector to attach the cleaning head to the cleaning device. In some embodiments, the connector insert is pivotally connected to the connector. In some embodiments, the cleaning head includes a support structure and a cleaning sheet, with the pocket being formed between the support structure and the cleaning sheet.

<CIT> discloses a refill designed for use with a cleaning tool, such as a mop or a cleaning mitt. The refill includes a mopping sheet, formed from a water absorbing material, and a dusting sheet. In one example, the dusting sheet is removed from the refill after dusting a surface to expose the mopping sheet. A single refill allows a surface to be dusted and then mopped using the same cleaning tool.

According to examples in accordance with an aspect of the invention there is provided a cleaning element for attaching to a cleaner head, which cleaner head has a structured portion and at least one dirt inlet, the cleaning element comprising: a cleaning material for contacting a surface to be cleaned, the cleaning material comprising a liquid pick-up zone alignable with, so as to cover, the at least one dirt inlet, and a cleaning liquid application zone adjacent the liquid pick-up zone for applying cleaning liquid to the surface to be cleaned; a plurality of guiding elements cooperable with the structured portion to join and align the cleaning element with the cleaner head; and a fastener for securing the aligned cleaning element to the cleaner head, the fastener being spaced apart from the plurality of guiding elements across the cleaning material.

Cleaning elements which are attachable and detachable from a cleaner head offer several advantages, in particular the capability to remove the cleaning element for washing after use and/or replacement when the cleaning material, e.g. cleaning fabric, has become overly worn. However, challenges have been encountered when designing such a cleaning element for a cleaner head having at least one dirt inlet for receiving dirty liquid when suction is applied to the at least one dirt inlet. In particular, alignment of the liquid pick-up zone of the cleaning material with the at least one dirt inlet, such that the liquid passes through the liquid pick-up zone to reach the at least one dirt inlet, has been found difficult to reliably achieve by conventional cleaning element attachment methods.

The use of a plurality, in other words more than one, guiding element may assist to minimise the risk of misalignment of the cleaning element with respect to the cleaner head. Moreover, the fastener being provided across the cleaning material from the plurality of guiding elements means that the cleaning element can be straightforwardly secured to the cleaner head via the fastener following alignment and joining of the cleaning element to the cleaner head via the guiding elements.

In some embodiments, the cleaning element is elongated so as to define a length of the cleaning element, with the plurality of guiding elements being arranged along the length. Such a lengthways arrangement of the plurality of guiding elements may assist alignment of the cleaning element with respect to the cleaner head (the structured portion of the latter correspondingly being provided along its length).

In such embodiments, each of the liquid pick-up zone and the cleaning liquid application zone may be elongated so as to each longitudinally extend parallel with the length of the cleaning element.

In some embodiments, the plurality of guiding elements comprises, or is defined by, a plurality of pockets. In such embodiments, each of the plurality of pockets is arranged to receive and engage a tooth of a plurality of teeth included in the structured portion of the cleaner head. The plurality of pockets may represent a particularly convenient way of providing the plurality of guiding elements, and may assist to minimise unwanted movement of the cleaning element with respect to the cleaner head in widthways, lengthways and depth directions.

The fastener may be configured to secure the cleaning element to the cleaner head in widthways, lengthways and depth directions.

In some embodiments, the fastener is arranged on an upper side of the cleaning element facing away from the surface to be cleaned. In such embodiments, the guiding elements, e.g. pockets, may also be provided on the upper side of the cleaning element. Thus, the cleaning element can be advantageously aligned with and secured to the cleaner head while the underside of the cleaning element remains in contact with the surface to be cleaned.

In some embodiments, the fastener is included in a section of the cleaning element that is configured to flex around an edge of the cleaner head to enable the fastener to be secured to said edge and/or an upper side of the cleaner head that faces away from the surface to be cleaned. This may result in the cleaning element being more tightly secured to the cleaner head. Such tensioning of the cleaning element may assist to reduce resistance to motion over the surface to be cleaned, and may also provide a more consistent motion resistance for the user as a smaller tolerance window of positioning of the cleaning element on the cleaner head may be associated with the relatively tight securement of the cleaning element to the cleaner head.

Alternatively or additionally, the fastener may comprise a hooks-loops fastener, e.g. Velcro®, portion. The hooks-loops fastener portion may, for example, be in the form of a hooks-loops fastener, e.g. Velcro®, strip extending along the length of the cleaning element. An advantage of such a hooks-loops fastener portion is that the aligned cleaning element and cleaner head can be secured together in a straightforward manner by pressing the hooks-loops fastener portion against a complementary loops-hooks fastener portion provided on the cleaner head.

More generally, the alignment provided by the guiding elements in combination with predetermined positioning of the fastener based on the alignment may mean that the securement via the fastener can be made without requiring visual alignment of the fastener with a complementary cleaner head fastener.

For example, each of the pockets may have a length corresponding to the length of the base of the teeth, be sufficiently wide for full insertion of the teeth into the pockets, and have a depth selected for restricting movement of the teeth in the pockets in the depth direction.

Thus full insertion of the teeth into the pockets may effectively provide a signal to the user that the cleaning element is properly aligned with the cleaner head.

In other words, when the teeth are inserted, e.g. slid, all the way into the pockets, this may provide a tactile signal to the user that alignment in the widthways direction is correct. At the same time, the pockets may hold the teeth in the depth direction. Moreover, by the maximum length of each of the teeth corresponding to the maximum length of each of the pockets, when the teeth are fully inserted, e.g. slid, all the way into the pockets, the cleaning element may be aligned relative to the cleaner head in the lengthways direction.

In some embodiments, the cleaning element comprises a protrusion arranged to protrude from a periphery of the cleaning element such as to enable a user to trap the protrusion against the surface to be cleaned and thereby immobilise the cleaning element for said joining and alignment with the cleaner head.

In such embodiments, the periphery from which the protrusion protrudes may be spaced apart from the plurality of guiding elements across the cleaning material. In this manner, the trapping of the protrusion against the surface to be cleaned can assist to avoid that the cleaning element is pushed away when the cleaning element is being aligned with and joined to the cleaner head, for instance when the teeth of the structured portion are being inserted into the pockets of the cleaning element.

In some embodiments, the cleaning material in the cleaning liquid application zone comprises tufts formed from fibers, and a backing layer supporting the tufts. Such tufts can assist the cleaning material to follow the contours of the surface to be cleaned and/or may assist the cleaning material to retain dirt particles whilst also minimising the risk of scratching the surface to be cleaned.

In some embodiments, the cleaning material has, at least in the liquid pick-up zone, a limiting pore diameter as measured using ASTM F316 - <NUM>, <NUM>, Test A equal to or greater than <NUM>.

Such a limiting pore diameter equal to or greater than <NUM> may assist to maintain a relatively large underpressure in the covered dirt inlet(s) whilst ensuring that pores are sufficiently large for efficient liquid transport therethrough.

Equivalently, a bubble point pressure of the liquid pick-up zone as measured using ASTM F316 - <NUM>, <NUM>, Test A may be equal to or less than <NUM> Pa.

In some embodiments, the cleaning material has, at least in the liquid pick-up zone, a limiting pore diameter as measured using ASTM F316 - <NUM>, <NUM>, Test A equal to or less than <NUM>. This upper limit for the limiting pore diameter may assist to ensure that sufficient underpressure in the dirt inlet(s) is maintainable by the cleaning material in the liquid pick-up zone covering the dirt inlet(s).

Equivalently, a bubble point pressure of the liquid pick-up zone as measured using ASTM F316 - <NUM>, <NUM>, Test A may be equal to or greater than <NUM> Pa.

In some embodiments, the cleaning material in the liquid pick-up zone comprises a woven fabric. Such a woven fabric may assist to maintain the above-mentioned underpressure in the dirt inlet(s).

For example, the woven fabric can be configured, in particular via the tightness of its weave, to satisfy the above ranges for the limiting pore diameter.

In some embodiments, the cleaning liquid application zone comprises a first applicator portion and a second applicator portion, with the liquid pick-up zone being arranged between the first applicator portion and the second applicator portion. Thus, the cleaning element, when attached to the cleaner head, can be moved in opposite directions with the liquid pick-up zone drying the surface to be cleaned initially wetted by the first applicator portion during movement in a first direction and initially wetted by the second applicator portion during movement in a second direction opposite to the first direction.

In some embodiments, the cleaning material is thinner in the liquid pick-up zone than in the cleaning liquid application zone. This may assist alignment and joining of the cleaner head with the cleaning element.

In some embodiments, the first and second applicator portions are both thicker than the liquid pick-up zone. This may make for an uneven landing space for a protruding element of the cleaner head on the upper side of the cleaning element, which may encourage the cleaner head to rotate such as to cause the structured portion to land on the upper side of the cleaning element in readiness for cooperation with the guiding elements.

According to another aspect there is provided a cleaner head to which a cleaning element having a plurality of guiding elements and a liquid pick-up zone is attachable, wherein the cleaner head comprises: at least one dirt inlet for receiving dirty liquid when suction is applied to the at least one dirt inlet, the at least one dirt inlet being alignable with, so as to be coverable by, the liquid pick-up zone; a structured portion having a plurality of guiding members, each of the plurality of guiding members being cooperable with one of the plurality of guiding elements to join and align the cleaner head with the cleaning element; and a cleaner head fastener for securing the aligned cleaner head to the cleaning element, the cleaner head fastener being spaced apart from the plurality of guiding members across the cleaner head.

The use of a plurality, in other words more than one, guiding member may assist to minimise the risk of misalignment of the cleaner head with respect to the cleaning element. Moreover, the cleaner head fastener being provided across the cleaner head from the plurality of guiding members means that the cleaner head can be straightforwardly secured to the cleaning element via the cleaner head fastener following alignment and joining of the cleaner head to the cleaning element via the guiding members.

In some embodiments, the guiding members comprise, or are defined by, a plurality of teeth, with each tooth of the plurality of teeth being arranged to be received in and engage a pocket of a plurality of pockets included in the plurality of guiding elements. The plurality of teeth may represent a particularly convenient way of providing the plurality of guiding members of the structured portion, and may assist to minimise unwanted movement of the cleaner head with respect to the cleaning element in widthways, lengthways and depth directions.

In some embodiments, each tooth of the plurality of teeth tapers with extension away from the cleaner head.

Such tapering can assist location of the tooth in the respective pocket of the cleaning element.

Each tooth may have a base arranged proximal to a main body of the cleaner head, with the tooth extending from the base to a tip of the tooth distal from the main body of the cleaner head.

In embodiments in which the tooth tapers with extension away from the cleaner head, i.e. away from the main body of the cleaner head, the tapering may mean that the tip is shorter than the base.

This tapering may, for instance, result in each of the teeth having a trapezoid shape in plan. Alternatively or additionally, the base and the tip may be connected by one or more curved sections, e.g. a pair of curved sections which curve inwardly towards each other, whose curvature means that the tip is shorter than the base.

In some embodiments, the cleaner head comprises a protruding element alignable with and protrudable into the liquid pick-up zone of the cleaning material in the direction of the surface to be cleaned.

In some embodiments, the protruding element is centrally arranged in the cleaner head between a rearward portion and a forward portion of the cleaner head to enable rocking of the cleaner head on the protruding element in a backwards direction to bring the rearward portion closer to and the forward portion further from the surface to be cleaned, and in a forwards direction to bring the forward portion closer to and the rearward portion further from the surface to be cleaned.

The above-described first applicator portion may be arranged adjacent the forward portion when the cleaning element is attached to the cleaner head. The second applicator portion may accordingly be arranged adjacent the rearward portion. Thus, rocking on the protruding element in the forwards direction may bring the first applicator portion to and space the second applicator portion apart from the surface to be cleaned, and rocking on the protruding element in the backwards direction may bring the second applicator portion to and space the first applicator portion apart from the surface to be cleaned.

In this way, re-wetting of the surface to be cleaned by the second applicator portion during forwards pushing of the cleaner head and cleaning element across the surface to be cleaned may be minimised. Similarly, re-wetting of the surface to be cleaned by the first applicator portion during backwards pulling of the cleaner head and cleaning element across the surface to be cleaned may be minimised.

The cleaner head fastener may be configured to secure the cleaner head to the cleaning element in widthways, lengthways and depth directions.

In some embodiments, the cleaner head fastener comprises a loops-hooks fastener, e.g. Velcro®, portion. The loops-hooks fastener portion may, for example, be in the form of a loops-hooks fastener, e.g. Velcro®, strip extending along the length of the cleaner head.

An advantage of such a loops-hooks fastener portion is that the aligned cleaning element and cleaner head can be secured together in a straightforward manner by pressing the loops-hooks fastener portion against a complementary hooks-loops fastener portion provided on the cleaning element.

In some embodiments, the cleaner head fastener is arranged on the underside of the cleaner head facing the surface to be cleaned. Accordingly, when the fastener of the cleaning element comprises the hooks-loops fastener portion on the upper side of cleaning element, securing of the aligned cleaning element to the cleaner head can be achieved by simply pressing the underside of the cleaner head, including the loops-hooks fastener portion, onto the upper side of the cleaning element.

Alternatively, the cleaner head fastener may be arranged on the upper side of the cleaner head that faces away from the surface to be cleaned and/or on an edge of the cleaner head that extends between the upper side and the underside of the cleaner head facing the surface to be cleaned.

In such embodiments, the cleaning element's fastener may be included in a section of the cleaning element that is configured to flex around an edge of the cleaner head to enable the fastener to be secured to the edge and/or the upper side of the cleaner head.

This may result in the cleaning element being more tightly secured to the cleaner head. Such tensioning of the cleaning element may assist to reduce resistance to motion over the surface to be cleaned, and may also provide a more consistent motion resistance for the user as a smaller tolerance window of positioning of the cleaning element on the cleaner head may be associated with the relatively tight securement of the cleaning element to the cleaner head.

In some embodiments, the fastener of the cleaning element comprises the hooks-loops fastener portion included in the section of the cleaning element that flexes around the edge of the cleaner head, with securing of the aligned cleaning element to the cleaner head being achieved by pressing of the hooks-loops fastener portion against a loops-hooks fastener portion arranged on the edge and/or the upper side of the cleaner head.

In at least some embodiments, the cleaner head comprises at least one cleaning liquid outlet through which cleaning liquid is deliverable.

In some embodiments, the at least one cleaning liquid outlet is arranged on the underside of the cleaner head facing the surface to be cleaned and is alignable with, so as to be coverable by, the cleaning liquid application zone.

Alternatively or additionally, the cleaner head may comprise a porous material covering each of the at least one dirt inlet. In such embodiments, the liquid pick-up zone of the cleaning element may align with, and in at least some cases contact, the porous material.

The porous material covering each of the at least one dirt inlet may assist to maintain an underpressure in the dirt inlet(s) with or without constant flow being applied thereto, for instance by an underpressure generator, e.g. pump, fluidly connected to the dirt inlet(s).

According to a further aspect there is provided a wet cleaning apparatus comprising the cleaning element as described herein, and the cleaner head as described herein.

In some embodiments, the wet cleaning apparatus comprises an underpressure generator for supplying suction to the at least one covered dirt inlet.

In some embodiments, the underpressure generator is configured to supply the suction by providing a flow through the liquid pick-up zone in the range of <NUM> to <NUM><NUM>/minute, more preferably <NUM> to <NUM><NUM>/minute, even more preferably <NUM> to <NUM><NUM>/minute, and most preferably <NUM> to <NUM><NUM>/minute.

Such a flow, i.e. flow rate, may capitalise on the underpressure-maintaining capability of the liquid pick-up zone and may ensure sufficient liquid pick-up whilst limiting energy consumption.

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 liquid pick-up zone and into the at least one dirt inlet, wherein the pressure difference is in a range of <NUM> Pa to <NUM> Pa.

The underpressure generator may, for example, be or comprise a positive displacement pump, such as a peristaltic pump. Such a positive displacement pump can assist to maintain the underpressure in the dirt inlet(s) after the underpressure generator has been deactivated, e.g. switched off, because the pump design inherently restricts backflow from the pump outlet. This, in turn, may alleviate problematic liquid release from the liquid pick-up zone, for instance following cleaning of the surface to be cleaned and/or during stowing of the wet cleaning apparatus in a storage area after use.

The wet cleaning apparatus may include a dirty liquid collection tank. In such embodiments, the underpressure generator may be arranged to draw liquid from the at least one dirt inlet to the dirty liquid collection tank.

Alternatively or additionally, the wet cleaning apparatus may comprise a cleaning liquid supply for supplying cleaning liquid for delivery towards the surface to be cleaned via the at least one cleaning liquid outlet. Such a cleaning liquid supply may, for example, comprise a cleaning liquid reservoir and a delivery arrangement, e.g. a delivery arrangement comprising a pump, for transporting the cleaning liquid to and through the at least one cleaning liquid outlet.

The cleaning liquid supply and the at least one cleaning liquid outlet may be configured to provide a continuous delivery of the cleaning liquid towards the surface to be cleaned. Such continuous delivery may, for instance, be provided at the same time as underpressure generator is supplying suction to the at least one dirt inlet.

The cleaning liquid supply and the underpressure generator may, for instance, be configured such that the flow of the cleaning liquid delivered through the at least one cleaning liquid outlet is equal to or lower than the flow provided through the liquid pick-up zone to the at least one dirt inlet by the underpressure generator. This may assist to ensure that the surface to be cleaned does not become excessively wet with the cleaning liquid. For example, the flow of cleaning liquid may be in the range of <NUM> to <NUM><NUM>/minute, and the flow provided by the underpressure generator may be in the range of <NUM> to <NUM><NUM>/minute, more preferably <NUM> to <NUM><NUM>/minute, even more preferably <NUM> to <NUM><NUM>/minute, and most preferably <NUM> to <NUM><NUM>/minute.

More generally, the wet cleaning apparatus may be or comprise, for example, a wet mopping device, a window cleaner, a sweeper, or a wet vacuum cleaner, such as canister-type, stick type, or upright type wet vacuum cleaner. The wet cleaning apparatus may in some examples be or comprise a robotic wet vacuum cleaner or a robotic wet mopping device configured to autonomously move the cleaner head on the surface to be cleaned, such as the surface of a floor. Particular mention is made of a wet mopping device.

In a particular non-limiting example, the wet cleaning apparatus is a battery-powered (or battery-powerable) wet cleaning apparatus, such as a battery-powered (or battery-powerable) wet mopping device, in which the underpressure generator, e.g. pump, is powered (or powerable) by a battery electrically connected (or connectable) thereto. Particular mention is made of this example due to the power consumption-reducing effect which can be provided by the liquid pick-up zone covering the dirt inlet(s) to which the suction of the underpressure generator is provided.

Embodiments described herein in relation to the cleaning element and the cleaner head may be applicable to the wet cleaning apparatus, and embodiments described herein in relation to the wet cleaning apparatus may be applicable to the cleaning element and the cleaner head.

Provided is a cleaning element for attaching to a cleaner head, which cleaner head has a structured portion and at least one dirt inlet. The cleaning element comprises a cleaning material for contacting a surface to be cleaned. The cleaning material comprises a liquid pick-up zone alignable with, so as to cover, the at least one dirt inlet, and a cleaning liquid application zone adjacent the liquid pick-up zone. The cleaning liquid application zone is for applying cleaning liquid to the surface to be cleaned. The cleaning element comprises a plurality of guiding elements cooperable with the structured portion to join and align the cleaning element with the cleaner head. The cleaner head further comprises a fastener for securing the aligned cleaning element to the cleaner head. The fastener is spaced apart from the plurality of guiding elements across the cleaning material. Further provided is the cleaner head having the structured portion and the at least one dirt inlet, and a wet cleaning apparatus comprising the cleaning element and the cleaner head.

Conventional attachment solutions employing, for example, a pair of Velcro® strips extending across opposing longitudinally extending edges of an upper side of the cleaning element facing away from the surface to be cleaned have been found to preclude proper alignment of the cleaning element with respect to the cleaner head after the connection has been established. Accordingly, any misalignment (if observed by the user) may require the user to disconnect the cleaning element from the cleaner head, try to re-align the cleaning element relative to the cleaner head by eye, and then re-connect the cleaner head. Such a trial-and-error process can be burdensome for the user. Moreover, if the misalignment is not observed by the user, the performance may not be optimal, e.g. leaving unwanted water stripes on the surface to be cleaned.

Other conventional solutions employing, for example, a pair of pockets opposing each other on the upper side of the cleaning element with the cleaner head having a folding mechanism for enabling portions of the cleaner head to be located in the pockets have been found to introduce alignment and securement difficulties. Moreover, such a folding mechanism may be difficult to combine with, for instance, parts within the cleaner head for fluidly connecting the dirt inlet(s) to an underpressure generator.

<FIG> schematically depicts a cleaning element <NUM> attached to a cleaner head <NUM>. The cleaning element <NUM> comprises a cleaning material including a liquid pick-up zone <NUM> for aligning with dirt inlet(s) (not visible in <FIG>) included in the cleaner head <NUM>.

The cleaning material, e.g. cleaning fabric, further comprises a cleaning liquid application zone 106A, 106B adjacent the liquid pick-up zone <NUM>. In some embodiments, such as that shown in <FIG>, the cleaning liquid application zone 106A, 106B comprises a first applicator portion 106A and a second applicator portion 106B, with the liquid pick-up zone <NUM> being arranged between the first applicator portion 106A and the second applicator portion 106B.

<FIG> schematically depicts proper alignment of the liquid pick-up zone <NUM> with the dirt inlet(s) such that, when the wet cleaning apparatus <NUM>, <NUM> comprising the cleaning element <NUM> attached to the cleaner head <NUM> is moved over the surface to be cleaned in the direction <NUM>, the first applicator portion 106A wets the surface (see the circled part <NUM> in <FIG>) to be cleaned and the liquid pick-up zone <NUM> subsequently dries the surface to be cleaned (see the circled part <NUM> in <FIG>).

Movement of the wet cleaning apparatus <NUM>, <NUM> in a direction opposite to the direction <NUM> may cause the second applicator portion 106B to wet the surface to be cleaned, with the liquid pick-up zone <NUM> subsequently drying the surface to be cleaned.

In such embodiments, the cleaner head <NUM> may comprise a protruding element <NUM> alignable with and protrudable into the liquid pick-up zone <NUM> of the cleaning material in the direction of the surface to be cleaned.

As shown for the non-limiting example depicted in <FIG>, the protruding element <NUM> may be centrally arranged in the cleaner head <NUM> between the first applicator portion 106A and the second applicator portion 106B to enable rocking on the protruding element <NUM> in a backwards direction to bring the first applicator portion 106A to and space the second applicator portion 106B apart from the surface to be cleaned, and in a forwards direction to bring the second applicator portion 106B to and space the first applicator portion 106A apart from the surface to be cleaned.

In this way, re-wetting of the surface to be cleaned by the second applicator portion 106B during backwards pulling of the cleaner head <NUM> and cleaning element <NUM> across the surface to be cleaned, in the direction <NUM>, may be minimised. Similarly, re-wetting of the surface to be cleaned by the first applicator portion 106A during forwards pushing of the cleaner head <NUM> and cleaning element <NUM> across the surface to be cleaned may be minimised.

<FIG> schematically depicts local misalignment of the cleaning element <NUM> with respect to the cleaner head <NUM> such that the liquid pick-up zone <NUM> is improperly aligned with the dirt inlet(s). This may mean that when the wet cleaning apparatus <NUM>, <NUM> is moved over the surface to be cleaned in the direction <NUM>, the first applicator portion 106A wets the surface (see the circled part <NUM> in <FIG>) to be cleaned but the liquid pick-up zone <NUM> subsequently provides insufficient drying of the surface to be cleaned (see the circled part <NUM> in <FIG>).

<FIG> schematically depicts local separation of the cleaning element <NUM> from the cleaner head <NUM> such that the second applicator portion 106B becomes detached from the cleaner head <NUM>. This may mean that when the wet cleaning apparatus <NUM>, <NUM> is moved over the surface to be cleaned in the direction <NUM>, the first applicator portion 106A wets the surface (see the circled part <NUM> in <FIG>) to be cleaned, the liquid pick-up zone <NUM> subsequently dries the surface to be cleaned (see the circled part <NUM> in <FIG>), but the detached second applicator portion 106B wets the surface to be cleaned again (see the circled part <NUM> in <FIG>). This may leave undesirable wet strips on the surface to be cleaned, and risk defeating the purpose of including the dirt inlet(s) in the cleaner head <NUM> for drying the surface to be cleaned.

To mitigate the risk of such misalignment and detachment issues being encountered, the present disclosure provides a cleaning element <NUM> comprising a plurality of guiding elements cooperable with a structured portion, e.g. a structured periphery, of the cleaner head <NUM> to join and align the cleaning element <NUM> with the cleaner head <NUM>, with the cleaning element <NUM> further comprising a fastener for securing the aligned cleaning element to the cleaner head. The fastener is spaced apart from the plurality of guiding elements across the cleaning material.

The use of a plurality, in other words more than one, guiding element may assist to minimise the risk of misalignment of the cleaning element <NUM> with respect to the cleaner head <NUM>. Moreover, the fastener being provided across the cleaning material from the plurality of guiding elements means that the cleaning element <NUM> can be straightforwardly secured to the cleaner head <NUM> via the fastener following alignment and joining of the cleaning element <NUM> to the cleaner head <NUM> via the guiding elements.

In some embodiments, such as that shown in <FIG>, the plurality of guiding elements 116A, 116B, 116C, 116D comprises, or is defined by, a plurality of pockets. In such embodiments, each of the plurality of pockets is arranged to receive and engage a tooth of a plurality of teeth included in the structured portion (not visible in <FIG>) of the cleaner head <NUM>. The plurality of pockets may represent a particularly convenient way of providing the plurality of guiding elements 116A, 116B, 116C, 116D, and may assist to minimise unwanted movement of the cleaning element <NUM> with respect to the cleaner head <NUM> in widthways, lengthways and depth directions.

Four pockets are included in the cleaning element <NUM> shown in <FIG>. This has been found to balance ease of manufacture with minimising the risk of misalignment of the cleaning element <NUM> with respect to the cleaner head <NUM>. In other non-limiting examples, the cleaning element <NUM> comprises two, three, five, six, seven, eight, nine, ten or more pockets.

The alignment provided by the guiding elements 116A, 116B, 116C, 116D in combination with predetermined positioning of the fastener based on the alignment may mean that the securement via the fastener can be made without requiring visual alignment of the fastener with a complementary cleaner head fastener.

For example, each of the pockets may have the same length as the length of the base of the teeth, be sufficiently wide for full insertion of the teeth into the pockets, and have a depth selected for restricting movement of the teeth in the pockets in the depth direction.

Thus full insertion of the teeth into the pockets may effectively provide a signal to the user that the cleaning element <NUM> is properly aligned with the cleaner head <NUM>.

In other words, when the teeth are inserted, e.g. slid, all the way into the pockets, this may provide a tactile signal to the user that alignment in the widthways direction is correct. At the same time, the pockets may hold the teeth in the depth direction. Moreover, by the maximum length of each of the teeth corresponding to the maximum length of each of the pockets, when the teeth are fully inserted, e.g. slid, all the way into the pockets, the cleaning element <NUM> may be aligned relative to the cleaner head <NUM> in the lengthways direction.

In some embodiments, such as that depicted in <FIG>, the cleaning material comprises a folded over portion 118A defined by folding of the cleaning material onto an upper side thereof facing away from the surface to be cleaned.

In such embodiments, the pockets may be provided between the folded over portion 118A and the upper side of the cleaning material. This may make the guiding elements 116A, 116B, 116C, 116D relatively straightforward to manufacture.

The folded over portion 118A may, for instance, be attached, e.g. stitched, to the upper side of the cleaning material between the pockets. Thus, attachment of the folded over portion 118A to the upper side of the cleaning material may define the pockets.

In some embodiments, the cleaning material comprises a further folded over portion 118B opposing the folded portion 118A across the cleaning material. The further folded over portion 118B may, similarly to the folded portion 118A, be defined by folding of the cleaning material onto an upper side thereof facing away from the surface to be cleaned.

In some embodiments, such as that shown in <FIG>, the cleaning material in the cleaning liquid application zone 106A, 106B comprises tufts <NUM> formed from fibers, and a backing layer <NUM> supporting the tufts <NUM>. Such tufts <NUM> can assist the cleaning material to follow the contours of the surface to be cleaned and/or may assist the cleaning material to retain dirt particles whilst also minimising the risk of scratching the surface to be cleaned.

The backing layer <NUM> can be formed of any suitable backing fabric material, such as polyester.

The tufts <NUM> can, for example, be formed from polyamide and/or polyester fibers.

In embodiments in which the cleaning material comprises the folded over portion 118A and/or the further folded over portion 118B defined by folding of the cleaning material onto the upper side thereof facing away from the surface to be cleaned, the folded over portion 118A and/or the further folded over portion 118B may include the backing layer <NUM> and tufts <NUM>.

In such embodiments, the tufts <NUM> may also be provided along, e.g. so as to laterally protrude from, a fold or folds of the cleaning element <NUM> where the folded portion 118A and/or the further folded portion 118B folds back onto the upper side of the cleaning material. This may assist the cleaning element <NUM> to, for instance, apply cleaning liquid to a corner located between a floor and a wall extending perpendicularly with respect to the floor.

Alternatively or additionally, the cleaning liquid application zone 106A, 106B may comprise the first applicator portion 106A and the second applicator portion 106B described above in relation to <FIG>, with the liquid pick-up zone <NUM> being arranged between the first applicator portion 106A and the second applicator portion 106B.

In such embodiments, the cleaning material in at least one, and preferably both, of the first applicator portion 106A and the second applicator portion 106B may comprise the tufts <NUM> formed from fibers, and a backing layer <NUM> supporting the tufts <NUM>. An example of this is shown in <FIG>.

In some embodiments, the cleaning material in the cleaning liquid application zone 106A, 106B is deformable to bring part of the cleaning material in the cleaning liquid application zone 106A, 106B into contact with the cleaning material in the liquid pick-up zone <NUM>.

Such deformability of the cleaning material in the cleaning liquid application zone 106A, 106B may enable some of the cleaning liquid to be transferred from the cleaning material in the cleaning liquid application zone 106A, 106B to the cleaning material in the liquid pick-up zone <NUM> in a controlled manner. In this way, excessive wetting of the surface to be cleaned, for instance by dripping of the cleaning liquid from the cleaning liquid application zone 106A, 106B onto the surface to be cleaned, may be minimised. Alternatively or additionally, by the cleaning material in the cleaning liquid application zone 106A, 106B deforming such that at least part of the cleaning material in the cleaning liquid application zone 106A, 106B contacts the cleaning material in the liquid pick-up zone <NUM>, the latter may be rinsed, e.g. cleaned in situ, with cleaning liquid from the former.

In at least some embodiments, the cleaning material in the cleaning liquid application zone 106A, 106B is configured to deform upon contact with the surface to be cleaned and/or upon being wetted by liquid, e.g. water.

Such wetting can be as a result of the cleaning liquid delivered to the cleaning liquid application zone 106A, 106B from cleaning liquid outlet(s) included in the cleaner head <NUM> and/or due to liquid being present on the surface to be cleaned.

In embodiments in which the cleaning material in the cleaning liquid application zone 106A, 106B comprises the tufts <NUM> formed from fibers, and the backing layer <NUM> supporting the tufts, such tufts <NUM> may be deformable to contact the cleaning material in the liquid pick-up zone <NUM>, e.g. upon contact with the surface to be cleaned and/or upon being wetted by liquid, e.g. water.

While the tufts <NUM> maintain contact with the cleaning material in the liquid pick-up zone <NUM>, the cleaning liquid can be transferred via the tufts <NUM> from the cleaning material in the cleaning liquid application zone 106A, 106B to the cleaning material in the liquid pick-up zone <NUM>.

A key purpose of the liquid pick-up zone <NUM> of the cleaning material may be to assist to maintain an underpressure in the dirt inlet(s) covered by the liquid pick-up zone <NUM> when the cleaning element <NUM> is aligned with the cleaner head <NUM>.

ASTM F316 - <NUM>, <NUM>, Test A provides a bubble point pressure measurement. Whilst this standard method was developed for nonfibrous membrane filters, the procedure can be replicated for the cleaning material, and in particular for the liquid pick-up zone <NUM> thereof, according to the present disclosure.

The bubble point test for determining the limiting pore diameter, in other words maximum pore size, is, in summary, performed by prewetting a sample of the cleaning material, increasing the pressure of gas upstream of the sample at a predetermined rate, and watching for gas bubbles downstream to indicate the passage of gas through the maximum diameter pores of the sample.

In common with the membrane filters described in ASTM F316 - <NUM>, <NUM>, Test A, the cleaning material in the liquid pick-up zone may (at least to an approximation) have discrete pores extending from one side of the liquid pick-up zone <NUM> to the other, similarly to capillary tubes. The bubble point test is based on the principle that a wetting liquid is held in these capillary pores by capillary attraction and surface tension, and the minimum pressure required to force liquid from these pores is a function of pore diameter. The pressure at which a steady stream of bubbles appears in this test is termed the "bubble point pressure".

It is noted that ASTM F316 - <NUM>, <NUM>, Test A is based on an approximation of the pores as capillary pores having circular cross-sections, and hence the limiting pore diameter should be regarded as merely an empirical estimate of the maximum pore diameter based on this premise.

The testing apparatus mandated in ASTM F316 - <NUM>, <NUM>, Test A was replicated, as was the test procedure.

It was found suitable to first raise the pressure relatively quickly, e.g. at about <NUM> Pa/second, to roughly determine the bubble point. Pressure was then relieved from the sample to allow the water to run back into the sample. The pressure was then raised to roughly <NUM>% of the expected pressure value, maintained at the <NUM>% level for about <NUM> seconds (to ensure all "free" water is pressed out of the sample), and then raised again at a lower rate of ≤ <NUM> Pa/second until the constant flow of bubbles was observed.

The limiting pore diameter, d, is then determined from the recorded bubble point pressure, p, using equation <NUM> of ASTM F316 - <NUM>, <NUM>, Test A: d = Cγ/p, where γ is the surface tension in mM/m (<NUM> for distilled water at <NUM>), and C is <NUM> when p is in Pa. Results for various cleaning material samples are provided in Table A.

In some embodiments, the cleaning material has, at least in the liquid pick-up zone <NUM>, a limiting pore diameter as measured using ASTM F316 - <NUM>, <NUM>, Test A equal to or greater than <NUM>.

Such a limiting pore diameter equal to or greater than <NUM> may assist to maintain a relatively large underpressure in the dirt inlet(s) of the cleaner head <NUM> whilst ensuring that pores are sufficiently large for efficient liquid transport therethrough.

In some embodiments, the cleaning material has, at least in the liquid pick-up zone <NUM>, a limiting pore diameter as measured using ASTM F316 - <NUM>, <NUM>, Test A equal to or less than <NUM>. This upper limit for the limiting pore diameter may assist to ensure that sufficient underpressure is maintainable by the cleaning material in the liquid pick-up zone <NUM>.

As noted above, ASTM F316 - <NUM>, <NUM>, Test A assumes cylindrical pores. Purely for the purposes of explanation/illustration (hence should not be regarded as limiting values provided herein for the limiting pore diameter from ASTM F316 - <NUM>, <NUM>, Test A), it is noted that the limiting pore diameter can be adjusted with a Tortuoise factor (TF), which is an empirical factor derived for solid wire filters, to compensate for non-roundness of the pores. The <NUM> to <NUM> spread for the TF suggested in ASTM E3278 - <NUM> (see section <NUM>. <NUM> of that standard) may result in an approximately <NUM>% pore size spread. For illustrative purposes only, Table B shows the above-described limiting pore diameter endpoints when adjusted using the TF. Note that the limiting pore diameter from ASTM F316 - <NUM>, <NUM>, Test A provides a measure of the largest pore size for particles to pass through, hence the TF can compensate for the fact that a "triangular" pore can only let a spherical particle through which is significantly smaller than the surface of the triangle.

In some embodiments, such as that shown in <FIG>, the cleaning material in the liquid pick-up zone <NUM> comprises a woven fabric 124A, 124B. Such a woven fabric 124A, 124B may assist to maintain the above-described underpressure in the dirt inlet(s) of the cleaner head <NUM>.

For example, the woven fabric, and in particular a woven microfiber fabric, can be configured, in particular via the tightness of its weave, to satisfy the above ranges for the limiting pore diameter.

It is noted that the term "woven microfiber fabric" as used herein may refer to a fabric formed of synthetic fibers, with the fabric being formed of threads whose titre is less than <NUM> decitex.

Such woven microfiber fabrics can comprise, for example, polyester fibers, polyamide fibers, and combinations of polyester and polyamide fibers.

The woven microfiber fabric may, for example, be a microfiber chamois.

In other examples, the cleaning material in the pick-up zone <NUM> is or comprises a natural chamois, e.g. made from a chamois, deer, goat or sheep hide.

In some embodiments, such as that shown in <FIG>, the woven fabric 124A, 124B comprises a plurality of woven fabric layers, e.g. a plurality of woven microfiber fabric layers.

Stacking a plurality of woven fabric layers 124A, 124B in this manner may assist maintenance of the underpressure in the dirt inlet(s).

A first woven fabric layer 124A, e.g. a first woven microfiber fabric layer 124A, may, for example, be arranged such as to be closest to the dirt inlet(s) when the cleaning element <NUM> is attached to the cleaner head <NUM>, with a second woven fabric layer 124B, e.g. a second woven microfiber fabric layer 124B, being arranged on the first woven fabric layer 124A such that the first woven fabric layer 124A is between the second woven fabric layer 124B and the dirt inlet(s).

The plurality of woven fabric layers 124A, 124B can be attached to each other in any suitable manner, for example via heat sealing, such as ultrasonic welding.

Adjacent woven fabric layers 124A, 124B may be attached, e.g. heat sealed, to each other around peripheries of the woven fabric layers 124A, 124B. In this manner, the risk of the attachment, e.g. heat seal, between such adjacent woven fabric layers 124A, 124B interfering with the passage of liquid in the liquid pick-up zone <NUM> towards the dirt inlet(s) may be minimised.

In embodiments in which the cleaning material in the cleaning liquid application zone 106A, 106B comprises tufts <NUM> formed from fibers, with a backing layer <NUM> supporting the tufts <NUM>, the backing layer <NUM> may be mounted on the woven fabric 124A, 124B.

In the non-limiting example shown in <FIG>, the backing layer <NUM> is mounted on the second woven fabric layer 124B.

In some embodiments, such as that shown in <FIG>, the cleaning element <NUM> is elongated so as to define a length <NUM> of the cleaning element <NUM>, with the plurality of guiding elements being arranged along the length <NUM>. Such a lengthways arrangement of the plurality of guiding elements may assist alignment of the cleaning element <NUM> with respect to the cleaner head <NUM> (the structured portion, e.g. structured periphery, of the latter correspondingly being provided along its length).

In such embodiments, each of the liquid pick-up zone <NUM> and the cleaning liquid application zone 106A, 106B may be elongated so as to each longitudinally extend parallel with the length <NUM> of the cleaning element <NUM>.

More generally, the cleaning element <NUM> comprises the above-mentioned fastener for securing the aligned cleaning element <NUM> to the cleaner head <NUM>, with the fastener being spaced apart from the plurality of guiding elements across the cleaning material.

The fastener may be configured to secure the cleaning element <NUM> to the cleaner head <NUM> in widthways (y), lengthways (x) and depth (z) directions.

In some embodiments, such as that shown in <FIG>, the fastener <NUM> comprises, or is defined by, a hooks-loops fastener, e.g. Velcro®, portion. The hooks-loops fastener portion may, for example, be in the form of a hooks-loops fastener, e.g. Velcro®, strip extending along the length <NUM> of the cleaning element <NUM>. An advantage of such a hooks-loops fastener portion is that the aligned cleaning element <NUM> and cleaner head <NUM> can be secured together in a straightforward manner by pressing the hooks-loops fastener portion against a complementary loops-hooks fastener portion provided on the cleaner head <NUM>.

In other non-limiting examples, the fastener <NUM> comprises a hole or button for securing to a complementary button or hole included in the cleaner head <NUM>. Such a hole/button may, similarly to the hooks-loops fastener portion, secure the cleaning element <NUM> to the cleaner head <NUM> in widthways (y), lengthways (x) and depth (z) directions.

In some embodiments, such as that shown in <FIG>, the fastener <NUM> is arranged on the upper side of the cleaning element <NUM> facing away from the surface to be cleaned. In such embodiments, the guiding elements 116A, 116B, 116C, 116D, e.g. pockets, may also be provided on the upper side of the cleaning element <NUM>. Thus, the cleaning element <NUM> can be advantageously aligned with and secured to the cleaner head <NUM> while the underside of the cleaning element <NUM> remains in contact with the surface to be cleaned.

In embodiments in which the fastener <NUM> comprises the hooks-loops fastener portion on the upper side of cleaning element <NUM>, securing of the aligned cleaning element <NUM> to the cleaner head <NUM> can be achieved by simply pressing the underside of the cleaner head <NUM> onto the upper side of the cleaning element <NUM>.

More generally, the fastener <NUM> may be spaced apart from the plurality of guiding elements across a width <NUM> of the cleaning element <NUM>, with the width <NUM> extending perpendicularly with respect to the length <NUM> of the cleaning element <NUM>.

In some embodiments, such as that shown in <FIG>, the cleaning element <NUM> comprises a protrusion <NUM> arranged to protrude from a periphery of the cleaning element <NUM> such as to enable a user to trap the protrusion <NUM> against the surface to be cleaned and thereby immobilise the cleaning element <NUM> for the joining and alignment with the cleaner head <NUM>.

In such embodiments, the periphery from which the protrusion <NUM> protrudes may be spaced apart from the plurality of guiding elements 116A, 116B, 116C, 116D across the cleaning material. In this manner, the trapping of the protrusion <NUM> against the surface to be cleaned can assist to avoid that the cleaning element <NUM> is pushed away when the cleaning element <NUM> is being aligned with and joined to the cleaner head <NUM>, e.g. via the pockets of the cleaning element <NUM> receiving and engaging teeth included in the structured portion, e.g. structured periphery, of the cleaner head <NUM>.

The user may, for example, trap the protrusion <NUM> against the surface to be cleaned by pressing down against the protrusion <NUM> with their foot.

<FIG> provide views of a cleaner head <NUM> to which a cleaning element <NUM>, e.g. the cleaning element <NUM> described herein in relation to <FIG>, having a plurality of guiding elements is attachable.

Such a cleaning element <NUM> may also have a cleaning material having liquid pick-up zone <NUM>, e.g. a liquid pick-up zone adjacent a cleaning liquid application zone 106A, 106B, as previously described.

The cleaner head <NUM> has at least one dirt inlet for receiving dirty liquid when suction is applied to the at least one dirt inlet. The at least one dirt inlet is alignable with, so as to be coverable by, the liquid pick-up zone <NUM> of the cleaning element <NUM>.

The cleaner head <NUM> comprises a structured portion <NUM>, e.g. a structured periphery, having a plurality of guiding members 136A, 136B, 136C, 136D, with each of the plurality of guiding members 136A, 136B, 136C, 136D being cooperable with one of the plurality of guiding elements 116A, 116B, 116C, 116D to join and align the cleaner head <NUM> with the cleaning element <NUM>. The cleaner head <NUM> further comprises a cleaner head fastener <NUM> for securing the aligned cleaner head <NUM> to the cleaning element <NUM>. The cleaner head fastener <NUM> is spaced apart from the plurality of guiding members 136A, 136B, 136C, 136D across the cleaner head <NUM>.

In some embodiments, such as that shown in <FIG>, the guiding members 136A, 136B, 136C, 136D comprise, or are defined by, a plurality of teeth, with each tooth of the plurality of teeth being arranged to be received in and engage a pocket of a plurality of pockets included in, or defining, the plurality of guiding elements 116A, 116B, 116C, 116D. The plurality of teeth may represent a particularly convenient way of providing the plurality of guiding members 136A, 136B, 136C, 136D of the structured portion <NUM>, and may assist to minimise unwanted movement of the cleaner head <NUM> with respect to the cleaning element <NUM> in widthways (y), lengthways (x) and depth (z) directions.

Four teeth are included in the cleaner head <NUM> shown in <FIG>. This has been found to balance ease of manufacture with minimising the risk of misalignment of the cleaner head <NUM> with respect to the cleaning element <NUM>. In other non-limiting examples, the structured portion <NUM> comprises two, three, five, six, seven, eight, nine, ten or more teeth.

In some embodiments, each tooth of the plurality of teeth tapers with extension away from the cleaner head <NUM>. Such tapering can assist location of the tooth in the respective pocket of the cleaning element <NUM>.

Each tooth may have a base arranged proximal to a main body of the cleaner head <NUM>, with the tooth extending from the base to a tip of the tooth distal from the main body of the cleaner head <NUM>.

In embodiments in which the tooth tapers with extension away from the cleaner head <NUM>, i.e. away from the main body of the cleaner head <NUM>, the tapering may mean that the tip is shorter than the base.

In some embodiments, and as briefly described above in relation to <FIG>, the cleaner head <NUM> comprises a protruding element <NUM> alignable with and protrudable into the liquid pick-up zone <NUM> of the cleaning material in the direction of the surface to be cleaned.

In some embodiments, and as best shown in <FIG>, the protruding element <NUM> is centrally arranged in the cleaner head <NUM> between a rearward portion <NUM> and a forward portion <NUM> of the cleaner head <NUM> to enable rocking of the cleaner head <NUM> on the protruding element <NUM> in a backwards direction to bring the rearward portion <NUM> closer to and the forward portion <NUM> further from the surface to be cleaned, and in a forwards direction to bring the forward portion <NUM> closer to and the rearward portion <NUM> further from the surface to be cleaned.

The above-described first applicator portion 106A may be arranged adjacent the forward portion <NUM> when the cleaning element <NUM> shown in <FIG> is attached to the cleaner head <NUM> shown in <FIG>. The second applicator portion 106B may accordingly be arranged adjacent the rearward portion <NUM>. Thus, rocking on the protruding element <NUM> in the forwards direction may bring the first applicator portion 106A to and space the second applicator portion 106B apart from the surface to be cleaned, and rocking on the protruding element <NUM> in the backwards direction may bring the second applicator portion 106B to and space the first applicator portion 106A apart from the surface to be cleaned.

In some embodiments, the cleaning material is thinner in the liquid pick-up zone <NUM> than in the cleaning liquid application zone 106A, 106B. This may assist alignment and joining of the cleaner head <NUM> with the cleaning element <NUM>, particularly when the cleaner head <NUM> includes the protruding element <NUM>, and the cleaning material comprises the first applicator portion 106A and the second applicator portion 106B with the liquid pick-up zone <NUM> being between the first applicator portion 106A and the second applicator portion 106B and being aligned with the protruding element <NUM>.

In such embodiments, the first and second applicator portions 106A, 106B being thicker than the liquid pick-up zone <NUM> may make for an uneven landing space for the protruding element <NUM> of the cleaner head <NUM> on the upper side of the cleaning element <NUM>. This may encourage the cleaner head <NUM> to rotate such as to assist the guiding members 136A, 136B, 136C, 136D, e.g. teeth, of the structured portion <NUM> to land on the upper side of the cleaning element <NUM> in readiness for cooperation with the guiding elements 116A, 116B, 116C, 116D, e.g. pockets, of the cleaning element <NUM>.

In some embodiments, the cleaner head <NUM> is elongated so as to define a length <NUM> of the cleaner head <NUM>, with the structured portion <NUM> being arranged along the length <NUM>. Such a lengthways arrangement of structured portion <NUM> may assist alignment of the cleaning element <NUM> with respect to the cleaner head <NUM> (the guiding elements 116A, 116B, 116C, 116D of the former correspondingly being provided along its length <NUM>).

More generally, the cleaner head <NUM> comprises the above-mentioned cleaner head fastener <NUM> for securing the cleaner head <NUM> to the aligned cleaning element <NUM>, with the cleaner head fastener <NUM> being spaced apart from the plurality of guiding members 136A, 136B, 136C, 136D across the cleaner head.

The cleaner head fastener <NUM> may be configured to secure the cleaner head <NUM> to the cleaning element <NUM> in widthways (y), lengthways (x) and depth (z) directions.

In some embodiments, such as that shown in <FIG>, the cleaner head fastener <NUM> comprises, or is defined by, a loops-hooks fastener, e.g. Velcro®, portion. The loops-hooks fastener portion may, for example, be in the form of a loops-hooks fastener, e.g. Velcro®, strip extending along the length <NUM> of the cleaner head <NUM>. An advantage of such a loops-hooks fastener portion <NUM> is that the aligned cleaning element <NUM> and cleaner head <NUM> can be secured together in a straightforward manner by pressing the loops-hooks fastener portion against a complementary hooks-loops fastener portion provided on the cleaning element <NUM>.

In other non-limiting examples, the cleaner head fastener <NUM> comprises a hole or button for securing to a complementary button or hole included in the cleaning element <NUM>. Such a hole/button may, similarly to the loops-hooks fastener portion, secure the cleaner head <NUM> to the cleaning element <NUM> in widthways (y), lengthways (x) and depth (z) directions.

In some embodiments, such as that shown in <FIG>, the cleaner head fastener <NUM> is arranged on the underside of the cleaner head <NUM> facing the surface to be cleaned. Accordingly, when the fastener <NUM> of the cleaning element <NUM> comprises the hooks-loops fastener portion on the upper side of cleaning element <NUM>, securing of the aligned cleaning element <NUM> to the cleaner head <NUM> can be achieved by simply pressing the underside of the cleaner head <NUM> onto the upper side of the cleaning element <NUM>.

More generally, the cleaner head fastener <NUM> may be spaced apart from the plurality of guiding members 136A, 136B, 136C, 136D, e.g. teeth, of the structured portion <NUM> across a width <NUM> of the cleaner head <NUM>, with the width <NUM> extending perpendicularly with respect to the length <NUM> of the cleaner head <NUM>.

In at least some embodiments, the cleaner head <NUM> comprises at least one cleaning liquid outlet <NUM> through which cleaning liquid is deliverable.

In some embodiments, the at least one cleaning liquid outlet <NUM> is arranged on the underside of the cleaner head <NUM> facing the surface to be cleaned and is alignable with, so as to be coverable by, the cleaning liquid application zone 106A, 106B.

It is noted that the at least one cleaning liquid outlet <NUM> need not to be provided on the underside of the cleaner head <NUM>, and may alternatively be provided elsewhere in the cleaner head <NUM> provided that the cleaning liquid can be delivered via the cleaning liquid outlet(s) <NUM> to reach the surface to be cleaned.

The cleaning liquid can comprise, or consist of, water. Hence, the cleaning liquid can be an aqueous cleaning liquid. In some non-limiting examples, the cleaning liquid is an aqueous detergent solution.

The cleaner head <NUM> may comprise a plurality of cleaning liquid outlets <NUM> arranged along the length <NUM> of the underside of the cleaner head <NUM>.

In some embodiments, the at least one cleaning liquid outlet <NUM> comprises a first plurality of cleaning liquid outlets <NUM> arranged along the length <NUM> of the cleaner head <NUM> and being alignable with the first applicator portion 106A included in the cleaning liquid application zone 106A, 106B, and a second plurality of cleaning liquid outlets <NUM> arranged along the length <NUM> of the cleaner head <NUM> and being alignable with the second applicator portion 106B included in the cleaning liquid application zone 106A, 106B.

In such embodiments, the first applicator portion 106A may be arranged to apply cleaning liquid delivered from the first plurality of cleaning liquid outlets <NUM> to the surface to be cleaned, and the second applicator portion 106B may be arranged to apply cleaning liquid delivered from the second plurality of cleaning liquid outlets <NUM> to the surface to be cleaned.

In some embodiments, the cleaner head <NUM> comprises a cleaning liquid distribution strip 150A comprising at least some of the cleaning liquid outlets <NUM>.

The cleaning liquid distribution strip 150A may comprise a channel which can be supplied with the cleaning liquid, e.g. from a suitable cleaning liquid reservoir (not visible in <FIG>) via one or more inlets. The inlet(s) may be provided at or proximal to an end or both ends of the cleaning liquid distribution strip 150A, however it is also conceivable that the inlet is provided in a central position along the length of the cleaning liquid distribution strip 150A.

The cleaning liquid may exit the cleaning liquid distribution strip 150A via apertures in the cleaning liquid distribution strip 150A which define the cleaning liquid outlets <NUM>. Such apertures may be dimensioned such that passage of the cleaning liquid, e.g. aqueous cleaning liquid, through the apertures is restricted, due to the surface tension of the cleaning liquid, while the channel is being filled, but with passage of the cleaning liquid through all of the apertures of the cleaning liquid distribution strip 150A at the same time being permitted once the channel has been filled. This may enable relatively uniform wetting of the surface to be cleaned across the length <NUM> of the cleaner head <NUM>.

To this end, each cleaning liquid outlet <NUM> may have, for example, a diameter less than <NUM>, for example a diameter in the range of <NUM> to <NUM>, preferably <NUM> to <NUM>, most preferably <NUM> to <NUM>, such as about <NUM>.

The cleaning liquid distribution strip 150A 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 150A from a polymer can make the cleaning liquid distribution strip 150A more lightweight and/or cheaper to manufacture.

In some embodiments, the cleaner head <NUM> comprises the cleaning liquid distribution strip 150A arranged to deliver cleaning liquid in the rearward portion <NUM> and a further cleaning liquid distribution strip 150B whose further apertures define cleaning liquid outlets <NUM> which deliver the cleaning liquid in the forward portion <NUM>.

Both the cleaning liquid distribution strip 150A and the further cleaning liquid distribution strip 150B may longitudinally extend parallel with the length <NUM> of the cleaner head <NUM>, as best shown in <FIG>.

In embodiments in which the cleaning element <NUM> comprises the first applicator portion 106A and the second applicator portion 106B, the first applicator portion 106A may be arranged to apply cleaning liquid delivered from the further cleaning liquid distribution strip 150B to the surface to be cleaned, and the second applicator portion 106B may be arranged to apply cleaning liquid delivered from the cleaning liquid distribution strip 150A to the surface to be cleaned.

The dirt inlet(s) can be provided in the cleaner head <NUM> in any suitable manner. In some embodiments, each of the at least one dirt inlet is defined by an opening of a tube or tubes fluidly connected or connectable to an underpressure generator (not visible).

Any suitable number of dirt inlets can be contemplated, such as one, two, three, four, five, six, or more.

In some embodiments, the at least one dirt inlet comprises a plurality of dirt inlets arranged along the length <NUM> of the cleaner head <NUM>.

When a plurality of dirt inlets are included in the cleaner head <NUM>, these may, for instance, have the same dimensions as each other.

Alternatively or additionally, when a plurality, e.g. a pair, of dirt inlets is employed, the dirt inlets may be spaced relative to each other along the length <NUM> of the cleaner head <NUM> such as to provide relatively uniform suction along the length <NUM> of the cleaner head <NUM>. For example, the distance along the length <NUM> between a centre position of the cleaner head <NUM> and a centre of one dirt inlet of a pair of dirt inlets may be the same, or substantially the same, as the distance along the length between the centre position and a centre of the other dirt inlet of the pair of dirt inlets.

Should a single dirt inlet be employed, this may be arranged in a central position of the cleaner head <NUM> to provide a relatively symmetrical suction profile along the length <NUM> of the cleaner head <NUM>.

More generally, the cleaner head <NUM> may comprise a porous material <NUM> covering each of the at least one dirt inlet.

The porous material <NUM> covering each of the at least one dirt inlet may assist to maintain an underpressure in the dirt inlet(s) with or without constant flow being applied thereto, for instance by an underpressure generator, e.g. pump, fluidly connected to the dirt inlet(s).

Similarly to the liquid pick-up zone <NUM> of the cleaning material, the surface tension of the liquid retained in the pores of the porous material <NUM> can assist to maintain the underpressure. This surface tension can be overcome, meaning that the air-liquid surface is removed, at a point (or points) on the exterior of the porous material <NUM> which come into contact with liquid, causing liquid to be transported through the porous material <NUM> in the direction of the dirt inlet(s).

In some embodiments, a limiting pore diameter of the porous material <NUM> as measured using ASTM F316 - <NUM>, <NUM>, Test A is equal to or greater than <NUM>.

Such a limiting pore diameter equal to or greater than <NUM> may assist to maintain a relatively large underpressure whilst ensuring that pores are sufficiently large for efficient liquid transport therethrough.

In some embodiments, a limiting pore diameter of the porous material <NUM> as measured using ASTM F316 - <NUM>, <NUM>, Test A is equal to or less than <NUM>. This upper limit for the limiting pore diameter may assist to ensure that sufficient underpressure is maintainable by the porous material <NUM>.

Bacteria tends to be characterized by having a relatively small size. For example, an Escherichia coli cell, which can be regarded as an "average" sized bacterium, is about <NUM> long and <NUM> in diameter.

Thus, porous materials <NUM> and cleaning materials (at least in the liquid pick-up zone <NUM>) whose pore size is larger than <NUM> may permit such bacteria to pass therethrough. In this way, bacteria can be removed from the surface to be cleaned.

Depending on the cleaning material (in the liquid pick-up zone <NUM>) and the porous material <NUM> selected, up to <NUM>% of bacteria can be drawn therethrough, away from the surface to be cleaned.

The porous material <NUM> can comprise one or more of a porous fabric, a porous plastic, and a foam.

Such a porous plastic may, for example, take the form of a sintered mesh of plastic granules.

In embodiments in which the porous material <NUM> includes such a porous plastic, one or more further porous material layers, e.g. comprising a porous fabric, such as a woven porous fabric, may be arranged on an external surface of the porous plastic. Such further porous material layer(s) may be more wettable by water than the porous plastic and thus more appropriate for being closer to the surface to be cleaned when wetted by water.

Particular mention is made of the porous material comprising a woven fabric, and most preferably a woven microfiber fabric. Such a woven microfiber fabric may facilitate attainment of the requisite underpressure in the wet cleaning apparatus.

Such a woven fabric, and in particular such a woven microfiber fabric, can be configured, in particular via the tightness of its weave, to satisfy the above ranges for the limiting pore diameter, as previously described in respect of the cleaning material (at least) in the liquid pick-up zone <NUM>.

Specifications of a particularly suitable woven fabric are provided in Table C as an illustrative non-limiting example.

In some embodiments, the porous material <NUM> comprises a porous material layer sealingly attached to the at least one dirt inlet.

Such sealing attachment can assist to maintain an underpressure in the covered dirt inlet(s) because loss of the underpressure via leakage between the dirt inlet(s) and the porous material layer is minimised or prevented.

The sealing attachment can be implemented in any suitable manner, such as by gluing or welding the porous material layer around each of the at least one dirt inlet, for example gluing and/or welding the porous material layer to the above-mentioned tube(s) around the opening(s) defining the dirt inlet(s).

Particular mention is made of sealingly attaching the porous material layer to the dirt inlet(s) by heat sealing, for example ultrasonic welding. This has been found to provide a particularly airtight seal in a straightforward manner which assists to maintain the underpressure in the dirt inlet(s).

A liquid pick-up region of the porous material layer may be delimited by sealing attachment of the porous material layer around the, e.g. each of the, at least one dirt inlet.

In some embodiments, the liquid pick-up region is arranged relative to the at least one cleaning liquid outlet <NUM> such as to allow the cleaning liquid to bypass, e.g. pass around a periphery of, the liquid pick-up region to reach, or at least be directed towards, the surface to be cleaned.

This may enable the cleaning liquid to be used more efficiently. This is because the cleaning liquid has a greater chance of reaching the surface to be cleaned, e.g. via the above-described cleaning liquid application zone 106A, 106B.

In other examples, the porous material <NUM> can be attached, e.g. against the cleaner head <NUM> or a component of the cleaner head <NUM>, around the dirt inlet(s) at least partly by being sucked thereagainst by the flow provided by an underpressure generator.

In some embodiments, the porous material <NUM> comprises, in addition to the porous material layer, one or more further porous material layers.

By the porous material <NUM> comprising a stack of porous material layers in this manner, a greater underpressure may be maintainable in the dirt inlet(s).

In such embodiments, the one or more further porous material layers may be arranged on an external surface of the porous material layer, with an external surface of the further porous material layer furthest from the at least one dirt inlet in a thickness direction of the porous material being adjacent to, e.g. contacting, the liquid pick-up zone <NUM> of the cleaning material of the cleaning element <NUM>.

In some embodiments, the porous material <NUM>, or the combination of the cleaning material in the liquid pick-up zone <NUM> and the porous material <NUM>, has a thickness of less than or equal to <NUM>, more preferably less than or equal to <NUM>, and most preferably less than or equal to <NUM>. Such a maximum thickness may contribute to minimising of flow resistance through the porous material <NUM> or, as the case may be, through the combination of the cleaning material in the liquid pick-up zone <NUM> and the porous material <NUM>.

The thickness of the porous material <NUM> or the combination of the cleaning material in the liquid pick-up zone <NUM> and the porous material <NUM> can be determined by using a <NUM> precision gauge and two ground metal plates (with the upper plate by which the normal pressure is applied being <NUM> x <NUM>, and the lower plate on which the sample is supported having a larger area than the <NUM> x <NUM> surface of the upper plate for ease of alignment) for receiving the sample therebetween. The arrangement is configured to apply a pressure normal to the sample of the porous material (<NUM> x <NUM>) of <NUM> N/m<NUM>. The relevant measurement parameters are provided in Table D:.

The thickness of several samples was determined using this method, and the data are provided in Table E:.

The porous material <NUM> and/or the cleaning material in the liquid pick-up zone <NUM> may be particularly susceptible to wear, and such wear can risk compromising underpressure-maintaining/liquid pick-up performance. Accordingly, the porous material <NUM> and/or the cleaning material in the liquid pick-up zone <NUM> can comprise a plurality of differently coloured layers which layers are progressively worn by use such that the colour of the porous material <NUM> and/or the cleaning material in the liquid pick-up zone <NUM> serves as a wear indicator.

It is noted that the cleaner head <NUM> can be attached or may be attachable to a suitable handle (not visible) to assist moving the cleaner head <NUM>. To this end, the cleaner head <NUM> may comprise a coupling point <NUM> to which such a handle may be coupled, e.g. pivotably coupled.

In some embodiments, the cleaner head <NUM> comprises an elastomeric material (not visible in <FIG>) on which the porous material <NUM> is arranged.

The resilient deformation of such an elastomeric material may lessen the risk of damage to the porous material <NUM> should, for example, a relatively hard protrusion be present on the surface to be cleaned which comes into contact with the porous material <NUM>. Alternatively or additionally, the elastomeric material may assist the porous material <NUM> to follow any contours of the surface to be cleaned, e.g. for the purpose of minimising the risk of liquid stripes being left on the surface to be cleaned.

The elastomeric material can, for instance, be or comprise silicone rubber. Other elastomeric materials, such as a polydiene, e.g. polybutadiene, a thermoplastic elastomer, and so on, can also be contemplated for inclusion in, or defining of, the elastomeric material.

Alternatively or additionally, the elastomeric material can be less than <NUM> Shore A, preferably less than <NUM> Shore A, most preferably less than <NUM> Shore A.

In a non-limiting example, the elastomeric material is <NUM> Shore A silicone rubber.

In embodiments in which the cleaner head <NUM> comprises the above-described protruding element <NUM>, the protruding element <NUM> may comprise the elastomeric material.

Alternatively or additionally, the cleaner head <NUM> may comprise a support <NUM>, e.g. a rigid support <NUM>, and the protruding element <NUM> is mounted via attachment to the support <NUM>.

In some embodiments, the at least one dirt inlet comprises, or is defined by, one or more channels extending through the elastomeric material.

The elastomeric material may comprise a curved surface on which the porous material <NUM> is arranged. In such embodiments, the porous material may follow the curvature of the curved surface.

Such a curved, e.g. rounded, surface of the elastomeric material may assist to minimise the area of the liquid pick-up region which approaches the surface to be cleaned, thereby assisting to minimise resistance to motion across the surface to be cleaned.

In some embodiments, the porous material layer is sealingly attached to the elastomeric material. The porous material layer may, for example, be sealingly attached to the elastomeric material via heat sealing.

In some embodiments, the cleaner head <NUM> comprises an impermeable portion to which the porous material layer is sealingly attached, with the at least one dirt inlet being defined by an aperture or apertures provided in the impermeable portion and/or being defined between the impermeable portion and the porous material layer.

In some embodiments, the at least one dirt inlet is exposed to a cavity between the porous material layer and the impermeable portion, with a liquid transporting support structure being arranged in the cavity, and providing one or more flow paths in the liquid pick-up region between the porous material layer and the at least one dirt inlet.

The liquid transporting support structure may provide one or more flow paths in the liquid pick-up region between the porous material layer and the at least one dirt inlet.

The porous material layer, e.g. a woven fabric, and/or the impermeable portion, e.g. a polymer film, may be pliable such that an underpressure may cause the porous material layer and the impermeable portion to be drawn towards each other. This may risk restriction of passage of liquid from the porous material layer to the at least one dirt inlet. The liquid transporting support structure may assist to ensure that, in spite of such drawing of the porous material layer and the impermeable portion towards each other, liquid can still be transported from the porous material layer, and in particular pores of the porous material layer, to the at least one dirt inlet.

The liquid transporting support structure can, for example, comprise one or more mesh layers.

More generally, the present disclosure provides an attachable (and/or detachable) member <NUM> per se. The attachable member <NUM> may be suitable for attaching to the cleaner head <NUM>.

In at least some embodiments, such as that shown in <FIG>, the attachable member <NUM> comprises the porous material layer <NUM>; and at least one dirt inlet <NUM> to which an underpressure generator is fluidly connectable when the attachable member <NUM> is attached to the cleaner head <NUM>, with a liquid pick-up region of the porous material layer <NUM> being delimited by sealing attachment of the porous material layer <NUM> around the at least one dirt inlet <NUM>.

Such an attachable member <NUM> may enable replacement of the porous material layer <NUM> without requiring re-sealing of the porous material layer <NUM> to the dirt inlet(s) <NUM>.

In some embodiments, the attachable member <NUM> comprises the elastomeric material <NUM> on which the porous material layer <NUM> is arranged. In this particular example, the porous material layer <NUM> is sealingly attached to a support member <NUM> included in the attachable member <NUM> via seals <NUM>, e.g. heat seals.

In this manner, the porous material layer <NUM> is sealingly attached to the dirt inlet(s) <NUM>, which dirt inlet(s) <NUM> is or are, in this example, defined in, i.e. delimited by, the elastomeric material <NUM>. In this particular example, the dirt inlets <NUM> are in the form of channels extending through the elastomeric material <NUM>.

The attachable member <NUM> can be attached, e.g. detachably coupled, to the support <NUM>, e.g. the rigid support <NUM>, included in the cleaner head <NUM> in any suitable manner, such as by the attachable member <NUM>, e.g. the support member <NUM> thereof, having a ridge member which push-fits into a slot defined in the support <NUM>, or by the support <NUM> having such a ridge member which push-fits into a slot defined in the attachable member <NUM>, e.g. in the support member <NUM>.

A further porous material layer <NUM> is also included in the attachable member <NUM> in the example shown in <FIG>. It is noted that the process of heat sealing, e.g. via ultrasonic welding, the porous material layer <NUM> to the plastic support member <NUM> also results in the further porous material layer <NUM> becoming adhered to the porous material layer <NUM>.

The examples shown in <FIG> differ from each other in that the liquid transporting support structure <NUM> shown in <FIG> is defined by a surface pattern arranged on and/or in the surface of the elastomeric material <NUM>, whereas the liquid transporting support structure <NUM> shown in <FIG> is in the form of a mesh layer.

The present disclosure further provides a wet cleaning apparatus comprising the cleaning element <NUM> as described herein and the cleaner head <NUM> as described herein.

<FIG> provide views of such a wet cleaning apparatus comprising the cleaning element <NUM> as described above in respect of <FIG> and the cleaner head <NUM> as described above in respect of <FIG> to which the cleaning element <NUM> is attached.

<FIG> schematically depicts a method of attaching a cleaning element <NUM> having a cleaning material to a cleaner head <NUM>. The method comprises cooperating <NUM> a plurality of guiding elements 116A, 116B, 116C, 116D of the cleaning element <NUM> with a structured portion <NUM> of the cleaner head <NUM> to join and align the cleaning element <NUM> with the cleaner head <NUM>, and securing <NUM> the aligned cleaning element <NUM> to the cleaner head <NUM> using a fastener <NUM> included in the cleaning element <NUM>, with the fastener <NUM> being spaced apart from the plurality of guiding elements 116A, 116B, 116C, 116D across the cleaning material.

While the cleaning element <NUM> and the cleaner head <NUM> are being aligned in step <NUM>, it is noted that the "triangular" shape of the cleaner head <NUM>, resulting from the protruding element <NUM> in this non-limiting example, may preclude securing of the fastener <NUM> to the cleaner head <NUM> while the cooperating <NUM> is taking place. Thus, a portion of the cleaner head <NUM> is free to touch and slide over the cleaning element <NUM> to facilitate the alignment.

Only when the cleaning element <NUM> and the cleaner head <NUM> are fully aligned with each other may the user either decide to gently tap the cleaner head <NUM>, tilting it backwards and connect the fasteners <NUM>, <NUM>, e.g. Velcro® strips, to fully fixate the cleaning element <NUM> to the cleaner head <NUM>, or implement this automatically by the first mopping stroke as this will also tilt the cleaner head <NUM> backwards to secure the cleaning element <NUM> to the cleaner head <NUM>.

It is noted that the cleaning element <NUM> can be detached from the cleaner head <NUM>, e.g. to enable washing of the cleaning element <NUM> and/or replacement of the cleaning element <NUM> when the cleaning material has become overly worn, by unfastening the fastener <NUM>, followed by disengaging the plurality of guiding elements 116A, 116B, 116C, 116D of the cleaning element <NUM> from the structured portion <NUM> of the cleaner head <NUM>.

Once attached, the cleaner head <NUM> and cleaning element <NUM> can be moved across the surface to be cleaned at a certain speed. This behaviour can be approximated using the following Bernoulli equation: <MAT> where ρ is the density of the fluid, υ is the fluid flow speed, P is the pressure, h is the elevation above a reference plane, in this case the floor, and g is the acceleration due to gravity.

The above Bernoulli equation can be re-written for the pressure underneath the liquid pick-up zone <NUM>: <MAT>.

For a speed of <NUM>/s, ΔP = <NUM> Pa; for a speed of <NUM>/s, ΔP = <NUM> Pa.

This indicates that at higher velocities, more liquid will be left on the floor, since at higher velocities the floor will be pulling harder at the liquid, and this has been observed with cleaner heads <NUM> and cleaning elements <NUM> according to the present disclosure.

The liquid pick-up performance of an exemplary wet cleaning apparatus whose cleaning element <NUM> is moved at <NUM>/s across the surface to be cleaned with different dirt inlet underpressures was evaluated. The results are presented in the Table F.

In at least some embodiments, the wet cleaning apparatus comprises an underpressure generator for supplying suction to the at least one covered dirt inlet.

In some embodiments, the underpressure generator is configured to provide a pressure difference between an inside of the wet cleaning apparatus and atmospheric pressure for drawing fluid through the liquid pick-up zone and, when present, the porous material <NUM> and into the at least one dirt inlet <NUM>, wherein the pressure difference is in a range of <NUM> Pa to <NUM> Pa.

Both endpoints of the <NUM> Pa to <NUM> Pa range for the pressure difference are purposively selected.

The <NUM> Pa lower limit reflects that the cleaner head <NUM> and cleaning element <NUM> will typically be moved over a surface to be cleaned, e.g. a floor, and as the speed of the cleaner head <NUM> and cleaning element <NUM> over the floor increases, the concomitant drop in static pressure means that liquid is pulled towards the floor. Such behaviour can be approximated by a Bernoulli equation, as described above.

Referring to Table F above, it has been found that below <NUM> Pa, too much liquid may remain on the surface to be cleaned when the cleaner head <NUM> is moved thereon at a typical speed.

The <NUM> Pa minimum underpressure is correspondingly set according to a minimum typical speed with which a user moves the cleaner head <NUM> and cleaning element <NUM> over the surface to be cleaned, thereby to ensure that the underpressure is sufficient to pull liquid into the inside of the wet cleaning apparatus without requiring that the user has to significantly slow or cease movement of the cleaner head <NUM> and cleaning element <NUM> over the surface to be cleaned in order for the liquid to be picked up.

The <NUM> Pa upper limit is defined for the purpose of ensuring that liquid transport through the liquid pick-up zone <NUM> and, when present, the porous material <NUM> is sufficiently rapid.

There is a trade-off between the magnitude of the underpressure which can be maintained and flow resistance through the liquid pick-up zone <NUM> and, when present, the porous material <NUM>. The flow resistance may determine the rate at which liquid can pass through the liquid pick-up zone <NUM> and, when present, the porous material <NUM>. This trade-off is reflected in the selection of the <NUM> Pa upper limit of the range.

In some embodiments, the pressure difference is <NUM> Pa to <NUM> Pa, and most preferably <NUM> Pa to <NUM> Pa. These ranges may reflect particularly enhanced liquid pick-up observed during movement of the cleaner head <NUM> and cleaning element <NUM>, combined with relatively low flow resistance through the liquid pick-up zone <NUM> and, when present, the porous material <NUM>.

The pressure difference can be directly and positively verified in a given wet cleaning apparatus in which the cleaning element <NUM> is attached to the cleaner head <NUM> by, for example, drilling a hole in a tube of the wet cleaning apparatus which is fluidly connected with the dirt inlet(s) <NUM> 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).

The pressure sensor is connected between the liquid pick-up zone <NUM> and the underpressure generator and as close to the liquid pick-up zone <NUM> as possible, to minimise the influence of other factors, such as flow resistance etc., on the sensed pressure difference.

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 the cavity between the porous material layer and the impermeable portion.

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.

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.

It is further noted that a column of water present between the pressure sensor and the liquid pick-up zone <NUM> 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.

Once the pressure sensor is arranged as described above, it may be ascertained that maintenance of the underpressure is due to the liquid pick-up zone <NUM> and, if present, the porous material <NUM>, and not some other element, such as a valve. Any such element that influences the underpressure that is presented to the liquid pick-up zone <NUM> and, if present, the porous material <NUM> should be rendered inoperable for the purpose of performing the measurement.

Component(s) that dispense cleaning liquid (should the wet cleaning apparatus be configured to deliver cleaning liquid) is/are disengaged when performing the pressure difference measurement.

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

The pick-up area of the cleaner head <NUM> is suspended in a layer of water, at max. <NUM> depth.

The pick-up area is then lifted from the water without tilting it in any way (so that the cleaner head <NUM> remains in a cleaning position, as if it were positioned to clean the floor), so that the water is no longer touching the liquid pick-up zone <NUM>. At this point, "free water" will be removed from the liquid pick-up zone <NUM> and, if present, the porous material <NUM>, all pores will go into their "blocked state", and the breaking pressure is determinable. The pressure difference is measured once an equilibrium is established in an end regime in which the applied flow results in an underpressure which causes no more fluid blocks to break.

The thus obtained breaking pressure is the "pressure difference between the inside of the wet cleaning apparatus and atmospheric pressure for drawing fluid through the liquid pick-up zone <NUM> and, if present, the porous material <NUM> and into the at least one dirt inlet <NUM>. " It is verified from the measurement result whether or not the <NUM> Pa to <NUM> Pa range is satisfied.

A further advantage of the liquid pick-up principle described herein may be the lower power consumption, particularly in examples in which the underpressure generator is powered.

A conventional vacuum cleaner that is capable of picking up water needs to generate significant airspeed and/or brushpower in order to generate enough shear force on water droplets to cause them to enter the vacuum cleaner. Typical power consumption values for such vacuum cleaners are several hundred watts.

The following calculation illustrates the relatively low mechanical power needed for liquid, e.g. water, pick-up according to the present disclosure. <MAT> where P is the mechanical power in watts; Φ is the fluid flow in m<NUM>/s; and ΔP is the underpressure in the dirt inlet(s) <NUM> in Pa.

Taking, for instance, an underpressure of <NUM> Pa, and a fluid flow of <NUM><NUM>/minute, the power is <NUM>*<NUM>-<NUM> watts.

Should the underpressure generator be powered using, for instance, a conventional battery providing a runtime of <NUM> minutes in a wet cleaning apparatus whose mechanical power consumption is around <NUM> watts, the runtime in the present case would be <NUM> minutes, in other words more than <NUM> days.

A powered wet cleaning apparatus having the cleaner head <NUM> and cleaning element <NUM> according to the present disclosure may therefore only rarely require recharging of its battery (in examples in which such a battery is included to power the wet cleaning apparatus), and/or may be made more lightweight, due to the minimal battery capacity needed for, for example, a <NUM> hour runtime. Regarding the latter, it is noted that a battery for a conventional handheld wet cleaning apparatus may weigh around <NUM>, and may thus contribute significantly to the overall weight of the wet cleaning apparatus.

In some embodiments, the underpressure generator is configured to supply suction by providing a flow rate through the cleaning material in the liquid pick-up zone <NUM> and, when present, the porous material <NUM> which is less than or equal to <NUM><NUM>/minute.

Such a flow rate may be significantly lower than for the conventional wet vacuum cleaners mentioned above. Since power is equal to flow rate multiplied by the pressure difference, by combining this maximum <NUM><NUM>/minute flow rate with the above-described maximum <NUM> Pa pressure difference as a maximum power consumption scenario, the power consumption of the wet cleaning apparatus may be minimised. This may enable the wet cleaning apparatus to made relatively compact, e.g. using a smaller battery, and/or to have a relatively long runtime.

Alternatively or additionally, the underpressure generator may be configured to supply suction by providing a flow rate through the liquid pick-up zone <NUM> of the cleaning material and, when present, the porous material <NUM> which is equal to or greater than <NUM><NUM>/minute. This may contribute to the pick-up of liquid from the surface to be cleaned being sufficiently rapid. The <NUM><NUM>/minute lower limit may, in some embodiments, be set to equal or exceed a flow rate of a cleaning liquid from cleaning liquid outlet(s) <NUM> included in the cleaner head <NUM>.

In some embodiments, the underpressure generator is configured to provide a flow rate through the liquid pick-up zone <NUM> and, when present, the porous material <NUM> which is equal to or greater than <NUM><NUM>/minute. As well as contributing to efficient liquid pick-up, this <NUM><NUM>/minute may, in some embodiments, be set to equal or exceed a flow rate of a cleaning liquid from cleaning liquid outlet(s) <NUM> included in the cleaner head <NUM>, with the minimum cleaning liquid flow rate being set to ensure plentiful supply of the cleaning liquid to the surface to be cleaned.

The underpressure generator may be configured to provide a flow rate through the liquid pick-up zone <NUM> of the cleaning material and, when present, the porous material <NUM> in the range of <NUM> to <NUM><NUM>/minute, even more preferably <NUM> to <NUM><NUM>/minute, and most preferably <NUM> to <NUM><NUM>/minute. Such a flow rate may capitalise on the underpressure-maintaining capability of the liquid pick-up zone <NUM> and, when present, the porous material <NUM>, and may ensure sufficient liquid pick-up whilst limiting energy consumption.

The wet cleaning apparatus may also include a dirty liquid collection tank. In such embodiments, the underpressure generator may be arranged to draw liquid from the at least one dirt inlet <NUM> to the dirty liquid collection tank.

In such embodiments, the dirty liquid collection tank can be arranged in any suitable manner relative to, e.g. upstream or downstream of, the underpressure generator.

In some embodiments, the wet cleaning apparatus comprises a cleaning liquid supply for supplying cleaning liquid to the cleaner head <NUM> for delivery towards the surface to be cleaned via the at least one cleaning liquid outlet(s) <NUM>. Such a cleaning liquid supply may, for example, comprise a cleaning liquid reservoir and a delivery arrangement, e.g. a delivery arrangement comprising a pump, for transporting the cleaning liquid to and through the at least one cleaning liquid outlet <NUM>.

In some embodiments, the above-mentioned handle may support or include at least part of the underpressure generator fluidly connected to the at least one dirt inlet <NUM> and/or the dirty liquid collection tank. Alternatively or additionally, at least part of the cleaning liquid supply, e.g. the cleaning liquid reservoir and/or the delivery arrangement, may be supported by or included in the handle.

The cleaning liquid supply and the at least one cleaning liquid outlet <NUM> may be configured to provide a continuous delivery of the cleaning liquid towards the surface to be cleaned.

The underpressure generator may be configured to provide suction to the at least one dirt inlet <NUM> at the same time as, in other words simultaneously to, the cleaning liquid supply supplying the cleaning liquid to and through the at least one cleaning liquid outlet <NUM>.

The cleaning liquid supply and the underpressure generator may, for instance, be configured such that the flow of the cleaning liquid delivered through the at least one cleaning liquid outlet <NUM> is equal to or lower than the flow provided through the liquid pick-up zone <NUM> and, when present, the porous material <NUM> to the at least one dirt inlet <NUM> by the underpressure generator. This may assist to ensure that the surface to be cleaned does not become excessively wet with the cleaning liquid. For example, the flow of cleaning liquid may be in the range of <NUM> to <NUM><NUM>/minute, and the flow provided by the underpressure generator may be in the range of <NUM> to <NUM><NUM>/minute, more preferably <NUM> to <NUM><NUM>/minute, even more preferably <NUM> to <NUM><NUM>/minute, and most preferably <NUM> to <NUM><NUM>/minute.

If a positive displacement pump is employed as the underpressure generator, at <NUM> or <NUM> liter/minute flows, such a pump may become relatively bulky and noisy, hence lower flow rates may assist in keeping the wet cleaning apparatus relatively small, quiet and lightweight.

In principle, a flow rate of the underpressure generator which is equal to the flow rate of the cleaning liquid provided by the cleaning liquid supply may suffice.

However, this may risk relatively significant disturbance to the system's equilibrium (requisite underpressure) if, for instance, a spill of water is encountered by the liquid pick-up zone <NUM>. For example, a <NUM><NUM> puddle of water encountered by the wet cleaning apparatus having a cleaning liquid flow rate of <NUM><NUM>/minute and a flow rate provided by the underpressure generator of <NUM><NUM>/minute may mean that it would take about <NUM> minutes to take in all the water (resulting in a <NUM> minute drop in underpressure, hence a <NUM> minute period in which the floor stays significantly more wet (because the puddle keeps on being spread). On the other hand, a <NUM><NUM>/minute flow rate provided by the underpressure generator may reduce this to a <NUM> second period. The flow rate provided by the underpressure generator being above the flow rate of the cleaning liquid provided by the cleaning liquid supply may permit the system to revert to equilibrium more quickly after such a disturbance.

More generally, the wet cleaning apparatus may be or comprise, for example, a wet mopping device, a window cleaner, a sweeper, or a wet vacuum cleaner, such as canister-type, stick type, or upright type wet vacuum cleaner.

In a particular non-limiting example, the wet cleaning apparatus is a battery-powered (or battery-powerable) wet cleaning apparatus, such as a battery-powered (or battery-powerable) wet mopping device, in which the underpressure generator, e.g. pump, is powered (or powerable) by a battery electrically connected (or connectable) thereto. Particular mention is made of this example due to the above-described power consumption-reducing effect which can be provided by the liquid pick-up zone <NUM> and, when present, the porous material <NUM> covering the dirt inlet(s) <NUM> to which the suction of the underpressure generator is provided.

<FIG> schematically depicts an exemplary wet cleaning apparatus <NUM> in the form of a wet vacuum cleaner. In this non-limiting example, the wet cleaning apparatus <NUM> comprises the above-described dirty liquid collection tank <NUM>, and the cleaning liquid reservoir <NUM>. The cleaner head <NUM> and cleaning element <NUM> included in the wet vacuum cleaner can be moved over the surface to be cleaned, in this example assisted by the wheels <NUM> included in the wet vacuum cleaner.

The wet cleaning apparatus <NUM> may in some examples be or comprise a robotic wet vacuum cleaner or a robotic wet mopping device configured to autonomously move the cleaner head <NUM> and cleaning element <NUM>, e.g. in a single cleaning direction, on the surface to be cleaned, such as the surface of a floor.

<FIG> schematically depicts an exemplary wet cleaning apparatus <NUM> in the form of a robotic wet vacuum cleaner. The robotic wet vacuum cleaner may move autonomously on the surface to be cleaned, e.g. via automated control over the wheels <NUM>.

The cleaning liquid stored in the cleaning liquid reservoir <NUM> can be delivered to the surface to be cleaned, and liquid can be picked up via the covered dirt inlet(s) <NUM> of the cleaner head <NUM> and collected in the dirty liquid collection tank <NUM>, during autonomous movement of the robotic wet vacuum cleaner. The underpressure generator and/or the cleaning liquid supply may also be under automated control.

Claim 1:
A cleaning element (<NUM>) for attaching to a cleaner head, which cleaner head has a structured portion and at least one dirt inlet, the cleaning element comprising:
a cleaning material for contacting a surface to be cleaned, the cleaning material comprising a liquid pick-up zone (<NUM>) alignable with, so as to cover, the at least one dirt inlet, and a cleaning liquid application zone (106A, 106B) adjacent the liquid pick-up zone for applying cleaning liquid to the surface to be cleaned;
a plurality of guiding elements (116A, 116B, 116C, 116D) cooperable with said structured portion to join and align the cleaning element with the cleaner head; and
a fastener (<NUM>) for securing the aligned cleaning element to the cleaner head following alignment and joining of the cleaning element to the cleaner head via the guiding elements, the fastener being spaced apart from the plurality of guiding elements across said cleaning material.