Surface cleaner

Abstract

A vapour cleaning system (100) for cleaning a surface. The vapour cleaning system comprises a liquid supply system (102) for supplying a liquid, a vapour outlet (112), a heater (114), and control circuitry (118). The control circuitry is configured to control an effective power supplied to the heater such that, in a vapour generation mode for generating the vapour, the heater vapourises a quantity of the liquid to generate a vapour that undergoes choked flow through the vapour outlet (112).

Description

1 P005325-W001SURFACE CLEANERBACKGROUND

[0001] Appliances for cleaning or treating surfaces may comprise a cleaner head that is in contact with the surface to be cleaned or treated in use. Some appliances utilise liquids, such as water, to clean or treat a surface. Such liquids may be utilised alongside a roller, mop, wipe, or other component for applying a wiping force to the surface.SUMMARY

[0002] According to a first aspect, there is provided a vapour cleaning system comprising: a liquid supply system for supplying a liquid; a vapour outlet; a heater; and control circuitry configured to control an effective power supplied to the heater such that, in a vapour generation mode for generating the vapour, the heater vapourises a quantity of the liquid to generate a vapour that undergoes choked flow through the vapour outlet.

[0003] Cleaning systems for cleaning a surface, such as vacuum cleaners, steam cleaners or wet floor cleaners, which may be referred to as surface cleaners, may be used for cleaning a surface for extended periods of time. It may be desirable for surface cleaners to be energy efficient, in order to reduce degradation of components and energy consumption. Some surface cleaners may be battery-powered. Reducing energy consumption for such surface cleaners may provide a better user experience, for example by reducing the frequency of recharging the surface cleaner, and allowing the surface cleaner to be used more effectively.

[0004] Choked flow of the vapour through the vapour outlet of the vapour cleaning system of examples herein for example allows the vapour cleaning system to generate a high-velocity vapour, for example with lower energy consumption than otherwise. In contrast to conventional steam cleaners, the high-velocity vapour through the vapour outlet may be achieved with a lower mass flow, involving a lower consumption of energy and liquid. Moreover, the high velocity of the vapour may be suitable for removing persistent debris more effectively than a conventional steam cleaner. The size of the vapour outlet may also make it possible to direct a release of vapour towards debris with a higher precision.

[0005] For a predetermined cross-sectional area of the vapour outlet, for example of an orifice of the vapour outlet, the effective power supplied to the heater in the vapour generation mode for example leads to heater vapourising the quantity of the liquid. This may2 P005325-W001generate a pressure within the vapour cleaning system that is above atmospheric pressure. As the pressure increases, a velocity and a mass flow rate of the vapour through the vapour outlet also increase. Both the velocity and mass flow rate may increase up to a point at which the velocity of the vapour through the vapour outlet approaches the speed of sound. Any further increase in the pressure inside the vapour cleaning system (e.g. referred to as upstream pressure) above a pressure level at which the vapour reaches the speed of sound through the vapour outlet may not cause a further increase in velocity and mass flow rate of the vapour through the vapour outlet, as the flow becomes choked. This regime may be referred to as a choked flow regime.

[0006] Choked flow is for example a phenomenon experienced by a compressible fluid, such as a vapour generated by the vapour cleaning system, flowing through a constriction, such as the vapour outlet. The velocity and mass flow rate of the fluid through the constriction can no longer increase as a result of a further decrease in downstream pressure for a fluid undergoing choked flow through the constriction. This point, at which a decrease in downstream pressure does not cause a further increase in velocity and mass flow of the fluid is typically when the velocity of the fluid approaches the speed of sound, such as Mach 1 speed. This causes the flow of the fluid to be choked.

[0007] Additional operating parameters of the vapour cleaning system may be controlled to aid in achieving choked flow of the vapour. The additional operating parameters may be, for example, a quantity of liquid supplied by the liquid supply system, an operating pressure of the vapour cleaning system, a size, shape or other configuration of the vapour outlet (such as a configuration of a nozzle and / or orifice of the vapour outlet, discussed further below), an internal volume of a vapour generation chamber of the vapour cleaning system within which the vapour may be generated (discussed further below) and / or a material of the of the vapour generation chamber.

[0008] The effective power supplied to the heater may be between 50 watts and 800 watts. Supplying the heater with an effective power in this range may facilitate attaining choked flow of the vapour through the vapour outlet.

[0009] The vapour outlet may comprise an orifice with a cross-sectional area of between 0.05 millimetres squared and 0.5 millimetres squared. This may reduce the required effective power supplied to the heater to achieve flow of the vapour in a choked flow regime.3 P005325-W001

[0010] An effective power as used herein for example provides an indication of a magnitude of a power that is deliverable to a component of the vapour cleaning system during a mode of operation of the vapour cleaning system. For example, when a delivered electrical power comprises one or more pulses of power, and each pulse of power has a different amplitude, the effective power may be the average, e.g. mean or root mean square, power delivered to the component during a relevant mode of operation of the vapour cleaning system. If the delivered electrical power has a constant amplitude, which is unvarying over time, the effective power may be taken as the amplitude of the power.

[0011] The vapour cleaning system may comprise a vapour generation chamber thermally coupled to the heater. In the vapour generation mode, the vapour generation chamber may be configured to receive the quantity of the liquid from the liquid supply system, for vapourisation of the quantity of the liquid within the vapour generation chamber to generate the vapour. The vapour outlet may be coupled to the vapour generation chamber to receive the vapour from the vapour generation chamber. The vapour generation mode is for example a mode that is suitable, e.g. based on operating parameters of the vapour cleaning system, for generating vapour.

[0012] The vapour generation chamber for example allows a quantity of liquid to be contained and heated up for vapour generation. This allows the quantity of liquid within the vapour generation chamber to be heated rather than, for example, heating a potentially larger quantity of liquid, such as that within another component of the liquid supply system for supplying the quantity of liquid to the liquid generation chamber. This may lead to the vapour cleaning system heating up a smaller amount of liquid than otherwise, thereby using a lower amount of energy.

[0013] The heater may be a so-called flash heater, which is for example a type of heater that is suitable for heating a continuous flow of liquid, for example without retaining the liquid internally. For example, liquid may be vapourised rapidly, e.g. on-demand or instantly, by a flash heater so as to generate a continuous stream of vapour. A flash heater may be arranged to heat up a relatively small quantity, e.g. a small mass, of liquid (although in other cases a flash heater may be configured to heat a continuous flow of liquid without necessarily having a small internal volume). A flash heater may be capable of vaporising the quantity of liquid within the vapour generation chamber to obtain a mass flow rate of vapour through the vapour outlet that exceeds a particular threshold mass flow rate, such as between 0.05 grams4 P005325-W001per second and 0.7 grams per second. This may correspond to the generation of, for example, between 3 grams and 42 grams of vapour in a minute. In a steady state condition, in the vapour generation mode, any further increase in an internal pressure within the vapour generation chamber may not cause the mass flow rate to increase above the aforementioned levels, due to the choked flow of the vapour through the vapour outlet. A flash heater may have a vapour generation chamber with a size for containing a suitable quantity of liquid that can be rapidly vaporised by the heater with a particular effective power, such as the effective power of between 50 watts and 800 watts. For example, the vapour generation chamber may have a volume of less than or equal to 2 millilitres (ml), 1 ml or 0.5 ml.

[0014] The vapour generation chamber may comprise any material that is suitable for withstanding: temperatures greater than or equal to 200 degrees Celsius within the vapour generation chamber; and pressures greater than or equal to 5 bars within the vapour generation chamber without the vapour generation chamber getting damaged or deformed. For example, the vapour generation chamber may comprise metal, and the metal may be, for example, brass, aluminium or stainless steel. The vapour generation chamber may comprise an internal cavity suitable for receiving the liquid from the liquid source, conducting heat from the heater to the liquid to generate the vapour, and supplying the vapour to the vapour outlet.

[0015] In the vapour generation mode, a pressure within the vapour generation chamber may be between 1 bar and 5 bars. This may be achieved in a relatively small vapour generation chamber, as discussed further above. The internal pressure within the vapour generation chamber, together with the cross-sectional area of the vapour outlet, may enable high-velocity vapour to be generated while using relatively small components. For example, the control circuitry may be configured to control the effective power supplied to the heater and supply of the liquid from the liquid supply system to the vapour generation chamber such that the pressure is between 1 bar and 5 bars. In such cases, the control circuitry may not control the effective power and liquid supply based on a measured pressure, but may instead control the effective power and liquid supply based on at least one other measurement (such as a temperature signal indicative of a temperature of the vapour generation chamber and / or heater) which is nevertheless related to or indicative of the pressure within the vapour generation chamber.5 P005325-W001

[0016] The vapour outlet may comprise a nozzle. The nozzle may be detachably coupled to the vapour generation chamber. A detachable nozzle may simplify the process of maintaining the vapour cleaning system, as the nozzle may be easily replaced, cleaned or unclogged, without compromising other components of the vapour cleaning system.

[0017] The nozzle may comprise a layer for limiting thermal conduction from an internal portion of the nozzle to an external portion of the nozzle. The layer may comprise silicon. The layer for limiting thermal conduction may reduce the temperature of the external portion of the nozzle, e.g. during the vapour generation mode, to a greater extent than otherwise. This may reduce a risk of harm to a user due to accidental contact with the exterior surface of the nozzle, for example if the layer limits the thermal conduction to an extent that the exterior surface of the nozzle remains at a temperature that is safe for the user to touch in the vapour generation mode. The layer for limiting thermal conduction may comprise any suitable thermally insulating material, for example to make the external portion of the nozzle safe for a user to touch.

[0018] The vapour cleaning system may comprise a temperature sensor configured to generate a temperature signal indicative of a temperature of the vapour. The temperature signal may be used for various control and safety purposes, such as, for example, ensuring that the temperature of the heater does not exceed a safety threshold, or ensuring that the vapour is at a desired temperature (which may be a desired temperature range). For example, the temperature of the vapour may be controlled, based on the temperature signal, to obtain a vapour with desired characteristic(s), e.g. so that the vapour is of a desired consistency and / or temperature for cleaning the surface. In contrast, a vapour that is too watery (e.g. due to a temperature that is lower than the desired temperature) may wet the surface to be cleaned excessively, and a vapour that is too hot (e.g. with a temperature above the desired temperature) may damage the surface to be cleaned. The temperature signal may therefore provide for flexibility in operating the vapour cleaning system.

[0019] The temperature sensor may be or comprise a thermistor, an infrared sensor, and / or a thermomechanical sensor.

[0020] The temperature sensor may be thermally coupled to at least one of the vapour generation chamber or the heater for sensing a temperature of the at least one of the vapour generation chamber or the heater, indicative of the temperature of the vapour. The temperature sensor may be detachable from the vapour cleaning system. This may facilitate6 P005325-W001maintenance or replacement of the temperature sensor. The temperature sensor may be detachably coupled using a fixing to provide a more reliable connection. The fixing may facilitate configuring the temperature sensor to have a fixed contact area with the vapour generation chamber and / or the heater, and the fixed contact area may allow a more reliable temperature signal to be obtained. This may also provide a more secure connection to the vapour generation chamber and / or to the heater.

[0021] The liquid supply system may comprise a pump for pumping the liquid to the heater, wherein the control circuitry may be configured to control an effective power supplied to the pump and the effective power supplied to the heater based on the temperature signal. Using a pump may ease the liquid supply process, as the volume of liquid supplied by the pump may be controlled in a straightforward manner, based on the temperature signal.

[0022] The control circuitry may be configured to, in the vapour generation mode: obtain a pump control signal for controlling the effective power supplied to the pump based on a first difference between the temperature signal and a first target temperature value; and obtain a heater control signal for controlling the effective power supplied to the heater based on a second difference between the temperature signal and a second target temperature value, wherein the first target temperature value may be lower than the second target temperature value. Controlling the pump and the heater independently simplifies the control circuitry, as it may be possible to independently design and tune two separate control loops. It is to be appreciated, though, that in some examples, the control circuitry may be designed as a single control loop. A single control loop may, for example, allow a calibration process to be automated more easily, as the effect of the first target temperature and the second target temperature may not have to be decoupled.

[0023] The first target temperature value may be between 125 and 135 degrees Celsius and the second target temperature value may be between 155 and 165 degrees Celsius. This combination of the first target temperature and the second target temperature may lead to the generation of vapour with desired characteristic(s) for cleaning the surface as explained above.

[0024] The control circuitry may be configured to control the effective power supplied to the heater to be substantially zero in response to the control circuitry identifying at least one of: an absence of the temperature signal; that the temperature signal exceeds a predetermined temperature threshold; that a volume of the liquid suppliable by the liquid supply system is7 P005325-W001below a predetermined liquid volume threshold; or determining that the effective power supplied to the pump is above a predetermined effective pump power threshold. The term substantially zero as used herein for example refers to an effective power that is zero, zero within manufacturing and / or measurement tolerances, or a power that is below a usable threshold The usable threshold may be a percentage of a nominal operating power of a component. The usable threshold may be, for example, 2% of the nominal operating power of the component.

[0025] The absence of the temperature signal may be caused by the temperature sensor malfunctioning or being disconnected, and / or at least part of the control circuitry malfunctioning. The temperature signal exceeding the predetermined temperature threshold may be caused by the heater being supplied with an excessive amount of effective power, the pump being supplied with an insufficient amount of effective power, the heater malfunctioning, the pump malfunctioning, and / or the control circuitry malfunctioning. The volume of the liquid suppliable by the liquid supply system being below the predetermined liquid volume threshold may be caused by a blockage in at least part of the liquid supply system, and / or an insufficient amount of liquid being available for supply. The effective power supplied to the pump being above the predetermined effective pump power threshold may be caused by a blockage in at least part of the liquid supply system, and / or an insufficient amount of liquid being available for supply. In any of these cases, controlling the effective power supplied to the heater to be substantially zero may reduce or prevent damage to the heater and vapour generation chamber. This may also reduce the risk of causing damage to the user or to a surface to be cleaned, for example by causing the vapour cleaning system to cease production of vapour.

[0026] The control circuitry may be configured to control the effective power supplied to the pump to be substantially zero in response to the control circuitry identifying at least one of: an absence of the temperature signal; that the temperature signal exceeds a predetermined temperature threshold; determining that a volume of the liquid suppliable by the liquid supply system is below a predetermined liquid volume threshold; or determining that the effective power supplied to the pump is above a predetermined effective pump power threshold.

[0027] The absence of the temperature signal, the temperature signal exceeding the predetermined temperature threshold, the volume of the liquid suppliable by the liquid8 P005325-W001supply system being below the predetermined liquid volume threshold, and / or the effective power supplied to the pump being above the predetermined effective pump power threshold may be caused by malfunctioning of at least one of the heater, the control circuitry or the liquid supply system, or a misconfiguration of at least part of the vapour cleaning system, as explained above. In any of these cases, controlling the effective power supplied to the pump to be substantially zero may reduce damage to the liquid supply system and leakage of the liquid onto other components of the vapour cleaning system, or onto a surface to be cleaned.

[0028] The vapour cleaning system may be operable in a further mode of operation in which the control circuitry is configured to: control a power supplied to the pump to be substantially zero; and control the effective power supplied to the heater such that the effective power supplied to the heater is a predetermined effective power. The predetermined effective power may be lower than the effective power supplied to the heater in the vapour generation mode. The control circuitry may be operable to switch the vapour cleaning system from the further mode of operation to the vapour generation mode in response to receiving a signal indicating that vapour generation is to begin.

[0029] The amount of time for the heater to reach an operating temperature for generating vapour, upon switching to the vapour generation mode, may be lower from the further mode of operation than from an off-state, allowing vapour to be generated more rapidly when desired. The further mode of operation may be used if the vapour cleaning system is to be used for cleaning a plurality of regions of the surface, with the heater switched to the further mode of operation rather than the off-state in between cleaning each of the plurality of regions. In a further example, the further mode may be used if the vapour cleaning system is in use for non-vapour cleaning, such as wet or dry cleaning, at which time it may be anticipated that vapour cleaning may be used subsequently. The further mode of operation may be considered a standby mode. The predetermined effective power in the further mode of operation may be lower than a minimum effective power delivered to the heater during the vapour generation mode. For example, the predetermined effective power in the further mode of operation may be lower than 50 watts.

[0030] The liquid supply system may comprise a tank for containing the liquid; and a reservoir for containing a substance for reducing ionisation of the liquid, wherein, in use, the liquid supply system is configured to supply the liquid from the tank to the reservoir for the substance within the reservoir to reduce the ionisation of the liquid. The substance for9 P005325-W001reducing ionisation of the liquid may reduce the amount of minerals in the liquid. This may reduce possible blockages of the vapour outlet due to accumulation of minerals. The reservoir may be separate from the tank, and a flow of liquid from the tank to the reservoir may be controlled, e.g. via a one-way valve. This may reduce utilisation of the substance for reducing ionisation of the liquid.

[0031] The vapour cleaning system may comprise an electrical conductivity monitoring system configured to, in use: generate an electrical conductivity signal indicative of an electrical conductivity of contents of the reservoir, the contents comprising the liquid and the substance; and in response to the electrical conductivity signal being indicative that the electrical conductivity of the contents is greater than or equal to a predetermined electrical conductivity threshold, generate a warning signal indicative that an amount of the substance within the reservoir is less than a threshold amount. This may provide an indication to the user that the reservoir is to be refilled with the substance for reducing ionisation of the liquid. This may help reduce blockages of the vapour outlet that may otherwise arise due to depletion of the substance for reducing ionisation of the liquid. In other examples, the control circuitry may be configured to supply a further quantity of the substance to the reservoir in response to the warning signal, e.g. from a substance supply system of the vapour cleaning system.

[0032] According to a second aspect of the present disclosure, there is provided a surface cleaner comprising the vapour cleaning system of the first aspect. This may provide the surface cleaner with a vapour cleaning system capable of generating a vapour with a relatively high velocity, e.g. for cleaning persistent dirt, with a relatively low power consumption.

[0033] The surface cleaner may comprise a wet cleaning system. This may be used to provide further cleaning options. For example, the surface cleaner may be used to remove persistent dirt by generating the vapour, and the wet cleaning system may be deployed for cleaning light dirt. Persistent dirt may be, for example, a deep stain of a surface, and the deep stain may persist for an extended period of time. An extended period of time for a stain may be, for example, a period of time greater than or equal to two hours. Light dirt may be, for example, surface debris, or a liquid that has been recently poured onto the surface. It is to be appreciated, though, that in some examples, the vapour may be used to clean other debris than persistent dirt, such as light dirt.10 P005325-W001

[0034] The liquid supply system may be configured to supply the liquid to the wet cleaning system. This may simplify the liquid supply system by having a single liquid supply system for supplying the liquid for both vapour generation and for the wet cleaning system.

[0035] The surface cleaner may comprise a wet cleaning system tank for containing the liquid for use by the wet cleaning system. This may allow a configuration, e.g. a size, of the tank and the wet cleaning system tank to be selected independently, for example based on a typical liquid consumption for vapour generation and wet cleaning.

[0036] The surface cleaner may be an autonomous surface cleaner. This may enable the user to automate cleaning of surfaces, which may be more efficient than manual cleaning.

[0037] The surface cleaner may comprise an image sensor for capturing image data, and the control circuitry may be configured to control, based on an image classification output indicative of at least one characteristic of a surface to be cleaned, operation of at least one aspect of the surface cleaner, wherein the image classification output is based on the image data. This may be used to autonomously control and, in some cases, optimise cleaning of a surface. For example, the image classification output may indicate at least one of a position of dirt; a segmentation output representative of a boundary of dirt; and a material of the surface to be cleaned. The surface cleaner may be controlled, based on the image classification output, to produce vapour to clean dirt in a particular location, produce vapour until dirt is removed, or optimise or otherwise determine a navigation path for the surface cleaner towards at least one location of the surface associated with the presence of dirt.

[0038] The control circuitry may be configured to, based on the image classification output, control switching of the surface cleaner to and / or from the vapour generation mode. The surface cleaner may use the image classification output to switch between the vapour generation mode and, for example, the further mode of operation or an off-state, to reduce power consumption. For example, the control circuitry may be configured to, in response to the image classification output being indicative that an image represented by the image data is an image of dirt, switch the surface cleaner to the vapour generation mode. In this way, the control circuitry may switch the surface cleaner to the vapour generation mode upon detection of dirt to be cleaned by the vapour, e.g. without maintaining the surface cleaner in the vapour generation mode in the absence of dirt. This may occur, for example, when the image classification output indicates that a surface comprises several instances of dirt, such as persistent dirt at several different locations on the surface.11 P005325-W001

[0039] The surface cleaner may use the image classification output to locate dirt and determine a navigation path across a surface to clean the surface. The image classification output may be indicative of a type of dirt, such as whether the dirt is persistent dirt, such as a stain, or light dirt. The type of dirt may be classified, for example, based on consistency of dirt, as determined based on the image data, such as granular, fibrous or liquid consistency, and / or an estimation that dirt contains at least part of a particular substance, based on the image data. For example, granular dirt such as gravel, or fibrous dirt such as hair, may be classified as light dirt. Food residuals, such as coffee or oil, may be classified as persistent dirt. The image classification output may also or instead be indicative of the image data representing a surface that is suitable for vapour cleaning. The surface cleaner may use the image classification output to switch to the vapour generation mode upon detection of a surface suitable for vapour cleaning and / or inhibit generation of vapour for unsuitable surfaces. Unsuitable surfaces may be, for example, wood, delicate fabrics, or painted surfaces. Suitable surfaces may be, for example, stone, porcelain, ceramic, vinyl or linoleum surfaces.BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure l is a schematic illustration of a surface cleaner.

[0041] Figure 2 is a schematic illustration of a vapour cleaning system of the surface cleaner of Figure 1.

[0042] Figure 3 is a perspective view of components of the vapour cleaning system of Figure 2.

[0043] Figure 4a is a schematic cross-sectional view of the components of the vapour cleaning system of Figure 3 and Figure 4b is a schematic view of the vapour cleaning system of Figure 3 along the line A-A in Figure 4a.

[0044] Figures 5a and 5b are schematic illustrations of a surface cleaner comprising a vapour cleaning system and a wet cleaning system.

[0045] Figure 6 is a schematic illustration of components of control circuitry of the vapour cleaning system of Figure 2.

[0046] Figure 7 is schematic illustration of a method to control a surface cleaner based on an image classification output.12 P005325-W001DETAILED DESCRIPTION

[0047] A surface cleaner 10 is illustrated schematically in Figure 1, and has a vapour cleaning system 100 and a battery 184. The battery 184 is configured to supply electrical power to the surface cleaner 10 and the vapour cleaning system 100 in use. In other examples, a surface cleaner otherwise the same as or similar to the surface cleaner 10 may be connectable to an external energy source, such as a mains power source, to receive electrical power from the external energy source. In such cases, the surface cleaner may comprise a battery or the battery may be omitted. The surface cleaner 10 is an autonomous surface cleaner.

[0048] The vapour cleaning system 100 of the surface cleaner 10 of Figure 1 is illustrated schematically in Figure 2, and has a tank 102, a reservoir 104, an electrical conductivity monitoring system 106, a pump 108, a vapour generation chamber 110, a vapour outlet 112, a heater 114, a temperature sensor 116, control circuitry 118 and an image sensor 120.

[0049] The vapour cleaning system 100 is configured to store a liquid in the tank 102 and deliver the liquid from the tank 102 to the vapour generation chamber 110 via a first channel, the reservoir 104, a second channel, the pump 108 and a third channel. In a vapour generation mode, the heater 114 heats a quantity of the liquid to convert the liquid to vapour within the vapour generation chamber 110. The generated vapour is emitted through the vapour outlet 112 to clean dirt on a surface, such as a floor. The control circuitry 118 is configured to control an effective power supplied to the heater 114, e.g. based on a temperature signal obtained by the temperature sensor 116, so that, in this mode, the vapour undergoes choked flow through the vapour outlet 112, as explained in more detail below with reference to Figure 6. The choked flow of vapour may be effective at removing the dirt from the surface, and may be generated with lower power consumption than other approaches. The tank 102, the reservoir 104 and the pump 108, may be considered to form part of a liquid supply system that is used for supplying the liquid to the vapour generation chamber 110. The liquid may be, for example, water, or a mixture between water and a cleaning liquid such as soap.

[0050] The tank 102 is connected to the reservoir 104 via the first channel so that the liquid can flow to the reservoir 104. The liquid flows from the tank 102 to the reservoir 104 because of a relative arrangement of the tank 102 with respect to the reservoir 104, such that gravity causes the liquid to flow from the tank 102 to the reservoir 104. In some other examples,13 P005325-W001though, an auxiliary pump pumps the liquid from the tank to the reservoir. In some examples in accordance with Figure 2, the flow of liquid from the tank 102 to the reservoir 104 is unidirectional. For example, a valve may be used to prevent flow of the liquid from the reservoir 104 into the tank 102.

[0051] The reservoir 104 is connected to the pump 108 via the second channel, and the pump 108 is connected to the vapour generation chamber 110 via the third channel. The liquid may flow through the second and / or third channels, due to gravity and / or due to at least one further pump. The vapour outlet 112, via which the vapour generated in the vapour generation chamber 110 is emitted from the vapour generation system 100, is mechanically connected to the vapour generation chamber 110. The connection between the vapour outlet 112 and the vapour generation chamber 110 in this example is direct (e.g., as per Figure 3 and Figure 4). In some examples, the connection between the vapour outlet and the vapour generation chamber is indirect. For example, the vapour outlet may be connected to the vapour generation chamber via a fourth channel.

[0052] The reservoir 104 contains a substance for reducing liquid ionisation. The substance for reducing liquid ionisation is, for example, a substance that is suitable for lowering a quantity of minerals in the liquid. A mineral in the liquid is, for example, a solid, naturally occurring inorganic substance, such as sodium, calcium, magnesium and potassium. The minerals may chemically bond with the liquid. Hence, reducing the quantity of minerals in the liquid by using the substance for reducing liquid ionisation may reduce mineral deposits in parts of the system, such as, for example, the pump 108, the vapour generation chamber 110 and the vapour outlet 112. This may allow descaling to be performed less frequently, reducing the use of chemicals for descaling, which may cause components to deteriorate. In some examples the substance for reducing liquid ionisation is a de-ionisation (DI) resin in the form of beads. After interacting with the substance for reducing liquid ionisation, the liquid may be, for example, a de-ionised liquid, or de-ionised water. A de-ionised liquid need not be completely de-ionised in the context described herein. A de-ionised liquid may be, for example, a liquid that has undergone a process for reducing ionisation, with a lower ionisation than that of a liquid that has not undergone the process for reducing ionisation. An electrical conductivity of the contents of the reservoir (e.g., the liquid and the substance for reducing ionisation of the liquid) generally depends on an extent to which the liquid is de-ionised, since a decrease in mineral content of the liquid may be associated with a14 P005325-W001decrease in electrical conductivity. The electrical conductivity of the contents is thus typically affected, e.g. reduced, by the presence of the substance for reducing liquid ionisation.

[0053] The electrical conductivity of the contents within the reservoir 104 is measured by the electrical conductivity monitoring system 106. The electrical conductivity monitoring system 106 for example comprises two electrodes that are electrically connected to an electrical circuit and which are, for example, placed at a fixed distance from each other. The electrodes are disposed within the reservoir 104, such that an impedance of a volume of liquid within the reservoir 104, referred to herein as the contents of the reservoir 104, can be inferred from a magnitude of voltage or current within the electrical circuit.

[0054] The electrical conductivity monitoring system 106 is configured to generate an electrical conductivity signal indicative of the electrical conductivity of the contents of the reservoir 104 to the control circuitry 118. Based on the electrical conductivity signal, the control circuitry 118 may take various actions (or no action). For example, if the electrical conductivity signal indicates that the electrical conductivity is greater than or equal to a predetermined electrical conductivity threshold, the electrical conductivity monitoring system 106 may generate a warning signal indicative that the amount of the substance within the reservoir 104 is less than a threshold amount. For example, the electrical conductivity monitoring system 106 may send the warning signal to the control circuitry 118, which may take various actions in response. For example, the control circuitry 118 may configure the vapour cleaning system 100 to provide more of the substance for reducing liquid ionisation to the reservoir 104, e.g. from a further tank for storing the substance (not shown in Figure 2), and / or the control circuitry 118 may generate an indication, such as a warning message for a user, which may be displayed via a display screen of the surface cleaner 10 or sent to a user device such as a smartphone via a suitable telecommunications protocol, that the substance for reducing liquid ionisation is to be replenished. If the signal indicates that the electrical conductivity is below the threshold electrical conductivity, the control circuitry 118 may take no further action relating to the substance for reducing liquid ionisation in response to the signal.

[0055] The pump 108 is configured to pump the liquid from the reservoir 104 to the vapour generation chamber 110. An effective power supplied to the pump 108 may be controlled by the control circuitry 118, for example to aid in obtaining a choked flow of the vapour through15 P005325-W001the vapour outlet 112 in the vapour generation mode, as described in more detail below with reference to Figure 6. In this example the control circuitry 118 is configured to regulate the power supplied to the pump 108 by changing the magnitude of a DC voltage supplied to the pump 108. In some other examples the control circuitry is configured to control the effective power supplied to the pump by a different mechanism, such as by providing pulses of voltage to the pump with a variable time duration (e.g., pulse-width modulation) and / or by modulating the amplitude of pulses of voltage supplied to the pump.

[0056] The image sensor 120 is for example a CMOS (complementary metal oxide semiconductor) or other image sensor of an image capture device, such as a camera. The image sensor 120 is configured to capture image data representing an environment around the surface cleaner 10, and transmit the image data to the control circuitry 118. The control circuitry 118 is configured to send the image data to an image classification system 160, for use in generating instructions for control of the surface cleaner 10, e.g. as described further with reference to Figures 6 and 7. However, in other examples, a vapour generation system otherwise the same as or similar to the vapour generation system 100 of Figure 2 may not comprise an image sensor and / or may not be controlled based on image data captured by an image sensor of or coupled to the surface cleaner 10. Although the image sensor 120 of Figure 2 is shown as part of the vapour cleaning system 100 in this example, in other examples, the image sensor may be considered to form part of the surface cleaner 10 instead of the vapour cleaning system 100.

[0057] Figures 3, 4a and 4b schematically show components of the vapour cleaning system 100 of Figure 2 downstream of the pump 108. The components illustrated in Figure 3 may be referred to as being part of a fluid conversion system 180 of the vapour cleaning system 100 in the context described herein.

[0058] The fluid conversion system 180 comprises a liquid supply interface 128 to supply liquid received from the reservoir 104 via the pump 108 to the vapour generation chamber 110. A quantity of the liquid within the vapour generation chamber 110 is converted to vapour, with the surface cleaner 10 in the vapour generation mode. Liquid may be supplied to the vapour generation chamber 110, e.g. continuously, in the vapour generation mode, so as to convert a steady flow of liquid into vapour. The vapour generation chamber 110 is a hollow structure suitable for containing at least the quantity of liquid, within which the quantity of liquid is vapourised due to heat from the heater 114, in the vapour generation16 P005325-W001mode. In Figures 3 and 4, the vapour generation chamber 110 is a generally cuboidal in form and is elongate along a longitudinal axis which extends horizontally in Figure 4b (which is e.g. parallel to a horizontal surface, with the vacuum cleaner located on the horizontal surface). The structure of the vapour generation chamber 110 is for example sufficiently strong to withstand an operating temperature or a pressure within the vapour generation chamber 110, e.g. after generating the vapour from the quantity of liquid, without appreciable deformation. The vapour generation chamber 110 is formed of a sufficiently thermally conductive material to enable transfer of heat from the heater 114 to the liquid within the vapour generation chamber 110, to vapourise a quantity of the liquid. In this example, the vapour generation chamber 110 is made of metal, although other materials may be used in other examples. The liquid supply interface 128 is a mechanical connector for securing a liquid delivery mechanism, such as a pipe, duct or other conduit coming from the pump 108, to the vapour generation chamber 110. A further mechanical connector 134 is used to secure the fluid conversion system 180 of the vapour cleaning system 100 to the surface cleaner 10. The vapour generation chamber 110 comprises a threading 133 at an end to be coupled to the vapour outlet 112, for mechanically securing the vapour outlet 112 to the vapour generation chamber 110.

[0059] The vapour outlet 112 is connected to the vapour generation chamber 110 by a vapour conduit portion 129 of the fluid conversion system 180. The vapour outlet 112 comprises a nozzle 138 and an orifice 136. The vapour conduit portion 129 is in communication with the vapour generation chamber 110 to receive vapour from the vapour generation chamber 110 and direct the vapour into the nozzle 138. The nozzle 138 comprises a chamber 131 to receive the vapour from the vapour conduit portion 129 and an internal channel 139 to receive the vapour from the chamber 131. The chamber 131 and the internal channel 139 are each generally cylindrical in form. The chamber 131 has a cross-sectional diameter that is larger than a cross-sectional diameter of the internal channel 139, so that the vapour is constricted as it flows from the chamber 131 into the internal channel 139. The diameter of the chamber 131 and the internal channel 139 are constant along their length. However, in other examples, a nozzle 138 may have at least a portion, such as at least one of a chamber and an internal channel, with a constriction with a size that varies along its length, such as a constriction of substantially conical shape, such as a conical shape within manufacturing or measurement tolerances. The internal channel 139 of the nozzle 138 terminates with the17 P005325-W001orifice 136at. In this example, the orifice 136 is an aperture corresponding to a terminal portion of the vapour outlet 112. In other examples, the nozzle has an internal shape that differs from the shape shown in Figure 4b. For example, the nozzle may not have a portion with a smaller cross-section than another portion, corresponding to a constriction. For example, the nozzle may have a cylindrical internal channel. In such cases, the vapour may nevertheless be constricted by the orifice 136, e.g. due to the orifice 136 having a smaller cross-sectional area than a cross-sectional area of the vapour generation chamber 110. The orifice 136 for example has a cross-sectional area of between 0.05 millimetres squared and 0.5 millimetres squared. The cross-sectional area is measured in a plane that is orthogonal to a direction of bulk flow of the vapour through the orifice 136. A direction of bulk flow of the vapour in this example is generally parallel to a longitudinal axis of the vapour generation chamber 110, which is horizontal in the orientation shown in Figure 4.

[0060] An outer surface of the chamber 131 of the nozzle 138 comprises a fixing 135, which in this example is a screw that is of complementary shape to the threading 133. The nozzle 138 is connected to the vapour generation chamber 110 via the fixing 135 and the corresponding threading 133 of the vapour generation chamber 110. The fixing 135 can be unfastened to detach the nozzle 138 from the vapour generation chamber 100, which may make it easier for a user to maintain and / or replace the nozzle 138. For example, it may be easier for a user to remove the nozzle 138 from the surface cleaner 10 so that the nozzle 138 can be unclogged. The nozzle 138 has a layer 137 for limiting thermal conduction from an internal portion of the nozzle to an external portion of the nozzle 138. The layer 137 is an outermost layer of the nozzle 138, although in other examples the layer 137 may not be the outermost layer of the nozzle 138 and may instead be at least partially covered by one or more further layer(s). The layer 137 is a silicon layer in this example (although other materials may be used in other examples), which may lower the temperature of exposed portions of the nozzle 138, making it safer for a user to touch.

[0061] The vapour generation chamber 110 is configured to receive heat from the heater 114, in a vapour generation mode. In the orientation of Figure 4, the vapour generation chamber 110 overlaps the heater 114, such that heat generated by the heater 114 can be transferred into the vapour generation chamber 110 to vapourise at least a quantity of the liquid therein. The heater 114 comprises a first heater unit 114a and a second heater unit 114b. In other examples, though, a heater of a vapour generation system may instead18 P005325-W001comprise more or fewer heater units than two. The first and second heater units 114a, 114b are generally cylindrical in form, and are elongate along a longitudinal axis parallel to a longitudinal axis of the vapour generation chamber 110. The first 114a and the second 114b heater units are connected to the control circuitry 118 via power cables 122a, 122b, 122c and 122d. The power cables form a heater power delivery interface 122, via which the control circuitry 118 can supply power to the heater 114, in use.

[0062] The heater 114 is a so-called flash heater, configured to rapidly heat up a relatively small mass to which the heater 114 is thermally coupled and which may itself have a relatively small volume. The heater 114 is configured to heat up liquid within the vapour generation chamber 110, which in this example is a relatively small quantity of liquid due to a relatively small volume of the vapour generation chamber 110. This makes it possible to generate high velocity vapour, e.g. without considerable power losses that would arise from heating up large volumes of liquid. The relatively small size of the vapour generation chamber 110 and heater 114 makes it possible for the vapour cleaning system 100 to heat up and cool down more rapidly than other arrangements. For example, the heater 114 may be heated to a sufficiently high temperature to begin vapourisation of the liquid, from an off state, in around 10 seconds or less, and may similarly cool down to a touch-safe temperature in around 10 seconds or less.

[0063] The vapour generation chamber 110 is a cavity within a thermally conductive structure 130 that is coupled to a conduit structure 132, within which the liquid supply interface 128, the further mechanical connector 134 and the vapour conduit portion 129 are formed. The first and second heater units 114a, 114b are disposed within the thermally conductive structure 130. The thermally conductive structure 130 is a metallic structure thermally coupled to the vapour generation chamber 110 and heater 114, although other thermally conductive materials may be used in other examples, to enable heat to be transferred from the heater 114 to the vapour generation chamber 110. A plurality of protrusions protrude from the thermally conductive structure 130 into the vapour generation chamber 110, to increase a heat transfer surface area between the thermally conductive structure 130 and the vapour generation chamber 110. One of the protrusions is labelled in Figure 4b with the reference numeral 141. The plurality of protrusions are for example an array of thermally conductive pins that project into the vapour generation chamber 110, so that the fluid within the vapour generation 110 is in close thermal contact with the first and19 P005325-W001second heater units 114a, 114b. In this example, thermal coupling occurs mainly through direct contact between components of the fluid conversion system, such as through direct contact between the first and second heater units 114a, 114b and the thermally conductive structure 130, however part of the thermal coupling may occur through indirect contact such as, for example, via thermal radiation.

[0064] The thermally conductive structure 130 and the conduit structure 132 each comprise mechanically complementary portions such that, when the conduit structure 132 is on the thermally conductive structure 130, a space between the thermally conductive structure 130 and the conduit structure 132 is reduced. This can allow the fluid entering the conduit structure 132 to be directed closer to the first and second heater units 114a, 114b within the thermally conductive structure 130. In this example the thermally conductive structure 130 and the conduit structure 132 comprise substantially flat surfaces that face each other. A thin heat-resistant gasket (omitted in Figures 3 and 4 for clarity) is disposed between the thermally conductive structure 130 and the conduit structure 132. The heat-resistant gasket is used to facilitate sealing of the vapour generation chamber 110. In some examples the thermally conductive structure 130 and the conduit structure 132 are formed integrally.

[0065] The temperature sensor 116 (shown in Figures 3 and 4a, but omitted from Figure 4b for clarity) is thermally coupled to the thermally conductive structure 130. Thermal coupling between the temperature sensor 116 and the thermally conductive structure 130is achieved by configuring the temperature sensor 116 such that there is thermal contact between the temperature sensor 116 and the thermally conductive structure 130. The temperature sensor 116 in this example is a thermistor that is located at least partly within the thermally conductive structure 130. In other examples, though, a temperature sensor may be located in a different position within the fluid conversion system 180. The temperature sensor 116 is configured to generate a temperature signal proportional to, or otherwise indicative of, a temperature of the vapour, and transmit the temperature signal to the control circuitry 118 via a temperature sensor interface 124 comprising a first wire 124a and a second wire 124b (shown in Figure 3 but omitted from Figures 4a and 4b, for clarity). Based on the temperature signal, the control circuitry 118 controls an effective power supplied to the heater 114 as described in more detail below with reference to Figure 6, to generate a vapour that undergoes choked flow through the vapour outlet 112. In other examples, the temperature20 P005325-W001sensor may be a type of temperature sensor other than a thermistor, such as an infrared sensor or a thermomechanical sensor.

[0066] Figure 5a shows schematically a surface cleaner 210 according to a further example. The surface cleaner 210 of Figure 5a comprises a vapour cleaning system and a wet cleaning system. Features of Figure 5a that are the same as or similar to corresponding features of Figures 1 to 4 are labelled with the same reference numerals incremented by 100; corresponding descriptions are to be taken to apply.

[0067] The surface cleaner 210 comprises a liquid supply system 270, a fluid conversion system 280 for a vapour cleaning system, and a wet cleaning system outlet 290. The liquid supply system 270 is configured to deliver the liquid to the fluid conversion system 280 of the vapour cleaning system and the wet cleaning system outlet 290.

[0068] The liquid supply system 270 comprises a tank 202, a first valve 264, a reservoir 204, an electrical conductivity monitoring system 206, a vapour cleaning system pump 208, a wet cleaning system pump 266 and a second valve 268.

[0069] The tank 202 is configured to provide the liquid to the reservoir 204 through the first valve 264. The first valve 264 inhibits flow of the liquid from the reservoir 204 back into the tank 202.

[0070] The reservoir 204 contains a substance for reducing liquid ionisation, which may be the same as the substance described with reference to Figure 2. The electrical conductivity monitoring system 206 is configured to measure the electrical conductivity of the contents of the reservoir 204, e.g. for use in determining when the substance is to be replenished. The vapour cleaning system pump 208 is configured to pump the liquid from the reservoir 204 to the fluid conversion system 280 for the vapour cleaning system, which may be the same as or similar to the fluid conversion system 180 shown in Figures 3 and 4.

[0071] The tank 202 is also configured to provide the liquid to the wet cleaning system pump 266 for the liquid to be pumped to the wet cleaning system outlet 290 through the second valve 268. The second valve 268 inhibits the liquid from flowing from the wet cleaning system outlet 290 back into the tank 202. Liquid is dispensed from the wet cleaning system outlet 290 to the surface to be cleaned.

[0072] The surface cleaner 210 of Figure 5a can be operated in a similar fashion to the previous example of the surface cleaner 10 of Figures 1 to 4. However, the surface cleaner 210 including a wet cleaning system may provide further cleaning options. For example, the21 P005325-W001surface cleaner 210 may be used to remove persistent dirt by generating vapour, and deploy the wet cleaning system to remove larger remaining debris and / or generic non-persistent dirt, such as oily liquids and light stains.

[0073] In the example of Figure 5a, the vapour cleaning system comprises the tank 202, the first valve 264, the reservoir 204, the electrical conductivity monitoring system 206, a vapour cleaning system pump 208 and the fluid conversion system 280. The wet cleaning system comprises the tank 202, the wet cleaning system pump 266, the second valve 268 and the wet cleaning system outlet 290. The tank 202 thus forms part of both the vapour cleaning system and the wet cleaning system.

[0074] In other examples, though, the wet cleaning system comprises a separate wet cleaning system tank for containing the liquid for use by the wet cleaning system, as illustrated schematically in Figure 5b. Features of Figure 5b that are the same as or similar to corresponding features of Figure 5a are labelled with the same reference numerals incremented by 100; corresponding descriptions are to be taken to apply. By having a separate tank and wet cleaning system tank, this may allow a configuration, e.g. a size, of the tank and the wet cleaning system tank to be selected independently, for example based on a typical liquid consumption for vapour cleaning and wet cleaning.

[0075] The surface cleaner 310 of Figure 5b comprises a wet cleaning system tank 382 configured to store a liquid. In this example the liquid may be the same type of liquid stored in the tank 302, although other examples where the type of liquid stored in the wet cleaning system tank 382 is different from the type of liquid stored in the tank 302 are also envisaged. The wet cleaning system tank 382 is configured to provide the liquid to the wet cleaning system pump 366 for the liquid to be pumped to the wet cleaning system outlet 390 through the second valve 368. The second valve 368 inhibits the liquid from flowing from the wet cleaning system outlet 390 back into the wet cleaning system tank 382. The tank 302 and the wet cleaning system tank 382 are not configured to for liquid to flow between each other in Figure 5b, but may be in other examples, e.g. via a valve, for example so that one of the tanks can be selectively refilled using liquid from the other tank as desired.

[0076] In some examples, the reservoir is part of the tank, and this may simplify the liquid supply system. Specifically, when the surface cleaner also comprises the wet cleaning system, the reservoir being part of the tank may allow further optimization of components sizes.22 P005325-W001

[0077] In some examples in accordance with Figures 1 to 4, 5a or 5b, the surface cleaner is configured to be supplied with liquid from a main liquid storage system. The control circuity of the surface cleaner may be configured to determine, based on monitoring of an amount of liquid in the tank, e.g. using a suitable sensor, when the liquid supply system needs to be replenished with liquid. Upon the control circuitry determining that liquid is to be resupplied to the liquid supply system, the surface cleaner may be configured to navigate towards the main liquid storage system and obtain liquid from the main liquid storage system.

[0078] Components of the control circuitry 118 of Figure 2 are illustrated schematically in Figure 6. It will be appreciated that various interfaces to components of the surface cleaner 10, such as, for example, the power delivery interface 122, and other power conversion components, are omitted from Figure 6 for the sake of simplicity. The control circuitry 118 has a processor 152, a memory 154 and a wireless communication system 156 that communicate over a common data bus 150.

[0079] The processor 152 is configured to process data from various components of the surface cleaner 10. The processor 152 is also configured to read and write data from and to the memory 154. The processor 152 is configured to control a mode of operation of at least the vapour cleaning system 100 of the surface cleaner 10. The processor 152 may further control a mode of operation of at least one other system of the surface cleaner 10, or the surface cleaner 10 itself, and may implement control algorithms to regulate the effective power supplied to various components of the surface cleaner 10. In this example, the processor 152 regulates the effective power supplied to the heater 114 and the pump 108 at least. The processor 152 may comprise temperature sensing circuitry (not shown in Figure 6) configured to interface with the temperature sensor 116 and convert an analogue temperature signal received from the temperature sensor 116, e.g. using an analogue to digital converter (ADC) to obtain a digital temperature signal.

[0080] The wireless communication system 156 is configured to communicate with a network 158, and exchange data with an image classifier 160 remote from the surface cleaner 10, e.g. on a remote server, via the network 158. In another example, though, the control circuitry itself comprises or is otherwise configured to implement an image classifier. For example, the image classifier may be implemented by a hardware accelerator configured for image classification tasks, and in communication with the processor via the bus. In this example the wireless communication system may be omitted (but need not be). In this23 P005325-W001example, the image classifier is configured to exchange data with the processor via the bus, without sending data remotely. In another example, the image classifier is implemented by the processor itself.

[0081] Returning to Figure 6, in use, the surface cleaner 10 and the vapour cleaning system 100 draw power from the battery 184. The control circuitry 118 controls a mode of operation of the surface cleaner 10 based on image data captured by the image sensor 120. The image sensor 120 captures image data representative of the surrounding environment of the surface cleaner 10 and sends the image data to the wireless communication system 156 for the image classifier to process the image data and send an image classification output to the control circuitry 118.

[0082] The control circuitry 118 may additionally or alternatively control the mode of operation of the surface cleaner 10 based on another input than the image data, such as user input. For example, the user may select the mode of operation of the surface cleaner 10 using a user interface, such as a system of buttons configured to interface with a display or a touchscreen display. The user may, for example, manually place the surface cleaner 10 in proximity of dirt and activate the vapour generation mode. When the user moves decides to clean another surface, the user may configure the surface cleaner 10 to operate in a further mode of operation, which is for example a standby mode, while the surface cleaner is being moved between two different surfaces.

[0083] The control circuitry 118 can configure the surface cleaner 10 in a vapour generation mode, e.g. based on the image classification output and / or a user input. In the vapour generation mode, the pump 108 is controlled by the control circuitry 118 to pump a quantity of liquid from the reservoir 104 to the vapour generation chamber 110. The control circuitry 118 controls the pump 108 by determining an effective power to be supplied to the pump 108 based on the temperature signal from the temperature sensor 116. The quantity of liquid pumped by the pump 108 is defined by the effective power supplied to the pump 108. For example, a larger effective power supplied to the pump 108 may cause a motor of the pump 108 to spin faster, and cause more liquid to be supplied to the vapour generation chamber 110. The heater 114 transfers heat to the vapour generation chamber 110, to vapourise the quantity of the liquid in the vapour generation chamber 110. The vapour obtained by the vapourisation of the quantity of the liquid exits the vapour cleaning system 100 through the vapour outlet 112. The vapour is forced out of the vapour outlet 112 as a result of a build up24 P005325-W001of pressure within the vapour generation chamber 110. The vapour exits the orifice 136 at a speed that approaches the speed of sound, as described in more detail below with reference to choked flow.

[0084] The control circuitry 118 controls the effective power supplied to the pump 108 such that the quantity of liquid delivered from the reservoir 104 to the vapour generation chamber 110 is suitable for the generation of vapour. For example, if a quantity of the liquid delivered by the pump 108 to the vapour generation chamber 110 is excessive, it may be difficult for the heater 114 to supply enough heat to the vapour generation chamber 110 to turn the liquid into vapour, and this may result in the vapour through the vapour outlet 112 to be too watery. On the other hand, if the quantity of liquid delivered by the pump 108 to the vapour generation chamber 110 is insufficient, this may result either in the vapour generation chamber 110 overheating, or the vapour through the vapour outlet 112 being so hot that it damages a surface to be cleaned.

[0085] The control circuitry 118 is configured to receive a temperature signal from the temperature sensor 116, and generate a pump control signal based on a difference between the temperature signal from the temperature sensor 116 and a target temperature value for controlling the pump 108. A pump proportional-integral-derivative (PID) controller may be used to generate the pump control signal. The target temperature value for controlling the pump may be set to a value between 125 and 135 degrees Celsius. When the liquid delivered by the pump 108 reaches the vapour generation chamber 110, the temperature within the vapour generation chamber 110 decreases, as the liquid delivered by the pump 108 is at a lower temperature than the contents of the vapour generation chamber 110. Since the contents of the vapour generation chamber 110, the vapour generation chamber 110 and the heater 114 are thermally coupled, a decrease in the temperature of the vapour generation chamber 110 may also cause a decrease in temperature of the vapour.

[0086] The control circuitry 118 also controls the effective power supplied to the heater 114 such that the heat delivered to the vapour generation chamber 110 is suitable for the generation of vapour. The control circuitry 118 controls the heater 114 by determining an effective power to be supplied to the heater 114 based on the temperature signal from the temperature sensor 116. The temperature of the heater 114 is defined by the effective power supplied to the heater 114. For example, a larger effective power supplied to the heater 114 may cause a resistive element within the heater 114 to be supplied with a larger amount of25 P005325-W001current, and in turn cause a larger generation of heat within the heater 114. This may cause a temperature of the vapour generation chamber 110 (and the contents of the vapour generation chamber 110) to increase. Similarly to the above-mentioned issues associated with improperly controlling the pump 108, if the delivered heat to the vapour generation chamber 110 by the heater 114 is excessive, this may cause overheating of the vapour generation chamber 110, or the temperature of the vapour through the vapour outlet 112 being so hot that the vapour damages a surface to be cleaned. In contrast, when the heat delivered from the heater 114 to the vapour generation chamber 110 is insufficient, this may result in the delivery of a watery vapour through the vapour outlet 112.

[0087] The control circuitry 118 is configured to receive a temperature signal from the temperature sensor 116, and generate a heater control signal based on a difference between the temperature signal from the temperature sensor 116 and a target temperature value for controlling the heater 114.

[0088] A heater proportional-integral-derivative (PID) controller may be used to generate the heater control signal. The target temperature value for controlling the heater may be set to a value between 155 and 165 degrees Celsius. When the effective power supplied to the heater increases, the amount of heat delivered to the vapour generation chamber 110 increases, causing the temperature of the vapour generation chamber 110, also indicative of the temperature of the vapour, to increase. The effective power supplied to the heater is a power of between 50 watts and 800 watts.

[0089] Since the target temperature value for controlling the heater 114 is larger than the target temperature value for controlling the pump 108, the heater PID controller and the pump PID controller will respectively try to heat up and cool down the vapour generation chamber 110. The heater PID controller and the pump PID controller will eventually reach a steady state associated with the appropriate quantity of heat and liquid delivered to the vapour generation chamber 110 for the generation of vapour that is neither excessively hot, so as to damage a surface, nor excessively watery, so as to soak the surface. The heater PID controller and the pump PID controller can be tuned independently from each other, such that the generated vapour is at a desired consistency (e.g., not so watery as to soak a surface, and not so hot as to damage the surface).

[0090] The control circuitry 118 is also configured to terminate power delivery to the heater 114 and / or to the pump 108 (e.g., controlling the effective power supplied to the heater 11426 P005325-W001and / or to the pump 108 to be substantially zero) under abnormal operating conditions. This may be, for example, when the temperature control signal is not received by the control circuitry 118, when the temperature signal exceeds a predetermined temperature threshold, when a volume of the liquid in one of the tank 102 or the reservoir 104 is below a predetermined liquid volume threshold, or when the effective power supplied to the pump 108 is above a predetermined effective pump power threshold.

[0091] If the temperature control signal is not received by the control circuitry 118, this may indicate that the temperature sensor 116 has been disconnected or has malfunctioned. In the absence of an accurate temperature control signal, the control circuitry 118 may compute unsuitable control parameters, and cause for example, overloading of components such as the pump 108, and the heater 114. Hence, in examples, terminating power delivery to the heater 114 and / or to the pump 108 may help prevent permanently damaging components of the surface cleaner 10.

[0092] If the temperature control signal exceeds the predetermined temperature threshold, this may indicate that the heater 114 has supplied excessive heat to the vapour generation chamber 110, and this may cause the fluid conversion system 180 to generate an excessive pressure within the vapour generation chamber 110. In some cases, this may also be associated with a malfunction of the control circuitry 118. Terminating power delivery to the heater 114 and / or to the pump 108 may help prevent permanently damaging the fluid conversion system 180.

[0093] If the volume of liquid within the tank 102 or the reservoir 104 is below a predetermined liquid volume threshold, this may cause an internal motor of the pump 108 to be supplied with power while unloaded (or underdamped). In some cases this may also be caused by a blockage between the tank 102 and the reservoir 104. This may cause the pump 108 to be permanently damaged if the pump 108 is operated for extensive periods of time with an insufficient amount of liquid to supply to the vapour generation chamber 110. Terminating power delivery to the heater 114 and / or the pump 108 may help prevent permanently damaging the pump 108 and / or the vapour generation chamber 110.

[0094] The effective power supplied to the pump 108 being above a predetermined effective pump power threshold may be an indication of a blockage in the liquid supply system. This may be caused by a blockage in any of the first, second and third channel, or a blockage in the vapour outlet 112. In some cases this may be associated with a deterioration of internal27 P005325-W001components of the pump 108, such as a motor. In some cases, this may also occur due to a lack of available liquid to supply to the vapour generation chamber 110. In some cases this may also cause overloading of the heater 114. Terminating power delivery to the pump 108 and to the heater 114 may help prevent permanently damaging components of the vapour cleaning system 100.

[0095] The combination of the quantity of liquid and / or vapour in the vapour generation chamber 110, together with the heat delivered by the heater 114, for example causes a pressure within the vapour generation chamber 110 to be between 1 bar and 5 bar. The difference between the pressure within the vapour generation chamber 110 (e.g., upstream pressure), and the pressure outside the surface cleaner 10, causes the vapour to exit through the vapour outlet 112 at a high velocity, which may enable cleaning of persistent dirt.

[0096] The velocity of the vapour through the vapour outlet 112 is dependent on the pressure within the vapour generation chamber 110 (which for example also depends on an internal volume of the vapour generation chamber 110) and a cross-sectional area of the orifice 136. In the vapour generation mode, the vapour undergoes choked flow through the orifice 136: as the pressure outside the surface cleaner is typically close to atmospheric pressure, a buildup in pressure within the vapour generation chamber 110 causes a pressure differential between an internal portion of the vapour generation chamber 110 and the surrounding environment. This causes the vapour to be forced through the orifice 136 at an increasingly higher speed. The speed of the vapour can only increase up to a value close to the speed of sound, as the flow becomes choked. A further increase in the pressure differential after the flow becomes choked does not result in a further increase in the speed of the vapour.

[0097] The control circuitry 118 can also configure the surface cleaner 10 in a further mode of operation, e.g. based on the image classification output and / or a user input. In the further mode of operation, the control circuitry 118 controls the effective power that is delivered to the pump 108 to be substantially zero, so that no liquid is delivered to the vapour generation chamber 110. In the further mode of operation, the control circuitry 118 also controls the effective power supplied to the heater 114 to be a predetermined effective power that is lower than the effective power supplied to the heater 114 in the vapour generation mode. The surface cleaner 10 may transition from the further mode of operation to the vapour generation mode more rapidly than from an off state, in which the heater 114 is switched off entirely.28 P005325-W001This transition may be in response to receiving a signal indicating that vapour generation is to begin.

[0098] A method 1000 of selecting the mode of operation of the surface cleaner 10 based on an image classification output from the image classifier 160 according to an example is summarised in Figure 7.

[0099] The image classifier 160 receives 1001 the image data, which is e.g. obtained by an image sensor of a surface cleaner. The image data may represent a single image or a plurality of images of an environment around the surface cleaner. The image classifier 160 processes 1002 the image data to obtain information regarding surfaces around the surface cleaner 10, and the presence and position of dirt within the surfaces. As the skilled person will understand, there are various classification algorithms suitable for classifying images into different groups or categories, such as artificial neural networks (e.g. trained on images representing dirt on surface and / or images of surfaces of different types), support vector machines (SVM) and so forth. The image classifier 160 may implement any such classification algorithms. The image classifier 160 may be configured to perform a plurality of classifications, such as classifying whether an image comprises dirt (or dirt of a particular type, such as persistent dirt, light dirt or granular dirt) or not, and the particular type of surface present in an image. For example, the image classifier 160 may comprise a plurality of classification models, each for performing a different respective classification into a different respective set of categories (such as categories relating to the presence or absence of dirt, and categories relating to surface type). The image classifier 160 generates an image classification output, e.g. indicative of the category or categories into which the image falls. The image classifier 160 may transmit the image classification output to the control circuitry 118, e.g. for use by the control circuitry 118 to determine a mode of operation for the surface cleaner 10, or the mode of operation may be determined based on the image classification output by the image classifier 160 itself or a remote server hosting the image classifier 160, for example.

[0100] In examples in which the image classifier determines and includes as part of the image classification output a type of dirt, such as whether the dirt is persistent dirt, such as a stain, or light dirt, the type of dirt may be classified, for example, based on consistency of dirt. The consistency of the dirt may be determined, e.g. by the image classifier 160, based on the image data, such as granular, fibrous or liquid consistency, and / or an estimation that29 P005325-W001dirt contains at least part of a particular substance, based on the image data. For example, granular dirt such as gravel, or fibrous dirt such as hair, may be classified by the image classifier 160 as light dirt. Food residuals, such as coffee or oil, may be classified by the image classifier 160 as persistent dirt.

[0101] Based on the image classification output generated by the image classifier 160, it is determined 1003, e.g. at the remote server hosting the image classifier 160, or by the control circuitry 118 of the surface cleaner 10, if the image data represents a surface that is suitable for vapour cleaning. Unsuitable surfaces may be, for example, wood, delicate fabrics, or painted surfaces. Suitable surfaces may be, for example, stone, porcelain, ceramic, vinyl or linoleum surfaces.

[0102] If the image data represents a surface that is not suitable for vapour cleaning, the the control circuitry 118 controls the surface cleaner 10 to use 1004a a different mode of operation, different from the vapour generation mode, e.g. by switching from the vapour generation mode to the different mode or by remaining in different mode. The different mode may be the off state or the further mode. For example, the control circuitry 118 may receive an indication from the remote server or the image classifier 160 itself that the surface is unsuitable (based on the image classification output) and, in response to the indication, exit the vapour generation mode. The control circuitry 118 may be configured to switch the surface cleaner 10 from the vapour generation mode to the further mode of operation in response to the surface being unsuitable. Alternatively, the control circuitry 118 may be configured to switch the surface cleaner 10 from the vapour generation mode to an off state (e.g. with substantially zero power supplied to the pump 108 and the heater 114) in response to the surface being unsuitable.

[0103] If the image data represents a surface that is suitable for cleaning, it is determined 1004b if dirt is present on the surface and, in this example, indicates a number of instances of dirt on the surface, e.g. a number of separate and distinct dirty areas (but need not in other examples). The determination 1004b may be performed, based on the image classification output, at the remote server hosting the image classifier 160 or by the control circuitry 118 of the surface cleaner 10, for example. If dirt is present, the image classifier 160 may determine a position of dirt, a segmentation output representative of a boundary of dirt, and a number of instances of dirt within a surface (which may be performed during processing 1002 of the image data to generate the image classification output or after determining 1004b30 P005325-W001that the image data represents dirt, e.g. using a segmentation unit of the image classifier 160 that differs from a classification unit of the image classifier 160 for generating the image classification output).

[0104] If the image classification output indicates that the surface is suitable for vapour cleaning and that dirt is present, the control circuitry 118 configures the surface cleaner 10 to use 1005a the vapour generation mode to produce vapour to clean dirt in a particular location and produce vapour, e.g. for a predetermined amount of time or until dirt is removed. If the surface cleaner 10 is already in the vapour generation mode, the control circuitry 118 configures the surface cleaner 10 to remain in the vapour generation mode in response. However, if the surface cleaner 10 is in a different mode, such as the off state or the further mode, the control circuitry 118 switches the surface cleaner 10 from the different mode to the vapour generation mode. The remote server and / or control circuitry 118 may additionally determine a navigation path for the surface cleaner towards at least one location of the surface associated with the presence of dirt.

[0105] If the image classification output indicates that the surface is suitable for vapour cleaning, but no dirt is present, the control circuitry 118 configures the surface cleaner 10 to use a different mode of operation than the vapour generation mode, such as the off state or the further mode. If the surface cleaner 10 is already in the different mode, the control circuitry 118 configures the surface cleaner to remain in the different mode in response. However, if the surface cleaner 10 is in the vapour generation mode, the control circuitry 118 switches the surface cleaner 10 from the vapour generation mode to the different mode.

[0106] The method 1000 of Figure 7 may be performed repeatedly as additional image data is captured by the image sensor 120. Based on subsequent image classification outputs, e.g. based on subsequent image data captured by the image sensor 120, the control circuitry 118 may switch the surface cleaner 10 between using 1005a the vapour generation mode and using 1005b the different mode until all identified dirt is cleaned and / or until a cleaning routine is complete. The control circuitry 118 may select the mode to be used as the different mode, e.g. based on a user or other input, or the control circuitry 118 may be configured to use a particular mode, such as the further mode, as the different mode. There may be a difference between the different mode used 1004a in response to determining 1003 that a surface is unsuitable for vapour cleaning and the different mode used 1005b in response to determining 1004b that the image data does not represent dirt (or the same mode may be31 P005325-W001used 1004a, 1005b in each case). For example, the off state may be used 1004a if there is an unsuitable surface (which may be relatively large for the surface cleaner 10 to navigate across) and the further mode may be used 1005b if the image data does not represent dirt (or vice versa).

[0107] The examples described above are illustrative of the present disclosure, and further examples are envisaged. In some examples, a surface cleaner otherwise similar to or the same as the surface cleaner of examples above may not be an autonomous surface cleaner. In such cases, switching between operating modes of the surface cleaner may be manually controlled by a user. The surface cleaner may still be configured to provide the user with an output or other indication indicating a suggested mode of operation for optimising cleaning. For example, the output may be a display output prompting the user to switch to the further mode of operation when multiple instances of dirt are detected. Additionally, or alternatively, the output may be an audio or other output prompting the user to enter a mode of operation such as vapour generation mode or the further mode of operation. In Figures 3 and 4, the vapour outlet 112 comprises a nozzle 138 and an orifice 136. In other examples, though, a vapour outlet need not comprise a nozzle. For example, the vapour outlet may be an orifice in a wall of the vapour generation chamber.

[0108] It is to be understood that any feature described in relation to any one example may be used alone or in combination with other features of the example, and may also be used in combination with one or more features of any other of the examples, or any combination of any other of the examples. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the disclosure, which is defined in the accompanying claims.

Claims

32 P005325-W001CLAIMS1. A vapour cleaning system for cleaning a surface, the vapour cleaning system comprising:a liquid supply system for supplying a liquid;a vapour outlet;a heater; andcontrol circuitry configured to control an effective power supplied to the heater such that, in a vapour generation mode for generating the vapour, the heater vapourises a quantity of the liquid to generate a vapour that undergoes choked flow through the vapour outlet.

2. The vapour cleaning system of claim 1, wherein the effective power supplied to the heater is between 50 watts and 800 watts.

3. The vapour cleaning system of claim 1 or claim 2, wherein the vapour outlet comprises an orifice with a cross-sectional area of between 0.05 millimetres squared and 0.5 millimetres squared.

4. The vapour cleaning system of any of the preceding claims, comprising a vapour generation chamber thermally coupled to the heater, and wherein, in the vapour generation mode, the vapour generation chamber is configured to:receive the quantity of the liquid from the liquid supply system, for vapourisation of the quantity of the liquid within the vapour generation chamber to generate the vapour, wherein the vapour outlet is coupled to the vapour generation chamber to receive the vapour from the vapour generation chamber.

5. The vapour cleaning system of claim 4, wherein, in the vapour generation mode, a pressure within the vapour generation chamber is between 1 bar and 5 bars.

6. The vapour cleaning system of claim 4 or claim 5, wherein the vapour outlet comprises a nozzle, and the nozzle is detachably coupled to the vapour generation chamber.33 P005325-W0017. The vapour cleaning system of claim 6, wherein the nozzle comprises a layer for limiting thermal conduction from an internal portion of the nozzle to an external portion of the nozzle.

8. The vapour cleaning system of any one of the preceding claims, comprising a temperature sensor configured to generate a temperature signal indicative of a temperature of the vapour.

9. The vapour cleaning system of any one of claims 4 to 7, comprising a temperature sensor to generate a temperature signal, wherein the temperature sensor is thermally coupled to at least one of the vapour generation chamber or the heater for sensing a temperature of the at least one of the vapour generation chamber or the heater, indicative of the temperature of the vapour, and the temperature sensor is detachable from the vapour cleaning system.

10. The vapour cleaning system of claim 8 or claim 9, wherein the liquid supply system comprises a pump for pumping the liquid to the heater, wherein the control circuitry is configured to control an effective power supplied to the pump and the effective power supplied to the heater based on the temperature signal.

11. The vapour cleaning system of claim 10, wherein the control circuitry is configured to, in the vapour generation mode:obtain a pump control signal for controlling the effective power supplied to the pump based on a first difference between the temperature signal and a first target temperature value; andobtain a heater control signal for controlling the effective power supplied to the heater based on a second difference between the temperature signal and a second target temperature value,wherein the first target temperature value is lower than the second target temperature value.34 P005325-W00112. The vapour cleaning system of claim 11, wherein the first target temperature value is between 125 and 135 degrees Celsius and the second target temperature value is between 155 and 165 degrees Celsius.

13. The vapour cleaning system of any one of claims 10 to 12, wherein the control circuitry is configured to control the effective power supplied to the heater to be substantially zero in response to the control circuitry identifying at least one of:an absence of the temperature signal;that the temperature signal exceeds a predetermined temperature threshold; that a volume of the liquid suppliable by the liquid supply system is below a predetermined liquid volume threshold; ordetermining that the effective power supplied to the pump is above a predetermined effective pump power threshold.

14. The vapour cleaning system of any one of claims 10 to 13, wherein the control circuitry is configured to control the effective power supplied to the pump to be substantially zero in response to the control circuitry identifying at least one of:an absence of the temperature signal;that the temperature signal exceeds a predetermined temperature threshold; determining that a volume of the liquid suppliable by the liquid supply system is below a predetermined liquid volume threshold; ordetermining that the effective power supplied to the pump is above a predetermined effective pump power threshold.

15. The vapour cleaning system of any one of claims 10 to 14, operable in a further mode of operation in which the control circuitry is configured to:control a power supplied to the pump to be substantially zero; andcontrol the effective power supplied to the heater such that the effective power supplied to the heater is a predetermined effective power, the predetermined effective power lower than the effective power supplied to the heater in the vapour generation mode,35 P005325-W001wherein the control circuitry is operable to switch the surface cleaner from the further mode of operation to the vapour generation mode in response to receiving a signal indicating that vapour generation is to begin.

16. The vapour cleaning system of any one of the preceding claims, wherein the liquid supply system comprises:a tank for containing the liquid; anda reservoir for containing a substance for reducing ionisation of the liquid, wherein, in use, the liquid supply system is configured to supply the liquid from the tank to the reservoir for the substance within the reservoir to reduce the ionisation of the liquid.

17. The vapour cleaning system of claim 16, comprising an electrical conductivity monitoring system configured to, in use:generate an electrical conductivity signal indicative of an electrical conductivity of contents of the reservoir, the contents comprising the liquid and the substance; andin response to the electrical conductivity signal being indicative that the electrical conductivity of the contents is greater than or equal to a predetermined electrical conductivity threshold, generate a warning signal indicative that an amount of the substance within the reservoir is less than a threshold amount.

18. A surface cleaner comprising the vapour cleaning system of any one of the preceding claims.

19. The surface cleaner of claim 18, comprising a wet cleaning system.

20. The surface cleaner of claim 19, wherein the liquid supply system is configured to supply the liquid to the wet cleaning system.

21. The surface cleaner of claim 19 or claim 20, comprising a wet cleaning system tank for containing the liquid for use by the wet cleaning system.36 P005325-W00122. The surface cleaner of any one of claims 18 to 21, wherein the surface cleaner is an autonomous surface cleaner.

23. The surface cleaner of claim 22, comprising an image sensor for capturing image data, wherein the control circuitry is configured to control, based on an image classification output indicative of at least one characteristic of a surface to be cleaned, operation of at least one aspect of the surface cleaner, wherein the image classification output is based on the image data.

24. The surface cleaner of claim 23, wherein the control circuitry is configured to, based on the image classification output, control switching of the surface cleaner to and / or from the vapour generation mode.

25. The surface cleaner of claim 24, wherein the control circuitry is configured to, in response to the image classification output being indicative that an image represented by the image data is an image of dirt, switch the surface cleaner to the vapour generation mode.

Images