A surface cleaner

Abstract

A surface cleaner10 or dock comprising a liquid collection tank 222 for collecting liquid from a surface to be cleaned. The tank has an inlet for liquids and an outlet coupled to the positive displacement pump 250. Preferably, the pump removes air from the liquid collection tank to draw the liquid through the inlet. Preferably, the liquid collection tank has lower and upper portions 222y and 222x and the inlet is in the upper portion. Preferably, liquid flowing into the pump triggers dirty liquid being returned to the surface through overflow conduits 242(t). Preferably, the pump is a flexible vane pump comprising a cam ring and flexible vanes that are deformable about solid debris. Preferably, there is a clean liquid tank 26 and the clean water flows through sieve 84, conduit 44, pump 82 to switchable valve 86. From here the water may go through valve 92 to spray device 94 or to spray bar 88 and onto roller 30a. Preferably, an ingress conduit 240 is connected to a sieve 38 for straining the liquid. Preferably, the pumps and valves are controlled by controller 256.

Description

Field of the Invention The present invention relates to a surface cleaner such as a floor cleaner. Background of the Invention 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 of the Invention According to a first aspect there is provided a surface cleaner comprising a liquid collection tank for collecting liquid from a surface to be cleaned; a positive displacement pump; wherein the liquid collection tank has an inlet for receiving the liquid from the surface to be cleaned, and an outlet coupled to the positive displacement pump. The positive displacement pump may be configured to remove air from the liquid collection tank to draw the liquid from the surface to be cleaned into the liquid collection tank. The use of a positive displacement pump downstream of the liquid collection tank reduces the need for sensors and control mechanisms to detect and handle pump blockages due to debris. In this arrangement the pump is able to handle overflow liquid which may contain debris, making such surface cleaners cheaper, simpler and more robust. The liquid collection tank may have a lower portion and an upper portion, the lower portion located in use closer to the surface to be cleaned than the upper portion, and wherein the outlet is located in the upper portion of the liquid collection tank. The inlet may be located in the upper portion of the liquid collection tank. The surface cleaner may be configured to deliver some of the liquid from the surface to be cleaned in the liquid collection tank back to the surface to be cleaned responsive to some of the liquid from the surface to be cleaned flowing from the outlet of the liquid collection tank to the positive displacement pump. Such an occurrence may alert the user that the liquid collection tank is full without the need for sensors and complex control mechanisms, leading to a cheaper, simpler and more robust cleaner head. The surface cleaner may comprise a first egress conduit coupled between the outlet of the liquid collection tank and an inlet of the positive displacement pump; and a second egress conduit having a first end coupled to an outlet of the positive displacement pump and a second end positioned in within 2cm of the surface to be cleaned. The positive displacement pump may be a rotary vane pump. The rotary vane pump may by a flexible vane pump. The flexible vane pump may comprise a plurality of flexible vanes each having a Shore A hardness between 30 and 70. The positive displacement pump may comprise a cam ring and the flexible vanes may be deformable about a solid debris between the cam ring and the flexible vanes. The surface cleaner may comprise a liquid distribution tank for storing liquid to be rlic+nhi iforl +a tho qiiiHFoao tn ho r'loonorl UI U5 LI IU UI Lc*UI LU LI It* oil 11 dvv LU UtS v / l111*UI ■ The surface cleaner may comprise a roller for removing liquid from the surface to be cleaned for collection in the liquid collection tank. The surface cleaner may be an autonomous cleaning robot or a manually operable cleaning assembly. According to a second aspect there is provided a surface cleaner dock for receiving a surface cleaner, the surface cleaner dock comprising: a coupler for coupling with the surface cleaner for receiving liquid from a surface to be cleaned from the surface cleaner; a liquid collection tank for collecting the liquid from the surface to be cleaned; a positive displacement pump; wherein the liquid collection tank has an inlet for receiving the liquid from the surface to be cleaned, and an outlet coupled to the positive displacement pump. The positive displacement pump may be configured to remove air from the liquid collection tank to draw the liquid from the surface to be cleaned into the liquid collection tank. The liquid collection tank may have a lower portion and an upper portion, the lower portion located in use closer to the surface to be cleaned than the upper portion, and wherein the outlet is located in the upper portion of the liquid collection tank. The inlet is located in the upper portion of the liquid collection tank. The positive displacement pump may be a rotary vane pump. The rotary vane pump may be a flexible vane pump. The flexible vane pump may comprise a plurality of flexible vanes each having a Shore A hardness between 30 and 70. The positive displacement pump may comprise a cam ring and wherein the flexible vanes are deformable about a solid debris between the cam ring and the flexible vanes. The surface cleaner dock may comprise a liquid distribution tank for storing liquid to be distributed to the surface to be cleaned. Optional features of aspects of the present invention may be equally applied to other aspects of the present invention, where appropriate. Brief Description of the Drawings Figure 1 is a perspective view of a surface cleaner; Figure 2 is a simplified section view of the cleaner head and lower part of the body of Figure 1, according to an embodiment; Figure 3 is a simplified section view of the body including dirty and clean water tanks of Figure 1, according to an embodiment; Figure 4 is a section view of a flexible vane pump according to an embodiment; Figure 5 is a perspective view of a rotor of the flexible vane pump of Figure 4, according to an embodiment; Figure 6 is a schematic diagram illustrating the operational configuration of a surface cleaner according to the embodiment of Figure 3; Figure 7 is a simplified section view of a surface cleaner dock according to another embodiment; Figure 8 is a further simplified section view of the body including dirty and clean water tanks of Figure 1, according to another embodiment; Figure 9 is a schematic diagram illustrating the operational configuration of a surface cleaner according to the embodiment of Figure 8. Detailed Description of the Invention A surface cleaner 10 is illustrated in Figure 1. The surface cleaner allows a user to clean a surface such as a floor, for example to remove unwanted liquid and / or solid debris from the surface to be cleaned. The surface cleaner 10 comprises a body 16 from which upper and lower support members 24 and 20 extend transversely. The upper support member 24 is configured to removably retain and interface with a clean water tank 26. The upper and / or lower support members 24 and 20 are configured to removably retain and interface with a dirty water or liquid collection tank 22. A handle 18 extends longitudinally from an upper portion of the body 16. A cleaner head 12 is rotatably coupled to the lower support member 24 of the body 16 by a coupler 14. A simplified section of the lower part of the surface cleaner is shown in Figure 2. The cleaner head 12 is mechanically coupled to the body 16 via the lower support member 20. The coupler 14 is formed using a body projection 14x extending from the lower support member 20 and a head projection 14y extending from the cleaner head 12. These projections 14x, 14y are connected together, for example using a universal joint mechanism to allow many degrees of freedom between the body 16 and the cleaner head 12. The coupler 14 is also configured to provide a fluid and in some embodiments electrical connections between the body 16 and the cleaner head 12. The cleaner head 12 comprises two counter rotating rollers 30a, 30b which are each rotatable about a respective axis parallel to the width of the cleaner head -see direction W of Figure 1. The rollers 30a, 30b are spaced apart in the depth direction - D. The rollers 30a, 30b may be electrically driven or driven by manual operation of the rollers across a surface to be cleaned 48, such as a floor. As the rollers 30a, 30b move across the floor 48, they pick up and retain liquid and solid debris. Each roller 30a, 30b is arranged to contact a mangle 32a, 32b which squeezes liquid from the respective roller 30a, 30b as it rotates past the mangle 32a, 32b. Each roller 30a, 30b is also arranged to contact a respective counter rotating brush member 34a, 34b. Solid debris from the rollers 30a, 30b is removed as the rollers 30a, 30b and rotating brush members 34a, 34b contact and rotate past each other. A removable tray 36 is arranged to collect the liquid and debris removed from the rollers 30a, 30b. A sieve 38 within the tray 36 allows liquid to pass into a lower collection portion of the tray 36, with the solid debris retained within the tray 36 above the sieve 38. An ingress conduit 40 allows the liquid collected in the tray 36 to be drawn up into the body 16 of the surface cleaner, through the coupler 14, and into the dirty water tank 22. A clean water conduit 44 supplies clean water from the clean water tank 26 to the cleaner head. The clean water may be applied to the rollers 30a, 30b and / or may be supplied to a spray device (not shown) to be applied directly to the floor 48. In some embodiments, an overflow conduit 42 may be employed to return dirty water from the dirty water tank 22 to the floor 48 in the event that the dirty water tank becomes full and overflows excess dirty water. The appearance of a pool of dirty water on the floor 48 would then alert a user to the dirty water tank being full and requiring emptying before further cleaning is undertaken. This simple overflow alerting mechanism avoids the need for sensors and / or complex control and signalling processes to alert the user, which reduces costs and improves robustness of the surface cleaner. A simplified section of the body 16 of the surface cleaner according to an embodiment is shown in Figure 3. Both the clean water tank 26 and the dirty water tank 22 are shown as being coupled to the body via respective upper and lower support members 24 and 20. However, both of these tanks are removeable, with the clean water tank 26 being removable to fill with clean water and the dirty water 22 tank being removable to empty dirty water removed from the floor 48 by the cleaner head 12. The support members 24, 20 include mechanical locating and retaining arrangements as well as fluid connections for the tanks 22,26. Fluid connections with various conduits 42, 42t, 44 are illustrated schematically, however any suitable mechanical arrangement may be employed for these fluid connections. The body 16 comprises a pump 50 which is driven by an electric motor 52. The arrow within the pump 50 illustrates the normal direction of flow of liquid through the pump when the surface washer is cleaning. The pump 50 is located upstream of the dirty water tank 22, being configured to pump liquid from the tray 36 to the dirty water tank 22. The body also comprises a motor controller 56 which powers and controls operation of the electric motor 52, and a rechargeable battery 54 which provides power for the motor controller 56 and optionally other electrically powered functions associated with the surface cleaner 10. These components are shown schematically and not to scale. Liquid from the surface to be cleaned and collected in the tray 36 is drawn up ingress conduit 40 into the pump 50 when the pump is normally driven by the electric motor 52. The liquid is then delivered into the dirty water tank 22 via tank conduit 40t - this is indicated by arrow I. The tank conduit 40t may connect with the dirty water tank 22 via an interface on the underside of the upper support member 24. The liquid from the surface to be cleaned is pumped by the pump 50 into the top or an upper portion 22x of the dirty water tank 22. The upper portion 22x is above a lower portion 22y of the dirty water tank 22 when the surface cleaner is in use, the lower portion 22y being closer to the surface to be cleaned than the upper portion 22x. The liquid collected in the dirty water tank 22 normally fills from the lower portion 22y up towards the upper portion 22x of the dirty water tank 22. The overflow conduit 42 also connects with the dirty water tank 22 via an interface on the underside of the upper support member 24. If the liquid collected in the dirty water tank 22 exceeds the volume available then some of this overflows out of the top of the dirty water tank 22 into the overflow conduit - indicated by arrow O. This overflow is delivered by the overflow conduit back to the cleaner head 12 as previously described. In an alternative embodiment, level sensors in the dirty water tank 22 may be used to detect that this is full or nearly full, and additional control algorithms may be used to stop further operation by the pump and / or alert a user. The clean water conduit 44 connects with the clean water tank 26 via an interface on the upper side of the upper support member 24. Clean water from the clean water tank 26 is delivered by the clean water conduit 44 to the cleaner head as previously described. The motor controller 56 may be configured to operate the electric motor 52 in one or more modes of operation. In a first cleaning or normal mode, the electric motor 52 drives the pump 50 in a direction that draws liquid up along the ingress conduit 40 from the tray 36 into the pump 50 and pushes the liquid along the tank conduit 40t into the dirty water tank 22. When the dirty water tank 22 is full, the force from the pump also forces liquid out of the dirty water tank 22 along the overflow conduit 44 back to the cleaner head 12. In a second enhanced cleaning mode, the motor controller 56 senses the current drawn by the electric motor 52 and uses this to determine whether the pump 50 has run dry - in other words there is no more liquid in the tray 36 to be drawn into the pump 50. When liquid is removed from the pump 50 and the rotor 60 is still rotating, friction between the flexible vanes 70 and the cam ring 62 increases. This causes the electric motor 52 to work harder to overcome the increased friction, causing the current drawn by the electric motor 52 to increase. A characteristic increase in current drawn by the electric motor can then be used by the motor controller 54 to detect a dry pump condition and stop the electric motor. The characteristic used may simply be a current above a predetermined threshold. In a third unblocking mode, the motor controller 56 controls the electric motor 54 to briefly reverse rotational direction thus reversing the normal direction of the pump 50. This operation may help to remove any debris lodged within the pump 50. In some examples, the pump may undergo a sequence of brief reverse and forward rotations. A section of the pump 50 is illustrated in Figure 4 and a perspective of a rotor 60 of the pump of Figure 4 is illustrated in Figure 5. The pump 50 is a flexible vane pump which comprises a rotor 60 arranged to rotate within a cam ring 62 which is housed within a pump housing 64. A pump inlet 66m connects with the ingress conduit 40 to deliver liquid into the pump and a pump outlet 66n connects with the tank conduit 40t to deliver liquid from the pump 50. The rotor 60 comprises a circular core 72 with an orifice 74 for receiving a spindle of the electric motor 52 to rotate the rotor and drive the pump 50. The rotor comprises a plurality of flexible vanes 70 extending therefrom. The flexible vanes may include any suitable side profile such as a linear shaft with a distal enlarged circular end as shown. However other side profiles may be used, such as a simple linear shaft. The ends of the flexible vanes 70 contact the cam ring 62 and rotate past this when the rotor 60 is drive by the electric motor 52. The flexible vanes are deformable and the centre of rotation of the rotor 60 is offset compared with the centre of the cam ring - this provides the suction required to pump liquid from the pump inlet 66m to the pump outlet 66n. The flexible vanes 70 are sufficiently flexible to deform about solid debris between the cam ring 62 and the flexible vanes 70. This prevents the debris from jamming or blocking the pump so that it no longer rotates. Whilst the sieve 38 is intended to prevent debris from being drawn into the ingress conduit 40, sometimes debris may still enter the ingress conduit 40 and travel into the pump 50. The use of a flexible vane pump allows the surface cleaner to handle these occasional events whilst continuing to operate. The arrangement improves robustness of the surface cleaner and reduces the need for skilled maintenance. The arrangement also reduces the need for sensors to detect pump blocking events and associated control mechanisms for shutting down and / or unblocking the pump. In some embodiments, the flexible vanes each have a shore A hardness of between 30 and 70. In some embodiments, the rotor comprises one or more of the following: between 4 and 8 flexible vanes; a shore hardness for each of the flexible vanes of between 45 and 55; a thickness of each of the flexible vanes of between 0.5 and 1,5mm; a width for each of the flexible vanes of between 5 and 10mm; a diameter of between 15 and 20mm. The operational configuration of the surface cleaner according to the embodiment of Figure 3 is illustrated in Figure 6. In addition to components already described, the surface cleaner also comprises a clean water sieve 84, a clean water pump 82, a switchable valve 86 which controls clean water delivered by the clean water pump 82 to a spray device 94 and / or a spray bar 88. Conduits 44 deliver clean water from the clean water tank 26, to the clean water pump 82 and to the switchable valve 86. The spray device may be located in or on the cleaner head 12 in order to deliver a controlled directional spray of clean water onto the floor 48. A one-way valve 92 is arranged between the spray device 94 and the switchable valve 85. The spray bar 88 is arranged over one of the rollers 30a within the cleaner head 12 such that clean water is delivered to the roller 30a. A second spray bar (not shown) may be arranged to deliver clean water to the other roller 30b. The switchable valve 86 is controllable to deliver clean water to one, both or neither of the spray device 94 and the spray bar 88. In other examples, one or both of the spray device 94 and the spray bar 88 may be omitted. For example, clean water may be simply allowed to drip onto the roller 30a to hydrate the roller 30a. The clean water pump 82 may be a diaphragm pump driven by a DC electric motor which is also controlled by the motor controller 56. The motor controller 52 may provide respective pulse wave modulated power signals to each of the clean water pump 82 and the flexible vane pump 50 used to pump the dirty water into the dirty water tank 22. As previously described, dirty water or other liquid removed from the floor by the rollers 30a, 30b is collected in a tray and drawn through a sieve 38 into the pump 50 via the ingress conduit 40. The pump 50 delivers this liquid into an upper portion 22x (e.g. the upper surface) of the dirty water tank 22 via the tank conduit 40t. Any overflow from the dirty water tank 22 is returned by overflow conduit 42 to the cleaner head for emptying onto the floor. The surface cleaner 10 has been illustrated as a manually operable cleaning assembly which is pushed across a floor by a user to clean liquid and / or debris from the floor. However in other embodiments, the surface cleaner may be incorporated into an autonomous cleaning robot. In such an embodiment, the physical arrangement of various components may be different to those already described, but the operation using the flexible vane pump may be the same. Whilst the flexible vane pump 50 has been described as being arranged upstream of the dirty water tank, it may alternatively be arranged downstream of the dirty water tank 22. In this alternative arrangement, the pump may be configured as an air pump that removes air from a sealed dirty water tank in order to suck liquid formed from the floor and collected in the tray into the dirty water tank. A surface cleaner dock is illustrated in Figure 7. The surface cleaner dock 100 is configured to receive a surface cleaner 10. The surface cleaner dock 100 comprises a liquid collection or dirty water tank 126 for receiving liquid from a surface to be cleaned from the surface cleaner 10. The surface cleaner dock 100 may also comprise a clean water tank 126 for supplying clean water to the surface cleaner. The surface cleaner dock 100 comprises a locating plate 132 for locating the surface cleaner 10 within the surface cleaner dock 100 and a coupler 130 for locating and interfacing with the surface cleaner 10. The coupler 130 may comprise fluid and electrical interfaces for connecting fluid and electrical lines between the surface cleaner 10 and the surface cleaner dock 100. For example, an electrical connection may be provided to charge a rechargeable battery of the surface cleaner 10. This may be provided from a mains outlet connection (not shown) to the surface cleaner dock 100. A fluid connection may be provided between the dirty water tank 22 of the surface cleaner 10 and the dirty water tank 122 of the surface cleaner dock 100. A fluid connection may also be provided between the clean water tank 26 of the surface cleaner 10 and the clean water tank 126 of the surface cleaner dock 100. The surface cleaner dock 100 also comprises a body 116 which may house a pump 50, an electric motor 52, a motor controller 54 and conduits 40, 40t as previously described in order to pump dirty water from the surface cleaner 10 into the dirty water tank 122 of the surface cleaner dock 100. The body 116 may also house one or more of a clean water sieve 84, a clean water pump 83 and conduits 44 to deliver clean water from the clean water tank 126 of the surface cleaner dock 100 to the surface cleaner 10. A simplified section of a body 216 of a surface cleaner 10 according to another embodiment is shown in Figure 8. The body 216 of this embodiment comprises some common components included in the body 16 of the embodiment of Figure 3. These common components have the same reference numerals and are as previously described. The body 216 additionally comprises a modified liquid collection or dirty water tank 222, differently configured upper and lower support members 224, 220, a differently configured pump 250, a differently configured electric motor 252 and motor controller 256 as well as a different arrangement of conduits 242, 242t, 240. In this embodiment the pump 250 is a positive displacement pump configured as an air pump downstream of the dirty water tank 222. This configuration sucks air from the dirty water tank which creates low or negative pressure in the dirty water tank 222. This low or negative pressure acts to draw liquid from the surface to be cleaned and collected in the tray 36, up into the dirty water tank 222. The dirty water tank 222 is coupled to the body 216 via respective upper and lower support members 224 and 220. The dirty water tank 222 is removable to empty of dirty water removed from the floor 48 by the cleaner head 12. Like the dirty water tank 22, the dirty water tank 222 comprises an upper portion 222x and a lower portion 222y. The support members 224,220 include mechanical locating and retaining arrangements as well as fluid connections for the tank 222. An ingress conduit 240 is coupled between the removable tray 36 in the cleaner head 12 and the upper portion 222x of the dirty water tank 222. Liquid from the surface to be cleaned is drawn up from the tray 36 into the dirty water tank 222 -this is illustrated by arrow I. Received liquid fills up the dirty water tank 222 from the lower portion 222y to the upper portion 222x. A tank conduit 242t is coupled between the upper portion 222x and the pump 250. An egress conduit 242 is coupled between the pump 250 and the cleaner head 12 or to an atmospheric outlet elsewhere on the surface cleaner. Operation of the pump causes air to be removed from the dirty water tank 222 - illustrated by arrow O - creating a suction force to draw the liquid into the tank 222. Fluid connections with various conduits 242, 242t, 240,44 are illustrated schematically, however any suitable mechanical arrangement may be employed for these fluid connections. As noted previously, the pump 250 is configured as an air pump, with the dirty water tank 222 and conduits 240,242t being sealed to enable the use of negative pressure to suck the liquid from the tray 36 into the tank 222. The pump 250 is driven by an electric motor 252. The arrow within the pump 250 illustrates the normal direction of flow of air or other fluid through the pump when the surface washer is cleaning. The body also comprises a motor controller 256 which powers and controls operation of the electric motor 252. These components are shown schematically and not to scale. The tank conduit 242t and the ingress conduit 240 may connect with the dirty water tank 222 via an interface on the underside of the upper support member 224. The egress conduit 242 may connect back with the cleaner head, similarly to overflow conduit 42 of the embodiment of Figure 3, or to a suitably located vent d Li IlUopi Ivi w. When the dirty water tank 222 becomes full, some of the received liquid may be sucked into the tank conduit 242t and through the pump 250 into the egress conduit 242. As with the overflow conduit 42 of the embodiment of Figure 3, the egress conduit 242 may be directed back to the cleaner head 12 such that overflowing liquid is allowed to pool on the floor, which alerts a user that the dirty water tank 222 requires emptying. The end of the egress conduit may be located within 2cm of the floor to contain pooling. The pump is a positive displacement pump which reduces the likelihood of blockages when liquid from the dirty water tank overflows into the tank conduit 242t. This overflow liquid may carry solid debris which then passes through the pump 250. Although the frequency and size of debris passing through the downstream pump 250 is likely to be lower than that passing through the upstream pump 50 of Figure 3, the use of a positive displacement pump 250 reduces the likelihood of such debris blocking or jamming the pump 250 of Figure 8. The positive displacement pump 250 may be a rotary vane pump which further reduces the likelihood of blockages in the pump 250. The rotary vane pump 250 may be a flexible vane pump, such as that described with respect to Figures 4 and 5. As previously described, this allows the vanes to deform around debris further reducing the likelihood of the debris blocking the flexible vane pump 250. The motor controller 256 may be configured to operate the electric motor 252 in one or more modes of operation. In a first cleaning or normal mode, the electric motor 252 drives the pump 250 in a direction that sucks air out of the dirty water tank 222, which draws liquid up along the ingress conduit 240 from the tray 36 into the dirty water tank 222. When the dirty water tank 222 is full, liquid from the dirty water tank 222 may also be sucked out of the along the tank conduit 242t through the pump 250. In a second unblocking mode, the motor controller 256 controls the electric motor 254 to briefly reverse rotational direction thus reversing the normal direction of the pump 250. This operation may help to remove any debris lodged within the pump 250. The operational configuration of the surface cleaner according to the embodiment of Figure 8 is illustrated in Figure 9. Operation of the clean water components is as previously described with respect to the embodiment of Figure 6. Handling of the dirty water and the configuration of the dirty water components is modified compared with the embodiment of Figure 6. Furthermore, pumps other than flexible vane pumps may be employed in the embodiment of Figure 9, such as a rotary vane pump without flexible vanes. As previously described, dirty water or other liquid removed from the floor by the rollers 30a, 30b is collected in the tray and filtered through the sieve 38. The liquid in the tray 36 is drawn into the sealed dirty water tank 222 by the action of downstream pump 250 which draws air out of the tank through tank conduit 242t, the pump 250 and into egress conduit 242 which delivers this air to atmosphere. Removal of air from the dirty water tank 222 causes a low or negative pressure in the tank which causes the liquid in the tray 36 to be drawn up ingress conduit 240 into the dirty water tank. As with the surface cleaner 10 of previous embodiments, a surface cleaner as configured according to Figures 8 or 9 may be implemented as a manually operable cleaning assembly which is pushed across a floor by a user to clean liquid and / or debris from the floor. Alternatively, this embodiment may be incorporated into an autonomous cleaning robot. In such an embodiment, the physical arrangement of various components may be different to those already described, but the cleaning operation using the downstream positive dicnlarnmont mimn mow ho fho Como u usjjiduu11it?11 l jju111i i idy ut? li its ssdi ■ it?■ The surface cleaner dock illustrated in Figure 7 may be modified to utilise the embodiment of Figures 8 or 9. In this case the body 116 of the surface cleaner dock may house a pump 250, an electric motor 252, a motor controller 254 and conduits 240, 242t as previously described in order to pump dirty water from the surface cleaner into the dirty water tank 122 of the surface cleaner dock 100. The body may also house one or more of a clean water sieve 84, a clean water pump 83 and conduits 44 to deliver clean water from the clean water tank 126 of the surface cleaner dock 100 to the surface cleaner 10. Whilst particular examples and embodiments have thus far been described, it should be understood that these are illustrative only and that various modifications may be made without departing from the scope of the invention as defined by the claims. For example, the values of various parameters and dimensions described in conjunction with the specific embodiment above may be varied within a reasonable tolerance range that will be apparent to a person skilled in the art without significantly modifying operation of the surface cleaner 10.

Claims

1. A surface cleaner comprising:a liquid collection tank for collecting liquid from a surface to be cleaned;a positive displacement pump;wherein the liquid collection tank has an inlet for receiving the liquid from the surface to be cleaned, and an outlet coupled to the positive displacement pump.

2. The surface cleaner of Claim 1, wherein the positive displacement pump is configured to remove air from the liquid collection tank to draw the liquid from the surface to be cleaned into the liquid collection tank.

3. The surface cleaner of Claim 1 or Claim 2, wherein the liquid collection tank has a lower portion and an upper portion, the lower portion located in use closer to the surface to be cleaned than the upper portion, and wherein the outlet is located in the upper portion of the liquid collection tank.

4. The surface cleaner of Claim 3, wherein the inlet is located in the upper portion of the liquid collection tank.

5. The surface cleaner of any one of Claims 1 to 4, configured to deliver some of the liquid from the surface to be cleaned in the liquid collection tank back to the surface to be cleaned responsive to some of the liquid from the surface to be cleaned flowing from the outlet of the liquid collection tank to the positive displacement pump.

6. The surface cleaner of Claim 5, comprising:a first egress conduit coupled between the outlet of the liquid collection tank and an inlet of the positive displacement pump;a second egress conduit having a first end coupled to an outlet of the positive displacement pump and a second end positioned in within 2cm of the qi irfor'Q tn ha r'loianaH □Uilclvv LU Uw vlvdllvU.

7. The surface cleaner of any one of Claims 1 to 6, wherein the positive displacement pump is a rotary vane pump.

8. The surface cleaner of Claim 7, wherein the rotary vane pump is a flexible vane pump.

9. The surface cleaner of any one of Claims 7 to 8, wherein the rotary vane pump comprises a cam ring and flexible vanes rotatable within the cam ring and wherein the flexible vanes are deformable about a solid debris between the cam ring and the flexible vanes.

10. The surface cleaner of any one of Claims 1 to 9, comprising a liquid distribution tank for storing liquid to be distributed to the surface to be cleaned.

11. The cleaner head of any one of Claims 1 to 10, comprising a roller for removing liquid from the surface to be cleaned for collection in the liquid collection tank.

12. The surface cleaner of any one of Claims 1 to 11, comprising an autonomous cleaning robot or a manually operable cleaning assembly.

13. A surface cleaner dock for receiving a surface cleaner, the cleaning surface cleaner dock comprising:a coupler for coupling with the surface cleaner for receiving liquid from a surface to be cleaned from the surface cleaner;a liquid collection tank for collecting the liquid from the surface to be cleaned;a positive displacement pump;wherein the liquid collection tank has an inlet for receiving the liquid from the surface to be cleaned, and an outlet coupled to the positive displacement pump.

14. The surface cleaner dock of Claim 13, wherein the positive displacement pump is configured to remove air from the liquid collection tank to draw the liquid from the surface to be cleaned into the liquid collection tank.

15. The surface cleaner dock of Claim 13 or Claim 14, wherein the liquid collection tank has a lower portion and an upper portion, the lower portion located in use closer to the surface to be cleaned than the upper portion, and wherein the outlet is located in the upper portion of the liquid collection tank.

16. The surface cleaner dock of Claim 15, wherein the inlet is located in the upper portion of the liquid collection tank.

17. The surface cleaner dock of any one of Claims 13 to 16, wherein the positive displacement pump is a rotary vane pump.

18. The surface cleaner dock of Claim 17, wherein the rotary vane pump is aflexible vane pump.

19. The surface cleaner dock of any one of Claims 17 to 19, wherein the flexible vane pump comprises a cam ring and flexible vanes rotatable within the cam ring and wherein the flexible vanes are deformable about a solid debris between the cam ring and the flexible vanes.

20. The surface cleaner dock of any one of Claims 13 to 20, comprising a liquid distribution tank for storing liquid to be distributed to the surface to be cloanorlV / i t»d I itJU ■