Autonomous surface treating appliance

An autonomous surface treating appliance comprising a main body defining an outer plan profile, and having a drive arrangement mounted inboard of the outer plan profile of the main body and configured to propel the appliance in a direction of movement across a surface to be cleaned, a surface treating assembly associated with the main body and carried transversely to the direction of movement, the surface treating assembly being generally elongate in form and having side edges extending substantially at a tangent to respective circular portions of the outer plan profile of the main body.

REFERENCE TO RELATED APPLICATIONS

This application claims the priority of United Kingdom Application No. 1115608.0, filed Sep. 9, 2011, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates in general to an autonomous floor treating appliance and particularly, though not exclusively, to an autonomous vacuum cleaner.

BACKGROUND OF THE INVENTION

Mobile robots are becoming increasingly commonplace and are used in such diverse fields as space exploration, lawn mowing and floor cleaning. The last decade has seen particularly rapid advancement in the field of robotic floor cleaning devices, especially vacuum cleaners, the primary objective of which is to navigate a user's home autonomously and unobtrusively whilst cleaning the floor.

In performing this task, a robotic vacuum cleaner has to navigate the area which it is required to clean and to avoid colliding with obstacles whilst doing so. A requirement for a robotic vacuum cleaner when exploring a room is to clean as close as possible up to the edges of a room. One approach to this is shown in U.S. Pat. No. 6,883,201 which equips a circular-bodied robotic floor cleaner with spinning side brushes on each of its forward flanks in order to brush debris into the path of a horizontally mounted brush bar exposed on the underside of the device and between its wheels. Such a system of opposed spinning brushes can result in debris being flicked away from the front of the device which reduces the effectiveness of this approach for cleaning the edges of a room.

SUMMARY OF THE INVENTION

It is against this background that the invention has been made. To this end, the invention provides an autonomous floor treating appliance comprising a main body defining an outer plan profile, and having a drive arrangement mounted inboard of the outer plan profile of the main body and configured to propel the appliance in a direction of movement across a surface to be cleaned, a surface treating assembly associated with the main body and carried transversely to the direction of movement, the surface treating assembly being generally elongate in form and having side edges extending parallel to the direction of movement and at a tangent to respective circular portions of the outer plan profile of the main body.

The invention in principle applies to any autonomous appliance directed to treating a floor surface which includes a surface treating assembly extending transversely to the direction of movement of the appliance, for example a floor sweeper, polisher or washer, or even a robotic lawnmower. However, the invention has particular utility for robotic vacuum cleaners, and so the invention will hereafter be described in this context. Thus, in one embodiment, the appliance is an autonomous vacuum cleaner and so further comprises a power source operatively connected to a suction generator operable to draw air from a dirty air inlet of the treating head into a removable dirt and dust separating apparatus.

Since the surface treating assembly or ‘head’ extends transversely across the main body of the appliance, such that side edges or faces extend parallel to the direction of movement and at a tangent to respective circular portions of the outer plan profile of the main body, the appliance has a configuration which allows it to clean right up to the edges of a room. Furthermore, since the plan profile of the appliance is at least partly circular, it has a beneficial shape for on-the-spot turning so it is more able to maneuver out of confined spaces and corners. Preferably, the main body is substantially circular in plan view.

In the exemplary embodiment, the treating head may extend transversely across a rear portion of the main body, and behind the supporting wheel arrangement. The treating assembly is therefore able to clean over the path covered by the support wheels, and so can pick up grit or dirt which may be deposited on the floor surface by the wheels.

In one embodiment, the main body includes a chassis and the treating head is provided on the chassis, and may be integral with the chassis. In this way, the chassis may define an elongate sole plate extending forward of the treating head along a longitudinal axis and in the movement direction.

The chassis may also include first and second recesses located on its opposite sides within which respective traction units of the drive arrangement are receivable. Therefore, the traction units are mountable on the chassis inboard of the outer periphery of the appliance and forward of the treating head. Beneficially, the treating assembly extends beyond the width of the traction units and so can clean the floor surface of dust and grit which the traction units may leave in their trail.

In order to accommodate the removable dirt separating apparatus, the main body may include a front portion defining an open platform within the dirt separating apparatus is received. Preferably, the dirt separating apparatus is substantially cylindrical and is received in the platform in an upright orientation such that its longitudinal axis extends substantially vertically, that is to say normal to the longitudinal and transverse axes of the main body.

Although the dirt separating apparatus can take other forms, in the exemplary embodiment it is a cyclonic separating apparatus which provides the vacuum cleaner with a particularly effective cleaning facility.

The dirt separating apparatus may be configured so that it forms part of the outer plan profile of the appliance, its shape therefore complementing the substantially circular profile of the appliance. Furthermore, a portion of the dirt separating apparatus may protrude beyond a front portion of the main body in the direction of movement and, in this way, the dirt separating apparatus provides the appliance with a resilient protective bumper in the event of a collision.

The main body structure may also include a body portion that is mounted on the chassis and movable relative thereto. This provides the appliance with the facility to detect collisions as the body will be cause to move relative to the chassis, such movement being detectable by a suitable sensing mechanism. Notably, the power source, the suction generator, the dirt separating apparatus receiving platform are provided on the body, all of which is movable with respect to the chassis.

DETAILED DESCRIPTION OF THE INVENTION

With reference toFIGS. 1, 2, 3, 4 and 5of the drawings, an autonomous surface treating appliance in the form of a robotic vacuum cleaner2(hereinafter ‘robot’) comprises has a main body having four principal assemblies: a chassis (or sole plate)4, a body6which is carried on the chassis4, a generally circular outer cover8which is mountable on the chassis4and provides the robot2with a generally circular profile, and a separating apparatus10that is carried on a forward part of the body6and which protrudes through a complementary shaped cut-out12of the outer cover8.

For the purposes of this specification, the terms ‘front’ and ‘rear’ in the context of the robot will be used in the sense of its forward and reverse directions during operation, with the separating apparatus10being positioned at the front of the robot. Similarly, the terms ‘left’ and ‘right’ will be used with reference to the direction of forward movement of the robot. As will be appreciated fromFIG. 1, the main body of the robot2has the general form of a relatively short circular cylinder, largely for maneuverability reasons, and so has a cylindrical major axis ‘C’ that extends substantially vertically relative to the surface on which the robot travels. Accordingly, the cylindrical axis C extends substantially normal to a longitudinal axis of the robot ‘L’ that is oriented in the fore-aft direction of the robot2and so passes through the centre of the separating apparatus10. The diameter of the main body is preferably between 200 mm and 300 mm, and more preferably between 220 mm and 250 mm. Most preferably, the main body has a diameter of 230 mm which has been found to be a particularly effective compromise between maneuverability and cleaning efficiency.

The chassis4supports several components of the robot2and is preferably manufactured from a high-strength injection moulded plastics material, such as ABS (Acrylonitrile Butadiene Styrene), although it could also be made from appropriate metals such as aluminium or steel, or composite materials such a carbon fibre composite. As will be explained, the primary function of the chassis4is as a drive platform and to carry cleaning apparatus for cleaning the surface over which the robot travels.

With particular reference toFIGS. 4 and 5, a front portion14of the chassis4is relatively flat and tray-like in form and defines a curved prow15that forms the front of the robot2. A drive arrangement is provided by first and second traction units20which are mounted in respective recesses16,18in each flank of the front portion of the chassis4. Note thatFIG. 4shows the chassis4with the traction units20attached andFIG. 5shows the chassis4without the traction units20attached.

The pair of traction units20are located on opposite sides of the chassis4and are operable independently to enable the robot to be driven in forward and reverse directions, to follow a curved path towards the left or right, or to turn on the spot in either direction, depending on the speed and direction of rotation of the traction units20. Such an arrangement is sometimes known as a differential drive, and detail of the traction units20will be described more fully later in the specification.

The relatively narrow front portion14of the chassis4widens into rear portion22which includes a surface treating assembly24or ‘cleaner head’ having a generally cylindrical form and which extends transversely across the entire width of the chassis4relative to the longitudinal axis ‘L’ and is positioned behind the traction units20with respect to the forward direction of travel.

With reference also toFIG. 2, which shows the underside of the robot2, the cleaner head24defines a rectangular suction opening26that faces the supporting surface and into which dirt and debris is drawn into when the robot2is operating. An elongate brush bar28is contained within the cleaner head24and is driven by an electric motor30via a reduction gear and drive belt arrangement32in a conventional manner, although other drive configurations such as a solely geared transmission are also envisaged.

The underside of the chassis4features an elongate sole plate section25extending forward of the suction opening26which includes a plurality of channels33(only two of which are labeled for brevity) which provide pathways for dirty air being drawn towards the suction opening26. The underside of the chassis4also carries a plurality (four in the illustrated embodiment) of passive wheel or rollers31which provide further bearing points for the chassis4when it is at rest on or moving over a floor surface. It should be noted that the rollers31support the chassis such that the underside thereof is in a parallel orientation relative to a floor surface. Furthermore, although wheels or rollers are preferred, they could also be embodied as hard bearing points such as skids or runners.

In this embodiment, the cleaner head24and the chassis4are a single plastics moulding, thus the cleaner head24is integral with the chassis4. Such a configuration is efficient to manufacture since the sole plate25and the cleaner head are provided by the same moulded component. However, this need not be the case and the two components could be separate, the cleaner head24being suitably affixed to the chassis4as by screws or an appropriate bonding technique as would be clear to the skilled person.

The cleaner head24has first and second end faces27,29that extend to the edge of the chassis4behind the traction units20and which are in line with the cover8of the robot. Considered in horizontal or plan profile as inFIGS. 2 and 3, it can be seen that the end faces27,29of the cleaner head24are flat and extend at a tangent (labeled as ‘T’) to the cover8at substantially diametrically opposed points along the lateral axis ‘X’ of the robot2. The benefit of this is that the cleaner head24is able to run extremely close to the walls of a room as the robot traverses in a ‘wall following’ mode therefore being able to clean right up to the wall. Moreover, since the end faces27,29of the cleaner head24extend tangentially to both sides of the robot2, it is able to clean right up to a wall whether the wall is on the right side or the left side of the robot2. It should be noted, also, that the beneficial edge cleaning ability is enhanced by the traction units20being located inboard of the cover8meaning that the robot can maneuver in such a way that the cover8and therefore also the end faces27,29of the cleaner head24are almost in contact with the wall during a wall following operation. Furthermore, since the cleaner head extends transversely across substantially the entire width of the chassis4and is positioned behind the traction units20, this means that the cleaner head24can clean the floor surface of dust and grit which the traction units may leave in their trail as the robot moves about. The cleaner head24is located behind the traction units20and as close to them as possible so that the cleaner head24can extend across the whole width of the robot whilst minimizing the ‘projections’ from the main circular form of the machine which could otherwise interfere with its ability to maneuver.

Dirt drawn into the suction opening26during a cleaning operation exits the cleaner head24via a conduit34which extends upwardly from the cleaner head24and curves towards the front of the chassis4through approximately 90° of arc until it faces in the forwards direction. The conduit34terminates in a rectangular mouth36having a flexible bellows arrangement38shaped to engage with a complementary shaped duct42provided on the body6.

The duct42is provided on a front portion46of the body6, and opens into a forward facing generally semi-cylindrical recess50having a generally circular base platform48. The recess50and the platform48provide a docking portion into which the separating apparatus10is mounted, in use, and from which it can be disengaged for emptying purposes.

It should be noted that in this embodiment the separating apparatus10consists of a cyclonic separator such as disclosed in WO2008/009886, the contents of which are incorporated herein by reference. The configuration of such separating apparatus is well known and will not be described any further here, save to say that the separating apparatus10may be removably attached to the body6by a suitable mechanism such as a quick-release fastening means to allow the apparatus10to be emptied when it becomes full. The nature of the separating apparatus10is not central to the invention and the cyclonic separating apparatus may instead separate dirt from the airflow by other means that are known in the art for example a filter-membrane, a porous box filter or some other form of separating apparatus. For embodiments of the apparatus which are not vacuum cleaners, the body6can house equipment which is appropriate to the task performed by the machine. For example, for a floor polishing machine the main body can house a tank for storing liquid polishing fluid.

When the separating apparatus10is engaged in the docking portion50, a dirty air inlet52of the separating apparatus10is received by the duct42and the other end of the duct42is connectable to the mouth36of the brush bar conduit34, such that the duct42transfers the dirty air from the cleaner head24to the separating apparatus10. The bellows38provide the mouth36of the duct34with a degree of resilience so that it can mate sealingly with the dirty air inlet52of the separating apparatus10despite some angular misalignment. Although described here as bellows, the duct34could also be provided with an alternative resilient seal, such as a flexible rubber cuff seal, to engage the dirty air inlet52.

Dirty air is drawn through the separating apparatus10by an airflow generator which, in this embodiment, is an electrically powered motor and fan unit (not shown), that is located in a motor housing60located on the left hand side of the body6. The motor housing60includes a curved inlet mouth62that opens at the cylindrical shaped wall of docking portion50thereby to match the cylindrical curvature of the separating apparatus10. Although not seen inFIG. 4, the separating apparatus10includes a clean air outlet which registers with the inlet mouth62when the separating apparatus10is engaged in the docking portion50. In use, the suction motor is operable to create low pressure in the region of the motor inlet mouth62, thereby drawing dirty air along an airflow path from the suction opening26of the cleaner head24, through the conduit34and duct42and through the separating apparatus10from dirty air inlet52to the clean air outlet. Clean air then passes through the motor housing60and is exhausted from the rear of the robot2through a filtered clean air outlet61.

The cover8is shown separated from the body6inFIG. 4and, since the chassis4and body6carry the majority of the functional components of the robot2, the cover8provides an outer skin that serves largely as a protective shell and to carry a user control interface70.

The cover8comprises a generally cylindrical side wall71and a flat upper surface72which provides a substantially circular profile corresponding to the plan profile of the body6, save for the part-circular cut-out12shaped to complement the shape of the docking portion50, and the cylindrical separating apparatus10. Furthermore, it can be seen that the flat upper surface72of the cover8is co-planar with an upper surface10aof the separating apparatus10, which therefore sits flush with the cover8when it is mounted on the main body.

As can be seen particularly clearly inFIG. 2, the part-circular cut-out12of the cover8and the semi-cylindrical recess50in the body6provides the docking portion a horseshoe shaped bay defining two projecting lobes or arms73awhich flank either side of the separating apparatus10and leave between approximately 5% and 40%, and preferably 20%, of the apparatus10protruding from the front of the docking portion50. Therefore, a portion of the separating apparatus10remains exposed even when the cover8is in place on the main body of the robot2, which enables a user ready access to the separating apparatus10for emptying purposes. The flanking lobes are particularly suited to housing sensor modules, identified here at82, which the robot may use to map its environment and/or to detect obstacles. In this case, the material of the projecting lobes73should be a suitable sensor-transparent material. The sensor modules may be any sensors suitable for robot navigation, such as laser range finders, ultrasonic transducers, position sensitive devices (PSDs) or optical sensors.

Opposite portions of the side wall71include an arched recess74(only one shown inFIG. 3) that fits over a respective end27,29of the cleaner head24when the cover8is connected to the body6. As can be seen inFIG. 1, a clearance exists between the ends of the cleaner head24and the respective arches74order to allow for relative movement therebetween in the event of a collision with an object.

As has been mentioned, the separating apparatus10in the exemplary embodiment is a cylindrical bin that sits within the docking bay portion50of the robot and protrudes from the cover8so as to define a front of the robot2. Note that the bin10has an upright orientation such that a longitudinal axis thereof is normal to both the longitudinal and lateral axes L, X of the robot2and, therefore, parallel to its cylindrical/vertical axis C. Having a portion of the separating apparatus10exposed at the front of the robot2in this way allows a user to gain easy access to the separating apparatus in order to remove it from the robot2when it needs to be emptied.

Therefore, a user does not need to manipulate doors, hatches or panels in order to gain access to the separating apparatus10. Furthermore, the separating apparatus may be transparent so that a user can see how full the separating apparatus is, thus avoiding the need for mechanical or electronic bin-full indicators. Furthermore, a separating apparatus, particularly a cyclonic separating apparatus is lighter than electronic components such as motors and batteries so the configuration of the separating apparatus on the front of the robot further assists the robot to climb up surfaces. In prior art machines, however, the heavier components tend to be positioned at the front whilst the dust containers are positioned at the rear or towards the centre of the machine.

A further advantage is that the separating apparatus10acts as a bumper for the robot2since being the forward most part of the robot means that it will be the first part of the robot to contact an obstacle during a collision. Preferably the bin is made from a plastics material of suitable mechanical properties to provide a degree of resilience in the event of the robot colliding with an obstacle. One example is transparent ABS (Acrylonitrile Butadiene Styrene) manufactured in a suitable thickness (for example between about 0.5 and 2 mm) to provide the bin10with a suitable degree of resilience. Therefore, the bin10provides a degree of protection for the main body of the robot2from hard and or sharp objects which may otherwise damage the cover8. Similarly, the resilience of the bin provides a degree of protection for obstacles during collisions which may be vulnerable to damage.

On the upper edge of the side wall71, the cover8includes a semi-circular carrying handle76which is pivotable about two diametrically opposite bosses78between a first, stowed position, in which the handle76fits into a complementary shaped recess80on upper peripheral edge of the cover8, and a deployed position in which it extends upwardly, (shown ghosted inFIG. 1). In the stowed position, the handle maintains the ‘clean’ circular profile of the cover8and is unobtrusive to the use during normal operation of the robot2. Also, in this position the handle76serves to lock a rear filter door (not shown) of the robot into a closed position which prevents accidental removal of the filter door when the robot2is operating.

In operation, the robot2is capable of propelling itself about its environment autonomously, powered by a rechargeable battery pack (not shown) housed within the body6. To achieve this, the robot2carries an appropriate control means which is interfaced to the battery pack, the traction units20and appropriate sensor modules82comprising for example infrared and ultrasonic transmitters and receivers on the front left and right side of the body6. The sensor suite82provides the control means with information representative of the distance of the robot from various features in an environment and the size and shape of the features. Additionally the control means is interfaced to the suction fan motor and the brush bar motor in order to drive and control these components appropriately. The control means is therefore operable to control the traction units20in order to navigate the robot2around the room which is to be cleaned. It should be noted that the particular method of operating and navigating the robotic vacuum cleaner is not material to the invention and that several such control methods are known in the art. For example, one particular operating method is described in more detail in WO00/38025 in which navigation system a light detection apparatus is used. This permits the cleaner to locate itself in a room by identifying when the light levels detected by the light detector apparatus is the same or substantially the same as the light levels previously detected by the light detector apparatus.

Having described the chassis4, body6and cover8, the traction units20will now be described in further detail with reference toFIGS. 6 to 10which show various perspective, sectional, and exploded views of a single traction unit20for clarity.

In overview, the traction unit20comprises a transmission case90, a linkage member92or ‘swing arm’, first and second pulley wheels94,96, and track or continuous belt98that is constrained around the pulley wheels94,96.

The transmission case90houses a gear system which extends between an input motor drive module100mounted on an inboard side of one end of the transmission case90, and an output drive shaft102that protrudes from the drive side of the transmission case90, that is to say from the other side of the transmission case90to which the motor module100is mounted. The motor module100in this embodiment is a brushless DC motor since such a motor is reliable and efficient, although this does not preclude other types of motors from being used, for example brushed DC motors, stepper motors or even hydraulic drives. As has been mentioned, the motor module100is interfaced with the control means to receive power and control signals and is provided with an integral electrical connector104for this purpose. The gear system in this embodiment is a gear wheel arrangement which gears down the speed of the motor module100whilst increasing available torque, since such a system is reliable, compact and lightweight. However, other gearing arrangements are envisaged within the context of the invention such as a belt or hydraulic transmission arrangement.

The traction unit20therefore brings together the drive, gearing and floor engaging functions into a self-contained and independently driven unit and is readily mounted to the chassis4by way of a plurality of fasteners91(four fasteners in this embodiment), for example screws or bolts, that are received into corresponding mounting lugs93defined around the recess of the chassis4.

The traction unit20is mountable to the chassis so that the first pulley wheel94is in a leading position when the robot2is traveling forwards. In this embodiment, the lead wheel94is the driven wheel and includes a centre bore104which is receivable onto the drive shaft102by way of a press fit. Alternative ways of securing the pulley wheel to the shaft are also envisaged, such as a part-circular clip (‘circlip’) attached to the shaft102. The leading wheel94may also be considered a sprocket since it is the driven wheel in the pair. In order to improve the transfer of drive force from the drive shaft102to the lead wheel94, the centre bore104of the pulley wheel may be internally keyed to mate with a corresponding external key on the drive shaft.

The swing arm92includes a leading end that is mounted to the transmission case90between it and the lead wheel94and is mounted so as to pivot about the drive shaft102. A bush106located in a mounting aperture108of the swing arm92is received on an outwardly projecting spigot110of the transmission case90through which the drive shaft102protrudes. The bush106therefore provides a bearing surface intermediate the spigot110and the swing arm92to allow the swing arm92to pivot smoothly and to prevent splaying relative to the transmission case90. The bush106is made preferably from a suitable engineering plastics such as polyamide which provides the required low friction surface yet high strength. However, the bush106may also be made out of metal such as aluminum, steel, or alloys thereof, which would also provide the necessary frictional and strength characteristics.

As shown in the assembled views, the swing arm92is mounted on the spigot110and the lead wheel94is mounted to the drive shaft102outboard of the leading end of the swing arm92. A stub axle112is press fit into a bore located on the opposite or ‘trailing’ end of the swing arm92and defines a mounting shaft for the rear pulley wheel96, or ‘trailing wheel’ along a rotational axis parallel to the axis of the drive shaft102. The trailing wheel96includes a centre bore113in which a bearing bush114is received in a press fit. The bush114is received over the axle112in a sliding fit so that the bush, and therefore also the trailing wheel96, are rotatable relative to the swing arm92. A circlip116secures the trailing wheel to the axle112.

The continuous belt or track98provides the interface between the robot2and the floor surface and, in this embodiment, is a tough rubberized material that provides the robot with high grip as the robot travels over the surface and negotiates changes in the surface texture and contours. Although not shown in the figures, the belt98may be provided with a tread pattern in order to increase traction over textured or rough terrain.

Similarly, although not shown in the figures, the inner surface98aof the belt98is serrated or toothed so as to engage with a complementary tooth formation94aprovided on the circumferential surface of the leading wheel94which reduces the likelihood of the belt98slipping on the wheel94. In this embodiment, the trailing wheel96does not carry a complementary tooth formation, although this could be provided if desired. To guard against the belt98slipping off the trailing wheel96, circumferential lips96a,96bare provided on its inner and outer rims. As for the leading wheel94, a circumferential lip94bis provided on only its outer rim since the belt98cannot slip off the inner rim due to the adjacent portion of the swing arm92.

As will be appreciated, the swing arm92fixes the leading and trailing wheels94,96in a spaced relationship and permits the trailing wheel96to swing angularly about the leading wheel94. The maximum and minimum limits of angular travel of the swing arm92are defined by opposed arch-shaped upper and lower stops122a,122bthat protrude from the drive side of the transmission case90. A stub or pin124extending from the in-board side of the swing arm92is engagable with the stops122a,122bto delimit the travel of the swing arm92.

The traction unit20also comprises swing arm biasing means in the form of a coil spring118that is mounted in tension between a mounting bracket126extending upwardly from the leading portion of the swing arm92and a pin128projecting from the trailing portion of the transmission case90. The spring118acts to bias the trailing wheel96into engagement with the floor surface, in use, and so improves traction when the robot2is negotiating an uneven surface such as a thick-pile carpet or climbing over obstacles such as electrical cables.FIG. 10shows three exemplary positions of the traction unit20throughout the range of movement of the swing arm92.

FIG. 7shows the relative position of the wheels94,96with respect to the floor surface F when the robot2is at rest, and in which position the swing arm92is at its minimum limit of travel, the pin124being engaged with the upper stop122a. In this position, a portion of the track98around the trailing wheel96defines a contact patch130with the floor surface whereas a portion of the track98forward of the contact patch and extending to the leading wheel is inclined relative to the floor surface F due to the larger radius of the trailing wheel96compared to the leading wheel94. This provides the traction unit20with a ramped climbing surface which improves the ability of the robot2to climb over imperfections in the floor surface, as well as over raised obstacles such as electrical cables/flexes or edges of rugs for example. As an alternative, it should be appreciated that the wheels94,96may also be similarly sized, or even equally sized, and mounted at different heights, either on the swing arm92or alternatively in fixed positions relative to the chassis4in order to provide a forward-facing ramped climbing surface in the direction of movement.

In addition to the improvement in climbing ability of the inclined track98compared to a simple wheel, the traction unit20maintains a small contact patch130by virtue of its single trailing wheel96which provides a maneuvering benefit since it does not suffer the extent of slippage that would be experienced if a significant portion of the track98was in contact with the floor surface.

A further traction enhancement is provided by the outer lip96bof the trailing wheel96which extends radially outwards further than the lip96aon the inboard side of the wheel96. As shown clearly inFIG. 8, the outer lip96bextends almost to the same radius as the outer surface of the track98and its edge is provided with a toothed or serrated formation. A benefit of this is that, in circumstances in which the robot is travelling over a soft surface such as a rug or carpet, the track98will tend to sink into the pile of the carpet whereby the serrated edge of the outer lip96bwill engage the carpet and provide the robot with increased traction. However, on hard surfaces, only the track98will contact the floor surface which will benefit the maneuvering ability of the robot.

A still further benefit is that the track arrangement provides the climbing ability of a much larger single wheel, but without the large dimension which allows the brush bar to be positioned very near to the lateral axis of the robot which is important in providing full width cleaning. As seen in this embodiment, the rotational axis of the trailing wheel96is substantially in line with the lateral axis of the robot which benefits maneuverability. The cleaner head is able to be positioned very close to the traction units20, and in this embodiment the axis of the cleaner head is spaced approximately 48 mm from the lateral axis of the robot, although it is envisaged that a spacing of up to 60 mm would be acceptable in order to minimise the amount that the cleaner head projects from the outer envelope of the main body.

In an alternative embodiment (not shown), the depth and the thickness of the outer lip96bis increased such that the surface of the lip96blies side by side with the outer surface of the track98surrounding the trailing wheel96, in effect providing a transverse extension of the surface of the track98. This increases the area of the contact patch130also on hard surfaces which may be desirable in some circumstances. In this embodiment, it should be appreciated that the climbing ability is also retained by the inclined track surface without increasing the contact patch in the longitudinal direction of the track98.

As has been explained, the traction units20of the robot2provide an improved ability to travel over deep pile rugs and carpets, and also to negotiate obstacles such as electrical cables on the floor and also small steps between floor surfaces. However, ‘caterpillar’ type drive units can be vulnerable to ingress of debris in the nip between the wheels and the belt. To guard against this, the swing arm92further includes a raised block-like portion132that extends outwardly from the swing arm92in the space bounded by the opposing parts of the leading and trailing wheels94,96and the inner surface of the track98. Side surfaces132a,132b,132c,132dof the debris guard block132are shaped to sit closely next to the adjacent surfaces of the wheels94,96and the belt98whilst an outboard surface134of the block132terminates approximately in line with the outer faces of the wheels94,96. The block132is therefore shaped to accommodate substantially all of the volume between the wheels94,96and so prevents debris such as grit or stones from fouling the drive arrangement. Although the block132could be solid, in this embodiment the block132includes openings136which reduce the weight of the spring arm92and also its cost. Although the block132preferably is integral with the swing arm92, it could also be a separate component fixed appropriately to the swing arm92, for example by clips, screws or adhesive.

Referring now toFIGS. 11, 12 and 13, these illustrate how the body6is attached to the chassis4to enable relative sliding movement between one another and how this relative moment is interpreted by the robot2to gather information about collisions with objects in its path.

To enable relative sliding movement between the chassis4and the body6, front and rear engagement means fix the chassis4and the body6together so that they cannot be separated in the vertical direction, in a direction normal to the lateral and longitudinal axes X, L of the robot2, but are permitted to slide with respect to one another by a small amount.

Turning firstly to the front portion of the main body, as best illustrated inFIG. 12, a front engagement means includes a slot-like opening140which is generally oval in form like a racetrack/stadium or a para-truncated circle that is defined in the front portion of the body6, specifically in a central position in the platform48. A slidable pivoting member in the form of a gudgeon pin142is received through the opening140and includes a sleeve section142athat extends a short way below the opening140and which defines an upper flange142bwhich bears against the sides of the opening and so prevents the gudgeon pin142passing through it.

The engagement means also includes a complementary structure on the forward portion of the chassis4in the form of a walled-recess144, which is also racetrack shaped to correspond to the shape of the opening140in the platform48. The body6is mountable on the chassis4so that the opening140on the platform140body6overlies the recess144in the chassis4. The gudgeon pin142is then secured to the floor of the recess144by a suitable mechanical fastener such as a screw; the gudgeon pin142is shown ghosted in its position in the recess144inFIG. 11. The body6is therefore joined to the chassis4against vertical separation. However, since the gudgeon pin142is fixed immovably to the chassis4whilst being held slidably in the opening140, the body6can slide relative to the gudgeon pin142and can pivot angularly about it due to its rounded shape.

The forward portion of the chassis4also includes two channels145, one located on either side of the recess144, which serve as a supporting surface for respective rollers147provided on the underside of the body6and, more specifically, on the platform48either side of the opening140. The rollers147provide support for the body6on the chassis4and promote smooth sliding movement between the two parts and are shown in ghosted form inFIG. 11.

The rear engagement means constrains movement of a rear portion150of the body6relative to the chassis4. From a comparison betweenFIG. 12andFIG. 13, it can be seen that a rear portion146of the chassis4behind the cleaner head24includes a bump detection means148which also serves as a secure mounting by which means the rear portion150of the body6is connected to the chassis4.

Each side of the bump detection means includes a body support means; both body support means are identical and so only one will be described in detail for brevity. The body support means comprises a sleeve-like tubular supporting member152that sits in a dished recess154defined in the chassis154. In this embodiment, the dished recess154is provided in a removable chassis portion in the form of a plate member155that is fixed across the rear portion146of the chassis4. However, the recesses154could equally be an integral part of the chassis4.

A spring156is connected to the chassis154at its lower end and extends through the sleeve member152, wherein the end of the spring terminates in an eyelet158. The sleeve152and the spring156engage with a complementary socket160on the underside of the body6, which socket160includes a raised wall160awith which the upper end of the sleeve152locates when the body6is mounted onto the chassis4. When mounted in this way, the spring156extends into a central opening162in the socket160and the eyelet158is secured to a securing pin within the body6. Note that the securing pin is not shown in the figures, but may be any pin or suitable securing point to which the spring156can attach.

Since the supporting sleeve members152are movably mounted between the chassis4and the body6, the sleeve members152can tilt in any direction which enables the body6to ‘rock’ linearly along the longitudinal axis ‘L’ of the robot, but also for the rear portion of the body6to swing angularly, pivoting about the gudgeon pin142by approximately 10 degrees as constrained by the rear engagement means as will now be explained further. In this embodiment, the springs156provide a self-centering force to the supporting sleeve members152which urge the sleeves members152into an upright position, this action also providing a resetting force for the bump detection system. In an alternative embodiment (not shown), the supporting sleeve members152could be solid, and a force to ‘reset’ the position of the body relative to the chassis could be provided by an alternative biasing mechanism.

Although the sleeve members152allow the body6to ‘ride’ on the chassis4with a certain amount of lateral movement, they do not securely connect the rear portion150of the body6to the chassis4against vertical separation. For this purpose, the bump detection means148includes first and second guiding members in the form of posts or rods160,162provided on the body6which engage with respective pins164,166provided on the chassis4. As can be seen inFIG. 13, the pins164,166extend through respective windows168,170defined in the plate member155and are retained there by a respective washer172,174. In order to mount the rear portion150of the body6onto the rear portion146of the chassis4, the guiding members160,162are push fit onto the pins164,166until they contact their respective washer172,174. The movement of the rear portion150of the body6is therefore constrained to conform to the shape of the windows168,170such that the windows serves as a guiding track. In this embodiment, the windows168,170are generally triangular in shape and so this will permit the body6to slide linearly with respect to the gudgeon pin142but also to swing angularly about it within the travel limits set by the windows168,170. However, it should be noted that the permitted movement of the body6can be altered by appropriate re-shaping of the windows168,170.

The bump detection means148also includes a switching means180to detect movement of the body6relative to the chassis4. The switching means180includes first and second miniature snap-action switches180a,180b(also commonly known as ‘micro switches’) provided on the underside of the rear portion150of the body6that, when the body6is mounted to the chassis4, are located either side of an actuator182provided in a central part of the rear portion146of the chassis4. In this embodiment, the actuator182takes the form of a wedge-shape having angled leading edges for activating the switches180a,180b. Although not shown in the Figures, the switches180a,180bare interfaced with the control means of the robot. The location of the switches180a,180brelative to the wedge-shaped actuator182is shown inFIG. 13; note that the switches180a,180bare shown in dotted lines. As can be seen, the switches180a,180bare positioned such that their activating arms183are positioned directly adjacent and either side of the angled forward edges of the wedge-shaped actuator182.

The switches180a,180bare activated in circumstances where the robot2collides with an obstacle when the robot is navigating around a room on cleaning task. Such a bump detection facility is desirable for an autonomous vacuum cleaner since sensing and mapping systems of such robots can be fallible and sometimes an obstacle will not be detected in time. Other robotic vacuum cleaners operate on a ‘random bounce’ methodology in which a means to detect a collision is essential. Therefore, a bump detection facility is needed to detect collisions so that a robot can take evasive action. For example the control means may determine simply to reverse the robot and then to resume forward movement in a different direction or, alternatively to stop forward movement, to turn 90° or 180° and then to resume forward movement once again.

Activation of the switches180a,180bwill now be explained with reference toFIGS. 14a, 14b, 14cand 14d, which show a schematic representation of the chassis4, body,6and bump detection means in different bump situations. In the following figures, the parts common with the previous figures are referred to with the same reference numerals.

FIG. 14ashows the relative positions of the body6, the chassis4, the gudgeon pin142, the body pivot opening140, the switches180a,180band the wedge-shaped actuator182in a non-collision position. As can be seen, neither switch180a,180bhas been activated as indicated by the reference ‘X’.

FIG. 14bshows the robot2in a collision with an obstacle in the ‘dead ahead’ position, as indicated by the arrow C. The body6is caused to move backward linearly, that is to say along its longitudinal axis L and, accordingly, the two switches180a,180bare moved backwards with respect to the wedge-shaped actuator182thereby triggering the switches180a,180bsubstantially at the same time as indicated by the check marks.

Alternatively, if the robot2collides with an obstacle on its right hand side, as indicated by the arrow C inFIG. 14c, the body6will be caused to swing about the gudgeon pin142to the left and, in these circumstances, the switches180a,180bwill move to the left with respect to the actuator182with the result that the right hand switch180bis activated before activation of the left hand switch180aas indicated by the check mark for switch180b.

Conversely, if the robot2collides with an obstacle on its left hand side, as indicated by the arrow C inFIG. 14d, the body6will be caused to swing to the right, in which case the switches180a,180bwill move to the right with respect to the actuator182, which therefore triggers the left hand switch180abefore the right hand switch180bas indicated by the check mark for switch180a.

Although in the oblique angle collisions shown inFIGS. 14cand 14donly one of the switches180a,180bis shown as activated, it should be appreciated that such a collision may also activate the other one of the switches, albeit at a later time than the first activated switch.

Since the switches180a,180bare interfaced to the control means of the robot, the control means can discern the direction of impact by monitoring the triggering of the switches180a,180b, and the relative timing between triggering events of the switches.

Since the robot2is able to detect collisions by sensing relative linear and angular movement between the body6and the chassis4, the invention avoids the need to mount a bump shell onto the front of the robot as is common with known robotic vacuum cleaners. Bump shells can be fragile and bulky so the invention increases the robustness of the robot and also makes possible a reduction in size and complexity.

Turning now toFIG. 15, this shows schematically the control means of the robot and its interfaces with the components described above. Control means in the form of a controller200includes appropriate control circuitry and processing functionality to process signals received from its various sensors and to drive the robot2in a suitable manner. The controller200is interfaced into the sensor suite82of the robot2by which means the robot gathers information about its immediate environment in order to map its environment and plan an optimum route for cleaning. A memory module201is provided for the controller to carry outs its processing functionality and it should be appreciated that the memory module201could alternatively be integrated into the controller200instead of being a separate component as shown here.

The controller200also has suitable inputs from the user interface70, the bump detection means206and suitable rotational sensing means208such as rotary encoders provided on the traction units20. Power and control inputs are provided to the traction units20from the controller200and also to the suction motor210and the brush bar motor212.

Finally, a power input is provided to the controller200from the battery pack214and a charger interface216is provided by which means the controller200can carry out charging of the battery pack214when the battery supply voltage has dropped below a suitable threshold.

Many variations are possible without departing from the inventive concept. For example, although the traction units20have been described as having a continuous rubberized belt or track, the invention could also be performed with a track that comprises numerous discrete track or tread sections linked together to form a chain.

In the embodiment above, the body6has been described as being able to move linearly as well as angularly about the chassis. However, it should be appreciated that this is such that collisions can be detected from a wide range of angles and that the invention resides also in a bump detection system in which the body moves linearly or angularly to the chassis instead of a combination of such movement.

The sensing means has been described as comprising snap-action switches disposed either side of a wedge-shaped actuator and that such an arrangement conveniently enables the switches to be activated when the body moves linearly (both switches activated simultaneously) or angularly (one switch activated before the other). However, the skilled person will appreciate that other switch mechanisms are possible, for example contactless switches such as a light-gate switch, or a magnetic/Hall effect switch.