FIELD OF THE INVENTION

The present invention relates to a cleaner head, as well as to a drive assembly and to a method of controlling an electric motor.

BACKGROUND OF THE INVENTION

The cleaner head of a cleaning appliance, such as a vacuum cleaner, may comprise an agitator for agitating a surface to be cleaned. With use, bacteria may grow on the agitator and/or debris, such as hair and long fibres, may accumulate on the agitator. The agitator may therefore be removed and cleaned.

SUMMARY OF THE INVENTION

In a first aspect, the present invention provides a cleaner head comprising: an agitator; and a drive assembly for driving the agitator, the drive assembly comprising an electric motor, a transmission for transmitting torque generated by the electric motor to the agitator, and a control unit for controlling the electric motor, wherein: the control unit is operable in one of a first mode and a second mode; in the first mode, the control unit applies a first pulsed voltage to the electric motor continuously over a drive period to cause the agitator to rotate at a first speed; and in the second mode, the control unit applies a second pulsed voltage to the electric motor discontinuously over the drive period to cause the agitator to rotate at a second lower speed.

The control unit may operate in the first mode during normal operation of the cleaner head. The agitator is then driven at the higher first speed to achieve good cleaning results. The control unit may then operate in the second mode during maintenance of the cleaner head. During maintenance, it may be desirable to drive the agitator at a relatively low speed For example, the agitator may be illuminated with high-intensity narrow- spectrum (HINS) or ultraviolet (UV) light in order to sterilise the agitator. By rotating the agitator at a relatively low speed, bacteria may be exposed to the light for a longer dwell period and thus a higher sterilisation efficiency may be achieved. In another example, a user may wish to inspect the slowly rotating agitator for damage or trapped debris. In a further example, a debris removal tool may be used to remove trapped debris, such as hair and long fibres, from the agitator and a relatively low speed may be required for safe operation of the tool.

By applying the second pulsed voltage to the electric motor discontinuously over the drive period, relatively low speeds can be achieved without stalling. In particular, the second pulsed voltage may be applied during a first part of the drive period to generate sufficient torque to cause the agitator to rotate. The second pulsed voltage may then be suspended (i.e., no voltage is applied to the electric motor) during a second part of the drive period. The net effect is that the rotation of the agitator is stepped. An alternative approach to achieving a lower rotation speed would be to apply the second pulsed voltage continuously over the drive period and to reduce the duty of the pulsed voltage. The torque generated by the electric motor would then be continuous rather than discontinuous over the drive period. Consequently, for a given speed of rotation, the instantaneous torque generated by the electric motor would be lower. Accordingly, for a given stall torque, the electric motor and agitator would stall at a higher rotational speed. By contrast, the control unit applies the second pulsed voltage to the electric motor discontinuously. As a result, a higher instantaneous torque may be generated over the first part of the drive period. Accordingly, for the same stall torque, lower speeds are possible without stalling.

In the second mode, the drive period may comprise an ON period and an OFF period. The control unit may then apply the second pulsed voltage to the electric motor over the ON period, and the control unit may apply no voltage to the electric motor over the OFF period. Torque is then generated during the ON period only. As a result, a relatively low second speed may be achieved without stalling. The relative lengths of the ON and the OFF periods may then be defined so as to achieve a particular stall-free speed of rotation.

The ON period may have a duty that is no greater than 10%. That is to say that the ON period is no greater than 10% of the drive period, and thus the OFF period is no less than 90% of the drive period. As a result, a relatively low, stall-free second speed of rotation may be achieved. For example, if the first and second pulsed voltages have the same frequencies and duties, the second speed may be at least ten times slower than the first speed. The ON period may have a duty that is no greater than 1%. As a result, the second speed may be at least a hundred times slower than the first speed. The second pulsed voltage may have a duty that is constant. That is to say that, over the part of the drive period when the second pulsed voltage is applied, the duty of the second pulsed voltage may be constant. As a result, a given torque may be generated for a lower maximum instantaneous current. Accordingly, where the motor is a brushed motor, sparking between the brushes and the commutator, which can significantly increase wear, may be avoided.

The first pulsed voltage and the second pulsed voltage may have the same frequency. As a result, the two pulsed voltages may be generated in a relatively simple and cost-effective manner. For example, the pulsed voltages may be generated using the same PWM module having a fixed frequency.

The control unit may pulse a supply voltage to generate each of the first pulsed voltage and the second pulsed voltage, and the control unit may vary one or more of a duty of the first pulsed voltage and a duty of the second pulsed voltage in response to changes in a magnitude of the supply voltage. As the magnitude of the supply voltage changes, the electrical power drawn by the electric motor will vary for a given duty of the pulsed voltage. Accordingly, by varying the duty of the pulsed voltage in response to changes in the supply voltage, better control over the torque and/or speed of the electric motor and the agitator may be achieved.

The control unit may increase one or more of the duty of the first pulsed voltage and the duty of the second pulsed voltage in response to a decrease in the magnitude of the supply voltage. As the magnitude of the supply voltage decreases, the electrical power drawn by the electric motor will decrease for a given duty of the pulsed voltage. Consequently, when operating in the first mode, the rotational speed of the agitator will be lower for a given load. Additionally, or alternatively, when operating in the second mode, the torque generated will be lower for a given speed of rotation. By increasing the duty of the pulsed voltage, the decrease in speed and/or torque arising from the decrease in the supply voltage may be mitigated. For example, the control unit may increase the duty such that the electrical power drawn by the electric motor is constant in the first mode and/or the second mode.

A magnitude of the second pulsed voltage may have a time-averaged value, and the control unit may vary the duty of the second pulsed voltage, in response to changes in the magnitude of the supply voltage, such that the time-averaged value is constant. As a result, the electrical power drawn by the electric motor, and thus the torque generated by the electric motor, is constant in the second mode. Stalling of the agitator therefore continues to be averted should the magnitude of the supply voltage change.

A magnitude of the second pulsed voltage may have a time-averaged value no greater than 10 V As a result, sufficient torque may be generated to drive the agitator without drawing excessive instantaneous current, which might otherwise result in sparking between the brushes and the commutator of the motor.

The second speed may be at least ten times lower than the first speed. Accordingly, when operating in the first mode (e.g., during normal operation), the agitator may be driven at a relatively high speed to achieve good cleaning results. The agitator may then be driven at a relatively low speed (i.e., at least ten times slower than the first speed) when operating in the second mode so as to achieve effective maintenance of the agitator.

The second speed may be at least one hundred times lower than the first speed. As a result, relatively low speeds can be achieved in the second mode without compromising the cleaning performance of the agitator when operating in the first mode. For example, when the cleaner head forms part of a vacuum cleaner, the agitator (when unloaded) may rotate at, say, 1200 rpm when operating in the first mode. At this speed, relatively good agitation of dirt and debris can be achieved on different floor surfaces (e.g., hard floor and carpeted surfaces). The agitator may then rotate at, say, 1 rpm when operating in the second mode. At this speed, the agitator may be illuminated with HINS or UV light in order to sterilise the agitator, and bacteria may be exposed to the light for a relatively long dwell period. As a result, a relatively high sterilisation efficiency may be achieved. Alternatively, a user may safely inspect the agitator and/or use a debris removal tool at this rotation speed.

When the agitator is unloaded, the first speed may be no less than 800 rpm and the second speed may be no greater than 50 rpm. As a result, relatively good cleaning performance may be achieved when operating in the first mode, and effective maintenance of the agitator may be achieved when operating in the second mode. Maintenance of the agitator may comprise illuminating the agitator with HINS or UV light in order to sterilise the agitator. At speeds in excess of 50 rpm, the dwell time of bacteria exposed to the light may be relatively short. As a result, a high sterilisation efficiency may be difficult to achieve without using a higher power HINS or UV source, which then has potential safety implications, and/or significantly increasing the overall sterilisation time, which then reduces the power efficiency.

The second speed may be no greater than 10 rpm. Moreover, the second speed may be around 1 rpm. Where the agitator is illuminated with HINS or UV light in order to sterilise the agitator, bacteria may be exposed to the light for a relatively long dwell period at these rotation speeds. As a result, a relatively high sterilisation efficiency may be achieved using a relatively low power light source. Alternatively, a user may safely inspect the agitator and/or use a debris removal tool at these rotation speeds.

When operating in the second mode, the acceleration and deceleration of the electric motor and the agitator may generate noise that is audible to a user. This noise would then be repeated every drive period. The drive period may therefore be around one second. As a result, the generated noise may resemble the ticking of a clock and thus may be more agreeable to a user.

The cleaner head may comprise a light source to illuminate the agitator with HINS or UV light, and the control unit may be operable to power on the light source when operating in the second mode. Furthermore, the control unit may be operable to power off the light source when operating in the first mode. As a result, the agitator may be sterilised whenever the cleaner head is not in use.

The control unit may be operable to: determine if the cleaner head is received in a docking station; operate in the first mode in response to determining that the cleaner head is not received in the docking station; and operate in the second mode in response to determining that the cleaner head is received in the docking station. Maintenance of the cleaner head may therefore be performed when the cleaner head is received in the docking station. For example, the docking station and/or the cleaner head may comprise a HINS or UV source to illuminate and sterilise the agitator, and the light source may be powered on only when the cleaner head is received in the docking station. In another example, the docking station may comprise a debris removal tool for removing trapped debris, such as hair and long fibres, from the agitator.

In a second aspect, the present invention provides a cleaning appliance comprising an agitator; and a drive assembly for driving the agitator, the drive assembly comprising an electric motor, a transmission for transmitting torque generated by the electric motor to the agitator, and a control unit for controlling the electric motor, wherein: the control unit is operable in one of a first mode and a second mode; in the first mode, the control unit applies a first pulsed voltage to the electric motor continuously over a drive period to cause the agitator to rotate at a first speed; and in the second mode, the control unit applies a second pulsed voltage to the electric motor discontinuously over the drive period to cause the agitator to rotate at a second lower speed.

In a third aspect, the present invention provides an assembly comprising a cleaner head or a cleaning appliance according to the first aspect or the second aspect, and a docking station for receiving the cleaner head or the cleaning appliance, wherein the control unit is operable in the first mode when the cleaner head or the cleaning appliance is not received in the docking station, and the control unit is operable in the second mode when the cleaner head or the cleaning appliance is received in the docking station.

The docking station may then be used, for example, to performance maintenance on the agitator. For example, the docking station may comprise a light source for sterilising the agitator using HINS or UV light. In another example, the docking station may comprise a debris removal tool for removing trapped debris, such as hair and long fibres, from the agitator.

The docking station may comprise a light source to illuminate the agitator with HINS or UV light and thus sterilise the agitator. By causing the agitator to rotate at the lower second speed when the cleaner head or the cleaning appliance is received in the docking station, bacteria present on the agitator may be exposed to the light for a longer dwell period and thus a higher sterilisation efficiency may be achieved. In a fourth aspect, the present invention provides a drive assembly comprising an electric motor and a control unit for controlling the electric motor, wherein: the control unit is operable in one of a first mode and a second mode; in the first mode, the control unit applies a first pulsed voltage to the electric motor continuously over a drive period to cause the electric motor to rotate at a first speed; and in the second mode, the control unit applies a second pulsed voltage to the electric motor discontinuously over the drive period to cause the electric motor to rotate at a second lower speed.

In a fifth aspect, the present invention provides a method of controlling an electric motor comprising: selecting one of a first mode and a second mode; in the first mode, applying a first pulsed voltage to the electric motor continuously over a drive period to cause the electric motor to rotate at a first speed; and in the second mode, applying a second pulsed voltage to the electric motor discontinuously over the drive period to cause the electric motor to rotate at a second lower speed.

Features described above in connection with the first aspect of the present invention are equally applicable to the other aspects of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is an isometric view of a cleaner head;

Figure 2 is a front section view through the cleaner head;

Figure 3 is a schematic of a control unit of the cleaner head;

Figure 4 illustrates (a) a first pulsed voltage and (b) a second pulsed voltage applied by the control unit to an electric motor of the cleaner head; and

Figure 5 is a simplified side section view through an assembly comprising the cleaner head and a docking station.

DETAILED DESCRIPTION OF THE INVENTION

The cleaner head 10 of Figures 1 and 2 comprises a main body 20 to which a neck 30 is pivotally attached. The main body 20 comprises a housing 40, an agitator 50, and a drive assembly 60.

The agitator 50 is rotatably mounted to the housing 40 and comprises a body to which means for agitating a surface are attached. In this example, the agitator 50 takes the form of a brushbar and comprises a cylindrical body 51 to which a plurality of bristle strips 52 and a plurality of plush strips 53 are attached. The bristles strips 52 and the plush strips 53 are each arranged helically about the body 51. In other examples, the agitator 50 may comprise an alternatively shaped body and/or alternative means for agitating the cleaning surface. By way of example, the body of the agitator may be conical, such as that described in GB2584445A, or curved such as that described in GB2588957A.

The drive assembly 60 is responsible for driving the agitator 50, i.e., causing the agitator 50 to rotate relative to the housing 40. The drive assembly 60 comprises an electric motor 61, a transmission 62,63 for transmitting torque generated by the electric motor 61 to the agitator 50, and a control unit 64 for controlling the electric motor 61. In this particular example, the drive assembly 60 is located inside the agitator 50. Furthermore, the electric motor 61 is a brushed DC motor, and the transmission comprises a gear train 62 and a drive dog 63 that engages with an interior feature of the body 51. In other examples, the drive assembly 60 may be located (wholly or in part) outside the agitator 50, the electric motor 61 may a different type of the motor that can be driven using a pulsed voltage (discussed further below), and the transmission 62,63 may comprise an alternative arrangement. For example, the transmission 62,63 may comprise a belt and pulley system.

The neck 30 is pivotally attached at a first end to the housing 40. A second, free end of the neck 30 is attachable to a cleaning appliance (not shown), such as a vacuum cleaner. The cleaning appliance is then used to manoeuvre the cleaner head 10 over a surface to be cleaned. The neck 30 comprises electrical terminals 31 that are electrically coupled to the electric motor 61 and the control unit 64. When attached to the cleaning appliance, the electrical terminals 31 couple with corresponding electrical terminals on the cleaning appliance such that electrical power is supplied to the electric motor 61 and the control unit 64 by the cleaning appliance. The electrical terminals 31 may also be used to transmit control signals between the cleaning appliance and the control unit 64. Referring now to Figure 3, the control unit 64 comprises a switch 66, a freewheel diode 67, and a controller 68. The switch 66 is coupled in series with the electric motor 61 between a supply voltage, Vs, and ground. Accordingly, when the switch 66 is closed, the supply voltage is applied to the electric motor 61, and when the switch 66 is open, no voltage is applied to the electric motor 61. The freewheel diode 67 is coupled in parallel with the electric motor 61 and enables current in the motor 61 to freewheel when the switch 66 is open. The controller 68 controls the switch 66 by means of a control signal, e g., SI or S2.

The controller 68, and thus the control unit 64, is operable in one of a first mode and a second mode. The controller 68 may operate in the first mode or the second mode in response to an input signal. For example, the cleaning appliance may transmit a control signal to the controller 68 which, in response, operates in either the first mode or the second mode. In both modes, the control unit 64 applies a pulsed voltage to the electric motor 61, which in turn causes the electric motor 61 and thus the agitator 50 to rotate.

When operating in the first mode, the controller 68 outputs a first control signal, SI, to the switch 66. The first control signal is a continuous PWM signal. As a result, a first pulsed voltage is applied continuously to the electric motor 61. The duty of the PWM signal, and thus the duty of the first pulsed voltage, determines the electrical input power of the motor 61, and thus the speed of the motor 61 for a given load. In this particular example, when the control unit 64 operates in the first mode, the agitator 50 is driven at a speed of around 1200 rpm when unloaded (e.g., when the cleaner head 10 is lifted from the cleaning surface, and the agitator 50 is free to rotate in air).

In this example, the agitator 50 is driven at a single unloaded speed when the control unit 64 operates in the first mode. In other examples, the agitator 50 may be driven at different unloaded speeds. For example, the control unit 64 may comprise a selector, such as a switch or dial, which a user may interact with to select different speeds. For example, in its simplest form, a user may select between high and low speeds. In response to the setting of the selector, the controller 68 may adjust the duty of the first control signal, and thus the duty of the first pulsed voltage, such that the agitator 50 is driven at a different unloaded speed. In another example, the selector may be provided on the cleaning appliance, and the setting of the selector may be transmitted to the controller 68 via the electrical terminals 31. When operating in the second mode, the controller 68 outputs a second control signal, S2, to the switch 66. The second control signal is discontinuous and comprises an ON period and an OFF period, which then repeat. The second control signal is then pulsed during the ON period and is off during the OFF period. As a result, a second pulsed voltage is applied discontinuously to the electric motor 61.

As shown in Figure 4, each pair of ON and OFF periods may be regarded as defining a drive period. The control unit 64 then applies a discontinuous pulsed voltage over the drive period when operating in the second mode, as shown in Figure 4(b). By contrast, the control unit 64 applies a continuous pulsed voltage to the electric motor 61 over the same drive period when operating in the first mode, as shown in Figure 4(a). As a result, the agitator 50 rotates at a higher first speed when the control unit 64 operates in the first mode, and the agitator 50 rotates at a lower second speed when the control unit 64 operates in the second mode.

By applying the second pulsed voltage to the electric motor 61 discontinuously over the drive period, relatively low speeds can be achieved without stalling. In particular, the second pulsed voltage is applied during the ON period (or first part) of the drive period, which generates sufficient torque to cause the agitator 50 to rotate. The second pulsed voltage is then suspended during the OFF period (or second part) of the drive period, during which time no torque is generated and the agitator 50 stops rotating. The net effect is that the rotation of the agitator 50 is stepped.

An alternative approach to achieving a low rotation speed would be to apply the second pulsed voltage to the electric motor 61 continuously, as with the first pulsed voltage, and to reduce the duty of the second pulsed voltage. The torque generated by the electric motor 61 would then be continuous rather than discontinuous. Consequently, for a given speed of rotation, the instantaneous torque generated by the electric motor 61 would be lower. Accordingly, for a given stall torque, the electric motor 61 and the agitator 50 would stall at a higher rotational speed. By contrast, the control unit 64 employs a second pulsed voltage having a relatively high duty, which is then applied discontinuously to the electric motor 61. As a result, a higher instantaneous torque is generated during the ON period, which is sufficient to overcome the stall torque. No torque is then generated during the OFF period such that a relatively low net rotation speed is achieved. Accordingly, for the same stall torque, significantly lower speeds are possible.

The length of the ON period and the duty of the pulsed voltage applied during the ON period are selected such that the torque generated by the electric motor 61 is greater than the stall torque. The length of the drive period is then selected to achieve a particular speed of rotation. In the present example, the length of the ON period is around 4 ms and the drive period is around 1 second. It will therefore be appreciated that the voltage waveforms illustrated in Figure 4 are not to scale and are intended only to illustrate the continuous and discontinuous nature of the two pulsed voltages. With this arrangement, the agitator 50 rotates at a speed of around 1 rpm. The speed of the agitator 50 is therefore significantly slower when operating in the second mode.

When operating in the second mode, the acceleration and deceleration of the electric motor 61 and the agitator 50 may generate noise that is audible to a user. This noise is then repeated every drive period. In this example, a drive period of around 1 second is selected. As a result, the generated noise resembles the ticking of a clock, which may be more agreeable to a user.

In order to more gradually accelerate and decelerate the electric motor 61 over each drive period, and thus reduce the aforementioned noise, the duty of the second pulsed voltage may be increased and decreased over the ON period (i.e., the duty may be ramped up and down). However, for a given generated torque, a higher maximum instantaneous current will be drawn by the electric motor 61. Sparking is then more likely to occur between the brushes and the commutator of the electric motor 61, which can significantly increase wear. Accordingly, in this example, the duty of the second pulsed voltage is constant. As a result, a given generated torque may be achieved for a lower maximum instantaneous current, thereby reducing or avoiding sparking.

Similarly, in order to avoid high instantaneous currents, the duty of the second pulsed voltage is selected such that the time-averaged value of the voltage (labelled VM in Figure 4) is no greater than a threshold. That is to say that second pulsed voltage, when averaged over the ON period, is no greater than a threshold. In the present example, the control unit 64 controls the duty of the second pulsed voltage such that the time-averaged value is no greater than 10 V. As a result, sufficient torque may be generated to drive the agitator 50 without drawing excessive instantaneous current, which might otherwise result in sparking between the brushes and the commutator of the motor 61 .

The supply voltage, Vs, may not be constant. Consequently, if the same duty is used for the pulsed voltage, the electrical power drawn by the electric motor 61, and thus the torque generated by the electric motor 61, will vary. The control unit 64 may therefore vary the duty of pulsed voltage, when operating in the first mode and/or the second mode, in response to changes in the supply voltage. For example, the controller 68 may receive an input signal indicative of the magnitude of the supply voltage, Vs, and vary the duty of the control signal, SI and/or S2, in response. As a result, better control may be achieved over the electrical input power and thus the torque of the motor 61 . In examples, the control unit 64 may vary the duty of the pulsed voltage such that the same electrical input power is drawn by the electric motor 61, and thus the same torque is generated by the electric motor 61, irrespective of the magnitude of the supply voltage.

The cleaning appliance, which is responsible for supplying electrical power to the cleaner head 10, may be battery-powered. As the battery pack of the cleaning appliance discharges, the supply voltage, Vs, will decrease. Consequently, if the same duty is used for the pulsed voltage, the torque generated by the electric motor 61, will decrease. When operating in the first mode, the decrease in torque will cause the rotational speed of the agitator 50 to decrease for a given load. As a result, the cleaning performance may worsen. When operating in the second mode, the decrease in torque may cause the electric motor 61 to stall (i.e., the torque generated during the ON period may be insufficient to overcome the stall torque). The control unit 64 may therefore increase the duty of the pulsed voltage, when operating in the first mode and/or the second mode, in response to a decrease in the magnitude of the supply voltage. As a result, the aforementioned effects may be mitigated. More particularly, the control unit 64 may increase the duty of the pulsed voltage such that, when operating in the first mode and/or the second mode, the time-averaged value of the pulsed voltage (labelled VM in Figure 4) is constant. As a result, the same electrical input power is drawn by the electric motor 61, and thus the same torque is generated, as the battery pack discharges. The same cleaning performance may therefore be achieved when operating in the first mode, and/or stalling of the motor 61 may continue to be averted when operating in the second mode.

When operating in both the first mode and the second mode, the frequency of the pulsed voltage is unchanged. That is to say that the first pulsed voltage and the second pulsed voltage have the same frequency. This then has the advantage that the pulsed voltages may be generated in a relatively simple and cost-effective manner In particular, the controller 68 can generate both pulsed control signals, SI and S2, using the same PWM module having a fixed frequency.

As noted above, the control unit 64 operates in the first mode during normal operation of the cleaner head 10, and operates in the second mode during maintenance of the cleaner head 10. The agitator 50 is then driven at a first higher speed in the first mode, and is driven at a second lower speed in the second mode. As a result, good cleaning results may be achieved in the first mode, whilst effective maintenance of the cleaner head 10 may be achieved in the second mode.

Maintenance of the cleaner head 10 may comprise sterilising the agitator 50. In particular, the agitator 50 may be illuminated with high-intensity narrow-spectrum (HINS) and/or ultraviolet (UV) light. By rotating the agitator 50 at a relatively low speed, bacteria on the agitator 50 may be exposed to the light for a longer dwell period and thus a higher sterilisation efficiency may be achieved. In another example, a user may wish to inspect the slowly rotating agitator 50 for damage or trapped debris. In a further example, a debris removal tool may be used to remove trapped debris, such as hair and long fibres, from the agitator 50 and a relatively low speed may be required for safe operation of the tool.

In the example described above, the rotational speed of the agitator 50 (when unloaded) is around 1200 rpm when operating in the first mode. As a result, relatively good agitation of dirt and debris can be achieved on different cleaning surfaces (e.g., hard floor and carpeted surfaces). When operating in the second mode, the rotational speed of the agitator 50 (when unloaded) is around 1 rpm. At this speed, should the agitator 50 be illuminated with HINS and/or UV light, bacteria may be exposed to the light for a relatively long dwell period. As a result, a relatively high sterilisation efficiency may be achieved. Alternatively, a user may safely inspect the agitator and/or use a debris removal tool at this rotation speed.

It will be appreciated that the agitator 50 may be driven at alternative speeds in the first mode and/or the second mode. Different speeds are possible by varying the duty of the pulsed voltages, as well as the duty of the ON period when operating in second mode. As already noted, by applying a discontinuous pulsed voltage to the electric motor 61 in the second mode, relatively low, stall-free speeds of rotation are possible. It is therefore possible to achieve a significant difference in speeds of the agitator 50 when operating in the first mode and the second mode For example, the speed of the agitator 50 when operating in the second mode may be at least a hundred times slower than that when operating in the first mode. Indeed, in the example described above, the speed of the agitator 50 when operating in the second mode (1 rpm) is over a thousand times slower than that when operating in the first mode (1200 rpm). The agitator 50 may therefore be driven at a relatively high speeds in the first mode to achieve good cleaning results, and at relatively low speeds when operating in the second mode to perform effective maintenance.

In some examples, the speed of the agitator 50 (unloaded) may be no less than 800 rpm when operating in the first mode, and may be no greater than 50 rpm when operating in the second mode. As a result, a relatively good cleaning performance may be achieved when operating in the first mode, whilst effective maintenance of the agitator 50 may be achieved when operating in the second mode. As noted, maintenance of the agitator 50 may comprise illuminating the agitator with HINS and/or UV light in order to sterilise the agitator 50. At speeds in excess of 50 rpm, the dwell time of bacteria exposed to the light may be relatively short. As a result, a high sterilisation efficiency may be difficult to achieve without using a higher power HINS and/or UV source, which then has potential safety implications. Additionally or alternatively, a longer sterilisation period may be required in order to achieve the same level of sterilisation. To this end, the speed of the agitator 50 may be no more than 10 rpm when operating in the second mode. As a result, a relatively high sterilisation efficiency may be achieved using a lower power source and/or a shorter sterilisation period.

Figure 5 illustrates an assembly 70 that comprises the cleaner head 10 and a docking station 80 for receiving the cleaner head 10. The docking station 80 comprises a main body 81, a power supply unit 82, a light source 83, and a control unit 84.

The power supply unit 82 is housed within the main body 81 and supplies electrical power from a mains power source to the light source 83 and the control unit 84.

The light source 83 comprises a strip of light-emitting diodes (LEDs) that emit sterilising light. In this example, the LEDs emit high-intensity narrow-spectrum (HINS) light having a wavelength of 405 nm. In other examples, the LEDs may emit HINS light of other wavelengths and/or ultraviolet (UV) light. For example, the LEDs may emit UV light having a wavelength of 222 nm. The light source 83 is located on the main body 81 such that, when the cleaner head 10 is received by the docking station 80, the light source 83 is located beneath and illuminates the underside of the agitator 50.

The control unit 84 is used to control (e.g., power on and off) the light source 83. More particularly, the control unit 84 is operable to control the light source 83 in response to an input signal.

In this example, the cleaner head 10 and the docking station 80 each comprises electrical contacts 69,89 that form an electrical connection when the cleaner head 10 is received by the docking station 80. The electrical contacts 69 of the cleaner head 10 are coupled to the electrical terminals 31. The cleaning appliance 10 is therefore able to determine when the cleaning head 10 is received by and correctly positioned in the docking station 80.

In response to determining that the cleaner head 10 is received in the docking station 80, the cleaning appliance may execute a sterilisation programme. A first control signal is transmitted by the cleaning appliance to the control unit 84 of the docking station 80, which in response powers on the light source 83. A second control signal is transmitted by the cleaning appliance to the control unit 64 of the cleaner head 10, which in response operates in the second mode. As a result, the agitator 50 rotates at the second slower speed. The cleaning appliance continues to transmit the control signals to the docking station 80 and the cleaner head 10 for a sterilisation period, which in this example is around 2 hours. At the end of the sterilisation period, the cleaning appliance stops transmitting the control signals. The control unit 84 of the docking station 80 then powers off the light source 83, and the control unit 64 of the cleaner head 10 powers off the electric motor 61.

The agitator 50 may therefore be sterilised when the cleaning appliance is not in use.

Should the cleaner head 10 be removed from the docking station 80 at any point during the sterilisation programme, the electrical connection formed by the electrical contacts 69,89 is broken. The control unit 84 of the docking station 80 therefore no longer receives the control signal from the cleaning appliance and, in response, powers off the light source 83. The cleaning appliance also determines that the cleaner head 10 is no longer received in the docking station 80 and ceases transmitting the control signal to the control unit 64 of the cleaner head 10, thereby causing the agitator to stop rotating.

In this example, the cleaning appliance is responsible for determining that the cleaner head 10 is received in the docking station 80 and for executing the sterilisation programme. In other examples, the control unit 64,84 of either the cleaner head 10 or the docking station 80 may be responsible for making the determination and for executing the sterilisation programme. For example, one of the control units 64,84 may determine that the cleaner head 10 is received in the docking station 80 when the electrical connection is established by the electrical contacts 69,89. In response, the control unit 64,84 may execute a sterilisation programme, which comprises transmitting a control signal to the other of the control units 84,64. The control unit 84 of the docking station 80 then powers on the light source 83, and the control unit 64 of the cleaner head 10 operates in the second mode. At the end of the sterilisation period, the control unit 64,84 ceases transmitting the control signal, and the light source 83 and the electric motor 61 are both powered off.

In the example described above, electrical power is supplied to the cleaner head 10 by the cleaning appliance when the cleaner head 10 is in the docking station 80. In other examples, electrical power may be supplied to the cleaner head 10 by the docking station 80. For example, the power supply unit 82 of the docking station 80 may supply power to the cleaner head 10 via the electrical contacts 69,89. The cleaner head 10 may then be removed from the cleaning appliance and sterilised in the docking station 80. This then has the advantage that the cleaning appliance can continue to be used, perhaps with a different cleaner head. Additionally or alternatively, where the cleaning appliance is battery-powered, the cleaning appliance may be recharged using the docking station 80. The docking station 80 may therefore be used to simultaneously recharge the cleaning appliance and sterilise the agitator 50.

Rather than employing a docking station 80 to sterilise the agitator 50, the cleaner head 10 may itself comprise a light source for illuminating the agitator 50 with sterilising light. Sterilisation may continue to be performed in response to determining that the cleaner head 10 is received in the docking station 80. Alternatively, or additionally, sterilisation may be performed in response to determining that the cleaner head 10 is not in use and/or is stowed in a particular position or orientation. For example, the cleaner head 10 may comprise an inertial measurement unit and the sterilisation programme may be initiated in response to determining that the cleaning appliance is powered off and the cleaner head 10 is hanging downwards and has therefore been lifted off the cleaning surface. In another example, the cleaner head 10 may comprises a contact switch or other means for determining when the cleaner head 10 is in contact with a cleaning surface, and the sterilisation programme may be initiated in response to determining that the cleaning appliance is powered off and the cleaner head 10 is not in contact with the cleaning surface.

In the example described above, the cleaner head is removably attachable to a cleaning appliance. In other examples, the cleaner head may form an integral part of the cleaning appliance. The cleaner head illustrated in the Figures is particularly well-suited for use with a vacuum cleaner, such as a stick, upright, canister, or autonomous vacuum cleaner. However, the agitator and the drive assembly may be used with other types of cleaning appliance, such as floor polishers and shampoo machines. In this regard, the agitator need not comprise a brushbar but may comprise alternative means for agitating a cleaning surface. For example, the agitator may comprise one or more rotating discs or pads that rotate about axes normal to the cleaning surface. Moreover, the drive assembly may be used in other appliances, not necessarily cleaning appliances, where it is desirable to operate an electric motor at two very different speeds, or over two very different speed ranges. 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.