GB2554780A

GB2554780A - Vacuum cleaner

Info

Publication number: GB2554780A
Application number: GB1709645.4A
Authority: GB
Inventors: Crichton Scott; Anthony Denny Bassett Alexander; Chengling Zhang
Original assignee: Conta sro
Current assignee: Conta sro
Priority date: 2016-10-10
Filing date: 2017-06-16
Publication date: 2018-04-11
Also published as: GB201709645D0; CN107913024A; CN107913024B

Abstract

A vacuum cleaner comprises a sensor 24 which senses movement of a cleaning head 10 of the cleaner. The sensor 24 is connected to a control unit 25 which reduces the power applied to a motor of a motor and fan unit 17 in the cleaner when the sensor detects that the head is accelerating or decelerating above a predetermined level, so that the cleaner momentarily consumes less power as the head decelerates, changes direction and accelerates again on successive cleaning strokes. The control unit 25 also reduces the power applied to the motor of the motor and fan unit 17 when the sensor 24 detects that the head 10 is static. The power applied to an agitator motor may also be reduced. The reduction in motor power provides the vacuum cleaner with an improved energy.

Description

(54) Title of the Invention: Vacuum cleaner Abstract Title: Vacuum cleaner

FIG. 1

1/2

FIG.1

2/2

Stroke length

FIG. 2

Acceleration/deceleration area

Test width

Dust-soiled Test surface

Acceleration/deceleration area

Vacuum Cleaner

This invention relates to a vacuum cleaner.

Regulations in some countries require that most kinds of vacuum cleaners are provided with information, which provides consumers with information about the annual energy consumption (AE) and the dust pick up performance or so-called DPU of the vacuum cleaner on hard floors and/or carpets depending on the intended use of the cleaner.

The standard test procedure whereby the energy efficiency grade of general purpose vacuum cleaners is determined involves evaluation of the DPU performance on both of the above types of floor surfaces. The value on which the AE energy consumption rating is based is a product of the sum of 50% of the observed DPU values for the respective floor types and the fan motor power needed to achieve the DPU for each floor type.

A problem with general purpose vacuum cleaners is that the cleaning head may not achieve a good DPU on one or both floor types, with the result that the overall DPU rating and the overall annual energy consumption (AE) rating of the cleaner may be poor.

The object of the present invention is to provide a vacuum cleaner having an improved AE energy consumption rating.

In accordance with the present invention, as seen from a first aspect, there is provided a vacuum cleaner having a head portion for engaging a floor surface being cleaned, a sensor for detecting the acceleration and/or deceleration of the head, a fan, a fan motor arranged to rotate the fan to draw air into the cleaner from the head and a control unit connected to the sensor and the fan motor, wherein the control unit is arranged to reduce the power applied to the fan motor when the sensor detects that the acceleration or deceleration is above a predetermined limit.

A vacuum cleaner in accordance with the present invention has power saving benefits during the specified standard test that is carried out to determine the DPU and AE energy consumption rating of the cleaner, whereby the head is moved repeatedly forwards and rearwards a set number of times at a set speed over a set length of dust-soiled test surface. An appropriate area at the end of each stroke over the test surface has to be allowed for acceleration to and deceleration from the set speed as the stroke direction changes, yet the power used whilst the head is accelerating and decelerating is taken into account when calculating the AE energy consumption. We have therefore realised that a significant power saving can be achieved by reducing the fan motor power whilst the head accelerates and/or decelerates, thereby reducing the total power consumed during the test and improving the AE rating of the cleaner.

Although the vacuum cleaner in accordance with the present invention can achieve a good AE rating under test, it also provides users with reduced energy consumption without any detrimental effects on the cleaning ability of the cleaner. Sensing acceleration and/or deceleration rather than just relying on a simple ON/OFF movement sensor allows the cleaner to anticipate or predict when the cleaner is likely to reverse direction and hence any change to the motor power can be made sooner. The result will be a smoother or quicker change in the motor power.

Another parameter provided on the required energy label is the noise emitted by the vacuum cleaner and it will be appreciated that a significant noise reduction can be achieved by reducing the fan motor power whilst the head accelerates and/or decelerates, thereby reducing the overall noise emitted during the test and improving the sound power rating of the cleaner.

Yet another parameter provided on the required energy label is the level of dust reemitted by the vacuum cleaner and it will be appreciated that a significant reduction in the level of dust re-emitted can be achieved by reducing the fan motor power whilst the head accelerates and/or decelerates, thereby improving the dust reemission rating of the cleaner.

In a first embodiment, the sensor detects the acceleration and deceleration of the head and the control unit reduces the power to the fan motor when the sensor detects that the acceleration or deceleration is above a predetermined limit.

In a second embodiment, the sensor detects the deceleration of the head and the control unit reduces the power to the fan motor when the sensor detects that the deceleration is above a predetermined limit, the control unit comprising a timer which increases the power to the fan motor after a set period of time. Since the time taken for the head to decelerate from the test speed, change direction and accelerate back to the test speed again can be determined, the present invention can be realised by sensing the onset of deceleration and using a timer. However, in a practical situation, the first embodiment is preferable because users may not move the head in the manner.

The limit may be a relatively low value since the head is supposed to pass over the test surface at a set speed (i.e. zero acceleration or deceleration).

The predetermined level for deceleration may be different from the predetermined level of acceleration. The or each level may be stored in the control unit. The control unit may be arranged to increase the power to the fan motor whilst the head is accelerating so that the fan motor is running at full speed when the head reaches the dust-soiled test surface.

The control unit may be arranged to apply no power to the fan motor when the sensor detects that the acceleration or deceleration is above the predetermined limit. However, since the time taken for the fan motor to reach full operating speed will be increased, it is preferred that the power to the fan motor is simply reduced to a lower value.

The lower power value may be a fixed lower value e.g. 20 - 60% of full power. In some instances, the fan motor may not be operating at full power during the test. Our co-pending Chinese Patent Application No. 20160675680.6 discloses a general purpose vacuum cleaner which has a good DPU ratings for hard floors and carpets yet is configured to reduce the fan motor power for hard floor cleaning so that it also achieves a good overall AE rating by virtue of the reduced energy consumption during hard floor cleaning. Accordingly, the cleaner may comprise a mode selector actuator arranged to set the power of the fan motor at a low value and a high value in first and second modes of cleaning respectively.

In one embodiment, according to the set mode of cleaning, the control unit may be arranged to reduce the set low or high power value by a respective set percentage when the sensor detects that the acceleration and/or deceleration is above a predetermined limit. The percentage may be different for the first and second modes of cleaning.

In an alternative embodiment, according to the set mode of cleaning, the control unit may be arranged to reduce the set low or high power to a respective set value when the sensor detects that the acceleration and/or deceleration is above a predetermined limit. The set value may be different for the first and second modes of cleaning.

The sensor may be mounted in any part of the cleaner although it is preferred that that the sensor is mounted in the head of the cleaner, so that it directly detects acceleration and/or deceleration of the head.

The cleaner may be a so-called upright cleaner comprising an upright body portion pivotally connected at its lower end to a wheeled floor-engaging head portion for partial rotation forwardly and rearwardly about a transverse axis, the body portion enclosing means for separating and collecting the dirt and dust that is drawn into the cleaner by the fan, an upstanding handle at the upper end of the body for guiding and maneuvering the cleaner, and a suction mouth on the underside of the head, through which air is drawn into the cleaner by the fan from the floor surface being cleaned. In such a cleaner, the sensor may be mounted anywhere in the cleaner since the whole cleaner is repeatedly moved forwardly and rearwardly during cleaning.

However, the cleaner could be a so-called canister vacuum cleaner having a head portion pivoted at the end of a tubular wand which is connected to the body of the cleaner by an elongate flexible hose. The body of the cleaner comprises a fan motor and fan unit that is arranged to draw air through the head, along the hose and into the body where any entrained dirt and dust in the air is separated and collected. In this embodiment, the sensor is provided in the head or the wand and is connected to the control circuit either wirelessly or via a cable which extends along the hose.

A rotary agitator brush may be mounted across a suction mouth in the head to beat and sweep the floor surface in the region of the airflow into the cleaner. The rotary agitator brush is either driven by the fan motor or by a separate agitator motor in the head. In the latter case, the control unit may also be arranged to decrease the power applied to the agitator motor when the sensor detects that the acceleration and/or deceleration is above a predetermined limit. In this manner further energy savings can be achieved. The fan motor and agitator motor may be controlled and power reduced when the sensor detects that the acceleration or deceleration above a predetermined limit.

Since the agitator is not needed for hard floor cleaning, the mode selector actuator may disconnect power from the agitator motor in the first mode of cleaning.

Also in accordance with the present invention, as seen from the first aspect, there is provided a method of operating a vacuum cleaner, the method comprising repeatedly moving a head of the cleaner forwards and rearwards over a surface to be cleaned, detecting acceleration and/or deceleration of the head, and decreasing the power applied to a fan motor of the cleaner when the detected acceleration and/or deceleration is above a predetermined limit.

Preferably the method comprises detecting the acceleration and deceleration of the head and decreasing the power to the fan motor when the detected acceleration or deceleration is above a predetermined limit.

Preferably the method comprises repeatedly moving the head at a substantially constant speed in one direction over the surface to be cleaned, decelerating the head, detecting the deceleration, reducing power to the fan motor, changing the direction of movement of the head to a second direction opposite the first direction, accelerating the head to a substantially constant speed and increasing the power to the fan motor when the speed of movement of the head is at or near constant speed.

Also in accordance with the present invention, as seen from a second aspect, there is provided a vacuum cleaner comprising a head portion for engaging a floor surface being cleaned, a sensor for detecting movement of the head, a fan, a fan motor arranged to rotate the fan to draw air into the cleaner through the head, a control unit connected to the sensor and the fan motor, and a mode selector actuator arranged to set the power of the fan motor at a low value and a high value in first and second modes of cleaning respectively, wherein the control unit is arranged to vary the set power applied to the fan motor in accordance with the detected movement of the head.

In one embodiment, according to the set mode of cleaning, the control unit may be arranged to vary the set low or high power value by a respective set percentage in accordance with the detected movement of the head. The percentage may be different for the first and second modes of cleaning.

In an alternative embodiment, according to the set mode of cleaning, the control unit may be arranged to vary the set low or high power to a respective set value in accordance with the detected movement of the head. The set value may be different for the first and second modes of cleaning.

The control unit may be arranged to vary the set power applied to the fan motor in accordance with detected acceleration and/or declaration of the head.

Alternatively or additionally, the control unit may be arranged to vary the set power applied to the fan motor in accordance with whether the head is detected as moving or static. In a static state of the cleaner, the power applied to the fan motor can be substantially reduced or removed, since this is often indicative that the cleaner is not being used. The power applied to the fan motor may be substantially reduced or removed a predetermined time period after the sensor has detected that the head is static.

Some upright cleaners may comprise a flexible hose having a distal end to which cleaning tools can be fitted, so that the user can carry out above floor cleaning. In such a cleaner, the suction developed by the fan is switched from the head to the hose in one of a plurality of different ways. Clearly it is desirable to prevent the power applied to the fan motor from being reduced or removed when the cleaner is brought into a static state for above-floor cleaning. Thus, the cleaner preferably comprises means for sensing when the cleaner is being used for above-floor cleaning and for preventing the power applied to the fan motor from being reduced or removed. The sensing means may comprise a switch or detector which detects when the distal end of the hose is detached from the cleaner or when a cleaning tool is removed from a stored position on the cleaner.

A rotary agitator brush may be mounted across a suction mouth in the head to beat and sweep the floor surface in the region of the airflow into the cleaner. The rotary agitator brush is either driven by the fan motor or by a separate agitator motor in the head. In the latter case, the control unit may also be arranged to vary the power applied to the agitator motor in accordance with the detected movement of the head.

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

Figure 1 is a schematic diagram of an upright vacuum cleaner in accordance with the present invention; and

Figure 2 is a diagram illustrating a vacuum cleaner carpet dust removal test.

Referring to Figure 1 of the drawings, there is shown an upright vacuum cleaner comprising a floor-engaging head 10 supported by front and rear wheels 12,13. An upright body portion 11 is pivotally mounted to the rear of the head 10 and comprises a handle 14 for guiding the cleaner. The head 10 comprises an elongate transverse suction mouth 15 disposed adjacent the front wheels 12. A rotary agitator brush 16 extends across the suction mouth 15 for beating and sweeping the floor surface during cleaning.

A motor and fan unit 17 disposed in the head 10 may drive the agitator brush 16 via a belt (not shown). In an alternative embodiment, the agitator brush 16 may be driven by a separate motor (not shown). In an alternative embodiment, the motor and fan unit 17 may be disposed in the upright body portion 11.

The motor and fan unit 17 creates a reduced air pressure in a duct 18, which leads via a neck 20 to the cleaned air outlet duct of a dust separation device 19 disposed in the body 11. In use the neck 20 acts as the point about which the body 11 can pivot relative to the head 10 between the shown parked position and an in-use position. An elongate flexible hose 21 is connected to the dirty air inlet of the dust separation device 19 disposed in the body 11.

In a floor cleaning mode of the cleaner, the distal end of the hose 21 is detachably connected to a port 22 on the head 10 of the cleaner which leads to the suction inlet 15. Dirt and dust is therefore drawn off the floor into the suction mouth 15 aided by the action of the rotary agitator 16. The dirt and dust is then carried up the hose 21 to the separation device 19. The cleaned air is then drawn downwardly via the neck 20 into the motor and fan unit 17, whereupon the air is discharged into the atmosphere through an exhaust 23.

In an above-floor cleaning mode of the cleaner, the distal end of the hose 21 is detachably connected to a cleaning tool (not shown). The hose 21 is flexible and extendible to allow the tool on the distal end thereof to be used to clean all kinds of surfaces within reach. Dirt and dust is therefore drawn off the surface and up the hose 21 to the separation device 19. The cleaned air is then drawn downwardly via the neck 20 into the motor and fan unit 17, whereupon the air is discharged into the atmosphere through an exhaust 23. It will be appreciated that the rotary agitator 16 is redundant in above-floor cleaning and the need to provide the conventional mechanism which lifts the cleaner head away from the floor surface during abovefloor cleaning can be avoided.

A motion sensor 24 is disposed in the head 10. The motion sensor may comprise one of the flowing:

1. A cell containing a movable member which operates a switch;

2. A reed switch cooperating with one or more magnet on one of the wheels;

3. A tilt or mercury switch;

4. An optical sensor which senses light reflected from the floor surface;

5. A photo cell cooperating with marks on one of the wheels or on a wheel axle;

6. An accelerometer such as micro electro-mechanical system (MEMS) accelerometer

The motion sensor 24 is connected to a control circuit 25 having an output connected to the motor of the motor and fan unit 17. The control circuit 25 may also be connected to the agitator motor if one is fitted.

A rotary mode selector actuator 26 is disposed on the upper surface of the head 10. The actuator 26 can be rotated into one of a plurality of different positions depending on the desired mode of the cleaner. In one embodiment there may be 4 different modes. The actuator 26 is arranged to displace the front wheels 12 of the head 10 upwardly and downwardly according to the selected mode of the cleaner as described more fully in our co-pending Chinese Patent Application No. 20160675680.6, the entire content and disclosure of which is hereby incorporated by reference.

In cleaners where rotation of the agitator 16 continues during hard floor cleaning, hard floor cleaning is best performed with the suction mouth 15 raised to avoid to avoid the floor from being damaged by the agitator, whereas carpet cleaning is best performed with the suction mouth 15 lowered to a position where it can beat and sweep the carpet.

In cleaners where rotation of the agitator 16 can be halted, better DPU values can be obtained with the suction mouth 15 lowered below the level at which carpet cleaning is best performed. When cleaning carpets, the amount by which the suction mouth 15 is raised is dependent on the length of pile of the carpet being cleaned. Also, when performing hard floor cleaning the mode selector actuator 26 is arranged to disconnect power from the agitator motor (if one is fitted) when the hard floor cleaning mode is selected by the actuator 26. Removing power from the agitator motor when performing hard floor cleaning helps to save power and improves the overall AE annual energy consumption of the cleaner.

The vacuum cleaner may therefore have the following modes of use selectable by rotation of the actuator 26 into an appropriate position:

Position	Mode	Agitator Motor	Fan Motor Power	Suction mouth 15
P1	Unspecified	On	W1 (full)	Fully lowered
P2	Hard floor	Off	W2 (reduced)	Lowered
P3	Short pile carpet	On	W1 (full)	Raised
P4	Long pile carpet	On	W1 (full)	Fully raised

Referring to Figure 2 of the drawings, the AE and DPU values of the cleaner are determined under test by repeatedly moving the head 10 forwards and rearwards a set number of times at a set speed over a set length (e.g. 700mm) of dust-soiled test surface. An appropriate area at the end of each stroke over the test surface has to be allowed for acceleration to and deceleration from the set speed as the stroke direction changes.

In accordance with the present invention, the control circuit 25 is arranged to decrease the power applied to the motor of the motor and fan unit 17 when the sensor 24 detects that the acceleration or deceleration of the head 10 is above a predetermined limit indicative of the fact that the head 10 is in an acceleration I deceleration area at the end of the test area.

When the hard floor cleaning mode is selected by turning the actuator 26 to position P2, the motor of the motor and fan unit 17 normally runs at reduced power level W1 during cleaning. However, when the sensor 24 detects that the acceleration or deceleration of the head 10 is above a predetermined limit, the power level W1 is reduced to a pre-set power level WT.

When a carpet cleaning mode is selected by turning the actuator 26 to position P3 or P4, the motor of the motor and fan unit 17 normally runs at its full power level W2 during cleaning. However, when the sensor 24 detects that the acceleration or deceleration of the head 10 is above a predetermined limit, the power level W2 is reduced to a pre-set power level W2’.

The reduced power levels WT and W2’ may be 50 - 60% of the power levels W1 and W2 respectively, although it will be appreciated that the percentages may be different.

It will be appreciated that a power saving can be achieved by reducing the power applied to the motor of the motor and fan unit 17 whilst the head 10 decelerates, changes direction and accelerates again at the end of each stroke. In this manner the total power consumed during the test is reduced and the AE rating of the cleaner is improved.

If the cleaner is fitted with an agitator motor, the motor may not be operating when the hard floor cleaning mode is selected by turning the actuator 26 to position P2. However, if it is operating or if a carpet cleaning mode is selected by turning the actuator 26 to position P3 or P4, the power applied to the agitator motor may be removed or reduced when the sensor 24 detects that the acceleration or deceleration of the head 10 is above a predetermined limit.

It will be appreciated that a further power saving can be achieved by reducing or removing the power applied to the agitator motor whilst the head 10 decelerates, changes direction and accelerates again at the end of each stroke. In this manner the total power consumed during the test is further reduced and the AE rating of the cleaner is further improved.

When the sensor 24 detects that the head 10 is static, the power applied to the motor of the motor and fan unit 17 may be reduced or removed, preferably after a delay of several seconds to avoid changes in the power level being caused by momentary interruptions in cleaning. If the power applied to the motor of the motor and fan unit 17 is reduced, it may be reduced to a pre-set power level which may be may be 50 60% of the power levels W1 and W2 respectively, although it will be appreciated that the percentages may be different.

If the cleaner is fitted with an agitator motor, the motor may not be operating when the hard floor cleaning mode is selected by turning the actuator 26 to position P2. However, if it is operating or if a carpet cleaning mode is selected by turning the actuator 26 to position P3 or P4, the power applied to the agitator motor may be removed or reduced when the sensor 24 detects that the head 10 is static.

Referring again to Figure 1 of the drawings, the cleaner comprises a switch 27 which changes state according to whether the distal end of the hose 21 is connected to or removed from the port 22 on the head 10 of the cleaner. The switch 17 acts to apply full power to the motor of the motor and fan unit 17 when the distal end of the hose 21 is removed from the port 22 for above-floor cleaning regardless of the static state of the cleaner. The switch 17 may also act to remove the power from the agitator motor when the distal end of the hose 21 is removed from the port 22 for above-floor cleaning, since the agitator is not needed when performing above-floor cleaning and indeed is undesirable because it can cause strain on the motor and can wear the floor surface.

In a first alternative embodiment, instead of the switch 17, the above-floor cleaning may be selected by turning the actuator 26 to another position P5. In a second alternative embodiment, a vacuum switch or sensor could be used to detect the vacuum inside the head, since the level vacuum level inside head is zero when the hose 21 is removed for above-floor cleaning. In a third alternative embodiment a switch or sensor, such as the sensor 24, may detect if the cleaner is stationary for above-floor cleaning.

A vacuum cleaner in accordance with the present invention is simple and inexpensive in construction, yet provides many of the following advantages:

• Reduced chance of damage or wear to the floor surface;

• Reduced energy consumption and an improved AE rating;

• Reduced noise and an improved sound level rating;

• Reduced dust re-emissions and an improved dust re-emission rating;

· Reduce risk of cord damage and potential danger from agitator when tipped over • Reduced drive belt wear • Increased motor life

Claims

1. A vacuum cleaner having a head portion for engaging a floor surface being cleaned, a sensor for detecting the acceleration and/or deceleration of the head, a fan, a fan motor arranged to rotate the fan to draw air into the cleaner through the head and a control unit connected to the sensor and the fan motor, wherein the control unit is arranged to reduce the power applied to the fan motor when the sensor detects that the acceleration and/or deceleration is above a predetermined limit.

2. A vacuum cleaner as claimed in claim 1, in which the sensor detects the acceleration and deceleration of the head and the control unit reduces the power to the fan motor when the sensor detects that the acceleration or deceleration is above the predetermined limit.

3. A vacuum cleaner as claimed in claim 1 or 2, in which the control unit is arranged to increase the power to the fan motor whilst the head is accelerating.

4. A vacuum cleaner as claimed in any preceding claim, in which the control unit is arranged to reduce the power to the fan motor to a fixed lower value.

5. A vacuum cleaner as claimed in any preceding claim, comprising a mode selector actuator arranged to set the power of the fan motor at a low value and a high value in first and second modes of cleaning respectively.

6. A vacuum cleaner as claimed in claim 5, in which the set power is reduced by a set percentage when the sensor detects that the acceleration and/or deceleration is above a predetermined limit.

7. A vacuum cleaner as claimed in claim 5, in which the set power is reduced to a respective set value.

8. A vacuum cleaner as claimed in any preceding claim, comprising a rotary agitator brush mounted across a suction mouth in the head, the rotary agitator brush being driven by an agitator motor separate from the fan motor, the control unit being also be arranged to reduce the power applied to the agitator motor when the sensor detects that the acceleration and/or deceleration is above the predetermined limit.

9. A method of operating a vacuum cleaner, the method comprising repeatedly moving a head of the cleaner forwards and rearwards over a surface to be cleaned, detecting acceleration and/or deceleration of the head, and decreasing the power applied to a fan motor of the cleaner when the detected acceleration and/or deceleration is above a predetermined limit.

10. A method as claimed in claim 9, comprising detecting the acceleration and deceleration of the head and decreasing the power to the fan motor when the detected acceleration or deceleration is above the predetermined limit.

11. A method as claimed in claim 9 or 10, comprising repeatedly moving the head at a substantially constant speed in one direction over the surface to be cleaned, decelerating the head, detecting the deceleration, reducing power to the fan motor, changing the direction of movement of the head to a second direction opposite the first direction, accelerating the head to a substantially constant speed and increasing the power to the fan motor when the speed of movement of the head is at or near constant speed.

12. A vacuum cleaner comprising a head portion for engaging a floor surface being cleaned, a sensor for detecting movement of the head, a fan, a fan motor arranged to rotate the fan to draw air into the cleaner through the head, a control unit connected to the sensor and the fan motor, and a mode selector actuator arranged to set the power of the fan motor at a low value and a high value in first and second modes of cleaning respectively, wherein the control unit is arranged to vary the set power applied to the fan motor in accordance with the detected movement of the head.

13. A vacuum cleaner as claimed in claim 12, in which the control unit is arranged to vary the set power value by a respective set percentage in accordance with the detected movement of the head.

14.1 A vacuum cleaner as claimed in claim 12 or 13, in which the control unit is arranged to vary the set power to a respective set value in accordance with the detected movement of the head.

15. A vacuum cleaner as claimed in any of claims 12 to 14, in which the control unit is arranged to vary the set power applied to the fan motor in accordance with detected acceleration and/or declaration of the head.

16. A vacuum cleaner as claimed in any of claims 12 to 15, in which the control unit is arranged to vary the set power applied to the fan motor in accordance with whether the head is detected as moving or static.

17. A vacuum cleaner as claimed in claim 16, in which the control unit is arranged to vary the set power applied to the fan motor a predetermined time after the head is detected as being static.

18. A vacuum cleaner as claimed in claim 16 or 17, comprising a flexible hose having a free distal end to which cleaning tools can be fitted for above-floor cleaning, the cleaner further comprising means for sensing when the cleaner is being used for above-floor cleaning and for preventing the power applied to the fan motor from being reduced or removed when head is detected as being static.

19. A vacuum cleaner as claimed in claim 18, in which the sensing means comprise a switch or detector which detects when the distal end of the hose is detached from the cleaner.

20. A vacuum cleaner as claimed in any of claims 12 to 19, comprising a rotary agitator brush mounted across a suction mouth in the head, the rotary agitator brush being driven by an agitator motor separate from the fan motor, the control unit being arranged to vary the power applied to the agitator motor in accordance with the detected movement of the head.

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