Patent Publication Number: US-2022233038-A1

Title: Cleaner head for a vacuum cleaner

Description:
FIELD OF THE INVENTION 
     The present invention relates to a cleaner head for a vacuum cleaner. 
     BACKGROUND OF THE INVENTION 
     A vacuum cleaner typically comprises a main body containing dirt and dust separating apparatus, a cleaner head connected to the main body and having an opening, and a motor-driven fan unit for drawing dirt-bearing air through the opening and the cleaner head, and into the main body. The opening is directed downwardly to face the floor surface to be cleaned. The dirt-bearing air is conveyed to the separating apparatus so that dirt and dust can be separated from the air before the air is expelled to the atmosphere. The separating apparatus can include one or more of a filter, a filter bag and a cyclonic arrangement. 
     A driven agitator, usually in the form of a brush bar, may be rotatably mounted within a suction cavity of the cleaner head. The brush bar typically comprises an elongate cylindrical core bearing bristles which extend radially outward from the core. The opening is in the form of an aperture, usually an elongate, rectangular aperture, defined by a sole plate located on the base of the cleaner head. The brush bar may be mounted within the suction cavity so that the bristles protrude by a small extent through the opening. 
     The brush bar is activated mainly when the vacuum cleaner is used to clean carpeted surfaces. Rotation of the brush bar may be driven by an electric motor powered by a power supply derived from the main body of the vacuum cleaner, or by a turbine driven by an air flow passing through or into the cleaner head. The brush bar may be driven by the motor via a drive belt, or may be driven directly by the motor, so as to rotate within the suction cavity. Rotation of the brush bar causes the bristles to sweep along the surface of the carpet, agitating both the fibres of the carpet and any dust or other detritus located on the surface of the carpet and/or between fibres of the carpet, and resulting in a significant amount of energy being imparted to the dust. With the brush bar rotating in such a direction that the bristles move from the front edge of the opening towards the rear edge, the rotating bristles sweep dust rearwardly through the opening and into the suction cavity. The suction of air causes air to flow underneath the sole plate and around the brush bar to help lift the dirt and dust from the surface of the carpet and then carry it from the opening through the cleaner head towards the separating apparatus. 
     During the passage of agitated dust through the dirty air inlet, long strands of debris, for example hair or thread or the like, may become wrapped around the brush bar or a mounting thereof. This may lead to an increased torque on the brush bar, and a sufficient build-up of strands of debris on the brush bar may lead to failure of the brush bar and a reduced pick-up performance. 
     SUMMARY OF THE INVENTION 
     In a first aspect the present invention provides a cleaner head for a vacuum cleaner, the cleaner head comprising: 
     a suction cavity comprising an opening through which debris enters the cleaner head, and a first air outlet; and 
     an agitator mounted in the suction cavity in a cantilevered manner for rotation relative thereto, the agitator being conical in shape and having a first, free end and a second end which has a larger diameter than the first end; 
     wherein the suction cavity comprises a second air outlet located adjacent the free end of the agitator, and the cleaner head defines a first airflow path extending downstream of the suction cavity from the first air outlet towards an outlet of the cleaner head, and a second airflow path extending downstream of the suction cavity from the second air outlet towards the first airflow path. 
     During the use of the cleaner head, any debris which has become wrapped around the agitator is encouraged by the conical shape of the agitator to migrate along the agitator towards the free end, where it can become released from the agitator. In order to minimise the risk of this released debris becoming re-wrapped around the agitator before it is conveyed away from the agitator within an airflow which is passing through the suction cavity, the suction cavity comprises a second air outlet located adjacent the free end of the agitator. A first part of the airflow passing through the suction cavity leaves the suction cavity through the first air outlet, and a second part of this airflow leaves the suction cavity through the second air outlet. The first part of the airflow, generally containing dust and other detritus which has been agitated from a floor surface by the agitator, passes along a first airflow path extending from the first air outlet to an outlet of the cleaner head. The second part of the airflow, into which debris which has been released from the agitator generally becomes entrained, passes along a second airflow path extending from the second air outlet towards the first airflow path so as to merge with the first part of the airflow between the first air outlet and the outlet of the cleaner head, and thus before any part of the airflow is emitted from the cleaner head. 
     As used herein, the term “conical shape” includes both conical and frustoconical shapes. The cone angle of a conical shape is the angle subtended between the longitudinal axis of the conical shape and the external conical surface of the conical shape. In a preferred embodiment, the cone angle is 7°. 
     As used herein the term “debris” refers to strands which have the potential to wrap around the agitator during operation of the cleaner head. For example, debris may be considered to comprise strands having a length which is greater than the maximum circumference of the agitator. Examples of debris include hairs, threads and other relatively long fibres and strands. 
     The agitator preferably comprises a conical core having helical ridges upstanding from an external conical surface of the core, and a row of bristles located between the helical ridges. The bristles may be mounted on a flexible bristle base which is inserted between the upstanding ridges of the core. The bristles may be arranged so as to bend freely, for example, against the upper surfaces of the helical ridges, as debris becomes wrapped around the agitator. This can further encourage the migration of the debris towards the free end of the agitator. For example, the bristles may be formed from relatively thin strands of nylon or carbon fibre. As measured in a direction perpendicular to the longitudinal axis of the core, the height of the upstanding ridges is preferably at least 50% of the height of the bristles. This can prevent the debris from sinking between the bristles towards the bristle base upon which the bristles are mounted, and so becoming trapped within the row of bristles. 
     The cleaner head preferably comprises a bottom surface, or sole plate, in which the opening is formed. The longitudinal axis of the agitator is preferably inclined at an acute angle to a plane containing the opening of the cleaner head. In a preferred embodiment the cone angle is 7°. In use, the lowermost portion of the external surface of the core is preferably parallel to the plane containing the opening so that the lowermost portion of the external surface of the core is evenly spaced along its length from this plane. The opening is preferably trapezoidal in shape. The opening may be defined by a relatively long leading edge, and relatively long trailing edge, and two side edges each extending between the leading edge and the trailing edge. The leading edge may be perpendicular to the side edges, or, as in a preferred embodiment, it may be inclined relative to the side edges so that it subtends an acute angle with one side edge and an obtuse angle with the other side edge. 
     The suction cavity is preferably defined by a conical housing of the cleaner head. The housing preferably has substantially the same shape as the agitator. 
     Each of the first air outlet and the second air outlet is preferably located rearwardly of the agitator. The second air outlet is preferably located directly behind the free end of the agitator, whereas the first air outlet is preferably located midway between the free end and the second end of the agitator. Where the agitator comprises a helical row of bristles, we have found that these locations of the first and second air outlets, and thus the directions in which air passes through the suction cavity, can encourage debris to wrap around the agitator in a direction which is generally orthogonal to the longitudinal axis of the agitator, as opposed to a direction extending generally along or alongside the helical row of bristles. This can promote the migration of debris along the agitator and its subsequent release from the agitator. 
     The first air outlet and the second air outlet are preferably spaced in a direction extending parallel to the longitudinal axis of the agitator. 
     The first airflow path is preferably defined, at least in part, by a neck for conveying air from the first air outlet to the outlet of the cleaner head. The neck preferably comprises a connector for connecting the cleaner head to a vacuum cleaner. The first part of the airflow and the second part of the airflow preferably merge within the neck. 
     The second airflow path is preferably defined, at least in part, by a duct for conveying air from the second air outlet to an air inlet port formed in the neck and from which the second part of the airflow enters the first part of the airflow. The air inlet port is located between the first air outlet and the outlet of the cleaner head. The second airflow path thus extends away from the suction cavity in parallel to the portion of the first airflow path located upstream from the air inlet port. 
     The duct, and thus the second airflow path, preferably extends externally of the housing from the second air outlet to the neck. To minimise turbulence, the duct is preferably curved, and preferably curves through 90° between the second air outlet and the air inlet port. The duct may have a constant or a varying radius of curvature along its length. To facilitate manufacture, the duct is preferably integral with at least part of the neck and/or at least part of the housing. 
     The cleaner head preferably comprises a single conical agitator which has a free end located adjacent to, but spaced from a side wall of the suction cavity, and a second end, located opposite to free end, which has a larger diameter than the free end. The agitator is preferably mounted, at or towards the second end of the agitator, to a drive for driving the rotation of the agitator relative to the suction cavity. The drive preferably comprises a motor located externally of the agitator, and a belt connecting the agitator to the motor. Alternatively, the motor may be located within the agitator. To maximise cleaning performance by preventing released debris from becoming trapped between the free end of the agitator and the side wall of the housing, the spacing between the free end of the agitator and the side wall is preferably in the range from 2 to 10 mm, more preferably in the range from 3 to 5 mm. 
     As the cleaner head is manoeuvred over a carpeted floor surface, a portion of the carpet can become raised and drawn into the suction cavity through the opening, in view of the relatively low air pressure generated within the suction cavity by the vacuum cleaner. This can cause the raised portion of the carpet to contact the agitator, in particular the bristles and the helical ridges upstanding from the external surface of the core. When debris has become wrapped around the agitator, the action of the carpet pressing upon the agitator can encourage this debris to become more tightly wrapped around the agitator. We have observed that tightly wrapping the debris around the agitator can promote its migration towards the free end of the agitator. 
     So as not to be reliant upon the movement of carpet into the suction cavity to urge debris against the agitator, to promote migration of the wrapped debris along the agitator the cleaner head preferably comprises an agitator engaging member for pressing against the agitator any debris which has become wrapped around the agitator. 
     In a second aspect, the present invention provides a cleaner head for a vacuum cleaner, the cleaner head comprising:
         a suction cavity comprising an opening through which debris enters the cleaner head, and an outlet;   an agitator mounted in the suction cavity in a cantilevered manner for rotation relative thereto, the agitator comprising a core which is conical in shape and has a first, free end and a second end which has a larger diameter than the first end; and   an agitator engaging member for pressing against the agitator any debris which has become wrapped around the agitator.       

     The engaging member preferably extends substantially the entire length of the agitator. With rotation of the agitator within the suction cavity, this enables the engaging member to press against substantially the entire length of the row of bristles and the ridges of the core. The engaging member preferably extends in a direction which is inclined at the cone angle to the longitudinal axis of the agitator. This can allow the engaging member to be aligned relative to the agitator so that it lies substantially parallel to a portion, preferably an upper portion of the external surface of the core of the agitator. This can enable the engaging member to apply a substantially uniform force to the agitator along its length. 
     The engaging member is preferably biased towards the agitator. The engaging member may comprise a plate or bar which is biased towards the agitator by one or more springs or other resilient members. Alternatively, the engaging member may be in the form of a resilient member which is biased internally towards the agitator. The resilient member may comprise a strip of resilient material, which preferably has a substantially uniform width. The width of the engaging member is selected such that the engaging member presses wrapped debris against at least the bristles of the agitator, and preferably against also the helical ridges of the core. In a preferred embodiment, the width of the strip of resilient material is in the range from 2 to 5 mm. 
     The engaging member may be mounted on any surface of the cleaner head so as to engage the agitator. The engaging member is preferably located opposite to the opening through which debris enters the cleaner head so that it is located opposite to any raised carpet which is also pressing against the agitator. This can enable the forces being applied to the agitator by the carpet and the engaging member to be balanced. In a preferred embodiment, the engaging member is mounted on the housing which defines the suction cavity. 
     As mentioned above, the bristles may be arranged so as to bend freely as debris becomes wrapped around the agitator so as to further encourage the migration of the debris towards the free end of the agitator. These bristles may be mounted on the bristle base so as to extend substantially perpendicular to the bristle base. As debris becomes wrapped around the agitator, the bristles flex towards an upper end of an upstanding ridge of the core, and/or so as to at least partially overlie adjacent bristles. 
     As an alternative, the bristles may be inclined relative to the bristle base, and thus relative to the external surface of the core, in a direction extending towards the free end of the core. This can reduce the risk of any wrapped debris becoming lodged between adjacent bristles and not migrating towards the bristle base, and so can further promote the migration of wrapped threads towards the free end of the agitator. 
     In a third aspect the present invention provides a cleaner head for a vacuum cleaner, the cleaner head comprising:
         a suction cavity comprising an opening through which debris enters the cleaner head, and an outlet;   an agitator mounted in the suction cavity in a cantilevered manner for rotation relative thereto, the agitator comprising:
           a core having a first, free end, a second end remote from the free end, and upstanding helical ridges extending between the free end and the second end; and   a row of bristles located between the helical ridges and inclined relative to the core in a direction extending towards the free end of the core.   
               

     The row of bristles extends in a row direction, and the bristles are preferably inclined at an acute angle to, and towards, the row direction. The row of bristles may be formed by securing the bristles to the flexible bristle base, and using a hot rolling technique to angle the bristles towards the bristle base. The row of bristles is then inserted between the ridges of the core so that the row of bristles adopts a helical shape which extends towards the free end of the core in a helical direction, and so that the bristles are inclined towards the free end of the core at an acute angle to the helical direction. The acute angle is preferably in the range from 20 to 60°, more preferably in the range from 30 to 50°. The row of bristles may comprise a continuous row of bristles, or it may comprise a plurality of discrete bristle tufts. 
     Features described above in connection with the first aspect of the invention are equally applicable to the second to third aspects of the invention, and vice versa. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred features of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a front view of a first embodiment of a cleaner head for a vacuum cleaner; 
         FIG. 2  is a top view of the cleaner head of  FIG. 1 ; 
         FIG. 3  is a rear view of the cleaner head of  FIG. 1 ; 
         FIG. 4  is a bottom view of the cleaner head of  FIG. 1 ; 
         FIG. 5  is a side view of the cleaner head of  FIG. 1 ; 
         FIG. 6( a )  is a sectional view taken along line A-A of  FIG. 5 , and  FIG. 6( b )  is a sectional view taken along line B-B of  FIG. 5 ; 
         FIG. 7( a )  is a front view of the core of an agitator of the cleaner head of  FIG. 1 , 
         FIG. 7( b )  is an end view of the agitator of  FIG. 7( a ) ,  FIG. 7( c )  is a side view of a row of bristles of the agitator, and  FIG. 7( d )  is a sectional view taken along line J-J in 
         FIG. 7( a )  but with the row of bristles located on the core; 
         FIG. 8( a )  is a front view of the cleaner head of  FIG. 1 ,  FIG. 8( b )  is a similar view to  FIG. 8( a )  but with all components removed except an agitator engaging member of the cleaner head, and  FIG. 8( c )  is a sectional view taken along line M-M of  FIG. 8( b ) ; 
         FIG. 9  is a front view of a second embodiment of a cleaner head for a vacuum cleaner; 
         FIG. 10  is a top view of the cleaner head of  FIG. 9 ; 
         FIG. 11  is a side view of the cleaner head of  FIG. 9 ; 
         FIG. 12  is a bottom view of the cleaner head of  FIG. 9 ; 
         FIG. 13  is a sectional view taken along line A-A of  FIG. 10 ; 
         FIG. 14  is a sectional view taken along line D-D of  FIG. 10 ; and 
         FIG. 15  is part of a sectional view taken along line B-B of  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 to 5  are external views of a first embodiment of a cleaner head  10  for a vacuum cleaner. The cleaner head  10  comprises a conical front housing  12 , a rear housing  14  connected to the front housing  12 , and a sole plate  16  connected to the front housing  12 . One or more of the rear housing  14  and the sole plate  16  may be integral with the front housing  12 , and are preferably formed from plastics material. In use, the sole plate  16  is placed upon the floor surface to be cleaned. 
     With particular reference to  FIG. 4 , the sole plate  16  comprises a leading section  18  and a trailing section  20  located on opposite sides of a suction opening  22  through which an airflow is drawn into the cleaner head  10 . The suction opening  22  is generally trapezoidal in shape, and is delimited by a front working edge  24 , a rear working edge  26  which is inclined relative to the front working edge  24 , a relatively long first side edge  28  and a relatively short, second side edge  30  which is parallel to the first side edge  28 . The front working edge  24  is defined by the intersection of the leading section  18  of the sole plate  16  with the front housing  12 , and the rear working edge  26  is defined by the intersection of the trailing section  20  of the sole plate  16  with the front housing  12 . The working edges  24 ,  26  agitate the fibres of a carpeted floor surface as the cleaner head is manoeuvred over such a surface. The second side edge  30  is defined by the bottom end of a side wall  32  of the front housing  12 . 
     With reference also to  FIGS. 6( a ) and 6( b ) , the front housing  12  defines a conical suction cavity  34  which receives the airflow drawn into the cleaner head  10  through the suction opening  22 . The suction cavity  34  houses an agitator  36  for agitating the fibres of a carpeted floor surface. The agitator  36  is in the form of a brush bar which is rotatable relative to the front housing  12 , and suction cavity  34 , about an axis which is collinear with the longitudinal axis of the agitator  36 . As illustrated in  FIGS. 7( a ) to 7( d ) , the agitator  36  comprises a hollow core  38 , which in this embodiment is conical in shape. The core  38  is formed from a relatively rigid plastics material, such as acrylonitrile butadiene styrene (ABS). The core  38  comprises a conical external surface  40  which extends between a relatively small first end  42  and a relatively large second end  44 . The cone angle of the core  38 , that is, the angle subtended between the longitudinal axis of the core and external surface  40  of the core  38 , is preferably in the range from 5 to 15°, and in this embodiment is approximately 7°. 
     A pair of helical ridges  46 ,  48  are upstanding from the external surface  40  of the core  38 , and extend helically along the external surface  40  of the core  38  from the second end  44  to the first end  42  thereof. The ridges  46 ,  48  extend substantially the entire length of the core  38 , and extend about the external surface  40  by around 450°. The ridges  46 ,  48  are preferably integral with the core  38  so that the ridges  46 ,  48  do not deform excessively upon contact with a floor surface. The ridges  46 ,  48  define a helical channel  50  therebetween which receives a bristle strip  52  (not shown in  FIG. 4 ). The bristle strip  52  comprises a flexible bristle base  54  and a row of bristles  56  woven into the bristle strip  54 . The bristles  56  are formed from nylon, and have sufficient strength to agitate dust and debris located upon a surface to be cleaned in use, whilst still having sufficient flexibility to resiliently deform relative to the bristle base  54 . As illustrated in  FIG. 7( c ) , the bristles  56  are arranged on the bristle base  54  so that the bristles  56  are inclined at an acute angle to the bristle base  54 . The inclination of the bristles  56  may be achieved following their attachment to the bristle base  54  by subjecting the bristles  56  to a hot rolling process to deform the bristles  56  so that they are inclined towards the bristle base  54 . The acute angle is preferably in the range from 20 to 60°, more preferably in the range from 30 to 50°. The bristle strip  52  is then inserted into, and secured to, the channel  50  so that the direction of the taper of the bristles  56 , as indicated in  FIG. 7( c ) , extends towards the first end  42  of the core  42 . The bristles  56  are thus inclined towards the first end  42  of the core  38 , but such that the direction of taper extends helically about the core  38  from the second end  44  towards the first end  42  of the core  38 . 
     The length of the bristles  56  is selected so that the bristles  56  protrude outwardly beyond the tips of the ridges  46 ,  48 . As measured in a direction perpendicular to the longitudinal axis of the core  38 , the height of the upstanding ridges  46 ,  48  is preferably at least 50% of the height of the bristles  56 . 
     The agitator  36  is mounted within the suction cavity  34  in a cantilevered manner so that the first end  42  of the core  38  is spaced from the side wall  32  of the front housing  12 . The first end  42  may thus be referred to as a free end of the agitator  36 . The spacing between the first end  42  of the core  38  and the side wall  32  is preferably in the range from 2 to 10 mm, more preferably in the range from 3 to 5 mm. The agitator  36  is mounted so that the longitudinal axis of the agitator is inclined at an acute angle to a plane containing the suction opening  22 . This acute angle is preferably in the range from 5 to 15°, and in this embodiment is approximately 7°. As illustrated in  FIG. 6( b ) , the agitator  36  is mounted such that the lowermost portion of the external surface  40  of the core  38  is parallel to the plane containing the suction opening  22 . The length of the bristles  56  is selected such that, when not subject to external forces, the lowermost tips of the bristle strip  52  are located in the plane containing the suction opening  22 . 
     The rotation of the agitator  36  is driven by a motor (not shown) which is housed inside the rear housing  14 . The motor is arranged to rotate the agitator  36  in such a direction that the bristles  56  sweep dirt and debris rearwardly, that is, over the rear working edge  26 , into the suction cavity  34 . The motor drives a belt  60  which extends between the front housing  12  and the rear housing  14  within a drive housing  62  which is closed by a cover  64 . The belt  60  is arranged to drive rotation of a belt drive  66 , which is mounted to a cantilever support defined by the drive housing  62 . The cantilever support projects away from the belt drive  66  and provides a mount onto which the agitator  36  is rotatably mounted via bearings  68  and agitator fixings  70 . A drive dog  72  is connected to the belt drive  66  so as to project through the cantilever support. The agitator  36  is connected to the drive dog  72  via an internal annular collar  74  of the core  38 . 
     With reference to  FIGS. 7( a ) and 7( b ) , the suction cavity  34  comprises a first air outlet  80  and a second air outlet  82  which is spaced from the first air outlet  80 . Each of the air outlets  80 ,  82  is located rearwardly of the agitator  36  and is located above the plane containing the suction opening  22 . The first air outlet  80  is larger than the second air outlet  82 . The first air outlet  80  is located generally midway between the first end  42  and the second end  44  of the core  38  of the agitator  36 . The first air outlet  80  conveys air into a neck  84  of the cleaner head  10 , within which the air is conveyed to an outlet  86  of the cleaner head  10 . The neck  84  includes a connector  88  for connecting the cleaner head  10  to a vacuum cleaner, and electrical connectors  90  for connecting the motor to a power source of the vacuum cleaner. 
     The second air outlet  82  is located adjacent to the first end  42  of the core  38 , and is preferably partially defined by the side wall  32  of the first housing  12 . The second air outlet  82  conveys air into a duct  92  which extends externally between the first housing  12  and the neck  84 . The duct  92  is preferably rigid and is preferably integral with at least part of the front housing  12  and/or at least part of the neck  84 . The duct  92  conveys air from the second air outlet  82  to an air inlet port located within the neck  84 , between the first air outlet  80  and the outlet  86  of the cleaner head  10 . 
     With reference to  FIG. 6( b )  and  FIGS. 8( a ) to 8( c ) , the cleaner head  10  also includes an agitator engaging member  96  for engaging the agitator  36 . The engaging member  96  is mounted on the first housing  12  so as to protrude into the suction cavity  34  to engage the agitator  36 . The engaging member  96  comprises a flexible strip  98  of resilient material which is gripped by a support  100  along its length, and which presses against the at least the bristles  56  of the agitator  36 . The engaging member  96  extends substantially the entire length of the agitator  36  so that, with rotation of the agitator  36 , the engaging member  96  presses against substantially the entire row of bristles  56 . As indicated in  FIGS. 8( a ) and 8( b ) , the engaging member  96  extends in a direction which is inclined at the cone angle to the longitudinal axis of the agitator  36  so that it lies substantially parallel to an upper portion of the external surface  40  of the core  38  of the agitator  36 . The flexible strip  98  has substantially uniform width. In this embodiment, the width of the strip of resilient material is approximately 5 mm, and is selected so as to protrude sufficiently into the suction cavity  22  so as to engage at least the bristles  56  of the agitator  36 , as shown in  FIG. 6( b ) , but preferably also the tips of the ridges  46 ,  48  of the core  38 . The engaging member  96  is located opposite to the suction opening  22 , and preferably protrudes into the suction cavity  22  through a slot formed in the front housing  12 . 
     In use, an airflow is drawn through the cleaner head  10  by the motor and fan unit of a vacuum cleaner to which the cleaner head  10  is attached. The airflow enters the suction cavity  34  through the suction opening  22 . A first part of the airflow leaves the suction cavity  34  through the first air outlet  80  and passes along a first airflow path extending within the neck  84  from the first air outlet  80  to the outlet  86  of the cleaner head  10 . A second part of the airflow leaves the suction cavity  34  through the second air outlet  82 , and passes along a second airflow path extending within the duct  92  from the second air outlet  82  to the air inlet port of the neck  84 , and thus towards the first airflow path. These parts of the airflow thus merge within the neck  84  of the cleaner head  10  before being emitted from the cleaner head  10  through the outlet  86 . 
     The agitator  36  is driven by the motor to rotate within the suction cavity  34 . With the sole plate  22  pressed against a carpeted floor surface, the rotating bristles  56  of the agitator  36  contact, and so transfer energy to, dust particles and debris located on the floor surface, or between the fibres of the floor surface. As the agitator  36  is rotated within the suction cavity  34  so that the bristles  56  pass from the front working edge  24  to the rear working edge  26 , the majority of the energised dust and debris is swept rearwardly through the suction opening  22 . Whilst the majority of the dust and debris will become entrained within the airflow passing through the suction cavity  34  and pass through the first air outlet  80  or second air outlet  82 , some debris, such as hairs, threads, fibres and the like, can become wrapped around the agitator  36 . Such debris is encouraged by the conical shape of the agitator  36  to migrate along the length of the agitator  36  from the second end  44  towards the first end  42 . Under the action of the engaging member  96 , such debris is pressed around the agitator  36  until it falls from the first end  42  of the agitator  36 , whereupon the released debris becomes entrained within the second part of the airflow and passes through the duct  92  and into the neck  84  of the cleaner head  10 . The inclination of the bristles  56  relative to the external surface  40  of the core  38  encourages the wrapped debris to migrate along the agitator, and not become trapped between the bristles  56 . The relative heights of the bristles  56  and the ridges  46 ,  48  of the core  38  means that any wrapped debris which begins to migrate between bristles  56  towards the bristle strip  54  will be blocked from doing so by its engagement with the tips of the ridges  46 ,  48 , and so continue to migrate along the agitator  36  towards the first end  42 . 
       FIGS. 9 to 12  are external views of a second embodiment of a cleaner head  110  for a vacuum cleaner. The cleaner head  110  comprises a housing formed from a lower housing section  112  and an upper housing section  114  which is moveable relative to, and about, the lower housing section  112 . A sole plate  116  is connected to, and is preferably integral with, the lower housing section  112 . Similar to the sole plate  16  of the first embodiment, the sole plate  116  comprises a leading section  118  and a trailing section  120  located on opposite sides of a suction opening  122  through which an airflow is drawn into the cleaner head  110 . The suction opening  122  is generally trapezoidal in shape, and is delimited by a front working edge  124 , a rear working edge  126  which is inclined relative to the front working edge  124 , a relatively long first side edge  128  and a relatively short, second side edge  130  which is generally parallel to the first side edge  128 . The working edges  124 ,  126  agitate the fibres of a carpeted floor surface as the cleaner head  110  is manoeuvred over such a surface. 
     With reference also to  FIGS. 13 and 15 , the lower housing section  112  and the upper housing section  114  define a conical suction cavity  134  which receives the airflow drawn into the cleaner head  110  through the suction opening  122 . The suction cavity  134  houses an agitator  136  for agitating the fibres of a carpeted floor surface. The agitator  136  is in the form of a brush bar which is rotatable relative to the housing sections  112 ,  114  and suction cavity  134 , about an axis which is collinear with the longitudinal axis of the agitator  136 . As illustrated in  FIG. 13 , the agitator  136  comprises a hollow core  138 , which in this embodiment is also conical in shape. The core  138  is formed from a relatively rigid plastics material, such as ABS. The core  138  comprises a conical external surface  140  which extends between a relatively small first end  142  and a relatively large second end  144 . In this embodiment, the cone angle of the core  138  is approximately 5°. 
     In this embodiment, tufts of bristles  156  are mounted on the core  138  of the agitator  136 . The tufts of bristles  156  are arranged in a helical row which extends about the core  138  of the agitator  136 . The tufts of bristles  156  may be individually connected to the core  138 , for example using a stapling technique. Alternatively, the tufts of bristles  156  may be provided in the form of a bristle strip in which tufts of bristles  156  are mounted on a bristle base which is inserted into a helical channel extending about the core  138 . 
     The bristles  156  are formed from nylon, and have sufficient strength to agitate dust and debris located upon a surface to be cleaned in use, whilst still having sufficient flexibility to resiliently deform relative to the bristle base or the core  138  of the agitator  136 . Similar to the first embodiment, the bristles  156  are arranged on the core  138  so that the bristles  156  are inclined towards the first end  142  of the core  138 , but such that the direction of the taper of the bristles  156  extends helically about the core  138  from the second end  144  towards the first end  142  of the core  138 . 
     As in the first embodiment, the agitator  136  is mounted within the suction cavity  134  in a cantilevered manner so that the first end  142  of the core  138  is spaced from the side wall  158  of the lower housing section  112 . In this embodiment, the spacing between the first end  142  of the core  138  and the side wall  158  is preferably in the range from 10 to 20 mm. The agitator  136  is mounted so that the longitudinal axis of the agitator  136  is inclined at an acute angle to a plane containing the suction opening  122 . This acute angle is preferably in the range from 5 to 15°, and in this embodiment is approximately 5°. As illustrated in  FIG. 13 , the agitator  136  is mounted such that the lowermost portion of the external conical surface  140  of the core  138  is parallel to the plane containing the suction opening  122 . The length of the bristles  156  is selected such that, when not subject to external forces, the lowermost tips of the bristles  156  are located beneath the plane containing the suction opening  122 . 
     The rotation of the agitator  136  is driven by a motor  160 , illustrated in  FIG. 14 , which is housed inside the upper housing section  114 . The motor is arranged to rotate the agitator  136  in such a direction that the bristles  156  sweep dirt and debris rearwardly, that is, over the rear working edge  126 , into the suction cavity  134 . The connection of the motor  160  to the agitator  136  is the same as the connection of the motor to the agitator  36  of the cleaner head  10 . 
     In this embodiment, the suction cavity  134  comprises a single air outlet  182 . The air outlet  182  is located in a similar position to the air outlet  82  of the cleaner head  10 ; the air outlet  182  is located rearwardly of the agitator  136  and is located above the plane containing the suction opening  122 . With particular reference to  FIG. 13 , in this embodiment though the air outlet  182  is spaced from the free end  142  of the agitator  136  along the longitudinal axis X of the agitator  136 . The spacing of the air outlet  182  from the free end  142  of the agitator  136  along this direction is preferably less than 10 mm, more preferably less than 5 mm. The air outlet  182  conveys air into a duct  192  which extends externally between the upper housing section  114  and a neck  184  of the cleaner head  110 . The duct  192  is preferably rigid and is preferably integral with the upper housing section  114  and/or at least part of the neck  184 . The duct  192  conveys air from the air outlet  182  to an air inlet port located within the neck  184  between the housing and the outlet  186  of the cleaner head  110 . As in the first embodiment, the neck  184  includes a connector  188  for connecting the cleaner head  110  to a vacuum cleaner, and electrical connectors  190  for connecting the motor  160  to a power source of the vacuum cleaner. 
     With reference to  FIG. 15 , the cleaner head  110  also includes an agitator engaging member  196  for engaging the agitator  136 . The engaging member  196  is mounted on the inner surface of the lower housing section  112  so as to protrude into the suction cavity  134  to engage the agitator  136 . The engaging member  196  extends substantially the entire length of the agitator  136  so that, with rotation of the agitator  136 , the engaging member  196  presses against substantially the entire row of bristles  156 . In this embodiment, the engaging member  196  is located adjacent the suction opening  122  of the cleaner head  110 . 
     In use, an airflow is drawn through the cleaner head  110  by the motor and fan unit of a vacuum cleaner to which the cleaner head  110  is attached. The airflow enters the suction cavity  134  through the suction opening  122 . The airflow leaves the suction cavity  134  through the air outlet  182 , and passes along an airflow path extending within the duct  192  from the air outlet  182  to the air inlet port of the neck  184 , and then from the air inlet port to the air outlet  186 . The agitator  136  is driven by the motor  160  to rotate within the suction cavity  134 . With the sole plate  122  pressed against a carpeted floor surface, the rotating bristles  156  of the agitator  136  contact, and so transfer energy to, dust particles and debris located on the floor surface, or between the fibres of the floor surface. As the agitator  136  is rotated within the suction cavity  134  so that the bristles  156  pass from the front working edge  124  to the rear working edge  126 , the majority of the energised dust and debris is swept rearwardly through the suction opening  122 . Whilst the majority of the energised dust and debris becomes entrained within the airflow passing through the suction cavity  134  and passes through the air outlet  182 , some debris, such as hairs, threads, fibres and the like, can become wrapped around the agitator  136 . Such debris is encouraged by the conical shape of the agitator  136  to migrate along the length of the agitator  136  from the second end  144  towards the first end  142 . Under the action of the engaging member  196 , such debris is pressed around the agitator  136  until it falls from the first end  412  of the agitator  136 , whereupon the released debris becomes entrained within the airflow and passes through the duct  192  and into the neck  184  of the cleaner head  10 . As in the first embodiment, the inclination of the bristles  156  relative to the external surface  140  of the core  138  encourages the wrapped debris to migrate along the agitator  136 .