Abstract:
A brushbar including: a body having a channel extending in the longitudinal direction and a retaining feature provided along each side of the channel and spaced away from a bottom, wherein a depth of the channel decreases in the longitudinal direction of the channel; an agitator element that includes a flexible strip and an agitator, wherein the flexible strip is disposed in the channel and extends between each retaining feature and the bottom of the channel such that the retaining features retain the flexible strip in the channel and the agitator extends radially from the channel; and a shim disposed between the flexible strip and the bottom of the channel such that the flexible strip abuts each retaining feature, wherein a thickness profile of the shim decreases in the longitudinal direction by an amount corresponding to the decrease in the depth of the channel.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of United Kingdom Application No. 1601216.3 filed Jan. 22, 2016, the entire contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    This invention relates to a brushbar, a cleaner head, a vacuum cleaner and a method of manufacturing a brushbar. 
       BACKGROUND OF THE INVENTION 
       [0003]    Brushbars are used in vacuum cleaners in order to agitate dirt on a surface being cleaned. Agitation helps lift dirt from a surface so that it can then be sucked up into a separator. 
         [0004]    An example of a brushbar is provided in GB2526512A. The brushbar comprises a cylindrical body and two strips of bristles, which may comprises a strip of NYLON bristles and a strip of carbon fibre bristles. The strips of bristles extend in respective helixes about the cylindrical body. Typically, each strip of bristles comprises a strip of material to which the bristles are attached. Carbon fibre bristles may, for example, be secured to a strip of relatively stiff polymeric material by stitching. NYLON bristles are typically bonded to a flexible strip of fabric which itself may be NYLON. Channels having retaining lips on each of their respective sides are typically formed along a body of the brushbar. The bristle strips extend along the respective channels and are held in place by the retaining lips. 
         [0005]    In order to assemble such a brushbar, each bristle strip must be threaded from one end along a channel. If the depth of the channel is too shallow, the force required to force a strip along the channel risks deforming the bristle strips and, in the case of NYLON strips which are typically more flexible than the carbon fibre strips described in the example above, can make it very difficult and potentially impossible to completely insert the strip into a channel Conversely, if the depth of the channel is too deep, the spacing between the underside of each strip and bottom of each channel is such that the strip moves in the radial direction during use of the brushbar. This makes floor clearance difficult to maintain and, in the case of the NYLON bristles which tend to be stiff, can result in a bristle strip being pushed up into the channel thereby reducing the amount by which the bristles penetrate a carpeted surface, and adversely affecting pick-up performance. 
         [0006]    A brushbar which does not have the drawbacks mentioned above is therefore desirable. 
       SUMMARY OF THE INVENTION 
       [0007]    According to a first aspect of the invention, there is provided a brushbar for a cleaner head comprising: a brushbar body having a channel which extends generally in the longitudinal direction of the brushbar and at least one retaining feature provided along a portion of each side of the channel and spaced away from a bottom of the channel, the channel having a varying portion in which a depth of the channel decreases from one end of the varying portion in the longitudinal direction of the channel; an agitator element comprising a flexible strip and an agitator, the flexible strip is disposed in the channel and extends between each retaining feature and the bottom of the channel such that the retaining features retain the flexible strip in the channel and the agitator extends radially outwardly from the channel; and a shim disposed between the flexible strip and the bottom of the channel such that the flexible strip is held in abutting contact with each retaining feature, wherein the shim has a varying portion in which the thickness profile decreases in the longitudinal direction of the shim by an amount which corresponds to the decrease in the depth of the channel. 
         [0008]    The shim and flexible strip cooperate such that the flexible strip is held against the retaining features. This prevents the bristle strip from moving in a radial direction during use, and so improves penetration of carpets etc. Furthermore, the brushbar is easy to assemble since the force required to insert the bristle strip along the shim into the channel is relatively low. It will be appreciated that the flexible strip, channel, retaining features and/or shim need not have a uniform cross section. For example, the varying portion on the shim could have a cross-section (as viewed along the length of the shim) which is stepped or tapered, but the thickness profile of the cross-section decreases along the length of the varying portion. 
         [0009]    The rate of change in thickness profile of the varying portion of the shim in the longitudinal direction of the shim may be between 0.001 mm/mm to 0.01 mm/mm, and preferably between 0.002 mm/mm and 0.005 mm/mm, such as 0.0026. 
         [0010]    The varying portion of the channel may extend along at least half of the length of the channel, and preferably at least 75% of the length of the channel. Preferably, the varying portion of the shim extends along the whole length of the varying portion of the channel. 
         [0011]    The thickness profile of the flexible strip may be substantially constant along the length of the flexible strip. 
         [0012]    The retaining features may comprise a first retaining lip which extends along at least part of one side of the channel and a second retaining lip which extends along at least part of the opposite side of the channel. 
         [0013]    The distance between each retaining lip and the bottom of the channel along the varying portion of the channel may decrease in the longitudinal direction of the channel. 
         [0014]    The channel has an opening towards one end on the channel for insertion of the flexible strip and the shim into the channel. The opening may be at the end of the channel of formed as a wider portion of a slot between the retaining features. 
         [0015]    The distance between the bottom of the channel along the varying portion and each retaining feature may decrease in the direction away from the opening. 
         [0016]    The brushbar may further comprise a retainer secured at the open end of the channel in order to secure the agitator strip and shim within the channel. The retainer may comprise a cap secured to the end of the brushbar body. 
         [0017]    The width of the varying portion of the channel may decrease in the longitudinal direction of the channel. The width of the varying portion of the shim may decrease along the varying portion of the shim by an amount which corresponds to the decrease in the width of the channel. 
         [0018]    The agitator may comprise bristles which are secured to the flexible strip. The flexible strip comprises a fabric, for example a non-woven fabric. The flexible strip may be made of a polymer such as NYLON. The thickness of the flexible strip may be less than 1 mm, for example lea than 0.5 mm. 
         [0019]    The channel may extend in a helix through at least 180 degrees. 
         [0020]    According to a second aspect of the invention there is provided a cleaner head for a vacuum cleaner comprising a brushbar in accordance with the first aspect of the invention. 
         [0021]    According to a third aspect of the invention there is provided a cleaning appliance comprising a brushbar in accordance with the first aspect of the invention. 
         [0022]    According to a fourth aspect of the invention, there is provided a method of manufacturing a brushbar comprising the steps: providing a brushbar body having a channel which extends generally in the longitudinal direction of the brushbar and at least one retaining feature provided along a portion of each side of the channel and spaced away from a bottom of the channel, the channel having a varying portion in which a depth of the channel decreases from one end of the varying portion in the longitudinal direction of the channel; inserting an agitator element comprising a flexible strip and an agitator into the channel such that the flexible strip is disposed in the channel and extends between each retaining feature and the bottom of the channel and the agitator extends radially outwardly from the channel; inserting a shim between the flexible strip and the bottom of the channel such that the flexible is pressed into abutting contact with each retaining feature, the shim having a varying portion in which the thickness profile decreases in the longitudinal direction of the shim by an amount which corresponds to the decrease in the depth of the channel. 
         [0023]    The brushbar may comprise one or more of the features of the brushbar in accordance with the first aspect of the invention. 
         [0024]    The channel may have an opening towards one end of the channel through which the flexible strip and shim are inserted. The method may further comprise the step of securing a retainer at the open end in order to retain the agitator strip and the shim within the channel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    In order to better understand the present invention, and to show more clearly how the invention may be put into effect, the invention will now be described, by way of example, with reference to the following drawings: 
           [0026]      FIG. 1  shows a stick vacuum cleaner; 
           [0027]      FIG. 2  shows the cleaner head of the stick vacuum cleaner shown in  FIG. 1 ; 
           [0028]      FIG. 3  shows a brushbar of the cleaner head shown in  FIG. 2 ; 
           [0029]      FIG. 4  shows an exploded view of a brushbar body of the brushbar shown in  FIG. 3 ; 
           [0030]      FIG. 5  is a schematic representation of a portion of the brushbar shown in  FIG. 3  in section; and 
           [0031]      FIG. 6  is an exploded view of the brushbar shown in  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0032]      FIG. 1  shows a stick vacuum  2  cleaner comprising a main body  4 , cyclonic separating apparatus  6 , a wand  8  and a cleaner head  10 . 
         [0033]      FIG. 2  shows the cleaner head  10  in isolation. The cleaner head  10  comprises a body  12 , an articulated neck  14  which is rotatably connected to the body  12  and a brushbar  16  (not visible in  FIG. 2 , but shown in isolation in  FIG. 3 ) housed within the body  12 . 
         [0034]    The brushbar  16  shown in  FIG. 3  comprises a brushbar body  18  comprising a tubular portion  20  formed of a single piece of material, an end cap  22 , a first bristle strip  24  and a second bristle strip  26 . The brushbar  16  has a longitudinal axis X. 
         [0035]    The first bristle strip  24  comprises a flexible strip  28 , which is shown in  FIGS. 5 and 6 , formed from a fabric, such as a non-woven fabric, and a plurality of bristles  30  bonded to the flexible strip  28 . The flexible strip  28  has a substantially constant thickness T F  along its length. The thickness of the flexible strip  28  is such that the flexible strip  28  flexes under its own weight and cannot, for example, support itself when held at one end. The thickness of the flexible strip  28  is less than 0.5 mm. In the embodiment shown, the bristles  30  are made of NYLON. 
         [0036]    The second bristle strip  26  comprises a stiff strip  32  which is relatively stiff compared with the flexible strip  28 , such as a strip made of plastic, and a plurality of bristles  34  that are secured to the stiff strip  32  by stitching. In the embodiment shown the bristles are carbon fibre bristles. 
         [0037]    An exploded view of the brushbar body  18  in isolation in  FIG. 4 . The brushbar body  18  has first and second raised helical formations  36 ,  38  formed about the circumference of the brushbar body  18 . Each formation  36 ,  38  extends through 360 degrees about the outer periphery of the brushbar body  18 . The formations  36 ,  38  are spaced apart from each other by 180 degrees so that they are diametrically opposite each other at any point along the longitudinal axis X of the brushbar  16 . 
         [0038]    Respective first and second channels  40 ,  42  are formed along the length of each formation  36 ,  38 . The end of each channel  40 ,  42  adjacent the end cap  22  is open. 
         [0039]    Retaining features in the form of first and second retaining lips  44 ,  46  extend along the upper edges of the first channel  40  respectively such that they overhang the first channel  40  to form a slot between the retaining lips  44 ,  46 . 
         [0040]    The first channel  40  has a depth D C  that decreases from the open end, which is the nearest the end cap  22 , along the length of the first channel  40 . The rate of change in the depth D C  of the first channel  40  along its length is substantially constant along the first channel  40 . The rate of change in the depth D C  along the length of the first channel  40  is between 0.001 mm/mm to 0.01 mm/mm, and preferably between 0.002 mm/mm and 0.005 mm/mm. The first and second retaining lips  44 ,  46  have a constant thickness profile along their length such that the distance D L  between the lower surface of each retaining lip  44 ,  46  and the bottom of the first channel  40  decreases along the length of the first channel  40  away from the open end adjacent the end cap  22 . Each retaining lip  44 ,  46  need not have a uniform thickness across its width, but the width profile of each retaining lip  44 ,  46  does not vary along its length. The second retaining lip  46  has a notch  47  in it adjacent the open end. 
         [0041]    Third and fourth retaining lips  48 ,  50  extend along the upper edges of the second channel  42  such that they overhang the second channel  42  to form a slot between the retaining lips  48 ,  50 . The depth of the second channel  42  is substantially constant along its length and the third and fourth retaining lips  48 ,  50  have a constant thickness profile such that the distance between the lower surface of each retaining lip  48 ,  50  and the bottom of the second channel  42  does not vary along the length of the second channel  42 . The open end of the second channel  42  is adjacent the end cap  22 . 
         [0042]    As shown in  FIG. 5 , the first bristle strip  24  is located within the first channel  40  such that the side edges of the flexible strip  28  extend underneath the retaining lips  44 ,  46  respectively and the bristles  30  protrude outwardly from the first channel  40  through the slot formed by the retaining lips  44 ,  46 . The first bristle strip  24  is therefore held captive within the first channel by the lips  44 ,  46 . 
         [0043]    A shim  52 , shown in  FIGS. 5 and 6 , is disposed between the flexible strip  28  and the bottom of the first channel  40  such that the shim  52  holds the flexible strip  28  in abutting engagement with the undersides of the retaining lips  44 ,  46 . The thickness T S  of the shim  52  decreases in the direction away from the end cap  22 . The shim  52  is therefore tapered along its length. The change in the thickness T S  of the shim  52  corresponds to the change in the depth D C  of the first channel  40 . For a shim  52  having a length of 230 mm the thickness T S  of the shim  52  may vary from 1.2 mm at the thicker end to 0.6 mm at the thinner end. The rate of change of thickness of the shim  52  in the longitudinal direction of the shim  52  can be between 0.001 mm/mm to 0.01 mm/mm, and preferably between 0.002 mm/mm and 0.005 mm/mm. The combined thickness T S  of the shim  52  and the thickness T F  of the flexible strip  28  is equal to the distance D L  between the lower surface of each retaining lip  44 ,  46  and the bottom of the first channel  40  along the length of the first channel  40 . The shim  52  has a tab  54  at the thickest end of the shim  52  which stands proud of the upper surface of the rest of the shim  52 . It will be appreciated that the cross-section of the shim  52  need not be uniform. For a shim  52  having a non-uniform cross-section, the cross-sectional profile of the shim  52  corresponds to the cross-sectional profile of the portion of the first channel  40  which it occupies. 
         [0044]    Assembly of the brushbar  16  will now be described with particular reference to  FIG. 6 . 
         [0045]    Firstly, the stiff strip  32  of the second bristle strip  26  is inserted through the open end of the second channel  42  formed in the tubular portion  20  of the brushbar body  18  such that the edges of the strip of material  32  slide along the second channel  42  underneath the retaining lips  48 ,  50  until the second bristle strip  26  has been inserted completely through the open end of the second channel  42 . Once fully inserted, the second bristle strip  26  is retained by the third and fourth retaining lips  48 ,  50  and the carbon fibre bristles  34  project radially outwardly from the brushbar body  18  through the slot formed between the retaining lips  48 ,  50 . The thickness of the stiff strip  32  is equal to the distance between the lower surface of the third and fourth retaining lips  48 ,  50  and so the upper surface of the stiff strip  32  contacts the respective lower surfaces of the retaining lips  48 ,  50  and the lower surface of the stiff strip  32  contacts the bottom of the second channel  42  such that the stiff strip  32  forms a friction fit within the second channel  42 . 
         [0046]    Secondly, the flexible strip  28  of the first bristle strip  24  is inserted through the open end of the first channel  40  such that the edges of the flexible strip  28  slide along the first channel  40  underneath the first and second retaining lips  44 ,  46  and the bristles  30  protrude outwardly from the first channel  40  between the retaining lips  44 ,  46 . The relatively large distance D L  between the bottom of the first channel  40  and the underside of the retaining lips  44 ,  46  ensures that the first bristle strip  24  can be pushed or drawn along the entire length of the channel unimpeded (i.e. there is very little friction between the flexible strip  28  and the bottom of the first channel  40  or the lower surfaces of the retaining lips  44 ,  46 ). Once the flexible bristle strip  28  has been inserted completely into the first channel  40 , the thinnest end of the shim  52  is inserted into the first channel  40  between the flexible strip  28  and the bottom of the first channel  40 . As the shim  52  is inserted, the flexible strip  28  is pushed radially outwardly by the shim  52  towards the retaining lips  44 ,  46 . As the shim  52  reaches the point of being completely inserted, it presses the flexible strip  28  against the underside of the lips  44 ,  46 . It is only as the shim  52  pushes the flexible strip  28  against the retaining lips  44 ,  46  that any significant resistive frictional force between the shim  52  and the base of the first channel  40 , is exerted on the shim  52 . Consequently, the force exerted on the shim  52  need not be excessive and so likelihood of damaging the shim  52  or the flexible strip  28  during assembly is low. Once fully inserted, the tab  54  engages with the notch  47  formed in the second retaining lip  46 . This prevents the shim  52 , which is slightly shorter than the length of the first channel  40 , from being pushed further into the first channel  40 . 
         [0047]    A benefit of the arrangement is that the flexible strip  28  can be very flexible since, unlike the stiff strip  32  of the second bristle strip  26 , the flexible strip  28  need not be designed to withstand a frictional force as it is inserted into the first channel  40 . The flexible strip  28  can also have a constant thickness. The bristle strip  26  can therefore be made using a fabrication process that is relatively simple and low cost. The arrangement is particularly beneficial when the length of the first channel  40  is relatively long in which case the relatively large frictional forces that would be generated by insertion of a bristle strip having frictional fit are avoided. This enable a much longer channel to be used than would otherwise be possible. In the embodiment shown, the shim  52  is stiffer than the flexible strip  28  and is of sufficient stiffness to ensure that it does not deform excessively as the shim  52  is pushed completely into the first channel  40 . 
         [0048]    A further benefit of the arrangement is that the shim  52  can be configured to provide a counter weight to the second bristle strip  26 , which in the embodiment described is heavier than the first bristle strip  24 . The shim  52  can therefore be used to balance the brushbar  16  about the longitudinal axis X. 
         [0049]    Once the first and second bristle strips  24 ,  26  have been assembled with the tubular portion  20  of the brushbar body  18 , the end cap  22  is secured in place at the end of the tubular portion  20 . The end cap  22  may be a push fit and/or may be secured by gluing and/or welding. The end cap  22  holds the first and second bristle strips  24 ,  26  and the shim  52  in place within the channels  40 ,  42 . 
         [0050]    It will be appreciated that in alternative embodiments, shims could be used for both sets of bristle strips. 
         [0051]    At least part of the first channel could have a width that decreases in the same direction as the depth of the first channel decreases and the width of the shim has a width which decreases by an amount which corresponds to the decrease in the width of the first channel. This would further aid insertion of the shim.