TECHNICAL FIELD

The invention relates generally to vacuum cleaner appliances, and particularly to a cleaner head or floor tool which forms part of the appliances. The invention is concerned specifically with rotationally-driven agitator assemblies used in such cleaner heads, whether or not the cleaner head is permanently or removably fixed to their respective appliance. The type of vacuum cleaner appliance is immaterial to the invention, and so the invention may relate to so-called bagged or bagless vacuum cleaner appliances.

BACKGROUND

A vacuum cleaning appliance or, more simply, “vacuum cleaner”, typically comprises a main body, equipped with a suction source and a dust separator, and a cleaner head connected to the dust separator usually by a separable coupling. The cleaner head has a suction opening with which it engages a surface to be cleaned and through which dirt-laden air is drawn into the vacuum cleaner towards the dust separator. The cleaner head performs a crucial role in the effectiveness of a vacuum cleaner in removing dirt from a surface, whether that surface is a hard floor covering such as wood or stone, or a soft floor covering such as carpet. Therefore, much effort is made by vacuum cleaner manufacturers to optimise cleaner head design to improve performance.

Some cleaner heads are passive devices which rely on stationary elements such as so-called ‘active edges’ and bristle strips to dislodge dirt from floor coverings. These types of cleaner heads are relatively simple but generally their effectiveness at removing dirt from surfaces is limited. Often, they are recommended mainly for use on hard surfaces.

Conventionally, the most effective cleaner heads incorporate some kind of powered brush bar or agitator. Examples are known in which the agitator is driven by a turbine which is actuated by the air flow through the cleaner head. Other known arrangements involve the use of an electric motor that is arranged to drive the agitator. In these known arrangements, it is usual for the motor to be coupled to the agitator by a suitable drive linkage such as a belt or gear mechanism, although it is also known for the motor to be housed within the agitator which provides a particularly space- efficient arrangement.

In either example, the powered agitator serves to wipe and beat the floor surface in order to improve the capability of the cleaner head to remove dirt from the surface. A common configuration is for the agitator to carry an array of bristles that extend outwardly from the outer radial surface of the agitator. The bristles are typically relatively stiff so that they engage the floor surface aggressively as the agitator rotates, thereby serving as a means to scrape and strike the floor surface to loosen embedded particles. Other strips of material such as rubber and carbon fibre bristles or filaments may be used to provide complementary characteristics to the agitator.

A significant design challenge is to optimise the way in which air flows through the cleaner head, from where air enters its interior, through the suction opening, to where air is discharged from an outlet towards the dust separator. It is known that air flow velocity is an important factor in pick-up performance since dirt particles are transported more effectively when the velocity of air moving through the tool is high. However, maintaining a high flow velocity is not straightforward, and generally correlates to high energy consumption. This is generally undesirable due to the drive towards energy efficient machines, and has particular relevance to battery powered vacuum cleaners where energy efficiency has a direct effect on available runtime. Even with high flow velocities, however, areas of comparatively low flow velocities can exist within the cleaner head, particularly at the extremities of the cleaner head. This takes away from the uniformity of the air flow through the cleaner head, which can reduce the evacuation of dirt particles and other lightweight debris from the cleaner head.

It is against this background that the invention has been devised.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a cleaner head for a vacuum cleaning appliance, the cleaner head comprising a main body defining an agitator chamber having an interior surface; and, an agitator assembly supported within the agitator chamber, wherein the agitator assembly comprises an elongate body configured to rotate about its longitudinal axis; an agitator formation comprising at least one agitator row extending from an outer surface of the elongate body for engaging a surface to be cleaned during use; and, a compressor formation comprising at least one compressor element extending from the outer surface of the elongate body such that a radial distance defined between the at least one compressor element and the interior surface of the agitator chamber is less than a radial distance defined between the outer surface of the elongate body and the interior surface of the agitator chamber. The compressor formation generally functions to displace air between the agitator assembly and the interior surface of the agitator chamber in order to disrupt a primary airflow structure within the agitator chamber, helping to avoid the accumulation of dirt particles, and other lightweight debris within agitator chamber.

Preferably, the at least one compressor element extends substantially axially along the elongate body. The elongate structure increases the area of the compressor elements that is used to push air against the interior surface of the agitator chamber, increasing the displacement of air to disrupt the primary airflow structure. More preferably, the at least one compressor element extends axially along the elongate body in a helical direction. Due to their helical arrangement, the compressor element substantially wraps around a circumference of the elongate body, increasing the period over which the compressor element disrupts the primary airflow structure per revolution of the elongate body.

Preferably, an axially inner end of the at least one compressor element is angularly further forward than an axially outer end of the at least one compressor element with respect to the direction in which the elongate body is configured to rotate. This arrangement helps to direct airflow from the axially inner end of the compressor element towards the axially outer end, and so an end of the agitator chamber where dirt particles and other lightweight debris are prone to accumulate.

Alternatively, an axially outer end of the at least one compressor element is angularly further forward than an axially inner end of the at least one compressor element with respect to the direction in which the elongate body is configured to rotate. This arrangement is advantageous as the compressor element is generally counter to the angled arrangement of the agitator rows, increasing the disruption of the primary airflow structure. Preferably, the at least one compressor element extends from a side edge of the elongate body.

This arrangement is advantageous as it displaces airflow near to an edge of the elongate body, which is adjacent the end of the agitator chamber where dirt particles and other lightweight debris tend to accumulate. Preferably, the at least one compressor element extends axially to the centre of the elongate body. This maximises displacement of air on one side of the cylindrical body.

Preferably, the agitator formation comprises a second agitator row and wherein the at least one compressor element is angularly positioned at an equal distance between the two agitator rows. This arrangement is advantageous since this causes a disruption to the primary airflow structure midway between the “pumping strokes” of the agitator rows where the displacement of air contributing to the primary airflow structure is a minimum.

Preferably, the at least one compressor element comprises a planar surface extending tangentially away from the outer surface of the elongate body. This channels the airflow between the planar surface and the interior surface of the agitator chamber to impose on the primary airflow structure a secondary airflow structure that has a high instantaneous velocity, increasing the disruption to the primary airflow structure. Preferably, the planar surface extends in a direction generally opposite to the direction in which the elongate body is configured to rotate. This arrangement provides a large compression at the trailing edge of the compressor element.

Preferably, the compressor formation comprises two compressor elements. This arrangement provides more disruption to the primary airflow structure per revolution of the elongate body.

Preferably, one compressor element of the two compressor elements is located one of either the left- or right-side of the elongate body and the other compressor element of the two compressor elements is located on the other of the left- or right-side of the elongate body, providing a disruptive flow on both sides of the elongate body.

Preferably, one compressor element of the two compressor elements is located on the opposite circumferential side of the elongate body from the other compressor element, providing alternating disruptive flows as the elongate body rotates.

According to another aspect of the invention, there is provided a vacuum cleaning appliance comprising the cleaner head according to the previous aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects 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 perspective view of a vacuum cleaner comprising a cleaner head;

FIG. 2 is a front perspective view of the cleaner head of FIG. 1 ;

FIG. 3 is a bottom view of the cleaner head of FIG. 1 showing a known agitator assembly;

FIG. 4 is a perspective view of the known agitator assembly of FIG. 3;

FIG. 5 is an upper sectional view of the cleaner head of FIG. 1 ;

FIG. 6 is a cross-sectional view of a cleaner head comprising an agitator assembly according to an embodiment of the invention;

FIG. 7 is a cross-sectional view of a cleaner head comprising an agitator assembly according to another embodiment of the invention; FIG. 8 is a perspective view of another embodiment of an agitator assembly according to the invention;

FIG. 9 is a perspective view of another embodiment of an agitator assembly according to the invention; and,

FIG. 10 is a perspective view of another embodiment of an agitator assembly according to the invention.

In the drawings, like features are denoted by like reference signs.

SPECIFIC DESCRIPTION

Specific embodiments of the invention will now be described in which numerous features will be discussed in detail in order to provide a thorough understanding of the inventive concept as defined in the appended claims. However, it will be apparent to the reader that the invention may be put in to effect without the specific details and that, in some instances, well known methods, techniques and structures have not been described in detail in order not to obscure the inventive concept unnecessarily.

FIG. 1 shows a known vacuum cleaning appliance or vacuum cleaner 2 comprising a dirt and dust separating unit 4, a motor-driven fan unit 6 and a cleaner head 8. The vacuum cleaner 2 further comprises a wand 10 connecting the dirt and dust separating unit 4 and the cleaner head 8. The motor-driven fan unit 6 draws dirt-bearing air through the cleaner head 8, from a surface to be cleaned, such as a floor surface, to the dirt and dust separating unit 4, where dirt and dust particles (hereinafter, “dirt particles) are separated from the dirt-bearing air and the comparatively clean air is expelled from the vacuum cleaner 2. The dirt and dust separating unit 4 shown in this example is a cyclonic separating unit. However, the type of separating unit is not material to the invention and the reader will understand that an alternative separating unit or a combination of different separating units could be used. Similarly, the vacuum cleaner 2 shown in FIG. 1 is a so- called stick vacuum cleaner but the nature of the vacuum cleaner is not important for the invention, and the reader will understand that the invention may be used with other types of vacuum cleaners such as, for example, upright or cylinder vacuum cleaners.

With reference to FIG. 2, the cleaner head 8 comprises a main body 12 rotatably attached to a coupling 14. The coupling 14 is configured to be removably connectable to the wand 10, a hose or other such duct of a vacuum cleaner. The main body 12 comprises a housing, generally designated by 16, comprising an upper section 18 and a lower plate or sole plate 20, which defines a generally rectangular suction opening 22 through which dirt-bearing air enters the cleaner head 8 from the floor surface. The housing 16 defines a suction passage extending through the internal volume of the main body 12 from the suction opening 22 to an outlet duct 24 located at a rear section 26 of the housing 16. The coupling 14 comprises a conduit (not visible in FIG. 2), which is supported by a rolling assembly 28. The conduit comprises a forward portion connected to the outlet duct 24 and a rearward portion, pivotably connected to the forward portion. The part of the coupling 14 defining the rearward portion of the conduit comprises a fixing arrangement, generally designated by 30, for connecting a free end 15 of the coupling 14 to the wand 10. A rigid curved hose arrangement is held within and extends between the forward and rearward portions of the conduit.

With reference to FIG. 3, two wheels 32 are mounted within recessed portions in the bottom surface of the sole plate 20 for supporting the cleaner head 8 on the floor surface. The wheels 32 are configured to support the sole plate 20 above the floor surface when the cleaner head 8 is located on a hard floor surface, and, when the cleaner head 8 is located on a carpeted floor surface, to sink into the pile of the carpet to enable the bottom surface of the sole plate 20 to engage the fibres of the carpet. The sole plate 20 may be moveable relative to the housing 16, allowing it to ride smoothly over the carpeted floor surface during cleaning.

The internal volume of the main body 12 comprises an agitator chamber 34, which is partially defined by the upper section 18 of the housing 16. An elongate brush bar or agitator assembly 36 is supported within the agitator chamber 34 and comprises a hollow, elongate body 42 rotatable about its longitudinal axis. In this example, the elongate body 42 is cylindrical, having a generally circular cross-section, and will from this point onward be referred to as the cylindrical body 42. The reader will understand, however, that the shape of the cylindrical body 42 is not material to the invention. The main body 12 further comprises two end caps 38, 40 mounted on the housing 16 at each end of the agitator chamber 34 for rotatably supporting the agitator assembly 36 within the agitator chamber 34. Preferably, at least one of the end caps 38, 40 is detachable from the housing 16, providing access to the agitator chamber 34 so that the agitator assembly 36 can be removed from and subsequently replaced within the agitator chamber 34. In the example shown, a recessed portion is provided in the end cap 40 for facilitating its removal from the housing 16 for accessing the agitator chamber 34. The agitator assembly 36 houses an electric motor and a drive mechanism, which connects the agitator assembly 36 to the electric motor for driving the agitator assembly 36 about its longitudinal axis. Such a drive arrangement is known and so will not be explained in further detail here, and alternative drive arrangements may be used.

Wth reference to FIG. 4, the cylindrical body 42 of the agitator assembly 36 bears an agitator formation, generally designated by 44. In this example of the agitator assembly 36, the agitator formation 44 comprises two agitator rows 46 extending axially along an outer surface 48 of the cylindrical body 42 in a helical formation, with each of the agitator rows 46 extending through 360° about the outer surface 48 of the cylindrical body 42. The agitator rows 46 extend in a direction away from the outer surface 48 the cylindrical body 42 for agitating dirt particles, together with other debris, located on the floor surface as the agitator assembly 36 is rotated in the agitator chamber 34 by the electric motor. The agitator rows 46 have a base fixed to the cylindrical body 42, by means of respective retaining members 47, and are configured to rotate with the cylindrical body 42 when the electric motor drives the agitator assembly 36. The retaining members 47 may comprise one or more channels for receiving and holding the agitator rows 46, and, in some examples, could form part of the cylindrical body 42. The agitator rows 46 may include a plurality of soft filaments, having tips that can flex relative to the cylindrical body 42 upon contact with the floor surface, stiff bristles or a strip of continuous material, and may be made of carbon fibre or nylon, to name two common material examples. Furthermore, instead of a continuous strip of bristles or filaments, as shown here, the agitator rows 46 could be made up of a row of discrete tufts of bristles or filaments. In examples where an agitator row 46 is made of nylon, the clearance formed between their outer radial ends and an interior surface 50 of the agitator chamber 34 is in the range of 0.5mm to 2mm when the agitator assembly 36 is mounted within agitator chamber 34. However, in examples where an agitator row 46 is made of carbon fibre, the agitator row 46 is configured to extend outwardly from the outer surface 48 of the cylindrical body 42 at an angle, so that they incline in the direction in which the agitator assembly 36 is configured to rotate.

The general arrangement of agitator formation 44, which in this example includes two agitator rows 46 arranged in a helical formation, and a negligible clearance between the agitator rows 46 and the interior surface 50 of the agitator chamber 34, gives rise to an asymmetric flow through the agitator chamber 34 during use, as will now be explained in more detail with reference to FIG. 5.

FIG. 5 shows an upper side of the agitator assembly 36, which, in this example, is configured to rotate forwards, away from the outlet duct 24, while the lower side rotates rearwards, towards the outlet duct 24. During use, air can enter the agitator chamber 34 at any point around the perimeter of the suction opening 22 whether the sole plate 20 is in clearance of the floor surface (e.g. on a hard floor surface) or on a porous media (e.g. a carpeted floor surface). The rotation of the agitator assembly 36 produces a so-called “brush bar induced flow” (hereinafter, “the primary airflow structure”) within the agitator chamber 34 that imposes a large lateral flow component on the airflow entering the agitator chamber 34 from the suction opening 22, pushing or pumping it from the left- to the right-hand side of the agitator chamber 34 before it then goes on to exit the cleaner head 8 through the outlet duct 24, as indicated by arrows 52. So, while one side of the agitator chamber 34, in this example the right-hand side, experiences a high velocity air flow, the velocity of the airflow on the other side is comparatively much lower. Over time, dirt particles will accumulate in the areas of the agitator chamber 34 subject to the lower velocity airflow, thereby decreasing the evacuation of dirt particles from the cleaner head 8 and increasing the likelihood of them inadvertently returning to the floor surface. One such area is circled in FIG. 5 and generally designated by 53. This “pumping” effect is especially prevalent when using agitator assemblies comprising at least one agitator row arranged in a helical formation, but it also present if agitator rows are arranged in a so-called chevron formation, where opposing agitator rows extend, at an angle, from opposite sides of the cylindrical body to meet at its centre.

FIG. 6 shows a cleaner head 8 comprising an embodiment of an agitator assembly 36 in accordance with the invention. The agitator assembly 36 of this embodiment is substantially the same as the previous agitator assembly 36 save the inclusion of a compressor formation, generally designated by 56, comprising at least one compressor element 58. Two compressor elements 58 are shown diametrically opposite each other, but the benefits derived from the invention could also be realised, at least partially, by using a single compressor element 58 or more than two compressor elements 58. The compressor elements 58 are distinct from the retaining formation 47 and the agitator rows 46, and are configured to extend from the outer surface 48 of the cylindrical body 42 such that a radial distance defined between the compressor elements 58 and the interior surface 50 of the agitator chamber 34 is less than a radial distance defined between the outer surface 48 of the cylindrical body 42 and the interior surface 50 of the agitator chamber 34. The compressor formation 56 generally functions to mitigate the effects of the primary airflow structure by displacing air between the agitator assembly 36 and the interior surface 50 of the agitator chamber 34 in order to disrupt the primary airflow structure. For example, the primary airflow structure within the agitator chamber 34 comprises a circumferential airflow component, designated by 60, in addition to the lateral airflow component, both of which are caused by the rotation of the agitator assembly 36. In the orientation of the cleaner head 8 shown in FIG. 6, the agitator assembly 36 is configured to rotate anticlockwise, establishing the primary airflow structure in the agitator chamber 34 having a circumferential airflow component 60 that also circulates anticlockwise. During the rotation of the agitator assembly 36, the compressor elements 58 compress the air between their radial ends and the interior surface 50 of the agitator chamber 34, effectively pushing the air against the interior surface 50 of the agitator chamber 34, inducing a secondary airflow structure within the agitator chamber 34 superimposed on the primary airflow structure. In this embodiment, the secondary airflow structure, generally designated by 62, rotates in a direction opposite to that of the circumferential flow component 60 to disrupt the primary airflow structure and reduce its asymmetry, providing higher velocity airflow in areas of the agitator chamber 34 that would otherwise be subject to the lower velocity airflow. In doing so, the accumulation of dirt particles, and other lightweight debris, within the agitator chamber 34 can be avoided, improving the evacuation of the cleaner head 8. In addition to the primary effect of reducing the asymmetry of the primary airflow structure, a secondary effect of the compressor elements 58 is that, as they rotate above the floor surface, they also compress the air above it to create a fanning effect across the floor surface that encourages dirt particles, together with other lightweight debris, from the floor surface into the agitator chamber 34, improving the pickup efficiency of the cleaner head 8. FIG. 7 shows a cleaner head 8 comprising another embodiment of an agitator assembly 36 in accordance with the invention. This embodiment of the agitator assembly 36 is the same as the previous embodiment save that the compressor elements 58 have a generally triangular profile in cross-section as opposed to the rectangular profiles shown in FIG. 6. In this embodiment, the radial distance defined between an apex 61 of the compressor elements 58 and interior surface 50 of the agitator chamber 34 is less than the radial distance defined between the outer surface 48 of the cylindrical body 42 and the interior surface 50 of the agitator chamber 34. The compressor elements 58 comprise a first planar surface 63 extending tangentially away from the outer surface 48 of the cylindrical body 42 and a second planar surface 65 arranged substantially perpendicular to the first planar surface 63 and extending between the first planar surface 63 and the outer surface 48 of the cylindrical body 42. In this embodiment, the first planar surface 63 is arranged to extend from the outer surface 48 of the cylindrical body 42 in a direction generally opposite to the direction in which the cylindrical body 42 is configured to rotate. This arrangement has the effect of progressively tapering the radial distance between the compressor elements 58 and the interior surface 50 of the agitator chamber 34, up to the apex 61 of the compressor elements 58, as the agitator assembly 36 rotates. This channels the airflow between the first planar surface 63 and the interior surface 50 of the agitator chamber 34 to impose on the primary airflow structure a secondary airflow structure 62 that has a comparatively higher instantaneous velocity when compared to the instantaneous velocity of the secondary airflow structure 62 induced by the abrupt or “stepped” reduction of the radial distance provided by the rectangular compressor elements 58 of FIG. 6.

In the embodiments shown in the previous two figures, comprising two diametrically opposite compressor elements 58, the compressor elements 58 are angularly positioned midway between the agitator rows 46. Spacing the compressor elements 58, or in embodiments comprising a single compressor element 58, midway between the agitator rows 46 is advantageous since this causes a disruption to the primary airflow structure midway between the “pumping strokes” of the agitator rows 46 where the displacement of air contributing to the primary airflow structure is a minimum.

The inventive concept, as defined in the appended claims, is intended to cover any compressor formations 56, separate from the retaining formations 47 and the agitator rows 46, comprising at least one compressor element 58 that reduces the radial distance to the interior surface 50 of the agitator chamber 34, when compared to the radial distance defined between the outer surface 48 of the cylindrical body 42 and the interior surface 50 of the agitator chamber 34, to induce the secondary airflow structure within the agitator chamber 34. There exists many embodiments of compressor formations 56 having different structures, orientations, number of compressor elements 58, etc., all of which meet the primary consideration of reducing the radial distance to the interior surface 50 of the agitator chamber 34 to promote the secondary airflow structure, thereby disrupting the primary airflow structure. It should be noted, however, that, unlike the agitator rows 46, none of the compressor elements 58 include a plurality of soft filaments, stiff bristles or strips of continuous material.

The agitator rows 46 may include a plurality of soft filaments, having tips that can flex relative to the cylindrical body 42 upon contact with the floor surface, stiff bristles or a strip of continuous material, and may be made of carbon fibre or nylon, to name two common material examples.

One such embodiment is illustrated in FIG. 8, which shows an agitator assembly 36 comprising a cylindrical body 42 and a compressor formation 56 having two compressor elements 58 located on the same diametric side of and upwardly standing from the outer surface 48 of the cylindrical body 42. One of the compressor elements 58 is located on the left side of the cylindrical body 42, while the other is located on the right side. The compressor elements 58 are elongate insofar that they generally extend axially in directions from respective edges of the cylindrical body 42 toward the axial centre of the cylindrical body 42. This elongate structure increases the area of the compressor elements 58 that is used to push air against the interior surface 50 of the agitator chamber 34, establishing a larger secondary airflow structure and further reducing the asymmetry of the primary airflow structure. The compressors elements 58 might axially extend substantially parallel with the longitudinal axis of the agitator assembly 36. Alternatively, either one or, as shown in FIG. 8, both compressor elements 58 could be angled such that axially inner ends 64 of the compressor elements 58 are angularly further forward than their axially outer ends 66 with respect to the direction in which the cylindrical body 42 is configured to rotate. This helps to direct airflow from the axially inner ends 64 of the compressor elements 58 towards their axially outer ends 66, and the ends of the agitator chamber 34. Conversely, either one or both of the compressor elements 58 could be arranged such that their axially outer ends 66 are angularly further forward than their axially inner ends 64 with respect to the direction in which the cylindrical body 42 is configured to rotate, as shown in FIG. 9. The angled arrangement of the compressor elements 58 is advantageous if it is generally counter to the angled arrangement of the agitator rows 46 as it increases the disruption of the primary airflow structure.

With reference to FIG. 10, in yet another embodiment, the compressor formation 56 comprises a plurality of compressor elements 58 interposed between the agitator rows 46 and collectively arranged such that they extend axially along the cylindrical body 42 in a helical direction from an edge of the cylindrical body 42 towards the axial centre of the cylindrical body 42. The compressor elements 58 are collectively arranged to extend in a direction opposite to the direction in which the agitator rows 46 extend, but embodiments are envisioned in which both the agitator rows 46 and compressor elements 46, 58 extend about the cylindrical body 42 in the same helical direction. In the embodiment shown, the compressor elements 58 are located only on one side of the cylindrical body 42 which, when installed within the agitator chamber 34, is subject to the low velocity airflow. This focuses the disruption to the primary airflow structure caused by the compressor elements 58 on the side of the agitator chamber 34 where it is most needed. However, locating the compressor formation 56 only on one side of the cylindrical body 42 is not dependent on the compressor elements 58 being helically arranged, and the reader will understand that other compressor formations could also be located only on one side of the cylindrical body 42. Moreover, embodiments are envisioned in which the helical compressor formation 56 extends across substantially the entire width of the cylindrical body 42. Due to their helical arrangement, the compressor elements 58 wrap around a larger circumferential part of the outer surface 48 of the cylindrical body 42 when compared to the previous embodiment, increasing the period over which the compressor elements 58 disrupt the primary airflow structure per revolution of the cylindrical body 42.

The compressor formations 56 shown in FIG. 8-10 comprises compressor elements 58 having substantially rectangular cross-sections, similar to the compressor elements 58 shown in FIG. 6. However, the reader will appreciate that these compressor formations 56, and any subsequently described compressor formations 56, may comprise compressor elements 58 having an alternative cross-sectional shape including that shown in FIG. 7.

In all embodiments, at least one of the compressor elements 58 may be arranged substantially to extend axially from a respective side edge towards the axial centre of the cylindrical body 42. This arrangement promotes the secondary airflow structure at the side edge of the cylindrical body 42, close to the ends of the agitator chamber 34, and is particularly advantageous for the end of the agitator chamber 34 that experiences the low velocity airflow in order to displace airflow in that region, preventing the accumulation of dirt particles.

In all of the embodiments comprising two compressor elements 58 located on the same diametric side of the cylindrical body 42, the compressor elements 58 may be arranged to extend substantially axially in a direction from respective edges of the cylindrical body 42 to meet at the axial centre of the cylindrical body 42. Alternatively, in all of the embodiments comprising two compressor elements 58 located on diametrically opposite sides of the cylindrical body 42, the compressor elements 58 may be arranged to extend substantially axially across the cylindrical body 42 from one edge or a region near one edge of the cylindrical body 42 to the other edge or a region near the other edge.

The agitator assemblies in accordance with the present disclosure have been described with reference to particular embodiments thereof in order to illustrate the principles of operation. The above description is thus by way of illustration and directional references (including: upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, side, above, below, front, middle, back, vertical, horizontal, height, depth width, and so forth) and any other terms having an implied orientation refer only to the orientation of the features as shown in the accompanying drawings. They should not be read to be requirements or limitations, particularly as to the position, orientation, or use of the invention unless specifically set forth in the appended claims. Connection references (e.g., attached, coupled, connected, holding, joined, secured and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, connection references do not necessarily infer that two elements are directly connected and in fixed relation to each other, unless specifically set forth in the appended claims.