GB2475312A

GB2475312A - Cyclone arrangement for a surface treating appliance

Info

Publication number: GB2475312A
Application number: GB0919999A
Authority: GB
Inventors: Thomas James Dunning Follows; Stephen Benjamin Courtney; Peter David Gammack
Original assignee: Dyson Technology Ltd
Current assignee: Dyson Technology Ltd
Priority date: 2009-11-16
Filing date: 2009-11-16
Publication date: 2011-05-18
Anticipated expiration: 2029-11-16
Also published as: GB2475312B; GB0919999D0

Abstract

A surface treating appliance comprises a first cyclonic separating unit and downstream from the first cyclonic separating unit 40 and a second cyclonic separating unit 42. The second cyclonic separating unit 42 comprises a plurality of cyclones 80 arranged in parallel about an axis (Y, fig 4a) and a dust collector (144, fig 4a) arranged to receive dust from each of the plurality of cyclones 80, each cyclone comprising a fluid inlet and a fluid outlet. The plurality of cyclones 80 are divided up into at least a first set of cyclones 100 and a second set of cyclones 102, the fluid inlets of the first set of cyclones 100 being arranged in a first group and the fluid inlets of the second set of cyclones 102 being arranged in a second group spaced along the axis (Y, fig 4a) from the first group 100. Preferably the second cyclonic separating unit 42 is above the first cyclonic separating unit 40.

Description

A Surface Treating Appliance The present invention relates to a surface treating appliance. In its preferred embodiment, the appliance is in the form of an upright vacuum cleaner.

Vacuum cleaners which utilise cyclonic separating apparatus are well known.

Examples of such vacuum cleaners are shown in EP 0042473, US 4,373,228, US 3,425,192, U5 6,607,572 and EP 1268076. The separating apparatus comprises first and second cyclonic separating units through which an incoming air passes sequentially.

This allows the larger dirt and debris to be extracted from the airflow in the first separating unit, enabling the second cyclone to operate under optimum conditions and so effectively to remove very fine particles in an efficient manner.

In some cases, the second cyclonic separating unit includes a plurality of cyclones arranged in parallel. These cyclones are usually arranged in a ring extending about the longitudinal axis of the separating apparatus. Through providing a plurality of relatively small cyclones in parallel instead of a single, relatively large cyclone, the separation efficiency of the separating unit, that is, the ability of the separating unit to separate entrained particles from an air flow, can be increased. This is due to an increase in the centrifugal forces generated within the cyclones which cause dust particles to be thrown from the air flow.

Increasing the number of parallel cyclones can further increase the separation efficiency, or pressure efficiency, of the separating unit for the same overall pressure resistance. However, when the cyclones are arranged in a ring this can increase the external diameter of the separating unit, which in turn can undesirably increase the size of the separating apparatus. While this size increase can be ameliorated through reducing the size of the individual cyclones, the extent to which the cyclones can be reduced in size is limited. Very small cyclones can become rapidly blocked and can be detrimental to the rate of the air flow through the vacuum cleaner, and thus its cleaning efficiency.

In a first aspect the present invention provides a surface treating appliance comprising a first cyclonic separating unit and, downstream from the first cyclonic separating unit, a second cyclonic separating unit comprising a plurality of cyclones arranged in parallel about an axis and a dust collector arranged to receive dust from each of the plurality of cyclones, each cyclone comprising a fluid inlet and a fluid outlet, the plurality of cyclones being divided into at least a first set of cyclones and a second set of cyclones, the fluid inlets of the first set of cyclones being arranged in a first group and the fluid inlets of the second set of cyclones being arranged in a second group spaced along said axis from the first group.

Separating the cyclones of the second cyclonic separating unit into first and second sets which are each arranged about a common axis and have fluid inlets grouped together can allow the sets of cyclones to be spaced along the axis. This can enable both the number and the size of cyclones of the second cyclonic separating unit to be chosen for optimized separation efficiency and cleaning efficiency within the dimensional constraints for the separating apparatus. For example, if the optimum number of cyclones for the second cyclonic separating unit is twenty four then these cyclones may be arranged in two sets of twelve cyclones, three sets of eight cyclones or four sets of six cyclones depending on the maximum diameter for the separating apparatus and/or the maximum height for the separating apparatus. The provision of a common dust collector for each of the sets of cyclones can facilitate emptying and cleaning of the second cyclonic separating unit.

The fluid inlets of the sets of cyclones may be arranged in one of a number of different arrangements. For example, the inlets may be arranged in helical arrangements extending about the axis. Preferably, the first group of fluid inlets is generally arranged in a first annular arrangement, and the second group of fluid inlets is generally arranged in a second annular arrangement spaced along said axis from the first annular arrangement. Each of these annular arrangements is preferably substantially orthogonal to the axis. The annular arrangements are preferably of substantially the same size.

Within each annular arrangement, the fluid inlets are preferably located substantially within a common plane. Alternatively, the fluid inlets may be located in a number of different planes which are each preferably substantially orthogonal to said axis.

The axis is preferably a longitudinal axis of the first cyclonic separating unit. The first cyclonic separating unit preferably comprises a single cyclone, which is preferably substantially cylindrical. The first cyclonic separating unit preferably at least partially surrounds the dust collector. The appliance preferably comprises a second dust collector arranged to receive dust from the first cyclonic separating unit. This second dust collector is preferably arranged to be emptied simultaneously with the dust collector for receiving dust from each of the cyclones of the second cyclonic separating unit. The second dust collector is preferably annular in shape.

The first set of cyclones is preferably arranged around part of the second set of cyclones. Each of the cyclones of the second cyclonic separating unit preferably has a tapering body, which is preferably frusto-conical in shape. Within each set, the cyclones are preferably substantially equidistant from said axis. Alternatively, or additionally, the cyclones may be substantially equidistantly, or equi-angularly, spaced about said axis. The first set of cyclones is preferably arranged so that the longitudinal axes of the cyclones approach one another. Similarly, the second set of cyclones is preferably arranged so that longitudinal axes of the cyclones approach one another. In either case, the longitudinal axes of the cyclones preferably intersect the longitudinal axis of the first cyclonic separating unit.

The appliance preferably comprises a plurality of conduits for conveying fluid from the first cyclonic separating unit to the second cyclonic separating unit. The fluid inlet of each cyclone may be connected to a respective conduit. However, to reduce the number of conduits the cyclones are preferably arranged within each set in a plurality of subsets, with each subset comprising at least two cyclones and with the fluid inlets of each subset of cyclones being arranged to receive fluid from a respective conduit. Therefore, in a second aspect the present invention provides a surface treating appliance comprising a first cyclonic separating unit, a second cyclonic separating unit comprising a plurality of cyclones arranged in parallel, each cyclone comprising a fluid inlet and a fluid outlet, the plurality of cyclones being divided into at least a first set of cyclones and a second set of cyclones, and a plurality of conduits for conveying fluid from the first cyclonic separating unit to the second cyclonic separating unit, wherein within each set the cyclones are arranged in a plurality of subsets, each subset comprising at least two cyclones, the fluid inlets of each subset of cyclones being arranged to receive fluid from a respective conduit.

The appliance preferably comprises a shroud forming an outlet from the first cyclonic separating unit, the shroud comprising a wall having a multiplicity of through-holes, and wherein each conduit comprises an inlet located behind the wall of the shroud.

Each conduit may be arranged to convey fluid to a single subset of cyclones. In other words, the plurality of conduits may be divided into a first set of conduits which each convey fluid from the first cyclonic separating unit to a respective subset of cyclones of the first set of cyclones, and a second set of conduits which each convey fluid from the second cyclonic separating unit to a respective subset of cyclones of the second set of cyclones. Each of the first set of conduits may be located between two adjacent conduits of the second set of conduits.

Alternatively, each conduit may be arranged to convey fluid to a respective subset of cyclones of each set of cyclones. This arrangement may be preferred when the second cyclonic separating unit comprises three or more sets of cyclones, as it can enable the number of conduits to be minimized.

The appliance preferably comprises a plurality of outlet conduits for conveying fluid from the second cyclonic separating unit to an outlet chamber. Each outlet conduit may be arranged to convey fluid from a respective cyclone to the outlet chamber.

Alternatively, each outlet conduit may be arranged to convey fluid from at least one of a subset of cyclones of the first set of cyclones and a subset of cyclones of the second set of cyclones to the outlet chamber. The outlet chamber is preferably arranged to convey fluid to an outlet duct. Each set of cyclones preferably extends about the outlet duct.

The first set of cyclones and the second set of cyclones preferably comprise the same number of cyclones. Each of the first set of cyclones and the second set of cyclones may comprise at least six cyclones.

The second set of cyclones is preferably located above at least part of the first set of cyclones, which is in turn preferably located above at least part of the first cyclonic separating unit. The first cyclonic separating unit and the second cyclonic separating unit preferably form part of a separating apparatus removably mounted on a main body of the appliance. The outlet duct preferably has an outlet located in the base of the separating apparatus.

The term "surface treating appliance" is intended to have a broad meaning, and includes a wide range of machines having a head for travelling over a surface to clean or treat the surface in some manner. It includes, inter alia, machines which apply suction to the surface so as to draw material from it, such as vacuum cleaners (dry, wet and wet/dry), as well as machines which apply material to the surface, such as polishing/waxing machines, pressure washing machines, ground marking machines and shampooing machines. It also includes lawn mowers and other cutting machines.

Features described above in connection with the first aspect of the invention are equally applicable to the second aspect, and vice versa.

An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a front perspective view of an upright vacuum cleaner; Figure 2 is a perspective view of a separating apparatus of the cleaner of Figure 1; Figure 3 is a top view of the separating apparatus; Figure 4(a) is a vertical section through the separating apparatus along line A in Figure 3, Figure 4(b) is vertical section through the separating apparatus along line B in Figure 3, and Figure 4(c) is vertical section through the separating apparatus along line C in Figure 3; Figure 5 is a horizontal section through the separating apparatus along line D in Figure 4(a); Figure 6 is a schematic illustration of the arrangement of the cyclones of the second cyclonic separating unit about the central axis of the separating apparatus; Figure 7 is a schematic illustration of a first alternative arrangement of the cyclones of the second cyclonic separating unit about the central axis of the separating apparatus; and Figure 8 is a schematic illustration of a second alternative arrangement of the cyclones of the second cyclonic separating unit about the central axis of the separating apparatus.

Figure 1 illustrates an example of a surface treating appliance, which is in the form of an upright vacuum cleaner. The vacuum cleaner 10 comprises a cleaner head 12, a main body 14 and a support assembly 16 for allowing the vacuum cleaner 10 to be rolled along a floor surface. The cleaner head 12 comprises a dirty air inlet located on the underside of the cleaner head 12 facing the surface to be treated. The cleaner head 12 is pivotably connected to a yoke 18 of the support assembly 16, which is in turn pivotably connected to the lower end of the main body 14. The support assembly 16 comprises a pair of wheels 20, 22 rotatably connected to the yoke 18. Each wheel 20, 22 is dome-shaped, and has an outer surface of substantially spherical curvature so that the yoke 18 and the wheels 20 combine to form an arcuate surface. A motor and fan unit (not shown) of the main body 14 is located between the wheels 20, 22 of the support assembly 16 for drawing an air flow through the vacuum cleaner 10. One of the wheels 20, 22 comprises a plurality of air outlets (not shown) for exhausting the air flow from the vacuum cleaner 10. The support assembly 16 further comprises a stand 24 which is moveable relative to the main body 14 between a supporting position, as illustrated in Figure 1, for supporting the main body 14 in an upright position and a refracted position for allowing the vacuum cleaner 10 to be manoeuvred over a floor surface.

The main body 14 includes separating apparatus 26 for removing dirt, dust and/or other debris from a dirt-bearing airflow which is drawn into the vacuum cleaner 10 by the motor and fan unit. A first ducting arrangement 28 provides communication between the dirty air inlet of the cleaner head 12 and the separating apparatus 26, whereas a second ducting arrangement (not shown) protruding from the top of the support assembly 16 provides communication between the separating apparatus 26 and the motor and fan unit. A first part of the first ducting arrangement 28 passes through the support assembly 16, and a second part of the first ducting arrangement 28 passes along the side of the separating apparatus 26 to convey the air flow into the separating apparatus 26. The base 30 of the separating apparatus 26 is mounted on an inlet section (not shown) of the second ducting arrangement, and a manually-operable catch 32 releasably retains the separating apparatus 26 on the spine 34 of the main body 14. The separating apparatus 26 may include a handle 36 to facilitate the removal of the separating apparatus 26 from the main body 14. The main body 14 also includes a hose and wand assembly 38 which is releasably connected to the spine 34 of the main body 14, and a handle 39.

In use, the motor and fan unit draws dust laden air into the vacuum cleaner 10 via either the dirty air inlet of the cleaner head 12 or the hose and wand assembly 38. The dust laden air is carried to the separating apparatus 26 via the first ducting arrangement 28.

Dirt and dust particles entrained within the air flow are separated from the air and retained in the separating apparatus 26. The cleaned air is conveyed by the second ducting arrangement to the motor and fan unit located within the support assembly 16, and is subsequently expelled through the air outlets 24.

In overview, the separating apparatus 26 comprises a first cyclonic separating unit 40 and a second cyclonic separating unit 42 located downstream from the first cyclonic separating unit 40. The second cyclonic separating unit 42 is disposed above the first cyclonic separating unit 40, and in this example the first cyclonic separating unit 40 extends about part of the second cyclonic separating unit 42.

The separating apparatus 26 is shown in more detail in Figures 2 to 6; the handle 34 has been omitted from these figures to show more clearly the arrangement of the second cyclonic separating unit 42. The specific overall shape of the separating apparatus 26 can be varied according to the type of vacuum cleaner 10 in which the separating apparatus 26 is to be used. For example, the overall length of the separating apparatus 6 can be increased or decreased with respect to the diameter of the separating apparatus 26.

The separating apparatus 26 comprises an outer bin 50 which has an outer wall 52 which is substantially cylindrical in shape, and which extends about a longitudinal axis Y. The lower end of the outer bin 50 is closed by the base 30 of the separating apparatus. The base 30 is pivotably attached to the outer wall 52 by means of a pivot 54 and held in a closed position by a catch (not shown). The separating apparatus 26 further comprises a second cylindrical wall 58 which is co-axial with the outer wall 52.

The second cylindrical wall 58 engages and is sealed against the base 30 when the base is in the closed position. The second cylindrical wall 58 is located radially inwardly of the outer wall 52 and spaced therefrom so as to form an annular chamber 60 therebetween. In this example the upper portion of the annular chamber 60 forms a cylindrical cyclone 62 of the first cyclonic separating unit 40 and the lower portion of the annular chamber 60 forms a dust collecting bin 64 of the first cyclonic separating unit 40.

A dirty air inlet 66 is provided at the upper end of the outer bin 50 for receiving an air flow from the first ducting arrangement 28. The dirty air inlet 66 is arranged tangentially to the outer bin 50 so as to ensure that incoming dirty air is forced to follow a helical path around the annular chamber 60.

A fluid outlet is provided in the outer bin 50 in the form of a shroud. The shroud has an upper wall 68 formed in a frusto-conical shape, a lower cylindrical wall 70 and a skirt 72 depending from the cylindrical wall 70. The skirt 72 tapers outwardly from the lower cylindrical wall 70 in a direction towards the outer wall 52. A large number of perforations 74 are formed in the lower cylindrical wall 70 of the shroud, and which provide the only fluid outlet from the outer bin 50.

A second annular chamber 76 is located behind the shroud. A plurality of conduits communicate with the chamber 76 for conveying air from the first cyclonic separating unit 40 and a second cyclonic separating unit 42. The second cyclonic separating unit 42 comprises a plurality of cyclones 80 arranged in parallel to receive air from the first cyclonic separating unit 40. With reference to Figures 4(a) to 4(c), in this example the cyclones 80 are substantially identical and each cyclone 80 comprises a cylindrical portion 82 and a tapering portion 84 depending therefrom. The cylindrical portion 82 comprises an air inlet 86 for receiving fluid from one of the conduits. The tapering portion 84 of each cyclone 80 is frusto-conical in shape and terminates in a cone opening 88. A vortex finder 90 is provided at the upper end of each cyclone 80 to allow air to exit the cyclone 80. Each vortex finder 90 extends downwardly from a vortex finder plate 92 which is disposed over the cylindrical portion 82.

With reference also to Figures 5 and 6, in this example the cyclones of the second cyclonic separating unit 42 are divided into a first set of cyclones 100 and a second set of cyclones 102. Each set of cyclones 100, 102 preferably comprises the same number of cyclones 80, and in this example each set of cyclones 100, 102 comprises ten cyclones 80. Each set of cyclones 100, 102 is arranged in a ring which is centred on a longitudinal axis Y of the outer wall 52. Within each set of cyclones 100, 102 each cyclone 80 has a longitudinal axis C which is inclined downwardly and towards the longitudinal axis Y of the outer wall 52. The longitudinal axes C are all inclined at the same angle to the longitudinal axis Y of the outer wall 52. Within each set of cyclones 100, 102, the cyclones 80 are substantially equidistant from the longitudinal axis Y, and are substantially equidistantly spaced about the longitudinal axis Y. To reduce the external diameter of the separating apparatus 26, the arrangement of the sets of cyclones 100, 102 is such that the air inlets 86 of the first set of cyclones 100 are arranged in a first group 104, and the air inlets 86 of the second set of cyclones 102 being arranged in a second group 106 which is spaced along the longitudinal axis Y from the first group 104. In this example each group 104, 106 of air inlets 86 is located within a respective plane Pi, P2, with each of these planes Pi, P2 being substantially orthogonal to the longitudinal axis Y. The planes Pi, P2 are located along the longitudinal axis Y so that the second set of cyclones 102 is located above the first set of cyclones 100. To minimise the increase in the height of the separating apparatus 26, the first cyclonic separating unit 40 extends about a lower part of the first set of cyclones 100 and the first set of cyclones 100 extends about a lower part of the second set of cyclones 102.

Within each set of cyclones 100, 102, the cyclones 80 are further divided into a plurality of subsets which each comprise at least two cyclones 80. In this example, each subset of cyclones 80 comprises an adjacent pair of cyclones 80 SO that the first set of cyclones is divided into five subsets of cyclones 110, 112, 114, 116, 118, and the second set of cyclones 102 is also divided into five subsets of cyclones 120, 122, 124, 126, 128.

Within each subset, the cyclones 80 are arranged so that the air inlets 86 are located opposite to each other.

In this example, each subset of cyclones is arranged to receive air from a respective one of the plurality of conduits for conveying air from the first cyclonic separating unit 40 to the second cyclonic separating unit 42. The plurality of conduits are thus divided into a first set of relatively short conduits 130 which each convey air from the annular chamber 76 located behind the shroud to the air inlets 86 of a respective one of the five subsets of cyclones 110, 112, 114, 116, 118 of the first set of cyclones 100, and a second set of relatively long conduits 132 which each convey air from the annular chamber 76 to the air inlets 86 of a respective one of the five subsets of cyclones 120, 122, 124, 126, 128 of the second set of cyclones 102. As shown in Figure 5, each set of conduits 130, 132 is arranged about the longitudinal axis Y, with the conduits of the first set of conduits 130 being arranged alternately with the conduits of the second set of conduits 132. The upper end of each conduit of the first set of conduits 130 may be closed by part of a vortex finder plate 92 shared between the cyclones of a respective subset of cyclones 110, 112, 114, 116, 118 of the first set of cyclones 100. Similarly, the upper end of each conduit of the second set of conduits 132 may be closed by part of a vortex finder plate 92 shared between the cyclones of a respective subset of cyclones 120, 122, 124, 126, 128 of the second set of cyclones 102.

Returning to Figures 4(a) to 4(c), each vortex finder 90 leads into a respective vortex finger 134 which communicates with a plenum or manifold 136 located at the top of the separating apparatus 26, and which is closed at the upper end thereof by a cover plate 138 of the separating apparatus 26. The cover plate 138 may also define part of the vortex fingers 134 for conveying air from the second set of cyclones 102 to the manifold 136. The manifold 136 communicates with an outlet duct 140 from which air is exhausted from the separating apparatus 26. The outlet duct 14 is arranged longitudinally down the centre of the separating apparatus 26, and is delimited by a third cylindrical wall 142 which depends from the second cyclonic separating unit 42.

The third cylindrical wall 142 is located radially inwardly of the second cylindrical wall 58 and is spaced from the second cylindrical wall 58 50 as to form a third annular chamber 144 therebetween. When the base 30 is in the closed position, the third cylindrical wall 142 may reach down to and be sealed against the base 30.

The third annular chamber 144 is surrounded by the first annular chamber 64, and is arranged so that the cone openings 88 of the cyclones 80 of the second cyclonic separating unit 42 protrude into the third annular chamber 144. Consequently, in use dust separated by the cyclones 80 of the second cyclonic separating unit 42 will exit through the cone openings 88 and will be collected in the third annular chamber 144.

The third annular chamber 144 thus forms a dust collecting bin of the second cyclonic separating unit 42, and which can be emptied simultaneously with the dust collecting bin 64 of the first cyclonic separating unit 40.

During use of the vacuum cleaner 10, dust laden air enters the separating apparatus 26 via the dirty air inlet 66. Due to the tangential arrangement of the dirty air inlet 66, the dust laden air follows a helical path around the outer wall 52. Larger dirt and dust particles are deposited by cyclonic action in the first annular chamber 60 and collected in the dust collecting bin 64. The partially-cleaned dust laden air exits the first annular chamber 60 via the perforations 74 in the shroud and enters the second annular chamber 76. The partially-cleaned air then passes into the conduits 130, 132 and is conveyed to the air inlets 86 of the cyclones 80. Cyclonic separation is set up inside the cyclones 80 so that separation of dust particles which are still entrained within the airflow occurs.

The dust particles which are separated from the airflow in the cyclones 80 are deposited in the third annular chamber 144. The further cleaned air then exits the cyclones 80 via the vortex finders 90 and passes into the manifold 136, from which the air enters the outlet duct 140. The further cleaned air then exhausts the separating apparatus 26 via an exit port 146 located in the base 30 of the separating unit 26.

The separating apparatus 26 thus includes two distinct stages of cyclonic separation.

The first cyclonic separating unit 20 comprises a single cylindrical cyclone 62. The relatively large diameter of the outer wall 52 means that mainly comparatively large particles of dirt and debris will be separated from the air because the centrifugal forces applied to the dirt and debris are relatively small. A large proportion of the larger debris will reliably be deposited in the dust collecting bin 64.

The second cyclonic separating unit comprise twenty cyclones 80, each of which has a smaller diameter than the cylindrical cyclone 62 and so is capable of separating finer dirt and dust particles than the cylindrical cyclone 62. They also have the added advantage of being challenged with air which has already been cleaned by the cylindrical cyclone 62 and so the quantity and average size of entrained dust particles is smaller than would otherwise have been the case. The separation efficiency of the cyclones 80 is considerably higher than that of the cylindrical cyclone 62.

If desired, a filter (not shown) may also be provided downstream from the second cyclonic separating unit 42 to remove finer dust particles remaining in the air emitted therefrom. This filter may be located in the separating apparatus 26, for example within one of the manifold 136 and the outlet duct 140, or it may be located in the second ducting arrangement for conveying air from the separating apparatus 26 to the motor and fan unit.

The invention is not limited to the detailed description given above. Variations will be apparent to the person skilled in the art.

A first alternative arrangement of the cyclones 80 of the second cyclonic separating unit 42 is illustrated in Figure 7, in which each of the conduits 150 for conveying air from the first cyclonic separating unit 40 to the second cyclonic separating unit 42 is arranged to convey air convey fluid to a subset of cyclones of the first set of cyclones 100, and to a subset of cyclones of the second set of cyclones 102. This can reduce the number of conduits from ten to five.

This arrangement of cyclones 80 can be readily divided into three or more sets of cyclones. For example, as illustrated in Figure 8 a third set of cyclones 158 may be located above the second set of cyclones 102. The air inlets 86 of the third set of cyclones 180 are arranged in a third group 159 which is spaced along the longitudinal axis Y from the second group 106. The third group 159 of air inlets 86 is located in a plane P3 which is substantially orthogonal to the longitudinal axis Y. Again, to minimise the increase in the height of the separating apparatus 26 the second set of cyclones 102 extends about a lower part of the third set of cyclones 158. The third set of cyclones 158 is also divided into five subsets of cyclones 160, 162, 164, 166, 168, with each of the conduits 150 being arranged to convey air to a respective subset of each of the first, second and third sets of cyclones.

Claims

CLAIMS1. A surface treating appliance comprising a first cyclonic separating unit and, downstream from the first cyclonic separating unit, a second cyclonic separating unit comprising a plurality of cyclones arranged in parallel about an axis and a dust collector arranged to receive dust from each of the plurality of cyclones, each cyclone comprising a fluid inlet and a fluid outlet, the plurality of cyclones being divided into at least a first set of cyclones and a second set of cyclones, the fluid inlets of the first set of cyclones being arranged in a first group and the fluid inlets of the second set of cyclones being arranged in a second group spaced along said axis from the first group.
2. An appliance as claimed in claim 1, wherein the first group of fluid inlets is generally arranged in a first annular arrangement, and the second group of fluid inlets is generally arranged in a second annular arrangement spaced along said axis from the first annular arrangement.
3. An appliance as claimed in claim 2, wherein each of the annular arrangements is substantially orthogonal to said axis.
4. An appliance as claimed in claim 2 or claim 3, wherein the annular arrangements are of substantially the same size.
5. An appliance as claimed in any of the preceding claims, wherein, within each set, the fluid inlets are substantially co-planar.
6. An appliance as claimed in any of the preceding claims, wherein, within each set, the cyclones are substantially equidistant from said axis.
7. An appliance as claimed in any of the preceding claims, wherein, within each set, the cyclones are substantially equidistantly spaced about said axis.
8. An appliance as claimed in any of the preceding claims, wherein the first cyclonic separating unit at least partially surrounds the dust collector.
9. An appliance as claimed in claim 8, comprising a second dust collector arranged to receive dust from the first cyclonic separating unit.
10. An appliance as claimed in any of the preceding claims, wherein the second cyclonic separating unit is substantially co-axial with the first cyclonic separating unit.
11. An appliance as claimed in any of the preceding claims, wherein each cyclone has a longitudinal axis, and wherein the longitudinal axes of the cyclones of the first set of cyclones approach one another and the longitudinal axes of the cyclones of the second set of cyclones approach one another.
12. An appliance as claimed in any of the preceding claims, wherein the first set of cyclones extends about part of the second set of cyclones.
13. An appliance as claimed in any of the preceding claims, comprising a plurality of conduits for conveying fluid from the first cyclonic separating unit to the second cyclonic separating unit.
14. An appliance as claimed in claim 13, comprising a shroud forming an outlet from the first cyclonic separating unit, the shroud comprising a wall having a multiplicity of through-holes, and wherein each conduit comprises an inlet located behind the wall of the shroud.
15. An appliance as claimed in any of the preceding claims, wherein the first set of cyclones and the second set of cyclones comprise the same number of cyclones.
16. An appliance as claimed in any of the preceding claims, wherein each of the first set of cyclones and the second set of cyclones comprises at least six cyclones.
17. An appliance as claimed in any of the preceding claims, wherein the second set of cyclones is located above at least part of the first set of cyclones.
18. An appliance as claimed in any of the preceding claims, wherein the first cyclonic separating unit and the second cyclonic separating unit form part of a separating apparatus removably mounted on a main body of the appliance.
19. A surface treating appliance substantially as herein described with reference to and as shown in the accompanying drawings.