Filter assembly

Abstract

A filter assembly 30 comprises a plurality of filter segments 31 arranged about a central axis 35. Each of the filter segments is moveable between a first position and a second position. Each of the f

Description

Field of the Invention The present invention relates to a filter assembly, and to a dirt separator and a 5 vacuum cleaner comprising the filter assembly. Background of the Invention A vacuum cleaner may comprise a filter assembly for removing dirt from an airflow. With use, the filter assembly can become clogged and may require cleaning or 10 replacement. Summary of the Invention In a first aspect, the present invention provides a filter assembly comprising a plurality of filter segments arranged about a central axis, and at least one CO 15 manipulator, wherein each of the filter segments is moveable between a first position and a second position, each of the filter segments has a profile in a direction normal to the central axis that is convex when in the first position and concave when i— in the second position, and actuation of the manipulator causes the manipulator to apply a force to the filter segments to move the filter segments between the first 20 position and the second position. Owing to the convex and concave profiles of the filter segments, movement of the filter segments between the two positions can be highly dynamic. As a result, dirt collected on the surface of the filter segments may be released upon moving the 25 filter segments between the two positions. The filter assembly may therefore be cleaned, at least partly, by moving the filter segments between the two positions. When employed in a product, such as a vacuum cleaner, the filter assembly may be cleaned without the need to remove the filter assembly. Alternatively, the filter assembly may be removed from the product, carried to a bin, and then the filter 30 segments moved in order to release dirt into the bin. The filter assembly comprises at least one manipulator, and actuation of the manipulator causes the manipulator to apply a force to the filter segments to move the filter segments between the first position and the second position. This then has the benefit that the filter segments may be moved, and thus the filter assembly may be cleaned, without the need for a user to touch or otherwise directly contact the filter segments. When employed in a product, the product may include an 5 actuator to actuate the manipulator. For example, the product may comprise an electrical actuator (e.g. electric motor and transmission) that actuates the manipulator periodically or in response to particular event or input (e.g. upon powering the product on or off, or in response to a user input to clean the filter assembly). Alternatively, the product may comprise a mechanical actuator (e.g. a 10 rotary dial, plunger, or depressible button) that is operated manually by a user in order to actuate the manipulator. The first position and the second position may be stable positions. Each of the filter segments is therefore bistable. The filter assembly may therefore be used with the CO 15 filter segments in either position without the need for an external force acting on the filter segments. As each filter segment is moved from one of the two stable CM        positions, the filter segment deforms and enters an unstable state. The potential energy of the filter segment increases due to the deformation in the filter segment. At a critical position (e.g. midway) between the two stable positions, the filter 20 segment enters an equilibrium but nevertheless unstable state. At this critical position, displacement of the filter segment from the critical position will cause the filter segment to move to one of the two stable positions. In moving to a stable position, the stored potential energy is transformed into kinetic energy, causing the filter segment to accelerate towards the stable position. The filter segment is then 25 arrested at the stable position, causing dirt attached to the surface of the filter segment to be released from the filter segment. Actuation of the manipulator in a first direction may cause the filter segments to move from the first position to the second position, and actuation of the manipulator 30 in a second, opposite direction may cause the filter segments to move from second position to first position. This then provides a convenient means for moving the filter segments back and forth between the two positions. For example, the filter assembly may be used with the filter segments in one of the two positions to provide filtration. During a cleaning cycle, the filter segments may be moved to the other position and then returned to the original position in readiness again for filtration. The filter segments may be moved repeatedly back and forth between the two positions during a cleaning cycle. By having a manipulator that actuates in both 5 directions to move the filter segments between the two positions, the filter assembly may be cleaned and then restored to a condition ready for filtration in a relatively convenient way. The filter assembly may comprise a plurality of manipulators, and actuation of each 10 of the manipulators may cause a respective filter segment to move between the first position and the second position. This then permits each filter segment to be moved independently of the other filter segments, if required. For example, the filter segments may be moved sequentially. As a result, the filter segments may be moved using a smaller force. By contrast if a single manipulator were used to move CO 15 the filter segments concurrently, a larger force may be required. CM CM Where the filter assembly comprises a plurality of manipulators, each of the manipulators may be attached along an edge of the respective filter segment. More particularly, each of the manipulators may be attached along a longitudinal edge of 20 the respective filter segment, i.e. along an edge that extends parallel to the central axis. This then has the advantage that, as the manipulator actuates, deformation of the filter segment propagates across the filter segment. At a critical position between the first and second positions, the filter segment may snap to the first or second position. As a result, a relatively high acceleration may be imparted to dirt 25 attached to the filter segments. The manipulator may comprise a body having a plurality of lobes, and actuation of the manipulator may cause each of the lobes to contact and move a respective filter segment. This then has the benefit that all filter segments may be moved by means 30 of a single manipulator, thus simplifying the process for cleaning the filter assembly. Actuation of the manipulator may comprise rotation of the manipulator about a rotation axis parallel to the central axis. Where the filter assembly comprises a piurahty of manipulators, actuation of each of the manipulators may comprise rotation of each manipulator about a rotation axis parallel to the central axis. As a result, movement of the filter segments between the two positions may be achieved in a relatively convenient and compact way. For example, each of the filter 5 segments may be moved between the two positions by means of a single rotary action. An outer perimeter of the filter assembly, in a plane normal to the central axis, maybe generally circular in shape when the filter elements are in the first position. This 10 then has the advantage that, should the filter assembly be employed in a dirt separation system for which a fluid moves around the filter assembly, movement of the fluid may be less turbulent. For example, the filter assembly may be located within a cyclone chamber for removing dirt from an airflow, and the airflow may spiral about the filter assembly. By employing a filter assembly have a circular outer CO 15 perimeter, turbulence within the airflow may be reduced. As a result, the separation efficiency may be improved and / or pressure losses may be reduced. CM The filter assembly may comprise at least four filter segments. As the number of filter segments increases, the degree of deflection or deformation through which 20 each filter segment undergoes as it moves between the two positions is reduced. As a result, each of the filter segments is subjected to less mechanical stress. However, as a consequence of the reduced deflection, the acceleration imparted to the dirt is reduced. Accordingly, the filter assembly may comprise no more than six filter segments. 25 Each of the filter segments may comprise a mesh screen or a pleated filter medium. Where a mesh screen is employed, dirt collects on a surface of the screen. As a result, each of the filter segments may be cleaned effectively by moving the mesh screen between the two positions. A pleated filter medium has the advantage that 30 relative coarse dirt may attach to the filter medium over a relatively small attachment area. Consequently, each of the filter segments may again be cleaned effectively by moving the segments between the two positions. Moreover, the filter assembly may be configured such that, when moving the filter segments between the two positions, the pitch of the pleats on the upstream side of the filter segments increases. As a result, the attachment area over which coarse dirt attaches to the filter medium decreases and thus the dirt may be more easily removed. 5 Each of the filter segments may comprise a filter medium attached to a strip, and the strip may be stiffer than the filter medium in a direction normal to the central axis. This then has the advantage that a relative flexible filter medium may be used, and the stiffness provided by the strip may ensure that movement of each of the filter segments between the two positions is highly dynamic. Where the filter 10 assembly comprises a manipulator(s), actuation of the manipulator(s) may cause the manipulator(s) to apply a force to the strips of the filter segments to move the filter segments between the first position and the second position. The strip of each of the filter segments may be attached at each end to the strip of CO 15 an adjacent filter segment. This then provides a relatively compact arrangement. Additionally, the filter assembly may be more easily mounted within a product. For CM example, the filter assembly may be mounted to the product at the joins or attachment points between each pair of strips. i— CM 20 The strip of each of the filter segments may be formed of a metal. The filter segments may be required to move many times between the two positions over the life of the filter assembly. By forming the strip of a metal, fatigue of the strip with repeated movement may be avoided or reduced. 25 In a second aspect, the present invention provides a dirt separator for separating dirt from an airflow, the dirt separator comprising: a separation chamber; and a filter assembly in accordance with the first aspect of the invention, wherein the filter assembly is located within the separation chamber. 30 The filter assembly may be the primary or sole means for separating dirt from the airflow. Alternatively, the filter assembly may be the secondary or additional means for separating dirt from the airflow. Over time, dirt that collects on the surface of the filter assembly may restrict the airflow through the dirt separator. By moving the filter segments between the two positions, dirt collected on the surface of the filter segments may be released. The separation chamber may comprise a cyclone chamber. The airflow then spirals 5 about the filter assembly, which then serves as an outlet of the cyclone chamber. The cyclone chamber may act as the primary means for removing dirt from the airflow. However, dirt that continues to be entrained in the airflow, such as hair and fluff, may be removed by the filter assembly. By moving the filter segments between the two positions, such dirt may be released from the filter assembly. 10 In a third aspect, the present invention provides a vacuum cleaner comprising a filter assembly in accordance with the first aspect or a dirt separator in accordance with the second aspect of the Invention. CO 15 In a fourth aspect, the present invention provides a vacuum cleaner comprising a filter assembly, at least one manipulator and an actuator to actuate the manipulator, CM wherein the filter assembly comprises a plurality of filter segments arranged about a central axis, each of the filter segments is moveable between a first position and a second position, each of the filter segments has a profile in a direction normal to 20 the central axis that is convex when in the first position and concave when in the second position, and actuation of the manipulator by the actuator causes the manipulator to apply a force to the filter segments to move the filter segments between the first position and the second position. 25 As noted above, owing to the convex and concave profiles of the filter segments, movement of the filter segments between the two positions can be highly dynamic. As a result, dirt collected on the surface of the filter segments may be released upon moving the filter segments between the two positions. 30 The vacuum cleaner comprises at least one manipulator and an actuator to actuate the manipulator. This then has the benefit that the filter segments may be moved, and thus the filter assembly may be cleaned or regenerated, without the need for a user to touch or otherwise directly contact the filter segments. The actuator may be an electrical actuator (e.g. an electric motor distinct from the suction motor), which actuates the manipulators periodically or in response to particular event or input (e.g. upon powering the product on or off, or in response to a user input to clean and regenerate the filter assembiy). Alternatively, the actuator may be a mechanical 5 actuator (e.g. a rotary dial, plunger, or depressible button) that is operated manually by a user. This then has the advantage that the filter assembly may be cleaned and regenerated in a more cost-effective way. The vacuum cleaner may comprise a suction motor, and the filter segments may be 10 caused to move between the first position and the second position in response to suction generated by the suction motor. This then has the advantage that the filter segments may be moved into a position for filtration when the suction motor is powered on. The filter segments may then be moved to the other position by the manipulator in order to release dirt from the filter segments, e.g. when the suction CO 15 motor is subsequently powered off. CM CM The vacuum cleaner may be operable in a filtration mode and a regeneration mode. Filtration mode may comprise drawing an airflow through the filter assembly to separate dirt from the airflow, and regeneration mode may comprise moving the 20 filter segments between the first position and the second position to release dirt from the filter assembly. This then has the advantage that the filter assembly may be cleaned or regenerated within the vacuum cleaner, thus avoiding the need to remove the filter assembly. 25 Filtration mode may comprise drawing the airflow through each of the filter segments in a radially inward direction towards the central axis, and regeneration mode may comprise moving each of the filter segments from the second position to the first position. As a result, dirt that collects on the upstream surface of filter segments is accelerated in a direction away from the central axis as the filter 30 segments move from the second position to the first position. Consequently, when the filter segments are arrested at the first position, dirt is thrown in a direction away from the surfaces of the filter segments. Each of the filter segments may comprise a mesh screen, each of the filter segments may be in the first position in filtration mode, and regeneration mode may comprise moving each of the filter segments to the second position and subsequently moving each of the filter segments to the first position. The filter segments therefore have 5 a convex profile when in filtration mode. The filter assembly may therefore be used in a cyclone chamber. In particular, the outer perimeter of the filter assembly, in a plane normal to the central axis, may be generally circular in shape when the filter elements are in the first position. During regeneration mode, the filter segments are initially moved from the first position to the second position. Dirt collected on the 10 upstream surface of the filter segments is then accelerated towards the central axis. When the filter segments are arrested at the second position, the dirt continues to move in a direction towards the filter segments. Consequently, relatively little dirt may be released. However, by subsequently moving the filter segments from the second position to the first position, the dirt on the upstream surface of filter CO 15 segments is then accelerated in a direction away from the central axis. Consequently, when the filter segments are arrested at the first position, the dirt is CM thrown in a direction away from the surfaces of the filter segments. i— Each of the filter segments may comprise a pleated filter medium having pleats, and 20 each of the filter segments may have an upstream side and a downstream side relative to the direction of the airflow through each of the filter segments. Each of the filter segments may then be in one of the first position and the second position in filtration mode, and regeneration mode may comprise moving each of the filter segments to the other of the first position and the second position such that a pitch 25 of the pleats on the upstream side increases. A pleated filter medium has the advantage that relative coarse dirt may attach to the filter medium over a relatively small attachment area. Relatively good cleaning of the filter segments may therefore be achieved by moving the filter segments between the two positions. Furthermore, when moving the filter segments between the two positions in 30 regeneration mode, the pitch of the pleats on the upstream side of the filter segments increases. As a result, the attachment area over which dirt is attached to the pleated filter medium decreases and thus more of the dirt may be released. In a fifth aspect, the present invention provides a filter assembly comprising a plurality of filter segments arranged about a central axis, wherein each of the filter segments is moveable between a first position and a second position, and each of the filter segments has a profile in a direction normal to the central axis that is 5 convex when in the first position and concave when in the second position. In a sixth aspect, the present invention provides a vacuum cleaner comprising a filter assembly in accordance with the fifth aspect. 10 The filter assembly may comprise one or more of the optional features of the first aspect of the invention. Similarly, the vacuum cleaner may comprise one or more of the optional features of the fourth aspect of the invention The filter assembly or the vacuum cleaner may comprise at least one manipulator, CO 15 and actuation of the manipulator may cause the manipulator to apply a force to the filter segments to move the filter segments between the first position and the second CM position. This then has the benefit that the filter segments may be moved, and thus the filter assembly may be cleaned, without the need for a user to touch or otherwise directly contact the filter segments. Where the manipulator forms part of the filter 20 assembly, the filter assembly may be removed from the vacuum cleaner, carried to a bin, and the manipulator may be actuated manually by a user in order to release dirt form the filter segments. The vacuum cleaner may comprise an actuator to actuate the manipulator. This 25 then has the benefit that the filter segments may be moved, and thus the filter assembly may be cleaned, without the need to remove the filter assembly from the vacuum cleaner. For example, the vacuum cleaner may comprise an electrical actuator (e.g. electric motor and transmission) that actuates the manipulator periodically or in response to particular event or input (e.g. upon powering the 30 product on or off, or in response to a user input to clean the filter assembly). Alternatively, the vacuum cleaner may comprise a mechanical actuator (e.g. a rotary dial, plunger, or depressible button) that is operated manually by a user in order to actuate the manipulator. Brief Description of the Drawings Figure 1 is a perspective view of a vacuum cleaner; Figure 2 is a sectional view through a handheld unit of the vacuum cleaner; 5 Figure 3 is a perspective view of a filter assembly of the vacuum cleaner; Figure 4 illustrates various states of a filter segment of the filter assembly as it moves between a first position and a second position; Figure 5 is a sectional view through the filter assembly with each of the filter segments in (a) the first position, and (b) the second position; 10 Figure 6 is a plan view of a transmission of an actuator of the vacuum cleaner; Figure 7 is a sectional view through an alternative handheld unit; and Figure 8 is a perspective view of a filter assembly of the alternative handheld unit. Detailed Description of the Invention CO 15 The vacuum cleaner 1 of Figure 1 comprises a handheld unit 2 attached to a cleaner head 4 by means of an elongate tube 3. The elongate tube 3 is detachable from the CM handheld unit 2 such that the handheld unit 2 may be used as a standalone vacuum i— cleaner. i— CM 20 Referring now to Figure 2, the handheld unit 2 comprises an inlet duct 9, a dirt separator 10, a pre-motor filter 11, a suction motor 12 and a post-motor filter 13. The inlet duct 9 extends along a side of the dirt separator 10. One end of the inlet duct 9 is attachable to the elongate tube 3 or an accessory tool, should the handheld 25 unit 2 be used as a standalone cleaner. An opposite end of the inlet duct 9 is attached to an inlet of the dirt separator 10. The pre-motor filter 11 is located downstream of the dirt separator 10 but upstream of the suction motor 12, and the post-motor filter 13 is located downstream of the 30 suction motor 12. During use, the suction motor 12 causes dirt-laden air to be drawn in through a suction opening in the underside of the cleaner head 4. From the cleaner head 4, the dirt-laden air is drawn along the elongate tube 3 and the inlet duct 9, and into the dirt separator 10. Dirt is then separated from the air and retained within the dirt separator 10. The cieansed air exits the dirt separator 10 and is drawn through the pre-motor filter 11, which removes residual dirt from the air before passing through the suction motor 12. Finally, the air expelled by the suction motor 12 passes through the post-motor filter 13 and is exhausted from the vacuum 5 cleaner 1 via vents 14 in the handheld unit 2. The dirt separator 10 comprises a container 20 and a filter assembly 30. The container 20 comprises a top wall 21, a cylindrical side wall 22, and a bottom 10 wall 23 that collectively define a separation chamber 24. An opening 25 in the side wall 22 of the container 20 defines an inlet of the dirt separator 10, and an opening 26 in the centre of the top wall 21 defines an outlet of the dirt separator 10. The bottom wall 23 is attached to the side wall 22 by means of a hinge 27. A catch 28 attached to the bottom wall 23 engages with a recess in the side wall 22 CO 15 to hold the bottom wall 23 in a closed position. Releasing the catch 28 then causes the bottom wall 23 to swing to an open position. CM The separation chamber 24 of the present embodiment comprises a cyclone chamber. The inlet 25 and the inlet duct 9 are therefore arranged such that dirt-20 laden air enters the separation chamber 24 in a tangential direction. Referring now to Figure 3, the filter assembly 30 is generally cylindrical in shape and comprises a plurality of filter segments 31, a plurality of supports 32, a plurality of manipulators 33 and a base 34. 25 The filter segments 31 are arranged about a central axis 35 of the filter assembly 30. In the present embodiment, the filter assembly 30 comprises four filter segments 31. However, as discussed below, the filter assembly 30 may comprise an alternative number of filter segments. Each of the filter segments 31 comprises a mesh screen 30 that is attached along one side to one of the supports 32, and along an opposite side to one of the manipulators 33. Each of the supports 32 and each of the manipulators 33 comprises a cylindrical rod having a slot that extends longitudinally along the length of the rod. The supports 32 and the manipulators 33 are similar in design and differ only in their lengths, with the manipulators 33 being longer than the supports 32. Each of the 5 supports 32 is attached to one side of a respective filter segment 31, and each of the manipulators 33 is attached to an opposite side of a respective filter segment 31. More particularly, each filter segment 31 is held within the slots of the respective support 32 and manipulator 33. 10 The base 34 is disc-shaped and comprises a number of recesses (not shown). Each of the supports 32 is seated at one end within a recess in the base 34, and at an opposite end within a recess in the top wall 21 of the container 20. The recesses are sized such that the supports 32 are free to rotate about their length, but are prevented from translation. Each of the manipulators 33 is likewise seated at one CO 15 end within a recess in the base 34. However, in contrast to the supports 32, each of the manipulators 33 extends through an opening in the top wall 21 of the CM container 20. Again, the recesses in the base 34 and the openings in the top wall 21 are sized such that the manipulators 33 are free to rotate about their length, but are prevented from translation. A bearing (e.g. plain or ball bearing) may be seated 20 within each of the recesses and / or openings so as to reduce friction and wear, as well as to reduce potential leak paths. With the supports 32 and manipulators 33 seated within the recesses and openings in the base 34 and the top wall 21, the bottom of each filter segment 31 is flush with 25 the base 34 of the filter assembly 30, and the top of each filter segment 31 is flush with the top wall 21 of the container 20. Additionally, each of the filter segments 31 has an arcuate profile. In Figure 3, each of the filter segments 31 bows outwardly and has a profile that is convex in a direction normal to the central axis 35. However, as will now be described, each of the filter segments 31 is moveable to a position in 30 which the profile is concave in a direction normal to the central axis 35. Each of the supports 32 and each of the manipulators 33 is free to rotate about an axis of rotation that is parallel to the central axis 35. Rotation of each of the manipulators 33 causes the manipulator 33 to apply a force to the respective filter segment 31 to which the manipulator 33 is attached. As will now be described with reference to Figure 4, rotation of a manipulator 33 causes the respective filter segment 31 to move between a first position and a second position. 5 Figure 4 is sectional view through one of the filter segments 31, taken in a plane normal to the central axis 35 of the filter assembly 30. The filter segment 31 is attached along one side (right) to a support 32 and along an opposite side (left) to a manipulator 33. 10 Figure 4(a) shows the filter segment 31 in a first position. In this first position, the filter segment 31 has a profile that is convex in a direction normal to the central axis 35. As the manipulator 33 rotates in a first direction (e.g. clockwise in Figure 4), one side of the filter segment 31 is turned inwardly. As the side of the filter CO 15 segment 31 turns inwardly, the filter segment 31 deforms and enters an unstable state. The potential energy of the filter segment 31 increases due to the deformation CM in the filter segment 31. As the manipulator 33 rotates further, the filter segment 31 reaches a critical position, shown in Figure 4(b). In this critical position, the filter segment is at an equilibrium but nevertheless unstable state. Further rotation of the 20 manipulator 33 at this point causes the filter segment 31 to move from the critical position. In moving from the critical position, the potential energy stored in the filter segment 31 is transformed into kinetic energy, causing the filter segment 31 to accelerate towards a second position, shown in Figure 4(c). In moving to the second position, the support 32 rotates freely about its rotational axis, and the 25 opposite side of the filter segment 31 turns inwardly. As a result, movement of the filter segment 31 from the critical position to the second position is highly dynamic and the filter segment 31 effectively snaps from the critical position (Figure 4(b)) to the second position (Figure 4(c)). The filter segment 31 is then arrested at the second position. In this second position, the filter segment 31 has a profile that is 30 concave in a direction normal to the central axis 35. With the filter segment 31 in the second position (Figure 4(c)), rotation of the manipulator 33 in a second opposite direction (e.g. counterclockwise in Figure 4) causes one side of the filter segment 31 to turn outwardly. As the side of the filter segment 31 turns outwardly, the filter segment 31 again deforms and enters an unstable state. As the manipulator 33 rotates further, the filter segment 31 reaches a critical position, shown in Figure 4(d). Further rotation of the manipulator 33 at 5 this point causes the filter segment to move from the critical position to the first position, shown in Figure 4(e). In moving from the critical position, the potential energy stored in the filter segment 31 is transformed into kinetic energy, causing the filter segment 31 to accelerate towards the first position. Again, in moving to the first position, the support 32 rotates freely about its rotational axis, and the 10 opposite side of the filter segment 31 turns outwardly. As a result, movement of the filter assembly 31 from the critical position (Figure 4(d)) to the first position (Figure 4(e)) is highly dynamic. The filter segment 31 is then arrested at the first position. CO 15 Each of the filter segments 31 is therefore moveable between a first position and a second position. When in the first position, each of the filter segments 31 has a CM        profile that is convex in a direction normal to the central axis 35. Conversely, when in the second position, each of the filter segments 31 has a profile that is concave ’ ,        in the direction normal to the central axis 35. As noted above, movement of the CM 20 filter segments 31 between the two positions is highly dynamic. In particular, each of the filter segments 31 may snap when moving between the two positions. This movement may then be used to release dirt that has collected on the surfaces of the filter segments 31. 25 The filter assembly 30 is located within the separation chamber 24. As noted above, the separation chamber 24 of the present embodiment comprises a cyclone chamber. The dirt-laden air drawn into the separation chamber 24 therefore spirals about the filter assembly 30. Dirt within the air is separated by the cyclonic action (i.e. centrifugal forces) and collects at the bottom of the container 20. The cleansed 30 air is then drawn through the filter segments 31, which act to remove some of the residual dirt that continues to be entrained in the air, such as hair and fluff. After passing through the filter segments 31, the cleansed air is drawn out of the dirt separator 20 via the outlet 26 in the top wall 21 of the container 20. Figure 5 is a sectional view through the filter assembly 30 with the filter segments in (a) the first position and (b) the second position. During normal use of the vacuum cleaner 1, the filter segments 31 are placed into the first position. As a result, the 5 outer perimeter of the filter assembly 30, in a plane normal to the central axis, is generally circular in shape. This then has the advantage that movement of the air about the filter assembly 30 is less turbulent. In order to clean the filter assembly 30, the filter segments 31 are first moved from the first position to the second position. In moving to the second position, dirt collected on the surface of the filter segments 10 may be released. When moving the filter segments 31 to the second position, dirt is accelerated in a generally inward direction. Nevertheless, the energy involved in the movement may nevertheless be sufficient to release loosely attached dirt and / or relatively heavy dirt from the surfaces of the filter segments 31. The filter segments 31 are then moved from the second position to the first position. In CO 15 moving the filter segments 31 to the first position, the dirt is now accelerated in an outward direction away from the filter segments 31. As a result, more of the dirt CM collected on the surfaces of the filter segments 31 may be released. i— C\j The vacuum cleaner 1 may he said to comprise a filtration mode and a regeneration 20 mode. In filtration mode, the filter assembly 30 removes dirt from an airflow moving through the vacuum cleaner 1. The filter segments 31 are in the first position and the airflow is drawn through the filter segments 31 in a radially inward direction (i.e. towards the central axis 35). In regeneration mode, the filter segments 31 are moved between the first position and the second position in order to at least partially 25 clean the filter assembly 30. In particular, the filter segments 31 are moved from the first position to the second position and then subsequently from the second position to the first position. The handheld unit 2 further comprises an actuator 40 for actuating (i.e. bringing 30 about rotation of) each of the manipulators 33. The actuator 40 comprises an electric motor 41 and a transmission 42 for transferring torque generated by the electric motor 41 to each of the manipulators 33. As shown in Figure 6, the transmission 42 comprises a larger inner gear 43 attached to a shaft 45 of the electric motor 41, and a plurality of smaller outer gears 44, each of which is attached to a respective manipulator 33. The electric motor 41 is a bidirectional, low speed, high torque motor. The actuator 40 is therefore capable of actuating (i.e. bringing about rotation of) each of the manipulators 33 in both directions (e.g. clockwise and 5 counterclockwise). That is to say that the actuator 40 may actuate the manipulators 33 in a first direction in order to move the filter segments 31 from the first position to the second position, and in a second, opposite direction in order to move the filter segments 31 from the second position to the first position. 10 The actuator 40 may actuate the manipulators 33 periodically or in response to particular event or input. For example, the actuator 40 may actuate the manipulators 33 in response to each power off of the suction motor 12. Alternatively, the actuator 40 may actuate the manipulators 33 only after the suction motor 12 has been powered on and off a set number of times, or if the suction CO 15 motor 12 has been used for a predetermined period of time. In another example, the actuator 40 may actuate the manipulators 33 in response to a user input. For CM example, the handheld unit 2 may comprise a button, switch or the like which a user operates in order to clean the filter assembly 30. i— CM 20 In the embodiment described above, the first and second positions of each filter segment 31 are stable positions, i.e. each filter segment 31 may be said to be bistable. Consequently, the actuator 40 is not required to maintain the filter segments 31 in the first position or the second position. Conceivably, however, one of the positions may be unstable. For example, the first position may be a stable 25 position and the second position may be an unstable position. In order to move the filter segments 31 to the second position, the actuator 40 actuates the manipulators 33 in the manner described above. However, in order to return the filter segments 31 to the first position, the actuator 40 need only release the manipulators 33. By way of example, the teeth on the larger gear 43 may be 30 incomplete such that, as the larger gear 43 rotates, the larger gear 43 initially engages the small gears 44 (causing the filter segments 31 to move to the second position) and then disengages the small gears 44 (causing the filter segments 31 to return to the first position). Each filter segment 31 is attached along one side to a support 32 and along an opposite side to a manipulator 33. The filter segment 31 is then moved between the two positions by rotation of the manipulator 33. In an alternative embodiment, 5 each filter segment 31 may be attached along both sides to a pair of manipulators, i.e. the support may be substituted by a second manipulator. The transmission 42 of the actuator 40 may then be configured (e.g. comprise additional gears) such that the second manipulator is actuated in an opposite direction to that of the first manipulator. Consequently, when moving a particular filter segment 31 between 10 the first and second positions, both manipulators rotate inwardly or outwardly. The filter assembly 30 comprises four filter segments 31. However, the filter assembly 30 may comprise an alternative number of filter segments 31. In particular, the filter assembly 30 may comprise a greater number of filter CO 15 segments 31. As the number of filter segments 31 increases, the degree of deflection or deformation through which each filter segment 31 undergoes as it CM moves between the two positions is reduced. As a result, each of the filter segments 31 is subjected to less mechanical stress. However, as a consequence of the reduced deflection, the acceleration imparted to the dirt is reduced. 20 Additionally, each additional filter segment 31 requires a further support 21 and manipulator 33. Accordingly, the filter assembly 30 may comprise no more than six filter segments 31. The filter segments 31 may be required to move many times between the two 25 positions over the life of the filter assembly 30. Accordingly, each of the filter segments 31 may be formed of a metal, such that fatigue of the filter segments 31 may be avoided or reduced. Nevertheless, the filter segments 31 may be formed of an alternative material, such as a plastic. 30 Figure 7 illustrates an alternative embodiment of a handheld unit 50. With the exception of the filter assembly 60 and the actuator 80, the handheld unit 50 is substantially the same as that of Figure 2. The filter assembly 60 is shown in Figure 8 and comprises a plurality of filter elements 61 and a base 62. Like the filter assembly of Figure 3, the filter segments 61 are arranged about a 5 central axis 65 of the filter assembly 60. In this particular embodiment, the filter assembly 60 comprises three filter segments 61. However, the filter assembly 60 may comprise a greater number of filter segments 61. Each of the filter segments 61 comprises a pleated filter medium 63 and a strip 64 10 attached along the top of the filter medium 63. The strip 64 is attached to the filter medium by an elastomeric material (not shown), such as a rubber potting compound. The elastomeric material provides a seal between the filter medium 63 and the strip 64, and is sufficiently flexible to maintain the seal as the filter segments 61 move between the first position and the second position, as described CO 15 below. Each of the filter segments 61 is attached along each side to an adjacent filter segment 61. In particular, the filter medium 63 of each filter segment 61 is CM attached (e.g. by gluing) to the filter media 63 of adjacent filter segments 61, and the strip 64 of each filter segment 61 is attached (e.g. by welding) to the strips 64 of adjacent filter segments 61. Asa result, the filter segments 61 collectively resemble 20 a triangular prism. The base 62 closes off the bottom of the filter assembly 60 and comprises an elastomeric material that extends between and is sealed to the bottom of the filter segments 61. 25 Each of the filter segments 61 is again moveable between a first position and a second position. When in the first position, each of the filter segments 61 has a profile that is convex in a direction normal to the central axis 65. Conversely, when in the second position, each of the filter segments 61 has a profile that is concave 30 in the direction normal to the central axis 65. In Figure 8, the filter segments 61 are in the second position. The strips 64 are stiffer than the fiiter media 63 in a direction normal to the central axis 65. Relatively flexible filter media may therefore be used, whilst the stiffness provided by the strips 64 ensures that movement of each of the filter segments between the two positions is highly dynamic. Each of the strips 64 is formed of a 5 metal, such that fatigue with repeated movement may be avoided or reduced. Nevertheless, an alternative material, such as a plastic, may be used. The filter segments 61 are moved from the second position to the first position by a manipulator 70. In contrast to the filter assembly 30 of Figure 3, the manipulator 70 10 is not attached to nor forms an integral part of the filter assembly 60. Consequently, the manipulator 70 may be said to form a distinct element of the vacuum cleaner. The manipulator 70 comprises a cam-like body having a plurality of lobes 72. The manipulator 70 is arranged to rotate about the central axis 65 of the filter assembly 60. As the manipulator 70 rotates, each of the lobes 72 contacts and CO 15 applies a force to a respective filter segment 61. More particularly, each of the lobes 72 contacts and applies a force to the strip 64 of a respective filter CM segment 61. As the manipulator 70 rotates, the force applied by the lobes 72 on the strips 64 causes the filter segments 61 to move from the second position to the first position. In moving to the first position, dirt collected on the surface of the filter 20 segments 61 may be released. In contrast to the embodiment of Figure 3, the manipulator 70 is capable only of moving the filter segments 61 from the second position to the first position. The filter segments 61 are then moved from the first position to the second position by 25 the suction generated by the suction motor 12. For example, the filter segments 61 may be returned to the second position upon powering on the suction motor 12. The vacuum cleaner may again be said to comprise a filtration mode and a regeneration mode. In filtration mode, the filter assembly 60 removes dirt from an 30 airflow moving through the vacuum cleaner. The filter segments 61 are moved to the second position by the suction motor 12, and the resulting airflow is drawn through the filter segments 61 in a radially inward direction (i.e. towards the central axis 65). In regeneration mode, the filter segments 61 are moved by the manipulator / 0 to the first position in order to at least partially clean the filter assembly 60. The filter assembly 60 is again located within the separation chamber 24 of the dirt 5 separator 10. However, in contrast to the embodiment of Figure 2, the primary mechanism for separating dirt for the air is not intended to be cyclonic. Instead, the filter assembly 60 acts as the primary mechanism for separating dirt from the air. The dirt-laden air may continue to enter the separation chamber 24 in a tangential direction. This then imparts a degree of swirl to the airflow, which in turn encourages 10 more uniform loading of the filter assembly 60. After passing through the filter segments 61, the cleansed air is drawn out of the dirt separator 10 via the outlet 26 in the top wail 21 of the container 20. Each of the filter segments 61 comprises a pleated filter medium. Conceivably, CO 15 each of the filter segments 61 may comprise a flat filter medium. However, there are advantages in employing a pleated medium. First, a higher surface area is CM achievable with a pleated medium. As a result, the filter assembly 60 is capable of capturing more dirt for a given restriction in the airflow. Second, relative coarse dirt may collect on the surface of the filter medium over a relatively small attachment 20 area. Consequently, when moving the filter segments 61 between the two positions, more of the dirt may be released. Third, when the filter segments 61 are in the second position, the pitch of the pleats on the upstream side of each filter segment 61 is smaller. Consequently, when moving the filter segments 61 from the second position to the first position, the pitch of the pleats on the upstream side of 25 the filter segments 61 increases. As a result, the attachment area over which dirt is attached to the filter media 63 decreases and thus the dirt may be more easily released. The actuator 80 is operable to actuate (i.e. bringing about rotation of) the 30 manipulator 70. The actuator 80 comprises an electric motor 81 having a shaft 85 that is attached to the manipulator 70. The electric motor 81 is again a low speed, high torque motor. However, the electric motor 81 need not be directional. As with the embodiment of Figure 2, the actuator 80 may actuate the manipulator 70 periodically or in response to particular event or input. As already noted, the manipulator 70 of this particular embodiment is neither 5 attached to nor forms an integral part of the filter assembly 60. As a result, the filter assembly 60 may be removed more easily from the dirt separator 10 in order to more thoroughly clean and / or replace the filter assembly 60, if required. Nevertheless, the manipulator 70 may form an integral part of the filter assembly 60. For example, the filter assembly 60 may comprise spokes that extend from each 10 join in the strips 84 towards a central hub to which the manipulator 70 is rotatable attached. Where the manipulator 70 forms an integral part of the filter assembly 60 and the filter assembly 60 is removable from the dirt separator 10, the actuator 80 may conceivably be omitted. Cleaning of the filter assembly 60 may then be achieved by removing the filter assembly 60 and actuating the manipulator 70 by CO 15 hand. CM CM In each of the embodiments described above, the filter assembly 30,80 is located within the separation chamber 24 of the dirt separator 10. In alternative ’ , embodiments, the filter assembly 30,80 may be located elsewhere within the CM 20 vacuum cleaner. That is to say that the filter assembly 30,80 may be used more generally within a vacuum cleaner to remove dirt from an airflow, and need not be located within the main separation chamber. For example, the filter assembly 30,80 may be used as the pre-motor filter or the post-motor filter of a vacuum cleaner. This is particularly true of the filter assembly 80 of Figure 8. 25 In each of the embodiments described above, the vacuum cleaner comprises an actuator 50,80 to actuate the manipulator(s) 33,70. The actuator 50,80 then comprises an electric motor 51,81 for generating the torque necessary to actuate the manipulator(s) 33,70. As an alternative to an electric motor, the vacuum cleaner 30 may comprise a mechanism that is operated manually by a user in order to generate the necessary torque. For example, the vacuum cleaner may comprise a rotary dial, plunger, or the like that transfers the force generated by the user to the manipulator(s) 33,70. 21 12 23 In the embodiments described above, actuation of the manipulators comprises rotation of the manipulators. In alternative embodiments, actuation of the manipulators may comprise a different type of motion for applying a force to each 5 of the filter segments. By way of example, actuation of a manipulator may comprise linear translation of the manipulator in a radial direction so as to apply a radial force to a respective filter segment. Reference has thus far been made to a vacuum cleaner 1 having a handheld 10 unit 2,50. However, the filter assembly 30,60 and / or the dirt separator 10 may be used in alternative types of vacuum cleaner, such as an upright, canister, stick or robotic vacuum cleaner. Moreover, the filter assembly 30,60 and / or the dirt separator 10 may be used to remove dirt from an airflow in other applications and products. 15 Whilst particular examples and embodiments have been described, it should be understood that these are illustrative only and that various modifications may be made without departing from the scope of the invention as defined by the claims. 20

Claims

1. A filter assembly comprising a plurality of filter segments arranged about a central axis, and at least one manipulator, wherein each of the filter segments is 5 moveable between a first position and a second position, each of the filter segments has a profile in a direction normal to the central axis that is convex when in the first position and concave when in the second position, and actuation of the manipulator causes the manipulator to apply a force to the filter segments to move the filter segments between the first position and the second position,10 wherein actuation of the manipulator in a first direction causes the filter segments to move from the first position to the second position, and actuation of the manipulator in a second, opposite direction causes the filter segments to move from second position to first position.CO 15   2. A filter assembly as claimed in claim 1, wherein the first position and thesecond position are stable positions.CM3. A filter assembly as claimed in any one of the preceding claims, wherein the filter comprises a plurality of manipulators, and actuation of each of the manipulators 20 causes a respective filter segment to move between the first position and the second position.

4. A filter assembly as claimed in claim 3, wherein each of the manipulators is attached along an edge of the respective filter segment.

255. A filter assembly as claimed in claim 1 or 2, wherein the manipulator comprises a body having a plurality of lobes, and actuation of the manipulator causes each of the lobes to contact and move a respective filter segment.30   6. A filter assembly as claimed in any one of the preceding claims, whereinactuation of the manipulator or each of the manipulators comprises rotation about a rotation axis parallel to the central axis.

7. A filter assembly as claimed in any one of the preceding claims, wherein an outer perimeter of the filter assembly in a plane normal to the central axis is generally circular in shape when the filter segments are in the first position.5   8. A filter assembly as claimed in any one of the preceding claims, wherein thefilter assembly comprises at least four filter segments.

9. A filter assembly as claimed in any one of the preceding claims, wherein each of the filter segments comprises a mesh screen or a pleated filter medium.1010. A filter assembly as claimed in any one of the preceding claims, wherein each of the filter segments comprises a filter medium attached to a strip, and the strip is stiffer than the filter medium in a direction normal to the central axis.CO 15   11. A filter assembly as claimed in claim 10, wherein actuation of the manipulatorcauses the manipulator to apply a force to the strips of the filter segments to moveCM the filter segments between the first position and the second position.i—12. A filter assembly as claimed in claim 10 or 11, wherein the strip of each of 20 the filter segments is attached at each end to the strip of a respective other of the filter segments.

13. A filter assembly as claimed in any one of claims 10 to 12, wherein the strip is formed of a metal.2514. A dirt separator for separating dirt from an airflow, the dirt separator comprising:a separation chamber: anda filter assembly as claimed in any one of the preceding claims, wherein the 30 filter assembly is located within the separation chamber.

15. A dirt separator as claimed in claim 14, wherein the separation chamber is a cyclone chamber.

16. A vacuum cleaner comprising a filter assembly, at least one manipulator and an actuator to actuate the manipulator wherein the filter assembly comprises a plurality of filter segments arranged about a central axis, each of the filter segments 5 is moveable between a first position and a second position, each of the filter segments has a profile in a direction normal to the central axis that is convex when in the first position and concave when in the second position, and actuation of the manipulator by the actuator causes the manipulator to apply a force to the filter segments to move the filter segments between the first position and the second 10 position.

17. A vacuum cleaner as claimed in claim 16, wherein the vacuum cleaner comprises a suction motor, and the filter segments are caused to move between the first position and the second position in response to suction generated by the CO 15 suction motor.CMCM 18. A vacuum cleaner as claimed in claim 17, wherein the filter segments are caused to move to one of the first position and the second position in response to the suction generated by the suction motor, and actuation of the manipulator causes 20 the filter segments to move to the other of the first position and the second position.

19. A vacuum cleaner as claimed in any one of claims 16 to 18, wherein the vacuum cleaner is operable in a filtration mode and a regeneration mode, filtration mode comprises drawing an airflow through the filter assembly, and regeneration 25 mode comprises moving the filter segments between the first position and the second position.

20. A vacuum cleaner as claimed in claim 19, wherein filtration mode comprises drawing the airflow through each of the filter segments in a radially inward direction 30 towards the central axis, and regeneration mode comprises moving each of the filter segments from the second position to the first position.21 12 2321. A vacuum cleaner as claimed in claim 19or 20, wherein each of the filter segments comprises a mesh screen, each of the filter segments is in the first position in filtration mode, and regeneration mode comprises moving each of the filter segments to the second position and subsequently moving each of the filter 5 segments to the first position.

22. A vacuum cleaner as claimed in claim 19 or 20, wherein each of the filter segments comprises a pleated filter medium having pleats, each of the filter segments has an upstream side and a downstream side relative to the direction of 10 the airflow through each of the filter segments, each of the filter segments is in one of the first position and the second position in filtration mode, and regeneration mode comprises moving each of the filter segments to the other of the first position and the second position such that a pitch of the pleats on the upstream side increases.1523. A vacuum cleaner as claimed in any one of claims 16 to 22, wherein the actuator is manually operable by a user.

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