GB2349105A

GB2349105A - Double layered vacuum cleaner filter

Info

Publication number: GB2349105A
Application number: GB0009660A
Authority: GB
Inventors: Mark Peter Storer
Original assignee: Notetry Ltd
Current assignee: Dyson Technology Ltd
Priority date: 1999-04-23
Filing date: 2000-04-20
Publication date: 2000-10-25
Anticipated expiration: 2020-04-20
Also published as: GB0009660D0; GB2349105B; GB2349105C

Abstract

A filter assembly, for use in a vacuum cleaner upstream of its motor, comprises a foam filter portion 14, 120 adjacent to and upstream of a second filter portion 16, 116 wherein the second filter portion consists of an electrostatic or HEPA grade filter medium, the first and second portions being held directly adjacent one another by means of a filter housing 12, 112. The first filter portion also has a tab 28, 328 located on a surface remote from the second filter portion to facilitate removal of the first filter portion from the filter housing when it is clogged with dust for washing or replacement. The first filter portion may also comprise an electrostatic filter located on the side of the foam filter facing the second filter (150, Fig 8a). The second filter portion is preferably washable. The filter assembly optionally includes a plate-like portion 26 to aid positioning the connector portion 24 in the correct orientation in the vacuum cleaner.

Description

A FILTER ASSEMBLY The invention relates to a filter assembly. Particularly, but not exclusively, the invention relates to a filter assembly designed and adapted for use in a vacuum cleaner.

Filter assemblies for removing dust or debris from the air stream of a vacuum cleaner or other dust retaining appliances are common. Such filter assemblies generally comprise at least one filter located in a filter housing. Through use, the filter can become clogged and will require cleaning or replacing. Removal of the filter from the filter housing can often be a messy and unhygienic task as it generally involves the user handling the dirty filter. In US 5,230,722 a handle is provided on the filter housing which allows the user to remove the filter housing and thereby the filter also from the vacuum cleaner when the filter needs to be cleaned. In this type of arrangement, the user would still need to touch the dirty filter in order to remove it from the filter housing.

It is an object of the present invention to provide a filter assembly which allows the user to remove a filter from the filter housing without having to touch the filter. It is a further object of the present invention to provide a filter assembly in which it is easier and more hygienic to remove the filter from the filter housing. Furthermore, an object of the invention is to provide a filter assembly for use in a vacuum cleaner or other appliance in which the motor of the vacuum cleaner is reliably protected and in which the maintenance costs of the vacuum cleaner are reduced.

In a first aspect, the invention provides a filter assembly for use in a vacuum cleaner having a first filter portion comprising a foam filter, and a second filter portion located downstream of the first filter portion and consisting of an electrostatic filter medium, the first and second filter portions being held directly adjacent one another by means of a filter housing, wherein the first filter portion has a tab located on a surface thereof remote from the second filter portion to facilitate removal of the first filter portion from the filter housing.

In a second aspect, the invention provides filter assembly for use in a vacuum cleaner having a first filter portion comprising a foam filter, and a second filter portion located downstream of the first filter portion and consisting of a HEPA grade filter medium, the first and second filter portions being held directly adjacent one another by means of a filter housing, wherein the first filter portion has a tab located on a surface thereof remote from the second filter portion to facilitate removal of the first filter portion from the filter housing.

These arrangements are advantageous in that the user does not have to handle the foam filter directly. Under normal circumstances, the fine dust entrained within the airflow is trapped within the pores of the foam filter with little or no accumulation in the electrostatic filter portion. The foam filter has a large dust retaining capacity and, in use, can become clogged with dust. When the first filter portion needs cleaning or replacing, the user can remove the first filter portion from the filter assembly by grasping the tab. The first filter portion can be held by the tab and washed.

Preferably, the tab consists of a flexible elongate strand having a securing portion at one end and a gripping portion at the other end. More preferably, the flexible elongate strand passes through the foam material of the first filter portion. This provides an effective means for securing the tab to the filter which would be easy and cheap to manufacture.

Alternatively, the tab maybe secured to the first filter portion by adhesive. The use of adhesive is a cost-effective means of securing the tab on to the filter. In a preferred embodiment, the tab is secured to the surface of the first filter portion remote from the second filter portion. Alternatively, the tab can be secured to a surface of the first filter portion adjacent the second filter portion.

Preferably, the first filter portion further comprises an electrostatic filter located on the side of the foam filter facing the second filter portion. Dust or dirt that may escape from the foam filter is trapped by the electrostatic filter. Advantageously, when the filter assembly becomes less efficient that is desirable, the user is able to wash the first filter portion by merely removing the first filter portion from the filter assembly by pulling the tab attached thereto and placing the filter under a tap. After drying, the first filter portion can be returned to the filter assembly and returned to the vacuum cleaner (or other appliance) for further use. The maintenance costs of the appliance are thus reduced.

More preferably, the second filter portion is washable. Advantageously, this would mean that replacement filters are not required.

Further advantageous features are set out in the subsidiary claims.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure la is a plan view of a filter assembly according to a first embodiment of the invention; Figure lb is a sectional view taken along line b-b of Figure la; Figure 2 is an exploded view of the filter assembly of Figure la; Figures 3a, 3b and 3c are plan, side and perspective views respectively of a first filter portion forming part of the filter assembly shown in Figures 1 and 2; Figures 4a and 4b are plan and side views respectively of a second filter portion forming part of the filter assembly shown in Figures 1 and 2; Figure 5a is a sectional side view of a filter assembly according to a second embodiment of the invention; Figure 5b is a plan view of a tab forcing part of the embodiment shown in Figure 5a ; Figure 6 is a sectional view of a filter assembly according to a third embodiment of the invention; Figures 7a and 7b are perspective and sectional views respectively of the filter assembly of Figure 6 on a reduced scale and showing the first filter portion in a partially removed position; and Figures 8a and 8b are sectional and perspective views respectively of a filter assembly according to a fourth embodiment of the invention.

A first embodiment of a filter assembly according to the present invention is shown Figures la, lb and 2. The filter assembly 10 essentially comprises a filter housing 12, a first filter portion 14 and a second filter portion 16. The filter housing 12 is cylindrical in shape and is manufactured from a suitable plastics material. The filter housing 12 has a cylindrical outer wall 18 which is adapted to receive the first and second filter portions 14,16. A cylindrical sleeve 20 is located inwardly of the cylindrical outer wall 18 and is connected thereto by radially projecting arms or spokes 22 which extend between an end face of the cylindrical sleeve 20 and an end face of the cylindrical outer wall 18. As can be seen from Figure 2, the spokes 22 lie generally in the plane of one end of the cylindrical outer wall 18. The cylindrical outer wall 18, the cylindrical sleeve 20 and the spokes 22 are manufactured integrally by means of known plastics forming techniques.

A central gripping portion 24 is provided on or within the cylindrical sleeve 20. It is also integrally moulded with the cylindrical outer wall 18, the cylindrical sleeve 20 and the spokes 22. The central gripping portion 24 essentially comprises a generally cylindrical portion 25 with a plate-like portion 26 extending therefrom along the axis of the filter housing 12. The plate-like portion 26 provides a user with the means to grasp the connector portion 24 in order to insert the filter assembly 10 into the appliance in which it is to be used, or to remove it therefrom. The plate-like portion 26 can incorporate a textured surface which will assist the user to grip the connector portion 24.

The plate-like portion 26 is dimensioned so that it projects beyond the end surface of the filter housing 12 as shown in Figure lb. This feature can be used in conjunction with the vacuum cleaner in order to prevent the user from inadvertently positioning the filter assembly 10 in the relevant appliance in an incorrect orientation. More specifically, the vacuum cleaner will include a recess or other shaping into which the filter housing 12 is to be received, but the recess will not include any accommodation for the projecting plate-like portion 26. This ensures that the user will be unable to seat the filter housing 12 in the recess in the vacuum cleaner if the filter housing 12 is turned the wrong way up. The user will be alerted to this and will be able to correct the orientation of the filter housing 12.

It will be appreciated that the central sleeve 20 and/or the central gripping portion 24 can carry means for fixedly connecting the filter assembly 10 to the relevant appliance.

The manner in which the filter assembly 10 is connected to the appliance is immaterial to this invention and a skilled reader will appreciate that the connection can be formed by the mating of camming surfaces, by screw-threaded portions, by snap-fitting/quickrelease fasteners or other equivalent means.

It is essential that the spokes 22 are arranged and configured so that a relatively small proportion of the area of the end face of the filter housing 12 in which the spokes 22 lie is obstructed by them. In the illustrated embodiment, eight spokes 22 are equi-angularly arranged about the cylindrical sleeve 20. However, the number of spokes 22 provided is not critical and it is envisaged that fewer or more than eight spokes 22 can be present.

As few as four spokes and as many as sixteen spokes are expected to be acceptable, with eight or twelve spokes being preferred.

The first and second filter portions will now be described with reference to Figures 3 and 4. The first filter portion 14 is made from a foam filter medium in the form of a cylindrical disc having a central aperture 14a. A suitable material from which the first filter portion 14 can be manufactured is 90ppi reticulated open cell polyurethane foam.

The shape of the first filter portion 14 is selected so as to substantially fill the interior of the filter housing 12. Therefore, the outer diameter of the first filter portion 14 is substantially the same as the diameter of the cylindrical outer wall 18 of the filter housing 12, and the diameter of the central aperture 14a of the first filter portion 14 is substantially the same as that of the cylindrical sleeve 20. In order to ensure that the interior of the filter housing 12 is reliably filled, it is preferred that the outer diameter of the first filter portion 14 is slightly larger than the interior diameter of the cylindrical outer wall 18, and the diameter of the central aperture 14a of the first filter portion 14 is slightly smaller than the outer diameter of the cylindrical sleeve 20.

A tab 28 is provided on the first filter portion 14 in order to assist with the removal of the first filter portion 14 from the filter housing 12. In the embodiment shown, the tab 28 consists of a flexible elongate strand 28a having a securing portion 28b at one end and a gripping portion 28c at the other end. The securing portion 28b is pushed through the foam material of the first filter portion 14 in a manner commonly used in relation to textile materials and goods made therefrom. The strand 28a is made sufficiently long to ensure that the gripping portion 28c is accessible to the user in order to effect the removal of the first filter portion 14 from the filter housing 12.

The second filter portion 16 is illustrated in Figures 4a and 4b. The second filter portion 16 consists of an electrostatic filter medium covered on both sides by a protective fabric. The layers are held together in known manner by stitching or other known means. The second filter portion 16 is circular in shape with a central aperture 16a for receiving the cylindrical sleeve 20 of the filter housing 12. The dimensions of the second filter portion 16 are chosen so that the second filter portion 16 covers the end face of the filter housing 16 in which the spokes 22 are formed. The second filter portion 16 is located directly adjacent the spokes 22 of the filter housing 12 and is bonded to the portion of the cylindrical outer wall 18 immediately adjacent the outer ends of the spokes 22. In this manner, the second filter portion 16 is held in a fixed position with respect to the filter housing 12. The second filter portion 16 is bonded to the filter housing 12 by any suitable method. Suitable methods include heat welding, ultra-sonic welding and adhesive. It is preferred that, during the bonding process, all of the layers of the second filter portion 16 are bonded to the filter housing 12 so that the risk of delamination of the second filter portion 16 during washing is reduced.

As can be seen from Figures 1 and 2, the assembly is arranged so that the second filter portion 16 is located directly adjacent the spokes 22 of the filter housing 12 and the first filter portion 14 is then located within the cylindrical outer wall 18 of the filter housing 12 directly adjacent the second filter portion 16. The tab 28 is located on a surface of the first filter portion 14 remote from the second filter portion 16.

In use, the filter assembly 10 is placed in the airflow path of the vacuum cleaner or other appliance in which the filter assembly 10 is to be used. The plate-like portion 26 is used to ensure that the filter housing is correctly orientated. Specifically, the filter assembly 10 is arranged so that the open face of the filter housing 12, i. e. the end face remote from that in which the spokes 22 are arranged, faces upstream. Air to be filtered therefore enters the first filter portion 14 initially. Filtration takes place within the foam filter medium which has a very significant capacity for trapping and retaining dust. However, continued use, particularly within a vacuum cleaner, may lead to an increase in the back pressure applied to the filter assembly 10. In the event that the first filter portion 14 is not removed and cleaned by washing before the back pressure applied across the filter assembly 10 reaches a critical value, dust previously retained within the first filter portion 14 will be expelled therefrom. However, the presence of the second filter portion 16 immediately downstream of the first filter portion 14 ensures that any dust released by the first filter portion 14 is retained within the filter assembly 10. When a filter assembly 10 of this sort is used as a pre-motor filter in a vacuum cleaner or other appliance, the motor is thereby reliably protected. Even when the filter assembly 10 is fully loaded with dust, there is still no emission of previously retained dust from the filter assembly 10 and the motor continues to be protected.

Indeed, in this event, either the back pressure across the filter assembly 10 or the rise in operating temperature of the motor will normally be sufficient to operate a warning light to indicate to the user that the filter assembly requires to be removed and cleaned.

Through use, the first filter portion 14 will become clogged with dust or dirt. Continued use would lead to a restriction in the airflow through the filter assembly 10. This causes a reduction in the filtration efficiency. In order to alleviate this, the first filter portion 14 must be washed. The first filter portion 14 is removed from the filter assembly 10 for washing by the user gripping the gripping portion 28c and pulling the tab 28 outwardly from the filter assembly 10 in the direction of arrow B (as shown in Figure lb). In this way, the user does not have to handle the clogged first filter portion 14 directly. This makes replacing or cleaning the first filter portion 14 a more hygienic task. The second filter portion 16 is also capable of being cleaned by washing. If the second filter portion 16 is bonded to the filter housing 12, the second filter portion 16 and the filter housing 12 must be washed together. If the second filter portion 16 is not bonded to the filter housing 12, then the second filter portion 16 can of course be washed independently of the filter housing 12. However, care must then be taken to replace the second filter portion 16 in the filter housing 12 in a position which does not allow any air to pass through the filter assembly 10 without passing through the second filter portion 16.

It will be appreciated that the filter assembly described above can be manufactured with any appropriate dimensions. Purely for the purposes of illustration and without any intent to limit the disclosure herein, the dimensions of the filter housing 12 illustrated above are in the region of 140mm diameter and 25mm depth.

A second embodiment of a filter assembly according to the invention is shown in Figures 5a and 5b. This embodiment of the filter assembly 100 is very similar to that shown in Figures 1 to 4 except that the tab 28 is omitted and in its place is a tab 228. In this embodiment, components illustrated and already described in relation to Figures 1 to 4 have like reference numerals. Two diametrically opposed tabs 228 are fixed to the first filter portion 14. Each tab 228 is generally elongate and comprises an intermediate portion 228a having a securing portion 228b at one end and a gripping portion 228c at the other end as shown in Figure 5b. The securing portion 228b is glued to the surface of the first filter portion 14 at a location remote from the central aperture 14a and on the surface of the first filter portion 14 adjacent the second filter portion 16. The intermediate portion 228a is held between the cylindrical side surface of the first filter portion 14 and the cylindrical outer wall 18 of the filter housing 12. The gripping portion 228c lies outside the filter housing 12 and is easily accessible to the user. In use, when the first filter portion 14 requires cleaning or replacing, the user can merely pull both the gripping portions 228c outwardly along the axis of the filter housing 12, in the direction of the arrow B. The user does not need to touch the first filter portion 14 which may be heavily loaded with dust or dirt.

A third embodiment of a filter assembly according to the invention is illustrated in Figures 6,7a and 7b. As can be seen from the Figures, the filter assembly 200 is again generally cylindrical in shape. In contrast to the embodiments illustrated in Figures 1 to 5, the axial length of the filter assembly 200 is greater than the diameter thereof.

The filter assembly 200 comprises a first housing portion 102 and a second housing portion 104. The first housing portion 102 is generally circular in shape and has a planar central portion 106 which is surrounded by a circular dished portion 108. Two outwardly projecting locating legs 110 are equispaced about the dished portion 108 and these extend away from the base of the dished portion 108 as shown in Figure 6. The second housing portion 104 is annular in shape having an aperture in the centre thereof and a side wall 112 which mirrors the outermost extremity of the dished portion 108 of the first housing portion 102. An annular lip 114 extends radially outwardly from the distal edge of the side wall 112.

A HEPA grade filter 116 is located between the first and second housing portions 102, 104. The HEPA grade filter 116 comprises a pleat pack of 102 pleats of washable HEPA grade filter material which is arranged in a cylindrical form. A first end 116a is seated in the dished portion 108 of the first housing portion 102 and is bonded thereto by suitable means. Suitable means include potting, adhesives, etc. The bonding of the first end 116a of the HEPA grade filter 116 into the dished portion 108 is of sufficient quality to prevent any passage of air around the end of the HEPA grade filter 116 within the dished portion 108. The other end 116b of the HEPA grade filter 116 is seated in the second housing portion 104 radially inwardly of the side wall 112. Again, the end 116b of the HEPA grade filter 116 is bonded to the second housing portion 104 by potting or adhesives or other suitable means. In this manner, the filter assembly 200 is given a cylindrical structure comprising the first and second housing portions 102,104 and the HEPA grade filter 116.

A cylindrical foam filter 120 is provided radially inwardly of the HEPA grade filter 116.

The outer diameter of the cylindrical foam filter 120 i essentially the same as the internal diameter of the HEPA grade filter 116. This ensures that, when the cylindrical foam filter 120 is located inside the HEPA grade filter 116, the cylindrical foam filter 120 abuts against the internal surface of the HEPA grade filter 116. The internal diameter of the cylindrical foam filter 120 is sufficiently large to allow unrestricted entry of a dust-laden airflow into the interior of the filter assembly 200.

A tab 328 is provided on the surface of the cylindrical foam filter 120 remote from the HEPA grade filter 116. In the embodiment shown, the tab 328 consists of a fixed end 328a and a free end 328b. The fixed end 328a is attached to the cylindrical foam filter 120 and the free end 328b extends away therefrom. In use, the free end 328b may be folded back so as to lie inside the filter housing 102 (as shown in Figure 6 by dotted line 328c) or alternatively the free end 328b may be folded over the end of the second housing portion 104 (as shown by dotted line 328d) until such time as the user requires to change the cylindrical foam filter 120.

A seal portion 122 is attached to a first end 120a of the cylindrical foam filter 120. The seal portion 122 is preferably formed from potting so as to provided a resiliently deformable seal portion 122 which is securely bonded to the end 120a of the cylindrical foam filter 120. Alternatively, the seal portion 122 could be moulded from a plastics material and bonded to the cylindrical foam filter 120 by a suitable adhesive. The seal portion 122 is dimensioned and shaped so that its outermost extremity 124 abuts against the periphery of the aperture in the second housing portion 104 in a sealing manner when the cylindrical foam filter 120 is inserted into the filter assembly 1000 as shown in Figure 6. The axial length of the cylindrical foam filter 120 is such that, when the outermost extremity 124 of the seal portion 122 is in sealing contact with the second housing portion 104, the opposite end 120b of the cylindrical foam filter 120 presses against the central portion 106 of the first housing portion 102. The seal portion 122 is annular in shape and has a central aperture communicating with the interior of the cylindrical foam filter 120.

In use, the filter assembly 200 is placed upstream of the motor and fan assembly of a vacuum cleaner. The airflow path of the vacuum cleaner is designed and arranged so that air exiting the main dirt and dust collecting apparatus, preferably a cyclonic separating apparatus, enters the filter assembly 200 by way of the aperture in the seal portion 122. The air then passes into the cylindrical passage surrounded and delimited by the cylindrical foam filter 120. The end of this passage remote from the portion 122 is closed by the central portion 106 of the first housing portion 102. Because the cylindrical foam filter 120 presses against the central portion 106, the only available exit from the passage is through the cylindrical foam filter 120. The air therefore moves radially outwardly away from the longitudinal axis 126 of the filter assembly 200.

Having passed through the cylindrical foam filter 120, the airflow continues radially outwardly in the direction of the arrow 128 and therefore passes through the HEPA grade filter 116 before exiting the filter assembly 200 in a radial direction.

Under normal operational circumstances, the vast majority of any fine dust entrained within the airflow entering the filter assembly 200 will be trapped within the pores of the cylindrical foam filter 120. Little or no dust will be collected in the HEPA grade filter 116 because the cylindrical foam filter 120 has a large capacity for retaining dust particles. When the cylindrical foam filter 120 is approaching its loading capacity, it should ideally be removed and cleaned. This can be achieved merely by the user gripping the free end 328b of the tab 328 and lifting the cylindrical foam filter 120 out of the housing 102 in the direction of arrow C as shown in Figure 7a. The cylindrical foam filter 120 is then washed by rinsing under a household tap in a known manner and allowed to dry. The cylindrical foam filter 120 is then re-inserted into the interior of the filter assembly 200 and operation can continue. The tab 328 ensures that the user does not need to directly handle the cylindrical foam filter 120.

The HEPA grade filter material from which the HEPA grade filter 116 is made can be washable. This ensures that the HEPA grade filter 116 does not degrade or deteriorate to any significant extent in the event that the cylindrical foam filter 120 is returned to use before it is completely dry. Also, it is possible that the cylindrical foam filter 120 will not be cleaned by washing before its loading capacity is exceeded. In this event, dust previously trapped by the cylindrical foam filter 120 maybe expelled therefrom.

Any and all dust expelled from the cylindrical foam filter 120 will inevitably be trapped and captured by the HEPA grade filter 116. If a significant amount of dust is allowed to accumulate on the HEPA grade filter 116, it can then be washed by rinsing under a household tap and allowed to dry. Operation of the vacuum cleaner can then be resumed.

The locating legs 110 are illustrated in Figures 6 and 7b as being equispaced about the longitudinal axis 126 of the filter assembly 200. If the vacuum cleaner or other apparatus in which the filter assembly 200 requires a specific rotational orientation of the filter assembly 200, then an asymmetrical arrangement of locating legs can be provided so that the filter assembly 200 cannot be properly located in the appliance in any orientation other than the correct one. However, with airflow entry being arranged axially and airflow exit being allowed in all rotational directions as illustrated in Figure 6, this is not necessary.

A fourth embodiment of the filter assembly according to the invention is illustrated in Figures 8a and 8b. The filter assembly 300 has essentially the same configuration as the third embodiment shown in Figures 6,7a and 7b. In this embodiment, components illustrated and already described in relation to Figures 6,7a and 7b have like reference numerals. In addition the filter assembly 300 has an electrostatic filter 150 positioned between the cylindrical foam filter 120 and the HEPA grade filter 116. The electrostatic filter 150 is located on the cylindrical foam filter 120 by suitable means to form a filter core 152. The filter core 152 is closed at a lower end by a circular disc portion 154. The filter core 152 is located radially inwardly of the HEPA grade filter 116 such that the filter core 152 abuts against the internal surface of the HEPA grade filter 116. In use, the airflow passes radially outwardly through the cylindrical foam filter 120 in the direction of the arrow 128. The airflow then passes through the electrostatic filter 150 and subsequently through the HEPA grade filter 116 before exiting the filter assembly 300 in a radial direction.

The tab 328 of the third embodiment is replaced in this embodiment by a tab 428 of a construction similar to that shown in Figures 1 to 4. Two alternative arrangements of fixing the tab 428 to the cylindrical foam filter 120 are shown in Figure 8a. In both arrangements, the tab 428 consists of a flexible elongate strand 428a having a securing portion 428b at one end and a gripping portion 428c at the other end. In the first arrangement, as shown in the upper half of Figure 8a, the tab 428 is located on the upstream end of the cylindrical foam filter 120. A slit 429 is made in the end of the cylindrical foam filter 120. A portion of the strand 428a and the securing portion 428b are pushed into the slit 429 and are fixed into the cylindrical foam filter 120 using suitable adhesive. The slit 429 can be bonded closed using adhesive to ensure that the tab 428 remains in a fixed position. The end of the strand 428a extends outwardly from the cylindrical foam filter 120 such that the gripping portion 428c lies outside the filter housing 102. In the second arrangement, as shown in the lower half of Figure 8a, the tab 428'is located adjacent the upstream end of the cylindrical foam filter 120. The securing portion 428b'is pushed through the foam material such that the securing portion 428b'lies adjacent the electrostatic filter 150. The strand 428a'extends through the foam material and passes generally parallel to the axis of the filter assembly 300 to project beyond the filter housing 102. In both arrangements, the strand 428a, 428a'is sufficiently long to ensure that the g in order to facilitate the removal of the filter core 152 from the filter housing 102. The gripping portion 428c, 428c'is shown to extend outwardly from the filter housing 102.

However, in use, the strand 428a, 428a'together with the gripping portion 428c, 428c' can be folded back inside the filter housing 102 such that the gripping portion 428c, 428c'lies adjacent the cylindrical foam filter 120. Through use, the cylindrical foam filter 120 will become clogged and will require replacing or cleaning. The user can grasp the gripping portion 428c, 428c'and pull the cylindrical foam filter 120 out of the filter housing 102 in a direction parallel to the longitudinal axis of the filter assembly 300.

Modifications and variations will be apparent to a skilled reader. It will be appreciated that the tab can be any suitable shape to facilitate removal of the filter from the filter assembly, for example, hook shaped. Means and devices for holding the filter assembly in the relevant appliance and for correctly orientating it in position, other than those mentioned above, are not intended to be excluded from protection. It will also be appreciated that the shape of the filter or filter housing need not be cylindrical and other shapes will be equally suitable. Indeed, the filter housing shown in Figures 1 to 5 need not be open on one side when the filter assembly is in use: the filter housing could take the form of a cage-like structure having closed side walls but with both end surfaces defined by spokes or a mesh. One or both end surfaces could be removable or openable to allow access to the tab to allow removal of filter portions for cleaning purposes.

Either or both of the cylindrical sleeve and the central gripping portion may be omitted from the filter housing. If the central sleeve is omitted, the central apertures of the first and second filter portions will also be omitted. Other variations will be apparent to a skilled reader.

Claims

CLAIMS 1. A filter assembly for use in a vacuum cleaner having a first filter portion comprising a foam filter, and a second filter portion located downstream of the first filter portion and consisting of an electrostatic filter medium, the first and second filter portions being held directly adjacent one another by means of a filter housing, wherein the first filter portion has a tab located on a surface thereof remote from the second filter portion to facilitate removal of the first filter portion from the filter housing.
2. A filter assembly for use in a vacuum cleaner having a first filter portion comprising a foam filter, and a second filter portion located downstream of the first filter portion and consisting of a HEPA grade filter medium, the first and second filter portions being held directly adjacent one another by means of a filter housing, wherein the first filter portion has a tab located on a surface thereof remote from the second filter portion to facilitate removal of the first filter portion from the filter housing
3. A filter assembly as claimed in Claims 1 or 2, wherein the tab consists of a flexible elongate strand having a securing portion at one end and a gripping portion at the other end.
4. A filter assembly as claimed in Claim 3, wherein the flexible elongate strand passes through the foam material of the first filter portion.
5. A filter assembly as claimed in Claims 1 or 2, wherein the tab is secured to the first filter portion by adhesive.
6. A filter assembly as claimed in Claim 5, wherein the tab is secured to the surface of the first filter portion remote from the second filter portion.
7. A filter assembly as claimed in Claim 5, wherein the tab is secured to a surface of the first filter portion adjacent the second filter portion.
8. A filter assembly as claimed in any one of the preceding claims, wherein the first filter portion further comprises an electrostatic filter located on the side of the foam filter facing the second filter portion.
9. A filter assembly as claimed in any one of the preceding claims, wherein, in use, the tab extends generally parallel to the longitudinal axis of the filter assembly.
10. A filter assembly as claimed in any one of the preceding claims, wherein the tab is formed from a plastics material.
11. A filter assembly as claimed in any one of the preceding claims, wherein the second filter portion is washable.
12. A filter assembly for use in a vacuum cleaner substantially as hereinbefore described with reference to any one of the embodiments shown in the accompanying drawings.
13. A vacuum cleaner having an airflow path and at least one filter assembly located in the airflow path, characterized in that the at least one filter assembly is a filter assembly as claimed in any one of the preceding claims.
14. A vacuum cleaner as claimed in Claim 13 and comprising a motor for causing air to flow along the airflow path, wherein the or a filter assembly is positioned upstream of the motor.