GB2611047A

GB2611047A - A serviceable part for an electrical appliance

Info

Publication number: GB2611047A
Application number: GB2113558.7A
Authority: GB
Inventors: George McManus James; David Morte Morris Gareth
Original assignee: Dyson Technology Ltd
Current assignee: Dyson Technology Ltd
Priority date: 2021-09-23
Filing date: 2021-09-23
Publication date: 2023-03-29
Also published as: GB202113558D0; CN117980051A; WO2023047108A1

Abstract

A serviceable part for an electrical appliance comprising a motor for generating an airflow through the appliance, in use, the serviceable part comprising a filter assembly 12 for filtering dust and/or particulate matter from the airflow, wherein the filter assembly includes a first support member 24 carrying a filter medium 22, the filter medium being treated or provided with an additive to alter a water retention characteristic of the filter medium compared to an untreated filter medium. The invention also extends to an electrical appliance comprising a serviceable part. The filter may be hydrophobic or hydrophilic. The filter assembly may include an untreated member that is an electrostatic member.

Description

A SERVICEABLE PART FOR AN ELECTRICAL APPLIANCE

The present invention relates to a serviceable part for an electrical appliance. Aspects of the invention relate to a serviceable part, a serviceable filter assembly and an electrical appliance. In particular, but not exclusively, the invention relates to a serviceable filter assembly for use in an electrical appliance, such as a vacuum cleaner.

A vacuum cleaning appliance or, more simply, "vacuum cleaner', typically comprises a main body which is equipped with a suction motor, a dust separator, and a cleaner head connected to the dust separator usually by a separable coupling. The dust separator is the main mechanism by which the vacuum cleaner removes dirt and debris from the airflow through the machine, and this applies whether the dust separator relies on a cyclonic separation system or otherwise.

Although dust separators are generally very efficient at removing dirt and debris from the airflow, fine particles remain in the airflow that exits the dust separator and travels towards the suction motor. It is important that the suction motor is protected from these fine particles as they can be potentially damaging to some of its components. It is also important to make the exhaust airflow that is discharged from the vacuum cleaner as clean as possible. Thus, typically, a vacuum cleaner includes two filters: a first filter, also called a "pre-motor filter" or "pre-filter", which is located in the airflow through the machine downstream of the dust separator but upstream of the suction motor; and a second filter, also called a "post-motor filter' or "post-filter", that is located in the airflow downstream of the suction motor, before the airflow exhausts from the machine.

It is known to house the pre-motor filter medium in a filter assembly which can be removed easily by the user for cleaning purposes. Sometimes the pre-filter is mounted in a common unit with the post-filter. Regardless, once the filter assembly is removed the appliance the pre-filter can be washed, and dried, and the filter assembly is replaced in the appliance.

It has been observed that dust and fine particulate matter which collects on the filter medium are difficult to wash off. This gives rise to a pressure drop across the filter medium which makes it harder for the air flow to be driven through the filter medium, in use, introducing inefficiency into the system. A further problem is that, when washed to remove the dust and fine particulate matter adequately, the filter medium can take a long time to dry thoroughly. This presents several problems. For example, the user is unable to use the device again until the filter medium has dried thoroughly, or, if used before the filter medium is fully dry, performance of the device may be affected and/or water ingress within the device may lead to water damage of water-sensitive componentry (i.e. PCBs, electronics and motor assembly parts).

It is an object of the invention to address at least one of the aforementioned problems and improve the washability of the filter medium.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a serviceable part for an electrical appliance having a motor for generating an airflow through the appliance, in use, the serviceable part comprising a filter assembly for filtering solid particles and/or liquid droplets from the airflow, wherein the filter assembly includes a first support member carrying a filter medium, the filter medium being treated or provided with an additive to alter a water retention characteristic of the filter medium compared to an untreated filter medium.

The drying time of the filter assembly of the invention is noticeably reduced after washing.

This is achieved by means of the treatment that is applied to alter the water retention characteristic of the filter medium. The water retention characteristic may also be considered as a water transfer characteristic, as the extent to which a medium retains water is directly related to the extent to which water is transferred away from the medium (e.g. to effect drying). In the present invention, the reduction in drying time means there is less device downtime for the use. However, importantly, the operation of the electrical appliance must not be otherwise affected by the treatment of the filter medium. Wien employed in a vacuum cleaner appliance, for example, the challenge in treating the fleece layer to alter the water retention characteristic is that the performance of the vacuum cleaning must not be prejudiced (e.g. by reduced suction power). In addition, the effectiveness of the post-filter stage must not be compromised and neither must the overall washability of the filter assembly (e.g. the effects of repeated wash cycles).

The invention is particularly useful when employed as a pre-filter (pre-motor filter) for filtering aerosols comprising solid particles and/or liquid droplets or a mixture thereof For example, the filter assembly may be a pre-filter for filtering solid particles and/or liquid droplets from the airflow upstream of the motor.

The water retention characteristic is representative of the mass of water that is retained in the filter medium after a wash service.

In some embodiments, the mass of water that is retained in the filter medium after a wash service is at least 40%, and preferably at least 60%, reduced compared to an untreated filter medium.

In some embodiments, the additive may be a hydrophobic material. In other embodiments, the additive may be a hydrophilic material. The additive may be applied through plasma treatment, surface patterning, chemical treatment with the additive to alter surface energy, direct impregnation of the fibres with the additive, additive coating or any other means of surface modification. Therefore, the additive, in some embodiments, may be an additive coating applied to the surface of the filter medium or may be an additive impregnated within the filter medium (i.e. within the fibre structure of the filter medium).

The filter assembly may include a second support member, wherein the filter medium is sandwiched between the first and second support structures to define a sandwich structure.

For example, the sandwich structure may include an untreated member adjacent to the treated filter medium.

The untreated member may have an electrostatic charge In one example, the filter assembly may be a cylindrical filter assembly in which the filter medium forms a cylindrical structure of the type suitable for use in a domestic electrical appliance, such as a vacuum cleaner.

The filter assembly may also include a post-filter which is located downstream of the motor to filter the airflow which has passed through the motor.

In some embodiments, the pre-filter and the post-filter may be located in the same serviceable unit.

According to a second aspect of the invention, there is provided an electrical appliance comprising the serviceable part of the first aspect.

The electrical appliance may be a dust separation device forming part of a vacuum cleaner.

It will be appreciated that preferred and/or optional features of the first aspect of the invention may be incorporated alone or in appropriate combination in the second aspect of the invention also.

Brief Description of Drawings

The present invention will now be described, by way of example only, with reference to the following figures in which: Figure 1 is a side view of a portable vacuum cleaner comprising a filter assembly of the present invention; Figure 2 is a side view of a filter assembly for use in the vacuum cleaner in Figure 1; Figure 3 is a schematic diagram of a first filter structure for use in the filter assembly in Figure 2 including a treated filter layer which is hydrophobic; Figure 4 shows a schematic diagram to show the contact angle for a surface treated with a hydrophobic material; Figure 5 is schematic diagram of a second filter structure for use in the filter assembly in Figure 2 including a treated filter layer which is hydrophillic; Figure 6 shows a schematic diagram to show the contact angle for a surface treated with a hydrophillic material; Figure 7 shows a bar chart comparison of the retained water characteristic for (a) an untreated filter medium compared to (b) a hydrophillic filter medium and (c) a hydrophobic filter medium; and Figure 8 illustrates the drying time for an untreated filter medium compared to a hydrophobic filter medium.

Detailed Description

Figure 1 shows a perspective view of a dust separation device, referred to generally as 10, with which a filter assembly 12 of an embodiment of the invention is used. The dust separation device 10 forms a part of a vacuum cleaner which includes, at one end of an elongated section (referred to as the wand), a cleaner head (not shown). The dust separation device 10 is located at the other end of the wand to the cleaner head. The dust separation device 10 connects to one end of a device housing 14 in a removable manner. The other end of the device housing 14 connects to the wand (not shown).

The dust separation device 10 includes the device housing 14 having a handle 16 for manipulation by the user. Typically, the handle 16 houses a battery pack inside one handle section 18 which may contain one or more replaceable or rechargeable batteries for powering the dust separation device 10. The device housing 14 houses various components of the dust separation device 10, as is known in the art, including a cyclone assembly 20 and a brushless electric motor (not shown). The dust separation device 10 utilises cyclonic separation to separate dirt and debris from an airflow through the device to enable the cleaning of a surface as the cleaner head is swept over the surface. The brushless electric motor is a direct current motor which is operated on a switched reluctance principle and is controlled by means of a printed circuit board (PCB) (not visible in Figure 1) which receives power from the battery pack 18.

The filter assembly 12 provides a pre-motor filter stage and a post-filter stage. The pre-filter stage (referred to as the pre-filter) provides filtration of the airflow through the device prior to the airflow reaching the motor and provides a relatively course filter stage. The post-filter stage (referred to as the post-filter) provides filtration of the airflow through the device downstream of the motor and provides a relatively fine filter stage.

As shown in more detail in Figure 2, the filter assembly 12 comprises an annular filter member 22, one end of which is received in an annular support 24. At the other end (the upper end), the filter member 22 extends into a vented casing 26. The vented casing 26 has an enlarged diameter compared to the diameter of the filter member 22.

In order to clean the filter assembly 12 it is necessary to first disconnect the filter assembly 12 from the dust separation device 10. It is a known problem that during use the filter assembly tends to become blocked with dirt and debris and therefore regular cleaning is required to ensure effective operation and prolonged service life for the vacuum cleaner. Wien the filter assembly 12 is removed from the dust separation device 10, upturning the filter assembly 12 from the orientation shown in Figure 2 allows the filter assembly 12 to be filled with water through the open annular support 24. As water fills the upturned filter assembly 12, it can be swirled around the filter member 22 to clean it, typically running the filter member 22 under a running water tap or immersing it in water. The filter member 22 and the remaining parts of the filter assembly 12 should then be fully dried before re-connecting to the dust separation device 10.

A potential problem with washing of the filter assembly 12 is that the drying times for the filter member are relatively long. This is inconvenient for the user and prevents use of the dust separation device again until the filter member has fully dried. In another scenario the filter assembly 12 may be replaced into the dust separation device 10 and used before the filter member has fully dried. The retention of water within the filter member creates a pressure drop across it which reduces the effectiveness of the device.

It can also lead to failure of the device due to water ingress within the device (e.g. water reaching the motor) due to retained water in the filter member.

Figure 3 shows the filter member 30 which represents the annular filter member 22, of a filter assembly 12 in accordance with a first embodiment of the invention which has been shown to reduce the drying time of the filter member 30 after washing, compared to a known arrangement. The arrow X indicates the direction of the airflow through the filter member 30, as driven by the motor. The filter member 30 is a structure including four layers: a first support layer 32 in the form of a mesh, for example a knitted support mesh (e.g. Taro mesh), a second layer 34 which provides a filter layer, a third layer 36 which provides a further filter layer and a fourth layer 38 which defines a second support layer similar to the first support layer 32 (i.e. a Taro mesh). The support layers 32, 38 therefore sandwich the filter layers 34, 36 between them and, being formed from a mesh, permit airflow to pass through them unaffected. Therefore, the mesh layers do not interfere with the filtration performance of the overall filter structure.

The third layer 36 is an electrostatically charged layer, which is not coated or treated, and which tends to capture fine dust particles carried in the airflow through the layer structure. The second layer 36 is a layer of non-woven fleece material which has been treated with a hydrophobic material to make the surface of the fleece layer hydrophobic.

Both filters are designed to capture and hold dust particles and these need to be washed off during servicing to preserve the functionality of the filter.

A hydrophobic material is one which tends to repel water. Examples of treatments which may be applied to the fleece layer 34 to provide the required hydrophobicity include plasma treatments, surface patterning (sometimes referred to as the lotus leaf effect), chemical treatment with an additive to alter surface energy (for example, fluorination) or direct impregnation of the fibres with surface active chemicals. A combination of one or more treatments is also possible. The fleece layer 34 may be treated, coated, developed or otherwise changed so as to change the surface chemistry of the layer to be hydrophobic. The treatment of the fleece layer 34 has the effect of altering the water retention characteristic of the layer so that, when the filter structure is washed, the transfer of water away from the surface of the treated filter layer through drying enables the dried state of the fleece layer 34 to be reached more quickly than it would otherwise for an untreated filter layer. This is because the hydrophobic treatment results in there being less water to be evaporated away from the surface.

Figure 4 illustrates the hydrophobic fleece layer 34 with a droplet of water 40 making contact with the surface of the layer 34. A hydrophobic material is defined as one in which the angle of contact A of the water droplet with the contact surface is relatively high (above 90 degrees). In the example illustration shown the contact angle A for the water droplet is around 140 degrees.

Importantly, the hydrophobic coating which is applied to the non-woven fleece layer 34 must not hinder the filtration of the airflow whilst dust particulates which are carried in the airflow are prevented from passing through the layer. The resistance to airflow through the coated fleece layer must also be unaffected by the treatment that is applied.

Figure 5 shows an alternative embodiment of the filter structure to that shown in Figure 3 in which the second layer 44 is a layer of non-woven fleece material which is treated with a hydrophilic material. A hydrophilic material is one which tends to attract water towards the surface. This has the effect that water that is held within the body of the filter layer 44 tends to be drawn towards the surface so that it can more readily transfer away from the filter layer during drying. Examples of treatments which may be applied to the fleece layer 44 to provide the required hydrophilicity include plasma treatments or chemical treatments that raise the surface energy of the fibre-air interfaces and reduce the surface energy of the fibre-water interfaces to promote the spreading out of the liquid. The fleece layer 44 may be treated, coated, developed or otherwise changed so as to change the surface chemistry of the layer to be hydrophillic.

Figure 6 illustrates the hydrophillic non-woven fleece layer with a droplet of water 46 making contact with the surface of the layer 44. A hydrophilic material is defined as one in which the angle of contact B of the water droplet 46 with the contact surface is relatively low (less than 30 degrees). In the example illustration shown the contact angle B for the water droplet is around 20 degrees. The water retention characteristic of the fleece layer is altered by the hydrophilic treatment compared to an untreated layer, so that the drying time for the fleece layer 44 is quicker.

The water retention characteristic of the filter structures in Figures 4 and 6 is represented in Figures 7(a)-(c). This is because the extent to which water is transferred within or away from the layer during drying is directly related to the extent to which the water is retained within the layer.

Figures 7(a) to (c) compare the water retention for a filter structure having (a) an untreated fleece layer with (b) a fleece layer treated with a hydrophilic material and (c) a fleece layer treated with a hydrophobic material. The bars in the chart represent the relative proportion of water that is retained in the filter structures in a drying test of comparable timing which is applied across all three samples. It can be seen that the untreated fleece layer retains the greatest proportion of water, the hydrophilic treated fleece material shows a reduction in water retention of around 50% (i.e. an improvement in water retention of around 50%) and the hydrophobic treated fleece material shows a reduction of around 90% compared to the untreated material (i.e. an improvement in water retention of around 90%). This is the data that was achieved for a flat sheet of material, when either hydrophobic or hydrophilic treatments are applied, compared to an untreated flat sheet. In practice, when in the product, the water retention reduction will be slightly lower than the flat sheet results. For example, for a hydrophilic treated fleece material the water retention may be reduced by between 30% and 60% (typically 50%) compared to an untreated material, and a hydrophobic treated material may result in water retention being reduced by between 60% and 90% (typically 60%) compared to an untreated material.

The bar charts of Figure 7 clearly illustrate the benefit of applying a treatment to the fleece layer in the form of a hydrophobic treatment or a hydrophilic treatment as the water retained in the fleece layer is noticeably reduced when the fleece is treated. Hence, the drying time for the filter structure once is has been washed is considerably reduced. This ensures that the filter assembly can be reassembled into the dust separation device more quickly so that device downtime is reduced. The reduced drying time also reduces the risk of a user starting to use the device again before the filter is fully dried.

For the hydrophobic fleece material in bar (c) of Figure 7 the benefit is considerable and, hence, this represents the preferred solution. However, treating the fleece material to be hydrophilic (as in bar (b)) also provides an advantage over the use of an untreated fleece layer (bar (a)).

Figure 8 shows a graph of the mass On grams) of a washed filter structure under test as a function of time On hours) at a drying temperature of around 23 degrees (room temperature) and compares a filter structure 52 having a hydrophobic treated fleece layer (bottom line) with a filter structure 50 having an untreated fleece layer (top line). The filter structure 52 is the same sandwich structure as that in Figure 3. The filter structure 50 has an untreated non-woven filter medium in place of the Hydrophobic filter medium. The mass of the washed filter medium at a particular time is directly proportional to the drying time, and the invention clearly benefits from a reduced drying time compared to known filter arrangements. It can be seen from Figure 8 that the filter structure which has a layer of treated non-woven fleece material (filter structure 52) is dry after approximately 9 hours after washing, whereas the filter structure for which the non-woven fleece layer is not treated (filter structure 50) is not dry until at least 24 hours after washing. Thus, there is a considerable improvement with the structure comprising the treated layer which ensures the electrical appliance has a reduced downtime when the filter assembly is drying, and also reduces the risk of a user impatiently reassembling the appliance and using it before the filter assembly is fully dry, hence risking water damage to parts of the appliance.

The challenge in treating the fleece layer with hydrophilic or hydrophobic material is that the performance of the filter structure in other ways must not be affected detrimentally by the treatment, even though the water retention characteristic of the fleece layer is altered. It is by no means straightforward to treat the filter structure so as to ensure that all aspects of device performance are maintained, in addition to the improved drying times for the pre-filter stage. For example, the pressure drop across the filter must not be affected by the treatment of the fleece layer otherwise more energy is required to drive the airflow through the filter structure. Also, the washability of the assembly must not be affected by the treatment (i.e. multiple washes of the filter structure must not lead to a more degraded filter performance compared to an untreated filter structure) and the performance of the post-filter stage, downstream of the pre-filter stage, must not be affected detrimentally. Finally, there must be no loss of suction in the device as a result of treating the fleece layer with hydrophobic or hydrophilic material. The device has to

II

provide consistent performance across a range of particulate matter to be removed from surfaces, including aerosols comprising solid particles, whether wet or dry (e.g. human and pet dander, microplastics, vegetables, hair and food debris), or liquid droplets, or a combination thereof. For these reasons, the selection of the material and/or the nature of the treatment applied to the fleece layer is important and not all hydrophobic or hydrophilic treatments will be appropriate. It is important that the treatment applied does not affect the overall filtration performance of the vacuum cleaner once the fibre layer is treated.

It will be appreciated that various alternative embodiments to those described previously are also envisaged without departing from the scope of the appended claims.

Claims

CLAIMS1 A serviceable part for an electrical appliance comprising a motor for generating an airflow through the appliance, in use, the serviceable part comprising a filter assembly for filtering dust and/or particulate matter from the airflow, wherein the filter assembly includes a first support member carrying a filter medium, the filter medium being treated or provided with an additive to alter a water retention characteristic of the filter medium compared to an untreated filter medium.
2 The serviceable part as claimed in claim 1, wherein the filter assembly is a pre-filter for filtering solid particles and/or liquid droplets from the airflow upstream of the motor.
3. The serviceable part as claimed in claim 1 or claim 2, wherein the water retention characteristic is representative of the mass of water that is retained in the filter medium after a wash service.
4. The serviceable part as claimed in any of claims 1 to 3, wherein the mass of water that is retained in the filter medium after a wash service is at least 40%, and preferably at least 60%, reduced compared to an untreated filter medium.
5. The serviceable part as claimed in any of claims 1 to 4, wherein the additive is a hydrophobic material.
6. The serviceable part as claimed in any of claims 1 to 4, wherein the additive is a hydrophilic material.
7. The serviceable part as claimed in claim 5 or claim 6, wherein the additive is an additive coating on the surface of the filter medium or a hydrophobic material impregnated within the filter medium.
8. The serviceable part as claimed in any of claims 1 to 7, further comprising a second support member, wherein the filter medium is sandwiched between the first and second support structures to define a sandwich structure. 1.3
9. The serviceable part as claimed in claim 8, wherein the sandwich structure includes an untreated member adjacent to the treated filter medium.
10. The serviceable part as claimed in claim 9, wherein the untreated member is an electrostatic member.
11. The serviceable part as claimed in any of claims 1 to 10, wherein the filter assembly is a cylindrical filter assembly in which the filter medium forms a cylinder structure.
12. The serviceable part as claimed in claim 11, wherein the filter assembly includes a post-filter which is located downstream of the motor to filter the airflow which has passed through the motor.
13. The serviceable part as claimed in claim 12 when dependent on claim 2, wherein the pre-filter and the post-filter are located in the same serviceable unit.
14. The serviceable part as claimed in any of claims 1 to 13, being a serviceable part of a vacuum cleaner.