Prevention of electrostatic accumulation at a surface of a core of a

Abstract

In a vacuum cleaner unit (2) comprising a core (17), the core (17) comprises a clean air discharge device (10) and an annular air vortex chamber (11), the core (17) is configured to prevent static electricity accumulation at a location of at least a portion of an outer surface (18) of the core (17). In this way, a beneficial effect on the separation performance of the unit (2) is obtained. According to one actual choice, the core (17) comprises, at least at the location of the outer surface (18), a material configured to not allow the generation of a triboelectric effect by the friction or sliding of dirt particles against the outer surface (18). According to another actual choice, an electrically conductive material is used in the core (17), may be used in the exterior trim layer of the core (17), such that charge may be directed away from the outer surface (18).

Description

Technical Field

[0001] This invention relates to a vacuum cleaner unit configured for use in a vacuum cleaner and for receiving incoming contaminated air and causing separation of contaminants from the air. The vacuum cleaner unit includes: a core including a clean air discharge device extending along a cyclone rotation axis, the clean air discharge device being configured to discharge air from the vacuum cleaner unit; an annular air vortex chamber surrounding the clean air discharge device in a direction about the cyclone rotation axis; and at least one inlet configured to allow contaminated air to enter the air vortex chamber; wherein the clean air discharge device has inwardly projecting blades and gaps between these blades.

[0002] The present invention also relates to a vacuum cleaner, preferably a handheld vacuum cleaner, the vacuum cleaner comprising: a conduit, a suction nozzle located at the end of the conduit, a vacuum cleaner unit as described above connected to the conduit, and means configured to generate air suction at the location of the suction nozzle and to generate an airflow from the suction nozzle toward the vacuum cleaner unit through the conduit. Background Technology

[0003] This invention belongs to the field of vacuum cleaners and vacuum vacuum purifiers, and more particularly to vacuum cleaners comprising a vacuum cleaner unit designed to separate dirt and air, relying on vortex motion of air around a clean air exhaust device in the process. In the related art, the term commonly used to refer to a vacuum cleaner unit is cyclone unit, and the term commonly used to refer to a clean air exhaust device is eddy current detector. A practical example of dirt is dust. Throughout this document, the terms "dirt," "dust," and "dirt particles" are used as appropriate, depending on the context.

[0004] In the context of this invention, the vacuum cleaner can be a handheld vacuum cleaner. Especially when the vacuum cleaner is battery-operated, a very flexible product solution is achieved, and market results demonstrate the increasing popularity of this type of vacuum cleaner. More and more people tend to use this type of vacuum cleaner as their primary / preferred indoor vacuum cleaner, rather than simply as a temporary supplement. This is mainly due to its ease of use. Unlike canister vacuum cleaners, handheld vacuum cleaners are easier to maneuver and lift.

[0005] WO 2022 / 002591 A1 discloses a vacuum cleaner comprising a dirt inlet, a motor and a fan for delivering suction to the dirt inlet, a cyclone unit for separating particles from a flow generated by the suction of the motor and fan, the cyclone unit comprising a vortex finder extending along a cyclone rotation axis and an annular chamber formed around the outside of the vortex finder, and a delivery duct for delivering air to the cyclone unit such that the air can flow to the annular chamber. The vacuum cleaner comprises for example a head having the dirt inlet and the delivery duct comprises a tube connecting the head to the cyclone unit. The vacuum cleaner comprises for example a stick vacuum cleaner.

[0006] It is known to use a cyclone unit in a vacuum cleaner for separating dirt from an air flow. In a cyclone unit, centrifugal forces are generated by rotating air within an annular chamber. The air follows a spiral pattern before leaving the cyclone unit. Particles that are dragged along in the rotating flow move outwardly by centrifugal acceleration. As a result, the particles do not travel along the tight curves of the air flow path, but hit the outer wall of the annular chamber and then move along the wall to enter a dirt collection chamber in which the particles are stored. In the vacuum cleaner known from WO 2022 / 002591 A1, the dirt collection chamber is arranged alongside the annular chamber and in particular is coupled to a space present between a roof of the annular chamber and a front end of the vortex finder.

[0007] Cyclone units are widely used as a device for separating dry particles from air. In the case of wet vacuum cleaners, cyclone units are also used for separating water droplets (and dirt particles) from air. The vortex finder comprised in a cyclone unit forms part of the core of the cyclone unit and typically has a central arrangement in the annular chamber. In one of the various known embodiments, the vortex finder is provided in the form of a hollow cylindrical plastic part having a gap along the length such that air can flow from the annular chamber to the inside of the vortex finder and further from this location to the location where the air leaves the cyclone unit. WO 2021 / 140041 A1 discloses that the vortex finder can have vanes around which the incoming air is guided into the vortex finder. This structure of the vortex finder increases the separation performance of the cyclone unit.

[0008] It has been found that in cases where the development of a cyclone unit is located at the border of a working window for a good separation performance with the cyclone unit, for example in cases where a very compact design of the cyclone unit is envisaged, it can happen that the actual separation performance is significantly less than the theoretical separation performance. It is an object of the present invention to provide a method that makes the cyclone unit less sensitive to disturbances. SUMMARY

[0009] The present invention provides a vacuum cleaner unit configured for a vacuum cleaner and receiving incoming dirt-laden air and causing separation of dirt from air in the vacuum cleaner, the vacuum cleaner unit comprising: a core comprising a clean air discharge device extending along a cyclone rotation axis, the clean air discharge device being configured for discharging air from the vacuum cleaner unit; an annular air vortex chamber surrounding the clean air discharge device in a direction around the cyclone rotation axis; and at least one inlet configured for letting dirt-laden air into the air vortex chamber; wherein the clean air discharge device has inwardly projecting vanes and gaps between the vanes; and wherein the core is configured to prevent electrostatic build-up at the location of at least a portion of an outer surface of the core.

[0010] From the above it follows that a unique feature of the present invention is that the core is configured to prevent electrostatic build-up at the location of at least a portion of an outer surface of the core. In fact, one insight of the present invention is that, on the basis of triboelectric effects occurring during operation of the vacuum cleaner unit, electrostatics are obtained on the core if no such measures are taken, and that the electrostatics on the core act to reduce the separation performance of the vacuum cleaner unit. In this case, dirt particles rubbing against surfaces of the clean air discharge device and other components of the vacuum cleaner unit cause a transfer of electric charges. Opposite charges of the dirt and the material of the clean air discharge device, which can be a plastic material, generate electrostatic forces that pull the dirt towards the surfaces. One of the results is that the function of the clean air discharge device is hampered because additional forces are obtained that counteract the centrifugal forces acting on the dirt particles at the location of the clean air discharge device, which results in the separation performance of the vacuum cleaner unit being impaired. The effectiveness of the measures of the present invention is beneficial if the core is configured to prevent electrostatic build-up at the location of at least a portion of an outer surface of the core at the location of the clean air discharge device.

[0011] It is noted that the application of anti-static measures is known per se in the field of cyclone units. The reason for this is, for example, to keep surfaces free from dirt, to avoid the nuisance of the user having to clean these surfaces regularly and to keep filter elements clean to prevent them from clogging. However, there is no suggestion in the relevant art to apply anti-static measures at the location of a core comprising a clean air discharge device having inwardly projecting vanes and gaps between the vanes for the purpose of maintaining the separation performance of the cyclone unit.

[0012] Advantageously, the core is configured to prevent the formation of static electricity at the location of at least a major part of the outer surface. This can be practical if the antistatic measure of the present invention is implemented substantially over the entire outer surface of the core, which is very likely when the antistatic measure involves a core made of a suitable material and also when the antistatic measure involves a core comprising a suitable outer finishing layer.

[0013] With regard to the configuration of the core in which the accumulation of static electricity is prevented at the location of at least a part of the outer surface of the core, the present invention covers two main options, namely the option that the core comprises a material configured to not allow the transfer of an electrical charge from a dirt particle rubbing against the outer surface at least at the location of the outer surface, and the option that the core comprises a material configured to guide the electrical charge obtained by a dirt particle rubbing against the outer surface away from the outer surface at least at the location of the outer surface. For the latter option, the clean air discharge device can comprise an electrically conductive material at least at the location of the outer surface. According to one practical example, the core comprises a thermoplastic polymer with electrically conductive additives such as carbon. Alternatively, the core can be provided with an electrically conductive outer finishing layer. According to one practical example, the core is provided with a spray painted outer finishing layer with electrically conductive additives such as carbon or zinc.

[0014] According to the insight of the present invention, in order to guide the electrical charge away from the outer surface of the core, the material of the core or the outer finishing layer should have a sufficiently low resistivity (p) and a sufficient volume (material thickness h) to store the electrical charge leaving the surface. The calculation of this is provided below. The definition of the sheet resistance is As shown, p represents the material resistivity, and h represents the material thickness.

[0015] Furthermore, from vector analysis V represents the voltage, e represents the elementary charge, which is 1.6 • 10 -19 Coulomb, t represents the time constant, m represents the electron mass, and E represents the electric field.

[0016] And, And g represents the electrical conductivity, and N represents the number of charges per volume.

[0017] The following equation applies for N: p m represents the density, m a represents the molecular weight, and NA represents the Avogadro constant, which is 6 • 10 23 .

[0018] For example, for a zinc spray coating, and .

[0019] This means that N = 3 • 10 27 m -3 .

[0020] The electric field from a charged plate is related to the surface charge.

[0021] A typical electric field is measured by: where V = 2 • 10 3 V and L = 5 • 10 -3 m.

[0022] The measured value Rs = 1.3 • 10 10 Ω and h = 50 μm.

[0023] From this it follows that .

[0024] Taking into account the atomic layer thickness (~ 10 -10 m) and the typical time of the presence of dirt particles in the cyclone (0.5 to 5 seconds), this is relatively fast.

[0025] In the case where the material of the core is just a thermoplastic polymer without any electrically conductive material and also without an electrically conductive outer finish, the following values are applicable: m -3 and Ωm where, R S > 2 • 10 -3 Ω and h = 2 • 10 -3 m.

[0026] From this it follows that Taking into account the atomic layer thickness and the typical time of the presence of dirt particles in the cyclone, this is relatively slow.

[0027] However, in the case where the thermoplastic polymer has an electrically conductive additive, the following is applicable: m -3 and Ωm where, R S >4 • 10 10 Ω, and h = 2 • 10 -3 m.

[0028] From this it follows that, This is relatively fast, considering the atomic layer thickness and the typical time a dirt particle is present in the cyclone.

[0029] Assuming there is 30 grams of dust in the cyclone unit and the effective contact area (A) in the cyclone unit is about 0.0225 m 2 , the following values are found: The number of particles per area is The charge per area is equal to f represents the number of elementary charges. Based on experiments, f ~ 1000.

[0030] Thus, as shown: To be able to store the charge, the capacity in the layer should be much larger: N represents the number of charges per volume.

[0031] As mentioned before, the N min of the resulting thermoplastic polymer is 9 • 1024m -3 .

[0032] The following results are obtained: For a 5 μm particle, ~ 1 nm or, for a 1 μm particle, ~ 125 nm.

[0033] It can be concluded that a sufficient capacity is obtained when the layer thickness is 0.5 pm, more preferably 1 pm - 5 pm. In the earlier used wording, the material configured to guide the charge obtained by the friction of the dirt particles against the outer surface away from the outer surface is present in at least the outer layer of the core with a thickness of at least 0.5 pm, more preferably with a thickness in the range of 1 pm to 5 pm, at which a sufficient capacity is obtained.

[0034] In selecting the material of the core or the optional outer finish, it is preferred to use a material with an electrical resistivity p below 10 10 Ωm, preferably below 10 9 Ωm, more preferably below 10 8 Ωm.

[0035] In a practical embodiment, the vacuum cleaner unit according to the application comprises a dirt collection chamber configured to receive and store dirt of the air load, wherein the dirt collection chamber is located in an extension of the clean air discharge and the air swirl chamber. Advantages of this location of the dirt collection chamber include the possibility of having a compact design of the vacuum cleaner unit and the possibility of providing the vacuum cleaner unit with an appealing slim appearance, as well as the possibility of forming an entrance of the dirt collection chamber such that relatively large particles such as leaves can more easily reach the dirt collection chamber.

[0036] In case the vacuum cleaner unit comprises a dirt collection chamber in the above described manner, the core of the vacuum cleaner unit can comprise an extension body extending along the cyclone rotation axis in an extension of the clean air discharge and towards the dirt collection chamber. It is a fact that such an extension body has the function of dissipating energy from the air flow at a location between the clean air discharge and the dirt collection chamber, such that the air at the location of the dirt collection chamber minimizes the risk of dirt being expelled from the dirt collection chamber. For reasons of achieving optimal separation performance of the vacuum cleaner unit, it is advantageous that the core is configured to prevent the build-up of static electricity at a location of at least a part of the outer surface of the core at the extension body. Otherwise, due to the relatively low air speed close to the surface, resulting in a low drag force and centrifugal force on the dirt particles on the surface, there is a risk of dirt particles sticking to the extension body and moving on the outside of the extension body in a direction towards the clean air discharge, similar to a water film moving along a surface. In this respect, it should be noted that some flow of dirt particles from the dirt collection chamber to the extension body can be expected. Dirt particles moving along the outer surface of the core and eventually reaching a gap in the clean air discharge can enter through the gap, thereby impairing the separation performance of the vacuum cleaner unit.

[0037] It is practical if the clean air discharge arrangement is generally tubular, having both a circular inner periphery and a circular outer periphery. Also, it is practical if the gap between the vanes of the clean air discharge arrangement is generally elongated, extending in the direction of the cyclone rotation axis. A practical example of the inlet width of the gap, i.e. the inlet dimension of the gap in the direction around the cyclone rotation axis, is an inlet width of about 1 mm. It is advantageous if the vanes of the clean air discharge arrangement have an overall airfoil profile, in view of the intended separation performance of the vacuum cleaner unit. In case the core comprises an extension body, it is further practical if the extension body is generally tubular, while having both a circular inner periphery and a circular outer periphery, which can not be necessary if the outer part of the extension body is flush with the outer part of the clean air discharge arrangement.

[0038] Generally, the core can comprise a guiding portion configured to guide the incoming dirt-laden air to flow along a helical path towards the clean air discharge arrangement. The presence of such a guiding portion contributes to the generation and maintenance of the cyclone. In order to achieve optimal separation performance of the vacuum cleaner unit, it is advantageous if the core is configured to prevent the build-up of static electricity at a location of at least a portion of the outer surface of the guiding portion. As explained earlier with respect to the extension body, this measure implies that it is avoided that dirt particles can pass through the gap of the clean air discharge arrangement from a location on the outer surface of the core, which otherwise can occur due to dirt particles adhering to the outer surface and there only being subjected to very limited drag and centrifugal forces, which are insufficient to separate the dirt particles from the surface.

[0039] With respect to other surfaces located in the vacuum cleaner unit, i.e. surfaces not comprised in the core, it should be noted that these surfaces need not have anti-static properties in a certain way. On the contrary, a contribution to the cyclone efficiency can be obtained if these surfaces are prone to attract dirt.

[0040] The present invention also relates to a vacuum cleaner comprising a conduit, a suction nozzle at one end of the conduit, a vacuum cleaner unit as defined and described earlier connected to the conduit, and an arrangement configured to generate an air suction at the location of the suction nozzle, and an air flow through the conduit from the suction nozzle towards the vacuum cleaner unit. The vacuum cleaner can in particular be handheld, but this does not change the fact that the present invention also comprises other types of vacuum cleaners. In general, the vacuum cleaner according to the present invention can be a canister vacuum cleaner, a stick vacuum cleaner, an upright vacuum cleaner, a robotic vacuum cleaner, or a sweeper.

[0041] The above and other aspects of the present application will become apparent from the following detailed description of aspects of a vacuum cleaner unit for a handheld vacuum cleaner. BRIEF DESCRIPTION OF DRAWINGS

[0042] The application will now be explained in more detail with reference to the drawings, wherein identical or similar parts are denoted by the same reference signs, and wherein: Figure 1 A handheld vacuum cleaner comprising a vacuum cleaner unit according to an embodiment of the application is shown; Figure 2 A cross-sectional view of the vacuum cleaner unit is shown schematically; Figure 3 A front view of the vacuum cleaner unit is shown schematically; Figure 4 A bottom view of the vacuum cleaner unit is shown schematically and illustrates how air is spiraled through the vacuum cleaner unit during operation; Figure 5 A side view of the vacuum cleaner unit is shown schematically and illustrates how air is spiraled through the vacuum cleaner unit during operation; and Figure 6 A view of a portion of a cross-section taken along the line A-A in Figure 1 is shown schematically. DETAILED DESCRIPTION

[0043] The present application belongs to the field of vacuum cleaning and vacuum cleaners, in particular vacuum cleaners comprising a vacuum cleaner unit designed for separating dirt and air. Figure 1 A handheld vacuum cleaner 1 comprising a vacuum cleaner unit 2 according to an embodiment of the application is shown in Fig. 1. The vacuum cleaner 1 comprises a conduit 3, a suction nozzle 4 at an end of the conduit 3, the vacuum cleaner unit 2 connected to the conduit 3, and a device 5 configured to generate an air suction at the location of the suction nozzle 4 and to generate an air flow through the conduit 3 from the suction nozzle 4 towards the vacuum cleaner unit 2, the device 5 typically comprising a motor of suitable type. The handheld vacuum cleaner 1 can be provided as a detachable part of a larger vacuum cleaner, such as a stick vacuum cleaner, but the handheld vacuum cleaner 1 can also be provided as a stand-alone device. Typically, a front side of the vacuum cleaner 1 is defined as the side where the suction nozzle 4 is present, and a rear side of the vacuum cleaner 1 is defined as the side where the device 5 comprising the motor is present. In Figure 1 In Fig. 1, the vacuum cleaner 1 is shown in a substantially horizontal orientation. For cleaning floors and other surfaces accessible from above, the vacuum cleaner 1 is held in a downward orientation, i.e. an orientation where the suction nozzle 4 is pointing downwards, and for cleaning ceilings and other surfaces accessible from below, the vacuum cleaner 1 is held in an upward orientation, i.e. an orientation where the suction nozzle 4 is pointing upwards.

[0044] The operation of the handheld vacuum cleaner 1 involves placing the device 5 comprising a motor in an active state, thereby generating an air suction force at the location of the suction nozzle 4. While the person using the vacuum cleaner 1 holds the vacuum cleaner 1 in a position in which the suction nozzle 4 is close to or on the surface to be cleaned, dirt is removed from the surface under the influence of the air suction force, wherein the dirt is carried with the air to the interior of the suction nozzle 4 and the duct 3. The dirt-laden air is moved towards the vacuum cleaner unit 2 and is supplied to the vacuum cleaner unit 2 at the location of the inlet 6 of the vacuum cleaner unit 2.

[0045] As mentioned above, the vacuum cleaner unit 2 is designed to separate dirt and air. To this end, the vacuum cleaner unit 2 is equipped with a cleaning air discharge 10 extending along a cyclone rotation axis A R and with an annular air vortex chamber 11 that surrounds the cleaning air discharge 10 in a direction around the cyclone rotation axis A R . A cross-sectional view of the cleaning air discharge 10 is shown separately in Figure 6 . In the present example, the cleaning air discharge 10 is roughly shaped like a hollow cylinder that is provided with inwardly protruding vanes 12 and gaps 13 between the vanes 12, which are elongated in shape and extend in a direction around the cyclone rotation axis A R . The vacuum cleaner unit 2 further has a dirt collection chamber 14. The above-mentioned inlet 6 of the vacuum cleaner unit 2 is in particular located at a position for letting the dirt-laden air into the air vortex chamber 11. The cleaning air discharge 10 is configured to discharge air from the vacuum cleaner unit 2, while the dirt collection chamber 14 is configured to receive and store dirt from the dirt-laden air.

[0046] During operation of the vacuum cleaner 1, the rotational flow movement of the air around the cleaning air discharge 10 in the air vortex chamber 11 is promoted based on a number of factors. In a first position, the dirt-laden air enters tangentially into the air vortex chamber 11 at a side of the vacuum cleaner unit 2, in a second position, the vacuum cleaner unit 2 is equipped with a guide 15 that is arranged and shaped such that the incoming air is guided to follow a helical path, and in a third position, a surface having a circular profile is generally present in the vacuum cleaner unit 2, as best visible in Figure 3 . The helical movement of the air in the vacuum cleaner unit 2 is shown in Figure 4 and 5 . While the air swirls around the cleaning air discharge 10, the air flows through the gaps 13 to the interior of the cleaning air discharge 10, while the dirt moves towards and collects in the dirt collection chamber 14.

[0047] As Figure 1 , Figure 2、 Figure 4 and Figure 5 As shown, the dirt collection chamber 14 is located in an extension of the clean air discharge arrangement 10 and the air vortex chamber 11 such that the dirt collection chamber 14 is located further down the clean air discharge arrangement 10 and the air vortex chamber 11 in the direction of the cyclone rotation axis A R In the present embodiment, the vacuum cleaner unit 2 comprises an extension body 16 extending along the cyclone rotation axis A R The extension body 16 has the function of ensuring that there is minimal energy in the air at the location of the dirt collection chamber 14 such that the dirt in the dirt collection chamber 14 is minimally at risk of being agitated by the air and thereby displaced from the dirt collection chamber 14.

[0048] According to the invention, the material used for the vacuum cleaner unit 2 is chosen with the consideration that it is desirable for the vacuum cleaner unit 2 to have optimal separation performance. In particular, measures are taken such that the core 17 of the vacuum cleaner unit 2 is configured to prevent electrostatic build-up at the location of at least a portion of the outer surface 18 of the core 17. Essentially, the core 17 comprises the clean air discharge arrangement 10. In the present example, the core 17 comprises all three of the clean air discharge arrangement 10, the guide 15 and the extension body 16, i.e. all components extending along the cyclone rotation axis A R According to the measures of the invention, it is aimed at avoiding that dirt particles are sucked towards the outer surface 18 of the core 17 and adhere to the outer surface 18 based on electrostatic forces. The fact is that if this happens, there is a risk that the separation performance of the vacuum cleaner unit 2 is reduced. The reason is that at exactly this location of the outer surface 18, the forces for moving the dirt particles away from the outer surface 18 are typically lower than the electrostatic forces such that the dirt particles freely travel from the location on the outer surface 18 to the gap 13 of the clean air discharge arrangement 10. One insight of the invention is that due to the triboelectric effect that accompanies the friction or sliding of dirt particles on surfaces in the vacuum cleaner unit 2, electrostatics can be generated and the mentioned situation can be avoided in a relatively uncomplicated manner, i.e. by cleverly using materials at appropriate locations in the vacuum cleaner unit 2. It is practical, but not necessary, if other surfaces in the vacuum cleaner unit 2, i.e. surfaces that are not the outer surface 18 of the core 17, are configured to attract dirt particles.

[0049] The measures of the application can be realized by using a material in the core 17 which is configured to not allow a transfer of an electrical charge from a dirt particle rubbing against the outer surface 18 at least at the location of the outer surface 18, or by using a material in the core 17 which is configured to guide an electrical charge obtained by a dirt particle rubbing against the outer surface 18 away from the outer surface 18 at least at the location of the outer surface 18. In the latter case, the core 17 can comprise an electrically conductive material at least at the location of the outer surface 18, or the core 17 is provided with an electrically conductive outer finish.

[0050] The essential aspects of the application are summarized as follows. In a vacuum cleaner unit 2 comprising a core 17, the core 17 comprises a cleaning air discharge 10 and an annular air vortex chamber 11 surrounding the cleaning air discharge 10, the core 17 is configured to prevent an electrostatic build-up at least at the location of an outer surface 18 of the core 17. In this way, a beneficial effect on the separation performance of the vacuum cleaner unit 2 is obtained. According to one practical option, the core 17 comprises at least at the location of the outer surface 18 a material which is configured to not allow a triboelectric effect caused by a dirt particle rubbing or sliding on the outer surface 18. According to another practical option, an electrically conductive material is used in the core 17, possibly in an outer finish of the core 17, so that an electrical charge can be guided away from the outer surface 18.

Claims

1. A vacuum cleaner unit (2) configured for use in a vacuum cleaner (1) and for receiving incoming contaminated air in the vacuum cleaner (1) and causing separation of contaminants from air, the vacuum cleaner unit (2) comprising: Core (17), the core comprising a portion along the cyclone rotation axis (A) R The clean air exhaust device (10) extends from the vacuum cleaner unit (2) and is configured to exhaust air from the vacuum cleaner unit (2). An annular air vortex chamber (11), the annular air vortex chamber (11) is located around the cyclone rotation axis (A) R The clean air emission device (10) is surrounded in the direction of the clean air emission device (10). as well as At least one inlet (6) is configured to allow polluted air to enter the air vortex chamber (11). The clean air emission device (10) has inwardly protruding blades (12) and gaps (13) between the blades (12); and The core (17) includes a material configured to guide the charge gained by friction of dirt particles against the outer surface (18) of the core (17) to prevent static electricity buildup at at least a portion of the outer surface (18). A waste collection chamber (14) is configured to receive and store waste from the contaminated air, wherein the waste collection chamber (14) is located in an extension of the clean air emission device (10) and the air vortex chamber (11), characterized in that, The core (17) includes an extension body (16) that is located within the extension of the clean air emission device (10) and extends toward the waste collection chamber (14) along the cyclone rotation axis (A). R The core (17) is configured to prevent static electricity buildup at a location at least a portion of the outer surface (18) of the core (17) located at the extension body (16).

2. The vacuum cleaner unit (2) according to claim 1, wherein, The core (17) includes conductive material at least at the location of the outer surface (18).

3. The vacuum cleaner unit (2) according to claim 2, wherein, The core (17) comprises a thermoplastic polymer with conductive additives.

4. The vacuum cleaner unit (2) according to claim 1, wherein, The core (17) is provided with a conductive outer decorative layer.

5. The vacuum cleaner unit (2) according to claim 4, wherein, The core (17) is provided with an external decorative layer of paint with conductive additives.

6. The vacuum cleaner unit (2) according to any one of claims 1-5, wherein, The material, configured to guide the charge gained by friction of dirt particles against the outer surface (18) away from the outer surface (18), is present in the core (17) in an outer layer with a thickness of at least 0.5 μm.

7. The vacuum cleaner unit (2) according to claim 6, wherein, The material, configured to guide the charge gained by friction of dirt particles against the outer surface (18) away from the outer surface (18), is present in the core (17) in an outer layer with a thickness ranging from 1 μm to 5 μm.

8. The vacuum cleaner unit (2) according to any one of claims 1-7, wherein, The resistivity (ρ) of the material configured to guide the charge gained by friction of dirt particles against the outer surface (18) away from the outer surface (18) is less than 10. 10 Ωm, preferably less than 10 9 Ωm, and more preferably less than 10 8 Ωm.

9. The vacuum cleaner unit (2) according to any one of claims 1-8, wherein, The core (17) includes a guide (15) configured to guide incoming contaminated air along a spiral path toward the clean air emission device (10), and wherein the core (17) is configured to prevent static buildup at a location at least a portion of the outer surface (18) of the core (17) located at the guide (15).

10. The vacuum cleaner unit (2) according to any one of claims 1-9, wherein, The blades (12) of the clean air exhaust device (10) have an overall airfoil profile.

11. A vacuum cleaner (1), preferably a handheld vacuum cleaner, comprising: The conduit (3), a suction nozzle (4) located at one end of the conduit (3), a vacuum cleaner unit (2) connected to the conduit (3) according to any one of claims 1-10, and a device (5) configured to generate air suction at the location of the suction nozzle (4) and generate an airflow through the conduit (3) from the suction nozzle (4) toward the vacuum cleaner unit (2).

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