WO2025078227A1

WO2025078227A1 - Cleaning apparatus and filter container for such an apparatus

Info

Publication number: WO2025078227A1
Application number: PCT/EP2024/077661
Authority: WO
Inventors: Arelys SOSA; Thomas TINGELÖF; Saieesh NAYAK
Original assignee: Drev AB
Current assignee: Drev AB
Priority date: 2023-10-12
Filing date: 2024-10-02
Publication date: 2025-04-17
Anticipated expiration: 2026-04-12
Also published as: SE547223C2; SE2351175A1

Abstract

The invention concerns a cleaning apparatus (30) for removing microparticles (51) from a surface (50) and collecting the microparticles in a filter container (1), the cleaning apparatus (30) comprising: an airflow duct (31); an airflow duct inlet (32) intended to be positioned in association with the surface to be 5 cleaned; a suction unit (33) arranged to generate a flow of air through the duct (31); a filter (2) configured to remove microparticles from an airflow passing through the filter (2), wherein the filter (2) is arranged inside the filter container (1), wherein the filter container (1) has an inlet opening (37) connected to the airflow duct (31), wherein the filter container (1) is arranged 10 in fluid communication with an airflow exhaust duct (35) downstream the filter container (1), wherein the filter (2) is arranged so that an air flow flowing through the airflow duct (31) and further through the filter container (1) is forced to pass through the filter (2); wherein the filter container (1) is detachably connected to the cleaning apparatus (30) so that the filter (2) is 15 removed from the cleaning apparatus (30) together with the filter container (1) when detaching and removing the filter container (1) from the cleaning apparatus (30); and wherein the filter container (1) is provided with an inlet closing element (3) arranged to keep the inlet opening (37) closed when detaching the filter container (1) and removing the filter container (1) from the 20 cleaning apparatus.

Description

Cleaning apparatus and filter container for such an apparatus

TECHNICAL FIELD

This invention relates to a cleaning apparatus for removing microparticles from a surface and collecting the microparticles in a filter container. In particular, the invention relates to a cleaning apparatus for battery manufacturing facilities and similar locations. The invention also relates to a filter container for such a cleaning apparatus.

BACKGROUND OF THE INVENTION

The battery industry and its value chain are facing a new challenge due to the increasing demand for lithium ion batteries to reduce CO2 emissions into the atmosphere. To meet this demand, battery manufacturers must increase their facility capacity by several orders of magnitude.

Besides increased production, a great challenge for the battery manufacturers is to clean the vast production areas, on daily basis, to meet the quality control requirements, which are one of the strictest controls in any industry for dry and clean rooms.

Battery manufacturing facilities currently utilize traditional methods comprising both dry and wet cleaning techniques. Dry cleaning equipment, such as dust collectors and industrial vacuum cleaners, are used to collect battery particles from tools and hard-to-reach areas. Wet cleaning equipment, such as wet mopping and scrubbers, are used due to their ability to cover large floor areas that dry cleaning equipment cannot. However, wet cleaning methods introduce water and solvents into the clean and dry room environment, which are contaminants. Additionally, no equipment collects the battery metal particles in a way that enables recycling, and it is instead discarded. There is no solution today for collection and recycling of these valuable and hazardous materials. The existing cleaning methods are not particularly suitable for this type of critical environment and they are in general associated with the following problems:

• Production stoppage or slowdown due to inefficient cleaning procedures currently affecting the dry and cleanroom quality control requirements such as dew point control (humidity) and safe collection of battery microparticles found in the process areas.

• Employee exposure to hazardous battery microparticles that can cause critical health problems such as cancer, respiratory problems, and skin and eye irritation.

• Irregular and inefficient floor cleaning, leading to Slip-Trip-Fall (STF) hazards due to the nature of carbon (graphite) material layered on the epoxy floor.

• The lithium particles violently react with water forming lithium hydroxide, highly flammable hydrogen and releasing enormous heat energy.

• A large amount of water or solvents like Isopropyl Alcohol (IPA) is used to clean these massive spaces, making the cleaning tasks unsustainable for the future once more battery factories get into production by 2030.

• All the battery microparticles collected during the cleaning are getting discarded instead of being recycled and reintroduced into the process to make it more sustainable.

There is thus a need for improved methods and equipment for cleaning of e.g. battery manufacturing facilities.

SUMMARY OF THE INVENTION

The invention concerns a cleaning apparatus for removing microparticles from a surface and collecting the microparticles in a filter container, the cleaning apparatus comprising: an airflow duct; an airflow duct inlet intended to be positioned in association with the surface to be cleaned; a suction unit arranged to generate a flow of air through the duct; a filter configured to remove microparticles from an airflow passing through the filter, wherein the filter is arranged inside the filter container, wherein the filter container has an inlet opening connected to the airflow duct, wherein the filter container is arranged in fluid communication with an airflow exhaust duct downstream the filter container, wherein the filter is arranged so that an air flow flowing through the airflow duct and further through the filter container is forced to pass through the filter, wherein the filter container is detachably connected to the cleaning apparatus so that the filter is removed from the cleaning apparatus together with the filter container when detaching and removing the filter container from the cleaning apparatus; and wherein the filter container is provided with an inlet closing element arranged to keep the inlet opening closed when detaching the filter container and removing the filter container from the cleaning apparatus.

During operation of the cleaning apparatus according to above, particles are sucked into the airflow duct inlet, transported through the airflow duct and collected inside the container, either trapped in the filter or situated onto e.g. a bottom surface of the filter container. When at some point it is decided that the filter container should be interchanged, for instance because the amount of particles collected in the container has reached some threshold level or the filter is considered to generate a too large pressure drop, the inlet closing element is activated (set in a closed position) and the filter container can be removed with the collected particles still contained therein. At the outlet side of the filter container, the collected particles are prevented from escaping from the container by means of the filter (that is likely to have relatively clean outer side). The cleaning apparatus, and in particular the suction unit, should typically be turned off before detaching the filter container from the apparatus.

The full/used filter container can then be handled in various ways for recycling of the collected particles. Before the actual recycling process, the handling may include transferring the particles from several filter containers to a larger common container for safe storage before shipped for recycling. When emptied, the filter containers can be reused. If desired, the filter may be interchanged.

The microparticles of interest to collect in a battery manufacturing facility may have a size/diameter in the range 0.1-100 pm. The filter should thus be configured to remove particles having a size down to around 1 pm, or down to around 0.5 pm, or down to around 0.3 pm, or even down to around 0.1 pm.

The filter intended to collect the microparticles may be a HEPA filter, or a combined filter comprising e.g. a HEPA filter and a chemical filter. The chemical filter may comprise activated carbon. The chemical filter is preferably arranged downstream the HEPA filter. The chemical filter may be arranged as a separate filter.

Microparticles are likely to stick to a surface by means of e.g. van der Waals forces, such as to a floor covered by epoxy as is common in a battery factory. Removing such stuck particles from a surface might be difficult even for high- power suction unit, and the cleaning apparatus is therefore preferably provided with a particle agitation device arranged to make particles located on the surface airborne. This is further explained below.

The cleaning apparatus may be handheld or may be provided with wheels for moving around on a floor. It may further be provided with an arrangement for driving the wheels and a steering arrangement so as to allow operation by an operator/driver or autonomous operation.

The filter container is sometimes referred to as “canister” in this disclosure.

In an embodiment, the cleaning apparatus comprises an actuator arranged to set the inlet closing element in a closed or open position. The canister/filter container inlet needs to be open during operation of the cleaning apparatus/machine, but closed when the canister is removed from the machine to make sure the collected material stays in the canister. This may be achieved by applying a gate with an actuator with a normally closed function, i.e. when the machine is off or the canister actuators are disconnected from the power supply the canister inlet will be closed by default.

In an embodiment, a humidity remover is arranged in the filter container. Humidity in the canister may cause exothermal chemical reactions when lithium is present, which may lead to fire. Humidity removal could be achieved by applying an absorbent, such as silica gel. The absorbent can be regenerated by heating inside the machine, or outside after removal.

In an embodiment, a first humidity sensor is arranged in the filter container. For safety reasons the humidity level in the filter container/canister can be measured using a humidity measurement sensor. Humidity sensors are typically integrated with temperature sensors as a temperature reading is needed for the analysis purposes, temperature and humidity readings from the same sensor unit. The humidity measurement will also indicate if the humidity remover in the canister needs to be regenerated.

In an embodiment, a second humidity sensor is arranged in association with the airflow duct upstream the filter container. Preferably, this second humidity sensor is located as far as possible from the filter container, such as at the airflow duct inlet. The second humidity sensor can detect presence of water in the airflow duct before it reaches the filter container, for instance caused by water present on a floor subject to cleaning, and a signal from the second humidity sensor indicating an increased humidity level can be used by a control system configured to control the cleaning apparatus to automatically stop operation of the suction unit, and/or close the inlet closing element, so as to prevent that water enters the filter container. The control system should have a rapid response time and be capable of sufficiently quickly take action to prevent water from reaching the filter container.

In an embodiment, a temperature sensor is arranged in the filter container. For safety reasons the temperature in the canister can be monitored using a thermal sensor to register rapid temperature increase resulting from exothermal reactions. The temperature rise caused by operating the machine, as well as temperature changes induced by the surrounding environment should be differentiated (by the control system) from effects of chemical reactions. The response time of the sensor and the interpretation of the sensor signal should be rapid to quickly warn the operator in case of a safety-related temperature event.

In an embodiment, an electrical conductivity sensor is arranged downstream of the filter so as to allow for measurement of the electrical conductivity of the airflow after having passed the filter. The HEPA/chemical filter will need replacement at end-of-life (EoL). Filter EoL may be detected by measuring electrical conductivity using a sensor placed after the filter. When conductivity at the sensor tip increases it indicates that conductive particles are passing though the filter body. There is also a safety aspect to this as the particles are no longer effectively contained in the canister.

In an embodiment, a level sensor is arranged in the filter container, wherein the level sensor is arranged to detect a level of collected particles in the filter container. The amount of collected particles in the canister is preferably monitored in order not to overfill, using a sensor for instance based on IR technology. Should the canister overfill particles may leave the canister to the ambient environment.

In an embodiment, the filter container is made of stainless steel. The material of the canister should be non-reactive. One option is stainless steel, for instance grade 304, which meets the clean room material ISO standards. A protective coating or film may be applied onto the surface of the filter container/canister, at least on the inside thereof.

In an embodiment, the filter is configured to remove particles having a size down to around 1 pm, or down to around 0.5 pm, or down to around 0.3 pm, or down to around 0.1 pm.

In an embodiment, the filter is a HEPA filter, for instance of type H13 or H14 (EN 1822).

In an embodiment, the filter is a chemical filter.

In an embodiment, the cleaning apparatus is provided with a vibration generator arranged to expose the filter to vibrations that release at least some of the particles collected in the filter. To increase the lifetime of the filter, a vibrating generation device may be used to dissociate at least some of the captured particles from the filter surface to the canister. Care should be taken not to apply too much vibration as this might disturb the filter function and may result in particles moving through the filter body back into the cleanroom environment.

In an embodiment, the cleaning apparatus further comprises a pre-filter arranged upstream the filter, in relation to a flow direction of the airflow. Preferably, the pre-filter is arranged inside the filter container. Preferably, the pre-filter has a mesh size of 0.5-1 .5 mm.

To enhance the lifetime of the main filter (the HEPA/chemical filter), an additional coarse pre-filter could be added as a pre-filtration step of larger particles, with a mesh size of e.g. about 1 mm. The pre-filter is preferably positioned relatively close to the main filter so that the collected material is contained in the same filter container/canister as the microparticles collected in/by the main filter. Another possibility is to make use of a dual canister system where the pre-filter is located in a separate, detachable filter container.

In an embodiment, the cleaning apparatus comprises a sealing member arranged to provide a sealed connection between the cleaning apparatus and the filter container. The filter container is removed from the machine for emptying and servicing. The interface areas may be sealed using compressible rubber gaskets, such as o-rings, made by for instance silicone rubber.

In an embodiment, the cleaning apparatus comprises a lock mechanism for locking the filter container to the cleaning apparatus, wherein the lock mechanism is configured to provide a control signal indicative of whether the filter container is properly locked to the cleaning apparatus. The filter container/canister may be locked to the cleaning apparatus by a magnetic force. The control system of the apparatus may be configured so that activation of the suction unit is possible only when the lock mechanism is activated and the container securely fixed to the apparatus.

In an embodiment, the filter container is provided with a discharge coupling for emptying the filter container of collected material. Typically, when the canister is full it will be removed from the machine and its contents will be moved to a larger container, such as a “hopper collector”, for safe storage until it is shipped for recycling. The connection between the canister and the hopper collector may be realized by a general purpose discharge coupling that is compatible with several types of products. The discharge coupling is typically kept closed most of the time and opened only when emptying the filter container. The discharge coupling is preferably arranged upstream of the filter and in a bottom region of the filter container where collected particles accumulate. The larger container, such as the “hopper collector” may be set under vacuum/low pressure conditions to reduce the partial pressure of oxygen and thereby increase fire safety. Also the filter container may be set under vacuum conditions when positioned in the cleaning apparatus and/or when removed from the apparatus, but this is likely to significantly increase complexity of the design.

To simplify logistics and improve the ergonomic environment for the operators, the filter container may be provided with wheels.

In an embodiment, the suction unit is arranged in an airflow exhaust duct downstream the filter container. The suction unit may comprise a blower, a pump, a compressor or some other type of air mover. The airflow may be guided by bristles, shirts, ducts etc. to make sure that the particles are not moving in the wrong direction. The velocity of the airflow may be adjusted so as to be laminar, i.e. not turbulent, to avoid or reduce thermal reactions, in particular when particles with residual charge from a dielectrophoretic treatment (see below) collide with the walls of the airflow duct.

In an embodiment, a check valve is arranged in an airflow exhaust duct downstream the filter container. The check valve may be arranged upstream the suction unit, i.e. between the filter container and the suction unit. The collected material is hold in place in the filter container at the outlet side by the filter. An additional check valve can be applied between the filter container outlet and the apparatus to ensure no material slip at the outlet. The check valve may be connected to the filter container so as to follow the filter container when removed from the cleaning apparatus.

In an embodiment, the cleaning apparatus further comprises a particle agitating device arranged in association with the airflow duct inlet, wherein the particle agitating device is configured to make particles located on the surface airborne. Particles located onto the surface to be cleaned are more prone to be sucked into the airflow duct if made airborne. Besides using some form of brush, that also may direct particles towards the airflow duct inlet, the particle agitating device may include electromagnetic or ultrasound means for making microparticles airborne, i.e. particles that are sufficiently small to stick to surfaces in a special way.

Microparticles typically bond to surfaces in their vicinity due to van der Waals forces. Van der Waals forces are distance dependent (between molecules) and not resulting in chemical electronic bonds. They are therefore relatively easy to disturb, compared to stronger chemical bonds.

One way of dissociating particles which are attracted to surfaces via van der Waals forces and to make them airborne is to introduce an electrical field which exerts counteracting forces through the so-called dielectrophoretic (DEP) force.

The dielectrophoretic force occurs due to the interaction between an external electric field and the dielectric properties of suspended particles. Applying an external electric field induces electric dipoles within the particles, causing the charges within the particles to redistribute. The polarization mechanism depends on the dielectric properties of the particles, which have a different permittivity than the surrounding medium (such as air). This difference in permittivity leads to the creation of electric dipole moments, resulting in the direction of the dielectrophoretic force. The direction of the dielectrophoretic force depends on the relative permittivity of the particle and the medium. Positive dielectrophoretic force (pDEP) occurs when the particles have a higher permittivity than the surrounding medium, attracting particles towards regions of higher field strength. Negative dielectrophoretic force (nDEP) arises when particles have lower permittivity than the surrounding medium, causing particle repulsion. Some elements dielectric constants are given in the following table:

Element Dielectric Constant

Li (Lithium) High (Infinite for metals)

C (Graphite) Low (Typically 3 to 5)

Na (Sodium) High (Infinite for metals)

Mg (Magnesium) High (Infinite for metals)

Al (Aluminum) High (Infinite for metals)

Si (Silicon) Moderate (Around 11-12 in crystalline form)

P (Phosphorus) Generally Low (Depends on form)

Mn (Manganese) High (Infinite for metals)

Fe (Iron) High (Infinite for metals)

Co (Cobalt) High (Infinite for metals)

Cu (Copper) (Highly conductive metal)

The dielectrophoretic force is the force exerted on charged (polarized) particles in a spatially non-uniform electric field. Negative particles will move towards the positive electrode and vice versa as in any electric field, but also non-charged particles are influenced due to the electrical field strength being non-uniform resulting in an induced charge distribution within the particles. When the particle is exposed to the dielectrophoretic force, it moves or rotates, cuts the van der Waal-bond to the surface, and gets airborne. To achieve a significant agitation/movement of non-charged microparticles, electrode geometries should be designed to generate an electric filed that is significantly non-uniform on the micro meter scale.

Although dielectrophoresis works also with a non-alternating voltage, varying the polarity of the electrodes using an alternating voltage source will introduce further gradients in the electrical field. An alternating voltage will also prevent build-up of charged particles on the electrode surfaces since the electrodes will interchangeably repel and attract charged particles during different phases of the voltage profile. The polarity of the electrodes can be changed continuously for instance by applying a sinusoidal wave generator which will create a continuously changing electrical field, but other voltage profiles (such as triangular, square wave, pulsed etc) may be applied.

Since the force that the particles will experience is dependent on the gradient in the electrical field, it is an advantage to arrange the electrodes close to each other to generate a great voltage change per length unit over the created air gap. An example of a suitable electrode distance is in this case 2- 200 micrometer. Since the field strength will decline rapidly with distance from the electrode surfaces it is also an advantage to bring the electrodes close to the particles to be agitated, i.e. close to the surface to which the (micro)particles are bonded. An example of a suitable distance between the electrodes and the surface is in this case <1 mm, preferably <200 micrometer.

Options for realizing efficient electrode designs for dielectrophoresis in air:

• Single bristle: Non-conductive cores are coated with a conductive material to create the bristles. The bristles are connected to either of two “bus-bars” with opposing polarity. At least two bristles with opposing polarity are needed to create the electrical field needed for dielectrophoresis. o An advantage of this design is that the bristles may interact with the agitated particles also after they have become air bom and that any particles sticking to the bristles are connected to ground via the voltage generator which counteracts static charge buildup. o A challenge is that the position of the individual bristles may be difficult to control.

• Di-bristle: Two conductive cores of similar or different geometries and/or sizes with insulating material in-between and around. The conductive cores are connected to two “bus-bars” of opposing polarity. Only the tip of the bristle is non-insulated. o A main advantage here is that the electrical field can be designed in an exact manner and that the field is strongest at the uninsulated tip where it is needed. The risk for short circuiting is low. o A challenge may be to control the distance between the tip of the bristle and the surface where the microparticles are located. However, with a large amount of di-bristles moving at or closely above the surface it is not necessary to control this distance; instead the large amount of di-bristles ensures that a sufficient amount of the di-bristles, i.e. a certain fraction of the total amount, always are located with their tip at an appropriate distance from the surface.

• PCB: The electrode structure can alternatively be printed on circuit board (PCB). In this case the electrode structure should be interdigitated and castellated in order to create a significantly non-uniform electrical field. o A main advantage here is that the electrical field can be designed in an even more exact manner than the di-bristle design and that in the same way the field is located at the surface of the PCB only. The risk for short circuiting is very low. o A challenge may be to control the distance between the electrodes (i.e. the surface of the PCB) and the surface where the microparticles are located. However, this can be solved by integration of a device that controls the distance between the bottom of the PCB and the surface, such as a low friction rounded tip or ball (similar to an old computer mouse). One may also make use of a spring action to push the PCB towards the surface. The PCB may be provided with through holes forming passages for the particles towards the airflow duct inlet.

Ultra sonification is an alternative way of dissociating the microparticles bonded to the surface and make them airborne. Other alternative ways include the use of pressurized air (air blade and/or nozzle with jet) or dry ice (solid CO2). Further, a sticky mat or mechanical agitation with a microfiber cloth may be used in a two-step process where the mat or cloth is used to remove the particles from the surface in a first step and the dielectrophoresis or other method is used in a second step to remove the particles from the mat or cloth to make them airborne. When the particles are located on the mat or cloth it might be easier to control the distance between the electrodes and the particles compared to when the particles are located on the surface to be cleaned, at least in cases where the surface is not very smooth. An additional alternative way is to make use of a closed wet system where a fluid used for releasing the particles from the surface is recirculated in wet, humid and dry zones (with the dry zone closest to the clean room environment).

The particle agitating device may comprise a combination of means for making the microparticles airborne.

In an embodiment, the particle agitating device comprises a movable brush provided with a plurality of brush bristles.

In an embodiment, the particle agitating device comprises a voltage source and a plurality of electrodes connected to the voltage source, wherein the plurality of electrodes are configured to, when operating the voltage source, generate an electric field that is spatially non-uniform on a micro-meter scale.

In an embodiment, the plurality of electrodes comprises a plurality of electrode pairs, each pair comprising a first and a second electrode, wherein the first electrode is connected to a first terminal of the voltage source and the second electrode is connected to a second terminal of the voltage source.

In an embodiment, the voltage source is configured to generate an alternating voltage. In an embodiment, the plurality of electrodes comprises a single bristle having a non-conducting core provided with a conductive coating.

In an embodiment, the plurality of electrodes comprises a pair of bristles extending along each other, each bristle having a conductive core surrounded by a non-conducting material except at a tip thereof.

In an embodiment, the plurality of electrodes are arranged on a printed circuit board.

In an embodiment, the particle agitating device comprises an ultrasound generator.

In an embodiment, the filter container has an outlet opening connected to an airflow exhaust duct, and wherein the container is provided with an outlet closing element arranged to keep the outlet opening closed when detaching the container and removing the container from the cleaning apparatus. The outlet closing element could be the check valve mentioned above, or another closing element. In this embodiment the container is closed when removed from the cleaning apparatus. Such a filter container may comprise a lid or other openable part that can be detached or opened to allow for access to its interior (for interchanging filter or humidity absorber, for replacing malfunctioning sensors, etc.).

In an embodiment, the cleaning apparatus comprises a control circuitry configured to control operation of the cleaning apparatus. Such control may include receiving and handling of sensor signals, activating actuators, controlling operation of the suction unit, displaying information for an operator, controlling a drive arrangement for moving the cleaning apparatus around (based on operator input or autonomously), etc. The invention also concerns a filter container for a cleaning apparatus adapted to remove microparticles from a surface and collect the microparticles in the filter container, the filter container comprising:

- an inlet opening connectable to an airflow duct for an incoming airflow;

- an outlet opening for an outgoing airflow;

- a filter configured to remove microparticles from an airflow passing through the filter, wherein the filter is fixed to the filter container and located between the inlet and outlet openings inside the filter container, wherein the filter is arranged so that an incoming airflow entering the filter container via the inlet opening is forced to pass through the filter before reaching the outlet opening; wherein the filter container is arranged to be detachably connected to the cleaning apparatus; and wherein the filter container is provided with an inlet closing element arranged to keep the inlet opening closed when detaching the filter container and removing the filter container from the cleaning apparatus.

In an embodiment, the filter container comprises an actuator arranged to keep the inlet closing element in a closed position.

In an embodiment, a humidity remover is arranged in the filter container.

In an embodiment, a first humidity sensor is arranged in the filter container.

In an embodiment, a temperature sensor is arranged in the filter container.

In an embodiment, a level sensor is arranged in the filter container, and wherein the level sensor is arranged to detect a level of collected particles in the filter container.

In an embodiment, the filter container is made of stainless steel. In an embodiment, the filter is configured to remove particles having a size down to around 1 pm, or down to around 0.5 pm, or down to around 0.3 pm, or down to around 0.1 pm.

In an embodiment, the filter is a HEPA filter.

In an embodiment, the filter is a chemical filter.

In an embodiment, the filter container is provided with a vibration generator arranged to expose the filter to vibrations that release at least some of the particles collected in the filter.

In an embodiment, the filter container comprises a pre-filter arranged upstream the filter, in relation to a flow direction of the airflow. The pre-filter may be arranged inside the filter container. The pre-filter may have a mesh size of 0.5-1 .5 mm.

In a further aspect, the invention concerns a cleaning apparatus for removing microparticles from a surface and collecting the microparticles in a filter container, the cleaning apparatus comprising: an airflow duct; an airflow duct inlet intended to be positioned in association with the surface to be cleaned; a suction unit arranged to generate a flow of air through the duct; a filter configured to remove microparticles from an airflow passing through the filter, wherein the filter is arranged inside the filter container, wherein the filter container has an inlet opening connected to the airflow duct, wherein the filter container is arranged in fluid communication with an airflow exhaust duct downstream the filter container, wherein the filter is arranged so that an air flow flowing through the airflow duct and further through the filter container is forced to pass through the filter, and wherein the filter container is provided with a discharge coupling for emptying the filter container of collected material. Such a cleaning apparatus allows for emptying the filter container without detaching and removing the filter container, which then may or may not be detachably connected to the cleaning apparatus. The discharge coupling is preferably arranged so as to be easily accessible from an outside of the cleaning apparatus, e.g. to allow connection to a suction device. In line with what is described above, the discharge coupling is preferably arranged upstream of the filter and in a bottom region of the filter container where collected particles accumulate.

In case the filter container of this variant of the cleaning apparatus is detachable, the filter container is preferably provided with an inlet closing element in line with what is described above. Irrespective of whether the filter container of this variant of the cleaning apparatus is detachable, it may be configured as described above, i.e. it may be provided with various sensors, means for lowering humidity, the filter(s) may be arranged in a similar way, etc. Also this variant of the cleaning apparatus may be configured in line with what is described above, i.e. it may for instance be provided with a particle agitation device arranged in different ways.

BRIEF DESCRIPTION OF DRAWINGS

In the description of the invention given below reference is made to the following figure, in which:

Figure 1 shows a schematic example of a cleaning apparatus according to this disclosure.

Figure 2 shows a filter container of the cleaning apparatus according to figure 1 , where the filter container is in an attached state.

Figure 3 shows the filter container according to figure 2 in a detached state. Figure 4 shows an underside of a particle agitating device of the cleaning apparatus according to figure 1 .

Figure 5 shows the principle of particle agitation using dielectrophoresis.

DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

Figure 1 shows a schematic example of a cleaning apparatus 30 comprising, for instance, a detachable filter container/canister 1 and a particle agitation device 34. Figures 2 and 3 show the filter container 1 when locked and sealed to the cleaning apparatus 30 (figure 2) and when detached from the cleaning apparatus 30 (figure 3). Figure 4 shows an underside of the particle agitation device 34. In this example the cleaning apparatus 30 is arranged to be driven around on a surface to be cleaned by an operator that is positioned on-board the apparatus.

The following table gives information about most parts of the cleaning apparatus 30:

As shown in figures 1-3, the cleaning apparatus 30 comprises an airflow duct 31 leading from an airflow duct inlet 32, positioned in association with the surface to be cleaned and with the particle agitation device 34, to the filter container 1. A suction pump 33 is arranged in an airflow exhaust duct 35 downstream the filter container 1 to generate a flow of air through the duct 31 and further through the filter container 1. In this case the apparatus 30 comprises a further airflow duct 36 that merge with the first-mentioned duct 31.

The filter container/canister 1 is, at an inside thereof, provided with a HEPA filter 2 that removes microparticles from the airflow when passing through the filter 2. The filter container 1 has an inlet opening 37 connected to the airflow duct 31 .

The filter container 1 is detachably connected to the cleaning apparatus by means of a magnetic lock mechanism 5 that is configured to provide a control signal indicative of whether the filter container 1 is properly locked to the cleaning apparatus 30. The filter container 1 can thus be detached and removed from the cleaning apparatus 30 while still carrying the microparticle filter 2. A sealing member 6 is arranged to provide a sealed connection between the cleaning apparatus 30 and the filter container 1 .

The filter container is further provided with an inlet closing element 3 (controllable via an actuator) arranged to keep the inlet opening 37 closed when detaching the filter container 1 and removing the filter container 1 from the cleaning apparatus 30. Particles collected in the filter container 1 are thus prevented from escaping the filter container 1 , by the inlet closing element 3, the filter 2, and the walls of the container 1 , when the filter container 1 is removed from the cleaning apparatus 30. The actuator sets the inlet closing element in an open position when the container 1 is properly attached to the cleaning apparatus 30 and sets it in a closed position when the filter container 1 is to be detached and removed (and optionally also when the container 1 is attached but the suction pump 33 is not in operation).

The filter container 1 is further provided with an absorbent 4 for reducing humidity inside the container 1 , a first humidity sensor 10, a temperature sensor 12, and a level sensor 13 arranged to detect a level of collected particles in the filter container 1 .

A second humidity sensor 38 is arranged in association with the airflow duct 31 , 36 upstream the filter container 1 .

Further, an electrical conductivity sensor 17 is arranged downstream of the filter 2 so as to allow for measurement of the electrical conductivity of the airflow after having passed the filter 2.

The filter container 1 is made of stainless steel.

The cleaning apparatus 30 is further provided with a vibration generator 11 arranged to expose the filter 2 to vibrations that release at least some of the particles collected in the filter 2.

In this example the cleaning apparatus 30 further comprises a pre-filter 8 arranged upstream the microparticle filter 2, in relation to a flow direction of the airflow. Also the pre-filter 8 is arranged inside the filter container 1 , and it has a mesh size of 0.5-1.5 mm.

When the suction pump 18 is operating, air flows via the particle agitation device 34 and the airflow duct inlet 32 through the airflow duct 31 and into the filter container 1 . Air flows also via the other duct 36 into the duct 32 and further to the filter container 1 . Inside the container 1 , the air flows through the pre-filter 8 and then through the microparticle filter 2 before leaving the container 1 via the airflow exhaust duct 35. Particles following the airflow into the filter container 1 will stop at the pre-filter 8 if larger than around 1 mm and nearly all of the smaller particles will be stopped by the microparticle filter 2. The particles will thus be collected in the filter container 1 , either located at a bottom of the container 1 or stuck at/in the filters 2, 8.

A discharge coupling 9 is arranged at the bottom of the container 1 for emptying the filter container 1 of collected material when the container has been removed from the cleaning apparatus 30. Material from many containers 1 may be collected in a common, larger container that may be transported to another location where a recycling process is carried out.

A check valve 18 is arranged in an airflow exhaust duct downstream the filter container 1 .

Figures 2 and 3 show a magnified view of the filter container 1 in a locked/attached and unlocked/detached position, respectively. As shown in figure 3, an upper side 45 of the detached filter container 1 forms an outlet opening.

The particle agitating device 34 is arranged in association with the airflow duct inlet 32 and is in close contact with the surface (floor) during operation of the cleaning device 30. The particle agitating device 30 is configured to make particles located on the surface airborne, and it comprises in this case a rotating unit provided with brush bristles as well as electrodes and other components configured to generate an electric field for releasing particles from the surface by dielectrophoresic forces as described above.

Figure 4 shows an underside of the particle agitating device 34. As shown in figure 4, an outer section 34a of the rotating part of the particle agitating device 34 is provided with regular brush bristles 19, a midsection 34b is provided with di-bristles 21 (as described above), each of which forming a pair of electrodes 21a, 21 b separated by non-conducting material 21c except at a tip thereof, and a central section 34c is provided with pairs of electrodes 20a, 20b arranged onto a PCB 40 provided with through holes 41 forming airflow channels to the airflow duct inlet 32. When the rotating part rotates, the brush bristles 19 and the electrodes 20a, 20b, 21a, 21b set the particles located on the surface/floor in motion, make bonded microparticles airborne and facilities removal of the particles from the surface to the airflow duct 31 and subsequent collection in the filter container 1 .

The particle agitating device 34 comprises a voltage source (not shown) and the plurality of electrodes are connected to the voltage source. As noted above, the electrodes form pairs where each pair comprises a first electrode 20a, 21a and a second electrode 20b, 21b, and the first electrode is connected to a first terminal of the voltage source and the second electrode is connected to a second terminal of the voltage source so as to, when operating the voltage source, provide a potential difference between the first and second electrode in each pair and thereby provide an electric field that is spatially non-uniform on a micro-meter scale. The voltage source is in this example configured to generate an alternating voltage to alternately attract and repel charged particles.

The cleaning apparatus 30 further comprises a control circuitry configured to control operation of the cleaning apparatus 30. The control circuit is indicated by items 14-16, see the table above. The control system 14-16 is adapted to, for instance, receive and handle sensor signals from the sensors 10, 12, 13, 17, 38, activating actuators and controlling opening and closing of the inlet closing element 3, controlling operation of the suction unit 18 and the particle agitation device 34 (including operation of the voltage source and the rotating unit), displaying information, and controlling a drive arrangement for moving the cleaning apparatus around (based on operator input or autonomously), etc.

Figure 5 shows the principle of particle agitation using dielectrophoresis. A pair of di-bristle electrodes 21a, 21b have different polarity and generates a non-uniform electric field at their tips. A polarizable microparticle 51 bonded to a surface 50 by means of van der Waals forces is subject to a dielectrophoresic force. This makes the particle 51 to rotate or move, which breaks the bond to the surface 50 and makes the particle airborne and available for being sucked into the airflow duct inlet 32 via passages between the bristles.

The distance Li between the tip of the electrodes 21a, 21b and the surface 50 may be <1 mm, preferably <200 micrometer. The distance L2 between the electrodes 21a, 21 b may be around 2-200 micrometer micro meter.

The invention is not limited by the embodiments described above but can be modified in various ways within the scope of the claims.

Claims

1. A cleaning apparatus (30) for removing microparticles (51 ) from a surface (50) and collecting the microparticles in a filter container (1 ), the cleaning apparatus (30) comprising:

- an airflow duct (31 );

- an airflow duct inlet (32) intended to be positioned in association with the surface to be cleaned;

- a suction unit (33) arranged to generate a flow of air through the duct (31 );

- a filter (2) configured to remove microparticles from an airflow passing through the filter (2), wherein the filter (2) is arranged inside the filter container (1 ), wherein the filter container (1) has an inlet opening (37) connected to the airflow duct (31 ), wherein the filter container (1 ) is arranged in fluid communication with an airflow exhaust duct (35) downstream the filter container (1 ), wherein the filter (2) is arranged so that an air flow flowing through the airflow duct (31 ) and further through the filter container (1 ) is forced to pass through the filter (2); wherein the filter container (1 ) is detachably connected to the cleaning apparatus (30) so that the filter (2) is removed from the cleaning apparatus (30) together with the filter container (1 ) when detaching and removing the filter container (1 ) from the cleaning apparatus (30); and wherein the filter container (1 ) is provided with an inlet closing element (3) arranged to keep the inlet opening (37) closed when detaching the filter container (1 ) and removing the filter container (1 ) from the cleaning apparatus.

2. The cleaning apparatus according to claim 1 , wherein the cleaning apparatus comprises an actuator arranged to set the inlet closing element in a closed or open position.

3. The cleaning apparatus according to claim 1 or 2, wherein a humidity remover is arranged in the filter container.

4. The cleaning apparatus according to any of the above claims, wherein a first humidity sensor is arranged in the filter container.

5. The cleaning apparatus according to any of the above claims, wherein a second humidity sensor is arranged in association with the airflow duct upstream the filter container.

6. The cleaning apparatus according to any of the above claims, wherein a temperature sensor is arranged in the filter container.

7. The cleaning apparatus according to any of the above claims, wherein an electrical conductivity sensor is arranged downstream of the filter so as to allow for measurement of the electrical conductivity of the airflow after having passed the filter.

8. The cleaning apparatus according to any of the above claims, wherein a level sensor is arranged in the filter container, and wherein the level sensor is arranged to detect a level of collected particles in the filter container.

9. The cleaning apparatus according to any of the above claims, wherein the filter container is made of stainless steel.

10. The cleaning apparatus according to any of the above claims, wherein the filter is configured to remove particles having a size down to around 1 pm, or down to around 0.5 pm, or down to around 0.3 pm, or down to around 0.1 pm.

11 . The cleaning apparatus according to any of the above claims, wherein the filter is a HEPA filter.

12. The cleaning apparatus according to any of the above claims, wherein the filter is a chemical filter.

13. The cleaning apparatus according to any of the above claims, wherein the cleaning apparatus is provided with a vibration generator arranged to expose the filter to vibrations that release at least some of the particles collected in the filter.

14. The cleaning apparatus according to any of the above claims, wherein the cleaning apparatus further comprises a pre-filter arranged upstream the filter, in relation to a flow direction of the airflow.

15. The cleaning apparatus according to claim 14, wherein the pre-filter is arranged inside the filter container.

16. The cleaning apparatus according to claim 14 or 15, wherein the pre-filter has a mesh size of 0.5-1.5 mm.

17. The cleaning apparatus according to any of the above claims, wherein the cleaning apparatus comprises a sealing member arranged to provide a sealed connection between the cleaning apparatus and the filter container.

18. The cleaning apparatus according to any of the above claims, wherein the cleaning apparatus comprises a lock mechanism for locking the filter container to the cleaning apparatus, wherein the lock mechanism is configured to provide a control signal indicative of whether the filter container is properly locked to the cleaning apparatus.

19. The cleaning apparatus according to any of the above claims, wherein the filter container is provided with a discharge coupling for emptying the filter container of collected material.

20. The cleaning apparatus according to any of the above claims, wherein the suction unit is arranged in an airflow exhaust duct downstream the filter container.

21. The cleaning apparatus according to any of the above claims, wherein a check valve is arranged in an airflow exhaust duct downstream the filter container.

22. The cleaning apparatus according to any of the above claims, wherein the cleaning apparatus further comprises a particle agitating device arranged in association with the airflow duct inlet, wherein the particle agitating device is configured to make particles located on the surface airborne.

23. The cleaning apparatus according to claim 22, wherein the particle agitating device comprises a movable brush provided with a plurality of brush bristles.

24. The cleaning apparatus according to claim 22 or 23, wherein the particle agitating device comprises a voltage source and a plurality of electrodes connected to the voltage source, wherein the plurality of electrodes are configured to, when operating the voltage source, generate an electric field that is spatially non-uniform on a micro-meter scale.

25. The cleaning apparatus according to claim 24, wherein the plurality of electrodes comprises a plurality of electrode pairs, each pair comprising a first and a second electrode, wherein the first electrode is connected to a first terminal of the voltage source and the second electrode is connected to a second terminal of the voltage source.

26. The cleaning apparatus according to any of claims 24-25, wherein the voltage source is configured to generate an alternating voltage.

27. The cleaning apparatus according to any of claims 24-26, wherein the plurality of electrodes comprises a single bristle having a non-conducting core provided with a conductive coating.

28. The cleaning apparatus according to any of claims 24-27, wherein the plurality of electrodes comprises a pair of bristles extending along each other, each bristle having a conductive core surrounded by a non-conducting material except at a tip thereof.

29. The cleaning apparatus according to any of claims 24-28, wherein the plurality of electrodes are arranged on a printed circuit board.

30. The cleaning apparatus according to any of claims 22-29, wherein the particle agitating device comprises an ultrasound generator.

31 . The cleaning apparatus according to any of the above claims, wherein the filter container has an outlet opening connected to an airflow exhaust duct, and wherein the container is provided with an outlet closing element arranged to keep the outlet opening closed when detaching the container and removing the container from the cleaning apparatus.

32. The cleaning apparatus according to any of the above claims, wherein the cleaning apparatus comprises a control circuitry configured to control operation of the cleaning apparatus.

33. A filter container (1 ) for a cleaning apparatus (30) adapted to remove microparticles (51 ) from a surface (50) and collect the microparticles in the filter container (1 ), the filter container (1 ) comprising:

- an inlet opening (37) connectable to an airflow duct (31 ) for an incoming airflow;

- an outlet opening (45) for an outgoing airflow; - a filter (2) configured to remove microparticles from an airflow passing through the filter (2), wherein the filter (2) is fixed to the filter container (1) and located between the inlet and outlet openings (37, 45) inside the filter container (1 ), wherein the filter (1) is arranged so that an incoming airflow entering the filter container (1 ) via the inlet opening (37) is forced to pass through the filter (2) before reaching the outlet opening (45); wherein the filter container (1 ) is arranged to be detachably connected to the cleaning apparatus (30); and wherein the filter container (1) is provided with an inlet closing element (3) arranged to keep the inlet opening (37) closed when detaching the filter container (1 ) and removing the filter container (1) from the cleaning apparatus (30).