INTERFACES FOR AIR CLEANERS AND LIDS FOR AIR CLEANERS

TECHNICAL FIELD

The present disclosure relates to air cleaners for use on construction sites and in other environments where it is desired to remove particulate matter from the ambient air. The air cleaners are active air cleaners which filter the ambient air by means of a fan and filter arrangement to capture harmful particulate matter in the surrounding environment.

BACKGROUND

Construction work such as concrete processing operations often involve dust generating processes that generate dust which can be harmful to personnel at the construction site. Construction site work tasks may also involve coating operations, such as painting and spraying, which release harmful matter into the ambient air.

An air cleaner can be used to filter the ambient air at a construction site in order to remove harmful particles and gasses from the air.

There is a desire for air cleaners which are efficient and easy to use. Cost is also an important factor; hence cost-effective solutions are sought. It is also important that the air cleaners are reliable.

SUMMARY

It is an objective of the present disclosure to provide features and functions for improving prior art air cleaners. This objective may at least in part be obtained by a user interface for an air cleaner. The interface comprises a light source arranged to emit light of at least two colors and in two or more blinking patterns, a diffusor connected to the light source, and a control unit. The control unit comprises processing circuitry and one or more sensor input ports configured to receive respective sensor signals. The control unit is arranged to detect a present operating state of the air cleaner based on the sensor signals, and to classify the present operating state of the air cleaner into one of at least three categories of operating states by the processing circuitry. The control unit is also arranged to control the color and blinking pattern of the light source in dependence of the category of the present operating state. This way the user interface is able to signal a plurality of different error events and operating states, to a user nearby the air cleaner, using a common interface. The light source can for instance be arranged to emit any of white, green, yellow, and red light, and the at least two blinking patterns may comprise periodic blinking at 1 Hz, and at 2Hz. The blinking pattern periodicity can advantageously be used to signal a level of urgency of the notification, where a faster blinking the indicates a higher urgency compared to a slower blinking rate. The user interface furthermore comprises an electrical energy storage module arranged to power the user interface in the event of power outage. This is an advantage since the user interface including the control unit is then able to remain operational in the event of power outage. At some construction sites it is important that the air cleaner is always operational, since otherwise personnel at the construction site may be exposed to harmful particulate matter at the construction site. In the event of power outage, it may not be possible to operate the fan of the air cleaner, but it will still be possible to generate a warning via the user interface to inform nearby persons that the air cleaner is no longer operational. Persons at the construction site may then evacuate the part of the work site comprising the failed air cleaner. The control unit can for instance be arranged to detect a power outage state if a current and/or voltage of an external power connection is outside of a pre-determined voltage and/or current range.

According to some preferred aspects the diffusor comprises an input end and an output end, where the input end is arranged in connection to the light source and has an input height and an input width matched to respective dimensions of the light source. The output end has an output width exceeding the input width and/or has an output height exceeding the input height, i.e., the output end is larger than the input end, at least in some dimension and preferably shaped as a light bar. The output end may thus implement a light bar of the user interface, which has improved noticeability due to its size. The combination of a light bar with a width and/or height which is comparably large in relation to the dimensions of the light source, and the ability of the light bar to blink with a combination of different colors and blinking patterns provide an effective mechanism for informing a person nearby the air cleaner of its current operating status. The light bar also remains operational in the event of a power outage, which is an advantage. The control unit can also be configured to inactivate a fan of the air cleaner in response to classifying the present operating state of the air cleaner as a critical fan malfunction operating state. This way damage to the air cleaner resulting from the critical malfunction state can be mitigated. It is an advantage that the control unit inactivates the fan and not the whole air cleaner since important control functions and user interface functions are then left in operational state. The malfunction may, e.g., be associated with a fan motor, such as an increased temperature of the fan motor, in which case powering down the fan may avoid doing damage to fan bearings or the like. The malfunction may also be associated with a too high consumed power by the fan, such as a drawn current above a predetermined fan current threshold.

The user interface optionally also comprises a buzzer. The control unit is then arranged to operate the buzzer in dependence of the classified category of the present operating state, thus further enforcing the noticeability of a message from the user interface.

The control unit is optionally also arranged to receive an air pressure sensor signal indicative of an air pressure downstream from a filter of the air cleaner, and to detect a filter malfunction state if the air pressure sensor signal is outside of a pre-determined air pressure range. This allows the control unit to detect when one or more filters of the air cleaner malfunctions, and to trigger a notification which informs nearby persons of the filter malfunction event.

According to some aspects, the control unit of the user interface is arranged to monitor a current and or power drawn by a fan of the air cleaner, and to detect an air cleaning malfunction state if the current drawn by the fan is outside of a pre-determined fan current range. The fan is, for instance, likely to draw less power if a filter upstream of the fan has been obstructed, since the fan blades then encounter less resistance compared to a normal operating state of the fan. Hence, a malfunction state can be declared by the control unit if the fan power consumption decreases below some predetermined low power threshold configured with a margin below a nominal fan power consumption value. A fan which starts to draw more power than it normally does may also be malfunctioning. Hence, a malfunction state can also be declared by the control unit if the power consumption of the fan exceeds a predetermined high power threshold configured with some margin above a nominal fan power consumption value. The user interface can also be configured to signal high particle concentrations to persons nearby the air cleaner in an efficient manner. The control unit is then arranged to monitor a particle concentration in the ambient environment of the air cleaner, e.g., by means of an integrated particle sensor, and to detect an air cleaning malfunction state if the particle concentration is outside of a pre-determined allowable particle concentration range. It is an advantage to integrate a particle sensor device with the user interface in this manner since the particle sensor benefits from the mechanical protection of the user interface and also from the power supply of the user interface. If combined with an electrical energy storage, such as a battery or a capacitor circuit, further advantages are obtained, since then the particle sensor and the control unit may remain operational even if the electrical mains connection suffers a power outage. The control unit can also be connected to a back-up power source, and comprise a wake-up timer. The control unit can then be configured to wake up from an inactivated state of operation according to a pre-determined schedule to monitor the particle concentration in the ambient environment of the air cleaner. This way the air cleaner can be used to monitor particle concentrations in the ambient environment even if the air cleaner is not active, i.e., even if the fan is not operating, which is an advantage. In fact, the monitoring function can remain active even if an electrical mains connection to the air cleaner is disconnected or powerless for some reason.

The user interface can be integrated in an air cleaner lid which also comprises a sealed compartment that forms part of the lid. The control unit, the light source and the diffusor can be located in the sealed compartment where they are protected from dirt and moisture as well as from mechanical impact from various objects at the construction site. The light bar of the user interface may form part of an external surface of the sealed compartment, thereby providing a sort of communication channel from inside the sealed compartment to the ambient environment. A power cable for an electrical mains connection may also extend out from the sealed compartment, thus providing a supply of energy into the sealed compartment in a reliable manner.

According to some aspects, a separating wall extends out from the lid. The separating wall comprises an opening with a fan arranged in the opening. A power cable extends out from the sealed compartment and to the fan. This means that all “electrically active” parts, i.e., user interface, control, unit, power supply, and fan are all integrated in a single module which can be removed from the air cleaner body in a convenient manner. The remaining parts of the air cleaner are then void of electrically powered components and can be managed accordingly.

The above-mentioned objective may also at least in part be obtained by an air cleaner comprising a pre-filter, an essential filter, and a fan arranged to generate a flow of air through the filters. The essential filter is preferably but not necessarily arranged upstream of the fan and downstream from the pre-filter, such that the flow of air first passes the pre-filter, then the essential filter, before finally passing the fan. The fan can, however, also be placed upstream of the filters, downstream of the filters, or inbetween the pre-filter and the essential filter. The air cleaner further comprises a control unit arranged to determine an air pressure based on an output signal from an air pressure sensor of the air cleaner arranged in-between the fan and the essential filter. The control unit is arranged to determine a particle load of the essential filter based on the determined air pressure, in response to a test signal triggered by activation of a control input device of the air cleaner. The pre-filter is configured such that it prevents a user from activating the control input device when it is in an installed position. In other words, the filter test function where the particle load of the essential filter is determined cannot be triggered if the pre-filter is installed, e.g., because the pre-filter itself covers a control input device such as a button, or because a bracket holding the pre-filter in its operating position covers the control input device. It can only be triggered if the pre-filter is first removed from the air cleaner. A user wanting to perform a filter test function that determines particle load of the essential filter is required to first remove the pre-filter before the control input device can be activated. Thus, the pre-filter will not have an impact on the filter test function, which means that the test function can be implemented in a more straight forward manner compared to if the pre-filter also has to be accounted for in the test routine. The control input device may for instance comprise a manual input device, such as a push-button, located between the pre-filter and the essential filter in use, such that it is hidden by an installed pre-filter. The user then has to manually remove the pre-filter before the button can be pushed. According to some other aspects, the control input device comprises a presence sensor arranged to detect if the pre-filter is installed. The control unit can then be arranged to determine the particle load of the essential filter in response to a user command received via a user interface of the air cleaner conditioned on that the presence sensor does not detect an installed pre-filter. The presence sensor may, e.g., be realized as an electrical switch which is actuated by the pre-filter in its installed position or a Hall effect sensor which senses presence of a metal object on the pre-filter when the pre-filter is in its installed position. A radio frequency identification (RFID) can also be used as presence sensor.

According to other aspects, the control unit is arranged to configure a pre-determined fan speed of the fan in response to the test signal. This way the particle load level of the essential filter can be measured in a more reliable manner based on a measured pressure drop over the filter since the fan speed is known. A variable unknown fan speed would have an impact on the flow through the filter and therefore also on the pressure drop over the filter caused by different levels of particle load.

According to some aspects, the air pressure determined by the air pressure sensor is determined relative to a reference pressure and the control unit is configured to determine the particle load of the essential filter based on a pre-determined relationship between the measured air pressure (relative to the reference pressure) and particle load. This pre-determined relationship can, e.g., be tabulated in a lookup table or the like, which provides for a detection mechanism of low computational complexity, which is an advantage. The reference pressure can for instance be ambient atmospheric pressure determined by an ambient pressure sensor, or a preconfigured reference pressure value. This way absolute pressure measurements are avoided, which normally require calibration.

The control unit may be arranged to indicate the determined particle load of the essential filter on a user interface of the air cleaner. This user interface may, e.g., comprise a light bar arrangement that can show different colors and also different blinking patterns. The particle load level of the essential filter can then be visualized in an efficient manner, e.g., by blinking faster for higher particle loads, or changing color from a first color light (such as green) towards a second color light (such as red). The control unit is optionally also arranged to generate a warning signal via the user interface of the air cleaner in case the determined particle load of the essential filter exceeds a pre-determined threshold level.

According to some aspects, the fan of the air cleaner is arranged in an aperture of a separating wall inside the air cleaner. The essential filter may then comprise a seal arranged to mate with a surface of the separating wall to form a sealed volume inbetween the fan and the essential filter. This sealed volume is particularly suitable for measuring pressure downstream of the essential filter and upstream of the fan, to be used, e.g., for estimating particle load level in the essential filter as part of a filter load test function of the air cleaner.

The control unit can also be arranged to monitor a current and/or power drawn by the fan in use, and to trigger an action, such as a warning signal and/or a request for an essential filter test procedure by the user interface, if the current drawn by the fan is outside of a pre-determined fan current range. The fan is, as mentioned above, likely to draw less power than it normally does if a filter upstream of the fan has been obstructed, since the fan blades then operate with less resistance in the lower air pressure environment. If it happens that the fan starts to draw less than nominal power (for a given fan speed), then it may be advisable to perform a filter test routine in order to determine if the filters of the air cleaner have too high particle load levels, or check if the filter aperture has been obstructed by a foreign object such as a plastic bag or the like.

The above-mentioned objective of providing features and functions for improving known air cleaners may also at least in part be obtained by a lid for an air cleaner which comprises a first part arranged in a sealing position to mate with and to seal an opening of an air cleaner body. The lid also comprises a second part comprised in the first part. The second part defines an enclosed volume which is sealed from an ambient environment of the air cleaner and also from an internal environment of the air cleaner. The enclosed volume is accessible in the sealing position of the first part via a service hatch formed in the second part. The first part also comprises a separating wall arranged to extend into the air cleaner body in the sealing position of the first part, where the separating wall comprises an opening with a fan arranged in the opening. A power cable is preferably supported on the separating wall by clamps, brackets, or the like, and extends from the fan and into the enclosed volume, although it is appreciated that the power cable can extend in an un-supported manner also. The lid and the air cleaner body thus cooperate to form a complete air cleaner, where all (or at least a majority of) the control functionality and electric components are comprised in the lid part, including the fan and the power supply to the fan. The control unit is preferably also located in the second part where it is protected from moisture and from being struck by objects at the construction site. The lid part with the integrated control circuit and fan module can be inserted into the air cleaner body in a convenient manner after, e.g., servicing or inspection of the internal volume of the air cleaner body. There is no need for electrical connections between lid and body since all electrical components are comprised in the lid part. The control unit located in the second part can also control a user interface integrated in the lid. The electrical components of the user interface, such as its light source, is preferably also enclosed in the second part.

According to some aspects, an air conduit extends from a location on the separating wall and into the enclosed volume of the second part, to a pressure sensor arranged in the enclosed volume of the second part. Thus, the pressure sensor benefits from the protected environment inside the second part. The air conduit, which may be a tubular member of some sort, provides controlled access to a volume downstream from an essential filter of the air cleaner. This allows the control unit to monitor a pressure downstream of the essential filter, thereby enabling filter test functions and the like.

The lid may also comprise one or more handles configured for vertically lifting the lid in a normal operating position of the air cleaner. This way the lid part can be extracted from the air cleaner body in a convenient manner in order to service or inspect the internal volume of the air cleaner body, which is an advantage. These handles, and/or other parts of the lid, are preferably matched to corresponding parts of the air cleaner body bottom portion, such that two or more air cleaners of the same type can be stacked on top of each other in case additional air cleaning capacity is required at a construction site. Two or more air cleaners in stacked configuration may also provide a required degree of air cleaning redundancy, allowing one of the air cleaners to fails with maintained air cleaning function, which could be desired at some construction sites. The user interfaces of the two or more stacked air cleaners can be connected when the air cleaners are in stacked configuration, such that, e.g., light bar operation is synchronized for enhanced visibility. One air cleaner can also indicate via its user interface that another air cleaner in the stack has failed. The communication link between the control units of the air cleaners in stacked configuration can be a wireless interface or a wired interface. In case of a wired interface, it may be advantageous to integrate plug and socket contacts of a data communication interface in the lid and in the bottom portion of the air cleaner body, respectively, such that the plug and sockets mate to establish the data communication link when the air cleaners are placed in stacked configuration.

To simplify operation in stacked configuration, the lid optionally comprises an electrical connector arranged to interface with a further air cleaner in stacked configuration with the air cleaner. Thus, as one air cleaner is placed on top of another air cleaner in stacked configuration, the two are electrically mated in an automatic manner. This means that only one cable to electrical mains is required, which is an advantage. The data communication interface and the power interface can be integrally formed as one set of connectors comprising both power pins and data communication pins.

The above-mentioned features and functions for improving known air cleaners may furthermore at least in part be obtained by an air cleaner comprising an air cleaner body arranged to hold a pre-filter, an essential filter, and a fan arranged to generate a flow of air through the pre-filter and the essential filter. The air cleaner body comprises a main air flow input aperture arranged to receive the air flow generated by the fan, which fan is preferably but not necessarily arranged downstream from the filters. It is appreciated that the fan can be arranged upstream of the filters, downstream of the filters, or inbetween the pre-filter and the essential filter. The air cleaner body also comprises first and second elongated pivotable and opposing brackets extending along two opposing sides of the main input aperture, where the opposing brackets are arranged to pivot about respective pivoting axes extending parallel to the opposing sides of the main input aperture, from respective open positions to respective closed positions. The opposing brackets, when in the open position, are arranged to allow the essential filter to be received in the air cleaner body. The opposing brackets, when in the closed position, are arranged to press against the essential filter received in the air cleaner body to hold the essential filter fixedly in position. Thus, an efficient and reliable arrangement for receiving and holding the essential filter of the air cleaner is provided. The opposing brackets preferably comprise respective slots extending parallel to the opposing sides. These slots are opposing in the closed position of the opposing brackets and arranged to slidably receive the pre-filter which, when received in the slots, prevents pivoting by the opposing brackets. This way a combined essential filter and pre-filter holding arrangement is provided. The mechanism allows for convenient assembly of the filtering solution as well as convenient disassembly.

The essential filter of the air cleaner optionally comprises a first gasket which extends around a periphery of the essential filter. The first gasket is arranged to seal against a separating wall of the air cleaner which supports a fan of the air cleaner downstream of the essential filter, in the closed position of the opposing brackets. The first gasket provides a sealed volume between the essential filter and the fan that promotes the air cleaning operation and also allows for making pressure measurements upon which filter test functions can be based, as discussed above.

The essential filter optionally also comprises a second gasket extending around a periphery of the essential filter on a side opposite to the first gasket side. This second gasket is arranged to seal against the opposing brackets in the closed position of the opposing brackets. The second gasket improves air cleaning further in that it prevents air flow past the essential filter towards the fan.

According to some aspects, the first and second elongated pivotable and opposing brackets also comprise respective opposing slots arranged to hold an impact protection grate upstream of the pre-filter, i.e., in front of the pre-filter seen from an outside of the air cleaner. The impact protection grate protects the pre-filter and the essential filter from mechanical impact. It is an advantage that the same elongated pivotable and opposing brackets are used also to hold the impact protection grate of the air cleaner.

There are also disclosed methods and control units associated with the same advantages as discussed above in connection to the different apparatuses.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realizes that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will now be described in more detail with reference to the appended drawings, where: Figures 1 A-B schematically shows an example air cleaner;

Figure 2 illustrates an example user interface with associated control unit;

Figure 3 schematically illustrates an example lightbar arrangement;

Figure 4A shows a lid for an air cleaner;

Figure 4B is a top view of an air cleaner;

Figure 5 illustrates a control unit arranged to classify an air cleaner operating state;

Figures 6A-C shows a filter holding arrangement;

Figure 7 illustrates a portable user interface for an air cleaner;

Figure 8 schematically illustrates user interface notifications;

Figures 9A-B are flow charts illustrating methods;

Figure 10 schematically illustrates a control unit;

Figure 1 1 schematically illustrates a computer program product; and

Figures 12-15 show views of an example air cleaner.

DETAILED DESCRIPTION

Aspects of the present disclosure will now be described more fully with reference to the accompanying drawings. The different devices and methods disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the aspects set forth herein. Like numbers in the drawings refer to like elements throughout.

The terminology used herein is for describing aspects of the disclosure only and is not intended to limit the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

An air cleaner is a device which filters the ambient air on a location such as a construction site, workshop, or laboratory. The present disclosure relates mainly to air cleaners for use at construction sites to remove harmful dust and other unwanted matter from the air. The air cleaners discussed herein may, for instance, be used with advantage to capture concrete dust generated by a floor grinding operation or from the use of cut-off tools and core drilling equipment. Some of the air cleaners disclosed herein may be connected via sleeve coupling to a suction hose, to draw air in through the suction hose and filter the air before releasing the filtered air into the ambient environment.

Air cleaners normally comprise a fan arranged to draw air through some form of filter arrangement, often a pre-filter followed by an essential filter. The direction of the flow of air generated by the fan is used herein to describe relative positions of various components in relation to each other. A first component which is upstream from a second component receives the air flow before it reaches the second component. The air stream through the air cleaner preferably but not necessarily first passes the prefilter, then the essential filter, before reaching the fan, in which case the fan is downstream from the pre-filter and from the essential filter. The fan can, however, be placed upstream of the filters, downstream of the filters, or inbetween the pre-filter and the essential filter.

A pre-filter is a relatively coarse filter which traps larger particles, while the essential filter is more fine and able to trap also very small particles. The fine particle dust trapped by the essential filter is often considered more harmful to a person compared to the more coarse particles trapped by the pre-filter.

Particle filters are discussed in, e.g., the International Electrotechnical Commission (IEC) standard IEC 60335-2-69 and IEC 60335-2-69. The essential filter, i.e., the finer filter arranged downstream from the coarser pre-filter, is sometimes referred to as a high efficiency particulate arresting (HEPA) filter, but this denomination is not entirely accurate. The term essential filter is to be interpreted broadly herein to mean a filter device with the ability to trap fine dust particles.

Figures 1A and 1 B schematically illustrate an air cleaner 100. Figure 1 A is a front view and Figure 1 B is a sectional side view. The air cleaner has a lid portion 120 which among other things comprises a user interface 1 10. The air cleaner 100 also comprises an air cleaner body 130 with a main input aperture 105 through which an air flow 165 generated by a fan 160 is drawn into the air cleaner. The air is then cleansed from particulate matter 101 by a pre-filter 140 which captures the larger particles followed by an essential filter 150 which removes more fine particulate matter. The air cleaner has an outlet (not shown) after the fan, which releases the filtered air back into the environment. One or more additional filters 151 , such as an activated carbon filter, may be arranged downstream of the essential filter 150. It is preferred that the fan 160 is arranged downstream of both the pre-filter 140 and the essential filter 150, as in the illustrated examples. However, it is appreciated that the fan 160 can be arranged upstream of the filters, downstream of the filters, or inbetween the pre-filter 140 and the essential filter 150.

An impact protection grate may be arranged in front of the pre-filter in order to protect the pre-filter from mechanical damage by objects at the construction site. An example impact protection grate 1230 is shown in Figure 12.

It is an advantage if the lid portion 120 has a shape which is matched to the bottom portion of the air cleaner 100, since this means that two or more air cleaners can be stacked on top of each other. To be matched may, e.g., comprise the lid portion having protrusions arranged to enter into corresponding recesses formed in the bottom portion of the air cleaner body 130 (the side facing the ground in a normal operating position of the air cleaner, e.g., as illustrated in Figure 12). The protrusions 1210 may be formed on the handles 460, as illustrated in Figure 12. A plurality of air cleaners in a stack can share the same electrical mains power connection. An electrical connector 191 , 192, 1240 can then be arranged in each air cleaner, e.g., as part of the lid portion and bottom portion (preferably in connection to the separating wall 190), such that an electrical connection is formed between two units in stacked configuration. Each lid portion can, for instance, comprise a male plug connector and each air cleaner body bottom portion can comprise a female socket connector such that two units become electrically linked when in stacked configuration. Only one of the air cleaner need then be connected to electrical mains via cable. A first electrical connector 191 and a second electrical connector 192 are illustrated in Figure 1 B. The first and second electrical connectors are arranged to mate with each other when two air cleaners are placed in stacked configuration. One air cleaner may then draw power through the electrical mains cable of the other air cleaner. The electrical connector 192 arranged at the bottom part of the air cleaner body is preferably integrated with the separating wall. This electrical connector then enters through a hole 193 formed in the bottom portion of the air cleaner body 130, preferably via a gasket arranged to seal against the connector 192, thus preventing air from being drawn into the air cleaner body through the hole 193. The electrical connectors may comprise magnetic connectors which are biased towards the mated position. The connectors may also be used to transfer data in addition to electrical power. Alternatively, or as a complement, in case one or more air cleaners in stacked configuration is battery powered, energy can be transferred from an air cleaner having a high state of charge to another air cleaner having a lower state of charge. This way the operating time of the air cleaners in a stack of air cleaners can be balanced to increase overall joint operating time of the units in stacked configuration. A data communication channel may be formed via wireless link between the control units of the air cleaners in stacked mode, or a wired communication channel (which could be integrated with the connectors 191 , 192). The control units of the air cleaners operating in stacked configuration may then exchange data indicative of a state of charge via the data communication channel, and thus balance the available power between the two battery powered air cleaners. In case one air cleaner is battery powered and is operating in stacked configuration with an air cleaner powered via electrical mains, then the battery powered air cleaner may charge its batteries via the connectors 191 , 192, 1240.

With reference also to Figure 2 and to Figure 3, the interface 110 comprises a light source 310 arranged to emit light of at least two colors in two or more blinking patterns, a diffusor 320 and a control unit 230. The light source may, e.g., be an array of light emitting diodes (LED) in different colors, or a multi-color LED, such as an RGB LED.

The diffusor 320 comprises an input end 321 and an output end 322. The input end 321 is arranged in connection to the light source 310 and has an input height and an input width matched to respective dimensions of the light source, which means that light emitted from the light source is guided by the diffusor 320. The output end 322 has an output width which exceeds the input width and/or has an output height exceeding the input height. The output end of the diffusor is thus larger in at least one dimension compared to the input end of the diffusor. The output end 322 implements a light bar 220 of the user interface 110. Herein, a light bar is a light permeable device having a surface arranged to emit light which is elongated, i.e., formed as a bar, with one side extending in the elongation direction of the bar that is longer than the other side that extends transversally to the elongation direction of the bar. It is an advantage that the light bar area is relatively large compared to the area of the light source. As will be explained in more detail in the following. The light source is arranged inside a sealed compartment, where it is protected from, e.g., dirt and water. Space inside this sealed compartment is relatively scarce, but a large area light bar can still be obtained by using a diffusor according to the present teaching. Another advantage is that the diffusor can form part of the wall of the sealed enclosure which houses the light source. The light bar is advantageously arranged in connection to a human-machine interface (HMI) 210, by which various notifications can be displayed to a user of the air cleaner 100. These notifications will be discussed in more detail below in connection to Figure 8.

The control unit 230 comprises processing circuitry 1010, the details of which will be discussed in more detail below in connection to Figure 10, and one or more sensor input ports configured to receive respective sensor signals, such as air pressure signals, particle sensor signals, electric current and voltage signals, fan power/current consumption signals, and temperature readings from various parts of the air cleaner. The control unit 230 is arranged to detect a present operating state of the air cleaner 100 based on the sensor signals, and to classify the present operating state of the air cleaner 100 into one of at least three categories of operating states by the processing circuitry 1010. The control unit 230 then controls the color and the blinking pattern of the light source in dependence of the category of the present operating state. Thus, by using a relatively simple notification device in the form of a light source capable of different colors and different blinking patterns, a user can be made aware of a plurality of different detected operating states, including both malfunction states as well as less critical states. By modulating color and blinking pattern, a sense of urgency can also be communicated. For instance, a rapidly blinking red light is more likely to be taken seriously and interpreted as an urgent notification by a user compared to a fixed or slowly blinking white or green light.

Figure 5 provides a general illustration of the classification function provided by the control unit 230. The control unit 230 receives one or more inputs comprising, e.g., main voltage data 510, filter air pressure data 510 (e.g., from the air pressure sensor 170), measurement of fan current 530, timer data 540 which can be used to schedule various events, and also temperature data from temperature sensors arranged in connection to, e.g., the fan. A plurality of categories 560 into which detected events are to be classified is obtained from configuration of the control unit 230. The control unit then implements a classification routine stored in memory 570, and outputs a classification. One example of a classification routine is a comparison to one or more threshold values. More advanced classification routines can also be used. However, such advanced classification routines are outside of the scope of the present disclosure and will therefore not be discussed in more detail herein. To summarize, the system 500 is arranged to monitor various signals and internal states 510-550 of the air cleaner 100 and process these signals by a classification module comprised in the control unit 230, which may comprise a random forest machine learning algorithm, or a neural network, or just a set of threshold comparison operations. The classification analysis system 500 may also comprise a memory device 570 arranged to store monitored parameter values and states of the air cleaner 100. The classification system 500 then outputs a category into which the present operating state has been classified.

Conceptually, the herein disclosed methods are based on measuring one or more operating parameters associated with the air cleaner, such as the current drawn by the fan, the air pressure downstream of the essential filter, and so on. Various transforms of the input data values can also be used with advantage, such as a D-Q transformed fan current. Various transforms may advantageously also be used for other obtained data as well, e.g., data relating to temperature. Fourier transforms, or wavelet transforms, or the like can also be used with advantage to classify the present operating state. For instance, the herein disclosed methods can be based on measuring one or more first parameters related to a condition internal to the air cleaner (such as an internal air pressure, particle level, temperature, and/or air flow) and one or more second parameters related to a condition external to the air cleaner (such as an ambient air pressure, temperature, and/or particle level in the ambient environment).

According to a preferred realization, the light source 310 is arranged to emit any of white, green, yellow, and red light, and the at least two blinking patterns comprise periodic blinking at 1 Hz, and at 2Hz. Red may generally be used for warnings associated with critical malfunctions states, such as a stopped fan or the like, while yellow can be used to signal less critical notifications. A fast blinking, i.e., around 2Hz can be used for the more critical notifications while a slower blink can be used for less time critical notifications and warnings.

The control unit 230 can also be configured to inactivate a fan of the air cleaner in response to classifying the present operating state of the air cleaner 100 as a critical fan malfunction operating state. In addition to inactivating the air cleaner fan, a warning signal can be generated. The warning signal uses the lightbar as discussed above, and may also comprise other components, such as a wireless signal transmitted using a radio frequency transceiver on-board the air cleaner. A buzzer 240 can also be used to reinforce warnings and notifications. The control unit 230 is then arranged to operate the buzzer 240 in dependence of the classified category of the present operating state. Some fault states may not trigger use of the buzzer while other will, hence increasing the signaling dimensionality beyond colors and blinking patterns of the light bar 220.

The control unit 230 can also be arranged to detect a power outage state if a current and/or voltage of an external power connection 430 is outside of a pre-determined voltage and/or current range.

The user interface 110 optionally comprises an electrical energy storage module 250, such as a battery or capacitor circuit, arranged to power the user interface in the event of electrical mains power outage. This way the system can remain operational even if there is no power available from the electrical mains. The electrical energy storage module 250 may, for instance, comprise a capacitor or a battery dimensioned to support warnings and notifications by the user interface 110 for a given period of time in the event of power outage, such as an hour or more. This way workers at a construction site can be notified in the event of a power outage causing interruption in the air cleaner operation, which is an advantage.

The connection between the control unit 230 and this type of back-up power source 250 also allows the control unit to wake up periodically even if the air cleaner is not in use to check on status. The control unit 230 may for instance comprise a wake-up timer and be configured to wake up periodically from an inactivated state of operation in response to a signal from the wake-up timer, e.g., according to a pre-determined schedule, to monitor a particle concentration 101 in the ambient environment of the air cleaner 100. This way the air cleaner 100 will warn users in vicinity of the air cleaner in the event of harmful particle levels even if the air cleaner is not operational, which is an advantage. This type of operation can also be maintained for a long period of time due to the intermittent nature of the operation. A particle sensor arranged to sense presence of particles in the ambient air surrounding the air cleaner can be used by the control unit 230 for this sensing task. Such sensors are generally known and will therefore not be discussed in more detail herein.

According to other aspects, the control unit 230 is arranged to receive an air pressure sensor signal indicative of an air pressure downstream from a filter of the air cleaner, such as the essential filter, and to detect a filter malfunction state if the air pressure sensor signal is outside of a pre-determined air pressure range. The air pressure signal can for instance be associated with an air pressure downstream of the essential filter. In case this air pressure drops too much, it may be inferred that the particle load level of the pre-filter and/or of the essential filter is too high to permit efficient air filtration due to obstruction of the filter or filters. In this case the function of the air cleaner may be in jeopardy, and some user action may be required, such as a filter replacement.

Filter particle load level data can also be inferred from the current and/or power drawn by the fan 160. In case the fan operates in vacuum, or at very low pressure, then the resistance encountered by the rotating fan blades will go down and therefore also the current consumption of the motor used to drive the fan 160. Thus, according to some aspects, the control unit 230 is arranged to monitor a current and/or power drawn by the fan 160, and to detect an air cleaning malfunction state if the current drawn by the fan 160 is outside of a pre-determined fan current range. The pre-determined fan current range may for instance be a threshold. A fan which draws too much power may also be indicative of malfunction. Hence, if the fan suddenly starts to draw an unusual amount of power in relation to the configured fan speed, a warning signal can be triggered.

The control unit 230 is optionally also arranged to monitor a particle concentration 101 in the ambient environment of the air cleaner 100, and to detect an air cleaning malfunction state if the particle concentration 101 is outside of a pre-determined allowable particle concentration range. In this case the control unit 230 is connected to one or more particle sensors inside the air cleaner and/or in connection to the external environment of the air cleaner. If one or more of these sensors start to report high particle levels, then the user interface 110 can be used to signal the occurrence to nearby personnel.

The user interface 110 and the associated components, such as the control unit 230, may advantageously be integrated into a lid 120, schematically illustrated in Figure 4A. This lid 120 comprises the user interface 110 and a sealed compartment 420, where the control unit 230, light source 310 and diffusor 320 are located inside the sealed compartment 420 where they are protected from dirt and water. The light bar 220 of the user interface 1 10 forms part of an external surface of the sealed compartment.

A power cable 430 for an electrical mains connection may be configured to extend out from the sealed compartment 420. In addition, a separating wall 190 may extend out from the lid. The separating wall comprises an opening with a fan 160 arranged in the opening and a power cable 450 extends out from the sealed compartment 420 and to the fan 160. This means that the user interface and its associated controls and peripheral components are integrated into a common module together with the fan and the sensor systems of the air cleaner. All intelligence and electrical components of the air cleaner are localized to the lid, which is an advantage, since it makes servicing easier and also provides for a more robust design which is easier to certify in terms of water resistance and the like.

To summarize, there is disclosed herein a lid 120 for an air cleaner 100. The lid is arranged to seal an opening of an air cleaner body 130 against an ambient environment of the air cleaner. The lid 120 comprises an enclosed volume which is sealed from the ambient (external) environment of the air cleaner and also from an internal environment of the air cleaner 100. This enclosed volume comprises power electronics and control circuitry to power and to control one or more operations of the air cleaner 100, as discussed elsewhere herein. The lid also comprises a separating wall 190, which is a planar member arranged to extend into the air cleaner body 130 to divide an internal volume of the air cleaner body in two parts, e.g., as illustrated in Figure 1 B. The separating wall 190 comprises an opening 195 and supports a fan 160 arranged to generate a flow of air 165 through the opening 195.

The air cleaner 100 illustrated in, e.g., Figure 1 B comprises a control unit 230 arranged to determine an air pressure P based on an output signal from an air pressure sensor 170 of the air cleaner 100. This air pressure sensor 170 may be a physical sensor device arranged in-between the fan 160 and the essential filter 150 and connected by wire to the control unit, or an air conduit arranged to connect a pressure sensor arranged closer to the control unit to the location in-between the fan 160 and the essential filter 150.

The control unit 230 can then be arranged to determine a particle load of the essential filter 150 based on the determined air pressure P, in response to a test signal triggered at least in part by activation of a control input device 180 of the air cleaner 100. Thus, a user may activate a filter test function by triggering the test signal, whereupon the control unit 230 determines the air pressure P using the air pressure sensor. A particle laden filter will give rise to a low pressure while an unladen filter will cause less pressure drop, and the filter particle load can therefore be determined by mapping the determined air pressure to particle load, e.g., using a look-up table or some form of pre-determined analytic function.

The filter test system, in its least complex version, only comprises a single air pressure sensor. Thus, if both the pre-filter 140 and the essential filter 150 are installed, then both filters will have an impact on the determined air pressure P. However, according to the present teaching, the pre-filter 140, in an installed position, prevents a user from activating the control input device 180, either because the pre-filter itself covers the control input device, or because a bracket holding the pre-filter in its operating position covers the control input device.

This means that a user must first remove the pre-filter before the control input device 180 can be activated, thereby ensuring that it is the essential filter only which generates the air pressure P from which particle load level of the essential filter can be determined in a reliable manner. The control input device 180 may for instance comprise a manual input device, such as a push-button, located between the pre-filter 140 and the essential filter 150 in use. In this case a user first has to remove the prefiler before the control input device 180 can be activated, thus ensuring that the air pressure measurement is performed without the pre-filter in place.

According to another example, the control input device 180 comprises a presence sensor arranged to detect if the pre-filter 140 is installed, and the control unit 230 is arranged to determine the particle load of the essential filter 150 in response to a user command received via a user interface 1 10 of the air cleaner 100. Although this realization is slightly more complex compared to having a push-button or the like hidden by the pre-filter, the function still ensures that the essential filter load test is conducted only when the pre-filter is not installed. The presence sensor can of course be combined with the manual input device or used separately without the manual input device.

The control unit 230 is preferably also arranged to configure a pre-determined fan speed of the fan 160 in response to the test signal. This pre-determined fan speed results in a more reliable particle load measurement, since fan speed of course has an effect on the measured pressure P, for a given particle load. Alternatively, the control unit 230 may be arranged to determine the particle load as a function of both the measured air pressure P and the current fan speed, in order to compensate for different fan speeds used during the filter load test. A mapping between pressure levels, fan speeds, and filter particle load can be determined by practical experimentation and/or by mathematical modelling and computer simulation.

The air pressure P can be determined relative to a reference pressure, in which case the control unit 230 is configured to determine particle load based on a pre-determined relationship between the air pressure P relative to the reference pressure and particle load. The reference pressure can, for instance, be ambient atmospheric pressure determined by a pressure sensor, or pre-configured reference pressure value.

Once the control unit 230 has determined the particle load level of the essential filter, the determined particle load of the essential filter can be shown on a user interface 110 of the air cleaner 100, e.g., on a scale from a value corresponding to a new clean filter to a fully laden filter in need of replacement. A warning may be triggered if the result of the particle load test indicates a particle load above an acceptable level, e.g., in case the determined particle load of the essential filter exceeds a pre-determined threshold level.

As shown in Figure 1 B, the fan 160 is arranged in an aperture 195 of a separating wall 190 inside the air cleaner 100. The essential filter 150 here comprises a seal 155 arranged to mate with a surface of the separating wall to form a sealed volume inbetween the fan 160 and the essential filter 150. In this manner a sealed volume is created between the fan and the essential filter 150, with a pressure that is primarily governed by the pressure drop over the essential filter 150 as long as the pre-filter is not installed. It is an advantage that the filter test can be performed by a single pressure sensor arranged in a single sealed volume. An alternative would be to arrange two pressure sensors, on both sides of the essential filter 150, and to use the pressure difference between the two to determine the pressure drop over the essential filter, and then use this pressure drop to determine particle load of the essential filter, but this approach requires two separate sensors, and also that the volume between the pre-filter and the essential filter is sealed.

As mentioned above, the control unit 230 can also be arranged to monitor a current and/or power drawn by the fan 160 in use, and to trigger an action, such as a warning signal and/or a request for an essential filter test procedure by the user interface 1 10, if the current drawn by the fan 160 is outside of a pre-determined fan current range. Generally, the lower the pressure P of the air encountered by the fan blades, the smaller the torque required to rotate the fan at a given fan speed. Hence, the smaller the current drawn by the fan the more particle laden the essential filter is. Thus, a suspiciously low current drawn by the fan 160 may be indicative of a particle laden essential filter and/or a particle laden pre-filter (in case one is installed).

The control input device can also be used to determine a total filter particle load, i.e., a joint resistance to the air flow 165 by both the pre-filter 140 and the essential filter 150. This can be achieved, e.g., by activating the filter test function from some other control input device, when pre-filter is installed, such that the air pressure P is a result of a pressure drop over both the pre-filter and the essential filter. One example way to exploit this is to first determine a particle load level of the essential filter with the pre-filter removed, and then determine the air pressure again with the pre-filter installed. This way the particle load of the pre-filter can also at least approximately be determined.

Figure 4A and Figure 4B illustrate some aspects of an air cleaner 100 which integrates the entirety or at least a majority of the control functions and the electrical components of the air cleaner 100 in the air cleaner lid 120. This is an advantage since it simplifies things like ingress protection (IP) rating, general electrical compliance, and servicing. The IP rating or IP code classifies the degree of protection provided by an enclosure, for electrical equipment with a rated voltage not exceeding 72.5 kV. IP ratings are defined by the international standard EN 60529.

The lid in Figure 4A comprises a first part 410 arranged in a sealing position to mate with and to seal an opening of an air cleaner body 130, and a second part 420 comprised in the first part 410. The second part defines an enclosed volume which is sealed from an ambient environment of the air cleaner and also from an internal environment of the air cleaner 100. The enclosed volume is accessible in the sealing position of the first part via a service hatch formed in the second part 420. Thus, all of the control circuitry, sensors, and power electronics can be placed in the enclosed volume which can, e.g., be IP-rated. The first part 410 further comprises a separating wall 190 arranged to extend into the air cleaner body 130 in the sealing position of the first part 410. This separating wall 190 comprises an opening 195 with a fan 160 arranged in the opening. A power cable 450 is preferably supported on the separating wall 190 and extends from the fan 160 and into the enclosed volume where it can be connected to, e.g., power electronics or the like. The power cable 450 may of course also extend between the fan and the enclosed volume in an unsupported manner. Also, the power cable may be relatively long or relatively short, it may even be realized by an electrical connector pin or the like which directly connects the fan to the power electronics in the enclosed volume. The control unit 230 discussed above can also be arranged in the enclosed volume of the second part 420, as well as the light source 310.

An air conduit optionally extends from a location on the separating wall 190 and into the enclosed volume of the second part 420, to a pressure sensor arranged in the enclosed volume of the second part 420. Thus, the pressure sensor is placed in the enclosed volume where it is protected from the often harsh conditions outside of the enclosed volume.

The separating wall may, as discussed above, also comprise an electrical and/or data connector 192 arranged to mate with a corresponding electrical and/or data connector 191 , 1240 on the lid portion of the air cleaner 100. This connector is then connected to the power circuitry and/or to the control unit enclosed in the lid portion of the air cleaner 100.

The lid 120 may also comprise one or more handles 460 configured for vertical lifting of the lid in a normal operating position of the air cleaner 100. This means that the entire lid, including the fan and all control components as well as the pressure sensor 170 can be lifted out from the air cleaner body 130 as one integral part. The air cleaner body which holds the pre-filter 140 and the essential filter 150 can then be serviced in a convenient manner, with good access from above.

The air cleaner body 130 optionally comprises vertically extending opposing slots 470 arranged to receive and to hold the separating wall 190. Thus, the separating wall 190 can be slided into position, whereupon it also guides the lid to the correct sealing position, where a seal 440 correctly engages, e.g., a matching surface on the air cleaner body 130. The vertically extending opposing slots 470 seen from above are illustrated in Figure 4B, together with the separating wall 190. The seal 440 is arranged to provide an air-tight or at least almost air-tight seal between lid portion 120 and air cleaner body 130. It extends along the lower edge of the lid portion 120, i.e., along the lid portion edge which engages the air cleaner body when the lid portion is assembled with the air cleaner body 130, e.g., as shown in Figure 1A or in Figure 12. The seal 440 may be a rubber seal of some other form of resilient material member which provides an air-tight or at least almost air tight seal between lid portion 120 and air cleaner body 130. The seal 440 may be attached to the lid portion 120 and/or to the air cleaner body 130. Figures 6A-C schematically illustrate details of an air cleaner, such as the air cleaner 100, which comprises an air cleaner body 130, 600 arranged to hold a pre-filter 140 and an essential filter 150 upstream of a fan 160. The air cleaner body 130, 600 comprises a main input aperture 105 arranged to receive an air flow 165 generated by the fan 165 in a known manner. The air cleaner body 130, 600 also comprises first and second elongated pivotable and opposing brackets 610, 620 extending along two opposing sides of the main input aperture 105, where the opposing brackets are arranged to pivot R about respective pivoting axes 630, 640 extending parallel to the opposing sides of the main input aperture 105, from respective open positions to respective closed positions.

The opposing brackets 610, 620, when in the open position, are arranged to allow the essential filter 150 to be received (see arrow I) in the air cleaner body 130, 600 at least partly via the main input aperture 105. The opposing brackets can then be rotated such that, when in the closed position, they press (see force arrow F) against the essential filter 150 received in the air cleaner body 130, 600 to hold the essential filter 150 in position. The opposing brackets can then be locked in this position to hold the essential filter securely in the air cleaner, which is a main purpose of the brackets.

According to an alternative, the essential filter instead comprises other holding means, such as a gasket or the like which holds the essential filter in position without requiring the press force F. Thus, there is also disclosed herein an air cleaner 100 comprising an air cleaner body 130, 600 arranged to hold a pre-filter 140, an essential filter 150 and a fan 160 arranged to generate a flow of air 165 through the filters. The air cleaner body 130, 600 comprises a main air flow input aperture 105 arranged to receive the air flow 165 generated by the fan 165, and also first and second elongated pivotable and opposing brackets 610, 620 extending along two opposing sides of the main input aperture 105. The opposing brackets are arranged to pivot R about respective pivoting axes 630, 640 extending parallel to the opposing sides of the main input aperture 105, from respective open positions to respective closed positions. The opposing brackets 610, 620, when in the open position, are arranged to allow the essential filter 150 to be received I in the air cleaner body 130, 600, The opposing brackets, when in the closed position, are arranged to allow a pre-filter to be received into its operational position (and held there). It is appreciated that the fan 160 can be arranged upstream of the filters, downstream of the filters, or inbetween the filters. The opposing brackets 610, 620 optionally comprise respective slots 615, 625 extending parallel to the opposing sides as illustrated in Figures 6A-C. The slots are opposing in the closed position of the opposing brackets (see Figure 6B and 6C) and arranged to slidably receive the pre-filter 140 which when received in the slots prevents pivoting by the opposing brackets 610, 620, as illustrated in Figure 6C.

According to some aspects, the pre-filter 140 is arranged to be inserted into the air cleaner body in a direction which is perpendicular to an insertion direction of the essential filter 150. For instance, as illustrated in the Figures, the pre-filter is insertable in the main direction of the air flow 165 into the air cleaner body while the essential filter is insertable in a vertical direction, down into the air cleaner body.

The fan 160, including the motor arranged to drive the fan 160, is mounted on a planar member (forming at least part of the separating wall 190) attached to the lid portion 120, in connection to an aperture 161 formed in the planar member through which the flow of air 165 is drawn by the fan 160. This feature can be clearly seen in Figure 15, which is discussed in more detail below.

The essential filter 150 in this example comprises a first gasket 155 extending around a periphery of the essential filter 150. The first gasket 155 is arranged to seal against a separating wall 190 of the air cleaner 100 downstream of the essential filter 150, in the closed position of the opposing brackets 610, 620. The essential filter 150 may also comprise a second gasket 650 extending around a periphery of the essential filter 150 on a side opposite to the first gasket side. The second gasket 650 is arranged to seal against the opposing brackets 610, 620 in the closed position of the opposing brackets 610, 620.

Figures 12-15 illustrate an example realization of the air cleaner 100 discussed above. The exploded view in Figure 15 in particular illustrates some of the key concepts discussed above. Following the air flow 165 downstream the air first passes the prefilter 140 and then through the essential filter 150 (here illustrated as a frame without filter media). The two filters are arranged to be inserted into the air cleaner body 130 in a convenient manner. The pre-filter 140 is insertable from the front of the air cleaner or from the top into the slot 145 formed in the air cleaner body 130. An additional filter 151 is here inserted downstream of the essential filter 150.

A major advantage of the design illustrated in Figures 12-15 and discussed above is that the fan, power electronics, and control circuitry is integrated in a single structure which comprises the lid 120, and the fan 160 supported by a planar fan supporting structure 165 which has a dedicated slot formed in the air cleaner body. This means that the fan, all the power electronics, and also the HMI and control circuitry can be conveniently removed from the main body 130 as a single integrated unit. The air pressure sensor arrangement 170 (not shown in Figures 12-15) comprises pressure sensor electronics and pressure sensing conduits which extend down into the main body 130. These pressure sensing conduits are attached to the planar fan supporting structure 165.

Figure 12 illustrates a feature of the lid portion 120 and air cleaner body 130 which allows stacking of two or more air cleaner units. The handle portions 460 comprise protrusions which are matched to corresponding recessed formed in a bottom portion of the air cleaner body 130. As discussed above, the air cleaners can be arranged to be electrically connected when in stacked configuration, such that only one cable to electrical mains from the stack is required, or such that battery capacity of the different stacked units can be shared in the stack.

Figure 12 also illustrates optional locking nuts 1220 which secures the pre-filter 140. A locking nut is also seen in Figure 14. The locking nuts can be replaced or complemented by a latch or other locking device.

An impact protection grate 1230 can be positioned in front of the pre-filter 140, i.e., upstream from the pre-filter 140, to protect the pre-filter from impact by objects. The impact protection grate can be a honeycomb structure as illustrated in Figure 12. This impact protection grate can be held in slots 1410 formed in the elongated pivotable and opposing brackets 610, 620.

Note the location of the control input device 180, and how it is hidden behind the prefilter 140 when the pre-filter 140 is in its intended operating position (as shown in Figure 12).

Figure 7 shows a complement to the user interface 1 10 discussed above, here a tablet device 700 or smart phone executing various applications related to the data obtained by the control unit 230 in the air cleaner 100.

The device 700 is optionally connected to a remote server 730 via wireless link 720, from which remote server 730 various configuration data and operating parameters can be obtained. The remote server 730 can also be configured to receive data from the air cleaner 100. The device 700 can be configured to display data associated with the air cleaner, such as the filter status 740 in terms of particle load, the filter load rate 750, i.e., how fast the filters are clogging up, and also an estimated time duration until the next filter replacement 760.

The current data on the device 700 can be compared to stored data, e.g., on the server 730, in order to determine if the current operation characteristics are as expected, or if some room for improvement is present. In this case the operator may be notified about this sub-optimal air cleaning operation and can then change one or more operating parameters in order to improve the performance of a given air cleaner.

Figure 8 illustrates some example notifications 810, 820 which can be displayed by the HMI 210. As long as the air cleaner is operating with satisfactory performance, without malfunction, an acknowledgement 810 of acceptable air cleaner performance can be displayed. This notification can be enforced by the light bar 220, as discussed above. In case unsatisfactory air cleaner performance is detected by the control unit 230, then a notification of the fact 820 can be displayed, optionally in combination with an error code 83O.This notification can also be enforced by operation of the light bar 220 as discussed above. An advantage of complementing the HMI 210 by the light bar 220 is that an operator more easily notices that a notification, such as a warning, has been triggered.

Figures 9A and 9B are flow charts illustrating methods that summarize some of the discussion above. Figure 9A illustrates a computer-implemented method performed in a user interface 1 10 of an air cleaner 100. The interface comprises a light source 310 arranged to emit light of at least two colors in two or more blinking patterns, a diffusor 320 and a control unit 230. The diffusor 320 comprises an input end 321 and an output end 322, where the input end 321 is arranged in connection to the light source 310 and has an input height and an input width matched to respective dimensions of the light source, where the output end 322 has an output width exceeding the input width and/or has an output height exceeding the input height, where the output end 322 implements a light bar 220 of the user interface 110. The method comprises receiving Sa1 at least one sensor signal by a control unit 230 comprising processing circuitry 1010 and one or more sensor input ports, detecting Sa2, by the control unit 230, a present operating state of the air cleaner 100 based on the sensor signals, and classifying Sa3, by the control unit 230, the present operating state of the air cleaner 100 into one of at least three categories of operating states by the processing circuitry 1010. The method also comprises controlling Sa4, by the control unit 230, the color and the blinking pattern of the light source in dependence of the category of the present operating state. Figure 9B illustrates a computer-implemented method performed in an air cleaner 100 comprising a pre-filter 140, an essential filter 150, and a fan 160 arranged to generate a flow of air 165 through the filters, where the essential filter 150 is arranged upstream of the fan and downstream from the pre-filter 140. The method comprises preventing Sb1 a user from activating a control input device 180 of the air cleaner 100 when the pre-filter 140 is in an installed position. The method also comprises, in response to a test signal triggered by activation of the control input device 180, determining Sb2, by a control unit 230 of the air cleaner 100, an air pressure P based on an output signal from an air pressure sensor 170 of the air cleaner 100 arranged in-between the fan 160 and the essential filter 150, and determining Sb3, by the control unit 230 of the air cleaner 100 a particle load of the essential filter 150 based on the determined air pressure P. Figure 10 schematically illustrates, in terms of a number of functional units, the general components of the control unit 230. Processing circuitry 1010 is provided using any combination of one or more of a suitable central processing unit CPU, multiprocessor, microcontroller, digital signal processor DSP, etc., capable of executing software instructions stored in a computer program product, e.g., in the form of a storage medium 1030. The processing circuitry 1010 may further be provided as at least one application specific integrated circuit ASIC, or field programmable gate array FPGA.

Particularly, the processing circuitry 1010 is configured to cause the automatic feed unit 100 to perform a set of operations, or steps, such as the methods discussed in connection to Figures 9A and 9B and the other discussions above. For example, the storage medium 1030 may store the set of operations, and the processing circuitry 1010 may be configured to retrieve the set of operations from the storage medium 1030 to cause the device to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus, the processing circuitry 1010 is thereby arranged to execute methods as herein disclosed.

The storage medium 1030 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory. The control unit 230 may further comprise an interface 1020 for communications with at least one external device. As such the interface 1020 may comprise one or more transmitters and receivers, comprising analogue and digital components and a suitable number of ports for wireline or wireless communication. The processing circuitry 1010 controls the general operation of the control unit 230, e.g., by sending data and control signals to the interface 1020 and the storage medium 1030, by receiving data and reports from the interface 1020, and by retrieving data and instructions from the storage medium 1030.

Figure 1 1 illustrates a computer readable medium 11 10 carrying a computer program comprising program code means 1120 for performing the methods illustrated in Figure

9, when said program product is run on a computer. The computer readable medium and the code means may together form a computer program product 1100.