A dust extractor with an improved drive unit

Abstract

A dust extractor (100) comprising at least one cyclone tank (110), a prefilter arrangement (120), an essential filter arrangement (130), a blower system (140) arranged to generate an air flow (F), and a control unit (150), where the blower system (140) comprises at least one centrifugal fan (210) driven by a respective brushless electric motor (220), the centrifugal fan (210) comprising a working air inlet (230) in fluid communication with a clean side of the essential filter arrangement (130), where the working air inlet (230) of the centrifugal fan is arranged in connection to a radial center of the centrifugal fan (210), and where a working air outlet (240) of the centrifugal fan (210) extends radially outwards from the centrifugal fan (210).

Description

[0001] TITLE

[0002] A DUST EXTRACTOR WITH AN IMPROVED DRIVE UNIT

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to dust extractors for use with construction equipment. There are disclosed improved drive units for generating air flow in heavy-duty dust extractors.

[0005] BACKGROUND

[0006] Dust and slurry are created by cutting, drilling, grinding and / or demolishing concrete, brick, and other hard construction materials at a construction site.

[0007] The dust and slurry can be efficiently collected by a dust extractor, accumulated in a dust container of the dust extractor, and removed from the construction site in a controlled manner. Dust extractors are heavy-duty vacuum devices which collect dust and slurry by generating an under-pressure in a cyclone tank by means of a fan or impeller and motor arrangement. This allows the dust extractor to collect larger quantities of dust compared to domestic vacuum cleaners which normally lack a cyclone tank. Some dust extractors comprise a coarse prefilter arranged inside the cyclone tank, followed by a finer filter downstream of the prefilter, such as a high-efficiency particulate air (HEPA) filter. The fine filter in a heavy-duty dust extractor is normally referred to as an essential filter, e.g., in IEC 60335-2-69:2021 (Ed. 6.0).

[0008] Many dust extractors are transported regularly at work sites and also between worksites. It is therefore desired to provide dust extractors which are lightweight and limited in size.

[0009] A dust extractor is normally powered by one or more electric motors. It is desired to provide efficient drive units that is capable of operating for extended periods of time. Cost and power efficiency are also key factors. SUMMARY

[0010] It is an object of the present disclosure to provide improved dust extractors and methods for operating dust extractors. This object is at least in part obtained by a dust extractor according to claim 1 .

[0011] Aspects of the present disclosure relate to a dust extractor comprising at least one cyclone tank, a prefilter arrangement, an essential filter arrangement, a blower system arranged to generate a working air flow to extract dust, and a control unit. The blower system comprises at least one centrifugal fan driven by a respective brushless electric motor. The at least one centrifugal fan comprises a working air inlet in fluid communication with a clean side of the essential filter arrangement. The working air inlet of the centrifugal fan is arranged in connection to a radial center of the centrifugal fan, and preferably extends generally along an axis of rotation of the centrifugal fan and in axial alignment with a motor axle of the brushless electric motor, i.e., the working air inlet preferably also faces in an extension direction of the motor axle. A working air outlet of the centrifugal fan extends radially outwards from the centrifugal fan, forming an angle between the working air inlet and the working air outlet. This angle between the working air inlet and the working air outlet is preferably larger than 45 degrees and preferable about 90 degrees. This drive unit based on a brushless electric motor and centrifugal fan arrangement is possible to make much lighter compared to known heavy-duty high air flow dust extractor drive units. The centrifugal fan arrangement can be made with impellers that are light weight, i.e., have low inertia, which means that the fan speed can be changed rapidly during operation, e.g., to maintain a constant air flow through the system.

[0012] The brushless electric motor is preferably a brushless direct current (BLDC) motor. The brushless electric motor is normally configured to operate at least in part on a three-phase (3ph) electric feed of the dust extractor, but it can also be configured to operate at least in part on an electric feed from an auxiliary energy source, such as a battery pack or a capacitor, of the dust extractor, or a one-phase connection to electrical mains. According to a preferred embodiment, the blower system comprises at least two brushless electric motors arranged to drive respective centrifugal fans. Each centrifugal fan is in fluid communication with a respective essential filter of the essential filter arrangement. This means that an essential filter can be inspected, replaced, or even serviced while the other fan and essential filter maintains dust extraction air flow, which is an advantage. The two fans together generate the required air flow necessary in many heavy-duty dust extraction applications. Each brushless electric motor of the blower system may comprise a cooling air inlet that is axially aligned with the motor axle, i.e., which opens up in the direction of the extension direction of the motor axle. The cooling air inlet and the working air inlet are arranged on opposite sides of the blower system. It is an advantage to separate the working air flow used for dust extraction and the cooling air flow used for cooling the electric motor, since the working air flow may be interrupted, and may comprise unwanted moisture and particles. The working air flow of the dust extractor may for instance be blocked occasionally during use and may also carry residual dust particles that can accumulate inside the electric motor and cause malfunction. When the working air flow is blocked the blower no longer encounters much air resistance and therefore the fan speed increases to a speed which generates significant heat. A dust extractor using the working air flow for cooling has problems dissipating this heat since there is no air flow past the blower motor when the working air flow is blocked.

[0013] According to some aspects, the blower system is supported by, and at least partially embedded in, a foam material body. At least one air channel extends through the foam material body to the blower system. The air channel extending through the foam material body is preferably at least partly defined by the foam material, which means that the foam material defines at least a part of the inner walls of the air channel. According to a preferred embodiment, the foam material body defines both one or more cooling air channels and one or more working air flow channels. This way a spatially efficient blower system with multiple integrated air channels is provided. The foam material body provides stable support for the blower system at the same time as it suppresses noise generated by the blower system, while also forming air channels. The foam material body can, for instance, be formed in a thermoplastic polymeric foam material, such as polypropylene or polystyrene.

[0014] According to a preferred embodiment, the foam material body comprises at least one cooling air channel that is at least partly delimited by the foam material body. The at least one cooling air channel extends between an ambient inlet port of the foam material body and a cooling air inlet of the blower system. The foam material body may also comprise at least one exhaust air channel that is at least partly delimited by the foam material body. The exhaust air channel extends between a working air outlet of the centrifugal fan and an exhaust port of the foam material body. The cooling air channel and the exhaust air channel are separated from the working air flow channels of the blower system, which is an advantage.

[0015] The total weight of an impeller of the centrifugal fan is normally below 2kg and preferably below 1 kg, and more preferably below 0,5kg. This light weight allows for a low-torque drive motor, and also for rapid adjustment of fan speed, as mentioned above. The blower system of the dust extractors described herein are dimensioned to generate an air flow of at least 500 m3 / h and preferably at least 700 m3 / h. The lightweight drive system allows for dust extractors that have a total weight of less than 200 kg. Some of the dust extractors described herein may weigh as little as 150 kg, or even about 100 kg. This is small in comparison to the air flow that is generated by the dust extractors. According to some aspects, the dust extractor has a weight to flow ratio in kg / m3 / h below 0,5, and preferably below 0,25. According to one example the total weight of the dust extractor is below 100kg, and the air flow generated by the dust extractor is around 700 m3 / h.

[0016] The dust extractor can also be made relatively small in size. According to some aspects the dust extractor has a ground surface footprint of at most one square meter. A total height measured along a vertical direction from a ground surface supporting the dust extractor to the vertical distalmost point is less than 2,0m.

[0017] According to some aspects, the control unit of the dust extractor is arranged to control a rotation speed of the at least one centrifugal fan based on a target air flow magnitude, e.g., to maintain the working air flow at the target air flow magnitude. The target air flow magnitude may be configured by a user of the dust extractor or be a preset air flow. The dust extractor can be configured to maintain a constant air flow even though the operating conditions off the dust extractor changes over time. The changing operating conditions may comprise, e.g., varying filter particle loads and different types of dust and slurry.

[0018] The centrifugal fan preferably comprises at least two axially aligned impellers serially arranged in direction of the air flow, i.e., arranged one after the other to generate the working air flow F of the dust extractor. This type of centrifugal fan has been found suitable for the type of heavy-duty dust extractors discussed herein. Two or more such centrifugal fans can be used in parallel to generate the required air flow.

[0019] At least some of the dust extractors described herein comprise hybrid electrical power systems, where a connection to electrical mains is complemented by an auxiliary energy source, such as a battery pack. This means that the dust extractor can draw a part of its operating power from electrical mains and the remainder of its operating power from the auxiliary energy source. In this case the control unit is configured to control the power outtake from the electrical mains connection and the power outtake from a battery system of the dust extractor in dependence of a power configuration. This power configuration can be a manual configuration determined from operator input, or it can be an automatic configuration set in dependence of a sensed state of the electrical mains feed. The control unit can, for instance, be configured to maintain power consumption from electrical mains below a given instantaneous current level, or such that the average current drawn from electrical mains over some time window meets predetermined acceptance criteria. A dust extractor with this type of hybrid electrical power system can often operate at work sites with an under-rated electrical mains, i.e., an electrical mains connection which is not able to provide sufficient electrical power for the dust extractor to perform its intended function.

[0020] The dust extractor may also comprise a status indicator light that is arranged to emit a plurality of different and selectable colors of light. In this case the control unit is configured to activate the status light in a first color, such as a green or white color, in case the blower system is activated. The control unit can also be configured to activate the status light in a second color, such as an orange color, in case a magnitude of the working air flow of the dust extractor does not satisfy an acceptance criterion. This way an operator understands if the dust extractor is active, i.e., if the blower system is generating the air flow. This becomes particularly important if the blower system is quiet, i.e., does not generate a lot of noise, which is the case for most of the dust extractors discussed herein. The same light source is used to notify the operator of problems, such as insufficient air flow, which is an advantage. The control unit can also be configured to activate the status light in a third color, such as a red color, in case the control unit has detected malfunction in the dust extractor.

[0021] The disclosed status indicator light system can be used to indicate if the blower system is active, e.g., by a green or a white colored light, and can optionally also be used to indicate malfunction, e.g., by a red colored light. A key technical feature of the disclosed status indicator light systems is that the same status indicator light system also indicates if the blower system generates sufficient working air flow, i.e., an air flow according to a predetermined acceptance criterion. This status light function is particularly useful in case the blower system is efficiently soundproofed, such as if an efficiently soundproofed brushless direct-current motor arrangement is used in the blower system. There are also disclosed herein control units, methods and systems associated with the above-mentioned advantages. 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.

[0022] BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present disclosure will now be described in more detail with reference to the appended drawings, where

[0024] Figures 1A-E show an example dust extractor;

[0025] Figures 2A-B illustrate an example blower system;

[0026] Figure 3 schematically shows a blower system with serially arranged impellers;

[0027] Figure 4 shows an example blower system support in a dust extractor;

[0028] Figures 5A-B illustrate two different hybrid electric feed systems;

[0029] Figure 6 schematically illustrates an air flow control system for a dust extractor;

[0030] Figure 7 is a graph showing air flow vs air pressure; and

[0031] Figure 8 shows an example control unit.

[0032] DETAILED DESCRIPTION

[0033] The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which certain aspects of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments and aspects set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout the description.

[0034] It is to be understood that the present invention is not limited to the embodiments described herein and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.

[0035] Figures 1A-E show an example dust extractor 100. The dust extractor can be connected via a hose to a dust generator (not shown in Figure 1 ), such as a core drill, a floor grinder, a concrete saw, or the like. The hose is secured to the dust extractor by means of an optional locking mechanism. The dust and slurry from the dust generator enters the dust extractor via an inlet 160 which opens up into a cyclone tank 1 10 configured to separate out larger debris and particles from the particle-laden airflow that enters the inlet 160. The material accumulated in the cyclone tank 110 can be emptied into a dust container 1 15, such as a plastic bag or a bucket, located underneath the cyclone tank 1 10.

[0036] The Longopac plastic bag system is a well-known dust container option suitable for heavy-duty dust extractors of the kind exemplified in Figures 1A- E. The Longopac plastic bag system essentially comprises a long plastic tube which is folded into an annular form. A part of the plastic tube is pulled out and sealed at one end, whereby an amount of dust can be held in the pulled out part. The pulled out part is then sealed at its upper end and cut from the rest of the tube, whereby a new part can be pulled out.

[0037] The dust extractor 100 comprises a frame structure 180, 181 , 182, 185 and is supported on wheels 195, 196.

[0038] The rear wheels 195 are not steerable in the illustrated examples, while the front wheels 196 are swiveling wheels allowing the dust extractor to be maneuvered on a ground surface. The frame structure 180, 181 , 182, 185 is a rigid structure made of, e.g., rigid tubular members that extend around the dust extractor to form a cage around the dust extractor 100, thereby protecting the dust extractor from impact at the work site. Metal pipes or other metal tubular elements can be used to form the frame structure. A rear part 180 of the frame structure extends transversally to the horizontal plane in use, such as vertically (V) along the dust extractor, to form a rail which the dust extractor can slide on when in a tilted position, e.g., when the dust extractor 100 is loaded or unloaded to / from a trailer or other elevated platform, as illustrated in Figure 1 C. The rear part 180 forming the rail constitutes the extreme distal portion of the dust extractor 100 along the side of the rail, thereby allowing the dust extractor 100 to slide on the rail over, e.g., a ledge. In other words, the rear part 180 of the frame structure forms the outer limit of the dust extractor along at least a portion of the back side of the dust extractor. The rear part 180 comprises two elongated members that extend down from top handle portion 181 towards the rear wheels 195. A portion of the rear part 180 of the frame structure is straight, allowing it to slide on a ledge, as illustrated in Figure 1 C.

[0039] An operator can pull on the upper part 181 of the frame structure which forms a handle, while letting the rear part 180 of the frame structure slide on the edge of the elevated platform, as illustrated in Figure 1 C.

[0040] A side part 185 of the frame structure extends horizontally along both sides of the dust extractor at a height of about 0,6-1 ,0m, and at least less than 1 ,5m. Note that only one side of the dust extractor is shown in Figure 1A. This relatively low side part 185 of the frame structure allows an operator to lift the dust extractor 100 from the ground in a convenient manner. Two operators can grip the side parts 185 on both sides in order to jointly lift the dust extractor from the ground. This facilitates handling of the dust extractor at a work site.

[0041] A front part 182 of the frame structure extends across the dust extractor front, as shown in Figures 1A-E. The front part of the frame structure protects the dust extractor, e.g., in case it tips over. Overall, the frame structure forms a cage around the dust extractor which protects it at the work site. The frame structure reduces the risk of damaging the dust extractor in case it falls over at the work site, which is an advantage.

[0042] Figure 1 D and Figure 1 E illustrate an additional optional feature of the frame structure on the dust extractor 100. In this example a top wheel 185 has been attached to the frame structure in vicinity of the upper part 181 that forms a handle section of the frame structure. The top wheel 185 extends out from the frame structure in a rearward direction (seen from the side as in Figure 1 E) to form the distalmost point of the dust extractor 100 together with the rearmost part of the rear wheel 195, where a plane 186 tangential to at least one of the rear wheels 195 and tangential to the top wheel 185 forms a rearmost limit of the dust extractor 100. This top wheel 185 in combination with the rear wheels 195 allows the dust extractor to be transported in horizontal position, i.e., lying down on the ground surface or on the floor of a cargo hold of a truck. An operator wanting to load the dust extractor, e.g., into a van or the like can first pull the dust extractor up into the cargo hold of the van using the back side of the frame structure as illustrated in Figure 1 C, and then roll the dust extractor into the van in horizontal position, using the rear wheels 195 in combination with the top wheel 185.

[0043] The top wheel 185 can be a swiveling wheel or a fixed wheel. The top wheel 185 can be permanently attached to the upper part 181 of the frame structure or releasably attached, such that the top wheel 185 can be removed in use and stored somewhere else. It is not necessary that the top wheel 185 is attached at the uppermost part of the frame structure, it can also be attached closer to the rear wheels 195. The top wheel 185 is normally mounted above a vertical midpoint of the frame structure, i.e., above a point on the frame structure which is at equal distance from the uppermost part of the frame structure and the rear wheels.

[0044] To summarize, there is disclosed a dust extractor 100 comprising at least one cyclone tank 110, a prefilter arrangement 120, an essential filter arrangement 130, a blower system 140, and a protective frame structure 180, 181 , 182. The protective frame structure comprises a rear part 180 that extends transversal to a horizontal plane in a normal operating position of the dust extractor 100, such as vertically V, along the dust extractor in use to form a rail which the dust extractor can slide on when in a tilted position. The rear part 180 extends from rear wheels 195 of the dust extractor 100 to an upper part 181 of the frame structure forming a handle section of the frame structure. A top wheel 185 is attached to the upper part 181 of the frame structure, where a plane 186 tangential to at least one of the rear wheels 195 and tangential to the top wheel 185 forms a rearmost limit of the dust extractor 100 such that the dust extractor can roll on a surface by the rear wheels 195 and the top wheel 185 when in a tilted position.

[0045] Note that the inlet 160 on the example dust extractors 100 in Figure 1 D and Figure 1 E extends out laterally from the dust extractor 100, i.e., towards the side. This arrangement of the inlet 160 has been shown to be more efficient in some operating scenarios. It, for instance, allows better access to the dust container since the hose extends out towards the side of the dust extractor 100. The inlet 160 in this example extends in a direction parallel to the wheel axis of the rear wheels 195 of the dust extractor 100.

[0046] To summarize, there is disclosed a dust extractor 100 comprising at least one cyclone tank 110, a prefilter arrangement 120, an essential filter arrangement 130, and a blower system 140, where an inlet 160 of the dust extractor arranged to receive a suction hose forms an opening into the cyclone tank 1 10. The dust extractor 100 is arranged to be supported on a ground surface 101 by rear wheels 195 associated with a real wheel axis, where the inlet 160 faces in an inlet angle which is within 30 degrees of the real wheel axis, and preferably aligned with the rear wheel axis. In other words, the inlet extends in a lateral direction of the dust extractor, transversal to a longitudinal direction of the dust extractor defined as perpendicular to the rear wheel axis or as horizontally aligned with a wheel plane of the rear wheels.

[0047] It is appreciated that the features related to the frame structure 180, 181 , 182 of the dust extractors described herein are not inextricably linked to any of the other features of the example dust extractors described herein. The frame structure and the wheel brake arrangements can be used independently of the other features discussed herein, without modification or with minimal modifications.

[0048] A wheel brake 190 is arranged in connection to the rear wheels 195 of the dust extractor 100. This wheel brake 190 prevents the rear wheels from moving when in its locked position, thereby immobilizing the dust extractor 100. According to a preferred embodiment, the wheel brake mechanism implements an auto-latch function, whereby the wheel brake engages the wheel in locking position in response to a vertical impact force acting on the dust extractor 100. This auto-latch function of the wheel brake 190 is particularly useful when the dust extractor is lowered from an elevated platform such as a loading bay or a trailer. The operator can then use the rear part 180 of the frame structure to slide the dust extractor along the edge of the elevated platform, as illustrated in Figure 1 C. Once the rear wheels 190 hit the ground surface, an impact force is generated which triggers the auto-latch function of the wheel brake 190, thereby automatically immobilizing the dust extractor on the ground surface below the elevated platform such that the operator can climb down from the elevated platform and continue handling the dust extractor 100 in a safe manner. An auto-latching brake of the type discussed herein can be implemented by adding a weight on a lever, where the weight is calibrated to the expected impact force. The downwards directed impulse force when the dust extractor rear wheels hit the ground will urge this weight downwards, manipulating the lever, and thereby engaging the wheel brakes, thus engaging the brake. The auto-latch function is preferably triggered by gravity, i.e., it is gravity-based. It is appreciated that there are several ways in which this type of gravity-triggered auto-latch function can be realized. Thus, as the dust extractor hits the ground, the inertia of a wheel brake components causes the brake to automatically engage. The operator can then disengage the wheel brake when he or she has climbed down from the elevated platform.

[0049] A prefilter 120 is arranged in the cyclone tank 1 10 after the inlet 160, i.e., downstream with respect to the airflow direction. The example prefilter 120 in Figure 1 B is a split filter, i.e., a prefilter divided into two filter sections. Each filter section has a respective suction valve 125 which draws air from the cyclone tank 1 10, through the filter media, and onwards to the blower system 140 of the dust extractor 100. This type of split filter arrangement was described in detail in Swedish patent application no. SE2250866-7 and will therefore not be discussed in more detail herein.

[0050] The dust extractor 100 comprises a lid which is closed in Figure 1A and open in Figure 1 B to expose the prefilter 120 located inside the cyclone tank 1 10. The lid comprises a valve arrangement that was described in detail in SE2250866-7. The air flow entering the dust extractor via the inlet 160 first passes through the cyclone tank 110, then through the prefilter 120, and onwards through air conduits formed in the lid. There are two air flows through the lid in Figures 1 A-E. Each such air flow passes a respective essential filter 130 located in the volume behind the cyclone tank 1 10. The air flows through the two essential filters then enter into the blower system 140 which will be discussed in more detail below.

[0051] One or more finer air filters 130 may be arranged downstream from the prefilter 120. Such an air filter 130 may, e.g., be a High-Efficiency Particulate Air (HEPA) filter, but other air filters may also be used. HEPA, also known as high- efficiency particulate absorbing and high-efficiency particulate arrestance, is an efficiency standard of air filters. Filters meeting the HEPA standard must satisfy certain levels of efficiency. It is noted that the techniques disclosed herein can be applied to dust extractors with any number of air filters, including dust extractors comprising combinations of different air filters. The essential filter is normally a finer filter compared to the prefilter, i.e., it captures smaller dust particles.

[0052] Generally, downstream refers to a relative location along the air flow, while upstream is a relative location in direction against the air flow. Thus, the blower system 140 is located downstream from the inlet 160, while the inlet 160 is located upstream from, e.g., the cyclone tank 1 10.

[0053] The dust extractor 100 is powered by a blower system 140. An example of the blower system 140 will be discussed in more detail below in connection to Figures 2A-B. The blower system 140 comprises a fan and motor assembly which is located downstream from the cyclone tank 1 10 and the one or more filters 120, 130. The blower system 140 generates a suction force which draws the particle-laden airflow in through the inlet 160 and via the cyclone tank 1 10, through any filters along the air flow path, before it is released from the dust extractor as filtered air. Heavy-duty dust extractors of the kind illustrated in Figures 1A-E require a substantial air flow in order to efficiently extract the often heavy dust that is generated by cutting, drilling, grinding and / or demolishing concrete, brick, and other hard construction materials at a construction site. A high air flow is also necessary to create the vortex inside the cyclone tank 1 10 which is necessary to obtain the desired function of separating dust and debris from the particle laden airflow entering the inlet 160. The air flow magnitude requirement on many portable heavy-duty dust extractors may be as high as 500 m3 / h (cubic meters per hour) and even as high as 700 m3 / h in some examples. The example dust extractor 100 in Figures 1A-E comprises a blower system with two motors connected to respective fans, used to generate two separate air flows. The single intake air flow through the inlet 160 is divided into two air flows by the split prefilter 120 and the dual suction valves 125. This dual air flow configuration allows for a blower system with two smaller electrical motors that together generate the required air flow, instead of one larger motor. It is appreciated that two separate prefilter units can be used instead of the split prefilter in the prefilter arrangement 120. In this case each suction valve 125 opens up into a respective prefilter unit. The prefilter units may, e.g., be formed as cylindrical prefilters, or as cone shaped prefilters.

[0054] The dust extractor 100 also comprises a control unit 150, schematically shown in Figure 1 . The control unit 150 is configured to control various operations of the dust extractor such as activating the motor of the blower system 140 to drive the fan of the blower system 140. The control unit 150 may also control the state of valves in the dust extractor, e.g., by activating currents in solenoid coils or by controlling other types of actuators such as servos. An example realization of this control unit will be discussed in more detail below in connection to Figure 8.

[0055] According to some aspects, the dust extractor 100 comprises a status indicator light 170 arranged to emit a plurality of different and selectable colors of light. This means that the light source is configured to emit light in more than one color, such as red, green, and orange. The selected light to be emitted is determined by a control signal from, e.g., the control unit 150. The control unit 150 is configured to activate the status light in a first color, such as a green or white color, in case the blower system 140 is activated. The control unit 150 is also configured to activate the status light in a second color, such as an orange color, in case a magnitude of the air flow does not satisfy an acceptance criterion. This way an operator can verify visually that the dust extractor is active, and that the dust extraction capability of the dust extractor is sufficient for the work task. It is an advantage that the same light source is used to indicate that the dust extractor is active and also to indicate that air flow is sufficient. It is particularly advantageous to combine the status light 170 with the brushless motor blower systems discussed herein, since these drive units are relatively quiet when active. It may be difficult for an operator to hear if the dust extractor 100 is active at a work site since it often does not make enough noise to be heard over the other sounds at the work site. The status light activated in the first color, such as a green or white color, ensures that personnel at the work site knows that the dust extractor is operational. There is preferably one status light on each side of the dust extractor 100, to ensure visibility from all sides. Note also that the status light 170 protrudes slightly from the dust extractor body, to ensure that it can be seen also from the front and rear of the dust extractor 100. A flow sensor and / or a pressure sensor can be used to detect when insufficient air flow is being generated. The control unit 150 controls the status indicator light 170 to emit light of the second color in case insufficient air flow is detected.

[0056] According to some aspects, the control unit 150 is configured to activate the status light in a third color, such as a red color, in case the control unit has detected malfunction in the dust extractor 100. A malfunction condition may, e.g., be a loss of power, insufficient electrical power in terms of voltage and / or current, overheating of the blower drive system, and so on.

[0057] Most high airflow dust extractors use side channel blowers to generate the required air flow on the order of 500 m3 / h, and preferably 700 m3 / h or more. A side channel blower is based on a heavy fan wheel which is rotated by an electric motor or by a combustion engine. Once the heavy fan wheel is brought up to speed it takes a long time to stop it, and also to change the rotation speed of the fan wheel due to its inertia. This inertia makes it difficult to quickly change fan speed to control air flow level. The heavy fan wheel and motor combination also makes the dust extractor heavy and therefore difficult to manually transport at a work site. At least some of these issues are alleviated in the dust extractors described herein, which comprise much lighter blower systems based on brushless electric motors arranged to drive lightweight impeller systems.

[0058] The present disclosure relates to dust extractors 100 that comprise at least one cyclone tank 110, a prefilter arrangement 120, an essential filter arrangement 130, a blower system 140 arranged to generate an air flow, and a control unit 150. To operate with satisfactory performance, it is desired to generate an air flow through the dust extractor system of at least 500 m3 / h, and preferable at least 700 m3 / h.

[0059] Due at least in part to the efficient blower system of the dust extractors disclosed herein, the dust extractor can have a total weight less than 200 kg, and preferably less than 150 kg, and more preferably about 100 kg. The total weight is measured in kg and includes the hardware of the dust extractor 100, but excludes dust accumulated in the dust extractor cyclone tank and dust container. This means that the dust extractor has a very small weight to flow ratio, i.e., that it generates a high magnitude flow in comparison to its weight. The dust extractors described herein can have a weight to flow ratio measured in kg / m3 / h (kilograms per cubic meter per hour) below 0,5, and preferably below 0,25. For instance, the example dust extractor 100 illustrated in Figures 1 A-E can have a weight of about 100 kg or less, and generate a flow of about 700 m3 / h, which gives a weight to flow ratio of less than 100 / 700, which is about 0,15 kg / m3 / h.

[0060] The dust extractors described herein can also be made spatially compact, due to the blower system and the efficient dust handling functions of the dust extractor. The dust extractor 100 may, e.g., have a ground surface footprint of at most one square meter. A ground surface footprint is a measure of the ground surface area occupied by the dust extractor. The footprint of the dust extractors described herein may be configured smaller than a rectangle of 1 ,2m by 0,8m, which means that the dust extractor does not occupy more ground surface area than a rectangle of 1 ,2m by 0,8m.

[0061] A bounding box enclosing the dust extractors described herein may have dimensions 650mm by 1500mm by 900mm.

[0062] The dust extractor 100 can have a total height, measured along a vertical direction V from a ground surface supporting the dust extractor to the vertical distalmost point of the dust extractor, of at most 2,0m, and preferably about 1 ,5m.

[0063] With reference to the example in Figures 2A-B, the blower system 140 comprises at least one centrifugal fan 210 driven by a respective brushless electric motor 220. The electric motor may, e.g., be a so-called brushless (BL) direct current (DC) motor, known as a BLDC motor. Not all details of the electric motor are shown in Figure 2A and in Figure 2B. A BLDC motor is also known as an electronically commutated motor. It is a synchronous motor using a DC electric power supply. It uses an electronic controller to switch DC currents to the motor windings producing magnetic fields that effectively rotate in space and which the permanent magnet rotor follows. The controller adjusts the phase and amplitude of the current pulses that control the speed and torque of the motor. It is an improvement on the mechanical commutator (brushes) used in many conventional electric motors. Brushless electric motors are generally known and therefore require no detailed description. The example centrifugal fan 210 in Figures 2A-B comprises two axially aligned impellers 250, 255 serially arranged in direction of the air flow. The air flow enters the fan 210 via the working air inlet, in the fan axle extension direction, which is also the motor axle extension direction. The first impeller 250 accelerates the air flow and pushes it radially outwards. The air flow is then pushed downwards along the rim of the first impeller into the intermediate space 251 between the two impellers 250, 255. The air flow moves radially inwards through the intermediate space 251 where it enters into engagement with the second impeller 255 such that it is once more pushed radially outwards. The air flow finally exits the fan 210 via the working air outlet. The two serially arranged impellers together generate a suction air flow in through the working air inlet 230 which air flow is then pushed out from the working air outlet 240.

[0064] Figure 3 schematically illustrates a centrifugal fan arrangement 210 driven by a brushless motor 220, such as a BLDC motor.

[0065] The centrifugal fan 210 comprises a working air inlet 230 in fluid communication with a clean side of the essential filter arrangement 130 of the dust extractor 100. The working air inlet 230 extends along an axis of rotation A of the centrifugal fan 210 and in axial alignment with a motor axle 225 of brushless electric motor 220. This means that the air flow from the cyclone tank 1 10 enters the centrifugal fan 210 from above in a direction essentially parallel with the rotation axis of the centrifugal fan and also essentially parallel with the motor axle 225, thereby providing a spatially efficient design. A working air outlet 240 of the centrifugal fan 210, i.e., it’s exhaust, extends radially outwards from the centrifugal fan 210.

[0066] The suction air flow enters the fan from above and is brought into rotation by a first impeller 250 which forces the air flow radially outwards. The air flow is then guided downwards and radially inwards to the second impeller 255, where it is once more brought into rotation before the air flow leaves the fan via a radial exhaust aperture forming the working air outlet 240 of the centrifugal fan 210.

[0067] This type of blower system is both compact and of relatively light weight. Yet, it meets the rather strict requirements on air flow in a heavy-duty dust extractor. The weight of an impeller 250, 255 of the centrifugal fan 210 is preferably below 2kg and more preferably below 1 kg, and even more preferably below 0,5kg. This is a significantly lighter fan compared to the commonly used side blower systems. The blower system 140 is, according to preferred aspects, dimensioned to generate an air flow of at least 500 m3 / h and preferably at least 700 m3 / h. The lightweight impeller system allows the control unit 150 to quickly change the rotation speed of the impellers in order to regulate the air flow to a desired target level. This allows the dust extractor to maintain a constant air flow, as will be discussed in more detail below in connection to Figure 6 and Figure 7.

[0068] According to a preferred embodiment, the blower system 140 comprises at least two brushless electric motors 220 arranged to drive respective centrifugal fans 210, where each centrifugal fan is in fluid communication with a respective essential filter of the essential filter arrangement 130. An example of this type of dual-fan blower system 140, with dual working air inlets 230 and dual working air outlets 240, is illustrated in Figure 4.

[0069] At least some of the dust extractors discussed herein comprise two or more brushless electric motors 220, where each machine generates a part of the air flow through the cyclone tank 1 10. According to an example, the blower system 140 comprises two BLDC electric motors arranged to drive respective centrifugal impeller arrangements. Each such impeller arrangement draws an air flow through a respective essential filter. The two essential filters are in fluid communication with respective suction valves 125 that open up in respective parts of the split filter 120. In this way two independent flow paths for the air flow are created, which is an advantage. In other words, there is disclosed herein a dust extractor 100 comprising at least one cyclone tank 1 10, a prefilter arrangement 120, an essential filter arrangement 130, and a blower system 140, where the blower system 140 comprises at least two electric motors 220 arranged to drive respective fan arrangements 210, where each fan arrangement 210 is in fluid communication with a respective essential filter of the essential filter arrangement 130, where each essential filter is in fluid communication with a respective suction valve 125 that opens up into a separate section of the prefilter arrangement 120. The prefilter arrangement 120 is a split filter with separate filter compartments as illustrated in Figure 1 B. Each such compartment has a separate suction valve which opens up into the compartment. Separate suction conduits are then formed from the suction valves 125 all the way to the blower system. Thus, there is a one-to-one mapping between drive motors and prefilter sections, with independent suction conduits there inbetween that pass respective essential filters off the essential filter arrangement 130.

[0070] With reference to Figures 2A-B, each brushless electric motor 220 of the blower system 140 may comprise a cooling air inlet 260 that is axially aligned with the motor axle 225, where the cooling air inlet 260 and the working air inlet 230 are arranged on opposite sides of the blower system 140. Thus, the electric motor draws in a separate cooling air flow 261 (indicated by a dashed line in Figure 2A) from the bottom of the motor and fan assembly (in its normal operating position). This flow of cooling air passes through the electric motor and exits radially through a cooling air exhaust port of the electric motor. The electric motor may comprise internal cooling flanges 270, as shown in Figure 2A, to promote heat transfer from the electric motor to the flow of cooling air passing the electric motor. It is an advantage that the motor uses a separate flow of air for cooling, since the working air flow F of the dust extractor may be blocked occasionally and may also carry residual dust particles that can accumulate inside the electric motor and cause malfunction.

[0071] With reference to Figure 4, the blower system 140 may be supported by and at least partially embedded in a foam material body 410. The foam material body 410 is preferably formed in a thermoplastic polymeric foam material, such as polypropylene or polystyrene. This foam material body supports the blower system 140 in fixed relation relative to the rest of the dust extractor 100, and at the same time provides noise isolation and noise absorption, thereby providing a dust extractor which operates at low noise. The foam material body 410 has a shape which fills the internal space of the dust extractor 100 at the location of the blower system 140 to reduce the noise that is generated by the electric motors in use. The foam material body encloses at least part of the electric motors 220 to hold the machines fixedly in position.

[0072] It is appreciated that the foam material body 410 described herein can be adapted for single motor blower systems, and also to blower systems comprising more than two electric motors and / or more than two centrifugal fan arrangements.

[0073] Tubular members 450, e.g., reinforced suction hoses, provide interfaces between the blower system 140 and the essential filters 130 of the dust extractor 100. The tubular members guide the air flow into the centrifugal fans 210 of the blower system 140, as exemplified in Figure 4.

[0074] The foam material body 410 is also used to define air channels to and from the blower system, in particular for the cooling air flows 261 of the brushless electric motors of the blower system 140. These air channels in the foam material body 410 is created as hollow passages leading through the foam material body 410. The foam material body 410 may for instance comprise at least one exhaust air channel 440 that extends between the working air outlet 240 of the centrifugal fan 210 and an exhaust port of the foam material body 410. T ubular members 460 can be used to guide the exhaust air flow from the blower system 140 to an outlet port of the dust extractor, as exemplified in Figure 4.

[0075] The foam material body 410 preferably comprises at least a first cooling air channel 420 that extends between an ambient inlet port 430 of the foam material body 410 and a cooling air inlet 260 of the blower system 140. This air channel allows the blower system 140 to draw in cool air from the ambient environment to cool the brushless electric motors of the blower system 140. The at least one cooling air channel 420 and / or the at least one exhaust air channel 440 are at least partly delimited by the foam material body, which means that the foam material makes up at least some of the inner surfaces of the air channel or channels, as exemplified in Figure 4. The foam material can make up the entire channel inner surface, forming all delimiting walls of the channel, or just some of the inner surfaces of the air channel, such as a lower surface and walls, but not the top surface, which can be formed by a lid or the like that allows access to the channel by a service technician.

[0076] The foam material body 410 preferably also comprises at least a second cooling air channel 425 that extends between a cooling air outlet 265 of the blower system 140 and an ambient outlet port 435 of the foam material body 410.

[0077] The brushless electric motor 220 in the blower system 140 can be configured to operate at least in part on a three-phase (3ph) electric feed of the dust extractor 100. This is a preferred way of providing electrical feed to the blower system 140. However, sometimes a suitable 3ph electrical feed is not available at the construction site where the dust extractor operates. The electrical mains connection at the work site can also be unstable in terms of voltage and / or frequency, and it may sometimes be fused at an insufficient current rating. In this case a hybrid electrical system can be used, which employs a combination of an auxiliary power source such as a battery pack and an electrical mains connection to power the blower system 140 and the other functions on the dust extractor 100. Thus, according to some aspects, the brushless electric motor 220 is configured to operate at least in part on an electric feed from a battery pack of the dust extractor 100. In some cases, the dust extractor can be configured to operate on electrical mains only, on a combination of electrical mains and battery power, or only on battery power. The selection of power source can be made by an operator of the machine using, e.g., a humanmachine interface, or automatically by the control unit 150, as will be discussed in more detail below. The control unit 150 can for instance be configured to control the power outtake from an electrical mains connection and the power outtake from a battery system of the dust extractor 100 in dependence of a power configuration made, e.g., by an operator of the machine.

[0078] Figure 5A schematically illustrates a power system 500 for a heavy-duty dust extractor 100 that is based on a direct current (DC) bus architecture. The power system 500 in Figure 5A comprises a rectifier or AC / DC module 510 which transforms alternating current (AC) from electrical mains 515 into DC that is fed onto a DC bus 520. A brushless electric motor 220, such as a BLDC motor, draws DC power from the DC bus via a first optional DC / DC module 525. To complement the power drawn from electrical mains 515, an auxiliary power source 530, such as a battery pack, is connected to the same DC bus 520 via a second DC / DC module 540. The control unit 150 controls both the AC / DC module 510 and the second DC / DC module 540 to balance the power outtakes from the two energy sources of the power system 500. The auxiliary energy source may provide electrical power to the DC bus during a discharge operation of the auxiliary energy source 530, and most auxiliary energy sources, such as batteries, can also be charged from the DC bus in case excess power from electrical mains is available. The control unit 150 controls the magnitude of the discharge current from the auxiliary power source 530 and also the magnitude of the charge current to the auxiliary energy source 530. An AC motor can also be powered from the DC bus 520 via an inverter or DC / AC module.

[0079] Note that the DC electrical fan motors in Figures 5A and 5B are just examples. Any electrical motor can be connected to a DC bus or an AC bus, as long as a suitable motor drive stage is used.

[0080] The control of the discharge current and charge current to the auxiliary energy source 530 can be performed based on data from a power sensor 155 and / or based on a sensed state of the DC or AC bus, such as a voltage level of the bus or a phase stability of the AC bus, or a frequency of the AC bus. The control unit can sense the state of the bus 150 using a voltage sensor 156 or a power sensor similar to the power sensor 155. The control unit may, e.g., be configured to maintain an electrical mains power consumption below a given threshold, or such as to satisfy one or more current consumption acceptance criteria, e.g., to stay below a rated current of the electrical mains connection. The control unit 150 of the dust extractor can be arranged to control a power transfer between the auxiliary energy source 530 and the blower system 140, in dependence of a power configuration of the dust extractor 100. The power configuration may comprise, e.g., a rated current of the electrical mains connection that is not to be exceeded (at least for more than some time period), a number of available phases from electrical mains, or a battery only operation in case an electrical mains connection is not available.

[0081] This power sensor can also be arranged to monitor frequency and / or voltage characteristics of an AC from electrical mains, such as a 3ph electrical mains. In this case the control unit 150 can be configured to detect a time variation in frequency and / or voltage of the AC based on an output signal from the power sensor 155, and to trigger one or more automated actions in response to detecting a time variation in frequency and / or voltage which fails to meet a power stability criterion. In other words, the control unit can be configured to monitor the output signal from the power sensor 155, which can be a voltage value as function of time, and / or a frequency value for one or more phases of the incoming AC, and check if the AC characteristics are as expected. If they are not, i.e., if there is a voltage deviation or a frequency instability on one or more phases, then an automated action is triggered. The control unit 150 can also use the power sensor 155 to detect phase unbalance between two or more phases in the incoming AC, and to draw power from the auxiliary energy source 530 to balance the electrical feed to the DC bus 520.

[0082] The power sensor 155 preferably comprises a frequency sensor of some sort that measures the frequency of one or more phases of the incoming AC from electrical mains. The frequency sensor may comprise, e.g., a digital frequency meter configured to directly measure the frequency of the AC power, a frequency-to-voltage converter arranged to convert the frequency of the AC power into a proportional voltage, or a phase-locked loop (PLL) that lock onto the frequency of the incoming AC and provides an output signal proportional to the frequency. The power sensor 155 may be implemented as a separate component and the output signal of the power sensor 155 can then be fed to the control unit 150 for further processing. The power sensor 155 can also be integrally formed with the control unit 150, i.e., comprised in the same physical unit as the processing circuitry of the control unit 150. The power sensor determines frequency characteristics of the AC over the power interface, which is to be construed broadly to mean that the power sensor at least provides some form of data from which frequency can be inferred or determined. It is appreciated that the power sensor does not have to be configured to perform any advanced processing of the measured data.

[0083] The power sensor 150 preferably also comprises a voltage sensor that measures the amplitude characteristics of one or more phases of the incoming AC. Voltage sensors are generally known and will therefore not be discussed in more detail herein.

[0084] Figure 5B shows a similar power system 550, but this system is instead based on an AC bus architecture, where an example DC motor 220 is powered by an AC / DC module 590. An AC motor can of course also be used here. The electrical mains interface 515 is connected to the AC bus 570 via an AC / AC module 560 and the auxiliary power source 530 is connected to the same AC bus 570 via a DC / AC module 580. The control unit 150 controls the power outtake from electrical mains 515 and from the auxiliary power source 530 based, e.g., on input from the power sensor 155, or based on manual configuration of the power system 550. An AC motor can also be powered from the AC bus 570.

[0085] According to some aspects, the drive motor arrangement of the blower system 140 generates a separate cooling air flow 261 for cooling the drive motor or motors. The cooling air flow 261 is separate from the working air flow used for dust extraction. This cooling air flow 261 can be used to also cool the auxiliary energy source 530. It is an advantage to use a separate cooling air flow for cooling the auxiliary energy source, since this air flow will not be restricted by actions related to the dust extraction, i.e., if the inlet 160 is blocked, or if a filter is clogged. This technical feature is not inextricably linked to any of the other features disclosed herein but can be practiced separately from the other features. In other words, there is disclosed herein a dust extractor 100 that comprises at least one cyclone tank 1 10, a prefilter arrangement 120, an essential filter arrangement 130, and a blower system 140. The blower system 140 comprises at least one electric motor 220 arranged to drive a fan arrangement 210 of the blower system. The dust extractor 100 comprises an auxiliary energy source 530 arranged to at least partly power the blower system 140 as part of a hybrid electric power system of the dust extractor 100, where at least one electric motor 220 of the blower system 140 is arranged to generate a cooling air flow 261 separate from the air flow used for dust extraction, where the cooling air flow 261 is arranged to be guided past the electric motor 220 and past the auxiliary energy source 530 to transport heat away from the electric motor 220 and from the auxiliary energy source. The cooling air flow may be guided from a fan on the electric motor, past the electric motor, and via a conduit to the auxiliary energy source 530, such as via a hose of an air channel. The air channel from the electric motor to the auxiliary energy source may be at least partly formed by the foam material body 410.

[0086] According to some aspects, the control unit 150 is configured to activate enhanced cooling of the auxiliary energy source by blocking the working air flow F used for dust extraction. This can be achieved, e.g., by closing one or more suction valves 125, or by actuating some other valve arranged between the inlet 160 and the working air inlet 230 of the blower system 140. When the working air flow F is blocked the fan encounters very small resistance, which means that the motor speed increases, this increasing the separate cooling air flow generated by the drive motor of the blower system 140. The control unit 150 may obtain temperature data from one or more temperature sensors arranged in connection to the auxiliary energy source and activate the enhanced cooling of the auxiliary energy source in case the temperature of the auxiliary energy source fails to satisfy a predetermined temperature criterion.

[0087] Figure 6 schematically illustrates an example fan and motor assembly 600 comprising the control unit 150. The control unit is here configured to control a blower system 140 which draws the particle-laden airflow 620 through the different filtering stages of the dust extractor 100, i.e., the cyclone tank 110 and the filter 120, 130. A sensor device 610 is arranged in connection to the airflow where it is configured to obtain sensor data 615 related to the airflow 620, such as, e.g., a pressure level in kPa under atmospheric pressure (sometimes referred to as vacuum level) and / or an air flow level (often measured in m3 / h). The more clogged the air filters 120, 130 on the dust extractor become, the higher the resistance encountered by the motor when drawing air through the air filters become. However, the load on the fan motor 220 actually reduces as the resistance for drawing air through the air filters increases. In other words, the harder it gets to draw air through the air filters 120, 130, the easier it becomes for the motor to turn the fan. This is because, as the vacuum level increases downstream from the air filters, the fan blades rotate more easily due to the reduced air pressure. In fact, in complete vacuum, the fan blades would not encounter any friction or resistance from air whatsoever.

[0088] This means that a normal fan motor draws the most power when the air filters 120, 130 are clean and airflow is large, i.e., when the dust extractor is operating in a high airflow operating range where the least suction force is needed.

[0089] This also means that a normal fan motor draws the least amount of power when the air filters are totally clogged, i.e., when the dust extractor is operating outside of the high airflow operating range where the most suction force is actually needed.

[0090] In light of this realization, it is proposed herein to detect when the dust extractor 100 is operating in the high airflow operating range and to reduce the airflow when the dust extractor is operating in the high airflow operating range, i.e., when the air filters 120, 130 are not overly clogged. This reduction in airflow will reduce requirements on motor starting current and allow for a more optimized overall operation of the dust extractor 100.

[0091] The sensor device 610 for obtaining the sensor data 615 related to the airflow into the dust extractor 100 may, e.g., comprise a pressure sensor, such as a pitot pipe arrangement, to determine a level of under-pressure or a vacuum level associated with the airflow 620. An air flow sensor may also be used to determine a level of air flow, in terms of, e.g., m3 / h, associated with the airflow into the dust extractor 100. Sensor data 615 related to the airflow into the dust extractor 100 may also be indirectly obtained from various correlated information sources, such as the amount of electrical current drawn by the fan motor 220. When the fan motor 220 operates under high load it draws more current than when the air filter gets clogged and the motor load decreases. In general, the higher the torque of the motor axle, the more current the motor draws.

[0092] The location of the sensor 610 along the airflow 620 depends on the type of device. A pressure sensor arranged to determine a level of under-pressure is preferably arranged somewhere between the fan and the air filters, where the under-pressure builds. However, under-pressure can also be measured at other locations in the airflow 620. An airflow sensor can be arranged at various places along the airflow. A plurality of airflow sensors may provide more refined sensor data 615. A sensor arranged to determine the amount of current drawn by the motor is necessarily arranged in connection to a power supply of the motor.

[0093] Herein, an under-pressure value indicates how far below a reference pressure level, such as atmospheric pressure, the pressure in the airflow is. Underpressure is also sometimes referred to as vacuum level.

[0094] Airflow can be measured in a number of different ways. For instance, airflow can be measured in terms of the volume of air in m3 (at some reference pressure) which passes some point in the system per unit of time, such as an hour h.

[0095] The herein disclosed techniques are not dependent on the exact definition of any of under-pressure or airflow, the skilled person is able to adjust the disclosed methods to work with most definitions and reference values.

[0096] Figure 7 shows a graph 700 of under-pressure (in kPa) vs airflow (in m3 / h) that illustrates some of the techniques proposed herein. The airflow in the graph is the airflow 620 that is also indicated in Figure 6, i.e., the air flow through the dust extractor system. The pressure in kPa decreases to the right, and the airflow magnitude increases upwards in the graph 700. An increased underpressure means that the air pressure has dropped. A dust extractor 100 with a fresh unclogged air filter will be able to generate airflow in a high airflow value range 710 starting at a peak airflow level 720. The maximum obtainable flow level 730 then decreases as the air filter becomes more and more loaded with particulate matter, eventually entering a low airflow value range 740. As the airflow reduces, the underpressure increases from a low underpressure value range 750 to a high underpressure value range 760. This is because the resistance in sucking air through the air filters increases which resistance builds the underpressure.

[0097] Detecting if the dust extractor is operating in the high airflow operating range can be performed by comparing a current airflow to some threshold value or to a range of airflow values, e.g., by using the sensor 610. Detecting if the dust extractor is operating in the high airflow operating range can also be performed by comparing a current under-pressure to some threshold value or to a range of under-pressure values.

[0098] The dust extractors described herein can be configured to reduce the airflow 620 to a reduced flow level 770 below the obtainable flow level 730 when the dust extractor is operating in the high airflow operating range 710, e.g., so as to maintain an essentially constant air flow over the low underpressure value range 750. As noted above, when the air filters are not overly laden with particulate matter, it is relatively easy to generate an airflow through the dust extractor system. The reduced flow level 770 is configured at a level where a sufficient suction power is generated. This way the dust extractor maintains acceptable performance, while conserving energy and not generating excessive noise, which is an advantage. The blower systems 140 disclosed herein are particularly suitable for this type of dynamic flow regulation since the impellers are lightweight and therefore easy to control in terms of rotation speed.

[0099] To summarize, according to some aspects the control unit 150 is arranged to control a rotation speed of the at least one centrifugal fan 210 based on a target air flow magnitude, such as the reduced air flow level 770. This way a constant air flow can be maintained, which is an advantage.

[0100] Figure 8 schematically illustrates, in terms of a number of functional units, the general components of a control unit 150. Processing circuitry 810 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 830. The processing circuitry 810 may further be provided as at least one application specific integrated circuit ASIC, or field programmable gate array FPGA.

[0101] Particularly, the processing circuitry 810 is configured to cause the control unit 150 to perform a set of operations, or steps, such as the methods discussed herein. For example, the storage medium 830 may store the set of operations, and the processing circuitry 810 may be configured to retrieve the set of operations from the storage medium 830 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 810 is thereby arranged to execute methods as herein disclosed.

[0102] The storage medium 830 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.

[0103] The control unit 150 may further comprise an interface 820 for communications with at least one external device. As such the interface 820 may comprise one or more transmitters and receivers, comprising analogue and digital components and a suitable number of ports for wireline or wireless communication.

[0104] The processing circuitry 810 controls the general operation of the control unit 150, e.g., by sending data and control signals to the interface 820 and the storage medium 830, by receiving data and reports from the interface 820, and by retrieving data and instructions from the storage medium 830.

[0105] The present disclosure also relates to various forms of computer readable media carrying respective computer programs comprising program code means for performing methods and / or for executing the various functions discussed above, when said program product is run on a computer. The computer readable medium and the code means may together form a computer program product.

Claims

CLAIMS1. A dust extractor (100) comprising at least one cyclone tank (1 10), a prefilter arrangement (120), an essential filter arrangement (130), a blower system (140) arranged to generate an air flow (F), and a control unit (150), the blower system (140) comprising at least two brushless electric motors (220) arranged to drive respective centrifugal fans (210), where each centrifugal fan (210) is in fluid communication with a respective essential filter of the essential filter arrangement (130), each centrifugal fan (210) comprising a working air inlet (230) in fluid communication with a clean side of the essential filter arrangement (130), where the working air inlet (230) of each centrifugal fan is arranged in connection to a radial center of the centrifugal fan (210), where a working air outlet (240) of the centrifugal fan (210) extends radially outwards from the centrifugal fan (210).

2. The dust extractor (100) according to claim 1 , where a weight of an impeller (250, 255) of the centrifugal fan (210) is below 2kg and preferably below 1 kg, and more preferably below 0,5kg.

3. The dust extractor (100) according to claim 1 or 2, where the blower system (140) is dimensioned to generate an air flow (F) having a magnitude of at least 500 m3 / h and preferably at least 700 m3 / h.

4. The dust extractor (100) according to any previous claim, having a total weight less than 200 kg, and preferably less than 150 kg, and more preferably less than 100 kg.

5. The dust extractor (100) according to any previous claim, having a weight to flow ratio in kg / m3 / h below 0,5, and preferably below 0,25.

6. The dust extractor (100) according to any previous claim, having a ground surface footprint of at most 1 ,0 m2.

7. The dust extractor (100) according to any previous claim, having a total height measured along a vertical direction from a ground surface supporting the dust extractor to the vertical distalmost point of at most 2,0 m.

8. The dust extractor (100) according to any previous claim, where the control unit (150) is arranged to control a rotation speed of the at least one centrifugal fan (210) based on a target air flow magnitude.

9. The dust extractor (100) according to any previous claim, where the centrifugal fan (210) comprises at least two axially aligned impellers (250, 255), where the at least two axially aligned impellers (250, 255) are arranged in series to generate the air flow (F).

10. The dust extractor (100) according to any previous claim, where the brushless electric motor (220) is a brushless direct current, BLDC, motor.

11. The dust extractor (100) according to any previous claim, where the brushless electric motor (220) is configured to operate at least in part on a three-phase, 3ph, electric feed of the dust extractor (100).

12. The dust extractor (100) according to any previous claim, where the brushless electric motor (220) is configured to operate at least in part on an electric feed from an auxiliary energy source (530) of the dust extractor (100), such as a battery pack or a capacitor arrangement.

13. The dust extractor (100) according to any previous claim, where the control unit (150) is configured to control the power outtake from an electrical mains connection (515) of the dust extractor (100) and the power outtake from an auxiliary energy source (530) of the dust extractor (100) in dependence of a power configuration of the dust extractor (100).

14. The dust extractor (100) according to claim 13, where the power configuration of the dust extractor (100) comprises a limit on instantaneous power consumption from electrical mains and / or a limit on an average current drawn from electrical mains over a time window.

15. The dust extractor (100) according to any previous claim, where each brushless electric motor (220) of the blower system (140) comprises a coolingair inlet (260) axially aligned with the motor axle (225), where the cooling air inlet (260) and the working air inlet (230) are arranged on opposite sides of the blower system (140).

16. The dust extractor (100) according to any previous claim, where the blower system (140) is supported by and at least partially embedded in a foam material body (410), where at least one air channel extends through the foam material body to the blower system (140).

17. The dust extractor (100) according to claim 16, where the foam material body (410) is formed in a thermoplastic polymeric foam material, such as polypropylene or polystyrene.

18. The dust extractor (100) according to claim 16 or 17, where the foam material body (410) comprises at least one cooling air channel (420) which is at least partly delimited by the foam material body, where the at least one cooling air channel (420) extends between an ambient inlet port (430) of the foam material body (410) and a cooling air inlet (260) of the blower system (140).

19. The dust extractor (100) according to any of claims 16-18, where the foam material body (410) comprises at least one exhaust air channel (440) at least partly delimited by the foam material body, where the at least one exhaust air channel (440) extends between a working air outlet (240) of the centrifugal fan (210) and an exhaust port of the foam material body (410).

20. The dust extractor (100) according to any previous claim, comprising a status indicator light (170) arranged to emit a plurality of different and selectable colors of light, where the control unit (150) is configured to activate the status light in a first color, such as a green or a white color, in case the blower system (140) is activated and generates the air flow (F), and where the control unit (150) is configured to activate the status light in a second color, such as an orange color, in case a magnitude of the air flow (F) does not satisfy an acceptance criterion.21 . The dust extractor (100) according to claim 20, where the control unit (150) is configured to activate the status light in a third color, such as a red color, in case the control unit has detected malfunction in the dust extractor (100).

22. The dust extractor (100) according to any previous claim, comprising an auxiliary energy source (530) arranged to at least partly power the blower system (140) as part of a hybrid electric power system of the dust extractor (100), where at least one brushless electric motor (220) of the blower system is arranged to generate a cooling air flow (261 ) separate from the air flow (F) used for dust extraction, where the cooling air flow (261 ) is arranged to be guided past the electric motor (220) and past the auxiliary energy source (530) to transport heat away from the electric motor (220) and from the auxiliary energy source.

23. A dust extractor (100) comprising at least one cyclone tank (1 10), a prefilter arrangement (120), an essential filter arrangement (130), and a blower system (140) arranged to generate an air flow (F), where the blower system (140) is supported by and at least partially embedded in a foam material body (410), where at least one air channel comprising a working air flow (F) of the dust extractor (100) extends through the foam material body to the blower system (140), the foam material body (410) comprises at least a first cooling air channel (420) which is at least partly delimited by the foam material body (410), the first cooling air channel (420) extends between an ambient inlet port (430) of the foam material body (410) and a cooling air inlet (260) of the blower system (140), the cooling air channel is separate from the working air flow (F) of the dust extractor (100).

24. The dust extractor (100) according to claim 23, where the foam material body (410) is formed in a thermoplastic polymeric foam material, such as polypropylene or polystyrene.

25. The dust extractor (100) according to any of claims 23-24, where the foam material body (410) comprises at least a second cooling air channel (425) at least partly delimited by the foam material body, where the second cooling air channel (425) extends between a cooling air outlet (265) of the blower system (140) and an ambient outlet port (435) of the foam material body (410).

26. The dust extractor (100) according to any of claims 23-25, where the foam material body (410) comprises at least one exhaust air channel (440) that extends between a working air outlet (240) of the centrifugal fan (210) and an exhaust port of the foam material body (410).

27. A dust extractor (100) comprising at least one cyclone tank (1 10), a prefilter arrangement (120), an essential filter arrangement (130), a blower system (140) arranged to generate an air flow, and a control unit (150), the dust extractor (100) comprising a status indicator light (170) arranged to emit a plurality of different and selectable colors of light, where the control unit (150) is configured to activate the status light in a first color, such as a green or white color, in case the blower system (140) is activated, and where the control unit (150) is configured to activate the status light in a second color, such as an orange color, in case a magnitude of the air flow does not satisfy an acceptance criterion.

28. The dust extractor (100) according to claim 27, where the control unit (150) is configured to activate the status light in a third color, such as a red color, in case the control unit has detected malfunction in the dust extractor (100).

29. A dust extractor (100) comprising at least one cyclone tank (1 10), a prefilter arrangement (120), an essential filter arrangement (130), a blower system (140), and a protective frame structure (180, 181 , 182), where the frame structure comprises a rear part (180) that extends transversally to a horizontal plane in use, such as vertically (V) along the dustextractor, to form a rail which the dust extractor can slide on when in a tilted position, where the rear part (180) extends from rear wheels (195) of the dust extractor (100) to an upper part (181 ) of the frame structure forming a handle section of the frame structure.

30. The dust extractor (100) according to claim 29, where the rear wheels comprise (195) a wheel brake (190) with a gravity-based auto-latch function configured to automatically engage upon impact with a ground surface..

31. The dust extractor (100) according to claim 30, where the wheel brake (190) comprises components having inertia which causes the brake to automatically engage upon impact with the ground surface.

32. The dust extractor (100) according to claim 30 or 31 , where the wheel brake (190) comprises a lever with a weight, where the weight is calibrated to an expected impact force of the impact with the ground surface.

33. The dust extractor (100) according to any of claims 29-32, where a side part (185) of the frame structure extends horizontally along both sides of the dust extractor at a height of about 0,6-1 ,0m, and at least less than 1 ,5m.

34. The dust extractor (100) according to any of claims 29-33, where a front part (182) of the frame structure extends across the dust extractor front.

35. A method for lowering a dust extractor (100) from an elevated platform, the dust extractor (100) comprising at least one cyclone tank (110), a prefilter arrangement (120), an essential filter arrangement (130), a blower system (140), and a protective frame structure (180, 181 , 182) arranged to enclose at least part of the dust extractor (100), where the frame structure comprises a rear part (180) that extends transversally to a horizontal plane in use, such as vertically (V) along the dust extractor (100), to form a rail which the dust extractor can slide on when in a tilted position, where the rear part (180) extends from rear wheels (195) of the dust extractor (100) to an upper part (181 ) of the frame structure forming a handle section of the frame structure, where the rear wheels comprise (195) awheel brake (190) with an automated latch function configured to automatically engage upon impact with a ground surface, the method comprising using the rear part (180) of the frame structure to slide the dust extractor (100) along an edge of the elevated platform, and automatically triggering the automated latch function of the wheel brake (190) upon impact with the ground surface, thereby immobilizing the dust extractor (100) on the ground surface below the elevated platform.

36. A dust extractor (100) comprising at least one cyclone tank (1 10), a prefilter arrangement (120), an essential filter arrangement (130), a blower system (140), and a protective frame structure (180, 181 , 182), where the frame structure comprises a rear part (180) that extends transversally to a horizontal plane in use, such as vertically (V) along the dust extractor, to form a rail which the dust extractor can slide on when in a tilted position, where the rear wheels comprise (195) a wheel brake (190) with a gravity-based auto-latch function configured to automatically engage upon impact with a ground surface.

37. A dust extractor (100) comprising at least one cyclone tank (1 10), a prefilter arrangement (120), an essential filter arrangement (130), and a blower system (140), where the blower system (140) comprises at least two independent electric motors (220) arranged to drive respective and separate fan arrangements (210), where each fan arrangement (210) is in fluid communication with a respective essential filter of the essential filter arrangement (130), where each essential filter is in fluid communication with a respective suction valve (125) that opens up into a respective section of the prefilter arrangement (120) or into a respective prefilter unit of the prefilter arrangement (120).

38. A dust extractor (100) comprising at least one cyclone tank (1 10), a prefilter arrangement (120), an essential filter arrangement (130), a control unit (150), and a blower system (140), where the blower system (140) comprises at least one electric motor (220) arranged to drive a fan arrangement (210), the dust extractor (100) comprising a power interface for connection to electrical mains (515), and an auxiliary energy source (530) arranged to power the blower system (140) at least partly as part of a hybrid electric power system (500, 550) of the dust extractor (100), where the control unit (150) is arranged to control a power transfer between the auxiliary energy source (530) and the blower system (140), in dependence of a predetermined power configuration of the dust extractor (100).

39. The dust extractor (100) according to claim 38, where at least one electric motor (220) of the blower system (140) is arranged to generate a cooling air flow (261 ) that is separate from the air flow (F) used for dust extraction, where the cooling air flow (261 ) is arranged to be guided past the electric motor (220) and past the auxiliary energy source (530) to transport heat away from the electric motor (220) and from the auxiliary energy source (530).

40. The dust extractor (100) according to claim 38 or 39, where the control unit 150 is configured to activate an enhanced cooling function to cool the auxiliary energy source (530) in case a temperature of the auxiliary energy source (530) fails to satisfy a predetermined temperature acceptance criterion, where the enhanced cooling function comprises restricting or blocking a working air flow (F) of the dust extractor (100).

41. A dust extractor (100) comprising at least one cyclone tank (1 10), a prefilter arrangement (120), an essential filter arrangement (130), a blower system (140), and a protective frame structure (180, 181 , 182), where the frame structure comprises a rear part (180) that extends transversally to a horizontal plane in use, such as vertically (V) along the dust extractor, to form a rail which the dust extractor can slide on when in a tilted position,where the rear part (180) extends from rear wheels (195) of the dust extractor (100) to an upper part (181 ) of the frame structure forming a handle section of the frame structure, where a top wheel (185) is attached to the upper part (181 ) of the frame structure, where a plane (186) tangential to at least one of the rear wheels (195) and tangential to the top wheel (185) forms a rearmost limit of the dust extractor(100).

42. A dust extractor (100) comprising at least one cyclone tank (1 10), a prefilter arrangement (120), an essential filter arrangement (130), and a blower system (140), where an inlet (160) of the dust extractor arranged to receive a suction hose forms an opening into the cyclone tank (1 10), where the dust extractor (100) is arranged to be supported on a ground surface(101 ) by rear wheels (195) associated with a real wheel axis, where the inlet (160) faces in an inlet angle which is within 30 degrees of the real wheel axis, and preferably aligned with the rear wheel axis.

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