SE2050615A1 - Improved blower arrangements and silencers for dust extractors - Google Patents

Abstract

A blower arrangement for a dust extractor, the blower arrangement comprising a first impeller arranged to rotate about a central axis, a first motor arranged to drive the first impeller, and a silencer arrangement, the silencer arrangement comprising a first volume extending radially outwards from the first impeller with respect to the central axis and a second volume extending radially outwards from the first motor with respect to the central axis,wherein the first volume is fluidly connected to the second volume by a conduit arranged peripherally with respect to the central axis,wherein an exhaust air flow from the first impeller is arranged to be guided radially outwards from the first impeller through the first volume, to peripherally enter the second volume via the conduit, and to be guided radially inwards through the second volume towards the first motor.

Description

TITLE IMPROVED BLOWER ARRANGEMENTS AND SILENCERS FOR DUSTEXTRACTORS TECHNICAL FIELD The present disclosure relates to dust extraction devices for use withconstruction equipment. There are disclosed blowers and silencer arrangements for efficient dust extraction at a reduced noise level.

BACKGROUND Dust and slurry are created by cutting, drilling, grinding and/or demolishingconcrete, brick and other hard construction materials. The dust and slurry maybe co||ected by a dust extractor and removed from the construction site in acontrolled manner. Dust extractors are vacuum devices which collect the dustand slurry by generating an under-pressure by means ofan impeller and motorarrangement, i.e., similar to the operation of a normal vacuum cleaner fordomestic use. Most dust extractors comprise a cyclone or pre-separator unitfollowed by an essential air filter such as a high-efficiency particulate air(HEPA) filter.

Dust extractors predominantly comprise electric motors used to power animpeller which builds up the static air pressure and air flow needed for efficientdust extraction. The motor and impeller arrangement generates noise duringoperation. lt is desired to reduce this generated noise with as little impact onthe dust extraction performance as possible.

A larger diameter impeller can be used at a reduced rotational speedcompared to a smaller diameter impeller to generate a comparable amount ofair flow with reduced noise level. However, it is desirable to minimize blower footprint since space is an issue in most dust extraction devices.

US4057370 discloses an impeller and motor arrangement for an electric blower assembly.

SUMMARY lt is an object of the present disclosure to provide blower arrangements whichprovide sufficient airflow rate and static air pressure for efficient dust extraction at a reduced noise level.

This object is at least in part obtained by a blower arrangement for a dustextractor. The blower arrangement comprises a first impeller arranged to rotateabout a central axis A, a first motor arranged to drive the first impeller, and asilencer arrangement. The silencer arrangement comprises a first volumeextending radially outwards from the first impeller with respect to the centralaxis A, and a second volume extending radially outwards from the first motorwith respect to the central axis A. The first volume is fluidly connected to thesecond volume by a conduit arranged peripherally with respect to the centralaxis A. An exhaust air flow from the first impeller is arranged to be guidedradially outwards from the first impeller through the first volume, to peripherallyenter the second volume via the conduit, and to be guided radially inwardsthrough the second volume towards the first motor. The second volumecomprises an exhaust outlet arranged opposite to the first volume; the exhaust outlet is preferably arranged axially with respect to the central axis.

This way noise is effectively suppressed by the first and by the secondvolumes, since the first and second volumes act as noise traps to prevent noisefrom escaping the blower arrangement. The airflow is at the same time guidedradially inward towards the motor, in order to cool the motor. Thus, both noisesuppression and motor cooling are obtained by the disclosed blowerarrangement. The air flow path is extended in distance by first being directedradially outwards and then radially inwards, which improves the noise suppression effect.

The blower arrangements disclosed herein can optionally be configuredserially for maintained airflow and increased air pressure and/or also parallelly for maintained air pressure and increased air flow, which is an advantage.

According to aspects, the peripherally arranged conduit comprises an annularslot delimited by a peripheral wall of a third volume arranged to enclose the first volume and the second volume.

This slot provides a further noise suppressing access from the first volume intothe second volume. The peripheral wall also provides mechanical integrity and protects the blower arrangement from external impacts and the like.

According to aspects, the peripherally arranged conduit is an aperturearranged peripherally in a common plane separating the first volume from thesecond volume. The design of this aperture may be used to control air flowinside the blower arrangement. The aperture may also be arranged with avariable size in order to provide means for regulating the flow of air betweenthe two volumes, i.e., acting as a control valve for controlling the flow between the two volumes.

According to aspects, the blower arrangement comprises a fourth volumeextending radially outwards from the central axis. The fourth volume comprisesa centrally arranged inlet aperture arranged in fluid connection with theexhaust outlet of the second volume. The exhaust air flow from the impeller isarranged to be guided radially outvvards from the inlet aperture through thefourth volume. The fourth volume provides further noise suppression ability ofthe blower arrangement. The fourth volume may also terminate the blowerarrangement and provide an exhaust from the impeller.

According to aspects, the fourth volume comprises a central conical protrusionarranged opposite from the inlet aperture of the fourth volume and pointingtowards the first motor. The conical protrusion is arranged to suppress an airturbulence inside the fourth volume in favor of a laminar flow inside the fourthvolume. The conical protrusion is preferably centered in the fourth volumearound the central axis. This conical protrusion promotes a laminar flow of circulating air inside the fourth volume which is beneficial for both air flow rate and noise suppression.

According to aspects, at least one of the first volume, second volume and/orfourth volume comprises a helical structure defining a volute passageextending radially with respect to the central axis. The volute passage(s)represent passages of increased length, whereby the air flow is in contact withthe walls of the volute passages for an extended duration of time. Thisprolonged contact promotes noise suppression, especially if the walls of thepassages are coated with a noise absorbing material such as rubber or some foam-like material.

According to aspects, at least two adjacently arranged volumes compriserespective helical structures defining volute passages, wherein the volutepassages are arranged to follow opposite rotational directions. The change inrotation direction further promotes noise suppression, which is an advantage.

According to aspects, at least one helical structure defines a plurality of volutepassages extending radially within the volume and with different angularoffsets. A plurality of volute passages means that the air flow is exposed to anincreased volute passage side wall area, which promotes noise suppression by the volute passages.

According to aspects, a sound absorbing material is arranged on an internalwall of at least one of the first volume, second volume and/or third volume.This sound absorbing material promotes noise suppression, as discussedabove, especially if the sound absorbing material is arranged on a wall of avolute passage extending radially within a volume to prolong air flow exposure to the sound absorbing material.

According to aspects, the blower arrangement comprises a second impellerarranged to rotate about the central axis, and a second motor arranged to drivethe second impeller. The second impeller and the second motor are arrangedaxially with respect to the central axis and in serial configuration with the firstimpeller and with the first motor. The silencer arrangement comprises a fifthvolume extending radially outwards from the second impeller with respect to the central axis and a sixth volume extending radially outwards from thesecond motor with respect to the central axis. The fifth volume is fluidlyconnected to the sixth volume by a second conduit arranged peripherally withrespect to the central axis. An exhaust air flow from the second impeller isarranged to be guided radially outwards from the second impeller through thefifth volume to peripherally enter the sixth volume via the second conduit, andto be guided radially inwards through the sixth volume towards the secondmotor. By stacking two or more impellers and motors serially in this way thecapacity of the blower arrangement is increased, which is an advantage. Bythis type of serial configuration, the use of a larger diameter impeller can beavoided, which is an advantage. A plurality of such serial configurations maybe arranged in parallel for increased airflow.

According to aspects, one or more control valves are arranged to control a fluidconnection between the first and/or second conduit and an exterior of theblower arrangement. This means that the serially stacked impellers can beengaged selectively to adapt the air flow to current vacuuming scenario. Forinstance, at least one of the one or more control valves are optionally arrangedto be electrically controllable by a control unit.

The silencer arrangements disclosed herein can, as noted above, also be usedfor parallel impeller architectures, where a plurality of motors and respectiveimpellers are arranged in parallel in order to increase an air flow level of, e.g.,a dust extractor.

Dust extractors, control units, and methods are also disclosed herein. Thesedust extractors, control units, and methods are associated with the above- mentioned advantages.

Generally, all terms used in the claims are to be interpreted according to theirordinary meaning in the technical field, unless explicitly defined othenNiseherein. All references to "a/an/the element, apparatus, component, means,step, etc." are to be interpreted openly as referring to at least one instance ofthe element, apparatus, component, means, step, etc., unless explicitly statedotherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. Furtherfeatures of, and advantages with, the present invention will become apparentwhen studying the appended claims and the following description. The skilledperson realizes that different features of the present invention may becombined 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 tothe appended drawings, where Figures 1A-B show example dust extractors; Figure 2 illustrates an example blower and filter arrangement; Figure 3 illustrates a blower and filter arrangement with a volute silencer;Figures 4-7 schematically illustrate different example silencer arrangements;connections with silencer Figure 8-9 show example serial blower arrangements;Figure 10 schematically illustrates a control unit;Figure 11 shows an example computer program product; and Figures 12-13 illustrate parallel arrangements of motors and corresponding impellers.

DETAILED DESCRIPTION The invention will now be described more fully hereinafter with reference to theaccompanying drawings, in which certain aspects of the invention are shown.This invention may, however, be embodied in many different forms and shouldnot 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 elementsthroughout the description. lt is to be understood that the present invention is not limited to theembodiments described herein and i||ustrated in the drawings; rather, theskilled person will recognize that many changes and modifications may bemade within the scope of the appended claims.

Figures 1A and 1B show example dust extraction devices 100, 100”. The dustextraction devices can be connected 130 via a hose to a dust generator (notshown in Figures 1A and 1B), such as a core dri||, a floor grinder, a concretesaw, or the like. The dust and slurry from the dust generator enters the dustextractor via the hose. A cyclone 110 or pre-separator unit is arranged afterthe inlet, i.e., downstream with respect to the airflow direction. The cyclone 110may, e.g., comprise a pre-filter for separating out larger debris particles fromthe particle-laden airflow entering the inlet. lt is noted that the techniquesblowers and silencers disclosed herein can be applied to dust extractiondevices with and without cyclone units 110.

An impeller and motor arrangement 120 is arranged downstream from thecyclone 110 to generate the necessary static air pressure for an efficient dustextraction operation in a known manner. Figure 1A illustrates a dust extractorwith one motor while Figure 1B illustrates a dust extractor with two motors. Airis drawn into an inlet 125 or into inlets 125' and then filtered by an air-filter orair-filters before being exhausted from the dust extractor 100, 100”.

The dust extractors 100, 100' may comprise a control unit 140, onlyschematically indicated in Figures 1A and 1B. These control units may beconfigured to control various functions on the dust extractor. A control unit willbe discussed in more detail below in connection to Figure 10.

Vacuum devices comprising cyclones 110, pre-filters, and airfilters are known in general and will not be discussed in more detail herein.

Figure 2 shows an exploded view of an example impeller and motorarrangement 120, where an airfilter 210 is arranged connected to the inlet 125 downstream from the cyclone 110. This air filter 210 is often referred to as anessenflalfifien The essential air filter 210 may in some cases also be referred to as a High-Efficiency Particulate Air (HEPA) filter, although other types of air filters mayequally well be used. HEPA, also known as high-efficiency particulateabsorbing and high-efficiency particulate arrestance, is an efficiency standardof air filters. Filters meeting the HEPA standard must satisfy certain levels ofefficiency. HEPA was commercialized in the 1950s, and the original termbecame a registered trademark and later a generic term for highly efficientfilters. lt is noted that the techniques disclosed herein can be applied to dustextraction devices with any number of air filters, including dust extractiondevices comprising combinations ofdifferent air filters. The air filter is normallyheld in a cylindrical air filter holder 220. The holder 220 is sealed against theblower 240 by a gasket 230 in a known manner.

Most dust extraction devices use impellers for generating static air pressureupstream from the air filter 210. Air pressure may be measured in terms of kPaunder atmospheric pressure (sometimes referred to as vacuum level). Air flowmay be measured in terms of volume of air passing some point in the system per unit of time, e.g., m3/h.

The blower arrangements discussed herein may also be referred to as fanarrangements or compressor arrangements. lt is customary to distinguishbetween different types of impeller-based air flow generating devices by theamount of energy transmitted to the transported media, i.e., to the flow of air.A fan transfers less energy compared to a blower, while a blower transfers lessenergy compared to a compressor. lt is appreciated that the silencerarrangements disclosed herein are applicable to both fans, blowers, andcompressors. A preferred ratio of discharge pressure to inlet pressure for someof the blower arrangements discussed herein is above 1.24, which means thatthe arrangements are in fact more correctly referred to as compressor arrangements.

The impellers discussed herein may, e.g., be realized as backward bendcentrifugal impellers, or side-channel blower impellers. Some types ofcentrifugal fans may also be used in some cases.

The silencer arrangements discussed herein can be used for both seriallyconfigured blower architectures and for parallelly configured blowerarchitectures, as will be discussed below in connection to Figures 7-9 andFigures 12-13. A serially configured blower architecture is an architecturewhere two or more impellers are arranged in series, while a parallellyconfigured blower architecture is an architecture where two or more impellersare arranged in parallel. Combinations of seria| and parallel architectures can also be used.

With reference to Figure 2, the blower 240 draws air axially A through the airfilter 210 and exhausts the air radially R from the blower 240. The examplemotor 250 in Figure 2 is an electric motor arranged integrated with the impellerhousing in a single unit. A mounting bracket 250 holds the components of the impeller and motor arrangement in place.

The impeller and motor arrangement generates a suction force, i.e., an under-pressure with respect to atmospheric pressure, which draws the particle-ladenairflow in through the hose connection 130, past the cyclone 110, and throughthe one or more airfilters 210. An upstream direction is a direction of the airflowtowards the hose connection and the dust generator, while a downstreamdirection is a direction away from the hose connection and the dust generator.

The impeller 240 and the motor 250 both generate noise during operation. lt isdesired to reduce this noise in order to provide as silent operation as possible.However, this reduction in noise should affect the dust extraction capability ofthe dust extractor 100, 100' as little as possible.

A noise level can be measured, e.g., with a sound level meter in a known manner. The intensity of the noise can be measured in dB.

Figure 3 shows an exploded view of an example blower arrangement 301 foruse, e.g., with a dust extractor 100, 100”. The blower arrangement comprises a first impeller 240 arranged to rotate about a central axis A, a first motor 250arranged to drive the first impeller, and a silencer arrangement 300.

The central axis A will be used hereinafter to describe relative locations ofvarious components and directions. An axial direction is a direction parallel tothe central axis A. A central location is a location centered with respect to axisA. A radial direction is a direction extending in a plane normal to the axis Aaway from or towards the central axis.

The example silencer arrangement 300 in Figure 3 is based on axiallyseparated volumes 311, 341, 361 extending radially outwards (as indicated byarrow R) from the impeller 240, from the motor 250, and from a point axiallydownstream from the motor 250, respectively. Each volume is delimited by acylindrically shaped body 310, 340, 360. These volumes act as sound trapsand therefore reduce the generated noise level. The airflow inside the volumesis guided along respective volute passages 312, 342, 362 in each volume. Avolute passage is a helically formed path. The volute passages shown inFigure 3 comprise volute slots, where the slots are parallel to the central axisA.

The volute passages herein are associated with respective rotationaldirections, i.e., clockwise or counterclockwise, when seen from the upstreamdirection (from the top in Figure 3). This rotational direction may be freely selected for the consecutive volute passages in the silencer arrangement.

Preferably, the rotational direction of the volute passage 312 at an impeller isopposite to the air flow from the compressor or blower. This means that in casethe air flow from the compressor or blower is in counterclockwise directionseen from the upstream direction, then the air in the silencer volute passageis preferably guided in clockwise direction. lf the air flow from the compressoris directed in clockwise direction, then the air in the silencer volute passage atthe impeller should preferably be guided in counterclockwise direction.

These volute passages improve the noise suppression capability of thevolumes, since the air flow will be in contact with the walls of the passages foran extended time duration, which traps the noise. Further noise suppressioncan be obtained by coating one or more of the internal walls defining the volutepassages by a sound suppressing material, such as rubber or a foam material.

The dimensions of the volumes and the volute passages are preferablymatched to the noise generated by the impeller and the motor. Suitabledimensions for the volumes and for the volute passages, i.e., the width andheight of the volute slots, may be determined based on computer simulationand/or based on laboratory experimentation.

The air flow through the example silencer arrangement 300 starts at the top inFigure 3 where air is first drawn into the filter 210. The air flow is directed generally downwards along the axial direction A.

After the air filter 210, the air flow enters the impeller housing via its centralaperture 241. The air is then ejected radially by the impeller, i.e., by the rotatingimpeller, into the first volume 311, where it is guided into two different volutepassages separated by an angular offset. This angular offset is about 180degrees in Figure 2. More than two volute passages can be defined pervolume, such as three orfour volute passages. The air is guided in a clockwisedirection 312 through the volute passages in the first volume 311, when seen from the upstream direction, i.e., from the top in Figure 3.

The air flow then exits the volute passages of the first volume 311 into a thirdvolume 321 defining a conduit 315 between the first volume 311 and a secondvolume 341. This second volume also comprises volute passages 342, butnow the air flow is guided radially inwards in a clockwise direction when seenfrom the upstream direction, i.e., from the top in Figure 3. This radially inwardsair flow extends past the motor 250 before exiting the second volume via anexhaust outlet O arranged centrally with respect to the central axis A andopposite to the first volume 311. Thus, noise is suppressed, and the motor isat the same time also cooled by the air flow extending past the motor. The clock-wise directed radial flows do not limit the air flow rate significantly, whichis an advantage. ln the example shown in Figure 3, the air flow then continues into a fourthvolume 361 where the air flow is again guided radially outwards from thecentral axis A through volute passages 362, again in the clockwise direction.Thus, the airflow alternates between a radially outwards and a radially inwardsdirection as it traverses the volute passages formed in the first, second andfourth volumes. The air flow finally exits the silencer arrangement 300 via radialexhaust outlets formed by the end points of the volute passages 362 in thefourth volume 361.

The design in Figure 3 provides a decrease in noise level, with not muchdecrease in air flow rate, which is an advantage. This is at least in part sincethe air flow through the volute passages are always in the same clockwisedirection.

According to another example, the rotation directions of consecutive volutepassages 312, 341, 362 are instead opposite to each other, e.g., the directionof the air flow though the volute passages in the cylindrically shaped body 340is instead counterclockwise. This change in air flow rotation direction providesan even more significant noise reduction but may potentially reduce air flowrate somewhat. According to this example, the cylindrically shaped body 340is flipped such that the volute passages 342 instead extend along acounterclockwise rotation direction. The bottom plate 343 on the cylindricallyshaped body 340 is of course not flipped but remains in position to seal thethird volume 321.

The elements 310, 330, 340 and 350 in Figure 3 are according to someaspects sealably fixed to each other by element 320. There is no slot betweenelement 340 and 350.

A conically shaped protrusion 370 is arranged centrally in the fourth volume 361 in order to promote a laminar flow in the fourth volume.

According to the example in Figure 3, at least the first and second volumes arecylindrically shaped.

Figure 4A schematically illustrates the general features of some silencerarrangements 400 disclosed herein. These silencer arrangements 400comprise a first volume 311 extending radially outwards from a first impeller240 with respect to a central axis A and a second volume 341 extendingradially outwards from a first motor 250 with respect to the central axis A. Thefirst volume 311 is fluidly connected 410 to the second volume by a conduitarranged peripherally with respect to the central axis A. Here, to be arrangedperipherally means that the conduit is peripheral to both the impeller housing and the impeller motor.

An exhaust air flow from the first impeller 240 is arranged to be guided radiallyoutwards E from the first impeller 240 through the first volume 311, toperipherally enter the second volume via the conduit, and to be guided radiallyinwards I through the second volume 341 towards the first motor 250, therebycooling the motor 250. Thus, the airflow first flows radially outwards throughthe first volume, then down into the second volume, before it changes directionto a radially inwards direction in order to also cool the motor.

The second volume 341 comprises an exhaust outlet O arranged axially withrespect to the central axis A and opposite to the first volume 311. This centrallyarranged exhaust outlet O enables serially stacking more than one impellerand motor arrangement, which will be discussed in more detail below in connection to Figures 8 and 9.

Figure 4B schematically illustrates some general aspects of the hereindisclosed silencer arrangements where the air flow is arranged to be guidedalong volute passages through the first and the second volumes. The volutepassages are directed in rotationally opposite directions, i.e., first counter-clockwise and then clockwise when seen from the upstream direction. Thevolute passages may, e.g., be formed as slots extending parallel to the centralaxis, as was exemplified in Figure 3.

The air flow in both Figures 4A and 4B enters the arrangement via a centralaperture 401 and exits the arrangement via the centrally arranged exhaust outlet O, however, the aperture 401 and the outlet O may of course be offsetaway from the central axis A.

Figures 5A and 5B, with reference also to Figure 3, schematically illustrateaspects of the disclosed silencer arrangements where the peripherallyarranged conduit 510 comprises an annular slot delimited by a peripheral wall320a, 320b, 520 of a third volume 321 arranged to enclose the first volume311 and the second volume 341. This third volume is here exemplified by acylindrical shape with a diameter slightly larger than the diameter of thecylindrically shaped first and second volumes, which means that an annularslot extending parallel to the central axis A is formed between the side wall ofthe third volume and the peripheral walls of the first and second volumes. Theair flow is guided radially outwards through the first volume 311, downstream via the annular slot, and then radially inwards through the second volume.

Figure 5B schematically illustrates an example where volute passages, similarto those illustrated in Figure 3, are comprised in the first and in the secondvolumes. The direction of rotation of the volute passages are indicated by arrows in Figure 5B.

The air flow in both Figures 5A and 5B enters the arrangement via a centralaperture 501 of the impeller housing and exits the arrangement via thecentrally arranged exhaust outlet O.

Figure 6A illustrates an alternative conduit arrangement between the first andthe second volumes. This peripherally arranged conduit 601 comprises anaperture arranged peripherally, i.e., distally with respect to the central axis A,in a common plane 620 separating the first volume 311 from the secondvolume 341. The air flow may according to some aspects be guideddownstream into the aperture 610 by a sloping wall as illustrated in Figure 6Bin order to reduce turbulence and promote a laminarflow from the first volume and into the second volume.

Figure 7 schematically illustrates aspects of the disclosed silencerarrangement 700 which further comprises a fourth volume 361 extending radially outwards R from the central axis A. The fourth volume 361 comprises a central inlet aperture 363 arranged aligned with and in fluid connection withthe exhaust outlet O of the second volume 341. This means that the air flow isguided downwards after cooling the motor 250 and into the fourth volume.

The exhaust air flow from the impeller 240 is then arranged to be guidedradially outwards E' from the inlet aperture through the fourth volume 361.Optionally, volute passages may be comprised in the first, second, and fourthvolumes. ln this case, it may be desirable to arrange the volute passages inopposite directions, as illustrated by the arrows R1, R2, and R3 in Figure 7.The volute passages may of course also be directed in the same direction,e.g., clockwise as in Figure 3. Any type of peripherally arranged conduitbetween the first and the second volume can be used, however, the type ofannular slotted conduit illustrated in Figures 3 and 5 is preferred for improved air flow and noise suppression performance.

Thus, generally, at least one ofthe first volume 311, second volume 341 and/orfourth volume 361 comprises a helical structure 310, 340, 360 defining a volutepassage 312, 342, 362 extending radially with respect to the central axis A.

According to aspects, as illustrated in, e.g., Figure 7, at least two adjacentlyarranged volumes comprise respective helical structures defining volutepassages, wherein the volute passages are arranged to follow oppositerotational directions. The volute passages may of course also be directed in the same rotational direction, e.g., clockwise as in Figure 3.

According to aspects, at least one of the helical structures defines a pluralityof volute passages extending radially within the volume and with differentangular offsets. The volumes in Figure 3 comprises two volute passages each, however, more than two angularly offset passages are also possible.

According to aspects, a sound absorbing material is arranged on an internalwall of at least one of the first volume 311, second volume 341 and/or thirdvolume 361. For instance, the sound absorbing material can be arranged on a wall of a volute passage extending radially within a volume 311, 341, 361.

According to aspects, similar to the silencer arrangement in Figure 3, the fourthvolume 361 comprises a conical protrusion 370 arranged opposite from the inlet aperture 363 ofthe fourth volume and pointing towards the first motor 250,i.e., in the upstream direction. This conical protrusion is arranged to suppressan air turbulence inside the fourth volume in favor of a laminar flow inside the fourth volume.

The arrangements in Figures 4-6 can be stacked along the central axis A toform a serial array of impellers and motors. This serial array provides anincreased static air pressure compared to a single impeller and motorarrangement. The silencer arrangements discussed above are suitable for thistype of stacking. By using more than one impeller, the impeller diameter canbe reduced with maintained performance in terms of static air pressure.

Figure 8 schematically illustrates an example of a serial concatenation of twoimpellers with respective motors. Figure 8 shows a blower arrangement 801comprising a second impeller 240B arranged to rotate about the central axisA, and a second motor 250B arranged to drive the second impeller 240B. Thesecond impeller 240B and the second motor 250B are arranged axially withrespect to the central axis A and in serial configuration with the first impeller240A and the first motor 250A. The silencer arrangement 800 comprises a fifthvolume 810 extending radially outwards R from the second impeller 240B withrespect to the central axis A and a sixth volume 820 extending radiallyoutwards R from the second motor 250B with respect to the central axis A. Thefifth volume 810 is fluidly connected to the sixth volume 820 by a secondconduit 830 arranged peripherally with respect to the central axis A. Anexhaust air flow from the second impeller 240B is arranged to be guidedradially outwards E' from the second impeller 240B through the fifth volume810, to peripherally enter the sixth volume 820 via the second conduit 830, andto be guided radially inwards I' through the sixth volume 820 towards the second motor 250B.

As above, volute passages may be defined by walls in the different volumes.The direction of rotation of such volute passages is preferably arranged inconsecutive opposite directions, as indicated by the arrows R1-R4 in Figure 8.

According to some aspects, a single electric motor may be arranged to drive more than one impeller.

Figure 9 illustrates another example where control valves 910, 911 arearranged to control a fluid connection between the first and/or second conduit and an exterior of the blower arrangement.

According to some aspects, at least one of the one or more control valves 910,911 are arranged to be electrically controllable by a control unit 140.

The valves in Figure 9 may be controlled based on a requested static pressurefor the current operation conditions. When a low static pressure is requestedduring vacuum operation, the valve besides the first stage impeller is openedand the second impeller is turned off. When a high static pressure is requestedduring vacuum operation, the valve besides the first stage impeller is closedand the second impeller is turned on and the valve besides the second stageimpeller is opened.

This way only a part of the maximum vacuum capacity can be activated, andthe vales controlled accordingly.

To summarize, there is disclosed a control unit 140 arranged to control one ormore control valves 910, 911 arranged to control a fluid connection between afirst and/or a second conduit and an exterior of a blower arrangement 801,901.

According to some aspects, the control unit is arranged to control the one ormore control valves 910, 911 based on a requested static air pressure set independence of a current operation condition. The requested static air pressuremay, e.g., be manually configured or automatically configured based on sensorinput signals. The sensor input signals may comprise, e.g., dust sensors andthe like.

According to some other aspects, a first valve 910 associated with a first stageimpeller is opened when a low static pressure is requested, and a second stage impeller is turned off. A second valve 911 associated with a second stage impeller is opened when a high static air pressure is requested wherethe second stage impeller is turned on.

There has also been disclosed herein a dust extractor 100, 100' comprisingthe control unit 140, and thereby arranged to perform the operations andmethods discussed above.

According to an example, the volumes are cylindrically shaped, although thisis not strictly necessary, other shapes may also be used. lt is appreciated that the direction of rotation in the volute passages can bealtered to be the same for two or more consecutive volumes as shown in Figure3, or to be in different directions as exemplified in, e.g., Figure 4B, 5B, 7, 8 and9.

The herein disclosed silencer arrangements can also be used in parallel blower configurations. Two such examples are shown in Figures 12 and 13.

Figure 12 schematically illustrates a top view of a blower arrangement 1201where three motor and impeller arrangements 1210 have been arranged inparallel to power a dust extractor 100, 100'. The motor and impellerarrangements 1210 are here shown separated by walls 1220, and enclosedby a silencer arrangement 1200 such as that discussed in connection withFigure 3 above, e.g., a silencer arrangement comprising the type of helicalstructures discussed above defining a volute passage extending radially withrespect to a central axis.

Figure 13 is a top view illustrating an example blower arrangement 1301 wherethree motor and impeller arrangements 1310 have been arranged in parallel,but where each motor and impeller arrangement is enclosed in a respective silencer arrangement 1300 according to the discussions above. lt is appreciated that the type of serially stacked motor and impeller can alsobe arranged in parallel in the manner shown in Figures 12 and 13.

Figure 10 schematically illustrates, in terms ofa number of functional units, thegeneral components of the control unit 140. Processing circuitry 1010 isprovided 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 programproduct, e.g. in the form of a storage medium 1030. The processing circuitry1010 may further be provided as at least one application specific integratedcircuit ASIC, or field programmable gate array FPGA.

Particularly, the processing circuitry 1010 is configured to cause the device140 to perform a set of operations, or steps, such as controlling one or moreimpeller motors 250A, 250B and/or control valves 910, 911. For example, thestorage medium 1030 may store the set of operations, and the processingcircuitry 1010 may be configured to retrieve the set of operations from thestorage 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 operationsand methods as herein disclosed.

The storage medium 1030 may also comprise persistent storage, which, forexample, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

The device 140 may further comprise an interface 1020 for communicationswith at least one external device. As such the interface 1020 may compriseone or more transmitters and receivers, comprising analogue and digitalcomponents and a suitable number of ports for wireline or wireless communication.

The processing circuitry 1010 controls the general operation of the control unit140, e.g., by sending data and control signals to the interface 1020 and thestorage medium 1030, by receiving data and reports from the interface 1020,and by retrieving data and instructions from the storage medium 1030.

Figure 11 schematically illustrates a computer program product 1100comprising a data storage part 1110 arranged to store a computer program1120. This computer program may comprise instructions for performing any ofthe methods disclosed herein when run, e.g., on processing circuitry 1010such as that discussed above in connection to Figure 10.

Claims (20)

1. A blower arrangement (301, 401, 501, 601, 701, 801, 901, 1201, 1301)for a dust extractor (100, 100'), the blower arrangement comprising a firstimpeller (240) arranged to rotate about a central axis (A), a first motor (250)arranged to drive the first impeller (240), and a silencer arrangement (300, 400,500, 600, 700, 800, 900, 1200, 1300), the silencer arrangement comprising afirst volume (311) extending radially outwards (R) from the first impeller (240)with respect to the central axis (A) and a second volume (341) extendingradially outwards (R) from the first motor (250) with respect to the central axis(A), wherein the first volume (311) is fluidly connected to the second volume (341)by a conduit (315, 410, 510, 610) arranged peripherally with respect to thecentral axis (A), wherein an exhaust air flow from the first impeller (240) is arranged to beguided radially outwards (E) from the first impeller (240) through the firstvolume (311), to peripherally enter the second volume via the conduit (315,410, 510, 610), and to be guided radially inwards (l) through the secondvolume (341) towards the first motor (250), wherein the second volume (341) comprises an exhaust outlet (O) arrangedopposite to the first volume (311).

2. The blowerarrangement (301,401, 501, 601, 701, 801, 901, 1201, 1301)according to claim 1, wherein the peripherally arranged conduit (315, 510)comprises an annular slot delimited by a peripheral wall (320a, 320b, 520) ofa third volume (321) arranged to enclose the first volume (31 1) and the secondvolume (341 ).

3. The blower arrangement (601) according to claim 1, wherein theperipherally arranged conduit (610) is an aperture arranged peripherally in acommon plane (620) separating the first volume (31 1 ) from the second volume(341).

4. The blower arrangement (301, 701, 801, 901, 1201, 1301) according toany previous claim, comprising a fourth volume (361) extending radiallyoutwards (R) from the central axis (A), wherein the second volume (341)comprises an exhaust outlet (O) arranged axially with respect to the centralaxis (A) and opposite to the first volume (311), the fourth volume (361)comprising a centrally arranged inlet aperture (363) arranged in fluidconnection with the exhaust outlet (O) of the second volume (341), whereinthe exhaust air flow from the impeller (240) is arranged to be guided radially outwards (E') from the inlet aperture through the fourth volume (361 ).

5. The blower arrangement (301, 701, 801, 901, 1201, 1301) according toclaim 4, wherein the fourth volume (361) comprises a conical protrusion (370)arranged about the central axis (A) opposite from the inlet aperture (363) ofthe fourth volume and pointing towards the first motor (250), wherein theconical protrusion (370) is arranged to suppress an air turbulence inside the fourth volume in favor of a laminarflow inside the fourth volume.

6. The blowerarrangement (301,401, 501, 601, 701, 801, 901, 1201, 1301)according to any previous claim, wherein at least one of the first volume (31 1 ),second volume (341) and/or fourth volume (361) comprises a helical structure(310, 340, 360) defining a volute passage (312, 342, 362, 1230, 1330)extending radially with respect to the central axis (A).

7. The blowerarrangement(301,401,501,601,701,801,901,1201,1301)according to claim 6, wherein at least two adjacently arranged volumescomprise respective helical structures defining volute passages, wherein thevolute passages are arranged to follow opposite rotational directions.

8. The blowerarrangement(301,401,501,601,701,801,901,1201,1301)according to claim 6 or 7, wherein at least one helical structure defines aplurality of volute passages extending radially within the volume and withdifferent angular offsets.

9. The blower arrangement (301 , 401, 501, 601, 701, 801, 901, 1201, 1301) according to any previous claim, wherein a sound absorbing material is arranged on an internal wall of at least one of the first volume (311), secondvolume (341) and/or third volume (361).

10. The blowerarrangement (301,401, 501, 601, 701, 801, 901, 1201, 1301)according to claim 9, wherein the sound absorbing material is arranged on awall of a volute passage extending radially within a volume (311, 341, 361).

11. The blower arrangement (801, 901, 1201, 1301) according to anyprevious claim, comprising a second impeller (240B) arranged to rotate aboutthe central axis (A), and a second motor (250B) arranged to drive the secondimpeller (240B), wherein the second impeller (240B) and the second motor(250B) are arranged axially with respect to the central axis (A) and in serialconfiguration with the first impeller (240A) and with the first motor (250A), the silencer arrangement comprising a fifth volume (810) extending radiallyoutwards (R) from the second impeller (240B) with respect to the central axis(A) and a sixth volume (820) extending radially outwards (R) from the secondmotor (250B) with respect to the central axis (A), wherein the fifth volume (810) is fluidly connected to the sixth volume (820) bya second conduit (830) arranged peripherally with respect to the central axis(A), wherein an exhaust air flow from the second impeller (240B) is arranged to beguided radially outwards (E') from the second impeller (240B) through the fifthvolume (810), to peripherally enter the sixth volume (820) via the secondconduit (830), and to be guided radially inwards (l') through the sixth volume(820) towards the second motor (250B).

12. The blower arrangement (801, 901, 1201, 1301) according to anyprevious claim, wherein one or more control valves (910, 911) are arranged tocontrol a fluid connection between the first and/or second conduit and an exterior of the blower arrangement.

13. The blower arrangement (801, 901, 1201, 1301) according to claim 12,wherein at least one of the one or more control valves (910, 911) are arrangedto be electrically controllable by a control unit (140).

14. The blowerarrangement (301,401, 501, 601, 701, 801, 901, 1201, 1301)according to any previous claim, wherein at least the first, second, and third volumes are cylindrically shaped.

15. The blower arrangement (1201) according to any previous claim,comprising a plurality of motors and corresponding impellers (1210) arrangedin parallel and enclosed by the silencer arrangement (1200).

16. The blower arrangement (1301) according to any previous claim,comprising a plurality of motors and corresponding impellers (1310) arranged in parallel and enclosed by respective silencer arrangements (1300).

17. A dust extractor (100, 100') comprising a blower arrangement according to any of claims 1-16.

18. A control unit (140) arranged to control one or more control valves (910,911) arranged to control a fluid connection between a first and/or a secondconduit and an exterior ofa blower arrangement (801, 901).

19. The control unit (140) according to claim 18, arranged to control the oneor more control valves (910, 911) based on a requested static air pressure set in dependence of a current operation condition.

20. The control unit (140) according to claim 19, wherein a first valve (910)associated with a first stage impeller is opened when a low static pressure isrequested and a second stage impeller is turned off, wherein a second valve(911) associated with a second stage impeller is opened when a high static airpressure is requested where the second stage impeller is turned on.