CLEANING APPARATUS WITH FLOW DEFLECTION ELEMENT WITH MODE FILTER

A cleaning apparatus is provided, including at least one noise source and an air guidance device having at least one flow deflection element, wherein the at least one flow deflection element has a first duct arm and a second duct arm, wherein the second duct arm is oriented transversely to the first duct arm, and wherein, during operation of the cleaning apparatus, there is sound propagation from the first duct arm to the second duct arm, wherein a mode filter device for transverse modes of sound propagation is arranged at the at least one flow deflection element, having at least one mode filter that is positioned at the second duct arm.

BACKGROUND OF THE INVENTION

The invention relates to a cleaning apparatus, comprising at least one noise source and an air guidance device having at least one flow deflection element, wherein the at least one flow deflection element has a first duct arm and a second duct arm, wherein the second duct arm is oriented transversely to the first duct arm, and wherein, during operation of the cleaning apparatus, there is sound propagation from the first duct arm to the second duct arm.

DE 36 30 710 A1 discloses an absorptive sound attenuator which is arranged in the dust-conveying line of a hand-held vacuum cleaner with downstream filter.

DE 10 2017 111 910 A1 discloses a cleaning device, comprising a tonal-noise source, a flow guidance device and a noise-reducing device, which is coupled to the flow guidance device. The noise-reducing device comprises at least one λ/4 resonator, which is adapted to the tonal-noise source, wherein the at least one λ/4 resonator is connected to at least one of the following devices: (i) at least one sound attenuator; (ii) a nozzle.

DE 10 2018 108 559 A1 discloses a cleaning device comprising at least one noise source, an air guidance device acted upon by sound, and a noise-reducing device that is arranged on the air guidance device, wherein the noise-reducing device comprises a combination comprising at least a perforated-plate resonator and a flow deflection element.

WO 2018/068850 A1 discloses a cleaning device, comprising at least one noise source and an air guidance device having at least one flow deflection element, wherein the at least one flow deflection element has a first arm with a first inlet duct and a second arm with an outlet duct, the outlet duct is oriented transversely to the inlet duct, the inlet duct has an inlet that extends in a first depth direction and a first width direction, the outlet duct has an outlet with a depth in a second depth direction and a width in a second width direction, the first depth direction and the second depth direction are oriented parallel to one another, and the first width direction and the second width direction are oriented transversely to one another, wherein the width in the second width direction is at least 1.2 times the depth in the second depth direction.

Known from WO 2015/043641 A1 is a suction apparatus comprising a fan device for generating a suction air stream, and an air guidance device that has at least one flow deflection element having an inlet duct and an outlet duct, wherein the outlet duct is oriented transversely to the inlet duct. Arranged at a region of transition from the inlet duct to the outlet duct is an acoustic mirror device at which sound is reflected and/or sound is absorbed.

Known from WO 2016/112959 is a suction device comprising a suction assembly, a dirt-collection container, a filter device, and a cleaning-off device for the filter device, wherein the cleaning-off device forms a noise source for noise emissions in a frequency range below 2,000 Hz, and at least one perforated-plate resonator is associated with the cleaning-off device.

In accordance with an embodiment of the invention, a cleaning apparatus of the type mentioned in the introduction is provided, which has effective sound attenuation at the same time as a high degree of flow efficiency.

SUMMARY OF THE INVENTION

In accordance with an embodiment of the invention, provision is made in the case of the cleaning apparatus of the type mentioned in the introduction that a mode filter device for transverse modes of sound propagation is arranged at the at least one flow deflection element, having at least one mode filter that is positioned at the second duct arm.

In the flow deflection element there occurs flow guidance and in particular guidance of an air stream. Further, sound propagation occurs in the at least one flow deflection element.

Fundamentally, sound can propagate in the at least one flow deflection element as a fundamental mode and as a first-order transverse mode and as higher-order transverse modes.

Transverse modes arise at a region of transition from the first duct arm to the second duct arm and then propagate in the second duct arm.

It has been found that if a mode filter for transverse modes is arranged at the second duct arm, transverse modes are accordingly suppressed, and effective sound attenuation is produced.

In this context, reference is made to the dissertation “Acoustic and aerodynamic phenomena in duct bends”, which is not a prior publication, by Dominik Scholl, Institute for Acoustics and Building Physics at the University of Stuttgart, 2021. The dissertation is explicitly referenced in its entirety.

In particular, the at least one flow deflection element has a sound deflection region for sound propagation from the first duct arm to the second duct arm, and in respect of sound propagation at least one mode filter for transverse modes is arranged downstream of the sound deflection region. Transverse modes arise at the sound deflection region, and these can be effectively attenuated at the second duct arm by the corresponding mode filter.

It is favorable if at least one of the following is provided:the at least one mode filter which is positioned at the second duct arm is at a spacing from a sound deflection region;the at least one mode filter which is positioned at the second duct arm is at a spacing from the first duct arm;a spacing of the at least one mode filter which is arranged at the second duct arm is at least 0.1 times and in particular at least 0.15 times (and preferably at least 0.2 times and preferably at least 0.3 times and preferably at least 0.4 times and preferably at least 0.5 times and preferably at least 0.6 times and preferably at least 0.7 times and preferably at least 0.8 times) a first width of the first duct arm in a first width direction or a second width of the second duct arm in a second width direction, wherein the spacing is parallel to a first width direction and relates to a side of the first duct arm that lies at an internal corner region of the at least one flow deflection element.

It has been found that this enables effective mode filtering for transverse modes with effective sound attenuation to be achieved.

It may also be provided for the mode filter device to comprise at least one mode filter for transverse modes which is arranged at the first duct arm. A mode filter for transverse modes that is arranged at the second duct arm has the greater effect, as a result of transverse modes arising as the sound is deflected.

It is favorable if the first duct arm has a first opening that extends in a first width direction and a first depth direction, wherein the first depth direction is perpendicular to the first width direction, and the second duct arm has a second opening that extends in a second width direction and a second depth direction perpendicular to the second width direction, having at least one of the following:the first width direction and the second width direction are transverse and in particular perpendicular to one another;the first depth direction and the second depth direction are at least approximately parallel to one another;the first depth direction and the second width direction are perpendicular to one another;the second depth direction and the first width direction are perpendicular to one another.

These indications accordingly determine the geometric relationships.

It is particularly advantageous if, during the propagation of sound through the at least one flow deflection element during operation of the cleaning apparatus, transverse modes that propagate in the first width direction and second width direction and transverse modes that propagate in the first depth direction and second depth direction may fundamentally be formed. Typically, transverse modes have a cutoff frequency. Below this cutoff frequency, these modes are evanescent and cannot propagate (that is to say, they drop off exponentially).

In that case, it is in particular provided for the at least one mode filter at the second duct arm to take a form for filtering transverse modes in the second width direction. These are the first transverse mode, the second transverse mode and so on. The transverse modes in the second depth direction are fundamentally also present, but do not play a major part in respect of sound attenuation.

A mode filter of the mode filter device for transverse modes is or comprises at least one of the following:an absorptive sound attenuator;a chamber-type sound attenuator;a perforated device that is positioned in an interior of the at least one flow deflection element.

The absorptive sound attenuator or chamber-type sound attenuator or perforated device is arranged in particular at the second duct arm. It may also be provided for a corresponding mode filter additionally to be arranged at the first duct arm. Fundamentally, it is also possible for a plurality of types of these mode filters to be used at the same time.

In an advantageous embodiment, the absorptive sound attenuator has material that is absorptive in relation to sound and is in particular arranged as an absorptive layer. This enables effective sound attenuation for transverse modes to be achieved.

For this purpose, it is in particular provided for the absorptive material to be flush with an inner side of the at least one flow deflection element, or to be set back in relation to an inner side of the at least one flow deflection element. In the case of being set back, the absorptive sound attenuator also takes the form of a chamber-type sound attenuator (with appropriate dimensions).

This enables effective mode filtering for transverse modes to be achieved.

In particular, the absorptive sound attenuator has at least one of the following parameters:a thickness of the absorptive material is at least 0.1 times, and in particular at least 0.15 times, and in particular at least 0.2 times, and in particular at least 0.25 times a width of the first duct arm or the second duct arm;a length of the absorptive sound attenuator parallel to a direction of extent of the duct arm at which the absorptive sound attenuator is arranged is at least 1.5 times, and in particular at least twice, and in particular at least 2.3 times a width of the first duct arm or the second duct arm;a spacing of the absorptive sound attenuator that is arranged at the second duct arm is at least 0.1 times a width of the first duct arm or the second duct arm.

If at least one of these parameters is fulfilled, effective mode filtering for transverse modes is produced, and accordingly a high level of transmission loss of the acoustic pressure—that is to say, effective sound attenuation.

In one embodiment, the chamber-type sound attenuator has a chamber that forms a widening in cross section at the duct element at which the chamber-type sound attenuator is arranged. With appropriate dimensions, this enables effective mode filtering to be achieved.

In particular, the chamber-type sound attenuator has at least one of the following parameters:a width of the chamber is at least twice a width of the first duct arm or the second duct arm;a length of the chamber-type sound attenuator parallel to a direction of extent of the duct arm at which the chamber-type sound attenuator is arranged is at least 1.2 times a width of the first duct arm and the second duct arm;a spacing of the chamber-type sound attenuator that is arranged at the second duct arm from the first duct arm is at least 0.1 times and in particular at least 0.15 times and in particular at least 0.5 times a width of the first duct arm or the second duct arm.

If at least one of these parameters is fulfilled, effective mode filtering is produced.

It is favorable if, in the case of the perforated device, at least one of the following is present:openings in the perforated device have an opening width of less than or equal to 1 mm;an opening density is greater than or equal to 10 openings per square centimeter;a wall thickness of the perforated device transversely to a width direction of the duct arm at which the perforated device is arranged is at least 1 mm.

With an appropriate configuration of the perforated device, it is likewise possible to implement a mode filter for transverse modes. In particular in this case, the perforated device is arranged in a through-flow region of the corresponding duct arm.

It is favorable if at least one of the following is provided:the perforated device is or comprises one or more plates provided with openings;the perforated device comprises one or more open-pore structures;an open-pore structure takes the form of a block;an open-pore structure is a foam structure and in particular an absorbent foam structure and/or a fiber material structure such as a nonwoven structure.

In this way, a mode filter can be implemented in a simple manner. For example, the perforated device comprises one or more plates that are accordingly provided with perforations (openings). In particular, the openings are open in relation to a width direction of the respective duct arm at which the perforated device is located. For example, a plate is arranged centrally in the corresponding duct arm and in so doing oriented for example parallel to a direction of extent of the corresponding duct arm. It is also possible for example for a plurality of plates that are at a spacing from one another to be correspondingly positioned in the interior. In particular, in that case it is possible for fluid to flow through in an intermediate space between the plates.

The perforated device may also comprise one or more open-pore structures in order to implement a corresponding mode filter. In particular, an open-pore structure takes the form of a block and may in this case be plate-like in form. An open-pore structure may for example be a foam structure and in particular an absorbent foam structure or a fiber material structure. As a result of using an absorbent foam structure, it is also possible in addition to achieve sound absorption at the perforated device. The fiber material structure may be for example a nonwoven structure. Fundamentally, a woven structure or knitted structure are for example also possible.

In this context, it may be provided for the absorptive sound attenuator or the chamber-type sound attenuator or the perforated device to take a form for attenuation of transverse modes only in a width direction. In particular in that case, no construction is present for attenuating transverse modes in the depth direction, which play only a subordinate part.

It is favorable for effective noise reduction if the first duct arm has a first opening and the second duct arm has a second opening, and a ratio of a first width of the first opening to a second width of the second opening is greater than 1.

It has been found that this enables a relatively high total transmission loss for the acoustic pressure (integrated over all frequencies).

This is attributable to the fact that evanescent modes arise—that is to say modes that cannot propagate—and accordingly greater transmission loss occurs.

In this context, reference is made explicitly and in its entirety to the dissertation “Acoustic and aerodynamic phenomena in duct bends”, which is not a prior publication, by Dominik Scholl, Institute for Acoustics and Building Physics at the University of Stuttgart, 2021.

In order to achieve relatively great (total) transmission losses in respect of the acoustic pressure, it is advantageous if the ratio is greater than or equal to 1.2 and in particular greater than or equal to 1.4 and in particular greater than or equal to 1.5.

It has been found that the influence on through-flow can be kept relatively small if the ratio is less than or equal to 3, and in particular less than or equal to 2.8, and in particular less than or equal to 2.6, and in particular less than or equal to 2.5.

In an advantageous embodiment, in which effective total transmission loss is achieved in respect of the acoustic pressure and good flow efficiency is achieved, the ratio is between 1.5 (inclusive) and 2 (inclusive).

It is in particular provided for the first opening to be an inlet opening for sound, and for the second opening to be an outlet opening for sound, and during operation of the cleaning apparatus for sound propagation to be from the first opening to the second opening. Sound is as it were fed in at the first opening and output (in attenuated form) at the second opening. In that case, in respect of sound propagation the first opening is closest to the at least one noise source. In principle, it is possible for the air stream to flow from the first opening to the second opening. However, it is also possible conversely for the air stream to flow from the second opening to the first opening. The influence that the direction of flow of the air stream in the at least one flow deflection element has on sound propagation is relatively small.

It is favorable if at least one of the following is provided:the first duct arm extends in a first direction of extent that is a direction normal to the first opening;the second duct arm extends in a second direction of extent that is a direction normal to the second opening;the first direction of extent and the second direction of extent are transverse and in particular perpendicular to one another;a first width direction, in which the first width is measured, is transverse and in particular perpendicular to the first direction of extent;a second width direction, in which the second width is measured, is transverse and in particular perpendicular to the second direction of extent;the first width direction and the second direction of extent are at least approximately parallel to one another;the second width direction and the first direction of extent are at least approximately parallel to one another;the first opening has an extent in a first depth direction that is perpendicular to the first width direction and transverse and in particular perpendicular to the second width direction;the second opening has an extent in a second depth direction that is oriented perpendicular to the second width direction and transverse and in particular perpendicular to the first width direction;the first width direction and the second width direction lie in a plane to which the first depth direction and the second depth direction are oriented transversely and in particular perpendicular.

As a result, the flow deflection element takes the form of an acoustic angle, wherein in particular the first duct arm and the second duct arm are perpendicular to one another. As a result of the mentioned geometric relationships, the first opening and the second opening are oriented transversely to one another.

Fundamentally, it is provided for the first width of the first opening to relate to a rectangular envelope which has sides having an extent in a first width direction and in a depth direction perpendicular to the first width direction, and for the second width of the second opening to relate to a rectangular envelope which has sides having an extent in a second width direction and in a second depth direction perpendicular to the second width direction. The first opening and the second opening need not necessarily be rectangular or square in shape. In that case, the first width and the second width are defined in relation to the rectangular envelope.

For the same reason, it is favorable if the first opening has a rectangular envelope which has sides extending in a first width direction and in a first depth direction perpendicular to the first width direction, and the second opening has a rectangular envelope which has sides extending in a second width direction and in a second depth direction perpendicular to the second width direction.

It is favorable if at least one of the following is provided:the first duct arm has a uniform cross section from the first opening to a region of transition to the second duct arm;the second duct arm has a uniform cross section from the second opening to a region of transition to the first duct arm.

As a result, the corresponding flow deflection element can be manufactured and also dimensioned in a simple manner.

In a structurally favorable simple embodiment, at least one of the following is provided:the first opening has a rectangular or square cross section;the first duct arm has a rectangular or square internal cross section;the second opening has a rectangular or square cross section;the second duct arm has a rectangular or square internal cross section.

In an advantageous embodiment, the at least one flow deflection element takes a flat form. As a result, at least one of the following is provided:the second width of the second opening is at least 1.2 times as large as a second depth of the second opening in a second depth direction perpendicular to a second width direction in which the second width is measured, and is in particular at least 1.9 times as large;the first width of the first opening is at least 1.2 times as large as a first depth of the first opening in a first depth direction perpendicular to a first width direction in which the first width is measured, and is in particular at least 1.9 times as large.

This produces a high degree of flow efficiency and also a broad band sound attenuation. In this context, reference is made to WO 2018/068850 A1.

In an advantageous embodiment, at an external corner region the first duct arm and the second duct arm have a common edge that extends in a depth direction, transversely to a first width direction and transversely to a second width direction. This produces effective sound attenuation at the region of transition from the first duct arm to the second duct arm. In particular, this enables a type of sound reflection to be achieved, wherein transverse modes arise.

This enables effective acoustic pressure reduction to be achieved.

In an advantageous embodiment, a region of transition from the first duct arm to the second duct arm has a curved wall, in particular having at least one of the following:the curved wall lies opposite a common edge of the first duct arm and the second duct arm;an internal radius at the curved wall is greater than half of a hydraulic diameter of the first duct arm.

This produces a high degree of flow efficiency. Pressure losses during flow through the at least one flow deflection element can be kept small.

In particular, at least one of the following is provided:the noise source is a fan or pump;the air guidance device is a guidance device for process air or cooling air;the air guidance device is a guidance device for cleaning air, and in particular blown air;the air guidance device is a guidance device for drying air.

In particular, the air guidance device is connected to the at least one noise source, as a fan, and in addition to its configuration as a noise source, the fan is also a source in particular for a blown stream or a suction-air stream.

The cleaning apparatus advantageously has a tool for application to a surface that is to be cleaned. This application tool may be a nozzle (such as a pressure nozzle or suction nozzle), such as a suction nozzle in the case of a vacuum cleaner or a pressure nozzle in the case of a leaf blower. It may be a roller from which for example moisture is removed by suction, or a squeegee in the case of a swabbing machine.

In one embodiment, the at least one application tool is coupled to the air guidance device. In the case of a corresponding nozzle, this is coupled directly to the air guidance device. In the case of wet-floor cleaning, it may for example be provided for a cleaning roller to have moisture removed from it by suction and thus to be coupled to the air guidance device.

The cleaning apparatus may take the form of a portable cleaning device or a fixed cleaning apparatus such as a gantry wash. The cleaning device may be self-propelling and self-steering, or take the form of a vehicle. It may be hand-held and/or manually guided.

A high degree of noise reduction is produced if the first duct arm and the second duct arm have a common edge at an external corner region.

A high degree of flow efficiency is produced if arranged in an interior of the at least one flow deflection element is a built-in wall which covers the edge in the interior, if the built-in wall faces a through-flow region in the interior, and if the built-in wall takes a form such that it guides flow and is sound-permeable.

As a result of the first duct arm and the second duct arm abutting against one another with the edge at the external corner region, effective noise reduction is produced by corresponding sound attenuation.

By providing the built-in wall in sound-permeable form, this effect of effective noise reduction as a result of the form taken by the edge is retained. As a result of the flow-guiding (flow-conducting) function of the built-in wall, a high degree of flow efficiency is produced, since the corresponding fluid stream that is guided through by the at least one flow deflection element is guided past in front of the edge.

According to the invention, a flow deflection element is provided that brings about effective sound attenuation at the same time as a high degree of flow efficiency. In this context, reference is made to the dissertation “Acoustic and aerodynamic phenomena in duct bends”, which is not a prior publication, by Dominik Scholl, Institute for Acoustics and Building Physics at the University of Stuttgart, 2021.

It is favorable if the built-in wall abuts against an inner side of the first duct arm and an inner side of the second duct arm. This produces effective flow guidance.

In one embodiment, at least one of the following is provided:a transition of the built-in wall to an inner side of the first duct arm and the second duct arm is in each case smooth and in particular free of edges;the built-in wall takes a form such that it is curved facing the through-flow region, and in particular is concavely curved.

This produces an effective flow-conducting function with a high degree of flow efficiency. In particular, turbulence of the fluidic flow at the transition from the built-in wall to an inner side of the duct arm is at least kept low.

It is favorable if at least one of the following is present:the built-in wall is or comprises a perforated element and in particular a perforated panel element or block element;the built-in wall is or comprises a porous foam element or fiber material element;an opening width of openings in the built-in wall toward the edge is at least λ/50, where λ is an upper sound wavelength of relevance to noise emission;an opening width of openings in the built-in wall toward the edge is at least 1 mm.

The built-in wall comprises sound-permeable openings. The built-in wall may be a perforated element, in particular a panel element or block element such as a sheet-metal element. It is also possible for the built-in wall to be or to comprise a porous foam element or fiber material element, and for example for the entire space of the through-flow region up to the edge to be filled.

It is favorable if an opening width of openings (for example perforations or pores) in the built-in wall is at least λ/50 for an upper sound wavelength of relevance to noise emission. This enables sound permeability toward the edge to be achieved. In particular, the opening width is at least 1 mm.

The edge is in particular a connection line between opposing external corners of the at least one flow deflection element. It is favorable if, at the edge, the first duct arm and the second duct arm are at an angle of between 70° and 110° and in particular at an angle of between 80° and 100°.

In an advantageous embodiment, the first duct arm and the second duct arm meet perpendicular to one another.

In a structurally simple embodiment, the built-in wall has a constant curvature—that is to say that, in particular toward the through-flow region thereof, it takes the shape of a portion of a cylinder outer face. In that case, simple manufacturability is produced at the same time as a high degree of flow efficiency.

It is favorable if a center point of a circle of curvature for the built-in wall lies between the first duct arm and the second duct arm. This produces a structurally simple configuration.

It has proved favorable if a region of transition from the first duct arm to the second duct arm has, at an internal corner region which lies opposite the external corner region, a wall that is curved relative to the interior of the at least one flow deflection element. This produces a high degree of flow efficiency.

In particular, the curved wall lies opposite the built-in wall, and a through-flow region in the interior lies between the curved wall and the built-in wall. The built-in wall and the curved wall conduct flow of the stream that flows through the through-flow region.

In an advantageous embodiment, the curved wall has a constant curvature.

It has proved favorable for a high degree of flow efficiency if a circle of curvature for the curved wall has an internal radius that is greater than half of a hydraulic diameter of a first opening of the first duct arm.

In a structurally favorable embodiment, the curved wall and the built-in wall are oriented parallel and have in particular a common center point.

In particular here, the built-in wall is oriented parallel to a first depth direction and/or parallel to a second depth direction, and is of uniform height in the first depth direction and/or the second depth direction. This produces a high degree of flow efficiency.

According to the invention, the use of a flow deflection element that has a first duct arm and a second duct arm, wherein the second duct arm is oriented transversely to the first duct arm and wherein, during operation of the cleaning apparatus, there is sound propagation from the first duct arm to the second duct arm, and wherein a mode filter device for transverse modes is arranged at the flow deflection element, having at least one mode filter that is positioned at the second duct arm, is provided in the case of a cleaning apparatus with a noise source.

This produces effective noise reduction.

The advantages of the use according to the invention were explained above in the context of the cleaning apparatus according to the invention.

Further advantageous embodiments were likewise explained above in the context of the cleaning apparatus according to the invention.

In particular, air flows through the flow deflection element during operation of the cleaning apparatus. The flow deflection element is thus a deflection element for both fluid flow and for sound propagation.

The description below of preferred embodiments serves, in conjunction with the drawings, to explain the invention in more detail.

DETAILED DESCRIPTION OF THE INVENTION

A cleaning apparatus according to the invention, of which exemplary embodiments are shown inFIGS.12to47and are explained in more detail below, comprises a (at least one) noise source. The noise source is a generator of sound.

An example of a noise source of this kind is a fan having at least one rotating impeller. Depending on the application, the fan serves for example to generate a suction stream or a blown stream. The cleaning apparatus comprises an air guidance device in order to guide an air stream. The air guidance device is coupled to the noise source and can fundamentally propagate sound in the air guidance device.

Connected to the air guidance device is a (at least one) flow deflection element, or the air guidance device comprises such a flow deflection element.

One exemplary embodiment of a flow deflection element of this kind is shown inFIG.1and designated10. The flow deflection element12serves to reduce noise emission by the cleaning apparatus. Flow deflection elements of this kind are therefore also designated as acoustic angles. The object of the flow deflection element10is to bring about the greatest possible acoustic loss. However, at the same time throughput through the air guidance device should not be substantially impaired by flow through the at least one flow deflection element10.

Furthermore, it is advantageous if flow noise that is generated in the flow deflection element10itself during operation of the cleaning apparatus is minimized.

The flow deflection element10takes the form of a duct12with an interior14configured to be flowed through. The flow deflection element10has a first duct arm16and a second duct arm18.

In one exemplary embodiment, the first duct arm16extends in a first direction of extent20. The second duct arm18extends in a second direction of extent22.

In particular, the first duct arm16extends out of a region24of transition into the second duct arm18, in a straight line along the first direction of extent20. Accordingly, the second duct arm18extends out of the region24of transition into the first duct arm16, in a straight line along the second direction of extent22.

The first duct arm16and the second duct arm18are oriented transversely and in particular perpendicular to one another. The first direction of extent20and the second direction of extent22are transverse to one another, being in particular perpendicular to one another.

The first duct arm16has a first opening26. The first opening26is at a spacing from the region24of transition. The second duct arm18has a second opening28. This is at a spacing from the region24of transition.

At the first opening26, sound is fed into the duct12. At the second opening28, sound is output from the duct12.

The first opening26may be an inlet opening for an air stream and the second opening28an outlet opening for the air stream, or the second opening28is an inlet opening for the air stream and the first opening26an outlet opening.

By way of the first opening26, the flow deflection element10is connected to the air guidance device of the cleaning device such that sound is generated, as an input side for sound propagation. Furthermore, the flow deflection element10is connected to the air guidance device of the cleaning apparatus by way of the second opening28such that sound is generated, as an output side. This is explained in more detail below with reference to embodiments of cleaning apparatus.

During operation of the cleaning apparatus, an air stream30flows in a direction for example from the first opening26to the second opening28, or from the second opening28to the first opening26.

A (surface) normal to the first opening26is parallel to the first direction of extent20. A (surface) normal to the second opening28is parallel to the second direction of extent22.

The first opening26and the second opening28are oriented transversely and in particular perpendicular to one another, in accordance with the orientation of the directions of extent20and22.

In the exemplary embodiment according toFIG.1, the first opening26and the second opening28each have a square or rectangular cross section. At the respective opening26and28, the first opening26and the second opening28have an envelope that is square or rectangular, wherein sides of these envelopes coincide with delimitation sides of the respective opening26and28.

The first duct arm16has, at least toward the region24of transition, a uniform cross section corresponding to the cross section at the first opening26. Furthermore, the second duct arm18has, at least as far as the region24of transition, a uniform cross section corresponding to the cross section of the second opening28.

The first opening26has, in a first width direction32, a first width H1. In a first depth direction34, the first opening26has a first depth T1. The first depth direction34is located perpendicular to the first width direction32.

The first opening26extends by a width H1in the first width direction32and by a depth T1in the first depth direction34.

Correspondingly, the second opening28has a width H2in a second width direction36and a depth T2in a second depth direction38. The second depth direction38is located perpendicular to the second width direction36.

The first width direction32and the second width direction36are located transversely and in particular perpendicular to one another.

The first depth direction34and the second depth direction38are located at least approximately parallel to one another. The first depth direction34and the second width direction36are perpendicular to one another. The second depth direction38and the first width direction32are perpendicular to one another.

The first width direction32and the first depth direction34are each perpendicular to the first direction of extent20. The second width direction36and the second depth direction38are each perpendicular to the second direction of extent22.

The first width direction32is at least approximately parallel to the second direction of extent22. The first depth direction34is perpendicular to the second direction of extent22. The second width direction36is at least approximately parallel to the first direction of extent20. The second depth direction38is located perpendicular to the first direction of extent20.

The flow deflection element10has a first delimitation plane40and, at a spacing, an opposing second delimitation plane42. In one exemplary embodiment, the first delimitation plane40and the second delimitation plane42are parallel to one another (FIG.1). The first width direction32and the second width direction36are preferably located in the same plane and are parallel to the first delimitation plane40and the second delimitation plane42.

The first depth direction34and the second depth direction38are located transversely and in particular perpendicular to the first delimitation plane40and the second delimitation plane42.

At the region24of transition, the flow deflection element10has an external corner region44and an internal corner region46. Formed at the external corner region44between the first duct arm16and the second duct arm18, for sound reduction, is an edge48. This edge48is a (straight) connection line between opposing corners50a,50bof the flow deflection element10. The corners50a,50bare located at a region of connection between the first duct arm16and the second duct arm18. The corner50ais located on the second delimitation plane42, and the corner50bis located on the first delimitation plane40.

In one exemplary embodiment, arranged in the interior14is a built-in wall52, which guides flow along it and at the same time covers the edge48in the interior14in relation to flow guidance. The built-in wall52is flow-conducting and at the same time sound-permeable.

In particular, the built-in wall52is curved toward the interior14, with a radius R0.

In relation to sound absorption, however, the edge48is effective, because of the sound permeability of the built-in wall52.

In one exemplary embodiment, the flow deflection element10comprises a curved wall54at the region24of transition, at the internal corner region46. The wall54is curved at least relative to the interior14and has for example a constant curvature, and has a radius R1.

In one exemplary embodiment, it is provided for the internal radius R1of this curved wall54to be greater than half of a hydraulic diameter of the first duct arm16.

Fundamentally, the first duct arm16and the second duct arm18may be located at an angle α to one another in respect of their directions of extent20,22. Preferably, this angle α is 90°—that is to say that the first direction of extent20and the second direction of extent22are perpendicular to one another.

InFIGS.2and3, the basic flow conditions that may occur when there is flow through the flow deflection element10(with the edge48and an edge at the internal corner region46) are shown schematically shown. In this context, reference is made to the dissertation by Dominik Scholl in “Acoustic and aerodynamic phenomena in duct bends”, Institute for Acoustics and Building Physics at the University of Stuttgart, 2021, which is not a prior publication, and in particular Chapter 2 there, “Flow efficiency of duct bends”. This document is explicitly referenced.

As fluid flows through the first duct arm16, a flow profile56has a velocity gradient close to the wall.

In the external corner region44, a dead zone58for the flow zone may be formed. In the second duct arm18, a flow separation zone60may be formed at the region24of transition, downstream of the internal corner region46.

In the second duct arm18, flow with a distorted flow profile62may fundamentally be formed.

In particular, it is also possible for a secondary stream64(seeFIG.3) to be formed in the second duct arm18. Fundamentally, turbulent flows that may be formed (FIGS.2and3) result in undesired losses of pressure. Such pressure losses may be kept small by appropriate flow guidance, in particular using the curved wall54and the built-in wall52.

By coupling the flow deflection element10to the air guidance device of the cleaning apparatus, with the air guidance device in turn coupled to the noise source of the cleaning apparatus, it is fundamentally possible for sound waves to propagate through the duct12.

Fundamentally, sound waves have a fundamental mode which propagates in the x direction (along the direction of extent20or22). Fundamental modes are schematically shown inFIG.4in the line designated (1).

As well, transverse modes may arise, and these may propagate in a y direction according toFIG.4(see alsoFIG.1) and in a z direction.

The x direction is parallel to the width direction32or36, and the z direction is parallel to the depth direction34or38. Of transverse modes, there are “width transverse modes”, which propagate in the y direction, and “depth modes”, which propagate in the z direction. The depth modes play a subordinate part in sound attenuation, and so are not further discussed below. Nor are the depth modes shown inFIG.4.

Columns (2) and (3) show (width) transverse modes (1st transverse mode, 2nd transverse mode) of sound propagation that correspond to different frequencies.

Frequency f1is 3,300 Hz, frequency f2is 6,700 Hz, and frequency f3is 8,000 Hz. The acoustic pressure is shown. Of the transverse modes, there are the first order (“first transverse mode”) and higher orders such as the second transverse mode, etc.

Transverse modes have a lower cutoff frequency below which they do not propagate, or at which an evanescent sound propagation is then present. InFIG.4, a cross next to the illustration of the acoustic pressure course indicates that the mode is evanescent—that is to say cannot propagate. This means for example that at frequency f1the first transverse mode (line (2)) and the second transverse mode (line (3)) cannot be formed, only the fundamental mode.

It can be seen that at frequency f2the fundamental mode and the first transverse mode can be formed, and at frequency f3the fundamental mode, the first transverse mode and the second transverse mode can be formed.

An essential element of the sound attenuation by the flow deflection element10is that at the region24of transition, and in particular at the external corner region44, fundamental modes are at least partly converted into transverse modes. As a result, on exiting at the second opening28, there is a reduction in acoustic pressure, or a transmission loss for the acoustic pressure, on passing through the flow deflection element10.

In this context, reference is made to the dissertation by Dominik Scholl for which the details are given above.

In particular for reducing pressure losses in the flow, it is advantageous if the flow deflection element10takes a flat form, inasmuch as the second width H2is larger than the depth T2, and in particular at least 1.2 times as large, and preferably at least 1.9 times as large. Correspondingly, the width H1takes a form larger than the depth T1. In this context, reference is explicitly made to WO 2018/068850 A1.

In a first aspect of the solution according to the invention, the first width H1at the first opening26is larger than the second width H2at the second opening28—that is to say that the ratio H1/H2is greater than 1. It has proved advantageous if this ratio is greater than or equal to 1.2 and in particular greater than or equal to 1.4 and in particular greater than or equal to 1.5.

Further, in order to enable a configuration with sufficient flow throughput, it is favorable if this ratio H1/H2is less than or equal to 3 and in particular less than or equal to 2.8 and in particular less than or equal to 2.6 and in particular less than or equal to 2.5.

It has been found that, in order on the one hand to enable a configuration with sufficient flow throughput and on the other to achieve a sufficient reduction in sound, it is particularly favorable if the ratio H1/H2is in the (inclusive) range between 1.5 and 2.

FIG.5shows the total transmission loss TL for the acoustic pressure on flow through the duct12(with a rectangular shape). Here, the total transmission loss is the transmission loss integrated over all frequencies. It is shown as a function of the parameter H1/H2—that is to say the ratio of the first width H1to the second width H2.

The result here is a total transmission loss of more than 5 dB (A) when this ratio is greater than 1. It is fundamentally the case that the greater this ratio, the greater the total transmission loss. However, large values of this ratio result in sufficient flow throughput no longer being configurable (as indeed do very small values of this ratio).

For this reason, it is favorable if this ratio is greater than 1 and in particular greater than or equal to 1.5 and preferably less than or equal to 3 and in particular less than or equal to 2.

With optimized flow guidance (with relatively small pressure losses), the result is then effective sound attenuation.

The transmission losses (integrated over all frequencies) resulting from the greater width H1of the first opening26by comparison with the width H2of the second opening28are attributable to the excitation of evanescent modes, in particular in the first duct arm16. As a result, additional peaks occur in the frequency-resolved transmission loss spectrum. In this context, reference is made to the above-mentioned dissertation by Dominik Scholl, and in particular to Chapters 1.2.4 and 1.2.5.

The above ratios have been described with reference to square or rectangular cross sections of the flow deflection element10(seeFIG.6(a)). They are also applicable to other cross sectional shapes of the flow deflection element10.

In the case of the flow deflection element10′ according toFIG.6(b), the rectangular shape is rounded. The first opening26′ and the second opening28′ each have an envelope66(shown only for the second opening28′ inFIG.6(b)) that is a rectangle. The widths H2and H1relate to this envelope66in each case.

FIG.6(c)shows a flow deflection element10″ that is oval or circular in shape.

The first opening26″ and the second opening28″ each have an envelope68that is rectangular. The widths H2and H1relate to the widths of these envelopes68.

FIG.6(d)shows a flow deflection element10′″ of which the cross section has a narrowing, and is in the shape of an eight on its side. The first opening26′″ and the second opening28′″ there each have a rectangular envelope70. The second width H2and the first width H1each relate to this envelope70.

The first aspect of the solution according to the invention, according to which the ratio of the first width H1and the second width H2is greater than 1, refers—where the corresponding openings are not themselves square or rectangular—to corresponding square and rectangular envelopes66,68,70at the respective openings26′ and28′,26″ and28″, and26′″ and28″ respectively.

In a second aspect of the solution according to the invention, transverse modes in the second duct arm18are attenuated in a targeted manner (FIGS.7,8).

The corresponding flow deflection element10is provided with a mode filter device72for transverse modes. Here, at least one mode filter74(FIG.7(a)) for transverse modes is provided, and is arranged on the second duct arm18.

The mode filter device72is configured in particular to form width transverse modes—that is to say transverse modes that propagate in the y direction, under the geometric conditions according toFIG.4.

As a result of the region24of transition, it is fundamentally possible for propagating transverse modes to be formed in the second duct arm18, as described above. The fact that the mode filter device72has a mode filter74on the second duct arm18makes it possible for transverse modes to be filtered in a targeted manner in order to achieve a reduction in sound levels (sound attenuation).

Fundamentally, it is possible for a corresponding mode filter for transverse modes also to be arranged on the first duct arm16, wherein the decisive influence of a mode filter74on transverse modes lies in the positioning thereof at the first duct arm16.

In a first exemplary embodiment of a mode filter74for transverse modes, this mode filter74takes the form of an absorptive sound attenuator76. The absorptive sound attenuator76has material78that is absorptive in relation to sound, such as a foam material. The absorptive material78takes a form or is arranged in particular as a layer.

The absorptive material78is arranged at an inner side80of the second duct arm18such that it is flush with this inner side80or set back in relation to this inner side.

In this case, it may fundamentally be provided for the absorptive material78to be arranged at the inner side80of the second duct arm18over the entire internal cross section.

It is also possible, and fundamentally sufficient for filtering width transverse modes, if the mode filter74for these transverse modes is positioned only in the second depth direction38.

In its layer arrangement, the absorptive material78has a certain thickness M.

Furthermore, it has an extent of length L in the second direction of extent22.

Basically, it is provided for the mode filter74to be at a spacing from the first duct arm16by a spacing D. In this arrangement, the spacing D is located between the mode filter74and an interface region between the first duct arm16and the second duct arm18at the internal corner region46.

It has proved favorable if, in order to achieve effective filtering of transverse modes, this spacing D is at least 0.1 times and preferably at least 0.15 times the first width H1of the first duct arm16.

In particular, a direction in which this spacing D is spaced is parallel to the second direction of extent22and parallel to the first width direction32and perpendicular to the second width direction38.

Further, this spacing relates to a side82of the first duct arm16at the internal corner region46.

It has proved favorable if the length L is at least 1.5 times and preferably at least 2.5 times the first width H1or the second width H2.

In one exemplary embodiment, it is provided for the length L to be at most 2.5 times the first width H1or the second width H2.

Further, it has proved favorable if the thickness M of the absorptive material78is at least 0.1 times the first width H1or the second width H2. In one exemplary embodiment, this thickness M is at most 0.3 times the first width H1or the second width H2.

In one concrete exemplary embodiment, in which the first width H1and the second width H2are of the same size, the thickness M is 0.2 H1, the length L is 2·H1, and the spacing D is 0.2 H1.

FIG.8shows the transmission loss over a standardized frequency fcfor the shown arrangement corresponding to the arrangement according toFIG.7(a)of the mode filter74. The standardized frequency fcis dimensionless and is defined as 2 fH1/c, where c is the speed of sound and f is the frequency.

FIG.8shows the transmission loss for the sound propagation from B to A (that is to say from the first opening26in the direction of the second opening28) and in the reverse direction (that is to say from the second opening28to the first opening26). The effectiveness as a result of providing the mode filter74at the second duct arm18when flow is from the first opening26to the second opening28can be seen in the increase in transmission loss.

The effectiveness of sound attenuation by the region24of transition (by the transverse arrangement of the first duct arm16and the second duct arm18) can be seen by comparing the curves, and the effectiveness of the mode filter74at the second duct arm18can then be seen fromFIG.8, wherein the flow is output at the second opening28, at the second duct arm18.

In this context, reference is made to the above-mentioned dissertation by Dominik Scholl, and in particular to Chapter 1.4.2 there.

In one exemplary embodiment, the mode filter device72comprises a mode filter84for transverse modes which is a chamber-type sound attenuator (FIG.7(b)).

The mode filter84comprises a chamber86which is arranged at the second duct arm18and is spaced from the first duct arm16at a spacing D, to a side88of the first duct arm16that is located at the internal corner region46.

The chamber86forms as it were a widening of the second duct arm18. The chamber86has a width W that is larger than the second width H2of the second duct arm18outside the chamber86; the chamber86forms a cross sectional widening on the second duct arm18.

Fundamentally, this widening may be to all sides. For mode filtering of width transverse modes, it is sufficient if the chamber86has the same depth T2as the second duct arm18and is only widened in the second width direction36.

The mode filter84(the chamber-type sound attenuator84) has a length L parallel to the second direction of extent22.

It is in particular provided for the spacing D to be at least 0.1 times and preferably at least 0.3 times the width H1or H2.

In one concrete exemplary embodiment, the spacing D is H1or H2.

It is provided for the width W of the chamber86in the second width direction36to be larger than the first width H1or the second width H2. In particular, the width W is at least twice as large as the first width H1or the second width H2.

In one concrete exemplary embodiment the width W is 3.15 H1, and in another concrete exemplary embodiment the width W is 2.87 H2, with the first width H1and the second width H2being the same in this concrete exemplary embodiment.

Further, it is provided for the length L of the chamber86to be larger than the first width H1or the second width H2, and at least 1.2 times as large.

In one concrete exemplary embodiment, the length L=1.42×H1(where W=3.15 H1). In another concrete exemplary embodiment, the length L=4.2 H1(where W=2.7 H1).

In both the said concrete exemplary embodiments, the spacing D=H1.

The mode filter device72with the mode filter84for transverse modes has fundamentally the same effects as the mode filter74. First-order and indeed higher-order transverse modes are attenuated by the mode filter84.

Another exemplary embodiment of a mode filter is a perforated device (90) that is arranged at the second duct arm18(FIG.7(c)).

In one exemplary embodiment (FIG.7(c)), this mode filter90for transverse modes is a plate93provided with openings91. The plate93is arranged inside the second duct arm18and is in particular oriented parallel to the second depth direction38; the mode filter90with the perforated plate93is oriented transversely and in particular perpendicular to the first width direction32. A plane of the mode filter90is spanned as it were by vectors in the second depth direction38and the second direction of extent22.

Preferably, the perforated plate93is arranged centrally such that its spacing from opposing sides92a,92bof the second duct arm18is the same.

The mode filter90(the plate93) is located at a spacing D from the first duct arm16(see above with reference to the mode filters74and84).

This spacing D is in particular at least 0.1 times the first width H1or the second width H2.

The openings91in the plate93are in particular arranged such that they are open in the second width direction36.

It is provided for the openings91in the plate93to have an opening width that is less than or equal to 1 mm.

It is furthermore in particular provided for an opening density to be greater than or equal to 10 openings per square centimeter.

Further, it is provided for a wall thickness (parallel to the second width direction36) of the plate93to be at least 1 mm.

In the exemplary embodiment shown inFIG.7(c), the perforated plate93is arranged inside the second duct arm18. A fluid stream can flow past the plate93on either side of it. It is also possible for a plurality of corresponding plates arranged in the interior14to be provided. In particular, adjacent plate93are at a spacing from one another, and fluid can flow through between adjacent plates. In this case, it is in particular provided for each of these plate93to be oriented parallel to the second direction of extent22.

A corresponding plate93takes the form for example of a sheet-metal part.

As an alternative or in addition, it may also be provided for the perforated device90to comprise one or more open-pore structures. The corresponding pores in the open-pore structure form openings that preferably have the above-mentioned parameters (opening width less than or equal to 1 mm; opening density greater than or equal to 10 openings per square centimeter; wall thickness greater than or equal to 1 mm). The open-pore structure takes the form for example of a block that is correspondingly arranged at the second duct arm18, in the interior14. The open-pore structure is for example a foam structure and in particular an absorbent foam structure. If an absorbent foam structure is provided, it is additionally possible for sound absorption (in addition to the “transverse mode canceling”) to take place at the perforated device90.

The open-pore structure may for example also be a fiber material structure such as a nonwoven, a woven material or a knitted material.

In a third aspect of the solution according to the invention, the built-in wall52is provided (seeFIG.10).

Fundamentally, with the flow deflection element10it is provided for the first duct arm16and the second duct arm18to meet in an edge48at the external corner region44, as described above (seeFIG.9(a)). This produces effective sound attenuation.

For flow guidance, it is favorable if a “smooth” wall along which the flow is guided and which is in particular free of edges is present (seeFIG.9(b)).

In the third aspect of the solution according to the invention, it is provided for the first duct arm16and the second duct arm18to meet at an edge48in an external corner region44, as already described above with reference to the flow deflection element10according toFIG.1.

The built-in wall52is arranged in the interior14. The built-in wall52covers the edge48in the interior14.

In one exemplary embodiment, the built-in wall52takes a form that is curved toward a through-flow region94located in the interior14(and that is concave toward the through-flow region94).

The built-in wall52approaches a corresponding wall96of the first duct arm16and a corresponding wall98of the second duct arm18smoothly and in particular in a manner that is free of edges.

The built-in wall52merges tangentially into the wall96and the wall98; where the line of merging is described by a corresponding curve, this curve is continuously differentiable at the transition.

The air stream that is guided through by the corresponding flow deflection element10is guided along a side100of the built-in wall52that is upstream of the edge48and faces the through-flow region94. The stream is thus “kept away” from the edge48.

The built-in wall52takes a form such that it conducts flow and is sound-permeable (at the sound frequencies occurring with the corresponding noise source). The permeability is achieved by perforations (openings).

In one exemplary embodiment, the built-in wall is formed by a wall element102that is for example a perforated sheet-metal part. This is then positioned accordingly in the interior14of the flow deflection element10.

The perforations are openings from the through-flow region94toward the edge48.

A width of the corresponding openings is in particular greater than λ/50, where λ is a typical upper sound wavelength that is to undergo sound attenuation.

In an alternative exemplary embodiment, the built-in wall52is formed by a porous element104and porous foam element. This has openings from the side100toward the edge48, the width thereof being in particular greater than λ/50.

In one concrete exemplary embodiment, the built-in wall has a constant curvature at the side100—that is to say it has a circular curvature. A center point106of a corresponding circle of curvature is in this case located between the first duct arm16and the second duct arm18.

As described above, it is advantageous if the corresponding transition wall at the internal corner region46is likewise curved (curved wall54). In this case, it may be provided for this curved wall54to have a constant curvature R1(which is in particular greater than half of a hydraulic diameter of the first opening26of the first duct arm16).

In one exemplary embodiment, the center point of the corresponding circle of curvature of the curved wall54coincides with the center point106.

This produces effective flow guidance.

In one concrete exemplary embodiment, the side100and an inner side of the curved wall54are parallel to one another.

If the first width H1is greater than the width H2, it may also be provided for the side100and the inner side of the curved wall54not to be parallel.

The built-in wall52extends in the first depth direction34and in the second depth direction38. The circle of curvature is as it were a cylinder of curvature having a cylinder axis parallel to the first depth direction34and the second depth direction38.

In a further exemplary embodiment (seeFIG.11), a built-in wall52′ is provided that does not take a curved form, and runs in a straight line between the first duct arm and the second duct arm. The built-in wall52′ is formed for example by a panel element that is positioned between the first duct arm and the second duct arm, or is implemented by a corresponding prism element, for example made from a foam material or fiber material.

The foam material or fiber material may in addition take the form of an absorbent material, for sound absorption.

A flow deflection element10in the case of the third aspect of the solution according to the invention, with the built-in wall52,52′, produces effective flow guidance at the same time as keeping pressure losses small.

For sound attenuation, the edge48in the interior14is effective. The disadvantage for flow guidance resulting from the edge48to the interior14is thus as it were compensated by the built-in wall52,52′. Flow guidance during flow through the flow deflection element10is improved, moreover with effective sound attenuation.

Three aspects for effective sound attenuation (while minimizing pressure losses during flow guidance) have been discussed above, namely: as a first aspect, an enlarged first width H1by comparison with the second width H2; as a second aspect, the provision of one or more mode filters for transverse modes at the second duct arm18; and as a third aspect, the provision of the built-in wall52, which covers the edge48in the interior14for flow guidance and at the same time is sound-permeable.

Fundamentally, these aspects are independent of one another, and no disruptive influence of these different configurations on one another has been found. It is thus to be expected that a combination of these aspects produces sound attenuation. It is possible to combine the first aspect with the second aspect, to combine the second aspect with the third aspect, the first aspect with the third aspect, or all three aspects with one another.

FIG.11shows, schematically, a flow deflection element108in which all three aspects are implemented.

A width H1at a first opening110of a first duct arm112is larger than a width H2at a second opening114of a second duct arm116. The second duct arm116is oriented transversely and in particular perpendicular to the first duct arm112, wherein an edge120is present at an external corner region118.

Arranged at the second duct arm116, in particular at a spacing from the first duct arm112, is a mode filter122for transverse modes (first transverse modes, second transverse modes, etc.).

Arranged in an interior124of the flow deflection element108is a curved built-in wall126, which covers the edge120in the interior124toward a through-flow region128, and in so doing guides flow. The built-in wall126is sound-permeable, resulting in effective sound attenuation.

A corresponding transition wall132takes a curved form at an internal corner region130(in particular having an internal radius that is greater than half of a hydraulic diameter of the first opening110).

Fundamentally, it may also be provided for the flow deflection element108to take a “flat” form, as described above, wherein the widths H1, H2are larger than depths perpendicular thereto (see WO 2018/068850 A1).

In respect of the said aspects of the invention, reference is made explicitly and in its entirety to the dissertation by Dominik Scholl for which the details are given above.

A flat form of the flow deflection element may be advantageous for flow efficiency and also for broad band transmission losses.

InFIGS.12to47are exemplary embodiments of cleaning apparatus having a (at least one) corresponding flow deflection element, in which one or more of the above-mentioned aspects according to the invention are implemented, shown.

One exemplary embodiment of a cleaning apparatus is a suction device134(FIGS.12to15). The suction device134is for example a stand-alone vacuum cleaner. This vacuum cleaner comprises a fan136that generates a suction stream. This suction stream acts on a suction hose138. A filter device140is provided, through which there is flow as a result of operation of the suction stream of the cleaning apparatus134.

Connected to the fan136is an air guidance device142. Process air is guided away in this air guidance device142. This process air is the exhaust air from the fan136. This is air cleaned by the filter device140.

This air guidance device142has a flow deflection element10as described above. In the schematic exemplary embodiment according toFIG.12, the air guidance device142is formed by a flow deflection element of this kind, wherein the first opening26is connected directly to an outlet of the fan136, and the second opening28opens to the exterior.

The air guidance device142may also comprise a flow deflection element10of this kind as a constituent part.

The fan136itself, which generates the corresponding air stream in the air guidance device142, is in this case also the sound-emitting noise source.

The flow deflection element10of the air guidance device142ensures corresponding sound attenuation, wherein the pressure loss during flow guidance is minimized as described above.

FIG.12shows, schematically, a flow deflection element10in which the ratio of the first width H1at the first opening26to the second width H2at the second opening28is greater than 1.

The fan136comprises a fan motor144with which a cooling fan146is associated. The cooling fan serves to cool the fan motor144, in particular using air; the fan motor144is air-cooled.

For this purpose, a corresponding air guidance device148is provided, which may likewise be provided with a flow deflection element150. The direction of sound propagation there is the opposite to the direction of the flow throughput.

A mode filter74may for example be arranged at the second duct arm18of the flow deflection element10and/or150(FIGS.13,14).

It is for example also possible for the flow deflection element10to be provided with a built-in wall52.

The flow deflection element150may also be provided with a mode filter for transverse modes at a flow arm that is an input arm.

FIGS.16to19show, schematically, as an exemplary embodiment of a cleaning apparatus, a high-pressure cleaner152. This comprises a motor154as the noise source. The motor154is air-cooled, and an air guidance device156is provided.

The air guidance device156comprises in particular a flow deflection element10, of which the input side is downstream of the motor154and the output side leads to the exterior. The flow deflection element10may take a form as described above, and have for example a greater width at a first opening26than at a second opening28(FIG.16). It may be provided with a mode filter74(FIGS.17,18). It may be provided with a built-in wall52(FIG.19).

A further exemplary embodiment of a cleaning apparatus is a wet-floor cleaner158, which is in particular hand-held and/or manually guided (FIGS.20to23). In particular, a user in a standing position can guide this wet-floor cleaner158over a floor that is to be cleaned.

The wet-floor cleaner158comprises at least one cleaning roller160, which is in particular a textile roller. Cleaning liquid is supplied to the at least one cleaning roller.

A fan162, which is a suction fan, is provided. Fluid from the cleaning roller160can be removed by suction by way of this fan. The fluid is cleaning liquid carrying dirt particles.

A corresponding dirt-collection container164is provided, with an associated and for example integrated separator.

The fan162comprises a fan motor166as the noise source. This is air-cooled. An air guidance device168which comprises a flow deflection element10according to the invention is provided.

In the exemplary embodiment shown, the flow deflection element10itself forms the air guidance device168.

In that case, it may in particular be provided for a first width of the flow deflection element10to be larger at the input side than an opening28on the output side (FIG.20). A mode filter74may be provided at the corresponding second duct arm18(FIGS.21,22).

A built-in wall52may be arranged at the flow deflection element.

A further exemplary embodiment of a cleaning apparatus according to the invention is a window vacuum cleaner170(FIGS.24to27).

This window vacuum cleaner comprises a fan172in the form of a suction fan.

Exhaust air is guided away from the fan in an air guidance device174. The fan172(having a fan and/or a corresponding impeller) is a noise source.

The air guidance device174comprises a flow deflection element10on which at least one of the aspects according to the invention (ratio of the first width to the second width; mode filter for transverse modes at the second duct arm; built-in wall) is implemented.

A further exemplary embodiment of a cleaning apparatus according to the invention is a leaf blower176(FIGS.28to31).

This leaf blower comprises a fan178that generates a blown stream180. Air (for generating the blown stream180) is supplied to the fan178by way of an air guidance device182.

The air guidance device182is or comprises a flow deflection element10which takes a form corresponding to at least one of the above-mentioned aspects.

A further exemplary embodiment of a cleaning apparatus according to the invention is a sweeper184, which is schematically shown inFIGS.32to35in the form of a sit-on sweeper. This sweeper184comprises a fan186as the noise source. Connected to the fan186is an air guidance device188that is or comprises an acoustic angle10according to the invention.

In particular, an input width is larger than an output width (FIG.32), and/or a mode filter for transverse modes is provided (FIGS.33,34), and/or a built-in wall52is provided (FIG.35).

A further exemplary embodiment of a cleaning apparatus according to the invention is a swabbing machine190, wherein a walk-behind floor cleaning machine is shown inFIGS.36to39. This comprises a fan192for generating a suction stream. The fan192forms the noise source. The fan192comprises an air guidance device194for exhaust air. This air guidance device194is or comprises a flow deflection element10according to the invention.

A further exemplary embodiment of a cleaning apparatus according to the invention is a municipal vehicle196(FIGS.40to43). This takes the form for example of a vehicle with center-pivot steering. It comprises a fan198having an air guidance device for exhaust air, wherein a flow deflection element is correspondingly connected to this air guidance device.

A further exemplary embodiment of a cleaning apparatus according to the invention is a gantry wash200, in particular for vehicles (FIGS.44to47). This gantry wash200comprises a fan202which generates a blown stream204. This blown stream204can be used to dry a vehicle.

A corresponding air guidance device206is provided for the blown stream, and is provided with a flow deflection element10according to the invention.

Further, an air guidance device208is provided by way of which air is supplied to the fan198. A flow deflection element10according to the invention may be seated on this air guidance device208as well.

LIST OF REFERENCE NUMERALS