Patent Application
20230038485
The invention pertains to a household appliance, particularly a floor treatment appliance, with an appliance housing, a fan arranged in the appliance housing, an outlet opening formed in the appliance housing downstream of the fan, a flow channel connecting the outlet opening to the fan in a flow-conducting manner, and a sound absorption device assigned to the flow channel in order to absorb sound generated by the operation of the household appliance.
Household appliances of the aforementioned type are known from the prior art. These household appliances are realized, for example, in the form of floor treatment appliances, particularly vacuum cleaning appliances, with a fan for vacuuming up dust and dirt from a surface to be cleaned. The vacuumed material usually is transferred into a vacuumed material chamber by means of the fan and collected therein while air cleaned by a filter flows to the fan and ultimately to the outlet opening.
The operation of the fan and an associated rotation of fan blades generate sound waves that inevitably become audible for a user during the operation of the household appliance. In order to reduce the associated background noise to such a degree that it is not perceived as annoying by the user, the prior art discloses sound absorbers that are installed into the appliance housing of the household appliance.
With respect to pipe sound absorbers for air ducts, for example, it is furthermore known from the prior art to equip the inside of flow channels with a perforated carrier structure that carries an acoustic foam or a nonwoven fabric. This results in an increased pressure loss such that a vacuum cleaning appliance would no longer be able to vacuum up material from a surface to be cleaned as well as it would be the case, for example, without such a sound absorber. In addition, the installation of known sound absorbers is frequently elaborate because they have to be individually adapted.
Based on the aforementioned prior art, the invention aims to develop a household appliance with a sound absorption device that can be integrated into the household appliance in a particularly simple manner.
In order to attain the above-defined objective, it is proposed that the sound absorption device comprises a plurality of sound-absorbing wall elements and a carrier body that accommodates the wall elements in a reversible manner, wherein a flow path is formed within the carrier body between opposing wall elements.
According to the invention, the sound absorption device essentially consists of a carrier body and wall elements accommodated therein, wherein the carrier body can be fitted with wall elements in a modular manner. The carrier body initially can be fitted with wall elements prior to the installation into the household appliance such that the sound absorption device initially is assembled in a modular manner before the sound absorption device is installed into the household appliance in the form of a unit. This allows a significantly simplified and flawless installation of the sound-absorbing wall elements into the flow channel of the household appliance. The modular construction of the sound absorption device also allows a subsequent modification. The wall elements are connected to the carrier body such that they can be removed without being destroyed. For example, the wall elements may be connected to the carrier body by means of a screw connection, a plug connection, a snap-on connection or the like. To this end, it is particularly preferred that the carrier body makes available sockets that are universally suitable for different sound-absorbing wall elements. The sound-absorbing wall elements significantly influence the acoustic and fluidic properties of the sound absorption device and therefore can be individually adapted to the respective household appliance with the invention. The carrier body serves as a universal holder for a plurality of different wall elements that differ, for example, with respect to the material type and/or material thickness. In addition, the carrier body can be inserted into the flow channel of the household appliance independently of the fan. It can be fluidically connected to the fan on the one hand and to the outlet opening of the appliance housing on the other hand. For example, the carrier body can be connected to an inner wall of the appliance housing within the appliance housing, e.g. by means of a screw connection, a snap-on connection, a plug connection or the like.
The carrier body preferably consists of a hard plastic such as ABS (acrylonitrile-butadiene-styrene) or PP (polypropylene). The carrier body only forms a complete sound absorption device in connection with the sound-absorbing wall elements accommodated by this carrier body. The flow paths of the flow channel therefore are jointly formed by the surfaces of the sound-absorbing wall elements on the one hand and the surfaces of the carrier body on the other hand. The sound-absorbing wall elements are inserted into the carrier body in an airtight manner such that the air flow conducted within the carrier body cannot exit the flow path through possible openings or gaps between the material of the carrier body and the material of the wall elements.
It is proposed that the carrier body and the wall elements jointly form at least a section of the flow channel. The flow path within the carrier body is closed as airtight as possible. The carrier body comprises its own walls or braces, which act as a flow-conducting contour, as well as holding elements for the acoustically active wall elements inserted into this carrier body. Since the wall surfaces of the wall elements facing the flow path also have flow-conducting functions, the flow channel or the section of the flow channel is only formed in its entirety once the carrier body completely accommodates all wall elements.
It is furthermore proposed that the wall elements have a curved wall surface referred to a direction of a longitudinal extent of the flow channel, and that the wall elements are positioned relative to one another by means of the carrier body in such a way that the flow path extends in a curved manner. In this way, the flow channel is designed in a curved manner referred to at least a section along its longitudinal extent such that the air flow conducted in the flow channel impinges on the sound-absorbing wall elements multiple times in the flow direction and can be at least partially absorbed by said wall elements. Consequently, the inside of the flow channel is on the one hand provided with sound-absorbing wall elements and the multiple reflections of the air flow on the wall elements on the other hand results in an increased overall absorptivity. The pressure losses are kept to a minimum in contrast to essentially abrupt or discontinuous changes in the direction of the flow channel. Consequently, a change in direction does not take place abruptly, but rather along a curved flow path. It is particularly preferred that a clear flow cross section between the opposing wall surfaces of the flow channel has a certain minimum size, which is dimensioned in dependence on the volume flow of the air being conducted in the flow channel. The clear flow cross section should optimally have at least a value that corresponds to 0.96-times the value of the volume flow2, i.e. 0.96 × Q2, wherein Q is the value of the volume flow. With respect to the sound-absorbing property of the wall elements, these wall elements should ideally absorb 100 percent of the sound energy. Since this is rarely possible in practical applications, the sound absorption device should altogether reach a sound absorption of at least 50 percent referred to the sound portion to be absorbed.
It is proposed that the flow path is designed in an s-shaped manner such that the flow channel has at least two direction reversals. The flow path therefore has at least two essentially opposite changes in direction for the air flow being conducted within the flow channel, wherein the shape of the flow path is in this context referred to as s-shaped. However, it goes without saying that the scope of the invention also includes other curvature shapes that have at least two opposite changes in direction, in particular essentially 180° changes, such as a z-shape of the flow channel. Changes in direction between 145° and 180° also can optimally achieve the inventive effect. The changes in direction of the flow path basically can lie at any location of the flow channel and may be interrupted by straight flow channel sections. It is also possible that not only the sound-absorbing wall elements contribute to the s-shape of the flow path, but also wall regions that essentially are designed in a sound-reflecting manner. In addition, straight wall regions of the flow channel may also be designed in a sound-absorbing manner. In a mixed design of predominantly sound-absorbing and predominantly sound-reflecting wall regions, as well as straight and curved wall regions, it is essential that the flow channel has at least one section that contains curved and sound-absorbing wall elements and therefore inevitably results in a curved routing of the flow path, in which the curved wall elements at the same time have an at least sectional absorption property.
It is proposed that the flow path has a constant flow cross section. According to this embodiment, the distance between the opposing wall elements remains constant, wherein the curved wall surfaces of the wall elements extend parallel to one another following the curvature. As a result, the flow cross section likewise remains constant along the flow path, preferably starting from the fan up to the outlet opening of the flow channel. The flow cross section ideally is - as mentioned above - greater than a minimum flow cross section, which is dimensioned as at least 0.96 × volume flow2.
The carrier body may have a carrier body wall at least in a section of the carrier body, wherein the carrier body wall and the wall elements inserted into the carrier body form a flow channel section that is closed outward in an airtight manner and connected to the fan on the one hand and to the outlet opening of the appliance housing on the other hand in an air-sealing manner. According to this embodiment, the air flow and the sound conducted in the air flow are effectively prevented from taking a shortcut around the carrier body or at least sections of the carrier body. According to a special embodiment of the invention, the carrier body wall of the carrier body may be positioned relative to an output opening of the fan in such a way that the air flow exiting the fan is split into two flow portions, which separately flow to the outlet opening of the appliance housing within the carrier body. In this respect, two partial flow channels may be formed within the carrier body, wherein said partial flow channels respectively extend in an s-shaped manner and subsequently lead into a common air outlet of the carrier body. The carrier body wall particularly may be positioned orthogonal to an outflow direction of the air flow exiting the fan such that a first change in direction of the air flow conducted in the flow path is already achieved during the inflow into the carrier body. For example, a 90° deflection and bisection of the air flow entering the carrier body therefore can already be achieved when the air flow enters the carrier body. The two partial air flows then extend toward one another in a 180° deflection downstream of the carrier body wall and can be deflected by 90° again by a wall element with a curved design such that the partial air flows then flow toward the outlet opening of the appliance housing parallel to one another, but preferably separately of one another.
The wall elements of the sound absorption device preferably are made of an open-pored foam. The wall elements particularly may be made of melamine resin foam or polyurethane foam. In practical applications, these materials proved particularly effective in absorbing customary sound frequencies in household appliances, particularly sound frequencies generated by a fan.
Furthermore, the wall elements preferably have a wall thickness that corresponds to at least one-fourth of a wavelength of a sound portion to be absorbed. The wall thickness of the wall element defines the so-called “cut-on frequency,” starting at which sound portions are absorbed. The sound particle velocity of a resonant mode of the sound has an amplitude of 0 on a reflective section of the wall element. Starting from this, the sound particle velocity then extends in the direction of the opposite wall element in a sine wave with the wavelength λ. The wall thickness of the wall element has to correspond to at least one-fourth of the wavelength λ of the respective sound portion in order to achieve the desired effect of the sound-absorbing material of the wall element. In this way, the nearest peak of the amplitude of the sound particle velocity can still lie within the absorbing material of the wall element such that the sound energy is effectively reduced.
It is furthermore proposed that the wall elements have a wall that produces an airtight seal on their outwardly directed outer side facing away from the conducted air flow. In this way, the air flow cannot completely flow through the otherwise open-pored material of the wall elements, but the conducted air rather remains within the flow channel. Consequently, the respective wall element has an insulation layer that prevents the escape of air and also sound from the flow channel.
It is ultimately proposed that the flow channel has a sound reduction wall, wherein a wall plane of the sound reduction wall is oriented parallel to the flow path, and wherein the sound reduction wall is arranged centrally between the opposing wall surfaces of the flow channel referred to a direction extending orthogonal to the longitudinal extent of the flow channel. The sound reduction wall is likewise designed for reducing the sound energy of the resonant sound portions in the respective flow channel section containing the sound reduction wall. The sound reduction wall is arranged in the flow channel centrally between the opposing wall surfaces of the flow channel such that the plane of the sound reduction wall lies precisely at the location, at which the amplitude of the sound particle velocity has a maximum. The sound reduction wall therefore is spaced apart from the inner wall of the flow channel and essentially lies centrally within the opening cross section of the flow channel. In this way, the sound-absorbing sound reduction wall is situated precisely at the location, at which a particularly large amount of sound energy is conducted in the air flow. Since the sound reduction wall furthermore extends parallel to the main flow direction of the air flow in the flow channel, the air flow is not significantly impaired such that the suction power of the fan or the household appliance remains as high as possible. In other words, the sound reduction wall is arranged within the flow channel in such a way that the air flow generated by the fan can flow to the outlet opening with the least pressure loss possible within the flow channel and the sound generated by the fan is at the same time optimally reduced. The sound reduction wall is oriented parallel to the direction of the air flow whereas the sound waves form between the opposing inner walls of the flow channel, i.e. transverse thereto. In this way, the air flow generated by the fan can flow through the flow channel with the least pressure loss possible and penetrate the material of the sound reduction wall. An optimal acoustic absorption simultaneously takes place by means of the sound reduction wall arranged in the maximum of the sound particle velocity. The partial air flows, which flow separately before they reach the sound reduction wall, may optionally intermix again while flowing through the sound reduction wall such that the air flow as a whole can flow through the flow channel with the least pressure loss possible. This increases the degree of efficiency of the sound absorption device, i.e. the ratio of sound reduction to pressure loss.
Other objects and features of the invention will become apparent from the following detailed description considered in connection with the accompanying drawings. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the invention.
In the drawings,
The base unit 18 of the household appliance 1 furthermore has a shaft 23 with a handle 22. A switch 24 is arranged on the handle 22 and enables the user to adjust a certain operating mode of the household appliance 1, e.g. an intensity level of the fan 3 and/or a rotational speed of the floor treatment element 21 of the attachment 19.
The operation of the fan 3 generates sound that is carried to the outlet opening 4 via the flow channel 5 and ultimately into the surroundings of the household appliance 1. In order to realize the household appliance 1 in such a way that its use is agreeable for a user, the household appliance 1 is equipped with a sound absorption device 6 that is illustrated in greater detail in the additional figures (see particularly
The sound absorption device 6 has a carrier body 12 that is illustrated in
The wall elements 7, 8, 9 are foam elements of an acoustically active open-pored foam such as melamine resin foam or polyurethane foam. The wall elements 7, 8, 9 have an outer side 14 of a sound-insulating material such that the sound waves entering the pores of the wall elements 7, 8, 9 cannot exit the wall elements 7, 8, 9 on the rear side, i.e., via the outer side 14, but the non-absorbed portions of the sound wave rather are reflected back into a flow path 11 formed between opposing wall elements 7, 8, 9 in order to subsequently enter an opposite wall element 7, 8, 9 again. The wall elements 7, 8, 9 have a certain wall thickness d. The wall thickness d defines the depth of the absorbing material of the respective wall element 7, 8, 9 from the flow path 11 in the direction of the sound-insulating, i.e. reflective, outer side 14 of the wall element 7, 8, 9. In order to enable the wall element 7, 8, 9 or its absorbing material to optimally absorb a sound wave with a defined frequency, it is necessary that the wall thickness d corresponds to at least one-fourth of the wavelength of the respective sound portion. In this way, a maximum of the sound particle velocity of the respective sound portion lies within the absorbing material of the wall element 7, 8, 9. The sound particle velocity of a sound wave standing between opposing wall elements 7, 8, 9 has an amplitude of 0 on the reflective outer side 14 of the wall element 7, 8, 9 and continues to the opposite wall element 7, 8, 9 in the form of a standing sine wave, namely likewise up to the inner wall of the sound-reflecting outer side 14 of the wall element 7, 8, 9. It is essential that the amplitude peak closest to the outer side 14 still lies within the absorbing material of the wall element 7, 8, 9 such that as much sound energy as possible is absorbed within the pores of the material and not returned back into the flow path 11.
It is furthermore advantageous to specify a minimum flow cross section for the clear flow cross section of the flow path 11 between the wall elements 7, 8, 9. In practical applications, the minimum cross section should referred to the value of the square of the volume flow amount to at least 0.96 x the square of the volume flow. This minimum flow cross section of the flow path 11 preferably is constant along the flow path 11, i.e. ideally from the fan 3 up to the outlet opening 4 in the appliance housing 2. In this way, the pressure loss within the flow channel 5 can be kept as low as possible and a degree of efficiency, which describes the ratio between sound reduction to pressure loss, can be improved to higher than 2:1 or even beyond.
The flow paths 11 flow onward separately of one another between the wall element 8 and the sound reduction wall 15 on the one hand and the wall element 9 and the sound reduction wall 15 on the other hand, wherein the flow paths 11 then initially extend parallel to a wall plane 16 of the sound reduction wall 15 and then flow around the respective curved wall element 8, 9 such that the flow direction is once again deflected by approximately 180°. All in all, the flow paths therefore essentially have an s-shape or z-shape from the fan 3 up to the outlet from the carrier body 12. A maximum number of interactions between the conducted air flow and the absorbing material of the wall elements 7, 8, 9 is achieved due to the curved extent of the respective flow path 11. The sound reduction wall 15 also has a sound-absorbing material, preferably a fiber-reinforced nonwoven fabric that in this example is reinforced with approximately 30% glass fibers or carbon fibers (referred to its volume). A wall thickness of the sound reduction wall 15 amounts, for example, to less than 4 mm. The sound reduction wall 15 may be permeable to air such that the air flows from the flow paths 11 extending parallel to the wall plane 16 of the sound reduction wall 15 basically can transfer into one another. In this way, the pressure loss within the flow channel 15 is as low as possible such that the overall degree of efficiency of the sound absorption device 6 (sound reduction:pressure loss) becomes as high as possible. A respective width of the flow paths 11 between the wall plane 16 of the sound reduction wall 15 and the wall element 8 and between the sound reduction wall 15 and the wall element 9 approximately corresponds to one-fourth of the wavelength of a sound portion to be absorbed. In this way, the central plane of the sound reduction wall 15 lies in the peak of the sound particle velocity of the resonant mode (the dominant sound portion).
Although only a few embodiments of the present invention have been shown and described, it is to be understood that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21189402.7 | Aug 2021 | EP | regional |
Applicant claims priority under 35 U.S.C. §119 of European Application No. 21189402.7 filed Aug. 3, 2021, the disclosure of which is incorporated by reference.
