HOUSEHOLD APPLIANCE WITH A SOUND ATTENUATOR

Abstract

A household appliance has a device housing, a blower arranged in the device housing, an outlet opening formed in a direction of flow behind the blower in the device housing, a flow channel that connects the outlet opening with the blower in terms of flow, and a sound attenuator allocated to the flow channel for attenuating sound arising from the operation of the household appliance. The sound attenuator has sound-absorbing wall elements that have a wall surface that is curved in relation to a direction of a longitudinal extension of the flow channel, a support body for receiving the sound-absorbing wall elements, and a sound-reducing wall with a wall plane oriented parallel to the flow path. The sound attenuator is modular in design, formed of the support body, wall elements and sound-reducing wall, and is installed as a whole into the device housing between the blower and outlet opening.

Claims

1. A household appliance comprising: a device housing, a blower arranged in the device housing, an outlet opening formed in a direction of flow behind the blower in the device housing, a flow channel that connects the outlet opening with the blower in terms of flow, and a sound attenuator allocated to the flow channel for attenuating sound arising from the operation of the household appliance, wherein the sound attenuator has a plurality of sound-absorbing wall elements, wherein the wall elements together form at least one section of the flow channel, and each wall element has a wall surface that is curved in relation to a direction of a longitudinal extension of the flow channel, wherein a flow path formed between opposing wall surfaces is curved, wherein the sound attenuator has a support body configured for receiving the sound-absorbing wall elements, wherein the flow channel has a sound-reducing wall, wherein a wall plane of the sound-reducing wall is oriented parallel to the flow path, and wherein the sound-reducing wall is centrally arranged between the opposing wall surfaces of the flow channel relative to a direction orthogonal to the longitudinal extension of the flow channel, and wherein the sound attenuator is modular in design, comprised of the support body, wall elements and sound-reducing wall, and is configured to be installed as a whole into the device housing between the blower and outlet opening.

2. The household appliance according to claim 1, wherein the flow path has an s-shaped design.

3. The household appliance according to claim 2, wherein the flow path has two opposite changes in direction.

4. The household appliance according to claim 1, wherein the flow channel has a constant flow cross section between the opposing wall elements along the flow path.

5. The household appliance according to claim 1, wherein the support body has a support body wall in at least one partial area of the support body, wherein the support body wall and the wall elements placed in the support body form a flow channel section closed airtight to the outside, the flow channel section being airtightly connected with the blower and the outlet opening of the device housing.

6. The household appliance according to claim 1, wherein the wall elements are comprised of an open-pored foam.

7. The household appliance according to claim 1, wherein the wall elements are fabricated out of melamine resin foam or polyurethane foam.

8. The household appliance according to claim 1, wherein the wall elements have a wall thickness (d) that corresponds to at least one fourth of a wavelength of a sound component to be attenuated.

9. The household appliance according to claim 1, wherein the wall elements have an airtight closing wall on an outwardly facing exterior side facing away from a guided airflow.

10. The household appliance according to claim 1, wherein the household appliance is a floor processing device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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.

[0018] In the drawings,

[0019] FIG. 1 is a household appliance according to the invention;

[0020] FIG. 2 is a schematic diagram of a flow channel with curved wall elements;

[0021] FIG. 3 is a longitudinal section of a flow channel with a sound attenuator, which has a support body and wall elements placed therein;

[0022] FIG. 4 is a cross section of the flow channel according to FIG. 3;

[0023] FIG. 5 is a wall element according to a first embodiment;

[0024] FIG. 6 is a wall element according to another embodiment;

[0025] FIG. 7 is a wall element according to another embodiment;

[0026] FIG. 8 is a wall element according to another embodiment; and

[0027] FIG. 9 is a support body for mounting wall elements.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0028] FIG. 1 shows an example of a possible embodiment of a household appliance 1 according to the invention, which is here designed as a floor processing device. The household appliance 1 here involves a vacuum cleaner to be manually operated by a user. The household appliance 1 has a base device 18 and an attachment 19 detachably connected with the base device 18. For example, the attachment 19 here involves a suction nozzle with a suction mouth 20 and a floor processing element 21 allocated to the suction mouth 20. The base device 18 of the household appliance 1 has a device housing 2, in which a suction material chamber 17 and a blower 3 are located, among other things. A flow channel 5 connects an outlet side of the blower 3 with an outlet opening 4. The blower 3 is used to suck suction material into the suction material chamber 17, wherein suction material located on a surface to be cleaned can be sucked through the suction mouth 20 of the attachment 19 and into the suction material chamber 17 of the base device 18. While the suction material remains within the suction material chamber 17, purified air flows through the blower 3 and flow channel 5 to the outlet opening 4 of the household appliance 1.

[0029] The base device 18 of the household appliance 1 further has a handle 23 with a grip 22. A switch 24 is arranged on the grip 22, with which a user can set a specific operating mode of the household appliance 1, for example an intensity stage of the blower and/or a speed of the floor processing element 21 of the attachment 19.

[0030] Operating the blower 3 generates noise, which is carried via the flow channel 5 to the outlet opening 4 and into the environment of the household appliance 1. In order to design the household appliance 1 in such a way as to make application comfortable to a user, the household appliance 1 has a sound attenuator 6 shown in greater detail with respect to the additional figures (see in particular FIG. 3). The sound frequencies emitted by the blower 3 depend on various parameters, for example a speed of a motor shaft of the blower 3. A so-called blade passing frequency of the blower 3 is of particular interest, which is determined by the speed of the motor shaft on the one hand, and by the number of blower blades of the blower 3 on the other. Therefore, the sound attenuator 6 is configured in particular in such a way as to absorb the characteristic sound frequencies of the blower 3 of the household appliance that arise at specific power levels of the blower 3.

[0031] The principle underlying the invention will now be explained in greater detail based on FIG. 2. One essential aspect of the invention is the geometric design of the flow channel 5 or sound attenuator 6, so as to be able to absorb sound components propagating within the flow channel 5 as best as possible. Therefore, the flow channel 5 is designed by means of a plurality of curved wall elements 7, 8, 9 of the sound attenuator 6 in such a way that a flow path 11 formed between the wall elements 7, 8, 9 is curved, the sound components hit a wall surface 10 of the wall elements 7, 8, 9 as often as possible while passing the flow path 11, and the energy of the sound components is further reduced with each reflection on the wall element 7, 8, 9. The component of sound energy absorbed by the material of the wall element 7, 8, 9 rises with the number of reflections (viewed in absolute terms).

[0032] The wall elements 7, 8, 9 are foam elements comprised of an open-pored, acoustically effective foam, for example melamine resin foam or polyurethane foam. On the side facing away from the flow path 11, the wall elements 7, 8, 9 have an exterior side 14 (not shown on FIG. 2) comprised of a sound-attenuating material, so that the soundwaves entering into the pores of the wall elements 7, 8, 9 cannot leave the wall elements 7, 8, 9 on the rear side, i.e., via the exterior side 14, with the unabsorbed components of the soundwaves instead being reflected back into the flow path 11, so as to then in turn enter into an opposing wall element 7, 8, 9. The wall elements 7, 8, 9 have a specific wall thickness d. The wall thickness d determines the depth of the absorbing material of the respective wall element 7, 8, 9 from the flow path 11 in the direction toward the sound-attenuating, i.e., reflecting exterior side 14 of the wall element 7, 8, 9. The wall thickness d of the wall element 7, 8, 9 differs for various entry angles of the sound. In order for the wall element 7, 8, 9 or its absorbing material to be able to optimally absorb a soundwave with a defined frequency, it is necessary that the wall thickness d be at least as large as one fourth of the wavelength of the respective sound component. As a result, a first maximum of the sound velocity of the respective sound component nearest the wall element 7, 8, 9 lies within the absorbing material of the wall element 7, 8, 9. The sound velocity of a soundwave standing between opposing wall elements 7, 8, 9 has an amplitude of 9 on the reflecting inner wall of the exterior side 14 of the wall element 7, 8, 9, and continues as a standing sinusoidal wave to an opposing wall element 7, 8, 9, namely likewise up to the inner wall of the sound-reflecting exterior side 14 of the wall element 7, 8, 9. What is essential is that the amplitude peak nearest the exterior side 14 still lie within the absorbing material of the wall element 7, 8, 9, so that as much sound energy as possible is absorbed within the pores of the material, and does not get back into the flow path 11.

[0033] In addition, it is recommended that a minimum flow cross section be established for the free flow cross section of the flow path 11 between the wall elements 7, 8, 9. In practice, the minimum flow cross section should measure at least 0.96×volume flow.sup.2 relative to the amount of the volume flow squared. This minimum flow cross section is preferably constant along the flow path 11, i.e., if possible from the blower 3 up to the outlet opening 4 in the device housing 2. As a result, the pressure loss within the flow channel 5 can be kept small, and an efficiency indicating the ratio between the sound reduction and pressure loss can be improved to more than 2:1 or even above that.

[0034] The wall elements 7, 8, 9 are held in the device housing 2 of the household appliance 1 by means of a support body 12. The support body 12 is shown on FIG. 9. The individual wall elements 7, 8, 9 are visible on FIGS. 5 to 7. The wall elements 7, 8, 9 as well as a sound reducing wall 15 also shown on FIG. 8 are inserted or plugged into corresponding receptacles of the support body 12, namely in such a way that no crevices or cracks arise between which air can escape from the sound attenuator 6. The support body 12 is fabricated out of a stiff plastic, such as ABS or PP.

[0035] As further shown on FIG. 3, the support body 12 in the flow channel 5 is arranged on the outlet side of the blower 3, namely between the blower 3 and the outlet opening 4. For example, the exterior side of the support body 12 here hits against the interior side of the device housing 2, and for example is fixed on the device housing 2, in particular by a screw connection, plug connection, latching connection or the like. Together with the wall elements 7, 8, 9 and the sound reducing wall 15 yet to be described later in detail, the support body 12 forms an installation module, which can be installed as a whole into the device housing 2 of the household appliance 1. The support body 12 comprises both its own walls, for example the support body wall 13 that acts as a flow-conducting contour, along with retaining elements for the wall elements 7, 8, 9 placed in the support body 12 as well as the sound reducing wall 15. Since the wall surfaces 10 of the wall elements 7, 8, 9 also have flow-conducting functions, only the support body 12 having completely all elements 7, 8, 9 as well as the sound reducing wall 15 fully forms the flow path 11 of the respective section of the flow channel 5.

[0036] As shown on FIG. 3, the outlet air of the blower 3 coming from the outlet opening of the blower 3 is divided into two separate flow paths 11, which at opposing marginal edges of the support body wall 13 flow in opposite directions around the support body wall 13, namely in a downward direction and an upward direction relative to the image plane on FIG. 3. The direction of the respective two flow paths 11 is here deflected by 180°, which is caused by the deflection of the outlet flow around the marginal edges of the support body wall 13. The flow paths 11 subsequently flow through between the wall elements 7, 8, 9, specifically a first flow path 11 between the wall element 8 and wall element 7, and a second flow path 11 between the wall element 9 and wall element 7. The wall element 7 is essentially inserted centrally into the support body wall 13, and in relation to the longitudinal section on FIG. 3 is shaped like a roughly isosceles triangle with concave lateral surfaces. The wall element 7 is shown in detail on FIG. 5. The wall element 7 continues the curvature of the support body wall 13 with its concave wall surfaces 10, and forms a flow path 11 running with essentially a constant opening cross section with the opposing wall element 8 or wall element 9. A tip of the wall element 7 here seamlessly adjoins the sound reducing wall 15, which is likewise placed in the support body 12 and shown in greater detail on FIG. 8.

[0037] After passing the wall element 7 between the wall element 8 and sound-reducing wall 15 on the one hand and the wall element 9 and sound-reducing wall 15 on the other, the flow paths 11 continue to flow, wherein the flow paths 11 then initially run parallel to a wall plane 16 of the sound-reducing wall 15, and then flow further around the respective curved wall element 8, 9, so that a flow deflection again arises. As a consequence, the flow paths 11 in the sound attenuator 6 essentially complete an s-shape or z-shape overall. The curved progression of the respective flow paths 11 leads to a maximum number of interactions between the guided airflow and the absorbing material of the wall elements 7, 8, 9. The sound-reducing wall 15 also has a sound-absorbing material, namely preferably a fiber-reinforced nonwoven, for example which is here reinforced to 30% (relative to the volume) with glass fibers or carbon fibers. For example, a wall thickness of the sound-reducing wall 15 measures less than 4 mm. The sound-reducing wall 15 can be air-permeable in design, so that the air components from the flow paths 11 running parallel to the wall plane 16 of the sound-reducing wall 15 can potentially intersect. As a result, the pressure loss within the flow channel 15 is kept as low as possible, so that the overall efficiency of the sound attenuator 6 (sound reduction:pressure loss) becomes as high as possible. Between the wall plane 16 of the sound-reducing wall 15 and the wall element 8 or wall element 9, the flow paths 11 each have a width that roughly corresponds to one fourth of the wavelength of a sound component to be attenuated. As a result, the central plane of the sound-reducing wall 15 lies in the peak of the sound velocity of a resonance mode (of the dominant sound component).

[0038] FIG. 4 shows a cross section through the flow channel 5 with the sound attenuator 6. The viewing direction therein is oriented parallel to the wall plane 16 of the sound-reducing wall 15 in the direction of the blower 3. Visible are the flow paths 11 running parallel on both sides of the sound-reducing wall 15, which come from the direction of the central wall element 7. As evident in particular from FIG. 3 as well as the shape of the wall elements 7, 8, 9 according to FIGS. 5 to 7, it is essential that the flow path 11 be as curved as possible in design, and not angular, for example. This ensures that the pressure losses caused within the flow channel 5 are kept as low as possible. In addition, the sound reduction effect due to the curvature and material of the absorbing wall elements 7, 8, 9 as well as the material of the absorbing sound-reducing wall 15 is increased, so that the efficiency of the sound attenuator 6 is as high as possible.

[0039] 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.

LIST OF REFERENCES

[0040] 1 Household appliance d Wall thickness [0041] 2 Device housing [0042] 3 Blower [0043] 4 Outlet opening [0044] 5 Flow channel [0045] 6 Sound attenuator [0046] 7 Wall element [0047] 8 Wall element [0048] 9 Wall element [0049] 10 Wall surface [0050] 11 Flow path [0051] 12 Support body [0052] 13 Support body wall [0053] 14 Exterior side [0054] 15 Sound-reducing wall [0055] 16 Wall plane [0056] 17 Suction material chamber [0057] 18 Base device [0058] 19 Attachment [0059] 20 Suction mouth [0060] 21 Floor processing element [0061] 22 Grip [0062] 23 Handle [0063] 24 Switch