EP1551269A1

EP1551269A1 - Noise reduction arrangement for a vacuum cleaner

Info

Publication number: EP1551269A1
Application number: EP03738842A
Authority: EP
Inventors: Göran Nilsson; Tommy Andersson
Original assignee: Electrolux AB
Current assignee: Electrolux AB
Priority date: 2002-07-04
Filing date: 2003-07-02
Publication date: 2005-07-13
Anticipated expiration: 2023-07-02
Also published as: ATE398959T1; AU2003245215A1; DE60321803D1; WO2004004535A1; EP1551269B1; SE0202109D0

Abstract

The present invention relates to a vacuum cleaner comprising at least one dust collector and one flow generator. The dust collector comprises means for collecting particles transported by an airflow (44), which flows into the collector via a first inlet and out of the collector via a first outlet. The flow generator comprises a second inlet (32) through which the airflow from the first outlet flows into the flow generator and a second outlet (41) through which the air flows out of the flow generator, the flow generator also comprising an electric motor-fan assembly (11), a motor cover (20) and a motor housing (40). The flow generator comprises at least a third outlet (27) through which flows essentially the entire airflow from the second inlet, the third outlet (27) essentially being covered by a air permeable material (28) through which flows essentially the entire airflow from the third outlet (27).

Description

Case P-10107

Applicant: Aktiebolaget Electrolux, Stockholm

Noise reduction arrangement for a vacuum cleaner

TECHNICAL FIELD

The present invention relates to a vacuum cleaner comprising at least one dust collector and one flow generator. The dust collector comprises means for collecting particles transported by an airflow that flows into the collector via a first inlet and out of the collector via a first outlet. The flow generator comprises a second inlet through which the air flow from the first outlet flows into the flow generator and a second outlet through which the air flows out of the flow generator, which also comprises an electric motor assembly, a motor cover and a motor housing.

TECHNICAL BACKGROUND

Vacuum cleaners are characterised by their properties to suck up particles. Improved suction performance is, among other ways, achieved by increasing the suction power of the vacuum cleaner. A natural way of increasing the power is to increase the power of the electric motor that is installed in the vacuum cleanser. However, increased motor power creates problems with electrical interference such as electromagnetic fields and harmonics. Efficiency is also considered when selecting the electric motor. The motor assembly does normally not only comprise a motor but also a rotating fan part and a motor enclosure. The rotating fan part forces the air to move and thereby generates the air flow, while the enclosure forces the air sucked in by the fan part to pass the motor assembly in a preferred way and then to flow out of the motor assembly through one or many outlets. The properties of the enclosure results in, amongst other Itangs, that the air will cool the electric motor and that the air velocity inside the motor assembly assumes required levels. The efficiency is here defined as the proportion of the electric power that results in a suction effect of the motor assembly.

Other possible ways to improve the suction power are to improve the possibility for the air to flow through the vacuum cleaner from the nozzle to the vacuum cleaner body's outlet, through which the air flows out of the body. One important way is to make the vacuum cleaner as tight as possible, in which the air does not choose other flow paths than the one intended, i.e. the one that can be controlled and influenced. The tightness is significant and sometimes difficult to achieve, especially at transitions from the hose to the vacuum cleaner housing and between the components of the vacuum cleaner body. Another way is to reduce the pressure drop of the flow. The air flows along and through different parts of the vacuum cleaner. The smoothness of the surfaces that the air is coming in contact with influences the pressure drop. Sharp edges, uneven inner surfaces of the vacuum cleaner hoses and long, curved flow paths result in increased air turbulence, which increases the pressure drop and thereby the loss of suction power. Surfaces that do not result in air turbulence are to be strived for. Pressure drop is also created when the air is passing through the vacuum cleaner bag or other materials that can be penetrated by air.

The suction power of the vacuum cleaner frequently stands in contradiction to the noise level it generates. Noise reduction is an essential aspect in the development of vacuum cleaners. Vacuum cleansers have mainly three noise sources. The predominant noise source is the electric motor in the motor-fan assembly, which generates the airflow. The motor itself radiates in a broad noise spectrum. The air turbulence, generated by aerodynamic imperfections along the air's flow path, also generates noise. Turbulence means that the air has varying velocity and direction in different parts of the same cross section. Particularly at higher air velocities (unit rn/s) and airflows (unit liter/s), there is a risk for turbulence. A third noise generator is vibrating surfaces coming into contact with air. When much air with high velocity collides with the walls, they start to vibrate and generate noise. If the wall vibrates at its resonance frequency, the noise will be amplified to a higher degree.

The development efforts to reduce the noise levels are ongoing. The unit for noise is dB and each dB of noise reduction achieved is a big step forward. Already two to three dB of noise reduction is noticeable for the user. Taking the entire vacuum cleaner into account, there are a certain portions of the air's flow path where measures can be applied, such as the nozzle, the hose, the dust collector and the flow generator (the compartment of the vacuum cleaner where, amongst other things, the motor-fan assembly is situated). The invention is mainly aimed at noise reducing measures in the flow generator.

The flow generator comprises a motor-fan assembly, suspensions, noise reducing material, air absorbing material and air channels. By working at improving the cooperation between these parts, noise reduction can be achieved. The suspensions reduce the vibration levels and the noise reducing materials screen off noise created within the flow generator. The air turbulence is reduced, i.e. laminar flow is created, by means of letting the airflow through air-penetrable materials. Furthermore, the material increases the cross sectional area through which the air passes, which means decreased air velocity. Besides, the material decreases the suction power of the vacuum cleaner. The ducts in the flow generator are aerodynamically shaped in order to achieve a more laminar flow. By giving the ducts a large cross sectional area, the velocity of the airflow is also reduced.

The problem with present solutions is that efforts to screen off noise from the motor- fan assembly have not been sufficient. Besides, the airflow in present solutions creates rather substantial vibrations in the materials of the vacuum cleaner. Furthermore, the turbulence is rather high due to the velocity of the airflow. The intention of the present invention is therefore to achieve a flow generator that generates less noise.

DESCRIPTION OF THE INVENTION

The present invention relates to lowering the vacuum cleaner's noise generating properties by means of changing the air's flow path in the flow generator. That is achieved by letting the flow generator comprise at least a third outlet through which mainly the whole airflow from the second inlet flows, the third outlet essentially being covered by an air-penetrable material through which mainly the whole airflow from the third outlet flows.

DESCRIPTION OF FIGURES

The invention is described in further detail in conjunction with the preferred embodiment and with reference to the enclosed drawings. Fig.l shows an exploded view of a flow generator and a dust collector in accordance with the invention.

Fig. 2 shows a perspective view of the dust collector in accordance with fig. 1.

Fig. 3 shows a perspective view of the front suspension of the flow generator in accordance with fig. 1.

Fig. 4 shows a front view of the front suspension in accordance with fig. 3.

Fig.5 shows an exploded view of the motor-fan assembly, the rubber bushing and the diffuser of the flow generator in accordance with fig. 1.

Fig. 6 shows a perspective view of the flow generator's motor cover in accordance with fig. 1.

Fig. 7 shows a side view of the motor cover in accordance with fig. 6.

Fig. 8 shows a front view of the motor cover in accordance with fig. 6.

Fig. 9 shows a cross section of the motor cover in accordance with fig. 6.

Fig. 10 shows a perspective view of the absorbent in the flow generator in accordance with fig. 1.

Fig. 11 shows a perspective view of the flow generator's motor housing in accordance with fig. 1.

Fig. 12 shows the airflow through a cross section of the flow generator in accordance with fig. 1.

PREFERRED EMBODIMENT

The figures show an example of an embodiment of a flow generator in accordance with the invention. The example of the embodiment shall not be interpreted as a limitation of the invention but its only purpose is to concretely shed light on a type of flow generator, which achieves the objective of the application. The aim is to clarify the thought behind the invention.

Fig. 1 shows an exploded view of a dust collector 10 and a flow generator including its parts. The parts comprise a motor-fan assembly 11, a rear rubber bushing 12 and a diffuser 13. Furthermore, the flow generator comprise a motor cover 20, two outer rubber bushings 25, an absorbent 28 and in addition a front suspension 30 and a motor housing 40.

Fig. 2 shows further detail of the dust collector. The collector in the embodiment example is intended to be used primarily together with a vacuum cleaner bag. The air is flowing into the collector via the vacuum cleaner hose connected to a first inlet in a cover part (not shown), which, placed over the aperture 14, encloses the interior 15 of the dust collector. The cover part and the dust collector shall co-operate in order to seal the interior in the best possible way. The tightness is important to achieve high suction power. The air flowing into the interior passes through the vacuum cleaner bag (not shown) and subsequently flows out through a first outlet 16. The bag can be replaced or complemented by a cyclone separator for collection of particles. The outlet is covered by a star-shaped grid 17, which acts as a protection against unintended contact and directs the airflow out through the outlet. In front of the grid there is also a catastrophe filter (not shown), which collects the particles if for instance the bag should break.

The intention with the front suspension 30 in fig. 3 - 4 is to carry the front part of the motor-fan assembly 11 and the motor cover 20 at the dust collector 10 and the motor housing 40. The suspension has rings 31 embodied at the front (the side directed towards the dust collector). These co-operate with the back of the dust collector (not shown), against which the suspension rests. Thereby the first outlet 16 is sealed against the second inlet 32 formed by the suspension, exiting in towards the flow generator so that no air chooses to flow in an alternative route than into the motor-fan assembly. The intention with the holes 33 is to facilitate to arrange the motor housing 40 at the dust collector 10 by means of trough-going screws/bolts. Fig. 4 shows the back of the suspension, towards which the motor-fan assembly 11 rests. The side is shaped 35 so that no air can escape other than through the assembly. Four guide parts 34 integrated into one piece with the suspension 30 supports the assembly against the motor cover's 20 inner side when the flow generator is assembled.

Simultaneous with the seal at the first outlet 16 and the second inlet 32, the front suspension 30, placed between the motor cover 20 and the dust collector 10, seals so that no air escapes out of the cover that way. In addition, the suspension, placed between the motor housing 40 and the dust collector, seals so that no air escapes out of the housing that way.

The front suspension 30 is intended to serve as an elastic suspension of the motor-fan assembly 11 and the motor cover 20, which vibrate during operation. By means of the suspension, vibration propagation to other parts is avoided. The suspension is, in order to achieve an elastic, compact and suitable solution, made from foamed PUR (Polyurethane) with air-bubbles. PUR is a soft integral foam that combines softness with shape stability. It is chock absorbing and wear resistant. By puncturing some of the air-bubbles, the PUR in this form can absorb some water. By using PUR, which has good stability properties, increased suspension thickness can be achieved without supporting arrangements.

Fig. 5 shows an exploded view of the motor-fan assembly including accompanying rear rubber bushing 12 and diffuser 13. The motor-fan assembly comprises an electric motor and rotating fan blades. An enclosing cover has an aperture 18, in through which the air from the second inlet 32 in the suspension 30 flows. The airflow through the vacuum cleaner is generated by the motor-driven fan blades. The air flows through the entire assembly and passes on its way at the same time the motor. Subsequently the air flows out through apertures (not shown) in the rear, narrower part of the assembly. When the motor-fan assembly is placed in the motor cover 20, the blades 19 of the diffuser cover the apertures in the rear part of the assembly. The air thereby passes straight through the diffuser and out at the rear side. The diffuser consists of a cloth made of foam plastic. The cloth is very air permeable and does basically not create any pressure drop. The rear rubber bushing, made of synthetic rubber (EPDM, TPE), is, when the assembly in the cover is arranged in the in the rear part of the assembly, also located at the inside of the motor cover. Thus vibration propagation from the assembly to the cover is avoided.

Fig. 6 - 9 show the motor cover 20. The shape of the cover comprises an essential part of the invention. The cover encloses the motor-fan assembly 11 and is, together with the assembly, sealed by the front suspension 30. The cover's front rectangular edge 21 co-operates with the guide parts 34 of the suspension to elastically fasten the front part of the assembly. By means of its rectangular shape, it can also co-operate with standard types of dust collectors 10. The shape of the assembly implies that it is guided into the cover by means of grooves 22 in the cover. The rear part 23 of the cover is narrowing. Fig. 7 shows the underside of the cover. There a two fastening points 24 in the rear part of the cover, which together with outer rubber bushings 25, made of synthetic rubber, co-operate with the inside of the motor housing 40 when the cover is placed inside the motor housing. The cover is thereby elastically fastened to the housing and propagation of vibration from the cover to the housing is avoided.

There is a flange at the cover's underside, i.e. a protrusion in the cover, by means of which an even edge 26 at the cover's underside is achieved. By an even edge is meant that if a plane disc is placed on the flange, then the plane disc shall essentially be in contact with principally the entire U-shaped edge. The flange protrudes somewhat, whereby a clearance of a few millimetres is created between the disc and the edge 21, over which the disc protrudes. Possibly the disc is parallel with the edge 21. The main purpose of the edge is to enable the absorbent 28 (described below) to seal the entire aperture. The flange encloses a bigger aperture consisting of a third outlet 27 out of the motor cover 20. The outlet extends between the edges of the flange at the flange's rear part. The aperture's front part is defined by a screen 29, which is also enclosed by the flange. Fig. 8 shows a frontal view of the motor cover and fig. 9 a vertical cross section of the motor cover 20, depicted in fig. 6, the cross section placed in the middle of the cover.

When the motor cover 20 is placed in the motor housing 40, it is partly enclosed by the absorbent 28, see fig. 1 and 10. The absorbent thereby fills the entire space between the edges 26 of the flange and the inside of the motor housing. Using an absorbent in this manner constitutes an essential part of the thought behind the invention. The absorbent sees to, by its location, that air, flowing out of the motor cover through the third outlet 27, will be forced to pass through the absorbent in a special way. The absorbent is made of polyester and in original condition approximately 15 mm thick. When compressed in the motor housing it is 10 - 12 mm thick. The absorbent does not have the same air permeation as the diffuser 13. The important thing is that it is sufficiently tight to reduce the air velocity and filter away noise. However, the tightness must not be so great that the pressure drop becomes too high. The vacuum cleaner must not loose too much suction power. Suitable absorbent specification is 450 grams per square metre. The airflow including results are described below in further detail. In the motor housing there is furthermore a larger outlet 41, over which an outer absorbent (42 in fig. 11) is placed.

Fig. 12 shows a vertical cross section of the flow generator with most parts shown, such as the motor-fan assembly 11, the front suspension 30, the motor cover 20 and the motor housing 40. Furthermore a cross section of the vacuum cleaner chassis 43 is shown, in which the flow generator is arranged. The rear 12 and the outer 25 rubber bushings with accompanying brackets 24 and the diffuser 13 are missing. The airflow is illustrated by means of two arrows 44. The flow paths and results as regards flow properties and noise generation are presented below:

Prior to describing the flow path of the air, it is important to understand that the flowing air is transporting a lot of the noise generated along the flow path. The noise sources are air turbulence, vibrations in walls and directly radiated noise from the electric motor. The airflow generated by the motor-fan assembly 11 begins in the vacuum cleaner nozzle and continues via the vacuum cleaner hose into the dust collector 10. In the dust collector's interior 15, a cyclone separator or a vacuum cleaner bag collects the particles brought in by the airflow via the hose. Since the interior is tight when the lid is closed, no air leaks out from the interior in the ideal case. Consequently the air does not lose any energy. The particle-free air flows out of the interior via the first outlet 16 and the grid 17. The catastrophe filter, placed before the outlet, catches some of the particles that have passed the dust collector. The filter might also assist in creating laminar airflow, which is somewhat turbulent after passing through the collector 10. The dust collector walls may possibly vibrate due to the airflow. The air, including some noise, then flows in through the inlet 18 into the motor-fan assembly 11. The front suspension 30 makes sure that no air leaks out other ways. The air passes between the rotating fan blades in the assembly and then passes the electric motor. Thus the motor gets cooled. The rotating fan blades add the energy that causes the air to flow. The air flowing out of the assembly via outlets in its rear part is turbulent. The turbulence implies that the vacuum cleaner loses suction power. The air also transports the noise radiating from the assembly's motor and the fan blades. The turbulence and to a certain extent the noise are filtered away by the diffuser 13, whereby the air loses some suction power. The laminar flow is then finding its way towards the flange and the third outlet 27. Because of the cross sectional area of the air duct formed between the assembly 11 and the motor cover 20 being larger then the outlets of the motor, the velocity of the airflow is decreased. The flow is consequently less likely to generate turbulence. Furthermore the imier walls of the cover are not exposed to the same velocity, thereby reducing their tendency to vibrate and emit noise. Besides, the walls of the cover are screening off a lot of the noise trying to penetrate out through the walls.

The relatively laminar air from the third outlet 27 penetrates into the absorbent 28. Due to the fact that the absorbent covers the entire second outlet 27, all air will pass through the absorbent. Because the absorbent fills the entire space between the edges 26 of the flange and the inner wall of the motor housing 40, the airflow will bend 90 degrees and move in the right direction, upwards and inwards in fig. 12. Once outside the edges of the flange, where there is a free duct, the air flows out from the absorbent. The flow path of the air and the relatively large cross sectional area of the flow duct through the absorbent (the air flows in many directions) means that the inner wall of the motor housing does not vibrate due to the air flowing out of the second outlet and further lamination of the airflow. In addition, quite a lot of the noise transported by the air out of the motor cover is filtered. The result is that the air flowing out the absorbent 28 has lower velocity, less turbulence and transports less noise than with previous solutions. However, the absorbent implies loss of suction power. An air duct with a large cross sectional area has been created in the space between the motor cover 20 and the motor housing 40. Furthermore, the absorbent 28 is located along the inner walls of the motor housing. These features in combination means decreased airflow velocity. In addition, the absorbent prevents the air from bouncing between the walls of the air duct and absorbs a certain amount of noise. The air flows out of the motor housing through the second outlet 41 and the absorbent 42. Thereby further noise and particles are filtered away. Finally the air passes out from the vacuum cleaner chassis 43 via an outlet filter.

Using an absorbent 28 together with a large third outlet 27 constitutes the thought behind the invention. The location of the absorbent forces the air to flow through the absorbent in a certain direction. Besides, the large outlet reduces the velocity. These features in combination mean that the slower flow passing through the absorbent generates less vibration, less turbulence and, above all, that quite a lot of noise is filtered away. Placing the absorbent over the outlet from the motor cover shall not be considered as limiting the thought behind the invention. The absorbent could as well be located somewhere else along the flow path of the air. Furthermore, many absorbents after each other and located in the same way could be used. Placing one or many absorbents so that the airflow is influenced according to above constitutes the thought behind the invention. The condition is just that the third outlet or third outlets is large and the absorbents are located so that all air passes through them, which reduces turbulence, velocity and noise. Further embodiments are therefore contained within the thought of invention as specified in patent claim 1. The invention is consequently not limited to what is described above or to the embodiment shown in the drawings, but the arrangement can be used within all areas where noise reducing absorbents are used.

Claims

PATENT CLAIMS

1. Vacuum cleaners comprising at least one dust collector (10) and one flow generator, the dust collector comprising means for collecting particles transported by an airflow (44) which flows into the collector via a first inlet and out of the collector via a first outlet (16), the flow generator comprising a second inlet (32) through which the airflow (44) from the first outlet (16) flows into the flow generator and a second outlet (41) through which the airflow (44) flows out of the flow generator, whereby the flow generator comprises an electric motor-fan assembly (11), a motor cover (20) and a motor housing (40), characterised in that the flow generator comprises at least a third outlet (27) through which flows essentially the total airflow from the second inlet (32), the third outlet (27) is essentially covered by an air permeable material (28) through which flows essentially the total airflow from the third outlet (27).

2. Vacuum cleaner according to the patent claim lcharacterised in that the airflow (44) from the third outlet (27) when flowing into the material (28) has an essential first direction and when it continues to flow out of the material (28) has an essential second direction that significantly differs from the first direction.

3. Vacuum cleaner according to patent claim 2characterised in that the first direction is essentially perpendicular to and/or opposed to the second direction.

4. Vacuum cleaner according to any of the previous patent claims characteris e d i n that the dust collector's (13) means for collection constitutes a dust filter preferably comprising a vacuum cleaner bag.

5. Vacuum cleaner according to any of the patent claims l-3characterised i n that the dust collector's (13) means for collection constitutes at least a cyclone separator.

6. Vacuum cleaner according to any of the previous patent claims characteris e d i n that the electric motor-fan assembly (11) generates the airflow (44).

7. Vacuum cleaner according to any of the previous patent claims characteris e d i n that the motor cover (20) entirely or partly encloses the motor-fan assembly (11), whereby the assembly (11) is elastically arranged at the motor cover (20) by means of assembly suspensions (12,30).

8. Vacuum cleaner according to the patent claim 7characterised in that the assembly suspension relates to at least one rear rubber bushing (12) arranged at the motor-fan assembly (11) and the motor cover (20) and at least one front suspension (30), which contributes to that the airflow (44) does not partly flow from the first outlet (16) into the space between the assembly (11) and the motor cover (20) without first passing through the assembly (11).

9. Vacuum cleaner according to any of the previous patent claims characteris e d i n that the motor housing (40) entirely or partly encloses the motor- fan assembly (11) and the motor cover (20), whereby the motor cover (20) is elastically arranged at the motor housing (40) by means of cover suspensions (24,25).

10. Vacuum cleaner according to the patent claim 9characterised in that the cover suspension relates to at least one outer rubber bushing (25) arranged at the motor cover (20) and the motor housing (40) and/or at least a front suspension (30), which contributes to that the airflow (44) does not partly flow from the first outlet (16) into the space between the motor cover (20) and the motor housing (40) without fist passing through the motor-fan assembly (11).

11. Vacuum cleaner according to any of the patent claims 8 and 10 characteri s e d i n that the front suspension (30) is made of polyurethane.

12. Vacuum cleaner according to any of the previous patent claims characteris e d i n that at least one absorbent (28) is arranged at least in parts of the space between the motor cover and the motor housing, whereby at least a portion of the airflow flows through the absorbent (28).

13. Vacuum cleaner according to any of the previous patent claims characteris e d i n that the third outlet (27) constitutes an aperture (26) in the motor cover (20), whereby the airflow (44) flows from the electric motor-fan assembly (11) out through the aperture (27).

14. Vacuum cleaner according to any of the previous patent claims characteris e d i n that the air permeable material (28) fills the entire space between the third aperture (27) and the surface that the aperture is directed towards.

15. Vacuum cleaner according to any of the previous patent claims characteris e d i n that the air permeable material (28) constitutes a fluffy material made of polyester.